WorldWideScience

Sample records for dental ceramic systems

  1. Fatigue of dental ceramics.

    Science.gov (United States)

    Zhang, Yu; Sailer, Irena; Lawn, Brian R

    2013-12-01

    Clinical data on survival rates reveal that all-ceramic dental prostheses are susceptible to fracture from repetitive occlusal loading. The objective of this review is to examine the underlying mechanisms of fatigue in current and future dental ceramics. The nature of various fatigue modes is elucidated using fracture test data on ceramic layer specimens from the dental and biomechanics literature. Failure modes can change over a lifetime, depending on restoration geometry, loading conditions and material properties. Modes that operate in single-cycle loading may be dominated by alternative modes in multi-cycle loading. While post-mortem examination of failed prostheses can determine the sources of certain fractures, the evolution of these fractures en route to failure remains poorly understood. Whereas it is commonly held that loss of load-bearing capacity of dental ceramics in repetitive loading is attributable to chemically assisted 'slow crack growth' in the presence of water, we demonstrate the existence of more deleterious fatigue mechanisms, mechanical rather than chemical in nature. Neglecting to account for mechanical fatigue can lead to gross overestimates in predicted survival rates. Strategies for prolonging the clinical lifetimes of ceramic restorations are proposed based on a crack-containment philosophy. Copyright © 2013 Elsevier Ltd. All rights reserved.

  2. Viscoelastic analysis of a dental metal-ceramic system

    Science.gov (United States)

    Özüpek, Şebnem; Ünlü, Utku Cemal

    2012-11-01

    Porcelain-fused-to-metal (PFM) restorations used in prosthetic dentistry contain thermal stresses which develop during the cooling phase after firing. These thermal stresses coupled with the stresses produced by mechanical loads may be the dominant reasons for failures in clinical situations. For an accurate calculation of these stresses, viscoelastic behavior of ceramics at high temperatures should not be ignored. In this study, the finite element technique is used to evaluate the effect of viscoelasticity on stress distributions of a three-point flexure test specimen, which is the current international standard, ISO 9693, to characterize the interfacial bond strength of metal-ceramic restorative systems. Results indicate that the probability of interfacial debonding due to normal tensile stress is higher than that due to shear stress. This conclusion suggests modification of ISO 9693 bond strength definition from one in terms of the shear stress only to that accounting for both normal and shear stresses.

  3. Thermal compatibility of dental ceramic systems using cylindrical and spherical geometries

    Science.gov (United States)

    DeHoff, Paul H.; Barrett, Allyson A.; Lee, Robert B.; Anusavice, Kenneth J.

    2009-01-01

    Objective To test the hypothesis that bilayer ceramic cylinders and spheres can provide valid confirmation of thermal incompatibility stresses predicted by finite element analyses. Methods A commercial core ceramic and an experimental core ceramic were used to fabricate open-ended cylinders and core ceramic spheres. The core cylinders and spheres were veneered with one of four commercial dental ceramics representing four thermally compatible groups and four thermally incompatible groups. Axisymmetric thermal and viscoelastic elements in the ANSYS finite element program were used to calculate temperatures and stresses for each geometry and ceramic combination. This process required a transient heat transfer analysis for each combination to determine input temperatures for the structural model. Results After fabrication, each specimen was examined visually using fiberoptic transillumination for evidence of cracking. There were 100% failures of the thermally incompatible cylinders while none of the thermally compatible combinations failed. Among the spheres, 100% of the thermally incompatible systems failed, 16% of one of the thermally compatible systems failed, and none of the remaining compatible combinations failed. The calculated stress values were in general agreement with the experimental observations, i.e., low residual stresses for the specimens that did not fail and high residual stresses for the specimens that did fail. Significance Simple screening geometries can be used to identify highly incompatible ceramic combinations, but they do not identify marginally incompatible systems. PMID:17949805

  4. Effect of different dental ceramic systems on the wear of human enamel: An in vitro study.

    Science.gov (United States)

    Zandparsa, Roya; El Huni, Rabie M; Hirayama, Hiroshi; Johnson, Marc I

    2016-02-01

    The wear of tooth structure opposing different advanced dental ceramic systems requires investigation. The purpose of this in vitro study was to compare the wear of advanced ceramic systems against human enamel antagonists. Four ceramic systems (IPS e.max Press, IPS e.max CAD, Noritake Super Porcelain EX-3, and LAVA Plus Zirconia) and 1 control group containing human enamel specimens were used in this study (n = 12). All specimens were fabricated as disks 11 mm in diameter and 3 mm thick. The mesiopalatal cusps of the maxillary third molars were prepared to serve as the enamel styluses. All specimens were embedded individually in 25 mm(3) autopolymerizing acrylic resin blocks. Wear was measured with a cyclic loading machine and a newly designed wear simulator. All enamel styluses (cusps) were scanned using the Activity 880 digital scanner (SmartOptics). Data from the base line and follow-up scans were collected and compared with Qualify 2012 3-dimensional (3D) and 2D digital inspection software (Geomagic), which aligned the models and detected the geometric changes and the wear caused by the antagonist specimen. One-way ANOVA was used to analyze the collected data. After 125,000 bidirectional loading cycles, the mean loss of opposing enamel volume for the enamel disks in the control group was 37.08 μm(3), the lowest mean value for IPS e.max Press system was 39.75 μm(3); 40.58 μm(3) for IPS e.max CAD; 45.08 μm(3) for Noritake Super Porcelain EX-3 system; and 48.66 μm(3) for the Lava Plus Zirconia system. No statically significant differences were found among the groups in opposing enamel volume loss (P=.225) or opposing enamel height loss (P=.149). In terms of opposing enamel height loss, Lava Plus Zirconia system showed the lowest mean value of 27.5 μm. The mean value for the IPS e.max CAD system was 27.91 μm; 29.08 μm for the control enamel; 33.25 μm for the IPS e.max Press system; and 34.75 μm for the Noritake Super Porcelain EX-3 system. Within the

  5. Uranium determination in dental ceramics

    International Nuclear Information System (INIS)

    Jacobson, I.; Gamboa, I.; Espinosa, G.; Moreno, A.

    1984-01-01

    There are many reports of high uranium concentration in dental ceramics, so they require to be controlled. The SSNTD is an optional method to determine the uranium concentration. In this work the analysis of several commercial dental ceramics used regularly in Mexico by dentists is presented. The chemical and electrochemical processes are used and the optimal conditions for high sensitivity are determined. CR-39 (allyl diglycol polycarbonate) was used as detector. The preliminary results show some materials with high uranium concentrations. Next step will be the analysis of equivalent dose and the effects in the public health. (author)

  6. A fractographic study of clinically retrieved zirconia–ceramic and metal–ceramic fixed dental prostheses

    OpenAIRE

    Pang, Zhen; Chughtai, Asima; Sailer, Irena; Zhang, Yu

    2015-01-01

    A recent 3-year randomized controlled trial (RCT) of tooth supported three- to five-unit zirconia-ceramic and metal-ceramic posterior fixed dental prostheses (FDPs) revealed that veneer chipping and fracture in zirconia-ceramic systems occurred more frequently than those in metal-ceramic systems [1]. This study seeks to elucidate the underlying mechanisms responsible for the fracture phenomena observed in this RCT using a descriptive fractographic analysis

  7. Dental ceramics: a review of new materials and processing methods.

    Science.gov (United States)

    Silva, Lucas Hian da; Lima, Erick de; Miranda, Ranulfo Benedito de Paula; Favero, Stéphanie Soares; Lohbauer, Ulrich; Cesar, Paulo Francisco

    2017-08-28

    The evolution of computerized systems for the production of dental restorations associated to the development of novel microstructures for ceramic materials has caused an important change in the clinical workflow for dentists and technicians, as well as in the treatment options offered to patients. New microstructures have also been developed by the industry in order to offer ceramic and composite materials with optimized properties, i.e., good mechanical properties, appropriate wear behavior and acceptable aesthetic characteristics. The objective of this literature review is to discuss the main advantages and disadvantages of the new ceramic systems and processing methods. The manuscript is divided in five parts: I) monolithic zirconia restorations; II) multilayered dental prostheses; III) new glass-ceramics; IV) polymer infiltrated ceramics; and V) novel processing technologies. Dental ceramics and processing technologies have evolved significantly in the past ten years, with most of the evolution being related to new microstructures and CAD-CAM methods. In addition, a trend towards the use of monolithic restorations has changed the way clinicians produce all-ceramic dental prostheses, since the more aesthetic multilayered restorations unfortunately are more prone to chipping or delamination. Composite materials processed via CAD-CAM have become an interesting option, as they have intermediate properties between ceramics and polymers and are more easily milled and polished.

  8. Dental ceramics: a review of new materials and processing methods

    Directory of Open Access Journals (Sweden)

    Lucas Hian da SILVA

    2017-08-01

    Full Text Available Abstract The evolution of computerized systems for the production of dental restorations associated to the development of novel microstructures for ceramic materials has caused an important change in the clinical workflow for dentists and technicians, as well as in the treatment options offered to patients. New microstructures have also been developed by the industry in order to offer ceramic and composite materials with optimized properties, i.e., good mechanical properties, appropriate wear behavior and acceptable aesthetic characteristics. The objective of this literature review is to discuss the main advantages and disadvantages of the new ceramic systems and processing methods. The manuscript is divided in five parts: I monolithic zirconia restorations; II multilayered dental prostheses; III new glass-ceramics; IV polymer infiltrated ceramics; and V novel processing technologies. Dental ceramics and processing technologies have evolved significantly in the past ten years, with most of the evolution being related to new microstructures and CAD-CAM methods. In addition, a trend towards the use of monolithic restorations has changed the way clinicians produce all-ceramic dental prostheses, since the more aesthetic multilayered restorations unfortunately are more prone to chipping or delamination. Composite materials processed via CAD-CAM have become an interesting option, as they have intermediate properties between ceramics and polymers and are more easily milled and polished.

  9. Ceramics for Dental Applications: A Review

    Directory of Open Access Journals (Sweden)

    Julie A. Holloway

    2010-01-01

    Full Text Available Over the past forty years, the technological evolution of ceramics for dental applications has been remarkable, as new materials and processing techniques are steadily being introduced. The improvement in both strength and toughness has made it possible to expand the range of indications to long-span fixed partial prostheses, implant abutments and implants. The present review provides a state of the art of ceramics for dental applications.

  10. Translucency of dental ceramics with different thicknesses.

    Science.gov (United States)

    Wang, Fu; Takahashi, Hidekazu; Iwasaki, Naohiko

    2013-07-01

    The increased use of esthetic restorations requires an improved understanding of the translucent characteristics of ceramic materials. Ceramic translucency has been considered to be dependent on composition and thickness, but less information is available about the translucent characteristics of these materials, especially at different thicknesses. The purpose of this study was to investigate the relationship between translucency and the thickness of different dental ceramics. Six disk-shaped specimens of 8 glass ceramics (IPS e.max Press HO, MO, LT, HT, IPS e.max CAD LT, MO, AvanteZ Dentin, and Trans) and 5 specimens of 5 zirconia ceramics (Cercon Base, Zenotec Zr Bridge, Lava Standard, Lava Standard FS3, and Lava Plus High Translucency) were prepared following the manufacturers' instructions and ground to a predetermined thickness with a grinding machine. A spectrophotometer was used to measure the translucency parameters (TP) of the glass ceramics, which ranged from 2.0 to 0.6 mm, and of the zirconia ceramics, which ranged from 1.0 to 0.4 mm. The relationship between the thickness and TP of each material was evaluated using a regression analysis (α=.05). The TP values of the glass ceramics ranged from 2.2 to 25.3 and the zirconia ceramics from 5.5 to 15.1. There was an increase in the TP with a decrease in thickness, but the amount of change was material dependent. An exponential relationship with statistical significance (Pceramics and zirconia ceramics. The translucency of dental ceramics was significantly influenced by both material and thickness. The translucency of all materials increased exponentially as the thickness decreased. All of the zirconia ceramics evaluated in the present study showed some degree of translucency, which was less sensitive to thickness compared to that of the glass ceramics. Copyright © 2013 The Editorial Council of the Journal of Prosthetic Dentistry. Published by Mosby, Inc. All rights reserved.

  11. Bioactive and inert dental glass-ceramics.

    Science.gov (United States)

    Montazerian, Maziar; Zanotto, Edgar Dutra

    2017-02-01

    The global market for dental materials is predicted to exceed 10 billion dollars by 2020. The main drivers for this growth are easing the workflow of dentists and increasing the comfort of patients. Therefore, remarkable research projects have been conducted and are currently underway to develop improved or new dental materials with enhanced properties or that can be processed using advanced technologies, such as CAD/CAM or 3D printing. Among these materials, zirconia, glass or polymer-infiltrated ceramics, and glass-ceramics (GCs) are of great importance. Dental glass-ceramics are highly attractive because they are easy to process and have outstanding esthetics, translucency, low thermal conductivity, high strength, chemical durability, biocompatibility, wear resistance, and hardness similar to that of natural teeth, and, in certain cases, these materials are bioactive. In this review article, we divide dental GCs into the following two groups: restorative and bioactive. Most restorative dental glass-ceramics (RDGCs) are inert and biocompatible and are used in the restoration and reconstruction of teeth. Bioactive dental glass-ceramics (BDGCs) display bone-bonding ability and stimulate positive biological reactions at the material/tissue interface. BDGCs are suggested for dentin hypersensitivity treatment, implant coating, bone regeneration and periodontal therapy. Throughout this paper, we elaborate on the history, processing, properties and applications of RDGCs and BDGCs. We also report on selected papers that address promising types of dental glass-ceramics. Finally, we include trends and guidance on relevant open issues and research possibilities. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 619-639, 2017. © 2016 Wiley Periodicals, Inc.

  12. A review of the strength properties of dental ceramics.

    Science.gov (United States)

    Hondrum, S O

    1992-06-01

    New ceramic materials for restorative dentistry have been developed and introduced in recent years. This article reviews advantages and disadvantages of dental ceramics, concentrating on strength properties. Included are factors affecting the strength of dental ceramic materials and the most common mechanisms for increasing the strength of dental ceramics. The properties of presently available materials such as dispersion-strengthened ceramics, cast ceramics, and foil-reinforced materials are discussed. Current research efforts to improve the fracture resistance of ceramic restorative materials are reviewed. A description of methods to evaluate the strength of ceramics is included, as a caution concerning the interpretation of strength data reported in the literature.

  13. Joining Dental Ceramic Layers With Glass

    Science.gov (United States)

    Saied, MA; Lloyd, IK; Haller, WK; Lawn, BR

    2011-01-01

    Objective Test the hypothesis that glass-bonding of free-form veneer and core ceramic layers can produce robust interfaces, chemically durable and aesthetic in appearance and, above all, resistant to delamination. Methods Layers of independently produced porcelains (NobelRondo™ Press porcelain, Nobel BioCare AB and Sagkura Interaction porcelain, Elephant Dental) and matching alumina or zirconia core ceramics (Procera alumina, Nobel BioCare AB, BioZyram yttria stabilized tetragonal zirconia polycrystal, Cyrtina Dental) were joined with designed glasses, tailored to match thermal expansion coefficients of the components and free of toxic elements. Scanning electron microprobe analysis was used to characterize the chemistry of the joined interfaces, specifically to confirm interdiffusion of ions. Vickers indentations were used to drive controlled corner cracks into the glass interlayers to evaluate the toughness of the interfaces. Results The glass-bonded interfaces were found to have robust integrity relative to interfaces fused without glass, or those fused with a resin-based adhesive. Significance The structural integrity of the interfaces between porcelain veneers and alumina or zirconia cores is a critical factor in the longevity of all-ceramic dental crowns and fixed dental prostheses. PMID:21802131

  14. A fractographic study of clinically retrieved zirconia–ceramic and metal–ceramic fixed dental prostheses

    Science.gov (United States)

    Pang, Zhen; Chughtai, Asima; Sailer, Irena; Zhang, Yu

    2015-01-01

    Objectives A recent 3-year randomized controlled trial (RCT) of tooth supported three- to five-unit zirconia–ceramic and metal–ceramic posterior fixed dental prostheses (FDPs) revealed that veneer chipping and fracture in zirconia–ceramic systems occurred more frequently than those in metal–ceramic systems [1]. This study seeks to elucidate the underlying mechanisms responsible for the fracture phenomena observed in this RCT using a descriptive fractographic analysis. Methods Vinyl-polysiloxane impressions of 12 zirconia–ceramic and 6 metal–ceramic FDPs with veneer fractures were taken from the patients at the end of a mean observation of 40.3 ± 2.8 months. Epoxy replicas were produced from these impressions [1]. All replicas were gold coated, and inspected under the optical microscope and scanning electron microscope (SEM) for descriptive fractography. Results Among the 12 zirconia–ceramic FDPs, 2 had small chippings, 9 had large chippings, and 1 exhibited delamination. Out of 6 metal–ceramic FDPs, 5 had small chippings and 1 had large chipping. Descriptive fractographic analysis based on SEM observations revealed that fracture initiated from the wear facet at the occlusal surface in all cases, irrespective of the type of restoration. Significance Zirconia–ceramic and metal–ceramic FDPs all fractured from microcracks that emanated from occlusal wear facets. The relatively low fracture toughness and high residual tensile stress in porcelain veneer of zirconia restorations may contribute to the higher chipping rate and larger chip size in zirconia–ceramic FDPs relative to their metal–ceramic counterparts. The low veneer/core interfacial fracture energy of porcelain-veneered zirconia may result in the occurrence of delamination in zirconia–ceramic FDPs. PMID:26233469

  15. Repair bond strength of resin composite to bilayer dental ceramics

    Science.gov (United States)

    2018-01-01

    PURPOSE The purpose of this study was to investigate the effect of various surface treatments (ST) on the shear bond strength of resin composite to three bilayer dental ceramics made by CAD/CAM and two veneering ceramics. MATERIALS AND METHODS Three different bilayer dental ceramics and two different veneering ceramics were used (Group A: IPS e.max CAD+IPS e.max Ceram; Group B: IPS e.max ZirCAD+IPS e.max Ceram, Group C: Vita Suprinity+Vita VM11; Group D: IPS e.max Ceram; Group E: Vita VM11). All groups were divided into eight subgroups according to the ST. Then, all test specimens were repaired with a nano hybrid resin composite. Half of the test specimens were subjected to thermocycling procedure and the other half was stored in distilled water at 37℃. Shear bond strength tests for all test specimens were carried out with a universal testing machine. RESULTS There were statistically significant differences among the tested surface treatments within the all tested fracture types (P.00125). CONCLUSION This study revealed that HF etching for glass ceramics and sandblasting for zirconia ceramics were adequate for repair of all ceramic restorations. The effect of ceramic type exposed on the fracture area was not significant on the repair bond strength of resin composites to different ceramic types. PMID:29713430

  16. [Comparison of machinability of two types of dental machinable ceramic].

    Science.gov (United States)

    Fu, Qiang; Zhao, Yunfeng; Li, Yong; Fan, Xinping; Li, Yan; Lin, Xuefeng

    2002-11-01

    In terms of the problems of now available dental machinable ceramics, a new type of calcium-mica glass-ceramic, PMC-I ceramic, was developed, and its machinability was compared with that of Vita MKII quantitatively. Moreover, the relationship between the strength and the machinability of PMC-I ceramic was studied. Samples of PMC-I ceramic were divided into four groups according to their nucleation procedures. 600-seconds drilling tests were conducted with high-speed steel tools (Phi = 2.3 mm) to measure the drilling depths of Vita MKII ceramic and PMC-I ceramic, while constant drilling speed of 600 rpm and constant axial load of 39.2 N were used. And the 3-point bending strength of the four groups of PMC-I ceramic were recorded. Drilling depth of Vita MKII was 0.71 mm, while the depths of the four groups of PMC-I ceramic were 0.88 mm, 1.40 mm, 0.40 mm and 0.90 mm, respectively. Group B of PMC-I ceramic showed the largest depth of 1.40 mm and was statistically different from other groups and Vita MKII. And the strength of the four groups of PMC-I ceramic were 137.7, 210.2, 118.0 and 106.0 MPa, respectively. The machinability of the new developed dental machinable ceramic of PMC-I could meet the need of the clinic.

  17. Transmission of Er:YAG laser through different dental ceramics.

    Science.gov (United States)

    Sari, Tugrul; Tuncel, Ilkin; Usumez, Aslihan; Gutknecht, Norbert

    2014-01-01

    The aim of this study was to determine the erbium-doped yttrium aluminum garnet (Er:YAG) laser transmission ratio through different dental ceramics with different thicknesses. Laser debonding procedure of adhesively luted all-ceramic restorations is based on the transmission of laser energy through the ceramic and the ablation of resin cement, because of the transmitted laser energy. Five different dental ceramics were evaluated in this study: sintered zirconium-oxide core ceramic, monolithic zirconium-oxide ceramic, feldspathic ceramic, leucite-reinforced glass ceramic, and lithium disilicate-reinforced glass ceramic. Two ceramic discs with different thicknesses (0.5 and 1 mm) were fabricated for each group. Ceramic discs were placed between the sensor membrane of the laser power meter and the tip of the contact handpiece of an Er:YAG laser device with the aid of a custom- made acrylic holder. The transmission ratio of Er:YAG laser energy (500 mJ, 2 Hz, 1 W, 1000 μs) through different ceramic discs was measured with the power meter. Ten measurements were made for each group and the results were analyzed with two way analysis of variance (ANOVA) and Tukey honestly significant difference (HSD) tests. The highest transmission ratio was determined for lithium disilicate-reinforced ceramic with 0.5 mm thickness (88%) and the lowest was determined for feldspathic ceramic with 1 mm thickness (44%). The differences among the different ceramics and between the different thicknesses were significant (pCeramic type and thickness should be taken into consideration to adjust the laser irradiation parameters during laser debonding of adhesively luted all-ceramic restorations.

  18. In vivo biofilm formation on different dental ceramics.

    Science.gov (United States)

    Bremer, Felicia; Grade, Sebastian; Kohorst, Philipp; Stiesch, Meike

    2011-01-01

    To investigate the formation of oral biofilm on various dental ceramics in vivo. Five different ceramic materials were included: a veneering glass- ceramic, a lithium disilicate glass-ceramic, a yttrium-stabilized zirconia (Y-TZP), a hot isostatically pressed (HIP) Y-TZP ceramic, and an HIP Y-TZP ceramic with 25% alumina. Test specimens were attached to individually designed acrylic appliances; five volunteers wore these appliances for 24 hours in the maxillary arch. After intraoral exposure, the samples were removed from the appliances and the adhering biofilms vitally stained. Then, the two-dimensional surface coating and thickness of the adhering biofilm were determined by confocal laser scanning microscopy. Statistical analysis was performed using one-way ANOVA with the level of significance set at .05. Significant differences (P ceramic materials. The lowest surface coating (19.0%) and biofilm thickness (1.9 Μm) were determined on the HIP Y-TZP ceramic; the highest mean values were identified with the lithium disilicate glass-ceramic (46.8%, 12.6 Μm). Biofilm formation on various types of dental ceramics differed significantly; in particular, zirconia exhibited low plaque accumulation. In addition to its high strength, low plaque accumulation makes zirconia a promising material for various indications (including implant abutments and telescopic crowns) that previously were met only with metal-based materials.

  19. Y-TZP ceramic processing from coprecipitated powders : A comparative study with three commercial dental ceramics

    NARCIS (Netherlands)

    Lazar, Dolores R. R.; Bottino, Marco C.; Ozcan, Mutlu; Valandro, Luiz Felipe; Amaral, Regina; Ussui, Valter; Bressiani, Ana H. A.

    2008-01-01

    Objectives. (1) To synthesize 3 mol% yttria-stabilized zirconia (3Y-TZP) powders via coprecipitation route, (2) to obtain zirconia ceramic specimens, analyze surface characteristics, and mechanical properties, and (3) to compare the processed material with three reinforced dental ceramics. Methods.

  20. Novel Translucent and Strong Submicron Alumina Ceramics for Dental Restorations.

    Science.gov (United States)

    Zhao, M; Sun, Y; Zhang, J; Zhang, Y

    2018-03-01

    An ideal ceramic restorative material should possess excellent aesthetic and mechanical properties. We hypothesize that the high translucency and strength of polycrystalline ceramics can be achieved through microstructural tailoring. The aim of this study is to demonstrate the superior optical and mechanical properties of a new class of submicron grain-sized alumina ceramics relative to the current state-of-the-art dental ceramic materials. The translucency, the in-line transmission ( T IT ) in particular, of these submicron alumina ceramics has been examined with the Rayleigh-Gans-Debye light-scattering model. The theoretical predictions related very well with the measured T IT values. The translucency parameter ( TP) and contrast ratio ( CR) of the newly developed aluminas were measured with a reflectance spectrophotometer on a black-and-white background. For comparison, the T IT , TP, and CR values for a variety of dental ceramics, mostly measured in-house but also cited from the literature, were included. The flexural strength of the aluminas was determined with the 4-point bending test. Our findings have shown that for polycrystalline alumina ceramics, an average grain size ceramic and zirconias, including the most translucent cubic-containing zirconias. The strength of these submicron grain-sized aluminas was significantly higher than that of the cubic-containing zirconia (e.g., Zpex Smile) and lithia-based glass-ceramics (e.g., IPS e.max CAD HT). A coarse-grained alumina could also reach a translucency level comparable to that of dental porcelain. However, the relatively low strength of this material has limited its clinical indications to structurally less demanding applications, such as orthodontic brackets. With a combined high strength and translucency, the newly developed submicron grain-sized alumina may be considered a suitable material for dental restorations.

  1. A new classification system for all-ceramic and ceramic-like restorative materials.

    Science.gov (United States)

    Gracis, Stefano; Thompson, Van P; Ferencz, Jonathan L; Silva, Nelson R F A; Bonfante, Estevam A

    2015-01-01

    Classification systems for all-ceramic materials are useful for communication and educational purposes and warrant continuous revisions and updates to incorporate new materials. This article proposes a classification system for ceramic and ceramic-like restorative materials in an attempt to systematize and include a new class of materials. This new classification system categorizes ceramic restorative materials into three families: (1) glass-matrix ceramics, (2) polycrystalline ceramics, and (3) resin-matrix ceramics. Subfamilies are described in each group along with their composition, allowing for newly developed materials to be placed into the already existing main families. The criteria used to differentiate ceramic materials are based on the phase or phases present in their chemical composition. Thus, an all-ceramic material is classified according to whether a glass-matrix phase is present (glass-matrix ceramics) or absent (polycrystalline ceramics) or whether the material contains an organic matrix highly filled with ceramic particles (resin-matrix ceramics). Also presented are the manufacturers' clinical indications for the different materials and an overview of the different fabrication methods and whether they are used as framework materials or monolithic solutions. Current developments in ceramic materials not yet available to the dental market are discussed.

  2. Randomized clinical trial of implant-supported ceramic-ceramic and metal-ceramic fixed dental prostheses: preliminary results.

    Science.gov (United States)

    Esquivel-Upshaw, Josephine F; Clark, Arthur E; Shuster, Jonathan J; Anusavice, Kenneth J

    2014-02-01

    The aim of this study was to determine the survival rates over time of implant-supported ceramic-ceramic and metal-ceramic prostheses as a function of core-veneer thickness ratio, gingival connector embrasure design, and connector height. An IRB-approved, randomized, controlled clinical trial was conducted as a single-blind pilot study involving 55 patients missing three teeth in either one or two posterior areas. These patients (34 women; 21 men; age range 52-75 years) were recruited for the study to receive a three-unit implant-supported fixed dental prosthesis (FDP). Two implants were placed for each of the 72 FDPs in the study. The implants (Osseospeed, Astra Tech), which were made of titanium, were grit blasted. A gold-shaded, custom-milled titanium abutment (Atlantis, Astra Tech), was secured to each implant body. Each of the 72 FDPs in 55 patients were randomly assigned based on one of the following options: (1) A. ceramic-ceramic (Yttria-stabilized zirconia core, pressable fluorapatite glass-ceramic, IPS e.max ZirCAD, and ZirPress, Ivoclar Vivadent) B. metal-ceramic (palladium-based noble alloy, Capricorn, Ivoclar Vivadent, with press-on leucite-reinforced glass-ceramic veneer, IPS InLine POM, Ivoclar Vivadent); (2) occlusal veneer thickness (0.5, 1.0, and 1.5 mm); (3) curvature of gingival embrasure (0.25, 0.5, and 0.75 mm diameter); and (4) connector height (3, 4, and 5 mm). FDPs were fabricated and cemented with dual-cure resin cement (RelyX, Universal Cement, 3M ESPE). Patients were recalled at 6 months, 1 year, and 2 years. FDPs were examined for cracks, fracture, and general surface quality. Recall exams of 72 prostheses revealed 10 chipping fractures. No fractures occurred within the connector or embrasure areas. Two-sided Fisher's exact tests showed no significant correlation between fractures and type of material system (p = 0.51), veneer thickness (p = 0.75), radius of curvature of gingival embrasure (p = 0.68), and connector height (p = 0

  3. An experimental bioactive dental ceramic for metal-ceramic restorations: Textural characteristics and investigation of the mechanical properties.

    Science.gov (United States)

    Goudouri, Ourania-Menti; Kontonasaki, Eleana; Papadopoulou, Lambrini; Manda, Marianthi; Kavouras, Panagiotis; Triantafyllidis, Konstantinos S; Stefanidou, Maria; Koidis, Petros; Paraskevopoulos, Konstantinos M

    2017-02-01

    The aim of this study was the evaluation of the textural characteristics of an experimental sol-gel derived feldspathic dental ceramic, which has already been proven bioactive and the investigation of its flexural strength through Weibull Statistical Analysis. The null hypothesis was that the flexural strength of the experimental and the commercial dental ceramic would be of the same order, resulting in a dental ceramic with apatite forming ability and adequate mechanical integrity. Although the flexural strength of the experimental ceramics was not statistically significant different compared to the commercial one, the amount of blind pores due to processing was greater. The textural characteristics of the experimental ceramic were in accordance with the standard low porosity levels reported for dental ceramics used for fixed prosthetic restorations. Feldspathic dental ceramics with typical textural characteristics and advanced mechanical properties as well as enhanced apatite forming ability can be synthesized through the sol-gel method. Copyright © 2016 Elsevier Ltd. All rights reserved.

  4. Y-TZP ceramic processing from coprecipitated powders: a comparative study with three commercial dental ceramics.

    Science.gov (United States)

    Lazar, Dolores R R; Bottino, Marco C; Ozcan, Mutlu; Valandro, Luiz Felipe; Amaral, Regina; Ussui, Valter; Bressiani, Ana H A

    2008-12-01

    (1) To synthesize 3mol% yttria-stabilized zirconia (3Y-TZP) powders via coprecipitation route, (2) to obtain zirconia ceramic specimens, analyze surface characteristics, and mechanical properties, and (3) to compare the processed material with three reinforced dental ceramics. A coprecipitation route was used to synthesize a 3mol% yttria-stabilized zirconia ceramic processed by uniaxial compaction and pressureless sintering. Commercially available alumina or alumina/zirconia ceramics, namely Procera AllCeram (PA), In-Ceram Zirconia Block (CAZ) and In-Ceram Zirconia (IZ) were chosen for comparison. All specimens (6mmx5mmx5mm) were polished and ultrasonically cleaned. Qualitative phase analysis was performed by XRD and apparent densities were measured on the basis of Archimedes principle. Ceramics were also characterized using SEM, TEM and EDS. The hardness measurements were made employing Vickers hardness test. Fracture toughness (K(IC)) was calculated. Data were analyzed using one-way analysis of variance (ANOVA) and Tukey's test (alpha=0.05). ANOVA revealed that the Vickers hardness (pceramic materials composition. It was confirmed that the PA ceramic was constituted of a rhombohedral alumina matrix, so-called alpha-alumina. Both CAZ and IZ ceramics presented tetragonal zirconia and alpha-alumina mixture of phases. The SEM/EDS analysis confirmed the presence of aluminum in PA ceramic. In the IZ and CAZ ceramics aluminum, zirconium and cerium in grains involved by a second phase containing aluminum, silicon and lanthanum were identified. PA showed significantly higher mean Vickers hardness values (H(V)) (18.4+/-0.5GPa) compared to vitreous CAZ (10.3+/-0.2GPa) and IZ (10.6+/-0.4GPa) ceramics. Experimental Y-TZP showed significantly lower results than that of the other monophased ceramic (PA) (pceramics (pceramic processing conditions led to ceramics with mechanical properties comparable to commercially available reinforced ceramic materials.

  5. Dental Encounter System (DES)

    Data.gov (United States)

    Department of Veterans Affairs — Dental Encounter System (DES) is an automated health care application designed to capture critical data about the operations of VA Dental Services. Information on...

  6. Topological design of all-ceramic dental bridges for enhancing fracture resistance.

    Science.gov (United States)

    Zhang, Zhongpu; Chen, Junning; Li, Eric; Li, Wei; Swain, Michael; Li, Qing

    2016-06-01

    Layered all-ceramic systems have been increasingly adopted in major dental prostheses. However, ceramics are inherently brittle, and they often subject to premature failure under high occlusion forces especially in the posterior region. This study aimed to develop mechanically sound novel topological designs for all-ceramic dental bridges by minimizing the fracture incidence under given loading conditions. A bi-directional evolutionary structural optimization (BESO) technique is implemented within the extended finite element method (XFEM) framework. Extended finite element method allows modeling crack initiation and propagation inside all-ceramic restoration systems. Following this, BESO searches the optimum distribution of two different ceramic materials, namely porcelain and zirconia, for minimizing fracture incidence. A performance index, as per a ratio of peak tensile stress to material strength, is used as a design objective. In this study, the novel XFEM based BESO topology optimization significantly improved structural strength by minimizing performance index for suppressing fracture incidence in the structures. As expected, the fracture resistance and factor of safety of fixed partial dentures structure increased upon redistributing zirconia and porcelain in the optimal topological configuration. Dental CAD/CAM systems and the emerging 3D printing technology were commercially available to facilitate implementation of such a computational design, exhibiting considerable potential for clinical application in the future. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.

  7. Properties and Clinical Application of Three Types of Dental Glass-Ceramics and Ceramics for CAD-CAM Technologies

    Science.gov (United States)

    Ritzberger, Christian; Apel, Elke; Höland, Wolfram; Peschke, Arnd; Rheinberger, Volker M.

    2010-01-01

    The main properties (mechanical, thermal and chemical) and clinical application for dental restoration are demonstrated for three types of glass-ceramics and sintered polycrystalline ceramic produced by Ivoclar Vivadent AG. Two types of glass-ceramics are derived from the leucite-type and the lithium disilicate-type. The third type of dental materials represents a ZrO2 ceramic. CAD/CAM technology is a procedure to manufacture dental ceramic restoration. Leucite-type glass-ceramics demonstrate high translucency, preferable optical/mechanical properties and an application as dental inlays, onlays and crowns. Based on an improvement of the mechanical parameters, specially the strength and toughness, the lithium disilicate glass-ceramics are used as crowns; applying a procedure to machine an intermediate product and producing the final glass-ceramic by an additional heat treatment. Small dental bridges of lithium disilicate glass-ceramic were fabricated using a molding technology. ZrO2 ceramics show high toughness and strength and were veneered with fluoroapatite glass-ceramic. Machining is possible with a porous intermediate product.

  8. Surface Characteristics and Biofilm Development on Selected Dental Ceramic Materials

    Directory of Open Access Journals (Sweden)

    Kyoung H. Kim

    2017-01-01

    Full Text Available Background. Intraoral adjustment and polishing of dental ceramics often affect their surface characteristics, promoting increased roughness and consequent biofilm growth. This study correlated surface roughness to biofilm development with four commercially available ceramic materials. Methods. Four ceramic materials (Vita Enamic®, Lava™ Ultimate, Vitablocs Mark II, and Wieland Reflex® were prepared as per manufacturer instructions. Seventeen specimens of each material were adjusted and polished to simulate clinical intraoral procedures and another seventeen remained unaltered. Specimens were analysed by SEM imaging, confocal microscopy, and crystal violet assay. Results. SEM images showed more irregular surface topography in adjusted specimens than their respective controls. Surface roughness (Ra values were greater in all materials following adjustments. All adjusted materials with the exception of Vitablocs Mark II promoted significantly greater biofilm growth relative to controls. Conclusion. Simulated intraoral polishing methods resulted in greater surface roughness and increased biofilm accumulation.

  9. Adjusting dental ceramics: An in vitro evaluation of the ability of various ceramic polishing kits to mimic glazed dental ceramic surface.

    Science.gov (United States)

    Steiner, René; Beier, Ulrike S; Heiss-Kisielewsky, Irene; Engelmeier, Robert; Dumfahrt, Herbert; Dhima, Matilda

    2015-06-01

    During the insertion appointment, the practitioner is often faced with the need to adjust ceramic surfaces to fit a restoration to the adjacent or opposing dentition and soft tissues. The purpose of this study was to assess the ceramic surface smoothness achieved with various commercially available ceramic polishing kits on different commonly used ceramic systems. The reliability of the cost of a polishing kit as an indicator of improved surface smoothness was assessed. A total of 350 ceramic surfaces representing 5 commonly available ceramic systems (IPS Empress Esthetic, IPS e.max Press, Cergo Kiss, Vita PM 9, Imagine PressX) were treated with 5 types of ceramic polishing systems (Cerapreshine, 94006C, Ceramiste, Optrafine, Zenostar) by following the manufacturers' guidelines. The surface roughness was measured with a profilometer (Taylor Hobson; Precision Taylor Hobson Ltd). The effects of ceramic systems and polishing kits of interest on surface roughness were analyzed by 2-way ANOVA, paired t test, and Bonferroni corrected significance level. The ceramic systems and polishing kits statistically affected surface roughness (Pceramic surface. No correlation could be established between the high cost of the polishing kit and low surface roughness. None of the commonly used ceramic polishing kits could create a surface smoother than that of glazed ceramic (Pceramic polishing kits is not recommended as a reliable indicator of better performance of ceramic polishing kits (P>.30). Copyright © 2015 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

  10. Microwave processing of a dental ceramic used in computer-aided design/computer-aided manufacturing.

    Science.gov (United States)

    Pendola, Martin; Saha, Subrata

    2015-01-01

    Because of their favorable mechanical properties and natural esthetics, ceramics are widely used in restorative dentistry. The conventional ceramic sintering process required for their use is usually slow, however, and the equipment has an elevated energy consumption. Sintering processes that use microwaves have several advantages compared to regular sintering: shorter processing times, lower energy consumption, and the capacity for volumetric heating. The objective of this study was to test the mechanical properties of a dental ceramic used in computer-aided design/computer-aided manufacturing (CAD/CAM) after the specimens were processed with microwave hybrid sintering. Density, hardness, and bending strength were measured. When ceramic specimens were sintered with microwaves, the processing times were reduced and protocols were simplified. Hardness was improved almost 20% compared to regular sintering, and flexural strength measurements suggested that specimens were approximately 50% stronger than specimens sintered in a conventional system. Microwave hybrid sintering may preserve or improve the mechanical properties of dental ceramics designed for CAD/CAM processing systems, reducing processing and waiting times.

  11. Wear of MgO-CaO-SiO2-P2O5-F-Based Glass Ceramics Compared to Selected Dental Ceramics

    Directory of Open Access Journals (Sweden)

    Jongee Park

    2007-01-01

    Full Text Available Wear of a glass-ceramic produced through controlled crystallization of a glass in the MgO-CaO-SiO2-P2O5-F system has been evaluated and compared to various commercial dental ceramics including IPS Empress 2, Cergo Pressable Ceramic, Cerco Ceram, and Super porcelain EX-3. Wear tests were performed in accord with the ASTM G99 for wear testing with a pin-on-disk apparatus. The friction coefficient and specific wear rate of the materials investigated were determined at a load of 10 N and at ambient laboratory conditions. Microhardness of the materials was also measured to elucidate the appropriateness of these materials for dental applications.

  12. Biomechanical Analysis of Individual All-Ceramic Abutments Used in Dental Implantology

    Directory of Open Access Journals (Sweden)

    Ziębowicz B.

    2016-09-01

    Full Text Available The paper presents the results of finite element analysis and experimental testing under simulated physiological loading conditions on issues shaping the functional properties of individual all-ceramic abutments manufactured by CAD/CAM technology. The conducted research have cognitive significance showing the all-ceramic abutment behavior, as a key element of the implantological system, under the action of cyclic load. The aim of this study was evaluation the fatigue behavior of yttria-stabilized zirconia abutment submitted to cyclic stresses, conducted in accordance with EN ISO 14801 applies to dynamic fatigue tests of endosseous dental implants.

  13. Machinability of lithium disilicate glass ceramic in in vitro dental diamond bur adjusting process.

    Science.gov (United States)

    Song, Xiao-Fei; Ren, Hai-Tao; Yin, Ling

    2016-01-01

    Esthetic high-strength lithium disilicate glass ceramics (LDGC) are used for monolithic crowns and bridges produced in dental CAD/CAM and oral adjusting processes, which machinability affects the restorative quality. A machinability study has been made in the simulated oral clinical machining of LDGC with a dental handpiece and diamond burs, regarding the diamond tool wear and chip control, machining forces and energy, surface finish and integrity. Machining forces, speeds and energy in in vitro dental adjusting of LDGC were measured by a high-speed data acquisition and force sensor system. Machined LDGC surfaces were assessed using three-dimensional non-contact chromatic confocal optical profilometry and scanning electron microscopy (SEM). Diamond bur morphology and LDGC chip shapes were also examined using SEM. Minimum tool wear but significant LDGC chip accumulations were found. Machining forces and energy significantly depended on machining conditions (pceramics (pceramics (pceramics. Surface roughness for machined LDGC was comparable for other glass ceramics. The removal mechanisms of LDGC were dominated by penetration-induced brittle fracture and shear-induced plastic deformation. Unlike most other glass ceramics, distinct intergranular and transgranular fractures of lithium disilicate crystals were found in LDGC. This research provides the fundamental data for dental clinicians on the machinability of LDGC in intraoral adjustments. Copyright © 2015 Elsevier Ltd. All rights reserved.

  14. Systematic approach to preparing ceramic-glass composites with high translucency for dental restorations.

    Science.gov (United States)

    Yoshimura, Humberto N; Chimanski, Afonso; Cesar, Paulo F

    2015-10-01

    Ceramic composites are promising materials for dental restorations. However, it is difficult to prepare highly translucent composites due to the light scattering that occurs in multiphase ceramics. The objective of this work was to verify the effectiveness of a systematic approach in designing specific glass compositions with target properties in order to prepare glass infiltrated ceramic composites with high translucency. First it was necessary to calculate from literature data the viscosity of glass at the infiltration temperature using the SciGlass software. Then, a glass composition was designed for targeted viscosity and refractive index. The glass of the system SiO2-B2O3-Al2O3-La2O3-TiO2 prepared by melting the oxide raw materials was spontaneously infiltrated into porous alumina preforms at 1200°C. The optical properties were evaluated using a refractometer and a spectrophotometer. The absorption and scattering coefficients were calculated using the Kubelka-Munk model. The light transmittance of prepared composite was significantly higher than a commercial ceramic-glass composite, due to the matching of glass and preform refractive indexes which decreased the scattering, and also to the decrease in absorption coefficient. The proposed systematic approach was efficient for development of glass infiltrated ceramic composites with high translucency, which benefits include the better aesthetic performance of the final prosthesis. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  15. Zirconia based dental ceramics: structure, mechanical properties, biocompatibility and applications.

    Science.gov (United States)

    Gautam, Chandkiram; Joyner, Jarin; Gautam, Amarendra; Rao, Jitendra; Vajtai, Robert

    2016-12-06

    Zirconia (ZrO 2 ) based dental ceramics have been considered to be advantageous materials with adequate mechanical properties for the manufacturing of medical devices. Due to its very high compression strength of 2000 MPa, ZrO 2 can resist differing mechanical environments. During the crack propagation on the application of stress on the surface of ZrO 2 , a crystalline modification diminishes the propagation of cracks. In addition, zirconia's biocompatibility has been studied in vivo, leading to the observation of no adverse response upon the insertion of ZrO 2 samples into the bone or muscle. In vitro experimentation has exhibited the absence of mutations and good viability of cells cultured on this material leading to the use of ZrO 2 in the manufacturing of hip head prostheses. The mechanical properties of zirconia fixed partial dentures (FPDs) have proven to be superior to other ceramic/composite restorations and hence leading to their significant applications in implant supported rehabilitations. Recent developments were focused on the synthesis of zirconia based dental materials. More recently, zirconia has been introduced in prosthetic dentistry for the fabrication of crowns and fixed partial dentures in combination with computer aided design/computer aided manufacturing (CAD/CAM) techniques. This systematic review covers the results of past as well as recent scientific studies on the properties of zirconia based ceramics such as their specific compositions, microstructures, mechanical strength, biocompatibility and other applications in dentistry.

  16. Natural radioactivity in zirconia-based dental ceramics

    International Nuclear Information System (INIS)

    Giussani, Augusto; Gerstmann, Udo; La Porta, Caterina; Cantone, Marie C.; Veronese, Ivan

    2008-01-01

    Zirconia-based ceramics are being increasingly used in dental prosthetics in substitution of metal cores, which are known to induce local toxic reactions and delayed allergic responses in the oral tissues. Some concerns have been however raised about the use of zirconia, since it is known that unpurified zirconia materials may contain non negligible levels of natural radionuclides of the U/Th series. Combined measurements of alpha and gamma spectrometry as well as beta dosimetry were conducted on zirconia samples used for dental applications. Samples were available in form of powder and/or solid blocks. The results showed that the beta dose rate in zirconia ceramics was on average only slightly higher than the levels measured in natural teeth, and generally lower than the values measured in feldspatic and glass ceramics. These materials are indeed known to deliver a beta dose significantly higher than that measured from natural teeth, due to the relatively high levels of 40 K (between 2 and 3 kBq·kg -1 ). The content of radionuclides of the U/Th series in the zirconia sample was estimated to be lower than 15 Bq·kg -1 , i.e. doubtlessly below the exclusion level of 1 kBq·kg -1 recommended by IAEA in the Safety Standard Series. Beta dosimetry measurements, however, gave indications of possible inhomogeneous clusters of radioactivity, which might give rise to local doses above the background. (author)

  17. Interpenetrating network ceramic-resin composite dental restorative materials.

    Science.gov (United States)

    Swain, M V; Coldea, A; Bilkhair, A; Guess, P C

    2016-01-01

    This paper investigates the structure and some properties of resin infiltrated ceramic network structure materials suitable for CAD/CAM dental restorative applications. Initially the basis of interpenetrating network materials is defined along with placing them into a materials science perspective. This involves identifying potential advantages of such structures beyond that of the individual materials or simple mixing of the components. Observations from a number of recently published papers on this class of materials are summarized. These include the strength, fracture toughness, hardness and damage tolerance, namely to pointed and blunt (spherical) indentation as well as to burr adjustment. In addition a summary of recent results of crowns subjected to simulated clinical conditions using a chewing simulator are presented. These results are rationalized on the basis of existing theoretical considerations. The currently available ceramic-resin IPN material for clinical application is softer, exhibits comparable strength and fracture toughness but with substantial R-curve behavior, has lower E modulus and is more damage tolerant than existing glass-ceramic materials. Chewing simulation observations with crowns of this material indicate that it appears to be more resistant to sliding/impact induced cracking although its overall contact induced breakage load is modest. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  18. Zirconia toughened mica glass ceramics for dental restorations.

    Science.gov (United States)

    Gali, Sivaranjani; K, Ravikumar; Murthy, B V S; Basu, Bikramjit

    2018-03-01

    The objective of the present study is to understand the role of yttria stabilized zirconia (YSZ) in achieving the desired spectrum of clinically relevant mechanical properties (hardness, elastic modulus, fracture toughness and brittleness index) and chemical solubility of mica glass ceramics. The glass-zirconia mixtures with varying amounts of YSZ (0, 5, 10, 15 and 20wt.%) were ball milled, compacted and sintered to obtain pellets of glass ceramic-YSZ composites. Phase analysis was carried out using X-ray diffraction and microstructural characterization with SEM revealed the crystal morphology of the composites. Mechanical properties such as Vickers hardness, elastic modulus, indentation fracture toughness and chemical solubility were assessed. Phase analysis of sintered pellets of glass ceramic-YSZ composites revealed the characteristic peaks of fluorophlogopite (FPP) and tetragonal zirconia. Microstructural investigation showed plate and lath-like interlocking mica crystals with embedded zirconia. Vickers hardness of 9.2GPa, elastic modulus of 125GPa, indentation toughness of 3.6MPa·m 1/2 , and chemical solubility of 30μg/cm 2 (well below the permissible limit) were recorded with mica glass ceramics containing 20wt.% YSZ. An increase in hardness and toughness of the glass ceramic-YSZ composites with no compromise on their brittleness index and chemical solubility has been observed. Such spectrum of properties can be utilised for developing a machinable ceramic for low stress bearing inlays, onlays and veneers. Copyright © 2018 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  19. Sliding contact fracture of dental ceramics: Principles and validation

    Science.gov (United States)

    Ren, Linlin; Zhang, Yu

    2014-01-01

    Ceramic prostheses are subject to sliding contact under normal and tangential loads. Accurate prediction of the onset of fracture at two contacting surfaces holds the key to greater long-term performance of these prostheses. In this study, building on stress analysis of Hertzian contact and considering fracture criteria for linear elastic materials, a constitutive fracture mechanics relation was developed to incorporate the critical fracture load with the contact geometry, coefficient of friction and material fracture toughness. Critical loads necessary to cause fracture under a sliding indenter were calculated from the constitutive equation, and compared with the loads predicted from elastic stress analysis in conjunction with measured critical load for frictionless normal contact—a semi-empirical approach. The major predictions of the models were calibrated with experimentally determined critical loads of current and future dental ceramics after contact with a rigid spherical slider. Experimental results conform with the trends predicted by the models. PMID:24632538

  20. [Machinable property of a novel dental mica glass-ceramic].

    Science.gov (United States)

    Chen, Ji-hua; Li, Na; Ma, Xin-pei; Zhao, Ying-hua; Sun, Xiang; Li, Guang-xin

    2007-12-01

    To investigate the machinability of a novel dental mica glass-ceramic and analyze the effect of heat-treatment on its ductile machinable behavior. The drilling and turning experiment were used to measure the machinabilities of the control group (feldspar ceramic: Vita Mark II) and 7 experiment groups treated with different crystallization techniques. The microstructures were analyzed using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The average drilling depths in 30 s of the experimental groups ranged from (0.5 +/- 0.1) mm to (7.1 +/- 0.8) mm. There were significant differences between the control [(0.8 +/- 0.1) mm] and the experimental groups (P machining at a high velocity and cut depth. The crystal portion of this group is only about 40%. This material has a satisfactory machinability. The mechanism could be attributed to a combination of the interlocked structure of mica crystals and the low viscosity of glassy phase.

  1. Luminescence characterization of dental ceramics for individual retrospective dosimetry

    Energy Technology Data Exchange (ETDEWEB)

    Correcher, V.; Gomesdarocha, R. [CIEMAT, Av. Complutense 40, 28040 Madrid (Spain); Garcia G, J. [Consejo Superior de Investigaciones Cientificas, Museo Nacional de Ciencias Naturales, Jose Gutierrez Abascal 2, 28006 Madrid (Spain); Rivera M, T., E-mail: v.correcher@ciemat.es [IPN, Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada, Av. Legaria 694, 11500 Mexico D. F. (Mexico)

    2015-10-15

    Full text: Ceramic materials in general and dental crowns in particular exhibit thermoluminescence (Tl) properties and are of interest in the field of individual retrospective dosimetry. This property could be potentially employed to provide a means of determining cumulative exposure to external gamma radiation arising from accidents or large-scale incidents (radiological terrorism) involving population groups where conventional monitoring has not been established. The thermal stability and dose effect of the UV-blue Tl emission of a well characterized Spanish samples (by means of cathodoluminescence and electron-probe microanalysis) are here reported. It displays (i) an excellent linearity in the range of 0.12 - 9.6 Gy, (II) good stability of the Tl signal of 0.6, 1.2 and 2.4 Gy irradiated samples after 6 months of storage showing an initial rapid decay (ca. 30%) maintaining the stability from 30 days onwards. It means that the electron population decreases asymptotically by the X - axis and the involved electrons are located in deeper traps at room temperature. (III) The reusability performed on the dental ceramic, involving successive cycles of irradiation (1.2 Gy) followed by readout (up to 500 degrees C), exhibited a negligible variation in the Tl response, when measured six times. (IV) The tests of thermal stability at different temperatures (in the range of 100-240 degrees C) confirms a continuum in the trap distribution with progressive changes in the glow curve shape, intensity and temperature position of the maximum peak. Therefore, these preliminary results suggest that dental ceramics could be used as suitable dosimeters in retrospective conditions. (Author)

  2. Luminescence characterization of dental ceramics for individual retrospective dosimetry

    International Nuclear Information System (INIS)

    Correcher, V.; Gomesdarocha, R.; Garcia G, J.; Rivera M, T.

    2015-10-01

    Full text: Ceramic materials in general and dental crowns in particular exhibit thermoluminescence (Tl) properties and are of interest in the field of individual retrospective dosimetry. This property could be potentially employed to provide a means of determining cumulative exposure to external gamma radiation arising from accidents or large-scale incidents (radiological terrorism) involving population groups where conventional monitoring has not been established. The thermal stability and dose effect of the UV-blue Tl emission of a well characterized Spanish samples (by means of cathodoluminescence and electron-probe microanalysis) are here reported. It displays (i) an excellent linearity in the range of 0.12 - 9.6 Gy, (II) good stability of the Tl signal of 0.6, 1.2 and 2.4 Gy irradiated samples after 6 months of storage showing an initial rapid decay (ca. 30%) maintaining the stability from 30 days onwards. It means that the electron population decreases asymptotically by the X - axis and the involved electrons are located in deeper traps at room temperature. (III) The reusability performed on the dental ceramic, involving successive cycles of irradiation (1.2 Gy) followed by readout (up to 500 degrees C), exhibited a negligible variation in the Tl response, when measured six times. (IV) The tests of thermal stability at different temperatures (in the range of 100-240 degrees C) confirms a continuum in the trap distribution with progressive changes in the glow curve shape, intensity and temperature position of the maximum peak. Therefore, these preliminary results suggest that dental ceramics could be used as suitable dosimeters in retrospective conditions. (Author)

  3. Microstructure characterization and SCG of newly engineered dental ceramics.

    Science.gov (United States)

    Ramos, Nathália de Carvalho; Campos, Tiago Moreira Bastos; Paz, Igor Siqueira de La; Machado, João Paulo Barros; Bottino, Marco Antonio; Cesar, Paulo Francisco; Melo, Renata Marques de

    2016-07-01

    The aim of this study was to characterize the microstructure of four dental CAD-CAM ceramics and evaluate their susceptibility to stress corrosion. SEM and EDS were performed for microstructural characterization. For evaluation of the pattern of crystallization of the ceramics and the molecular composition, XRD and FTIR, respectively, were used. Elastic modulus, Poisson's ratio, density and fracture toughness were also measured. The specimens were subjected to biaxial flexure under five stress rates (0.006, 0.06, 0.6, 6 and 60MPa/s) to determine the subcritical crack growth parameters (n and D). Twenty-five specimens were further tested in mineral oil for determination of Weibull parameters. Two hundred forty ceramic discs (12mm diameter and 1.2mm thick) were made from four ceramics: feldspathic ceramic - FEL (Vita Mark II, Vita Zahnfabrik), ceramic-infiltrated polymer - PIC (Vita Enamic, Vita Zahnfabrik), lithium disilicate - LD (IPS e.max CAD, Ivoclar Vivadent) and zirconia-reinforced lithium silicate - LS (Vita Suprinity, Vita Zahnfabrik). PIC discs presented organic and inorganic phases (n=29.1±7.7) and Weibull modulus (m) of 8.96. The FEL discs showed n=36.6±6.8 and m=8.02. The LD discs showed a structure with needle-like disilicate grains in a glassy matrix and had the lowest value of n (8.4±0.8) and m=6.19. The ZLS discs showed similar rod-like grains, n=11.2±1.4 and m=9.98. The FEL and PIC discs showed the lowest susceptibility to slow crack growth (SCG), whereas the LD and ZLS discs presented the highest. PIC presented the lowest elastic modulus and no crystals in its composition, while ZLS presented tetragonal zirconia. The overall strength and SCG of the new materials did not benefit from the additional phase or microconstituents present in them. Copyright © 2016 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  4. Synthesis and ceramic processing of alumina and zirconia based composites infiltrated with glass phase for dental applications

    International Nuclear Information System (INIS)

    Duarte, Daniel Gomes

    2009-01-01

    The interest for the use of ceramic materials for dental applications started due to the good aesthetic appearance promoted by the similarity to natural teeth. However, the fragility of traditional ceramics was a limitation for their use in stress conditions. The development of alumina and zirconia based materials, that associate aesthetic results, biocompatibility and good mechanical behaviour, makes possible the employment of ceramics for fabrication of dental restorations. The incorporation of vitreous phase in these ceramics is an alternative to minimize the ceramic retraction and to improve the adhesion to resin-based cements, necessary for the union of ceramic frameworks to the remaining dental structure. In the dentistry field, alumina and zirconia ceramic infiltrated with glassy phase are represented commercially by the In-Ceram systems. Considering that the improvement of powder's synthesis routes and of techniques of ceramic processing contributes for good performance of these materials, the goal of the present work is the study of processing conditions of alumina and/or 3 mol% yttria-stabilized zirconia ceramics infiltrated with aluminum borosilicate lanthanum glass. The powders, synthesized by hydroxide coprecipitation route, were pressed by uniaxial compaction and pre-sintered at temperature range between 950 and 1650 degree C in order to obtain porous ceramics bodies. Vitreous phase incorporation was performed by impregnation of aluminum borosilicate lanthanum powder, also prepared in this work, followed by heat treatment between 1200 and 1400 degree C .Ceramic powders were characterized by thermogravimetry, X-ray diffraction, scanning and transmission electron microscopy, gaseous adsorption (BET) and laser diffraction. Sinterability of alumina and /or stabilized zirconia green pellets was evaluated by dilatometry. Pre-sintered ceramics were characterized by apparent density measurements (Archimedes method), X-ray diffraction and scanning electron

  5. Description and Documentation of the Dental School Dental Delivery System.

    Science.gov (United States)

    Chase, Rosen and Wallace, Inc., Alexandria, VA.

    A study was undertaken to describe and document the dental school dental delivery system using an integrated systems approach. In late 1976 and early 1977, a team of systems analysts and dental consultants visited three dental schools to observe the delivery of dental services and patient flow and to interview administrative staff and faculty.…

  6. Optical properties of pre-colored dental monolithic zirconia ceramics.

    Science.gov (United States)

    Kim, Hee-Kyung; Kim, Sung-Hun

    2016-12-01

    The purposes of this study were to evaluate the optical properties of recently marketed pre-colored monolithic zirconia ceramics and to compare with those of veneered zirconia and lithium disilicate glass ceramics. Various shades of pre-colored monolithic zirconia, veneered zirconia, and lithium disilicate glass ceramic specimens were tested (17.0×17.0×1.5mm, n=5). CIELab color coordinates were obtained against white, black, and grey backgrounds with a spectrophotometer. Color differences of the specimen pairs were calculated by using the CIEDE2000 (ΔE 00 ) formula. The translucency parameter (TP) was derived from ΔE 00 of the specimen against a white and a black background. X-ray diffraction was used to determine the crystalline phases of monolithic zirconia specimens. Data were analyzed with 1-way ANOVA, Scheffé post hoc, and Pearson correlation testing (α=0.05). For different shades of the same ceramic brand, there were significant differences in L * , a * , b * , and TP values in most ceramic brands. With the same nominal shade (A2), statistically significant differences were observed in L * , a * , b * , and TP values among different ceramic brands and systems (Pceramics of the corresponding nominal shades ranged beyond the acceptability threshold. Due to the high L * values and low a * and b * values, pre-colored monolithic zirconia ceramics can be used with additional staining to match neighboring restorations or natural teeth. Due to their high value and low chroma, unacceptable color mismatch with adjacent ceramic restorations might be expected. Copyright © 2016 Elsevier Ltd. All rights reserved.

  7. Machinable glass-ceramics forming as a restorative dental material.

    Science.gov (United States)

    Chaysuwan, Duangrudee; Sirinukunwattana, Krongkarn; Kanchanatawewat, Kanchana; Heness, Greg; Yamashita, Kimihiro

    2011-01-01

    MgO, SiO(2), Al(2)O(3), MgF(2), CaF(2), CaCO(3), SrCO(3), and P(2)O(5) were used to prepare glass-ceramics for restorative dental materials. Thermal properties, phases, microstructures and hardness were characterized by DTA, XRD, SEM and Vickers microhardness. Three-point bending strength and fracture toughness were applied by UTM according to ISO 6872: 1997(E). XRD showed that the glass crystallized at 892°C (second crystallization temperature+20°C) for 3 hrs consisted mainly of calcium-mica and fluorapatite crystalline phases. Average hardness (3.70 GPa) closely matched human enamel (3.20 GPa). The higher fracture toughness (2.04 MPa√m) combined with the hardness to give a lower brittleness index (1.81 µm(-1/2)) which indicates that they have exceptional machinability. Bending strength results (176.61 MPa) were analyzed by Weibull analysis to determine modulus value (m=17.80). Machinability of the calcium mica-fluorapatite glass-ceramic was demonstrated by fabricating with CAD/CAM.

  8. Non-destructive thermo-mechanical behavior assessment of glass-ceramics for dental applications

    Science.gov (United States)

    Kordatos, E. Z.; Abdulkadhim, Z.; Feteira, A. M.

    2017-05-01

    Every year millions of people seek dental treatment to either repair damaged, unaesthetic and dysfunctional teeth or replace missing natural teeth. Several dental materials have been developed to meet the stringent requirements in terms of mechanical properties, aesthetics and chemical durability in the oral environment. Glass-ceramics exhibit a suitable combination of these properties for dental restorations. This research is focused on the assessment of the thermomechanical behavior of bio-ceramics and particularly lithium aluminosilicate glass-ceramics (LAS glass-ceramics). Specifically, methodologies based on Infrared Thermography (IRT) have been applied in order the structure - property relationship to be evaluated. Non-crystallized, partially crystallized and fully crystallized glass-ceramic samples have been non-destructively assessed in order their thermo-mechanical behavior to be associated with their micro-structural features.

  9. Plastic damage induced fracture behaviors of dental ceramic layer structures subjected to monotonic load.

    Science.gov (United States)

    Wang, Raorao; Lu, Chenglin; Arola, Dwayne; Zhang, Dongsheng

    2013-08-01

    The aim of this study was to compare failure modes and fracture strength of ceramic structures using a combination of experimental and numerical methods. Twelve specimens with flat layer structures were fabricated from two types of ceramic systems (IPS e.max ceram/e.max press-CP and Vita VM9/Lava zirconia-VZ) and subjected to monotonic load to fracture with a tungsten carbide sphere. Digital image correlation (DIC) and fractography technology were used to analyze fracture behaviors of specimens. Numerical simulation was also applied to analyze the stress distribution in these two types of dental ceramics. Quasi-plastic damage occurred beneath the indenter in porcelain in all cases. In general, the fracture strength of VZ specimens was greater than that of CP specimens. The crack initiation loads of VZ and CP were determined as 958 ± 50 N and 724 ± 36 N, respectively. Cracks were induced by plastic damage and were subsequently driven by tensile stress at the elastic/plastic boundary and extended downward toward to the veneer/core interface from the observation of DIC at the specimen surface. Cracks penetrated into e.max press core, which led to a serious bulk fracture in CP crowns, while in VZ specimens, cracks were deflected and extended along the porcelain/zirconia core interface without penetration into the zirconia core. The rupture loads for VZ and CP ceramics were determined as 1150 ± 170 N and 857 ± 66 N, respectively. Quasi-plastic deformation (damage) is responsible for crack initiation within porcelain in both types of crowns. Due to the intrinsic mechanical properties, the fracture behaviors of these two types of ceramics are different. The zirconia core with high strength and high elastic modulus has better resistance to fracture than the e.max core. © 2013 by the American College of Prosthodontists.

  10. Updating Classifications of Ceramic Dental Materials: A Guide to Material Selection.

    Science.gov (United States)

    McLaren, Edward A; Figueira, Johan

    2015-06-01

    The indications for and composition of today's dental ceramic materials serve as the basis for determining the appropriate class of ceramics to use for a given case. By understanding the classifications, composition, and characteristics of the latest all-ceramic materials, which are presented in this article in order of most to least conservative, dentists and laboratory technicians can best determine the ideal material for a particular treatment.

  11. Effect of Ceramic Surface Treatments After Machine Grinding on the Biaxial Flexural Strength of Different CAD/CAM Dental Ceramics.

    Science.gov (United States)

    Bagheri, Hossein; Hooshmand, Tabassom; Aghajani, Farzaneh

    2015-09-01

    This study aimed to evaluate the effect of different ceramic surface treatments after machining grinding on the biaxial flexural strength (BFS) of machinable dental ceramics with different crystalline phases. Disk-shape specimens (10mm in diameter and 1.3mm in thickness) of machinable ceramic cores (two silica-based and one zirconia-based ceramics) were prepared. Each type of the ceramic surfaces was then randomly treated (n=15) with different treatments as follows: 1) machined finish as control, 2) machined finish and sandblasting with alumina, and 3) machined finish and hydrofluoric acid etching for the leucite and lithium disilicate-based ceramics, and for the zirconia; 1) machined finish and post-sintered as control, 2) machined finish, post-sintered, and sandblasting, and 3) machined finish, post-sintered, and Nd;YAG laser irradiation. The BFS were measured in a universal testing machine. Data based were analyzed by ANOVA and Tukey's multiple comparisons post-hoc test (α=0.05). The mean BFS of machined finish only surfaces for leucite ceramic was significantly higher than that of sandblasted (P=0.001) and acid etched surfaces (P=0.005). A significantly lower BFS was found after sandblasting for lithium disilicate compared with that of other groups (Pceramics was affected by the type of ceramic material and surface treatment method. Sandblasting with alumina was detrimental to the strength of only silica-based ceramics. Nd:YAG laser irradiation may lead to substantial strength degradation of zirconia.

  12. Wear Potential of Dental Ceramics and its Relationship with Microhardness and Coefficient of Friction.

    Science.gov (United States)

    Freddo, Rafael Augusto; Kapczinski, Myriam Pereira; Kinast, Eder Julio; de Souza Junior, Oswaldo Baptista; Rivaldo, Elken Gomes; da Fontoura Frasca, Luis Carlos

    2016-10-01

    To evaluate, by means of pin-on-disk testing, the wear potential of different dental ceramic systems as it relates to friction parameters, surface finish, and microhardness. Three groups of different ceramic systems (Noritake EX3, Eris, Empress II) with 20 disks each (10 glazed, 10 polished) were used. Vickers microhardness (Hv) was determined with a 200-g load for 30 seconds. Friction coefficients (μ) were determined by pin-on-disk testing (5 N load, 600 seconds, and 120 rpm). Wear patterns were assessed by scanning electron microscopy (SEM). The results were analyzed using one-way ANOVA and Tukey's test, with the significance level set at α = 0.05. The coefficients of friction were as follows: Noritake EX3 0.28 ± 0.12 (polished), 0.33 ± 0.08 (glazed); Empress II 0.38 ± 0.08 (polished), 0.45 ± 0.05 (glazed); Eris 0.49 ± 0.05 (polished), 0.49 ± 0.06 (glazed). Microhardness measurements were as follows: Noritake EX3 530.7 ± 8.7 (polished), 525.9 ± 6.2 (glazed); Empress II 534.1 ± 8 (polished), 534.7 ± 4.5 (glazed); Eris, 511.7 ± 6.5 (polished), 519.5 ± 4.1 (glazed). The polished and glazed Noritake EX3 and polished and glazed Eris specimens showed statistically different friction coefficients. SEM image analysis revealed more surface changes, such as small cracks and grains peeling off, in glazed ceramics. Wear potential may be related to the coefficient of friction in Noritake ceramics, which had a lower coefficient than Eris ceramics. Within-group analysis showed no differences in polished or glazed specimens. The differences observed were not associated with microhardness. © 2015 by the American College of Prosthodontists.

  13. A particle swarm-based algorithm for optimization of multi-layered and graded dental ceramics.

    Science.gov (United States)

    Askari, Ehsan; Flores, Paulo; Silva, Filipe

    2018-01-01

    The thermal residual stresses (TRSs) generated owing to the cooling down from the processing temperature in layered ceramic systems can lead to crack formation as well as influence the bending stress distribution and the strength of the structure. The purpose of this study is to minimize the thermal residual and bending stresses in dental ceramics to enhance their strength as well as to prevent the structure failure. Analytical parametric models are developed to evaluate thermal residual stresses in zirconia-porcelain multi-layered and graded discs and to simulate the piston-on-ring test. To identify optimal designs of zirconia-based dental restorations, a particle swarm optimizer is also developed. The thickness of each interlayer and compositional distribution are referred to as design variables. The effect of layers number constituting the interlayer between two based materials on the performance of graded prosthetic systems is also investigated. The developed methodology is validated against results available in literature and a finite element model constructed in the present study. Three different cases are considered to determine the optimal design of graded prosthesis based on minimizing (a) TRSs; (b) bending stresses; and (c) both TRS and bending stresses. It is demonstrated that each layer thickness and composition profile have important contributions into the resulting stress field and magnitude. Copyright © 2017 Elsevier Ltd. All rights reserved.

  14. Laser treatment of dental ceramic/cement layers: transmitted energy, temperature effects and surface characterisation.

    Science.gov (United States)

    Pich, Olena; Franzen, René; Gutknecht, Norbert; Wolfart, Stefan

    2015-02-01

    In the present paper, we investigate the behaviour of different dental materials under laser irradiation. We have used e.max Ceram, e.max ZirCAD, and e.max Press dental ceramics and glass ionomer cement Ketac Cem in the present study. The dental ceramics were prepared in the form of samples with thickness of 0.5-2 mm. We used two lasers [solid-state laser (Er:YAG, Fidelis III+, Fotona) and an 810- nm diode laser (FOX, A.R.C)] for the transillumination of ceramic samples. It has been shown that the laser energy transmitted through the ceramic material decreases to 30-40% of the original values along with an increase in the thickness of the irradiated sample. Pigmented ceramic samples show more laser energy loss compared to the samples containing no pigment. We investigated the temperature evolution in composite sandwiched ceramic/cement samples under laser treatment. The increase in the irradiation time and laser power led to a temperature increase of up to 80 °C. The surfaces of irradiated ceramic samples were examined with X-ray photoelectron spectroscopy to evaluate changes in chemical composition, such as a decrease in the C signal, accompanied by a strong increase in the Zr peak for the Er:YAG laser, while the 810-nm diode laser showed no change in the ratio of elements on the surface.

  15. Improved performance of diatomite-based dental nanocomposite ceramics using layer-by-layer assembly

    Science.gov (United States)

    Lu, Xiaoli; Xia, Yang; Liu, Mei; Qian, Yunzhu; Zhou, Xuefeng; Gu, Ning; Zhang, Feimin

    2012-01-01

    To fabricate high-strength diatomite-based ceramics for dental applications, the layer-by-layer technique was used to coat diatomite particles with cationic [poly(allylamine hydrochloride)] and anionic [poly(sodium 4-styrenesulfonate)] polymers to improve the dispersion and adsorption of positively charged nano-ZrO2 (zirconia) as a reinforcing agent. The modified diatomite particles had reduced particle size, narrower size distribution, and were well dispersed, with good adsorption of nano-ZrO2. To determine the optimum addition levels for nano-ZrO2, ceramics containing 0, 20, 25, 30, and 35 wt% nano-ZrO2 were sintered and characterized by the three-point bending test and microhardness test. In addition to scanning electron microscopy, propagation phase-contrast synchrotron X-ray microtomography was used to examine the internal structure of the ceramics. The addition of 30 wt% nano-ZrO2 resulted in the highest flexural strength and fracture toughness with reduced porosity. Shear bond strength between the core and veneer of our diatomite ceramics and the most widely used dental ceramics were compared; the shear bond strength value for the diatomite-based ceramics was found to be significantly higher than for other groups (P ceramics are good potential candidates for ceramic-based dental materials. PMID:22619551

  16. Improved performance of diatomite-based dental nanocomposite ceramics using layer-by-layer assembly.

    Science.gov (United States)

    Lu, Xiaoli; Xia, Yang; Liu, Mei; Qian, Yunzhu; Zhou, Xuefeng; Gu, Ning; Zhang, Feimin

    2012-01-01

    To fabricate high-strength diatomite-based ceramics for dental applications, the layer-by-layer technique was used to coat diatomite particles with cationic [poly(allylamine hydrochloride)] and anionic [poly(sodium 4-styrenesulfonate)] polymers to improve the dispersion and adsorption of positively charged nano-ZrO(2) (zirconia) as a reinforcing agent. The modified diatomite particles had reduced particle size, narrower size distribution, and were well dispersed, with good adsorption of nano-ZrO(2). To determine the optimum addition levels for nano-ZrO(2), ceramics containing 0, 20, 25, 30, and 35 wt% nano-ZrO(2) were sintered and characterized by the three-point bending test and microhardness test. In addition to scanning electron microscopy, propagation phase-contrast synchrotron X-ray microtomography was used to examine the internal structure of the ceramics. The addition of 30 wt% nano-ZrO(2) resulted in the highest flexural strength and fracture toughness with reduced porosity. Shear bond strength between the core and veneer of our diatomite ceramics and the most widely used dental ceramics were compared; the shear bond strength value for the diatomite-based ceramics was found to be significantly higher than for other groups (P < 0.05). Our results show that diatomite-based nanocomposite ceramics are good potential candidates for ceramic-based dental materials.

  17. Fracture and shear bond strength analyses of different dental veneering ceramics to zirconia

    International Nuclear Information System (INIS)

    Diniz, Alexandre C.; Nascimento, Rubens M.; Souza, Julio C.M.; Henriques, Bruno B.; Carreiro, Adriana F.P.

    2014-01-01

    The purpose of this work was to evaluate the interaction of different layering porcelains with zirconia via shear bond strength test and microscopy. Four different groups of dental veneering porcelains (VM9, Zirkonzanh, Ceramco, IPS) were fused onto forty zirconia-based cylindrical substrates (8 mm in diameter and 12 mm in height) (n = 10), according to the manufacturer's recommendations. Additionally, layered dental porcelain (D-sign, Ivoclar) was fired on ten Ni–Cr cylindrical substrates Shear bond strength tests of the veneering porcelain to zirconia or Ni–Cr were carried out at a crosshead speed of 0.5 mm/min. After the shear bond tests, the interfaces were analyzed by scanning electron microscopy (SEM). The fracture type exhibited by the different systems was also assessed. The results were statistically analyzed by ANOVA at a significant level of p < .05. The shear bond strength values of the porcelain-to-NiCr interfaces (25.3 ± 7.1 MPa) were significantly higher than those recorded for the following porcelain-to-zirconia systems: Zirkonzanh (18.8 ± 1 MPa), Ceramco (18.2 ± 4.7 MPa), and IPS (16 ± 4.5 MPa). However, no significant differences were found in the shear bond strength values between the porcelain-to-NiCr and porcelain (VM9)-to-zirconia (23.2 ± 5.1 MPa) groups (p > .05). All-ceramic interfaces revealed mixed failure type, cohesive in the porcelain and adhesive at the interface. This study demonstrated that all-ceramic systems do not attain yet the same bond strength standards equivalent to metal–ceramic systems. Therefore, despite the esthetic appeal of all-ceramic restorations, the adhesion between the porcelain and zirconia framework is still an issue considering the long term success of the restoration. - Highlights: • This study assessed the shear bond strength of different porcelains to zirconia. • The porcelain Vita VM9 showed a high shear bond strength to zirconia. • The fracture surface of all-ceramic systems revealed

  18. Fracture and shear bond strength analyses of different dental veneering ceramics to zirconia

    Energy Technology Data Exchange (ETDEWEB)

    Diniz, Alexandre C. [School of Dentistry (DOD), Division of Prosthodontics, Universidade Federal do Rio Grande do Norte -UFRN, 59056-000, Natal (Brazil); Nascimento, Rubens M. [Materials Engineering Department, Universidade Federal do Rio Grande do Norte - UFRN, Natal (Brazil); Souza, Julio C.M. [Centre for Mechanics and Materials Technologies - CT2M, Department of Mechanical Engineering (DEM), Universidade do Minho, Campus Azurém, 4800-058, Guimarães (Portugal); Henriques, Bruno B. [Materials Engineering Department, Universidade Federal do Rio Grande do Norte - UFRN, Natal (Brazil); Centre for Mechanics and Materials Technologies - CT2M, Department of Mechanical Engineering (DEM), Universidade do Minho, Campus Azurém, 4800-058, Guimarães (Portugal); Carreiro, Adriana F.P., E-mail: adrianadafonte@hotmail.com [School of Dentistry (DOD), Division of Prosthodontics, Universidade Federal do Rio Grande do Norte -UFRN, 59056-000, Natal (Brazil)

    2014-05-01

    The purpose of this work was to evaluate the interaction of different layering porcelains with zirconia via shear bond strength test and microscopy. Four different groups of dental veneering porcelains (VM9, Zirkonzanh, Ceramco, IPS) were fused onto forty zirconia-based cylindrical substrates (8 mm in diameter and 12 mm in height) (n = 10), according to the manufacturer's recommendations. Additionally, layered dental porcelain (D-sign, Ivoclar) was fired on ten Ni–Cr cylindrical substrates Shear bond strength tests of the veneering porcelain to zirconia or Ni–Cr were carried out at a crosshead speed of 0.5 mm/min. After the shear bond tests, the interfaces were analyzed by scanning electron microscopy (SEM). The fracture type exhibited by the different systems was also assessed. The results were statistically analyzed by ANOVA at a significant level of p < .05. The shear bond strength values of the porcelain-to-NiCr interfaces (25.3 ± 7.1 MPa) were significantly higher than those recorded for the following porcelain-to-zirconia systems: Zirkonzanh (18.8 ± 1 MPa), Ceramco (18.2 ± 4.7 MPa), and IPS (16 ± 4.5 MPa). However, no significant differences were found in the shear bond strength values between the porcelain-to-NiCr and porcelain (VM9)-to-zirconia (23.2 ± 5.1 MPa) groups (p > .05). All-ceramic interfaces revealed mixed failure type, cohesive in the porcelain and adhesive at the interface. This study demonstrated that all-ceramic systems do not attain yet the same bond strength standards equivalent to metal–ceramic systems. Therefore, despite the esthetic appeal of all-ceramic restorations, the adhesion between the porcelain and zirconia framework is still an issue considering the long term success of the restoration. - Highlights: • This study assessed the shear bond strength of different porcelains to zirconia. • The porcelain Vita VM9 showed a high shear bond strength to zirconia. • The fracture surface of all-ceramic systems revealed

  19. Survival of anterior cantilevered all-ceramic resin-bonded fixed dental prostheses made from zirconia ceramic.

    Science.gov (United States)

    Sasse, Martin; Kern, Matthias

    2014-06-01

    This study evaluated the clinical outcome of all-ceramic resin-bonded fixed dental prostheses (RBFDPs) with a cantilevered single-retainer design made from zirconia ceramic. Forty-two anterior RBFDPs with a cantilevered single-retainer design were made from yttrium oxide-stabilized zirconium oxide ceramic. RBFDPs were inserted using Panavia 21 TC as luting agent after air-abrasion of the ceramic bonding surface. During a mean observation time of 61.8 months two debondings occurred. Both RBFDPs were rebonded using Panavia 21 TC and are still in function. A caries lesion was detected at one abutment tooth during recall and was treated with a composite filling. Therefore, the overall six-year failure-free rate according to Kaplan-Meier was 91.1%. If only debonding was defined as failure the survival rate increased to 95.2%. Since all RBFDPs are still in function the overall survival rate was 100% after six years. Cantilevered zirconia ceramic RBFDPs showed promising results within the observation period. Single-retainer resin-bonded fixed dental prostheses made from zirconia ceramic show very good mid-term clinical survival rates. They should therefore be considered as a viable treatment alternative for the replacement of single missing anterior teeth especially as compared to an implant therapy. Copyright © 2014 Elsevier Ltd. All rights reserved.

  20. [Preliminary study of bonding strength between diatomite-based dental ceramic and veneering porcelains].

    Science.gov (United States)

    Lu, Xiao-li; Gao, Mei-qin; Cheng, Yu-ye; Zhang, Fei-min

    2015-04-01

    In order to choose the best veneering porcelain for diatomite-based dental ceramic substrate, the bonding strength between diatomite-based dental ceramics and veneering porcelains was measured, and the microstructure and elements distribution of interface were analyzed. The coefficient of thermal expansion (CTE) of diatomite-based dental ceramics was detected by dilatometry. Three veneering porcelain materials were selected with the best CTE matching including alumina veneering porcelain (group A), titanium porcelain veneering porcelain (group B), and E-max veneering porcelain (group C). Shear bonding strength was detected. SEM and EDS were used to observe the interface microstructure and element distribution. Statistical analysis was performed using SPSS 17.0 software package. The CTE of diatomite-based dental ceramics at 25-500 degrees centigrade was 8.85×10-6K-1. The diatomite-based substrate ceramics combined best with group C. Shear bonding strength between group A and C and group B and C both showed significant differences(P<0.05). SEM and EDS showed that the interface of group C sintered tightly and elements permeated on both sides of the interface. The diatomite-based substrate ceramics combines better with E-max porcelain veneer.

  1. Dental therapeutic systems.

    Science.gov (United States)

    Iqbal, Zeenat; Jain, Nilu; Jain, Gaurav K; Talegaonkar, Sushama; Ahuja, Alka; Khar, Roop K; Ahmad, Farhan J

    2008-01-01

    The recognition of periodontal diseases as amenable to local antibiotherapy has resulted in a paradigmatic shift in treatment modalities of dental afflictions. Moreover the presence of antimicrobial resistance, surfacing of untoward reactions owing to systemic consumption of antibiotics has further advocated the use of local delivery of physiologically active substances into the periodontal pocket. While antimicrobials polymerized into acrylic strips, incorporated into biodegradable collagen and hollow permeable cellulose acetate fibers, multiparticulate systems, bio-absorbable dental materials, biodegradable gels/ointments, injectables, mucoadhesive microcapsules and nanospheres will be more amenable for direct placement into the periodontal pockets the lozenges, buccoadhesive tablets, discs or gels could be effectively used to mitigate the overall gingival inflammation. Whilst effecting controlled local delivery of a few milligram of an antibacterial agent within the gingival crevicular fluid for a longer period of time, maintaining therapeutic concentrations such delivery devices will circumvent all adverse effects to non- oral sites. Since the pioneering efforts of Goodson and Lindhe in 1989, delivery at gingival and subgingival sites has witnessed a considerable progress. The interest in locally active systems is evident from the patents being filed and granted. The present article shall dwell in reviewing the recent approaches being proffered in the field. Patents as by Shefer, et al. US patent, 6589562 dealing with multicomponent biodegradable bioadhesive controlled release system for oral care products, Lee, et al. 2001, US patent 6193994, encompassing a locally administrable, biodegradable and sustained-release pharmaceutical composition for periodontitis and process for preparation thereof and method of treating periodontal disease as suggested by Basara in 2004via US patent 6830757, shall be the types of intellectual property reviewed and presented in

  2. Effect of acidic agents on surface roughness of dental ceramics

    Directory of Open Access Journals (Sweden)

    Boonlert Kukiattrakoon

    2011-01-01

    Conclusion: Acidic agents used in this study negatively affected the surface of ceramic materials. This should be considered when restoring the eroded tooth with ceramic restorations in patients who have a high risk of erosive conditions.

  3. Soft tissue adhesion of polished versus glazed lithium disilicate ceramic for dental applications.

    Science.gov (United States)

    Brunot-Gohin, C; Duval, J-L; Azogui, E-E; Jannetta, R; Pezron, I; Laurent-Maquin, D; Gangloff, S C; Egles, C

    2013-09-01

    Ceramics are widely used materials for prosthesis, especially in dental fields. Despite multiple biomedical applications, little is known about ceramic surface modifications and the resulting cell behavior at its contact. The aim of this study is to evaluate the biological response of polished versus glazed surface treatments on lithium disilicate dental ceramic. We studied a lithium disilicate ceramic (IPS e.max(®) Press, Ivoclar Vivadent) with 3 different surface treatments: raw surface treatment, hand polished surface treatment, and glazed surface treatment (control samples are Thermanox(®), Nunc). In order to evaluate the possible modulation of cell response at the surface of ceramic, we compared polished versus glazed ceramics using an organotypic culture model of chicken epithelium. Our results show that the surface roughness is not modified as demonstrated by equivalent Ra measurements. On the contrary, the contact angle θ in water is very different between polished (84°) and glazed (33°) samples. The culture of epithelial tissues allowed a very precise assessment of histocompatibility of these interfaces and showed that polished samples increased cell adhesion and proliferation as compared to glazed samples. Lithium disilicate polished ceramic provided better adhesion and proliferation than lithium disilicate glazed ceramic. Taken together, our results demonstrate for the first time, how it is possible to use simple surface modifications to finely modulate the adhesion of tissues. Our results will help dental surgeons to choose the most appropriate surface treatment for a specific clinical application, in particular for the ceramic implant collar. Copyright © 2013 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  4. The effect of abrading and cutting instruments on machinability of dental ceramics.

    Science.gov (United States)

    Sakoda, Satoshi; Nakao, Noriko; Watanabe, Ikuya

    2018-03-16

    The aim was to investigate the effect of machining instruments on machinability of dental ceramics. Four dental ceramics, including two zirconia ceramics were machined by three types (SiC, diamond vitrified, and diamond sintered) of wheels with a hand-piece engine and two types (diamond and carbide) of burs with a high-speed air turbine. The machining conditions used were abrading speeds of 10,000 and 15,000 r.p.m. with abrading force of 100 gf for the hand-piece engine, and a pressure of 200 kPa and a cutting force of 80 gf for the air-turbine hand-piece. The machinability efficiency was evaluated by volume losses after machining the ceramics. A high-abrading speed had high-abrading efficiency (high-volume loss) compared to low-abrading speed in all abrading instruments used. The diamond vitrified wheels demonstrated higher volume loss for two zirconia ceramics than those of SiC and diamond sintered wheels. When the high-speed air-turbine instruments were used, the diamond points showed higher volume losses compared to the carbide burs for one ceramic and two zirconia ceramics with high-mechanical properties. The results of this study indicated that the machinability of dental ceramics depends on the mechanical and physical properties of dental ceramics and machining instruments. The abrading wheels show autogenous action of abrasive grains, in which ground abrasive grains drop out from the binder during abrasion, then the binder follow to wear out, subsequently new abrasive grains come out onto the instrument surface (autogenous action) and increase the grinding amount (volume loss) of grinding materials.

  5. Temperature variations in sintering ovens for metal ceramic dental prostheses: non-destructive assessment using OCT

    Science.gov (United States)

    Sinescu, C.; Bradu, A.; Duma, V.-F.; Topala, F. I.; Negrutiu, M. L.; Podoleanu, A. G.

    2018-02-01

    We present a recent investigation regarding the use of optical coherence tomography (OCT) in the monitoring of the calibration loss of sintering ovens for the manufacturing of metal ceramic dental prostheses. Differences in the temperatures of such ovens with regard to their specifications lead to stress and even cracks in the prostheses material, therefore to the failure of the dental treatment. Evaluation methods of the ovens calibration consist nowadays of firing supplemental samples; this is subjective, expensive, and time consuming. Using an in-house developed swept source (SS) OCT system, we have demonstrated that a quantitative assessment of the internal structure of the prostheses, therefore of the temperature settings of the ovens can be made. Using en-face OCT images acquired at similar depths inside the samples, the differences in reflectivity allow for the evaluation of the differences in granulation (i.e., in number and size of ceramic grains) of the prostheses material. Fifty samples, divided in five groups, each sintered at different temperatures (lower, higher, or equal to the prescribed one) have been analyzed. The consequences of the temperature variations with regard to the one prescribed were determined. Rules-of-thumb were extracted to monitor objectively, using only OCT images of currently manufactured samples, the settings of the oven. The method proposed allows for avoiding producing prostheses with defects. While such rules-of-thumb achieve a qualitative assessment, an insight in our on-going work on the quantitative assessment of such losses of calibration on dental ovens using OCT is also made.

  6. On the use of dental ceramics as a possible second-line approach to accident irradiation dosimetry

    International Nuclear Information System (INIS)

    Davies, J.E.

    1979-01-01

    Recent development in dental ceramic production has resulted in natural or depleted uranium, used for over half a century to mimic the fluorescence of natural teeth, being substituted in such ceramics by non-radioactive fluorescent materials. This creates the possibility of using dental ceramics incorporating the latter as second-line dosimeters in cases of accidental irradiation. This pilot study shows the feasbility of such an approach using both thermally stimulated exoelectron and thermoluminescent techniques. In conclusion, it is considered that it would be of interest to continue this investigation of dental ceramic materials as second-line accident dosimeters

  7. In Vitro Comparison of the Bond Strength between Ceramic Repair Systems and Ceramic Materials and Evaluation of the Wettability.

    Science.gov (United States)

    Kocaağaoğlu, Hasan; Manav, Taha; Albayrak, Haydar

    2017-04-01

    When fracture of an all-ceramic restoration occurs, it can be necessary to repair without removing the restoration. Although there are many studies about the repair of metal-ceramic restorations, there are few about all-ceramic restorations. The aim of this study was to evaluate the shear bond strength between ceramic repair systems and esthetic core materials and to evaluate the wettability of all-ceramic core materials. Disk-like specimens (N = 90) made of three dental ceramic infrastructure materials (zirconia ceramic, alumina ceramic, glass ceramic) were polished with silicon carbide paper, prepared for bonding (abrasion with 30 μm diamond rotary cutting instrument). Thirty specimens of each infrastructure were obtained. Each infrastructure group was divided into three subgroups; they were bonded using 3 repair systems: Bisco Intraoral Repair Kit, Cimara & Cimara Zircon Repair System, and Clearfil Repair System. After 1200 thermocycles, shear bond strength was measured in a universal testing machine at a 0.5 mm/min crosshead speed. In addition, the contact angle values of the infrastructures after surface treatments were examined for wettability. Data were analyzed by using ANOVA and Tukey post hoc tests. Although there were no significant differences among the repair systems (p > 0.05) in the glass ceramic and zirconia groups, a significant difference was found among the repair systems in alumina infrastructure (p 0.05); however, a statistically significant difference was found among the repair systems (p < 0.05). No difference was found among the infrastructures and repair systems in terms of contact angle values. Cimara & Cimara Zircon Repair System had higher bond strength values than the other repair systems. Although no difference was found among the infrastructures and repair systems, contact wettability angle was decreased by surface treatments compared with polished surfaces. © 2015 by the American College of Prosthodontists.

  8. Luminescence characteristics of dental ceramics for retrospective dosimetry: a preliminary study

    International Nuclear Information System (INIS)

    Bailiff, I.K.; Correcher, V.; Delgado, A.; Goksu, Y.; Huebner, S.

    2002-01-01

    Ceramic materials that are widely employed in dental prosthetics and repairs exhibit luminescent properties. Because of their use in the body, these materials are potentially of interest in situations where retrospective dosimetry for individuals is required but where monitoring was not planned. The luminescent properties of dental ceramics obtained in Germany, Spain and the UK were examined. Linear dose-response characteristics were obtained in the range <100 mGy to 10 Gy using thermoluminescence (TL), optically stimulated luminescence and infrared-stimulated luminescence measurement techniques. Measurements of time-resolved luminescence were also performed to examine the nature of the luminescence recombination under visible (470 nm) and IR (855 nm) stimulation. The results obtained by TL and optically stimulated techniques suggest that there may be deeper traps than previously observed in certain types of dental ceramic. Such traps may be less susceptible to optical and athermal fading than was reported in earlier studies. (author)

  9. A randomized controlled clinical trial of 3-unit posterior zirconia-ceramic fixed dental prostheses (FDP) with layered or pressed veneering ceramics: 3-year results.

    Science.gov (United States)

    Naenni, Nadja; Bindl, Andreas; Sax, Caroline; Hämmerle, Christoph; Sailer, Irena

    2015-11-01

    The aim of the present pilot study was to test whether or not posterior zirconia-ceramic fixed dental prostheses (FDPs) with pressed veneering ceramic exhibit less chipping than FDPs with layered veneering ceramics. Forty patients (13 female, 27 male; mean age 54 years (range 26.1-80.7 years) in need of one maxillary or mandibular three-unit FDP in the second premolar or molar region were recruited and treated at two separate centers at the University of Zurich according to the same study protocol. The frameworks were made out of zirconia using a CAD/CAM system (Cerec Sirona, Bensheim, Germany). The patients were randomly assigned to either the test group (zirconia frameworks veneered with pressed ceramic; IPS e.max ZirPress, Ivoclar Vivadent AG, Schaan, Liechtenstein; n=20) or the control group (layered veneering ceramic; IPS e.max Ceram, Ivoclar Vivadent AG, Schaan, Liechtenstein; n=20). All FDPs were adhesively cemented and evaluated at baseline (i.e., cementation), at 6 months and at 1 and 3 years of clinical service. The survival of the reconstruction was recorded. The technical outcome was assessed using modified United States Public Health Services (USPHS) criteria. The biologic parameters analyzed at abutment teeth and analogous non-restored teeth included probing pocket depth (PPD), plaque control record (PCR), bleeding on probing (BOP), and tooth vitality (CO2). Data was descriptively analyzed and survival was calculated using Kaplan-Meier statistics. 36 patients (25 female, 11 male; mean age 52.3 years) with 18 test and 18 control FDPs were examined after a mean follow-up of 36 months (95% CI: 32.6-39.1 months). Comparison of groups was done by Crosstabulation showing even distribution of the respective restored teeth amidst the groups. Survival rate was 100% for both test and control FDPs. Chipping of the veneering ceramic tended to occur more frequently in test (n=8; 40%) than in control (n=4; 20%) FDPs, albeit not significantly (p=0.3). No further

  10. Process Development of Porcelain Ceramic Material with Binder Jetting Process for Dental Applications

    Science.gov (United States)

    Miyanaji, Hadi; Zhang, Shanshan; Lassell, Austin; Zandinejad, Amirali; Yang, Li

    2016-03-01

    Custom ceramic structures possess significant potentials in many applications such as dentistry and aerospace where extreme environments are present. Specifically, highly customized geometries with adequate performance are needed for various dental prostheses applications. This paper demonstrates the development of process and post-process parameters for a dental porcelain ceramic material using binder jetting additive manufacturing (AM). Various process parameters such as binder amount, drying power level, drying time and powder spread speed were studied experimentally for their effect on geometrical and mechanical characteristics of green parts. In addition, the effects of sintering and printing parameters on the qualities of the densified ceramic structures were also investigated experimentally. The results provide insights into the process-property relationships for the binder jetting AM process, and some of the challenges of the process that need to be further characterized for the successful adoption of the binder jetting technology in high quality ceramic fabrications are discussed.

  11. Layered Manufacturing of Dental Ceramics: Fracture Mechanics, Microstructure, and Elemental Composition of Lithography-Sintered Ceramic.

    Science.gov (United States)

    Uçar, Yurdanur; Aysan Meriç, İpek; Ekren, Orhun

    2018-02-11

    To compare the fracture mechanics, microstructure, and elemental composition of lithography-based ceramic manufacturing with pressing and CAD/CAM. Disc-shaped specimens (16 mm diameter, 1.2 mm thick) were used for mechanical testing (n = 10/group). Biaxial flexural strength of three groups (In-Ceram alumina [ICA], lithography-based alumina, ZirkonZahn) were determined using the "piston on 3-ball" technique as suggested in test Standard ISO-6872. Vickers hardness test was performed. Fracture toughness was calculated using fractography. Results were statistically analyzed using Kruskal-Wallis test followed by Dunnett T3 (α = 0.05). Weibull analysis was conducted. Polished and fracture surface characterization was made using scanning electron microscope (SEM). Energy dispersive spectroscopy (EDS) was used for elemental analysis. Biaxial flexural strength of ICA, LCM alumina (LCMA), and ZirkonZahn were 147 ± 43 MPa, 490 ± 44 MPa, and 709 ± 94 MPa, respectively, and were statistically different (P ≤ 0.05). The Vickers hardness number of ICA was 850 ± 41, whereas hardness values for LCMA and ZirkonZahn were 1581 ± 144 and 1249 ± 57, respectively, and were statistically different (P ≤ 0.05). A statistically significant difference was found between fracture toughness of ICA (2 ± 0.4 MPa⋅m 1/2 ), LCMA (6.5 ± 1.5 MPa⋅m 1/2 ), and ZirkonZahn (7.7 ± 1 MPa⋅m 1/2 ) (P ≤ 0.05). Weibull modulus was highest for LCMA (m = 11.43) followed by ZirkonZahn (m = 8.16) and ICA (m = 5.21). Unlike LCMA and ZirkonZahn groups, a homogeneous microstructure was not observed for ICA. EDS results supported the SEM images. Within the limitations of this in vitro study, it can be concluded that LCM seems to be a promising technique for final ceramic object manufacturing in dental applications. Both the manufacturing method and the material used should be improved. © 2018 by the American College of Prosthodontists.

  12. Optical properties of CAD-CAM ceramic systems.

    Science.gov (United States)

    Della Bona, Alvaro; Nogueira, Audrea D; Pecho, Oscar E

    2014-09-01

    To evaluate the direct transmittance (T%), translucency, opacity and opalescence of CAD-CAM ceramic systems and the correlation between the translucency parameter (TP) and the contrast ratio (CR). Specimens of shades A1, A2 and A3 (n=5) were fabricated from CAD-CAM ceramic blocks (IPS e.max(®) CAD HT and LT, IPS Empress(®) CAD HT and LT, Paradigm™ C, and VITABLOCS(®) Mark II) and polished to 1.0±0.01mm in thickness. A spectrophotometer (Lambda 20) was used to measure T% on the wavelength range of 400-780nm. Another spectrophotometer (VITA Easyshade(®) Advance) was used to measure the CIE L(*)a(*)b(*) coordinates and the reflectance value (Y) of samples on white and black backgrounds. TP, CR and the opalescence parameter (OP) were calculated. Data were statistically analysed using VAF (variance accounting for) coefficient with Cauchy-Schwarz inequality, one-way ANOVA, Tukey's test, Bonferroni correction and Pearson's correlation. T% of some ceramic systems is dependent on the wavelength. The spectral behaviour showed a slight and constant increase in T% up to approximately 550nm, then some ceramics changed the behaviour as the wavelength gets longer. TP and CR values ranged, respectively, from 16.79 to 21.69 and from 0.52 to 0.64 (r(2)=-0.97). OP values ranged from 3.01 to 7.64. The microstructure of CAD-CAM ceramic systems influenced the optical properties. TP and CR showed a strong correlation for all ceramic systems evaluated. Yet, all ceramics showed some degree of light transmittance. In addition to shade, this study showed that other optical properties influence on the natural appearance of dental ceramics. Copyright © 2014 Elsevier Ltd. All rights reserved.

  13. Comparison of Metal-Ceramic and All-Ceramic Three-Unit Posterior Fixed Dental Prostheses: A 3-Year Randomized Clinical Trial.

    Science.gov (United States)

    Nicolaisen, Maj H; Bahrami, Golnosh; Schropp, Lars; Isidor, Flemming

    2016-01-01

    The aim of this randomized clinical study was to compare the 3-year clinical outcome of metal-ceramic fixed dental prostheses (MC-FDPs) and zirconia all-ceramic fixed dental prostheses (AC-FDPs) replacing a posterior tooth. A sample of 34 patients with a missing posterior tooth were randomly chosen to receive either a MC-FDP (n = 17) or an AC-FDP (n = 17). The FDPs were evaluated at baseline and yearly until 3 years after cementation. They were assessed using the California Dental Association assessment system. Periodontal parameters were measured at the abutment teeth, and the contralateral teeth served as control. The statistical unit was the FDP/patient. The survival rates for MC-FDPs and AC-FDPs were 100%. The success rate was 76% and 71% for MC-FDPs and AC-FDPs, respectively. Three technical complications were observed in the MC-FDP group and five in the AC-FDP group, all chipping fractures of the ceramic veneer. Furthermore, one biologic complication in the MC-FDP group (an apical lesion) was observed. No framework fractures occurred. All patients had optimal oral hygiene and showed no bleeding on periodontal probing at any of the recalls. Only minor changes in the periodontal parameters were observed during the 3 years of observation. Three-unit posterior MC-FDPs and AC-FDPs showed similar high survival rates and acceptable success rates after 3 years of function, and ceramic veneer chipping fracture was the most frequent complication for both types of restorations.

  14. Improved performance of diatomite-based dental nanocomposite ceramics using layer-by-layer assembly

    Directory of Open Access Journals (Sweden)

    Lu X

    2012-04-01

    Full Text Available Xiaoli Lu1,2, Yang Xia1, Mei Liu1, Yunzhu Qian3, Xuefeng Zhou4, Ning Gu4, Feimin Zhang1,41Institute of Stomatology, Nanjing Medical University, Nanjing, 2Nantong Stomatological Hospital, Nantong, 3Center of Stomatology, The Second Affiliated Hospital of Suzhou University, Suzhou, 4Suzhou Institute, Southeast University, Suzhou, People's Republic of ChinaAbstract: To fabricate high-strength diatomite-based ceramics for dental applications, the layer-by-layer technique was used to coat diatomite particles with cationic [poly(allylamine hydrochloride] and anionic [poly(sodium 4-styrenesulfonate] polymers to improve the dispersion and adsorption of positively charged nano-ZrO2 (zirconia as a reinforcing agent. The modified diatomite particles had reduced particle size, narrower size distribution, and were well dispersed, with good adsorption of nano-ZrO2. To determine the optimum addition levels for nano-ZrO2, ceramics containing 0, 20, 25, 30, and 35 wt% nano-ZrO2 were sintered and characterized by the three-point bending test and microhardness test. In addition to scanning electron microscopy, propagation phase-contrast synchrotron X-ray microtomography was used to examine the internal structure of the ceramics. The addition of 30 wt% nano-ZrO2 resulted in the highest flexural strength and fracture toughness with reduced porosity. Shear bond strength between the core and veneer of our diatomite ceramics and the most widely used dental ceramics were compared; the shear bond strength value for the diatomite-based ceramics was found to be significantly higher than for other groups (P < 0.05. Our results show that diatomite-based nanocomposite ceramics are good potential candidates for ceramic-based dental materials.Keywords: layer-by-layer, diatomite, nanoceramics, zirconia (ZrO2, dental materials

  15. Morphological characterization of ceramic fillers made from Indonesian natural sand as restorative dental materials

    Science.gov (United States)

    Karlina, E.; Susra, S.; Fatmala, Y.; Hartoyo, H. M.; Takarini, V.; Usri, K.; Febrida, R.; Djustiana, N.; Panatarani, C.; Joni, I. M.

    2018-02-01

    Dental composite as restorative dental materials can be reinforced using ceramic fillers. Homogeneous distribution of filler particles shall improve its mechanical properties. This paper presents the results of the preliminary study on the ZrO2-Al2O3-SiO2 ceramic fillers made from Indonesian natural sand that can increase the mechanical properties of dental composite. The synthesis was done using zirconium silicate sand (ZrSiO4) and aluminium oxide (Al2O3) precursors, which dissolved together with 70:30 weight ratios. Two types of sand were used: (1) manufactured sand (mesh #80) and (2) natural sand (mesh #400). The samples then heated in the furnace at 1100 °C for 8 hours. The morphological characterization was then evaluated using JEOL Scanning Electron Microscope (SEM) for the surface structure that analyze particles size and distribution. Ceramic fillers made from natural sand is homogenous, well distributed with average particle size of 5-10 µm. Comparably, ceramic filler made from the manufactured sand is heterogeneous, poorly distributed and appear as agglomerates with average particle size are 30-50 µm. The results suggest that ceramic fillers made from natural sand demonstrate better character to represent as a functional restorative dental material.

  16. Clinical performance - a reflection of damage accumulation in ceramic dental crowns

    Energy Technology Data Exchange (ETDEWEB)

    Rekow, D.E. [Univ. of Medicine and Dentistry of New Jersey, Newark, NJ (United States). Dept. of Orthodontics; Thompson, V.P. [Univ. of Medicine and Dentistry of New Jersey, Newark, NJ (United States). New Jersey Dental School

    2001-07-01

    All-ceramic dental crowns have tremendous appeal for patients - their esthetics nearly match those of natural teeth. Unfortunately, the most esthetic materials are brittle and, consequently, are vulnerable to damage relating to shaping which is exacerbated during cyclic loading during normal chewing. Clinical performance of all-ceramic dental prostheses are directly dependent on damage introduced during fabrication and during fatigue loading associated with function. The accumulation of damage results in unacceptably high failure rates (where failure is defined as a complete fracture requiring replacement of the prosthesis). The relation between shaping damage and fatigue damage on clinical performance of all-ceramic dental crowns was investigated. Materials used commercially for all-ceramic crowns and investigated in this study included a series of different microstructures of machinable glass ceramics (Corning), aluminas and porcelains (Vita Zahnfabrik), and zirconia (Norton). As monolithic materials, strong, tough, fatigue-resistant materials are not sufficiently esthetic for crowns. Crowns fabricated from monolithic esthetic materials have high failure rates. Layering ceramics could provide acceptable strength through management of damage accumulation. (orig.)

  17. Evaluation of machinability and flexural strength of a novel dental machinable glass-ceramic.

    Science.gov (United States)

    Qin, Feng; Zheng, Shucan; Luo, Zufeng; Li, Yong; Guo, Ling; Zhao, Yunfeng; Fu, Qiang

    2009-10-01

    To evaluate the machinability and flexural strength of a novel dental machinable glass-ceramic (named PMC), and to compare the machinability property with that of Vita Mark II and human enamel. The raw batch materials were selected and mixed. Four groups of novel glass-ceramics were formed at different nucleation temperatures, and were assigned to Group 1, Group 2, Group 3 and Group 4. The machinability of the four groups of novel glass-ceramics, Vita Mark II ceramic and freshly extracted human premolars were compared by means of drilling depth measurement. A three-point bending test was used to measure the flexural strength of the novel glass-ceramics. The crystalline phases of the group with the best machinability were identified by X-ray diffraction. In terms of the drilling depth, Group 2 of the novel glass-ceramics proves to have the largest drilling depth. There was no statistical difference among Group 1, Group 4 and the natural teeth. The drilling depth of Vita MK II was statistically less than that of Group 1, Group 4 and the natural teeth. Group 3 had the least drilling depth. In respect of the flexural strength, Group 2 exhibited the maximum flexural strength; Group 1 was statistically weaker than Group 2; there was no statistical difference between Group 3 and Group 4, and they were the weakest materials. XRD of Group 2 ceramic showed that a new type of dental machinable glass-ceramic containing calcium-mica had been developed by the present study and was named PMC. PMC is promising for application as a dental machinable ceramic due to its good machinability and relatively high strength.

  18. Use of the Empress all-ceramic restoration system.

    Science.gov (United States)

    Goulet, M K

    1997-01-01

    New dental materials and techniques have been introduced in the past few years to fabricate aesthetic ceramic restorations with improved strength, biocompatibility, resistance to wear, and better fit. Aesthetic concerns and increasing demand for tooth-colored posterior restorations have led to a number of all-ceramic restorations such as IPS Empress (Ivoclar-Williams, Amherst, NY). The Empress system offers superior aesthetics and physical properties. New generation ceramics along with the current adhesive techniques have resulted in the ability to provide higher strength, therefore indicating crowns for posterior restorations as well. These materials are being used more frequently and in more extensive oral prosthetic rehabilitations such as the case that will be presented. We discuss the different properties and advantages of IPS Empress.

  19. [Microstructure and mechanical property of a new IPS-Empress 2 dental glass-ceramic].

    Science.gov (United States)

    Luo, Xiao-ping; Watts, D C; Wilson, N H F; Silsons, N; Cheng, Ya-qin

    2005-03-01

    To investigate the microstructure and mechanical properties of a new IPS-Empress 2 dental glass-ceramic. AFM, SEM and XRD were used to analyze the microstructure and crystal phase of IPS-Empress 2 glass-ceramic. The flexural strength and fracture toughness were tested using 3-point bending method and indentation method respectively. IPS-Empress 2 glass-ceramic mainly consisted of lithium disilicate crystal, lithium phosphate and glass matrix, which formed a continuous interlocking structure. The crystal phases were not changed before and after hot-pressed treatment. AFM showed nucleating agent particles of different sizes distributed on the highly polished ceramic surface. The strength and fracture toughness were 300 MPa and 3.1 MPam(1/2). The high strength and fracture toughness of IPS-Empress 2 glass ceramic are attributed to the fine lithium disilicate crystalline, interlocking microstructure and crack deflection.

  20. Additive colours approach for dental ceramics translucency characteristics made from Sumatra and Java natural sands

    Science.gov (United States)

    Takarini, V.; Gunawan, J.; Hasratiningsih, Z.; Rudyawan, A.

    2018-04-01

    Translucency is one of dental ceramics desirable aesthetic characteristics, which can be used as an indirect restoration. Dental ceramics can also be made using Computed Aided Design/Computer Aided Manufacturing (CAD/CAM) unit that can create variety blocks as an ingot into a customized restoration. This paper presents the results of self-synthesized porcelain blocks generated from natural sand of Sumatera and Java Islands to promote national independency. This research aims to determine the translucency of dental ceramics made from Indonesia’s natural sand. Six samples each of two different synthesized temperatures, 1150 °C and 1200 °C, were made. To analyse translucency of the sample, their image was taken in bright light background in a black box, then additive green and blue colours histogram channel with range 0 (opaque) to 255 (transparent) were evaluated using Matlab R2015B. The result revealed that mean of green peaks on 1150 °C has an average translucency value of 41%, compared to 34% of blue peaks. Lower percentage of translucency, 31% and 25% on the green and blue channel respectively were attained in samples synthesized in 1200 °C. These suggest that 1150 °C is the optimum temperature for translucency for these ceramic samples from natural sands as they contain leucite crystals shown by the XRD analyses as a result of silica-undersaturated mixture indicated by the Electron Dispersive Spectroscopy. SEM (Scanning Electron Microscope) results show remnant of air pocket in the samples sintered at higher temperature.In conclusion, natural sand from Sumatera and Java can be considered as reliable, cheap basic material options in developing self-synthesized dental ceramics with a desirable translucency. These preliminary results indicate that better balance between strength and translucency could potentially be achieved by making nano-sized dental ceramics.

  1. Wear resistance of a pressable low-fusing ceramic opposed by dental alloys.

    Science.gov (United States)

    Faria, Adriana Cláudia Lapria; de Oliveira, André Almeida; Alves Gomes, Érica; Silveira Rodrigues, Renata Cristina; Faria Ribeiro, Ricardo

    2014-04-01

    Dental alloys have increasingly replaced by dental ceramics in dentistry because of aesthetics. As both dental alloys and ceramics can be present in the oral cavity, the evaluation of the wear resistance of ceramics opposed by dental alloys is important. The aim of the present study was to evaluate wear resistance of a pressable low-fusing ceramic opposed by dental alloys as well as the microhardness of the alloys and the possible correlation of wear and antagonist microhardness. Fifteen stylus tips samples of pressable low-fusing ceramic were obtained, polished and glazed. Samples were divided into three groups according to the disk of alloy/metal to be used as antagonist: Nickel-Chromium (Ni-Cr), Cobalt-Chromium (Co-Cr) and commercially pure titanium (cp Ti). Vickers microhardness of antagonist disks was evaluated before wear tests. Then, antagonist disks were sandblasted until surface roughness was adjusted to 0.75μm. Wear tests were performed at a speed of 60 cycles/min and distance of 10mm, in a total of 300,000 cycles. Before and after wear tests, samples were weighted and had their profile designed in an optical comparator to evaluate weight and height loss, respectively. Ni-Cr and cp Ti caused greater wear than Co-Cr, presenting greater weight (p=.009) and height (p=.002) loss. Cp Ti microhardness was lower than Ni-Cr and Co-Cr (pceramic presents different wear according to the dental alloy used as antagonist and the wear is not affected by antagonist microhardness. Copyright © 2013 Elsevier Ltd. All rights reserved.

  2. Fracture strength of three all-ceramic systems: Top-Ceram compared with IPS-Empress and In-Ceram.

    Science.gov (United States)

    Quran, Firas Al; Haj-Ali, Reem

    2012-03-01

    The purpose of this study was to investigate the fracture loads and mode of failure of all-ceramic crowns fabricated using Top-Ceram and compare it with all-ceramic crowns fabricated from well-established systems: IPS-Empress II, In-Ceram. Thirty all-ceramic crowns were fabricated; 10 IPS-Empress II, 10 In-Ceram alumina and 10 Top-Ceram. Instron testing machine was used to measure the loads required to introduce fracture of each crown. Mean fracture load for In-Ceram alumina [941.8 (± 221.66) N] was significantly (p > 0.05) higher than those of Top-Ceram and IPS-Empress II. There was no statistically significant difference between Top-Ceram and IPS-Empress II mean fracture loads; 696.20 (+222.20) and 534 (+110.84) N respectively. Core fracture pattern was highest seen in Top- Ceram specimens.

  3. Fractographic features of glass-ceramic and zirconia-based dental restorations fractured during clinical function.

    Science.gov (United States)

    Oilo, Marit; Hardang, Anne D; Ulsund, Amanda H; Gjerdet, Nils R

    2014-06-01

    Fractures during clinical function have been reported as the major concern associated with all-ceramic dental restorations. The aim of this study was to analyze the fracture features of glass-ceramic and zirconia-based restorations fractured during clinical use. Twenty-seven crowns and onlays were supplied by dentists and dental technicians with information about type of cement and time in function, if available. Fourteen lithium disilicate glass-ceramic restorations and 13 zirconia-based restorations were retrieved and analyzed. Fractographic features were examined using optical microscopy to determine crack initiation and crack propagation of the restorations. The material comprised fractured restorations from one canine, 10 incisors, four premolars, and 11 molars. One crown was not categorized because of difficulty in orientation of the fragments. The results revealed that all core and veneer fractures initiated in the cervical margin and usually from the approximal area close to the most coronally placed curvature of the margin. Three cases of occlusal chipping were found. The margin of dental all-ceramic single-tooth restorations was the area of fracture origin. The fracture features were similar for zirconia, glass-ceramic, and alumina single-tooth restorations. Design features seem to be of great importance for fracture initiation. © 2014 Eur J Oral Sci.

  4. Experimental observation of silver and gold penetration into dental ceramic by means of a radiotracer technique

    International Nuclear Information System (INIS)

    Moya, F.; Payan, J.; Bernardini, J.; Moya, E.G.

    1987-01-01

    A radiotracer technique was used to study silver and gold diffusion into dental porcelain under experimental conditions close to the real conditions in prosthetic laboratories for porcelain bakes. It was clearly shown that these non-oxidizable elements were able to diffuse into the ceramic as well as oxidizable ones. The penetration depth varied widely according to the element. The ratio DAg/DAu was about 10(3) around 850 degrees C. In contrast to gold, the silver diffusion rate was high enough to allow silver, from the metallic alloy, to be present at the external ceramic surface after diffusion into the ceramic. Hence, the greening of dental porcelains baked on silver-rich alloys could be explained mainly by a solid-state diffusion mechanism

  5. Esthetic modification of cast dental-ceramic restorations.

    Science.gov (United States)

    Campbell, S D

    1990-01-01

    The advantages and disadvantages of conventional opaque substructures (eg, metal ceramic restorations) used for creating esthetic complete crown restorations are reviewed, and the esthetic advantages of veneering a translucent crown (Dicor) are considered. An appropriate aluminous veneering porcelain was identified (Vitadur Veneer). This veneer porcelain was chosen to match the thermal coefficient of expansion of the cast glass-ceramic substructure. A flexural strength study was then completed and it showed no difference in the strength of the veneered and nonveneered translucent cast glass-ceramic specimens. Scanning electron microscopy revealed that the interface between the porcelain veneer and cast glass-ceramic substructure had no visible porosity and resulted in a continuous-appearing structure. Potential coping designs, as well as the clinical applications and ramifications of this modified crown, are discussed.

  6. Effects of Ceramic Density and Sintering Temperature on the Mechanical Properties of a Novel Polymer-Infiltrated Ceramic-Network Zirconia Dental Restorative (Filling) Material.

    Science.gov (United States)

    Li, Weiyan; Sun, Jian

    2018-05-10

    BACKGROUND Polymer-infiltrated ceramic-network (PICN) dental material is a new and practical development in orthodontics. Sintering is the process of forming a stable solid mass from a powder by heating without melting. The aim of this study was to evaluate the effects of sintering temperature on the mechanical properties of a PICN zirconia dental material. MATERIAL AND METHODS A dense zirconia ceramic and four PICN zirconia dental materials, with varying porosities, were sintered at three different temperatures; 12 PICN zirconia dental materials based on these porous ceramics were prepared, as well as a pure polymer. After the specimen preparation, flexural strength and elastic modulus values were measured using the three-point bending test, and fracture toughness were determined by the single-edge notched beam (SENB) method. The Vickers hardness test method was used with an indentation strength (IS) test. Scanning electron microscopy (SEM) was used to examine the microstructure of the ceramic surface and the fracture surface. RESULTS Mechanical properties of the PICN dental materials, including flexural strength, elastic modulus, fracture toughness, and hardness, were more similar to the properties of natural teeth when compared with traditional dental ceramic materials, and were affected by the density and sintering temperature. SEM showed that the porous ceramic network became cohesive and that the length of cracks in the PICN dental material was reduced. CONCLUSIONS PICN zirconia dental materials were characterized by similar mechanical properties to natural dental tissues, but further studies are required continue to improve the similarities with natural human enamel and dentin.

  7. Characterization of Conventional and High-Translucency Y-TZP Dental Ceramics Submitted to Air Abrasion.

    Science.gov (United States)

    Tostes, Bhenya Ottoni; Guimarães, Renato Bastos; Noronha-Filho, Jaime Dutra; Botelho, Glauco Dos Santos; Guimarães, José Guilherme Antunes; Silva, Eduardo Moreira da

    2017-01-01

    This study evaluated the effect of air-abrasion on t®m phase transformation, roughness, topography and the elemental composition of three Y-TZP (Yttria-stabilized tetragonal zirconia polycrystal) dental ceramics: two conventional (Lava Frame and IPS ZirCad) and one with high-translucency (Lava Plus). Plates obtained from sintered blocks of each ceramic were divided into four groups: AS (as-sintered); 30 (air-abrasion with 30 mm Si-coated Al2O3 particles); 50 (air-abrasion with 50 mm Al2O3 particles) and 150 (air-abrasion with 150 mm Al2O3 particles). After the treatments, the plates were submitted to X-ray diffractometry; 3-D profilometry and SEM/EDS. The AS surfaces were composed of Zr and t phases. All treatments produced t®m phase transformation in the ceramics. The diameter of air-abrasion particles influenced the roughness (150>50>30>AS) and the topography. SEM analysis showed that the three treatments produced groove-shaped microretentions on the ceramic surfaces, which increased with the diameter of air-abrasion particles. EDS showed a decrease in Zr content along with the emergence of O and Al elements after air-abrasion. Presence of Si was also detected on the plates air-abraded with 30 mm Si-coated Al2O3 particles. It was concluded that irrespective of the type and diameter of the particles, air-abrasion produced t®m phase transformation, increased the roughness and changed the elemental composition of the three Y-TZP dental ceramics. Lava Plus also behaved similarly to the conventional Y-TZP ceramics, indicating that this high translucency ceramic could be more suitable to build monolithic ceramic restorations in the aesthetic restorative dentistry field.

  8. Synthesis of bioactive and machinable miserite glass-ceramics for dental implant applications.

    Science.gov (United States)

    Saadaldin, Selma A; Dixon, S Jeffrey; Costa, Daniel O; Rizkalla, Amin S

    2013-06-01

    To synthesize and characterize machinable, bioactive glass-ceramics (GCs) suitable for dental implant applications. A glass in the SiO2-Al2O3-CaO-CaF2-K2O-B2O3-La2O3 system was synthesized by wet chemical methods, followed by calcination, melting and quenching. Crystallization kinetics were determined by differential thermal analysis (DTA). GC discs were produced by cold pressing of the glass powder and sintered using schedules determined by DTA. The crystalline phases and microstructure of GC samples were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. Dynamic Young's modulus (E), true hardness (Ho), fracture toughness (KIC) and brittleness index (BI) were evaluated. Bioactivity was studied by examining the formation of hydroxyapatite (HA) on the GC surfaces after soaking in simulated body fluid (SBF). Attachment and proliferation of MC3T3-E1 osteoblastic cells were assessed in vitro. Miserite [KCa5(Si2O7)(Si6O15)(OH)F] was the main crystalline phase of the GC with additional secondary phases. Microstructural studies revealed interlocking lath-like crystalline morphology. E, Ho, and KIC values for the GCs were 96±3 GPa, 5.27±0.26 GPa and 4.77±0.27 MPa m(0.5), respectively. The BI was found to be 1.11±0.05 μm(-0.5), indicating outstanding machinability. An HA surface layer was formed on the GC surfaces when soaked in SBF, indicating potential bioactivity. MC3T3-E1 cells exhibited attachment, spreading and proliferation on GC surfaces, demonstrating excellent biocompatibility. We present a novel approach for the synthesis of miserite GC with the physical and biological properties required for non-metallic dental implant applications. Copyright © 2013 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  9. Ceramics for applications in fusion systems

    International Nuclear Information System (INIS)

    Clinard, F.W. Jr.

    1979-01-01

    Six critical applications for ceramics in fusion systems are reviewed, and structural and electrical problem areas discussed. Fusion neutron radiation effects in ceramics are considered in relation to fission neutron studies. A number of candidate materials are proposed for further evaluation

  10. Clinical and Radiographic Assessment of Reasons for Replacement of Metal- Ceramic Fixed Dental Prostheses in Patients Referring to Dental School.

    Science.gov (United States)

    Al Refai, Roa'a; Saker, Samah

    2018-01-01

    The expected length of service and reasons for fixed dental prostheses (FDPs) replacement are a frequent inquiry by patients while the answers were mainly based on studies reports that was conducted outside the middle east region. This clinical and radiographic survey was constructed to assess and survey clinically and radiographically the reasons of replacement of metal-ceramic fixed dental prostheses, amongst patients reporting at dental school in Taibah University. Between January and May 2016, 151 patients were recruited for this study. Interview (include questions pertained to the length of service of the prosthesis, the nature of complaint as told by patient in her own words), clinical examination, intra-oral photographs, and periapical radiographs, were done by the researchers. The parameters assessed were secondary caries, open margins, loss of retention, failure of endodontic treatment of the abutment and periodontal diseases. A total number of 249 failed fixed dental prostheses were evaluated. Of which 180 (39.7%) were single crowns, 159 (35.0%) were retainers and 117 (25.8%) were pontics in 69 fixed partial denture. The most common reason for replacement of fixed restorations was periodontal diseases affecting 92.8% of all types' restorations, followed by defective margin in 90.4% of examined restoration, poor aesthetic in 88% of restorations, while periapical involvement was found in 85.5% of fixed dental prosthesis. The survival rates of fixed prostheses were not predictable, and no association was found between number of years in service and the number of restorations. The most common reasons for replacing single unit fixed dental prostheses are periodontal diseases and periapical involvement, while defective margins and poor aesthetic mainly associated with multi-unit fixed dental prostheses. Key words: Failure, Fixed dental prosthesis, Survival, Replacement.

  11. Illuminating light-dependent color shifts in core and veneer layers of dental all-ceramics

    Science.gov (United States)

    Lee, Yong-Keun; Cha, Hyun-Suk; Yu, Bin

    2014-09-01

    The color of an object is perceived differently depending on the ambient light conditions. Since dental all-ceramic restorations are fabricated by building up several layers to reproduce the tooth shade, the optical properties of each layer should be optimized for successful shade reproduction. This study aimed to determine the separate contributions of the color shifts in each of the core and veneer layers of all-ceramics by switching the illuminating lights on the color shifts of layered ceramics. Specimens of seven kinds of core ceramics and the corresponding veneer ceramics for each core were fabricated with a layered thickness of 1.5 mm. A sintering ceramic was used as a reference core material. The Commission Internationale de l'Eclairage (CIE) color coordinates of core, veneer, and layered specimens were measured with a spectroradiometer under the CIE illuminant D65 (daylight), A (incandescent lamp), and F9 (fluorescent lamp) simulating lights. Color shifts of the layered specimens were primarily determined by the CIE a* shifts (D65 to A switch) or by the CIE b* shifts (D65 to F9 switch) of the veneer layer. The color coordinates shifts in the constituent layers differentially influenced those of the layered specimens by the kind of switched lights. Therefore, the optical properties of the constituent layers of all-ceramics should be controlled to reflect these findings.

  12. Mechanical fatigue degradation of ceramics versus resin composites for dental restorations.

    Science.gov (United States)

    Belli, Renan; Geinzer, Eva; Muschweck, Anna; Petschelt, Anselm; Lohbauer, Ulrich

    2014-04-01

    For posterior partial restorations an overlap of indication exists where either ceramic or resin-based composite materials can be successfully applied. The aim of this study was to compare the fatigue resistance of modern dental ceramic materials versus dental resin composites in order to address such conflicts. Bar specimens of five ceramic materials and resin composites were produced according to ISO 4049 and stored for 14 days in distilled water at 37°C. The following ceramic materials were selected for testing: a high-strength zirconium dioxide (e.max ZirCAD, Ivoclar), a machinable lithium disilicate (e.max CAD, Ivoclar), a pressable lithium disilicate ceramic (e-max Press, Ivoclar), a fluorapatite-based glass-ceramic (e.max Ceram, Ivoclar), and a machinable color-graded feldspathic porcelain (Trilux Forte, Vita). The composite materials selected were: an indirect machinable composite (Lava Ultimate, 3M ESPE) and four direct composites with varying filler nature (Clearfil Majesty Posterior, Kuraray; GrandioSO, Voco; Tetric EvoCeram, Ivoclar-Vivadent; and CeramX Duo, Dentsply). Fifteen specimens were tested in water for initial strength (σin) in 4-point bending. Using the same test set-up, the residual flexural fatigue strength (σff) was determined using the staircase approach after 10(4) cycles at 0.5 Hz (n=25). Weibull parameters σ0 and m were calculated for the σin specimens, whereas the σff and strength loss in percentage were obtained from the fatigue experiment. The zirconium oxide ceramic showed the highest σin and σff (768 and 440 MPa, respectively). Although both lithium disilicate ceramics were similar in the static test, the pressable version showed a significantly higher fatigue resistance after cyclic loading. Both the fluorapatite-based and the feldspathic porcelain showed equivalent initial and cyclic fatigue properties. From the composites, the highest filled direct material Clearfil Majesty Posterior showed superior fatigue performance

  13. Biocompatibility study of lithium disilicate and zirconium oxide ceramics for esthetic dental abutments

    Science.gov (United States)

    2016-01-01

    Purpose The increasing demand for esthetically pleasing results has contributed to the use of ceramics for dental implant abutments. The aim of this study was to compare the biological response of epithelial tissue cultivated on lithium disilicate (LS2) and zirconium oxide (ZrO2) ceramics. Understanding the relevant physicochemical and mechanical properties of these ceramics will help identify the optimal material for facilitating gingival wound closure. Methods Both biomaterials were prepared with 2 different surface treatments: raw and polished. Their physicochemical characteristics were analyzed by contact angle measurements, scanning white-light interferometry, and scanning electron microscopy. An organotypic culture was then performed using a chicken epithelium model to simulate peri-implant soft tissue. We measured the contact angle, hydrophobicity, and roughness of the materials as well as the tissue behavior at their surfaces (cell migration and cell adhesion). Results The best cell migration was observed on ZrO2 ceramic. Cell adhesion was also drastically lower on the polished ZrO2 ceramic than on both the raw and polished LS2. Evaluating various surface topographies of LS2 showed that increasing surface roughness improved cell adhesion, leading to an increase of up to 13%. Conclusions Our results demonstrate that a biomaterial, here LS2, can be modified using simple surface changes in order to finely modulate soft tissue adhesion. Strong adhesion at the abutment associated with weak migration assists in gingival wound healing. On the same material, polishing can reduce cell adhesion without drastically modifying cell migration. A comparison of LS2 and ZrO2 ceramic showed that LS2 was more conducive to creating varying tissue reactions. Our results can help dental surgeons to choose, especially for esthetic implant abutments, the most appropriate biomaterial as well as the most appropriate surface treatment to use in accordance with specific clinical

  14. Towards the synthesis of an experimental bioactive dental ceramic. Part I: Crystallinity characterization and bioactive behavior evaluation

    Energy Technology Data Exchange (ETDEWEB)

    Goudouri, O.-M. [Physics Department, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece); Kontonasaki, E. [School of Dentistry, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece); Papadopoulou, L.; Kantiranis, N. [Department of Geology, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece); Lazaridis, N.K. [Chemistry Department, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece); Chrissafis, K.; Chatzistavrou, X. [Physics Department, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece); Koidis, P. [School of Dentistry, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece); Paraskevopoulos, K.M., E-mail: kpar@auth.gr [Physics Department, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece)

    2014-05-01

    An attachment between the dental ceramic and the surrounding marginal tissues in fixed prosthetic restorations could eliminate secondary carries prevalence. The development of dental ceramics with apatite forming ability could provide the biological surface required for selective spread and attachment of specific cell types able to promote tissue attachment. Dental ceramics/bioactive glass composites synthesized by the sol gel method have been previously reported to develop carbonated hydroxyapatite (HCAp) in biomimetic solutions, requiring though a high amount of bioactive glass, which resulted in the compromise of their mechanical integrity. Thus, the aim of the present work was the synthesis and characterization of an experimental sol–gel derived dental ceramic with low amount of bioactive glass and the evaluation of its in vitro bioactivity. Differential thermal and thermogravimetric analysis (TG–DTA), Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffractometry (XRD), Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) were used to evaluate the crystal structure and the in vitro apatite forming ability of the synthesized material. The results of this study indicated the successful sol–gel synthesis of an experimental dental ceramic containing low amount of bioactive glass that presented similar structural and morphological characteristics with a commercial feldspathic dental ceramic, while exhibiting in vitro bioactivity. The apatite forming ability of the experimental sol–gel derived feldspathic dental ceramic may trigger the appropriate cellular mechanisms towards the establishment of attachment with the surrounding connective tissue. This attachment could provide a barrier to oral bacteria penetration, prolonging the life expectation of the restorations. - Highlights: • Synthesis of a bioactive sol–gel dental ceramic for fixed prosthetic restorations. • The sol–gel technique promoted the crystallization of

  15. Towards the synthesis of an experimental bioactive dental ceramic. Part I: Crystallinity characterization and bioactive behavior evaluation

    International Nuclear Information System (INIS)

    Goudouri, O.-M.; Kontonasaki, E.; Papadopoulou, L.; Kantiranis, N.; Lazaridis, N.K.; Chrissafis, K.; Chatzistavrou, X.; Koidis, P.; Paraskevopoulos, K.M.

    2014-01-01

    An attachment between the dental ceramic and the surrounding marginal tissues in fixed prosthetic restorations could eliminate secondary carries prevalence. The development of dental ceramics with apatite forming ability could provide the biological surface required for selective spread and attachment of specific cell types able to promote tissue attachment. Dental ceramics/bioactive glass composites synthesized by the sol gel method have been previously reported to develop carbonated hydroxyapatite (HCAp) in biomimetic solutions, requiring though a high amount of bioactive glass, which resulted in the compromise of their mechanical integrity. Thus, the aim of the present work was the synthesis and characterization of an experimental sol–gel derived dental ceramic with low amount of bioactive glass and the evaluation of its in vitro bioactivity. Differential thermal and thermogravimetric analysis (TG–DTA), Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffractometry (XRD), Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) were used to evaluate the crystal structure and the in vitro apatite forming ability of the synthesized material. The results of this study indicated the successful sol–gel synthesis of an experimental dental ceramic containing low amount of bioactive glass that presented similar structural and morphological characteristics with a commercial feldspathic dental ceramic, while exhibiting in vitro bioactivity. The apatite forming ability of the experimental sol–gel derived feldspathic dental ceramic may trigger the appropriate cellular mechanisms towards the establishment of attachment with the surrounding connective tissue. This attachment could provide a barrier to oral bacteria penetration, prolonging the life expectation of the restorations. - Highlights: • Synthesis of a bioactive sol–gel dental ceramic for fixed prosthetic restorations. • The sol–gel technique promoted the crystallization of

  16. Standardizing failure, success, and survival decisions in clinical studies of ceramic and metal-ceramic fixed dental prostheses.

    Science.gov (United States)

    Anusavice, Kenneth J

    2012-01-01

    The recent increase in reports from clinical studies of ceramic chipping has raised the question of which criteria should constitute success or failure of total-ceramic prostheses. Terminologies such as minor chipping [1], partial chipping, technical complications [2,3], and biological complications have crept into the dental terminology and they have complicated our classification of success and failure of these crown and bridge restorations. Some journals have permitted the reporting of fractures as "complications" and they are not necessarily classified as failures in the study. One study has attempted to classify chipping fractures according to their severity and subsequent treatment [4]. This is a promising approach to resolve the challenges to the classification of chipping fracture. The term 'chipping fracture' is more descriptive than 'chipping' since the latter term tends to imply an event of minor consequence. Two types of statistics are reported routinely in these studies, i.e., percent success, which is a measure of restorations that survive without any adverse effects, and percent survival, which is a measure of all restorations that survive even though they may have exhibited chipping fracture or they may have been repaired. Why has this scenario occurred? One possible explanation is that many of these types of fractures are very small and do not affect function or esthetics. Another reason is that corporate sponsors prefer to use the term chipping since it does not connote failure in the sense that the term fracture does. In any event, we need to be more precise in our scientific observations of fracture and classifications of the various types of fracture including details on the location of fracture and the prosthesis design configuration. Because of the lack of standardized methods for describing chipping fractures, materials scientists are unable to properly analyze the effect of material properties and design factors on the time

  17. Chemical adhesion rather than mechanical retention enhances resin bond durability of a dental glass-ceramic with leucite crystallites

    International Nuclear Information System (INIS)

    Meng, X F; Yoshida, K; Gu, N

    2010-01-01

    This study aims to evaluate the effect of chemical adhesion by a silane coupler and mechanical retention by hydrofluoric acid (HFA) etching on the bond durability of resin to a dental glass ceramic with leucite crystallites. Half of the ceramic plates were etched with 4.8% HFA (HFA group) for 60 s, and the other half were not treated (NoHFA group). The scale of their surface roughness and rough area was measured by a 3D laser scanning microscope. These plates then received one of the following two bond procedures to form four bond test groups: HFA/cement, NoHFA/cement, HFA/silane/cement and NoHFA/silane/cement. The associated micro-shear bond strength and bond failure modes were tested after 0 and 30 000 thermal water bath cycles. Four different silane/cement systems (Monobond S/Variolink II, GC Ceramic Primer/Linkmax HV, Clearfil Ceramic Primer/Clearfil Esthetic Cement and Porcelain Liner M/SuperBond C and B) were used. The data for each silane/cement system were analyzed by three-way ANOVA. HFA treatment significantly increased the surface R a and R y values and the rough area of the ceramic plates compared with NoHFA treatment. After 30 000 thermal water bath cycles, the bond strength of all the test groups except the HFA/Linkmax HV group was significantly reduced, while the HFA/Linkmax HV group showed only adhesive interface failure. The other HFA/cement groups and all NoHFA/cement groups lost bond strength completely, and all NoHFA/silane/cement groups with chemical adhesion had significantly higher bond strength and more ceramic cohesive failures than the respective HFA/cement groups with mechanical retention. The result of the HFA/silane/cement groups with both chemical adhesion and mechanical retention revealed that HFA treatment could enhance the bond durability of resin/silanized glass ceramics, which might result from the increase of the chemical adhesion area on the ceramic rough surface and subsequently reduced degradation speed of the silane coupler

  18. Chemical adhesion rather than mechanical retention enhances resin bond durability of a dental glass-ceramic with leucite crystallites

    Energy Technology Data Exchange (ETDEWEB)

    Meng, X F [Department of Prosthodontics, The Stomatological Hospital Affiliated Medical School, Nanjing University, Nanjing 210008 (China); Yoshida, K [Division of Applied Prosthodontics, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki 852-8588 (Japan); Gu, N, E-mail: mengsoar@nju.edu.c [Jiangsu Key Laboratory for Biomaterials and Devices, School of Biological Science and Medical Engineering, Southeast University, Nanjing 210096 (China)

    2010-08-01

    This study aims to evaluate the effect of chemical adhesion by a silane coupler and mechanical retention by hydrofluoric acid (HFA) etching on the bond durability of resin to a dental glass ceramic with leucite crystallites. Half of the ceramic plates were etched with 4.8% HFA (HFA group) for 60 s, and the other half were not treated (NoHFA group). The scale of their surface roughness and rough area was measured by a 3D laser scanning microscope. These plates then received one of the following two bond procedures to form four bond test groups: HFA/cement, NoHFA/cement, HFA/silane/cement and NoHFA/silane/cement. The associated micro-shear bond strength and bond failure modes were tested after 0 and 30 000 thermal water bath cycles. Four different silane/cement systems (Monobond S/Variolink II, GC Ceramic Primer/Linkmax HV, Clearfil Ceramic Primer/Clearfil Esthetic Cement and Porcelain Liner M/SuperBond C and B) were used. The data for each silane/cement system were analyzed by three-way ANOVA. HFA treatment significantly increased the surface R{sub a} and R{sub y} values and the rough area of the ceramic plates compared with NoHFA treatment. After 30 000 thermal water bath cycles, the bond strength of all the test groups except the HFA/Linkmax HV group was significantly reduced, while the HFA/Linkmax HV group showed only adhesive interface failure. The other HFA/cement groups and all NoHFA/cement groups lost bond strength completely, and all NoHFA/silane/cement groups with chemical adhesion had significantly higher bond strength and more ceramic cohesive failures than the respective HFA/cement groups with mechanical retention. The result of the HFA/silane/cement groups with both chemical adhesion and mechanical retention revealed that HFA treatment could enhance the bond durability of resin/silanized glass ceramics, which might result from the increase of the chemical adhesion area on the ceramic rough surface and subsequently reduced degradation speed of the silane

  19. Influence of surfactants on the microstructure of dental zirconia ceramics

    International Nuclear Information System (INIS)

    Il'icheva, A. A.; Michalina, N. A.; Podzorova, L. I.; Pen'kova, O. I.; Kutsev, S. V.; Berezina, S.

    2013-01-01

    This work studies the influence of different surfactants included in the synthesis of precursor powders on the microstructure of ceramic material to search for an optimal agents providing an uniform grain microstructure required for accurate medical products with a high degree of surface cleanliness. (authors)

  20. Standardizing Failure, Success, and Survival Decisions in Clinical Studies of Ceramic and Metal-Ceramic Fixed Dental Prostheses

    Science.gov (United States)

    Anusavice, Kenneth J.

    2011-01-01

    “Nothing worthwhile is ever without complications.”– Nora Roberts The recent increase in reports from clinical studies of ceramic chipping has raised the question of which criteria should constitute success or failure of total-ceramic prostheses. Terminology such as minor chipping[1], partial chipping, technical complications[2, 3], and biological complications have crept into the dental terminology and they have complicated our classification of success and failure of these crown and bridge restorations. Some journals have permitted the reporting of fractures as “complications” and they are not necessarily classified as failures in the study. One study has attempted to classify chipping fractures according to their severity and subsequent treatment.[4] This is a promising approach to resolve the challenges to the classification of chipping fracture. The term ‘chipping fracture’ is more descriptive than ‘chipping’ since the latter term tends to imply an event of minor consequence. Two types of statistics are reported routinely in these studies, i.e., percent success, which is a measure of restorations that survive without any adverse effects, and percent survival, which is a measure of all restorations that survive even though they may have exhibited chipping fracture or they may have been repaired. Why has this scenario occurred? One possible explanation is that many of these types of fractures are very small and do not affect function or esthetics. Another reason is that corporate sponsors prefer to use the term chipping since it does not connote failure in the sense that the term fracture does. In any event, we need to be more precise in our scientific observations of fracture and classifications of the various types of fracture including details on the location of fracture and the prosthesis design configuration. Because of the lack of standardized methods for describing chipping fractures, materials scientists are unable to properly analyze

  1. A comparison of the marginal vertical discrepancies of zirconium and metal ceramic posterior fixed dental prostheses before and after cementation.

    Science.gov (United States)

    Gonzalo, Esther; Suárez, Maria J; Serrano, Benjamin; Lozano, Jose F L

    2009-12-01

    Marginal discrepancies of zirconia posterior fixed dental prostheses (FDPs) fabricated using various systems have been assessed to determine the quality of the restorations and facilitate clinical use; however, studies are limited and results are ambiguous because of the sample sizes and measurement methods. The purpose of this in vitro study was to compare changes in marginal fit of posterior fixed dental prostheses of 3 zirconia systems manufactured using CAD/CAM technology and metal ceramic posterior fixed dental protheses fabricated with the conventional lost-wax technique, before and after cementation. Forty standardized master steel dies with 2 abutments simulating first mandibular premolars were fabricated to receive a posterior 3-unit FDP (from first molar to first premolar) and divided into 4 groups (n=10): Lava All-Ceramic System, Procera Bridge Zirconia, VITA In-Ceram 2000 YZ, and metal ceramic (control group). All FDPs were prepared for an internal space of 50 microm. The external marginal gap of the restorations was investigated by measuring 30 points in the middle of the buccal and lingual surfaces; therefore, 60 measurements per abutment were recorded. Measurements were made with an image analysis program on the master steel model before and after conventional cementation with a glass ionomer agent (Ketac Cem Easymix). The data obtained were statistically analyzed using 1-way ANOVA, Duncan's multiple range post hoc test, and Student's paired t test (alpha=.05). No significant differences in the vertical marginal fit before and after cementation were recorded for the analyzed groups. The marginal discrepancy of Procera abutments before and after cementation (9 +/-10 microm and 12 +/-9 microm, respectively) was less than that of the other groups. Significant differences (P=.001) were observed in marginal adaptation between Procera Bridge Zirconia and the other groups. The results of this study showed that cementation did not cause a significant

  2. Stress and Reliability Analysis of a Metal-Ceramic Dental Crown

    Science.gov (United States)

    Anusavice, Kenneth J; Sokolowski, Todd M.; Hojjatie, Barry; Nemeth, Noel N.

    1996-01-01

    Interaction of mechanical and thermal stresses with the flaws and microcracks within the ceramic region of metal-ceramic dental crowns can result in catastrophic or delayed failure of these restorations. The objective of this study was to determine the combined influence of induced functional stresses and pre-existing flaws and microcracks on the time-dependent probability of failure of a metal-ceramic molar crown. A three-dimensional finite element model of a porcelain fused-to-metal (PFM) molar crown was developed using the ANSYS finite element program. The crown consisted of a body porcelain, opaque porcelain, and a metal substrate. The model had a 300 Newton load applied perpendicular to one cusp, a load of 30ON applied at 30 degrees from the perpendicular load case, directed toward the center, and a 600 Newton vertical load. Ceramic specimens were subjected to a biaxial flexure test and the load-to-failure of each specimen was measured. The results of the finite element stress analysis and the flexure tests were incorporated in the NASA developed CARES/LIFE program to determine the Weibull and fatigue parameters and time-dependent fracture reliability of the PFM crown. CARES/LIFE calculates the time-dependent reliability of monolithic ceramic components subjected to thermomechanical and/Or proof test loading. This program is an extension of the CARES (Ceramics Analysis and Reliability Evaluation of Structures) computer program.

  3. ADVANCED CERAMIC MATERIALS FOR DENTAL APPLICATIONS SINTERED BY MICROWAVE HEATING

    OpenAIRE

    Presenda Barrera, Álvaro

    2016-01-01

    [EN] Zirconia has become a widely utilized structural ceramic material with important applications in dentistry due to its superb mechanical properties, biocompatibility, aesthetic characteristics and durability. Zirconia needs to be stabilized in the t-phase to obtain improved mechanical properties such as hardness and fracture toughness. Fully dense yttria-stabilized tetragonal zirconia polycrystalline (Y-TZP) materials are normally consolidated through the energy-intensive processing of po...

  4. Deformation of a dental ceramic following adhesive cementation.

    LENUS (Irish Health Repository)

    2010-01-01

    Stress-induced changes imparted in a \\'dentin-bonded-crown\\' material during sintering, annealing, pre-cementation surface modification, and resin coating have been visualized by profilometry. The hypothesis tested was that operative techniques modify the stressing pattern throughout the material thickness. We polished the upper surfaces of 10 ceramic discs to remove surface imperfections before using a contact profilometer (40-nm resolution) to measure the \\'flatness\\'. Discs were re-profiled after annealing and after alumina particle air-abrasion and resin-coating of the \\'fit\\' surface. Polished surfaces were convex, with a mean deflection of 8.4 + or - 1.5 microm. Mean deflection was significantly reduced (P = 0.029) following alumina particle air-abrasion and increased (P < 0.001) on resin-coating. Polishing induced a tensile stress state, resulting in surface convexity. Alumina particle air-abrasion reduced the relative tensile stress state of the contralateral polished surface. Resin-polymerization generated compression within the resin-ceramic \\'hybrid layer\\' and tension in the polished surface and is likely to contribute to the strengthening of ceramics by resin-based cements.

  5. Hydrothermal degradation of tetragonal ZrO2 ceramic components used in dental applications

    International Nuclear Information System (INIS)

    Mukaeda, L.E.; Robin, A.; Taguchi, S.P.

    2009-01-01

    With the evolution of the dental restoration techniques, a considerable growth in the demand of ceramic products occurred. These materials present good strength associated to reliability. In this work, micrometric and nanometric scale tetragonal ZrO 2 blocks were sintered at 1500 deg C-2h and 1350 deg C-2h, respectively, ground and polished. Ceramics with relative density higher than 98% were obtained. The specimens were immersed in hot water (150 deg C), for times ranging from 10h to 30h. The mass variation of the samples was measured and the crystalline phases present before and after the degradation tests were identified by X-ray diffractometry, in order to evaluate the capacity of these ceramics in resisting to aqueous medium exposure. Materials with nanometric structure present higher resistance to degradation than those with micrometric scale, and this interferes in structural stability after the test, and reduces the martensitic transformation. (author)

  6. Comparative study of flexural strength test methods on CAD/CAM Y-TZP dental ceramics.

    Science.gov (United States)

    Xu, Yongxiang; Han, Jianmin; Lin, Hong; An, Linan

    2015-12-01

    Clinically, fractures are the main cause of computer-aided design and computer-aided manufacturing (CAD/CAM) 3 mol%-yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) all-ceramic dental restorations failure because of repetitive occlusal loading. The goal of this work is to study the effect of test methods and specimen's size on the flexural strength of five ceramic products. Both bi-axial flexure test (BI) and uni-axial flexure tests (UNI), including three-point flexure test (3PF) and four-point flexure test (4PF), are used in this study. For all five products, the flexural strength is as follows: BI > 3PF > 4PF. Furthermore, specimens with smaller size (3PF-s) have higher values than the bigger ones (3PF). The difference between BI and UNI resulted from the edge flaws in ceramic specimens. The relationship between different UNI (including 3PF-s, 3PF and 4PF) can be explained according to Weibull statistical fracture theory. BI is recommended to evaluate the flexural strength of CAD/CAM Y-TZP dental ceramics.

  7. Comparative study of flexural strength test methods on CAD/CAM Y-TZP dental ceramics

    Science.gov (United States)

    Xu, Yongxiang; Han, Jianmin; Lin, Hong; An, Linan

    2015-01-01

    Clinically, fractures are the main cause of computer-aided design and computer-aided manufacturing (CAD/CAM) 3 mol%-yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) all-ceramic dental restorations failure because of repetitive occlusal loading. The goal of this work is to study the effect of test methods and specimen’s size on the flexural strength of five ceramic products. Both bi-axial flexure test (BI) and uni-axial flexure tests (UNI), including three-point flexure test (3PF) and four-point flexure test (4PF), are used in this study. For all five products, the flexural strength is as follows: BI > 3PF > 4PF. Furthermore, specimens with smaller size (3PF-s) have higher values than the bigger ones (3PF). The difference between BI and UNI resulted from the edge flaws in ceramic specimens. The relationship between different UNI (including 3PF-s, 3PF and 4PF) can be explained according to Weibull statistical fracture theory. BI is recommended to evaluate the flexural strength of CAD/CAM Y-TZP dental ceramics. PMID:26816646

  8. Fabrication of Silicon Nitride Dental Core Ceramics with Borosilicate Veneering material

    Science.gov (United States)

    Wananuruksawong, R.; Jinawath, S.; Padipatvuthikul, P.; Wasanapiarnpong, T.

    2011-10-01

    Silicon nitride (Si3N4) ceramic is a great candidate for clinical applications due to its high fracture toughness, strength, hardness and bio-inertness. This study has focused on the Si3N4 ceramic as a dental core material. The white Si3N4 was prepared by pressureless sintering at relative low sintering temperature of 1650 °C in nitrogen atmosphere. The coefficient of thermal expansion (CTE) of Si3N4 ceramic is lower than that of Zirconia and Alumina ceramic which are popular in this field. The borosilicate glass veneering was employed due to its compatibility in thermal expansion. The sintered Si3N4 specimens represented the synthetic dental core were paintbrush coated by a veneer paste composed of borosilicate glass powder (tube furnace between 1000-1200°C. The veneered specimens fired at 1100°C for 15 mins show good bonding, smooth and glossy without defect and crazing. The veneer has thermal expansion coefficient as 3.98×10-6 °C-1, rather white and semi opaque, due to zirconia addition, the Vickers hardness as 4.0 GPa which is closely to the human teeth.

  9. Fabrication of Silicon Nitride Dental Core Ceramics with Borosilicate Veneering material

    International Nuclear Information System (INIS)

    Wananuruksawong, R; Jinawath, S; Wasanapiarnpong, T; Padipatvuthikul, P

    2011-01-01

    Silicon nitride (Si 3 N 4 ) ceramic is a great candidate for clinical applications due to its high fracture toughness, strength, hardness and bio-inertness. This study has focused on the Si 3 N 4 ceramic as a dental core material. The white Si 3 N 4 was prepared by pressureless sintering at relative low sintering temperature of 1650 deg. C in nitrogen atmosphere. The coefficient of thermal expansion (CTE) of Si 3 N 4 ceramic is lower than that of Zirconia and Alumina ceramic which are popular in this field. The borosilicate glass veneering was employed due to its compatibility in thermal expansion. The sintered Si 3 N 4 specimens represented the synthetic dental core were paintbrush coated by a veneer paste composed of borosilicate glass powder ( 2 O 3 - partial stabilized zirconia) and 30 wt% of polyvinyl alcohol (5 wt% solution). After coating the veneer on the Si 3 N 4 specimens, the firing was performed in electric tube furnace between 1000-1200 deg. C. The veneered specimens fired at 1100 deg. C for 15 mins show good bonding, smooth and glossy without defect and crazing. The veneer has thermal expansion coefficient as 3.98x10 -6 deg. C -1 , rather white and semi opaque, due to zirconia addition, the Vickers hardness as 4.0 GPa which is closely to the human teeth.

  10. Stereolithography: A new method for processing dental ceramics by additive computer-aided manufacturing.

    Science.gov (United States)

    Dehurtevent, Marion; Robberecht, Lieven; Hornez, Jean-Christophe; Thuault, Anthony; Deveaux, Etienne; Béhin, Pascal

    2017-05-01

    The aim of this study was to compare the physical and mechanical properties of stereolithography (SLA)- manufactured alumina ceramics of different composition to those of subtractive- manufactured ceramics and to produce suitable dental crown frameworks. The physical and mechanical properties of a control and six experimental SLA ceramics prepared from slurries with small (S) and large (L) particles (0.46±0.03 and 1.56±0.04μm, respectively) and three dry matter contents (70%, 75%, 80%) were evaluated by dynamic rheometry, hydrostatic weighing, three3-point flexural strength measurements, and Weibull analyses, and by the micrometrics measurement of shrinkage ratio before and after the heat treatments. S75 was the only small particle slurry with a significantly higher viscosity than L70. The viscosity of the S80 slurry made it impossible to take rheological measurements. The viscosities of the S75 and S80 slurries caused deformations in the printed layers during SLA manufacturing and were excluded from further consideration. SLA samples with low dry matter content had significantly lower and densityflexural strengths. Only SLA samples with a large particle size and high dry matter content (L75 and L80) were similar in density and flexural strength to the subtractive- manufactured samples. The 95% confidence intervals of the Weibull modulus of the L80 ceramic were higher (no overlap fraction) than those of the L75 ceramic and were similar to the control (overlap fraction). The Weibull characteristics of L80 ceramic were higher than those of L75 ceramic and the control. SLA can be used to process suitable crown frameworks but shows results in anisotropic shrinkage. The hH High particle size and dry matter content of the L80 slurry allowed made it possible to produce a reliable ceramic by SLA manufacturing with an anisotropic shrinkage, and a density, and flexural strength similar to those of a subtractive-manufactured ceramic. SLA allowed made it possible to build

  11. Systemic Assessment of Patients Undergoing Dental Implant ...

    African Journals Online (AJOL)

    Background: Procedure‑related and patient‑related factors influence the prognosis of dental implants to a major extent. Hence, we aimed to evaluate and analyze various systemic factors in patients receiving dental implants. Materials and Methods: Fifty‑one patients were included in the study, in which a total of 110 dental ...

  12. OSL and TL retrospective dosimetry with a fluorapatite glass-ceramic used for dental restorations

    International Nuclear Information System (INIS)

    Ekendahl, Daniela; Judas, Libor; Sukupova, Lucie

    2013-01-01

    Optically Stimulated Luminescence (OSL) and Thermoluminescence (TL) properties of a fluorapatite glass-ceramic have been investigated, with a view to developing a dose assessment technique for medical triage following unplanned exposures of individuals to ionizing radiation. The ceramic is an innovative material used in dental prostheses and restorations. It is strongly sensitive to radiation and the intensity of both the OSL and TL signals are proportional to the absorbed radiation dose. We focused on the optimization of the measuring procedure and investigated characteristics such as reproducibility, fading, minimum detectable dose (MDD), dose response and photon energy response of TL and OSL signals. The dental ceramic exhibited very good reproducibility (<5% at 2σ level) when measured and a linear dose response for a wide range of doses (50 mGy–20 Gy). The MDD values for the samples investigated were ∼5 mGy. The material is not tissue equivalent and the OSL and TL signals are strongly dependent on incident photon energy. Both the luminescence signals exhibited significant fading during the first few hours after irradiation. Its rate was dependent on the parameters of measurement. The results indicate that the material can be used for the purposes of accident dosimetry, however, the fading and photon energy response have to be properly corrected for a reliable dose assessment. - Highlights: ► A dental ceramic was considered as a retrospective and accident dosimeter. ► Dosimetry application was investigated using OSL and TL. ► TL and OSL signals are proportional to absorbed radiation dose. ► Accuracy is dependent on correction of fading and photon energy response

  13. Rugometric and microtopographic non-invasive inspection in dental-resin composites and zirconia ceramics

    Science.gov (United States)

    Fernández-Oliveras, Alicia; Costa, Manuel F. M.; Pecho, Oscar E.; Rubiño, Manuel; Pérez, María. M.

    2013-11-01

    Surface properties are essential for a complete characterization of biomaterials. In restorative dentistry, the study of the surface properties of materials meant to replace dental tissues in an irreversibly diseased tooth is important to avoid harmful changes in future treatments. We have experimentally analyzed the surface characterization parameters of two different types of dental-resin composites and pre-sintered and sintered zirconia ceramics. We studied two shades of both composite types and two sintered zirconia ceramics: colored and uncolored. Moreover, a surface treatment was applied to one specimen of each dental-resin. All the samples were submitted to rugometric and microtopographic non-invasive inspection with the MICROTOP.06.MFC laser microtopographer in order to gather meaningful statistical parameters such as the average roughness (Ra), the root-mean-square deviation (Rq), the skewness (Rsk), and the kurtosis of the surface height distribution (Rku). For a comparison of the different biomaterials, the uncertainties associated to the surface parameters were also determined. With respect to Ra and Rq, significant differences between the composite shades were found. Among the dental resins, the nanocomposite presented the highest values and, for the zirconia ceramics, the pre-sintered sample registered the lowest ones. The composite performance may have been due to cluster-formation variations. Except for the composites with the surface treatment, the sample surfaces had approximately a normal distribution of heights. The surface treatment applied to the composites increased the average roughness and moved the height distribution farther away from the normal distribution. The zirconia-sintering process resulted in higher average roughness without affecting the height distribution.

  14. Cytotoxicity of dental alloys, metals, and ceramics assessed by millipore filter, agar overlay, and MTT tests.

    Science.gov (United States)

    Sjögren, G; Sletten, G; Dahl, J E

    2000-08-01

    Biocompatibility of dental materials is dependent on the release of elements from the materials. In addition, the composition, pretreatment, and handling of the materials influence the element release. This study evaluated the cytotoxicity of dental alloys, metals, and ceramics, with specific emphasis on the effects of altering the composition and the pretreatment. By using cells from a mouse fibroblast cell line and the agar overlay test, Millipore filter test, and MTT test, cytotoxicity of various metals, metal alloys, and ceramics for dental restoration were studied. Effects of altering the composition of a high noble gold alloy and of pretreatment of a ceramic-bonding alloy were also studied. In addition, the release of elements into the cell culture medium by the materials studied was measured using an inductively coupled plasma optical emission spectrophotometer. The results of the MTT test were analyzed statistically using ANOVA and Scheffé test at a significance level of P filter tests. For the MTT test, no significant differences were observed between these materials and controls, with the exception of JS C-gold and unalloyed titanium. The modified materials were ranked from "mildly cytotoxic" to "moderately cytotoxic" in the agar overlay and Millipore filter tests and from "noncytotoxic" to "moderately cytotoxic" in the MTT test. Thus, cytotoxicity was related to the alloy composition and treatment. The release of Cu and Zn seemed to be important for the cytotoxic effect. Alterations in the composition and the pretreatment can greatly influence the cytotoxicity, and the results stress the importance of carefully following the manufacturers' instructions when handling dental materials.

  15. Ceramic-like wear behaviour of human dental enamel.

    Science.gov (United States)

    Arsecularatne, J A; Hoffman, M

    2012-04-01

    This paper reports a transmission electron microscopy (TEM) analysis of subsurfaces of enamel specimens following in vitro reciprocating wear tests with an enamel cusp sliding on a flat enamel specimen under hydrated conditions. The obtained results show that crack formation occurred in the wear scar subsurface. The path followed by these cracks seems to be dictated either by the histological structure of enamel or by the contact stress field. Moreover, the analysis of a set of enamel wear results obtained from the literature and application of fracture-based models, originally developed for ceramics, correlate well, confirming the similar wear processes taking place in these materials. This analysis also reveals a marked influence of coefficient of friction on the enamel wear rate: for a higher coefficient of friction value, enamel wear can be severe even under forces generated during normal operation of teeth. Copyright © 2011 Elsevier Ltd. All rights reserved.

  16. The preparation of dental glass-ceramic composites with controlled fraction of leucite crystals

    Directory of Open Access Journals (Sweden)

    Martina Mrázová

    2008-06-01

    Full Text Available This work is dealing with synthesis of leucite powder, which can be used for the preparation of dental glassceramic composites by subsequent thermal treatment. Newly developed procedure is based on preparation of dental raw material as a mixture of two separate compounds: the crystalline leucite powder prepared at relatively low temperature and a commercial matrix powder.Hydrothermal synthesis of tetragonal leucite particles (KAlSi2O6 with the average size of about 3 μm was developed in our laboratory. The leucite dental raw material was prepared by mixing of 20 wt.% of synthetic tetragonal leucite with commercial matrix. Dental composites were prepared from the dental raw material by uniaxial pressing and firing up to 960°C. Dilatometric measurements confirmed that the coefficient of thermal expansion increased by 32% when 20 wt.% of the tetragonal leucite was added into the basic matrix. In addition, it was showed that the synthesized leucite powder was suitable for the preparation of leucite composites with controlled coefficient of thermal expansion. High value of the thermal expansion coefficient enables application of prepared composite in metal-ceramics restorations.

  17. Clinical performance of IPS-Empress 2 ceramic crowns inserted by general dental practitioners.

    Science.gov (United States)

    Mansour, Yasar F; Al-Omiri, Mahmoud K; Khader, Yousef Saleh; Al-Wahadni, Ahed

    2008-05-01

    The aim of this study was to evaluate the clinical performance of IPS-Empress 2(R) all-ceramic crowns placed by general dental practitioners. Eighty-two IPS-Empress 2 crowns placed in 64 patients (27 females and 37 males) were evaluated. These crowns had been in place for 15.2 to 57.2 months (mean 25.3 months, SD=9.3). Survival analysis was conducted using the Kaplan-Meier method. Of the 82 crowns 93.9% were rated satisfactory. In terms of the integrity of the restorations, fracture was observed in three crowns and two showed a crack upon transillumination. Five crowns were rated unsatisfactory for color match; one for marginal adaptation; and none for discoloration, secondary caries, or sensitivity. IPS-Empress 2(R) is a suitable material to fabricate all-ceramic crowns; when these all-ceramic crowns were inserted by general dental practitioners, they functioned satisfactorily with low failure rates during an observation period ranging between 15.2 to 57.2 months.

  18. Effects of surface treatments on the translucency, opalescence, and surface texture of dental monolithic zirconia ceramics.

    Science.gov (United States)

    Kim, Hee-Kyung; Kim, Sung-Hun; Lee, Jai-Bong; Ha, Seung-Ryong

    2016-06-01

    Surface polishing or glazing may increase the appearance of depth of monolithic zirconia restorations. The purpose of this in vitro study was to investigate the effects of surface treatments on the translucency, opalescence, and surface texture of dental monolithic zirconia ceramics. Forty-five monolithic zirconia specimens (16.3×16.4×2.0 mm) were divided into groups I to V, according to the number of colorings each received. Each group was then divided into 3 subgroups (n=3) according to the surface treatment: N=no treatment; P=polished; and G=glazed. CIElab color coordinates were obtained relative to D65 on a reflection spectrophotometer. The translucency parameter (TP) and opalescence parameter (OP) were calculated. One specimen per subgroups I and V was selected for evaluation of surface roughness (Ra) and was examined with scanning electron microscopy (SEM). Data were analyzed with 2-way ANOVA and pairwise comparisons (α=.05). Statistical powers were verified to evaluate results (α=.05). The interaction effects of surface treatments combined with the number of colorings were significant for TP, OP, and Ra (P.05), whereas glazing significantly decreased OP and Ra in most groups. SEM images demonstrated that surface treatments affected the surface texture of monolithic zirconia ceramics. Surface treatments combined with coloring strongly affect the surface texture of dental monolithic zirconia ceramics. Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

  19. Retention of metal-ceramic crowns with contemporary dental cements.

    Science.gov (United States)

    Johnson, Glen H; Lepe, Xavier; Zhang, Hai; Wataha, John C

    2009-09-01

    New types of crown and bridge cement are in use by practitioners, and independent studies are needed to assess their effectiveness. The authors conducted a study in three parts (study A, study B, and study C) and to determine how well these new cements retain metal-ceramic crowns. The authors prepared teeth with a 20-degree taper and a 4-millimeter length. They cast high-noble metal-ceramic copings, then fitted and cemented them with a force of 196 newtons. The types of cements they used were zinc phosphate, resin-modified glass ionomer, conventional resin and self-adhesive modified resin. They thermally cycled the cemented copings, then removed them. They recorded the removal force and calculated the stress of dislodgment by using the surface area of each preparation. They used a single-factor analysis of variance to analyze the data (alpha = .05). The mean stresses necessary to remove crowns, in megapascals, were 8.0 for RelyX Luting (3M ESPE, St. Paul, Minn.), 7.3 for RelyX Unicem (3M ESPE), 5.7 for Panavia F (Kuraray America, New York) and 4.0 for Fuji Plus (GC America, Alsip, Ill.) in study A; 8.1 for RelyX Luting, 2.6 for RelyX Luting Plus (3M ESPE) and 2.8 for Fuji CEM (GC America) in study B; and 4.9 for Maxcem (Kerr, Orange, Calif.), 4.0 for BisCem (Bisco, Schaumburg, Ill.), 3.7 for RelyX Unicem Clicker (3M ESPE), 2.9 for iCEM (Heraeus Kulzer, Armonk, N.Y.) and 2.3 for Fleck's Zinc Cement (Keystone Industries, Cherry Hill, N.J.) in study C. Powder-liquid versions of new cements were significantly more retentive than were paste-paste versions of the same cements. The mean value of crown removal stress for the new self-adhesive modified-resin cements varied appreciably among the four cements tested. All cements retained castings as well as or better than did zinc phosphate cement. Powder-liquid versions of cements, although less convenient to mix, may be a better clinical choice when crown retention is an issue. All cements tested will retain castings

  20. Modeling dental radiographic systems

    International Nuclear Information System (INIS)

    Webber, R.L.

    1980-01-01

    The Bureau of Radiological Health has been actively collaborating with the Clinical Investigations Branch, NIDR, in applied research involving diagnostic use of ionizing radiation in dentistry. This work has centered on the search for alternatives to conventional radiographic systems in an attempt to improve diagnostic performance while reducing the required exposure. The basic approach involves analysis of factors limiting performance of properly defined diagnostic tasks and the modeling alternative systems with an eye toward increasing objective measures of performance. Previous collaborative work involved using a nonlinear model to compare various x-ray spectra. The data were expressed as brightness-contrast versus exposure for simulated tasks of clinical interest. This report supplements these findings by extending the number of parameters under investigation and modifying the mode of data display so that an actual radiographic image can be simulated on a television screen

  1. Determination of the slow crack growth susceptibility coefficient of dental ceramics using different methods.

    Science.gov (United States)

    Gonzaga, Carla Castiglia; Cesar, Paulo Francisco; Miranda, Walter Gomes; Yoshimura, Humberto Naoyuki

    2011-11-01

    This study compared three methods for the determination of the slow crack growth susceptibility coefficient (n) of two veneering ceramics (VM7 and d.Sign), two glass-ceramics (Empress and Empress 2) and a glass-infiltrated alumina composite (In-Ceram Alumina). Discs (n = 10) were prepared according to manufacturers' recommendations and polished. The constant stress-rate test was performed at five constant stress rates to calculate n(d) . For the indentation fracture test to determine n(IF) , Vickers indentations were performed and the crack lengths were measured under an optical microscope. For the constant stress test (performed only for d.Sign for the determination of n(s) ) four constant stresses were applied and held constant until the specimens' fracture and the time to failure was recorded. All tests were performed in artificial saliva at 37°C. The n(d) values were 17.2 for Empress 2, followed by d.Sign (20.5), VM7 (26.5), Empress (30.2), and In-Ceram Alumina (31.1). In-Ceram Alumina and Empress 2 showed the highest n(IF) values, 66.0 and 40.2, respectively. The n(IF) values determined for Empress (25.2), d.Sign (25.6), and VM7 (20.1) were similar. The n(s) value determined for d.Sign was 31.4. It can be concluded that the n values determined for the dental ceramics evaluated were significantly influenced by the test method used. 2011 Wiley Periodicals, Inc.

  2. A comparative study of progressive wear of four dental monolithic, veneered glass-ceramics.

    Science.gov (United States)

    Zhang, Zhenzhen; Yi, Yuanping; Wang, Xuesong; Guo, Jiawen; Li, Ding; He, Lin; Zhang, Shaofeng

    2017-10-01

    This study evaluated the wear performance and wear mechanisms of four dental glass-ceramics, based on the microstructure and mechanical properties in the progressive wear process. Bar (N = 40, n = 10) and disk (N = 32, n = 8) specimens were prepared from (A) lithium disilicate glass-ceramic (LD), (B) leucite reinforced glass-ceramic (LEU), (C) feldspathic glass-ceramic (FEL), and (D) fluorapatite glass-ceramic (FLU). The bar specimens were tested for three-point flexural strength, hardness, fracture toughness and elastic modulus. The disk specimens paired with steatite antagonists were tested in a pin-on-disk tribometer with 10N up to 1000,000 wear cycles. The wear analysis of glass-ceramics was performed using a 3D profilometer after every 200,000 wear cycles. Wear loss of steatite antagonists was calculated by measuring the weight and density using sensitive balance and Archimedes' method. Wear morphologies and microstructures were analyzed by scanning electron microscopy (SEM). The crystalline phase compositions were determined using X-ray diffraction (XRD). One-way analysis of variance (ANOVA) was used to analyze the data. Multiple pair-wise comparison of means was performed by Tukey's post-hoc test. LD showed the highest fracture toughness, flexural strength, elastic modulus and crystallinity, followed by LEU and FEL, and FLU showed the lowest. However, the hardness of LD was lower than all the other three types of ceramics. For steatite antagonists, LD produced the least wear loss of antagonist, followed by LEU and FEL, and FLU had the most wear loss. For glass-ceramic materials, LD exhibited similar wear loss as LEU, but more than FLU and FEL did. Moreover, fracture occurred on the wear surface of FLU. In the progressive wear process, veneering porcelains showed better wear resistance but fluorapatite veneering porcelains appeared fracture surface. Monolithic lithium disilicate glass-ceramics with higher mechanical properties showed more wear loss, however

  3. All-ceramic or metal-ceramic tooth-supported fixed dental prostheses (FDPs)? A systematic review of the survival and complication rates. Part I: Single crowns (SCs).

    Science.gov (United States)

    Sailer, Irena; Makarov, Nikolay Alexandrovich; Thoma, Daniel Stefan; Zwahlen, Marcel; Pjetursson, Bjarni Elvar

    2015-06-01

    To assess the 5-year survival of metal-ceramic and all-ceramic tooth-supported single crowns (SCs) and to describe the incidence of biological, technical and esthetic complications. Medline (PubMed), Embase, Cochrane Central Register of Controlled Trials (CENTRAL) searches (2006-2013) were performed for clinical studies focusing on tooth-supported fixed dental prostheses (FDPs) with a mean follow-up of at least 3 years. This was complimented by an additional hand search and the inclusion of 34 studies from a previous systematic review [1,2]. Survival and complication rates were analyzed using robust Poisson's regression models to obtain summary estimates of 5-year proportions. Sixty-seven studies reporting on 4663 metal-ceramic and 9434 all-ceramic SCs fulfilled the inclusion criteria. Seventeen studies reported on metal-ceramic crowns, and 54 studies reported on all-ceramic crowns. Meta-analysis of the included studies indicated an estimated survival rate of metal-ceramic SCs of 94.7% (95% CI: 94.1-96.9%) after 5 years. This was similar to the estimated 5-year survival rate of leucit or lithium-disilicate reinforced glass ceramic SCs (96.6%; 95% CI: 94.9-96.7%), of glass infiltrated alumina SCs (94.6%; 95% CI: 92.7-96%) and densely sintered alumina and zirconia SCs (96%; 95% CI: 93.8-97.5%; 92.1%; 95% CI: 82.8-95.6%). In contrast, the 5-year survival rates of feldspathic/silica-based ceramic crowns were lower (pceramic and zirconia crowns exhibited significantly lower survival rates in the posterior region (pceramic fractures than metal-ceramic SCs (pceramic SCs than for metal-ceramic SCs. Survival rates of most types of all-ceramic SCs were similar to those reported for metal-ceramic SCs, both in anterior and posterior regions. Weaker feldspathic/silica-based ceramics should be limited to applications in the anterior region. Zirconia-based SCs should not be considered as primary option due to their high incidence of technical problems. Copyright © 2015 Academy

  4. Fifteen-year survival of anterior all-ceramic cantilever resin-bonded fixed dental prostheses.

    Science.gov (United States)

    Kern, Matthias

    2017-01-01

    The aim of this follow-up study was to report the long-term outcome of all-ceramic cantilever resin-bonded fixed dental prostheses (RBFDPs). In 16 patients (mean age of 33.3±17.5years) 22 RBFDPs made from a glass-infiltrated alumina ceramic (In-Ceram) were inserted with a phosphate monomer containing luting agent after air-abrasion of the retainer wings. The abutment preparation included a shallow groove on the cingulum and a small proximal box. The restorations replacing 16 maxillary and 6 mandibular incisors were followed over a mean observation time of 188.7 months. No restoration debonded. Two RBFDPs fractured and were lost 48 and 214 months after insertion, respectively. The 10-year and 15-year survival rates were both 95.4% and dropped to 81.8% after 18 years. Anterior all-ceramic cantilever RBFDPs exhibited an excellent clinical longevity. Copyright © 2016 Elsevier Ltd. All rights reserved.

  5. [The effect of core veneer thickness ratio on the flexural strength of diatomite-based dental ceramic].

    Science.gov (United States)

    Jiang, Jie; Zhang, Xin; Gao, Mei-qin; Zhang, Fei-min; Lu, Xiao-li

    2015-06-01

    To evaluate the effect of different core veneer thickness ratios on the flexural strength and failure mode of bilayered diatomite-based dental ceramics. Diatomite-based dental ceramics blocks (16 mm×5.4 mm×1 mm) were sintered with different thickness of veneer porcelains: 0 mm (group A), 0.6 mm (group B), 0.8 mm (group C) and 1.0 mm (group D). Flexural strength was detected and scanning electron microscope was used to observe the interface microstructure. Statistical analysis was performed using SPSS 17.0 software package. With the increase of the thickness of the veneer porcelain, flexural strength of group C showed highest flexural strength up to (277.24±5.47) MPa. Different core veneer thickness ratios can significantly influence the flexural strength of bilayered diatomite-based dental ceramics. Supported by Science and Technology Projects of Nantong City (HS2013010).

  6. Mechanochemically synthesized kalsilite based bioactive glass-ceramic composite for dental vaneering

    Science.gov (United States)

    Kumar, Pattem Hemanth; Singh, Vinay Kumar; Kumar, Pradeep

    2017-08-01

    Kalsilite glass-ceramic composites have been prepared by a mechanochemical synthesis process for dental veneering application. The aim of the present study is to prepare bioactive kalsilite composite material for application in tissue attachment and sealing of the marginal gap between fixed prosthesis and tooth. Mechanochemical synthesis is used for the preparation of microfine kalsilite glass-ceramic. Low temperature frit and bioglass have been prepared using the traditional quench method. Thermal, microstructural and bioactive properties of the composite material have been examined. The feasibility of the kalsilite to be coated on the base commercial opaque as well as the bioactive behavior of the coated specimen has been confirmed. This study indicates that the prepared kalsilite-based composites show similar structural, morphological and bioactive behavior to that of commercial VITA VMK95 Dentin 1M2.

  7. Fabrication of Silicon Nitride Dental Core Ceramics with Borosilicate Veneering material

    Energy Technology Data Exchange (ETDEWEB)

    Wananuruksawong, R; Jinawath, S; Wasanapiarnpong, T [Research Unit of Advanced Ceramic, Department of Materials Science, Faculty of Science, Chulalongkorn University, Bangkok (Thailand); Padipatvuthikul, P, E-mail: raayaa_chula@hotmail.com [Faculty of Dentistry, Srinakharinwirot University, Bangkok (Thailand)

    2011-10-29

    Silicon nitride (Si{sub 3}N{sub 4}) ceramic is a great candidate for clinical applications due to its high fracture toughness, strength, hardness and bio-inertness. This study has focused on the Si{sub 3}N{sub 4} ceramic as a dental core material. The white Si{sub 3}N{sub 4} was prepared by pressureless sintering at relative low sintering temperature of 1650 deg. C in nitrogen atmosphere. The coefficient of thermal expansion (CTE) of Si{sub 3}N{sub 4} ceramic is lower than that of Zirconia and Alumina ceramic which are popular in this field. The borosilicate glass veneering was employed due to its compatibility in thermal expansion. The sintered Si{sub 3}N{sub 4} specimens represented the synthetic dental core were paintbrush coated by a veneer paste composed of borosilicate glass powder (<150 micrometer, Pyrex) with 5 wt% of zirconia powder (3 wt% Y{sub 2}O{sub 3} - partial stabilized zirconia) and 30 wt% of polyvinyl alcohol (5 wt% solution). After coating the veneer on the Si{sub 3}N{sub 4} specimens, the firing was performed in electric tube furnace between 1000-1200 deg. C. The veneered specimens fired at 1100 deg. C for 15 mins show good bonding, smooth and glossy without defect and crazing. The veneer has thermal expansion coefficient as 3.98x10{sup -6} deg. C{sup -1}, rather white and semi opaque, due to zirconia addition, the Vickers hardness as 4.0 GPa which is closely to the human teeth.

  8. Translucence in dental prosthesis based on zirconia ceramics: effect of the sintering parameters

    International Nuclear Information System (INIS)

    Santos, C.

    2011-01-01

    In this work the translucence of Zirconia dental ceramics was evaluated as function of sintering conditions (temperature and isothermal holding time). Samples with 15x15x1mm, were sintered at 1450 to 1600 deg C, with holding of 2h or 4h. Sintered samples were characterized by relative density, crystalline phases and microstructural aspects. Full density was obtained in samples sintered at 1530 and 1600 deg C, which presented higher grain sizes. Na increasing of translucence was observed in samples sintered at 1530 and 1600, correlating these properties with increasing of density and grain size of the samples. (author)

  9. Static and fatigue mechanical behavior of three dental CAD/CAM ceramics.

    Science.gov (United States)

    Homaei, Ehsan; Farhangdoost, Khalil; Tsoi, James Kit Hon; Matinlinna, Jukka Pekka; Pow, Edmond Ho Nang

    2016-06-01

    The aim of this study was to measure the mechanical properties and fatigue behavior of three contemporary used dental ceramics, zirconia Cercon(®) (ZC), lithium disilicate e.max(®) CAD (LD), and polymer-infiltrated ceramic Enamic(®) (PIC). Flexural strength of each CAD/CAM ceramic was measured by three point bending (n=15) followed by Weibull analysis. Elastic modulus was calculated from the load-displacement curve. For cyclic fatigue loading, sinusoidal loading with a frequency of 8Hz with minimum load 3N were applied to these ceramics (n=24) using three point bending from 10(3) to 10(6) cycles. Fatigue limits of these ceramics were predicted with S-N fatigue diagram. Fracture toughness and Vickers hardness of the ceramics were measured respectively by single edge V-notch beam (SEVNB) and microindentation (Hv 0.2) methods. Chemical compositions of the materials׳ surfaces were analyzed by EDS, and microstructural analysis was conducted on the fracture surfaces by SEM. One-way ANOVA was performed and the level of significance was set at 0.05 to analyze the numerical results. The mean flexural strength of ZC, LD, and PIC was respectively 886.9, 356.7, and 135.8MPa. However, the highest Weibull modulus belonged to PIC with 19.7 and the lowest was found in LD with 7.0. The fatigue limit of maximum load for one million cycles of ZC, LD, and PIC was estimated to be 500.1, 168.4, and 73.8GPa. The mean fracture toughness of ZC, LD, and PIC was found to be respectively 6.6, 2.8, and 1.4MPam(1/2), while the mean Vickers hardness was 1641.7, 676.7, and 261.7Hv. Fracture surfaces followed fatigue loading appeared to be smoother than that after monotonic loading. Mechanical properties of ZC were substantially superior to the two other tested ceramics, but the scattering of data was the least in PIC. The fatigue limit was found to be approximately half of the mean flexural strength for all tested ceramics. Copyright © 2016 Elsevier Ltd. All rights reserved.

  10. Characterization of the bioactive and mechanical behavior of dental ceramic/sol-gel derived bioactive glass mixtures.

    Science.gov (United States)

    Abbasi, Zahra; Bahrololoum, Mohammad E; Bagheri, Rafat; Shariat, Mohammad H

    2016-02-01

    Dental ceramics can be modified by bioactive glasses in order to develop apatite layer on their surface. One of the benefits of such modification is to prolong the lifetime of the fixed dental prosthesis by preventing the formation of secondary caries. Dental ceramic/sol-gel derived bioactive glass mixture is one of the options for this modification. In the current study, mixtures of dental ceramic/bioactive glass with different compositions were successfully produced. To evaluate their bioactive behavior, prepared samples were immersed in a simulated body fluid at various time intervals. The prepared and soaked specimens were characterized using Fourier transform infrared spectroscopy, X-ray diffractometry and scanning electron microscopy. Since bioactive glasses have deleterious effects on the mechanical properties of dental ceramics, 3-point bending tests were used to evaluate the flexural strength, flexural strain, tangent modulus of elasticity and Weibull modulus of the specimens in order to find the optimal relationship between mechanical and bioactive properties. Copyright © 2015 Elsevier Ltd. All rights reserved.

  11. Impact of Gastric Acid Induced Surface Changes on Mechanical Behavior and Optical Characteristics of Dental Ceramics.

    Science.gov (United States)

    Kulkarni, Aditi; Rothrock, James; Thompson, Jeffery

    2018-01-14

    To test the impact of exposure to artificial gastric acid combined with toothbrush abrasion on the properties of dental ceramics. Earlier research has indicated that immersion in artificial gastric acid has caused increased surface roughness of dental ceramics; however, the combined effects of acid immersion and toothbrush abrasion and the impact of increased surface roughness on mechanical strength and optical properties have not been studied. Three commercially available ceramics were chosen for this study: feldspathic porcelain, lithium disilicate glass-ceramic, and monolithic zirconium oxide. The specimens (10 × 1 mm discs) were cut, thermally treated as required, and polished. Each material was divided into four groups (n = 8 per group): control (no exposure), acid only, brush only, acid + brush. The specimens were immersed in artificial gastric acid (50 ml of 0.2% [w/v] sodium chloride in 0.7% [v/v] hydrochloric acid mixed with 0.16 g of pepsin powder, pH = 2) for 2 minutes and rinsed with deionized water for 2 minutes. The procedure was repeated 6 times/day × 9 days, and specimens were stored in deionized water at 37°C. Toothbrush abrasion was performed using an ISO/ADA design brushing machine for 100 cycles/day × 9 days. The acid + brush group received both treatments. Specimens were examined under SEM and an optical microscope for morphological changes. Color and translucency were measured using spectrophotometer CIELAB coordinates (L*, a*, b*). Surface gloss was measured using a gloss meter. Surface roughness was measured using a stylus profilometer. Biaxial flexural strength was measured using a mechanical testing machine. The data were analyzed by one-way ANOVA followed by Tukey's HSD post hoc test (p gloss, and surface roughness for porcelain and e.max specimens. No statistically significant changes were found for any properties of zirconia specimens. The acid treatment affected the surface roughness, color, and gloss of porcelain and e

  12. Wear properties of dental ceramics and porcelains compared with human enamel.

    Science.gov (United States)

    D'Arcangelo, Camillo; Vanini, Lorenzo; Rondoni, Giuseppe D; De Angelis, Francesco

    2016-03-01

    Contemporary pressable and computer-aided design/manufacturing (CAD/CAM) ceramics exhibit good mechanical and esthetic properties. Their wear resistance compared with human enamel and traditional gold based alloys needs to be better investigated. The purpose of this in vitro study was to compare the 2-body wear resistance of human enamel, gold alloy, and 5 different dental ceramics, including a recently introduced zirconia-reinforced lithium silicate ceramic (Celtra Duo). Cylindrical specimens were fabricated from a Type III gold alloy (Aurocast8), 2 hot pressed ceramics (Imagine PressX, IPS e.max Press), 2 CAD/CAM ceramics (IPS e.max CAD, Celtra Duo), and a CAD/CAM feldspathic porcelain (Vitablocs Mark II) (n=10). Celtra Duo was tested both soon after grinding and after a subsequent glaze firing cycle. Ten flat human enamel specimens were used as the control group. All specimens were subjected to a 2-body wear test in a dual axis mastication simulator for 120000 loading cycles against yttria stabilized tetragonal zirconia polycrystal cusps. The wear resistance was analyzed by measuring the vertical substance loss (mm) and the volume loss (mm(3)). Antagonist wear (mm) was also recorded. Data were statistically analyzed with 1-way ANOVA tests (α=.05). The wear depth (0.223 mm) of gold alloy was the closest to that of human enamel (0.217 mm), with no significant difference (P>.05). The greatest wear was recorded on the milled Celtra Duo (wear depth=0.320 mm), which appeared significantly less wear resistant than gold alloy or human enamel (Pceramics did not statistically differ in comparison with the human enamel. Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

  13. Novel, Ceramic Membrane System For Hydrogen Separation

    Energy Technology Data Exchange (ETDEWEB)

    Elangovan, S.

    2012-12-31

    Separation of hydrogen from coal gas represents one of the most promising ways to produce alternative sources of fuel. Ceramatec, teamed with CoorsTek and Sandia National Laboratories has developed materials technology for a pressure driven, high temperature proton-electron mixed conducting membrane system to remove hydrogen from the syngas. This system separates high purity hydrogen and isolates high pressure CO{sub 2} as the retentate, which is amenable to low cost capture and transport to storage sites. The team demonstrated a highly efficient, pressure-driven hydrogen separation membrane to generate high purity hydrogen from syngas using a novel ceramic-ceramic composite membrane. Recognizing the benefits and limitations of present membrane systems, the all-ceramic system has been developed to address the key technical challenges related to materials performance under actual operating conditions, while retaining the advantages of thermal and process compatibility offered by the ceramic membranes. The feasibility of the concept has already been demonstrated at Ceramatec. This project developed advanced materials composition for potential integration with water gas shift rectors to maximize the hydrogenproduction.

  14. Synthesis and characterization of wollastonite glass-ceramics for dental implant applications.

    Science.gov (United States)

    Saadaldin, Selma A; Rizkalla, Amin S

    2014-03-01

    To synthesize a glass-ceramic (GC) that is suitable for non-metallic one-piece dental implant application. Three glasses in a SiO2-Al2O3-CaO-CaF2-K2O-B2O3-P2O5-CeO2-Y2O3 system were produced by wet chemistry. Differential thermal analysis (DTA) was carried out to determine the glass crystallization kinetic parameters and the heating schedules that were used for sintering of GCs. Crystalline phases and crystal morphologies were studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. Mechanical properties of the GCs were determined by ultrasonic and indentation tests and its machinability were evaluated. Chemical durability was carried out according to ISO 6872, whereas testing chemical degradation in tris buffered solution was executed according to ISO 10993-14. XRD of the GC specimens showed that wollastonite was the main crystalline with other secondary phases; GC2 had cristobalite as an additional phase. SEM of the GCs revealed dense acicular interlocking crystals. Young's modulus of elasticity (E), true hardness (Ho) and fracture toughness (KIC) of the GCs were 89-100GPa, 4.85-5.17GPa and 4.62-5.58MPam(0.5), respectively. All GCs were demonstrated excellent machinability. The GCs exhibited various chemical durability and degradation rates. KIC values of the GCs following chemical durability testing were not significantly different from those of the original materials (p>0.05). GC2 exhibited significantly higher KIC value compared with GC1 and GC3 (pmachinability and chemical durability. Copyright © 2014. Published by Elsevier Ltd.

  15. Ceramic and polymeric dental onlays evaluated by photo-elasticity, optical coherence tomography, and micro-computed tomography

    Science.gov (United States)

    Sinescu, Cosmin; Negrutiu, Meda; Topala, Florin; Ionita, Ciprian; Negru, Radu; Fabriky, Mihai; Marcauteanu, Corina; Bradu, Adrian; Dobre, George; Marsavina, Liviu; Rominu, Mihai; Podoleanu, Adrian

    2011-10-01

    Dental onlays are restorations used to repair rear teeth that have a mild to moderate amount of decay. They can also be used to restore teeth that are cracked or fractured if the damage is not severe enough to require a dental crown. The use of onlays requires less tooth reduction than does the use of metal fillings. This allows dentists to conserve more of a patient's natural tooth structure in the treatment process. The aims of this study are to evaluate the biomechanical comportment of the dental onlays, by using the 3D photo elasticity method and to investigate the integrity of the structures and their fitting to the dental support. For this optical coherence tomography and micro-computed tomography were employed. Both methods were used to investigate 37 dental onlays, 17 integral polymeric and 20 integral ceramic. The results permit to observe materials defects inside the ceramic or polymeric onlays situate in the biomechanically tensioned areas that could lead to fracture of the prosthetic structure. Marginal fitting problems of the onlays related to the teeth preparations were presented in order to observe the possibility of secondary cavities. The resulted images from the optical coherence tomography were verified by the micro-computed tomography. In conclusion, the optical coherence tomography can be used as a clinical method in order to evaluate the integrity of the dental ceramic and polymeric onlays and to investigate the quality of the marginal fitting to the teeth preparations.

  16. Influence of Resin Cements on Color Stability of Different Ceramic Systems.

    Science.gov (United States)

    Rodrigues, Renata Borges; Lima, Erick de; Roscoe, Marina Guimarães; Soares, Carlos José; Cesar, Paulo Francisco; Novais, Veridiana Resende

    2017-01-01

    The purpose of this study was to evaluate color stability of two dental ceramics cemented with two resin cements, assessing the color difference (ΔE00) by the measurement of L*, a*, b*, c* and h* of transmittance. The combination of two ceramic system (feldspathic and lithium disilicate) and two resin cements - color A3 (RelyX ARC and Variolink II) resulted in 4 groups (n=5). Ten disks-shaped specimens were fabricated for each ceramic system (10x1.5 mm), etched with hydrofluoric acid (10%) and silanized prior to cementation. The color analysis was performed 24 h after cementation of the samples and after 6 months of storage in relative humidity by means of spectrophotometry. The ΔE00 values were analyzed statistically by two-way ANOVA followed by the Tukey test (p<0.05). One-way ANOVA were calculated for the means of individual color coordinates (L*, a*, b*, c* and h*). Two-way ANOVA showed that only the ceramic factor was significant (p=0.003), but there was no difference for the cement factor (p=0.275) nor for the ceramic/cement interaction (p=0.161). The feldspathic ceramic showed the highest values of ΔE00. Variations in L*, a*, b*, c* and h* were more significant for feldspathic ceramic. In conclusion, storage alters similarly the optical properties of the resin cements and feldspathic porcelain was more susceptible to cement color change after aging.

  17. Study of TSL and OSL properties of dental ceramics for accidental dosimetry applications

    International Nuclear Information System (INIS)

    Veronese, Ivan; Galli, Anna; Cantone, Marie Claire; Martini, Marco; Vernizzi, Fabrizio; Guzzi, Gianpaolo

    2010-01-01

    Interest is increasing in the development of new methodologies for accidental dose assessment, exploiting the luminescence and dosimetric properties of objects and materials which can be usually found directly on exposed subjects and/or in the contaminated area. In this work, several types of ceramics employed for dental prosthetics restoration, including both innovative materials used as sub-frames for the construction of the inner part of dental crowns (core), and conventional porcelains used for the fabrication of the external layer (veneer), were investigated with regard to their thermally and optically stimulated luminescence (TSL and OSL respectively) properties, in view of their potential application in accidental dosimetry. The sensitivity to ionizing radiation proved to strongly depend on the type and brand of ceramic, with minimum detectable dose ranging from few mGy up to several tens of mGy. A linear dose-response was observed for most of the samples. However, the luminescence signals were characterised by a significant fading, which has to be taken into account for a reliable accidental dose assessment after a radiation exposure event.

  18. [Effect of compaction pressure on the properties of dental machinable zirconia ceramic].

    Science.gov (United States)

    Huang, Hui; Wei, Bin; Zhang, Fu-qiang; Sun, Jing; Gao, Lian

    2010-10-01

    To investigate the effect of compaction pressure on the linear shrinkage, sintering property and machinability of the dental zirconia ceramic. The nano-size zirconia powder was compacted at different isostatic pressure and sintered at different temperature. The linear shrinkage of sintered body was measured and the relative density was tested using the Archimedes method. The cylindrical surface of pre-sintering blanks was traversed using a hard metal tool. Surface and edge quality were checked visually using light stereo microscopy. The sintering behaviour depended on the compaction pressure. Increasing compaction pressure led to higher sintering rate and lower sintering temperature. Increasing compaction pressure also led to decreasing linear shrinkage of the sintered bodies, from 24.54% of 50 MPa to 20.9% of 400 MPa. Compaction pressure showed only a weak influence on machinability of zirconia blanks, but the higher compaction pressure resulted in the poor surface quality. The better sintering property and machinability of dental zirconia ceramic is found for 200-300 MPa compaction pressure.

  19. Functional and Esthetic Comparison of Metal-Ceramic and All-Ceramic Posterior Three-Unit Fixed Dental Prostheses.

    Science.gov (United States)

    Nicolaisen, Maj H; Bahrami, Golnosh; Schropp, Lars; Isidor, Flemming

    2016-01-01

    The aim of this study was to assess functional and esthetic satisfaction plus evaluate changes in oral health-related quality of life (OHRQoL) using the Oral Health Impact Profile (OHIP-14) after insertion of a metal-ceramic (MC-FDP) or a veneered zirconia all-ceramic (AC-FDP) posterior three-unit fixed dental prosthesis (FDP). Additionally, patients' and professionals' esthetic evaluations were compared. A convenience sample of 34 patients was randomized to receive a MC-FDP (n = 17) or an AC-FDP (n = 17). Patients were assessed using the OHIP-14 and also answered a questionnaire regarding satisfaction with function and esthetics using visual analog scales (VAS) before treatment and after 2 weeks, after 3 months, and after 1, 2, and 3 years. A fully dentate control group (n = 20) was also assessed using the OHIP-14. The operator and another observer evaluated the esthetics of the FDPs using VAS. The patients assessed the two FDP types similarly for all parameters. In contrast, there was a statistically significant difference in OHIP-14 results between the treated patients and the control group before treatment. After treatment, a statistically significant improvement in OHIP-14 was observed at all examinations. Patients were highly satisfied with the function and esthetics of the FDPs. The overall satisfaction with esthetics was statistically significantly higher among the patients than among the professionals at three out of five examinations. The patients experienced improved OHRQoL and increased satisfaction with function and esthetics after receiving a posterior three-unit FDP. No important differences were observed between the two types of FDPs when evaluated by the patient or the professionals.

  20. Utilization of dental health services by Danish adolescents attending private or public dental health care systems

    DEFF Research Database (Denmark)

    Christensen, Lisa Bøge; Petersen, Poul Erik; Bastholm, Annelise

    2002-01-01

    The objectives of the study were: 1) to describe the choice of dental care system among 16-year-olds, 2) to describe the utilization of dental services among 16-17-year-olds enrolled in either public or private dental care systems, and to compare the dental services provided by the alternative...

  1. Current all-ceramic systems in dentistry: a review.

    Science.gov (United States)

    Santos, Maria Jacinta M C; Costa, Max Dorea; Rubo, José H; Pegoraro, Luis Fernando; Santos, Gildo C

    2015-01-01

    This article describes the ceramic systems and processing techniques available today in dentistry. It aims to help clinicians understand the advantages and disadvantages of a myriad of ceramic materials and technique options. The microstructural components, materials' properties, indications, and names of products are discussed to help clarify their use. Key topics will include ceramics, particle-filled glasses, polycrystalline ceramics, CAD/CAM, and adhesive cementation.

  2. The influence of silane evaporation procedures on microtensile bond strength between a dental ceramic and a resin cement

    Directory of Open Access Journals (Sweden)

    Pereira Carolina

    2010-01-01

    Full Text Available Aim: To assess the influence of silane evaporation procedures on bond strength between a dental ceramic and a chemically activated resin cement. Materials and Methods: Eighteen blocks (6 mm Χ 14 mm Χ 14 mm of ceramic IPS Empress 2 were cemented (C and B to composite resin (InTen-S blocks using a chemical adhesive system (Lok. Six groups were analyzed, each with three blocks divided according to ceramic surface treatment: two control groups (no treatment, NT; 10% hydrofluoric acid plus silane Monobond-S dried at room temperature, HFS; the other four groups comprised different evaporation patterns (silane rinsed and dried at room temperature, SRT; silane rinsed in boiling water and dried as before, SBRT; silane rinsed with boiling water and heat dried at 50°C, SBH; silane dried at 50 ± 5°C, rinsed in boiling water and dried at room temperature, SHBRT. The cemented blocks were sectioned to obtain specimens for microtensile test 7 days after cementation and were stored in water for 30 days prior to testing. Fracture patterns were analyzed by optical and scanning electron microscopy. Statistics and Results: All blocks of NT debonded during sectioning. One way ANOVA tests showed higher bond strengths for HFS than for the other groups. SBRT and SBH were statistically similar, with higher bond strengths than SRT and SHBRT. Failures were 100% adhesive in SRT and SHBRT. Cohesive failures within the "adhesive zone" were detected in HFS (30%, SBRT (24% and SBH (40%. Conclusion: Silane treatment enhanced bond strength in all conditions evaluated, showing best results with HF etching.

  3. Processing and properties of ceramic matrix-polymer composites for dental applications

    Science.gov (United States)

    Huang, Hsuan Yao

    The basic composite structure of natural hard tissue was used to guide the design and processing of dental restorative materials. The design incorporates the methodology of using inorganic minerals as the main structural phase reinforced with a more ductile but tougher organic phase. Ceramic-polymer composites were prepared by slip casting a porous ceramic structure, heating and chemical treating the porous preform, infiltrating with monomer and then curing. The three factors that determined the mechanical properties of alumina-polymer composites were the type of polymer used, the method of silane treatments, and the type of bond between particles in the porous preforms. Without the use of silane coupling agents, the composites were measured to have a lower strength. The composite with a more "flexible" porous alumina network had a greater ability to plastically dissipate the energy of propagating cracks. However, the aggressive nature of the alumina particles on opposing enamel requires that these alumina-polymer composites have a wear compatible coating for practical application. A route to dense bioactive apatite wollastonite glass ceramics (AWGC)-polymer composites was developed. The problems associated with glass dissolution into the aqueous medium for slip casting were overcome with the use of silane. The role of heating rate and development of ceramic compact microstructure on composite properties was explored. In general, if isothermal heating was not applied, decreasing heating rate increased glass crystallinity and particle-particle fusion, but decreased pore volume. Also composite strength and fracture toughness decreased while modulus and hardness increased with decreasing heating rate. If isothermal heating was applied, glass crystallinity, pore content, and composite mechanical properties showed relatively little change regardless of the initial heating rate. The potential of AWGC-polymer composites for dental and implant applications was explored

  4. Influence of different surface treatments on the fracture toughness of a commercial ZTA dental ceramic

    Directory of Open Access Journals (Sweden)

    Flavio Teixeira da Silva

    2007-03-01

    Full Text Available The objective of this study was to investigate how mechanical surface treatments performed for removal of excess of molten glass, influence the fracture toughness of a dental zirconia toughened alumina (In-Ceram® Zirconia. Infiltrated ZTA disks were submitted to three different surface treatments (grinding, sandblasting and grinding + sandblasting + annealing. Fracture toughness was accessed through indentation strength test (IS. X ray diffraction was used to investigate the metastability of tetragonal zirconia particles under all treatments proposed. Kruskall-Wallis non-parametrical test and Weibull statistics were used to analyze the results. Grinding (group 1 introduced defects which decreased the fracture toughness and reliability, presenting the lowest K IC. On the other hand, grinding followed by sandblasting and annealing (group 3 presented the highest K IC. Sandblasting (group 2 presented the highest reliability but lower K IC compared to group 3.

  5. The effect of TiO2 concentration on properties of apatite-mullite glass-ceramics for dental use.

    Science.gov (United States)

    Fathi, Hawa M; Johnson, Anthony

    2016-02-01

    The aim of this study was to evaluate the effect of TiO2 concentration on the properties of apatite-mullite glass-ceramics namely strength and the chemical solubility to comply with the ISO standard recommendations for dental ceramics (BS EN ISO 6872-2008). Ten novel glass-ceramic materials were produced based on the general formula (4.5SiO2-3Al2O3-1.5P2O5-3CaO-CaF2-xTiO2) where x varied from 0.5 to 5 wt%. Glass with no TiO2 added (HG1T0.0) was used as a reference. Discs of 12 mm diameter and 1.6 mm (±0.2 mm) thickness were prepared for both biaxial flexural strength (BFS) and chemical solubility testing, in accordance with the BS EN ISO 6872-2008 for dental ceramics. All produced materials were investigated using differential thermal analysis (DTA), X-ray diffraction (XRD), and scanning electron microscopy (SEM). Energy dispersive X-ray analysis (EDS) was also carried out on some samples to identify the element composition of samples. Increasing the concentration of TiO2 from 0.5 wt% to 2 wt% significantly (Pceramic only up to 2.5 wt% concentration. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  6. Disilicate Dental Ceramic Surface Preparation by 1070 nm Fiber Laser: Thermal and Ultrastructural Analysis

    Directory of Open Access Journals (Sweden)

    Carlo Fornaini

    2018-01-01

    Full Text Available Lithium disilicate dental ceramic bonding, realized by using different resins, is strictly dependent on micro-mechanical retention and chemical adhesion. The aim of this in vitro study was to investigate the capability of a 1070 nm fiber laser for their surface treatment. Samples were irradiated by a pulsed fiber laser at 1070 nm with different parameters (peak power of 5, 7.5 and 10 kW, repetition rate (RR 20 kHz, speed of 10 and 50 mm/s, and total energy density from 1.3 to 27 kW/cm2 and the thermal elevation during the experiment was recorded by a fiber Bragg grating (FBG temperature sensor. Subsequently, the surface modifications were analyzed by optical microscope, scanning electron microscope (SEM, and energy dispersive X-ray spectroscopy (EDS. With a peak power of 5 kW, RR of 20 kHz, and speed of 50 mm/s, the microscopic observation of the irradiated surface showed increased roughness with small areas of melting and carbonization. EDS analysis revealed that, with these parameters, there are no evident differences between laser-processed samples and controls. Thermal elevation during laser irradiation ranged between 5 °C and 9 °C. A 1070 nm fiber laser can be considered as a good device to increase the adhesion of lithium disilicate ceramics when optimum parameters are considered.

  7. Three-unit posterior zirconia-ceramic fixed dental prostheses (FDPs) veneered with layered and milled (CAD-on) veneering ceramics: 1-year follow-up of a randomized controlled clinical trial.

    Science.gov (United States)

    Grohmann, Philipp; Bindl, Andreas; Hämmerle, Christoph; Mehl, Albert; Sailer, Irena

    2015-01-01

    The aim of this multicenter randomized controlled clinical trial was to test posterior zirconia-ceramic fixed dental prostheses (FDPs) veneered with a computer-aided design/computer- assisted manufacture (CAD/CAM) lithium disilicate veneering ceramic (CAD-on) and manually layered zirconia veneering ceramic with respect to survival of the FDPs, and technical and biologic outcomes. Sixty patients in need of one posterior three-unit FDP were included. The zirconia frameworks were produced with a CAD/CAM system (Cerec inLab 3D/Cerec inEOS inLab). Thirty FDPs were veneered with a CAD/CAM lithium disilicate veneering ceramic (Cad-on) (test) and 30 were veneered with a layered zirconia veneering ceramic (control). For the clinical evaluation at baseline, 6, and 12 months, the United States Public Health Service (USPHS) criteria were used. The biologic outcome was judged by comparing the plaque control record (PCR), bleeding on probing (BOP), and probing pocket depth (PPD). Data were statistically analyzed. Fifty-six patients were examined at a mean follow-up of 13.9 months. At the 1-year follow-up the survival rate was 100% in the test and in the control group. No significant differences of the technical outcomes occurred. Major chipping occurred in the control group (n = 3) and predominantly minor chipping in the test group (minor n = 2, major n = 1). No biologic problems or differences were found. Both types of zirconia-ceramic FDPs exhibited very good clinical outcomes without differences between groups. Chipping occurred in both types of FDPs at small amounts, yet the extension of the chippings differed. The test FDPs predominantly exhibited minor chipping, the control FDPs major chipping.

  8. Structure, mechanical and thermal behaviour of mixtures of polyester resin and dental ceramic waste

    Science.gov (United States)

    Peña Rodríguez, G.; Martínez Maldonado, L.; Dulce Moreno, H. J.

    2016-02-01

    The tensile strength and bending strength, structure and thermal behaviour of mixtures of polyester resin (P-2000) and powders (ASTM sieve 200, dental ceramic wastes (dentals impressions, alginate and gypsum) was reported. The samples consisted of mixtures with percentage weights of 50-50%, 60-40%, 70-30%, 80-20%, 90-10%, where the resin was the majority phase, the Mekc (4% wt) was used as catalyst. The structure was studied using SEM and XRD, the thermal behaviour using DSC, TGA and DMA, while the mechanical strength was tested using standards ASTM D790 and D638. Irregular morphology and presence of small agglomerations was observed, with particle sizes between 29.63 and 38.67μm, the presence of different phases of calcium sulphate was found, and that to the increasing the concentration of the powder, the materials becomes more crystalline, increasing its density. An average service temperature of 69.15±4.60°C was found. Vickers hardness values are reported in ranges from 18.65 to 27.96. Considering the elastic modules was established that the materials become more rigid by having more powder concentration.

  9. Characterisation and Properties of Lithium Disilicate Glass Ceramics in the SiO2-Li2O-K2O-Al2O3 System for Dental Applications

    Directory of Open Access Journals (Sweden)

    Naruporn Monmaturapoj

    2013-01-01

    Full Text Available This work proposes four different glass formulas derived from the SiO2-Li2O-K2O-Al2O3 system to investigate the effect of glass composition on their crystal formations and properties. Glass LD1 was SiO2-Li2O-K2O-Al2O3 system with the addition of P2O5 and CaF2 as nucleating agents. In Glass LD2, a slight amount of MgO was mixed in order to increase the viscosity of the melting glass. Finally, the important factor of Si : Li ratio was increased in Glasses LD3 and LD4 with compositions otherwise the same as LD1 and LD2. The results found that P2O5 and CaF2 served as a nucleating site for lithium phosphate and fluorapatite to encourage heterogenous nucleation and produce a fine-grained interlocking microstructure of lithium disilicate glass ceramics. MgO content in this system seemed to increase the viscosity of the melting glass and thermal expansion coefficient including the chemical solubility. Increasing the Si : Li ratio in glass compositions resulted in the change of the microstructure of Li2Si2O5 crystals.

  10. Effects of surface treatment on bond strength between dental resin agent and zirconia ceramic

    Energy Technology Data Exchange (ETDEWEB)

    Moradabadi, Ashkan [Department of Electrochemistry, Universität Ulm, Ulm (Germany); Roudsari, Sareh Esmaeily Sabet [Department of Optoelectonics, Universität Ulm, Ulm (Germany); Yekta, Bijan Eftekhari [School of Materials Engineering, Iran University of Science and Technology, Tehran (Iran, Islamic Republic of); Rahbar, Nima, E-mail: nrahbar@wpi.edu [Department of Civil and Environmental Engineering, Worcester Polytechnic Institute, Worcester, MA 01609 (United States)

    2014-01-01

    This paper presents the results of an experimental study to understand the dominant mechanism in bond strength between dental resin agent and zirconia ceramic by investigating the effects of different surface treatments. Effects of two major mechanisms of chemical and micromechanical adhesion were evaluated on bond strength of zirconia to luting agent. Specimens of yttrium-oxide-partially-stabilized zirconia blocks were fabricated. Seven groups of specimens with different surface treatment were prepared. 1) zirconia specimens after airborne particle abrasion (SZ), 2) zirconia specimens after etching (ZH), 3) zirconia specimens after airborne particle abrasion and simultaneous etching (HSZ), 4) zirconia specimens coated with a layer of a Fluorapatite-Leucite glaze (GZ), 5) GZ specimens with additional acid etching (HGZ), 6) zirconia specimens coated with a layer of salt glaze (SGZ) and 7) SGZ specimens after etching with 2% HCl (HSGZ). Composite cylinders were bonded to airborne-particle-abraded surfaces of ZirkonZahn specimens with Panavia F2 resin luting agent. Failure modes were examined under 30 × magnification and the effect of surface treatments was analyzed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). SZ and HSZ groups had the highest and GZ and SGZ groups had the lowest mean shear bond strengths among all groups. Mean shear bond strengths were significantly decreased by applying a glaze layer on zirconia surfaces in GZ and SGZ groups. However, bond strengths were improved after etching process. Airborne particle abrasion resulted in higher shear bond strengths compared to etching treatment. Modes of failure varied among different groups. Finally, it is concluded that micromechanical adhesion was a more effective mechanism than chemical adhesion and airborne particle abrasion significantly increased mean shear bond strengths compared with another surface treatments. - Highlights: • Understanding the dominant mechanism of bonding

  11. Three-Point Bending Tests of Zirconia Core/Veneer Ceramics for Dental Restorations

    Directory of Open Access Journals (Sweden)

    Massimo Marrelli

    2013-01-01

    Full Text Available Introduction. The mechanical strength and the surface hardness of commercially available yttrium-doped zirconia were investigated. Furthermore, a comparative study of eight different ceramic veneers, to be used for the production of two-layered all-ceramic restorative systems, was carried out. Materials and Methods. Four types of zirconia specimens were analyzed, according to a standard ISO procedure (ISO 6872. Besides, two-layered zirconia-veneer specimens were prepared for three-point bending tests. Results. A strong effect of the surface roughness on the mechanical strength of zirconia specimens was observed. Finally, a comparative study of eight commercially available veneering ceramics shows different modes of failure between the selected veneers. Conclusion. The results indicate that close attention should be paid to the preparation of zirconia-based crowns and bridges by CAD/CAM process, because surface roughness has an important effect on the mechanical strength of the material. Finally, the results of the mechanical tests on two-layered specimens represent an important support to the choice of the veneering ceramic.

  12. Strength, toughness and aging stability of highly-translucent Y-TZP ceramics for dental restorations.

    Science.gov (United States)

    Zhang, Fei; Inokoshi, Masanao; Batuk, Maria; Hadermann, Joke; Naert, Ignace; Van Meerbeek, Bart; Vleugels, Jef

    2016-12-01

    The aim was to evaluate the optical properties, mechanical properties and aging stability of yttria-stabilized zirconia with different compositions, highlighting the influence of the alumina addition, Y 2 O 3 content and La 2 O 3 doping on the translucency. Five different Y-TZP zirconia powders (3 commercially available and 2 experimentally modified) were sintered under the same conditions and characterized by X-ray diffraction with Rietveld analysis and scanning electron microscopy (SEM). Translucency (n=6/group) was measured with a color meter, allowing to calculate the translucency parameter (TP) and the contrast ratio (CR). Mechanical properties were appraised with four-point bending strength (n=10), single edge V-notched beam (SEVNB) fracture toughness (n=8) and Vickers hardness (n=10). The aging stability was evaluated by measuring the tetragonal to monoclinic transformation (n=3) after accelerated hydrothermal aging in steam at 134°C, and the transformation curves were fitted by the Mehl-Avrami-Johnson (MAJ) equation. Data were analyzed by one-way ANOVA, followed by Tukey's HSD test (α=0.05). Lowering the alumina content below 0.25wt.% avoided the formation of alumina particles and therefore increased the translucency of 3Y-TZP ceramics, but the hydrothermal aging stability was reduced. A higher yttria content (5mol%) introduced about 50% cubic zirconia phase and gave rise to the most translucent and aging-resistant Y-TZP ceramics, but the fracture toughness and strength were considerably sacrificed. 0.2mol% La 2 O 3 doping of 3Y-TZP tailored the grain boundary chemistry and significantly improved the aging resistance and translucency. Although the translucency improvement by La 2 O 3 doping was less effective than for introducing a substantial amount of cubic zirconia, this strategy was able to maintain the mechanical properties of typical 3Y-TZP ceramics. Three different approaches were compared to improve the translucency of 3Y-TZP ceramics. Copyright

  13. Crack tip fracture toughness of base glasses for dental restoration glass-ceramics using crack opening displacements.

    Science.gov (United States)

    Deubener, J; Höland, M; Höland, W; Janakiraman, N; Rheinberger, V M

    2011-10-01

    The critical stress intensity factor, also known as the crack tip toughness K(tip), was determined for three base glasses, which are used in the manufacture of glass-ceramics. The glasses included the base glass for a lithium disilicate glass-ceramic, the base glass for a fluoroapatite glass-ceramic and the base glass for a leucite glass-ceramic. These glass-ceramic are extensively used in the form of biomaterials in restorative dental medicine. The crack tip toughness was established by using crack opening displacement profiles under experimental conditions. The crack was produced by Vickers indentation. The crack tip toughness parameters determined for the three glass-ceramics differed quite significantly. The crack tip parameters of the lithium disilicate base glass and the leucite base glass were higher than that of the fluoroapatite base glass. This last material showed glass-in-glass phase separation. The discussion of the results clearly shows that the droplet glass phase is softer than the glass matrix. Therefore, the authors conclude that a direct relationship exists between the chemical nature of the glasses and the crack tip parameter. Copyright © 2011 Elsevier Ltd. All rights reserved.

  14. Investigation of firing temperature variation in ovens for ceramic-fused-to-metal dental prostheses using swept source optical coherence tomography

    Science.gov (United States)

    Todor, Raluca; Negrutiu, Meda-Lavinia; Sinescu, Cosmin; Topala, Florin Ionel; Bradu, Adrian; Duma, Virgil-Florin; Romînu, Mihai; Podoleanu, Adrian G.

    2018-03-01

    One of the most common fabrication techniques for dental ceramics is sintering, a process of heating of the ceramic to ensure densification. This occurs by viscous flow when the firing temperature is reached. Acceptable restorations require the alloy and ceramic to be chemically, thermally, mechanically, and aesthetically compatible. Thermal and mechanical compatibility include a fusing temperature of ceramic that does not cause distortion of the metal substructure. Decalibration of ovens used for firing of the ceramic layers for metal ceramic dental prostheses leads to stress and cracks in the veneering material, and ultimately to the failure of the restoration. 25 metal ceramic prostheses were made for this study. They were divided in five groups, each sintered at a different temperature: a group at the temperature prescribed by the producer, two groups at lower and two groups at higher temperatures set in the ceramic oven. An established noninvasive biomedical imaging method, swept source (SS) optical coherence tomography (OCT) was employed, in order to evaluate the modifications induced when using temperatures different from those prescribed for firing the samples. A quantitative assessment of the probes is performed by en-face OCT images, taken at constant depths inside the samples. The differences in granulation, thus in reflectivity allow for extracting rules-of-thumb to evaluate fast, by using only the prostheses currently produced the current calibration of the ceramic oven. OCT imaging can allow quick identification of the oven decalibration, to avoid producing dental prostheses with defects.

  15. Hard tissue formation in a porous HA/TCP ceramic scaffold loaded with stromal cells derived from dental pulp and bone marrow.

    NARCIS (Netherlands)

    Zhang, W.; Walboomers, X.F.; Osch, G.J.V.M. van; Dolder, J. van den; Jansen, J.A.

    2008-01-01

    The aim of this study was to compare the ability of hard tissue regeneration of four types of stem cells or precursors under both in vitro and in vivo situations. Primary cultures of rat bone marrow, rat dental pulp, human bone marrow, and human dental pulp cells were seeded onto a porous ceramic

  16. Effect of elasticity on stress distribution in CAD/CAM dental crowns: Glass ceramic vs. polymer-matrix composite.

    Science.gov (United States)

    Duan, Yuanyuan; Griggs, Jason A

    2015-06-01

    Further investigations are required to evaluate the mechanical behaviour of newly developed polymer-matrix composite (PMC) blocks for computer-aided design/computer-aided manufacturing (CAD/CAM) applications. The purpose of this study was to investigate the effect of elasticity on the stress distribution in dental crowns made of glass-ceramic and PMC materials using finite element (FE) analysis. Elastic constants of two materials were determined by ultrasonic pulse velocity using an acoustic thickness gauge. Three-dimensional solid models of a full-coverage dental crown on a first mandibular molar were generated based on X-ray micro-CT scanning images. A variety of load case-material property combinations were simulated and conducted using FE analysis. The first principal stress distribution in the crown and luting agent was plotted and analyzed. The glass-ceramic crown had stress concentrations on the occlusal surface surrounding the area of loading and the cemented surface underneath the area of loading, while the PMC crown had only stress concentration on the occlusal surface. The PMC crown had lower maximum stress than the glass-ceramic crown in all load cases, but this difference was not substantial when the loading had a lateral component. Eccentric loading did not substantially increase the maximum stress in the prosthesis. Both materials are resistant to fracture with physiological occlusal load. The PMC crown had lower maximum stress than the glass-ceramic crown, but the effect of a lateral loading component was more pronounced for a PMC crown than for a glass-ceramic crown. Knowledge of the stress distribution in dental crowns with low modulus of elasticity will aid clinicians in planning treatments that include such restorations. Copyright © 2015 Elsevier Ltd. All rights reserved.

  17. Electrochemical behavior of 45S5 bioactive ceramic coating on Ti6Al4V alloy for dental applications

    Science.gov (United States)

    Machado López, M. M.; Espitia Cabrera, M. I.; Faure, J.; Contreras García, M. E.

    2016-04-01

    Titanium and its alloys are widely used as implant materials because of their mechanical properties and non-toxic behavior. Unfortunately, they are not bioinert, which means that they can release ions and can only fix the bone by mechanical anchorage, this can lead to the encapsulation of dense fibrous tissue in the body. The bone fixation is required in clinical conditions treated by orthopedic and dental medicine. The proposal is to coat metallic implants with bioactive materials to establish good interfacial bonds between the metal substrate and bone by increasing bioactivity. Bioactive glasses, ceramics specifically 45 S5 Bioglass, have drawn attention as a serious functional biomaterial because osseointegration capacity. The EPD method of bioglass gel precursor was proposed in the present work as a new method to obtain 45S5/Ti6A14V for dental applications. The coatings, were thermally treated at 700 and 800°C and presented the 45 S5 bioglass characteristic phases showing morphology and uniformity with no defects, quantification percentages by EDS of Si, Ca, Na, P and O elements in the coating scratched powders, showed a good proportional relationship demonstrating the obtention of the 45S5 bioglass. The corrosion tests were carried out in Hank's solution. By Tafel extrapolation, Ti6Al4V alloy showed good corrosion resistance in Hank's solution media, by the formation of a passivation layer on the metal surface, however, in the system 45S5/Ti6Al4V there was an increase in the corrosion resistance; icon-, Ecorr and corrosion rate decreased, the mass loss and the rate of release of ions, were lower in this system than in the titanium alloy without coating.

  18. [Study on friction and wear properties of dental zirconia ceramics processed by microwave and conventional sintering methods].

    Science.gov (United States)

    Guoxin, Hu; Ying, Yang; Yuemei, Jiang; Wenjing, Xia

    2017-04-01

    This study evaluated the wear of an antagonist and friction and wear properties of dental zirconia ceramic that was subjected to microwave and conventional sintering methods. Ten specimens were fabricated from Lava brand zirconia and randomly assigned to microwave and conventional sintering groups. A profile tester for surface roughness was used to measure roughness of the specimens. Wear test was performed, and steatite ceramic was used as antagonist. Friction coefficient curves were recorded, and wear volume were calculated. Finally, optical microscope was used to observe the surface morphology of zirconia and steatite ceramics. Field emission scanning electron microscopy was used to observe the microstructure of zirconia. Wear volumes of microwave and conventionally sintered zirconia were (6.940±1.382)×10⁻², (7.952±1.815) ×10⁻² mm³, respectively. Moreover, wear volumes of antagonist after sintering by the considered methods were (14.189±4.745)×10⁻², (15.813±3.481)×10⁻² mm³, correspondingly. Statistically significant difference was not observed in the wear resistance of zirconia and wear volume of steatite ceramic upon exposure to two kinds of sintering methods. Optical microscopy showed that ploughed surfaces were apparent in zirconia. The wear surface of steatite ceramic against had craze, accompanied by plough. Scanning electron microscopy showed that zirconia was sintered compactly when subjected to both conventional sintering and microwave methods, whereas grains of zirconia sintered by microwave alone were smaller and more uniform. Two kinds of sintering methods are successfully used to produce dental zirconia ceramics with similar friction and wear properties.
.

  19. All-ceramic crowns: bonding or cementing?

    Science.gov (United States)

    Pospiech, Peter

    2002-12-01

    Despite the wide variety of all-ceramic systems available today, the majority of dental practitioners hesitate to recommend and insert all-ceramic crowns. This article regards the nature of the ceramic materials, the principles of bonding and adhesion, and the clinical problems of the acid-etch technique for crowns. Advantages and disadvantages are discussed, and the influences of different factors on the strength of all-ceramic crowns are presented. Finally, the conclusion is drawn that conventional cementing of all-ceramic crowns is possible when the specific properties of the ceramics are taken into consideration.

  20. Assessment of ceramic composites for MMW space nuclear power systems

    International Nuclear Information System (INIS)

    Besmann, T.M.

    1987-01-01

    Proposed multimegawatt nuclear power systems which operate at high temperatures, high levels of stress, and in hostile environments, including corrosive working fluids, have created interest in the use of ceramic composites as structural materials. This report assesses the applicability of several ceramic composites in both Brayton and Rankine cycle power systems. This assessment considers an equilibrium thermodynamic analysis and also a nonequilibrium assessment. (FI)

  1. Assessment of exposures and potential risks to the US adult population from wear (attrition and abrasion) of gold and ceramic dental restorations.

    Science.gov (United States)

    Richardson, G Mark; Clemow, Scott R; Peters, Rachel E; James, Kyle J; Siciliano, Steven D

    2016-01-01

    Little has been published on the chemical exposures and risks of dental restorative materials other than from dental amalgam and composite resins. Here we provide the first exposure and risk assessment for gold (Au) alloy and ceramic restorative materials. Based on the 2001-2004 US National Health and Nutrition Examination Survey (NHANES), we assessed the exposure of US adults to the components of Au alloy and ceramic dental restorations owing to dental material wear. Silver (Ag) is the most problematic component of Au alloy restorations, owing to a combination of toxicity and proportional composition. It was estimated that adults could possess an average of four tooth surfaces restored with Au alloy before exceeding, on average, the reference exposure level (REL) for Ag. Lithium (Li) is the most problematic component of dental ceramics. It was estimated that adults could possess an average of 15 tooth surfaces restored with ceramics before exceeding the REL for Li. Relative risks of chemical exposures from dental materials decrease in the following order: Amalgam>Au alloys>ceramics>composite resins.

  2. Dental implant customization using numerical optimization design and 3-dimensional printing fabrication of zirconia ceramic.

    Science.gov (United States)

    Cheng, Yung-Chang; Lin, Deng-Huei; Jiang, Cho-Pei; Lin, Yuan-Min

    2017-05-01

    This study proposes a new methodology for dental implant customization consisting of numerical geometric optimization and 3-dimensional printing fabrication of zirconia ceramic. In the numerical modeling, exogenous factors for implant shape include the thread pitch, thread depth, maximal diameter of implant neck, and body size. Endogenous factors are bone density, cortical bone thickness, and non-osseointegration. An integration procedure, including uniform design method, Kriging interpolation and genetic algorithm, is applied to optimize the geometry of dental implants. The threshold of minimal micromotion for optimization evaluation was 100 μm. The optimized model is imported to the 3-dimensional slurry printer to fabricate the zirconia green body (powder is bonded by polymer weakly) of the implant. The sintered implant is obtained using a 2-stage sintering process. Twelve models are constructed according to uniform design method and simulated the micromotion behavior using finite element modeling. The result of uniform design models yields a set of exogenous factors that can provide the minimal micromotion (30.61 μm), as a suitable model. Kriging interpolation and genetic algorithm modified the exogenous factor of the suitable model, resulting in 27.11 μm as an optimization model. Experimental results show that the 3-dimensional slurry printer successfully fabricated the green body of the optimization model, but the accuracy of sintered part still needs to be improved. In addition, the scanning electron microscopy morphology is a stabilized t-phase microstructure, and the average compressive strength of the sintered part is 632.1 MPa. Copyright © 2016 John Wiley & Sons, Ltd.

  3. Evaluation of metal-ceramic bond characteristics of three dental Co-Cr alloys prepared with different fabrication techniques.

    Science.gov (United States)

    Wang, Hongmei; Feng, Qing; Li, Ning; Xu, Sheng

    2016-12-01

    Limited information is available regarding the metal-ceramic bond strength of dental Co-Cr alloys fabricated by casting (CAST), computer numerical control (CNC) milling, and selective laser melting (SLM). The purpose of this in vitro study was to evaluate the metal-ceramic bond characteristics of 3 dental Co-Cr alloys fabricated by casting, computer numerical control milling, and selective laser melting techniques using the 3-point bend test (International Organization for Standardization [ISO] standard 9693). Forty-five specimens (25×3×0.5 mm) made of dental Co-Cr alloys were prepared by CAST, CNC milling, and SLM techniques. The morphology of the oxidation surface of metal specimens was evaluated by scanning electron microscopy (SEM). After porcelain application, the interfacial characterization was evaluated by SEM equipped with energy-dispersive spectrometry (EDS) analysis, and the metal-ceramic bond strength was assessed with the 3-point bend test. Failure type and elemental composition on the debonding interface were assessed by SEM/EDS. The bond strength was statistically analyzed by 1-way ANOVA and Tukey honest significant difference test (α=.05). The oxidation surfaces of the CAST, CNC, and SLM groups were different. They were porous in the CAST group but compact and irregular in the CNC and SLM groups. The metal-ceramic interfaces of the SLM and CNC groups showed excellent combination compared with those of the CAST group. The bond strength was 37.7 ±6.5 MPa for CAST, 43.3 ±9.2 MPa for CNC, and 46.8 ±5.1 MPa for the SLM group. Statistically significant differences were found among the 3 groups tested (P=.028). The debonding surfaces of all specimens exhibited cohesive failure mode. The oxidation surface morphologies and thicknesses of dental Co-Cr alloys are dependent on the different fabrication techniques used. The bond strength of all 3 groups exceed the minimum acceptable value of 25 MPa recommended by ISO 9693; hence, dental Co-Cr alloy

  4. [In vitro evaluation of low-temperature aging effects of Y2O3 stabilized tetragonal zirconia polycrystals dental ceramics].

    Science.gov (United States)

    Yi, Yuan-fu; Liu, Hong-chen; Wang, Chen; Tian, Jie-mo; Wen, Ning

    2008-03-01

    To investigate the influence of in vitro low-temperature degradation (LTD) treatment on the structural stability of 5 kinds of Y2O3 stabilized tetragonal zirconia polycrystals (Y-TZP) dental ceramics. TZ-3YS powder was compacted at 200 MPa using cold isostatic pressure and pre-sintered at 1050 degrees C for 2 h forming presintered blocks. Specimens were sectioned into 15 mm x 15 mm x 1.5 mm slices from blocks of TZ-3YS, Vita In-Ceram YZ, Ivoclar, Cercon Smart, and Kavo Y-TZP presintered blocks, 18 slices for each brand, and then densely sintered. Specimens were divided into 6 groups and subjected to an accelerated aging test carried out in an autoclave in steam at 134 degrees C, 0.2 MPa, for 0, 1, 2, 3, 4, and 5 h. X-ray diffraction (XRD) was used to identify crystal phases and relative content of monoclinic phase was calculated. Specimens for three-point bending test were fabricated using TZ-3YS ceramics according to the ISO 6872 standard and bending strength was tested before and after aging. The polished and aging specimens of TZ-3YS and Cercon Smart zirconia ceramics were observed by atomic force microscopy (AFM) to evaluate surface microstructure. Tetragonal-to-monoclinic phase transformation was detected for specimens of TZ-3YS, Vita In-Ceram YZ, Ivoclar, and Kavo zirconia ceramics except for Cercon Smart ceramics after aging, and the relative content of monoclinic phase was increasing with the prolonged aging time. TZ-3YS was the most affected material, Kavo took the second, and Vita and Ivoclar were similar. Aging had no significant negative effects on flexural strength of TZ-3YS with average bending strength being over 1100 MPa. The nucleation and growth of monoclinic phase were detected by AFM in surface of Cercon Smart zirconia in which monoclinic phase was not detected by XRD. The results suggest that LTD of dental Y-TZP is time dependent, but the aging test does not reduce the flexural strength of TZ-3YS. The long-term clinical serviceability of dental

  5. Advancements in all-ceramics for dental restorations and their effect on the wear of opposing dentition

    Science.gov (United States)

    Rashid, Haroon; Sheikh, Zeeshan; Misbahuddin, Syed; Kazmi, Murtaza Raza; Qureshi, Sameer; Uddin, Muhammad Zuhaib

    2016-01-01

    Tooth wear is a process that is usually a result of tooth to tooth and/or tooth and restoration contact. The process of wear essentially becomes accelerated by the introduction of restorations inside the oral cavity, especially in case of opposing ceramic restorations. The newest materials have vastly contributed toward the interest in esthetic dental restorations and have been extensively studied in laboratories. However, despite the recent technological advancements, there has not been a valid in vivo method of evaluation involving clinical wear caused due to ceramics upon restored teeth and natural dentition. The aim of this paper is to review the latest advancements in all-ceramic materials, and their effect on the wear of opposing dentition. The descriptive review has been written after a thorough MEDLINE/PubMed search by the authors. It is imperative that clinicians are aware of recent advancements and that they should always consider the type of ceramic restorative materials used to maintain a stable occlusal relation. The ceramic restorations should be adequately finished and polished after the chair-side adjustment process of occlusal surfaces. PMID:28042280

  6. Highly-translucent, strong and aging-resistant 3Y-TZP ceramics for dental restoration by grain boundary segregation.

    Science.gov (United States)

    Zhang, Fei; Vanmeensel, Kim; Batuk, Maria; Hadermann, Joke; Inokoshi, Masanao; Van Meerbeek, Bart; Naert, Ignace; Vleugels, Jef

    2015-04-01

    Latest trends in dental restorative ceramics involve the development of full-contour 3Y-TZP ceramics which can avoid chipping of veneering porcelains. Among the challenges are the low translucency and the hydrothermal stability of 3Y-TZP ceramics. In this work, different trivalent oxides (Al2O3, Sc2O3, Nd2O3 and La2O3) were selected to dope 3Y-TZP ceramics. Results show that dopant segregation was a key factor to design hydrothermally stable and high-translucent 3Y-TZP ceramics and the cation dopant radius could be used as a controlling parameter. A large trivalent dopant, oversized as compared to Zr(4+), exhibiting strong segregation at the ZrO2 grain boundary was preferred. The introduction of 0.2 mol% La2O3 in conventional 0.1-0.25 wt.% Al2O3-doped 3Y-TZP resulted in an excellent combination of high translucency and superior hydrothermal stability, while retaining excellent mechanical properties. Copyright © 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  7. Effect of pH and fluoride on behavior of dental ZrO2 ceramics in artificial saliva

    International Nuclear Information System (INIS)

    Mukaeda, L.E.; Robin, A.; Santos, C.; Taguchi, S.P.; Borges Junior, L.A.

    2009-01-01

    A considerable increase in the ceramic products demand occurred due to the evolution of dental restoration techniques and these materials must resist to the complex mouth environment. The pH of saliva can decrease significantly due to the ingestion of acidic foods and beverages and mainly due to reactions occurring during bacteria metabolism that lead to the formation of organic acids. Fluorides are also present in the mouth since fluorides are usually added in drinking water, mouth washes, tooth pastes and gels for the prevention of plaque and caries formation. The combination of low pH and presence of fluorides can lead to the formation of HF and HF 2 - which are detrimental to metallic and probably to ceramic devices. In this work, commercial blocks of ZrO 2 ceramics (ProtMat Materiais Avancados® and Ivoclar®) were immersed in Fusayama artificial saliva of different pHs and fluoride concentrations. The properties of the as-produced ceramics (crystalline phases (XRD), microstructure (SEM), roughness (3D surface topography AFM) and mechanical resistance - Vickers hardness (Hv) and fracture toughness (KIC) were evaluated. Some of these properties were also determined after the immersion tests as well as the mass variation of the samples in order to evaluate the resistance of these ZrO 2 ceramics to degradation under these conditions. (author)

  8. Effect of pH and fluoride on behavior of dental ZrO{sub 2} ceramics in artificial saliva

    Energy Technology Data Exchange (ETDEWEB)

    Mukaeda, L.E.; Robin, A.; Santos, C.; Taguchi, S.P.; Borges Junior, L.A., E-mail: luizamukaeda@gmail.com, E-mail: alain@demar.eel.usp.br, E-mail: claudinei@demar.eel.usp.br, E-mail: simone@demar.eel.usp.br, E-mail: borges.jr@itelefonica.com.br [Universidade de Sao Paulo (EEL/DEMAR/USP), Lorena, SP (Brazil). Escola de Engenharia; Machado, J.P.B., E-mail: joaopaulo@las.inpe.br [Instituto Nacional de Pesquisas Espaciais (INPE), Sao Jose dos Campos, SP (Brazil)

    2009-07-01

    A considerable increase in the ceramic products demand occurred due to the evolution of dental restoration techniques and these materials must resist to the complex mouth environment. The pH of saliva can decrease significantly due to the ingestion of acidic foods and beverages and mainly due to reactions occurring during bacteria metabolism that lead to the formation of organic acids. Fluorides are also present in the mouth since fluorides are usually added in drinking water, mouth washes, tooth pastes and gels for the prevention of plaque and caries formation. The combination of low pH and presence of fluorides can lead to the formation of HF and HF{sub 2}{sup -} which are detrimental to metallic and probably to ceramic devices. In this work, commercial blocks of ZrO{sub 2} ceramics (ProtMat Materiais Avancados® and Ivoclar®) were immersed in Fusayama artificial saliva of different pHs and fluoride concentrations. The properties of the as-produced ceramics (crystalline phases (XRD), microstructure (SEM), roughness (3D surface topography AFM) and mechanical resistance - Vickers hardness (Hv) and fracture toughness (KIC) were evaluated. Some of these properties were also determined after the immersion tests as well as the mass variation of the samples in order to evaluate the resistance of these ZrO{sub 2} ceramics to degradation under these conditions. (author)

  9. AFM and SEM study of the effects of etching on IPS-Empress 2 TM dental ceramic

    Science.gov (United States)

    Luo, X.-P.; Silikas, N.; Allaf, M.; Wilson, N. H. F.; Watts, D. C.

    2001-10-01

    The aim of this study was to investigate the effects of increasing etching time on the surface of the new dental material, IPS-Empress 2 TM glass ceramic. Twenty one IPS-Empress 2 TM glass ceramic samples were made from IPS-Empress 2 TM ingots through lost-wax, hot-pressed ceramic fabrication technology. All samples were highly polished and cleaned ultrasonically for 5 min in acetone before and after etching with 9.6% hydrofluoric acid gel. The etching times were 0, 10, 20, 30, 60, 90 and 120 s respectively. Microstructure was analysed by scanning electron microscopy (SEM) and atomic force microscopy (AFM) was used to evaluate the surface roughness and topography. Observations with SEM showed that etching with hydrofluoric acid resulted in preferential dissolution of glass matrix, and that partially supported crystals within the glass matrix were lost with increasing etching time. AFM measurements indicated that etching increased the surface roughness of the glass-ceramic. A simple least-squares linear regression was used to establish a relationship between surface roughness parameters ( Ra, RMS), and etching time, for which r2>0.94. This study demonstrates the benefits of combining two microscopic methods for a better understanding of the surface. SEM showed the mode of action of hydrofluoric acid on the ceramic and AFM provided valuable data regarding the extent of surface degradation relative to etching time.

  10. Ceramic dental biomaterials and CAD/CAM technology: state of the art.

    Science.gov (United States)

    Li, Raymond Wai Kim; Chow, Tak Wah; Matinlinna, Jukka Pekka

    2014-10-01

    Ceramics are widely used as indirect restorative materials in dentistry because of their high biocompatibility and pleasing aesthetics. The objective is to review the state of the arts of CAD/CAM all-ceramic biomaterials. CAD/CAM all-ceramic biomaterials are highlighted and a subsequent literature search was conducted for the relevant subjects using PubMed followed by manual search. Developments in CAD/CAM technology have catalyzed researches in all-ceramic biomaterials and their applications. Feldspathic glass ceramic and glass infiltrated ceramic can be fabricated by traditional laboratory methods or CAD/CAM. The advent of polycrystalline ceramics is a direct result of CAD/CAM technology without which the fabrication would not have been possible. The clinical uses of these ceramics have met with variable clinical success. Multiple options are now available to the clinicians for the fabrication of aesthetic all ceramic restorations. Copyright © 2014 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.

  11. Fracture toughness improvements of dental ceramic through use of yttria-stabilized zirconia (YSZ) thin-film coatings.

    Science.gov (United States)

    Chan, Ryan N; Stoner, Brian R; Thompson, Jeffrey Y; Scattergood, Ronald O; Piascik, Jeffrey R

    2013-08-01

    The aim of this study was to evaluate strengthening mechanisms of yttria-stabilized zirconia (YSZ) thin film coatings as a viable method for improving fracture toughness of all-ceramic dental restorations. Bars (2mm×2mm×15mm, n=12) were cut from porcelain (ProCAD, Ivoclar-Vivadent) blocks and wet-polished through 1200-grit using SiC abrasive. A Vickers indenter was used to induce flaws with controlled size and geometry. Depositions were performed via radio frequency magnetron sputtering (5mT, 25°C, 30:1 Ar/O2 gas ratio) with varying powers of substrate bias. Film and flaw properties were characterized by optical microscopy, scanning electron microscopy (SEM), and X-ray diffraction (XRD). Flexural strength was determined by three-point bending. Fracture toughness values were calculated from flaw size and fracture strength. Data show improvements in fracture strength of up to 57% over unmodified specimens. XRD analysis shows that films deposited with higher substrate bias displayed a high %monoclinic volume fraction (19%) compared to non-biased deposited films (87%), and resulted in increased film stresses and modified YSZ microstructures. SEM analysis shows critical flaw sizes of 67±1μm leading to fracture toughness improvements of 55% over unmodified specimens. Data support surface modification of dental ceramics with YSZ thin film coatings to improve fracture toughness. Increase in construct strength was attributed to increase in compressive film stresses and modified YSZ thin film microstructures. It is believed that this surface modification may lead to significant improvements and overall reliability of all-ceramic dental restorations. Copyright © 2013 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  12. Performance of zirconia ceramic cantilever fixed dental prostheses: 3-year results from a prospective, randomized, controlled pilot study.

    Science.gov (United States)

    Zenthöfer, Andreas; Ohlmann, Brigitte; Rammelsberg, Peter; Bömicke, Wolfgang

    2015-07-01

    Little is known about the clinical performance of ceramic cantilever fixed dental prostheses on natural teeth. The purpose of this randomized controlled pilot study was to evaluate the clinical performance of ceramic and metal ceramic cantilever fixed dental prostheses (CFDPs) after 3 years of service. Twenty-one participants were randomly allocated to 2 treatment groups. Participants in the ceramic (ZC) group (n=11) each received 1 CFDP made of yttria-stabilized, tetragonal zirconia polycrystal; the others (n=10) were fitted with a metal ceramic (MC) CFDP. All CFDPs were retained by 2 complete crown abutments and replaced 1 tooth. The clinical target variables were survival, incidence of complications, probing pocket depth (PPD), probing attachment level (PAL), plaque index (PI), gingival index (GI), and esthetic performance as rated by the participants. The United States Public Health Service (USPHS) criteria were used to evaluate chipping, retention, color, marginal integrity, and secondary caries. Descriptive statistics and nonparametric analyses were applied to the target variables in the 2 groups. The esthetic performance of the CFDPs was also visualized by using a pyramid comparison. The overall survival of the CFDPs was 100% in both groups. During the 3-year study, 6 clinically relevant complications requiring aftercare were observed among 5 participants (4 in the ZC group and 2 in the MC group). Changes in the PI, GI, PPD, and PAL of the abutment teeth were similar for both groups (P>.05). The participants regarded the esthetic performance of ZC-CFDPs and MC-CFDPs as satisfactory. Within the 3-year observation period, the clinical performance of MC-FDPs and ZC-FDPs was acceptable. More extensive research with larger sample sizes is encouraged, however, to confirm the evaluation of the survival of Y-TZP hand-veneered cantilever FPDs. Copyright © 2015 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

  13. All-ceramic or metal-ceramic tooth-supported fixed dental prostheses (FDPs)? A systematic review of the survival and complication rates. Part II: Multiple-unit FDPs.

    Science.gov (United States)

    Pjetursson, Bjarni Elvar; Sailer, Irena; Makarov, Nikolay Alexandrovich; Zwahlen, Marcel; Thoma, Daniel Stefan

    2015-06-01

    To assess the 5-year survival of metal-ceramic and all-ceramic tooth-supported fixed dental prostheses (FDPs) and to describe the incidence of biological, technical and esthetic complications. Medline (PubMed), Embase and Cochrane Central Register of Controlled Trials (CENTRAL) searches (2006-2013) were performed for clinical studies focusing on tooth-supported FDPs with a mean follow-up of at least 3 years. This was complemented by an additional hand search and the inclusion of 10 studies from a previous systematic review [1]. Survival and complication rates were analyzed using robust Poisson's regression models to obtain summary estimates of 5-year proportions. Forty studies reporting on 1796 metal-ceramic and 1110 all-ceramic FDPs fulfilled the inclusion criteria. Meta-analysis of the included studies indicated an estimated 5-year survival rate of metal-ceramic FDPs of 94.4% (95% CI: 91.2-96.5%). The estimated survival rate of reinforced glass ceramic FDPs was 89.1% (95% CI: 80.4-94.0%), the survival rate of glass-infiltrated alumina FDPs was 86.2% (95% CI: 69.3-94.2%) and the survival rate of densely sintered zirconia FDPs was 90.4% (95% CI: 84.8-94.0%) in 5 years of function. Even though the survival rate of all-ceramic FDPs was lower than for metal-ceramic FDPs, the differences did not reach statistical significance except for the glass-infiltrated alumina FDPs (p=0.05). A significantly higher incidence of caries in abutment teeth was observed for densely sintered zirconia FDPs compared to metal-ceramic FDPs. Significantly more framework fractures were reported for reinforced glass ceramic FDPs (8.0%) and glass-infiltrated alumina FDPs (12.9%) compared to metal-ceramic FDPs (0.6%) and densely sintered zirconia FDPs (1.9%) in 5 years in function. However, the incidence of ceramic fractures and loss of retention was significantly (p=0.018 and 0.028 respectively) higher for densely sintered zirconia FDPs compared to all other types of FDPs. Survival rates of all

  14. Investigations of subcritical crack propagation of the Empress 2 all-ceramic system.

    Science.gov (United States)

    Mitov, Gergo; Lohbauer, Ulrich; Rabbo, Mohammad Abed; Petschelt, Anselm; Pospiech, Peter

    2008-02-01

    The mechanical properties and slow crack propapagation of the all-porcelain system Empress 2 (Ivoclar Vivadent, Schaan, Liechtenstein) with its framework compound Empress 2 and the veneering compounds "Empress 2 and Eris were examined. For all materials, the fracture strength, Weibull parameter and elastic moduli were experimentally determined in a four-point-bending test. For the components of the Empress 2 system, the fracture toughness K(IC) was determined, and the crack propagation parameters n and A were determined in a dynamic fatigue method. Using these data, life data analysis was performed and lifetime diagrams were produced. The development of strength under static fatigue conditions was calculated for a period of 5 years. The newly developed veneering ceramic Eris showed a higher fracture strength (sigma(0)=66.1 MPa) at a failure probability of P(F)=63.2%, and crack growth parameters (n=12.9) compared to the veneering ceramic Empress 2 (sigma(0)=60.3 MPa). For Empress 2 veneer the crack propagation parameter n could only be estimated (n=9.5). This is reflected in the prognosis of long-term resistance presented in the SPT diagrams. For all materials investigated, the Weibull parameter m values (Empress 2 framework m=4.6; Empress 2 veneer m=7.9; Eris m=6.9) were much lower than the minimum demanded by the literature (m=15). The initial fracture strength value alone is not sufficient to characterize the mechanical resistance of ceramic materials, since their stressability is time-dependent. Knowledge about the crack propagation parameters n and A are of great importance when preclinically predicting the clinical suitability of dental ceramic materials. The use of SPT diagrams for lifetime calculation of ceramic materials is a valuable method for comparing different ceramics.

  15. Resistance to bond degradation between dual-cure resin cements and pre-treated sintered CAD-CAM dental ceramics

    Science.gov (United States)

    Osorio, Raquel; Monticelli, Francesca; Osorio, Estrella; Toledano, Manuel

    2012-01-01

    Objective: To evaluate the bond stability of resin cements when luted to glass-reinforced alumina and zirconia CAD/CAM dental ceramics. Study design: Eighteen glass-infiltrated alumina and eighteen densely sintered zirconia blocks were randomly conditioned as follows: Group 1: No treatment; Group 2: Sandblasting (125 µm Al2O3-particles); and Group 3: Silica-coating (50 µm silica-modified Al2O3-particles). Composite samples were randomly bonded to the pre-treated ceramic surfaces using different resin cements: Subgroup 1: Clearfil Esthetic Cement (CEC); Subgroup 2: RelyX Unicem (RXU); and Subgroup 3: Calibra (CAL). After 24 h, bonded specimens were cut into 1 ± 0.1 mm2 sticks. One-half of the beams were tested for microtensile bond strength (MTBS). The remaining one-half was immersed in 10 % NaOCl aqueous solution (NaOClaq) for 5 h before testing. The fracture pattern and morphology of the debonded surfaces were assessed with a field emission gun scanning electron microscope (FEG-SEM). A multiple ANOVA was conducted to analyze the contributions of ceramic composition, surface treatment, resin cement type, and chemical challenging to MTBS. The Tukey test was run for multiple comparisons (p ceramic interfacial longevity depended on cement selection rather than on surface pre-treatments. The MDP-containing and the self-adhesive resin cements were both suitable for luting CAD/CAM ceramics. Despite both cements being prone to degradation, RXU luted to zirconia or untreated or sandblasted alumina showed the most stable interfaces. CAL experimented spontaneous debonding in all tested groups. Key words:CAD/CAM ceramic, alumina, zirconia, resin cement, surface pre-treatment, sandblasting, silica-coating, chemical aging, bond degradation, microtensile bond strength. PMID:22322517

  16. Control of dental prosthesis system with microcontroller.

    Science.gov (United States)

    Kapidere, M; Müldür, S; Güler, I

    2000-04-01

    In this study, a microcontroller-based electronic circuit was designed and implemented for dental prosthesis curing system. Heater, compressor and valve were controlled by 8-bit PIC16C64 microcontroller which is programmed using MPASM package. The temperature and time were controlled automatically by preset values which were inputted from keyboard while the pressure was kept constant. Calibration was controlled and the working range was tested. The test results showed that the system provided a good performance.

  17. Colour parameters and shade correspondence of CAD-CAM ceramic systems.

    Science.gov (United States)

    Della Bona, Alvaro; Pecho, Oscar E; Ghinea, Razvan; Cardona, Juan C; Pérez, María M

    2015-06-01

    To evaluate colour differences between (1) CAD-CAM ceramic systems considering shades A1, A2 and A3 and the corresponding nominal shade of VC (Vita Classical shade guide) and (2) shades A1-A2, A2-A3 and A1, A2 and A3 within the same ceramic system. Samples of shades A1, A2 and A3 were fabricated (n=5) from CAD-CAM ceramic blocks (IPS e.max(®) CAD LT and HT, IPS Empress(®) CAD LT and HT, Paradigm™ C, and VITABLOCS(®) Mark II) and polished to 1.0±0.01mm in thickness. Spectral reflectance and colour coordinates were measured using a spectroradiometer inside a viewing booth using the CIE D65 illuminant and the d/0° geometry. Spectral reflectance curves were compared using VAF coefficient and were statistically analyzed using Kruskal-Wallis and the Mann-Whitney U test (α=0.05). Colour coordinates were statistically analyzed using one-way ANOVA, Tukey's test with Bonferroni correction (α=0.001). All colour differences (ΔEab(*) and ΔE00) were analyzed through comparisons with the PT - perceptibility and AT - acceptability thresholds for dental ceramics. ΔE between ceramic systems and its corresponding shade ranged from 6.32 to 13.42 (ΔEab(*)) and 4.48 to 9.30 (ΔE00). ΔE between shades A1-A2, A2-A3 and A1, A2 and A3 ranged, respectively, 1.93-4.82, 1.22-5.59 and 3.63-8.84 (ΔEab(*)); 1.54-3.87, 1.03-3.90 and 2.95-6.51 (ΔE00). Considering the corresponding nominal shade from VC, none of the ceramic systems showed colour differences below the AT. In addition, some ceramic systems showed colour differences below AT (shades A1-A2 and A2-A3) and below PT (shades A2-A3). Careful adjustments should be made to the final shade of CAD-CAM ceramic restorations to reach a clinically acceptable shade match. Copyright © 2015 Elsevier Ltd. All rights reserved.

  18. KROME Ceramics: color management system for the ceramics industry; KROME: Ceramics Sistema de gestion del color para la industra ceramica

    Energy Technology Data Exchange (ETDEWEB)

    Martin, A.; Luque, J.; Pla, O.; Selvi, S.

    2013-05-01

    Digital Decoration Systems, SL (DIGIT-S) with Unicer, SL, has implemented a system to improve and optimize the process of decorating by inkjet printing for ceramic industry. It provides a comprehensive solution, KROME Ceramics, to improve the cost effectiveness of product and process through the implementation of a working system based on the control of digital decoration process and the synchronization of all elements that make up the decorative modules, including the creation of a work flow, management of files that are generated during the process, a correct color management system, and of course, optimizing and evaluating ink jet inks integrating all elements involved: Lighting, Computer, Software, Monitor, Plotter, Paper, Ink, Ink jet, Body's, Enamels and Oven. (Author)

  19. A dose monitoring system for dental radiography

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Chena; Lee, Sam Sun; Kim, Jo Eun; Huh, Kyung Hoe; Yi, Woo Jin; Heo, Min Suk; Choi, Soon Chul [Dept. of Oral and Maxillofacial Radiology and Dental Research Institute, School of Dentistry, Seoul National University, Seoul (Korea, Republic of); Symkhampha, Khanthaly [Dept. of Oral and Maxillofacial Radiology, Department of Basic Science, Faculty of Dentistry, University of Health Sciences, Vientiane (Lao People' s Democratic Republic); Lee, Woo Jin [Dept. of Interdisciplinary Program in Radiation, Applied Life Sciences Major, College of Medicine, BK21, and Dental Research Institute, Seoul National University, Seoul (Korea, Republic of); Yeom, Heon Young [School of Computer Science Engineering, Seoul National University, Seoul (Korea, Republic of)

    2016-06-15

    The current study investigates the feasibility of a platform for a nationwide dose monitoring system for dental radiography. The essential elements for an unerring system are also assessed. An intraoral radiographic machine with 14 X-ray generators and five sensors, 45 panoramic radiographic machines, and 23 cone-beam computed tomography (CBCT) models used in Korean dental clinics were surveyed to investigate the type of dose report. A main server for storing the dose data from each radiographic machine was prepared. The dose report transfer pathways from the radiographic machine to the main sever were constructed. An effective dose calculation method was created based on the machine specifications and the exposure parameters of three intraoral radiographic machines, five panoramic radiographic machines, and four CBCTs. A viewing system was developed for both dentists and patients to view the calculated effective dose. Each procedure and the main server were integrated into one system. The dose data from each type of radiographic machine was successfully transferred to the main server and converted into an effective dose. The effective dose stored in the main server is automatically connected to a viewing program for dentist and patient access. A patient radiation dose monitoring system is feasible for dental clinics. Future research in cooperation with clinicians, industry, and radiologists is needed to ensure format convertibility for an efficient dose monitoring system to monitor unexpected radiation dose.

  20. A dose monitoring system for dental radiography

    International Nuclear Information System (INIS)

    Lee, Chena; Lee, Sam Sun; Kim, Jo Eun; Huh, Kyung Hoe; Yi, Woo Jin; Heo, Min Suk; Choi, Soon Chul; Symkhampha, Khanthaly; Lee, Woo Jin; Yeom, Heon Young

    2016-01-01

    The current study investigates the feasibility of a platform for a nationwide dose monitoring system for dental radiography. The essential elements for an unerring system are also assessed. An intraoral radiographic machine with 14 X-ray generators and five sensors, 45 panoramic radiographic machines, and 23 cone-beam computed tomography (CBCT) models used in Korean dental clinics were surveyed to investigate the type of dose report. A main server for storing the dose data from each radiographic machine was prepared. The dose report transfer pathways from the radiographic machine to the main sever were constructed. An effective dose calculation method was created based on the machine specifications and the exposure parameters of three intraoral radiographic machines, five panoramic radiographic machines, and four CBCTs. A viewing system was developed for both dentists and patients to view the calculated effective dose. Each procedure and the main server were integrated into one system. The dose data from each type of radiographic machine was successfully transferred to the main server and converted into an effective dose. The effective dose stored in the main server is automatically connected to a viewing program for dentist and patient access. A patient radiation dose monitoring system is feasible for dental clinics. Future research in cooperation with clinicians, industry, and radiologists is needed to ensure format convertibility for an efficient dose monitoring system to monitor unexpected radiation dose

  1. Decontamination factors of ceramic filter in radioactive waste incineration system

    International Nuclear Information System (INIS)

    Kanbe, Hiromi; Mayuzumi, Masami; Ono, Tetsuo; Yoshiki, Shinya; Kouyama, Hiroaki; Nagae, Madoka; Sekiguchi, Ryosaku; Takaoku, Yoshinobu; Hozumi, Masahiro.

    1987-01-01

    A suspension-firing type radioactive waste incineration system is developed and cold demonstration testing of ceramic filters for the system are carried out. The incineration system, which is useful for a wide variety of waste materials, can serve to simplify the facilities and to reduce the costs for waste disposal. The incineration system can be used for drying-processing of concentrated waste liquids and disposal of flame resistant materials including ion exchange resins and rubber, as well as for ordinary combustible solid materials. An on-line backwash system is adopted to allow the ceramic filters to operate stably for a long period of time. For one-step filtering using the ceramic filter, the decontamination factor is greater than 10 5 for the processing of various wastes. In a practical situation, there exist vapor produced by the spray drier and the cladding in used ion exchange resin, which act to increase the decontamination performance of the ceramic filters to ensure safe operation. For the waste incineration system equipped with a waste gas processing apparatus consisting of a ceramic filter and HEPA filter, the overall decontamination factor is expected to be greater than 10 6 at portions down to the outlet of the ceramic filter and greater than 10 8 at portions down to the outlet of the HEPA filter. (Nogami, K.)

  2. [An experimental study of the wear behavior of dental feldspathic glass-ceramic and lithium disilicate glass-ceramic].

    Science.gov (United States)

    Tian, Bei-min; Zhang, Shao-feng; He, Lin; Guo, Jia-wen; Yu, Jin-tao; Wu, Xiao-hong

    2013-11-01

    To investigate the tribology characteristics of two ceramic materials in vitro:feldspathic glass-ceramic (veneer porcelain) and lithium disilicate glass-ceramic (heat-pressed ceramic), and to evaluate the wear resistance of different ceramic materials from the dynamic chewing perspective. Wear tests were performed in simulated oral environment with stainless steel ball antagonists (r = 3 mm), veneer porcelain (CERAMCO 3) and heat-pressed ceramic (IPS e.max Press HT type) in the chewing simulator. The tribological tests were carried out under artificial saliva lubrication condition in room temperature with a vertical load of 10 N for 1.2×10(6) cycles (f = 1.5 Hz, uniform circular motion, revolving speed = 90 r/min, radius = 0.5 mm). The wear volumes were measured using three-dimensional profiling, and surface microscopic morphology were observed using scanning electron microscopy at time point of 200 000, 400 000, 600 000, 800 000, 1 000 000, and 1 200 000 cycles. In a simulated oral environment, the wear rates of veneer porcelain were (0.001 20 ± 0.00 018) , (0.000 10 ± 0.000 03) , (0.000 50 ± 0.000 05), (0.000 10 ± 0.000 02) , (0.004 10 ± 0.000 38) , and (0.019 00 ± 0.003 53) (×10(-4) mm(3)/cycles) at 200 000, 400 000, 600 000, 800 000, 1 000 000, 1 200 000 cycles. The wear rates of heat-pressed ceramic were (0.139 50 ± 0.030 94), (0.124 40 ± 0.031 20), (0.054 80 ± 0.005 38), (0.038 80 ± 0.006 10), (0.011 10 ± 0.003 75), (0.198 90 ± 0.045 80) (×10(-4) mm(3)/cycles) at 200 000, 400 000, 600 000, 800 000, 1 000 000, 1 200 000 cycles. Three stages were observed in the wear loss process of the two materials: running-in stage, steady wear stage and severe wear stage. In running-in and steady wear stage, the shallow wear tracks of veneer porcelain were produced by the fatigue effect.While in severe wear stage, the wear tracks turned into ploughing. In running-in stage, the surface of heat-pressed ceramic was characterized by dense and shallow ploughing

  3. Practical implications of incentive systems are utilized by dental franchises.

    Science.gov (United States)

    Yavner, S B

    1989-01-01

    The success of any dental practice depends, among other factors, on the critical role of staff employees. In order to encourage desired staff behaviors, incentive systems can be designed for employee dentists, assistants/hygienists and managers. A survey of dental franchises was conducted in 1987 for the purpose of examining their incentive control systems. The specific incentives employed by these dental franchises for their employees are analyzed. The implications of these incentive systems used by dental franchise organizations for all dental practices are then discussed.

  4. Impact of Bruxism on Ceramic Defects in Implant-Borne Fixed Dental Prostheses: A Retrospective Study.

    Science.gov (United States)

    Mikeli, Aikaterini; Walter, Michael H

    2016-01-01

    Ceramic veneer fracture is a frequent complication in implant-borne fixed restorations. The retrospective clinical study assesses the effect of bruxism on this complication. A sample of 507 implant-borne fixed units inserted between 1995 and 2011 in 144 patients were examined. Any detected veneer fractures were assigned to one of four groups according to extent and position. A hypothetical correlation between bruxism and ceramic veneer fractures was examined. Of 34 patients (23.6%) with at least one ceramic veneer fracture, 24 were bruxers (70%) and 10 were nonbruxers (30%) (P = .002). Bruxism may pose a risk for ceramic fractures.

  5. Comparative measurements of external radiation exposure using mobile phones, dental ceramic, household salt and conventional personal dosemeters

    International Nuclear Information System (INIS)

    Ekendahl, Daniela; Bulánek, Boris; Judas, Libor

    2015-01-01

    Because retrospective dosimetry utilises commonly occurring materials and objects, it is particularly useful in cases of large-scale radiation accidents or malevolent acts with radioactive materials where casualties are inflicted on the general public and first emergency responders. The aim of this study was to investigate whether retrospective dosemeters can provide dose estimates with comparable accuracy like conventional personal dosemeters. Using an external source of radiation 137 Cs and an anthropomorphic phantom, we simulated serious irradiation of a human body in anterior-posterior and rotational geometries. Retrospective luminescence dosimetry objects, such as mobile phones, dental ceramic and household salt, and conventional personal dosemeters (thermoluminescent and electronic) were fixed to the anthropomorphic phantom. The doses obtained were compared with specific reference values. In most cases, relative deviations between the measured doses and the reference values did not exceed 20%. As the retrospective and conventional dosemeters show no significant differences in laboratory conditions, the retrospective luminescence dosimetry objects represent a very promising tool if handled properly. - Highlights: • A serious external exposure of human body was simulated. • Doses were measured using both retrospective and conventional dosemeters. • Utilised retrospective dosimetry materials were alumina resistors from mobile phones, household salt and dental ceramic. • Doses obtained were compared with reference values. • Both retrospective and conventional dosemeters gave similar results

  6. Standards of teeth preparations for anterior resin bonded all-ceramic crowns in private dental practice in Jordan

    Directory of Open Access Journals (Sweden)

    Ziad Nawaf AL-Dwairi

    2011-08-01

    Full Text Available OBJECTIVES: To investigate if general dental practitioners (GDPs in private practice in Jordan follow universal guidelines for preparation of anterior teeth for resin bonded all-ceramic crowns (RBCs. MATERIAL AND METHODS: A sample (n=100 of laboratory models containing 208 tooth preparations for IPS Empress and In Ceram, featuring work from different GDPs, was obtained from 8 commercial dental laboratories. Aspects of preparations were quantified and compared with accepted criteria defined following a review of the literature and recommendations of the manufactures' guidelines. RESULTS: Subgingival margins on the buccal aspect were noticed in 36% of the preparations, 54% demonstrated overpreparation with a tendency to overprepare the teeth on the mesiodistal plane more than buccolingual plane. Twenty percent of samples presented a shoulder finish line while a chamfer margin design was noticed in 39%. Twenty-nine percent and 12% of samples had either a feathered or no clear margin design respectively. Incisal underpreparation was observed in 18% of dies of each type. Only 17% of all preparations were found to follow the recommended anatomical labial preparations while 29% of the RBC preparations were found to have the recommended axial convergence angle. In total, 43% of preparations were found to have the recommended depth of the finish line. CONCLUSIONS: It was found that relevant guidelines for RBC preparations were not being fully adhered to in private practice in Jordan.

  7. Influence of ageing on glass and resin bonding of dental glass-ceramic veneer adhesion to zirconia: A fracture mechanics analysis and interpretation.

    Science.gov (United States)

    Swain, M V; Gee, C; Li, K C

    2018-04-26

    Adhesion plays a major role in the bonding of dental materials. In this study the adhesion of two glass-ceramic systems (IPS e.max and VITABLOCS) to a zirconia sintered substrate using a glass (for IPS e.max) and resin (VITABLOCS) before and after exposure to ageing for 14 days in distilled water at 37 °C are compared using two interfacial fracture mechanics tests, the 3 point bend Schwickerath (Kosyfaki and Swain, 2014; Schneider and Swain, 2015) and 4 point bend (Charalambides et al., 1989) approaches. Both tests result in stable crack extension from which the strain energy release rate (G, N/m or J/m 2 ) can be determined. In the case of the 3 PB test the Work of Fracture was also determined. In addition, the Schwickerath test enables determination of the critical stress for the onset of cracking to occur, which forms the basis of the ISO (ISO9693-2:2016) adhesion test for porcelain ceramic adhesion to zirconia. For the aged samples there was a significant reduction in the resin-bonded strengths (Schwickerath) and strain energy release rate (both 3 and 4 PB tests), which was not evident for the glass bonded specimens. Critical examination of the force-displacement curves showed that ageing of the resin resulted in a major change in the form of the curves, which may be interpreted in terms of a reduction in the critical stress to initiate cracking and also in the development of an R-curve. The extent of the reduction in strain energy release rate following ageing was greater for the Schwickerath test than the Charalambides test. The results are discussed in terms of; the basic mechanics of these two tests, the deterioration of the resin bonding following moisture exposure and the different dimensions of the specimens. These in-vitro results raise concerns regarding resin bonding to zirconia. The present study uses a novel approach to investigate the role of ageing or environmental degradation on the adhesive bonding of two dental ceramics to zirconia

  8. Marginal Vertical Discrepancies of Monolithic and Veneered Zirconia and Metal-Ceramic Three-Unit Posterior Fixed Dental Prostheses.

    Science.gov (United States)

    Lopez-Suarez, Carlos; Gonzalo, Esther; Pelaez, Jesus; Serrano, Benjamin; Suarez, Maria J

    2016-01-01

    The aim of this study was to investigate and compare the marginal fit of posterior fixed dental prostheses (FDPs) made of monolithic and veneered computer-aided design/computer-assisted manufacture (CAD/CAM) zirconia ceramic with metal-ceramic posterior FDPs. Thirty standardized steel dies were prepared to receive posterior three-unit FDPs. Specimens were randomly divided into three groups (n = 10): (1) metal-ceramic (control group), (2) veneered zirconia, and (3) monolithic zirconia. All FDPs were cemented using a glass-ionomer cement. The specimens were subjected to thermal cycling (5°C to 55°C). A scanning electron microscope (SEM) with a magnification of ×500 was used for measurements. The data were statistically analyzed using one-way analysis of variance and paired t test. Both zirconia groups showed similar vertical marginal discrepancies, and no significant differences (P = .661) in marginal adaptation were observed among the groups. No differences were observed in either group in marginal discrepancies between surfaces or abutments. Monolithic zirconia posterior FDPs exhibit similar vertical marginal discrepancies to veneered zirconia posterior FDPs. No influence of localization measurements was observed.

  9. Seating load parameters impact on dental ceramic reinforcement conferred by cementation with resin-cements.

    LENUS (Irish Health Repository)

    Addison, Owen

    2010-09-01

    Cementation of all-ceramic restorations with resin-cements has been demonstrated to reduce the incidence of fracture in service. The aim was to investigate the influence of loading force and loading duration applied during cementation on the reinforcement conferred by a resin-cement on a leucite reinforced glass-ceramic.

  10. Information system analysis of an e-learning system used for dental restorations simulation.

    Science.gov (United States)

    Bogdan, Crenguţa M; Popovici, Dorin M

    2012-09-01

    The goal of using virtual and augmented reality technologies in therapeutic interventions simulation, in the fixed prosthodontics (VirDenT) project, is to increase the quality of the educational process in dental faculties, by assisting students in learning how to prepare teeth for all-ceramic restorations. Its main component is an e-learning virtual reality-based software system that will be used for the developing skills in grinding teeth, needed in all-ceramic restorations. The complexity of the domain problem that the software system dealt with made the analysis of the information system supported by VirDenT necessary. The analysis contains the following activities: identification and classification of the system stakeholders, description of the business processes, formulation of the business rules, and modelling of business objects. During this stage, we constructed the context diagram, the business use case diagram, the activity diagrams and the class diagram of the domain model. These models are useful for the further development of the software system that implements the VirDenT information system. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

  11. Current dental adhesives systems. A narrative review.

    Science.gov (United States)

    Milia, Egle; Cumbo, Enzo; Cardoso, Rielson Jose A; Gallina, Giuseppe

    2012-01-01

    Adhesive dentistry is based on the development of materials which establish an effective bond with the tooth tissues. In this context, adhesive systems have attracted considerable research interest in recent years. Successful adhesive bonding depends on the chemistry of the adhesive, on appropriate clinical handling of the material as well as on the knowledge of the morphological changes caused on dental tissue by different bonding procedures. This paper outlines the status of contemporary adhesive systems, with particular emphasis on chemical characteristics and mode of interaction of the adhesives with enamel and dentinal tissues. Dental adhesives are used for several clinical applications and they can be classified based on the clinical regimen in "etch-and-rinse adhesives" and "self-etch adhesives". Other important considerations concern the different anatomical characteristics of enamel and dentine which are involved in the bonding procedures that have also implications for the technique used as well as for the quality of the bond. Etch-and-rinse adhesive systems generally perform better on enamel than self-etching systems which may be more suitable for bonding to dentine. In order to avoid a possible loss of the restoration, secondary caries or pulp damage due to bacteria penetration or due to cytotoxicity effects of eluted adhesive components, careful consideration of several factors is essential in selecting the suitable bonding procedure and adhesive system for the individual patient situation.

  12. [The study of the colorimetric characteristics of the cobalt-chrome alloys abutments covered by four different all-ceramic crowns by using dental spectrophotometer].

    Science.gov (United States)

    Chen, Yifan; Liu, Hongchun; Meng, Yukun; Chao, Yonglie; Liu, Changhong

    2015-06-01

    This study aims to evaluate the optical data of the different sites of the cobalt-chrome (Co-Cr) alloy abutments covered by four different all-ceramic crowns and the color difference between the crowns and target tab using a digital dental spectrophotometer. Ten Co-Cr alloy abutments were made and tried in four different groups of all-ceramic crowns, namely, Procera aluminia, Procera zirconia, Lava zirconia (Lava-Zir), and IPS E.max glass-ceramic lithium disilicate-reinforced monolithic. The color data of the cervical, body, and incisal sites of the samples were recorded and analyzed by dental spectrophotometer. The CIE L*, a*, b* values were again measured after veneering. The color difference between the abutments covered by all-ceramic crowns and A2 dentine shade tab was evaluated. The L* and b* values of the abutments can be increased by all of the four groups of all-ceramic copings, but a* values were decreased in most groups. A statistical difference was observed among four groups. After being veneered, the L* values of all the copings declined slightly, and the values of a*, b* increased significantly. When compared with A2 dentine shade tab, the ΔE of the crowns was below 4. Four ceramic copings were demonstrated to promote the lightness and hue of the alloy abutments effecttively. Though the colorimetric baseline of these copings was uneven, veneer porcelain can efficiently decrease the color difference between the samples and thee target.

  13. Ceramic Integration Technologies for Advanced Energy Systems: Critical Needs, Technical Challenges, and Opportunities

    Science.gov (United States)

    Singh, Mrityunjay

    2010-01-01

    Advanced ceramic integration technologies dramatically impact the energy landscape due to wide scale application of ceramics in all aspects of alternative energy production, storage, distribution, conservation, and efficiency. Examples include fuel cells, thermoelectrics, photovoltaics, gas turbine propulsion systems, distribution and transmission systems based on superconductors, nuclear power generation and waste disposal. Ceramic integration technologies play a key role in fabrication and manufacturing of large and complex shaped parts with multifunctional properties. However, the development of robust and reliable integrated systems with optimum performance requires the understanding of many thermochemical and thermomechanical factors, particularly for high temperature applications. In this presentation, various needs, challenges, and opportunities in design, fabrication, and testing of integrated similar (ceramic ceramic) and dissimilar (ceramic metal) material www.nasa.gov 45 ceramic-ceramic-systems have been discussed. Experimental results for bonding and integration of SiC based Micro-Electro-Mechanical-Systems (MEMS) LDI fuel injector and advanced ceramics and composites for gas turbine applications are presented.

  14. Pressures on the dental care system in the United States.

    Science.gov (United States)

    Wotman, S; Goldman, H

    1982-07-01

    A number of significant pressures are creating tensions in the dental profession and the dental care delivery system. These pressures may be categorized in five major areas: 1) regulation and deregulation pressures involve changes in the state dental practice acts, court decisions concerning antitrust and advertising, and the inclusion of consumers on State professional regulatory boards; 2) cost of services includes factors involving the out-of-pocket cost of dental care and the growth of dental insurance; 3) dentist-related factors include the increased number of dentists and the indebtedness of dental graduates; 4) the pressures of changes in the American populations include the decline in population growth and the increase in proportion of elderly people; 5) changes in the distribution of dental care are based on new epidemiologic data concerning dental caries and progress in the prevention of periodontal disease. Many of these pressures are inducing competition in the dental care system. It is clear that the dental care system is in the process of change as it responds to these complex pressures.

  15. Towards long lasting zirconia-based composites for dental implants: Transformation induced plasticity and its consequence on ceramic reliability.

    Science.gov (United States)

    Reveron, Helen; Fornabaio, Marta; Palmero, Paola; Fürderer, Tobias; Adolfsson, Erik; Lughi, Vanni; Bonifacio, Alois; Sergo, Valter; Montanaro, Laura; Chevalier, Jérôme

    2017-01-15

    Zirconia-based composites were developed through an innovative processing route able to tune compositional and microstructural features very precisely. Fully-dense ceria-stabilized zirconia ceramics (84vol% Ce-TZP) containing equiaxed alumina (8vol%Al 2 O 3 ) and elongated strontium hexa-aluminate (8vol% SrAl 12 O 19 ) second phases were obtained by conventional sintering. This work deals with the effect of the zirconia stabilization degree (CeO 2 in the range 10.0-11.5mol%) on the transformability and mechanical properties of Ce-TZP-Al 2 O 3 -SrAl 12 O 19 materials. Vickers hardness, biaxial flexural strength and Single-edge V-notched beam tests revealed a strong influence of ceria content on the mechanical properties. Composites with 11.0mol% CeO 2 or above exhibited the classical behaviour of brittle ceramics, with no apparent plasticity and very low strain to failure. On the contrary, composites with 10.5mol% CeO 2 or less showed large transformation-induced plasticity and almost no dispersion in strength data. Materials with 10.5mol% of ceria showed the highest values in terms of biaxial bending strength (up to 1.1GPa) and fracture toughness (>10MPa√m). In these ceramics, as zirconia transformation precedes failure, the Weibull modulus was exceptionally high and reached a value of 60, which is in the range typically reported for metals. The results achieved demonstrate the high potential of using these new strong, tough and stable zirconia-based composites in structural biomedical applications. Yttria-stabilized (Y-TZP) zirconia ceramics are increasingly used for developing metal-free restorations and dental implants. Despite their success related to their excellent mechanical resistance, Y-TZP can undergo Low Temperature Degradation which could be responsible for restoration damage or even worst the failure of the implant. Current research is focusing on strategies to improve the LTD resistance of Y-TZP or to develop alternative composites with better

  16. Development of laundry drainage treatment system with ceramic ultra filter

    International Nuclear Information System (INIS)

    Kanda, Masanori; Kurahasi, Takafumi

    1995-01-01

    A compact laundry drainage treatment system (UF system hereafter) with a ceramic ultra filter membrane (UF membrane hereafter) has been developed to reduce radioactivity in laundry drainage from nuclear power plants. The UF membrane is made of sintered fine ceramic. The UF membrane has 0.01 μm fine pores, resulting in a durable, heat-resistant, and corrosion-resistant porous ceramic filter medium. A cross-flow system, laundry drainage is filtrated while it flows across the UF membrane, is used as the filtration method. This method creates less caking when compared to other methods. The UF membrane is back washed at regular intervals with permeated water to minimize caking of the filter. The UF membrane and cross-flow system provides long stable filtration. The ceramic UF membrane is strong enough to concentrate suspended solids in laundry drainage up to a weight concentration of 10%. The final concentrated laundry drainage can be treated in an incinerator. The performance of the UF system was checked using radioactive laundry drainage. The decontamination factor of the UF system was 25 or more. The laundry drainage treatment capacity and concentration ratio of the UF system, as well as the service life of the UF membrane were also checked by examination using simulated non-radioactive laundry drainage. Even though laundry drainage was concentrated 1000 times, the UF system showed good permeated water quality and permeated water flux. (author)

  17. Interfacial characterization of ceramic core materials with veneering porcelain for all-ceramic bi-layered restorative systems.

    Science.gov (United States)

    Tagmatarchis, Alexander; Tripodakis, Aris-Petros; Filippatos, Gerasimos; Zinelis, Spiros; Eliades, George

    2014-01-01

    The aim of the study was to characterize the elemental distribution at the interface between all-ceramic core and veneering porcelain materials. Three groups of all-ceramic cores were selected: A) Glass-ceramics (Cergo, IPS Empress, IPS Empress 2, e-max Press, Finesse); B) Glass-infiltrated ceramics (Celay Alumina, Celay Zirconia) and C) Densely sintered ceramics (Cercon, Procera Alumina, ZirCAD, Noritake Zirconia). The cores were combined with compatible veneering porcelains and three flat square test specimens were produced for each system. The core-veneer interfaces were examined by scanning electron microscopy and energy dispersive x-ray microanalysis. The glass-ceramic systems showed interfacial zones reach in Si and O, with the presence of K, Ca, Al in core and Ca, Ce, Na, Mg or Al in veneer material, depending on the system tested. IPS Empress and IPS Empress 2 demonstrated distinct transitional phases at the core-veneer interface. In the glassinfiltrated systems, intermixing of core (Ce, La) with veneer (Na, Si) elements occurred, whereas an abrupt drop of the core-veneer elemental concentration was documented at the interfaces of all densely sintered ceramics. The results of the study provided no evidence of elemental interdiffusion at the core-veneer interfaces in densely sintered ceramics, which implies lack of primary chemical bonding. For the glass-containing systems (glassceramics and glass-infiltrated ceramics) interdiffusion of the glass-phase seems to play a critical role in establishing a primary bonding condition between ceramic core and veneering porcelain.

  18. Effect of CNC-milling on the marginal and internal fit of dental ceramics: a pilot study.

    Science.gov (United States)

    Schaefer, Oliver; Kuepper, Harald; Thompson, Geoffrey A; Cachovan, Georg; Hefti, Arthur F; Guentsch, Arndt

    2013-08-01

    Machined restorations have been investigated for their preciseness before, while detailed information on the milling-step itself are lacking. Therefore, the aim of this laboratory study was to quantify the effect of a novel milling-procedure on the marginal and internal fit of ceramic restorations. An acrylic model of a lower left first molar was prepared to receive a ceramic partial crown and was duplicated by one step dual viscosity impressions. Gypsum casts were formed and laser-scanned to realize virtual datasets, before restorations were designed, exported (PRE) and machined from lithium disilicate blanks. Crowns were digitized by a structure-light-scanner to obtain post-milling-data (POST). PRE and POST were virtually superimposed on the reference tooth and subjected to computer-aided-inspection. Visual fit-discrepancies were displayed with colors, while root mean square deviations (RMSD) and degrees of similarity (DS) were computed and analysed by t-tests for paired samples (n=5, α=0.05). The milling procedure resulted in a small increase of the marginal and internal fit discrepancies (RMSD mean: 3μm and 6μm, respectively). RMSD differences were not statistically significant (p=0.495 and p=0.160 for marginal and internal fit, respectively). These results were supported by the DS data. The products of digital dental workflows are prone to imprecisions. However, the present findings suggest that differences between computer-aided designed and actually milled restorations are small, especially when compared to typical fit discrepancies observed clinically. Imprecisions introduced by digital design or production processes are small. Copyright © 2013 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  19. Effect of zircon-based tricolor pigments on the color, microstructure, flexural strength and translucency of a novel dental lithium disilicate glass-ceramic.

    Science.gov (United States)

    Yuan, Kun; Wang, Fu; Gao, Jing; Sun, Xiang; Deng, Zai-Xi; Wang, Hui; Jin, Lei; Chen, Ji-Hua

    2014-01-01

    The purpose of this study was to investigate the effect of zircon-based tricolor pigments (praseodymium zircon yellow, ferrum zircon red, and vanadium zircon blue) on the color, thermal property, crystalline phase composition, microstructure, flexural strength, and translucency of a novel dental lithium disilicate glass-ceramic. The pigments were added to the glass frit, milled, pressed, and sintered. Ninety monochrome samples were prepared and the colors were analyzed. The effect of the pigments on thermal property, crystalline phase composition, and microstructure were determined by differential scanning calorimetry (DSC), X-ray diffraction (XRD), and scanning electron microscopy (SEM), respectively. Addition of the pigments resulted in the acquisition of subtractive primary colors as well as tooth-like colors, and did not demonstrate significant effects on the thermal property, crystalline phase composition, microstructure, and flexural strength of the experimental glass-ceramic. Although significant differences (p ceramics, the translucencies of the latter were sufficient to fabricate dental restorations. These results indicate that the zircon-based tricolor pigments can be used with dental lithium disilicate glass-ceramic to produce abundant and predictable tooth-like colors without significant adverse effects, if mixed in the right proportions. Copyright © 2013 Wiley Periodicals, Inc.

  20. Modeling of thermal explosion under pressure in metal ceramic systems

    International Nuclear Information System (INIS)

    Shapiro, M.; Dudko, V.; Skachek, B.; Matvienko, A.; Gotman, I.; Gutmanas, E.Y.

    1998-01-01

    The process of reactive in situ synthesis of dense ceramic matrix composites in Ti-B-C, Ti-B-N, Ti-Si-N systems is modeled. These ceramics are fabricated on the basis of compacted blends of ceramic powders, namely Ti-B 4 C and/or Ti-BN. The objectives of the project are to identify and investigate the optimal thermal conditions preferable for production of fully dense ceramic matrix composites. Towards this goal heat transfer and combustion in dense and porous ceramic blends are investigated during monotonous heating at a constant rate. This process is modeled using a heat transfer-combustion model with kinetic parameters determined from the differential thermal analysis of the experimental data. The kinetic burning parameters and the model developed are further used to describe the thermal explosion synthesis in a restrained die under pressure. It is shown that heat removal from the reaction zone affects the combustion process and the final phase composition

  1. Changes to Glazed Dental Ceramic Shade, Roughness, and Microhardness after Bleaching and Simulated Brushing.

    Science.gov (United States)

    Rodrigues, Carlos Roberto Teixeira; Turssi, Cecilia Pedroso; Amaral, Flávia Lucisano Botelho; Basting, Roberta Tarkany; França, Fabiana Mantovani Gomes

    2017-09-05

    To evaluate shade stability, surface roughness, microhardness, and compressive strength of a glazed feldspathic ceramic subjected to bleaching and simulated brushing. Eighty-eight glazed feldspathic ceramic specimens were made from microparticulate leucite and divided into eight groups (n = 10). The whitening products used were: Opalescence Trèswhite Supreme (Ultradent), Opalescence®\\ PF 15% (Ultradent), and Oral-B 3D White Whitestrips. All substances for whitening were used for 4 hours/day for a period of 14 days; the control group was not bleached. Next, half of the specimens were individually brushed. Microhardness and surface roughness data were subjected to three-way ANOVA and Tukey test. The diametrical tensile strength data were subjected to two-way ANOVA. The shade change data were analyzed using Kruskal-Wallis, Mann-Whitney, and the Student-Newman-Keuls test. The significance level was set at 5%. Glazed feldspathic ceramic surface microhardness was significantly affected by bleaching agents (p = 0.007). Initially, glazed ceramic microhardness was significantly higher than that observed after contact with the bleaching agents, whether or not brushing was performed. The specimens submitted to bleaching in preloaded trays presented lower surface roughness values after brushing (p = 0.037). The surface roughness was significantly lower in the brushed specimens (p = 0.044). The diametrical tensile strength was not significantly affected by the application of bleaching agents (p = 0.563) or by brushing (p = 0.477). When the specimens were brushed, however, shade change was significantly influenced by the bleaching agent used (p = 0.041). Bleaching agents associated with brushing cycles can alter surface properties and shade stability of glazed feldspathic ceramics, though such findings may not reflect the performance of unglazed feldspathic ceramics. © 2017 by the American College of Prosthodontists.

  2. Rotating Ceramic Water Filter Discs System for Water Filtration

    Directory of Open Access Journals (Sweden)

    Riyadh Z. Al Zubaidy

    2017-04-01

    Full Text Available This work aimed to design, construct and operate a new laboratory scale water filtration system. This system was used to examine the efficiency of two ceramic filter discs as a medium for water filtration. These filters were made from two different ceramic mixtures of local red clay, sawdust, and water. The filtration system was designed with two rotating interfered modules of these filters. Rotating these modules generates shear force between water and the surfaces of filter discs of the filtration modules that works to reduce thickness of layer of rejected materials on the filters surfaces. Each module consists of seven filtration units and each unit consists of two ceramic filter discs. The average measured hydraulic conductivity of the first module was 13.7mm/day and that for the second module was 50mm/day. Results showed that the water filtration system can be operated continuously with a constant flow rate and the filtration process was controlled by a skin thin layer of rejected materials. The ceramic water filters of both filtration modules have high removal efficiency of total suspended solids up to 100% and of turbidity up to 99.94%.

  3. Evaluation of a high fracture toughness composite ceramic for dental applications

    NARCIS (Netherlands)

    Aboushelib, M.N.; Kleverlaan, C.J.; Feilzer, A.J.

    2008-01-01

    Purpose: The introduction of yttrium partially stabilized zirconia polycrystals (Y-TZP) has pushed the application limits of all-ceramic restorations. The mechanical properties of these materials can be further improved by the addition of a secondary dopant phase. The aim of this work was to

  4. Systemic Assessment of Patients Undergoing Dental Implant ...

    African Journals Online (AJOL)

    These days, dental implants are becoming routinely used as a treatment option for rehabilitation of lost teeth. Conventionally, it is only after the completion of bone healing that the dental implants are loaded into the bone. Bone healing time is approximately 3 months and. 6 months for the mandible and maxilla, respectively.

  5. A high temperature testing system for ceramic composites

    Science.gov (United States)

    Hemann, John

    1994-01-01

    Ceramic composites are presently being developed for high temperature use in heat engine and space power system applications. The operating temperature range is expected to be 1090 to 1650 C (2000 F to 3000 F). Very little material data is available at these temperatures and, therefore, it is desirable to thoroughly characterize the basic unidirectional fiber reinforced ceramic composite. This includes testing mainly for mechanical material properties at high temperatures. The proper conduct of such characterization tests requires the development of a tensile testing system includes unique gripping, heating, and strain measuring devices which require special considerations. The system also requires an optimized specimen shape. The purpose of this paper is to review various techniques for measuring displacements or strains, preferably at elevated temperatures. Due to current equipment limitations it is assumed that the specimen is to be tested at a temperature of 1430 C (2600F) in an oxidizing atmosphere. For the most part, previous high temperature material characterization tests, such as flexure and tensile tests, have been performed in inert atmospheres. Due to the harsh environment in which the ceramic specimen is to be tested, many conventional strain measuring techniques can not be applied. Initially a brief description of the more commonly used mechanical strain measuring techniques is given. Major advantages and disadvantages with their application to high temperature tensile testing of ceramic composites are discussed. Next, a general overview is given for various optical techniques. Advantages and disadvantages which are common to these techniques are noted. The optical methods for measuring strain or displacement are categorized into two sections. These include real-time techniques. Finally, an optical technique which offers optimum performance with the high temperature tensile testing of ceramic composites is recommended.

  6. Effect of intra-oral aging on t→m phase transformation, microstructure, and mechanical properties of Y-TZP dental ceramics.

    Science.gov (United States)

    Miragaya, Luciana Meireles; Guimarães, Renato Bastos; Souza, Rodrigo Othávio de Assunção E; Santos Botelho, Glauco Dos; Antunes Guimarães, José Guilherme; da Silva, Eduardo Moreira

    2017-08-01

    The aim of the present study was to evaluate the influence of intra-oral aging on the tetragonal-to-monoclinic (t→m) phase transformation of two Y-TZP dental ceramics - Lava Frame (Frame) and Lava Plus (Plus) - and determine the impact of this response on their microstructures and mechanical properties: flexural strength, Young's modulus, microhardness and fracture toughness. Standardized ceramic specimens were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). After the baseline analysis, the specimens were attached to personalized intra-oral resin appliances and exposed to the oral cavity of 20 subjects for 60 days and then analyzed again. Specimens produced for mechanical properties evaluation were also analyzed before and after the 60-day intra-oral aging. The data were analyzed using two-way ANOVA and Tukey HSD's post hoc test (α=0.05). Weibull analysis was used to evaluate the strength reliability. Both Y-TZP ceramics suffered t→m phase transformation after 60-day intra-oral aging (Plus=4.7%/Frame=7.7%). SEM and AFM analyses showed dislodgement of ZrO 2 grains and a significant increase in roughness after intra-oral aging for both ceramics. Both Y-TZP ceramics suffered a decrease on flexural strength, Young's modulus and fracture toughness after intra-oral aging (pdental ceramics. Copyright © 2017 Elsevier Ltd. All rights reserved.

  7. Mechanical properties of polymer-infiltrated-ceramic (sodium aluminum silicate) composites for dental restoration.

    Science.gov (United States)

    Cui, Bencang; Li, Jing; Wang, Huining; Lin, Yuanhua; Shen, Yang; Li, Ming; Deng, Xuliang; Nan, Cewen

    2017-07-01

    To fabricate indirect restorative composites for CAD/CAM applications and evaluate the mechanical properties. Polymer-infiltrated-ceramic composites were prepared through infiltrating polymer into partially sintered sodium aluminum silicate ceramic blocks and curing. The corresponding samples were fabricated according to standard ISO-4049 using for mechanical properties measurement. The flexural strength and fracture toughness were measured using a mechanical property testing machine. The Vickers hardness and elastic modulus were calculated from the results of nano-indentation. The microstructures were investigated using secondary electron detector. The density of the porous ceramic blocks was obtained through TG-DTA. The conversion degrees were calculated from the results of mid-infrared spectroscopy. The obtained polymer infiltrated composites have a maximum flexural strength value of 214±6.5MPa, Vickers hardness of 1.76-2.30GPa, elastic modulus of 22.63-27.31GPa, fracture toughness of 1.76-2.35MPam 1/2 and brittleness index of 0.75-1.32μm -1/2 . These results were compared with those of commercial CAD/CAM blocks. Our results suggest that these materials with good mechanical properties are comparable to two commercial CAD/CAM blocks. The sintering temperature could dramatically influence the mechanical properties. Restorative composites with superior mechanical properties were produced. These materials mimic the properties of natural dentin and could be a promising candidate for CAD/CAM applications. Copyright © 2017 Elsevier Ltd. All rights reserved.

  8. Evaluating the fracture toughness and flexural strength of pressable dental ceramics: an in vitro study.

    Science.gov (United States)

    Gurram, Ravi; Krishna, C H Vamsi; Reddy, K Mahendranadh; Reddy, G V K Mohan; Shastry, Y Mahadev

    2014-12-01

    The study was undertaken to evaluate the biaxial flexural strength, biaxial flexural strength after etching with 9 % HF acid and fracture toughness of three commonly used pressable all ceramic core materials. Ninety glass ceramic specimens were fabricated from three commercially available leucite based core ceramic material (1) Esthetic Empress, (2) Cergo, and (3) Performance Plus. Thirty discs of each material were divided into three groups of 10 discs each. Biaxial flexural strength (30 discs,) Biaxial flexural strength for samples treated with 9 % HF acid (30 discs) and fracture toughness (30 discs) were evaluated. Core material Performance Plus had the lowest biaxial strength of 124.89 MPa, Cergo had strength of 152.22 MPa and the highest value of 163.95 was reported for Esthetic Empress. For samples treated 9 % HF, Performance Plus had the lowest biaxial strength of 98.37 MPa, Cergo had strength of 117.42 MPa and the highest value of 143.74 was reported for Esthetic Empress. Core material Performance Plus had the lowest fracture toughness of 1.063 MPa, Cergo had strength of 1.112 MPa and the highest value of 1.225 was reported for Esthetic Empress. The results shows that Esthetic Empress had better mechanical properties compared to Cergo had Performance Plus in relation to the parameters tested.

  9. Production and Characterization of Glass-Ceramic Materials for Potential Use in Dental Applications: Thermal and Mechanical Properties, Microstructure, and In Vitro Bioactivity

    Directory of Open Access Journals (Sweden)

    Francesco Baino

    2017-12-01

    Full Text Available Multicomponent silicate glasses and their corresponding glass-ceramic derivatives were prepared and tested for potential applications in dentistry. The glasses were produced via a melting-quenching process, ground and sieved to obtain fine-grained powders that were pressed in the form of small cylinders and thermally treated to obtain sintered glass-ceramic samples. X-ray diffraction investigations were carried out on the materials before and after sintering to detect the presence of crystalline phases. Thermal analyses, mechanical characterizations (assessment of bending strength, Young’s modulus, Vickers hardness, fracture toughness, and in vitro bioactivity tests in simulated body fluid were performed. On the basis of the acquired results, different potential applications in the dental field were discussed for the proposed glass-ceramics. The use of such materials can be suggested for either restorative dentistry or dental implantology, mainly depending on their peculiar bioactive and mechanical properties. At the end of the work, the feasibility of a novel full-ceramic bilayered implant was explored and discussed. This implant, comprising a highly bioactive layer expected to promote osteointegration and another one mimicking the features of tooth enamel, can have an interesting potential for whole tooth substitution.

  10. Clinical acceptability of metal-ceramic fixed partial dental prosthesis fabricated with direct metal laser sintering technique-5 year follow-up.

    Science.gov (United States)

    Prabhu, Radhakrishnan; Prabhu, Geetha; Baskaran, Eswaran; Arumugam, Eswaran M

    2016-01-01

    In recent years, direct metal laser sintered (DMLS) metal-ceramic-based fixed partial denture prostheses have been used as an alternative to conventional metal-ceramic fixed partial denture prostheses. However, clinical studies for evaluating their long-term clinical survivability and acceptability are limited. The aim of this study was to assess the efficacy of metal-ceramic fixed dental prosthesis fabricated with DMLS technique, and its clinical acceptance on long-term clinical use. The study group consisted of 45 patients who were restored with posterior three-unit fixed partial denture prosthesis made using direct laser sintered metal-ceramic restorations. Patient recall and clinical examination of the restorations were done after 6months and every 12 months thereafter for the period of 60 months. Clinical examination for evaluation of longevity of restorations was done using modified Ryge criteria which included chipping of the veneered ceramic, connector failure occurring in the fixed partial denture prosthesis, discoloration at the marginal areas of the veneered ceramic, and marginal adaptation of the metal and ceramic of the fixed denture prosthesis. Periapical status was assessed using periodical radiographs during the study period. Survival analysis was made using the Kaplan-Meier method. None of the patients had failure of the connector of the fixed partial denture prostheses during the study period. Two exhibited biological changes which included periapical changes and proximal caries adjacent to the abutments. DMLS metal-ceramic fixed partial denture prosthesis had a survival rate of 95.5% and yielded promising results during the 5-year clinical study.

  11. [Influence of La2O3 and Li2O on glass powder for infiltrating ZTA all-ceramic dental material formed by gel-casting].

    Science.gov (United States)

    Jin, Qiong; Wang, Xiao-fei; Yang, Zheng-yu; Tong, Yi-ping; Zhu, Li; Ma, Jian-feng

    2012-10-01

    The influence of La2O3 and Li2O on glass powder was studied in this paper, which is to infiltrate ZTA all-ceramic dental material formed by gel-casting. The performance of different component was analyzed to optimize glass formula. Six groups of glass powder were designed and prepared by conventional melt-quenching method. ZTA ceramic blocks were covered with glass paste, which were formed by gel-casting and sintered in 1200 degrees centigrade, then infiltrated in 1150 degrees centigrade for twice to make glass/ZTA ceramic composites. By detecting differential thermal analysis and melting range of infiltration glass power, as well as flexural strength, linear shrinkage, SEM and EDS of glass/ZTA ceramic composites, the optimized glass group was determined out. Statistical analysis was performed using SPSS 13.0 software package by means of paired t test or one way ANOVA. The bending strength of group Li1 was (291.2±27.9) MPa, significantly higher than group Li2 and group La2(Pglass of group Li1 can lubricate ZTA ceramics well, their structure was compact and had a few small pores. Intergranular fracture existed on cross surface as well as transgranular fracture. The results showed that Li1(30%La2O3-15%Al2O3-15%SiO2-15%B2O3-5%Li2O) glass infiltrated ZTA ceramic composite had the best capability. Glass/ZTA composite material can be prepared by gel-casting and infiltrating way, and this process is simple and economically suitable for general dental laboratory.

  12. All-ceramic inlay-retained fixed dental prostheses for replacing posterior missing teeth: A systematic review.

    Science.gov (United States)

    Castillo-Oyagüe, Raquel; Sancho-Esper, Rocío; Lynch, Christopher D; Suárez-García, María-Jesús

    2018-01-01

    To evaluate the current status of all-ceramic inlay-retained fixed dental prostheses (CIR-FDPs) for the replacement of posterior teeth. Screening of titles and abstracts, full-text analysis for inclusion eligibility, quality assessment, data extraction and evaluation of the scientific evidence were performed independently by two reviewers. The electronic databases MEDLINE/PubMed, EMBASE, Cochrane Central Register of Controlled Trials, and Compludoc were searched with no restriction to publication date or language. The quality of the studies was evaluated through: the original 'QDP' ('Questionnaire for selecting articles on Dental Prostheses') (for research papers); the 'Guidelines for managing overviews' of the Evidence-Based Medicine Working Group (for reviews); the Cochrane risk of bias tool; and the GRADE scale for grading scientific evidence. This review started with 4942 articles, which were narrowed down to 23 according to the selection criteria. The data was not statistically treated because of the heterogeneity of the studies. Zirconia-based CIR-FDPs may be recommended for restoring posterior single missing teeth, although the prosthesis/tooth bonded interface has yet to be improved. The addition of lateral wings to the classical inlay preparation seems promising. The weakest parts of CIR-FDPs are the connectors and retainers, while caries and endodontic problems are the most common biological complications. The fabrication of CIR-FDPs with monolithic zirconia may eliminate chipping problems. A three-unit CIR-FDP is a viable treatment option for replacing a posterior missing tooth. Appropriate case selection, abutment preparation and luting procedures may be decisive for clinical success. Copyright © 2017 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.

  13. Melter viewing system for liquid-fed ceramic melters

    International Nuclear Information System (INIS)

    Westsik, J.H. Jr.; Brenden, B.B.

    1988-01-01

    Melter viewing systems are an integral component of the monitoring and control systems for liquid-fed ceramic melters. The Pacific Northwest Laboratory (PNL) has designed cameras for use with glass melters at PNL, the Hanford Waste Vitrification Plant (HWVP), and West Valley Demonstration Project (WVDP). This report is a compilation of these designs. Operating experiences with one camera designed for the PNL melter are discussed. A camera has been fabricated and tested on the High-Bay Ceramic Melter (HBCM) and the Pilot-Scale Ceramic Melter (PSCM) at PNL. The camera proved to be an effective tool for monitoring the cold cap formed as the feed pool developed on the molten glass surface and for observing the physical condition of the melter. Originally, the camera was built to operate using the visible light spectrum in the melter. It was later modified to operate using the infrared (ir) spectrum. In either configuration, the picture quality decreases as the size of the cold cap increases. Large cold caps cover the molten glass, reducing the amount of visible light and reducing the plenum temperatures below 600 0 C. This temperature corresponds to the lowest level of blackbody radiation to which the video tube is sensitive. The camera has been tested in melter environments for about 1900 h. The camera has withstood mechanical shocks and vibrations. The cooling system in the camera has proved effective in maintaining the optical and electronic components within acceptable temperature ranges. 10 refs., 15 figs

  14. Quality Assurance System in dental radiology

    International Nuclear Information System (INIS)

    Yacobenco, A.; Tauhata, L.; Infantosi, A.F.

    1998-01-01

    According to data published by the National Commission of Nuclear Energy (CNEN) it was observed that in Dental Radiology more than 80% of the exams reveal entrance skin doses higher than 5,0 mGy, that proximately 85% of the dentists sub-develop the films and 40% of the equipment have low performance regarding collimation, filtration and other problems. This is a critical situation for the population regarding life quality and requires prompt attention from the sanitary authority. Face and universe of 30,000 dentist in the state of Sao Paulo, it was necessary to organize a technical and administrative structure to establish procedures, elaborate training course and create an adequate software system to control all the inspections. The inspection control was based on monitoring the geometrical and exposure parameters as well as the implementation of internal procedures. It was also implemented a control of reject rate and a routine check of the control books. Results show a great improvement of the parameters in 152 of the x ray tubes considered here. Entrance skin dose up to 2,5 mGy increased from 19% to 57%, field size up to 6 cm, increased from 33 % to 96%, k Vp exactitude (13%) and exposure time (67%) jumped to 100%. Also 100% were attained with regards to filtration, collimation and several internal procedures. By the results showed above, we can conclude that we are in the right direction and that all goals will be reached

  15. Image-guided navigation system for placing dental implants.

    Science.gov (United States)

    Casap, Nardy; Wexler, Alon; Lustmann, Joshua

    2004-10-01

    Navigation-guided surgery has recently been introduced into various surgical disciplines, including oral and maxillofacial surgery. Since the advent of dental implants, dental computed tomography (CT) scans have been used as a diagnostic tool for preoperative planning, but not as part of the surgical phase. This article explains the principles of computer-assisted surgery and describes the use of a computer-guided navigation system in dental implantology. The system uses preoperative dental CT scans for planning and as an integral part of the surgical procedure. This system allows continuous intraoperative coordination of the implantation phase with the preoperative plan, optimizing the accuracy of implant surgery. Deviations from the planned location of the implants are minimal. Several cases are discussed.

  16. Quantitative Evaluation of Contamination on Dental Zirconia Ceramic by Silicone Disclosing Agents after Different Cleaning Procedures

    Directory of Open Access Journals (Sweden)

    Sebastian Wille

    2015-05-01

    Full Text Available The aim of this study was to evaluate the effectiveness of cleaning procedures for air-abraded zirconia after contamination with two silicone disclosing agents. Air-abraded zirconia ceramic specimens (IPS e.max ZirCAD were contaminated with either GC Fit Checker white or GC Fit Checker II. Untreated zirconia specimens were used as control. Afterwards the surfaces were cleaned either with waterspray or ultrasonically in 99% isopropanol or using a newly developed cleaning paste (Ivoclean. After cleaning X-ray photoelectron spectroscopy (XPS was performed and the relative peak intensities of Zr, C and Si were used for a qualitative comparison of the residuals. There was no significant difference between the two different silicone disclosing agents. An additional cleaning step with isopropanol led to a significantly lower amount of residuals on the surface, but an additional cleaning process with Ivoclean did not reduce the amount of carbon residuals in comparison to the isopropanol cleaning. Just the silicone amount on the surface was reduced. None of the investigated cleaning processes removed all residuals from the contaminated surface. Standard cleaning processes do not remove all residuals of the silicone disclosing agent from the surface. This may lead to a failure of the resin-ceramic bonding.

  17. Influence of Different Ceramic Systems on Marginal Misfit.

    Science.gov (United States)

    Vargas, S P; Neves, A C C; Vitti, R; Amaral, M; Henrique, M N; Silva-Concílio, L R

    2017-09-01

    the aim of this study was to evaluate the marginal misfit at the interface between a ceramic coping and its abutment. Twenty-four specimens were made with solid abutments. The specimens were divided into 3 groups according to the ceramic system (n = 8): Lava (zirconia), IPS e.max Press (lithium disilicate), and IPS Empress Esthetic (leucite). All copings were cemented with resin luting agent (RelyX U200) and the marginal misfit were evaluated at 3 different times: initial, after cementation, and after mechanical cycling using a linear measuring microscope (Measuring Microscope STM-Olympus) at a magnification of 40x. All specimens were subjected to mechanical cycling (1 million cycles) by an universal testing machine (Instron 8800). The results were statistically analyzed using Analysis of Variance and Student's t-test (α = 0.05). all groups showed an increase in the marginal misfit after cementation. The lithium disilicate group demonstrated the lowest interacial gap values at each evaluation (p = 0.001). The zirconia and leucite groups showed similar interfacial gap values (initial, p = 0.244; and post cementation, p = 0.751). the cementation increase the marginal misfit, but the mechanical cycling did not influence the marginal misfit of the ceramics systems evaluated. Copyright© 2017 Dennis Barber Ltd.

  18. Automated dental identification system: An aid to forensic odontology

    Directory of Open Access Journals (Sweden)

    Parvathi Devi

    2011-01-01

    Full Text Available Automated dental identification system is computer-aided software for the postmortem identification of deceased individuals based on dental characteristics specifically radiographs. This system is receiving increased attention because of the large number of victims encountered in the mass disasters and it is 90% more time saving and accurate than the conventional radiographic methods. This technique is based on the intensity of the overall region of tooth image and therefore it does not necessitate the presence of sharp boundary between the teeth. It provides automated search and matching capabilities for digitized radiographs and photographic dental images and compares the teeth present in multiple digitized dental records in order to access their similarity. This paper highlights the functionality of its components and techniques used in realizing these components.

  19. Physical and adhesive properties of dental enamel after radiotherapy and bonding of metal and ceramic brackets.

    Science.gov (United States)

    Santin, Gabriela Cristina; Palma-Dibb, Regina Guenka; Romano, Fábio Lourenço; de Oliveira, Harley Francisco; Nelson Filho, Paulo; de Queiroz, Alexandra Mussolino

    2015-08-01

    The increasing success rates for cancer patients treated with radiotherapy and the frequent occurrence of tooth loss during treatment have led to an increased demand for orthodontic treatment after radiotherapy. The aim of this study was to evaluate tooth enamel of irradiated teeth after the bonding and debonding of metal and ceramic brackets. Ten permanent molars were cut into enamel fragments measuring 1 mm(2) and divided into an irradiated group (total dose of 60 Gy) and a nonirradiated group. The fragments were subjected to microshear testing to evaluate whether radiotherapy altered the strength of the enamel. Furthermore, 90 prepared premolars were divided into 6 groups and subgroups (n = 15): group 1, nonirradiated and nonaged; group 2, nonirradiated and aged (thermal cycled); group 3, irradiated and aged; each group was divided into 2 subgroups: metallic and ceramic brackets. After thermal cycling and radiotherapy, the brackets were bonded onto the specimens with Transbond XT (3M Unitek, Monrovia, Calif). After 24 hours, the specimens were subjected to the shear tests. Images of the enamel surfaces were classified using the adhesive remnant index. The composite resin-enamel interface was also evaluated. Enamel fragments subjected to radiation had lower strength than did the nonirradiated samples (P enamel interface, resin tags were more extensive on irradiated tooth enamel. Radiation decreased tooth enamel strength, and the specimens treated with radiotherapy had higher frequencies of adhesive failure between the bracket and the composite resin as well as more extensive tags. Copyright © 2015 American Association of Orthodontists. Published by Elsevier Inc. All rights reserved.

  20. Survey on multisensory feedback virtual reality dental training systems.

    Science.gov (United States)

    Wang, D; Li, T; Zhang, Y; Hou, J

    2016-11-01

    Compared with traditional dental training methods, virtual reality training systems integrated with multisensory feedback possess potentials advantages. However, there exist many technical challenges in developing a satisfactory simulator. In this manuscript, we systematically survey several current dental training systems to identify the gaps between the capabilities of these systems and the clinical training requirements. After briefly summarising the components, functions and unique features of each system, we discuss the technical challenges behind these systems including the software, hardware and user evaluation methods. Finally, the clinical requirements of an ideal dental training system are proposed. Future research/development areas are identified based on an analysis of the gaps between current systems and clinical training requirements. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  1. Opalescence: Tooth Whitening Systems | Fischer | Tanzania Dental ...

    African Journals Online (AJOL)

    Tanzania Dental Journal. Journal Home · ABOUT THIS JOURNAL · Advanced Search · Current Issue · Archives · Journal Home > Vol 15, No 2 (2009) >. Log in or Register to get access to full text downloads. Username, Password, Remember me, or Register · Download this PDF file. The PDF file you selected should load ...

  2. Ceramic Defects in Metal-Ceramic Fixed Dental Prostheses Made from Co-Cr and Au-Pt Alloys: A Retrospective Study.

    Science.gov (United States)

    Mikeli, Aikaterini; Boening, Klaus W; Lißke, Benjamin

    2015-01-01

    Ceramic defects in porcelain-fused-to-metal (PFM) restorations may depend on framework alloy type. This study assessed ceramic defects on cobalt-chromium- (Co-Cr-) and gold-platinum- (Au-Pt-) based PFM restorations. In this study, 147 Co-Cr-based and 168 Au-Pt-based PFM restorations inserted between 1998 and 2010 (139 patients) were examined for ceramic defects. Detected defects were assigned to three groups according to clinical defect relevance. Ceramic defect rates (Co-Cr-based: 12.9%; Au-Pt-based: 7.2%) revealed no significant difference but a strong statistical trend (U test, P = .082). Most defects were of little clinical relevance. Co-Cr PFM restorations may be at higher risk for ceramic defects compared to Au-Pt-based restorations.

  3. Ceramic Foams from Pre-Ceramic Polymer Routes for Reusable Acreage Thermal Protection System Applications

    Science.gov (United States)

    Stackpoole, Mairead; Chien, Jennifer; Schaeffler, Michelle

    2004-01-01

    Contents include the following: Motivation. Current light weight insulation. Advantages of preceramic-polymer-derived ceramic foams. Rigid insulation materials. Tailor foam microstructures. Experimental approach. Results: sacrificial materials, sacrificial fillers. Comparison of foam microstructures. Density of ceramic foams. Phase evolution and properties: oxidation behavior. mechanical properties, aerothermal performance. Impact damage of microcellular foams. Conclusions.

  4. Phantom-based interactive simulation system for dental treatment training.

    Science.gov (United States)

    Sae-Kee, Bundit; Riener, Robert; Frey, Martin; Pröll, Thomas; Burgkart, Rainer

    2004-01-01

    In this paper, we propose a new interactive simulation system for dental treatment training. The system comprises a virtual reality environment and a force-torque measuring device to enhance the capabilities of a passive phantom of tooth anatomy in dental treatment training processes. The measuring device is connected to the phantom, and provides essential input data for generating the graphic animations of physical behaviors such as drilling and bleeding. The animation methods of those physical behaviors are also presented. This system is not only able to enhance interactivity and accessibility of the training system compared to conventional methods but it also provides possibilities of recording, evaluating, and verifying the training results.

  5. Enhanced Hydrophilicity and Biocompatibility of Dental Zirconia Ceramics by Oxygen Plasma Treatment

    Directory of Open Access Journals (Sweden)

    Ching-Chou Wu

    2015-02-01

    Full Text Available Surface properties play a critical role in influencing cell responses to a biomaterial. The objectives of this study were (1 to characterize changes in surface properties of zirconia (ZrO2 ceramic after oxygen plasma treatment; and (2 to determine the effect of such changes on biological responses of human osteoblast-like cells (MG63. The results indicated that the surface morphology was not changed by oxygen plasma treatment. In contrast, oxygen plasma treatment to ZrO2 not only resulted in an increase in hydrophilicity, but also it retained surface hydrophilicity after 5-min treatment time. More importantly, surface properties of ZrO2 modified by oxygen plasma treatment were beneficial for cell growth, whereas the surface roughness of the materials did not have a significant efficacy. It is concluded that oxygen plasma treatment was certified to be effective in modifying the surface state of ZrO2 and has the potential in the creation and maintenance of hydrophilic surfaces and the enhancement of cell proliferation and differentiation.

  6. Mechanical properties and porosity of dental glass-ceramics hot-pressed at different temperatures

    Directory of Open Access Journals (Sweden)

    Carla Castiglia Gonzaga

    2008-09-01

    Full Text Available The objective of this work was to evaluate biaxial-flexural-strength (σf, Vickers hardness (HV, fracture toughness (K Ic, Young's modulus (E, Poisson's ratio (ν and porosity (P of two commercial glass-ceramics, Empress (E1 and Empress 2 (E2, as a function of the hot-pressing temperature. Ten disks were hot-pressed at 1065, 1070, 1075 and 1080 °C for E1; and at 910, 915, 920 and 925 °C for E2. The porosity was measured by an image analyzer software and s f was determined using the piston-on-three-balls method. K Ic and HV were determined by an indentation method. Elastic constants were determined by the pulse-echo method. For E1 samples treated at different temperatures, there were no statistical differences among the values of all evaluated properties. For E2 samples treated at different temperatures, there were no statistical differences among the values of σf, E, and ν, however HV and K Ic were significantly higher for 910 and 915 °C, respectively. Regarding P, the mean value obtained for E2 for 925 °C was significantly higher compared to other temperatures.

  7. Ceramics in Restorative and Prosthetic DENTISTRY1

    Science.gov (United States)

    Kelly, J. Robert

    1997-08-01

    This review is intended to provide the ceramic engineer with information about the history and current use of ceramics in dentistry, contemporary research topics, and potential research agenda. Background material includes intra-oral design considerations, descriptions of ceramic dental components, and the origin, composition, and microstructure of current dental ceramics. Attention is paid to efforts involving net-shape processing, machining as a forming method, and the analysis of clinical failure. A rationale is presented for the further development of all-ceramic restorative systems. Current research topics receiving attention include microstructure/processing/property relationships, clinical failure mechanisms and in vitro testing, wear damage and wear testing, surface treatments, and microstructural modifications. The status of the field is critically reviewed with an eye toward future work. Significant improvements seem possible in the clinical use of ceramics based on engineering solutions derived from the study of clinically failed restorations, on the incorporation of higher levels of "biomimicry" in new systems, and on the synergistic developments in dental cements and adhesive dentin bonding.

  8. Real time neutron diffraction and NMR of the Empress II glass-ceramic system.

    Science.gov (United States)

    O'Donnell, M D; Hill, R G; Karpukhina, N; Law, R V

    2011-10-01

    This study reports real time neutron diffraction on the Empress II glass-ceramic system. The commercial glass-ceramics was characterized by real time neutron diffraction, ³¹P and ²⁹Si solid-state MAS-NMR, DSC and XRD. On heating, the as-received glass ceramic contained lithium disilicate (Li₂Si₂O₅), which melted with increasing temperature. This was revealed by neutron diffraction which showed the Bragg peaks for this phase had disappeared by 958°C in agreement with thermal analysis. On cooling lithium metasilicate (Li₂SiO₃) started to form at around 916°C and a minor phase of cristobalite at around 852°C. The unit cell volume of both Li-silicate phases increased linearly with temperature at a rate of +17×10⁻³ ų.°C⁻¹. Room temperature powder X-ray diffraction (XRD) of the material after cooling confirms presence of the lithium metasilicate and cristobalite as the main phases and shows, in addition, small amount of lithium disilicate and orthophosphate. ³¹P MAS-NMR reveals presence of the lithiorthophosphate (Li₃PO₄) before and after heat treatment. The melting of lithium disilicate on heating and crystallisation of lithium metasilicate on cooling agree with endothermic and exotermic features respectively observed by DSC. ²⁹Si MAS-NMR shows presence of lithium disilicate phase in the as-received glass-ceramic, though not in the major proportion, and lithium metasilicate in the material after heat treatment. Both phases have significantly long T₁ relaxation time, especially the lithium metasilicate, therefore, a quantitative analysis of the ²⁹Si MAS-NMR spectra was not attempted. Significance. The findings of the present work demonstrate importance of the commercially designed processing parameters in order to preserve desired characteristics of the material. Processing the Empress II at a rate slower than recommended 60°C min⁻¹ or long isothermal hold at the maximal processing temperature 920°C can cause

  9. Surface modifications of dental ceramic implants with different glass solder matrices: in vitro analyses with human primary osteoblasts and epithelial cells.

    Science.gov (United States)

    Markhoff, Jana; Mick, Enrico; Mitrovic, Aurica; Pasold, Juliane; Wegner, Katharina; Bader, Rainer

    2014-01-01

    Ceramic materials show excellent esthetic behavior, along with an absence of hypersensitivity, making them a possible alternative implant material in dental surgery. However, their surface properties enable only limited osseointegration compared to titanium implants. Within this study, a novel surface coating technique for enhanced osseointegration was investigated biologically and mechanically. Specimens of tetragonal zirconia polycrystal (TZP) and aluminum toughened zirconia (ATZ) were modified with glass solder matrices in two configurations which mainly consisted of SiO2, Al2O3, K2O, and Na2O. The influence on human osteoblastic and epithelial cell viability was examined by means of a WST-1 assay as well as live/dead staining. A C1CP-ELISA was carried out to verify procollagen type I production. Uncoated/sandblasted ceramic specimens and sandblasted titanium surfaces were investigated as a reference. Furthermore, mechanical investigations of bilaterally coated pellets were conducted with respect to surface roughness and adhesive strength of the different coatings. These tests could demonstrate a mechanically stable implant coating with glass solder matrices. The coated ceramic specimens show enhanced osteoblastic and partly epithelial viability and matrix production compared to the titanium control. Hence, the new glass solder matrix coating could improve bone cell growth as a prerequisite for enhanced osseointegration of ceramic implants.

  10. Surface Modifications of Dental Ceramic Implants with Different Glass Solder Matrices: In Vitro Analyses with Human Primary Osteoblasts and Epithelial Cells

    Science.gov (United States)

    Mick, Enrico

    2014-01-01

    Ceramic materials show excellent esthetic behavior, along with an absence of hypersensitivity, making them a possible alternative implant material in dental surgery. However, their surface properties enable only limited osseointegration compared to titanium implants. Within this study, a novel surface coating technique for enhanced osseointegration was investigated biologically and mechanically. Specimens of tetragonal zirconia polycrystal (TZP) and aluminum toughened zirconia (ATZ) were modified with glass solder matrices in two configurations which mainly consisted of SiO2, Al2O3, K2O, and Na2O. The influence on human osteoblastic and epithelial cell viability was examined by means of a WST-1 assay as well as live/dead staining. A C1CP-ELISA was carried out to verify procollagen type I production. Uncoated/sandblasted ceramic specimens and sandblasted titanium surfaces were investigated as a reference. Furthermore, mechanical investigations of bilaterally coated pellets were conducted with respect to surface roughness and adhesive strength of the different coatings. These tests could demonstrate a mechanically stable implant coating with glass solder matrices. The coated ceramic specimens show enhanced osteoblastic and partly epithelial viability and matrix production compared to the titanium control. Hence, the new glass solder matrix coating could improve bone cell growth as a prerequisite for enhanced osseointegration of ceramic implants. PMID:25295270

  11. Surface Modifications of Dental Ceramic Implants with Different Glass Solder Matrices: In Vitro Analyses with Human Primary Osteoblasts and Epithelial Cells

    Directory of Open Access Journals (Sweden)

    Jana Markhoff

    2014-01-01

    Full Text Available Ceramic materials show excellent esthetic behavior, along with an absence of hypersensitivity, making them a possible alternative implant material in dental surgery. However, their surface properties enable only limited osseointegration compared to titanium implants. Within this study, a novel surface coating technique for enhanced osseointegration was investigated biologically and mechanically. Specimens of tetragonal zirconia polycrystal (TZP and aluminum toughened zirconia (ATZ were modified with glass solder matrices in two configurations which mainly consisted of SiO2, Al2O3, K2O, and Na2O. The influence on human osteoblastic and epithelial cell viability was examined by means of a WST-1 assay as well as live/dead staining. A C1CP-ELISA was carried out to verify procollagen type I production. Uncoated/sandblasted ceramic specimens and sandblasted titanium surfaces were investigated as a reference. Furthermore, mechanical investigations of bilaterally coated pellets were conducted with respect to surface roughness and adhesive strength of the different coatings. These tests could demonstrate a mechanically stable implant coating with glass solder matrices. The coated ceramic specimens show enhanced osteoblastic and partly epithelial viability and matrix production compared to the titanium control. Hence, the new glass solder matrix coating could improve bone cell growth as a prerequisite for enhanced osseointegration of ceramic implants.

  12. Ultrathin CAD-CAM Ceramic Occlusal Veneers and Anterior Bilaminar Veneers for the Treatment of Moderate Dental Biocorrosion: A 1.5-Year Follow-Up.

    Science.gov (United States)

    Resende, T H; Reis, K R; Schlichting, L H; Magne, P

    2018-03-27

    Dental biocorrosion can produce a devastating impact on oral health. The restorative phase of the treatment should not cause additional damage of the remaining sound tooth structure. Ultrathin occlusal veneers are a conservative alternative to traditional onlays and complete crowns for the treatment of severe biocorrosive lesions. This strategy is explained in the present case report through a full-mouth rehabilitation of a patient with moderate biocorrosion. Maxillary anterior teeth were restored using the bilaminar technique (lingual direct composite veneers with labial ceramic veneers) and posterior teeth using ultrathin CAD-CAM ceramic occlusal veneers. The technical aspects required for the implementation of this new restorative design are presented with a special emphasis on the control of tooth preparation based on diagnostic wax-up, provisionalization, and the use of CAD-CAM technology.

  13. Flexural strength and microstructure of two lithium disilicate glass ceramics for CAD/CAM restoration in the dental clinic

    Directory of Open Access Journals (Sweden)

    Suk-Ho Kang

    2013-08-01

    Full Text Available Objectives There has been a growing interest in glass ceramic systems with good esthetics, high fracture resistance and bonding durability, and simplified fabrication techniques using CAD/CAM. The aim of this study is to compare flexural strength before and after heat treatment of two lithium disilicate CAD/CAM blocks, IPS e.max CAD (Ivoclar Vivadent and Rosetta SM (Hass, and to observe their crystalline structures. Materials and Methods Biaxial flexural strength was tested according to ISO 6872 with 20 disc form specimens sliced from each block before and after heat treatment. Also, the crystalline structures were observed using field-emission scanning microscopy (FE-SEM, Hitachi and x-ray diffraction (XRD, Rigaku analysis. The mean values of the biaxial flexural strength were analyzed by the Mann-Whitney U test at a significance level of p = 0.05. Results There were no statistically significant differences in flexural strength between IPS e.max CAD and Rosetta SM either before heat treatment or after heat treatment. For both ceramics, the initial flexural strength greatly increased after heat treatment, with significant differences (p < 0.05. The FE-SEM images presented similar patterns of crystalline structure in the two ceramics. In the XRD analysis, they also had similar patterns, presenting high peak positions corresponding to the standard lithium metasilicate and lithium disilicate at each stage of heat treatment. Conclusions IPS e.max CAD and Rosetta SM showed no significant differences in flexural strength. They had a similar crystalline pattern and molecular composition.

  14. Similar Marginal Precision of Zirconia- and Metal-Ceramic Fixed Dental Prostheses

    DEFF Research Database (Denmark)

    Nicolaisen, Maj Høygaard; Bahrami, Golnosh; Schropp, Lars

    clinical trial, 34 patients were randomized into two groups to receive a 3-unit fixed dental prosthesis (FDP) replacing a second premolar or a first molar. 17 ZC FDPs (BeCe CAD Zirkon, BEGO with Vita VM9, VITA ) and 17 MC FDPs (Bio PontoStar, BEGO with Vita VM13, VITA). All FDPs were made in accordance...... with the manufacturer’s guidelines by one operator. Before and after veneering, the FDPs were placed on the abutment teeth with a light-body A-silicone impression material (Extrude Wash, Kerr) between the restoration and the abutment teeth. After setting, the FDPs were removed and the light-body material was stabilized...... with a heavy-body impression material (Extrude, Kerr). The impression specimens were segmented to allow measurements of the thickness of the light-body material corresponding to the marginal gap at 12 points for each abutment. The measurements were done under 32X magnification with SPOT Advanced. Statistical...

  15. Temperature control system for liquid-fed ceramic melters

    International Nuclear Information System (INIS)

    Westsik, J.H. Jr.

    1986-10-01

    A temperature-feedback system has been developed for controlling electrical power to liquid-fed ceramic melters (LFCM). Software, written for a microcomputer-based data acquisition and process monitoring system, compares glass temperatures with a temperature setpoint and adjusts the electrical power accordingly. Included in the control algorithm are steps to reject failed thermocouples, spatially average the glass temperatures, smooth the averaged temperatures over time using a digital filter, and detect foaming in the glass. The temperature control system has proved effective during all phases of melter operation including startup, steady operation, loss of feed, and shutdown. This system replaces current, power, and resistance feedback control systems used previously in controlling the LFCM process

  16. Comparison of marginal and internal fit of 3-unit ceramic fixed dental prostheses made with either a conventional or digital impression.

    Science.gov (United States)

    Su, Ting-Shu; Sun, Jian

    2016-09-01

    For 20 years, the intraoral digital impression technique has been applied to the fabrication of computer aided design and computer aided manufacturing (CAD-CAM) fixed dental prostheses (FDPs). Clinical fit is one of the main determinants of the success of an FDP. Studies of the clinical fit of 3-unit ceramic FDPs made by means of a conventional impression versus a digital impression technology are limited. The purpose of this in vitro study was to evaluate and compare the internal fit and marginal fit of CAD-CAM, 3-unit ceramic FDP frameworks fabricated from an intraoral digital impression and a conventional impression. A standard model was designed for a prepared maxillary left canine and second premolar and missing first premolar. The model was scanned with an intraoral digital scanner, exporting stereolithography (STL) files as the experimental group (digital group). The model was used to fabricate 10 stone casts that were scanned with an extraoral scanner, exporting STL files to a computer connected to the scanner as the control group (conventional group). The STL files were used to produce zirconia FDP frameworks with CAD-CAM. These frameworks were seated on the standard model and evaluated for marginal and internal fit. Each framework was segmented into 4 sections per abutment teeth, resulting in 8 sections per framework, and was observed using optical microscopy with ×50 magnification. Four measurement points were selected on each section as marginal discrepancy (P1), mid-axial wall (P2), axio-occusal edge (P3), and central-occlusal point (P4). Mean marginal fit values of the digital group (64 ±16 μm) were significantly smaller than those of the conventional group (76 ±18 μm) (Pdigital group (111 ±34 μm) were significantly smaller than those of the conventional group (132 ±44 μm) (Pdigital and conventional impressions showed clinically acceptable marginal and internal fit. The marginal and internal fit of frameworks fabricated from the intraoral

  17. Systemic assessment of patients undergoing dental implant surgeries: A trans- and post-operative analysis

    OpenAIRE

    Sanjay Byakodi; Sachin Kumar; Rajesh Kumar Reddy; Vipin Kumar; Shipra Sepolia; Shivangi Gupta; Harkanwal Preet Singh

    2017-01-01

    Background: Procedure-related and patient-related factors influence the prognosis of dental implants to a major extent. Hence, we aimed to evaluate and analyze various systemic factors in patients receiving dental implants. Materials and Methods: Fifty-one patients were included in the study, in which a total of 110 dental implants were placed. Complete examination of the subjects was done before and after placement of dental implants. Implant surgery was planned, and osseointegrated dental i...

  18. [A new port catheter system of aluminum oxide ceramics].

    Science.gov (United States)

    Haindl, H; Schmoll, E; Willmann, G

    1995-03-01

    Implantable port catheter systems are becoming increasingly important, as they often permit out-patient treatment for many indications that would otherwise require hospitalization. Moreover, they also increase the safety/reliability of infusion therapy in critical inpatients. For a variety of reasons, the materials used so far, i.e. steel, titanium and various plastics have not been completely satisfactory. The main disadvantage of metallic systems is the formation of artefacts in tomographic images, while the shortcomings of plastics are mechanical, e.g. chip formation and early membrane failure. Against this background, a port catheter system made of alumina ceramic, which is largely free of the disadvantages of the other materials, was developed. The expected advantages in terms of complication rate and radiological artefacts, were fully confirmed by the evaluation of 160 monitored patients.

  19. Influence of implant abutment material on the color of different ceramic crown systems.

    Science.gov (United States)

    Dede, Doğu Ömür; Armağanci, Arzu; Ceylan, Gözlem; Celik, Ersan; Cankaya, Soner; Yilmaz, Burak

    2016-11-01

    Ceramics are widely used for anterior restorations; however, clinical color reproduction still constitutes a challenge particularly when the ceramic crowns are used on titanium implant abutments. The purpose of this in vitro study was to investigate the effect of implant abutment material on the color of different ceramic material systems. Forty disks (11×1.5 mm, shade A2) were fabricated from medium-opacity (mo) and high-translucency (ht) lithium disilicate (IPS e.max) blocks, an aluminous ceramic (VITA In-Ceram Alumina), and a zirconia (Zirkonzahn) ceramic system. Disks were fabricated to represent 3 different implant abutments (zirconia, gold-palladium, and titanium) and dentin (composite resin, A2 shade) as background (11×2 mm). Disk-shaped composite resin specimens in A2 shade were fabricated to represent the cement layer. The color measurements of ceramic specimens were made on composite resin abutment materials using a spectrophotometer. CIELab color coordinates were recorded, and the color coordinates measured on composite resin background served as the control group. Color differences (ΔE 00 ) between the control and test groups were calculated. The data were analyzed with 2-way analysis of variance (ANOVA) and compared with the Tukey HSD test (α=.05). The ceramics system, abutment material, and their interaction were significant for ΔE 00 values (P2.25) were observed for lithium disilicate ceramics on titanium abutments (2.46-2.50). The ΔE 00 values of lithium disilicate ceramics for gold-palladium and titanium abutments were significantly higher than for other groups (P2.25) of an implant-supported lithium disilicate ceramic restoration may be clinically unacceptable if it is fabricated over a titanium abutment. Zirconia may be a more suitable abutment material for implant-supported ceramic restorations. Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

  20. Integrated Medical-Dental Delivery Systems: Models in a Changing Environment and Their Implications for Dental Education.

    Science.gov (United States)

    Jones, Judith A; Snyder, John J; Gesko, David S; Helgeson, Michael J

    2017-09-01

    Models and systems of the dental care delivery system are changing. Solo practice is no longer the only alternative for graduating dentists. Over half of recent graduates are employees, and more than ever before, dentists are practicing in groups. This trend is expected to increase over the next 25 years. This article examines various models of dental care delivery, explains why it is important to practice in integrated medical-dental teams, and defines person-centered care, contrasting it with patient-centered care. Systems of care in which teams are currently practicing integrated oral health care delivery are described, along with speculation on the future of person-centered care and the team approach. Critical steps in the education of dental and other health care professionals and the development of clinical models of care in moving forward are considered. This article was written as part of the project "Advancing Dental Education in the 21 st Century."

  1. Electrical characterization of strontium titanate borosilicate glass ceramics system with bismuth oxide addition using impedance spectroscopy

    International Nuclear Information System (INIS)

    Thakur, O.P.; Kumar, Devendra; Parkash, Om; Pandey, Lakshman

    2003-01-01

    The ac electrical data, measured in the frequency range 0.1 kHz-1 MHz, were used to study the electrical response of strontium titanate borosilicate glass ceramic system with bismuth oxide addition. Complex plane plots from these electrical data for various glass ceramic samples reveal contributions from simultaneously operating polarization mechanisms to overall dielectric behavior. The complex modulus (M * ) representation of electrical data for various glass ceramic samples were found to be more informative. Equivalent circuit models, which represent the electrical behavior of glass ceramic samples, were determined using complex non-linear least square (CNLS) fitting. An attempt has been made to understand the dielectric behavior of various glass ceramics in terms of contributions arising from different polarization processes occurring at glassy matrix, crystalline phases, glass to crystal interface region and blocking electrodes. Glass ceramics containing SrTiO 3 and TiO 2 (rutile) phases show thermally stable dielectric behavior

  2. Strengths and Weaknesses of the Current Dental Hygiene Educational System.

    Science.gov (United States)

    Theile, Cheryl Westphal

    2017-09-01

    The state of the dental hygiene educational system in the United States is evolving. The numbers of programs, extent of curricula, and diversity of students, faculty, and practice settings vary significantly across the country. New trends in workforce utilization and delivery models are challenging current educational foundations and mandating an interprofessional approach to both the education and practice of dental hygienists. This article presents an overview of the current state of dental hygiene education to create a baseline for discussion of desired educational models for 2040. The strengths and weaknesses are defined to motivate change. Limitations of the current two-year associate degree are emphasized, along with the need to add expanded content and development of new skills. The developing non-traditional practice settings bring both a challenge to dental hygiene education and a promise of increasing potential in primary care interprofessional settings for the 21 st century. This article was written as part of the project "Advancing Dental Education in the 21 st Century."

  3. Relative translucency of six all-ceramic systems. Part I: core materials.

    Science.gov (United States)

    Heffernan, Michael J; Aquilino, Steven A; Diaz-Arnold, Ana M; Haselton, Debra R; Stanford, Clark M; Vargas, Marcos A

    2002-07-01

    All-ceramic restorations have been advocated for superior esthetics. Various materials have been used to improve ceramic core strength, but it is unclear whether they affect the opacity of all-ceramic systems. This study compared the translucency of 6 all-ceramic system core materials at clinically appropriate thicknesses. Disc specimens 13 mm in diameter and 0.49 +/- 0.01 mm in thickness were fabricated from the following materials (n = 5 per group): IPS Empress dentin, IPS Empress 2 dentin, In-Ceram Alumina core, In-Ceram Spinell core, In-Ceram Zirconia core, and Procera AllCeram core. Empress and Empress 2 dentin specimens also were fabricated and tested at a thickness of 0.77 +/- 0.02 mm (the manufacturer's recommended core thickness is 0.8 mm). A high-noble metal-ceramic alloy (Porc. 52 SF) served as the control, and Vitadur Alpha opaque dentin was used as a standard. Sample reflectance (ratio of the intensity of reflected light to that of the incident light) was measured with an integrating sphere attached to a spectrophotometer across the visible spectrum (380 to 700 nm); 0-degree illumination and diffuse viewing geometry were used. Contrast ratios were calculated from the luminous reflectance (Y) of the specimens with a black (Yb) and a white (Yw) backing to give Yb/Yw with CIE illuminant D65 and a 2-degree observer function (0.0 = transparent, 1.0 = opaque). One-way analysis of variance and Tukey's multiple-comparison test were used to analyze the data (P In-Ceram Spinell > Empress, Procera, Empress 2 > In-Ceram Alumina > In-Ceram Zirconia, 52 SF alloy.

  4. Influence of sodalite zeolite infiltration on the coefficient of thermal expansion and bond strength of all-ceramic dental prostheses.

    Science.gov (United States)

    Naji, Ghassan Abdul-Hamid; Omar, Ros Anita; Yahya, Rosiyah

    2017-03-01

    In all-ceramic systems, a high incidence of veneer chip-off has been reported in clinical studies. Coefficient of thermal expansion (CTE) behaviour is one of the factors that may increase residual stress in the interface and influence the veneer/core bond strength. Therefore, this study aimed to evaluate the effect of sodalite zeolite-infiltration on the CTE behaviour and bond strength of different all-ceramic prostheses. The case-study groups were synthesized sodalite zeolite-infiltrated alumina (IA-SOD) and synthesized sodalite zeolite-infiltrated zirconia-toughened alumina (ZTA) (IZ-SOD), while the control groups were glass-infiltrated alumina (IA-glass) and glass-infiltrated ZTA (IZ-glass). Forty cylindrical-shaped samples measuring 5 mm in diameter and 10 mm in height were tested for CTE using a thermo-mechanical analyser machine, and forty disc-shaped ceramic samples measuring 12 mm in diameter and 1.2 ± 0.2 mm in thickness were prepared using specially designed stainless steel split mould and veneered by cylinder-shaped (2 mm high × 2 mm diameter) low-fusing porcelain (Vita VM7). The veneer/core samples were sintered and tested for shear bond strength using a high precision universal testing machine. Scanning electron microscope, stereo microscope, atomic force microscope, and energy-dispersive X-ray spectroscopy were used to investigate the structural characteristics of samples at the fracture surface. The collected data were analyzed with a one-way ANOVA and Tukey HSD test (α=.05). IZ-SOD revealed highest CTE and shear bond strength values, while the IA-glass revealed the lowest values than the other groups. There was no significant difference in CTE and bond strength among IZ-SOD, IA-SOD and IZ-glass samples (p>0.05). The experimental SOD zeolite-infiltrated samples revealed higher CTE mismatch and bond strength along with a more favourable mode of failure than did the commercial glass-infiltrated samples. Sandblast technique is considered as effective

  5. Accuracy of optical scanning methods of the Cerec®3D system in the process of making ceramic inlays

    Directory of Open Access Journals (Sweden)

    Trifković Branka

    2010-01-01

    Full Text Available Background/Aim. One of the results of many years of Cerec® 3D CAD/CAM system technological development is implementation of one intraoral and two extraoral optical scanning methods which, depending on the current indications, are applied in making fixed restorations. The aim of this study was to determine the degree of precision of optical scanning methods by the use of the Cerec®3D CAD/CAM system in the process of making ceramic inlays. Methods. The study was conducted in three experimental groups of inlays prepared using the procedure of three methods of scanning Cerec ®3D system. Ceramic inlays made by conventional methodology were the control group. The accuracy of optical scanning methods of the Cerec®3D system computer aided designcomputer aided manufacturing (CAD/CAM was indirectly examined by measuring a marginal gap size between inlays and demarcation preparation by scanning electron microscope (SEM. Results. The results of the study showed a difference in the accuracy of the existing methods of scanning dental CAD/CAM systems. The highest level of accuracy was achieved by the extraoral optical superficial scanning technique. The value of marginal gap size inlays made with the technique of extraoral optical superficial scanning was 32.97 ± 13.17 μ. Techniques of intraoral optical superficial and extraoral point laser scanning showed a lower level of accuracy (40.29 ± 21.46 μ for inlays of intraoral optical superficial scanning and 99.67 ± 37.25 μ for inlays of extraoral point laser scanning. Conclusion. Optical scanning methods in dental CAM/CAM technologies are precise methods of digitizing the spatial models; application of extraoral optical scanning methods provides the hightest precision.

  6. Assessment of exposures and potential risks to the US adult population from the leaching of elements from gold and ceramic dental restorations.

    Science.gov (United States)

    Richardson, G Mark; James, Kyle Jordan; Peters, Rachel Elizabeth; Clemow, Scott Richard; Siciliano, Steven Douglas

    2016-01-01

    Using data from the 2001 to 2004 US National Health and Nutrition Examination Survey (NHANES) on the number and placement of tooth restorations in adults, we quantified daily doses due to leaching of elements from gold (Au) alloy and ceramic restorative materials. The elements with the greatest leaching rates from these materials are often the elements of lowest proportional composition. As a result, exposure due to wear will predominate for those elements of relatively high proportional composition, while exposure due leaching may predominate for elements of relatively low proportional composition. The exposure due to leaching of silver (Ag) and palladium (Pd) from Au alloys exceeded published reference exposure levels (RELs) for these elements when multiple full surface crowns were present. Six or more molar crowns would result in exceeding the REL for Ag, whereas three or more crowns would be necessary to exceed the REL for Pd. For platinum (Pt), the majority of tooth surfaces, beyond just molar crowns, would be necessary to exceed the REL for Pd. Exposures due to leaching of elements from ceramic dental materials were less than published RELs for all components examined here, including having all restorations composed of ceramic.

  7. Digital decoration by continuous ink jet system for ceramic products based in water inks

    International Nuclear Information System (INIS)

    Colores Ceramicos, S. A.; Talleres Foro, S. L.

    2010-01-01

    A new continuous ink jet system for digital ceramic decoration using water based dispersed ceramic pigment has been developed, that increases drastically the sustainability of the process. During the development of this work, different equipment for any application and the consumables and design tools have been also developed. (Author)

  8. Ballistic Performance of Porous-Ceramic, Thermal-Protection-Systems

    Science.gov (United States)

    Christiansen, E. L.; Davis, B. A.; Miller, J. E.; Bohl, W. E.; Foreman, C. D.

    2009-01-01

    Porous-ceramic, thermal protection systems are used heavily in current reentry vehicles like the Space Shuttle and are currently being proposed for the next generation of manned spacecraft, Orion. These materials insulate the structural components of a spacecraft against the intense thermal environments of atmospheric reentry. Furthermore, these materials are also highly exposed to space environmental hazards like meteoroid and orbital debris impacts. This paper discusses recent impact testing up to 9 km/s, and the findings of the influence of material equation-of-state on the simulation of the impact event to characterize the ballistic performance of these materials. These results will be compared with heritage models1 for these materials developed from testing at lower velocities. Assessments of predicted spacecraft risk based upon these tests and simulations will also be discussed.

  9. Microstructure, hardness, corrosion resistance and porcelain shear bond strength comparison between cast and hot pressed CoCrMo alloy for metal-ceramic dental restorations.

    Science.gov (United States)

    Henriques, B; Soares, D; Silva, F S

    2012-08-01

    The purpose of this study was to compare the microstructure, hardness, corrosion resistance and metal-porcelain bond strength of a CoCrMo dental alloy obtained by two routes, cast and hot pressing. CoCrMo alloy substrates were obtained by casting and hot pressing. Substrates' microstructure was examined by the means of Optical Microscopy (OM) and by Scanning Electron Microscope (SEM) and Energy Dispersive X-ray Spectroscopy (EDS). Hardness tests were performed in a microhardness indenter. The electrochemical behavior of substrates was investigated through potentiodynamic tests in a saline solution (8g NaCl/L). Substrates were bonded to dental porcelain and metal-porcelain bond strength was assessed by the means of a shear test performed in a universal test machine (crosshead speed: 0.5 mm/min) until fracture. Fractured surfaces as well as undestroyed interface specimens were examined with Stereomicroscopy and SEM-EDS. Data was analyzed with Shapiro-Wilk test to test the assumption of normality. The t-test (pmicrostructures whereas hot pressed specimens exhibited a typical globular microstructure with a second phase spread through the matrix. The hardness registered for hot pressed substrates was greater than that of cast specimens, 438±24HV/1 and 324±8HV/1, respectively. Hot pressed substrates showed better corrosion properties than cast ones, i.e. higher OCP; higher corrosion potential (E(corr)) and lower current densities (i(corr)). No significant difference was found (p<0.05) in metal-ceramic bond strength between cast (116.5±6.9 MPa) and hot pressed (114.2±11.9 MPa) substrates. The failure type analysis revealed an adhesive failure for all specimens. Hot pressed products arise as an alternative to cast products in dental prosthetics, as they impart enhanced mechanical and electrochemical properties to prostheses without compromising the metal-ceramic bond strength. Copyright © 2012 Elsevier Ltd. All rights reserved.

  10. Adhesive luting of all-ceramic restorations--the impact of cementation variables and short-term water storage on the strength of a feldspathic dental ceramic.

    LENUS (Irish Health Repository)

    Addison, Owen

    2008-08-01

    To investigate the impact of resin cement luting variables and short-term water storage on the strength of an adhesively luted all-ceramic restorative material. An understanding of the strengthening mechanisms will result in optimisation of operative techniques and materials selection criteria.

  11. CO2 and Nd:YAP laser interaction with lithium disilicate and Zirconia dental ceramics: A preliminary study

    Science.gov (United States)

    Rocca, Jean-Paul; Fornaini, Carlo; Brulat-Bouchard, Nathalie; Bassel Seif, Samy; Darque-Ceretti, Evelyne

    2014-04-01

    Lithium disilicate and Zirconia ceramics offer a high level of accuracy when used in prosthetic dentistry. Their bonding using different resins is highly dependent on micro-mechanical interlocking and adhesive chemical bonding. Investigation of the performances of high strength ceramics when their surface is modified for chemical and mechanical bonding is then required. The aim of this study is to investigate the possibility of using laser for surface treatment of different high strength CAD/CAM ceramics and thus to improve their mechanical and chemical properties. Thirty two CAD/CAM ceramic discs were divided into two different groups: lithium disilicate ceramics (IPS e.max CAD®, Ivoclar, Vivadent, Italy) and Zirconia ceramics (IPS e.max ZirCAD®, Ivoclar, Vivadent, Italy). The Laser surface treatment was performed by Carbon Dioxide laser (Dream Pulse Laser®, Daeshin Enterprise Corp., Korea) at 20 W, 25 W and 30 W CW and by Neodymium Yttrium Aluminum Perovskite laser (Nd:YAP Lokki®, Lobel Medical, France) at 10 W and 30 Hz. Physical modifications of the irradiated ceramic discs were observed by scanning electron microscopy (SEM) and chemically analyzed by Energy-Dispersive Spectroscopy (EDS). Surface wettability was tested using the water drop test and the crystalline structure was investigated using X-ray diffraction (XRD). The macroscopic observation showed a shinier structure in all the groups, while at the SEM observation only CO2 25 W and 30 W treated groups showed cracks and fissures. In the conditions of this study, CO2 laser and Nd:YAP laser with the parameters used create chemical and physical surface modifications of the ceramics, indicating the possibility of an improvement in adhesion of the tested ceramics.

  12. Calculation and experimental investigation of multi-component ceramic systems

    International Nuclear Information System (INIS)

    Rother, M.

    1994-12-01

    This work shows a way to combine thermodynamic calculations and experiments in order to get useful information on the constitution of metal/non-metal systems. Many data from literature are critically evaluated and used as a basis for experiments and calculations. The following multi-component systems are treated: 1. Multi-component systems of 'ceramic' materials with partially metallic bonding (carbides, nitrides, oxides, borides, carbonitrides, borocarbides, oxinitrides of the 4-8th transition group metals) 2. multi-component systems of non-metallic materials with dominant covalent bonding (SiC, Si 3 N 4 , SiB 6 , BN, Al 4 C 3 , Be 2 C) 3. multi-component systems of non-metallic materials with dominant heteropolar bonding (Al 2 O 3 , TiO 2 , BeO, SiO 2 , ZrO 2 ). The interactions between 1. and 2., 2. and 3., 1. and 3. are also considered. The latest commercially available programmes for the calculation of thermodynamical equilibria and phase diagrams are evaluated and compared considering their facilities and limits. New phase diagrams are presented for many presently unknown multi-component systems; partly known systems are completed on the basis of selected thermodynamic data. The calculations are verified by experimental investigations (metallurgical and powder technology methods). Altogether 690 systems are evaluated, 126 are calculated for the first time and 52 systems are experimentally verified. New data for 60 ternary phases are elaborated by estimating the data limits for the Gibbs energy values. A synthesis of critical evaluation of literature, calculations and experiments leads to new important information about equilibria and reaction behaviour in multi-component systems. This information is necessary to develop new stable and metastable materials. (orig./MM) [de

  13. Automated Dental Epidemiology System. II. Systems Analysis and Functional Design,

    Science.gov (United States)

    1983-08-01

    involvement or debilitating soft tissue pathology (e.g., pericoronitis or periodontal abscess ). Therefore it is desired that urgently needed treatment...through the naval population. Developing this kind of information requires extensive use of dental epidemiology. The incidence of caries and periodontal ...Navy Dental Corps efforts toward reducing the incidence and detrimental effects of caries and periodontal disease in the field and afloat. In this

  14. Coating system to permit direct brazing of ceramics

    Science.gov (United States)

    Cadden, Charles H.; Hosking, F. Michael

    2003-01-01

    This invention relates to a method for preparing the surface of a ceramic component that enables direct brazing using a non-active braze alloy. The present invention also relates to a method for directly brazing a ceramic component to a ceramic or metal member using this method of surface preparation, and to articles produced by using this brazing method. The ceramic can be high purity alumina. The method comprises applying a first coating of a silicon-bearing oxide material (e.g. silicon dioxide or mullite (3Al.sub.2 O.sub.3.2SiO.sub.2) to the ceramic. Next, a thin coating of active metal (e.g. Ti or V) is applied. Finally, a thicker coating of a non-active metal (e.g. Au or Cu) is applied. The coatings can be applied by physical vapor deposition (PVD). Alternatively, the active and non-active metals can be co-deposited (e.g. by sputtering a target made of mullite). After all of the coatings have been applied, the ceramic can be fired at a high temperature in a non-oxidizing environment to promote diffusion, and to enhance bonding of the coatings to the substrate. After firing, the metallized ceramic component can be brazed to other components using a conventional non-active braze alloy. Alternatively, the firing and brazing steps can be combined into a single step. This process can replace the need to perform a "moly-manganese" metallization step.

  15. Ceramic joining

    Energy Technology Data Exchange (ETDEWEB)

    Loehman, R.E. [Sandia National Lab., Albuquerque, NM (United States)

    1996-04-01

    This paper describes the relation between reactions at ceramic-metal interfaces and the development of strong interfacial bonds in ceramic joining. Studies on a number of systems are described, including silicon nitrides, aluminium nitrides, mullite, and aluminium oxides. Joints can be weakened by stresses such as thermal expansion mismatch. Ceramic joining is used in a variety of applications such as solid oxide fuel cells.

  16. [Different forms of payment systems for dental services and their impact on care].

    Science.gov (United States)

    Sória, Marina Lara; Bordin, Ronaldo; da Costa Filho, Luiz Cesar

    2002-01-01

    The Brazilian dental care sector is facing a paradoxical crisis characterized by a surplus of dentists and a large contingent of people lacking dental care, thus highlighting the need to improve management strategies. One necessary step is to analyze the various payment schemes for dental services. This paper reviews two important approaches, fee for service and capitation, and considers the impacts and consequences of payment strategies on the dental care system.

  17. Quality control procedures of dental diagnostic radiology systems

    International Nuclear Information System (INIS)

    Andrade, Paula Serra Sasaki

    2007-01-01

    This work presents quality control reference procedures for dental diagnostic radiology systems, following the recommendations of the Publication 453 of the Brazilian Health Ministry (PF453), to be applied in dental clinics, in order to achieve an improvement in the radiological image qualities and the patient dose reduction. All tests were applied in an intraoral X rays system, following the methodology developed and the requirements of the PF 453. In order to verify the best quality of the image in relation to the smaller exposition time an object test was also developed in this work. The use of this object allowed the reduction of the exposition time of 0.5 seconds, the maximum value of the linear region of the characteristic curve, for 0.2 seconds. The tested X rays system showed a very good agreement with the applied procedures, detaching the reduction of the skin entrance dose using the film-holding devices. However, the size of the field increased and exceeded the maximum value of 6 cm recommended in the standard. The importance of the quality control in dental diagnostic radiology systems is essential due to the constant use of X radiation in dental clinics. The PF453 recommends the frequency of at least two years for the constancy tests. However, it is suggested that the professional, surgeon-dentist, should be responsible for the internal control of the image quality obtained from the X rays device. This can be done through monthly exposures of the object test developed in this work. (author)

  18. Investigation of the sinterability of ZrO_2 (Y_2O3_)-bioglass dental ceramics by dilatometry

    International Nuclear Information System (INIS)

    Bicalho, Luiz de Araujo; Barboza, Miguel Ribeiro Justino; Santos, Claudinei dos; Habibe, Alexandre Fernandes; Magnago, Roberto de Oliveira

    2013-01-01

    The objective of this work is to study by dilatometry, the liquid phase sintering of ZrO_2 ceramics using bioglass as sintering additive. Y_2 O_3 - stabilized ZrO_2 powders were mixed with 3, 5 and 10 wt% of bioglass with the composition based on 3CaOP_2 O_5 -MgO-SiO_2 system. Specimens were prepared by cold uniaxial pressing under 80MPa and the green relative density was determined. The sintering behavior was studied by measuring the linear shrinkage of samples in a dilatometer in relation to the temperature. The heating and cooling rates used in this study were 10 deg C/min and the maximum sintering temperatures was 1300 deg C with a 120 min isothermal holding time. The results of the shrinkage and shrinkage rates in regard of the sintering temperature and time were related to the amount of bioglass added. The sintered samples were characterized by X-ray diffraction analysis and their relative density. SEM micrographs indicates similar microstructure, and an increase of bioglass content leads to increasing of monoclinic ZrO_2 phase content. The dilatometry results indicate a reduction of the temperature where a maximum shrinkage rate occurs, as function of bioglass increasing. Furthermore, the use of liquid phase reduces the maximum sintering temperature of 1447 deg C to 1250-1280 deg C. (author)

  19. Ballistic Performance of Porous-Ceramic, Thermal Protection Systems

    Science.gov (United States)

    Miller, J. E.; Bohl, W. E.; Christiansen, Eric C.; Davis, B. A.; Foreman, C. D.

    2011-01-01

    Porous-ceramic, thermal protection systems are used heavily in current reentry vehicles like the Orbiter, and they are currently being proposed for the next generation of US manned spacecraft, Orion. These systems insulate reentry critical components of a spacecraft against the intense thermal environments of atmospheric reentry. Additionally, these materials are highly exposed to space environment hazards like solid particle impacts. This paper discusses impact studies up to 10 km/s on 8 lb/cu ft alumina-fiber-enhanced-thermal-barrier (AETB8) tiles coated with a toughened-unipiece-fibrous-insulation/ reaction-cured-glass layer (TUFI/RCG). A semi-empirical, first principals impact model that describes projectile dispersion is described that provides excellent agreement with observations over a broad range of impact velocities, obliquities and projectile materials. Model extensions to look at the implications of greater than 10 GPa equation of state is also discussed. Predicted penetration probabilities for a vehicle visiting the International Space Station is 60% lower for orbital debris and 95% lower for meteoroids with this model compared to an energy scaled approach.

  20. Biaxial flexural strength of Turkom-Cera core compared to two other all-ceramic systems

    Directory of Open Access Journals (Sweden)

    Bandar Mohammed Abdullah Al-Makramani

    2010-12-01

    Full Text Available Advances in all-ceramic systems have established predictable means of providing metal-free aesthetic and biocompatible materials. These materials must have sufficient strength to be a practical treatment alternative for the fabrication of crowns and fixed partial dentures. OBJECTIVES: The aim of this study was to compare the biaxial flexural strength of three core ceramic materials. MATERIAL AND METHODS: Three groups of 10 disc-shaped specimens (16 mm diameter x 1.2 mm thickness - in accordance with ISO-6872, 1995 were made from the following ceramic materials: Turkom-Cera Fused Alumina [(Turkom-Ceramic (M Sdn Bhd, Puchong, Selangor, Malaysia], In-Ceram (Vita Zahnfabrik, Bad Säckingen, Baden-Württemberg, Germany and Vitadur-N (Vita Zahnfabrik, Bad Säckingen, Baden-Württemberg, Germany, which were sintered according to the manufacturer's recommendations. The specimens were subjected to biaxial flexural strength test in an universal testing machine at a crosshead speed of 0.5 mm/min. The definitive fracture load was recorded for each specimen and the biaxial flexural strength was calculated from an equation in accordance with ISO-6872. RESULTS: The mean biaxial flexural strength values were: Turkom-Cera: 506.8±87.01 MPa, In-Ceram: 347.4±28.83 MPa and Vitadur-N: 128.7±12.72 MPa. The results were analyzed by the Levene's test and Dunnett's T3 post-hoc test (SPSS software V11.5.0 for Windows, SPSS, Chicago, IL, USA at a preset significance level of 5% because of unequal group variances (P<0.001. There was statistically significant difference between the three core ceramics (P<0.05. Turkom-Cera showed the highest biaxial flexural strength, followed by In-Ceram and Vitadur-N. CONCLUSIONS: Turkom-Cera core had significantly higher flexural strength than In-Ceram and Vitadur-N ceramic core materials.

  1. Flexural resistance of Cerec CAD/CAM system ceramic blocks. Part 2: Outsourcing materials.

    Science.gov (United States)

    Sedda, Maurizio; Vichi, Alessandro; Del Siena, Francesco; Louca, Chris; Ferrari, Marco

    2014-02-01

    To test different Cerec CAD/CAM system ceramic blocks, comparing mean flexural strength (sigma), Weibull modulus (m), and Weibull characteristic strength (sigma0) in an ISO standardized set-up. Following the recent ISO Standard (ISO 6872:2008), 11 types of ceramic blocks were tested: IPS e.max CAD MO, IPS e.max CAD LT and IPS e.max CAD HT (lithium disilicate glass-ceramic); In-Ceram SPINELL, In-Ceram Alumina and In-Ceram Zirconia (glass-infiltrated materials); inCoris AL and In-Ceram AL (densely sintered alumina); In-Ceram YZ, IPS e.max Zir-CAD and inCoris ZI (densely sintered zirconia). Specimens were cut out from ceramic blocks, finished, crystallized/infiltrated/sintered, polished, and tested in a three-point bending test apparatus. Flexural strength, Weibull characteristic strength, and Weibull modulus were obtained. A statistically significant difference was found (P ceramic (sigma = 272.6 +/- 376.8 MPa, m = 6.2 +/- 11.3, sigma0 = 294.0 +/- 394.1 MPa) and densely sintered alumina (sigma = 441.8 +/- 541.6 MPa, m = 11.9 +/- 19.0, sigma0 = 454.2 +/- 565.2 MPa). No statistically significant difference was found (P = 0.254) in glass infiltrated materials (sigma = 376.9 +/- 405.5 MPa, m = 7.5 +/- 11.5, sigma0 = 393.7 +/- 427.0 MPa). No statistically significant difference was found (P = 0.160) in densely sintered zirconia (sigma = 1,060.8 +/- 1,227.8 MPa, m = 5.8 +/- 7.4, sigma0 = 1,002.4 +/- 1,171.0 MPa). Not all the materials tested fulfilled the requirements for the clinical indications recommended by the manufacturer.

  2. Sensitive Ceramics

    DEFF Research Database (Denmark)

    2014-01-01

    Sensitive Ceramics is showing an interactive digital design tool for designing wall like composition with 3d ceramics. The experiment is working on two levels. One which has to do with designing compositions and patterns in a virtual 3d universe based on a digital dynamic system that responds on ...... with realizing the modules in ceramics by 3d printing directly in porcelain with a RapMan printer that coils up the 3d shape in layers. Finally the ceramic modules are mounted in a laser cut board that reflects the captured composition of the movement of the hands....

  3. Sol-gel dip coating of yttria-stabilized tetragonal zirconia dental ceramic by aluminosilicate nanocomposite as a novel technique to improve the bonding of veneering porcelain.

    Science.gov (United States)

    Madani, Azamsadat; Nakhaei, Mohammadreza; Karami, Parisa; Rajabzadeh, Ghadir; Salehi, Sahar; Bagheri, Hossein

    2016-01-01

    The aim of this in vitro study was to evaluate the effect of silica and aluminosilicate nanocomposite coating of zirconia-based dental ceramic by a sol-gel dip-coating technique on the bond strength of veneering porcelain to the yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) in vitro. Thirty Y-TZP blocks (10 mm ×10 mm ×3 mm) were prepared and were assigned to four experimental groups (n=10/group): C, without any further surface treatment as the control group; S, sandblasted using 110 μm alumina powder; Si, silica sol dip coating + calcination; and Si/Al, aluminosilicate sol dip coating + calcination. After preparing Y-TZP samples, a 3 mm thick layer of the recommended porcelain was fired on the coated Y-TZP surface. Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray analysis were used to characterize the coating and the nature of the bonding between the coating and zirconia. To examine the zirconia-porcelain bond strength, a microtensile bond strength (μTBS) approach was chosen. FT-IR study showed the formation of silica and aluminosilicate materials. XRD pattern showed the formation of new phases consisting of Si, Al, and Zr in coated samples. SEM showed the formation of a uniform coating on Y-TZP samples. Maximum μTBS values were obtained in aluminosilicate samples, which were significantly increased compared to control and sandblasted groups (P=0.013 and Pcoating can be considered as a convenient, less expensive reliable method for improving the bond strength between dental Y-TZP ceramics and veneering porcelain.

  4. Maintenance of an Adequate Dental Hygiene Education System.

    Science.gov (United States)

    Ley, Eugene; And Others

    1984-01-01

    Administrative decisions about the future of dental hygiene programs are often based on inadequate information about employment trends and about the importance of the dental hygienist in dental practices. Studies indicate that demand for dental hygiene services will remain high in the 1980s. (Author/MLW)

  5. Porosity Dependence of Piezoelectric Properties for Porous Potassium Niobate System Ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Wada, S; Mase, Y; Shimizu, S; Maeda, K; Fujii, I; Nakashima, K; Pulpan, P; Miyajima, N, E-mail: swada@yamanashi.ac.jp [Interdisciplinary Graduate School of Medical and Engineering, University of Yamanashi, 4-4-37 Takeda, Kofu, Yamanashi 400-8510 (Japan)

    2011-10-29

    Porous potassium niobate (KNbO{sub 3}, KN) system ceramics were prepared by a conventional sintering method using carbon black (CB) nanoparticles. First, KN nanoparticles with a size of 100 nm was mixed with CB nanoparticles and binder using ball milling with ethanol. The mixture was dried, and pressed into pellets using uniaxial pressing. After binder burnout, these ceramics was sintered in air. Their piezoelectric properties were measured and discussed a relationship between porosity and piezoelectric properties. As the results, with increasing porosity, piezoelectric g33 constant increased significantly, which suggested that porous ceramics were effective for stress sensor application.

  6. Porosity Dependence of Piezoelectric Properties for Porous Potassium Niobate System Ceramics

    International Nuclear Information System (INIS)

    Wada, S; Mase, Y; Shimizu, S; Maeda, K; Fujii, I; Nakashima, K; Pulpan, P; Miyajima, N

    2011-01-01

    Porous potassium niobate (KNbO 3 , KN) system ceramics were prepared by a conventional sintering method using carbon black (CB) nanoparticles. First, KN nanoparticles with a size of 100 nm was mixed with CB nanoparticles and binder using ball milling with ethanol. The mixture was dried, and pressed into pellets using uniaxial pressing. After binder burnout, these ceramics was sintered in air. Their piezoelectric properties were measured and discussed a relationship between porosity and piezoelectric properties. As the results, with increasing porosity, piezoelectric g33 constant increased significantly, which suggested that porous ceramics were effective for stress sensor application.

  7. Hydrothermal degradation of a 3Y-TZP translucent dental ceramic: A comparison of numerical predictions with experimental data after 2 years of aging.

    Science.gov (United States)

    Cattani-Lorente, Maria; Durual, Stéphane; Amez-Droz, Michel; Wiskott, H W Anselm; Scherrer, Susanne S

    2016-03-01

    The purpose of the study was to assess the hydrothermal resistance of a translucent zirconia with two clinical relevant surface textures by means of accelerated tests (LTD) and to compare predicted monoclinic fractions with experimental values measured after two years aging at 37°C. Polished (P) and ground (G) specimens were subjected to hydrothermal degradation by exposure to water steam at different temperatures and pressures. The t-m phase transformation was quantified by grazing incidence X-ray diffraction (GIXDR). The elastic modulus and hardness before- and after LTD were determined by nanoindentation. G specimens presented a better resistance to hydrothermal degradation than P samples. Activation energies of 89 and 98kJ/mol and b coefficients of 2.0×10(-5) and 1.8×10(-6) were calculated for P and G samples respectively. The coefficients were subsequently used to predict transformed monoclinic fractions at 37°C. A good correlation was found between the predicted values and the experimental data obtained after aging at 37°C during 2 years. Hydrothermal degradation led to a significant decrease of the elastic moduli and hardness in both groups. The dependency of the t-m phase transformation rate on temperature must be determined to accurately predict the hydrothermal behavior of the zirconia ceramics at oral temperatures. The current prevailing assumption, that 5h aging at 134°C corresponds to 15-20 years at 37°C, will underestimate the transformed fraction of the translucent ceramic at 37°C. In this case, the mechanical surface treatment influences the ceramic's transformability. While mild grinding could potentially retard the hydrothermal transformation, polishing after occlusal adjustment is recommended to prevent wear of the antagonist teeth and maintain structural strength. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  8. Dental implant suprastructures using cobalt-chromium alloy compared with gold alloy framework veneered with ceramic or acrylic resin: a retrospective cohort study up to 18 years.

    Science.gov (United States)

    Teigen, Kyrre; Jokstad, Asbjørn

    2012-07-01

    An association between the long-term success and survival of implant-supported prostheses as a function of biomaterial combinations has not been established. The use of cast cobalt-chromium for the suprastructure framework may be an alternative to the conventional approach of using type 3 gold alloys. A retrospective chart audit of all patients who had received implant-supported fixed dental prostheses (FDP) before 1996 was identified in a private practice clinic. Data were recorded for FDPs made from four combinations of alloy frameworks and veneering material, i.e. type 3 gold and cobalt-chromium with ceramic or prefabricated acrylic teeth. The extracted data from the charts were subjected to explorative statistical tests including Kaplan-Meier survival analyses. Patients (n=198) with 270 short and extensive FDPs supported entirely by 1117 implants were identified. The average follow-up observation periods varied between 4 and 220 months, with an average of 120 months. The success and survival, as well as event rates and types of biological and technical complications, were similar for implant-supported FDPs using cobalt-chromium and type 3 gold alloy frameworks veneered with ceramics or prefabricated acrylic teeth. An influence of the suprastructure biomaterial combination on the clinical performance of the individual supporting implants could not be established. Implant-supported FDPs made from type 3 gold or cobalt-chromium frameworks and veneered with ceramic or prefabricated acrylic teeth demonstrate comparable clinical performance. The biomaterial combinations do not appear to influence the success or survival of the individual implants. © 2011 John Wiley & Sons A/S.

  9. The effect of ZrO2 and TiO 2 on solubility and strength of apatite-mullite glass-ceramics for dental applications.

    Science.gov (United States)

    Fathi, Hawa M; Miller, Cheryl; Stokes, Christopher; Johnson, Anthony

    2014-03-01

    The effect of ZrO2 and TiO2 on the chemical and mechanical properties of apatite-mullite glass-ceramics was investigated after sample preparation according to the ISO (2768:2008) recommendations for dental ceramics. All materials were characterized using differential thermal analysis, X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. X-ray fluorescence spectroscopy was used to determine the concentrations of elements present in all materials produced. The chemical solubility test and the biaxial flexural strength (BFS) test were then carried out on all the samples. The best solubility value of 242 ± 61 μg/cm(2) was obtained when HG1T was heat-treated for 1 h at the glass transition temperature plus 20 °C (Tg + 20 °C) followed by 5 h at 1200 °C. The highest BFS value of 174 ± 38 MPa was achieved when HG1Z and HG1Z+T were heat-treated for 1 h at the Tg + 20 °C followed by 7 h at 1200 °C. The present study has demonstrated that the addition of TiO2 to the reference composition showed promise in both the glass and heat-treated samples. However, ZrO2 is an effective agent for developing the solubility or the mechanical properties of an apatite-mullite glass-ceramic separately but does not improve the solubility and the BFS simultaneously.

  10. Planar ceramic membrane assembly and oxidation reactor system

    Science.gov (United States)

    Carolan, Michael Francis; Dyer, legal representative, Kathryn Beverly; Wilson, Merrill Anderson; Ohm, Ted R.; Kneidel, Kurt E.; Peterson, David; Chen, Christopher M.; Rackers, Keith Gerard; Dyer, deceased, Paul Nigel

    2007-10-09

    Planar ceramic membrane assembly comprising a dense layer of mixed-conducting multi-component metal oxide material, wherein the dense layer has a first side and a second side, a porous layer of mixed-conducting multi-component metal oxide material in contact with the first side of the dense layer, and a ceramic channeled support layer in contact with the second side of the dense layer. The planar ceramic membrane assembly can be used in a ceramic wafer assembly comprising a planar ceramic channeled support layer having a first side and a second side; a first dense layer of mixed-conducting multi-component metal oxide material having an inner side and an outer side, wherein the inner side is in contact with the first side of the ceramic channeled support layer; a first outer support layer comprising porous mixed-conducting multi-component metal oxide material and having an inner side and an outer side, wherein the inner side is in contact with the outer side of the first dense layer; a second dense layer of mixed-conducting multi-component metal oxide material having an inner side and an outer side, wherein the inner side is in contact with the second side of the ceramic channeled layer; and a second outer support layer comprising porous mixed-conducting multi-component metal oxide material and having an inner side and an outer side, wherein the inner side is in contact with the outer side of the second dense layer.

  11. Effects of Dental 3D Multimedia System on the Performance of Junior Dental Students in Preclinical Practice: A Report from China

    Science.gov (United States)

    Hu, Jian; Yu, Hao; Shao, Jun; Li, Zhiyong; Wang, Jiawei; Wang, Yining

    2009-01-01

    Background: Computer-assisted tools are rarely adopted for dental education in China. In China, 3D digital technology, such as Virtual Reality Systems, are often rejected in the dental field due to prohibitive pricing. There is also a reluctance to move away from traditional patterns of dental education. Objective: The current study is one of a…

  12. Pyroelectric Ceramics as Temperature Sensors for Energy System Applications

    Science.gov (United States)

    Silva, Jorge Luis

    Temperature is continuously monitored in energy systems to ensure safe operation temperatures, increase efficiency and avoid high emissions. Most of energy systems operate at high temperature and harsh environments to achieve higher efficiencies, therefore temperature sensing devices that can operate under these conditions are highly desired. The interest has increased in temperature sensors capable to operate and in harsh environments and temperature sensors capable to transmit thermal information wirelessly. One of the solutions for developing harsh environment sensors is to use ceramic materials, especially functional ceramics such as pyroelectrics. Pyroelectric ceramics could be used to develop active sensors for both temperature and pressure due to their capabilities in coupling energy among mechanical, thermal, and electrical domains. In this study, two different pyroelectric materials were used to develop two different temperature sensors systems. First, a high temperature sensor was developed using a lithium niobate (LiNbO3) pyroelectric ceramic. With its Curie temperature of 1210 °C, lithium niobate is capable to maintain its pyroelectric properties at high temperature making it ideal for temperature sensing at high temperature applications. Lithium niobate has been studied previously in the attempt to use its pyroelectric current as the sensing mechanism to measure temperatures up to 500 °C. Pyroelectric coefficient of lithium niobate is a function of temperature as reported in a previous study, therefore a dynamic technique is utilized to measure the pyroelectric coefficient of the lithium niobate used in this study. The pyroelectric coefficient was successfully measured up to 500 °C with coefficients ranging from -8.5 x 10 -5 C/m2 °C at room temperature to -23.70 x 10 -5 C/m2 °C at 500 °C. The lithium niobate sensor was then tested at higher temperatures: 220 °C, 280 °C, 410 °C and 500 °C with 4.31 %, 2.1 %, 0.4 % and 0.6 % deviation

  13. Bond strength of the porcelain repair system to all-ceramic copings and porcelain.

    Science.gov (United States)

    Lee, Sang J; Cheong, Chan Wook; Wright, Robert F; Chang, Brian M

    2014-02-01

    The purpose of this study was to investigate the shear bond strength of the porcelain repair system on alumina and zirconia core ceramics, comparing this strength with that of veneering porcelain. Veneering ceramic (n = 12), alumina core (n = 24), and zirconia core (n = 24) blocks measuring 10 × 5 × 5 mm(3) were fabricated. Veneering ceramic blocks were used as the control. Alumina and zirconia core blocks were divided into 2 groups (n = 12 each), and a slot (2 × 2 × 4 mm(3)) filled with veneering ceramics was prepared into one of the alumina and zirconia core groups (n = 12). Followed by surface treatments of micro-abrasion with 30 μm alumina particles, etching with 35% phosphoric acid and silane primer and bond, composite resin blocks (2 × 2 × 2 mm(3)) were built up and light polymerized onto the treated surfaces by 3 configurations: (a) composite blocks bonded onto veneering ceramic surface alone, (b) composite blocks bonded onto alumina core or zirconia core surfaces, (c) a 50% surface area of the composite blocks bonded to veneering ceramics and the other 50% surface area of the composite blocks to alumina core or zirconia core surfaces. The shear bond strength of the composite to each specimen was tested by a universal testing machine at a 0.5 mm/min crosshead speed. The shear bond strength was analyzed by unpaired t-tests for within the configuration groups and ANOVA for among the different configuration groups. When the mean shear bond strength was compared within groups of the same configuration, there were no statistically significant differences. Comparison of the shear bond strength among groups of different configurations revealed statistically significant differences. The mean shear bond strength of composite onto 100% veneering ceramic surface and composite onto 50% veneering 50% all-ceramic cores was statistically higher than that of composite onto 100% all-ceramic cores; however, the differences of the shear bond strength of composite bonded

  14. Development of the mitigation method for carbon steel corrosion with ceramics in PWR secondary system

    International Nuclear Information System (INIS)

    Okamura, Masato; Shibasaki, Osamu; Miyazaki, Toyoaki; Kaneko, Tetsuji

    2012-09-01

    To verify the effect of depositing ceramic (TiO 2 , La 2 O 3 , and Y 2 O 3 ) on carbon steel to mitigate corrosion, corrosion tests were conducted under simulated chemistry conditions in a PWR secondary system. Test specimens (STPT410) were prepared with and without deposited ceramics. The ceramics were deposited on the specimens under high-temperature and high-pressure water conditions. Corrosion tests were conducted under high pH conditions (9.8) with a flow rate of 1.0-4.7 m/s at 185 deg. C for 200 hours. At a flow rate of 1.0 m/s, the amount of corrosion of the specimens with the ceramics was less than half of that of the specimens without the ceramics. As the flow rate increased, the amount of corrosion increased. However, even at a flow rate of 4.7 m/s, the amount of corrosion was reduced by approximately 30% by depositing the ceramics. After the corrosion tests, the surfaces of the specimens were analyzed with SEM and XRD. When the deposited ceramic was TiO 2 , the surface was densely covered with fine particles (less than 1 μm). From XRD analysis, these particles were identified as ilmenite (FeTiO 3 ). We consider that ilmenite may play an important role in mitigating the corrosion of carbon steel. (authors)

  15. [Effect of repeated sintering and variations in thickness on the color and microstructure of dental lithium disilicate-based glass ceramic veneers].

    Science.gov (United States)

    Cui, Huang; Jia, Yu; Shaofeng, Meng; Biyun, Gao

    2017-08-01

    Objective The aim of this study is to evaluate the effect of repeated sintering and variation in thickness on the color and microstructure of dental lithium disilicate-based glass ceramic veneers. Methods A total of 24 computer aided design and computer aided manufacturing (CAD/CAM) veneers was fabricated using the IPS e.max-CAD LS2 and then randomly divided into four groups (S0, S1, S2, S3; n=6). Each group was sintered 0, 1, 2, 3 times individually according to the manufacturer's recommendation. The color parameters (L, C, H, a, b values) of all the specimens were measured by a Vita easyshade dental colorimeter. The results were statistically analyzed using the SAS 9.1.3 software for MANOVA and LSD. Subsequently, the microstructures of the intersecting surfaces of the specimens were observed by scanning electron microscopy (SEM). Results After repeated sintering, the L value significantly decreased (P<0.05). For the C and b values, statistical differences were observed among the groups except between S2 and S3. SEM results showed that the interlocking microstructures of rod-shaped Li₂Si₂O₅ crystals became more compact when the number of sintering times was increased. Conclusion Repeated sintering exhibited significant influence on the color of the IPS e.max-CAD LS2 veneers.

  16. Avaliação da tenacidade à fratura de diferentes sistemas cerâmicos Relative fracture toughness of differents dental ceramics

    Directory of Open Access Journals (Sweden)

    Clovis Pagani

    2003-03-01

    Full Text Available Embora as cerâmicas possuam alta resistência à compressão, apresentam friabilidade devido à sua baixa resistência à tração e, desta forma, possuem menor capacidade de absorver impactos. Este trabalho avaliou a tenacidade à fratura de diferentes sistemas cerâmicos, que refere-se à medida da habilidade de absorção da energia de deformação de um material friável. Foram confeccionados 30 corpos-de-prova em forma de discos (5mmx3mm utilizando-se três diferentes materiais cerâmicos, os quais foram divididos em 3 grupos: G1-10 amostras confeccionadas com a cerâmica Vitadur Alpha (Vita-Zahnfabrik; G2-10 amostras confeccionadas com a cerâmica IPS Empress 2 (Ivoclar-Vivadent e G3-10 amostras confeccionadas com a cerâmica In-Ceram Alumina (Vita-Zahnfabrik. Para a obtenção dos valores de tenacidade foi utilizada a técnica da indentação que se baseia na série de fissuras que se formam sob uma carga pesada. Foram realizadas 4 impressões por amostra, utilizado um microdurômetro (Digital Microhardness Tester FM com uma carga de 500gf, durante 10 segundos. A análise estatística dos dados (Testes ANOVA de Kruskal-Wallis e Dunn, indica que a cerâmica In-Ceram Alumina apresentou valor mediano (2,96N/m3/2, estatisticamente diferente do apresentado pela IPS Empress 2 (1,05N/m3/2, enquanto que a cerâmica Vitadur Alpha apresentou valores intermediários (2,08N/m3/2, sem diferenças estatísticas dos outros dois materiais. Conclui-se que as cerâmicas apresentam diferentes desempenhos de tenacidade à fratura, sendo a In-Ceram capaz de absorver maior energia comparada a Vitadur Alpha e ao IPS Empress2.Although ceramics present high compressive strength, they are brittle materials due to their low tensile strength so they have lower capacity to absorb shocks. This study evaluated the fracture toughness of different ceramic systems, which refers to the ability of a friable material to absorb defformation energy. Three ceramic systems were

  17. Emerging Ceramic-based Materials for Dentistry

    Science.gov (United States)

    Denry, I.; Kelly, J.R.

    2014-01-01

    Our goal is to give an overview of a selection of emerging ceramics and issues for dental or biomedical applications, with emphasis on specific challenges associated with full-contour zirconia ceramics, and a brief synopsis on new machinable glass-ceramics and ceramic-based interpenetrating phase composites. Selected fabrication techniques relevant to dental or biomedical applications such as microwave sintering, spark plasma sintering, and additive manufacturing are also reviewed. Where appropriate, the authors have added their opinions and guidance. PMID:25274751

  18. Ceramic/polymer functionally graded material (FGM) lightweight armor system

    Energy Technology Data Exchange (ETDEWEB)

    Petrovic, J.J.; McClellan, K.J.

    1998-12-31

    This is the final report of a two-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). Functionally graded material is an enabling technology for lightweight body armor improvements. The objective was to demonstrate the ability to produce functionally graded ceramic-polymer and ceramic-metal lightweight armor materials. This objective involved two aspects. The first and key aspect was the development of graded-porosity boron-carbide ceramic microstructures. The second aspect was the development of techniques for liquid infiltration of lightweight metals and polymers into the graded-porosity ceramic. The authors were successful in synthesizing boron-carbide ceramic microstructures with graded porosity. These graded-porosity boron-carbide hot-pressed pieces were then successfully liquid-infiltrated in vacuum with molten aluminum at 1,300 C, and with liquid polymers at room temperature. Thus, they were able to demonstrate the feasibility of producing boron carbide-aluminum and boron carbide-polymer functionally graded materials.

  19. An unusual dental phenomenon in systemic scleroderma

    International Nuclear Information System (INIS)

    ElCridly, Mahmoud

    1989-01-01

    Systemic scleroderma is a disease of unknown etiology characterized by excessive deposition of collagen and other connective tissue components in the skin and several internal organs. The most common oral findings are rigidity and thinness of lips, circumoral fibrosis which causes microstomia and inability to open the mouth widely. Involvement of tongue may lead to its decreased mobility and diminished size. Radiographic findings that have been classically associated with systemic scleroderma are widening of the periodontal ligament spaces and destruction of lamina dura, usually in posterior teeth. Intraoral radiographs of presented cases revealed apical resorption of the roots and destruction of the lamina dura verified on extraction of the teeth. This oral finding appears not to have been recorded by previous investigators of scleroderma. (author)

  20. Relative translucency of six all-ceramic systems. Part II: core and veneer materials.

    Science.gov (United States)

    Heffernan, Michael J; Aquilino, Steven A; Diaz-Arnold, Ana M; Haselton, Debra R; Stanford, Clark M; Vargas, Marcos A

    2002-07-01

    STATEMENT OF PROBLEM All-ceramic core materials with various strengthening compositions have a range of translucencies. It is unknown whether translucency differs when all-ceramic materials are fabricated similarly to the clinical restoration with a veneered core material. This study compared the translucency of 6 all-ceramic materials veneered and glazed at clinically appropriate thicknesses. Core specimens (n = 5 per group) of Empress dentin, Empress 2 dentin, In-Ceram Alumina, In-Ceram Spinell, In-Ceram Zirconia, and Procera AllCeram were fabricated as described in Part I of this study and veneered with their corresponding dentin porcelain to a final thickness of 1.47 +/- 0.01 mm. These specimens were compared with veneered Vitadur Alpha opaque dentin (as a standard), a clear glass disc (positive control), and a high-noble metal-ceramic alloy (Porc. 52 SF) veneered with Vitadur Omega dentin (negative control). Specimen reflectance was measured with an integrating sphere attached to a spectrophotometer across the visible spectrum (380 to 700 nm); 0-degree illumination and diffuse viewing geometry were used. Measurements were repeated after a glazing cycle. Contrast ratios were calculated from the luminous reflectance (Y) of the specimens with a black (Yb) and a white backing (Yw) to give Yb/Yw with CIE illuminant D65 and a 2-degree observer function (0.0 = transparent, 1.0 = opaque). One-way analysis of variance and Tukey's multiple-comparison test were used to analyze the data (P<.05). Significant differences in contrast ratios were found among the ceramic systems tested when they were veneered (P<.0001) and after the glazing cycle (P<.0001). Significant changes in contrast ratios (P<.0001) also were identified when the veneered specimens were glazed. Within the limitations of this study, a range of translucency was identified in the veneered all-ceramic systems tested. Such variability may affect their ability to match natural teeth. The glazing cycle resulted

  1. Radiation-hard ceramic Resistive Plate Chambers for forward TOF and T0 systems

    Energy Technology Data Exchange (ETDEWEB)

    Akindinov, A., E-mail: Alexander.Akindinov@cern.ch [Institute for Theoretical and Experimental Physics, Moscow (Russian Federation); Dreyer, J.; Fan, X.; Kämpfer, B. [Helmholtz-Zentrum Dresden-Rossendorf, Dresden (Germany); Kiselev, S. [Institute for Theoretical and Experimental Physics, Moscow (Russian Federation); Kotte, R.; Garcia, A. Laso [Helmholtz-Zentrum Dresden-Rossendorf, Dresden (Germany); Malkevich, D. [Institute for Theoretical and Experimental Physics, Moscow (Russian Federation); Naumann, L. [Helmholtz-Zentrum Dresden-Rossendorf, Dresden (Germany); Nedosekin, A.; Plotnikov, V. [Institute for Theoretical and Experimental Physics, Moscow (Russian Federation); Stach, D. [Helmholtz-Zentrum Dresden-Rossendorf, Dresden (Germany); Sultanov, R.; Voloshin, K. [Institute for Theoretical and Experimental Physics, Moscow (Russian Federation)

    2017-02-11

    Resistive Plate Chambers with ceramic electrodes are the main candidates for a use in precise multi-channel timing systems operating in high-radiation conditions. We report the latest R&D results on these detectors aimed to meet the requirements of the forward T0 counter at the CBM experiment. RPC design, gas mixture, limits on the bulk resistivity of ceramic electrodes, efficiency, time resolution, counting rate capabilities and ageing test results are presented.

  2. Refractory Materials for Flame Deflector Protection System Corrosion Control: Refractory Ceramics Literature Survey

    Science.gov (United States)

    Calle, Luz Marina; Hintze, Paul E.; Parlier, Christopher R.; Curran, Jerome P.; Kolody, Mark; Perusich, Stephen; Whitten, Mary C.; Trejo, David; Zidek, Jason; Sampson, Jeffrey W.; hide

    2009-01-01

    Ceramics can be defmed as a material consisting of hard brittle properties produced from inorganic and nonmetallic minerals made by firing at high temperatures. These materials are compounds between metallic and nonmetallic elements and are either totally ionic, or predominately ionic but having some covalent character. This definition allows for a large range of materials, not all applicable to refractory applications. As this report is focused on potential ceramic materials for high temperature, aggressive exposure applications, the ceramics reviewed as part of this report will focus on refractory ceramics specifically designed and used for these applications. Ceramic materials consist of a wide variety of products. Callister (2000) 1 characterized ceramic materials into six classifications: glasses, clay products, refractories, cements, abrasives, and advanced ceramics. Figure 1 shows this classification system. This review will focus mainly on refractory ceramics and cements as in general, the other classifications are neither applicable nor economical for use in large structures such as the flame trench. Although much work has been done in advanced ceramics over the past decade or so, these materials are likely cost prohibitive and would have to be fabricated off-site, transported to the NASA facilities, and installed, which make these even less feasible. Although the authors reviewed the literature on advanced ceramic refractories 2 center dot 3 center dot 4 center dot 5 center dot 6 center dot 7 center dot 8 center dot 9 center dot 10 center dot 11 center dot 12 after the review it was concluded that these materials should not be ' the focus of this report. A review is in progress on materials and systems for prefabricated refractory ceramic panels, but this review is focusing more on typical refractory materials for prefabricated systems, which could make the system more economically feasible. Refractory ceramics are used for a wide variety of applications

  3. In vitro shear bond strength of Y-TZP ceramics to different core materials with the use of three primer/resin cement systems.

    Science.gov (United States)

    Al-Harbi, Fahad A; Ayad, Neveen M; Khan, Zahid A; Mahrous, Amr A; Morgano, Steven M

    2016-01-01

    Durability of the bond between different core materials and zirconia retainers is an important predictor of the success of a dental prosthesis. Nevertheless, because of its polycrystalline structure, zirconia cannot be etched and bonded to a conventional resin cement. The purpose of this in vitro study was to compare the effects of 3 metal primer/resin cement systems on the shear bond strength (SBS) of 3 core materials bonded to yttria-stabilized tetragonal zirconia polycrystalline (Y-TZP) ceramic retainers. Zirconia ceramic (Cercon) disks (5×3 mm) were airborne-particle abraded, rinsed, and air-dried. Disk-shaped core specimens (7×7 mm) that were prepared of composite resin, Ni-Cr, and zirconia were bonded to the zirconia ceramic disks by using one of 3 metal primer/cement systems: (Z-Prime Plus/BisCem, Zirconia Primer/Multilink Automix, or Clearfil Ceramic Primer/Clearfil SA). SBS was tested in a universal testing machine. Stereomicroscopy was used to evaluate the failure mode of debonded specimens. Data were analyzed using 2-way ANOVA and post hoc analysis using the Scheffe procedure (α=.05). Clearfil SA/Clearfil Ceramic Primer system with an Ni-Cr core yielded the highest SBS value (19.03 MPa), whereas the lowest SBS value was obtained when Multilink Automix/Zirconia Primer system was used with the zirconia core group (4.09 MPa). Differences in mean SBS values among the cement/primer groups were statistically significant, except for Clearfil SA and BisCem with both composite resin and zirconia cores. Differences in mean SBS values among the core subgroups were not statistically significant, except for zirconia core with BisCem, Multilink, and Clearfil SA. The predominant failure mode was adhesive, except for Clearfil SA and BisCem luting agents with composite resin cores, which displayed cohesive failure, and Multilink Automix with a composite resin, core as well as Clearfil SA with Ni-Cr cores, where the debonded specimens of each group displayed a mixed

  4. Longevity of Single-Tooth All-Ceramic CAD/CAM Restorations: A Meta-Analysis

    Science.gov (United States)

    2013-07-01

    to the application of CAD/CAM technology in dentistry . The initial monetary investment for the equipment is significant. Systems currently on the...CURRENT DENTAL CAD/CAM SYSTEMS Current CAD/CAM systems in dentistry include: CEREC (CEramic REConstruction) and CEREC Acquisition Center (AC) with...of Adhesive Dentistry , 1 (3), 255- 265. 42     Bindl A, & Mörmann W. (2002). An up to 5-year clinical evaluation of posterior In- Ceram CAD

  5. Development plan of Pu NDA system using ZnS ceramic scintillator

    International Nuclear Information System (INIS)

    Kureta, Masatoshi; Soyama, Kazuhiko; Seya, Michio; Ohzu, Akira; Haruyama, Mitsuo; Takase, Misao; Sakasai, Kaoru; Nakamura, Tatsuya; Toh, Kentaro

    2012-01-01

    Alternative techniques to neutron detection by He-3 for nuclear security and safeguards systems are necessary to be developed since He-3 shortage is serious. With support of Japanese government (the Ministry of Education, Culture, Sports, and Technology), we have started an R and D project of Pu NDA system using ZnS ceramic scintillator. Here we present development plan, production of a new type of ZnS ceramic scintillator experimentally and basic design of a PCAS alternative Pu NDA system. We are planning the demonstration tests using the alternative NDA system comparing with the current PCAS in which the He-3 counters are installed. (author)

  6. Marginal discrepancy of noble metal-ceramic fixed dental prosthesis frameworks fabricated by conventional and digital technologies.

    Science.gov (United States)

    Afify, Ahmed; Haney, Stephan; Verrett, Ronald; Mansueto, Michael; Cray, James; Johnson, Russell

    2018-02-01

    Studies evaluating the marginal adaptation of available computer-aided design and computer-aided manufacturing (CAD-CAM) noble alloys for metal-ceramic prostheses are lacking. The purpose of this in vitro study was to evaluate the vertical marginal adaptation of cast, milled, and direct metal laser sintered (DMLS) noble metal-ceramic 3-unit fixed partial denture (FDP) frameworks before and after fit adjustments. Two typodont teeth were prepared for metal-ceramic FDP abutments. An acrylic resin pattern of the prepared teeth was fabricated and cast in nickel-chromium (Ni-Cr) alloy. Each specimen group (cast, milled, DMLS) was composed of 12 casts made from 12 impressions (n=12). A single design for the FDP substructure was created on a laboratory scanner and used for designing the specimens in the 3 groups. Each specimen was fitted to its corresponding cast by using up to 5 adjustment cycles, and marginal discrepancies were measured on the master Ni-Cr model before and after laboratory fit adjustments. The milled and DMLS groups had smaller marginal discrepancy measurements than those of the cast group (PDMLS and cast groups (F=30.643, P<.001). Metal-ceramic noble alloy frameworks fabricated by using a CAD-CAM workflow had significantly smaller marginal discrepancies compared with those with a traditional cast workflow, with the milled group demonstrating the best marginal fit among the 3 test groups. Manual refining significantly enhanced the marginal fit of all groups. All 3 groups demonstrated marginal discrepancies within the range of clinical acceptability. Copyright © 2017 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

  7. Characterization of the alumina-zirconia ceramic system by ultrasonic velocity measurements

    International Nuclear Information System (INIS)

    Carreon, Hector; Ruiz, Alberto; Medina, Ariosto; Barrera, Gerardo; Zarate, Juan

    2009-01-01

    In this work an alumina-zirconia ceramic composites have been prepared with α-Al 2 O 3 contents from 10 to 95 wt.%. The alumina-zirconia ceramic system was characterized by means of precise ultrasonic velocity measurements. In order to find out the factors affecting the variation in wave velocity, the ceramic composite have been examined by X-ray diffraction (XRD) and (SEM) scanning electron microscopy. It was found that the ultrasonic velocity measurements changed considerably with respect to the ceramic composite composition. In particular, we studied the behavior of the physical material property hardness, an important parameter of the ceramic composite mechanical properties, with respect to the variation in the longitudinal and shear wave velocities. Shear wave velocities exhibited a stronger interaction with microstructural and sub-structural features as compared to that of longitudinal waves. In particular, this phenomena was observed for the highest α-Al 2 O 3 content composite. Interestingly, an excellent correlation between ultrasonic velocity measurements and ceramic composite hardness was observed.

  8. Hydrothermal degradation of tetragonal ZrO{sub 2} ceramic components used in dental applications; Efeito da degradacao em meio aquoso de componentes ceramicos a base de ZrO{sub 2} tetragonal para uso odontologico

    Energy Technology Data Exchange (ETDEWEB)

    Mukaeda, L.E.; Robin, A.; Taguchi, S.P. [Universidade de Sao Paulo (DEMAR/EEL/USP), Lorena, SP (Brazil). Escola de Engenharia de Lorena. Dept. de Engenharia de Materiais; Santos, C. [ProtMat Materiais Avancados, Guaratingueta, SP (Brazil)

    2009-07-01

    With the evolution of the dental restoration techniques, a considerable growth in the demand of ceramic products occurred. These materials present good strength associated to reliability. In this work, micrometric and nanometric scale tetragonal ZrO{sub 2} blocks were sintered at 1500 deg C-2h and 1350 deg C-2h, respectively, ground and polished. Ceramics with relative density higher than 98% were obtained. The specimens were immersed in hot water (150 deg C), for times ranging from 10h to 30h. The mass variation of the samples was measured and the crystalline phases present before and after the degradation tests were identified by X-ray diffractometry, in order to evaluate the capacity of these ceramics in resisting to aqueous medium exposure. Materials with nanometric structure present higher resistance to degradation than those with micrometric scale, and this interferes in structural stability after the test, and reduces the martensitic transformation. (author)

  9. Influence of the photoinitiator system and light photoactivation units on the degree of conversion of dental composites.

    Science.gov (United States)

    Porto, Isabel Cristina Celerino de Moraes; Soares, Luis Eduardo Silva; Martin, Airton Abrahão; Cavalli, Vanessa; Liporoni, Priscila Christiane Suzy

    2010-01-01

    The aim of this study was to observe the influence of two light polymerization units (LED or halogen light) on the degree of conversion (DC) of three dental composites with lighter shades and a different photoinitiator system. The top (T) and bottom (B) surfaces of 60 discs of composite resin (Filtek™ Supreme, Filtek™ Z250, Tetric™ Ceram Bleach) cured either by LED or by halogen lamp (HL) were studied using an FT-Raman spectrometer. The degree of conversion (DC) was evaluated by following the changes in the intensity of the methacrylate C=C stretching mode at 1640 cm⁻¹. The calculated DC ranged from 54.2% (B) to 73.4% (T) and from 60.2% (B) to 76.6% (T) for the LED and HL, respectively. LED and halogen devices were able to produce an adequate DC for all the resins tested.

  10. Influence of the photoinitiator system and light photoactivation units on the degree of conversion of dental composites

    Directory of Open Access Journals (Sweden)

    Isabel Cristina Celerino de Moraes Porto

    2010-12-01

    Full Text Available The aim of this study was to observe the influence of two light polymerization units (LED or halogen light on the degree of conversion (DC of three dental composites with lighter shades and a different photoinitiator system. The top (T and bottom (B surfaces of 60 discs of composite resin (Filtek™ Supreme, Filtek™ Z250, Tetric™ Ceram Bleach cured either by LED or by halogen lamp (HL were studied using an FT-Raman spectrometer. The degree of conversion (DC was evaluated by following the changes in the intensity of the methacrylate C=C stretching mode at 1640 cm-1. The calculated DC ranged from 54.2% (B to 73.4% (T and from 60.2% (B to 76.6% (T for the LED and HL, respectively. LED and halogen devices were able to produce an adequate DC for all the resins tested.

  11. Comparative characterization of a novel cad-cam polymer-infiltrated-ceramic-network.

    Science.gov (United States)

    Albero, Alberto; Pascual, Agustín; Camps, Isabel; Grau-Benitez, María

    2015-10-01

    The field of dental ceramics for CAD-CAM is enriched with a new innovative material composition having a porous three-dimensional structure of feldspathic ceramic infiltrated with acrylic resins.The aim of this study is to determine the mechanical properties of Polymer-Infiltrated-Ceramic-Network (PICN) and compare its performance with other ceramics and a nano-ceramic resin available for CAD-CAM systems. In this study a total of five different materials for CAD-CAM were investigated. A polymer-infiltrated ceramic (Vita Enamic), a nano-ceramic resin (Lava Ultimate), a feldspathic ceramic (Mark II), a lithium disilicate ceramic (IPS-e max CAD) and finally a Leucite based ceramic (Empress - CAD). From CAD-CAM blocks, 120 bars (30 for each material cited above) were cut to measure the flexural strength with a three-point-bending test. Strain at failure, fracture stress and Weibull modulus was calculated. Vickers hardness of each material was also measured. IPS-EMAX presents mechanical properties significantly better from the other materials studied. Its strain at failure, flexural strength and hardness exhibited significantly higher values in comparison with the others. VITA ENAMIC and LAVA ULTIMATE stand out as the next most resistant materials. The flexural strength, elastic modulus similar to a tooth as well as having less hardness than ceramics make PICN materials an option to consider as a restorative material. Ceramic infiltrated with resin, CAD-CAM, Weibull modulus, flexural strength, micro hardness.

  12. In vitro study of the effect of three hydrogen peroxide concentrations on the corrosion behavior and surface topography of alumina-reinforced dental ceramic.

    Science.gov (United States)

    Abu-Eittah, Manal R; Mandour, Mona H

    2011-10-01

    This in vitro investigation studied the effect of three hydrogen peroxide (HP) concentrations (30%, 35%, 38% v/v) at two time intervals (1 and 2 hours) on the corrosion behavior and surface topography of a dental ceramic. A total of 62 Vitadur Alpha discs were constructed following manufacturer instructions. Specimens were divided into four main groups (n = 8). Group 1 (control): specimens were immersed in 4% acetic acid for 18 hours at 80°C. Groups 2, 3, and 4: specimens were immersed in 30%, 35%, and 38% HP concentrations, respectively. Each of the three groups was divided into two subgroups (a and b) according to the immersion time (1 and 2 hours, respectively). Specimens of subgroup a were further immersed in 4% acetic acid for 18 hours at 80°C and were designated as subgroup c. The corrosion behavior of the ceramic specimens were tested by solution analysis using the atomic absorption method, weight loss percent, and corrosion rate. Surface topography was investigated by surface roughness (Ra) measurements and scanning electron microscopy (SEM). Results were statistically analyzed. There was a significant increase for ions leached with the increase in time of immersion for all ions at 35% and 38% HP, while at 30% HP, ions of K(+) , Al(3+) , and Si(4+) did not increase significantly with time. The results also showed that at a fixed time of immersion, all ions released were dependent on the increase of HP concentration except for Al(3+) ions (p SEM. The amount of released ions is directly proportional to HP concentration and time of immersion. Specimens exposed to both HP and acetic acid showed increased weight loss and a higher corrosion rate than those exposed to acetic acid only. Surface roughness values were time and HP concentration dependent. © 2011 by The American College of Prosthodontists.

  13. Dose reference levels in Spanish intraoral dental radiology: stabilisation of the incorporation of digital systems in dental clinical practices

    International Nuclear Information System (INIS)

    Alcaraz, M.; Velasco, F.; Olivares, A.; Velasco, E.; Canteras, M.

    2016-01-01

    A total of 34 044 official quality assurance reports in dental radiodiagnostic surgery from 16 regions of Spain, compiled from 2002 to 2014, were studied in order to determine the progress of diagnostic reference levels (DRLs) for obtaining diagnostic images under normal conditions for clinical practice in Spanish dental clinics. A DRL of 2.8 mGy was set in 2014, which represents a 41.7 % decrease compared with that of 2002 (4.8 mGy). Over the same time period, the mean dose fell by 55.2 %. However, over the last 3 y, the stabilisation of the mean dose administered to patients has been observed with only a 6.7 % reduction in DRLs, which corresponds to the stabilisation of dental radiodiagnostic surgery on replacing the use of radiographic film with digital imaging systems. (authors)

  14. Ceramics and healthy heating and cooling systems: thermal ceramic panels in buildings. Conditions of comfort and energy demand versus convective systems

    Directory of Open Access Journals (Sweden)

    V. Echarri Iribarren

    2016-12-01

    Full Text Available Porcelain stoneware is a widely used building material. In recent years, its range of uses has expanded to encompass a new spectrum of innovative and inventive applications in architecture. In this research, we analysed the patented Thermal Ceramic Panel. This consists of a thin porcelain stoneware panel that incorporates a capillary system of polypropylene tubes measuring 3.5 mm in diameter embedded in a conductive ceramic interface. The system works with hot or cold water, producing healthy heating and cooling by means of radiant surfaces. Following an initial prototype test in which panels were placed on the walls of an office, we conducted simulations at the University of Alicante Museum using wall, ceiling and baffle panels, having previously monitored the state of the building. Thermal behaviour parameters were analysed and compared with those of other standard finishing materials, obtaining results for thermal comfort and energy savings in comparison with all-air systems.

  15. Bi-layered zirconia/fluor-apatite bridges supported by ceramic dental implants: a prospective case series after thirty months of observation.

    Science.gov (United States)

    Spies, Benedikt Christopher; Witkowski, Siegbert; Butz, Frank; Vach, Kirstin; Kohal, Ralf-Joachim

    2016-10-01

    The aim of this study was to determine the success and survival rate of all-ceramic bi-layered implant-supported three-unit fixed dental prostheses (IS-FDPs) 3 years after implant placement. Thirteen patients (seven males, six females; age: 41-78 years) received two one-piece ceramic implants (alumina-toughened zirconia) each in the region of the premolars or the first molar and were finally restored with adhesively cemented bi-layered zirconia-based IS-FDPs (3 in the maxilla, 10 in the mandible) composed of CAD/CAM-fabricated zirconia frameworks pressed-over with fluor-apatite glass-ceramic ingots. At prosthetic delivery and the follow-ups after 1, 2 and 3 years, the restorations were evaluated using modified United States Public Health Service (USPHS) criteria. Restorations with minor veneer chippings, a small-area occlusal roughness, slightly soundable restoration margins, minimal contour deficiencies and tolerable color deviations were regarded as success. In case of more distinct defects that could, however, be repaired to a clinically acceptable level, IS-FDPs were regarded as surviving. Kaplan-Meier plots were used for the success/survival analyses. To verify an impact on subjective patients' perceptions, satisfaction was evaluated by visual analog scales (VAS). All patients were seen 3 years after implant installation. No IS-FDP had to be replaced, resulting in 100% survival after a mean observation period of 29.5 months (median: 30.7). At the 3-year follow-up, 7/13 IS-FDPs showed a veneer chipping, 13/13 an occlusal roughness and 12/13 minimal deficiencies of contour/color. Since six restorations showed a major chipping and/or a major occlusal roughness, the Kaplan-Meier success rate was 53.8%. However, patients' significantly improved perceptions of function, esthetics, sense, and speech at prosthetic delivery remained stable over time. Bi-layered zirconia/fluor-apatite IS-FDPs entirely survived the observation period but showed a high frequency of

  16. Use of digital impression systems with intraoral scanners for fabricating restorations and fixed dental prostheses.

    Science.gov (United States)

    Takeuchi, Yoshimasa; Koizumi, Hiroyasu; Furuchi, Mika; Sato, Yohei; Ohkubo, Chikahiro; Matsumura, Hideo

    2018-01-01

    Accurate impressions are essential in fabri-cating dental restorations and fixed dental prostheses. During the last decade, digital impression systems have improved substantially. This review discusses the accuracy of digital impression systems for fabrication of dental restorations and fixed dental prostheses. A literature search in PubMed was performed for the period from July 2010 through June 2017. The search keywords were Cerec, digital impression, direct digitalization, indirect digitalization, and intraoral scanner. Only relevant studies are summarized and discussed in this review. In general, the latest systems have considerably reduced the time required for impression making, and the accuracy and marginal fit of digital impression systems have recently improved. Restorations and fixed dental prostheses fabricated with currently available digital impression systems and intraoral scanners exhibit clinically acceptable ranges of marginal gap in both direct and indirect procedures.

  17. Oxide ceramics

    International Nuclear Information System (INIS)

    Ryshkewitch, E.; Richerson, D.W.

    1985-01-01

    The book explores single-phase ceramic oxide systems from the standpoint of physical chemistry and technology. This second edition also focuses on advances in technology since publication of the original edition. These include improvements in raw materials and forming and sintering techniques, and the major role that oxide ceramics have had in development of advanced products and processes. The text is divided into five major sections: general fundamentals of oxide ceramics, advances in aluminum oxide technology, advances in zirconia technology, and advances in beryllium oxide technology

  18. Construction and testing of a system for the electrical characterization of ceramic thermistors at low temperatures

    Directory of Open Access Journals (Sweden)

    F. C. S. Luz

    2014-03-01

    Full Text Available A high-precision and low cost system was built for the electrical characterization of ceramic thermistors at low temperatures, using components readily available in materials research laboratories. The system presented excellent reproducibility in the electrical characterization of NTC ceramic sensors from -75 ºC (195 K to 23 ºC (296 K. The behavior of the NTC sensor was comparable to that of commercial thermistors only below room temperature (α = -3.2%/K, demonstrating the importance of fully characterizing these materials at both low and high temperatures.

  19. Effect of core ceramic grinding on fracture behaviour of bilayered zirconia veneering ceramic systems under two loading schemes.

    Science.gov (United States)

    Jian, Yu-Tao; Tang, Tian-Yu; Swain, Michael V; Wang, Xiao-Dong; Zhao, Ke

    2016-12-01

    The aim of this in vitro study was to evaluate the effect of core ceramic grinding on the fracture behaviour of bilayered zirconia under two loading schemes. Interfacial surfaces of sandblasted zirconia disks (A) were ground with 80 (B), 120 (C) and 220 (D) grit diamond discs, respectively. Surface roughness and topographic analysis were performed using a confocal scanning laser microscope (CSLM) and a scanning electron microscopy (SEM). Relative monoclinic content was evaluated using X-ray diffraction analysis (XRD) then reevaluated after simulated veneer firing. Biaxial fracture strength (σ) and Weibull modulus (m) were calculated either with core in compression (subgroup Ac-Dc) or in tension (subgroup At-Dt). Facture surfaces were examined by SEM and energy dispersive X-ray spectroscopy (EDS). Maximum tensile stress at fracture was estimated by finite element analysis. Statistical data analysis was performed using Kruskal-Wallis and one-way ANOVA at a significance level of 0.05. As grit size of the diamond disc increased, zirconia surface roughness decreased (pgrinding. No difference in initial (p=0.519 for subgroups Ac-Dc) and final fracture strength (p=0.699 for subgroups Ac-Dc; p=0.328 for subgroups At-Dt) was found among the four groups for both loading schemes. While coarse grinding slightly increased final fracture strength reliability (m) for subgroups Ac-Dc. Two different modes of fracture were observed according to which material was on the bottom surface. Components of the liner porcelain remained on the zirconia surface after fracture for all groups. Technician grinding changed surface topography of zirconia ceramic material, but was not detrimental to the bilayered system strength after veneer application. Coarse grinding slightly improved the fracture strength reliability of the bilayered system tested with core in compression. It is recommended that veneering porcelain be applied directly after routine lab grinding of zirconia ceramic, and its

  20. Recent research activities on functional ceramics for insulator, breeder and optical sensing systems in fusion reactors

    Energy Technology Data Exchange (ETDEWEB)

    Nagata, S., E-mail: nagata@imr.tohoku.ac.jp [Institute for Materials Research, Tohoku University, Sendai (Japan); Katsui, H.; Hoshi, K. [Institute for Materials Research, Tohoku University, Sendai (Japan); Tsuchiya, B. [Meijo University, Faculty of Science and Technology, Nagoya (Japan); Toh, K. [J-PARC Center Japan Atomic Energy Agency, Tokai (Japan); Zhao, M.; Shikama, T. [Institute for Materials Research, Tohoku University, Sendai (Japan); Hodgson, E.R. [Euratom/CIEMAT Fusion Association, Madrid (Spain)

    2013-11-15

    The paper presents a brief overview of current research activities on functional ceramic materials for insulating components, tritium breeder and optical sensing systems, mainly carried out at Institute for Materials Research (IMR), Tohoku University. Topics include recent experimental results related to the electrical degradation and optical changes in typical oxide ceramics (e.g. Al{sub 2}O{sub 3} and SiO{sub 2}) concerning radiolytic effects. Hydrogen effects on the electrical conductivity in the Perovskite-type oxide ceramics and the interaction between hydrogen and irradiation induced defects in ternary Li oxides used as breeder materials, were dynamically observed under the irradiation environment. Further attention is focused on several challenging qualifications required for an advanced sensing system using optical characteristics (e.g., thermoluminescence in SiO{sub 2} core fiber, neutron-induced long lasting emission from oxides doped with rare-earth elements, and gasochromic coloration phenomenon of WO{sub 3})

  1. Advances in dental veneers: materials, applications, and techniques.

    Science.gov (United States)

    Pini, Núbia Pavesi; Aguiar, Flávio Henrique Baggio; Lima, Débora Alves Nunes Leite; Lovadino, José Roberto; Terada, Raquel Sano Suga; Pascotto, Renata Corrêa

    2012-01-01

    Laminate veneers are a conservative treatment of unaesthetic anterior teeth. The continued development of dental ceramics offers clinicians many options for creating highly aesthetic and functional porcelain veneers. This evolution of materials, ceramics, and adhesive systems permits improvement of the aesthetic of the smile and the self-esteem of the patient. Clinicians should understand the latest ceramic materials in order to be able to recommend them and their applications and techniques, and to ensure the success of the clinical case. The current literature was reviewed to search for the most important parameters determining the long-term success, correct application, and clinical limitations of porcelain veneers.

  2. Emerging ceramic-based materials for dentistry.

    Science.gov (United States)

    Denry, I; Kelly, J R

    2014-12-01

    Our goal is to give an overview of a selection of emerging ceramics and issues for dental or biomedical applications, with emphasis on specific challenges associated with full-contour zirconia ceramics, and a brief synopsis on new machinable glass-ceramics and ceramic-based interpenetrating phase composites. Selected fabrication techniques relevant to dental or biomedical applications such as microwave sintering, spark plasma sintering, and additive manufacturing are also reviewed. Where appropriate, the authors have added their opinions and guidance. © International & American Associations for Dental Research.

  3. ADM guidance-Ceramics: all-ceramic multilayer interfaces in dentistry.

    Science.gov (United States)

    Lohbauer, Ulrich; Scherrer, Susanne S; Della Bona, Alvaro; Tholey, Michael; van Noort, Richard; Vichi, Alessandro; Kelly, J Robert; Cesar, Paulo F

    2017-06-01

    This guidance document describes the specific issues involved in dental multilayer ceramic systems. The material interactions with regard to specific thermal and mechanical properties are reviewed and the characteristics of dental tooth-shaped processing parameters (sintering, geometry, thickness ratio, etc.) are discussed. Several techniques for the measurement of bond quality and residual stresses are presented with a detailed discussion of advantages and disadvantages. In essence no single technique is able to describe adequately the all-ceramic interface. Invasive or semi-invasive methods have been shown to distort the information regarding the residual stress state while non-invasive methods are limited due to resolution, field of focus or working depth. This guidance document has endeavored to provide a scientific basis for future research aimed at characterizing the ceramic interface of dental restorations. Along with the methodological discussion it is seeking to provide an introduction and guidance to relatively inexperienced researchers. Copyright © 2017 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  4. Evaluation of fracture toughness in dental ceramics using indentation and SEVNB (Single Edge V-Notched Beam)-method

    International Nuclear Information System (INIS)

    Santos, L.A.; Santos, C.; Souza, R.C.; Ribeiro, S.

    2009-01-01

    In this work, the fracture toughness of different ceramics based on Al 2 O 3 and ZrO 2 were evaluated using, comparatively two methods, Vickers indentation and SEVNB (Single Edge V-Notched Beam) method. Al 2 O 3 , ZrO 2 (3%Y 2 O 3 ) micro-particled and ZrO 2 (3%Y 2 O 3 ) nanometric, ZrO 2 -Al 2 O 3 and Al 2 O 3 -ZrO 2 composites were sintered at different temperatures. Samples were characterized by relative density, X-ray diffraction, SEM, and mechanical evaluation by hardness, bending strength and fracture toughness obtained by ickers indentation and SEVNB-method. The results were presented comparing the densification and microstructural results. Furthermore, the advantages and limitations of each method were discussed. (author)

  5. Ballistic Performance of Porous-Ceramic, Thermal Protection Systems to 9 km/s

    Science.gov (United States)

    Miller, Joshua E.; Bohl, William E.; Foreman, Cory D.; Christiansen, Eric C.; Davis, Bruce A.

    2010-01-01

    Porous-ceramic, thermal protection systems are used heavily in current reentry vehicles like the Orbiter, and they are currently being proposed for the next generation of US manned spacecraft, Orion. These materials insulate the structural components and sensitive components of a spacecraft against the intense thermal environments of atmospheric reentry. These materials are also highly exposed to solid particle space environment hazards. This paper discusses recent impact testing up to 9.65 km/s on ceramic tiles similar to those used on the Orbiter. These tiles are a porous-ceramic insulator of nominally 8 lb/ft(exp 3) alumina-fiber-enhanced-thermal-barrier (AETB8) coated with a damage-resistant, toughened-unipiece-fibrous-insulation/reaction-cured-glass layer (TUFI/RCG).

  6. Radioactivity decontamination efficiency of ceramic filter in an incineration volume reduction system of radioactive waste

    International Nuclear Information System (INIS)

    Kanbe, Hiromi; Mayuzumi, Masami; Yoshiki, Sinya; Sema, Toru; Koyama, Hiroaki; Ono, Tetsuo; Nagae, Madoka; Takaoku, Yoshinobu; Hozumi, Masahiro.

    1987-01-01

    The small pilot facility of a cyclone type suspension incineration system of radioactive waste was set up in order to evaluate the decontamination efficiency of a high efficiency ceramic filter. The evaluation was made by use of 54 Mn, 59 Fe, 60 Co, 65 Zn and 137 Cs. 1. The decontamination factor by one line of ceramic filter for every species were over 10 5 . 2. The decontamination factor increased by one oder when water vapor exists in off-gas. The same tendency was also observed when iron dioxide existed at the incineration of cation exchange resin. (author)

  7. Does use of an electronic health record with dental diagnostic system terminology promote dental students' critical thinking?

    Science.gov (United States)

    Reed, Susan G; Adibi, Shawn S; Coover, Mullen; Gellin, Robert G; Wahlquist, Amy E; AbdulRahiman, Anitha; Hamil, Lindsey H; Walji, Muhammad F; O'Neill, Paula; Kalenderian, Elsbeth

    2015-06-01

    The Consortium for Oral Health Research and Informatics (COHRI) is leading the way in use of the Dental Diagnostic System (DDS) terminology in the axiUm electronic health record (EHR). This collaborative pilot study had two aims: 1) to investigate whether use of the DDS terms positively impacted predoctoral dental students' critical thinking skills measured by the Health Sciences Reasoning Test (HSRT), and 2) to refine study protocols. The study design was a natural experiment with cross-sectional data collection using the HSRT for 15 classes (2013-17) of students at three dental schools. Characteristics of students who had been exposed to the DDS terms were compared with students who had not, and the differences were tested by t-tests or chi-square tests. Generalized linear models were used to evaluate the relationship between exposure and outcome on the overall critical thinking score. The results showed that exposure was significantly related to overall score (p=0.01), with not-exposed students having lower mean overall scores. This study thus demonstrated a positive impact of using the DDS terminology in an EHR on the critical thinking skills of predoctoral dental students in three COHRI schools as measured by their overall score on the HSRT. These preliminary findings support future research to further evaluate a proposed model of critical thinking in clinical dentistry.

  8. Does Use of an Electronic Health Record with Dental Diagnostic System Terminology Promote Dental Students’ Critical Thinking?

    Science.gov (United States)

    Reed, Susan G.; Adibi, Shawn S.; Coover, Mullen; Gellin, Robert G.; Wahlquist, Amy E.; AbdulRahiman, Anitha; Hamil, Lindsey H.; Walji, Muhammad F.; O’Neill, Paula; Kalenderian, Elsbeth

    2015-01-01

    The Consortium for Oral Health Research and Informatics (COHRI) is leading the way in use of the Dental Diagnostic System (DDS) terminology in the axiUm electronic health record (EHR). This collaborative pilot study had two aims: 1) to investigate whether use of the DDS terms positively impacted predoctoral dental students’ critical thinking skills measured by the Health Sciences Reasoning Test (HSRT), and 2) to refine study protocols. The study design was a natural experiment with cross-sectional data collection using the HSRT for 15 classes (2013–17) of students at three dental schools. Characteristics of students who had been exposed to the DDS terms were compared with students who had not, and the differences were tested by t-tests or chi-square tests. Generalized linear models were used to evaluate the relationship between exposure and outcome on the overall critical thinking score. The results showed that exposure was significantly related to overall score (p=0.01), with not-exposed students having lower mean overall scores. This study thus demonstrated a positive impact of using the DDS terminology in an EHR on the critical thinking skills of predoctoral dental students in three COHRI schools as measured by their overall score on the HSRT. These preliminary findings support future research to further evaluate a proposed model of critical thinking in clinical dentistry. PMID:26034034

  9. Radiopaque strontium fluoroapatite glass-ceramics

    Directory of Open Access Journals (Sweden)

    Wolfram eHöland

    2015-10-01

    Full Text Available The controlled precipitation of strontium fluoroapatite crystals, was studied in four base glass compositions derived from the SiO2 – Al2O3 – Y2O3 – SrO – Na2O – K2O/Rb2O/Cs2O – P2O5 – F system. The crystal phase formation of these glasses and the main properties of the glass-ceramics, such as thermal and optical properties and radiopacity were compared with a fifth, a reference glass-ceramic. The reference glass-ceramic was characterized as Ca-fluoroapatite glass-ceramic. The four strontium fluoroapatite glass-ceramics showed the following crystal phases: a Sr5(PO43F – leucite, KAlSi2O6 , b Sr5(PO43F – leucite, KAlSi2O6, and nano-sized NaSrPO4 c Sr5(PO43F – pollucite, CsAlSiO4 , and nano-sized NaSrPO4, d Sr5(PO43F – Rb-leucite, RbAlSi2O6, and nano-sized NaSrPO4.The proof of crystal phase formation was possible by X-ray diffraction (XRD. The microstructures, which were studied using scanning electron microscopy (SEM demonstrated a uniform distribution of the crystals in the glass matrix. The Sr-fluoroapatites were precipitated based on an internal crystallization process, and the crystals demonstrated a needlelike morphology. The study of the crystal growth of needlelike Sr-fluoroapatites gave a clear evidence of an Ostwald ripening mechanism.The formation of leucite, pollucite and Rb-leucite was based on a surface crystallization mechanism. Therefore, a twofold crystallization mechanism was successfully applied to develop these types of glass-ceramics. The main focus of this study was the controlled development of glass-ceramics exhibiting high radiopacity in comparison to the reference glass-ceramic. This goal could be achieved with all four glass-ceramics with the preferred development of the Sr-fluoroapatite – pollucite-type glass-ceramic. In addition to this main development, it was possible to control the thermal properties. Especially the Rb-leucite containing glass-ceramic showed the highest coefficient of thermal

  10. Parkinson disease: systemic and orofacial manifestations, medical and dental management.

    Science.gov (United States)

    Friedlander, Arthur H; Mahler, Michael; Norman, Keith M; Ettinger, Ronald L

    2009-06-01

    More than 1.5 million Americans have Parkinson disease (PD), and this figure is expected to rise as the population ages. However, the dental literature offers little information about the illness. The authors conducted a MEDLINE search using the key terms "Parkinson's disease," "medical management" and "dentistry." They selected contemporaneous articles published in peer-reviewed journals and gave preference to articles reporting randomized controlled trials. PD is a progressive neurodegenerative disorder caused by loss of dopaminergic and nondopaminergic neurons in the brain. These deficits result in tremor, slowness of movement, rigidity, postural instability and autonomic and behavioral dysfunction. Treatment consists of administering medications that replace dopamine, stimulate dopamine receptors and modulate other neurotransmitter systems. Oral health may decline because of tremors, muscle rigidity and cognitive deficits. The dentist should consult with the patient's physician to establish the patient's competence to provide informed consent and to determine the presence of comorbid illnesses. Scheduling short morning appointments that begin 90 minutes after administration of PD medication enhances the patient's ability to cooperate with care. Inclination of the dental chair at 45 degrees, placement of a bite prop, use of a rubber dam and high-volume oral evacuation enhance airway protection. To avoid adverse drug interactions with levodopa and entacapone, the dentist should limit administration of local anesthetic agents to three cartridges of 2 percent lidocaine with 1:100,000 epinephrine per half hour, and patients receiving selegiline should not be given agents containing epinephrine or levonordefrin. The dentist should instruct the patient and the caregiver in good oral hygiene techniques.

  11. The bonding effectiveness of five luting resin cements to the IPS Empress 2 all ceramic system.

    Science.gov (United States)

    Bookhan, V; Essop, A R M; Du Preez, I C

    2005-04-01

    Variolink II is the only resin cement used for bonding IPS (Ivoclar Porcelain System) Empress 2 ceramic restorations. Alternative luting resin cements need to be investigated for their bonding effectiveness with the IPS Empress 2 ceramic. To determine the shear bond strength (SBS) and the effect of thermocycling, on the bonding effectiveness, of five resin cements to IPS Empress 2 ceramic. The projecting surfaces of one hundred ceramic discs were ground wet on silicone carbide paper. The specimens were divided into 5 groups of 20. The resin cements were bonded to the prepared ceramic surfaces, in the form of a stub. The specimens were stored under distilled water at 37 degrees C in an oven for 24 hours. Ten specimens in each group were thermocycled for 300 cycles between 5 degrees C and 55 degrees C. All the specimens were stressed to failure in an Instron Materials Testing Machine. The results were subjected to a one-way analysis of variance (ANOVA). Statistically similar mean SBS values were grouped using the Bonferroni (Dunn) multiple comparison test. The means for the non-thermocycled group were: 26.21, 19.41, 17.69, 17.43, and 15.76. The means for the thermocycled group were: 22.90, 15.72, 14.34, 13.96 and 13.45. The differences between the means were highly significant (p Empress 2 ceramic was effective. Thermocycling had a significant effect on the mean SBS values of Calibra. Thermocycling had no significant effect on the mean SBS values of the other resin cements.

  12. Effects of different surface-treatment methods on the bond strengths of resin cements to full-ceramic systems

    Directory of Open Access Journals (Sweden)

    Gülay Kansu

    2011-09-01

    Conclusions: The in vitro findings from this study indicate that surface-treatment procedures applied to the IPS Empress and the IPS Empress 2 full-ceramic systems are important when cement types are considered. In contrast, cement types and surface-treatment methods had no effect on changing the bond strength of the In-Ceram ceramic system.

  13. The Effect of Hydrofluoric Acid Etching Duration on the Surface Micromorphology, Roughness, and Wettability of Dental Ceramics

    Science.gov (United States)

    Ramakrishnaiah, Ravikumar; Alkheraif, Abdulaziz A.; Divakar, Darshan Devang; Matinlinna, Jukka P.; Vallittu, Pekka K.

    2016-01-01

    The current laboratory study is evaluating the effect of hydrofluoric acid etching duration on the surface characteristics of five silica-based glass ceramics. Changes in the pore pattern, crystal structure, roughness, and wettability were compared and evaluated. Seventy-five rectangularly shaped specimens were cut from each material (IPS e-max™, Dentsply Celtra™, Vita Suprinity™, Vita mark II™, and Vita Suprinity FC™); the sectioned samples were finished, polished, and ultrasonically cleaned. Specimens were randomly assigned into study groups: control (no etching) and four experimental groups (20, 40, 80 and 160 s of etching). The etched surfaces’ microstructure including crystal structure, pore pattern, pore depth, and pore width was studied under a scanning electron microscope, and the surface roughness and wettability were analyzed using a non-contact surface profilometer and a contact angle measuring device, respectively. The results were statistically analyzed using one-way analysis of variance (ANOVA) and the post hoc Tukey’s test. The results showed a significant change in the pore number, pore pattern, crystal structure, surface roughness, and wettability with increased etching duration. Etching for a short time resulted in small pores, and etching for longer times resulted in wider, irregular grooves. A significant increase in the surface roughness and wettability was observed with an increase in the etching duration. The findings also suggested a strong association between the surface roughness and wettability. PMID:27240353

  14. Anterior provisional restorations used to determine form, function, and esthetics for complex restorative situations, using all-ceramic restorative systems.

    Science.gov (United States)

    Reshad, Mamaly; Cascione, Domenico; Kim, Tae

    2010-02-01

    A technique is proposed for the restoration of a large and visible maxillary anterior defect. The importance of proper diagnosis, treatment planning, and communication is emphasized. Irreversible treatment should only be rendered once patient approval has been obtained through objective evaluation with provisional restorations. The techniques presented in this article use a combination of ceramic systems currently available to satisfy functional demands while achieving acceptable esthetics. A controlled series of steps, where the provisional restorative components are being replaced by the definitive ones is planned. The only difference between the provisional and definitive restorative components is the material used. The definitive restorations consisted of an implant-supported zirconium oxide framework. Individual pressed porcelain restorations were luted to the framework and a natural tooth. CLINICAL SIGNIFICANCE Provisional restorations allow an objective form of communication. Vertical and horizontal transitional lines can be effectively masked with appropriate treatment planning and a skilled ceramist. Many traditional dental laboratory steps may be eliminated or simplified without compromising the definitive restorations.

  15. An 8-year evaluation of sintered ceramic and glass ceramic inlays processed by the Cerec CAD/CAM system

    DEFF Research Database (Denmark)

    Pallesen, U.; Dijken van, J.W.V.

    2000-01-01

    The purpose of this study was to evaluate Cerec CAD/CAM inlays processed of two industrially made machinable ceramics during an 8-yr follow-up period. Each of 16 patients received two similar ceramic inlays. Half the number of the inlays were made of a feldspathic (Vita Mark II) and the other...... of a glass ceramic (Dicor MGC) block. The inlays were luted with a dual resin composite and evaluated clinically using modified USPHS criteria at baseline, 8 months, 2, 3, 5, 6 and 8 yr, and indirectly using models. At baseline, 84% of the inlays were estimated as optimal and 16% as acceptable. Postoperative...... sensitivity was reported by one patient for 8 months. Of the 32 inlays evaluated during the 8 yr, 3 failed due to fracture of the material. No secondary caries was found adjacent to the inlays. No significant differences in the clinical performance were found between inlays made of the two ceramics. It can...

  16. A dense cell retention culture system using stirred ceramic membrane reactor.

    Science.gov (United States)

    Suzuki, T; Sato, T; Kominami, M

    1994-11-20

    A novel reactor design incorporating porous ceramic tubes into a stirred jar fermentor was developed. The stirred ceramic membrane reactor has two ceramic tubular membrane units inside the vessel and maintains high filtration flux by alternating use for filtering and recovering from clogging. Each filter unit was linked for both extraction of culture broth and gas sparging. High permeability was maintained for long periods by applying the periodical control between filtering and air sparging during the stirred retention culture of Saccharomyces cerevisiae. The ceramic filter aeration system increased the k(L)a to about five times that of ordinary gas sparing. Using the automatic feeding and filtering system, cell mass concentration reached 207 g/L in a short time, while it was 64 g/L in a fed-batch culture. More than 99% of the growing cells were retained in the fermentor by the filtering culture. Both yield and productivity of cells were also increased by controlling the feeding of fresh medium and filtering the supernatant of the dense cells culture. (c) 1994 John Wiley & Sons, Inc.

  17. Percolative ionic conduction in the LiAlSiO4 glass-ceramic system

    International Nuclear Information System (INIS)

    Biefeld, R.M.; Pike, G.E.; Johnson, R.T. Jr.

    1977-01-01

    The effect f crystallinity on the lithium ion conductivity in LiAlSiO 4 glass and glass-ceramic solid electrolytes has been determined. The ionic conductivity is thermally activated with an activation energy and pre-exponential factor that change in a marked and nonsimple manner as the volume fraction of crystallinity changes. These results are explained by using a continuum percolation model (effective-medium approximation) which assumes that ionic conduction in the glass-ceramic is almost entirely within the glass phase until the crystalline volume fraction rises above approx. 55%. The LiAlSiO 4 system would seem to be nearly ideal for application of percolation theory since the crystalline phase, β eucryptite, has nearly the same composition as the glass phase. Hence, as the crystallite volume fraction increases in the glass ceramic, the residual glass composition and conductivity remain the same. This is the first application of percolation theory to ionic transport in glass-ceramics and excellent agreement is obtained between theory and experiment for the LiAlSiO 4 system

  18. Machinability of IPS Empress 2 framework ceramic.

    Science.gov (United States)

    Schmidt, C; Weigl, P

    2000-01-01

    Using ceramic materials for an automatic production of ceramic dentures by CAD/CAM is a challenge, because many technological, medical, and optical demands must be considered. The IPS Empress 2 framework ceramic meets most of them. This study shows the possibilities for machining this ceramic with economical parameters. The long life-time requirement for ceramic dentures requires a ductile machined surface to avoid the well-known subsurface damages of brittle materials caused by machining. Slow and rapid damage propagation begins at break outs and cracks, and limits life-time significantly. Therefore, ductile machined surfaces are an important demand for machine dental ceramics. The machining tests were performed with various parameters such as tool grain size and feed speed. Denture ceramics were machined by jig grinding on a 5-axis CNC milling machine (Maho HGF 500) with a high-speed spindle up to 120,000 rpm. The results of the wear test indicate low tool wear. With one tool, you can machine eight occlusal surfaces including roughing and finishing. One occlusal surface takes about 60 min machining time. Recommended parameters for roughing are middle diamond grain size (D107), cutting speed v(c) = 4.7 m/s, feed speed v(ft) = 1000 mm/min, depth of cut a(e) = 0.06 mm, width of contact a(p) = 0.8 mm, and for finishing ultra fine diamond grain size (D46), cutting speed v(c) = 4.7 m/s, feed speed v(ft) = 100 mm/min, depth of cut a(e) = 0.02 mm, width of contact a(p) = 0.8 mm. The results of the machining tests give a reference for using IPS Empress(R) 2 framework ceramic in CAD/CAM systems. Copyright 2000 John Wiley & Sons, Inc.

  19. Fatigue failure load of two resin-bonded zirconia-reinforced lithium silicate glass-ceramics: Effect of ceramic thickness.

    Science.gov (United States)

    Monteiro, Jaiane Bandoli; Riquieri, Hilton; Prochnow, Catina; Guilardi, Luís Felipe; Pereira, Gabriel Kalil Rocha; Borges, Alexandre Luiz Souto; de Melo, Renata Marques; Valandro, Luiz Felipe

    2018-06-01

    To evaluate the effect of ceramic thickness on the fatigue failure load of two zirconia-reinforced lithium silicate (ZLS) glass-ceramics, adhesively cemented to a dentin analogue material. Disc-shaped specimens were allocated into 8 groups (n=25) considering two study factors: ZLS ceramic type (Vita Suprinity - VS; and Celtra Duo - CD), and ceramic thickness (1.0; 1.5; 2.0; and 2.5mm). A trilayer assembly (ϕ=10mm; thickness=3.5mm) was designed to mimic a bonded monolithic restoration. The ceramic discs were etched, silanized and luted (Variolink N) into a dentin analogue material. Fatigue failure load was determined using the Staircase method (100,000 cycles at 20Hz; initial fatigue load ∼60% of the mean monotonic load-to-failure; step size ∼5% of the initial fatigue load). A stainless-steel piston (ϕ=40mm) applied the load into the center of the specimens submerged in water. Fractographic analysis and Finite Element Analysis (FEA) were also performed. The ceramic thickness influenced the fatigue failure load for both ZLS materials: Suprinity (716N up to 1119N); Celtra (404N up to 1126N). FEA showed that decreasing ceramic thickness led to higher stress concentration on the cementing interface. Different ZLS glass-ceramic thicknesses influenced the fatigue failure load of the bonded system (i.e. the thicker the glass ceramic is, the higher the fatigue failure load will be). Different microstructures of the ZLS glass-ceramics might affect the fatigue behavior. FEA showed that the thicker the glass ceramic is, the lower the stress concentration at the tensile surface will be. Copyright © 2018 The Academy of Dental Materials. Published by Elsevier Inc. All rights reserved.

  20. Prototype of a silicon nitride ceramic-based miniplate osteofixation system for the midface.

    Science.gov (United States)

    Neumann, Andreas; Unkel, Claus; Werry, Christoph; Herborn, Christoh U; Maier, Horst R; Ragoss, Christian; Jahnke, Klaus

    2006-06-01

    The favorable properties of silicon nitride (Si3N4) ceramics, such as high mean strength level and fracture toughness, suggest biomedical use as an implant material. Minor reservations about the biocompatibility of Si3N4 ceramics were cleared up by previous in vitro and in vivo investigations. A Si3N4 prototype minifixation system was manufactured and implanted for osteosynthesis of artificial frontal bone defects in 3 minipigs. After 3 months, histological sections, computed tomography (CT) scans, and magnetic resonance imaging (MRI) scans were obtained. Finite element modeling (FEM) was used to simulate stresses and strains on Si3N4 miniplates and screws to calculate survival probabilities. Si3N4 miniplates and screws showed satisfying intraoperative workability. There was no implant loss, displacement, or fracture. Bone healing was complete in all animals. The formation of new bone was observed in direct contact to the implants. The implants showed no artifacts on CT and MRI scanning. FEM simulation confirmed the mechanical reliability of the screws, whereas simulated plate geometries regarding pullout forces at maximum load showed limited safety in a bending situation. Si3N4 ceramics show a good biocompatibility outcome both in vitro and in vivo. In ENT surgery, this ceramic may serve as a biomaterial for osteosynthesis (eg, of the midface including reconstruction the floor of the orbit and the skull base). To our knowledge, this is the first introduction of a ceramic-based miniplate-osteofixation system. Advantages compared with titanium are no risk of implantation to bone with mucosal attachment, no need for explantation, and no interference with radiologic imaging. Disadvantages include the impossibility of individual bending of the miniplates.

  1. An Application of Geospatial Information Systems (GIS) Technology to Anatomic Dental Charting

    OpenAIRE

    Bartling, William C.; Schleyer, Titus K.L.

    2003-01-01

    Historically, an anatomic dental chart is a compilation of color-coded symbols and numbers used within a template, either paper or computerized, to create a graphic record of a patient’s oral health status. This poster depicts how Geospatial Information System (GIS) technology can be used to create an accurate, current anatomic dental chart that contains detailed information not present in current charting systems.

  2. Danish dental education:

    DEFF Research Database (Denmark)

    Moore, Rod

    1985-01-01

    The effects of Danish cultural traditions on dental education in Denmark are described, as well as the system's current structure and developing issues. Some Danish ideas for future exports of dental education programs and dental personnel are also discussed.......The effects of Danish cultural traditions on dental education in Denmark are described, as well as the system's current structure and developing issues. Some Danish ideas for future exports of dental education programs and dental personnel are also discussed....

  3. Systemic Assessment of Patients Undergoing Dental Implant Surgeries: A Trans- and Post-operative Analysis.

    Science.gov (United States)

    Byakodi, Sanjay; Kumar, Sachin; Reddy, Rajesh Kumar; Kumar, Vipin; Sepolia, Shipra; Gupta, Shivangi; Singh, Harkanwal Preet

    2017-01-01

    Procedure-related and patient-related factors influence the prognosis of dental implants to a major extent. Hence, we aimed to evaluate and analyze various systemic factors in patients receiving dental implants. Fifty-one patients were included in the study, in which a total of 110 dental implants were placed. Complete examination of the subjects was done before and after placement of dental implants. Implant surgery was planned, and osseointegrated dental implants were placed in the subjects. Postoperative evaluation of the dental implant patients was done after 3 weeks. Anxiety levels were determined using State-Trait Anxiety Inventory (STAI) questionnaire on the surgery day and after 1 week of surgery. The participant describes how they feel at the moment by responding to twenty items as follows: (1) absolutely not, (2) slightly, (3) somewhat, or (4) very much. All the results were recorded and statistical analyzed by SPSS software. Out of 51, 29 patients were males while 22 were females, with ratio of 1.32:1. Female patients' mean age was 50.18 years while male patients' mean age was 52.71 years, with statistically nonsignificant difference between them. Functional rehabilitation was the main purpose of choosing dental implants in more than 90% of the subjects. Diameter of 3.75 mm was the shortest implants to be placed in the present study, whereas in terms of length, 8.5 mm was the shortest length of dental implant used in the present study. Tooth area in which maximum implants were placed in our study was 36 tooth region. Maximum implants were placed in Type II bone quality ( n = 38). Implants installed in the mandible were clamped more efficiently than implants placed in the maxilla ( P < 0.001). The difference of average STAI-State subscore before and after the surgery was statistically significant ( P < 0.05; significant). Mandibular dental implants show more clamping (torque) than maxillary dental implants.

  4. Lightweight Ablative and Ceramic Thermal Protection System Materials for NASA Exploration Systems Vehicles

    Science.gov (United States)

    Valentine, Peter G.; Lawrence, Timothy W.; Gubert, Michael K.; Milos, Frank S.; Kiser, James D.; Ohlhorst, Craig W.; Koenig, John R.

    2006-01-01

    As a collaborative effort among NASA Centers, the "Lightweight Nonmetallic Thermal Protection Materials Technology" Project was set up to assist mission/vehicle design trade studies, to support risk reduction in thermal protection system (TPS) material selections, to facilitate vehicle mass optimization, and to aid development of human-rated TPS qualification and certification plans. Missions performing aerocapture, aerobraking, or direct aeroentry rely on advanced heatshields that allow reductions in spacecraft mass by minimizing propellant requirements. Information will be presented on candidate materials for such reentry approaches and on screening tests conducted (material property and space environmental effects tests) to evaluate viable candidates. Seventeen materials, in three classes (ablatives, tiles, and ceramic matrix composites), were studied. In additional to physical, mechanical, and thermal property tests, high heat flux laser tests and simulated-reentry oxidation tests were performed. Space environmental effects testing, which included exposures to electrons, atomic oxygen, and hypervelocity impacts, was also conducted.

  5. Experiments on a ceramic electrolysis cell and a palladium diffuser at the tritium systems test assembly

    International Nuclear Information System (INIS)

    Konishi, Satoshi; Yoshida, Hiroshi; Ohno, Hideo; Naruse, Yuji; Coffin, D.O.; Walthers, C.R.; Binning, K.E.

    1985-01-01

    A ceramic electrolysis cell and a palladium diffuser are developed in Japan and is tested with tritium in Tritium Systems Test Assembly (TSTA) of the Los Alamos National Laboratory, in order to confirm the feasibility as possible upgrades for the fuel cleanup system (PCU). The ceramic electrolysis cell made of stabilized zirconia was operated at 630 0 C for an extended period with a mixture of 3% T 2 O in He carrier gas in the circulation system with oxidizing catalyst bed. The palladium diffuser was tested with circulated pure tritium gas at 280 0 C to verify the compatibility of the alloy with tritium, since the 3 He produced in the metal could cause a degradation. The isotopic effects were also measured for both devices

  6. Ceramic Laser Materials

    Directory of Open Access Journals (Sweden)

    Guillermo Villalobos

    2012-02-01

    Full Text Available Ceramic laser materials have come a long way since the first demonstration of lasing in 1964. Improvements in powder synthesis and ceramic sintering as well as novel ideas have led to notable achievements. These include the first Nd:yttrium aluminum garnet (YAG ceramic laser in 1995, breaking the 1 KW mark in 2002 and then the remarkable demonstration of more than 100 KW output power from a YAG ceramic laser system in 2009. Additional developments have included highly doped microchip lasers, ultrashort pulse lasers, novel materials such as sesquioxides, fluoride ceramic lasers, selenide ceramic lasers in the 2 to 3 μm region, composite ceramic lasers for better thermal management, and single crystal lasers derived from polycrystalline ceramics. This paper highlights some of these notable achievements.

  7. Ceramic Laser Materials

    Science.gov (United States)

    Sanghera, Jasbinder; Kim, Woohong; Villalobos, Guillermo; Shaw, Brandon; Baker, Colin; Frantz, Jesse; Sadowski, Bryan; Aggarwal, Ishwar

    2012-01-01

    Ceramic laser materials have come a long way since the first demonstration of lasing in 1964. Improvements in powder synthesis and ceramic sintering as well as novel ideas have led to notable achievements. These include the first Nd:yttrium aluminum garnet (YAG) ceramic laser in 1995, breaking the 1 KW mark in 2002 and then the remarkable demonstration of more than 100 KW output power from a YAG ceramic laser system in 2009. Additional developments have included highly doped microchip lasers, ultrashort pulse lasers, novel materials such as sesquioxides, fluoride ceramic lasers, selenide ceramic lasers in the 2 to 3 μm region, composite ceramic lasers for better thermal management, and single crystal lasers derived from polycrystalline ceramics. This paper highlights some of these notable achievements. PMID:28817044

  8. Evaluation of Surface Treatment Methods on the Bond Strength of Zirconia Ceramics Systems, Resin Cements and Tooth Surface

    Directory of Open Access Journals (Sweden)

    Akkuş Emek

    2015-07-01

    Full Text Available Objectives: To compare the effects of airborne-particle abrasion (APA and tribochemical silica coating (TSC surface treatment methods on the shear bond strength of zirconia ceramics systems, resin cements and tooth surface

  9. Fracture toughness of esthetic dental coating systems by nanoindentation and FIB sectional analysis.

    Science.gov (United States)

    Pecnik, Christina Martina; Courty, Diana; Muff, Daniel; Spolenak, Ralph

    2015-07-01

    Improving the esthetics of Ti-based dental implants is the last challenge remaining in the optimization process. The optical issues were recently solved by the application of highly and selectively reflective coatings on Ti implants. This work focuses on the mechanical durability of these esthetic ceramic based coating systems (with and without adhesion layers). The coating systems (Ti-ZrO2, Ti-Al-ZrO2, Ti-Ti-Al-ZrO2, Ti-Ag-ZrO2, Ti-Ti-Ag-ZrO2, Ti-Bragg and Ti-TiO2-Bragg) were subjected to nanoindentation experiments and examined using scanning electron microscopy and focused ion beam cross sectional analysis. Three coating systems contained adhesion layers (10nm of Ti or 60nm of TiO2 layers). The fracture toughness of selected samples was assessed applying two different models from literature, a classical for bulk materials and an energy-based model, which was further developed and adjusted. The ZrO2 based coating systems (total film thickness<200nm) followed a circumferential cracking behavior in contrast to Bragg coated samples (total film thickness around 1.5μm), which showed radial cracking emanating from the indent corners. For Ti-ZrO2 samples, a fracture toughness between 2.70 and 3.70MPam(1/2) was calculated using an energy-based model. The classical model was applied to Bragg coated samples and their fracture toughness ranged between 0.70 and 0.80MPam(1/2). Furthermore, coating systems containing an additional layer (Ti-Ti-Al-ZrO2, Ti-Ti-Ag-ZrO2 and Ti-TiO2-Bragg) showed an improved adhesion between the substrate and the coating. The addition of a Ti or TiO2 layer improved the adhesion between substrate and coating. The validity of the models for the assessment of the fracture toughness depended on the layer structure and fracture profile of the samples investigated here (classical model for thick coatings and energy-based model for thin coatings). Copyright © 2015 Elsevier Ltd. All rights reserved.

  10. Development of physical and mathematical models for the Porous Ceramic Tube Plant Nutrification System (PCTPNS)

    Science.gov (United States)

    Tsao, D. Teh-Wei; Okos, M. R.; Sager, J. C.; Dreschel, T. W.

    1992-01-01

    A physical model of the Porous Ceramic Tube Plant Nutrification System (PCTPNS) was developed through microscopic observations of the tube surface under various operational conditions. In addition, a mathematical model of this system was developed which incorporated the effects of the applied suction pressure, surface tension, and gravitational forces as well as the porosity and physical dimensions of the tubes. The flow of liquid through the PCTPNS was thus characterized for non-biological situations. One of the key factors in the verification of these models is the accurate and rapid measurement of the 'wetness' or holding capacity of the ceramic tubes. This study evaluated a thermistor based moisture sensor device and recommendations for future research on alternative sensing devices are proposed. In addition, extensions of the physical and mathematical models to include the effects of plant physiology and growth are also discussed for future research.

  11. Marginal Integrity of Glass Ionomer and All Ceramic Restorations

    Science.gov (United States)

    2015-06-01

    North Carolina), scanned by the CEREC Omnicam , and milled by CEREC inLab MC XL system. 15 List of Procedures in Chronological Order 1. The...Fuji II LC, GC America, Alsip, Illinois). Forty lithium disilicate porcelain ceramic inlays will be milled from CEREC Block PC (Sirona, Charlotte...evolution of the CEREC system. Journal of the American Dental Association, 137, 7s-13s. Mount G.J. (1991). Adhesion of glass-ionomer cement in the clinical

  12. Comparison of three and four point bending evaluation of two adhesive bonding systems for glass-ceramic zirconia bi-layered ceramics.

    Science.gov (United States)

    Gee, C; Weddell, J N; Swain, M V

    2017-09-01

    To quantify the adhesion of two bonding approaches of zirconia to more aesthetic glass-ceramic materials using the Schwickerath (ISO 9693-2:2016) three point bend (3PB) [1] test to determine the fracture initiation strength and strain energy release rate associated with stable crack extension with this test and the Charalamabides et al. (1989) [2] four point bend (4PB) test. Two glass-ceramic materials (VITABLOCS Triluxe forte, Vita Zahnfabrik, Germany and IPS.emax CAD, Ivoclar Vivadent, Liechtenstein) were bonded to sintered zirconia (VITA InCeram YZ). The former was resin bonded using a dual-cure composite resin (Panavia F 2.0, Kuraray Medical Inc., Osaka, Japan) following etching and silane conditioning, while the IPS.emax CAD was glass bonded (IPS e.max CAD Crystall/Connect) during crystallization of the IPS.emax CAD. Specimens (30) of the appropriate dimensions were fabricated for the Schwickerath 3PB and 4PB tests. Strength values were determined from crack initiation while strain energy release rate values were determined from the minima in the force-displacement curves with the 3PB test (Schneider and Swain, 2015) [3] and for 4PB test from the plateau region of stable crack extension. Strength values for the resin and glass bonded glass ceramics to zirconia were 22.20±6.72MPa and 27.02±3.49MPa respectively. The strain energy release rates for the two methods used were very similar and for the glass bonding, (4PB) 15.14±5.06N/m (or J/m 2 ) and (3PB) 16.83±3.91N/m and resin bonding (4PB) 8.34±1.93N/m and (3PB) 8.44±2.81N/m respectively. The differences in strength and strain energy release rate for the two bonding approaches were statistically significant (pceramics to zirconia. Copyright © 2017 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  13. Upconversion studies of Er3+/Yb3+ doped SrO.TiO2 borosilicate glass ceramic system

    International Nuclear Information System (INIS)

    Maheshwari, Aditya; Om Prakash; Kumar, Devendra; Rai, S.B.

    2011-01-01

    Upconversion behaviour has been studied in various matrices and fine powders of SrTiO 3 by previous workers. In present work, Er 3+ /Yb 3+ were doped in appropriate ratio in SrO.TiO 2 borosilicate glass ceramic system to study the upconversion phenomenon. Dielectric properties of this class of glass ceramic system have been extensively investigated by Thakur et al. It has been observed that both upconversion efficiency and dielectric constant increases with transformation of glass into glass ceramic. Therefore, present investigation is based upon the study of optical as well as the electrical properties of same glass ceramic system. In order to prepare different crystalline matrices, two different Er 3+ /Yb 3+ :SrO.TiO 2 borosilicate glasses with same amount of Er 2 O 3 and Yb 2 O 3 were prepared by melt quench method. Glasses were transparent with light-wine colour. Glass ceramics were prepared from the glasses by heat treatment based on DTA (Differential thermal analysis) results. Glass ceramics were fully opaque with brownish-cream colour. Powder X-ray diffraction (XRD) patterns confirmed that two different crystalline matrices, Sr 3 Ti 2 O 7 , Ti 10 O 19 and SrTiO 3 , TiO 2 were present in two glass ceramic samples respectively. Luminescence properties of glass and glass ceramic samples with 976nm laser irradiation showed that the intensities of the green and red emission increased multiple times in glass ceramic than that of the glass. Possible mechanisms responsible for upconversion eg. Energy Transfer (ET) and Excited State Absorption (ESA), were studied through laser pumping power log dependence

  14. Effects of bleaching agents and adhesive systems in dental pulp: a literature review

    OpenAIRE

    Oliveira, Maria Antonieta Veloso Carvalho de; Quagliatto, Paulo Sérgio; Magalhães, Denildo; Biffi, João Carlos Gabrielli

    2012-01-01

    The dental pulp may be exposed to several irritants that are potentially noxious to the health and functions of this tissue. Each type of irritant or injury has different effects on the pulp, which are generally characterized by acute inflammation, chronic inflammation or necrosis. Common examples of irritants are dental caries, cavity preparation procedures, traumatic injuries, and chemical substances like bleaching agents and adhesive systems. The present study aimed to review the current k...

  15. Use of quality measurement across US dental delivery systems: a qualitative analysis.

    Science.gov (United States)

    Alrqiq, Hosam M; Edelstein, Burton L

    2016-03-01

    Dentistry is increasingly challenged by payers and the public to demonstrate quality measurement (QM) activities that substantiate value. Unknown is how various components of the US oral health-care financing and delivery systems have adopted QM. The objective of this study is to explore QM activities by US dental delivery, management, financing, and related organizations. Using a structured interview guide based on a novel conceptual framework that incorporates factors influencing QM intention, adoption, and implementation, 19 key informant interviews were conducted. Informants represented safety net delivery programs (health center, nonprofit mobile, hospital-based, Veterans Administration, and tribal dental programs), private delivery organizations (private practice, closed panel HMO, and for-profit mobile dental programs), training programs that deliver care (dental and dental therapy programs), management organizations (private and Medicaid group practice management companies), care financing organizations (Medicaid managed care plan, state Medicaid program, dental benefits companies), and dental quality organizations (institute and dental professional organization). Interviews were transcribed and analyzed qualitatively. Informants report wide variation in the intensity of QM efforts with organizational leadership cited as most influential. Motivation to adopt QM efforts is more often internal than imposed. Data management and information technology both facilitate and limit QM activities. QM activities are associated with operational improvements including use of guidelines and refinements of mission. Organizational type and size appear to influence QM programs. The current status of QM is highly variable across dental organizations because organizational leadership, needs, and requirements vary according to mission and structure. © 2015 American Association of Public Health Dentistry.

  16. Ballistic Performance of Porous Ceramic Thermal Protection Systems at 9 km/s

    Science.gov (United States)

    Miller, Joshua E.; Bohl, W. E.; Foreman, C. D.; Christiansen, Eric L.; Davis, B. A.

    2009-01-01

    Porous-ceramic, thermal-protection-systems are used heavily in current reentry vehicles like the Orbiter, and they are currently being proposed for the next generation of manned spacecraft, Orion. These materials insulate the structural components and sensitive electronic components of a spacecraft against the intense thermal environments of atmospheric reentry. Furthermore, these materials are also highly exposed to space environmental hazards like meteoroid and orbital debris impacts. This paper discusses recent impact testing up to 9 km/s on ceramic tiles similar to those used on the Orbiter. These tiles have a porous-batting of nominally 8 lb/cubic ft alumina-fiber-enhanced-thermal-barrier (AETB8) insulating material coated with a damage-resistant, toughened-unipiece-fibrous-insulation (TUFI) layer.

  17. Switching and energy-storage characteristics in PLZT 2/95/5 antiferroelectric ceramic system

    Directory of Open Access Journals (Sweden)

    A. Peláiz-Barranco

    2016-12-01

    Full Text Available Switching mechanisms and energy-storage properties have been investigated in (Pb0.98La0.02(Zr0.95Ti0.050.995O3 antiferroelectric ceramics. The electric field dependence of polarization (P–E hysteresis loops indicates that both the ferroelectric (FE and antiferroelectric (AFE phases coexist, being the AFE more stable above 100∘C. It has been observed that the temperature has an important influence on the switching parameters. On the other hand, the energy-storage density, which has been calculated from the P–E hysteresis loops, shows values higher than 1J/cm3 for temperatures above 100∘C with around 73% of efficiency as average. These properties indicate that the studied ceramic system reveals as a promising AFE material for energy-storage devices application.

  18. Thin film ceramic thermocouples

    Science.gov (United States)

    Gregory, Otto (Inventor); Fralick, Gustave (Inventor); Wrbanek, John (Inventor); You, Tao (Inventor)

    2011-01-01

    A thin film ceramic thermocouple (10) having two ceramic thermocouple (12, 14) that are in contact with each other in at least on point to form a junction, and wherein each element was prepared in a different oxygen/nitrogen/argon plasma. Since each element is prepared under different plasma conditions, they have different electrical conductivity and different charge carrier concentration. The thin film thermocouple (10) can be transparent. A versatile ceramic sensor system having an RTD heat flux sensor can be combined with a thermocouple and a strain sensor to yield a multifunctional ceramic sensor array. The transparent ceramic temperature sensor that could ultimately be used for calibration of optical sensors.

  19. Radio-opaque dental compositions

    International Nuclear Information System (INIS)

    Temin, S.C.

    1979-01-01

    Thorium oxide or tantalum oxide, or combinations thereof are used as the x-ray material for radio-opaque filler compositions having particular applicability in dental restorative compositions. The filler compositions contain from about 3% by weight to about 10% by weight, based on the total filler composition, of the x-ray absorbing materials and the remainder being conventional particulate glass or silica, quarts or ceramic filler material. The radio opaque filler compositions are insoluble and non-leachable in alkaline, acidic or neutral aqueous environments, are essentially non-toxic, are either essentially colorless or translucent, and are compatible with acrylic monomers and other polymerizable binder systems

  20. Integral ceramic superstructure evaluation using time domain optical coherence tomography

    Science.gov (United States)

    Sinescu, Cosmin; Bradu, Adrian; Topala, Florin I.; Negrutiu, Meda Lavinia; Duma, Virgil-Florin; Podoleanu, Adrian G.

    2014-02-01

    Optical Coherence Tomography (OCT) is a non-invasive low coherence interferometry technique that includes several technologies (and the corresponding devices and components), such as illumination and detection, interferometry, scanning, adaptive optics, microscopy and endoscopy. From its large area of applications, we consider in this paper a critical aspect in dentistry - to be investigated with a Time Domain (TD) OCT system. The clinical situation of an edentulous mandible is considered; it can be solved by inserting 2 to 6 implants. On these implants a mesostructure will be manufactured and on it a superstructure is needed. This superstructure can be integral ceramic; in this case materials defects could be trapped inside the ceramic layers and those defects could lead to fractures of the entire superstructure. In this paper we demonstrate that a TD-OCT imaging system has the potential to properly evaluate the presence of the defects inside the ceramic layers and those defects can be fixed before inserting the prosthesis inside the oral cavity. Three integral ceramic superstructures were developed by using a CAD/CAM technology. After the milling, the ceramic layers were applied on the core. All the three samples were evaluated by a TD-OCT system working at 1300 nm. For two of the superstructures evaluated, no defects were found in the most stressed areas. The third superstructure presented four ceramic defects in the mentioned areas. Because of those defects the superstructure may fracture. The integral ceramic prosthesis was send back to the dental laboratory to fix the problems related to the material defects found. Thus, TD-OCT proved to be a valuable method for diagnosing the ceramic defects inside the integral ceramic superstructures in order to prevent fractures at this level.

  1. Heat generation caused by ablation of dental hard tissues with an ultrashort pulse laser (USPL) system.

    Science.gov (United States)

    Braun, Andreas; Krillke, Raphael Franz; Frentzen, Matthias; Bourauel, Christoph; Stark, Helmut; Schelle, Florian

    2015-02-01

    Heat generation during the removal of dental hard tissues may lead to a temperature increase and cause painful sensations or damage dental tissues. The aim of this study was to assess heat generation in dental hard tissues following laser ablation using an ultrashort pulse laser (USPL) system. A total of 85 specimens of dental hard tissues were used, comprising 45 specimens of human dentine evaluating a thickness of 1, 2, and 3 mm (15 samples each) and 40 specimens of human enamel with a thickness of 1 and 2 mm (20 samples each). Ablation was performed with an Nd:YVO4 laser at 1,064 nm, a pulse duration of 9 ps, and a repetition rate of 500 kHz with an average output power of 6 W. Specimens were irradiated for 0.8 s. Employing a scanner system, rectangular cavities of 1-mm edge length were generated. A temperature sensor was placed at the back of the specimens, recording the temperature during the ablation process. All measurements were made employing a heat-conductive paste without any additional cooling or spray. Heat generation during laser ablation depended on the dental hard tissue (enamel or dentine) and the thickness of the respective tissue (p dental hard tissues, heat generation has to be considered. Especially during laser ablation next to pulpal tissues, painful sensations and potential thermal injury of pulp tissue might occur.

  2. Sol-gel synthesis and characterization of fine-grained ceramics in the alumina-titania system

    Energy Technology Data Exchange (ETDEWEB)

    Otterstein, E. [Institute of Physics, University of Rostock, August-Bebel-Strasse 55, 18055 Rostock (Germany)], E-mail: otterstein@physik1.uni-rostock.de; Karapetyan, G. [Institute of Chemistry, University of Rostock, Albert-Einstein-Strasse 3a, 18059 Rostock (Germany); Nicula, R. [Institute of Physics, University of Rostock, August-Bebel-Strasse 55, 18055 Rostock (Germany); Stir, M. [Institute of Physics, University of Rostock, August-Bebel-Strasse 55, 18055 Rostock (Germany); National Institute for Materials Physics, 105b Atomistilor Strasse, P.O.B. MG7, 077125 Bucharest-Magurele (Romania); Schick, C. [Institute of Physics, University of Rostock, Universitaetsplatz 3, 18051 Rostock (Germany); Burkel, E. [Institute of Physics, University of Rostock, August-Bebel-Strasse 55, 18055 Rostock (Germany)

    2008-02-05

    Fine-grained ceramics of the Al{sub 2}O{sub 3}-TiO{sub 2} system were synthesised by reactive sintering of sol-gel precursors (Al- and Ti-alkoxides). The thermal behaviour of the as-prepared xerogels was examined by thermal analysis and X-ray powder diffraction. Preliminary results concerning powder consolidation into bulk ceramic parts using spark plasma sintering (SPS) are discussed.

  3. FIB/SEM and SEM/EDS microstructural analysis of metal-ceramic and zirconia-ceramic interfaces.

    Science.gov (United States)

    Massimi, F; Merlati, G; Sebastiani, M; Battaini, P; Menghini, P; Bemporad, E

    2012-01-10

    Recently introduced FIB/SEM analysis in microscopy seems to provide a high-resolution characterization of the samples by 3D (FIB) cross-sectioning and (SEM) high resolution imaging. The aim of this study was to apply the FIB/SEM and SEM/EDS analysis to the interfaces of a metal-ceramic vs. two zirconia-ceramic systems. Plate samples of three different prosthetic systems were prepared in the dental lab following the manufacturers' instructions, where metal-ceramic was the result of a ceramic veneering (porcelain-fused-to-metal) and the two zirconia-ceramic systems were produced by the dedicated CAD-CAM procedures of the zirconia cores (both with final sintering) and then veneered by layered or heat pressed ceramics. In a FIB/SEM equipment (also called DualBeam), a thin layer of platinum (1 μm) was deposited on samples surface crossing the interfaces, in order to protect them during milling. Then, increasingly deeper trenches were milled by a focused ion beam, first using a relatively higher and later using a lower ion current (from 9 nA to 0.28 nA, 30KV). Finally, FEG-SEM (5KV) micrographs (1000-50,000X) were acquired. In a SEM the analysis of the morphology and internal microstructure was performed by 13KV secondary and backscattered electrons signals (in all the samples). The compositional maps were then performed by EDS probe only in the metal-ceramic system (20kV). Despite the presence of many voids in all the ceramic layers, it was possible to identify: (1) the grain structures of the metallic and zirconia substrates, (2) the thin oxide layer at the metal-ceramic interface and its interactions with the first ceramic layer (wash technique), (3) the roughness of the two different zirconia cores and their interactions with the ceramic interface, where the presence of zirconia grains in the ceramic layer was reported in two system possibly due to sandblasting before ceramic firing.

  4. CERCON- SMART CERAMICS, FROM THEORY TO PRACTICE

    Directory of Open Access Journals (Sweden)

    Daniela POPA

    2015-03-01

    Full Text Available Introduction of the CAD/CAM systems in dentistry has resulted in highly accurate and quality dentures, meeting the needs of both dental technician and dentist. The present study aims at illustrating the benefits and peculiarities of using CAD/CAM systems in current practice. To this aim, the case of a 29 year-old patient who wanted to have a 2.1 coverage crown replaced, being dissatisfied with its aesthetics, was considered. The fixed single tooth prosthesis was restored with the CAD/CAM CERCON (DeguDent - Smart Ceramics.

  5. Radiation effects in cubic zirconia: A model system for ceramic oxides

    Science.gov (United States)

    Thomé, L.; Moll, S.; Sattonnay, G.; Vincent, L.; Garrido, F.; Jagielski, J.

    2009-06-01

    Ceramics are key engineering materials for electronic, space and nuclear industry. Some of them are promising matrices for the immobilization and/or transmutation of radioactive waste. Cubic zirconia is a model system for the study of radiation effects in ceramic oxides. Ion beams are very efficient tools for the simulation of the radiations produced in nuclear reactors or in storage form. In this article, we summarize the work made by combining advanced techniques (RBS/C, XRD, TEM, AFM) to study the structural modifications produced in ion-irradiated cubic zirconia single crystals. Ions with energies in the MeV-GeV range allow exploring the nuclear collision and electronic excitation regimes. At low energy, where ballistic effects dominate, the damage exhibits a peak around the ion projected range; it accumulates with a double-step process by the formation of a dislocation network. At high energy, where electronic excitations are favored, the damage profiles are rather flat up to several micrometers; the damage accumulation is monotonous (one step) and occurs through the creation and overlap of ion tracks. These results may be generalized to many nuclear ceramics.

  6. Conditions for testing the corrosion rates of ceramics in coal gasification systems

    Energy Technology Data Exchange (ETDEWEB)

    Hurley, J.P.; Nowok, J.W. [Univ. of North Dakota, Grand Forks, ND (United States)

    1996-08-01

    Coal gasifier operating conditions and gas and ash compositions affect the corrosion rates of ceramics used for construction in three ways: (1) through direct corrosion of the materials, (2) by affecting the concentration and chemical form of the primary corrodents, and (3) by affecting the mass transport rate of the primary corrodents. To perform an accurate corrosion test on a system material, the researcher must include all relevant corrodents and simulate conditions in the gasifier as closely as possible. In this paper, the authors present suggestions for conditions to be used in such corrosion tests. Two main types of corrosion conditions are discussed: those existing in hot-gas cleanup systems where vapor and dry ash may contribute to corrosion and those experienced by high-temperature heat exchangers and refractories where the main corrodent will be coal ash slag. Only the fluidized-bed gasification systems such as the Sierra Pacific Power Company Pinon Pine Power Project system are proposing the use of ceramic filters for particulate cleanup. The gasifier is an air-blown 102-MWe unit employing a Westinghouse{trademark} ceramic particle filter system operating at as high as 1100{degrees}F at 300 psia. Expected gas compositions in the filter will be approximately 25% CO, 15% H{sub 2}, 5% CO{sub 2}, 5% H{sub 2}O, and 50% N{sub 2}. Vapor-phase sodium chloride concentrations are expected to be 10 to 100 times the levels in combustion systems at similar temperatures, but in general the concentrations of the minor primary and secondary corrodents are not well understood. Slag corrosiveness will depend on its composition as well as viscosity. For a laboratory test, the slag must be in a thermodynamically stable form before the beginning of the corrosion test to assure that no inappropriate reactions are allowed to occur. Ideally, the slag would be flowing, and the appropriate atmosphere must be used to assure realistic slag viscosity.

  7. Awareness of dental surgeons in Pune and Mumbai, India, regarding chemomechanical caries removal system.

    Science.gov (United States)

    Bijle, Mohammed Nadeem Ahmed; Patil, Shankargouda; Mumkekar, Shahzad S; Arora, Nitin; Bhalla, Monika; Murali, K V

    2013-01-01

    To evaluate awareness of dental surgeons in Pune and Mumbai, India regarding chemomechanical caries removal system (CMCR). Sixty practicing dental surgeons from Mumbai (30) and Pune (30) were surveyed using questionnaire. Qualitative data was collected on the basis of structured schedule questionnaire method. Statistical analysis was done using SPSS v. 12.0. To test statistical significance, Chi-square test, Fishers exact test and Mann-Whitney U test were used. Of total respondents, 46.7% dental surgeons in Pune and 13.3% in Mumbai were aware about CMCR products. Carisolv® was known to 57.1% of dental surgeons in Pune and 75% in Mumbai, whereas, Papacarie® was known to 28.6% of dentists in Pune and none in Mumbai among the respondents aware about CMCR products. A significantly higher proportion of dental surgeons from Pune were aware about CMCR products compared to Mumbai. Dental surgeons from Mumbai were unaware about Papacarie®. Almost equal proportion of Dentists from Mumbai and Pune would like to undergo CDE programs to seek knowledge on CMCR, particularly Papacarie®.

  8. [Research progress on a nanodrug delivery system for prevention and control of dental caries and periodontal diseases].

    Science.gov (United States)

    Yaling, Jiang; Mingye, Feng; Lei, Cheng

    2017-02-01

    Dental caries and periodontal diseases are common chronic infectious diseases that cause serious damage to oral health. Bacteria is the primary factor leading to such conditions. As a dental plaque control method, chemotherapeutic agents face serious challenges in dental care because of the specific physiological and anatomical characteristics of the oral cavity. Nanodrug delivery system is a series of new drug delivery systems at nanoscale, and it can target cells, promote sustainedrelease effects, and enhance biodegradation. This review focuses on research progress on nanodrug delivery systems for prevention and control of dental caries and periodontal diseases.

  9. Portfolio: Ceramics.

    Science.gov (United States)

    Hardy, Jane; And Others

    1982-01-01

    Describes eight art activities using ceramics. Elementary students created ceramic tiles to depict ancient Egyptian and medieval European art, made ceramic cookie stamps, traced bisque plates on sketch paper, constructed clay room-tableaus, and designed clay relief masks. Secondary students pit-fired ceramic pots and designed ceramic Victorian…

  10. Frequency of dental caries in active and inactive systemic lupus erythematous patients: salivary and bacterial factors.

    Science.gov (United States)

    Loyola Rodriguez, J P; Galvan Torres, L J; Martinez Martinez, R E; Abud Mendoza, C; Medina Solis, C E; Ramos Coronel, S; Garcia Cortes, J O; Domínguez Pérez, R A

    2016-10-01

    The objective of this study was to determine dental caries frequency and to analyze salivary and bacterial factors associated with active and inactive systemic lupus erythematous (SLE) patients. Also, a proposal to identify dental caries by a surface, teeth, and the patient was developed. A cross-sectional, blinded study that included 60 SLE patients divided into two groups of 30 subjects each, according to the Activity Index for Diagnosis of Systemic Lupus Erythematous (SLEDAI). The decayed, missing, and filled teeth (DMFT) index and Integrative Dental Caries Index (IDCI) were used for analyzing dental caries. The saliva variables recorded were: flow, pH, and buffer capacity. The DNA copies of Streptococcus mutans and Streptococcus sobrinus were estimated by real-time PCR. The caries frequency was 85% for SLE subjects (73.3% for inactive systemic lupus erythematous (ISLE) and 100% for active systemic lupus erythematous (ASLE)); DMFT for the SLE group was 12.6 ± 5.7 and the IDCI was (9.8 ± 5.9). The ASLE group showed a salivary flow of 0.65 compared with 0.97 ml/1 min from the ISLE group; all variables mentioned above showed a statistical difference (p dental caries in epidemiological studies. © The Author(s) 2016.

  11. 885-nm laser diode array pumped ceramic Nd:YAG master oscillator power amplifier system

    Science.gov (United States)

    Yu, Anthony W.; Li, Steven X.; Stephen, Mark A.; Seas, Antonios; Troupaki, Elisavet; Vasilyev, Aleksey; Conley, Heather; Filemyr, Tim; Kirchner, Cynthia; Rosanova, Alberto

    2010-04-01

    The objective of this effort is to develop more reliable, higher efficiency diode pumped Nd:YAG laser systems for space applications by leveraging technology investments from the DoD and other commercial industries. Our goal is to design, build, test and demonstrate the effectiveness of combining 885 nm laser pump diodes and the use of ceramic Nd:YAG for future flight missions. The significant reduction in thermal loading on the gain medium by the use of 885 nm pump lasers will improve system efficiency.

  12. The art of the technology: construction of structures by domed ceramic with industrial systems

    Directory of Open Access Journals (Sweden)

    J. Trias de Bes

    2016-12-01

    Full Text Available The reconciliation between traditional construction and new technologies encourage the development of a new catalonian vaulted through prefabrication technology of reinforced concrete in which it is incorporated in the construction process a ceramic fabric. The example of a prototype house with this system is shown. The article presents two fundamental considerations: a Expose the influence of the imagery of traditional techniques as motivation and activation of technological construction processes, and b confront System Vs. Skill as a constructive belonging to the Technical and Technology, respectively. In this sense, the article concludes by highlighting that humanism is involved between both as a determinant factor in the architectural design process.

  13. Evaluation of the field size in dental diagnostic radiology system

    International Nuclear Information System (INIS)

    Andrade, P.S.; Potiens, M.P.A.

    2006-01-01

    In this work the field size of a dental X rays machine was evaluated considering the recommendation of the Brazilian Health Ministry Regulation 453 which established basic lines of radiological protection in medical and dental diagnostic radiology. The diameter of the field should not be superior to 6 cm in the localized end point, limiting the radiated area and protecting the head-neck region. The measurements were carried out in a dental X rays machine, Dabi Atlante, model Spectro 70X Seletronic. For the field size or useful beam determination, the intra-oral films were positioned on a plain surface to be exposed in four stages and two focus-film distances (FFD), 20 cm and 27.5 cm: 1) with spacer cone; 2) without spacer cone; 3) with spacer cone and film-holding device; 4) without spacer cone and film-holding device. The results show that the diameter of the field size is satisfactory only for FFD = 20 cm. When the film-holding device is used, which is recommended by the Regulation 453, item 5.8 d(ii), the diameter of the field size exceeds the maximum recommended value of 6 cm. (authors)

  14. Effect of Dental Restorative Material Type and Shade on Characteristics of Two-Layer Dental Composite Systems

    Directory of Open Access Journals (Sweden)

    Atefeh Karimzadeh

    Full Text Available Abstract The purpose of this study was to investigate the effects of shade and material type and shape in dental polymer composites on the hardness and shrinkage stress of bulk and two-layered restoration systems. For this purpose, some bulk and layered specimens from three different shades of dental materials were prepared and light-cured. The experiments were carried out on three types of materials: conventional restorative composite, nanohybrid composite and nanocomposite. Micro-indentation experiment was performed on the bulk and also on each layer of layered restoration specimens using a Vicker's indenter. The interface between the two layers was studied by scanning electron microscopy (SEM. The results revealed significant differences between the values of hardness for different shades in the conventional composite and also in the nanohybrid composite. However, no statistically significant difference was observed between the hardness values for different shades in the nanocomposite samples. The layered restoration specimens of different restorative materials exhibited lower hardness values with respect to their bulk specimens. The reduction in the hardness value of the layered conventional composite samples was higher than those of the nanocomposite and nanohybrid composite specimens indicating more shrinkage stresses generated in the conventional composite restorations. According to the SEM images, a gap was observed between the two layers in the layered restorations.

  15. Ceramic Seal.

    Energy Technology Data Exchange (ETDEWEB)

    Smartt, Heidi A. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Romero, Juan A. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Custer, Joyce Olsen [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Hymel, Ross W. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Krementz, Dan [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Gobin, Derek [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Harpring, Larry [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Martinez-Rodriguez, Michael [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Varble, Don [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); DiMaio, Jeff [Tetramer Technologies, Pendleton, SC (United States); Hudson, Stephen [Tetramer Technologies, Pendleton, SC (United States)

    2016-11-01

    Containment/Surveillance (C/S) measures are critical to any verification regime in order to maintain Continuity of Knowledge (CoK). The Ceramic Seal project is research into the next generation technologies to advance C/S, in particular improving security and efficiency. The Ceramic Seal is a small form factor loop seal with improved tamper-indication including a frangible seal body, tamper planes, external coatings, and electronic monitoring of the seal body integrity. It improves efficiency through a self-securing wire and in-situ verification with a handheld reader. Sandia National Laboratories (SNL) and Savannah River National Laboratory (SRNL), under sponsorship from the U.S. National Nuclear Security Administration (NNSA) Office of Defense Nuclear Nonproliferation Research and Development (DNN R&D), have previously designed and have now fabricated and tested Ceramic Seals. Tests have occurred at both SNL and SRNL, with different types of tests occurring at each facility. This interim report will describe the Ceramic Seal prototype, the design and development of a handheld standalone reader and an interface to a data acquisition system, fabrication of the seals, and results of initial testing.

  16. Ceramic Seal

    International Nuclear Information System (INIS)

    Smartt, Heidi A.; Romero, Juan A.; Custer, Joyce Olsen; Hymel, Ross W.; Krementz, Dan; Gobin, Derek; Harpring, Larry; Martinez-Rodriguez, Michael; Varble, Don; DiMaio, Jeff; Hudson, Stephen

    2016-01-01

    Containment/Surveillance (C/S) measures are critical to any verification regime in order to maintain Continuity of Knowledge (CoK). The Ceramic Seal project is research into the next generation technologies to advance C/S, in particular improving security and efficiency. The Ceramic Seal is a small form factor loop seal with improved tamper-indication including a frangible seal body, tamper planes, external coatings, and electronic monitoring of the seal body integrity. It improves efficiency through a self-securing wire and in-situ verification with a handheld reader. Sandia National Laboratories (SNL) and Savannah River National Laboratory (SRNL), under sponsorship from the U.S. National Nuclear Security Administration (NNSA) Office of Defense Nuclear Nonproliferation Research and Development (DNN R&D), have previously designed and have now fabricated and tested Ceramic Seals. Tests have occurred at both SNL and SRNL, with different types of tests occurring at each facility. This interim report will describe the Ceramic Seal prototype, the design and development of a handheld standalone reader and an interface to a data acquisition system, fabrication of the seals, and results of initial testing.

  17. Process engineering of ceramic composite coatings for fuel cell systems

    Energy Technology Data Exchange (ETDEWEB)

    Li, G.; Kim, H.; Chen, M.; Yang, Q.; Troczynski, T. [British Columbia Univ., Vancouver, BC (Canada). Dept. of Metals and Materials Engineering

    2003-07-01

    Researchers at UBCeram at the Department of Metals and Materials Engineering at the University of British Columbia have developed a technology to chemically bond composite sol-gel (CB-CSG) coating onto metallic surfaces of complex or concave shapes. The process has been optimized for electrically resistive coatings and corrosion-resistant coatings. The CSG is sprayed onto metallic surfaces and is heat-treated at 300 degrees C to partially dehydrate the hydroxides. The CSG film is then chemically bonded through reaction of active alumina with metal phosphates, such as aluminium phosphate. A new chromate-free process is being developed to address the issue of coatings porosity. The electrodeposition technique involves polymer particles mixed with suspended fine alumina particles which are co-deposited by electrophoretic means or by electrocoagulation. The composite e-coatings have excellent mechanical properties and are being considered as a protective coating for various components of fuel cell systems. 9 refs., 7 figs.

  18. A portable high-power diode laser-based single-stage ceramic tile grout sealing system

    Science.gov (United States)

    Lawrence, J.; Schmidt, M. J. J.; Li, L.; Edwards, R. E.; Gale, A. W.

    2002-02-01

    By means of a 60 W high-power diode laser (HPDL) and a specially developed grout material the void between adjoining ceramic tiles has been successfully sealed. A single-stage process has been developed which uses a crushed ceramic tile mix to act as a tough, inexpensive bulk substrate and a glazed enamel surface to provide an impervious surface glaze. The single-stage ceramic tile grout sealing process yielded seals produced in normal atmospheric conditions that displayed no discernible cracks and porosities. The single-stage grout is simple to formulate and easy to apply. Tiles were successfully sealed with power densities as low as 200 kW/ mm2 and at rates of up to 600 mm/ min. Bonding of the enamel to the crushed ceramic tile mix was identified as being primarily due to van der Waals forces and, on a very small scale, some of the crushed ceramic tile mix material dissolving into the glaze. In terms of mechanical, physical and chemical characteristics, the single-stage ceramic tile grout was found to be far superior to the conventional epoxy tile grout and, in many instances, matched and occasionally surpassed that of the ceramic tiles themselves. What is more, the development of a hand-held HPDL beam delivery unit and the related procedures necessary to lead to the commercialisation of the single-stage ceramic tile grout sealing process are presented. Further, an appraisal of the potential hazards associated with the use of the HPDL in an industrial environment and the solutions implemented to ensure that the system complies with the relevant safety standards are given.

  19. Making ceramics used for compound environment into multi-composite and evaluation of their multi-dimensional system

    International Nuclear Information System (INIS)

    Mitsuhashi, Takefumi

    1996-01-01

    In order to advance current nuclear power technology greatly, the development of the boundary materials suitable to between the environments with largely different properties is indispensable. In the research of first period, the ceramic having the corrosion resistance in liquid sodium which is far superior to metals was found. As boundary material, in addition, thermal, mechanical and radiation resistant properties are required. In the project of second period, it is aimed at to establish the basic technology for the synthesis techniques for multi-composite materials that possess the combination of the excellent characteristics of individual monolithic system ceramics. The liquid sodium immersion test of various ceramics in the research of first period is reported. The diffusion of sodium in ceramics was also examined. As the simplified quick evaluation technique, the corrosion test in KOH solution was carried out. As for ceramic multi-composites, Y ions were implanted in the surface of alumina, and the changes of structure and corrosion resistance were examined. The surface condition of ceramics and the adsorption of alkali metals were investigated. (K.I.)

  20. Effects of surface-finishing protocols on the roughness, color change, and translucency of different ceramic systems.

    Science.gov (United States)

    Akar, Gülcan Coşkun; Pekkan, Gürel; Çal, Ebru; Eskitaşçıoğlu, Gürcan; Özcan, Mutlu

    2014-08-01

    Surface-finishing protocols have a mechanical impact on ceramic surfaces that could eventually affect surface topography and light scattering. An optimum protocol is needed to avoid damaging the optical properties of ceramics. The purpose of this study was to determine the effects of different surface-finishing protocols on the surface roughness, color change, and translucency of ceramic and metal ceramic restorations. Standardized disk-shaped specimens (1.5 × 10 mm, n=128) were fabricated from 3 different ceramic core materials (aluminum oxide [Al2O3]-AL, zirconium oxide [ZrO2]-ZR, lithium disilicate [Li2Si2O5]-LIT), veneered (V) with dentin ceramics (n=32 per group), and placed in the following groups: ALV, ZRV, and LITV. The metal ceramic group acted as the control (n=32). Four different surface-finishing methods were tested. Airborne-particle abrasion with 50 μm Al2O3, polishing with adjustment kit, polishing with adjustment kit plus diamond polishing paste, and autoglazing (n=8 subgroup) were applied on the veneering ceramics. The specimens were analyzed with a profilometer for surface roughness, and color change and translucency were measured with a clinical spectrophotometer. Statistical analyses were performed with 1-way ANOVA and the Tukey honest significant difference tests (α=.05). Specimens treated with the airborne particle abrasion method showed significantly higher mean profilometer for surface roughness values in all groups (P.05). With the diamond polishing paste method, lower surface roughness values were achieved in the ZRV and metal ceramic groups acted as the control groups. Different surface-finishing methods affected the color change of the ceramic systems, except for ZRV. Surface-finishing protocols significantly affected the translucency values of the ALV, LITV, and metal ceramic groups (Pceramics tested. The airborne-particle abrasion protocol created rougher surfaces and decreased translucency, and color change in zirconia was not

  1. Systemic assessment of patients undergoing dental implant surgeries: A trans- and post-operative analysis

    Directory of Open Access Journals (Sweden)

    Sanjay Byakodi

    2017-01-01

    Full Text Available Background: Procedure-related and patient-related factors influence the prognosis of dental implants to a major extent. Hence, we aimed to evaluate and analyze various systemic factors in patients receiving dental implants. Materials and Methods: Fifty-one patients were included in the study, in which a total of 110 dental implants were placed. Complete examination of the subjects was done before and after placement of dental implants. Implant surgery was planned, and osseointegrated dental implants were placed in the subjects. Postoperative evaluation of the dental implant patients was done after 3 weeks. Anxiety levels were determined using State-Trait Anxiety Inventory (STAI questionnaire on the surgery day and after 1 week of surgery. The participant describes how they feel at the moment by responding to twenty items as follows: (1 absolutely not, (2 slightly, (3 somewhat, or (4 very much. All the results were recorded and statistical analyzed by SPSS software. Results: Out of 51, 29 patients were males while 22 were females, with ratio of 1.32:1. Female patients' mean age was 50.18 years while male patients' mean age was 52.71 years, with statistically nonsignificant difference between them. Functional rehabilitation was the main purpose of choosing dental implants in more than 90% of the subjects. Diameter of 3.75 mm was the shortest implants to be placed in the present study, whereas in terms of length, 8.5 mm was the shortest length of dental implant used in the present study. Tooth area in which maximum implants were placed in our study was 36 tooth region. Maximum implants were placed in Type II bone quality (n = 38. Implants installed in the mandible were clamped more efficiently than implants placed in the maxilla (P < 0.001. The difference of average STAI-State subscore before and after the surgery was statistically significant (P < 0.05; significant. Conclusion: Mandibular dental implants show more clamping (torque than maxillary

  2. Integrated nitrogen removal biofilter system with ceramic membrane for advanced post-treatment of municipal wastewater.

    Science.gov (United States)

    Son, Dong-Jin; Yun, Chan-Young; Kim, Woo-Yeol; Zhang, Xing-Ya; Kim, Dae-Gun; Chang, Duk; Sunwoo, Young; Hong, Ki-Ho

    2016-12-01

    The pre-denitrification biofilm process for nitrogen removal was combined with ceramic membrane with pore sizes of 0.05-0.1 µm as a system for advanced post-treatment of municipal wastewater. The system was operated under an empty bed hydraulic retention time of 7.8 h, recirculation ratio of 3, and transmembrane pressure of 0.47 bar. The system showed average removals of organics, total nitrogen, and solids as high as 93%, 80%, and 100%, respectively. Rapid nitrification could be achieved and denitrification was performed in the anoxic filter without external carbon supplements. The residual particulate organics and nitrogen in effluent from biofilm process could be also removed successfully through membrane filtration and the removal of total coliform was noticeably improved after membrane filtration. Thus, a system composed of the pre-denitrification biofilm process with ceramic membrane would be a compact and flexible option for advanced post-treatment of municipal wastewater.

  3. Dental erosion in groups of Yemeni children and adolescents and the modification of an erosion partial recording system

    OpenAIRE

    Al-Ashtal, Amin Mohsen Saleh; Johansson, Anders; Ridwaan, Omar; Johansson, Ann-Katrin

    2016-01-01

    Background: Dental erosion is a multifactorial oral health problem with an increasing prevalence among children and adolescents in many countries. Awareness of the condition among lay people is generally lacking, and methods for its clinical grading also need further improvements. Aim: The aims of this thesis was to investigate various aspects of dental erosion including prevalence and risk indicators, to evaluate the recording system used, and to assess the awareness of dental erosion in ...

  4. Basic research in crystalline and noncrystalline ceramic systems. Annual report, August 1, 1980-October 31, 1981

    International Nuclear Information System (INIS)

    1981-01-01

    The Basic Research Programs in Ceramics sponsored by the US Department of Energy supports a significant fraction of the research effort and graduate student training in ceramics at MIT. Various research activities involving ceramic materials include electrical properties; kinetic studies; defect structures, defect interactions, grain boundaries and surfaces; sintering studies; and mechanical properties

  5. Transition duct system with arcuate ceramic liner for delivering hot-temperature gases in a combustion turbine engine

    Energy Technology Data Exchange (ETDEWEB)

    Wiebe, David J.

    2017-11-07

    A transition duct system (10) for delivering hot-temperature gases from a plurality of combustors in a combustion turbine engine is provided. The system includes an exit piece (16) for each combustor. The exit piece may include an arcuate connecting segment (36). An arcuate ceramic liner (60) may be inwardly disposed onto a metal outer shell (38) along the arcuate connecting segment of the exit piece. Structural arrangements are provided to securely attach the ceramic liner in the presence of substantial flow path pressurization. Cost-effective serviceability of the transition duct systems is realizable since the liner can be readily removed and replaced as needed.

  6. [Evaluation of dental plaque by quantitative digital image analysis system].

    Science.gov (United States)

    Huang, Z; Luan, Q X

    2016-04-18

    To analyze the plaque staining image by using image analysis software, to verify the maneuverability, practicability and repeatability of this technique, and to evaluate the influence of different plaque stains. In the study, 30 volunteers were enrolled from the new dental students of Peking University Health Science Center in accordance with the inclusion criteria. The digital images of the anterior teeth were acquired after plaque stained according to filming standardization.The image analysis was performed using Image Pro Plus 7.0, and the Quigley-Hein plaque indexes of the anterior teeth were evaluated. The plaque stain area percentage and the corresponding dental plaque index were highly correlated,and the Spearman correlation coefficient was 0.776 (Pchart showed only a few spots outside the 95% consistency boundaries. The different plaque stains image analysis results showed that the difference of the tooth area measurements was not significant, while the difference of the plaque area measurements significant (P<0.01). This method is easy in operation and control,highly related to the calculated percentage of plaque area and traditional plaque index, and has good reproducibility.The different plaque staining method has little effect on image segmentation results.The sensitive plaque stain for image analysis is suggested.

  7. [Ceramic inlays and onlays].

    Science.gov (United States)

    van Pelt, A W; de Kloet, H J; van der Kuy, P

    1996-11-01

    Large direct composite restorations can induce shrinkage related postoperative sensitivity. Indirect resin-bonded (tooth colored) restorations may perhaps prevent these complaints. Indirect bonded ceramics are especially attractive because of their biocompatibility and esthetic performance. Several procedures and techniques are currently available for the fabrication of ceramic restorations: firing, casting, heat-pressing and milling. In this article the different systems are described. Advantages, disadvantages and clinical performance of ceramic inlays are compared and discussed.

  8. Industrial ceramics

    International Nuclear Information System (INIS)

    Mengelle, Ch.

    1999-04-01

    After having given the definition of the term 'ceramics', the author describes the different manufacturing processes of these compounds. These materials are particularly used in the fields of 1)petroleum industry (in primary and secondary reforming units, in carbon black reactors and ethylene furnaces). 2)nuclear industry (for instance UO 2 and PuO 2 as fuels; SiC for encapsulation; boron carbides for control systems..)

  9. CLINICAL CONSIDERATIONS OF DENTAL IMPLANT SYSTEM IN IMMEDIATE LOADING IMPLANT CASES

    Directory of Open Access Journals (Sweden)

    Carolina Damayanti Marpaung

    2015-06-01

    Full Text Available Immediate loading of dental implant has been researched intensively in the development of Branemark’s early concept of 2 stages implant placement. This was embarked from both patients and practiitioner’s convenience towards a simpler protocol and shorter time frame. Many recent researchers later found that micromotions derived from occlusal loading for a certain degree, instead of resulting a fibrous tissue encapsulation, can enhance the osseointegration process. Dental Implant system enhancement towards maximizing the primary stability held a key factor in Branemark’s concept development. Surgical protocol and implant design was found to give a significant contribution to the prognosis of immediate-loading implants.

  10. Development of a mobile device optimized cross platform-compatible oral pathology and radiology spaced repetition system for dental education.

    Science.gov (United States)

    Al-Rawi, Wisam; Easterling, Lauren; Edwards, Paul C

    2015-04-01

    Combining active recall testing with spaced repetition increases memory retention. The aim of this study was to evaluate and compare students' perception and utilization of an electronic spaced repetition oral pathology-radiology system in dental hygiene education and predoctoral dental education. The study employed an open-source suite of applications to create electronic "flashcards" that can be individually adjusted for frequency of repetition, depending on a user's assessment of difficulty. Accessible across multiple platforms (iOS, Android, Linux, OSX, Windows) as well as via any web-based browser, this framework was used to develop an oral radiology-oral pathology database of case-based questions. This system was introduced in two courses: sophomore oral pathology for dental students and sophomore radiology for dental hygiene students. Students were provided free software and/or mobile tablet devices as well as a database of 300 electronic question cards. Study participants were surveyed on frequency and extent of use. Perception-based surveys were used to evaluate their attitudes towards this technology. Of the eligible students, 12 of 22 (54.5%) dental hygiene and 49 of 107 (45.8%) dental students responded to the surveys. Adoption rates and student feedback were compared between the two groups. Among the respondents, acceptance of this technology with respect to educational usefulness was similar for the dental and dental hygiene students (median=5 on a five-point scale; dental hygiene interquartile range (IQR)=0; dental IQR=1). Only a minority of the survey respondents (25% dental, 33% dental hygiene) took advantage of one of the main benefits of this technology: automated spaced repetition.

  11. Federal Aviation Administration (FAA airworthiness certification for ceramic matrix composite components in civil aircraft systems

    Directory of Open Access Journals (Sweden)

    Gonczy Stephen T.

    2015-01-01

    Full Text Available Ceramic matrix composites (CMCs are being designed and developed for engine and exhaust components in commercial aviation, because they offer higher temperature capabilities, weight savings, and improved durability compared to metals. The United States Federal Aviation Administration (FAA issues and enforces regulations and minimum standards covering the safe manufacture, operation, and maintenance of civil aircraft. As new materials, these ceramic composite components will have to meet the certification regulations of the FAA for “airworthiness”. The FAA certification process is defined in the Federal Aviation Regulations (Title 14 of the Code of Federal Regulations, FAA policy statements, orders, advisory circulars, technical standard orders, and FAA airworthiness directives. These regulations and documents provide the fundamental requirements and guidelines for design, testing, manufacture, quality assurance, registration, operation, inspection, maintenance, and repair of aircraft systems and parts. For metallic parts in aircraft, the FAA certification and compliance process is well-established for type and airworthiness certification, using ASTM and SAE standards, the MMPDS data handbook, and FAA advisory circulars. In a similar manner for polymer matrix composites (PMC, the PMC industry and the FAA have jointly developed and are refining parallel guidelines for polymer matrix composites (PMCs, using guidance in FAA circulars and the CMH-17 PMC handbook. These documents discuss design methods and codes, material testing, property data development, life/durability assessment, production processes, QA procedures, inspection methods, operational limits, and repairs for PMCs. For ceramic composites, the FAA and the CMC and aerospace community are working together (primarily through the CMH-17 CMC handbook to define and codify key design, production, and regulatory issues that have to be addressed in the certification of CMC components in

  12. Medical devices; exemption from premarket notification; Class II devices; optical impression systems for computer assisted design and manufacturing. Final rule.

    Science.gov (United States)

    2003-04-22

    The Food and Drug Administration (FDA) is publishing an order granting a petition requesting exemption from the premarket notification requirements for data acquisition units for ceramic dental restoration systems. This rule exempts from premarket notification data acquisition units for ceramic dental restoration systems and establishes a guidance document as a special control for this device. FDA is publishing this order in accordance with the Food and Drug Administration Modernization Act of 1997 (FDAMA).

  13. Performance of Hybrid Photocatalytic-Ceramic Membrane System for the Treatment of Secondary Effluent.

    Science.gov (United States)

    Song, Lili; Zhu, Bo; Gray, Stephen; Duke, Mikel; Muthukumaran, Shobha

    2017-03-28

    Evaluation of an advanced wastewater treatment system that combines photocatalysis with ceramic membrane filtration for the treatment of secondary effluent was undertaken. The results showed that, after photocatalysis and ceramic membrane filtration, the removal of dissolved organic carbon and UV 254 was 60% and 54%, respectively, at a concentration of 4 g/L of TiO₂. Dissolved organic matter (DOM) present in the secondary effluent was characterised with a liquid chromatography-organic carbon detector (LC-OCD) technique. The results showed low removal of humics, building blocks, the other oxidation by-products and no removal of biopolymers after TiO₂/UV photocatalytic treatment. This suggested that the radical non-selective oxidation mechanisms of TiO₂/UV process resulted in secondary effluent in which all of the DOM fractions were present. However, the hybrid system was effective for removing biopolymers with the exception of low molecular weight (LMW) compounds acids, which accumulated from the beginning of the reaction. In addition, monitoring of the DOM fractions with LC-OCD analysis demonstrated that the reduction of the effluent aromaticity was not firmly correlated with the removal of humic substances for the combined processes.

  14. The development of a learning management system for dental radiology education: A technical report.

    Science.gov (United States)

    Chang, Hee-Jin; Symkhampha, Khanthaly; Huh, Kyung-Hoe; Yi, Won-Jin; Heo, Min-Suk; Lee, Sam-Sun; Choi, Soon-Chul

    2017-03-01

    This study was conducted to suggest the development of a learning management system for dental radiology education using the Modular Object-Oriented Dynamic Learning Environment (Moodle). Moodle is a well-known and verified open-source software-learning management system (OSS-LMS). The Moodle software was installed on a server computer and customized for dental radiology education. The system was implemented for teaching undergraduate students to diagnose dental caries in panoramic images. Questions were chosen that could assess students' diagnosis ability. Students were given several questions corre-sponding to each of 100 panoramic images. The installation and customization of Moodle was feasible, cost-effective, and time-saving. By having students answer questions repeatedly, it was possible to train them to examine panoramic images sequentially and thoroughly. Based on its educational efficiency and efficacy, the adaptation of an OSS-LMS in dental school may be highly recommended. The system could be extended to continuing education for dentists. Further studies on the objective evaluation of knowledge acquisition and retention are needed.

  15. The development of a learning management system for dental radiology education: A technical report

    International Nuclear Information System (INIS)

    Chang, Hee Jin; Huh, Kyung Hoe; Yi, Won Jin; Heo, Min Suk; Lee, Sam Sun; Choi, Soon Chul; Symkhampha, Khanthaly

    2017-01-01

    This study was conducted to suggest the development of a learning management system for dental radiology education using the Modular Object-Oriented Dynamic Learning Environment (Moodle). Moodle is a well-known and verified open-source software-learning management system (OSS-LMS). The Moodle software was installed on a server computer and customized for dental radiology education. The system was implemented for teaching undergraduate students to diagnose dental caries in panoramic images. Questions were chosen that could assess students' diagnosis ability. Students were given several questions corresponding to each of 100 panoramic images. The installation and customization of Moodle was feasible, cost-effective, and time-saving. By having students answer questions repeatedly, it was possible to train them to examine panoramic images sequentially and thoroughly. Based on its educational efficiency and efficacy, the adaptation of an OSS-LMS in dental school may be highly recommended. The system could be extended to continuing education for dentists. Further studies on the objective evaluation of knowledge acquisition and retention are needed

  16. The development of a learning management system for dental radiology education: A technical report

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Hee Jin; Huh, Kyung Hoe; Yi, Won Jin; Heo, Min Suk; Lee, Sam Sun; Choi, Soon Chul [Dept. of Oral and Maxillofacial Radiology and Dental Research Institute, School of Dentistry, Seoul National University, Seoul (Korea, Republic of); Symkhampha, Khanthaly [Div. of Oral and Maxillofacial Radiology, Dept. of Basic Science, Faculty of Dentistry, University of Health Sciences, Vientiane (Lao People' s Democratic Republic)

    2017-03-15

    This study was conducted to suggest the development of a learning management system for dental radiology education using the Modular Object-Oriented Dynamic Learning Environment (Moodle). Moodle is a well-known and verified open-source software-learning management system (OSS-LMS). The Moodle software was installed on a server computer and customized for dental radiology education. The system was implemented for teaching undergraduate students to diagnose dental caries in panoramic images. Questions were chosen that could assess students' diagnosis ability. Students were given several questions corresponding to each of 100 panoramic images. The installation and customization of Moodle was feasible, cost-effective, and time-saving. By having students answer questions repeatedly, it was possible to train them to examine panoramic images sequentially and thoroughly. Based on its educational efficiency and efficacy, the adaptation of an OSS-LMS in dental school may be highly recommended. The system could be extended to continuing education for dentists. Further studies on the objective evaluation of knowledge acquisition and retention are needed.

  17. Mechanical performance of a biocompatible biocide soda-lime glass-ceramic.

    Science.gov (United States)

    López-Esteban, S; Bartolomé, J F; Dí Az, L A; Esteban-Tejeda, L; Prado, C; López-Piriz, R; Torrecillas, R; Moya, J S

    2014-06-01

    A biocompatible soda-lime glass-ceramic in the SiO2-Na2O-Al2O3-CaO-B2O3 system containing combeite and nepheline as crystalline phases, has been obtained at 750°C by two different routes: (i) pressureless sintering and (ii) Spark Plasma Sintering. The SPS glass-ceramic showed a bending strength, Weibull modulus, and toughness similar values to the cortical human bone. This material had a fatigue limit slightly superior to cortical bone and at least two times higher than commercial dental glass-ceramics and dentine. The in vitro studies indicate that soda-lime glass-ceramic is fully biocompatible. The in vivo studies in beagle jaws showed that implanted SPS rods presented no inflammatory changes in soft tissues surrounding implants in any of the 10 different cases after four months implantation. The radiological analysis indicates no signs of osseointegration lack around implants. Moreover, the biocide activity of SPS glass-ceramic versus Escherichia coli, was found to be >4log indicating that it prevents implant infections. Because of this, the SPS new glass-ceramic is particularly promising for dental applications (inlay, crowns, etc). Copyright © 2014 Elsevier Ltd. All rights reserved.

  18. THE USE OF POROUS CERAMICS FOR EVAPORATIVE AND EVAPORATIVE – VAPOR –COMPRESSION SYSTEMS

    Directory of Open Access Journals (Sweden)

    Cheban D.N.

    2013-04-01

    Full Text Available The use of natural evaporative cooling is one of technical solutions of problem of energy efficiency in air conditioning systems. The use of evaporative cooling in the first combined cooling stage allows reducing the load on the condenser of the cooling machine due to reducing of the condensing temperature. This combination allows the use of this type of system in any climatic conditions, including regions with small water resources. Multi-porous ceramic structure is used in evaporative air coolers and water coolers in this case. The objective of this paper is to show advantages of the using of porous ceramic as a working attachment, and to show advantages of the proposed scheme of compression-evaporation systems in comparison with standard vapor compression systems. Experimental research proved the fact, that in the film mode cooling efficiency of air flow is between EA=0,6÷0,7 and is slightly dependent of water flow. For countries with hot and dry climate where reserves of water are limited, it is recommended to use cyclical regime with EA≈0,65 value, or to use channel regime with a value of EA≈0,55. This leads to considerable energy savings. It has been determined, that combined air conditioning system is completely closed on the consumption of water at the parameters of the outside air equal to tA =32ºC and XA>13g/kg (in system with direct evaporative cooling machine, and tA=32ºC and XA>12g/kg (in system with indirect evaporative cooling machine. With these parameters, the cost of water in evaporative cooling stage can be fully compensated by condensate from the evaporator chiller.

  19. Gating Systems for Sizeable Castings from Al Alloys Cast into Ceramic Moulds

    Directory of Open Access Journals (Sweden)

    I. Stachovec

    2012-04-01

    Full Text Available In contrast to casting to conventional non-reusable “sand” moulds, for which calculating technique for an optimum design of the gating system is comparatively well-developed, a trial-and-error method is applied mostly for casting to ceramic shell moulds made by the investment casting technology. A technologist selects from gating systems of several types (that are standardized by the foundry mostly on the basis of experience. However, this approach is not sustainable with ever growing demands on quality of castings and also the economy of their fabrication as well as with new types of complex sizeable castings introduced to the production gradually (by new customers from the aircraft industry above all any more. The simulation software may be used as a possible tool for making the process of optimising gating systems more effective.

  20. Arc-discharge system for nondestructive detection of flaws in thin ceramic coatings

    International Nuclear Information System (INIS)

    Scott, G.W.; Davis, E.V.

    1978-04-01

    The feasibility of nondestructively detecting small cracks or holes in plasma-sprayed ceramic coatings with an electric arc-discharge system was studied. We inspected ZrO 2 coatings 0.46 mm (0.018 in.) thick on Incoloy alloy 800 substrates. Cracks were artificially induced in controlled areas of the specimens by straining the substrates in tension. We designed and built a system to scan the specimen's surface at approximately 50 μm (0.002 in.) clearance with a sharp-pointed metal-tipped probe at high dc potential. The system measures the arc currents occurring at flaws, or plots a map of the scanned area showing points where the arc current exceeds a preset threshold. A theoretical model of the probe-specimen circuit shows constant dc potential to be the best choice for arc-discharge inspection of insulating coatings. Experimental observations and analysis of the data disclosed some potential for flaw description

  1. Effect of moisture on dental enamel in the interaction of two orthodontic bonding systems.

    Science.gov (United States)

    Bertoz, André Pinheiro de Magalhães; de Oliveira, Derly Tescaro Narcizo; Gimenez, Carla Maria Melleiro; Briso, André Luiz Fraga; Bertoz, Francisco Antonio; Santos, Eduardo César Almada

    2013-01-01

    The purpose of this study was to assess by means of scanning electron microscopy (SEM) the remaining adhesive interface after debonding orthodontic attachments bonded to bovine teeth with the use of hydrophilic and hydrophobic primers under different dental substrate moisture conditions. Twenty mandibular incisors were divided into four groups (n = 5). In Group I, bracket bonding was performed with Transbond MIP hydrophilic primer and Transbond XT adhesive paste applied to moist substrate, and in Group II a bonding system comprising Transbond XT hydrophobic primer and adhesive paste was applied to moist substrate. Brackets were bonded to the specimens in Groups III and IV using the same adhesive systems, but on dry dental enamel. The images were qualitatively assessed by SEM. The absence of moisture in etched enamel enabled better interaction between bonding materials and the adamantine structure. The hydrophobic primer achieved the worst micromechanical interlocking results when applied to a moist dental structure, whereas the hydrophilic system proved versatile, yielding acceptable results in moist conditions and excellent interaction in the absence of contamination. The authors assert that the best condition for the application of primers to dental enamel occurs in the absence of moisture.

  2. Application of dental nanomaterials: potential toxicity to the central nervous system.

    Science.gov (United States)

    Feng, Xiaoli; Chen, Aijie; Zhang, Yanli; Wang, Jianfeng; Shao, Longquan; Wei, Limin

    2015-01-01

    Nanomaterials are defined as materials with one or more external dimensions with a size of 1-100 nm. Such materials possess typical nanostructure-dependent properties (eg, chemical, biological, optical, mechanical, and magnetic), which may differ greatly from the properties of their bulk counterparts. In recent years, nanomaterials have been widely used in the production of dental materials, particularly in light polymerization composite resins and bonding systems, coating materials for dental implants, bioceramics, endodontic sealers, and mouthwashes. However, the dental applications of nanomaterials yield not only a significant improvement in clinical treatments but also growing concerns regarding their biosecurity. The brain is well protected by the blood-brain barrier (BBB), which separates the blood from the cerebral parenchyma. However, in recent years, many studies have found that nanoparticles (NPs), including nanocarriers, can transport through the BBB and locate in the central nervous system (CNS). Because the CNS may be a potential target organ of the nanomaterials, it is essential to determine the neurotoxic effects of NPs. In this review, possible dental nanomaterials and their pathways into the CNS are discussed, as well as related neurotoxicity effects underlying the in vitro and in vivo studies. Finally, we analyze the limitations of the current testing methods on the toxicological effects of nanomaterials. This review contributes to a better understanding of the nano-related risks to the CNS as well as the further development of safety assessment systems.

  3. Subjective image quality comparison between two digital dental radiographic systems and conventional dental film

    Directory of Open Access Journals (Sweden)

    Muhammed Ajmal

    2014-10-01

    Recommendations: Improved software and hardware for digital imaging systems are now available and these improvements may now yield images that are comparable in quality to conventional film. However, we recommend that studies still use more observers and other statistical methods to produce ideal results.

  4. Ceramic heat exchanger

    Science.gov (United States)

    LaHaye, Paul G.; Rahman, Faress H.; Lebeau, Thomas P. E.; Severin, Barbara K.

    1998-01-01

    A tube containment system. The tube containment system does not significantly reduce heat transfer through the tube wall. The contained tube is internally pressurized, and is formed from a ceramic material having high strength, high thermal conductivity, and good thermal shock resistance. The tube containment system includes at least one ceramic fiber braid material disposed about the internally pressurized tube. The material is disposed about the tube in a predetermined axial spacing arrangement. The ceramic fiber braid is present in an amount sufficient to contain the tube if the tube becomes fractured. The tube containment system can also include a plurality of ceramic ring-shaped structures, in contact with the outer surface of the tube, and positioned between the tube and the ceramic fiber braid material, and/or at least one transducer positioned within tube for reducing the internal volume and, therefore, the energy of any shrapnel resulting from a tube fracture.

  5. Dental Hygienist-Led Chronic Disease Management System to Control Early Childhood Caries.

    Science.gov (United States)

    Ng, Man Wai; Fida, Zameera

    2016-06-01

    Management of the complex chronic disease of early childhood caries requires a system of coordinated health care interventions which can be led by a dental hygienist and where patient self-care efforts are paramount. Even after receiving costly surgical treatment under general anesthesia in the operating room, many children develop new and recurrent caries after only 6-12 months, a sequela that can be prevented. This article describes the chronic disease management (CDM) of dental caries, a science-based approach that can prevent and control caries. In this article, we (1) introduce the concept of CDM of dental caries, (2) provide evidence that CDM improves oral health outcomes, and (3) propose a dental hygienist-led team-based oral health care approach to CDM. Although we will be describing the CDM approach for early childhood caries, CDM of caries is applicable in children, adolescents, and adults. Early childhood caries disease control requires meaningful engagement of patients and parents by the oral health care team to assist them with making behavioral changes in the unique context of their families and communities. The traditional dentist/hygienist/assistant model needs to evolve to a collaborative partnership between care providers and patients/families. This partnership will be focused on systematic risk assessment and behaviorally based management of the disease itself, with sensitivity toward the familial environment. Early pilot study results demonstrate reductions in the rates of new caries, dental pain, and referral to the operating room compared with baseline rates. Dental hygienists are the appropriate team members to lead this approach because of their expertise in behavior change and prevention. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

  6. Comparative study of energy-efficiency and conservation systems for ceramic metal-halide discharge lamps

    International Nuclear Information System (INIS)

    Hermoso Orzáez, Manuel Jesús; Andrés Díaz, José Ramón de

    2013-01-01

    Interest in energy savings in urban lighting is gaining traction and has become a priority for municipal administrations. LED (light-emitting diode) technology appears to be the clear future lighting choice. However, this technology is still rapidly developing and has not been sufficiently tested. As an intermediate step, alternative proposals for energy-saving equipment for traditional discharge lamps are desirable so that the current technologies can coexist with the new LED counterparts for the short and medium term. This article provides a comparative study between two efficiency and energy-saving systems for discharge lamps with metal-halide and ceramic technologies, i.e., a lighting flow dimmer-stabilizer and a double-level electronic ballast. - Highlights: ► It has been demonstrated the possibility of regulating ceramic metal-halide lamps with lighting flow dimmer-stabilizer. ► Electronic ballasts can save approximately double quantity of energy than lighting flow dimmer-stabilizers. ► The use of lighting flow dimmer-stabilizer is more profitable than electronic ballasts due to costs and reliability

  7. Performance Study of Ceramic Filter Module in Recirculated Aquaculture System (RAS)

    Science.gov (United States)

    Ng, L. Y.; Ng, C. Y.

    2017-06-01

    The growth of world population has led to significant increase in seafood demand over the world. Aquaculture has been widely accepted by many countries to increase the seafood production owing to the decline of natural seafood resources. The aquaculture productivity, however, is directly linked to the pond water quality. In this study, attempts were made to employ ceramic micro-filter to improve the pond water quality through filtration processes. There were two batches of filtration processes, short term (1 hour) and long term (48 hours). Significant improvements on real pond water quality were recorded through the short term microfiltration process, which reduced turbidity (96%), total suspended solids (TSS) (80%), biochemical oxygen demand (BOD) (72%), chemical oxygen demand (COD) (55%), ammonia (60%), nitrate (96%) and phosphorus (83%). The long term filtration process also showed high efficiency in the removal of solid particle and organic matters. The results showed that all of the parameters were successfully reduced to acceptable ranges (turbidityfiltered pond water. Current study showed that the microfiltration using ceramic micro-filter has high potential to be used in recirculating aquaculture system throughout the aquaculture activities in order to maintain the pond water quality, thus, increase the survival rate of cultured species.

  8. Biocompatibility of dental alloys

    Energy Technology Data Exchange (ETDEWEB)

    Braemer, W. [Heraeus Kulzer GmbH and Co. KG, Hanau (Germany)

    2001-10-01

    Modern dental alloys have been used for 50 years to produce prosthetic dental restorations. Generally, the crowns and frames of a prosthesis are prepared in dental alloys, and then veneered by feldspar ceramics or composites. In use, the alloys are exposed to the corrosive influence of saliva and bacteria. Metallic dental materials can be classified as precious and non-precious alloys. Precious alloys consist of gold, platinum, and small amounts of non-precious components such as copper, tin, or zinc. The non-precious alloys are based on either nickel or cobalt, alloyed with chrome, molybdenum, manganese, etc. Titanium is used as Grade 2 quality for dental purposes. As well as the dental casting alloys, high purity electroplated gold (99.8 wt.-%) is used in dental technology. This review discusses the corrosion behavior of metallic dental materials with saliva in ''in vitro'' tests and the influence of alloy components on bacteria (Lactobacillus casei and Streptococcus mutans). The test results show that alloys with high gold content, cobalt-based alloys, titanium, and electroplated gold are suitable for use as dental materials. (orig.)

  9. [Effect of solution environments on ceramic membrane microfiltration of model system of Chinese medicines].

    Science.gov (United States)

    Zhang, Lianjun; Lu, Jin; Le, Kang; Fu, Tingming; Guo, Liwei

    2010-07-01

    To investigate the effect of differents solution environments on the ceramic membrane microfiltration of model system of Chinese medicines. Taking binary system of soybean protein-berberine as the research object, flux, transmittance of berberine and traping rate of protein as indexes, different solution environment on membrane process were investigated. When the concentration of soybean protein was under 1 g x L(-1), the membrane flux was minimum with the traping of berberine decreased slightly as the concentration increased. When pH was 4, the flux was maximum with the traping rate of protein was 99%, and the transmittance of berberine reached above 60%. The efficiency of membrane separation can be improved by optimizing the solution environment of water-extraction of chinese medicines. The efficiency of membrane separation is the best when adjust the pH to the isoelectric point of proteins for the proteins as the main pollutant in aqueous solution.

  10. Clinical Performance Measures and Quality Improvement System Considerations for Dental Education.

    Science.gov (United States)

    Parkinson, Joseph W; Zeller, Gregory G

    2017-03-01

    Quality improvement and quality assurance programs are an integral part of providing excellence in health care delivery. The Dental Quality Alliance and the Commission on Dental Accreditation recognize this and have created standards and recommendations to advise health care providers and health care delivery systems, including dental schools, on measuring the quality of the care delivered to patients. Overall health care expenditures have increased, and the Affordable Care Act has made health care, including dentistry, available to more people in the United States. These increases in cost and in the number of patients accessing care contribute to a heightened interest in measurable quality improvement outcomes that reflect efficiency, effectiveness, and overall value. Practitioners and administrators, both in academia and in the "real world," need an understanding of various quality improvement methodologies available in order to select approaches that support effective monitoring of the quality of care delivered. This article compares and contrasts various quality improvement approaches, programs, and systems currently in use in order to assist dental providers and administrators in choosing quality improvement methodologies pertinent to their practice or institution.

  11. Dental Amalgam

    Science.gov (United States)

    ... Products and Medical Procedures Dental Devices Dental Amalgam Dental Amalgam Share Tweet Linkedin Pin it More sharing options Linkedin Pin it Email Print Dental amalgam is a dental filling material which is ...

  12. Ceramic composites: Enabling aerospace materials

    Science.gov (United States)

    Levine, S. R.

    1992-01-01

    Ceramics and ceramic matrix composites (CMC) have the potential for significant impact on the performance of aerospace propulsion and power systems. In this paper, the potential benefits are discussed in broad qualitative terms and are illustrated by some specific application case studies. The key issues in need of resolution for the potential of ceramics to be realized are discussed.

  13. Ultra High Temperature and Multifunctional Ceramic Matrix Composite – Coating Systems for Light-Weight Space and Aero Systems

    Data.gov (United States)

    National Aeronautics and Space Administration — Revolutionary ultra-high temperature, high mechanical loading capable, oxidation resistant, durable ceramic coatings and light-weight fiber-reinforced Ceramic Matrix...

  14. Photoacoustic imaging of hidden dental caries by using a fiber-based probing system

    Science.gov (United States)

    Koyama, Takuya; Kakino, Satoko; Matsuura, Yuji

    2017-04-01

    Photoacoustic method to detect hidden dental caries is proposed. It was found that high frequency ultrasonic waves are generated from hidden carious part when radiating laser light to occlusal surface of model tooth. By making a map of intensity of these high frequency components, photoacoustic images of hidden caries were successfully obtained. A photoacoustic imaging system using a bundle of hollow optical fiber was fabricated for using clinical application, and clear photoacoustic image of hidden caries was also obtained by this system.

  15. Design And Implementation of Microcontroller Based Curing Light Control of Dental System.

    OpenAIRE

    Ali hussein hamed

    2006-01-01

    In this paper, a microcontroller-based electronic circuit have been designed and implemented for dental curing system using 8-bit MCS-51 microcontroller. Also a new control card is designed while considering advantages of microcontroller systems the time of curing was controlled automatically by preset values which were input from a push-button switch. An ignition based on PWM technique was used to reduce the high starting current needed for the halogen lamp. This paper and through the test r...

  16. Assessment of the Possibility of Applying Ceramic Materials in Common Rail Injection Systems

    Directory of Open Access Journals (Sweden)

    Mateusz Bor

    2018-03-01

    The second part concerns analysis conduct by means of the finite element method and a specialized simulation environment, based on comparing ceramic materials and bearing steel. This comparison was conducted by using a CAD strength model of a piston in a specific application, being a pump with CP3 design. Simulation results confirmed the beneficial qualities of ceramic materials – the level of material deformation is lower for ceramics in comparison to steel.

  17. A method for the easy fabrication of all-ceramic bridges with the Cerec system.

    Science.gov (United States)

    Kurbad, A; Schnock, H A

    2009-01-01

    Both pressing technology and CAD/CAM methods have proven themselves clinically for the fabrication of all-ceramic restorations. The advantages of the Cerec technology for the economic fabrication of all-ceramic bridges can be exploited by the use of burn-out blanks of polymer material. The milling process of very hard ceramics in the milling unit, which has some disadvantages, is replaced by the pressing process and makes the IPS e.max press material accessible to CAD/CAM users, primarily for extending the range of indications to splinted crowns and small all-ceramic bridges.

  18. The effect of core material, veneering porcelain, and fabrication technique on the biaxial flexural strength and weibull analysis of selected dental ceramics.

    Science.gov (United States)

    Lin, Wei-Shao; Ercoli, Carlo; Feng, Changyong; Morton, Dean

    2012-07-01

    The objective of this study was to compare the effect of veneering porcelain (monolithic or bilayer specimens) and core fabrication technique (heat-pressed or CAD/CAM) on the biaxial flexural strength and Weibull modulus of leucite-reinforced and lithium-disilicate glass ceramics. In addition, the effect of veneering technique (heat-pressed or powder/liquid layering) for zirconia ceramics on the biaxial flexural strength and Weibull modulus was studied. Five ceramic core materials (IPS Empress Esthetic, IPS Empress CAD, IPS e.max Press, IPS e.max CAD, IPS e.max ZirCAD) and three corresponding veneering porcelains (IPS Empress Esthetic Veneer, IPS e.max Ceram, IPS e.max ZirPress) were selected for this study. Each core material group contained three subgroups based on the core material thickness and the presence of corresponding veneering porcelain as follows: 1.5 mm core material only (subgroup 1.5C), 0.8 mm core material only (subgroup 0.8C), and 1.5 mm core/veneer group: 0.8 mm core with 0.7 mm corresponding veneering porcelain with a powder/liquid layering technique (subgroup 0.8C-0.7VL). The ZirCAD group had one additional 1.5 mm core/veneer subgroup with 0.7 mm heat-pressed veneering porcelain (subgroup 0.8C-0.7VP). The biaxial flexural strengths were compared for each subgroup (n = 10) according to ISO standard 6872:2008 with ANOVA and Tukey's post hoc multiple comparison test (p≤ 0.05). The reliability of strength was analyzed with the Weibull distribution. For all core materials, the 1.5 mm core/veneer subgroups (0.8C-0.7VL, 0.8C-0.7VP) had significantly lower mean biaxial flexural strengths (p Empress and e.max groups, regardless of core thickness and fabrication techniques. Comparing fabrication techniques, Empress Esthetic/CAD, e.max Press/CAD had similar biaxial flexural strength (p= 0.28 for Empress pair; p= 0.87 for e.max pair); however, e.max CAD/Press groups had significantly higher flexural strength (p Empress Esthetic/CAD groups. Monolithic core

  19. Dental mesenchymal stem cells encapsulated in alginate hydrogel co-delivery microencapsulation system for cartilage regeneration

    Science.gov (United States)

    Moshaverinia, Alireza; Xu, Xingtian; Chen, Chider; Akiyama, Kentaro; Snead, Malcolm L; Shi, Songtao

    2013-01-01

    Dental-derived MSCs are promising candidates for cartilage regeneration, with high chondrogenic differentiation capacity. This property contributes to making dental MSCs an advantageous therapeutic option compared to current treatment modalities. The MSC delivery vehicle is the principal determinant for the success of MSC-mediated cartilage regeneration therapies. The objectives of this study were to: (1) develop a novel co-delivery system based on TGF-β1 loaded RGD-coupled alginate microspheres encapsulating Periodontal Ligament Stem Cells (PDLSCs) or Gingival Mesenchymal Stem Cells (GMSCs); and (2) investigate dental MSC viability and chondrogenic differentiation in alginate microspheres. The results revealed the sustained release of TGF-β1 from the alginate microspheres. After 4 weeks of chondrogenic differentiation in vitro, PDLSCs, GMSCs as well as human bone marrow mesenchymal stem cells (hBMMSC) (as positive control) revealed chondrogenic gene expression markers (Col II and Sox-9) via qPCR, as well as matrix positively stained by toluidine blue and safranin-O. In animal studies, ectopic cartilage tissue regeneration was observed inside and around the transplanted microspheres, confirmed by histochemical and immunofluorescent staining. Interestingly, PDLSCs showed more chondrogenesis than GMSCs and hBMMSCs (Palginate microencapsulating dental MSCs make a promising candidate for cartilage regeneration. Our results highlight the vital role played by the microenvironment, as well as value of presenting inductive signals for viability and differentiation of MSCs. PMID:23891740

  20. Biofilm problems in dental unit water systems and its practical control.

    LENUS (Irish Health Repository)

    Coleman, D C

    2009-05-01

    Dental chair units (DCUs) contain integrated systems that provide the instruments and services for a wide range of dental procedures. DCUs use water to cool and irrigate DCU-supplied instruments and tooth surfaces during dental treatment. Water is supplied to these instruments by a network of interconnected narrow-bore (2-3 mm) plastic tubes called dental unit waterlines (DUWLs). Many studies over the last 40 years demonstrated that DUWL output water is often contaminated with high densities of micro-organisms, predominantly Gram-negative aerobic heterotropic environmental bacteria, including Legionella and Pseudomonas species. Untreated DUWLs host biofilms that permit micro-organisms to multiply and disperse through the water network and which are aerosolized by DCU instrument use, thus exposing patients and staff to these micro-organisms, to fragments of biofilm and bacterial endotoxins. This review concentrates on how practical developments and innovations in specific areas can contribute to effective DUWL biofilm control. These include the use of effective DUWL treatment agents, improvements to DCU supply water quality, DCU design changes, development of automated DUWL treatment procedures that are effective at controlling biofilm in the long-term and require minimal human intervention, are safe for patients and staff, and which do not cause deterioration of DCU components following prolonged use.

  1. Treatment of abraded teeth using metal free ceramics and conventional metal-ceramic restorations

    Directory of Open Access Journals (Sweden)

    Bošković Mirjana V.

    2012-01-01

    Full Text Available Introduction. Contemporary reconstructive dentistry is considered to be a bioesthetic discipline, the study of the beauty of living creatures in their original form and functions. A discussion of esthetic dentistry, the sophisticated artificial restorations in the patient mouth, hardly discernible to an observer or expert eye, implies a whole series of qualities. Damage of hard tooth-tissue, which is not caused by caries, is a physiological process present throughout the whole life, but some factors can bring about great losses of the hard tissue. This damage can be caused by a combination of different etiological factors, such as genetical and functional ones. Case report. A patient is coming in dental surgery complaining of a large damage of the hard-tooth tissue, ugly appearance of his teeth, speech dysfunction and masticatory problems. An intraoral view shows the presence of a large teeth-abrasion. The treatment plan simplified the treatment with a combination of metal-ceramic restorations and a new ceramic system IPS e.max (Ivoclar Vivadentm Schaan, Liechtenstien. Conclusion. In this clinical case with presented abrasion the treatment was presented using all-ceramic restorations and classical metal-ceramic restorations to establish good health, function and estehetic. The use of restorations based on zirconium (IPS e.max ZirPress, Ivoclar Vivadent, Schaan, Liechtenstein can produce excellent clinical results in the frontal, as well as in lateral segments.

  2. Does dental health of 6-year-olds reflect the reform of the Israeli dental care system?

    Science.gov (United States)

    Natapov, Lena; Sasson, Avi; Zusman, Shlomo P

    2016-01-01

    The National health insurance law enacted in 1995 did not include dental care in its basket of services. Dental care for children was first included in 2010, initially up till 8 years of age. The eligibility age rose to 12 years in 2013. The dental survey of 6 year-olds in 2007 found that the average of decayed, missing and filled teeth index (dmft) was 3.31 and 35 % of children were caries free. The current cross sectional survey of dental health for 6 year-olds was conducted as a comparison to the pre-reform status. Twenty-three local authorities were randomly selected nationwide. Two Grade 1 classes were randomly chosen in each. The city of Jerusalem was also included in the survey because of its size. The children were examined according to the WHO Oral Health Survey Methods 4th ed protocol. The dental caries index for deciduous teeth (dmft: decayed, missing, filled teeth) was calculated. One thousand two hundred ten children were examined. 61.7 % of the children suffered from dental decay and only 38.3 % were caries free. The mean dmft was 2.56; d = 1.41 (teeth with untreated caries), f = 1.15 (teeth damaged by decay and restored), virtually none were missing due to caries. Dental caries prevalence was rather consistent, an average of over 2 teeth affected per child. Although there is no major change in comparison to former surveys, there is more treated than untreated disease. In the present survey the f component is higher than in the past, especially in the Jewish sector where it is the main component. It is still lower in the Arab sector. Although the level of dental disease remained rather constant, an increase in the treatment component was observed. In order to reduce caries prevalence, preventive measures such as school dental services and drinking water fluoridation should be extended and continued. Primary preventive dental services should be established for children from birth, with an emphasis on primary health care and educational

  3. Radiopaque Strontium Fluoroapatite Glass-Ceramics

    Science.gov (United States)

    Höland, Wolfram; Schweiger, Marcel; Dittmer, Marc; Ritzberger, Christian

    2015-01-01

    The controlled precipitation of strontium fluoroapatite crystals was studied in four base glass compositions derived from the SiO2–Al2O3–Y2O3–SrO–Na2O–K2O/Rb2O/Cs2O–P2O5–F system. The crystal phase formation of these glasses and the main properties of the glass-ceramics, such as thermal and optical properties and radiopacity were compared with a fifth, a reference glass-ceramic. The reference glass-ceramic was characterized as Ca-fluoroapatite glass-ceramic. The four strontium fluoroapatite glass-ceramics showed the following crystal phases: (a) Sr5(PO4)3F – leucite, KAlSi2O6, (b) Sr5(PO4)3F – leucite, KAlSi2O6, and nano-sized NaSrPO4, (c) Sr5(PO4)3F – pollucite, CsAlSi2O6, and nano-sized NaSrPO4, and (d) Sr5(PO4)3F – Rb-leucite, RbAlSi2O6, and nano-sized NaSrPO4. The proof of crystal phase formation was possible by X-ray diffraction. The microstructures, which were studied using scanning electron microscopy, demonstrated a uniform distribution of the crystals in the glass matrix. The Sr-fluoroapatites were precipitated based on an internal crystallization process, and the crystals demonstrated a needle-like morphology. The study of the crystal growth of needle-like Sr-fluoroapatites gave a clear evidence of an Ostwald ripening mechanism. The formation of leucite, pollucite, and Rb-leucite was based on a surface crystallization mechanism. Therefore, a twofold crystallization mechanism was successfully applied to develop these types of glass-ceramics. The main focus of this study was the controlled development of glass-ceramics exhibiting high radiopacity in comparison to the reference glass-ceramic. This goal could be achieved with all four glass-ceramics with the preferred development of the Sr-fluoroapatite – pollucite-type glass-ceramic. In addition to this main development, it was possible to control the thermal properties. Especially the Rb-leucite containing glass-ceramic showed the highest coefficient of thermal

  4. Radiopaque Strontium Fluoroapatite Glass-Ceramics.

    Science.gov (United States)

    Höland, Wolfram; Schweiger, Marcel; Dittmer, Marc; Ritzberger, Christian

    2015-01-01

    The controlled precipitation of strontium fluoroapatite crystals was studied in four base glass compositions derived from the SiO2-Al2O3-Y2O3-SrO-Na2O-K2O/Rb2O/Cs2O-P2O5-F system. The crystal phase formation of these glasses and the main properties of the glass-ceramics, such as thermal and optical properties and radiopacity were compared with a fifth, a reference glass-ceramic. The reference glass-ceramic was characterized as Ca-fluoroapatite glass-ceramic. The four strontium fluoroapatite glass-ceramics showed the following crystal phases: (a) Sr5(PO4)3F - leucite, KAlSi2O6, (b) Sr5(PO4)3F - leucite, KAlSi2O6, and nano-sized NaSrPO4, (c) Sr5(PO4)3F - pollucite, CsAlSi2O6, and nano-sized NaSrPO4, and (d) Sr5(PO4)3F - Rb-leucite, RbAlSi2O6, and nano-sized NaSrPO4. The proof of crystal phase formation was possible by X-ray diffraction. The microstructures, which were studied using scanning electron microscopy, demonstrated a uniform distribution of the crystals in the glass matrix. The Sr-fluoroapatites were precipitated based on an internal crystallization process, and the crystals demonstrated a needle-like morphology. The study of the crystal growth of needle-like Sr-fluoroapatites gave a clear evidence of an Ostwald ripening mechanism. The formation of leucite, pollucite, and Rb-leucite was based on a surface crystallization mechanism. Therefore, a twofold crystallization mechanism was successfully applied to develop these types of glass-ceramics. The main focus of this study was the controlled development of glass-ceramics exhibiting high radiopacity in comparison to the reference glass-ceramic. This goal could be achieved with all four glass-ceramics with the preferred development of the Sr-fluoroapatite - pollucite-type glass-ceramic. In addition to this main development, it was possible to control the thermal properties. Especially the Rb-leucite containing glass-ceramic showed the highest coefficient of thermal expansion (CTE). These

  5. Structural Design of Glass and Ceramic Components for Space System Safety

    Science.gov (United States)

    Bernstein, Karen S.

    2007-01-01

    Manned space flight programs will always have windows as part of the structural shell of the crew compartment. Astronauts and cosmonauts need to and enjoy looking out of the spacecraft windows at Earth, at approaching vehicles, at scientific objectives and at the stars. With few exceptions spacecraft windows have been made of glass, and the lessons learned over forty years of manned space flight have resulted in a well-defined approach for using this brittle, unforgiving material in NASA's vehicles, in windows and other structural applications. This chapter will outline the best practices that have developed at NASA for designing, verifying and accepting glass (and ceramic) windows and other components for safe and reliable use in any space system.

  6. The feasibility analysis for the merger of powder from steel making dedusting system in red ceramic

    International Nuclear Information System (INIS)

    Santos, D.M.S.; Goncalves, S.S.; Mocbel, E.B.B.; Barbosa, A.C.C.; Leal, A.P.S.; Lopes, S.A.; Feitosa, E.F.; Silva, G.S.; Rabelo, A.A.; Fagury Neto, E.

    2016-01-01

    The aim of this work was to study the variation of physical and mechanical properties of ceramics made from two clays with the addition of dedusting system powder from a local steel making plant (SDP), which was added in proportions of 3%, 5 %, 7 % and 10 %. The test-bodies were shaped by uniaxial two-stage pressing, calcined for 2 hours at 300 °C and sintered at temperatures of 900 °C, 1000 °C and 1100 °C. The analyzed properties were apparent density, water absorption, apparent porosity, linear firing shrinkage, flexural strength and plasticity index. The starting materials were characterized by XRF as well, in order to evaluate the chemical composition. This methodology showed good results in the development of future work related to the area. (author)

  7. Production of perovskite catalysts on ceramic monoliths with nanoparticles for dual fuel system automobiles

    International Nuclear Information System (INIS)

    Khanfekr, A.; Arzani, K.; Nemati, A.; Hosseini, M.

    2009-01-01

    (Lanthanum, Cerium)(Iron, Manganese, Cobalt, Palladium)(Oxygen) 3 ,-Perovskite catalyst was prepared by the citrate route and deposited on ceramic monoliths via dip coating procedure. The catalyst was applied on a car with X U 7 motors and the amount of emission was monitored with vehicle emission test systems in Sapco company. The results were compared with the imported catalyst with noble metals such as Palladium, Platinum and Rhodium by Iran Khodro company based on the Euro III standards. The catalysts were characterized by specific surface area measurements, scanning electron microscopy, X-ray diffraction, line scan and map. In the results, obtained in the home made sample, the amount of carbon monoxide, nitrogen oxides and hydrocarbons were lower than imported catalyst with Iran Khodro company with nobel metals. The illustration shows nano particles size on coat. The microstructure evaluation showed that the improved properties can be related to the existence of nano particles on coating

  8. Methodological approach of load sintering of ceramics (superconductor, alumina, alumina-aluminium nitride-magnesia system)

    International Nuclear Information System (INIS)

    Roy, J.F.

    1993-05-01

    Sintering parameters knowledge of ceramic powders by improvements of a high temperature pressing (computer piloting and data acquiring) allow a better control of fabrication and of the desired properties (mechanical, electro-magnetic...). By using experiences plan, maximum of informations are obtained with a minimum of experimental tests. This is applied to the sintering of three compounds; for YBaCuO, the superconductive phase is obtained at 450 deg and without post heat treatment; for Al 2 O 3 , mechanical properties and a partial microstructure controls are obtained; for the Al 2 O 3 -AlN-MgO system, an optimization of the mechanical properties is obtained. (A.B.). 63 refs., figs., tabs

  9. Micrometric precision of prosthetic dental crowns obtained by optical scanning and computer-aided designing/computer-aided manufacturing system

    Science.gov (United States)

    das Neves, Flávio Domingues; de Almeida Prado Naves Carneiro, Thiago; do Prado, Célio Jesus; Prudente, Marcel Santana; Zancopé, Karla; Davi, Letícia Resende; Mendonça, Gustavo; Soares, Carlos José

    2014-08-01

    The current study evaluated prosthetic dental crowns obtained by optical scanning and a computer-aided designing/computer-aided manufacturing system using micro-computed tomography to compare the marginal fit. The virtual models were obtained with four different scanning surfaces: typodont (T), regular impressions (RI), master casts (MC), and powdered master casts (PMC). Five virtual models were obtained for each group. For each model, a crown was designed on the software and milled from feldspathic ceramic blocks. Micro-CT images were obtained for marginal gap measurements and the data were statistically analyzed by one-way analysis of variance followed by Tukey's test. The mean vertical misfit was T=62.6±65.2 μm; MC=60.4±38.4 μm; PMC=58.1±38.0 μm, and RI=89.8±62.8 μm. Considering a percentage of vertical marginal gap of up to 75 μm, the results were T=71.5%, RI=49.2%, MC=69.6%, and PMC=71.2%. The percentages of horizontal overextension were T=8.5%, RI=0%, MC=0.8%, and PMC=3.8%. Based on the results, virtual model acquisition by scanning the typodont (simulated mouth) or MC, with or without powder, showed acceptable values for the marginal gap. The higher result of marginal gap of the RI group suggests that it is preferable to scan this directly from the mouth or from MC.

  10. Flexural strength and translucent characteristics of lithium disilicate glass-ceramics with different P2O5 content

    International Nuclear Information System (INIS)

    Wang, Fu; Gao, Jing; Wang, Hui; Chen, Ji-hua

    2010-01-01

    Lithium disilicate glass-ceramics derived from the SiO 2 -Li 2 O-K 2 O-Al 2 O 3 -ZrO 2 -P 2 O 5 system with different P 2 O 5 content (from 0.5 mol.% to 2.0 mol.% at a step of 0.5 mol.%) were prepared for dental restorative application. Flexural strength of final glass-ceramics and translucent characteristics expressed in term of contrast ratio (CR) were measured. The interrelations between P 2 O 5 content, microstructure and properties were discussed. Glass-ceramic with a P 2 O 5 content of 1.0 mol.%, in which elongated rod-like Li 2 Si 2 O 5 crystals formed an interlocking microstructure, showed the highest flexural strength and suitable contrast ratio for dental restorative application.

  11. Shear Bond Strengths between Three Different Yttria-Stabilized Zirconia Dental Materials and Veneering Ceramic and Their Susceptibility to Autoclave Induced Low-Temperature Degradation

    Directory of Open Access Journals (Sweden)

    Manoti Sehgal

    2016-01-01

    Full Text Available A study was undertaken to evaluate the effect of artificial aging through steam and thermal treatment as influencing the shear bond strength between three different commercially available zirconia core materials, namely, Upcera, Ziecon, and Cercon, layered with VITA VM9 veneering ceramic using Universal Testing Machine. The mode of failure between zirconia and ceramic was further analyzed as adhesive, cohesive, or mixed using stereomicroscope. X-ray diffraction and SEM (scanning electron microscope analysis were done to estimate the phase transformation (m-phase fraction and surface grain size of zirconia particles, respectively. The purpose of this study was to simulate the clinical environment by artificial aging through steam and thermal treatment so as the clinical function and nature of the bond between zirconia and veneering material as in a clinical trial of 15 years could be evaluated.

  12. 3-dimensional orthodontics visualization system with dental study models and orthopantomograms

    Science.gov (United States)

    Zhang, Hua; Ong, S. H.; Foong, K. W. C.; Dhar, T.

    2005-04-01

    The aim of this study is to develop a system that provides 3-dimensional visualization of orthodontic treatments. Dental plaster models and corresponding orthopantomogram (dental panoramic tomogram) are first digitized and fed into the system. A semi-auto segmentation technique is applied to the plaster models to detect the dental arches, tooth interstices and gum margins, which are used to extract individual crown models. 3-dimensional representation of roots, generated by deforming generic tooth models with orthopantomogram using radial basis functions, is attached to corresponding crowns to enable visualization of complete teeth. An optional algorithm to close the gaps between deformed roots and actual crowns by using multi-quadratic radial basis functions is also presented, which is capable of generating smooth mesh representation of complete 3-dimensional teeth. User interface is carefully designed to achieve a flexible system with as much user friendliness as possible. Manual calibration and correction is possible throughout the data processing steps to compensate occasional misbehaviors of automatic procedures. By allowing the users to move and re-arrange individual teeth (with their roots) on a full dentition, this orthodontic visualization system provides an easy and accurate way of simulation and planning of orthodontic treatment. Its capability of presenting 3-dimensional root information with only study models and orthopantomogram is especially useful for patients who do not undergo CT scanning, which is not a routine procedure in most orthodontic cases.

  13. Ceramic Technology Project

    Energy Technology Data Exchange (ETDEWEB)

    1992-03-01

    The Ceramic Technology Project was developed by the USDOE Office of Transportation Systems (OTS) in Conservation and Renewable Energy. This project, part of the OTS's Materials Development Program, was developed to meet the ceramic technology requirements of the OTS's automotive technology programs. Significant accomplishments in fabricating ceramic components for the USDOE and NASA advanced heat engine programs have provided evidence that the operation of ceramic parts in high-temperature engine environments is feasible. These programs have also demonstrated that additional research is needed in materials and processing development, design methodology, and data base and life prediction before industry will have a sufficient technology base from which to produce reliable cost-effective ceramic engine components commercially. A five-year project plan was developed with extensive input from private industry. In July 1990 the original plan was updated through the estimated completion of development in 1993. The objective is to develop the industrial technology base required for reliable ceramics for application in advanced automotive heat engines. The project approach includes determining the mechanisms controlling reliability, improving processes for fabricating existing ceramics, developing new materials with increased reliability, and testing these materials in simulated engine environments to confirm reliability. Although this is a generic materials project, the focus is on the structural ceramics for advanced gas turbine and diesel engines, ceramic bearings and attachments, and ceramic coatings for thermal barrier and wear applications in these engines. To facilitate the rapid transfer of this technology to US industry, the major portion of the work is being done in the ceramic industry, with technological support from government laboratories, other industrial laboratories, and universities.

  14. NOVEL EMBEDDED CERAMIC ELECTRODE SYSTEM TO ACTIVATE NANOSTRUCTURED TITANIUM DIOXIDE FOR DEGRADATION OF MTBE

    Science.gov (United States)

    A novel reactor combining a flame-deposited nanostructured titanium dioxide film and a set of embedded ceramic electrodes was designed, developed and tested for degradation of methyl tert-butyl ether (MTBE) in water. On applying a voltage to the ceramic electrodes, a surface coro...

  15. Structural synthesis of electrical engineering complex’ control system of a plant for plastic shaping of the ceramic mixture

    Directory of Open Access Journals (Sweden)

    Galitskov Stanislav

    2017-01-01

    Full Text Available Production of ceramic bricks with the required strength imposes significant restrictions on the process control of plastic shaping of the ceramic mixture in the auger extruder. It is due to several factors. Firstly, the certain nonstationarity of rheological properties of the source raw materials necessitates the automatic task-oriented changes in combinations of such values as shear rate, ceramic mixture moisture and vacuum pressure in the vacuum chamber of the extruder. To solve this problem it is necessary to maintain a coordinated control of the relevant automatic control systems of the electrical engineering complex. The second problem is the lack of technical tools to measure the values of shear rate in the pressure head of the extruder. And finally, the third factor is a necessity for monitoring and modeling of operating steps in brick production – from shaping to finished product output, that is a necessity to assess the impact of drying and firing processes on the possibility to make bricks of specified strength. The paper considers structural synthesis of the electrical engineering complex’ control system for plastic shaping of the ceramic mixture, including the problem of coordinated control: of the vacuum pump’ electrical drive, of the solenoid valve for water dosing, of the belt feeder’ electrical drives, of the mixer and the auger, as well as the use of digital observers of technological controlled coordinates and models in further phases of brick production.

  16. Design features of the radioactive Liquid-Fed Ceramic Melter system

    International Nuclear Information System (INIS)

    Holton, L.K. Jr.

    1985-06-01

    During 1983, the Pacific Northwest Laboratory (PNL), at the request of the Department of Energy (DOE), undertook a program with the principal objective of testing the Liquid-Fed Ceramic Melter (LFCM) process in actual radioactive operations. This activity, termed the Radioactive LFCM (RLFCM) Operations is being conducted in existing shielded hot-cell facilities in B-Cell of the 324 Building, 300 Area, located at Hanford, Washington. This report summarizes the design features of the RLFCM system. These features include: a waste preparation and feed system which uses pulse-agitated waste preparation tanks for waste slurry agitation and an air displacement slurry pump for transferring waste slurries to the LFCM; a waste vitrification system (LFCM) - the design features, design approach, and reasoning for the design of the LFCM are described; a canister-handling turntable for positioning canisters underneath the RLFCM discharge port; a gamma source positioning and detection system for monitoring the glass fill level of the product canisters; and a primary off-gas treatment system for removing the majority of the radionuclide contamination from the RLFCM off gas. 8 refs., 48 figs., 6 tabs

  17. Advanced Ceramics

    International Nuclear Information System (INIS)

    1989-01-01

    The First Florida-Brazil Seminar on Materials and the Second State Meeting about new materials in Rio de Janeiro State show the specific technical contribution in advanced ceramic sector. The others main topics discussed for the development of the country are the advanced ceramic programs the market, the national technic-scientific capacitation, the advanced ceramic patents, etc. (C.G.C.) [pt

  18. Field-scale electrolysis/ceramic membrane system for the treatment of sewage from decentralized small communities.

    Science.gov (United States)

    Son, Dong-Jin; Kim, Woo-Yeol; Yun, Chan-Young; Kim, Dae-Gun; Chang, Duk; Sunwoo, Young; Hong, Ki-Ho

    2017-07-05

    The electrolysis process adopting copper electrodes and ceramic membrane with pore sizes of 0.1-0.2 μm were consisted to a system for the treatment of sewage from decentralized small communities. The system was operated under an HRT of 0.1 hour, voltage of 24 V, and TMP of 0.05 MPa. The system showed average removals of organics, nitrogen, phosphorus, and solids of up to 80%, 52%, 92%, and 100%, respectively. Removal of organics and nitrogen dramatically increased in proportion to increment of influent loading. Phosphorus and solids were remarkably eliminated by both electro-coagulation and membrane filtration. The residual particulate constituents could also be removed successfully through membrane process. A system composed of electrolysis process with ceramic membrane would be a compact, reliable, and flexible option for the treatment of sewage from decentralized small communities.

  19. Assessing the contribution of the dental care delivery system to oral health care disparities.

    Science.gov (United States)

    Pourat, Nadereh; Andersen, Ronald M; Marcus, Marvin

    2015-01-01

    Existing studies of disparities in access to oral health care for underserved populations often focus on supply measures such as number of dentists. This approach overlooks the importance of other aspects of the dental care delivery system, such as personal and practice characteristics of dentists, that determine the capacity to provide care. This study aims to assess the role of such characteristics in access to care of underserved populations. We merged data from the 2003 California Health Interview Survey and a 2003 survey of California dentists in their Medical Study Service Areas (MSSAs). We examined the role of overall supply and other characteristics of dentists in income and racial/ethnic disparities in access, which was measured by annual dental visits and unmet need for dental care due to costs. We found that some characteristics of MSSAs, including higher proportions of dentists who were older, white, busy or overworked, and did not accept public insurance or discounted fees, inhibited access for low-income and minority populations. These findings highlight the importance of monitoring characteristics of dentists in addition to traditional measures of supply such as licensed-dentist-to-population ratios. The findings identify specific aspects of the delivery system such as dentists' participation in Medicaid, provision of discounted care, busyness, age, race/ethnicity, and gender that should be regularly monitored. These data will provide a better understanding of how the dental care delivery system is organized and how this knowledge can be used to develop more narrowly targeted policies to alleviate disparities. © 2014 American Association of Public Health Dentistry.

  20. Low temperature sintering of fluorapatite glass-ceramics.

    Science.gov (United States)

    Denry, Isabelle; Holloway, Julie A

    2014-02-01

    Fluorapatite glass-ceramics have been shown to be excellent candidates as scaffold materials for bone grafts, however, scaffold production by sintering is hindered by concurrent crystallization of the glass. Objective, our goal was to investigate the effect of Ca/Al ratio on the sintering behavior of Nb-doped fluorapatite-based glasses in the SiO2-Al2O3-P2O5-MgO-Na2O-K2O-CaO-CaF2 system. Methods, glass compositions with Ca/Al ratio of 1 (A), 2 (B), 4 (C) and 19 (D) were prepared by twice melting at 1525°C for 3h. Glasses were either cast as cylindrical ingots or ground into powders. Disk-shaped specimens were prepared by either sectioning from the ingots or powder-compacting in a mold, followed by heat treatment at temperatures ranging between 700 and 1050°C for 1h. The density was measured on both sintered specimens and heat treated discs as controls. The degree of sintering was determined from these measurements. Results and Significance XRD showed that fluorapatite crystallized in all glass-ceramics. A high degree of sintering was achieved at 775°C for glass-ceramic D (98.99±0.04%), and 900°C for glass-ceramic C (91.31±0.10). Glass-ceramics A or B were only partially sintered at 1000°C (63.6±0.8% and 74.1±1.5%, respectively). SEM revealed a unique microstructure of micron-sized spherulitic fluorapatite crystals in glass-ceramics C and D. Increasing the Ca/Al ratio promoted low temperature sintering of fluorapatite glass-ceramics, which are traditionally difficult to sinter. Copyright © 2013 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  1. Transition duct system with straight ceramic liner for delivering hot-temperature gases in a combustion turbine engine

    Science.gov (United States)

    Wiebe, David J.

    2017-05-16

    A transition duct system (10) for delivering hot-temperature gases from a plurality of combustors in a combustion turbine engine is provided. The system includes an exit piece (16) for each combustor. The exit piece may include a straight path segment (26) for receiving a gas flow from a respective combustor. A straight ceramic liner (40) may be inwardly disposed onto a metal outer shell (38) along the straight path segment of the exit piece. Structural arrangements are provided to securely attach the ceramic liner in the presence of substantial flow path pressurization. Cost-effective serviceability of the transition duct systems is realizable since the liner can be readily removed and replaced as needed.

  2. Design of a self-adaptive fuzzy PID controller for piezoelectric ceramics micro-displacement system

    Science.gov (United States)

    Zhang, Shuang; Zhong, Yuning; Xu, Zhongbao

    2008-12-01

    In order to improve control precision of the piezoelectric ceramics (PZT) micro-displacement system, a self-adaptive fuzzy Proportional Integration Differential (PID) controller is designed based on the traditional digital PID controller combining with fuzzy control. The arithmetic gives a fuzzy control rule table with the fuzzy control rule and fuzzy reasoning, through this table, the PID parameters can be adjusted online in real time control. Furthermore, the automatic selective control is achieved according to the change of the error. The controller combines the good dynamic capability of the fuzzy control and the high stable precision of the PID control, adopts the method of using fuzzy control and PID control in different segments of time. In the initial and middle stage of the transition process of system, that is, when the error is larger than the value, fuzzy control is used to adjust control variable. It makes full use of the fast response of the fuzzy control. And when the error is smaller than the value, the system is about to be in the steady state, PID control is adopted to eliminate static error. The problems of PZT existing in the field of precise positioning are overcome. The results of the experiments prove that the project is correct and practicable.

  3. Applications of Piezoelectric Ceramics

    Indian Academy of Sciences (India)

    Applications of Piezoelectric Ceramics. Piezoelectric Actuators. Nano and Micropositioners. Vibration Control Systems. Computer Printers. Piezoelectric Transformers,Voltage Generators, Spark Plugs, Ultrasonic Motors,. Ultrasonic Generators and Sensors. Sonars, Medical Diagnostic. Computer Memories. NVFRAM ...

  4. Basic research in crystalline and noncrystalline ceramic systems. Annual report, May 1, 1975--April 1, 1976

    International Nuclear Information System (INIS)

    1976-01-01

    Activities in research programs on ceramics are reported in sections on electric conductivity and dielectric properties, microstructure and properties, ion transport and diffusion, defect interactions and grain boundary phenomena, and future developments

  5. Ceramic Composite Mechanical Fastener System for High-Temperature Structural Assemblies, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Hot structures fabricated from ceramic composite materials are an attractive design option for components of future high-speed aircraft, re-entry vehicles and...

  6. Crack Driving Forces in a Multilayered Coating System for Ceramic Matrix Composite Substrates

    Science.gov (United States)

    Ghosn, Louis J.; Zhu, Dongming; Miller, Robert A.

    2005-01-01

    The effects of the top coating thickness, modulus and shrinkage strains on the crack driving forces for a baseline multilayer Yttria-Stabilized-Zirconia/Mullite/Si thermal and environment barrier coating (TEBC) system for SiC/SiC ceramic matrix composite substrates are determined for gas turbine applications. The crack driving forces increase with increasing modulus, and a low modulus thermal barrier coating material (below 10 GPa) will have no cracking issues under the thermal gradient condition analyzed. Since top coating sintering increases the crack driving forces with time, highly sintering resistant coatings are desirable to maintain a low tensile modulus and maintain a low crack driving force with time. Finite element results demonstrated that an advanced TEBC system, such as ZrO2/HfO2, which possesses improved sintering resistance and high temperature stability, exhibited excellent durability. A multi-vertical cracked structure with fine columnar spacing is an ideal strain tolerant coating capable of reducing the crack driving forces to an acceptable level even with a high modulus of 50 GPa.

  7. Knowledge of risk factors and the periodontal disease-systemic link in dental students' clinical decisions.

    Science.gov (United States)

    Friesen, Lynn Roosa; Walker, Mary P; Kisling, Rebecca E; Liu, Ying; Williams, Karen B

    2014-09-01

    This study evaluated second-, third-, and fourth-year dental students' ability to identify systemic conditions associated with periodontal disease, risk factors most important for referral, and medications with an effect on the periodontium and their ability to apply this knowledge to make clinical decisions regarding treatment and referral of periodontal patients. A twenty-one question survey was administered at one U.S. dental school in the spring semester of 2012 to elicit the students' knowledge and confidence regarding clinical reasoning. The response rate was 86 percent. Periodontal risk factors were accurately selected by at least 50 percent of students in all three classes; these were poorly controlled diabetes, ≥6 mm pockets posteriorly, and lack of response to previous non-surgical therapy. Confidence in knowledge, knowledge of risk factors, and knowledge of medications with an effect on the periodontium improved with training and were predictive of better referral decision making. The greatest impact of training was seen on the students' ability to make correct decisions about referral and treatment for seven clinical scenarios. Although the study found a large increase in the students' abilities from the second through fourth years, the mean of 4.6 (out of 7) for the fourth-year students shows that, on average, those students missed correct treatment or referral on more than two of seven clinical cases. These results suggest that dental curricula should emphasize more critical decision making with respect to referral and treatment criteria in managing the periodontal patient.

  8. AFFORDABLE MULTI-LAYER CERAMIC (MLC) MANUFACTURING FOR POWER SYSTEMS (AMPS)

    Energy Technology Data Exchange (ETDEWEB)

    E.A. Barringer, Ph.D.

    2002-11-27

    McDermott Technology, Inc. (MTI) is attempting to develop high-performance, cost-competitive solid oxide fuel cell (SOFC) power systems. Recognizing the challenges and limitations facing the development of SOFC stacks comprised of electrode-supported cells and metallic interconnects, McDermott Technology, Inc. (MTI) has chosen to pursue an alternate path to commercialization. MTI is developing a multi-layer, co-fired, planar SOFC stack that will provide superior performance and reliability at reduced costs relative to competing designs. The MTI approach combines state-of-the-art SOFC materials with the manufacturing technology and infrastructure established for multi-layer ceramic (MLC) packages for the microelectronics industry. The rationale for using MLC packaging technology is that high quality, low-cost manufacturing has been demonstrated at high volumes. With the proper selection of SOFC materials, implementation of MLC fabrication methods offers unique designs for stacks (cells and interconnects) that are not possible through traditional fabrication methods. The MTI approach eliminates use of metal interconnects and ceramic-metal seals, which are primary sources of stack performance degradation. Co-fired cells are less susceptible to thermal cycling stresses by using material compositions that have closely matched coefficients of thermal expansion between the cell and the interconnect. The development of this SOFC stack technology was initiated in October 1999 under the DOE cosponsored program entitled ''Affordable Multi-layer Ceramic Manufacturing for Power Systems (AMPS)''. The AMPS Program was conducted as a two-phase program: Phase I--Feasibility Assessment (10/99--9/00); and Phase II--Process Development for Co-fired Stacks (10/00-3/02). This report provides a summary of the results from Phase I and a more detailed review of the results for Phase II. Phase I demonstrated the feasibility for fabricating multi-layer, co-fired cells and

  9. Results of tritium experiments on ceramic electrolysis cells and palladium diffusers for application to fusion reactor fuel cleanup systems

    International Nuclear Information System (INIS)

    Carlson, R.V.; Binning, K.E.; Konishi, S.; Yoshida, H.; Naruse, Y.

    1987-01-01

    Tritium tests at the Tritium Systems Test Assembly have demonstrated that ceramic electrolysis cells and palladium alloy diffuser developed in Japan are possible components for a fusion reactor fuel cleanup system. Both components have been successfully operated with tritium for over a year. A failure of the first electrolysis cell was most likely the result of an over voltage on the ceramic. A simple circuit was developed to eliminate this mode of failure. The palladium diffusers tubes exhibited some degradation of mechanical properties as a result of the build up of helium from the tritium decay, after 450 days of operation with tritium, however the effects were not significant enough to affect the performance. New models of the diffuser and electrolysis cell, providing higher flow rates and more tritium compatible designs are currently being tested with tritium. 8 refs., 5 figs

  10. Clinical use of virtual reality distraction system to reduce anxiety and pain in dental procedures.

    Science.gov (United States)

    Wiederhold, Mark D; Gao, Kenneth; Wiederhold, Brenda K

    2014-06-01

    Virtual reality (VR) has been used by clinicians to manage pain in clinical populations. This study examines the use of VR as a form of distraction for dental patients using both subjective and objective measures to determine how a VR system affects patients' reported anxiety level, pain level, and physiological factors. As predicted, results of self-evaluation questionnaires showed that patients experienced less anxiety and pain after undergoing VR treatment. Physiological data reported similar trends in decreased anxiety. Overall, the favorable subjective and objective responses suggest that VR distraction systems can reduce discomfort and pain for patients with mild to moderate fear and anxiety.

  11. Investigation of corrosion experienced in a spray calciner/ceramic melter vitrification system

    International Nuclear Information System (INIS)

    Dierks, R.D.; Mellinger, G.B.; Miller, F.A.; Nelson, T.A.; Bjorklund, W.J.

    1980-08-01

    After periodic testing of a large-scale spray calciner/ceramic melter vitrification system over a 2-yr period, sufficient corrosion was noted on various parts of the vitrification system to warrant its disassembly and inspection. A majority of the 316 SS sintered metal filters on the spray calciner were damaged by chemical corrosion and/or high temperature oxidation. Inconel-601 portions of the melter lid were attacked by chlorides and sulfates which volatilized from the molten glass. The refractory blocks, making up the walls of the melter, were attacked by the waste glass. This attack was occurring when operating temperatures were >1200 0 C. The melter floor was protected by a sludge layer and showed no corrosion. Corrosion to the Inconel-690 electrodes was minimal, and no corrosion was noted in the offgas treatment system downstream of the sintered metal filters. It is believed that most of the melter corrosion occurred during one specific operating period when the melter was operated at high temperatures in an attempt to overcome glass foaming behavior. These high temperatures resulted in a significant release of volatile elements from the molten glass, and also created a situation where the glass was very fluid and convective, which increased the corrosion rate of the refractories. Specific corrosion to the calciner components cannot be proven to have occurred during a specific time period, but the mechanisms of attack were all accelerated under the high-temperature conditions that were experienced with the melter. A review of the materials of construction has been made, and it is concluded that with controlled operating conditions and better protection of some materials of construction corrosion of these systems will not cause problems. Other melter systems operating under similar strenuous conditions have shown a service life of 3 yr

  12. Development of an Electrochemical Ceramic Membrane Filtration System for Efficient Contaminant Removal from Waters.

    Science.gov (United States)

    Zheng, Junjian; Wang, Zhiwei; Ma, Jinxing; Xu, Shaoping; Wu, Zhichao

    2018-04-03

    Inability to remove low-molecular-weight anthropogenic contaminants is a critical issue in low-pressure membrane filtration processes for water treatment. In this work, a novel electrochemical ceramic membrane filtration (ECMF) system using TiO 2 @SnO 2 -Sb anode was developed for removing persistent p-chloroaniline (PCA). Results showed that the ECMF system achieved efficient removal of PCA from contaminated waters. At a charging voltage of 3 V, the PCA removal rate of TiO 2 @SnO 2 -Sb ECMF system under flow-through mode was 2.4 times that of flow-by mode. The energy consumption for 50% of PCA removal for TiO 2 @SnO 2 -Sb ECMF at 3 V under flow-through mode was 0.38 Wh/L, much lower than that of flow-by operation (1.5 Wh/L), which was attributed to the improved utilization of the surface adsorbed HO· and dissociated HO· driven by the enhanced mass transfer of PCA toward the anode surface. Benefiting from the increased production of reactive oxygen species such as O 2 •- , H 2 O 2 , and HO· arising from excitation of anatase TiO 2 , TiO 2 @SnO 2 -Sb ECMF exhibited a superior electrocatalytic activity to the SnO 2 -Sb ECMF system. The degradation pathways of PCA initiated by OH· attack were further proposed, with the biodegradable short-chain carboxylic acids (mainly formic, acetic, and oxalic acids) identified as the dominant oxidized products. These results highlight the potential of the ECMF system for cost-effective water purification.

  13. Milestones of dental history

    OpenAIRE

    Rajesh Mahant; S Vineet Agrawal; Sonali Kapoor; Isha Agrawal

    2017-01-01

    Since ages, human beings suffer from the dental problems. With the journey as time elapsed the person treating the teeth changed (i.e., from barbers and monks to present dentists), equipment changed (i.e., from bow drills to airotor and laser handpieces), materials changed (i.e., from ground mastic alum/honey to tooth colored composite and ceramics). There has been drastic change in treatment planning from extraction to the conservation of teeth and from manual restoration to computerized res...

  14. Use of a gesture user interface as a touchless image navigation system in dental surgery: Case series report

    Energy Technology Data Exchange (ETDEWEB)

    Rosa, Guillermo M.; Elizondo, Maria L. [CORE Dental Clinic, Resistencia (Argentina)

    2014-06-15

    The purposes of this study were to develop a workstation computer that allowed intraoperative touchless control of diagnostic and surgical images by a surgeon, and to report the preliminary experience with the use of the system in a series of cases in which dental surgery was performed. A custom workstation with a new motion sensing input device (Leap Motion) was set up in order to use a natural user interface (NUI) to manipulate the imaging software by hand gestures. The system allowed intraoperative touchless control of the surgical images. For the first time in the literature, an NUI system was used for a pilot study during 11 dental surgery procedures including tooth extractions, dental implant placements, and guided bone regeneration. No complications were reported. The system performed very well and was very useful. The proposed system fulfilled the objective of providing touchless access and control of the system of images and a three-dimensional surgical plan, thus allowing the maintenance of sterile conditions. The interaction between surgical staff, under sterile conditions, and computer equipment has been a key issue. The solution with an NUI with touchless control of the images seems to be closer to an ideal. The cost of the sensor system is quite low; this could facilitate its incorporation into the practice of routine dental surgery. This technology has enormous potential in dental surgery and other healthcare specialties.

  15. Use of a gesture user interface as a touchless image navigation system in dental surgery: Case series report

    Science.gov (United States)

    Elizondo, María L.

    2014-01-01

    Purpose The purposes of this study were to develop a workstation computer that allowed intraoperative touchless control of diagnostic and surgical images by a surgeon, and to report the preliminary experience with the use of the system in a series of cases in which dental surgery was performed. Materials and Methods A custom workstation with a new motion sensing input device (Leap Motion) was set up in order to use a natural user interface (NUI) to manipulate the imaging software by hand gestures. The system allowed intraoperative touchless control of the surgical images. Results For the first time in the literature, an NUI system was used for a pilot study during 11 dental surgery procedures including tooth extractions, dental implant placements, and guided bone regeneration. No complications were reported. The system performed very well and was very useful. Conclusion The proposed system fulfilled the objective of providing touchless access and control of the system of images and a three-dimensional surgical plan, thus allowing the maintenance of sterile conditions. The interaction between surgical staff, under sterile conditions, and computer equipment has been a key issue. The solution with an NUI with touchless control of the images seems to be closer to an ideal. The cost of the sensor system is quite low; this could facilitate its incorporation into the practice of routine dental surgery. This technology has enormous potential in dental surgery and other healthcare specialties. PMID:24944966

  16. Use of a gesture user interface as a touchless image navigation system in dental surgery: Case series report

    International Nuclear Information System (INIS)

    Rosa, Guillermo M.; Elizondo, Maria L.

    2014-01-01

    The purposes of this study were to develop a workstation computer that allowed intraoperative touchless control of diagnostic and surgical images by a surgeon, and to report the preliminary experience with the use of the system in a series of cases in which dental surgery was performed. A custom workstation with a new motion sensing input device (Leap Motion) was set up in order to use a natural user interface (NUI) to manipulate the imaging software by hand gestures. The system allowed intraoperative touchless control of the surgical images. For the first time in the literature, an NUI system was used for a pilot study during 11 dental surgery procedures including tooth extractions, dental implant placements, and guided bone regeneration. No complications were reported. The system performed very well and was very useful. The proposed system fulfilled the objective of providing touchless access and control of the system of images and a three-dimensional surgical plan, thus allowing the maintenance of sterile conditions. The interaction between surgical staff, under sterile conditions, and computer equipment has been a key issue. The solution with an NUI with touchless control of the images seems to be closer to an ideal. The cost of the sensor system is quite low; this could facilitate its incorporation into the practice of routine dental surgery. This technology has enormous potential in dental surgery and other healthcare specialties.

  17. A Low Temperature Co-fired Ceramics Manufactured Power Inductor Based on A Ternary Hybrid Material System

    Science.gov (United States)

    Xie, Yunsong; Chen, Ru

    Low temperature co-fired ceramics (LTCC) is one of the most important techniques to produce circuits with high working frequency, multi-functionality and high integration. We have developed a methodology to enable a ternary hybrid material system being implemented into the LTCC manufacturing process. The co-firing sintering process can be divided into a densification and cooling process. In this method, a successful ternary hybrid material densification process is achieved by tuning the sintering profile of each material to match each other. The system integrity is maintained in the cooling process is obtained by develop a strong bonding at the interfaces of each materials. As a demonstration, we have construct a power inductor device made of the ternary material system including Ag, NiCuZn ferrite and non-magnetic ceramic. The power inductors well maintains its physical integrity after sintering. The microscopic images show no obvious sign of cracks or structural deformation. More importantly, despite the bonding between the ferrite and ceramic is enhanced by non-magnetic element diffusion, the undesired magnetic elements diffusion is effectively suppressed. The electric performance shows that the power handling capability is comparable to the current state of art device.

  18. Bond strength of dental adhesive systems irradiated with ionizing radiation.

    Science.gov (United States)

    Dibo da Cruz, Adriana; Goncalves, Luciano de Souza; Rastelli, Alessandra Nara de Souza; Correr-Sobrinho, Lorenco; Bagnato, Vanderlei Salvador; Boscolo, Frab Norberto

    2010-04-01

    The aim of the present paper was to determine the effect of different types of ionizing radiation on the bond strength of three different dentin adhesive systems. One hundred twenty specimens of 60 human teeth (protocol number: 032/2007) sectioned mesiodistally were divided into 3 groups according to the adhesives systems used: SB (Adper Single Bond Plus), CB (Clearfil SE Bond) and AP (Adper Prompt Self-Etch). The adhesives were applied on dentin and photo-activated using LED (Lec 1000, MMoptics, 1000 mW/cm2). Customized elastomer molds (0.5 mm thickness) with three orifices of 1.2 mm diameter were placed onto the bonding areas and filled with composite resin (Filtek Z-250), which was photo-activated for 20 s. Each group was subdivided into 4 subgroups for application of the different types of ionizing radiation: ultraviolet radiation (UV), diagnostic x-ray radiation (DX), therapeutic x-ray radiation (TX) and without irradiation (control group, CG). Microshear tests were carried out (Instron, model 4411), and afterwards the modes of failure were evaluated by optical and scanning electron microscope and classified using 5 scores: adhesive failure, mixed failures with 3 significance levels, and cohesive failure. The results of the shear bond strength test were submitted to ANOVA with Tukey's test and Dunnett's test, and the data from the failure pattern evaluation were analyzed with the Mann Whitney test (p = 0.05). No change in bond strength of CB and AP was observed after application of the different radiation types, only SB showed increase in bond strength after UV (p = 0.0267) irradiation. The UV also changed the failure patterns of SB (p = 0.0001). The radio-induced changes did not cause degradation of the restorations, which means that they can be exposed to these types of ionizing radiation without weakening the bond strength.

  19. Tailoring of K0.8Al0.7Fe0.15Si2.25O6 Leucite Based Dental Ceramic Material

    Directory of Open Access Journals (Sweden)

    Aleksandar Kremenović

    2016-06-01

    Full Text Available Potassium based ceramic materials composed from leucite in which 5 % of Al is exchanged with Fe and 4 % of hematite was synthesized by mechanochemical homogenization and annealing of K2O-SiO2-Al2O3-Fe2O3 mixtures. Synthesized material was characterized by X-ray Powder Diffraction (XRPD and Scanning Electron Microscopy coupled with Energy Dispersive X-ray spectroscopy (SEM/EDX. The two methods are in good agreement in regard to the specimen chemical composition suggesting that a leucite chemical formula is K0.8Al0.7Fe0.15Si2.25O6. Rietveld structure refinement results reveal that about 20 % of vacancies exist in the position of K atoms. This work is licensed under a Creative Commons Attribution 4.0 International License.

  20. Ultrasonic examination of ceramics and composites for porosities in an automatic scanning system

    Energy Technology Data Exchange (ETDEWEB)

    Gundtoft, H.E.

    1988-05-01

    Using a very precise scanning system and computer evaluation, we can get quantitative results from automatic ultrasonic examination. In this paper two examples dealing with nonmetallic materials are presented. In a ceramic plate (>1 inch thick) small spherical prorosities (down to 0.1 mm) would harm the final product. Several artificial defects made in the plate were used for calibration and optimisation of the technique. Areas with with a microscope. Good agreement with the predicted values from the ultrasonic examination was found. From the NDT-examination the exact position of a porosity is known in all 3 coordinates (x, y and z). The size of the defect can also be measured. A single porosity with a diameter of 0.1 mm can be detected. Carbon-reinforced composites were examined. 8 prepregs were stacked and hardened in an autoclave to form a sheet (1 mm thick). Air trapped in the material resulted in porosities in the final product. A double trough transmission-scanning technique was used for the examination. The porosity percentages were determined by the NDT-technique, and agreement with destructivly determined values on samples from the same sheet was found.

  1. Rheological and thermal performance of newly developed binder systems for ceramic injection molding

    Science.gov (United States)

    Hausnerova, Berenika; Kasparkova, Vera; Hnatkova, Eva

    2016-05-01

    In a novel binder system, carnauba wax was considered to replace the synthetic backbone polymers (polyolefins) enhancing the environmental sustainability of Ceramic Injection Molding (CIM) technology. The paper presents comparison of the rheological performance and thermal behavior of the aluminum oxide CIM feedstocks based on a binder containing carnauba wax with those consisting of a commercial binder. Further, acrawax (N, N'-Ethylene Bis-stearamide) has been considered as another possible substitute of polyolefins. For both proposed substitutes there is a significant reduction in viscosity, and in case of carnauba wax based feedstock also in processing temperature, which is essential for injection molding of reactive powders. Thermal characterization comprised analyses of single neat binders, their mixtures and mixtures with aluminum oxide. The presence of powder lowered melting temperatures of all tested binders except of polyolefin. Further depression in melting point of poly(ethylene glycol) is observed in combination with polyolefin in the presence of powder, and it is related to changes in size of the crystalline domains.

  2. Systemic conditions and treatments as risk for therapy with dental implants

    International Nuclear Information System (INIS)

    Arguedas Vega, Natalia; Alfaro Mayorga, Erika

    2013-01-01

    The possible risks for osseointegration are described in patients with specific systemic conditions, medical treatment such as radiation, cardiovascular diseases, HIV and smoking habit. The principal complications for osseointegration of diseases and systemic treatments are exposed. The review and search of the available literature are realized in databases. The scientific literature obtained from human studies has reported the survival of patients with dental implants. The implants are placed in patients with at least one of the conditions studied. The risks of the surgical procedures required for the placement of implants are analyzed in systemically compromised patients. Comparisons of patients with and without systemic conditions in controlled form have remained without analyzing. The level of evidence of absolute and relative contraindications has been low for the therapy with implants in patients with systemic diseases. The revised information is detailed according the systemic conditions, and each of them are evaluated separately [es

  3. Selecting Ceramics - Introduction

    OpenAIRE

    Cassidy, M.

    2002-01-01

    AIM OF PRESENTATION: To compare a number of materials for extracoronal restoration of teeth with particular reference to CAD-CAM ceramics. CASE DESCRIPTION AND TREATMENT CARRIED OUT: This paper will be illustrated using clinical examples of patients treated using different ceramic restorations to present the advantages and disadvantages and each technique. The different requirements of tooth preparation, impression taking and technical procedures of each system will be presented and compar...

  4. Effect of dental bleaching after bracket bonding and debonding using three different adhesive systems

    Directory of Open Access Journals (Sweden)

    Lucianna de Oliveira Gomes

    2013-04-01

    Full Text Available OBJECTIVE: To evaluate the influence of bonding and debonding of orthodontic brackets on dental in-home bleaching, taking into account three different adhesive systems. METHODS: Forty-four bovine incisors were divided into four groups according to the primer system used for orthodontic bracket bonding. Following the debonding of orthodontic brackets, the teeth were stored in staining solution for 96 hours. Then, teeth were whitened using 10% carbamide peroxide for two weeks at a 6-hour-a-day regime. Standardized digital photographs were taken at the following intervals: T0 (initial; T1 (after debonding; T2 (after pigmentation; T3, T4 and T5 representing 1, 7, and 14 days of bleaching. Repeatability and stability tests were carried out to check the method accuracy. Images were analyzed using Adobe Photoshop 7.0 software considering (L*a*b*color coordinate values and a modified color difference total (Δ;E'. RESULTS: The results of this study (ANOVA and Tukey; p < 0.01 demonstrated that after 7 days of bleaching, experimental groups showed significantly less teeth whitening compared to the control group. However, there were no significant color differences between the groups after 14 days, according to values of lightness (L*. CONCLUSIONS: Regardless of the adhesive primer system applied, bonding and debonding of orthodontic brackets alters the outcome of tooth whitening in the first 7 days of bleaching, however it has no influence on the whitening of the dental structure after 14 days of in-home dental bleaching with 10% carbamide peroxide.

  5. [Single- and multi-unit fixed dental prostheses in relation to the occlusal system].

    Science.gov (United States)

    Witter, D J; Gerritsen, A E; van Spijker, A; Creugers, N H J

    2013-02-01

    Occlusion concepts based on functional aspects offer more solid ground in the diagnostic process and in the treatment of (reduced) dentitions than morphologically and mechanically oriented occlusion concepts. Nevertheless, for occlusal reconstruction morphologically oriented guidelines are necessary. These guidelines are based on the border movements and positions of the mandible in the orofacial system, and on the location and modelling of the occlusal contacts in the occlusal system. The modelling of single- and multi-unit fixed dental prostheses must harmonize with the occlusal system. Moreover, an important feature is the relation of the anterior teeth which enables mutually protected occlusion. Characteristics of a healthy orofacial and occlusal system are: absence of pathology, perceived sufficient oral functions, variability inform and function, and adaptive capacity. When designing single- or multiunit fixed dental prostheses, a pragmatic starting point is to maintain the existing occlusion and the existing speech pattern unless arguments can be provided for alterations. The occlusal design should aim at optimizing oral functions, such as mandibular and occlusal stability.

  6. Intelligent tutoring system for clinical reasoning skill acquisition in dental students.

    Science.gov (United States)

    Suebnukarn, Siriwan

    2009-10-01

    Learning clinical reasoning is an important core activity of the modern dental curriculum. This article describes an intelligent tutoring system (ITS) for clinical reasoning skill acquisition. The system is designed to provide an experience that emulates that of live human-tutored problem-based learning (PBL) sessions as much as possible, while at the same time permitting the students to participate collaboratively from disparate locations. The system uses Bayesian networks to model individual student knowledge and activity, as well as that of the group. Tutoring algorithms use the models to generate tutoring hints. The system incorporates a multimodal interface that integrates text and graphics so as to provide a rich communication channel between the students and the system, as well as among students in the group. Comparison of learning outcomes shows that student clinical reasoning gains from the ITS are similar to those obtained from human-tutored sessions.

  7. Classification review of dental adhesive systems: from the IV generation to the universal type

    OpenAIRE

    Sofan, Eshrak; Sofan, Afrah; Palaia, Gaspare; Tenore, Gianluca; Romeo, Umberto; Migliau, Guido

    2017-01-01

    Adhesive dentistry has undergone great progress in the last decades. In light of minimal-invasive dentistry, this new approach promotes a more conservative cavity design, which relies on the effectiveness of current enamel-dentine adhesives. Adhesive dentistry began in 1955 by Buonocore on the benefits of acid etching. With changing technologies, dental adhesives have evolved from no-etch to total-etch (4th and 5th generation) to self-etch (6th, 7th and 8th generation) systems. Currently, bon...

  8. High Q ceramics in the ACe2(MoO4)4 (A = Ba, Sr and Ca) system for LTCC applications

    International Nuclear Information System (INIS)

    Surjith, A.; Ratheesh, R.

    2013-01-01

    Highlights: ► Solid state synthesis of phase pure ACe 2 (MoO 4 ) 4 (A = Ba, Sr and Ca) ceramics. ► Structural and microstructural evaluation of the synthesized ceramic materials. ► Microwave dielectric property studies of ACe 2 (MoO 4 ) 4 (A = Ba, Sr and Ca) ceramics. ► Structure-property correlation through Laser Raman studies. - Abstract: Novel low temperature sinterable high Q ceramic systems ACe 2 (MoO 4 ) 4 (A = Ba, Sr and Ca) have been prepared through solid state ceramic method. The effect of ionic radii of alkaline earth cations on the structure, microstructure and microwave dielectric properties of these ceramics were studied using powder X-ray diffraction, Laser Raman spectroscopy, scanning electron microscopy and Vector Network Analyzer. A structural change from monoclinic to tetragonal structure was observed while substituting Sr 2+ and Ca 2+ cations in place of Ba 2+ . The Sr and Ca analogues possess better microwave dielectric properties compared to BaCe 2 (MoO 4 ) 4 . All the ceramics were well sintered below 840 °C with dielectric constant in the range 10.2–12.3 together with good quality factor. The SrCe 2 (MoO 4 ) 4 ceramic exhibits an unloaded quality factor of 6762 at 8.080662 GHz with a temperature coefficient of resonant frequency of −46 ppm/°C while the CaCe 2 (MoO 4 ) 4 ceramic shows an unloaded quality factor of 7549 at 6.928868 GHz and a temperature coefficient of resonant frequency of −44 ppm/°C.

  9. Effect of three filler types on mechanical properties of dental composite

    Directory of Open Access Journals (Sweden)

    Pahlavan A.

    2005-06-01

    Full Text Available Statement of Problem: Despite the improvements achieved in the field of dental composites, their strength, longevity, and service life specially in high stress areas is not confirmed. Finding better fillers can be a promising step in this task. Purpose: The purpose of this study was to investigate the effect of the filler type on the mechanical properties of a new experimental dental composite and compare these with the properties of composite containing conventional glass filler. Materials and Methods: Experimental composites were prepared by mixing silane-treated fillers with monomers, composed of 70% Bis-GMA and 30% TEGDMA by weight. Fillers were different among the groups. Glass, leucite ceramic and lithium disilicate were prepared as different filler types. All three groups contained 73% wt filler. Comphorquinone and amines were chosen as photo initiator system. Post curing was done for all groups. Diametral tensile strength (DTS, flexural strength and flexural modulus were measured and compared among groups. Data were analyzed with SPSS package using one-way ANOVA test with P<0.05 as the limit of significance. Results: The results showed that the stronger ceramic fillers have positive effect on the flexural strength. Ceramic fillers increased the flexural strength significantly. No significant differences could be determined in DTS among the groups. Flexural modulus can be affected and increased by using ceramic fillers. Conclusion: Flexural strength is one of the most significant properties of restorative dental materials. The higher flexural strength and flexural modulus can be achieved by stronger ceramic fillers. Any further investigation in this field would be beneficial in the development of restorative dental materials.

  10. Effects of Rating Training on Inter-Rater Consistency for Developing a Dental Hygiene Clinical Rater Qualification System

    Directory of Open Access Journals (Sweden)

    Jeong Ran Park

    2007-12-01

    Full Text Available We tried to develop itemized evaluation criteria and a clinical rater qualification system through rating training of inter-rater consistency for experienced clinical dental hygienists and dental hygiene clinical educators. A total of 15 clinical dental hygienists with 1-year careers participated as clinical examination candidates, while 5 dental hygienists with 3-year educations and clinical careers or longer participated as clinical raters. They all took the clinical examination as examinees. The results were compared, and the consistency of competence was measured. The comparison of clinical competence between candidates and clinical raters showed that the candidate group?占퐏 mean clinical competence ranged from 2.96 to 3.55 on a 5-point system in a total of 3 instruments (Probe, Explorer, Curet, while the clinical rater group?占퐏 mean clinical competence ranged from 4.05 to 4.29. There was a higher inter-rater consistency after education of raters in the following 4 items: Probe, Explorer, Curet, and insertion on distal surface. The mean score distribution of clinical raters ranged from 75% to 100%, which was more uniform in the competence to detect an artificial calculus than that of candidates (25% to 100%. According to the above results, there was a necessity in the operating clinical rater qualification system for comprehensive dental hygiene clinicians. Furthermore, in order to execute the clinical rater qualification system, it will be necessary to keep conducting a series of studies on educational content, time, frequency, and educator level.

  11. Evaluation of the roughness of the surface of porcelain systems with the atomic force microscope

    International Nuclear Information System (INIS)

    Chavarria Rodriguez, Bernal

    2013-01-01

    The surface of a dental ceramic was evaluated and compared with an atomic force microscope after being treated with different systems of polishing. 14 identical ceramic Lava® Zirconia discs were used to test the different polishing systems. 3 polishing systems from different matrix houses were used to polish dental porcelain. The samples were evaluated quantitatively with an atomic force microscope in order to study the real effectiveness of each system, on the roughness average (Ra) and the maximum peak to valley roughness (Ry) of the ceramic surfaces. A considerable reduction of the surface roughness was obtained by applying different polishing systems on the surface of dental ceramics. Very reliable values of Ra and Ry were obtained by making measurements on the structure reproduced by the atomic force microscope. The advanced ceramics of zirconium oxide presented the best physical characteristics and low levels of surface roughness. A smoother surface was achieved with the application of polishing systems, thus demonstrating the reduction of the surface roughness of a dental ceramic [es

  12. Glass-ceramic coating material for the CO2 laser based sintering of thin films as caries and erosion protection.

    Science.gov (United States)

    Bilandžić, Marin Dean; Wollgarten, Susanne; Stollenwerk, Jochen; Poprawe, Reinhart; Esteves-Oliveira, Marcella; Fischer, Horst

    2017-09-01

    The established method of fissure-sealing using polymeric coating materials exhibits limitations on the long-term. Here, we present a novel technique with the potential to protect susceptible teeth against caries and erosion. We hypothesized that a tailored glass-ceramic material could be sprayed onto enamel-like substrates to create superior adhesion properties after sintering by a CO 2 laser beam. A powdered dental glass-ceramic material from the system SiO 2 -Na 2 O-K 2 O-CaO-Al 2 O 3 -MgO was adjusted with individual properties suitable for a spray coating process. The material was characterized using X-ray fluorescence analysis (XRF), heating microscopy, dilatometry, scanning electron microscopy (SEM), grain size analysis, biaxial flexural strength measurements, fourier transform infrared spectroscopy (FTIR), and gas pycnometry. Three different groups of samples (each n=10) where prepared: Group A, powder pressed glass-ceramic coating material; Group B, sintered hydroxyapatite specimens; and Group C, enamel specimens (prepared from bovine teeth). Group B and C where spray coated with glass-ceramic powder. All specimens were heat treated using a CO 2 laser beam process. Cross-sections of the laser-sintered specimens were analyzed using laser scanning microscopy (LSM), energy dispersive X-ray analysis (EDX), and SEM. The developed glass-ceramic material (grain size d50=13.1mm, coefficient of thermal expansion (CTE)=13.310 -6 /K) could be spray coated on all tested substrates (mean thickness=160μm). FTIR analysis confirmed an absorption of the laser energy up to 95%. The powdered glass-ceramic material was successfully densely sintered in all sample groups. The coating interface investigation by SEM and EDX proved atomic diffusion and adhesion of the glass-ceramic material to hydroxyapatite and to dental enamel. A glass-ceramic material with suitable absorption properties was successfully sprayed and laser-sintered in thin films on hydroxyapatite as well as on

  13. Effect of simulated mastication on the surface roughness of three ceramic systems.

    Science.gov (United States)

    Amer, Rafat; Kürklü, Duygu; Johnston, William

    2015-08-01

    Zirconia complete coverage crowns are being widely used as restorations because of their high strength and improved esthetics. Data are sparse about the change in surface roughness of this ceramic material after repeated mastication cycles of opposing enamel. The purpose of this study was to investigate changes in the surface roughness after being subjected to 3-body wear-opposing human enamel of 3 types of ceramics: dense sintered yttrium-stabilized zirconia (Z); lithium disilicate (L); and a conventional low-fusing feldspathic porcelain (P) treated to impart a rough, smooth, or glazed surface. Twenty-four specimens of each of the Z and L ceramic were sectioned from computer-aided design and computer-aided manufacturing blocks into rectangular plates (15×12×2 mm). Twenty-four specimens of the feldspathic porcelain were formed into disks (12-mm diameter) from powders compressed in a silicone mold. All specimens (n=72) were prepared according to the manufacturers' recommendations. Specimens of each ceramic group were placed into 1 of 3 groups: group R, rough surface finish; group S, smooth surface finish; and group G, glazed surface finish. A total of 72 specimens (9 groups with 8 specimens each) was placed in a 3-body wear simulator, with standardized enamel specimens (n=72) acting as the substrate. The changes in surface roughness of the ceramic specimens were evaluated after 50,000 cycles. Data were analyzed by a repeated measures 3-way ANOVA mixed procedure with the Satterthwaite method for degrees of freedom and maximum likelihood estimation of the covariance parameters (α=.05). Data showed that the PS group exhibited the largest change in surface roughness, becoming significantly rougher (P<.004). The LR group became significantly smoother (P=.012). The surfaces of monolithic zirconia ceramic and lithium disilicate did not become as rough as the surface of conventional feldspathic porcelain after enamel wear. Copyright © 2015 Editorial Council for the

  14. Dental education in Peru.

    Science.gov (United States)

    Komabayashi, Takashi; Sato, Manuel; Rodiguez, Lyly; Sato, Doris; Bird, William F

    2008-09-01

    This paper provides information about Peru's dental history and dental school system, including the curriculum and dental licensure. With the increase in the number of dental schools in Peru, the number of dentists is also increasing. Until 1965, Peru had only three dental schools; currently, there are 14. Four of these dental schools are public, and ten are private. A five- or six-year dental program leads to the B.D.S. degree. After successful completion of a thesis defense or competency examination, the D.D.S. degree is awarded. The D.D.S. is mandatory for practicing dentistry in Peru. Currently, there are approximately 14,000 active dentists, with a dentist-patient ratio of approximately 1:2,000.

  15. Methods of three-dimensional electrophoretic deposition for ceramic and cermet applications and systems thereof

    Science.gov (United States)

    Rose, Klint Aaron; Kuntz, Joshua D.; Worsley, Marcus

    2016-09-27

    A ceramic, metal, or cermet according to one embodiment includes a first layer having a gradient in composition, microstructure and/or density in an x-y plane oriented parallel to a plane of deposition of the first layer. A ceramic according to another embodiment includes a plurality of layers comprising particles of a non-cubic material, wherein each layer is characterized by the particles of the non-cubic material being aligned in a common direction. Additional products and methods are also disclosed.

  16. [Ceramic posts].

    Science.gov (United States)

    Mainjot, Amélie; Legros, Caroline; Vanheusden, Alain

    2006-01-01

    As a result of ceramics and all-ceram technologies development esthetic inlay core and abutments flooded the market. Their tooth-colored appearance enhances restoration biomimetism principally on the marginal gingiva area. This article reviews indications and types of cores designed for natural teeth and implants.

  17. Preparation and characterization of TiO2 and Si-doped octacalcium phosphate composite coatings on zirconia ceramics (Y-TZP) for dental implant applications

    Science.gov (United States)

    Bao, Lei; Liu, Jingxiao; Shi, Fei; Jiang, Yanyan; Liu, Guishan

    2014-01-01

    In order to prevent the low temperature degradation and improve the bioactivity of zirconia ceramic implants, TiO2 and Si-doped octacalcium phosphate composite coating was prepared on zirconia substrate. The preventive effect on low temperature degradation and surface morphology of the TiO2 layer were studied. Meanwhile, the structure and property changes of the bioactive coating after doping Si were discussed. The results indicate that the dense TiO2 layer, in spite of some microcracks, inhibited the direct contact of the water vapor with the sample's surface and thus prevented the low temperature degradation of zirconia substrates. The acceleration aging test shows that the ratio of the monoclinic phase transition decreased from 10% for the original zirconia substrate to 4% for the TiO2-coated substrate. As to the Si-doped octacalcium phosphate coating prepared by biomimetic method, the main phase composition of the coating was octacalcium phosphate. The morphology of the coating was lamellar-like, and the surface was uniform and continuous with no cracks being observed. It is suggested that Si was added into the coating both through substituting for PO43- and doping as NaSiO3.

  18. In vitro evaluation of microleakage of various types of dental cements

    Directory of Open Access Journals (Sweden)

    Medić Vesna

    2010-01-01

    Full Text Available Introduction. Microleakage is defined as the clinically undetectable seepage of oral fluids containing bacteria and debris between cement layer and tooth restoration. Objective. This in vitro study investigated the effect of different dental cements (zinc-phosphate, polycarboxylate, glass-ionomer and resin cement on microleakage in different ceramic crown systems (metal ceramic crown, metal ceramic crown with a porcelain margin, Empress 2 and In Ceram all-ceramic crowns fixed on extracted human teeth. Methods. One hundred and sixty intact human premolars were randomized to four groups of forty teeth each, according to the different ceramic crown systems. They were prepared in a standardized manner for metal-ceramic and all-ceramic crowns. Crowns were made following a standard laboratory technique, and each group of crowns were divided into four groups according to the different cement agents and cemented on their respective abutments. The specimens were subjected to thermocycling, placed in methylene blue solutions, embedded in resin blocks and vertically cut in the bucco-oral and meso-distal direction. The microleakage in the area of tooth-cement interface was defined as linear penetration of methylene blue and was determined with a microscope to assign microleakage scores using a five-point scale. Results. A significant association was found between a cement type and degree of microleakage (p=0.001. No statistically significant differences were found among the different ceramic crown systems luted with the same dental cement. The smallest degree of microleakage was observed in specimens luted with resin cement (X=1.73, followed by glass-ionomer cement (X=2.45 and polycarboxylate cement (X=3.20. The greatest degree of microleakage was detected in the crowns fixed with zincphosphate cement (X=3.33. Conclusion. The investigated dental cements revealed different sealing abilities. The use of resin cement resulted in the percentage of 0

  19. Classification review of dental adhesive systems: from the IV generation to the universal type

    Science.gov (United States)

    Sofan, Eshrak; Sofan, Afrah; Palaia, Gaspare; Tenore, Gianluca; Romeo, Umberto; Migliau, Guido

    2017-01-01

    Summary Adhesive dentistry has undergone great progress in the last decades. In light of minimal-invasive dentistry, this new approach promotes a more conservative cavity design, which relies on the effectiveness of current enamel-dentine adhesives. Adhesive dentistry began in 1955 by Buonocore on the benefits of acid etching. With changing technologies, dental adhesives have evolved from no-etch to total-etch (4th and 5th generation) to self-etch (6th, 7th and 8th generation) systems. Currently, bonding to dental substrates is based on three different strategies: 1) etch-and-rinse, 2) self-etch and 3) resin-modified glass-ionomer approach as possessing the unique properties of self-adherence to the tooth tissue. More recently, a new family of dentin adhesives has been introduced (universal or multi-mode adhesives), which may be used either as etch-and-rinse or as self-etch adhesives. The purpose of this article is to review the literature on the current knowledge for each adhesive system according to their classification that have been advocated by many authorities in most operative/restorative procedures. As noted by several valuable studies that have contributed to understanding of bonding to various substrates helps clinicians to choose the appropriate dentin bonding agents for optimal clinical outcomes. PMID:28736601

  20. A new cone-beam computed tomography system for dental applications with innovative 3D software

    Energy Technology Data Exchange (ETDEWEB)

    Pasini, Alessandro; Bianconi, D.; Rossi, A. [University of Bologna, Department of Physics, Bologna (Italy); NECTAR Imaging srl Imola (Italy); Casali, F. [University of Bologna, Department of Physics, Bologna (Italy); Bontempi, M. [CEFLA Dental Group Imola (Italy)

    2007-02-15

    Objective Cone beam computed tomography (CBCT) is an important image technique for oral surgery (dentoalveolar surgery and dental implantology) and maxillofacial applications. This technique requires compact sized scanners with a relatively low radiation dosage, which makes them suitable for imaging of the craniofacial region. This article aims to present the concept and the preliminary findings obtained with the prototype of a new CBCT scanner with dedicated 3D software, specifically designed for dental imaging. Methods The prototype implements an X-ray tube with a nominal focal spot of 0.5 mm operating at 70-100 kVp and 1-4 mA. The detector is a 6 in. image intensifier coupled with a digital CCD camera. Dosimetry was performed on a RANDO anthropomorphic phantom using Beryllium Oxide thermo-luminescent dosimeters positioned in the phantom in the following site: eyes, thyroid, skin (lips, cheeks, back of the neck), brain, mandible, maxilla and parotid glands. Doses were measured using four configurations, changing the field-of-view (4'' and 6'') and acquisition time (10 and 20 s) of the CBCT. Acquisitions were performed with different parameters regarding the x-ray tube, pixel size and acquisition geometries to evaluate image quality in relation to modulation transfer function (MTF), noise and geometric accuracy. Results The prototype was able to acquire a complete maxillofacial scan in 10-15 s. The CT reconstruction algorithm delivered images that were judged to have high quality, allowing for precise volume rendering. The radiation dose was determined to be 1-1.5 times that of the dose applied during conventional dental panoramic studies. Conclusion Preliminary studies using the CBCT prototype indicate that this device provides images with acceptable diagnostic content at a relatively low radiation dosage, if compared to systems currently available on the market. (orig.)

  1. A new cone-beam computed tomography system for dental applications with innovative 3D software

    International Nuclear Information System (INIS)

    Pasini, Alessandro; Bianconi, D.; Rossi, A.; Casali, F.; Bontempi, M.

    2007-01-01

    Objective Cone beam computed tomography (CBCT) is an important image technique for oral surgery (dentoalveolar surgery and dental implantology) and maxillofacial applications. This technique requires compact sized scanners with a relatively low radiation dosage, which makes them suitable for imaging of the craniofacial region. This article aims to present the concept and the preliminary findings obtained with the prototype of a new CBCT scanner with dedicated 3D software, specifically designed for dental imaging. Methods The prototype implements an X-ray tube with a nominal focal spot of 0.5 mm operating at 70-100 kVp and 1-4 mA. The detector is a 6 in. image intensifier coupled with a digital CCD camera. Dosimetry was performed on a RANDO anthropomorphic phantom using Beryllium Oxide thermo-luminescent dosimeters positioned in the phantom in the following site: eyes, thyroid, skin (lips, cheeks, back of the neck), brain, mandible, maxilla and parotid glands. Doses were measured using four configurations, changing the field-of-view (4'' and 6'') and acquisition time (10 and 20 s) of the CBCT. Acquisitions were performed with different parameters regarding the x-ray tube, pixel size and acquisition geometries to evaluate image quality in relation to modulation transfer function (MTF), noise and geometric accuracy. Results The prototype was able to acquire a complete maxillofacial scan in 10-15 s. The CT reconstruction algorithm delivered images that were judged to have high quality, allowing for precise volume rendering. The radiation dose was determined to be 1-1.5 times that of the dose applied during conventional dental panoramic studies. Conclusion Preliminary studies using the CBCT prototype indicate that this device provides images with acceptable diagnostic content at a relatively low radiation dosage, if compared to systems currently available on the market. (orig.)

  2. Recent Advances in Material and Geometrical Modelling in Dental Applications

    Directory of Open Access Journals (Sweden)

    Waleed M. S. Al Qahtani

    2018-06-01

    Full Text Available This article touched, in brief, the recent advances in dental materials and geometric modelling in dental applications. Most common categories of dental materials as metallic alloys, composites, ceramics and nanomaterials were briefly demonstrated. Nanotechnology improved the quality of dental biomaterials. This new technology improves many existing materials properties, also, to introduce new materials with superior properties that covered a wide range of applications in dentistry. Geometric modelling was discussed as a concept and examples within this article. The geometric modelling with engineering Computer-Aided-Design (CAD system(s is highly satisfactory for further analysis or Computer-Aided-Manufacturing (CAM processes. The geometric modelling extracted from Computed-Tomography (CT images (or its similar techniques for the sake of CAM also reached a sufficient level of accuracy, while, obtaining efficient solid modelling without huge efforts on body surfaces, faces, and gaps healing is still doubtable. This article is merely a compilation of knowledge learned from lectures, workshops, books, and journal articles, articles from the internet, dental forum, and scientific groups' discussions.

  3. Development of 4D jaw movement visualization system for dental diagnosis support

    Science.gov (United States)

    Aoki, Yoshimitsu; Terajima, Masahiko; Nakasima, Akihiko

    2004-10-01

    A person with an asymmetric morphology of maxillofacial skeleton reportedly possesses an asymmetric jaw function and the risk to express temporomandibular disorder is high. A comprehensive analysis from the point of view of both the morphology and the function such as maxillofacial or temporomandibular joint morphology, dental occlusion, and features of mandibular movement pathways is essential. In this study, the 4D jaw movement visualization system was developed to visually understand the characteristic jaw movement, 3D maxillofacial skeleton structure, and the alignment of the upper and lower teeth of a patient. For this purpose, the 3D reconstructed images of the cranial and mandibular bones, obtained by computed tomography, were measured using a non-contact 3D measuring device, and the obtained morphological images of teeth model were integrated and activated on the 6 DOF jaw movement data. This system was experimentally applied and visualized in a jaw deformity patient and its usability as a clinical diagnostic support system was verified.

  4. Light Weight Ceramic Ablators for Mars Follow-on Mission Vehicle Thermal Protection System

    Science.gov (United States)

    Tran, Huy K.; Rasky, Daniel J.; Hsu, Ming-Ta; Turan, Ryan

    1994-01-01

    New Light Weight Ceramic Ablators (LCA) were produced by using ceramic and carbon fibrous substrates, impregnated with silicone and phenolic resins. The special infiltration techniques (patent pending) were developed to control the amount of organic resins in the highly porous fiber matrices so that the final densities of LCA's range from 0.22 to 0.24 g/cc. This paper presents the thermal and ablative performance of the Silicone Impregnated Reusable Ceramic Ablators (SIRCA) in simulated entry conditions for Mars-Pathfinder in the Ames 60 MW Interaction Heating Facility (I HF). Arc jet test results yielded no evidence of char erosion and mass loss at high stagnation pressures to 0.25 atm. Minimal silica melt was detected on surface char at a stagnation pressure of 0.31 atm. Four ceramic substrates were used in the production of SIRCA's to obtain the effective of boron oxide present in substrate so the thermal performance of SIRCA's. A sample of SIRCA was also exposed to the same heating condition for five cycles and no significant mass loss or recession was observed. Tensile testing established that the SIRCA tensile strength is about a factor of two higher than that of the virgin substrates. Thermogravimetric Analysis (TGA) of the char in nitrogen and air showed no evidence of free carbon in the char. Scanning Electron Microscopy of the post test sample showed that the char surface consists of a fibrous structure that was sealed with a thin layer of silicon oxide melt.

  5. Experimental Investigations on the Influence of Adhesive Oxides on the Metal-Ceramic Bond

    Directory of Open Access Journals (Sweden)

    Susanne Enghardt

    2015-01-01

    Full Text Available The objective of this study was to test the influence of selected base metals, which act as oxide formers, on the metal-ceramic bond of dental veneer systems. Using ion implantation techniques, ions of Al, In and Cu were introduced into near-surface layers of a noble metal alloy containing no base metals. A noble metal alloy with base metals added for oxide formation was used as a reference. Both alloys were coated with a low-temperature fusing dental ceramic. Specimens without ion implantation or with Al2O3 air abrasion were used as controls. The test procedures comprised the Schwickerath shear bond strength test (ISO 9693-1, profile height (surface roughness measurements (ISO 4287; ISO 4288; ISO 25178, scanning electron microscopy (SEM imaging, auger electron spectroscopy (AES and energy dispersive X-ray analysis (EDX. Ion implantation resulted in no increase in bond strength. The highest shear bond strengths were achieved after oxidation in air and air abrasion with Al2O3 (41.5 MPa and 47.8 MPa respectively. There was a positive correlation between shear bon