[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

Effect of in vitro aging on the flexural strength and probability to fracture of Y-TZP zirconia ceramics for all-ceramic restorations.

Science.gov (United States)

Siarampi, Eleni; Kontonasaki, Eleana; Andrikopoulos, Konstantinos S; Kantiranis, Nikolaos; Voyiatzis, George A; Zorba, Triantafillia; Paraskevopoulos, Konstantinos M; Koidis, Petros

2014-12-01

Dental zirconia restorations should present long-term clinical survival and be in service within the oral environment for many years. However, low temperature degradation could affect their mechanical properties and survival. The aim of this study was to investigate the effect of in vitro aging on the flexural strength of yttrium-stabilized (Y-TZP) zirconia ceramics for ceramic restorations. One hundred twenty bar-shaped specimens were prepared from two ceramics (ZENO Zr (WI) and IPS e.max(®) ZirCAD (IV)), and loaded until fracture according to ISO 6872. The specimens from each ceramic (nx=60) were divided in three groups (control, aged for 5h, aged for 10h). One-way ANOVA was used to assess statistically significant differences among flexural strength values (Pceramics, however statistically significant was for the WI group (Pceramics presented a t→m phase transformation, with the m-phase increasing from 4 to 5% at 5h to around 15% after 10h. The significant reduction of the flexural strength after 10h of in vitro aging, suggests high fracture probability for one of the zirconia ceramics tested. Copyright © 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

The phase stability and toughening effect of 3Y-TZP dispersed in the lanthanum zirconate ceramics

International Nuclear Information System (INIS)

Wang, Yanfei; Xiao, Ping

2014-01-01

The low fracture toughness of lanthanum zirconate (La 2 Zr 2 O 7 , LZ) greatly impedes its wide application as thermal barrier coatings (TBC). The 3 mol% Y 2 O 3 -stabilized tetragonal zirconia polycrystals (3Y-TZP) have been introduced to toughen the brittle LZ ceramics. The dispersive 3Y-TZP undergoes a simultaneous t–m transformation upon cooling below a critical volume fraction x of 3Y-TZP, above which its tetragonal phases can however be preserved. The different stabilities of 3Y-TZP second phases arise from a variation of residual tensile stress within them. The fracture toughness has been greatly improved by dispersing the tetragonal particulates (t-3YSZ) in the LZ matrix and the primary toughening mechanisms are phase transformations of the dispersive second phases and the residual compressive stress within the matrix. An anticipated increase of fracture toughness from the ferroelastic toughening and the residual compressive stress toughening highlights the great potentials to improve coating durability by depositing t′-3YSZ/LZ composite TBCs by the industrial non-equilibrium route

Ceramic Composites of 3Y-TZP Doped with CuO: Processing, Microstructure and Tribology

NARCIS (Netherlands)

Ran, S.

2006-01-01

The work described in this thesis is about processing, microstructure and tribology of CuO doped 3Y-TZP (3 mol% yttria stabilised tetragonal zirconia polycrystals) composite ceramics. This group of materials has shown attractive properties such as superplastic behaviour at elevated temperature and a

Effect of Grinding and Multi-Stimuli Aging on the Fatigue Strength of a Y-TZP Ceramic.

Science.gov (United States)

Silvestri, Tais; Pereira, Gabriel Kalil Rocha; Guilardi, Luis Felipe; Rippe, Marilia Pivetta; Valandro, Luiz Felipe

2018-01-01

This study aimed to investigate the effect of grinding and multi-stimuli aging on the fatigue strength, surface topography and the phase transformation of Y-TZP ceramic. Discs were manufactured according to ISO-6872:2008 for biaxial flexure testing (diameter: 15 mm; thickness: 1.2 mm) and randomly assigned considering two factors "grinding" and "aging": C- control (as-sintered); CA- control + aging; G- ground; GA- ground + aging. Grinding was carried out with coarse diamond burs under water-cooling. Aging protocols consisted of: autoclave (134°C, 2 bars pressure, 20 hours), followed by storage for 365 days (samples were kept untouched at room temperature), and by mechanical cycling (106 cycles by 20 Hz under a load of 50% from the biaxial flexure monotonic tests). Flexural fatigue strengths (20,000 cycles; 6 Hz) were determined under sinusoidal cyclic loading using staircase approach. Additionally, surface topography analysis by FE-SEM and phase transformation analysis by X-ray Diffractometry were performed. Dixon and Mood methodology was used to analyze the fatigue strength data. Grinding promotes alterations of topographical pattern, while aging apparently did not alter it. Grinding triggered t-m phase transformation without impacting the fatigue strength of the Y-TZP ceramic; and aging promoted an intense t-m transformation that resulted in a toughening mechanism leading to higher fatigue strength for as-sintered condition, and a tendency of increase for ground condition (C grinding and aging procedures did not affect deleteriously the fatigue strength of the evaluated Y-TZP ceramic, although, it promotes surface topography alterations, except to aging, and t-m phase transformation.

Influence of firing time and framework thickness on veneered Y-TZP discs curvature.

Science.gov (United States)

Jakubowicz-Kohen, Boris D; Sadoun, Michaël J; Douillard, Thierry; Mainjot, Amélie K

2014-02-01

The objective of the present work was to study the curvature of very thinly, veneered Y-TZP discs of different framework thicknesses submitted to different firing times. Fifteen 20-mm-wide Y-TZP discs were produced in three different thicknesses: 0.75, 1, 1.5mm. One disc from each group was left unveneered while the others were layered with a 0.1mm veneering ceramic layer. All discs underwent five firing cycles for a total cumulative firing time of 30 min, 1, 2, 5 and 10h at 900°C. The curvature profile was measured using a profilometer after the veneering process and after each firing cycle respectively. A fitted curve was then used to estimate the, curvature radius. The coefficient of thermal expansion (CTE) measurements were taken on veneering, ceramic and Y-TZP beam samples that underwent the same firing schedule. Those data were used to calculate the curvature generated by CTE variations over firing time. All bilayered samples exhibited a curvature that increased over firing time inversely to framework thickness. However non-veneered samples did not exhibit any curvature modification. The results of the present study reveal that even a very thin veneer layer (0.1mm) can induce a significant curvature of Y-TZP discs. The dilatometric results showed that Tg and CTE, variations are not sufficient to explain this curvature. A chemical-induced zirconia volume, augmentation located at the framework sub-surface near the interface could explain the sample, curvature and its increase with firing time. Copyright © 2013 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

The effect of grinding on the mechanical behavior of Y-TZP ceramics: A systematic review and meta-analyses

NARCIS (Netherlands)

Pereira, G.K.R.; Fraga, S.; Montagner, A.F.; Soares, F.Z.M.; Kleverlaan, C.J.; Valandro, L.F.

2016-01-01

The aim of this study was to systematically review the literature to assess the effect of grinding on the mechanical properties, structural stability and superficial characteristics of Y-TZP ceramics. The MEDLINE via PubMed and Web of Science (ISI – Web of Knowledge) electronic databases were

The effect of grinding on the mechanical behavior of Y-TZP ceramics: A systematic review and meta-analyses.

Science.gov (United States)

Pereira, G K R; Fraga, S; Montagner, A F; Soares, F Z M; Kleverlaan, C J; Valandro, L F

2016-10-01

The aim of this study was to systematically review the literature to assess the effect of grinding on the mechanical properties, structural stability and superficial characteristics of Y-TZP ceramics. The MEDLINE via PubMed and Web of Science (ISI - Web of Knowledge) electronic databases were searched with included peer-reviewed publications in English language and with no publication year limit. From 342 potentially eligible studies, 73 were selected for full-text analysis, 30 were included in the systematic review with 20 considered in the meta-analysis. Two reviewers independently selected the studies, extracted the data, and assessed the risk of bias. Statistical analyses were performed using RevMan 5.1, with random effects model, at a significance level of 0.05. A descriptive analysis considering phase transformation, Y-TZP grain size, Vickers hardness, residual stress and aging of all included studies were executed. Four outcomes were considered in the meta-analyses (factor: grinding x as-sintered) in global and subgroups analyses (grinding tool, grit-size and cooling) for flexural strength and roughness (Ra) data. A significant difference (pgrinding; subgroup analyses revealed that different parameters also lead to different effects on roughness. High heterogeneity was found in some comparisons. Generally grinding promotes decrease in strength and increase in roughness of Y-TZP ceramics. However, the use of a grinding tool that allows greater accuracy of the movement (i.e. contra angle hand-pieces coupled to slowspeed turbines), small grit size (<50μm) and the use of plenty coolant seem to be the main factors to decrease the defect introduction and allow the occurrence of the toughening transformation mechanism, decreasing the risk of deleterious impact on Y-TZP mechanical properties. Copyright © 2016 Elsevier Ltd. All rights reserved.

Graphite and PMMA as pore formers for thermoplastic extrusion of porous 3Y-TZP oxygen transport membrane supports

DEFF Research Database (Denmark)

Bjørnetun Haugen, Astri; Gurauskis, Jonas; Kaiser, Andreas

2016-01-01

A gas permeable porous support is a crucial part of an asymmetric oxygen transport membrane (OTM). Here, we develop feedstocks for thermoplastic extrusion of tubular, porous 3Y-TZP (partially stabilized zirconia polycrystals, (Y2O3)0.03(ZrO2)0.97)) ceramics, using graphite and/or polymethyl....... This demonstrates the suitability of thermoplastic extrusion for fabrication of porous 3Y-TZP OTM supports, or for other technologies requiring porous ceramics....

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

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.

Lost mold-rapid infiltration forming: Strength control in mesoscale 3Y-TZP ceramics

Science.gov (United States)

Antolino, Nicholas E.

The strength of nanoparticulate enabled microdevices and components is directly related to the interfacial control between particles and the flaws introduced as these particles come together to form the device or component. One new application for micro-scale or meso-scale (10's microm to 100's microm) devices is surgical instruments designed to enter the body, perform a host of surgeries within the body cavity, and be extracted with no external incisions to the patient. This new concept in surgery, called natural orifice transluminal endoscopic surgery (NOTES), requires smaller and more functional surgical tools. Conventional processing routes do not exist for making these instruments with the desired size, topology, precision, and strength. A process, called lost mold-rapid infiltration forming (LM-RIF), was developed to satisfy this need. A tetragonally stabilized zirconia polycrystalline material (3Y-TZP) is a candidate material for this process and application because of its high strength, chemical stability, high elastic modulus, and reasonably high toughness for a ceramic. Modern technical ceramics, like Y-TZP, are predicated on dense, fine grained microstructures and functional mesoscale devices must also adhere to this standard. Colloid and interfacial chemistry was used to disperse and concentrate the Y-TZP nanoparticles through a very steep, yet localized, potential energy barrier against the van der Waals attractive force. The interparticle interaction energies were modeled and compared to rheological data on the suspension. At high concentrations, the suspension was pseudoplastic, which is evidence that a structure was formed within the suspension that could be disrupted by a shearing force. The LM-RIF process exploits this rheological behavior to fill mold cavities created by photolithography. The premise of the LM-RIF process is to process the particulate material into a dense ceramic body while the unsintered mesoscale parts are supported en masse

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

Deposition of Crystalline Hydroxyapatite Nanoparticles on Y-TZP Ceramic: A Potential Solution to Enhance Bonding Characteristics of Y-TZP Ceramics

Directory of Open Access Journals (Sweden)

Abbas Azari

2017-08-01

Full Text Available Objectives: Many advantages have been attributed to dental zirconia ceramics in terms of mechanical and physical properties; however, the bonding ability of this material to dental structure and/or veneering ceramics has always been a matter of concern. On the other hand, hydroxyapatite (HA shows excellent biocompatibility and good bonding ability to tooth structure, with mechanically unstable and brittle characteristics, that make it clinically unacceptable for use in high stress bearing areas. The main purpose of this study was to introduce two simple yet practical methods to deposit the crystalline HA nanoparticles on zirconia ceramics. Materials and Methods: zirconia blocks were treated with HA via two different deposition methods namely thermal coating and air abrasion. Specimens were analyzed by scanning electron microscopy, energy dispersive spectroscopy (EDS and X-ray diffraction (XRD.Results: In both groups, the deposition techniques used were successfully accomplished, while the substrate showed no structural change. However, thermal coating group showed a uniform deposition of crystalline HA but in air abrasion method, there were dispersed thin islands of HA.Conclusions: Thermal coating method has the potential to significantly alter the surface characteristics of zirconia. The simple yet practical nature of the proposed method may be able to shift the bonding paradigm of dental zirconia ceramics. This latter subject needs to be addressed in future investigations.Keywords: Zirconium Oxide; Hydroxyapatites; Dental Bonding; Microscopy, Electron, Scanning; X-Ray Diffraction; Spectrometry, X-Ray Emission

Effect of low-temperature aging on the mechanical behavior of ground Y-TZP

NARCIS (Netherlands)

Pereira, G.K.R.; Amaral, M.; Cesar, P.F.; Bottino, M.C.; Kleverlaan, C.J.; Valandro, L.F.

2015-01-01

This study evaluated the effects of low-temperature aging on the surface topography, phase transformation, biaxial flexural strength, and structural reliability of a ground Y-TZP ceramic. Disc-shaped specimens were manufactured and divided according to two factors: "grinding" - without grinding

Cytotoxicity and biocompatibility of Zirconia (Y-TZP posts with various dental cements

Directory of Open Access Journals (Sweden)

Hyeongsoon Shin

2016-08-01

Full Text Available Objectives Endodontically treated teeth with insufficient tooth structure are often restored with esthetic restorations. This study evaluated the cytotoxicity and biological effects of yttria partially stabilized zirconia (Y-TZP blocks in combination with several dental cements. Materials and Methods Pairs of zirconia cylinders with medium alone or cemented with three types of dental cement including RelyX U200 (3M ESPE, FujiCEM 2 (GC, and Panavia F 2.0 (Kuraray were incubated in medium for 14 days. The cytotoxicity of each supernatant was determined using 3-(4,5-dimethylthiazole-2-yl-2,5-diphenyltetrazolium bromide (MTT assays on L929 fibroblasts and MC3T3-E1 osteoblasts. The levels of interleukin-6 (IL-6 mRNA were evaluated by reverse transcription polymerase chain reaction (RT-PCR, and IL-6 protein was evaluated by enzyme-linked immunosorbent assays (ELISA. The data were analyzed using one-way ANOVA and Tukey post-hoc tests. A p < 0.05 was considered statistically significant. Results The MTT assays showed that MC3T3-E1 osteoblasts were more susceptible to dental cements than L929 fibroblasts. The resin based dental cements increased IL-6 expression in L929 cells, but reduced IL-6 expression in MC3T3-E1 cells. Conclusions Zirconia alone or blocks cemented with dental cement showed acceptable biocompatibilities. The results showed resin-modified glass-ionomer based cement less produced inflammatory cytokines than other self-adhesive resin-based cements. Furthermore, osteoblasts were more susceptible than fibroblasts to the biological effects of dental cement.

Micropatterned Silica Films with Nanohydroxyapatite for Y-TZP Implants.

Science.gov (United States)

Miranda, R B P; Grenho, L; Carvalho, A; Fernandes, M H; Monteiro, F J; Cesar, P F

2018-03-01

This investigation aimed at developing micropatterned silica thin films (MSTFs) containing nanohydroxyapatite (nano-HA) microaggregates that were not completely covered by silica so that they could directly interact with the surrounding cells. The objectives were 1) to evaluate the effect of the presence of 2 films (MSTF with or without nano-HA addition) on the characteristic strength (σ 0 ) and Weibull modulus ( m) of a yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) and 2) to evaluate the effect of these 2 films, as applied onto the Y-TZP surface, on the morphology, orientation, and proliferation of MG63 cells. Sol-gel process and soft lithography were used to apply the MSTF onto the Y-TZP specimens. Three experimental groups were produced: Y-TZP, Y-TZP + MSTF, and Y-TZP + MSTF + sprayed nano-HA. All surfaces were characterized by scanning electron microscopy and energy-dispersive X-ray spectroscopy and tested for 4-point flexural strength ( n = 30) in water at 37 °C. Weibull analysis was used to determine m and σ 0 (maximum likelihood method). In vitro biological behavior was performed with human osteoblast-like cells (MG63). Y-TZP was successfully coated with MSFT and MSFT + nano-HA. Scanning electron microscopy micrographs indicated that the microaggregates of nano-HA were not entirely covered by the silica. There was no statistically significant difference among the experimental groups for σ 0 and m. In the groups containing the films, the cells were elongated and aligned along the lines. The MSFT + nano-HA group showed significantly higher cell metabolic activity than that obtained for the Y-TZP group at day 7. This investigation was successful in producing an MSTF containing nano-HA microaggregates that remained exposed to the environment. The developed films did not jeopardize the structural reliability of a commercial Y-TZP, as confirmed by the Weibull statistics. The MG63 cells seeded over the films became elongated and aligned along the

The effect of some factors on Ms and SME in Ce-TZP ceramics

International Nuclear Information System (INIS)

Jiang, B.; Tu, J.; Hsu, T.Y.; Qi, X.; Zheng, X.; Zhong, J.

1992-01-01

As known to all, shape memory behaviour has been observed in a variety of metallic alloys. This phenomenon, however, is not only observed in that field but also in other materials recently, such as in polymers, intermetallic compounds and ceramics, especially in zirconia ceramics. Swain observed the shape recovery of a bent magnesia-partially-stabilized zirconia (Mg-PSZ) bar upon heating above a certain temperature. The maximum deflection which was nearly completely recovered on heating is about 300 μm. Chen et al., investigated the pseudoelasticity and shape memory effect (SME) in ceria-stabilized tetragonal zirconia polycrystals (Ce-TZP) containing 12 mol% CeO 2 . Wang et al., also observed the SME in Ce-TZP containing 10 mol% CeO 2 . In this paper, the authors would like to introduce some of results conducted recently in our group on SME in Ce-TZP ceramics

Preparación y densificación de monolitos cerámicos nanoestructurados de Y-TZP por Sol-gel

Directory of Open Access Journals (Sweden)

Tartaj, J.

1999-12-01

Full Text Available Y-TZP seeded gel monoliths have been prepared by a sol-gel method based on the coprecipitation of Zr4+ and Y3+ precursors as hydroxides and the stabilisation of the suspension in pure ethanol with a disc turbine. The addition of solid Y-TZP nanometer- size seed particles into the Y-TZP precursor solution play a crucial role during cristallisation and densification of monoliths. Basically, induced a preferential nucleation, which enhance the crystallisation kinetics and the activation energy is reasonably lowered. As a result of the increased nucleation frequency for the crystallisation process a well-developed homogeneous porous microstructure is obtained facilitating the sintering and so the densification at lower temperatures. In this way, Y-TZP highly densificated ceramics monoliths have been obtained at 1050ºC, with a grain size within the nanometer range.

Monolitos de geles de Y-TZP semillados han sido preparados por un método de sol-gel basado en la coprecipitación de precursores de Zr4+ y Y3+ en forma de hidróxidos y la estabilización de la suspensión en etanol puro con una turbina de disco. La adición de partículas nanométricas de Y-TZP cristalizadas a la solución precursora juega un papel fundamental durante la cristalización y densificación de los monolitos. Básicamente, se induce una nucleación preferente, que mejora la cinética de cristalización y reduce razonablemente la energía de activación. Como resultado del incremento de la frecuencia de nucleación para el proceso de cristalización, se obtiene una microestructura porosa, homogénea y bien desarrollada que facilita la sinterización y por tanto la densificación del material a temperaturas más bajas. De esta forma, monolitos cerámicos de Y-TZP altamente densificados han sido obtenidos a 1050ºC, con un tamaño de grano dentro de un rango nanométrico.

Effect of TiN Addition on 3Y-TZP Ceramics with Emphasis on Making EDM-Able Bodies

Science.gov (United States)

Khosravifar, Mahnoosh; Mirkazemi, Seyyed Mohammad; Taheri, Mahdiar; Golestanifard, Farhad

2018-04-01

In this study, to produce electrically conductive ceramics, rapid hot press (RHP) sintering of 3 mol.% yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP) and 3Y-TZP/TiN composites with TiN amounts of 25, 35, and 45 vol.% was performed at 1300, 1350, and 1400 °C. Interestingly, the toughness and hardness were improved in the presence of TiN up to 35 vol.% and maximum fracture toughness and hardness of 5.40 ± 0.05 MPa m1/2 and 14.50 ± 0.06 GPa, respectively, were obtained. However, the bending strength was decreased which could be attributed to the rather weak interfaces of nitride and oxide phases. Regarding the zirconia matrix, the effect of grain size on fracture toughness of the samples has been studied using x-ray diffraction and field emission scanning electron microscope (FESEM) analysis. It was also found that electrical resistivity decreased to the value of 6.88 × 10-6 Ω m at 45 vol.% of TiN. It seems the TiN grains form a network to impose conductivity on the ZrO2 body; however, below 35 vol.% TiN, due to lack of percolation effect, this conductivity could not be maintained according to FESEM studies. Finally, electrically conductive samples were successfully machined by electrical discharge machining (EDM).

High temperature microplasticity of fine-grained Y-TZP zirconia studied by mechanical spectroscopy

International Nuclear Information System (INIS)

Donzel, L.; Schaller, R.

1997-01-01

Mechanical spectroscopy has been used to study the early stage of the plastic deformation, i.e. the microplasticity of Y-TZP ceramics. Measurements on samples with different grain sizes have shown that the mechanical loss is proportional to the inverse of the square root of the grain size. The existence of a threshold stress has been observed. (orig.)

Effect of bioglass additions on the sintering of Y-TZP bioceramics

Energy Technology Data Exchange (ETDEWEB)

Habibe, A.F.; Maeda, L.D.; Souza, R.C.; Barboza, M.J.R.; Daguano, J.K.M.F. [USP-EEL, Universidade de Sao Paulo, Escola de Engenharia de Lorena, Polo Urbo-Industrial, Gleba AI6, s/n, P.O. Box 116, CEP 12600-970, Lorena-SP (Brazil); Rogero, S.O. [IPEN/CNEN-SP, Instituto de Pesquisas Energeticas e Nucleares, Av. Prof. Lineu Prestes, 2242, Sao Paulo-SP, CEP 05508-900 (Brazil); Santos, C., E-mail: claudinei@demar.eel.usp.br [USP-EEL, Universidade de Sao Paulo, Escola de Engenharia de Lorena, Polo Urbo-Industrial, Gleba AI6, s/n, P.O. Box 116, CEP 12600-970, Lorena-SP (Brazil)

2009-08-01

The objective of this work was to evaluate the influence of bioglass additions on the sintering and mechanical properties of yttria-stabilized zirconia ceramics, Y-TZP. Samples containing different bioglass additions, varying between 0 and 30 wt.%, were cold uniaxial pressed at 80 MPa and sintered in air at 1200 deg. C or 1300 deg. C for 120 min. Sintered samples were characterized by X-ray Diffractometry and Scanning Electron Microscopy. Hardness and fracture toughness were determined using Vickers indentation method. As a preliminary biological evaluation, in vitro cytotoxicity tests by Neutral Red Uptake method (using mouse connective tissue cells, NCTC clone L929 from ATCC bank) were realized to determine the cytotoxicity level of ZrO{sub 2}-bioglass ceramics. The increasing of bioglass amount leads to the decreasing of relative density due to martensitic (tetragonal-monoclinic) transformation during cooling of the sintered samples. Y-TZP samples sintered at 1300 deg. C containing 5 wt.% of bioglass presented the best results, with high relative density, hardness and fracture toughness of 11.3 GPa and 6.1 MPa m{sup 1/2}, respectively. Furthermore, the un-cytotoxic behavior was observed in all sintering conditions and bioglass amounts used in this study.

Y-TZP zirconia regeneration firing: Microstructural and crystallographic changes after grinding.

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Ryan, Daniel Patrick Obelenis; Fais, Laiza Maria Grassi; Antonio, Selma Gutierrez; Hatanaka, Gabriel Rodrigues; Candido, Lucas Miguel; Pinelli, Ligia Antunes Pereira

2017-07-26

This study evaluated microstructural and crystallographic phase changes after grinding (G) and regeneration firing/anneling (R) of Y-TZP ceramics. Thirty five bars (Lava TM and Ice Zirkon) were divided: Y-TZP pre-sintered, control (C), regeneration firing (R), dry grinding (DG), dry grinding+regeneration firing (DGR), wet grinding (WG) and wet grinding+regeneration firing (WGR). Grinding was conducted using a diamond bur and annealing at 1,000°C. The microstructure was analyzed by SEM and the crystalline phases by X-ray diffraction (XRD). XRD showed that pre-sintered specimens contained tetragonal and monoclinic phases, while groups C and R showed tetragonal, cubic and monoclinic phases. After grinding, the cubic phase was eliminated in all groups. Annealing (DGR and WGR) resulted in only tetragonal phase. SEM showed semi-circular cracks after grinding and homogenization of particles after annealing. After grinding, surfaces show tetragonal and monoclinic phases and R can be assumed to be necessary prior to porcelain layering when grinding is performed.

Performance of 3Y-TZP bioceramics under cyclic fatigue loading

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Renato Chaves Souza

2008-03-01

Full Text Available In this work, the static mechanical properties and cyclic fatigue life of 3 mol. (% Y2O3-stabilized tetragonal zirconia polycrystalline (3Y-TZP ceramics were investigated. Pre-sintered samples were sintered in air at 1600 °C for 120 minutes, and characterized by X ray diffraction and scanning electronic microscopy. Hardness and fracture toughness were determined by Vicker's indentation method, and Modulus of Rupture was determined by four-point bending testing. Fully dense sintered samples, near to 100% of theoretical density, presented hardness, fracture toughness and bending strength of 13.5 GPa, 8.2 MPa.m½ and 880 MPa, respectively. The cyclic fatigue tests were also realized using four-point bending testing, within a frequency of 25 Hz and stress ratio R of 0.1. The increasing of load stress lead to decreasing of the number of cycles and the run-out specimens number. The tetragonal-monoclinic (t-m ZrO2-transformation observed by X ray diffraction contributes to the increasing of the fatigue life. The 3Y-TZP samples clearly presents a range of loading conditions where cyclic fatigue can be detected.

Neutron diffraction investigation for possible anisotropy within monolithic Al2O3/Y-TZP composites fabricated by stacking together cast tapes

International Nuclear Information System (INIS)

Ruiz-Hervias, J.; Bruno, G.; Gurauskis, J.; Sanchez-Herencia, A.J.; Baudin, C.

2006-01-01

The development of residual stresses in two Al 2 O 3 + 5 vol.% yttria-tetragonal zirconia polycrystal (Y-TZP) ceramic composites fabricated by conventional slip casting and by joining green cast tapes was investigated. Neutron diffraction profiles revealed compressive microstresses (-200 MPa) in the Al 2 O 3 matrix and tensile ones (2200 MPa) in the Y-TZP particles, irrespective of the processing route and the direction of measurement, which demonstrates the lack of residual macrostresses due to the joining procedure

Effect of airborne particle abrasion protocols on surface topography of Y-TZP ceramic Efeito do protocolo de jateamento com partículas na topografia da superfície de uma cerâmica Y-TZP

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J. R. C. Queiroz

2012-06-01

Full Text Available This study aimed to evaluate Y-TZP surface after different airborne particle abrasion protocols. Seventy-six Y-TZP ceramic blocks (5×4×4 mm³ were sintered and polished. Specimens were randomly divided into 19 groups (n=4 according to control group and 3 factors: a protocol duration (2 and 4 s; b particle size (30 µm, alumina coated silica particle; 45 µm, alumina particle; and 145 µm, alumina particle and; c pressure (1.5, 2.5 and 4.5 bar. Airborne particle abrasion was performed following a strict protocol. For qualitative and quantitative results, topography surfaces were analyzed in a digital optical profilometer (Interference Microscopic, using different roughness parameters (Ra, Rq, Rz, X-crossing, Mr1, Mr2 and Sdr and 3D images. Surface roughness also was analyzed following the primer and silane applications on Y-TZP surfaces. One-way ANOVA revealed that treatments (application period, particle size and pressure of particle blasting provided significant difference for all roughness parameters. The Tukey test determined that the significant differences between groups were different among roughness parameters. In qualitative analysis, the bonding agent application reduced roughness, filing the valleys in the surface. The protocols performed in this study verified that application period, particle size and pressure influenced the topographic pattern and amplitude of roughness.O objetivo deste estudo foi avaliar a superfície de uma cerâmica à base de zircônia tetragonal estabilizada por ítria (Y-TZP após diferentes protocolos de jateamento com partículas. Setenta e seis blocos cerâmicos de Y-TZP (5 x 4 x 4 mm³ foram sinterizados e polidos. As amostras foram randomicamente divididas em 19 grupos (n=4 sendo um controle e 18 grupos utilizando 3 fatores: a tempo (2 e 4 s; b tamanho de partícula (30 µm - partículas de alumina revestida por sílica; 45 µm - partículas de alumina; 145 µm - partículas de alumina e; c pressão (1

Repair bond strength of composite resin to sandblasted and laser irradiated Y-TZP ceramic surfaces.

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Kirmali, Omer; Barutcigil, Çağatay; Ozarslan, Mehmet Mustafa; Barutcigil, Kubilay; Harorlı, Osman Tolga

2015-01-01

This study investigated the effects of different surface treatments on the repair bond strength of yttrium-stabilized tetragonal zirconia polycrystalline ceramic (Y-TZP) zirconia to a composite resin. Sixty Y-TZP zirconia specimens were prepared and randomly divided into six groups (n = 10) as follows: Group 1, surface grinding with Cimara grinding bur (control); Group 2, sandblasted with 30 µm silica-coated alumina particles; Group 3, Nd:YAG laser irradiation; Group 4, Er,Cr:YSGG laser irradiation; Group 5, sandblasted + Nd:YAG laser irradiation; and Group 6, sandblasted + Er,Cr:YSGG laser irradiation. After surface treatments, the Cimara(®) System was selected for the repair method and applied to all specimens. A composite resin was built-up on each zirconia surface using a cylindrical mold (5 × 3 mm) and incrementally filled. The repair bond strength was measured with a universal test machine. Data were analyzed using a one-way ANOVA and a Tukey HSD test (p = 0.05). Surface topography after treatments were evaluated by a scanning electron microscope (SEM). Shear bond strength mean values ranged from 15.896 to 18.875 MPa. There was a statistically significant difference between group 3 and the control group (p < 0.05). Also, a significant increase in bond strength values was noted in group 6 (p < 0.05). All surface treatment methods enhanced the repair bond strength of the composite to zirconia; however, there were no significant differences between treatment methods. The results revealed that Nd:YAG laser irradiation along with the combination of sandblasting and Er,Cr:YSGG laser irradiation provided a significant increase in bond strength between the zirconia and composite resin. © Wiley Periodicals, Inc.

FEA and microstructure characterization of a one-piece Y-TZP abutment.

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da Silva, Lucas Hian; Ribeiro, Sebastião; Borges, Alexandre Luís Souto; Cesar, Paulo Francisco; Tango, Rubens Nisie

2014-11-01

The most important drawback of dental implant/abutment assemblies is the need for a fixing screw. This study aimed to develop an esthetic one-piece Y-TZP abutment to suppress the use of the screw. Material characterization was performed using a bar-shaped specimen obtained by slip-casting to validate the method prior to prototype abutment fabrication by the same process. The mechanical behavior of the prototype abutment was verified and compared with a conventional abutment by finite element analysis (FEA). The abutment was evaluated by micro-CT analysis and its density was measured. FEA showed stress concentration at the first thread pitch during installation and in the cervical region during oblique loading for both abutments. However, stress concentration was observed at the base of the screw head and stem in the conventional abutment. The relative density for the fabricated abutment was 95.68%. Micro-CT analysis revealed the presence of elongated cracks with sharp edges over the surface and porosity in the central region. In the light of these findings, the behavior of a one-piece abutment is expected to be better than that of the conventional model. New studies should be conducted to clarify the performance and longevity of this one-piece Y-TZP abutment. Copyright © 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

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

Effect of grinding and aging on subcritical crack growth of a Y-TZP ceramic.

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Amaral, Marina; Weitzel, Isabela Sandim Souza Leite; Silvestri, Tais; Guilardi, Luis Felipe; Pereira, Gabriel Kalil Rocha; Valandro, Luiz Felipe

2018-01-01

This study aimed to investigate slow crack growth (SCG) behavior of a zirconia ceramic after grinding and simulated aging with low-temperature degradation (LTD). Complementary analysis of hardness, surface topography, crystalline phase transformation, and roughness were also measured. Disc-shaped specimens (15 mm Ø × 1.2 mm thick, n = 42) of a full-contour Y-TZP ceramic (Zirlux FC, Amherst) were manufactured according to ISO:6872-2008, and then divided into: Ctrl - as-sintered condition; Ctrl LTD - as-sintered after aging in autoclave (134°C, 2 bar, 20 h); G - ground with coarse diamond bur (grit size 181 μm); G LTD - ground and aged. The SCG parameters were measured by a dynamic biaxial flexural test, which determines the tensile stress versus stress rate under four different rates: 100, 10, 1 and 0.1 MPa/s. LTD led to m-phase content increase, as well as grinding (m-phase content: Ctrl - 0%; G - 12.3%; G LTD - 59.9%; Ctrl LTD - 81%). Surface topography and roughness analyses showed that grinding created an irregular surface (increased roughness) and aging did not promote any relevant surface change. There was no statistical difference on surface hardness among different conditions. The control group presented the lowest strength values in all tested rates. Regarding SCG, ground conditions were less susceptible to SCG, delaying its occurrence. Aging (LTD) caused an increase in SCG susceptibility for the as-sintered condition (i.e. G < G LTD < Ctrl < Ctrl LTD).

CeO2-stabilized tetragonal ZrO2 polycrystals (Ce-TZP ceramics)

International Nuclear Information System (INIS)

Andrade Nono, M.C. de.

1990-12-01

This work presents the development and the characterization of CeO 2 -stabilized tetragonal ZrO 2 polycrystals (Ce-TZP ceramics), since it is considered candidate material for applications as structural high performance ceramics. Sintered ceramics were fabricated from mixtures of powders containing different CeO 2 content prepared by conventional and nonconventional techniques. These powders and their resultant sintered ceramics were specified by chemical and physical characterization, compactation state and mechanical properties. The chemical characteristics were determined by chemical analysis and the physical characteristics were evaluated by phase content, particle and agglomerate size and aspect, and powder porosity. (author)

Influence of thermal expansion mismatch on residual stress profile in veneering ceramic layered on zirconia: Measurement by hole-drilling.

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Mainjot, Amélie K; Najjar, Achref; Jakubowicz-Kohen, Boris D; Sadoun, Michaël J

2015-09-01

Mismatch in thermal expansion coefficient between core and veneering ceramic (Δα=αcore-αveneer, ppm/°C) is reported as a crucial parameter influencing veneer fractures with Yttria-tetragonal-zirconia-polycrystal (Y-TZP) prostheses, which still constitutes a misunderstood problem. However, the common positive Δα concept remains empirical. The objective of this study is to investigate the Δα dependence of residual stress profiles in veneering ceramic layered on Y-TZP frameworks. The stress profile was measured with the hole-drilling method in bilayered disc samples of 20mm diameter with a 0.7mm thick Y-TZP framework and a 1.5mm thick veneer layer. 3 commercial and 4 experimental veneering ceramics (n=3 per group) were used to obtain different Δα varying from -1.3ppm/°C to +3.2ppm/°C, which were determined by dilatometric analyses. Veneer fractures were observed in samples with Δα≥+2.3 or ≤-0.3ppm/°C. Residual stress profiles measured in other groups showed compressive stresses in the surface, these stresses decreasing with depth and then becoming more compressive again near the interface. Small Δα variations were shown to induce significant changes in residual stress profiles. Compressive stress near the framework was found to decrease inversely to Δα. Veneer CTE close to Y-TZP (+0.2ppm/°C Δα) gived the most favorable stress profile. Yet, near the framework, Δα-induced residual stress varied inversely to predictions. This could be explained by the hypothesis of structural changes occurrence within the Y-TZP surface. Consequently, the optimum Δα value cannot be determined before understanding Y-TZP's particular behavior when veneered. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Characterization of a Diamond Ground Y-TZP and Reversion of the Tetragonal to Monoclinic Transformation.

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Candido, L M; Fais, Lmg; Ferreira, E B; Antonio, S G; Pinelli, Lap

To characterize the surface of an yttria-stabilized zirconia (Y-TZP) ceramic after diamond grinding in terms of its crystalline phase, morphology, mean roughness (Ra), and wettability as well as to determine a thermal treatment to reverse the resulting tetragonal to monoclinic (t-m) transformation. Y-TZP specimens were distributed into different groups according to the actions (or no action) of grinding and irrigation. Grinding was accomplished using a diamond stone at a low speed. The samples were characterized by x-ray diffraction (XRD), scanning electron microscopy, goniometry, and profilometry. In situ high-temperature XRD was used to determine an annealing temperature to reverse the t-m transformation. Ra was submitted to the Kruskal-Wallis test, followed by the Dunn test (α=0.05). The volume fraction of the monoclinic phase and contact angle were submitted to one-way analysis of variance, followed by the Tukey test (α=0.05). Monoclinic zirconia was observed on the surface of samples after dry and wet grinding with a diamond stone. The volume fraction of the monoclinic phase was smaller on the dry ground samples (3.6%±0.3%) than on the wet ground samples (5.6%±0.3%). High-temperature XRD showed reversion of the t-m phase transformation, which started at 700°C and completed at 800°C in a conventional oven. Grinding with a diamond stone partially transformed the crystalline phase on the surface of a Y-TZP ceramic from tetragonal to monoclinic zirconia while simultaneously increasing the surface roughness and wettability. The t-m transformation could be reversed by heat treatment at 800°C or 900°C for 60 minutes or 1000°C for 30 minutes.

Effect of Alumina Addition to Zirconia Nano-composite on Low Temperature Degradation Process and Biaxial Strength

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Moluk Aivazi

2016-12-01

Full Text Available Ceramic dental materials have been considered as alternatives to metals for dental implants application. In this respect, zirconia tetragonal stabilized with %3 yttrium, is of great importance among the ceramic materials for endosseous dental implant application. Because of its good mechanical properties and color similar to tooth. The aim and novelty of this study was to design and prepare Y-TZP nano-composite to reduce the degradation process at low temperature by alumina addition and maintaining submicron grain sized. Also, flexural strength of nano-composite samples was evaluated. Toward this purpose, alumina-Y-TZP nano-composites containing 0–30 vol% alumina (denoted as A-Y-TZP 0-30 were fabricated using α-alumina and Y-TZP nano-sized by sintering pressure less method. The synthesized samples were characterized using x-ray diffraction, field emission scanning electron microscopy equipped with energy dispersive x-ray spectroscopy techniques. Nano-composite samples with high density (≥96% and grain sized of ≤ 400 nm was obtained by sintering at 1270 °C for 170 min. After low temperature degradation test (LTD, A-Y-TZP20 and A-Y-TZP30 not showed monoclinic phase and the flexural strength in all of samples were higher than A-Y-TZP0. It was concluded that the grains were remained in submicron sized and A-Y-TZP20 and A-Y-TZP30 did not present biaxial strength reduction after LTD test.

Tetragonal zirconia ceramics in Zr O2-Ce O2 system (Ce-TZP): preparation, characterization and mechanical properties

International Nuclear Information System (INIS)

Andrade Nono, M.C. de.

1992-01-01

This paper describes and discusses the results achieved in a study about Ce-TZP ceramics prepared from conventional powder mixtures of Zr O 2 and Ce O 2 (with composition in the range of 8 to 16 mol% Ce O 2 ). Physical and chemical characteristics were related with the powder compaction behavior and with the sintering state. The sintered ceramics showed a level of high porosity (≅ 4%), mainly due to the fairly adequate powder characteristics and compaction. The crystalline phases were analysed from X-rays diffraction data and showed that these ceramics can present tetragonal-to-monoclinic stress induced transformation. The bending strength, fracture toughness and Vickers hardness results were influenced by Ce O 2 content microstructure and sintering temperature. These Ce-TZP ceramics showed mechanical strength results comparable to those published in the international literature. (author)

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...

Correlación entre la microestructura y el comportamiento plástico a alta temperatura de compuestos TZP-Ni (40% vol.

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Morales-Rodríguez, A.

2005-10-01

Full Text Available Microstructure and high-temperature mechanical behaviour of TZP-Ni composites with 40 vol.% of nickel above the percolation threshold (placed in 34 vol.% in these wet‑processed ceramic-metal composites has been studied. The microstructure has been characterized using scanning electron microscopy. The composite plasticity has been studied by means of uniaxial compressive creep tests under constant load in argon atmosphere carried out in the temperature range between 900 and 1250 ºC and stresses between 9 and 144 MPa. TZP skeleton has been deformed in similar conditions to study nickel effect in global cermet behavior. The metallic phase has been removed from the cermets using chemical etching with HNO3. The plastic behavior of these materials is controlled by the ceramic matrix. The deformation rates are higher than monolithic TZP ones. This fact has been explained taking into account the metallic phase distribution into the matrix in these composites. Metal percolation provides materials with high ductility allowing the cermets to deform at temperatures as low as 900 ºC.

Se ha estudiado la microestructura y el comportamiento mecánico a alta temperatura de compuestos de circona tetragonal (3Y-TZP con un 40% en volumen de níquel (referidos en adelante como TZP-Ni. El contenido en níquel está por encima del punto de percolación, que en estos compuestos cerámico-metal procesados en vía húmeda se sitúa en el 34% vol. de contenido metálico. La caracterización microestructural se ha realizado mediante observaciones de microscopía electrónica de barrido. La plasticidad de los compuestos se ha estudiado mediante ensayos de fluencia en compresión uniaxial a carga constante en atmósfera de argón realizados en el rango de temperaturas entre 900 y 1250 ºC y tensiones entre 9 y 144 MPa. Para estudiar el efecto del níquel en el comportamiento del cermet se ensayaron en condiciones similares esqueletos de TZP, obtenidos mediante la

Effect of different surface treatments on bond strength, surface and microscopic structure of zirconia ceramic

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Zeinab R. El-Shrkawy

2016-06-01

Conclusions: (1 Surface treatments of Y-TZP ceramic together with MDP primer and silane-coupling agent application improve the bond strength to resin cement. (2 Plasma-Silica coating and plasma-oxygen treatment, both are valuable methods that improve the bond strength of resin cement to Y-TZP ceramic. (3 Silica coating by plasma technology provides durable bond strength and can be a promising alternative pretreatment before silane application to enhance bonding with zirconia ceramic. (4 Tetragonal-monoclinic phase transformation had occurred in Y-TZP samples received both types of plasma treatment.

Retention Load Values of Telescopic Crowns Made of Y-TZP and CoCr with Y-TZP Secondary Crowns: Impact of Different Taper Angles

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Susanne Merk

2016-05-01

Full Text Available This study aimed to examine and compare the retention load values (RL of different telescopic crown assemblies (Y-TZP and CoCr primary crowns with electroformed and Y-TZP secondary crowns each with three different taper angles (0°, 1° and 2°. Thirty Y-TZP primary crowns with electroformed gold copings (Z/G group and Y-TZP secondary crowns (Z/Z group and 30 CoCr primary crowns with electroformed gold copings (C/G group and Y-TZP secondary crowns (C/Z group, each with taper angles of 0°, 1° and 2°, were fabricated, respectively. With the exception of the electroformed gold copings, all specimens were Computer-Aided-Design/Computer-Aided-Manufacturing (CAD/CAM-milled, then sintered and afterwards manually adapted. In order to stabilize the gold copings, they were fixed in a tertiary structure. The secondary crowns were constructed with a hook, which ensured self-alignment with an upper chain. Afterwards, 20 pull-off test cycles were performed in a universal testing machine under artificial saliva and after weighing the secondary crowns with a 5 kg object for 20 s. Data were analyzed by one-way and two-way Analysis of Variance (ANOVA. C/Z with 1° showed higher (p = 0.009 RL than 0° and 2° tapers. C/G at 1° also showed higher (p = 0.001 RL than at tapers of 0° and 2°. Z/G and C/G at 0° showed lower RL than Z/Z and C/Z (p < 0.001. Primary crowns had no impact on the 0° group. Z/G showed lower RL as compared to C/Z within the 1° group (p = 0.007 and Z/Z in the 2° group (p = 0.006. The primary crown material had no influence on RL. Electroformed copings showed lower RL. Further investigations for 1° as well as for the long-term performance after thermomechanical aging are necessary.

Alumina reinforced tetragonal zirconia (TZP) composites. Final technical report, July 1, 1993--December 31, 1996

International Nuclear Information System (INIS)

Shetty, D.K.

1997-01-01

This final technical report summarizes the significant research results obtained during the period July 1, 1993 through December 31, 1996 in the DOE-supported research project entitled, open-quotes Alumina Reinforced Tetragonal Zirconia (TZP) Compositesclose quotes. The objective of the research was to develop high-strength and high-toughness ceramic composites by combining mechanisms of platelet, whisker or fiber reinforcement with transformation toughening. The approach used included reinforcement of Celia- or yttria-partially-stabilized zirconia (Ce-TZP or Y-TZP) with particulates, platelets, or continuous filaments of alumina

Zirconia toughened ceramics for heat engine applications

International Nuclear Information System (INIS)

Rossi, G.A.; Blum, J.B.; Manwiller, K.E.; Knapp, C.E.

1986-01-01

Three classes of zirconia toughened ceramics (ZTC) were studied, i.e. Mg-PSZ (MgO-partially stabilized zirconia), Y-TZP (Y/sub 2/O/sub 3/-tetragonal zirconia polycrystals) and ZTA (zirconia toughened alumina). The main objective was to improve the high temperature strength and toughness, which are not satisfactory in the ''state of the art'' ZTC materials. Powders prepared by melting/rapid solidification and by chemical routes were used. The green parts were made by both dry and wet shape forming methods. Fine grained Mg-PSZ ceramics with unique microstructures were produced using the rapidly solidified powders. The Y-TZP materials were improved mainly through microstructure control and by addition of alpha alumina as a dispersed phase. Preliminary results on ZTA ceramics made with the rapidly solidified powders were also obtained. It is concluded that the Al/sub 2/O/sub 3//Y-TZP composites offer a good chance of meeting the program objectives

Dynamic grain growth in superplastic Y-TZP and Al2O3/YTZ

International Nuclear Information System (INIS)

Nieh, T.G.; Tomasello, C.M.; Wadsworth, J.

1990-01-01

This paper reports that both static and dynamic grain growth have been studied during superplastic deformation of fine-grained yttria-stabilized tetragonal zirconia (Y-TZP) and alumina reinforced yttria-stabilized tetragonal zirconia (Al 2 O 3 /YTZ). Grain growth was observed in both materials at temperatures above 1350 degrees C. In the case of Y-TZP, both static and dynamic grain growth were found to obey a similar equation of the form: D 3 -D 0 3 = kt where D is the instantaneous grain size, D 0 is the initial grain size, t is the time, and k is a kinetic constant which depends primarily on temperature and grain boundary energy. The activation energies for Y-TZP were approximately 580 and 520 kJ/mol, for static and dynamic grain growth, respectively. In the case of Al 2 O 3 /YTZ, it was found that the grain growth rate for the Al 2 O 3 phase was slower than that for the ZrO 2 phase. The growth rate of the ZrO 2 phase in Al 2 O 3 /YTZ is, however, similar to that in monolithic ZrO 2 i.e., Y-TZP

A wear-resistant zirconia ceramic for low friction application

International Nuclear Information System (INIS)

Winnubst, A.J.A.; Ran, S.; Wiratha, K.W.; Blank, D.H.A.; Pasaribu, H.R.; Sloetjes, J.W.; Schipper, D.J.

2004-01-01

A high wear-resistant ceramic/ceramic couple is described associated with low friction. By adding a small amount CuO to yttria-doped tetragonal zirconia (Y-TZP) the (dry) coefficient of friction against alumina is only 0.2 during a sliding distance of 3-5 km after which the coefficient drastically increases and a transition from mild to sever wear occurs. Pure Y-TZP exhibits a coefficient of friction of 0.7 under the same experimental conditions but wear remains mild during the test (upto 10 km of sliding distance). These small amounts of CuO also strongly influence the densification behaviour. Sintering of this system occurs in several steps where among other things dissolution of CuO in the Y-TZP matrix as well as liquid phase sintering takes place. Non-uniform shrinkage of the CuO-doped system resulting in relative large microcracks in the ceramic can explain its sudden drastic increase in coefficient of friction and wear rate after 3-5 km of operation. (orig.)

Effect of ceramic thickness, grinding, and aging on the mechanical behavior of a polycrystalline zirconia.

Science.gov (United States)

Prado, Rodrigo Diniz; Pereira, Gabriel Kalil Rocha; Bottino, Marco Antonio; Melo, Renata Marques de; Valandro, Luiz Felipe

2017-11-06

Monolithic restorations of Y-TZP have been recommended as a restorative alternative on prosthetic dentistry as it allows a substantial reduction of ceramic thickness, which means a greater preservation of tooth structure. However, the influence of grinding and aging when using a thinner layer of the material is unclear. This investigation aimed to evaluate and compare the effects of ceramic thickness (0.5 mm and 1.0 mm), grinding and aging (low-temperature degradation) on the mechanical behavior and surface characteristics of a full-contour Y-TZP ceramic. Y-TZP disc-shaped specimens (15 mm diameter) were manufactured with both thicknesses and randomly assigned into 4 groups considering the factors 'grinding with diamond bur' and 'aging in autoclave'. Surface topography (roughness, 3D profilometry and SEM), phase transformation, flexural strength and structural reliability (Weibull) analyses were executed. Grinding affected the surface topography, while aging did not promote any effect. An increase in m-phase content was observed after grinding and aging, although different susceptibilities were observed. Regardless of zirconia's thickness, no deleterious effect of grinding or aging on the mechanical properties was observed. Thus, in our testing assembly, reducing the thickness of the Y-TZP ceramic did not alter its response to grinding and low temperature degradation and did not impair its mechanical performance.

Properties and clinical application of zirconia bioceramics in medicine

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Čedomir Oblak

2014-01-01

Full Text Available Background: A group of inorganic non-metal biomaterials, that are commonly used in clinical medicine to replace or repair tissues, can be classified as a bioceramics. This group includes bioactive glasses, glass-ceramics, hydroxy-apatite and some other calcium phosphates. In addition, some bio-inert engineering ceramics materials have become increasingly utilised, aluminum oxide, zirconium oxide and their composites being the most popular. With the developement of yttria stabilized tetragonal zirconium oxide ceramics (Y-TZP medical community received a high strength biomaterial that is currently a material of choice for the manufacturing of medical devices. Y-TZP ceramics is becoming also increasingly used in dental medicine, where frameworks are manufactured by the use of computer-assisted technology.Conclusions: The article describes the basic properties of zirconia oxide ceramics important for the use in clinical medicine; high strength and fracture toughness, biocompatibility and negligible radiation. The ageing issue of this particular material, which is attributable to the thermo-dynamical instability of tetragonal zirconium oxide in hydrothermal conditions, is also discussed. When exposed to an aqueous environment over long periods of time, the surface of the Y-TZP ceramic will start transforming spontaneously into the monoclinic structure. The mechanism leading to the t-m transformation is temperature-dependent and is accompanied by extensive micro-cracking, which ultimately leads to strength degradation. The degradation might influence the clinical success rate of medical devices and therefore Y-TZP femoral heads are no longer made of pure zirconium oxide. Composites of zirconium and aluminium oxides are used instead, that are currently the strongest ceramic materials used in clinical medicine. In this work the clinical application of zirconia oxide ceramics in dental medicine is also presented. Conventional porcelain fused to metal

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

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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.

Effect of ceramic thickness, grinding, and aging on the mechanical behavior of a polycrystalline zirconia

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Rodrigo Diniz PRADO

2017-11-01

Full Text Available Abstract Monolithic restorations of Y-TZP have been recommended as a restorative alternative on prosthetic dentistry as it allows a substantial reduction of ceramic thickness, which means a greater preservation of tooth structure. However, the influence of grinding and aging when using a thinner layer of the material is unclear. This investigation aimed to evaluate and compare the effects of ceramic thickness (0.5 mm and 1.0 mm, grinding and aging (low-temperature degradation on the mechanical behavior and surface characteristics of a full-contour Y-TZP ceramic. Y-TZP disc-shaped specimens (15 mm diameter were manufactured with both thicknesses and randomly assigned into 4 groups considering the factors ‘grinding with diamond bur’ and ‘aging in autoclave’. Surface topography (roughness, 3D profilometry and SEM, phase transformation, flexural strength and structural reliability (Weibull analyses were executed. Grinding affected the surface topography, while aging did not promote any effect. An increase in m-phase content was observed after grinding and aging, although different susceptibilities were observed. Regardless of zirconia’s thickness, no deleterious effect of grinding or aging on the mechanical properties was observed. Thus, in our testing assembly, reducing the thickness of the Y-TZP ceramic did not alter its response to grinding and low temperature degradation and did not impair its mechanical performance.

Crystal orientation mapping applied to the Y-TZP/WC composite

CERN Document Server

Faryna, M; Sztwiertnia, K

2002-01-01

Crystal orientation measurements made by electron backscattered diffraction (EBSD) in the scanning electron microscope (SEM) and microscopic observations provided the basis for a quantitative investigation of microstructure in an yttria stabilized, tetragonal zirconia-based (Y-TZP) composite. Automatic crystal orientation mapping (ACOM) in a SEM can be preferable to transmission electron microscopy (TEM) for microstructural characterization, since no sample thinning is required, extensive crystal data is already available, and the analysis area is greatly increased. A composite with a 20 vol.% tungsten carbide (WC) content was chosen since it revealed crystal relationships between the matrix and carbide phase already established by TEM analysis. However, this composite was difficult to investigate in the EBSD/ SEM since it is non-conductive, the Y-TZP grain size is of the order of the system resolution, and the sample surface, though carefully prepared, reveals a distinctive microtopography. In this paper, so...

Improving bioactivity of inert bioceramics by a novel Mg-incorporated solution treatment

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Dehestani, Mahdi; Zemlyanov, Dmitry; Adolfsson, Erik; Stanciu, Lia A.

2017-12-01

Zirconia/alumina ceramics possess outstanding mechanical properties for dental and orthopedic applications, but due to their poor surface bioactivities they exhibit a weak bone-bonding ability. This work proposes an effective 30-min solution treatment which could successfully induce formation of bone-like apatite on the surface of 3Y-TZP and a ternary composite composed of yttria-stabilized zirconia, ceria-stabilized zirconia, and alumina (35 vol% 3Y-TZP + 35 vol% 12Ce-TZP + 30 vol% Al2O3) after 3 weeks immersion in simulated body fluid (SBF). XRD was used for phase identification in the ceramic materials. The influence of solution treatment on the surface chemistry and its role on apatite formation were investigated via SEM, EDS and XPS. In vitro apatite-forming ability for the solution-treated and untreated samples of the composite and individual substrates of 3Y-TZP, 12Ce-TZP, and Al2O3 was evaluated by immersion in SBF. Apatite crystals were formed only on 3Y-TZP and composite substrates, implying that it is mainly the 3Y-TZP constituent that contributes to the bioactivity of the composite. Further, it was found from the XPS analysis that the zirconia material with higher phase stability (12Ce-TZP) produced less Zrsbnd OH functional groups on its surface after solution treatment which accounts for its weaker bioactivity compared to 3Y-TZP.

Mechanical characterization of the 3Y-TZP co-doped with yttria and niobia Equimolar addition

International Nuclear Information System (INIS)

Assis, Joao Marcos Kruszynski de; Nono, Maria do Carmo de Andrade; Dorat, Daniele Ramos; Fonseca, Flavia Baccaro; Reis, Danieli Aparecida

2010-01-01

The main goal of this work is to study the effect of the yttria and niobia equimolar addition in the 3Y-TZP on the mechanical properties (hardness, fracture toughness and four point bending strength) aiming to get a stable tetragonal phase (t´) under applied stress, to use as TBC´s. Four compositions with equimolar addition of yttria and niobia in the 3Y-TZP were produced, 13%, 14.5%, 16% and 17.5%. The mixtures were prepared in high energy ball milling for 10 minutes and the samples prepared on uniaxial and isostatic pressing. The selected temperature sintering was 1.550 deg C for 1 hour. Analyses of X-Ray Diffraction, hardness, fracture toughness and four point bending strength were performed. An increase on the mechanical properties analyzed was expected with yttria and niobia addition in comparison to 3Y-TZP, but instead a decrease was observed after these additions. (author)

The effect of continuous application of MDP-containing primer and luting resin cement on bond strength to tribochemical silica-coated Y-TZP.

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Lim, Myung-Jin; Yu, Mi-Kyung; Lee, Kwang-Won

2018-05-01

This study investigated the effect of continuous application of 10-methacryloyloxydecyldihydrogen phosphate (MDP)-containing primer and luting resin cement on bond strength to tribochemical silica-coated yttria-stabilized tetragonal zirconia polycrystal (Y-TZP). Forty bovine teeth and Y-TZP specimens were prepared. The dentin specimens were embedded in molds, with one side of the dentin exposed for cementation with the zirconia specimen. The Y-TZP specimen was prepared in the form of a cylinder with a diameter of 3 mm and a height of 10 mm. The bonding surface of the Y-TZP specimen was sandblasted with silica-coated aluminium oxide particles. The forty tribochemical silica-coated Y-TZP specimens were cemented to the bovine dentin (4 groups; n = 10) with either an MDP-free primer or an MDP-containing primer and either an MDP-free resin cement or an MDP-containing resin cement. After a shear bond strength (SBS) test, the data were analyzed using 1-way analysis of variance and the Tukey test (α = 0.05). The group with MDP-free primer and resin cement showed significantly lower SBS values than the MDP-containing groups ( p Y-TZP was the best choice among the alternatives tested in this study.

Superplastic characteristics and microstructure of neutron irradiated 3Y-TZP

International Nuclear Information System (INIS)

Shibata, Taiju; Motohashi, Yoshinobu; Ishihara, Masahiro; Baba, Shinichi; Sawa, Kazuhiro

2006-01-01

Fast neutrons (energy > 1.6 x 10 -13 J) were irradiated to 3Y-TZP specimens, typical superplastic ceramics, at the fluence of 2.5 x 10 24 and 4.3 x 10 24 m -2 at JMTR of JAEA. The Vickers hardness with indentation load of 4.9 and 9.8 N at room temperature was seemed to be slightly increased by the irradiation. Through the superplastic tensile tests in a temperature range from 1623 to 1773 K with initial strain rates of 5.0 x 10 -4 and 1.0 x 10 -3 s -1 , it was found that the superplastic flow stress is decreased with increasing the neutron fluence. The microstructural features of the fractured specimens were observed by a SEM. It implies that the grain boundary microstructure of the irradiated specimens would be changed by annealing in the superplastic tests are elevated temperatures. It is quite probable that the irradiation-induced vacancy clusters might play an important role to weaken the grain boundary cohesion which may be an important factor to determine the superplastic properties, and hence they would decrease the superplastic flow stress. (author)

Injection molding of Y-TZP powders prepared by colloidal processing

International Nuclear Information System (INIS)

Kimura, Y.; Mineshita, O.; Kaga, T.; Tokinaga, T.; Obitsu, M.

1991-01-01

TZP powders containing 3mol% Y 2 O 3 were prepared from ZrOCl 2 solution via an aqueous colloidal suspension of ZrO 2 . Processing variables were optimized to obtain powders suitable for injection molding. Wettability of powders with binders, fluidity of melting compound, removal of binder from green body, and properties of sintered body were investigated

Effect of Grinding and Resintering on the Fatigue Limit and Surface Characterization of a Y-TZP Ceramic.

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Polli, Gabriela Scatimburgo; Hatanaka, Gabriel Rodrigues; Abi-Rached, Filipe de Oliveira; Pinelli, Lígia Antunes Pereira; Góes, Márcio de Sousa; Cesar, Paulo Francisco; Reis, José Maurício Dos Santos Nunes

2016-01-01

This study evaluated the effect of grinding protocols and resintering on flexural fatigue limit and surface characterization of LavaTM Y-TZP. Bar-shaped specimens (20×4.0×1.2 mm, n=40; 20×4.0×1.5 mm, n=80) were obtained. Half of the thinner specimens (1.2 mm) constituted the as-sintered group (AS), while the thicker ones (1.5 mm) were ground with diamond burs under irrigation (WG) or not (G). The other half of thinner and half of ground specimens were resintered (1000 ºC, 30 min), forming the groups ASR, WGR and GR. Fatigue limit (500,000 cycles, 10 Hz) was evaluated by staircase method in a 4-point flexural fixture. Data were analyzed by 2-way ANOVA and Tukey's test (α=0.05). Surface topography (n=3) and fracture area (n=3) were evaluated by SEM. X-ray diffraction data (n=1) was analyzed by Rietveld refinement. ANOVA revealed significant differences (pgrinding protocol, resintering and their interaction. Grinding increased the fatigue limit of non-resintered groups. There was no significant difference among the resintered groups. Resintering significantly increased the fatigue limit of the AS group only. Both protocols created evident grooves on zirconia surface. The failures initiated at the tensile side of all specimens. The percentages (wt%) of monoclinic phase were AS (8.6), ASR (1.2), G (1.8), GR (0.0), WG (8.2), WGR (0.0) before, and AS (7.4), ASR (6.5), G (3.2), GR (0.2), WG (4.6), WGR (1.1) after cyclic loading. Grinding increased the fatigue limit of non-resintered Y-TZP and formed evident grooves on its surface. Resintering provided significant increase in the fatigue limit of as-sintered specimens. In general, grinding and resintering decreased or zeroed the monoclinic phase.

Sinterização e propriedades mecânicas do compósito Y-TZP/Al2O3 Sintering and mechanical properties of the Y-TZP/Al2O3 composites

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L. H. P. Teixeira

2007-09-01

Full Text Available Foi estudado o efeito da adição de Al2O3 nas propriedades de cerâmicas à base de ZrO2 tetragonal estabilizada com ítria (Y-TZP visando sua aplicação como material dentário. Amostras contendo 0, 10, 20 e 30% em peso de Al2O3 foram compactadas por prensagem uniaxial a frio (80 MPa e em seguida sinterizadas ao ar a 1500, 1550 e 1600 °C por 120 min. Os efeitos destas condições de sinterização nas propriedades dos materiais foram analisados por difração de raios X e microscopia eletrônica de varredura. As propriedades mecânicas de dureza e tenacidade à fratura foram determinadas, utilizando-se o método de indentação Vickers. Além disso, algumas amostras foram submetidas a ensaio de flexão em 4 pontos. Cerâmicas de elevada densidade relativa foram obtidas, com dureza variando entre 13,4 e 15,8 GPa, dependendo da quantidade de Al2O3 adicionada à matriz de ZrO2. Por outro lado, não foi verificada uma influencia significativa da adição de Al2O3 na tenacidade à fratura, que apresentou valores próximos de 8 MPa.m½, em quase todas as situações. A boa dureza, a elevada tenacidade à fratura, a boa resistência à fratura (sigmaf = 685 MPa e o módulo de Weibull (m=11 apresentados pelos materiais com adições de 20% de Al2O3, indicam a confiabilidade do compósito como um potencial biomaterial para uso na implantodontia.In this work, the influence of Al2O3 addition on the tetragonal ZrO2 ceramic properties was studied, aiming the use of this ceramic as dental materials. Samples containing 0, 10, 20 e 30 wt.% were cold pressed (80 MPa, and sintered in air, at 1500, 1550 e 1600 °C, for 120 min. The effects of the sintering conditions were analyzed by X-ray diffraction and Scanning Electron Microscopy. Hardness and fracture toughness were determined by Vicker's indentation method. Furthermore, samples were submitted to the 4 point bending test. Dense ceramics were obtained, with hardness values varying around 13.4 and 15.8 GPa

Fatigue of dental ceramics.

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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.

A comparison of the tribological behaviour of Y-TZP in tea and coffee under micro-abrasion conditions

International Nuclear Information System (INIS)

Sharifi, S; Stack, M M

2013-01-01

The micro-abrasion of Y-TZP, a candidate dental restorative material, was investigated in a range of caffeine-containing solutions which included tea and coffee. Additions of sugar and milk were used to test the effects of viscosity and pH on the wear rate. The results indicated a significant increase in wear rate in the various solutions, with some correlation between wear rate and increases in viscosity and this was linked to enhance particle entrainment in the more viscous solutions. The generally lower wear rate in tea compared to coffee was associated with a longer ageing period in this solution before uniform wear was observed. Micro-abrasion maps were used to characterize the differences in performance for the material in the environments studied. (paper)

A comparison of the tribological behaviour of Y-TZP in tea and coffee under micro-abrasion conditions

Science.gov (United States)

Sharifi, S.; Stack, M. M.

2013-10-01

The micro-abrasion of Y-TZP, a candidate dental restorative material, was investigated in a range of caffeine-containing solutions which included tea and coffee. Additions of sugar and milk were used to test the effects of viscosity and pH on the wear rate. The results indicated a significant increase in wear rate in the various solutions, with some correlation between wear rate and increases in viscosity and this was linked to enhance particle entrainment in the more viscous solutions. The generally lower wear rate in tea compared to coffee was associated with a longer ageing period in this solution before uniform wear was observed. Micro-abrasion maps were used to characterize the differences in performance for the material in the environments studied.

Surface roughness and hardness of yttria stabilized zirconia (Y-TZP after 10 years of simulated brushing

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Lucas Miguel Candido

Full Text Available Introduction: The Y-TZP zirconia used for prosthetic infrastructure, in some clinical situations, can be exposed to the oral environment. In these situations, a polished surface without changes is extremely important. Objective: The aim of this study was to evaluate the mean roughness (Ra and Vickers hardness of Y-TZP zirconia (Lava™ after simulating ten years of brushing. Material and method: Thirty-six Y-TZP bar-shaped specimens (20mm X 4mm X 1.2mm were divided into three groups: storage in distilled water (DW, n=12, control; brushing with distilled water (BDW, n=12 and brushing with distilled water and fluoride toothpaste (BFT, n=12. Brushing was performed using a brushing machine with a soft-bristled toothbrush, simulating 10 years of brushing (878.400 cycles, 100gf. The mean roughness (Ra in μm and Vickers hardness (VHN of all specimens were measured twice: before and after the experimental treatment, in profilometer and microhardness tester (500gf, 30 seconds, respectively. Data were analyzed using the two-way ANOVA test (α = 0.05. Result: The interaction between groups was not significant for roughness (p = 0.701 nor for hardness (p = 0.928. The final averages for Ra (μm were equal to: DW - 0.63; BDW - 0.64; and, BFT - 0.68. The final averages for Vickers hardness (VHN were: DW - 1301.16; BDW - 1316.60; and, BFT - 1299.58. Conclusion: It was concluded that the brushing with distilled or fluoridated toothpaste was not able to change the roughness and hardness of Y-TZP zirconia used in this study.

3Y-TZP/Si2N2O composite obtained by pressureless sintering

International Nuclear Information System (INIS)

Santos, Carlos Augusto Xavier

2006-01-01

Zirconia 3YTZP presents excellent properties at room temperature. These properties decrease as the temperature increases because high temperature acts negatively over the stress induced transformation toughening in the matrix. The addition of Si 3 N 4 and SiC in a Y-TZP matrix is very interesting because leads to formation of silicon oxynitride and it increases the mechanical properties like toughness and hardness. Certainly the mechanical properties increment is limited by several difficulties which have appeared during processing and heating of these materials. This paper studies the Y-TZP/Si 2 N 2 0 pressureless sintered composite, under different temperatures, showing the behavior of 20 vol %Si 3 N 4 -SiC when added in YTZP matrix and heated under no pressure system. Al 2 O 3 and Y 2 O 3 were used as sintering aids. The mixture was milled and molded by cold isostatic pressure. Samples were heated at 1500 deg, 1600 deg and 17000 deg C x 2h without pressure under atmospheric conditions using Si 3 N 4 bed-powder. Samples were characterized by XRD and density, hardness, toughness, bending strength were measured. The structure of the material was observed in SEMITEM/EPMA to verify the distribution and composition of the materials in the composite and the contact between filler surface and the matrix. The formation of SiON 2 was observed in the sintered material due to reaction between both nitride and carbide with Y - TZP matrix. Furthermore the material showed an increment of both hardness and toughness as temperature increases. The samples presented considerable resistance to oxidation below 1000 deg C. (author)

Bioactive and inert dental glass-ceramics.

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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.

Fatigue limit of polycrystalline zirconium oxide ceramics: effect of grinding and low-temperature aging

NARCIS (Netherlands)

Pereira, G.K.R.; Silvestri, T.; Amaral, M.; Rippe, M.P.; Kleverlaan, C.J.; Valandro, L.F.

2016-01-01

The following study aimed to evaluate the effect of grinding and low-temperature aging on the fatigue limit of Y-TZP ceramics for frameworks and monolithic restorations. Disc specimens from each ceramic material, Lava Frame (3M ESPE) and Zirlux FC (Ivoclar Vivadent) were manufactured according to

Synthesis and crystallization behavior of 3 mol% yttria stabilized tetragonal zirconia polycrystals (3Y-TZP) nanosized powders prepared using a simple co-precipitation process

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Hsu, Yu-Wei [Graduate Institute of Applied Science, National Kaohsiung University of Applied Sciences, 415 Chien-Kung Road, Kaohsiung 80782, Taiwan (China); Yang, Ko-Ho, E-mail: yangkoho@cc.kuas.edu.tw [Graduate Institute of Applied Science, National Kaohsiung University of Applied Sciences, 415 Chien-Kung Road, Kaohsiung 80782, Taiwan (China); Department of Mold and Die Engineering, National Kaohsiung University of Applied Sciences, 415 Chien-Kung Road, Kaohsiung 80782, Taiwan (China); Chang, Kuo-Ming [Department of Mechanical Engineering, National Kaohsiung University of Applied Sciences, 415 Chien-Kung Road, Kaohsiung 80782, Taiwan (China); Dental Materials Research Center, National Kaohsiung University of Applied Sciences, 415 Chien-Kung Road, Kaohsiung 80782, Taiwan (China); Yeh, Sung-Wei [Metal Industries Research and Development Centre, 1001 Kaohsiung Highway, Kaohsiung 811, Taiwan (China); Wang, Moo-Chin, E-mail: mcwang@kmu.edu.tw [Department of Fragrance and Cosmetics Science, Kaohsiung Medical University, 100, Shihchuan 1st Road, Kaohsiung 80728, Taiwan (China)

2011-06-16

Highlights: > The thermal behavior of 3Y-TZP precursor powders had been investigated. > The crystallization behavior of 3Y-TZP nanopowders had been investigated. > The activation energy for crystallization of tetragonal ZrO{sub 2} was obtained. > The growth morphology parameter n is approximated as 2.0. > The crystallites show a plate-like morphology. - Abstract: The synthesis and crystallization behavior of 3 mol% yttria stabilized tetragonal zirconia polycrystals (3Y-TZP) nanopowders prepared using a simple co-precipitation process at 348 K and pH = 7 were investigated using differential scanning calorimetry/thermogravimetry (DSC/TG), an X-ray diffractometer (XRD), the Raman spectra, transmission electron microscopy (TEM), selected area electron diffraction (SAED), and an energy dispersive spectrometer (EDS). The activation energy of tetragonal ZrO{sub 2} crystallization from 3Y-TZP freeze-dried precursor powders using a non-isothermal method, namely, 169.2 {+-} 21.9 kJ mol{sup -1}, was obtained. The growth morphology parameter n was approximated as 2.0, which indicated that it had a plate-like morphology. The XRD, Raman spectra, and SAED patterns showed that the phase of the tetragonal ZrO{sub 2} was maintained at 1273 K. The crystallite size of 3Y-TZP freeze-dried precursor powders calcined at 1273 K for 5 min was 21.3 nm.

Synthesis and crystallization behavior of 3 mol% yttria stabilized tetragonal zirconia polycrystals (3Y-TZP) nanosized powders prepared using a simple co-precipitation process

International Nuclear Information System (INIS)

Hsu, Yu-Wei; Yang, Ko-Ho; Chang, Kuo-Ming; Yeh, Sung-Wei; Wang, Moo-Chin

2011-01-01

Highlights: → The thermal behavior of 3Y-TZP precursor powders had been investigated. → The crystallization behavior of 3Y-TZP nanopowders had been investigated. → The activation energy for crystallization of tetragonal ZrO 2 was obtained. → The growth morphology parameter n is approximated as 2.0. → The crystallites show a plate-like morphology. - Abstract: The synthesis and crystallization behavior of 3 mol% yttria stabilized tetragonal zirconia polycrystals (3Y-TZP) nanopowders prepared using a simple co-precipitation process at 348 K and pH = 7 were investigated using differential scanning calorimetry/thermogravimetry (DSC/TG), an X-ray diffractometer (XRD), the Raman spectra, transmission electron microscopy (TEM), selected area electron diffraction (SAED), and an energy dispersive spectrometer (EDS). The activation energy of tetragonal ZrO 2 crystallization from 3Y-TZP freeze-dried precursor powders using a non-isothermal method, namely, 169.2 ± 21.9 kJ mol -1 , was obtained. The growth morphology parameter n was approximated as 2.0, which indicated that it had a plate-like morphology. The XRD, Raman spectra, and SAED patterns showed that the phase of the tetragonal ZrO 2 was maintained at 1273 K. The crystallite size of 3Y-TZP freeze-dried precursor powders calcined at 1273 K for 5 min was 21.3 nm.

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.

Microbial adhesion on novel yttria-stabilized tetragonal zirconia (Y-TZP) implant surfaces with nitrogen-doped hydrogenated amorphous carbon (a-C:H:N) coatings.

Science.gov (United States)

Schienle, Stefanie; Al-Ahmad, Ali; Kohal, Ralf Joachim; Bernsmann, Falk; Adolfsson, Erik; Montanaro, Laura; Palmero, Paola; Fürderer, Tobias; Chevalier, Jérôme; Hellwig, Elmar; Karygianni, Lamprini

2016-09-01

Biomaterial surfaces are at high risk for initial microbial colonization, persistence, and concomitant infection. The rationale of this study was to assess the initial adhesion on novel implant surfaces of Enterococcus faecalis, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Candida albicans upon incubation. The tested samples were 3 mol% yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP) samples with nitrogen-doped hydrogenated amorphous carbon (a-C:H:N) coating (A) and 3Y-TZP samples coated with ceria-stabilized zirconia-based (Ce-TZP) composite and a-C:H:N (B). Uncoated 3Y-TZP samples (C) and bovine enamel slabs (BES) served as controls. Once the surface was characterized, the adherent microorganisms were quantified by estimating the colony-forming units (CFUs). Microbial vitality was assessed by live/dead staining, and microbial-biomaterial surface topography was visualized by scanning electron microscopy (SEM). Overall, A and B presented the lowest CFU values for all microorganisms, while C sheltered significantly less E. faecalis, P. aeruginosa, and C. albicans than BES. Compared to the controls, B demonstrated the lowest vitality values for E. coli (54.12 %) and C. albicans (67.99 %). Interestingly, A (29.24 %) exhibited higher eradication rates for S. aureus than B (13.95 %). Within the limitations of this study, a-C:H:N-coated 3Y-TZP surfaces tended to harbor less initially adherent microorganisms and selectively interfered with their vitality. This could enable further investigation of the new multi-functional zirconia surfaces to confirm their favorable antimicrobial properties in vivo.

Synthesis and characterisation of dual-phase Y-TZP and RuO2 nanopowders: dense electrode precursors.

NARCIS (Netherlands)

van Zyl, W.E.; Winnubst, Aloysius J.A.; Raming, T.P.; Schmuhl, R.; Verweij, H.

2002-01-01

The synthesis and characterisation of nanopowders in the dual-phase system tetragonal-Y2O3-doped ZrO2 (Y-TZP) and RuO2 are described. Five powders were prepared from a co-precipitation (CP) method with stoichiometric variation in the RuO2 content (5–46 mol%) and two powders were prepared from

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.

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.

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.

[Influence of compaction pressure and pre-sintering temperature on the machinability of zirconia ceramic].

Science.gov (United States)

Huang, Huil; Li, Jing; Zhang, Fuqiang; Sun, Jing; Gao, Lian

2011-10-01

In order to make certain the compaction pressure as well as pre-sintering temperature on the machinability of the zirconia ceramic. 3 mol nano-size 3 mol yttria partially stabilized zirconia (3Y-TZP) powder were compacted at different isostatic pressure and sintered at different temperature. The cylindrical surface was traversed using a hard metal tool. Surface and edge quality were checked visually using light stereo microscopy. Pre-sintering temperature had the obviously influence on the machinability of 3Y-TZP. The cutting surface was smooth, and the integrality of edge was better when the pre-sintering temperature was chosen between 800 degrees C to 900 degrees C. Compaction pressure showed only a weak influence on machinability of 3Y-TZP blanks, but the higher compaction pressure result in the poor surface quality. The best machinability of pre-sintered zirconia body was found for 800-900 degrees C pre-sintering temperature, and 200-300 MPa compaction pressure.

The role of powder preparation method in enhancing fracture toughness of zirconia ceramics with low alumina amount

International Nuclear Information System (INIS)

Danilenko, I.; Konstantinova, T.; Volkova, G.; Burkhovetski, V.; Glazunova, V.

2015-01-01

In most cases zirconia-alumina composites for scientific investigations and industry are prepared by means of mechanical mixing of powders, compaction and sintering. In our opinion, this is one of the reasons for the low values for fracture toughness of the sintered materials. In this study, we investigated the effect of nanopowder synthesis methods on the structure and mechanical properties of 3Y-TZP/alumina ceramic composites and determined the mechanisms involved in composite toughening. We show that the addition of a small amount of alumina (1 - 2 wt%) to zirconia ceramics has the potential to increase the fracture toughness of zirconia ceramics. The starting powders were obtained by means of co-precipitation and ball milling. It turned out that at equal density, bending strength and hardness values, the fracture toughness in ceramic composites sintered from co-precipitated nanopowders is higher in comparison with fracture toughness values in matrix material and traditional 3Y-TZP/alumina composites. We believed that the role of the crack deflection process in ceramic composites sintered from co-precipitated nanopowders increased significantly. This can be conditioned by means of a series of processes for composite structure formation during precipitation, crystallization, and sintering of nanopowders.

The role of powder preparation method in enhancing fracture toughness of zirconia ceramics with low alumina amount

Energy Technology Data Exchange (ETDEWEB)

Danilenko, I.; Konstantinova, T.; Volkova, G.; Burkhovetski, V.; Glazunova, V. [NAS of Ukraine, Donetsk (Ukraine). Donetsk Inst. for Physics and Engineering

2015-07-01

In most cases zirconia-alumina composites for scientific investigations and industry are prepared by means of mechanical mixing of powders, compaction and sintering. In our opinion, this is one of the reasons for the low values for fracture toughness of the sintered materials. In this study, we investigated the effect of nanopowder synthesis methods on the structure and mechanical properties of 3Y-TZP/alumina ceramic composites and determined the mechanisms involved in composite toughening. We show that the addition of a small amount of alumina (1 - 2 wt%) to zirconia ceramics has the potential to increase the fracture toughness of zirconia ceramics. The starting powders were obtained by means of co-precipitation and ball milling. It turned out that at equal density, bending strength and hardness values, the fracture toughness in ceramic composites sintered from co-precipitated nanopowders is higher in comparison with fracture toughness values in matrix material and traditional 3Y-TZP/alumina composites. We believed that the role of the crack deflection process in ceramic composites sintered from co-precipitated nanopowders increased significantly. This can be conditioned by means of a series of processes for composite structure formation during precipitation, crystallization, and sintering of nanopowders.

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.

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.

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

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)

Experimental investigation on shrinkage and surface replication of injection moulded ceramic parts

DEFF Research Database (Denmark)

Islam, Aminul; Giannekas, Nikolaos; Marhöfer, David Maximilian

2014-01-01

Ceramic moulded parts are increasingly being used in advanced components and devices due to their unprecedented material and performance attributes. The surface finish, replication quality and material shrinkage are of immense importance for moulded ceramic parts intended for precision applications....... The current paper presents a thorough investigation on the process of ceramic moulding where it systematically characterizes the surface replication and shrinkage behaviours of precision moulded ceramic components. The test parts are moulded from Catamold TZP-A which is Y2O3-stabilised ZrO2 having widespread...... distribution for the moulded ceramic parts is presented....

Microstructural changes in ground 3Y-TZP and their effect on mechanical properties

Energy Technology Data Exchange (ETDEWEB)

Munoz-Tabares, J.A., E-mail: j.a.munoz.tabares@gmail.com [Departament de Ciencia dels Materials i Enginyeria Metallurgica, Universitat Politecnica de Catalunya, Avda. Diagonal 647 (ETSEIB), 08028 Barcelona (Spain); Jimenez-Pique, E. [Departament de Ciencia dels Materials i Enginyeria Metallurgica, Universitat Politecnica de Catalunya, Avda. Diagonal 647 (ETSEIB), 08028 Barcelona (Spain); Centre de Recerca en Nanoenginyeria (CRnE), C. Pascual i Vila 15, 08028 Barcelona (Spain); Reyes-Gasga, J. [Instituto de Fisica, Universidad Nacional Autonoma de Mexico, Circuito de la Investigacion Cientifica s/n, Cd Universitaria, 04510 Mexico DF (Mexico); Anglada, M. [Departament de Ciencia dels Materials i Enginyeria Metallurgica, Universitat Politecnica de Catalunya, Avda. Diagonal 647 (ETSEIB), 08028 Barcelona (Spain); Centre de Recerca en Nanoenginyeria (CRnE), C. Pascual i Vila 15, 08028 Barcelona (Spain)

2011-10-15

In the present work we studied the changes in the microstructure and mechanical properties that are produced by grinding of tetragonal polycrystalline zirconia doped with 3 mol.% yttria (3Y-TZP). It is shown that the X-ray diffraction spectrum of ground 3Y-TZP presents asymmetric broadening of the (1 1 1) tetragonal peak, reversal of the intensity of the (0 0 2) and (2 0 0) tetragonal peaks, and tetragonal to monoclinic (t-m) phase transformation. The in-depth monoclinic phase distribution obtained by micro-Raman spectroscopy has been related with the compression residual stresses profile generated during grinding. These compressive residual stresses are also responsible for the observed increase in mechanical properties (strength and apparent fracture toughness). The subsurface microstructure of ground specimens has been analyzed by transmission electron microscopy and three different regions were found from the interior to the surface: (1) a t-m phase transformation zone in the deeper region, (2) a plastically deformed zone, with dynamically recovered dislocation cells, and (3) a surface recrystallized zone with grains of {approx}20 nm in diameter, resulting from in situ recrystallization. In addition, microcracking is concentrated on the sides of the grinding grooves, corresponding to the zone of maximum tensile stress during contact with an abrasive particle.

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

Effect of Surface Treatment on Shear Bond Strength between Resin Cement and Ce-TZP/Al2O3

Directory of Open Access Journals (Sweden)

Jong-Eun Kim

2016-01-01

Full Text Available Purpose. Although several studies evaluating the mechanical properties of Ce-TZP/Al2O3 have been published, to date, no study has been published investigating the bonding protocol between Ce-TZP/Al2O3 and resin cement. The aim of this study was to evaluate the shear bond strength to air-abraded Ce-TZP/Al2O3 when primers and two different cement types were used. Materials and Methods. Two types of zirconia (Y-TZP and Ce-TZP/Al2O3 specimens were further divided into four subgroups according to primer application and the cement used. Shear bond strength was measured after water storage for 3 days or 5,000 times thermocycling for artificial aging. Results. The Y-TZP block showed significantly higher shear bond strength than the Ce-TZP/Al2O3 block generally. Primer application promoted high bond strength and less effect on bond strength reduction after thermocycling, regardless of the type of cement, zirconia block, or aging time. Conclusions. Depending on the type of the primer or resin cement used after air-abrasion, different wettability of the zirconia surface can be observed. Application of primer affected the values of shear bond strength after the thermocycling procedure. In the case of using the same bonding protocol, Y-TZP could obtain significantly higher bond strength compared with Ce-TZP/Al2O3.

Grinding damage assessment on four high-strength ceramics.

Science.gov (United States)

Canneto, Jean-Jacques; Cattani-Lorente, Maria; Durual, Stéphane; Wiskott, Anselm H W; Scherrer, Susanne S

2016-02-01

The purpose of this study was to assess surface and subsurface damage on 4 CAD-CAM high-strength ceramics after grinding with diamond disks of 75 μm, 54 μm and 18 μm and to estimate strength losses based on damage crack sizes. The materials tested were: 3Y-TZP (Lava), dense Al2O3 (In-Ceram AL), alumina glass-infiltrated (In-Ceram ALUMINA) and alumina-zirconia glass-infiltrated (In-Ceram ZIRCONIA). Rectangular specimens with 2 mirror polished orthogonal sides were bonded pairwise together prior to degrading the top polished surface with diamond disks of either 75 μm, 54 μm or 18 μm. The induced chip damage was evaluated on the bonded interface using SEM for chip depth measurements. Fracture mechanics were used to estimate fracture stresses based on average and maximum chip depths considering these as critical flaws subjected to tension and to calculate possible losses in strength compared to manufacturer's data. 3Y-TZP was hardly affected by grinding chip damage viewed on the bonded interface. Average chip depths were of 12.7±5.2 μm when grinding with 75 μm diamond inducing an estimated loss of 12% in strength compared to manufacturer's reported flexural strength values of 1100 MPa. Dense alumina showed elongated chip cracks and was suffering damage of an average chip depth of 48.2±16.3 μm after 75 μm grinding, representing an estimated loss in strength of 49%. Grinding with 54 μm was creating chips of 32.2±9.1 μm in average, representing a loss in strength of 23%. Alumina glass-infiltrated ceramic was exposed to chipping after 75 μm (mean chip size=62.4±19.3 μm) and 54 μm grinding (mean chip size=42.8±16.6 μm), with respectively 38% and 25% estimated loss in strength. Alumina-zirconia glass-infiltrated ceramic was mainly affected by 75 μm grinding damage with a chip average size of 56.8±15.1 μm, representing an estimated loss in strength of 34%. All four ceramics were not exposed to critical chipping at 18 μm diamond grinding. Reshaping a

Effect of adhesive luting on the fracture resistance of zirconia compared to that of composite resin and lithium disilicate glass ceramic

Directory of Open Access Journals (Sweden)

Myung-Jin Lim

2017-02-01

Full Text Available Objectives The purpose of this study was to evaluate the effect of adhesive luting on the fracture resistance of zirconia compared to that of a composite resin and a lithium disilicate glass ceramic. Materials and Methods The specimens (dimension: 2 mm × 2 mm × 25 mm of the composite resin, lithium disilicate glass ceramic, and yttria-stabilized tetragonal zirconia polycrystal (Y-TZP were prepared. These were then divided into nine groups: three non-luting groups, three non-adhesive luting groups, and three adhesive luting groups, for each restorative material. In the non-luting groups, specimens were placed on the bovine tooth without any luting agents. In the non-adhesive luting groups, only zinc phosphate cement was used for luting the specimen to the bovine tooth. In the adhesive luting groups, specimens were pretreated, and the adhesive luting procedure was performed using a self-adhesive resin cement. For all the groups, a flexural test was performed using universal testing machine, in which the fracture resistance was measured by recording the force at which the specimen was fractured. Results The fracture resistance after adhesive luting increased by approximately 29% in the case of the composite resin, 26% in the case of the lithium disilicate glass ceramic, and only 2% in the case of Y-TZP as compared to non-adhesive luting. Conclusions The fracture resistance of Y-TZP did not increased significantly after adhesive luting as compared to that of the composite resin and the lithium disilicate glass ceramic.

Phase transformation of dental zirconia following artificial aging.

Science.gov (United States)

Lucas, Thomas J; Lawson, Nathaniel C; Janowski, Gregg M; Burgess, John O

2015-10-01

Low-temperature degradation (LTD) of yttria-stabilized zirconia can produce increased surface roughness with a concomitant decrease in strength. This study determined the effectiveness of artificial aging (prolonged boiling/autoclaving) to induce LTD of Y-TZP (yttria-tetragonal zirconia-polycrystals) and used artificial aging for transformation depth progression analyses. The null hypothesis is aging techniques tested produce the same amount of transformation, transformation is not time/temperature dependent and LTD causes a constant transformation throughout the Y-TZP samples. Dental-grade Y-TZP samples were randomly divided into nine subgroups (n = 5): as received, 3.5 and 7 day boiling, 1 bar autoclave (1, 3, 5 h), and 2 bar autoclave (1, 3, 5 h). A 4-h boil treatment (n = 2) was performed post-experiment for completion of data. Transformation was measured using traditional X-ray diffraction and low-angle X-ray diffraction. The fraction of t → m transformation increased with aging time. The 3.5 day boil and 2 bar 5 h autoclave produced similar transformation results, while the 7 day boiling treatment revealed the greatest transformation. The surface layer of the aged specimen underwent the most transformation while all samples displayed decreasing transformation with depth. Surface transformation was evident, which can lead to rougher surfaces and increased wear of opposing dentition/materials. Therefore, wear studies addressing LTD of Y-TZP are needed utilizing accelerated aging. © 2014 Wiley Periodicals, Inc.

Grinding With Diamond Burs and Hydrothermal Aging of a Y-TZP Material: Effect on the Material Surface Characteristics and Bacterial Adhesion.

Science.gov (United States)

Dutra, Dam; Pereira, Gkr; Kantorski, K Z; Exterkate, Ram; Kleverlaan, C J; Valandro, L F; Zanatta, F B

The aim of this study was to evaluate the effect of grinding with diamond burs and low-temperature aging on the material surface characteristics and bacteria adhesion on a yttrium-stabilized tetragonal zirconia polycrystalline (Y-TZP) surface. Y-TZP specimens were made from presintered blocks, sintered as recommended by the manufacturer, and assigned into six groups according to two factors-grinding (three levels: as sintered, grinding with extra-fine diamond bur [25-μm grit], and grinding with coarse diamond bur [181-μm grit]) and hydrothermal aging-to promote low-temperature degradation (two levels: presence/absence). Phase transformation (X-ray diffractometer), surface roughness, micromorphological patterns (atomic force microscopy), and contact angle (goniometer) were analyzed. Bacterial adhesion (colony-forming units [CFU]/biofilm) was quantified using an in vitro polymicrobial biofilm model. Both the surface treatment and hydrothermal aging promoted an increase in m-phase content. Roughness values increased as a function of increasing bur grit sizes. Grinding with a coarse diamond bur resulted in significantly lower values of contact angle (p0.05). Grinding with diamond burs and hydrothermal aging modified the Y-TZP surface properties; however, these properties had no effect on the amount of bacteria adhesion on the material surface.

Low Friction in CuO-Doped Yttria-Stabilized Tetragonal Zirconia Ceramics: A Complementary Macro- and Nanotribology Study

NARCIS (Netherlands)

Tocha, E.; Pasaribu, H.R.; Schipper, Dirk J.; Schönherr, Holger; Vancso, Gyula J.

2008-01-01

The tribological behavior of CuO-doped yttria-stabilized tetragonal zirconia (3Y-TZP) ceramics in the absence of additional lubricants was characterized by macroscale pin-on-disk measurements and nanoscale atomic force microscopy (AFM) for a broad range of velocities. The previously observed low

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.

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.

Influence of core design, production technique, and material selection on fracture behavior of yttria-stabilized tetragonal zirconia polycrystal fixed dental prostheses produced using different multilayer techniques: split-file, over-pressing, and manually built-up veneers.

Science.gov (United States)

Mahmood, Deyar Jallal Hadi; Linderoth, Ewa H; Wennerberg, Ann; Vult Von Steyern, Per

2016-01-01

To investigate and compare the fracture strength and fracture mode in eleven groups of currently, the most commonly used multilayer three-unit all-ceramic yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) fixed dental prostheses (FDPs) with respect to the choice of core material, veneering material area, manufacturing technique, design of connectors, and radii of curvature of FDP cores. A total of 110 three-unit Y-TZP FDP cores with one intermediate pontic were made. The FDP cores in groups 1-7 were made with a split-file design, veneered with manually built-up porcelain, computer-aided design-on veneers, and over-pressed veneers. Groups 8-11 consisted of FDPs with a state-of-the-art design, veneered with manually built-up porcelain. All the FDP cores were subjected to simulated aging and finally loaded to fracture. There was a significant difference (Pdesigns, but not between the different types of Y-TZP materials. The split-file designs with VITABLOCS(®) (1,806±165 N) and e.max(®) ZirPress (1,854±115 N) and the state-of-the-art design with VITA VM(®) 9 (1,849±150 N) demonstrated the highest mean fracture values. The shape of a split-file designed all-ceramic reconstruction calls for a different dimension protocol, compared to traditionally shaped ones, as the split-file design leads to sharp approximal indentations acting as fractural impressions, thus decreasing the overall strength. The design of a framework is a crucial factor for the load bearing capacity of an all-ceramic FDP. The state-of-the-art design is preferable since the split-file designed cores call for a cross-sectional connector area at least 42% larger, to have the same load bearing capacity as the state-of-the-art designed cores. All veneering materials and techniques tested in the study, split-file, over-press, built-up porcelains, and glass-ceramics are, with a great safety margin, sufficient for clinical use both anteriorly and posteriorly. Analysis of the fracture pattern shows

Dental ceramics: a review of new materials and processing methods

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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.

Grain boundary engineering of highly deformable ceramics

International Nuclear Information System (INIS)

Mecartney, M.L.

2000-01-01

Highly deformable ceramics can be created with the addition of intergranular silicate phases. These amorphous intergranular phases can assist in superplastic deformation by relieving stress concentrations and minimizing grain growth if the appropriate intergranular compositions are selected. Examples from 3Y-TZP and 8Y-CSZ ceramics are discussed. The grain boundary chemistry is analyzed by high resolution analytical TEM is found to have a strong influence on the cohesion of the grains both at high temperature and at room temperature. Intergranular phases with a high ionic character and containing large ions with a relatively weak bond strength appear to cause premature failure. In contrast, intergranular phases with a high degree of covalent character and similar or smaller ions than the ceramic and a high ionic bond strength are the best for grain boundary adhesion and prevention of both cavitation at high temperatures and intergranular fracture at room temperature

Inlay-Retained Fixed Dental Prosthesis: A Clinical Option Using Monolithic Zirconia

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Davide Augusti

2014-01-01

Full Text Available Different indirect restorations to replace a single missing tooth in the posterior region are available in dentistry: traditional full-coverage fixed dental prostheses (FDPs, implant-supported crowns (ISC, and inlay-retained FDPs (IRFDP. Resin bonded FDPs represent a minimally invasive procedure; preexisting fillings can minimize tooth structure removal and give retention to the IRFDP, transforming it into an ultraconservative option. New high strength zirconia ceramics, with their stiffness and high mechanical properties, could be considered a right choice for an IRFDP rehabilitation. The case report presented describes an IRFDP treatment using a CAD/CAM monolithic zirconia IRFDP; clinical and laboratory steps are illustrated, according to the most recent scientific protocols. Adhesive procedures are focused on the Y-TZP and tooth substrate conditioning methods. Nice esthetic and functional integration of indirect restoration at two-year follow-up confirmed the success of this conservative approach.

Clinical prospective evaluation of zirconia-based three-unit posterior fixed dental prostheses: Up-to ten-year results.

Science.gov (United States)

Ioannidis, Alexis; Bindl, Andreas

2016-04-01

Only a few studies exist, which assess the clinical long-term behavior of all-ceramic FDPs in the posterior region. The aim of the present prospective clinical study was to evaluate the clinical performance of posterior three-unit FDPs manufactured from Y-TZP after a service period up to 10 years. 55 patients received 59 three-unit FDPs in the posterior region of the maxilla or mandible. Abutment teeth were prepared and full-arch impressions were taken. Definitive casts were fabricated and optically scanned. Frameworks were fabricated with computer-aided design (CAD) and manufacturing (CAM) technology. Y-TZP frameworks were veneered and adhesively luted to the abutment teeth. Baseline and follow-up examinations (service time: ≥ 48 months) were recorded by applying modified United States Public Health Services (USPHS) rating criteria. Cumulative survival rate was analyzed with Kaplan-Meier. Percentage of biological and technical complication was calculated. Fifty-three patients with 57 FDPs attended the last follow-up visit and a mean observation period of the remaining was 6.3 ± 1.9 years was calculated. Biological complications occurred in 17.5%, technical complications in 28% of the FDPs. The 10-year cumulative survival rate amounted 85.0%. Three FDPs failed to survive, two due to a root fracture of the abutment tooth and one due to secondary caries. Three-unit FDPs made from Y-TZP, veneered with ceramic offer a treatment option with a high rate of chipping. However, the manufacturing processes nowadays are modified in order to avoid this complication. The results of the present investigation suggest that three-unit Y-TZP posterior FDPs may are a possible treatment option. However, a high rate of chipping can be expected. Copyright © 2016. Published by Elsevier Ltd.

Microestructura de Al2O3/TZP codopado con Fe2O3 y TiO2 fabricado por reacción (RBAO

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Jiménez, M.

2003-02-01

Full Text Available Reaction-bonded 80 vol% Al2O3/TZP (2 mol% Y2O3-stabilized tetragonal zirconia polycrystals composites co-doped with 1 vol% Fe2O3 and 1 vol% TiO2 have been produced, and then presureless sintered (1450 ºC, 60 min or sinter-forged (20 MPa, 1200 ºC, 60 min. The resulting microstructures have been characterized using scanning electron microscopy. Both types of materials are dense, with a fine and homogeneous dual microstructure consisting of Al2O3 and TZP grains without intermediate grain boundary phases. Sinter-forged composites exhibit a very narrow pore size distribution, essentially smaller than the grain size of the alumina and zirconia phases. Co-doping promotes the sintering of alumina at lower temperatures, while still retains a fine grain size due to the presence of the dispersed zirconia phase. First results on presureless sintered RBAO materials show a fracture strength higher than in conventionally sintered and sinter-forged composites.Se han fabricado compuestos de 80% vol. Al2O3/TZP (ZrO2 estabilizada con 2% mol Y2O3 codopados con 1% vol. Fe2O3 y 1% vol. TiO2 mediante la tecnología RBAO (“Reaction Bonding of Aluminum Oxide”, que se han sinterizado libremente (1450 ºC, 60 min y bajo carga uniaxial (20 MPa, 1200 ºC, 60 min. Se ha caracterizado la microestructura mediante microscopía electrónica de barrido. Ambos materiales son densos con una microestructura homogénea formada por granos de alúmina y de circona, sin fases en juntas de grano. En el caso de la sinterización bajo carga, la distribución del tamaño de los poros es muy estrecha, y esencialmente menor que las correspondientes a los granos de Al2O3 y TZP. El codopado promueve la sinterización de la alúmina, mientras que los granos dispersos de circona inhiben su crecimiento de grano. Los ensayos preliminares de flexión en cuatro puntos realizados sobre los materiales sinterizados sin carga indican una resistencia a la fractura superior a la que presentan los

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.

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

Influence of core design, production technique, and material selection on fracture behavior of yttria-stabilized tetragonal zirconia polycrystal fixed dental prostheses produced using different multilayer techniques: split-file, over-pressing, and manually built-up veneers

Directory of Open Access Journals (Sweden)

Mahmood DJH

2016-02-01

Full Text Available Deyar Jallal Hadi Mahmood, Ewa H Linderoth, Ann Wennerberg, Per Vult Von Steyern Department of Prosthetic Dentistry, Faculty of Odontology, Malmö University, Malmö, Sweden Aim: To investigate and compare the fracture strength and fracture mode in eleven groups of currently, the most commonly used multilayer three-unit all-ceramic yttria-stabilized tetragonal zirconia polycrystal (Y-TZP fixed dental prostheses (FDPs with respect to the choice of core material, veneering material area, manufacturing technique, design of connectors, and radii of curvature of FDP cores. Materials and methods: A total of 110 three-unit Y-TZP FDP cores with one intermediate pontic were made. The FDP cores in groups 1–7 were made with a split-file design, veneered with manually built-up porcelain, computer-aided design-on veneers, and over-pressed veneers. Groups 8–11 consisted of FDPs with a state-of-the-art design, veneered with manually built-up porcelain. All the FDP cores were subjected to simulated aging and finally loaded to fracture. Results: There was a significant difference (P<0.05 between the core designs, but not between the different types of Y-TZP materials. The split-file designs with VITABLOCS® (1,806±165 N and e.max® ZirPress (1,854±115 N and the state-of-the-art design with VITA VM® 9 (1,849±150 N demonstrated the highest mean fracture values. Conclusion: The shape of a split-file designed all-ceramic reconstruction calls for a different dimension protocol, compared to traditionally shaped ones, as the split-file design leads to sharp approximal indentations acting as fractural impressions, thus decreasing the overall strength. The design of a framework is a crucial factor for the load bearing capacity of an all-ceramic FDP. The state-of-the-art design is preferable since the split-file designed cores call for a cross-sectional connector area at least 42% larger, to have the same load bearing capacity as the state-of-the-art designed

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.

Thickness dependence of light transmittance, translucency and opalescence of a ceria-stabilized zirconia/alumina nanocomposite for dental applications.

Science.gov (United States)

Shiraishi, Takanobu; Watanabe, Ikuya

2016-05-01

This study was conducted to investigate thickness dependence of light transmittance, translucency and opalescence of a commercially available fully-sintered ceria-stabilized zirconia/alumina nanocomposite for dental all-ceramic restorations. Three disk samples of 16 mm in diameter and thickness ranging from 0.2 to 0.6 mm with 0.1 mm increment each were cut from a fully-sintered rod-shaped Ce-TZP/alumina nanocomposite (NANOZR, Panasonic Healthcare, Japan) and polished flat by using diamond slurry. Spectral light transmittance data under the CIE standard illuminant D65 were recorded at 10nm intervals from 360 to 740 nm using a computer-controlled spectrophotometer. Average transmittance, translucency and opalescence parameters were determined as a function of sample thickness. Optical properties of a fully-sintered yttria-stabilized tetragonal zirconia polycrystals (Cercon(®) base, DeguDent GmbH, Germany) were also investigated as a reference. Two-way ANOVA was performed to determine the significant differences in various optical parameters among types of ceramic and thicknesses at α=0.05. Results of the two-way ANOVA showed that the average transmittance, translucency and opalescence parameters of both ceramic materials were significantly influenced by the type of ceramic and thickness (popalescence parameters exceeding 20 CIE units when the sample thickness was nearly 0.3 mm. The prominent characteristics of high opalescence and low transmittance of light in the NANOZR was considered to be caused by its specific very fine interpenetrated intragranular microstructure and by a large difference of refractive indices of Ce-TZP and alumina components. High opalescence and low transmittance of light of the ceria-stabilized zirconia/alumina nanocomposite (NANOZR) are attractive properties for use as a substructure in fabricating porcelain-veneering-type esthetic all-ceramic restorations. Copyright © 2016 Academy of Dental Materials. Published by Elsevier Ltd. All

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.

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.

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.)

New Coating Technique of Ceramic Implants with Different Glass Solder Matrices for Improved Osseointegration-Mechanical Investigations.

Science.gov (United States)

Mick, Enrico; Markhoff, Jana; Mitrovic, Aurica; Jonitz, Anika; Bader, Rainer

2013-09-11

Ceramics are a very popular material in dental implant technology due to their tribological properties, their biocompatibility and their esthetic appearance. However, their natural surface structure lacks the ability of proper osseointegration, which constitutes a crucial process for the stability and, thus, the functionality of a bone implant. We investigated the application of a glass solder matrix in three configurations-consisting mainly of SiO₂, Al₂O₃, K₂O and Na₂O to TZP-A ceramic specimens. The corresponding adhesive strength and surface roughness of the coatings on ceramic specimens have been analyzed. Thereby, high adhesive strength (70.3 ± 7.9 MPa) was found for the three different coatings. The obtained roughness (R z ) amounted to 18.24 ± 2.48 µm in average, with significant differences between the glass solder configurations. Furthermore, one configuration was also tested after additional etching which did not lead to significant increase of surface roughness (19.37 ± 1.04 µm) or adhesive strength (57.2 ± 5.8 MPa). In conclusion, coating with glass solder matrix seems to be a promising surface modification technique that may enable direct insertion of ceramic implants in dental and orthopaedic surgery.

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.

Development of a novel zirconia dental post resistant to hydrothermal degradation

International Nuclear Information System (INIS)

Camposilvan, E; Marro, F G; Mestra, A; Anglada, M J

2012-01-01

Tetragonal Zirconia Polycrystals stabilized with 3% mol. content of yttria (3Y-TZP) has excellent properties in terms of strength and fracture toughness. These properties are mostly imputable to the transformation toughening mechanism, by which the doped metastable tetragonal phase of zirconia transforms to monoclinic under applied stress ahead of a crack. This phenomenon is accompanied by a volume expansion of 5%, and increases the resistance to crack growth, thus leading to higher toughness and strength. An important drawback of this material is represented by the Low Temperature Degradation (LTD or aging), which consists in the progressive tetragonal-to-monoclinic phase transformation by the influence of water. This work focuses on the improvement of 3Y-TZP aging behavior in order to develop a novel dental post, by means of the addition of ceria from the surface. This was achieved through the impregnation of the pre-sintered samples with a solution containing Cerium, followed by sintering. Various pre-sintering temperatures were studied in terms of microstructure, mechanical properties and aging resistance. The novel zirconia dental posts developed in this work are much more resistant to LTD as compared to the base material with no loss in mechanical properties.

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

[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.

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.

[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.

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.

Effect of Initial ZrOCl₂ Concentration on the Homogeneous Precipitation of Nanoscale 3Y-TZP Powder.

Science.gov (United States)

Jeong, Hyeongdo; Lee, Jong Kook

2018-09-01

Nanoscale yttria-stabilized zirconia (Y-TZP) powder was synthesized by homogeneous precipitation via urea hydrolysis, and the influence of a dispersing agent and the initial ZrOCl2 concentration on the powder characteristics was investigated. A precipitated gel was obtained from the reaction of the precursor solution with zirconium oxychloride, yttrium chloride, and urea with heating at 110 °C for 5 h. The initial ZrOCl2 concentration was controlled from 0.25 to 1 M. To observe the effect of adding a dispersing agent on the agglomeration of primary particles, we used two starting compositions, one with and the other without a dispersing agent, ammonium polymethacrylate. Two crystalline powders were obtained after drying, calcination, and milling the gel, and we investigated the powder characteristics, such as particle agglomeration, the specific surface area, the microstructure, and phase composition. Two scales of agglomerates were observed in the particle size distribution, namely, 190 to 362 nm at the primary scale and 1.6-4.0 μm at the secondary scale. The amount of secondary agglomerate increased from 6 to 20 vol% with the increasing initial ZrOCl2 concentration. The size of both types of agglomerate and the amount of secondary agglomerates decreased due to the addition of the dispersing agent, especially the primary agglomerate size. The sintered density and microstructure of Y-TZP were affected by the agglomeration behavior, especially the amount of secondary agglomerates.

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.

Daño por contacto de cerámicas Y-TZP sometidas a degradación hidrotérmica

OpenAIRE

Trinel, Jérémy

2009-01-01

Este trabajo evalúa el comportamiento del daño por contacto en cerámicas de circona 3Y-TZP sometida a diferentes tiempos de degradación hidrotérmica (0, 5, 10, 30 y 60 horas), mediante la utilización de metodologías de indentación esférica (hertziana) Se analiza el comportamiento plástico del material mediante la evaluación del daño que se genera producto de la aplicación de cargas monotónicas en la superficie. Así mismo se desarrolla un mapa de daño y se evalúa el comportamie...

New Coating Technique of Ceramic Implants with Different Glass Solder Matrices for Improved Osseointegration-Mechanical Investigations

Directory of Open Access Journals (Sweden)

Rainer Bader

2013-09-01

Full Text Available Ceramics are a very popular material in dental implant technology due to their tribological properties, their biocompatibility and their esthetic appearance. However, their natural surface structure lacks the ability of proper osseointegration, which constitutes a crucial process for the stability and, thus, the functionality of a bone implant. We investigated the application of a glass solder matrix in three configurations—consisting mainly of SiO2, Al2O3, K2O and Na2O to TZP-A ceramic specimens. The corresponding adhesive strength and surface roughness of the coatings on ceramic specimens have been analyzed. Thereby, high adhesive strength (70.3 ± 7.9 MPa was found for the three different coatings. The obtained roughness (Rz amounted to 18.24 ± 2.48 µm in average, with significant differences between the glass solder configurations. Furthermore, one configuration was also tested after additional etching which did not lead to significant increase of surface roughness (19.37 ± 1.04 µm or adhesive strength (57.2 ± 5.8 MPa. In conclusion, coating with glass solder matrix seems to be a promising surface modification technique that may enable direct insertion of ceramic implants in dental and orthopaedic surgery.

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.

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.

Preparation and properties of yttria doped tetragonal zirconia polycrystal/Sr-doped barium hexaferrite ceramic composites

International Nuclear Information System (INIS)

Wang, Shanshan; Zhang, Chao; Guo, Ruisong; Liu, Lan; Yang, Yuexia; Li, Kehang

2015-01-01

Highlights: • The 3Y-TZP/Sr-doped barium ferrite composites were prepared. • The saturation magnetization was improved by 15% with Sr-doping. • The dispersion coefficient p could reflect the microscopic lattice variation. • The composite with x = 0.5 had the maximum fracture toughness of 8.3 MPa m 1/2 . - Abstract: The effects of substitution of Ba 2+ by Sr 2+ on the magnetic property of barium ferrite and addition barium ferrite secondary phase to the 3 mol% yttria-doped tetragonal zirconia polycrystal (3Y-TZP) matrix on the mechanical property of composites were investigated. The Sr-doped barium ferrite (Ba 1−x Sr x Fe 12 O 19 , x = 0, 0.25, 0.50 and 0.75) was synthesized by solid-state reaction in advance. Then 3Y-TZP/20 wt% Sr-doped barium ferrite composites were prepared by means of conventional ceramic method. It was found that a moderate amount of Sr added to barium ferrite could boost the saturation magnetization by 15% compared with the composites without Sr-doping. Besides, the composite with x = 0.50 possessed the best mechanical properties, such as 11.5 GPa for Vickers hardness and 8.3 MPa m 1/2 for fracture toughness, respectively. It was demonstrated that magnetic and mechanical properties of the composites could be harmonized by the incorporation of barium ferrite secondary phase

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

Fracture mechanics of ceramics. Vol. 7

International Nuclear Information System (INIS)

Bradt, R.C.; Evans, A.G.; Hasselman, D.P.; Lange, F.F.

1986-01-01

This volume, together with volume 8, constitutes the proceedings of an international symposium on the fracture mechanics of ceramics. The topics discussed in this volume include the toughening of ceramics by whisker reinforcement; the mechanical properties of SiCwhisker-reinforced TZP; the fracture of brittle rock and oil shale under dynamic explosive loading; impact damage models of ceramic coatings used in gas turbine and diesel engines; the use of exploratory data analysis for the safety evaluation of structural ceramics; and proof testing methods for the reliability of structural ceramics used in gas turbines

Properties of lithium disilicate reinforced with ZrO_2 (3mol%Y_2O_3

International Nuclear Information System (INIS)

Alves, M.F.R.P.; Cossu, C.M.F.A.; Santos, C.; Simba, B.G.

2016-01-01

The new generation of dental ceramics based on lithium disilicate, Li_2Si_2O_5, allows the production of restorative prosthetic with reduced times compared to alumina and / or zirconia (Y-TZP). A great limitation of their use is related low fracture strength of such glass-ceramics, which reduces their use in unit fixed prosthesis. In this work, lithium disilicate reinforced with 10% ZrO_2 (3-mol% Y_2O_3) is characterized by relative density, crystalline phase, hardness, fracture toughness and microstructural aspects. Lithium metasilicate and tetragonal zirconia, prior to heat treatment. After thermal treatment under vacuum at 840 deg C-8min the lithium metasilicate is converted to lithium disilicate as the ZrO_2 phase remains in the tetragonal structure. This maintenance of the tetragonal phase ensures the material a good fracture toughness, reaching average values near 2MPam"1"/"2, while the average hardness of 600HV. Morphological analysis of the samples indicates that ZrO_2 particles are uniformly dispersed in the matrix composed of high aspect ratio lithium disilicate grains, which contributes to the results presented.. A critical analysis of the performance of toughening mechanisms such as cracks deflection, phase transformation of ZrO_2 (T-M), residual stress between the matrix and the reinforcement are presented, discussed and compared with other ceramic materials used in dentistry restorer. (author)

On the interfacial fracture of porcelain/zirconia and graded zirconia dental structures.

Science.gov (United States)

Chai, Herzl; Lee, James J-W; Mieleszko, Adam J; Chu, Stephen J; Zhang, Yu

2014-08-01

Porcelain fused to zirconia (PFZ) restorations are widely used in prosthetic dentistry. However, their susceptibility to fracture remains a practical problem. The failure of PFZ prostheses often involves crack initiation and growth in the porcelain, which may be followed by fracture along the porcelain/zirconia (P/Z) interface. In this work, we characterized the process of fracture in two PFZ systems, as well as a newly developed graded glass-zirconia structure with emphases placed on resistance to interfacial cracking. Thin porcelain layers were fused onto Y-TZP plates with or without the presence of a glass binder. The specimens were loaded in a four-point-bending fixture with the thin porcelain veneer in tension, simulating the lower portion of the connectors and marginal areas of a fixed dental prosthesis (FDP) during occlusal loading. The evolution of damage was observed by a video camera. The fracture was characterized by unstable growth of cracks perpendicular to the P/Z interface (channel cracks) in the porcelain layer, which was followed by stable cracking along the P/Z interface. The interfacial fracture energy GC was determined by a finite-element analysis taking into account stress-shielding effects due to the presence of adjacent channel cracks. The resulting GC was considerably less than commonly reported values for similar systems. Fracture in the graded Y-TZP samples occurred via a single channel crack at a much greater stress than for PFZ. No delamination between the residual glass layer and graded zirconia occurred in any of the tests. Combined with its enhanced resistance to edge chipping and good esthetic quality, graded Y-TZP emerges as a viable material concept for dental restorations. Copyright © 2014 Acta Materialia Inc. All rights reserved.

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

Lifetime estimation of zirconia ceramics by linear ageing kinetics

International Nuclear Information System (INIS)

Zhang, Fei; Inokoshi, Masanao; Vanmeensel, Kim; Van Meerbeek, Bart; Naert, Ignace; Vleugels, Jef

2015-01-01

Up to now, the ageing kinetics of zirconia ceramics were mainly derived from the sigmoidal evolution of the surface phase transformation as a function of time, as quantified by means of X-ray diffraction (XRD). However, the transformation propagation into the material should be better to monitor the ageing kinetics. In this work, μ-Raman spectroscopy was used to quantitatively measure the transformation profiles in depth as a function of ageing time at 160 °C, 140 °C, 134 °C and 110 °C. A linear relationship between the transformed depth and the ageing time was observed for all investigated yttria stabilized tetragonal zirconia polycrystals (3Y-TZP). Furthermore, the μ-Raman investigation of residual stresses in the subsurface of aged 3Y-TZPs showed that the highest tensile stress was located just ahead of the transformation front, indicating the key responsibility of stress accumulation for transformation front propagating into the material. Moreover, the linear kinetics of the transformation propagation were more accurate to calculate the apparent activation energy of the ageing process and allowed a more straightforward estimation of the lifetime of 3Y-TZP at body temperature, as compared to the conventional ageing kinetic parameters obtained from the surface transformation analysis by XRD

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)

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

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.

Effects of multiple firings on the microstructure of zirconia and veneering ceramics.

Science.gov (United States)

Alkurt, Murat; Yeşil Duymus, Zeynep; Gundogdu, Mustafa

2016-01-01

The aim of study was to evaluate the effects of multiple firings on the microstructures of zirconia and two ceramics. Vita VM9 (VMZ) and Cerabien ZR (C-Z) ceramics on a zirconia framework and zirconia without veneering ceramic (WO-Z) were evaluated. Firing methods included firing two, five, and ten times (n=10). The effects of multiple firings on the surface hardness of the materials were evaluated using a Vickers hardness (HV) tester. Data were analyzed by two-way ANOVA and Tukey's test (α=0.05). After firing five and ten times, the hardness of VM-Z and C-Z increased significantly (p0.05). In the XRD analysis, zirconia had similar tetragonal (t)-monoclinic (m) phase transformations of Y-TZP after the different firing times. Clinically, multiple firings did not affect the microstructure of zirconia, but the structures of the two ceramics were affected.

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.

An investigation of neutron irradiation test on superplastic zirconia-ceramic materials

International Nuclear Information System (INIS)

Shibata, Taiju; Ishihara, Masahiro; Baba, Shinichi; Hayashi, Kimio

2000-05-01

A neutron irradiation test on superplastic ceramic materials at high temperature has been proposed as an innovative basic research on high-temperature engineering using the High Temperature Engineering Test Reactor (HTTR). For the effective execution of the test, we reviewed the superplastic deformation mechanism of ceramic materials and discussed neutron irradiation effects on the superplastic deformation process of stabilized Tetragonal Zirconia Polycrystal (TZP), which is a representative superplastic ceramic material. As a result, we pointed out that the decrease in the activation energy for superplastic deformation is expected by the radiation-enhanced diffusion. We selected a fast neutron fluence of 5x10 20 n/cm 2 and an irradiation temperature of about 600degC as test conditions for the first irradiation test on TZP and decided to perform a preliminary irradiation test by the Japan Materials Testing Reactor (JMTR). Moreover, we estimated the radioactivity of irradiated TZP and indicated that it is in the order of 10 10 Bq/g (about 0.3 Ci/g) immediately after irradiation to a thermal neutron fluence of 3x10 20 n/cm 2 and that it decays to about 1/100 in a year. (author)

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

Effect of various intermediate ceramic layers on the interfacial stability of zirconia core and veneering ceramics.

Science.gov (United States)

Yoon, Hyung-In; Yeo, In-Sung; Yi, Yang-Jin; Kim, Sung-Hun; Lee, Jai-Bong; Han, Jung-Suk

2015-01-01

The purposes of this study were to evaluate the effects of intermediate ceramics on the adhesion between the zirconia core and veneer ceramics. The polished surfaces of fully sintered Y-TZP blocks received three different treatments: (1) connector (C), (2) liner (L) or (3) wash layer (W). All the treated zirconia blocks were veneered with either (a) fluorapatite glass-ceramic (E) or (b) feldspathic porcelain (V) and divided into four groups (CE, CV, LE and WV). For the control group, the testing surfaces of metal blocks were veneered with feldspathic porcelain (VM). A half of the samples in each group (n = 21) were exposed to thermocycling, while the other half of the specimens were stored at room temperature under dry conditions. All specimens were subjected to the shear test and the failed surfaces were microscopically examined. The elemental distribution at the zirconia core/veneer interface was analyzed. The specimens in Groups CE and CV exhibited significantly greater mean bond strength values than those in Groups LE and WV, respectively (p ceramic substances into the zirconia surface. A glass-ceramic based connector is significantly more favorable to core/veneer adhesion than the other intermediate ceramics evaluated in the study. However, thermal cycling affected the bond strength at the core/veneer interface differently according to the intermediate ceramics.

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

Influence of full-contour zirconia surface roughness on wear of glass-ceramics.

Science.gov (United States)

Luangruangrong, Palika; Cook, N Blaine; Sabrah, Alaa H; Hara, Anderson T; Bottino, Marco C

2014-04-01

The purpose of this study was to evaluate the influence of full-contour (Y-TZP) zirconia surface roughness (glazed vs. as-machined) on the wear behavior of glass-ceramics. Thirty-two full contour Y-TZP (Diazir®) specimens (hereafter referred to as zirconia sliders) (ϕ = 2 mm, 1.5 mm in height) were fabricated using CAD/CAM and sintered according to the manufacturer's instructions. Zirconia sliders were embedded in brass holders using acrylic resin and then randomly assigned (n = 16) according to the surface treatment received, that is, as-machined or glazed. Glass-ceramic antagonists, Empress/EMP and e.max/EX, were cut into tabs (13 × 13 × 2 mm(3) ), wet-finished, and similarly embedded in brass holders. Two-body pin-on-disk wear testing was performed at 1.2 Hz for 25,000 cycles under a 3 kg load. Noncontact profilometry was used to measure antagonist height (μm) and volume loss (mm(3) ). Qualitative data of the zirconia testing surfaces and wear tracks were obtained using SEM. Statistics were performed using ANOVA with a significance level of 0.05. As-machined yielded significantly higher mean roughness values (Ra = 0.83 μm, Rq = 1.09 μm) than glazed zirconia (Ra = 0.53 μm, Rq = 0.78 μm). Regarding glass-ceramic antagonist loss, as-machined zirconia caused significantly less mean height and volume loss (68.4 μm, 7.6 mm(3) ) for EMP than the glazed group (84.9 μm, 9.9 mm(3) ), while no significant differences were found for EX. Moreover, EMP showed significantly lower mean height and volume loss than EX (p glass-ceramics tested. e.max wear was not affected by zirconia surface roughness; however, Empress wear was greater when opposing glazed zirconia. Overall, surface glazing on full-contour zirconia did not minimize glass-ceramic wear when compared with as-machined zirconia. © 2013 by the American College of Prosthodontists.

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

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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.

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

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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.

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.

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

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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.

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

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

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

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.

Can low-fusing glass application affect the marginal misfit and bond strength of Y-TZP crowns?

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Antunes, Monize Carelli Felipe; Miranda, Jean Soares; Carvalho, Ronaldo Luís Almeida de; Carvalho, Rodrigo Furtado de; Kimpara, Estevão Tomomitsu; Assunção E Souza, Rodrigo Othávio de; Leite, Fabíola Pessôa Pereira

2018-01-01

To evaluate the effect of different surface treatments on the marginal misfit and retentive strength between Y-TZP crowns and an epoxy resin. Forty (40) epoxy resin (G10) abutments (height: 5mm, conicity: 60, finish line: large chamfer) with equal dimensions were milled and included in polyurethane to simulate the periodontal ligament. Next, 40 Y-TZP crowns (thickness: 1mm) were milled (Cerec in Lab) and randomly divided into four groups (n=10) according to the surface treatment: GS(glaze spray), GP(glaze powder/liquid), P(zirconia primer) and RS(tribochemical silica coating). The conditioned surfaces were cemented with dual self-adhesive cement, light cured and submitted to thermomechanical cycling (2x106, 100N, 4Hz, 5°/55°C). Marginal misfit was analyzed by a stereomicroscope and SEM. Retentive strength test was performed (1mm/min) until crown debonding. Glaze layer thickness was also performed to GS and GP groups. Marginal misfit data were analyzed by Kruskal Wallis and Dunn tests; one-way ANOVA and Tukey (5%) analyzed the tensile strength data. The marginal misfit of the GS (48.6±19.9μm) and GP (65.4±42.5μm) were statistically lower than the RS (96±62.9μm) and P (156±113.3μm) (p=0.001). The retentive strength of the GP (470.5±104.1N) and GS (416.8±170.2N) were similar to the P (342.1±109.7N), but statistically higher than those of the RS (208.9±110N). The GS and GP glaze layer was 11.64μm and 9.73μm respectively. Thus, glaze application promoted lower marginal discrepancy and higher retentive strength values than conventional techniques.

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

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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.

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.

Desarrollo y caracterización de materiales compuestos basados en óxido de circona estabilizado con itrio y cerio

OpenAIRE

Veiro Suárez, Sabela

2013-01-01

En los últimos años, se han realizado gran número de investigaciones acerca de las cerámicas basadas en óxido de circonio (ZrO2) debido a su gran interés como material estructural avanzado y a su uso en, por ejemplo, restauraciones dentales (pilares y prótesis). El interés reside principalmente en las cerámicas basadas en circona policristalina tetragonal (TZP) debido a sus buenas propiedades mecánicas, tanto de tenacidad, resistencia al desgaste como biocompatibilidad. A pesar del amplio ...

Properties of lithium disilicate reinforced with ZrO{sub 2} (3mol%Y{sub 2}O{sub 3}; Propriedades de dissilicato de litio reforcado com ZrO{sub 2} (3mol%Y{sub 2}O{sub 3})

Energy Technology Data Exchange (ETDEWEB)

Alves, M.F.R.P.; Cossu, C.M.F.A.; Santos, C., E-mail: manuelfellipealves@gmail.com [Universidade do Estado do Rio de Janeiro (UERJ), Resende, RJ (Brazil). Faculdade de Tecnologia; Silva, C.L.M. [Centro Universitario de Volta Redonda (UniFOA), Volta Redonda, RJ (Brazil); Simba, B.G. [Universidade Estadual Paulista Julio de Mesquita Filho (UNESP), Guaratingueta, SP (Brazil). Faculdade de Engenharia; Fernandes, M.H.F. [Universidade de Aveiro (Portugal)

2016-07-01

The new generation of dental ceramics based on lithium disilicate, Li{sub 2}Si{sub 2}O{sub 5}, allows the production of restorative prosthetic with reduced times compared to alumina and / or zirconia (Y-TZP). A great limitation of their use is related low fracture strength of such glass-ceramics, which reduces their use in unit fixed prosthesis. In this work, lithium disilicate reinforced with 10% ZrO{sub 2} (3-mol% Y{sub 2}O{sub 3}) is characterized by relative density, crystalline phase, hardness, fracture toughness and microstructural aspects. Lithium metasilicate and tetragonal zirconia, prior to heat treatment. After thermal treatment under vacuum at 840 deg C-8min the lithium metasilicate is converted to lithium disilicate as the ZrO{sub 2} phase remains in the tetragonal structure. This maintenance of the tetragonal phase ensures the material a good fracture toughness, reaching average values near 2MPam{sup 1/2}, while the average hardness of 600HV. Morphological analysis of the samples indicates that ZrO{sub 2} particles are uniformly dispersed in the matrix composed of high aspect ratio lithium disilicate grains, which contributes to the results presented.. A critical analysis of the performance of toughening mechanisms such as cracks deflection, phase transformation of ZrO{sub 2} (T-M), residual stress between the matrix and the reinforcement are presented, discussed and compared with other ceramic materials used in dentistry restorer. (author)

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)

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)

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)

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.

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.

Attachment and growth behaviour of human gingival fibroblasts on titanium and zirconia ceramic surfaces

International Nuclear Information System (INIS)

Pae, Ahran; Kim, Hyeong-Seob; Woo, Yi-Hyung; Lee, Heesu; Kwon, Yong-Dae

2009-01-01

The attachment, growth behaviour and the genetic effect of human gingival fibroblasts (HGF) cultured on titanium and different zirconia surfaces were investigated. HGF cells were cultured on (1) titanium discs with a machined surface, (2) yttrium-stabilized tetragonal zirconia polycrystals (Y-TZP) with a smooth surface and (3) Y-TZP with 100 μm grooves. The cell proliferation activity was evaluated through a MTT assay at 24 h and 48 h, and the cell morphology was examined by SEM. The mRNA expression of integrin-β1, type I and III collagen, laminin and fibronectin in HGF were evaluated by RT-PCR after 24 h. From the MTT assay, the mean optical density values for the titanium and grooved zirconia surfaces after 48 h of HGF adhesion were greater than the values obtained for the smooth zirconia surfaces. SEM images showed that more cells were attached to the grooves, and the cells appeared to follow the direction of the grooves. The results of RT-PCR suggest that all groups showed comparable fibroblast-specific gene expression. A zirconia ceramic surface with grooves showed biological responses that were comparable to those obtained with HGF on a titanium surface.

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.

Tribological properties of toughened zirconia-based ceramics

International Nuclear Information System (INIS)

Stachowiak, G.W.; Stachowiak, G.B.

1991-01-01

The physical and mechanical properties of toughened zirconia ceramics are briefly characterized and described with a special emphasis on their tribological behaviour. The wear and friction properties of PSZ and TZP ceramics at room and elevated temperatures are described. The influence of the environment on the tribological characteristics of zirconia ceramics is discussed. Both lubricated and unlubricated conditions for ceramic/ceramic and metal/ceramic sliding contacts are analysed. One of the main, and as yet unresolved problems, lubrication of ceramic at elevated temperatures and/or space environment, is addressed and the possible solutions to the problem are suggested. The critical needs in the research and development area of improving the tribological properties of zirconia ceramics are defined and its future market potentials stated. 30 refs., 2 tabs., 4 figs

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

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

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.

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.

Origin of unusual sintering phenomena in compacts of chloride-derived 3Y-TZP nanopowders

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Sweeney Sean M.

2014-01-01

Full Text Available After evaluating three alternative possibilities, the present study shows that seemingly minor amounts (at least as low as 0.06 wt% of chlorine impurities are responsible for the poor sintering behavior observed in chloride-derived 3 mol% yttria stabilized zirconia (3Y-TZP nanopowders. Models and quantitative estimates are used to explain the role of evolved HCl and ZrCl4 gases in such anomalous behaviors as reduced sintered densities for higher green densities, de-densification, improved sintering in nitrogen over oxygen, and formation of a dense shell microstructure. Two solutions to problematic residual chlorides are compared: 1 a thermal treatment composed of an extended hold at 1000°C to allow HCl gas removal before the onset of closed porosity, and 2 a chemical treatment performed by washing bisque-fired samples at room temperature using a concentrated ammonium hydroxide solution to remove chlorides. The thermal treatment was found to be superior.

Resistencia al choque térmico de Y-TZP con fisuras Palmqvist

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Fargas Ribas, G.

2003-02-01

Full Text Available The thermal shock response of two tetragonal zirconia polycrystals stabilised with 2.5% molar yttria, with two different levels of fracture toughness, has been investigated. Palmqvist cracks are generated by indentation and the crack extension is quantified by assuming that the residual thermal stresses responsible for its extension during thermal shock are smaller than those acting on the crack immediately after indentation. It is proposed to use a thermal shock resistance parameter that only depends on the crack extension induced by thermal stresses generated during the abrupt changes in temperature. The results are applied to the study of thermal shock resistance and they are compared with experimental results.

Se analiza el comportamiento frente al choque térmico de policristales de circona tetragonal dopados con 2.5% molar de itria (Y-TZP, con dos niveles distintos de tenacidad y con fisuras de indentación del tipo Palmqvist. El proceso de extensión de la fisura se cuantifica suponiendo que las tensiones residuales responsables de su propagación estable durante el choque térmico son inferiores a las presentes en el material inmediatamente después de aplicar la indentación. Se propone la utilización de un parámetro de resistencia al choque térmico que solamente depende de la extensión de las fisuras por efecto de las tensiones térmicas generadas durante el cambio brusco de temperatura. Los resultados del análisis se aplican al estudio del choque térmico y se comparan con los resultados experimentales.

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.

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

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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.

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.

Random walk analysis of grain motion during superplastic deformation of TZP

International Nuclear Information System (INIS)

Okamoto, T; Yasuda, K; Shiota, T

2009-01-01

This study focuses on grain motion in TZP (Tetragonal Zirconia Polycrystal) ceramics during superplastic deformation. The specimen was 16 times elongated repeatedly at 1400 0 C in air. The increment of true plastic strain was set to be 2%, and the specimen was deformed up to 30.3% true plastic strain finally. After each deformation, displacement vectors of specified 748 grains were measured from their position vectors determined by FE-SEM micrographs. As a result, the grains move to the tensile loading direction in zigzag way. And also, the zigzag motion changes with plastic strain: The grains move randomly (random walk motion) by the first 15% true plastic strain, and then grain motion becomes spatially uniform gradually. It is related to changes of constraint of surrounding matrix.

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

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.

Cyclic fatigue resistance of yttria-stabilized tetragonal zirconia polycrystals with hot isostatic press processing.

Science.gov (United States)

Koyama, Taku; Sato, Toru; Yoshinari, Masao

2012-01-01

This study investigated the influence of surface roughness and cyclic loading on fatigue resistance in Y-TZP subjected to hot isostatic pressing (HIP). Fifty Y-TZP cylinders 3.0 mm in diameter were divided into Group A (polished by centerless method; TZP-CP) or Group B (blasted and acid-etched: TZP-SB150E). Twenty five cp-titanium cylinders (Ti-SB150E) were used as a control. Static and cyclic tests were carried out according to ISO 14801. The cyclic fatigue test was performed in distilled water at 37°C. Surface morphology and roughness as well as crystal phase on the surfaces were also evaluated. Fracture force under the static test was 1,765N (TZP-CP), 1,220N (TZP-SB150E), and 850 N (yield force, Ti-SB150E). Fracture values under the cyclic test decreased to approximately 70% of those under the static tests. These results indicate that HIPed Y-TZP with a 3.0-mm diameter has sufficient durability for application to dental implants.

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.

Ghrelin receptor agonist (TZP-101) accelerates gastric emptying in adults with diabetes and symptomatic gastroparesis

DEFF Research Database (Denmark)

Ejskjaer, N; Vestergaard, E T; Hellström, P M

2009-01-01

BACKGROUND: TZP-101 is a synthetic, selective ghrelin agonist in development for gastroparesis. AIM: To assess safety and effects of TZP-101 in diabetes patients with symptomatic gastroparesis. METHODS: Adults with type 1 or type 2 diabetes mellitus received placebo and TZP-101 (80, 160, 320 or 600...... between TZP-101 and placebo. CONCLUSIONS: This proof-of-concept study demonstrates that the ghrelin agonist TZP-101 is well-tolerated in diabetes patients with moderate-to-severe chronic gastroparesis and shows statistically significant improvements in gastric emptying....

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.

[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).

Milling properties of low temperature sintered zirconia blocks for dental use

Energy Technology Data Exchange (ETDEWEB)

Lan, Ting-Hsun; Wang, Chau-Hsiang [Department of Prosthodontics, Kaohsiung Medical University Hospital, Kaohsiung 80756, Taiwan (China); School of Dentistry, College of Dental Medicine, Kaohsiung Medical University, Kaohsiung 80728, Taiwan (China); Chen, Ker-Kong [Department of Conservation, Kaohsiung Medical University Hospital, Kaohsiung 80756, Taiwan (China); School of Dentistry, College of Dental Medicine, Kaohsiung Medical University, Kaohsiung 80728, Taiwan (China); Wang, Moo-Chin, E-mail: mcwang@kmu.edu.tw [Department of Fragrance and Cosmetic Science, Kaohsiung Medical University, 100 Shih-Chuan 1st Road, Kaohsiung 80728, Taiwan (China); Department of Medical Research, Kaohsiung Medical University Hospital, Kaohsiung, 80756, Taiwan (China); Lee, Huey-Er, E-mail: huerle@kmu.edu.tw [Department of Prosthodontics, Kaohsiung Medical University Hospital, Kaohsiung 80756, Taiwan (China); School of Dentistry, College of Dental Medicine, Kaohsiung Medical University, Kaohsiung 80728, Taiwan (China)

2017-04-01

To investigate the milling properties of different yttria-tetragonal zirconia polycrystalline (Y-TZP) block materials by applying a dental computer numerical control (CNC) milling center. Low temperature sintering zirconia block denoted by KMUZ (experimental) with two commercial zirconia blocks for T block made in Taiwan and a G block made in Germany were compared for the milling properties. Seventy-two specimens were milled using the same CNC milling center, and properties were evaluated by measuring the weight loss (g), milling time (s), margin integrity (%) and broken diameter (μm). The crystalline phases contents were identified by X-ray diffraction and the microstructures of the sintering specimens were observed by scanning electron microscopy and transmission electron microscopy. The mean milling time of G and KMUZ were significantly shorter than T (P < 0.05). The KMUZ samples exhibited the least weight loss among the three kinds of blocks (P < 0.05). The percentages of marginal integrity after milling were high in G and KMUZ but low in T (P < 0.05). The mean broken diameters were from 90 μm to 120 μm. The phase transformation of t-ZrO{sub 2} (KMUZ: 7.4%, G: 5.9%, T: 3.2%) to m-ZrO{sub 2} when facing the milling pressure in ZrO{sub 2} blocks was observed by XRD. The result of TEM microstructure of KMUZ revealed that Y and Si were soluble in grain boundaries. The results show that the milling properties of KMUZ were better than one commercial T and near the G. The hindered grain growth, as a result of the Y{sup 3+} content in the grain boundaries, also plays a role in promoting the abnormal grain growth of 3Y-TZP. - Highlights: • The phase transformation of t-ZrO{sub 2} to m-ZrO{sub 2} affects the milling properties. • The phase content of t-ZrO2 was 100% when sintering at 1350 °C for 2 h. • The Y{sup 3+} content in the grain boundaries that hinders grain growth. • The Y{sup 3+} content in boundaries also promotes the abnormal grain growth of 3Y-TZP.

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.

Fracture Toughness and Micro-Strain of Y-TZP Nanoceramics at Different Sintering Temperature

Directory of Open Access Journals (Sweden)

Rabiha S. Yaseen

2017-11-01

Full Text Available The objective of this research is to study the effect of sintering temperature on the mechanical properties and micro-strain of yttria tetragonal zirconia polycrystalls (Y-TZP nanostructure.   Where green disk formed by uniaxially press, sintered at (1500 – 1550 – 1600⁰C in air for 2hr then polished to mirror shape for fracture toughness and micro-hardness measurement by Vickers indenter at (60 kg to 100gm loads. Atomic force microscopy (AFM technique was use to measure the change in grain size and shape of the samples, X-ray diffraction (XRD evaluated to identify the phases and to measure the micro-strain of the samples.          The Results show that increasing sintering temperature will increase the grain size with increasing the average of micro-strain. Tetragonal  phase is the prevailing phase with small amount of cubic phase and the amount of monoclinic phase was under detection limite after sintering but there is increas in lattice dimension according to micro-strain calculation and grinding process produce micro-strain. With increasing the sintering temperature micro-hardness and fracture toughness will increas.

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.

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.

Fabrication and properties of yttria, ceria doped zirconia-aluminia ceramic composites

International Nuclear Information System (INIS)

Lyubushkin, R.A.; Ivanov, O.N.; Chuev, V.P.; Buzov, A.A.

2011-01-01

At present, zirconia-based ceramics are gaining popularity in dentistry, particularly in fixed prosthodontics. clinically, it is important that ceramic restorations reproduce the translucency and color of natural teeth. Zirconia based ceramics is a high performance material with excellent biocompatibility and mechanical properties, which suggest its suitability for posterior fixed partial dentures. Y 2 O 3 -stabilized tetragonal zirconia polycrystalline (YTZ/Al 2 O 3 ) and CeO 2 -stabilized tetragonal zirconia polycrystalline (CZA) ceramics with high-performance were prepared for dental application by use the wet chemical route, consolidated by cold isostatic pressing, and two-step sintering method. Physical and mechanical properties test results show that the bending strength, fracture toughness, and the density of full sintered ceramics suggest that the material is relatively suitable for dental restoration.

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

Effect of 10Ce-TZP/Al2O3 nanocomposite particle amount and sintering temperature on the microstructure and mechanical properties of Al/(10Ce-TZP/Al2O3) nanocomposites

International Nuclear Information System (INIS)

Soltani, N.; Pech-Canul, M.I.; Bahrami, A.

2013-01-01

Highlights: • Increasing the 10Ce-TZP/Al 2 O 3 content up to 7 wt.%, enhanced composites’ hardness. • Significant enhancement in compressive strength is obtained with 7% 10Ce-TZP/Al 2 O 3 . • Sintering at 450 °C, hardness and compressive strength are higher than at 400 °C. - Abstract: A zirconia/alumina nanocomposite stabilized with cerium oxide (Ce-TZP/Al 2 O 3 nanocomposite) can be a good substitute as reinforcement in metal matrix composites. In the present study, the effect of the amount of 10Ce-TZP/Al 2 O 3 particles on the microstructure and properties of Al/(10Ce-TZP/Al 2 O 3 ) nanocomposites was investigated. For this purpose, aluminum powders with average size of 30 μm were ball-milled with 10Ce-TZP/Al 2 O 3 nanocomposite powders (synthesized by aqueous combustion) in varying amounts of 1, 3, 5, 7, and 10 wt.%. Cylindrical-shape samples were prepared by pressing the powders at 600 MPa for 60 min while heating at 400–450 °C. The specimens were then characterized by scanning and transmission electron microscopy (SEM and TEM) in addition to different physical and mechanical testing methods in order to establish the optimal processing conditions. The highest compression strength was obtained in the composite with 7 wt.% (10Ce-TZP/Al 2 O 3 ) sintered at 450 °C

Effects of core-to-dentin thickness ratio on the biaxial flexural strength, reliability, and fracture mode of bilayered materials of zirconia core (Y-TZP) and veneer indirect composite resins.

Science.gov (United States)

Su, Naichuan; Liao, Yunmao; Zhang, Hai; Yue, Li; Lu, Xiaowen; Shen, Jiefei; Wang, Hang

2017-01-01

Indirect composite resins (ICR) are promising alternatives as veneering materials for zirconia frameworks. The effects of core-to-dentin thickness ratio (C/Dtr) on the mechanical property of bilayered veneer ICR/yttria-tetragonal zirconia polycrystalline (Y-TZP) core disks have not been previously studied. The purpose of this in vitro study was to assess the effects of C/Dtr on the biaxial flexural strength, reliability, and fracture mode of bilayered veneer ICR/ Y-TZP core disks. A total of 180 bilayered 0.6-mm-thick composite resin disks in core material and C/Dtr of 2:1, 1:1, and 1:2 were tested with either core material placed up or placed down for piston-on-3-ball biaxial flexural strength. The mean biaxial flexural strength, Weibull modulus, and fracture mode were measured to evaluate the variation trend of the biaxial flexural strength, reliability, and fracture mode of the bilayered disks with various C/Dtr. One-way analysis of variance (ANOVA) and chi-square tests were used to evaluate the variation tendency of fracture mode with the C/Dtr or material placed down during testing (α=.05). Light microscopy was used to identify the fracture mode. The mean biaxial flexural strength and reliability improved with the increase in C/Dtr when specimens were tested with the core material either up and down, and depended on the materials that were placed down during testing. The rates of delamination, Hertzian cone cracks, subcritical radial cracks, and number of fracture fragments partially depended on the C/Dtr and the materials that were placed down during testing. The biaxial flexural strength, reliability, and fracture mode in bilayered structures of Y-TZP core and veneer ICR depend on both the C/Dtr and the material that was placed down during testing. Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

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.

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.

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.

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.

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.

[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.

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.

Comparison of resin cement adhesion to Y-TZP ceramic following manufacturers' instructions of the cements only

NARCIS (Netherlands)

Ozcan, Mutlu; Kerkdijk, Sandra; Valandro, Luiz Felipe

The objectives of this study were (1) to evaluate the bond strength of four resin materials with various chemical compositions following the manufacturers' instructions only and (2) to test their durability in dry and thermal aged conditions when they were bonded to zirconia ceramic. Four types of

Ceramic Technology Project data base: September 1992 summary report

Energy Technology Data Exchange (ETDEWEB)

Keyes, B.L.P.

1993-06-01

Data presented in this report represent an intense effort to improve processing methods, testing methods, and general mechanical properties (rupture modulus, tensile, creep, stress-rupture, dynamic and cyclic fatigue, fracture toughness) of candidate ceramics for use in advanced heat engines. This work was performed by many facilities and represents only a small part of the data generated by the Ceramic Technology Project (CTP) since 1986. Materials discussed include GTE PY6, GN-10, NT-154, NT-164, SN-260, SN-251, SN-252, AY6, silicon nitride combined with rare-earth oxides, Y-TZP, ZTA, NC-433, NT-230, Hexoloy SA, MgO-PSZ-to-MgO-PSZ joints, MgO-PSZ-to-cast iron, and a few whisker/fiber-reinforced ceramics. Information in this report was taken from the project`s semiannual and bimonthly progress reports and from final reports summarizing the results of individual studies. Test results are presented in tabular form and in graphs. All data, including test rig descriptions and material characterizations, are stored in the CTP data base and are available to all project participants on request. The objective of this report is to make available the test results from these studies but not to draw conclusions from those data.

[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.

Protection of yttria-stabilized zirconia for dental applications by oxidic PVD coating.

Science.gov (United States)

Hübsch, C; Dellinger, P; Maier, H J; Stemme, F; Bruns, M; Stiesch, M; Borchers, L

2015-01-01

In this study, the application of transparent physical vapor deposition (PVD) coatings on zirconia ceramics was examined as an approach to retard the low-temperature degradation of zirconia for dental applications. Transparent monolayers of titanium oxide (TixOy) and multilayers consisting of titanium oxide-alumina-titanium oxide (TixOy-AlxOy-TixOy) were deposited onto standardized discs of 3Y-TZP using magnetron sputtering. Using X-ray photospectroscopy and time-of-flight secondary-ion mass spectrometry, the compositions of the coatings were verified, and an approximate thickness of 50 nm for each type of coating was ascertained. After aging the coated and uncoated samples in water vapor at 134°C and 3 bar for 4, 8, 16, 32, 64 and 128 h, the monoclinic phase content was determined using X-ray diffraction, and its impact on mechanical properties was assessed in biaxial flexural strength tests. In addition, the depth of the transformation zone was measured from scanning electron microscopy images of the fracture surfaces of hydrothermally aged samples. The results revealed that the tetragonal-to-monoclinic phase transformation of the zirconia ceramic was retarded by the application of PVD coatings. During the first stages of aging, the coated samples exhibited a significantly lower monoclinic phase content than the uncoated samples and, after 128 h of aging, showed a transformation zone which was only ∼12-15 μm thick compared to ∼30 μm in the control group. Biaxial flexural strength decreased by ∼10% during aging and was not influenced by the application of a PVD coating. Copyright © 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

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

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

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

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

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

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.

Bending properties of Ce-TZP/A nanocomposite clasps for removable partial dentures.

Science.gov (United States)

Urano, Shinjiro; Hotta, Yasuhiro; Miyazaki, Takashi; Baba, Kazuyoshi

2015-01-01

Ceria-stabilized zirconia/alumina nanocomposite (Ce-TZP/A) has excellent fracture toughness and bending strength that could be useful for partial denture framework application. The aim of this study was to investigate the effects of three-dimensional (3D) geometry on the bending and fatigue properties of a model simulation of Ce-TZP/A clasps. Half oval-shaped Ce-TZP/A rods were prepared in six 3D designs. Specimens were either of standard (width divided by thickness: 2.0/1.0 mm) or flat type (2.5/0.8 mm) cross-sectional areas with taper ratios of 1.0, 0.8, or 0.6. As a comparison, cobalt-chromium (Co-Cr) alloy rods of the same shape as the Ce-TZP/A standard shape rod were prepared. All specimens were subjected to the cantilever test and loaded until fracture. They were also cyclically loaded 106 times with various constant displacements, and the maximum displacement prior to fracture was determined for each specimen. Three-dimensional finite element analysis (3D FEA), simulating the cantilever test, was performed to determine the stress distribution during loading. Specimens with the standard cross-sectional shape exhibited higher rigidity and higher fracture loads than the flat specimens by the cantilever test. In addition, lower taper ratios were consistently associated with larger displacements at fracture. Fatigue tests revealed that the maximum displacement prior to fracture of Ce-TZP/A specimens was comparable to that of Co-Cr alloy specimens. The 3D FEA showed that specimens with a taper ratio of 0.6 had the least stress concentration. Ce-TZP/A clasp specimens with a standard cross-sectional shape and a 0.6 taper ratio exhibited the best bending properties among those tested.

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.

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

Viscoelastic finite element analysis of residual stresses in porcelain-veneered zirconia dental crowns.

Science.gov (United States)

Kim, Jeongho; Dhital, Sukirti; Zhivago, Paul; Kaizer, Marina R; Zhang, Yu

2018-06-01

The main problem of porcelain-veneered zirconia (PVZ) dental restorations is chipping and delamination of veneering porcelain owing to the development of deleterious residual stresses during the cooling phase of veneer firing. The aim of this study is to elucidate the effects of cooling rate, thermal contraction coefficient and elastic modulus on residual stresses developed in PVZ dental crowns using viscoelastic finite element methods (VFEM). A three-dimensional VFEM model has been developed to predict residual stresses in PVZ structures using ABAQUS finite element software and user subroutines. First, the newly established model was validated with experimentally measured residual stress profiles using Vickers indentation on flat PVZ specimens. An excellent agreement between the model prediction and experimental data was found. Then, the model was used to predict residual stresses in more complex anatomically-correct crown systems. Two PVZ crown systems with different thermal contraction coefficients and porcelain moduli were studied: VM9/Y-TZP and LAVA/Y-TZP. A sequential dual-step finite element analysis was performed: heat transfer analysis and viscoelastic stress analysis. Controlled and bench convection cooling rates were simulated by applying different convective heat transfer coefficients 1.7E-5 W/mm 2 °C (controlled cooling) and 0.6E-4 W/mm 2 °C (bench cooling) on the crown surfaces exposed to the air. Rigorous viscoelastic finite element analysis revealed that controlled cooling results in lower maximum stresses in both veneer and core layers for the two PVZ systems relative to bench cooling. Better compatibility of thermal contraction coefficients between porcelain and zirconia and a lower porcelain modulus reduce residual stresses in both layers. Copyright © 2018 Elsevier Ltd. All rights reserved.

Protocol of thermal treatments for the recovery of tetragonal phase in infrastructures of dental prostheses base of ZrO_2 (3-Y_2O_3) mills in CAD / CAM systems or panthories

International Nuclear Information System (INIS)

Simba, B.G.; Ferreira, B.; Santos, C.

2011-01-01

ZrO_2(3%Y_2O_3) bioceramics are used as dental materials mainly as prosthesis components, because present high mechanical properties and translucence. The use of CAD/CAM machining technique needs final grinding which promotes tetragonal monoclinic transformation reducing the reliability of this ceramic. In this work, ZrO_2(3%Y_2O_3) ceramics were sintered at 1450-0h, 1530-2h or 1600-4h and characterized. Different heat-treatment (400-1200 deg C) are proposed aiming the recuperation of the tetragonal crystalline phase. (author)

The Effects of Ammonium Polyacrylate and Diammonium Citrate as Base and Acid Dispersion Agents on Yttria-Stabilized Zirconia (3Y-TZP Dispersion Properties

Directory of Open Access Journals (Sweden)

Pestaria Sinaga

2018-01-01

Full Text Available Stable slurries in dispersions of 3Y-TZP in aqueous suspension with the addition of different concentrations of dispersants such as ammonium polyacrylate (APA and diammonium citrate (DAC were investigated. The dispersion properties were investigated by measuring the particle size, zeta potential, sedimentation, and viscosity as a function of the wt.% of the dispersant. Both dispersant agents were attached to the 3Y-TZP surface by the carboxylic group, as shown by the FTIR results. The addition of dispersants was found to produce more dispersed and stabilized aqueous suspension. As shown the viscosity result, that there is no being viscosity peak has been occurring and viscosity going decrease as the shear rates increasing which mean that the suspension has shear thinning behavior and there is no agglomeration as the shear rate is increased. It was determined that 3.5 wt.% of DAC and APA produced the best and most stable slurry; when 3.5 wt.% of DAC and APA was added, the zeta potential showed the largest value in the monodisperse condition. The low pH value of DAC has obtained the higher zeta potential value than APA, which was assumed due to low pH of DAC suspension. At low pH, the adsorption of the adsorbate will occur in a flat adsorbed, while at higher pH the polyelectrolyte will dangle into solution, thus reducing electrostatic repulsion as it is found in the case of APA addition. In this condition, the particle size was decreased to the lower value and the slurry’s stability was obtained with the lowest sedimentation height after the sedimentation test for 30 days. The sample was milled in an attrition mill at 1,000 rpm for four hours.

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

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

[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.

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.

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.

Translucency of Zirconia Ceramics before and after Artificial Aging.

Science.gov (United States)

Walczak, Katarzyna; Meißner, Heike; Range, Ursula; Sakkas, Andreas; Boening, Klaus; Wieckiewicz, Mieszko; Konstantinidis, Ioannis

2018-03-11

The aging of zirconia ceramics (Y-TZP) is associated with tetragonal to monoclinic phase transformation. This change in microstructure may affect the optical properties of the ceramic. This study examines the effect of aging on the translucency of different zirconia materials. 120 disc-shaped specimens were fabricated from four zirconia materials: Cercon ht white, BruxZir Solid Zirconia, Zenostar T0, Lava Plus (n = 30 per group). Accelerated aging was performed in a steam autoclave (134°C, 0.2 MPa, 5 hours). CIELab coordinates (L*, a*, b*) and luminous reflectance (Y) were measured with a spectrophotometer before and after aging. Contrast ratio (CR) and translucency parameter (TP) were calculated from the L*, a*, b*, and Y tristimulus values. The general linear model (Bonferroni adjusted) was used to compare both parameters before and after aging, as well as between the different zirconia materials (p ≤ 0.05). CR and TP differed significantly before and after aging in all groups tested. Before aging, Zenostar T showed the highest and Lava Plus showed the lowest translucency. After aging, Cercon ht and Zenostar T showed the highest and BruxZir and Lava Plus the lowest translucency. Aging reduced the translucency in all specimens tested. Furthermore, translucency differed between the zirconia brands tested. Nevertheless, the differences were below the detectability threshold of the human eye. The aging process can influence the translucency and thus the esthetic outcome of zirconia restorations; however, the changes in translucency were minimal and probably undetectable by the human eye. © 2018 by the American College of Prosthodontists.

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

La hipomineralización incisivo molar y la caries dental

OpenAIRE

Negre Barber, Adela

2017-01-01

La formación dental es un proceso largo y complejo que se inicia antes de nacer y termina con la mineralización de los terceros molares al final de la adolescencia. Durante este tiempo, cualquier alteración en el órgano dental puede derivar en un defecto en el desarrollo del esmalte (DDE) observándose al erupcionar el diente.La caries dental y los defectos del esmalte son actualmente los problemas mas frecuentes observados en la dentición temporal y joven permanente. Existen protocolos de pre...

Ansiedad y miedos dentales en escolares hondureños

OpenAIRE

Ivette Carolina Rivera Zelaya; Antonio Fernández Parra

2005-01-01

La ansiedad a la atención y tratamiento dental puede afectar de forma significativa a la salud oral de los niños así como a la calidad del tratamiento dental recibido. A pesar de su importancia se han realizado muy pocos estudios sobre la ansiedad y miedo dental infantil en Latinoamérica, concretamente en Honduras. En este estudio se evaluó la ansiedad dental de una muestra aleatoria de 170 escolares (6-11 años) de la región metropolitana de Tegucigalpa. La evaluación se realiz...

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.

Combined mode I-mode II fracture of 12-mol%-ceria-doped tetragonal zirconia polycrystalline ceramic

International Nuclear Information System (INIS)

Tikare, V.; Choi, S.R.

1997-01-01

The mode I, mode II, and combined mode I-mode II fracture behavior of ceria-doped tetragonal zirconia polycrystalline (Ce-TZP) ceramic was studied. The single-edge-precracked-beam (SEPB) samples were fractured using the asymmetric four-point-bend geometry. The ratio of mode I to mode II loading was varied by varying the degree of asymmetry in the four-point-bend geometry. The minimum strain energy density theory best described the mixed-mode fracture behavior of Ce-TZP with the mode I fracture toughness, K IC = 8.2 ± 0.6 MPa·m 1/2 , and the mode II fracture toughness, K IIC = 8.6 ± 1.3 MPa·m 1/2

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.

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.

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.

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.

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

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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.

Preparation and characterization of TiO2 and Si-doped octacalcium phosphate composite coatings on zirconia ceramics (Y-TZP) for dental implant applications

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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.

Machinable glass-ceramics forming as a restorative dental material.

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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.

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

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

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.

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

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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.

Yb:Y2O3 transparent ceramics processed with hot isostatic pressing

Science.gov (United States)

Wang, Jun; Ma, Jie; Zhang, Jian; Liu, Peng; Luo, Dewei; Yin, Danlei; Tang, Dingyuan; Kong, Ling Bing

2017-09-01

Highly transparent 5 at.% Yb:Y2O3 ceramics were fabricated by using a combination method of vacuum sintering and hot isostatic pressing (HIP). Co-precipitated Yb:Y2O3 powders, with 1 at.% ZrO2 as the sintering aid, were used as the starting material. The Yb:Y2O3 ceramics, vacuum sintered at 1700 °C for 2 h and HIPed at 1775 °C for 4 h, exhibited small grain size of 1.9 μm and highly dense microstructure. In-line optical transmittance of the ceramics reached 83.4% and 78.9% at 2000 and 600 nm, respectively. As the ceramic slab was pumped by a fiber-coupled laser diode at about 940 nm, a maximum output power of 0.77 W at 1076 nm was achieved, with a corresponding slope efficiency of 10.6%.

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

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.

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

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)

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

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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.
.

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.

Diagnóstico y epidemiología de erosión dental Diagnosis and epidemiology of dental erosion

Directory of Open Access Journals (Sweden)

Maria Claudia Fajardo Santacruz

2011-08-01

Full Text Available La erosión dental es la pérdida localizada, crónica y patológica de tejido duro dental. Ésta es causada por soluciones químicas las cuales entran en contacto con los dientes. La apariencia de los dientes erosionados es suave, sedosa y brillante, a veces mate, la superficie del esmalte tiene una ausencia de periquimatíes y esmalte intacto en el margen gingival. Se ha hipotetizado que la banda de esmalte preservado a lo largo del margen vestibular y lingual pudiera ser debido a que algunos remanentes de placa podían actuar como una barrera de difusión para los ácidos. Un diagnóstico temprano de este daño del tejido duro dental es de importancia clínica. El objetivo de este artículo es mostrar algunos aspectos básicos de erosión dental en términos de diagnóstico y epidemiología. Este documento enfatiza sobre factores de riesgo extrínsecos los cuales son discutidos con respecto a su relevancia para el desarrollo de erosión dental. Salud UIS 2011; 43 (2: 179-189Dental erosion is a pathologic, chronic, localized loss of dental hard tissue. It is caused by chemical solutions which come into contact with the teeth. The appearance of eroded teeth is smoothing, silky-glazed, sometimes dull, the enamel surface has an absence of perikymata and intact enamel on the gingival margin. It has been hypothesized that the preserved enamel band along the oral and facial gingival margin could be due to some plaque remnants could act as a diffusion barrier for acids. Early diagnosis of this damage of dental hard tissue is of clinical importance. The aim of this article is to show some basic aspects of dental erosion in terms of diagnosis and epidemiology. This paper emphasize on extrinsic risk factors which are discussed with respect to their relevance for the development of dental erosion. Salud UIS 2011; 43 (2: 179-189

The Ghrelin agonist TZP-101 for management of postoperative ileus after partial colectomy: a randomized, dose-ranging, placebo-controlled clinical trial.

Science.gov (United States)

Popescu, Irinel; Fleshner, Phillip R; Pezzullo, John C; Charlton, Philippa A; Kosutic, Gordana; Senagore, Anthony J

2010-02-01

Ghrelin agonist TZP-101 is a potent prokinetic. This phase 2b study evaluated TZP-101 safety and efficacy in postoperative ileus management. Adults undergoing open partial colectomy were adaptively randomized to receive 20, 40, 80, 160, 320, 480 or 600 microg/kg TZP-101 (n = 168) or the placebo (n = 68) by 30-minute IV infusion within 1 hour of surgical closure and then daily for up to 7 days. The primary efficacy end point was the time to first bowel movement. Secondary end points included the percentage of patients with return of gastrointestinal function within 72 hours, and the time to readiness for discharge. TZP-101 accelerated the time to first bowel movement in all groups, with Cox proportional hazard ratios of 1.57 (P = .056) for the low-efficacious dose (80 microg/kg) and 1.67 (P = .03) for the most efficacious dose (480 microg/kg). Using Kaplan-Meier analysis, the median time to first bowel movement was reduced in all TZP-101 groups by 10 to 22 hours vs. the placebo. A greater number of patients who received TZP-101 achieved recovery (P readiness for hospital discharge was significantly accelerated by 20.4 hours at the 480 microg/kg TZP-101 dose compared with the placebo (hazard ratio = 1.69; P = .03). The most common treatment-emergent adverse events were nausea and vomiting, which were reduced in the TZP-101 group compared with the placebo group. In patients undergoing major abdominal surgery, the first-in-class ghrelin agonist TZP-101 was well-tolerated and accelerated recovery of the upper and lower gastrointestinal tract, with a large proportion of subjects recovering within 72 hours compared with the placebo.

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

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.

Scintillation properties of polycrystalline LaxY1-xO3 ceramic

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Sahi, Sunil; Chen, Wei; Kenarangui, Rasool

2015-03-01

Scintillators are the material that absorbs the high-energy photons and emits visible photons. Scintillators are commonly used in radiation detector for security, medical imaging, industrial applications and high energy physics research. Two main types of scintillators are inorganic single crystals and organic (plastic or liquid) scintillators. Inorganic single crystals are expensive and difficult to grow in desire shape and size. Also, some efficient inorganic scintillator such as NaI and CsI are not environmental friendly. But on the other hand, organic scintillators have low density and hence poor energy resolution which limits their use in gamma spectroscopy. Polycrystalline ceramic can be a cost effective alternative to expensive inorganic single crystal scintillators. Here we have fabricated La0.2Y1.8O3 ceramic scintillator and studied their luminescence and scintillation properties. Ceramic scintillators were fabricated by vacuum sintering of La0.2Y1.8O3 nanoparticles at temperature below the melting point. La0.2Y1.8O3 ceramic were characterized structurally using XRD and TEM. Photoluminescence and radioluminescence studies were done using UV and X-ray as an excitation source. We have used gamma isotopes with different energy to studies the scintillation properties of La0.2Y1.8O3 scintillator. Preliminary studies of La0.2Y1.8O3 scintillator shows promising result with energy resolution comparable to that of NaI and CsI.

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

Relación entre obesidad y caries dental en niños

Directory of Open Access Journals (Sweden)

Farith Damián González Martínez

Full Text Available El estado de salud bucal se ha relacionado con la presencia de algunas alteraciones sistémicas; en la población infantil se ha sugerido que la caries dental se asocia con la obesidad. El objetivo de esta revisión fue comparar los resultados de la evidencia sobre la relación entre obesidad y caries dental en niños, por lo cual se realizó una búsqueda computarizada y sistemática utilizando el término "dental caries" combinado con "obesity", "overweight" y "underweight" en las bases de datos Medline, Embase, Pubmed y Ovid, arrojando 439 artículos, de estos se seleccionaron 15 artículos que cumplieron con los criterios de inclusión y superaron una evaluación de calidad metodológica. Los hallazgos fueron almacenados y organizados en una base de datos, se procesaron y analizaron estadísticamente teniendo en cuenta razones de disparidad y el coeficiente de correlación de Pearson reportados. Se presentó un prevalencia general de caries dental de 49,6 %, para los obesos fue de 52,5 % y para los no obesos de 46,8 %. No se encontró asociación entre caries y obesidad en 9 de 15 estudios. La evidencia consultada sugiere que no existe relación entre obesidad y caries dental en niños, pues la prevalencia de caries no mostró diferencias estadísticamente significantes entre niños obesos y no obesos.

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.

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

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.

The effect of sintering temperature on the 3Y-TZP co-doped with equimolar addition of the yttria and niobia

International Nuclear Information System (INIS)

Fonseca, Flavia Baccaro; Dorat, Daniele Ramos; Melo, Francisco Cristovao Lourenco de; Piorino Neto, Francisco; Reis, Danieli Aparecida

2010-01-01

The aim of this work is to identify the better sintering temperature to densify zirconia co-doped with yttria and niobia and to verify the existence of the stable tetragonal phase (t´) under applied stress at room temperature to be applied as a TBC material. Four compositions with equimolar addition of yttria and niobia in the 3Y-TZP were produced, 13.0 %, 14.5 %, 16.0 % and 17.5 %. The mixtures were prepared in high energy ball milling for 10 minutes and the samples prepared on uniaxial and isostatic pressing. The selected sintering temperatures were 1500 deg C, 1550 deg C, 1600 deg C and 1650 deg C, for 1 hour. Analysis of conventional and high resolution X-Ray Diffraction and measures of specific mass by Archimedes method were performed. Through measures of the specific mass, the best sintering temperature was 1550 deg C, with relative specific mass above 95 %. The x-ray diffraction analysis indicate a probable existence of t´ in all samples. (author)

Diagnóstico y tratamiento del trauma dental

Directory of Open Access Journals (Sweden)

Juana María Abreu Correa

1997-12-01

Full Text Available Se realizó un estudio acerca del diagnóstico y tratamiento del trauma dental en un grupo de 40 pacientes cuyas edades oscilaron entre 5 y 25 años. La edad en que ocurrió el trauma con mayor frecuencia fue de 5 a 11 años y la porción dentaria más afectada fue la corona, aunque tenemos 2 casos con fracturas radiculares. Se atendieron 31 pacientes que habían sufrido trauma pasados varios días y habían sido atendidos por otros estomatólogos. La conducta que seguimos fue realizar tratamiento en correspondencia con la afección que presentaba el paciente en ese momento. Tres pacientes acudieron a consulta entre 6 y 24 horas y 6 antes de las 5 horas, a los que se les realizó el tratamiento correcto. Todos los pacientes atendidos después de las 24 horas del trauma presentaron sintomatología dolorosa; no ocurrió así para los pacientes atendidos entre las 5 y 24 horas, que su posoperatorio fue exitoso.It was conducted a study on the diagnosis and treatment of dental trauma in a group of 40 patients aged 5-25. The trauma occurred more frequently among those aged 5-11 and the crown was the most affected dental portion, eventhough there were 2 cases with radicular fractures. 31 patients who had suffered from trauma some days later and had been seen by other stomatologists were attended. 3 patients went to the dental office between 6 and 24 hours after the trauma, whereas 6 did it before the 5 hours. These patients received the correct treatment. The rest of the patients that were given attention 24 hours after the trauma presented a painful symptomatology. It was not so for the patients attended between 5 and 24 hours and whose postoperative was successful.

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

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.

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.

A new approach to measure the elasticity modulus for ceramics using the deformation energy method

International Nuclear Information System (INIS)

Foschini, Cesar R.; Souza, Edson A.; Borges, Ana F. S.; Pintao, Carlos A.

2016-01-01

This paper presents an alternative method to measure the modulus of elasticity to traction, E, for relatively limited sample sizes. We constructed a measurement system with a Force sensor (FS) and a Rotation movement sensor (RMS) to obtain a relationship between force (F) and bending (ΔL). It was possible by calculating the strain energy and the work of a constant force to establish a relationship between these quantities; the constant of proportionality in this relationship depends on E, I and L. I and L are the moment of inertia of the uniform cross-section in relation to an oriented axis and length, respectively, of the sample for bending. An expression that could achieve the value of E was deduced to study samples of Y-TZP ceramics. The advantages of this system compared to traditional systems are its low cost and practicality in determining E

A new approach to measure the elasticity modulus for ceramics using the deformation energy method

Energy Technology Data Exchange (ETDEWEB)

Foschini, Cesar R.; Souza, Edson A. [Dept. of EngineeringFeb-UNESPBauru (Brazil); Borges, Ana F. S. [Dept. of MaterialFOB-USP, Bauru (Brazil); Pintao, Carlos A. [Dept. of PhysicsFC-UNESP, Bauru (Brazil)

2016-08-15

This paper presents an alternative method to measure the modulus of elasticity to traction, E, for relatively limited sample sizes. We constructed a measurement system with a Force sensor (FS) and a Rotation movement sensor (RMS) to obtain a relationship between force (F) and bending (ΔL). It was possible by calculating the strain energy and the work of a constant force to establish a relationship between these quantities; the constant of proportionality in this relationship depends on E, I and L. I and L are the moment of inertia of the uniform cross-section in relation to an oriented axis and length, respectively, of the sample for bending. An expression that could achieve the value of E was deduced to study samples of Y-TZP ceramics. The advantages of this system compared to traditional systems are its low cost and practicality in determining E.

Perspectives on the dental school learning environment: putting theory X and theory Y into action in dental education.

Science.gov (United States)

Connor, Joseph P; Troendle, Karen

2008-12-01

Theory X and Theory Y are terms coined by Douglas McGregor to express the belief that managers' behaviors are shaped by their assumptions about the motivation of their subordinates. The theories were applied to dental education in a Perspectives article published in the August 2007 issue of the Journal of Dental Education. This article explains how those seemingly contradictory theories can be reconciled using the concept of the "emotional bank account" introduced by Stephen Covey in The 7 Habits of Highly Effective People. Understanding the underlying concept of an emotional bank account helps dental educators to bridge the generation gap between instructors, born during the baby boom period of 1946-63, and dental students, born after 1980, who are referred to as "Generation Y" or "millennials."

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.

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

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.

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.

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.

Estabilidad y funcionalidad de sellantes dentales en altas temperaturas ambientales

OpenAIRE

Mishina, Anastasia; Mayelín Guerra, Rosa; Durán Ramos, Ivette; Sabatier, Juan D.

2000-01-01

Los sellantes dentales son materiales que se emplean en estomatología para sellar las fosas y fisuras oclusales de los dientes y evitar la adherencia del estreptococus mutans agente que produce la caries dental. Estos materiales se suministran en dos partes que al mezclarse producen el endurecimiento de la resina. Sin embargo, estos productos presentan dificultades para su comercialización en los países tropicales, debido a que las altas temperaturas ambientales traen problemas en...

Fatigue limit of polycrystalline zirconium oxide ceramics: Effect of grinding and low-temperature aging.

Science.gov (United States)

Pereira, G K R; Silvestri, T; Amaral, M; Rippe, M P; Kleverlaan, C J; Valandro, L F

2016-08-01

The following study aimed to evaluate the effect of grinding and low-temperature aging on the fatigue limit of Y-TZP ceramics for frameworks and monolithic restorations. Disc specimens from each ceramic material, Lava Frame (3M ESPE) and Zirlux FC (Ivoclar Vivadent) were manufactured according to ISO:6872-2008 and assigned in accordance with two factors: (1) "surface treatment"-without treatment (as-sintered, Ctrl), grinding with coarse diamond bur (181µm; Grinding); and (2) "low-temperature aging (LTD)" - presence and absence. Grinding was performed using a contra-angle handpiece under constant water-cooling. LTD was simulated in an autoclave at 134°C under 2-bar pressure for 20h. Mean flexural fatigue limits (20,000 cycles) were determined under sinusoidal loading using stair case approach. For Lava ceramic, it was observed a statistical increase after grinding procedure and different behavior after LTD stimuli (Ctrl

Effects of artificial aging conditions on yttria-stabilized zirconia implant abutments.

Science.gov (United States)

Basílio, Mariana de Almeida; Cardoso, Kátia Vieira; Antonio, Selma Gutierrez; Rizkalla, Amin Sami; Santos Junior, Gildo Coelho; Arioli Filho, João Neudenir

2016-08-01

Most ceramic abutments are fabricated from yttria-stabilized tetragonal zirconia (Y-TZP). However, Y-TZP undergoes hydrothermal degradation, a process that is not well understood. The purpose of this in vitro study was to assess the effects of artificial aging conditions on the fracture load, phase stability, and surface microstructure of a Y-TZP abutment. Thirty-two prefabricated Y-TZP abutments were screwed and tightened down to external hexagon implants and divided into 4 groups (n = 8): C, control; MC, mechanical cycling (1×10(6) cycles; 10 Hz); AUT, autoclaving (134°C; 5 hours; 0.2 MPa); and TC, thermal cycling (10(4) cycles; 5°/55°C). A single-load-to-fracture test was performed at a crosshead speed of 0.5 mm/min to assess the assembly's resistance to fracture (ISO Norm 14801). X-ray diffraction (XRD) analysis was applied to observe and quantify the tetragonal-monoclinic (t-m) phase transformation. Representative abutments were examined with high-resolution scanning electron microscopy (SEM) to observe the surface characteristics of the abutments. Load-to-fracture test results (N) were compared by ANOVA and Tukey test (α=.05). XRD measurements revealed the monoclinic phase in some abutments after each aging condition. All the aging conditions reduced the fracture load significantly (Paging conditions. Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

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.

Factores de riesgo ambientales y alimentarios para la fluorosis dental, Andes, Antioquia, 2015

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Gustavo A. Posada-Jaramillo

2017-01-01

Full Text Available Objetivo: determinar los factores ambientales y alimentarios asociados a la fluorosis dental en la población de 12 a 15 años del municipio de Andes en el año 2015, para generar propuestas de intervención en salud bucal. Metodología: estudio de casos y controles, con un control por caso. Con una población de 206 adolescentes de 12 a 15 años. Criterios de selección: adolescentes con diagnóstico de fluorosis dental entre 2012 y 2014, reportados al Sistema de Vigilancia Epidemiológica; se excluyeron aquellas personas que no tuvieran dientes erupcionados en más de un 50%, restauraciones amplias o caries extensas, dientes fracturados y edentulos totales. Los casos fueron seleccionados por muestreo aleatorio simple, los controles a conveniencia. Se realizó examen clínico para clasificar según el Índice de Dean la presencia y nivel de fluorosis dental, se aplicó encuesta a los padres para indagar sobre hábitos de autocuidado, e identificar posibles fuentes de exposición a flúor. Se analizaron variables sociodemográficas, alimentarias y comportamentales, ambientales y clínicas, se utilizaron Chi2 de Pearson – or con intervalos de confianza del 95%. Se efectúo análisis de contenido de concentración de flúor en muestras de agroquímicos, alimentos, agua de consumo humano, sal, cremas dentales y suelos. Resultados: mediante regresión logística binaria usando el método stepwise los resultados mostraron una asociación entre manipulación de agroquímicos y fluorosis dental (or = 2,093; 95% 1,017 y 4,307. Conclusión: la manipulación de agroquímicos es un factor de riesgo para la aparición de la fluorosis dental en los adolescentes del municipio de Andes.

Fluorosis y caries dental en niños de 6 a 12 años

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Ana María Dobarganes Coca

2015-02-01

Full Text Available El conocimiento de los factores de riesgo de la fluorosis y la caries dental es importante para disminuir la prevalencia de estas enfermedades. Se realizó un estudio descriptivo en niños de la zona rural de Ingenio Viejo, del municipio de Camagüey, con el objetivo de caracterizar la fluorosis y la caries dental, desde septiembre de 2011 hasta septiembre de 2012. La población de estudio estuvo conformada por 67 escolares, a los que se les determinó la presencia de fluorosis dental y los índices de dientes cariados, perdidos y obturados, en la dentición temporal y en la permanente (ceo-d y COP-D, respectivamente. Los factores de riesgo asociados a la caries dental que se tomaron en consideración fueron: susceptibilidad del esmalte, dieta cariogénica e higiene bucal deficiente. Se detectó la presencia de higiene bucal deficiente (71,6 % y dieta cariogénica (82,1 %, sin embargo, el 29,8 % y el 41,8 % de los niños, respectivamente, aunque estuvieron sometidos a estos factores de riesgo no desarrollaron caries dental. El mayor por ciento de los niños sin caries (70,3 % presentó esmalte resistente. Se observó un índice ceo-d de 1,50 y COP-D de 0,20. De los pacientes sin fluorosis, el 60,6 % no presentó caries dental

[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.

Protocol of thermal treatments for the recovery of tetragonal phase in infrastructures of dental prostheses base of ZrO{sub 2} (3-Y{sub 2}O{sub 3}) mills in CAD / CAM systems or panthories; Protocolo de tratamentos termicos visando recuperacao da fase tetragonal em infraestruturas de proteses dentarias a base de ZrO{sub 2}(3-Y{sub 2}O{sub 3}) fresadas em sistemas CAD/CAM ou pantografos

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Simba, B.G.; Ferreira, B.; Santos, C. [Universidade de Sao Paulo (EEL/USP), Lorena, SP (Brazil). Escola de Engenharia; Costa, L. [Centro Universitario de Volta Redonda (MeMAT/UNIFOA), RJ (Brazil). Pro-Reitoria de Pesquisa e Extensao; Sa, L.F.C. de, E-mail: brgalvao@yahoo.com.br [PROTMAT Materiais Avancados, Volta Redonda, RJ (Brazil)

2011-07-01

ZrO{sub 2}(3%Y{sub 2}O{sub 3}) bioceramics are used as dental materials mainly as prosthesis components, because present high mechanical properties and translucence. The use of CAD/CAM machining technique needs final grinding which promotes tetragonal monoclinic transformation reducing the reliability of this ceramic. In this work, ZrO{sub 2}(3%Y{sub 2}O{sub 3}) ceramics were sintered at 1450-0h, 1530-2h or 1600-4h and characterized. Different heat-treatment (400-1200 deg C) are proposed aiming the recuperation of the tetragonal crystalline phase. (author)

Biomolecular modification of zirconia surfaces for enhanced biocompatibility

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Hsu, Shih-Kuang; Hsu, Hsueh-Chuan [Department of Dental Technology and Materials Science, Central Taiwan University of Science and Technology, Taichung 40601, Taiwan, ROC (China); Ho, Wen-Fu [Department of Chemical and Materials Engineering, National University of Kaohsiung, Taiwan, ROC (China); Yao, Chun-Hsu [Department of Biomedical Imaging and Radiological Science, China Medical University, Taichung 40402, Taiwan, ROC (China); Chang, Pai-Ling [Taoyuan General Hospital, Taoyuan 33004, Taiwan, ROC (China); Wu, Shih-Ching, E-mail: scwu@ctust.edu.tw [Department of Dental Technology and Materials Science, Central Taiwan University of Science and Technology, Taichung 40601, Taiwan, ROC (China)

2014-12-01

Yttria-tetragonal zirconia polycrystal (Y-TZP) is a preferred biomaterial due to its good mechanical properties. In order to improve the biocompatibility of zirconia, RGD-peptide derived from extracellular matrix proteins was employed to modify the surface of Y-TZP to promote cell adhesion in this study. The surface of Y-TZP specimens was first modified using a hydrothermal method for different lengths of time. The topographies of modified Y-TZP specimens were analyzed by contact angle, XRD, FTIR, AFM, and FE-SEM. The mechanical properties were evaluated using Vickers hardness and three point bending strength. Then, the RGD-peptide was immobilized on the surface of the Y-TZP by chemical treatment. These RGD-peptide immobilized Y-TZP specimens were characterized by FTIR and AFM, and then were cocultured with MG-63 osteoblast cells for biocompatibility assay. The cell morphology and proliferation were evaluated by SEM, WST-1, and ALP activity assay. The XRD results indicated that the phase transition, from tetragonal phase to monoclinic phase, was increased with a longer incubation time of hydrothermal treatment. However, there were no significant differences in mechanical strengths after RGD-peptide was successfully grafted onto the Y-TZP surface. The SEM images showed that the MG-63 cells appeared polygonal, spindle-shaped, and attached on the RGD-peptide immobilized Y-TZP. The proliferation and cellular activities of MG-63 cells on the RGD-peptide immobilized Y-TZP were better than that on the unmodified Y-TZP. From the above results, the RGD-peptide can be successfully grafted onto the hydrothermal modified Y-TZP surface. The RGD-peptide immobilized Y-TZP can increase cell adhesion, and thus, improve the biocompatibility of Y-TZP. - Highlights: • Covalent bonding between peptide and Y-TZP was proposed. • Stable biomimetic structures produced on the surface of zirconia. • The biocompatibility was improved.

Evaluation of hot hardness, creep, fatigue and fracture properties of zirconia ceramics by an indentation technique

International Nuclear Information System (INIS)

Kutty, T.R.G.; Ganguly, C.; Upadhyaya, D.D.

1996-01-01

Zirconia ceramics have wide range engineering applications at room and elevated temperatures. For understanding the mechanical behaviour, the indentation technique was adapted for quick evaluation of hot hardness, creep, fatigue and fracture properties. A Vicker's diamond indentor with 10 N load was employed for hot hardness and creep measurement up to 1300 deg. The fatigue data were evaluated at room temperature by repeated indentation with a constant load (10-2500N) at the same location for a dwell time of 5s until it resulted in the formation of a lateral chip on the sample surface. Thus, the number of cycles for chip formation at a specific indentation load was obtained. The fracture toughness was evaluated at room temperature with a load of 300N using a Vicker's diamond indentor. The results of hot hardness, creep, fatigue, and fracture data ol 3Y-TZP and Mg-PSZ are discussed along with their microstructural features. (authors)

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

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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.

Laser sintering of ceramics of Y2O3 pure e doped

International Nuclear Information System (INIS)

Oliveira, T.C. de; Goncalves, R.S.; Silva, R.S. da

2012-01-01

The Yttria (Y 2 O 3 ) is one of the most promising materials for refractory and optical applications due mainly to its high corrosion resistance, wide range of optical transmission and high melting point. However, due to its high melting point, ceramic bodies to obtain high density Y 2 O 3 high temperatures and require special sintering. Recently it has been proposed in the literature a new method of sintering in which a CO 2 laser, in continuous mode, is employed as the primary source of heat during sintering. Irradiation with laser light produces heating surface at elevated temperatures in a time interval of a few seconds, allowing to obtain dense ceramic bodies at elevated temperatures and with different properties from those sintered by conventional methods. In this paper, Y 2 O 3 powders of pure and doped with Mn, Ca and Zn were synthesized by the polymeric precursors and after calcination at 600 ° C/4h showed single phase. For the production and characterization of the samples used techniques DTA / TG, XRD Dilatometry, SEM and Radioluminescence. The sintered ceramics had a high relative density and strong dependence on the dopant used, which accelerate the densification process. Measures Radioluminescence showed characteristic peaks of Y 2 O 3 and dependence on the dopant used. (author)

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

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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.

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

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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

Mercurio y salud en la odontología Mercury and health in the dental practice

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Ivelin Morales Fuentes

2003-04-01

Full Text Available El mercurio es un metal pesado ampliamente utilizado por el hombre. Se considera muy tóxico por generar afecciones sobre el sistema nervioso central, perturbaciones en el comportamiento y trastornos renales, inmunes y sexuales, entre otros. Desde hace más de un siglo, el mercurio es utilizado en la práctica odontológica por su capacidad de unir metales (amalgamar, su bajo costo y su rápida fijación en la reparación de piezas dentales. Actualmente, existe una gran controversia acerca de la seguridad del uso de las amalgamas dentales y se ha demostrado el riesgo ocupacional al que están expuestos dentistas y asistentes dentales. El objetivo del trabajo es revisar aspectos relacionados con la toxicidad del mercurio metálico tanto para el personal involucrado en la práctica odontológica como para los pacientes con amalgamas. De igual modo, se presentan las rutas de exposición a este metal en la odontología, los riesgos ocupacionales a los cuales están expuestos los odontólogos y asistentes dentales y las medidas para prevenir la intoxicación por mercurio. Se realizó la búsqueda bibliográfica sobretudo en las bases de datos Biological Abstracts y Science Citation Index para el período comprendido entre los años 1990 y 2000.Mercury is a heavy metal widely used by man. It is considered very toxic causing conditions in the central nervous system, behavior disturbances, and renal and sexual disorders. For a century, mercury has been used in the dental practice for its capacity of joining metals (amalgamate, its low cost and its rapid fixing in dental pieces repair. Currently, there is much controversy about the safety of dental amalgams and it has been demonstrated it poses occupational risks to dental practitioners and their assistants. The objective of this study is review aspects related to metallic mercury toxicity for personnel involved in the dental practice and patients with dental amalgams. Routes of mercury exposure in

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)

Perspectives on the dental school learning environment: theory X, theory Y, and situational leadership applied to dental education.

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Connor, Joseph P; Troendle, Karen

2007-08-01

This article applies two well-known management and leadership models-Theory X and Theory Y, and Situational Leadership-to dental education. Theory X and Theory Y explain how assumptions may shape the behaviors of dental educators and lead to the development of "cop" and "coach" teaching styles. The Situational Leadership Model helps the educator to identify the teaching behaviors that are appropriate in a given situation to assist students as they move from beginner to advanced status. Together, these models provide a conceptual reference to assist in the understanding of the behaviors of both students and faculty and remind us to apply discretion in the education of our students. The implications of these models for assessing and enhancing the educational environment in dental school are discussed.

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

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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.

Nanosecond Tm:Y2O3 ceramic laser passively Q-switched by a Ho:LuAG ceramic

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Wang, Hui; Huang, Haitao; Wang, Shiqiang; Shen, Deyuan

2018-02-01

A passively Q-switched 2.05-μm Tm:Y2O3 ceramic laser, employing Ho:LuAG ceramic as a saturable absorber, was demonstrated for the first time. Under the absorbed pump power of 20.5 W, a maximum output power of 497 mW was obtained. Pulses with a minimum pulse width of 642 ns under the repetition rate of 33 kHz were achieved. Our works validate that Ho-doped materials have good potential for passive Q-switching of Tm-doped lasers at 2-μm wavelength region.

All-Ceramic Single Crown Restauration of Zirconia Oral Implants and Its Influence on Fracture Resistance: An Investigation in the Artificial Mouth

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Ralf-Joachim Kohal

2015-04-01

Full Text Available The aim of the current investigation was to evaluate the fracture resistance of one-piece zirconia oral implants with and without all-ceramic incisor crowns after long-term thermomechanical cycling. A total of 48 implants were evaluated. The groups with crowns (C, 24 samples and without crowns (N, 24 samples were subdivided according to the loading protocol, resulting in three groups of 8 samples each: Group “0” was not exposed to cyclic loading, whereas groups “5” and “10” were loaded with 5 and 10 million chewing cycles, respectively. This resulted in 6 different groups: C0/N0, C5/N5 and C10/N10. Subsequently, all 48 implants were statically loaded to fracture and bending moments were calculated. All implants survived the artificial aging. For the static loading the following average bending moments were calculated: C0: 326 Ncm; C5: 339 Ncm; C10: 369 Ncm; N0: 339 Ncm; N5: 398 Ncm and N10: 355 Ncm. To a certain extent, thermomechanical cycling resulted in an increase of fracture resistance which did not prove to be statistically significant. Regarding its fracture resistance, the evaluated ceramic implant system made of Y-TZP seems to be able to resist physiological chewing forces long-term. Restauration with all-ceramic single crowns showed no negative influence on fracture resistance.

The relationship between milling a new silica-doped zirconia and its resistance to low-temperature degradation (LTD): a pilot study.

Science.gov (United States)

Nakamura, Takashi; Usami, Hirofumi; Ohnishi, Hiroshi; Nishida, Hisataka; Tang, Xuehua; Wakabayashi, Kazumichi; Sekino, Tohru; Yatani, Hirofumi

2012-02-03

The aim of this study was to determine the machinability of new silica-doped Y-TZP by CAD/CAM and the resistance to low temperature degradation of the milled sample by comparing with a commercial HIP type Y-TZP material. The copings could be milled from silica-doped Y-TZP blocks without chipping, and there was no significant difference between the two types of Y-TZP materials in either the marginal or the inner gap between the abutment and the coping. After aging, the monoclinic content in the commercial Y-TZP copings increased from 25% before testing to 65%, while that of silica-doped Y-TZP copings slightly increased from 23% to 30%. The silica-doped Y-TZP copings did not have any significant difference in fracture load in a comparison between the control group and the aging group, while the commercial Y-TZP copings had a significantly lower fracture load for the aging group than for the control group.

Resin-composite blocks for dental CAD/CAM applications.

Science.gov (United States)

Ruse, N D; Sadoun, M J

2014-12-01

Advances in digital impression technology and manufacturing processes have led to a dramatic paradigm shift in dentistry and to the widespread use of computer-aided design/computer-aided manufacturing (CAD/CAM) in the fabrication of indirect dental restorations. Research and development in materials suitable for CAD/CAM applications are currently the most active field in dental materials. Two classes of materials are used in the production of CAD/CAM restorations: glass-ceramics/ceramics and resin composites. While glass-ceramics/ceramics have overall superior mechanical and esthetic properties, resin-composite materials may offer significant advantages related to their machinability and intra-oral reparability. This review summarizes recent developments in resin-composite materials for CAD/CAM applications, focusing on both commercial and experimental materials. © International & American Associations for Dental Research.

ADM guidance-Ceramics: Fracture toughness testing and method selection.

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

2017-06-01

The objective is within the scope of the Academy of Dental Materials Guidance Project, which is to provide dental materials researchers with a critical analysis of fracture toughness (FT) tests such that the assessment of the FT of dental ceramics is conducted in a reliable, repeatable and reproducible way. Fracture mechanics theory and FT methodologies were critically reviewed to introduce basic fracture principles and determine the main advantages and disadvantages of existing FT methods from the standpoint of the dental researcher. The recommended methods for FT determination of dental ceramics were the Single Edge "V" Notch Beam (SEVNB), Single Edge Precracked Beam (SEPB), Chevron Notch Beam (CNB), and Surface Crack in Flexure (SCF). SEVNB's main advantage is the ease of producing the notch via a cutting disk, SEPB allows for production of an atomically sharp crack generated by a specific precracking device, CNB is technically difficult, but based on solid fracture mechanics solutions, and SCF involves fracture from a clinically sized precrack. The IF test should be avoided due to heavy criticism that has arisen in the engineering field regarding the empirical nature of the calculations used for FT determination. Dental researchers interested in FT measurement of dental ceramics should start with a broad review of fracture mechanics theory to understand the underlying principles involved in fast fracture of ceramics. The choice of FT methodology should be based on the pros and cons of each test, as described in this literature review. Copyright © 2017 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

A study of the bending resistance of implant-supported reinforced alumina and machined zirconia abutments and copies.

Science.gov (United States)

Sundh, Anders; Sjögren, Göran

2008-05-01

The purpose of the present study was to evaluate the bending resistance of implant-supported CAD/CAM-processed restorations made out of zirconia or manually shaped made out of reinforced alumina. Units of abutments and copies made of (i) a prefabricated hot isostatic pressed (HIPed) yttrium oxide partially-stabilized zirconia (Y-TZP) (Denzir), (ii) a prefabricated densely-sintered magnesia partially stabilized zirconia (Mg-PSZ) (Denzir-M) or, copies made of (iii) a prefabricated partially-sintered, porous reinforced alumina ceramic (RN synOcta-In-Ceram) were subjected to static loading perpendicularly at the long axis. The abutments were attached to either stainless steel analogs or titanium implant fixtures. The Y-TZP and Mg-PSZ copies were bonded onto the ceramic abutments with a dual-cured resin composite (Rely-X Unicem). Units of titanium abutment attached to a titanium implant fixtures were used as reference. The units comprising Denzir abutments as delivered (pstainless steel analogs exhibited significantly higher bending resistance than the control. The heat-treated Denzir copies bonded to the heat-treated Denzir M abutments attached to titanium implant fixtures and the In-Ceram specimens attached to stainless steel analogs showed significantly (pstainless steel analogs. No statistically significant (p>0.05) differences were seen among the other groups studied. All the ceramic abutments and copies exhibited values that were equal or superior to that of the control and exceeded the reported value, up to 300 N, for maximum incisal bite forces. To assess the clinical behavior long-term clinical studies should be conducted.

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)

[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.

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.

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.

Dental prostheses mimic the natural enamel behavior under functional loading: A review article

Directory of Open Access Journals (Sweden)

Ahmed A. Madfa

2016-02-01

Full Text Available Alumina- and zirconia-based ceramic dental restorations are designed to repair functionality as well as esthetics of the failed teeth. However, these materials exhibited several performance deficiencies such as fracture, poor esthetic properties of ceramic cores (particularly zirconia cores, and difficulty in accomplishing a strong ceramic–resin-based cement bond. Therefore, improving the mechanical properties of these ceramic materials is of great interest in a wide range of disciplines. Consequently, spatial gradients in surface composition and structure can improve the mechanical integrity of ceramic dental restorations. Thus, this article reviews the current status of the functionally graded dental prostheses inspired by the dentino-enamel junction (DEJ structures and the linear gradation in Young's modulus of the DEJ, as a new material design approach, to improve the performance compared to traditional dental prostheses. This is a remarkable example of nature's ability to engineer functionally graded dental prostheses. The current article opens a new avenue for recent researches aimed at the further development of new ceramic dental restorations for improving their clinical durability.

Rehabilitación dental y trastornos temporomandibulares en adolescentes de Puebla, México / Dental rehabilitations and temporomandibular disorders in adolescents of Puebla, Mexico

Directory of Open Access Journals (Sweden)

Gabriel Muñoz Q

2014-05-01

Full Text Available Objetivo: determinar el factor de riesgo para desarrollar trastornos temporomandibulares (ttm en adolescentes sometidos a rehabilitación dental. Métodos: cohorte realizada en 153 adolescentes, (52,9% mujeres y 47% hombres libres de ttm. Para diagnosticar los ttm se utilizaron los Criterios Diagnósticos para la Investigación de los ttm (cdi/ttm, para determinar caries se aplicó el índice cpod. Se formaron dos grupos, el grupo expuesto a rehabilitación dental (74, y el grupo no expuesto (79. Se realizaron seguimientos a las dos semanas, tres y seis meses de la rehabilitación dental. Se utilizó estadística descriptiva y se calculó el riesgo relativo con intervalos de confianza al 95%. Para el grupo de los expuestos, se incluyeron adolescentes libres de ttm en los que fue necesario realizar tratamiento de rehabilitación dental en órganos posteriores con caries en esmalte y dentina en fosas y fisuras. Para el grupo no expuesto, se incluyeron adolescentes pareados por edad y sexo con los expuestos, libres de ttm sin necesidades de rehabilitación dental. Resultados: la incidencia de ttm a los quince días de los expuestos (18,9% fue superior en contraste con los no expuestos (5,0%. El riesgo relativo de desarrollar ttm en los adolescentes rehabilitados con resina a las dos semanas posteriores a la rehabilitación fue de 2.412 (I.C. 95% 1.001-5,81 veces más que en aquellos que no fueron sometidos a la rehabilitación. Conclusión: la rehabilitación dental es un factor de riesgo mínimo para desarrollar ttm a corto plazo (15 días de realizado el procedimiento, dicho padecimiento inducido por la rehabilitación dental es agudo y auto limitante Objective: determine the risk factor involved with developing temporomandibular disorders (tmd in adolescents undergoing dental rehabilitation. Methodology: cohort study carried out on 153 tmd-free adolescents (52.9% women and 47% women. In order to diagnose tmds the Diagnostic Criteria for Research

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.

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.

Zirconia dental implants : a clinical, radiographic, and microbiologic evaluation up to 3 years

NARCIS (Netherlands)

Brüll, Felix; van Winkelhoff, Arie Jan; Cune, Marco S.

2014-01-01

PURPOSE: To retrospectively evaluate the clinical performance of zirconia endosseous implants. MATERIALS AND METHODS: Partially edentulous patients with adequate bone volume to fit yttria tetragonal zirconia polycrystal (Y-TZP) implants at least 3.5 mm wide and 8.0 mm long were included. Full-mouth

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.

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.

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)

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

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

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.

Thermally and optically stimulated luminescence of AlN-Y2O3 ceramics after ionising irradiation

DEFF Research Database (Denmark)

Trinkler, L.; Bos, A.J.J.; Winkelman, A.J.M.

1999-01-01

, an essential drawback of AlN-Y2O3 is its high fading rate. Special attention has been focused on understanding and improving the fading properties. In particular, the influence of the ceramics production conditions and the additive concentration on the fading rate have been studied. Experimental results......Thermally (TL) and optically stimulated luminescence (OSL) were studied in AlN-Y2O3 ceramics after irradiation with ionising radiation. The extremely high TL sensitivity (approximately 60 times the sensitivity of LiF:Mg,Tl (TLD-100)) makes AlN-Y2O3 ceramics attractive as a TLD material. However...... on spectral properties and thermal evolution of OSL are also presented. The stimulation spectrum covers the spectral range from green to infrared light. A combination of thermal and optical stimulation allowed a correlation to be found between parameters of OSL and TL after the same irradiation dose...

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

Fragilidad y comportamiento mecánico del esmalte dental

OpenAIRE

Rivera-Velásquez, C. A. (Camilo Alberto); Ossa, A. (Alexander); Arola, D. (Dwayne)

2012-01-01

El esmalte dental es el tejido duro más mineralizado del cuerpo humano. En este trabajo se estudiaron las propiedades mecánicas fundamentales de este tejido para terceros molares de pacientes jóvenes colombianos. Se establecieron la dureza, la tenacidad a la fractura aparente y la fragilidad del esmalte dental en función de la profundidad a partir de la superficie oclusal mediante técnicas de medición de microindentación. Se encontró que las mediciones de dureza son altamente dependi...

Satisfacción con el aspecto dental general y tratamientos deseados en estudiantes universitarios

Directory of Open Access Journals (Sweden)

Clarisse Virginia Díaz Reissner

2015-08-01

Full Text Available La apariencia dental es considerada un componente de la belleza facial, que al ser restaurada por el odontólogo, podría influir con un efecto positivo en la valoración personal y la calidad de vida. El objetivo del estudio fue determinar la satisfacción general con la apariencia dental en estudiantes de las carreras de Artes Visuales y Diseño de Indumentaria del Instituto Superior de Arte de la Facultad de Arquitectura Diseño y Arte de la Universidad Nacional de Asunción, matriculados en el 2014. Se aplicó un cuestionario que contenía preguntas sobre datos demográficos, satisfacción con el aspecto dental general y con diversos aspectos dentales, así como también sobre el tratamiento estético deseado. La muestra quedó conformada por 108 estudiantes, que corresponde al 49,1% de la población. Se observó que el 48,2% se encontraba insatisfecho con el aspecto general de sus dientes, siendo los tratamientos de elección: blanqueamiento (63,9% y ortodoncia (47,2%. Los factores predisponentes a la insatisfacción fueron residir en Gran Asunción e interior del país y percibir sus dientes como desalineados. Por otro lado, favoreció la satisfacción el haberse sentirse a gusto con el color de sus dientes.

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.

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

International Conference on the Science and Technology of Zirconia (ZrO2IV) (4th) Held in Anaheim, California on Nov 1-3, 1989

Science.gov (United States)

1990-02-01

niobia-zirconia powder from freshly precipitated hydrous zirconia and niobium- Different ceria stabilized TZP ceram- ammonium oxalate . Zirconia powders...is mol% Nb205 showed single orthorhombic phase an acid soluble Zr-Y-REE-Nb-Ta-sili- while this phase always coexisted with mono- cate occurring in a...C :1RCONIA, Chen-Feng Kao and Tsu-Meng BY HYDROTHERMAL PRECIPITATION METHOD, S. P Fueng, Dept of Chemical Engineering, Somiya*, Nishi-Tokyo Univ

PROCESSING OF CONCENTRATED AQUEOUS ZIRCONIA-BIOGLASS SLIPS BY SLIP CASTING

Directory of Open Access Journals (Sweden)

Beltina Leon

2017-03-01

Full Text Available 3 mol% yttria-partially stabilized zirconia (Y-TZP powder and a sol-gel derived CaO- P₂O₅- SiO₂ (64S bioglass, were used to produce Y-TZP- bioglass slip cast compacts. The rheological properties of concentrated aqueous Y-TZP- 64S suspensions prepared with two different glass contents: 10.5 vol% and 19.9 vol%, and ammonium polyacrylate (NH₄PA as dispersant, were investigated and compared with those of Y-TZP. The density of green cast samples was related to the degree of slip dispersion. The substitution of Y-TZP by 64S glass in the mixtures resulted in greater adsorption of NH₄PA; however, the viscosity and yield stress values of Y-TZP-64S slips were higher than those of Y-TZP ones for the solid loadings studied. The increase in the glass content from 10.5 to 19.9 vol% increased the viscosity and yield stress values. The presence of 64S glass in the mixtures resulted in a less dense packing of cast samples.

3D-WOVEN FIBER-REINFORCED COMPOSITE FOR CAD/CAM DENTAL APPLICATION.

Science.gov (United States)

Petersen, Richard; Liu, Perng-Ru

2016-05-01

Three-dimensional (3D)-woven noncrimp fiber-reinforced composite (FRC) was tested for mechanical properties in the two principal directions of the main XY plane and compared to different Computer-Aided-Design/Computer-Aided-Machining (CAD/CAM) Dental Materials. The Dental Materials included ceramic with Vitablock Mark II®, ProCAD®, InCeram® Spinel, InCeram® Alumina and InCeram® Zirconia in addition to a resin-based 3M Corp. Paradigm® particulate-filled composite. Alternate material controls included Coors 300 Alumina Ceramic and a tungsten carbide 22% cobalt cermet. The 3D-woven FRC was vacuum assisted resin transfer molding processed as a one-depth-thickness ~19-mm preform with a vinyl-ester resin and cut into blocks similar to the commercial CAD/CAM Dental Materials. Mechanical test samples prepared for a flexural three-point span length of 10.0 mm were sectioned for minimum-depth cuts to compare machinability and fracture resistance between groups. 3D-woven FRC improved mechanical properties with significant statistical differences over all CAD/CAM Dental Materials and Coors Alumina Ceramic for flexural strength (p<0.001), resilience (p<0.05), work of fracture (p<0.001), strain energy release (p<0.05), critical stress intensity factor (p<0.001) and strain (p<0.001).

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.

Caries y pérdida dental en estudiantes preuniversitarios mexicanos Dental decay and tooth loss at the high school level in Mexican students

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Javier de la Fuente-Hernández

2008-06-01

Full Text Available OBJETIVOS: Conocer la prevalencia de caries y pérdida dental para calcular las necesidades terapéuticas en estudiantes de educación media superior que ingresan a la Universidad Nacional Autónoma de México (UNAM. MATERIAL Y MÉTODOS: Se realizó un estudio transversal descriptivo en el que se obtuvo una muestra de 77 191 estudiantes correspondientes a las generaciones de ingreso al bachillerato 2003, 2004 y 2005. Los datos de salud bucal se obtuvieron a partir del índice CPOD incluido en el Examen Médico Automatizado (EMA, instrumento de autorrespuesta estandarizado que aplica la Dirección General de Servicios Médicos (DGSM. El análisis del EMA fue univariado con la finalidad de identificar la distribución y la frecuencia de las variables. RESULTADOS: La prevalencia de caries y pérdida dental fue de 48.0 y 34.2%, respectivamente, con una cuantificación del índice CPOD de 5. Las necesidades de tratamiento para caries y pérdida dental se obtuvieron en al menos un diente por estudiante. CONCLUSIONES: Cerca de la mitad de los alumnos que ingresan al bachillerato de la UNAM requiere al menos la atención de una caries o prótesis dental. Lo anterior evidencia que las políticas en salud bucal instrumentadas no han alcanzado los índices en salud esperados en relación con los objetivos internacionales, así como la necesidad de impulsar nuevas líneas de investigación orientadas a identificar la gravedad de la enfermedad y factores vinculados con el deterioro de la salud bucal.OBJECTIVE: To determine the prevalence of dental decay and tooth loss, and to consider the treatment needs for students at the Mexican National Autonomous University (UNAM. MATERIALS AND METHODS: A cross sectional study was designed including 77 191 students corresponding to the years of entrance to high school 2003, 2004 and 2005. Oral health data were obtained from the DMF-T index included in the Automatized Medical Exam (AME, a student self-answer instrument

Optical properties of CAD-CAM ceramic systems.

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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.

Caries dental y factores de riesgo en adultos jóvenes: Distrito Capital, Venezuela Dental caries and risk factors present in young adults

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Amílcar González Sánchez

2009-09-01

Full Text Available Se realizó un estudio epidemiológico transversal o de prevalencia con el objetivo de describir la morbilidad por caries dental y factores de riesgo seleccionados en adultos jóvenes en el periodo de enero de 2006 a diciembre de 2006, en el municipio "Libertador" del Distrito Capital. El universo de estudio estuvo conformado 245 trabajadores sociales venezolanos "luchadores sociales", que laboraron en la Misión Energía. Se confeccionó un formulario en el cual se recogió toda la información necesaria, se utilizó para ellos los métodos empíricos de la observación e interrogatorio al paciente, se determinó la morbilidad de la caries dental así como la asociación entre estas y factores de riesgos modificables y se calcularon los indicadores de riesgo e impacto potencial. El 90,6 % de los examinados presentaron caries dental, la edad más afectada fue la de 30 años y más con un 94,4 % y el sexo masculino con un 91,2 %, aunque no se determinaron diferencias significativas en cuanto a ellas (p> 0,05. Se determinó asociación significativa en orden de importancia entre las caries y la experiencia anterior de la enfermedad (razón de prevalencia (RP= 2,63; fracción etiológica en los expuestos (EEe= 62,0 y fracción etiológica en la población (FEp= 55,1; ingestión de dieta cariogénica (RP= 2,33; FEe= 57,1 y FEp= 49,9; higiene bucal no adecuada (RP= 1,63, FEe= 38,6 y FEp= 31,55; nivel de conocimiento no adecuado sobre salud bucal (RP= 1,30, FEe= 23,1 y FEp= 16,4 y la no visita sistemática a la consulta estomatológica (RP= 1,27; FEe= 21,3 y FEp= 15,5. Se recomienda diseñar y aplicar estrategias de intervención educativas con participación comunitaria, con el objetivo de modificar los conocimientos, actitudes y prácticas para la prevención de la Caries dental.A cross-sectional epidemiologic or of prevalence study was conducted to describe the morbidity by dental caries and risk factors selected in young adults from January, 2006

Agenesia dental: Epidemiología, clínica y genética en pacientes antioqueños

OpenAIRE

J. Echeverri Escobar; L.A. Restrepo Perdomo; G. Vásquez Palacio; N. Pineda Trujillo; D.M. Isaza Guzmán; H.A. Manco Guzmán; M.L. Marín Botero

2013-01-01

Introducción: La odontogénesis es un proceso molecular complejo, susceptible a errores durante las etapas del desarrollo, que puede generar alteraciones, como agenesias dentales. Metodología: Se realizó una descripción epidemiológica de la agenesia dental en 814 pacientes de la Facultad de Odontología de la Universidad de Antioquía entre 2006 y 2008, con base en la historia clínica y radiografías panorámicas. Se evaluó clínica y genéticamente una familia con agenesia dental no sindrómica, se ...

[Research progress in CoCr metal-ceramic alloy fabricated by selective laser melting].

Science.gov (United States)

Yan, X; Lin, H

2018-02-09

Cobalt-chromium alloys have been applied to dental porcelain fused to metal (PFM) restorations over the past decades owing to their excellent corrosion resistance, good biocompatibility and low price. The production of CoCr metal-ceramic restorations has always been based on traditional lost-wax casting techniques. However, in recent years, selective laser melting (SLM) is becoming more and more highly valued by dental laboratories and dental practitioners due to its individuation, precision and efficiency. This paper mainly reviews the recent researches on the production process of copings, microstructure, mechanical property, metal-ceramic bond strength, fit of copings, corrosion resistance and biocompatibility of SLM CoCr metal-ceramic alloy.

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.

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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.

Temperature variation in metal ceramic technology analyzed using time domain optical coherence tomography

Science.gov (United States)

Sinescu, Cosmin; Topala, Florin I.; Negrutiu, Meda Lavinia; Duma, Virgil-Florin; Podoleanu, Adrian G.

2014-01-01

The quality of dental prostheses is essential in providing good quality medical services. The metal ceramic technology applied in dentistry implies ceramic sintering inside the dental oven. Every ceramic material requires a special sintering chart which is recommended by the producer. For a regular dental technician it is very difficult to evaluate if the temperature inside the oven remains the same as it is programmed on the sintering chart. Also, maintaining the calibration in time is an issue for the practitioners. Metal ceramic crowns develop a very accurate pattern for the ceramic layers depending on the temperature variation inside the oven where they are processed. Different patterns were identified in the present study for the samples processed with a variation in temperature of +30 °C to +50 °C, respectively - 30 0°C to -50 °C. The OCT imagistic evaluations performed for the normal samples present a uniform spread of the ceramic granulation inside the ceramic materials. For the samples sintered at a higher temperature an alternation between white and darker areas between the enamel and opaque layers appear. For the samples sintered at a lower temperature a decrease in the ceramic granulation from the enamel towards the opaque layer is concluded. The TD-OCT methods can therefore be used efficiently for the detection of the temperature variation due to the ceramic sintering inside the ceramic oven.

SEM evaluation of human gingival fibroblasts growth onto CAD/CAM zirconia and veneering ceramic for zirconia

Science.gov (United States)

Zizzari, Vincenzo; Borelli, Bruna; De Colli, Marianna; Tumedei, Margherita; Di Iorio, Donato; Zara, Susi; Sorrentino, Roberto; Cataldi, Amelia; Gherlone, Enrico Felice; Zarone, Fernando; Tetè, Stefano

2013-01-01

Summary Aim To evaluate the growth of Human Gingival Fibroblasts (HGFs) cultured onto sample discs of CAD/CAM zirconia and veneering ceramic for zirconia by means of Scanning Electron Microscope (SEM) analysis at different experimental times. Methods A total of 26 experimental discs, divided into 2 groups, were used: Group A) CAD/CAM zirconia (3Y-TZP) discs (n=13); Group B) veneering ceramic for zirconia discs (n=13). HGFs were obtained from human gingival biopsies, isolated and placed in culture plates. Subsequently, cells were seeded on experimental discs at 7,5×103/cm2 concentration and cultured for a total of 7 days. Discs were processed for SEM observation at 3h, 24h, 72h and 7 days. Results In Group A, after 3h, HGFs were adherent to the surface and showed a flattened profile. The disc surface covered by HGFs resulted to be wider in Group A than in Group B samples. At SEM observation, after 24h and 72h, differences in cell attachment were slightly noticeable between the groups, with an evident flattening of HGFs on both surfaces. All differences between Group A and group B became less significant after 7 days of culture in vitro. Conclusions SEM analysis of HGFs showed differences in terms of cell adhesion and proliferation, especially in the early hours of culture. Results showed a better adhesion and cell growth in Group A than in Group B, especially up to 72h in vitro. Differences decreased after 7 days, probably because of the rougher surface of CAD/CAM zirconia, promoting better cell adhesion, compared to the smoother surface of veneering ceramic. PMID:24611089

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.

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

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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.

Effects of different lasers and particle abrasion on surface characteristics of zirconia ceramics.

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Sakineh Arami

2014-04-01

Full Text Available The aim of this study was to assess the surface of yttrium-stabilized tetragonal zirconia (Y-TZP after surface treatment with lasers and airborne-particle abrasion.First, 77 samples of presintered zirconia blocks measuring 10 × 10 × 2 mm were made, sintered and polished. Then, they were randomly divided into 11 groups (n=7 and received surface treatments namely, Er:YAG laser irradiation with output power of 1.5, 2 and 2.5 W, Nd:YAG laser with output power of 1.5, 2 and 2.5 W, CO2 laser with output power of 3, 4 and 5 W, AL2O3 airborne-particle abrasion (50μ and no treatment (controls. Following treatment, the parameters of surface roughness such as Ra, Rku and Rsk were evaluated using a digital profilometer and surface examination was done by SEM.According to ANOVA and Tukey's test, the mean surface roughness (Ra after Nd:YAG laser irradiation at 2 and 2.5 W was significantly higher than other groups. Roughness increased with increasing output power of Nd:YAG and CO2 lasers. Treated surfaces by Er:YAG laser and air abrasion showed similar surface roughness. SEM micrographs showed small microcracks in specimens irradiated with Nd:YAG and CO2 lasers.Nd:YAG laser created a rough surface on the zirconia ceramic with many microcracks; therefore, its use is not recommended. Air abrasion method can be used with Er:YAG laser irradiation for the treatment of zirconia ceramic.

Masking properties of ceramics for veneer restorations.

Science.gov (United States)

Skyllouriotis, Andreas L; Yamamoto, Hideo L; Nathanson, Dan

2017-10-01

The translucency and opacity of ceramics play a significant role in emulating the natural color of teeth, but studies of the masking properties and limitations of dental ceramics when used as monolayer restorations are lacking. The purpose of this in vitro study was to determine the translucency of 6 materials used for veneer restorations by assessing their translucency parameters (TPs), contrast ratios (CRs), and potential to mask dark tooth colors. Ten square- or disk-shaped specimens (0.5-mm thickness, shade A2) were fabricated from Vitablocks Mark II (VMII; Vita Zahnfabrik), IPS e.max CAD LT (EMXC LT; Ivoclar Vivadent AG), IPS e.max CAD HT (EMXC HT; Ivoclar Vivadent AG), IPS Empress CAD LT (EMP LT; Ivoclar Vivadent AG), IPS e.max Press LT (EMXP LT; Ivoclar Vivadent AG), and CZR (CZR; Kuraray Noritake Dental Inc). Their luminance (Y) values over black and over white tiles were measured, followed by their color (CIELab) over black tiles and white tiles and shaded A2 (control group), A3.5, A4, and B4 acrylic resin blocks. All measurements were performed using a spectrophotometer in 2 different areas on each specimen. Then CRs, TPs, and color differences (over shaded backgrounds) were determined. Data were subjected to 1-way and 2-way ANOVA (α=.05) for analysis. Mean CR values of EMXP LT were significantly higher than those of the other tested materials, whereas VMII and EMXC HT had the lowest values (Pmasking properties against the A4 background. The color differences of most tested ceramics were more acceptable when tested against the B4 background (ΔE*≤3.3). Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Prototyping of Dental Structures Using Laser Milling

Science.gov (United States)

Andreev, A. O.; Kosenko, M. S.; Petrovskiy, V. N.; Mironov, V. D.

2016-02-01

The results of experimental studies of the effect of an ytterbium fiber laser radiation parameters on processing efficiency and quality of ZrO2 ceramics widely used in stomatology are presented. Laser operating conditions with optimum characteristics for obtaining high quality final surfaces and rapid material removal of dental structures are determined. The ability of forming thin-walled ceramic structures by laser milling technology (a minimum wall thickness of 50 μm) is demonstrated. The examples of three-dimensional dental structures created in computer 3D-models of human teeth using laser milling are shown.

Experimental study of stress-induced localized transformation plastic zones in tetragonal zirconia polycrystalline ceramics

International Nuclear Information System (INIS)

Sun, Q.; Zhao, Z.; Chen, W.; Qing, X.; Xu, X.; Dai, F.

1994-01-01

Stress-induced martensitic transformation plastic zones in ceria-stabilized tetragonal zirconia polycrystalline ceramics (Ce-TZP), under loading conditions of uniaxial tension, compression, and three-point bending, are studied by experiments. The transformed monoclinic phase volume fraction distribution and the corresponding plastic strain distribution and the surface morphology (surface uplift) are measured by means of moire interferometry, Raman microprobe spectroscopy, and the surface measurement system. The experimental results from the above three kinds of specimens and methods consistently show that the stress-induced transformation at room temperature of the above specimen is not uniform within the transformation zone and that the plastic deformation is concentrated in some narrow band; i.e., macroscopic plastic flow localization proceeds during the initial stage of plastic deformation. Flow localization phenomena are all observed in uniaxial tension, compression, and three-point bending specimens. Some implications of the flow localization to the constitutive modeling and toughening of transforming thermoelastic polycrystalline ceramics are explored

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.

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.

Patologías dentales en incisivos, caninos y primer premolar en caballos chilenos adultos Dental pathologies in incisors, canines and first premolar in adult Chilean horses

OpenAIRE

L Muñoz; F Vidal; O Sepúlveda; O Ortiz; C Rehhof

2010-01-01

Las patologías dentales han ido tomando mayor relevancia clínico veterinaria, aumentando el número de consultas, tratamientos y procedimientos preventivos. En caballos chilenos, la información existente de patologías dentales es nula, por lo que se hace primordial la investigación y recolección de datos en esta raza. Se analizaron 100 caballos pertenecientes a la Asociación de Rodeo Concepción, entre los meses de junio y septiembre del año 2007. Los materiales que se utilizaron fueron puro, l...

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

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

Radiopaque strontium fluoroapatite glass-ceramics

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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

Luminescence and scintillation enhancement of Y2O3:Tm transparent ceramic through post-fabrication thermal processing

International Nuclear Information System (INIS)

Chapman, M.G.; Marchewka, M.R.; Roberts, S.A.; Schmitt, J.M.; McMillen, C.; Kucera, C.J.; DeVol, T.A.; Ballato, J.; Jacobsohn, L.G.

2015-01-01

The effects of post-fabrication thermal processing in O 2 flux on the luminescence and scintillation of a Y 2 O 3 :Tm transparent ceramic were investigated. The results showed that the strategy of post-fabrication processing can be beneficial to the performance of the ceramics, depending on the cumulative processing time. After the first hour of processing, about 40% enhancement in the luminescence output together with about 20% enhancement in the scintillation light yield were obtained. The enhancements were tentatively assigned to the incorporation of oxygen into vacancy sites. Longer cumulative processing times lead to the incorporation of oxygen as interstitials that is detrimental to scintillation light yield but not to luminescence output. This work also revealed that thermoluminescence measurements are a useful tool to predict scintillation light yield of Y 2 O 3 :Tm. - Highlights: • Scintillation and PL enhancement of transparent ceramics through thermal processing. • First thermoluminescence measurements of Y 2 O 3 :Tm above room temperature. • Observation of correlation between TL and scintillation light yield results

Synthesis and properties of nasicon prepared from different zirconia-based precursors

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Fuentes, R. O.

1999-12-01

Full Text Available This work reports on the synthesis and characterization of NASICON prepared from SiO2, Na3PO4.12H2O and two types of zirconia: pure monoclinic ZrO2 and TZP (Tetragonal Polycrystalline Zirconia, with 3 mol% Y2O3 as raw materials. The classical ceramic method was used in all cases. SEM, XRD and DTA were used to follow the synthesis and sintering process, and impedance spectroscopy (IS was used to study the electrical properties of sintered pellets. Results obtained with different NASICON samples showed a significant role of composition and processing conditions on the electrical properties. Samples based on TZP, sintered at 1210ºC, exhibited densities of about 3.20 g/cm3 (98% of theoretical density of NASICON and ionic conductivities of about 2x10-3 S.cm-1 at room temperature a rather interesting result when compared with data obtained with the material prepared from pure ZrO2.

Este trabajo trata de la síntesis y caracterización de NASICON preparado a partir de SiO2 , Na3PO4.12H2O y dos tipos de circonia, ZrO2 monoclínica pura y TZP (circonia policristalina tetragonal, con 3 moles% Y2O3 como materia prima. Se emplea el método cerámico clásico en todos los casos. Las técnicas de MEB, DRX y ATD se emplean para seguir la síntesis y el proceso de sinterización. La espectroscopia de impedancia compleja se emplea para estudiar las propiedades eléctricas de las muestras sinterizadas. Los resultados obtenidos con diferentes muestras de NASICON mostraron un papel significativo de la composición y condiciones de procesamiento sobre las propiedades eléctricas. Las muestras basadas en TZP, sinterizadas a 1210ºC, presentan densidades alrededor de 3.20 g/cm3 (98% de la densidad teórica del NASICON y conductividad iónica de 2x 10-3 5.cm-1 a temperatura ambiente, un resultado bastante interesante cuando se compara con datos obtenidos con material preparado de ZrO2 pura.

Crystallization of high-strength nano-scale leucite glass-ceramics.

Science.gov (United States)

Theocharopoulos, A; Chen, X; Wilson, R M; Hill, R; Cattell, M J

2013-11-01

Fine-grained, high strength, translucent leucite dental glass-ceramics are synthesized via controlled crystallization of finely milled glass powders. The objectives of this study were to utilize high speed planetary milling of an aluminosilicate glass for controlled surface crystallization of nano-scale leucite glass-ceramics and to test the biaxial flexural strength. An aluminosilicate glass was synthesized, attritor or planetary milled and heat-treated. Glasses and glass-ceramics were characterized using particle size analysis, X-ray diffraction and scanning electron microscopy. Experimental (fine and nanoscale) and commercial (Ceramco-3, IPS Empress Esthetic) leucite glass-ceramics were tested using the biaxial flexural strength (BFS) test. Gaussian and Weibull statistics were applied. Experimental planetary milled glass-ceramics showed an increased leucite crystal number and nano-scale median crystal sizes (0.048-0.055 μm(2)) as a result of glass particle size reduction and heat treatments. Experimental materials had significantly (p0.05) strength difference. All other groups' mean BFS and characteristic strengths were found to be significantly different (pglass-ceramics with high flexural strength. These materials may help to reduce problems associated with brittle fracture of all-ceramic restorations and give reduced enamel wear. Copyright © 2013 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Mechanical properties of polymer-infiltrated-ceramic-network materials.

Science.gov (United States)

Coldea, Andrea; Swain, Michael V; Thiel, Norbert

2013-04-01

To determine and identify correlations between flexural strength, strain at failure, elastic modulus and hardness versus ceramic network densities of a range of novel polymer-infiltrated-ceramic-network (PICN) materials. Four ceramic network densities ranging from 59% to 72% of theoretical density, resin infiltrated PICN as well as pure polymer and dense ceramic cross-sections were subjected to Vickers Indentations (HV 5) for hardness evaluation. The flexural strength and elastic modulus were measured using three-point-bending. The fracture response of PICNs was determined for cracks induced by Vickers-indentation. Optical and scanning electron microscopy (SEM) was employed to observe the indented areas. Depending on the density of the porous ceramic the flexural strength of PICNs ranged from 131 to 160MPa, the hardness values ranged between 1.05 and 2.10GPa and the elastic modulus between 16.4 and 28.1GPa. SEM observations of the indentation induced cracks indicate that the polymer network causes greater crack deflection than the dense ceramic material. The results were compared with simple analytical expressions for property variation of two phase composite materials. This study points out the correlation between ceramic network density, elastic modulus and hardness of PICNs. These materials are considered to more closely imitate natural tooth properties compared with existing dental restorative materials. Copyright © 2013 Academy of Dental Materials. All rights reserved.

Asociación del Estreptococos mutans y lactobacilos con la caries dental en niños Association of Streptococcus mutans and lactobacilli with dental caries in children

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José Alberto Pérez Quiñones

2007-12-01

Full Text Available La caries dental es una enfermedad ampliamente extendida en el mundo, por lo que ha sido y sigue siendo la enfermedad más frecuente del hombre moderno. Dada la alta incidencia que presenta esta enfermedad bucal, así como la gran necesidad de prevenirla, decidimos realizar esta investigación, con el objetivo de evaluar la relación de los microorganismos cariogénicos y algunas variables demográficas con la caries dental en niños. Se realizó un estudio analítico del tipo de casos y controles en el municipio de Matanzas, provincia de Matanzas, en el período comprendido por el curso académico 2004-2005. El universo estuvo constituido por 11 311 niños entre 6 y 12 años de edad, determinándose una muestra aleatoria de 900 niños (300 casos y 600 controles. Se obtuvo que el mayor porcentaje (62 % de niños de piel blanca estaba afectados por caries, el 91,3 % y el 40 % de los niños pertenecientes al grupo de casos, tenían un alto grado de infección por Estreptococo mutans y lactobacilos, respectivamente, lo que demuestra una asociación positiva entre la caries dental y estas variables.Dental caries is a disease widely spread in the world, therefore, it has been and it is still the most frequent disease of modern man. Due to the high incidence of this oral disease, and to the great need to prevent it, it was decided to conduct this investigation in order to evaluate the connection of the cariogenic microorganisms and some demographic variables with dental caries in children. A case-control analytical study was undertaken in the municipality of Matanzas, province of Matanzas, during the academic course 2004-2005. The study group was composed of 11 311 children aged 6-12. A randomized sample of 900 children (300 cases and 600 controls was selected. The highest percentage of white children (62 % were affected by caries, 91.3 % and 40 % of the children from the case group had an elevated degree of infection caused by Streptococcus mutans y

Diode-pumped high power 2.7 μm Er:Y2O3 ceramic laser at room temperature

Science.gov (United States)

Wang, Li; Huang, Haitao; Shen, Deyuan; Zhang, Jian; Chen, Hao; Tang, Dingyuan

2017-09-01

Investigation of room temperature laser performance of the polycrystalline Er:Y2O3 ceramic at 2.7 μm with respect to dopant concentrations was conducted. With 7 at.% Er3+ concentration Er:Y2O3 ceramic as laser gain medium, over 2.05 W of CW output power at 2.7 μm was generated with a slope efficiency of 11.1% with respect to the absorbed LD pump power. The prospects for improvement in lasing efficiency and output power are considered.

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.

Asociación del sobrepeso y caries dental en niños de 3 a 6 años

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Carmen de la Luz-Ayala-Escandón

2013-01-01

Full Text Available Antecedentes: En los últimos años de nuestro país, los cambios en los patrones de alimentación han incrementado los casos de obesidad y sobrepeso en los niños. Objetivo: determinar si la prevalencia de caries dental se asocia al sobrepeso y obesidad en preescolares de la Zona Metropolitana Zacatecas-Guadalupe. Materiales y Métodos: Se realizó estudio observacional de cohorte retrospectivo, en dos grupos de estudio: niños con peso normal (n=108 y niños con sobrepeso u obesidad (n=54. Para determinar el sobrepeso o peso normal, se utilizó un estadiómetro y una báscula digital, los datos se analizaron de acuerdo a los puntos de corte de IMC para cada edad según género con tablas de percentiles del Center for Diseases Control (CDC. Para el registro de la enfermedad caries dental se realizó examen clínico de las superfi\tdentales bajo luz artifi espejo dental plano, sonda de la OMS y barreras de protección, utilizando los criterios del Sistema Internacional de Evaluación y Detección de Caries Dental (ICDAS II. Los datos recopilados se procesaron en el paquete estadístico SPSS 17 para la obtención de tablas y fi\tPara determinar la asociación entre las variables de estudio se utilizó las pruebas X2 y riesgo relativo (RR. Resultados: En los niños con peso normal la prevalencia de caries fue de 77.8% mientras que en los niños con sobrepeso fue de 69.1%. Conclusiones: Este estudio no encontró evidencia de asociación entre caries dental y sobrepeso.

Microstructures and mechanical properties of Gd{sub 2}Zr{sub 2}O{sub 7}/ZrO{sub 2}(3Y) ceramics

Energy Technology Data Exchange (ETDEWEB)

Ma, Lei [Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), Northeastern University, Shenyang, Liaoning 110819 (China); Key Laboratory for Advanced Ceramics and Application of Shenyang, Shenyang University of Chemical Technology, Shenyang, Liaoning 110142 (China); Ma, Weimin, E-mail: maleisy2003@163.com [Key Laboratory for Advanced Ceramics and Application of Shenyang, Shenyang University of Chemical Technology, Shenyang, Liaoning 110142 (China); Sun, Xudong, E-mail: xdsun@mail.neu.edu.cn [Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), Northeastern University, Shenyang, Liaoning 110819 (China); Ji, Lianyong; Liu, Jianan; Hang, Kai [Key Laboratory for Advanced Ceramics and Application of Shenyang, Shenyang University of Chemical Technology, Shenyang, Liaoning 110142 (China)

2015-09-25

Highlights: • Gd{sub 2}Zr{sub 2}O{sub 7}/ZrO{sub 2}(3Y) composites were prepared using vacuum sintering. • The phase composition and microstructure are studied. • Gd{sub 2}Zr{sub 2}O{sub 7}/ZrO{sub 2}(3Y) materials show superior mechanical properties. • The solid solution strengthening and stress-induced phase transformation toughening mechanism are proposed. • Two kinds of mechanisms explain the improvement of mechanical properties. - Abstract: Gd{sub 2}Zr{sub 2}O{sub 7}/ZrO{sub 2}(3Y) composite ceramics were prepared by vacuum sintering using Gd{sub 2}Zr{sub 2}O{sub 7} and ZrO{sub 2}(3Y) nanoparticles. The ceramics were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), the three-point-bending technique and single-edge-notched-beam tests. The effect of various proportions of ZrO{sub 2}(3Y) on the phase composition, microstructure, bending strength and fracture toughness of the final Gd{sub 2}Zr{sub 2}O{sub 7}/ZrO{sub 2}(3Y) composite ceramics was also analyzed. The change from m-ZrO{sub 2} to t-ZrO{sub 2} phase contents, before and after fracture, was measured using XRD quantitative phase analysis. The results confirm that, with the increasing content of ZrO{sub 2}(3Y), a phase transition from solid solution to saturated precipitation occurs and the bending strength and fracture toughness of the samples increase gradually. When the content of ZrO{sub 2}(3Y) reached 95 vol.%, the Gd{sub 2}Zr{sub 2}O{sub 7}/ZrO{sub 2}(3Y) composite ceramics had a bending strength of 547 MPa and a fracture toughness of 5.5 MPa m{sup 1/2}, indicating that stress-induced phase transformation toughening was an efficient way to increase the mechanical properties of the Gd{sub 2}Zr{sub 2}O{sub 7} ceramics.

Propiedades mecánicas y degradación de implantes dentales de circona estabilizada con itria

OpenAIRE

Sevilla Sánchez, Pablo

2007-01-01

En la actualidad, el campo de la implantología se encuentra en pleno crecimiento. En pocos años han surgido numerosas empresas fabricantes de implantes dentales y la competencia es cada vez más fuerte. Por esta razón las empresas de implantes dentales apuestan por la innovación y tratan de lanzar al mercado nuevos productos a fin de aumentar su cota de mercado. En odontología la estética es uno de los factores de mayor impacto en el éxito de un tratamiento. Y por ello, cada día...

Peculiarities of the temperature dependences of trapped magnetic field in Y-HTSC ceramics

International Nuclear Information System (INIS)

Sukhanov, A.A.; Omel'chenko, V.I.

2001-01-01

The temperature dependence H t (T) of trapped magnetic field (TMF) in Y-HTSC ceramics are studied. For the fields-cooled trapping the H t (T) dependences coincide with the dependences of H t on trapping temperature T t . Both dependences fall off monotonously with increasing temperature, and for low fields they reach saturation as temperature is decreased. When the trapping is induced by the field pulse after zero cooling the H t (T t ) dependences show a maximum while the H t (T) curves drop monotonously with increase in temperature. In this case the rate of their dropping increases with decrease in pulse magnitude and the temperature of TMF vanishing decreases with T t and H. The results are discussed and it is shown that contrast to the Been model the theory based on the model of TMF in superconductive loops gives an adequate analytical description of the observed features of the temperature dependences of trapped magnetic field in the Y-HTSC ceramics

Ceramic and non-ceramic hydroxyapatite as a bone graft material: a brief review.

Science.gov (United States)

Dutta, S R; Passi, D; Singh, P; Bhuibhar, A

2015-03-01

Treatment of dental, craniofacial and orthopedic defects with bone graft substitutes has shown promising result achieving almost complete bone regeneration depending on product resorption similar to human bone's physicochemical and crystallographic characteristics. Among these, non-ceramic and ceramic hydroxyapatite being the main inorganic salt of bone is the most studied calcium phosphate material in clinical practices ever since 1970s and non-ceramic since 1985. Its "chemical similarity" with the mineralized phase of biologic bone makes it unique. Hydroxyapatite as an excellent carrier of osteoinductive growth factors and osteogenic cell populations is also useful as drug delivery vehicle regardless of its density. Porous ceramic and non-ceramic hydroxyapatite is osteoconductive, biocompatible and very inert. The need for bone graft material keeps on increasing with increased age of the population and the increased conditions of trauma. Recent advances in genetic engineering and doping techniques have made it possible to use non-ceramic hydroxyapatite in larger non-ceramic crystals and cluster forms as a successful bone graft substitute to treat various types of bone defects. In this paper we have mentioned some recently studied properties of hydroxyapatite and its various uses through a brief review of the literatures available to date.

Remakes of Colorlogic and IPS Empress ceramic restorations in general practice.

Science.gov (United States)

Hekland, Helge; Riise, Trond; Berg, Einar

2003-01-01

The aim of this article was to study frequencies and distribution of remakes of all-ceramic inlays/onlays, veneers, and crowns occurring before and after cementation. A total of 2,069 sintered feldspathic ceramic restorations (Colorlogic) and 1,136 pressure-molded ceramic restorations (IPS Empress 1 and 2) were produced during the study period by one dental laboratory. The laboratory gave an unqualified and unlimited guarantee for their ceramic restorations. The outcome variable was reports from the clinicians to the dental laboratory about any problems related to the restoration, necessitating remake. Problems occurring before cementation occurred in 4.4% of the restorations. Veneers were remade more frequently than the other types of restorations (6.6%). After cementation, the overall 2-year rate of remakes was 1%, indicating a survival rate of the ceramic restorations of 99%, with inlays/onlays exhibiting the highest (99.8%) and crowns the lowest (98.4%) rates. This difference in rates was significant. No significant differences in remakes between ceramics or tooth categories were found. There were few problems in a short- to medium-term perspective that, in the opinion of general practitioners, necessitated remakes of all-ceramic restorations.

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.

Effect of furnace type and ceramming heat treatment conditions on the biaxial flexural strength of a canasite glass-ceramic.

Science.gov (United States)

Johnson, A; Shareef, M Y; van Noort, R; Walsh, J M

2000-07-01

To assess the effect of different heat treatment conditions when using two different furnace types on the biaxial flexural strength (BFS) of a fluorcanasite castable glass-ceramic. Two furnace types, one a programmable furnace (PF), the other a dental laboratory burnout furnace (DLF), were used with various ceramming times to determine their effect on the BFS of a fluorcanasite castable glass-ceramic. The glass-ceramic material was cast to produce discs of 12 mm diameter and 2 mm thickness using the lost wax casting process (n = 80). After casting, both furnace types were used to ceram the discs. Half the discs were not de-vested from the casting ring before ceramming but cerammed in situ (DLF) and half were de-vested before ceramming (PF). All the discs were given a nucleation heat treatment at 520 degrees C for 1 h and then cerammed at 860 degrees C using four heat soak times (0.5, 1, 2 and 3 h). The DLF furnace had a rate of climb of 13 degrees C/min and the PF furnace had a rate of climb of 5 degrees C/min to 520 degrees C and 3 degrees C/min to 860 degrees C. After ceramming the discs were de-vested and the BFS determined using a Lloyd 2000R tester. The maximum BFS values seen for both furnace types were almost identical (280 MPa), but were achieved at different heat soak times (1 h DLF, and 2 h PF). The only significant differences in BFS values for the two furnaces were between the 0.5 and 2 h heat soak times (p < or = 0.05). Individual differences were seen between results obtained from each furnace type/heat soak times evaluated (p < or = 0.05). Already available dental laboratory burnout furnaces can be used to ceram fluorcanasite glass-ceramic castings to the same BFS values as more expensive and slower specialist programmable furnaces.

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

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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.

Sterilization can change properties of bioceramics

International Nuclear Information System (INIS)

Willmann, G.

2003-01-01

Bioceramics made of bioinert alumina or zirconia and bioactive hydroxyapatite are well established implant materials. Implants have to be cleaned and sterilized. When sterilized some bioceramics change their color. This may effect their properties. No decrease of mechanical strength is observed when sterilizing alumina and the novel ceramic biocomposite AMC (Alumina Matrix Composite) with steam or Co 60 Gamma irradiation. When sterilizing Y-TZP zirconia with steam a decrease of strength is observed. (Abstract Copyright [2003], Wiley Periodicals, Inc.) [de

Influence of surface treatment of yttria-stabilized tetragonal zirconia polycrystal with hot isostatic pressing on cyclic fatigue strength.

Science.gov (United States)

Iijima, Toshihiko; Homma, Shinya; Sekine, Hideshi; Sasaki, Hodaka; Yajima, Yasutomo; Yoshinari, Masao

2013-01-01

Hot isostatic pressing processed yttria-stabilized tetragonal zirconia polycrystal (HIP Y-TZP) has the potential for application to implants due to its high mechanical performance. The aim of this study was to investigate the influence of surface treatment of HIP Y-TZP on cyclic fatigue strength. HIP Y-TZP specimens were subjected to different surface treatments. Biaxial flexural strength was determined by both static and cyclic fatigue testing. In the cyclic fatigue test, the load was applied at a frequency of 10 Hz for 10(6) cycles in distilled water at 37°C. The surface morphology, roughness, and crystal phase of the surfaces were also evaluated. The cyclic fatigue strength (888 MPa) of HIP Y-TZP with sandblasting and acid-etching was more than twice that of Y-TZP as specified in ISO 13356 for surgical implants (320 MPa), indicating the clinical potential of this material.

Asociación entre agenesia dental y maloclusión en pacientes pediátricos

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A. Carolina Medina

2013-07-01

Full Text Available Introducción: La agenesia dental es la anomalía del desarrollo más frecuente en el ser humano, asociándose a maloclusiones y alteraciones funcionales. Objetivo: El objetivo de la presente investigación es determinar la asociación entre la agenesia de dientes permanentes y la presencia de maloclusiones en pacientes pediátricos en el área Metropolitana de Caracas, Venezuela. Material y métodos: Fueron evaluados 1.188 radiografías panorámicas y 648 registros ortodóncicos de pacientes sanos con edades entre 5 y 18 años, registrando agenesia de dientes permanentes, exceptuando terceros molares. La maloclusión se diagnosticó según Angle. Fueron calculados estadísticos descriptivos, diferencias entre promedios y correlaciones entre variables (t de Student, rho de Pearson, p=0,05, odds ratio. Resultados: La prevalencia de agenesia fue 5,6%, siendo la media 1,64 y afectando mayormente al sexo femenino (1,44:1. Los dientes más afectados fueron segundos premolares inferiores (35,19%, e incisivos laterales superiores (30,55%. La prevalencia de maloclusión fue mayor en el grupo con agenesia dental (Clase I 52%, Clase II 31%, Clase III 17% al comparar con el grupo control (Clase I 77%, Clase II 14%, Clase III 9%; habiendo correlación estadísticamente significativa entre el número de dientes ausentes y Clase III. Conclusión: La prevalencia y distribución de agenesia dental variaron entre géneros, siendo el femenino el más afectado. Hubo correlación positiva estadísticamente significativa entre el número de dientes afectados y la maloclusión Clase III.

Relación de caries dental y el índice de masa corporal en niños de edad preescolar

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Mónica Vianey-García-Padilla

2013-01-01

Full Text Available La caries dental sigue siendo un problema con alta prevalencia así como el sobrepeso y la obesidad en los preescolares de México. Objetivo: determinar la relación de Caries Dental y el Índice de Masa Corporal en los preescolares. Material y métodos: se realizó un estudio transversal con una muestra de 348 preescolares del municipio de Tepatitlán Jalisco, midiéndose el Índice de masa corporal, Índice de caries dental, el índice de higiene oral simplificado y los momentos de azúcar/día. Resultados: se observó que en los 348 niños se encontró una prevalencia de caries del 75.3% con solo un 0.4 ±0.05 de dientes obturados; el 56.3 % estuvieron dentro del peso normal y 43.7% se encontraron con problemas de nutrición. Los niños que presentaron índice de caries más alto fueron los eutróficos y los de obesidad grave presentaron más lesiones cariosas. Sin embargo, los niños en sobrepeso y obesidad son los que tuvieron menores porcentajes de lesiones cariosas. Conclusiones: no existe una relación significativa entre la caries dental y el índice de masa corporal en el grupo estudiado, sin embargo, la prevalencia de caries y problemas nutricionales en los niños de edad preescolar son altos. Observándose que con un aumento del índice de higiene oral existe un aumento en el índice de caries siendo así de gran importancia fomentar cuidados orales preventivos y una atención dental temprana

Influence of interface point defect on the dielectric properties of Y doped CaCu3Ti4O12 ceramics

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Jianming Deng

2016-03-01

Full Text Available CaCu3Ti4−xYxO12 (0≤x≤0.12 ceramics were fabricated with conventional solid-state reaction method. Phase structure and microstructure of prepared ceramics were characterized by X-ray diffraction (XRD and scanning electron microscopy (SEM, respectively. The impedance and modulus tests both suggested the existence of two different relaxation behavior, which were attributed to bulk and grain boundary response. In addition, the conductivity and dielectric permittivity showed a step-like behavior under 405K. Meanwhile, frequency independence of dc conduction became dominant when above 405K. In CCTO ceramic, rare earth element Y3+ ions as an acceptor were used to substitute Ti sites, decreasing the concentration of oxygen vacancy around grain-electrode and grain boundary. The reason to the reduction of dielectric behavior in low frequencies range was associated with the Y doping in CCTO ceramic.

Phase evolution and aqueous durability of Zr{sub 1−x−y}Ce{sub x}Nd{sub y}O{sub 2−y/2} ceramics designed to immobilize actinides with multi-valences

Energy Technology Data Exchange (ETDEWEB)

Ding, Yi, E-mail: dingyi2279@126.com [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang, Sichuan, 621900 (China); Key Subject Laboratory of National Defense for Radioactive Waste and Environmental Security, Southwest University of Science and Technology, Mianyang 621010 (China); Long, Xinggui, E-mail: xingguil@caep.cn [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang, Sichuan, 621900 (China); Peng, Shuming [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang, Sichuan, 621900 (China); Zhang, Dong, E-mail: zd0823@sina.com [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang, Sichuan, 621900 (China); Tan, Zhaoyi [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang, Sichuan, 621900 (China); Lu, Xirui [Key Subject Laboratory of National Defense for Radioactive Waste and Environmental Security, Southwest University of Science and Technology, Mianyang 621010 (China)

2017-04-15

Zr{sub 1−x−y}Ce{sub x}Nd{sub y}O{sub 2−y/2} ceramics, which were designed as waste form materials, were obtained by simultaneous substitution of Ce{sup 4+} and Nd{sup 3+} for Zr{sup 4+} in ZrO{sub 2}. The influences of the simultaneous substitution of Ce and Nd on phase transformation of ZrO{sub 2} were investigated systematically. Also, the aqueous durability of the ceramics was evaluated. The results show that the phase transformation caused by the simultaneous substitution mainly relates to the total content of Ce and Nd. The ZrO{sub 2} ceramics containing Ce + Nd < 30 mol% exhibit both monoclinic and cubic phases, while the ceramics containing Ce + Nd ≥ 30 mol% are cubic phase. And the cubic phase can be stabilized by incorporating 30 mol% Ce + Nd. Moreover, LR{sub i} are modified by the incorporation of Ce and Nd, because of the presence of oxygen vacancies. The Nd and Ce co-doped zirconia waste form exhibit excellent aqueous durability (∼10{sup −5} g m{sup −2} d{sup −1}). - Highlights: •Zr{sub 1−x−y}Ce{sub x}Nd{sub y}O{sub 2−y/2} were obtained by substitution of Ce and Nd for Zr in ZrO{sub 2}. •Phase transformation mainly relates to the total content of Ce and Nd. •Samples with Ce + Nd < 30 mol% show monoclinic and cubic phases, while ≥30 mol% are cubic. •Stabilized cubic zirconia can be obtained by doping with 30 mol% Ce and Nd. •LR{sub Ce} and LR{sub Nd} (42 d) are ∼ 10{sup −5} g m{sup −2} d{sup −1}, exhibiting excellent aqueous durability.

Dental-Implantate und ihre Werkstoffe

Science.gov (United States)

Newesely, Heinrich

1983-07-01

Some new trends in materials for dental implants, which also effect in the operative techniques and implant design, are described. Advantages and shortcomings of the different material types are exemplified and correlated with their bioinert resp. bioactive functions. The practical interest in metallic implants focussed in titanium resp. oxide ceramics in the ceramic field, whereas the special goal of implant research follows from the improvement of the bioactive principle with loaded calcium phosphate implants.

Luminescence and scintillation enhancement of Y{sub 2}O{sub 3}:Tm transparent ceramic through post-fabrication thermal processing

Energy Technology Data Exchange (ETDEWEB)

Chapman, M.G.; Marchewka, M.R. [Department of Materials Science and Engineering, Clemson University, Clemson, SC 29634 (United States); Roberts, S.A.; Schmitt, J.M. [COMSET – Center for Optical Materials Science and Engineering Technologies, Clemson University, Anderson, SC 29625 (United States); McMillen, C. [Department of Chemistry, Clemson University, Clemson, SC 29634 (United States); Kucera, C.J. [COMSET – Center for Optical Materials Science and Engineering Technologies, Clemson University, Anderson, SC 29625 (United States); DeVol, T.A. [Environmental Engineering and Earth Sciences Department, Clemson University, Clemson, SC 29625 (United States); Ballato, J. [Department of Materials Science and Engineering, Clemson University, Clemson, SC 29634 (United States); COMSET – Center for Optical Materials Science and Engineering Technologies, Clemson University, Anderson, SC 29625 (United States); Jacobsohn, L.G., E-mail: luiz@clemson.edu [Department of Materials Science and Engineering, Clemson University, Clemson, SC 29634 (United States); COMSET – Center for Optical Materials Science and Engineering Technologies, Clemson University, Anderson, SC 29625 (United States)

2015-09-15

The effects of post-fabrication thermal processing in O{sub 2} flux on the luminescence and scintillation of a Y{sub 2}O{sub 3}:Tm transparent ceramic were investigated. The results showed that the strategy of post-fabrication processing can be beneficial to the performance of the ceramics, depending on the cumulative processing time. After the first hour of processing, about 40% enhancement in the luminescence output together with about 20% enhancement in the scintillation light yield were obtained. The enhancements were tentatively assigned to the incorporation of oxygen into vacancy sites. Longer cumulative processing times lead to the incorporation of oxygen as interstitials that is detrimental to scintillation light yield but not to luminescence output. This work also revealed that thermoluminescence measurements are a useful tool to predict scintillation light yield of Y{sub 2}O{sub 3}:Tm. - Highlights: • Scintillation and PL enhancement of transparent ceramics through thermal processing. • First thermoluminescence measurements of Y{sub 2}O{sub 3}:Tm above room temperature. • Observation of correlation between TL and scintillation light yield results.

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)

Prevalencia de erosión dental en escolares de Tampico, Madero, Altamira y su relación con el pH salival

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Diana Monserrat-Gutiérrez-Oviedo

2011-07-01

Full Text Available Introducción: La erosión dental es la pérdida de la superficie del diente causada por el ataque ácido y es un problema de salud dental en el mundo moderno; determinar su etiología y factores de riesgo permitirán tratarla y prevenirla correctamente antes de que se presente un daño más severo. Objetivo: Identificar la prevalencia de erosión dental en escolares de Tampico, Madero, Altamira y su relación con el pH salival. Material y Métodos: Fue un estudio observacional y transversal, se examinaron a 510 escolares de Tampico, Madero y Altamira. Se utilizó el índice de erosión de Aine. Resultados: De los 510 escolares, 63 presentaron una frecuencia de erosión dental del 12.35%, de los cuales 35 (13.67% fueron niñas y 28 (11.02% niños. No se encontraron diferencias estadísticamente significativas entre niños y niñas (p=.36. En relación con el pH salival no se encontró diferencias estadísticamente significativas. (p=.11. El órgano dental más afectado fue el 46 (7.20% y el 63 (4.93%. El grado que más prevaleció fue grado 1 (8.03%. En cuanto a la superficie más afectada fue la vestibular. Conclusiones: Es importante para el odontopediatra detectar los signos de erosión en etapas iníciales, identificar la causa y vigilar la nutrición de los niños que presentan erosión para prevenirla oportunamente.

Influence of Y2O3 Addition on Crystallization, Thermal, Mechanical, and Electrical Properties of BaO-Al2O3-B2O3-SiO2 Glass-Ceramic for Ceramic Ball Grid Array Package

Science.gov (United States)

Li, Bo; Li, Wei; Zheng, Jingguo

2018-01-01

Y2O3 addition has a significant influence on the crystallization, thermal, mechanical, and electrical properties of BaO -Al2O3 -B2O3 -SiO2 (BABS) glass-ceramics. Semi-quantitative calculation based on x-ray diffraction demonstrated that with increasing Y2O3 content, both the crystallinity and the phase content of cristobalite gradually decreased. It is effective for the additive Y2O3 to inhibit the formation of cristobalite phase with a large coefficient of thermal expansion value. The flexural strength and the Young's modulus, thus, are remarkably increased from 140 MPa to 200 MPa and 56.5 GPa to 63.7 GPa, respectively. Also, the sintering kinetics of BABS glass-ceramics with various Y2O3 were investigated using the isothermal sintering shrinkage curve at different sintering temperatures. The sintering activation energy Q sharply decreased from 99.8 kJ/mol to 81.5 kJ/mol when 0.2% Y2O3 was added, which indicated that a small amount of Y2O3 could effectively promote the sintering procedure of BABS glass-ceramics.

Synthesis and mechanical properties of stabilized zirconia ceramics: MgO-ZrO_2 and Y_2O_3-MgO- ZrO_2

International Nuclear Information System (INIS)

Yamagata, C.; Mello-Castanho, S.R.H.; Paschoal, J.O.A.

2014-01-01

Precursor MgO-ZrO_2 and Y_2O_3-MgO-ZrO_2 ceramic powders were synthesized by the method of co-precipitation and characterized by techniques such as laser diffraction, QELS (Quasi Elastic Light Scattering), XRD, BET, and SEM. Nanoscale powders with specific surface area higher than 60 m"2. g"-"1 was achieved. Sintered ceramic obtained from the synthesized powders, were characterized to mechanical tests using Vickers indentation technique. The addition of Y_2O_3 promoted an increase in hardness of the ceramics and total cubic crystalline phase stabilization. (author)

La Stevia rebaudiana como coadyuvante en la prevención y el control de la caries dental: una revisión de literatura

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Andrea Elena Paredes Vélez

2016-07-01

Full Text Available Introducción: La caries dental es la enfermedad crónica más prevalente en el mundo, y en Colombia, como en otros países, es considerada como un problema de salud pública. Es una enfermedad compleja, dinámica, y para su desarrollo intervienen muchos factores; la dieta rica en carbohidratos, es uno de los más significativos. La sacarosa se ha relacionado con problemas de salud como la caries, por ello, es deseable su reemplazo por edulcorantes con menos efectos adversos, y que aporten beneficios a la salud general y bucal de los humanos. Objetivo: fundamentar, si la Stevia, podría ser considerada como un coadyuvante en la prevención y control de la caries dental. Metodología: se realizó una búsqueda de literatura utilizando las bases de datos: Pubmed, Academic Search Complete, Embase, ScienceDirect, y el motor de búsqueda Google académico, mediante los términos MESH: “Dental Caries”, “Stevia”, “Anti-bacterial Agents”, “Sweetening Agents” y palabras clave en español: “Caries dental”, “Edulcorantes”, “Stevia”. Resultados: Los estudios revisados in vivo e in vitro mostraron: actividad antibacteriana de extractos de Stevia sobre microorganismos relacionados con caries dental, bajo potencial acidogénico y disminución en la formación de biopelícula dental, debido a la disminución de la hidrofobicidad celular e inhibición de la síntesis de polisacáridos extracelulares. Conclusiones: Aunque la evidencia científica aún es insuficiente, la Stevia rebaudiana es una adecuada candidata a reemplazar la sacarosa y puede considerarse como coadyuvante potencial para disminuir los niveles de caries dental, sin embargo, se recomienda realizar más estudios controlados y aleatorizados para que dicho rol se confirme.

The Validity of Subjects in Korean Dental Technicians' Licensing Examination

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Woong-chul Kim

2005-06-01

Full Text Available This study prepared a basic framework for the development and improvement of Korean Dental Technicians' Licensing Examination, based on actual test questions. A peer review was conducted to ensure relevance to current practices in dental technology. For the statistical analysis, 1000 dental laboratory technicians were selected; specialists in dental laboratory technology (laboratory owners, educators, etc. were involved in creating valid and reliable questions. Results indicated that examination subjects should be divided into three categories: basic dental laboratory theory, dental laboratory specialties, and a practical examination. To ensure relevance to current practice, there should be less emphasis on basic dental laboratory theory, including health-related laws, and more emphasis on dental laboratory specialties. Introduction to dental anatomy should be separated from oral anatomy and tooth morphology; and fixed prosthodontics should be separated from crown and bridge technology and dental ceramics technology. Removable orthodontic appliance technology should be renamed 'orthodontic laboratory technology'. There should be less questions related to health related law, oral anatomy, dental hygiene, dental materials science and inlay, while the distribution ratio of questions related to tooth morphology should be maintained. There should be a decrease in the distribution ratio of questions related to crown and bridge technology, dental ceramics technology, complete dentures and removable partial dentures technology, and orthodontic laboratory technology. In the practical examination, the current multiple choice test should be replaced with tooth carving using wax or plaster. In dental laboratory specialties, subjects related to contemporary dental laboratory technology should be included in the test items.

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.)

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.

DENTAL TRANSPOSITION: CHARACTERIZATION AND DENTAL ANOMALIES ASSOCIATED WITH A POPULATION OF CALI, COLOMBIA, 1997-2011

OpenAIRE

Hernández, José Jesús A.; Villavicencio, Judy; Arango, María Cristina

2013-01-01

Introducción: el objetivo de esta investigación fue caracterizar la transposición dental en una población que asistió a la consulta de odontopediatría en Cali, Colombia, entre enero de 1997 y octubre de 2011 y describir las anomalías dentales asociadas. Métodos: estudio descriptivo de tipo retrospectivo. Un total de 1.809 radiografías panorámicas se revisaron estableciendo la presencia de la transposición dental y las anomalías dentales asociadas. Las siguientes variables se registraron: edad...

Determination of dose rates from natural radionuclides in dental materials

International Nuclear Information System (INIS)

Veronese, I.; Guzzi, G.; Giussani, A.; Cantone, M.C.; Ripamonti, D.

2006-01-01

Different types of materials used for dental prosthetics restoration, including feldspathic ceramics, glass ceramics, zirconia-based ceramics, alumina-based ceramics, and resin-based materials, were investigated with regard to content of natural radionuclides by means of thermoluminescence beta dosimetry and gamma spectrometry. The gross beta dose rate from feldspathic and glass ceramics was about ten times higher than the background measurement, whereas resin-based materials generated negligible beta dose rate, similarly to natural tooth samples. The specific activity of uranium and thorium was significantly below the levels found in the period when addition of uranium to dental porcelain materials was still permitted. The high-beta dose levels observed in feldspathic porcelains and glass ceramics are thus mainly ascribable to 4 K, naturally present in these specimens. Although the measured values are below the recommended limits, results indicate that patients with prostheses are subject to higher dose levels than other members of the population. Alumina- and zirconia-based ceramics might be a promising alternative, as they have generally lower beta dose rates than the conventional porcelain materials. However, the dosimetry results, which imply the presence of inhomogeneously distributed clusters of radionuclides in the sample matrix, and the still unsuitable structural properties call for further optimization of these materials

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.

Evaluación de la adherencia del biofilm sobre salivaderas dentales de acero inoxidable, cerámica y opalina

OpenAIRE

Butler, Teresa Adela

2009-01-01

El objetivo principal de esta investigación fue estudiar el desarrollo de la biopelícula depositada sobre las salivaderas dentales de tres materiales diferentes (acero inoxidable, cerámica y opalina), de equipos odontológicos correspondientes a dos zonas diferentes del casco urbano de la ciudad de La Plata (Z1 y Z2). Para ello se realizaron 38 cortes de salivaderas dentales de los tres materiales, de cada zona En primer lugar se realizó el análisis de la microbiota planctónica y sé...

Effect of acidic agents on surface roughness of dental ceramics

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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.

[Research on the aging of all-ceramics restoration materials].

Science.gov (United States)

Zhang, Dongjiao; Chen, Xinmin

2011-10-01

All-ceramic crowns and bridges have been widely used for dental restorations owing to their excellent functionality, aesthetics and biocompatibility. However, the premature clinical failure of all-ceramic crowns and bridges may easily occur when they are subjected to the complex environment of oral cavity. In the oral environment, all-ceramic materials are prone to aging. Aging can lead all-ceramic materials to change color, to lower bending strength, and to reduce anti-fracture toughness. There are many factors affecting the aging of the all-ceramic materials, for example, the grain size, the type of stabilizer, the residual stress and the water environment. In order to analyze the aging behavior, to optimize the design of all-ceramic crowns and bridges, and to evaluate the reliability and durability, we review in this paper recent research progress of aging behavior for all-ceramics restoration materials.

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.

The Y2BaCuO5 oxide as green pigment in ceramics

International Nuclear Information System (INIS)

Fernandez, F.; Colon, C.; Duran, A.; Barajas, R.; Llopis, J.; Paje, S.E.; Saez-Puche, R.; Julian, I.

1998-01-01

Fine particles of green yttrium-barium-copper-oxide pigments Y 2 BaCuO 5 have been prepared using two different synthesis methods. The process of combustion of mixed nitrates and urea needs a maximal temperature of 900 C and provides samples formed by aggregates of homogeneous small particles with a size of about 0.3 μm. However, the ceramic method requires 1050 C as synthesis temperature, and yields rather higher particle sizes. Even after grinding, these samples are formed by heterogeneous particles with mean sizes of about 3 μm. Diffuse reflectance spectra reveal that the samples obtained using the former method present a higher brilliancy, so they have been selected to be tested as green pigment in ceramics with good results. (orig.)

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.

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.

Condición periodontal y pérdida dental en pacientes diabéticos

Directory of Open Access Journals (Sweden)

Sandra Paola Ochoa

2012-03-01

Conclusiones. En conclusión, la condición periodontal en pacientes diabéticos fue mala, y presentaban periodontitis en la mayoría de los casos. Esto puede ser una causa importante de pérdida dental en sujetos diabéticos y requiere de especial atención por parte de los odontólogos y médicos.   DOI: http://dx.doi.org/10.7705/biomedica.v32i1.387

Thermoluminescence properties of AlN ceramics

DEFF Research Database (Denmark)

Trinkler, L.; Christensen, P.; Agersnap Larsen, N.

1998-01-01

The paper describes thermoluminescence (TL) properties of AlN:Y2O3 ceramics irradiated with ionising radiation. A high TL sensitivity of AlN:Y2O3 ceramics to radiation encouraged a study of the AlN ceramics for application as a dosimetric material. The paper presents experimental data on: glow...... curve, emission spectrum, dose response, energy dependence, influence of heating rate and fading rate. The measured TL characteristics were compared with those of well-known, widely used TLDs, i.e. LiF:Mg,Ti, LiF:Mg,Cu,P and Al2O3:C. It is concluded that AlN:Y2O3 ceramics showing a radiation sensitivity...... which is approximately 50 times greater than that of LiF:Mg,Ti is an interesting dosimetry material; however due to a high fading rate of the TL of AlN:Y2O3 on storage at room temperature, a further development of the material for improving the fading characteristics is needed for its application...

Gloss measurements and rugometric inspection in dental biomaterials

Science.gov (United States)

Fernández-Oliveras, Alicia; Costa, Manuel F. M.; Yebra, Ana; Rubiño, Manuel; Pérez, María. M.

2013-11-01

In dental applications, optimizing appearance is desirable and increasingly demanded by patients. The specular gloss is among the major appearance properties of dental biomaterials, and its relationship with surface roughness has been reported. Roughness and gloss are key surface aspects that complement each other. We have experimentally analyzed the specular gloss and surface roughness of two different types of dental-resin composites and pre-sintered and sintered zirconia ceramics. We have 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. Gloss measurements were performed with a standardized reflectometer and the corresponding gloss percentages were calculated. All the samples were submitted to rugometric non-invasive inspection with the MICROTOP.06.MFC laser microtopographer in order to determine meaningful statistical parameters such as the average roughness (Ra) and the root-mean-square deviation (Rq). For a comparison of the different biomaterials, the uncertainties associated to the measure of the surface gloss and roughness were also determined. The differences between the two shades of both kinds of composites proved significant in the case of the roughness parameters but not for the specular gloss. The surface treatment applied to the dental-resin composites increased the average roughness but the changes in the specular gloss were significant only for the A2 enamel nano-composite. For the zirconia ceramic the sintered process resulted in an increase in the surface roughness with a decrease of the specular gloss, corroborating that the relationship between the gloss and the roughness shows the expected behavior.

Report on achievements in fiscal 1999. Research and development of synergy ceramics (research and development of technologies to prevent corrosion in petroleum production systems); 1999 nendo synergy ceramics no kenkyu kaihatsu seika hokokusho. Sekiyu seisan system fushoku boshi gijutsu kenkyu kaihatsu

Energy Technology Data Exchange (ETDEWEB)

NONE

2000-03-01

This research and development has been performed on the following themes: 1. Material realizing technology, and advanced evaluation and design technology (1-(1) ultra precision materials, 1-(2) high-temperature energy materials, 1-(3) basic member design technology, 1-(4) materials having function to detect stresses and micro destruction, 1-(5) porous materials to control gas hole patterns, and 1-(6) materials having self-restoring/self-lubricating function); 2. Application technology (2-(1) materials having substance and light selecting function, 2-(2) high wear resistant and easy-to-process materials, 2-(3) high-performance resistance materials for electric power devices, and 2-(4) flexible sliding materials); 3. Formation of common base technologies. 4. Report on achievements in countries making joint researches. In Item 1-(1), micro destruction mechanisms were analyzed, and the directionality of material structure control was clarified. In Item 1-(2), controlled closing holes were introduced. In Item 1-(3), polycrystalline alumina, polycrystalline zirconia, and zirconia particle dispersed alumina were evaluated microscopically and macroscopically. In Item (4), Y-TZP/Ni nano-compound materials were fabricated successfully. In Item 1-(5), destruction behavior of porous ceramics was studied. In Item 1-(6), characteristics were investigated on Fe(Al)Al2O3 which was fabricated on the trial basis. (NEDO)

Estudio comparativo del efecto del cepillado con una crema dental con propóleos rojos y de un gel con clorofila

OpenAIRE

Estela Gispert Abreu; Elena Cantillo Estrada; Aracelys Rivero López; Berta Oramas Rodríguez

1998-01-01

Se analiza comparativamente el efecto de un gel dental de clorofila y de una crema dental con propóleos rojos sobre varios parámetros relacionados con la caries dental, en escolares que se cepillaron durante 21 días con dichos productos. Se obtuvieron resultados favorables principalmente en la disminución del grado de infección por Streptococcus mutans y la elevación de la capacidad individual de remineralización; salvo en este último no hubo diferencias estadísticamente significativas.Author...

Desarrollo y validación de una nueva tecnología, basada en arginina al 1.5%, un compuesto de calcio insoluble y fluoruro, para el uso diario en la prevención y tratamiento de la caries dental.

Science.gov (United States)

Cummins, D

2013-10-22

este artículo discute brevemente la prevalencia de caries, la naturaleza multifactorial de su etiología, el riesgo de caries y el papel y eficacia del fluoruro. Resalta también la investigación sobre el metabolismo bacteriano, que ha aportado conocimientos sobre la defensa natural oral contra la caries y la base para el desarrollo de una nueva tecnología para la prevención diaria y el tratamiento de la caries. Por último, se resume la evidencia que respalda que la tecnología complementa y mejora la eficacia anti-caries de la crema dental con fluoruro. los datos globales muestran que a pesar de la exitosa introducción del fluoruro, la caries dental es una enfermedad prevalente. La experiencia de caries depende del balance entre el consumo de azúcares, la higiene oral y el uso del fluoruro. Hay tres conceptos científicos que son fundamentales en las nuevas mediciones para detectar, tratar y monitorear la caries: (1) la caries dental es un proceso dinámico, (2) la caries dental es un proceso continuo de etapas que van desde reversible (pre-clínica) hasta irreversible (lesiones clínicamente detectables), y (3) el proceso de la caries es un balance de factores patológicos y protectores que pueden modularse para el manejo de la caries. El fluoruro funciona como factor protector al detener y revertir el proceso de la caries, pero el fluoruro no previene los factores patológicos que inician el proceso. Se ha identificado una tecnología novedosa, basada en arginina y un compuesto insoluble de calcio, que está dirigida a la placa dental para prevenir la iniciación del proceso de caries al reducir los factores patológicos. Como los mecanismos de acción de la arginina y el fluoruro son altamente complementarios, se ha desarrollado un nuevo dentífrico que combina la arginina y el fluoruro, y se ha probado clínicamente que brinda una prevención superior contra la caries. Copyright © 2013 Elsevier Ltd. All rights reserved.

Processing and properties of pressable ceramic with non-uniform reinforcement for selective-toughening

Energy Technology Data Exchange (ETDEWEB)

Yi, Wei [School of Mechanical and Chemical Engineering, The University of Western Australia, Perth, WA 6009 (Australia); School of Dentistry, The University of Western Australia, WA 6009 (Australia); Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), Northeastern University, Shenyang 110004 (China); Hu, Xiaozhi, E-mail: xiao.zhi.hu@uwa.edu.au [School of Mechanical and Chemical Engineering, The University of Western Australia, Perth, WA 6009 (Australia); Ichim, Paul [School of Dentistry, The University of Western Australia, WA 6009 (Australia); Sun, Xudong [Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), Northeastern University, Shenyang 110004 (China)

2012-12-15

Brittle low-strength and low-toughness pressable dental ceramic can be reinforced by ductile elongated gold-particles (GP). A customized crown structure can be adequately strengthened by distributing GP only in critical sections of the crown, where high tensile stresses are experienced. In the present study, a non-uniformly structured ceramic-matrix composite with excellent interfacial bonding, twofold fracture toughness and strength at desired locations, is fabricated using pressable dental ceramic and GP. The layout pattern and sequence of different GP/ceramic powder mixtures, high-temperature flow properties of these mixtures during hot-pressing and the sample mold geometry are used to control the distribution and locations of GP for selective toughening and strengthening. Nano-crystalline structures of the pressable ceramic-matrix and the nano-scaled interfacial region around GP have been revealed by high-magnification field-emission scanning electron microscopy. Toughening and strengthening mechanisms of the elongated GP including residual stresses from composite processing and ductile fracture of GP are discussed together with SEM observations. Bulk flexural strength and local micro-indentation fracture and deformation characteristics of the selective-toughened ceramic/metal composite have been compared to those of the monolithic pressable ceramic to validate the toughening and strengthening mechanisms.

Long-term stability and properties of zirconia ceramics for heavy duty diesel engine components

Science.gov (United States)

Larsen, D. C.; Adams, J. W.

1985-01-01

Physical, mechanical, and thermal properties of commercially available transformation-toughened zirconia are measured. Behavior is related to the material microstructure and phase assemblage. The stability of the materials is assessed after long-term exposure appropriate for diesel engine application. Properties measured included flexure strength, elastic modulus, fracture toughness, creep, thermal shock, thermal expansion, internal friction, and thermal diffusivity. Stability is assessed by measuring the residual property after 1000 hr/1000C static exposure. Additionally static fatigue and thermal fatigue testing is performed. Both yttria-stabilized and magnesia-stabilized materials are compared and contrasted. The major limitations of these materials are short term loss of properties with increasing temperature as the metastable tetragonal phase becomes more stable. Fine grain yttria-stabilized material (TZP) is higher strength and has a more stable microstructure with respect to overaging phenomena. The long-term limitation of Y-TZP is excessive creep deformation. Magnesia-stabilized PSZ has relatively poor stability at elevated temperature. Overaging, decomposition, and/or destabilization effects are observed. The major limitation of Mg-PSZ is controlling unwanted phase changes at elevated temperature.

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

Structural evolution and dielectric properties of (Ba{sub 1−x}Nd{sub x})(Ti{sub 1−y}Fe{sub y})O{sub 3} ceramics

Energy Technology Data Exchange (ETDEWEB)

Han, D.-D. [Research Center for Materials Science and Engineering, Jilin Institute of Chemical Technology, Jilin 132022 (China); College of Chemistry, Northeast Normal University, Changchun 130024 (China); Lu, D.-Y., E-mail: cninjp11232000@yahoo.com [Research Center for Materials Science and Engineering, Jilin Institute of Chemical Technology, Jilin 132022 (China); Sun, X.-Y. [Research Center for Materials Science and Engineering, Jilin Institute of Chemical Technology, Jilin 132022 (China)

2013-11-05

Highlights: •Structural evolution and dielectric properties of (Ba{sub 1−x}Nd{sub x})(Ti{sub 1−y}Fe{sub y})O{sub 3} were studied. •A cubic ceramic with x = y = 0.05 exhibits a high-k Y5V behavior (ε{sub RT}{sup ′} = 6790). •The T{sub m} in BNTF with x = 0.05 decreased linearly at a rate of −5 °C/mol% Fe ions. •Evolution in the 840 cm{sup −1} Raman band gives evidence for Nd{sup 3+}–Fe{sup 3+} complex formation. •Defect chemistry associated with structure evolution is discussed. -- Abstract: The influence of donor and acceptor co-doping on structure and dielectric properties of (Ba{sub 1−x}Nd{sub x})(Ti{sub 1−y}Fe{sub y})O{sub 3} (BNTF) (x = 0.05, y = 0.01–0.07; and x = 0–0.08, y = 0.05) ceramics was investigated with X-ray diffraction (XRD), scanning electron microscopy (SEM), electron paramagnetic resonance (EPR), Raman spectroscopy, and dielectric measurements. When x < y, two types of Nd{sup 3+}–Fe{sup 3+} and Fe{sup 3+}–V{sub O}–Fe{sup 3+} defect complexes formed and could not coexist, leading to the mixed phases of cubic and hexagonal. A single-phase ceramic with a cubic or tetragonal structure formed for x ⩾ y and the dielectric-peak temperature (T{sub m}) in BNTF with x = 0.05 decreased linearly with increasing y at a rate of −5 °C/mol% Fe ions. A high-k Y5V behavior can be realized at x = y = 0.05 (i.e., C-N5F5). The same concentrations of Nd{sup 3+} and Fe{sup 3+} formed Nd{sup 3+}–Fe{sup 3+} complexes, which could effectively suppress the dielectric loss and silence the 840 cm{sup −1} band called “Raman charge effect” associated with Nd{sup 3+} donors. C-N5F5 exhibited a cubic structure, medium-sized grains (3.3 μm), low dielectric loss (<0.06), and high-k Y5V behavior (ε{sub RT}{sup ′} = 6790). Defect chemistry associated with structure evolution is discussed.

Synthesis of low loss, thermally stable CexY1-xTiTaO6 microwave ceramics

International Nuclear Information System (INIS)

Padma Kumar, H.; John, Annamma; Vijayakumar, C.; Thomas, J.K.; Varma, Manoj Raama; Solomon, Sam

2009-01-01

Ce x Y 1-x TiTaO 6 ceramics were prepared through the solid-state ceramic route. The materials were sintered in the range 1520-1580 deg. C. The structure of the system was analyzed by X-ray diffraction and Raman spectroscopic methods. The cell parameters of solid solutions were calculated using the least square method. The microstructure was analyzed using scanning electron microscopy. The dielectric constant (ε r ), temperature coefficient of resonant frequency (τ f ) and the unloaded quality factor (Q u ) are measured in the microwave frequency region using cavity resonator method. The dielectric constant increases with higher concentrations of Ce in the solid solutions. Nearly zero temperature coefficient of resonant frequency (τ f ) was obtained for Ce 0.24 Y 0.76 TiTaO 6 . The samples are of high quality factor and are useful electronic materials for microwave applications

Glass-ceramic material and method of making

Science.gov (United States)

Meinhardt, Kerry D [Richland, WA; Vienna, John D [West Richland, WA; Armstrong, Timothy R [Pasco, WA; Pederson, Larry R [Kennewick, WA

2002-08-13

The present invention is a glass-ceramic material and method of making useful for joining at least two solid ceramic parts. The seal is a blend of M.sub.A O--M.sub.B O.sub.y --SiO.sub.2 that substantially matches a coefficient of thermal expansion of the solid electrolyte. According to the present invention, a series of glass ceramics in the M.sub.A O--M.sub.B O.sub.y --SiO.sub.2 system can be used to join or seal both tubular and planar ceramic solid oxide fuel cells, oxygen electrolyzers, and membrane reactors for the production of syngas, commodity chemicals and other products.

Enfoque de ciencia, tecnología y sociedad de la Implantología dental en Camagüey

Directory of Open Access Journals (Sweden)

Judith Aúcar López

Full Text Available Existe un auge en la colocación de implantes dentales, dispositivos que mejoran la salud del paciente y restauran su estética y función, lo cual motivó la realización de este trabajo con el objetivo de argumentar la importancia del servicio de implantes dentales en Camagüey desde el enfoque de ciencia, tecnología y sociedad. Cuba es el único país que tiene un servicio de implantología social, que se ha convertido en una herramienta complementaria de los tratamientos protésicos. Desde 2006 se desarrolla en la provincia para mejorar la calidad de vida de la población.

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.

Yttria-Ceria stabilized tetragonal zirconia polycrystals: Sintering, grain growth and grain boundary segregation

NARCIS (Netherlands)

Boutz, M.M.R.; Boutz, M.M.R.; Winnubst, Aloysius J.A.; Burggraaf, Anthonie; Burggraaf, A.J.

1994-01-01

An analysis is presented of grain growth and densification of yttria-ceria stabilized tetragonal zirconia polycrystals (Y, Ce-TZPs) using both isothermal and non-isothermal techniques. The characteristics of Y, Ce-TZPs are compared to those of Y-TZP and Ce-TZP and the effect of increasing ceria

Asociación entre agenesia dental y maloclusión en pacientes pediátricos

OpenAIRE

A. Carolina Medina; Rodrigo Del Pozo

2013-01-01

Introducción: La agenesia dental es la anomalía del desarrollo más frecuente en el ser humano, asociándose a maloclusiones y alteraciones funcionales. Objetivo: El objetivo de la presente investigación es determinar la asociación entre la agenesia de dientes permanentes y la presencia de maloclusiones en pacientes pediátricos en el área Metropolitana de Caracas, Venezuela. Material y métodos: Fueron evaluados 1.188 radiografías panorámicas y 648 registros ortodóncicos de pacientes sanos con e...

Effects of superplastic deformations on thermophysical properties of tetragonal zirconia polycrystals

International Nuclear Information System (INIS)

Motohashi, Y.; Wan, C.; Sakuma, T.; Harjo, S.; Shibata, T.; Ishihara, M.; Baba, S.; Hoshiya, T.

2004-01-01

Neutron irradiation studies on superplastic zirconia-based ceramics are now in progress as an innovative basic project using the High-temperature Engineering Test Reactor (HTTR) in Japan. The characteristics of the zirconia-based engineering components, made through the formation of superplastic, may be strongly affected by their response to transient or steady-state heat flow. Reliable thermophysical properties such as the coefficients of thermal expansion and thermal conductivity are, therefore, needed to estimate and predict the influence of a high-temperature environment. Accordingly, one of this project's targets is to study the thermophysical properties of superplastic zirconia-based ceramics. The first stage of the research addresses the effects of superplastic deformations on the thermophysical properties of a typical superplastic ceramic, 3 mol% yttria-stabilised tetragonal zirconia polycrystals (3Y-TZP), in its un-irradiated state. First, superplastic tensile deformations were conducted on 3Y-TZP specimens under different conditions in order to obtain specimens with different microstructural characteristics. Afterwards, the following actions were taken: - Specific heat measurements were conducted on the specimens at temperatures ranging from 473 K to 1273 K. - The thermal diffusivity was measured using a laser flash method. The thermal conductivity was then calculated from the measured thermal diffusivity, specific heat and density. - The linear thermal expansion was measured by a push-rod type dilatometer from 300 K to 1473 K. The coefficient of linear thermal expansion (CTE) was estimated from the thermal expansion data. The results obtained from the above measurements are discussed, as is the microstructural evolution caused by the superplastic deformations. It was found that the specific heat was almost independent of microstructural evolution, whereas the thermal diffusivity, thermal conductivity and thermal expansion were quite sensitive to