Warrner, Stephen S; Fischer, Robert U; Holtrop, Ann M; Hinz, Leon C; Novak, James M
Stream habitat assessments are conducted to evaluate biological potential, determine anthropogenic impacts, and guide restoration projects. Utilizing these procedures, managers must first select a representative stream reach, which is typically selected based on several criteria. To develop a consistent and unbiased procedure for choosing sampling locations, the Illinois Department of Natural Resources and the Illinois Natural History Survey have proposed a technique by which watersheds are divided into homogeneous stream segments called valley segments. Valley segments are determined by GIS parameters including surficial geology, predicted flow, slope, and drainage area. To date, no research has been conducted to determine if the stream habitat within a valley segment is homogeneous and if different valley segments have varying habitat variables. Two abutting valley segments were randomly selected within 13 streams in the Embarras River watershed, located in east-central Illinois. One hundred meter reaches were randomly selected within each valley segment, and a transect method was used to quantify habitat characteristics of the stream channel. Habitat variables for each stream were combined through a principal components analysis (PCA) to measure environmental variation between abutting valley segments. A multivariate analysis of variance (MANOVA) was performed on PCA axes 1-3. The majority of abutting valley segments were significantly different from each other indicating that habitat variability within each valley segment was less than variability between valley segments (5.37 ≤ F ≤ 245.13; P ≤ 0.002). This comparison supports the use of the valley segment model as an effective management tool for identifying representative sampling locations and extrapolating reach-specific information.
Ochiai, Kent T; Ozawa, Shogo; Caputo, Angelo A; Nishimura, Russell D
There is some question about whether implant abutment selection affects the transfer of load between connected implants and natural teeth. The purpose of this study was to compare stress transfer patterns with either 1 or 2 posterior implants connected to a single anteriorly located simulated natural tooth with either 1 or 2 segmented and nonsegmented implant abutments under relevant functional loads by use of the photoelastic stress analysis technique. A model of a human left mandible, edentulous posterior to the first premolar, with two 3.75-mm x 13-mm screw-type implants embedded within the edentulous area, was fabricated from photoelastic materials. The implants were in the first and second molar positions. Two fixed partial denture prosthetic restorations were fabricated with either segmented conical abutments or nonsegmented UCLA abutments. Vertical occlusal loads were applied at fixed locations on the restorations. The photoelastic stress fringes that developed in the supporting mandible were monitored visually and recorded photographically. The stress intensity (number of fringes), stress concentrations (closeness of fringes), and their locations were subjectively compared. Loading on the restoration over the simulated tooth generated apical stresses of similar intensity (fringe order) at the tooth and the first molar implant for both abutment types. Low-level stress was transferred to the second molar implant. Loading directed on the implant-supported region of the restoration demonstrated low transfer of stress to the simulated tooth. Nonvertical stress transfer with slightly higher intensity was observed for the nonsegmented abutment. Within the limitations of this simulation study, stress distribution and intensity for the 2 implant conditions was similar for segmented and nonsegmented abutment designs. Magnitude of stresses observed for both abutment designs was similar for the single implant condition. Vertical loading produced more nonaxial stresses
Bin, Shi; Hao, Zeng
An increasing number of implant restoration abutment types are produced with the rapid development of dental implantology. Although various abutments can meet different clinical demands, the selection of the appropriate abutment is both difficult and confusing. This article aims to help clinicians select the appropriate abutment by describing abutment design, types, and selection criteria.
Wendy Trowbridge; Jeanne C. Chambers; Dru Germanoski; Mark L. Lord; Jerry R. Miller; David G. Jewett
Great Basin riparian meadows are highly sensitive to both natural and anthropogenic disturbance. As detailed in earlier chapters, streams in the central Great Basin have a natural tendency to incise due to their geomorphic history (Miller and others 2001, 2004). Anthropogenic disturbances, including overgrazing by livestock, mining activities, and roads in the valley...
healing collars, abutments, transfer copings and analogs, which increases inventory costs and complexity. Limitations of external hex became more evident ..... 0.75mm or bone platform switching which involves an inward bone ring in the coronal part of the implant. 34 that is in continuity with the alveolar bone crest .
Chadwell, C.; Gagnon, K. L.
From 1994 to 1999, direct acoustic ranging across the 1-km-wide axial valley floor of the south Cleft Segment of the Juan de Fuca Ridge showed no appreciable extension (Chadwell et al., 1999, GRL; Chadwick and Stapp, 2002, JOE). Meanwhile, at 25 km east of this site full-plate motion was observed with the GPS- Acoustic technique from 2000 through 2004 (Chadwell and Spiess, 2008, JGR). Thus full-plate strain is occurring somewhere between the axial valley floor and 25 km east. Relevant to this is GPS-Acoustic data collected at two triangular arrays of seafloor transponders one extending from the axial valley floor to approximately 4.3 km west and another 4.3 km east. Data were collected in 1994, 1995, and 1996, but limited understanding of the GPS-Acoustic approach prevented robust processing of these data. We have refined the processing of GPS-Acoustic data and these new approaches were applied to the mid-1990s data with the goal of documenting motion across an 8.7-km-wide span of the axial valley floor and most importantly the axial valley walls. Results show no significant extension occurring across the axial valley walls. This result does not support the hypothesis that the axial valley walls are a region of concentrated active motion, but instead support s a view that, like the axial valley floor, axial valley wall extension occurs primarily during episodic magmatic/tectonic events. Adding this new information to that of previous seafloor geodetic studies suggests that approximately 26 mm/a (1/2 the full plate rate) should be accommodated within a region between approximately 5 to 25 km off axis. These seafloor geodetic studies are the first direct kinematic constraints across a wide (30 km) region of an oceanic spreading center. This work was supported by NSF-OCE-Marine Geology and Geophysics Program Grant 05-51765.
Vinayak S Gowda
Full Text Available Dental implants with their increasing success rates and predictability of final outcome are fast becoming the treatment of choice for replacing missing teeth. Considering the success of immediate implant placement in reducing tissue loss and achieving good esthetic results, is making it a more popular treatment modality in implant dentistry. Understanding the management of gingival tissues in relation to implants to obtain maximum esthetics is of utmost importance. The use of provisional abutments and immediate temporization has a proven track record of their ability to produce optimal esthetics and to guide the tissue response during the healing phase. With careful patient selection and execution, customized healing abutments can provide an effective method to enhance the esthetic and emergence profile for anterior implant restorations.
Ardashev, K.A.; Borisovets, V.A.; Kozel, A.M.
The purpose of the invention is to increase the service life of the abutment between a mine shaft and near shaft drifts by eliminating the irregularity of the near shaft rock massif. The stated purpose is achieved by the fact that in the mine abutment, which includes a mine shaft and near shaft chambers, the mine shaft is made within the near shaft chambers with an expansion and is equipped with a cylindrical shell installed in its widened part with an inside cross section equal to the cross section of the shaft which with the shaft forms a cavity for positioning the near shaft chambers. Moreover, the mine shaft in the expansion zone may be made in the form of a cone in its upper part and in the form of a cylinder in its lower part.
Serra-Pastor, Blanca; Roig-Vanaclocha, Ana; Román-Rodriguez, Juan-Luis; Fons-Font, Antonio
Introduction: Implant-supported prostheses have to overcome a major difficulty presented by the morphology and esthetics of peri-implant tissues in the anterior sector. Diverse therapeutic techniques are used for managing the mucosa adjacent to the implant and the most noteworthy is immediate/deferred fixed provisionalization. Objectives: In vitro testing of strength and deformation of implant prosthetic abutments made from different materials (Titanium/PEEK/methacrylate). Material and Methods: Forty Sweden&Martina® implant prosthetic abutments (n=40) were divided into five groups: Group MP: methacrylate provisional abutments with machined titanium base; Group PP: Poly ether ether ketone (PEEK) provisional abutments; Group TP: titanium provisional abutments; Group TAD: titanium anti-rotational definitive abutments; Group TRD: titanium rotational definitive abutments. Their mechanical behavior under static loading was analyzed. Samples were examined under a microscope to determine the type of fracture produced. Results and Conclusions: Definitive anti-rotational titanium abutments and definitive rotational titanium abutments achieved the best mean compression strength, while PEEK resin provisional abutments obtained the lowest. The group that showed the greatest elastic deformation was the group of titanium provisional abutments. Key words:Immediate loading, immediate provisionalization, implant prosthetic abutment, definitive implant prosthetic abutment. PMID:25129253
This article is an introduction to single implant abutments and aims to provide basic information about abutments which are essential for all dental personnel who are involved in dental implantology. Clinical Relevance: This article provides a basic knowledge of implants and implant abutments which are of paramount importance, as replacement of missing teeth with oral implants has become a well-established clinical procedure.
Full Text Available Background and Aims: In response to esthetic demand of patients, ceramic abutments have been developed. Despite esthetic of zirconia abutments, machining accuracy of these abutments has always been a question. Any misfit in the abutment-implant interface connection can lead to detorque and screw loosening. The aim of this study was to compare torque loss value of manually aided design/manually aided manufacture (MAD/MAM zirconia abutments with prefabricated titanium abutments. Materials and Methods: Seven titanium abutments (Branemark RP, Easy abutment and seven copy milled abutments which were duplicated from the prefabricated Zirkonzhan (ZirkonZahn, Sand in Taufers, Italy were prepared. After sintering process of zirconia abutment, all abutments were fastened with a torque screw under 35 Ncm. Detorque measurements were performed per group pushing the reverse button of the Torque controller soon after screw tightening with values registered. The mean torque loss were calculated and compared using Student's t test. Results: The mean of torque loss was 12.71 Ncm with standard deviation of 1.70 for prefabricated titanium abutments and 15.50 Ncm with standard deviation of 4.67 for MAD-MAM abutments. The difference between the two groups was not statistically significant (P=0.23. Conclusion: Within the limitation of this study, MAD-MAM ceramic abutments could maintain the applied torque comparing to the prefabricated abutments.
Lalithamma, Jaini Jaini; Mallan, Sreekanth Anantha; Murukan, Pazhani Appan; Zarina, Rita
The study compared the marginal accuracy of premade and cast abutments. Premade titanium, stainless steel, and gold abutments formed the control groups. Plastic abutments were cast in nickel-chromium, cobalt-chromium and grade IV titanium. The abutment/implant interface was analyzed. Analysis of variance and Duncan's multiple range test revealed no significant difference in mean marginal microgap between premade gold and titanium abutments and between premade stainless steel and cast titanium abutments. Statistically significant differences (P < .001) were found among all other groups.
Giglio, G D
Selecting the appropriate abutment can be both complex and confusing with the ever-increasing number of implant choices and transepithelial abutments available. Many restorative dentists resort to fabricating costly custom abutments to avoid the selection process. Although custom abutments are at times necessary, prefabricated abutments are usually more desirable. This article will describe the various abutments available and how to select the correct abutment for a given clinical situation in an organized, systematic fashion. Criteria discussed include implant position, angulation, soft tissue height, and interocclusal space. The latest modifications and developments in implant abutments are reviewed along with an indirect method of selecting abutments in a laboratory setting.
Corazza, Pedro Henrique; de Moura Silva, Alecsandro; Cavalcanti Queiroz, José Renato; Salazar Marocho, Susana María; Bottino, Marco Antonia; Massi, Marcos; de Assunção e Souza, Rodrigo Othávio
To evaluate the effect of diamond-like carbon (DLC) coating of prefabricated implant abutment on screw removal torque (RT) before and after mechanical cycling (MC). Fifty-four abutments for external-hex implants were divided among 6 groups (n = 9): S, straight abutment (control); SC, straight coated abutment; SCy, straight abutment and MC; SCCy, straight coated abutment and MC; ACy, angled abutment and MC; and ACCy, angled coated abutment and MC. The abutments were attached to the implants by a titanium screw. RT values were measured and registered. Data (in Newton centimeter) were analyzed with analysis of variance and Dunnet test (α = 0.05). RT values were significantly affected by MC (P = 0.001) and the interaction between DLC coating and MC (P = 0.038). SCy and ACy showed the lowest RT values, statistically different from the control. The abutment coated groups had no statistical difference compared with the control. Scanning electron microscopy analysis showed DLC film with a thickness of 3 μm uniformly coating the hexagonal abutment. DLC film deposited on the abutment can be used as an alternative procedure to reduce abutment screw loosening.
Karunagaran, Sanjay; Paprocki, Gregory J; Wicks, Russell; Markose, Sony
With an increase in the availability of implant restorative components, the selection of an appropriate implant abutment for a given clinical situation has become more challenging. This article describes a classification system that will help the practitioner understand the different implant abutments available and therefore be able to understand the selection of abutments for single and multiple unit fixed implant prosthesis.
As a result of abutment spalling on the integral abutment bridge over 400 South Street in Salt Lake City, Utah, the Utah Department of Transportation (UDOT) instigated research measures to better understand the behavior of integral abutment bridges. ...
R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22
Kwan T F 1988 A study of abutment scour. Rep. No. 451, School of Engineering, University of. Auckland, Auckland, New Zealand. Kwan T F, Melville B W 1994 Local scour and flow measurements at bridge abutments. J. Hydraul. Res. 32: 661–673. Laursen E M 1952 Observations on the nature of scour. Proc. 5th Hydraul.
Siadat, Hakimeh; Pirmoazen, Salma; Beyabanaki, Elaheh; Alikhasi, Marzieh
A significant vertical space that is corrected with vertical ridge augmentation may necessitate selection of longer abutments, which would lead to an increased vertical cantilever. This study investigated the influence of different abutment collar heights on single-unit dental implant screw-loosening after cyclic loading. Fifteen implant-abutment assemblies each consisted of an internal hexagonal implant were randomly assigned to 3 groups: Group1, consisting of 5 abutments with 1.5 mm gingival height (GH); Group2, 5 abutments with 3.5 mm GH; and Group3, 5 abutments with 5.5 mm GH. Each specimen was mounted in transparent auto-polymerizing acrylic resin block, and the abutment screw was tightened to 35 Ncm with an electric torque wrench. After 5 minutes, initial torque loss (ITL) was recorded for all specimens. Metal crowns were fabricated with 45° occlusal surface and were placed on the abutments. A cyclic load of 75 N and frequency of 1 Hz were applied perpendicular to the long axis of each specimen. After 500 000 cycles, secondary torque loss (STL) was recorded. One-way ANOVA analysis was used to evaluate the effects of abutment collar height before and after cyclic loading. One-way ANOVA showed that ITL among the groups was not significantly different (P = .52), while STL was significantly different among the groups (P = .008). Post-hoc Tukey HSD tests showed that STL values were significantly different between the abutments with 1.5 mm GH (Group1) and with 5.5 mm GH (Group3) (P = .007). A paired comparison t-test showed that cyclic loading significantly influenced the STL in comparison with the ITL in each group. Within the limitations of this study, it can be concluded that increase in height of the abutment collar could adversely affect the torque loss of the abutment screw.
Nissan, J; Zenziper, E; Rosner, O; Kolerman, R; Chaushu, L; Chaushu, G
Soft tissue shrinkage during the course of restoring dental implants may result in biological and prosthodontic difficulties. This study was conducted to measure the continuous shrinkage of the mucosal cuff around dental implants following the removal of the healing abutment up to 60 s. Individuals treated with implant-supported fixed partial dentures were included. Implant data--location, type, length, diameter and healing abutments' dimensions--were recorded. Mucosal cuff shrinkage, following removal of the healing abutments, was measured in bucco-lingual direction at four time points--immediately after 20, 40 and 60 s. anova was used to for statistical analysis. Eighty-seven patients (49 women and 38 men) with a total of 311 implants were evaluated (120 maxilla; 191 mandible; 291 posterior segments; 20 anterior segments). Two-hundred and five (66%) implants displayed thick and 106 (34%) thin gingival biotype. Time was the sole statistically significant parameter affecting mucosal cuff shrinkage around dental implants (P < 0.001). From time 0 to 20, 40 and 60 s, the mean diameter changed from 4.1 to 4.07, 3.4 and 2.81 mm, respectively. The shrinkage was 1%, 17% and 31%, respectively. The gingival biotype had no statistically significant influence on mucosal cuff shrinkage (P = 0.672). Time required replacing a healing abutment with a prosthetic element should be minimised (up to 20/40 s), to avoid pain, discomfort and misfit. © 2015 John Wiley & Sons Ltd.
Starch-Jensen, Thomas; Christensen, Ann-Eva; Lorenzen, Henning
OBJECTIVES: The objective was to test the hypothesis of no difference in implant treatment outcome after installation of implants with a scalloped implant-abutment connection compared to a flat implant-abutment connection. MATERIAL AND METHODS: A MEDLINE (PubMed), Embase and Cochrane library search...
Abrahamsson, Ingemar; Berglundh, Tord; Sekino, Satoshi; Lindhe, Jan
Standard protocols for the clinical use of dental implants often include the placement of healing abutments prior to standard or custom-made abutments. The tissue response to a single shift from a healing abutment to a permanent abutment has not been studied. The aim of the present experiment was to study tissue reactions that may occur following the removal of a healing abutment and the placement of a permanent abutment. In six beagle dogs, all mandibular premolars were extracted. Three months later three fixtures of the Astra Tech Implants Dental System (Astra Tech AB, Mölndal, Sweden) were installed in each edentulous premolar region. An additional 3 months later, the first abutment connection was performed. In two sites on each side of the mandible, healing abutments were placed; in the remaining site, a Uni-abutment (Astra Tech AB) was used. The two healing abutments were removed 2 weeks later, and one Uni-abutment and one prepable abutment were placed. A plaque-control period was initiated, and 6 months later block biopsies were obtained. The biopsies were prepared for histometric and morphometric examination. Radiographs were obtained at fixture placement, 2 weeks after the first abutment connection, and 6 months later. The length of the barrier epithelium, the height of the connective tissue attachment, and the level of the marginal bone did not differ between the three abutment groups. The major part of the radiographic bone loss during the experiment took place prior to or immediately after abutment connection; only small bone level alterations occurred during the subsequent 6-month period. The shift from a healing abutment to a permanent abutment resulted in the establishment of a transmucosal attachment, the dimension and quality of which did not differ from those of the mucosal barrier formed to a permanent abutment placed during a second-stage surgery.
Full Text Available The aim of the paper is controlling the behavior of the bridge supports of the motorway viaduct WA-164 on strengthened subsoil using soil-cement columns made in DSM technology. Monitoring of the construction was carried out for a period of 16 months by measuring the settlement and rotation of the structure. The settlements were measured by means of the geodesic precision leveling method. Changes in the rotation of the supports were recorded using a inclinometer sensors installed on the walls of the abutments. For mapping of the construction work, numerical models of span and abutments were performed. The abutment was modeled in computer program SOFiSTiK. The stiffness of subsoil was calibrated with regard to the measured settlement of the abutment on DSM columns. The results of field measurements shows that after backfilling the abutments, it leaned in the embankments direction. This is also confirmed by numerical analysis. Monitoring conducted in 2014 showed that settlement is stabilized, and the measured values are safe and lower than the SLS limit stage. Numerical modeling along with geotechnical and geodetic monitoring has enabled a better understanding of the behavior of the bridge foundation on strengthened subsoil and verify the calculation assumptions taken at the stage of design calculations.
Judy, K W
Rapid, accurate seating of screw-retained implant abutment heads, where timing is controlled by internal or external hex designs, can be readily accomplished with individual, custom-cast abutment head location devices. The devices are especially useful when the abutment head-implant body complex is to be permanently cemented. The use and design of abutment seating jigs for single tooth implants and completely implant or implant and natural tooth-supported prostheses are described.
... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Endosseous dental implant abutment. 872.3630... (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Prosthetic Devices § 872.3630 Endosseous dental implant abutment. (a) Identification. An endosseous dental implant abutment is a premanufactured prosthetic component...
Jo, Jae-Young; Yang, Dong-Seok; Huh, Jung-Bo; Heo, Jae-Chan; Yun, Mi-Jung
PURPOSE This study evaluated the influence of abutment materials on the stability of the implant-abutment joint in internal conical connection type implant systems. MATERIALS AND METHODS Internal conical connection type implants, cement-retained abutments, and tungsten carbide-coated abutment screws were used. The abutments were fabricated with commercially pure grade 3 titanium (group T3), commercially pure grade 4 titanium (group T4), or Ti-6Al-4V (group TA) (n=5, each). In order to assess the amount of settlement after abutment fixation, a 30-Ncm tightening torque was applied, then the change in length before and after tightening the abutment screw was measured, and the preload exerted was recorded. The compressive bending strength was measured under the ISO14801 conditions. In order to determine whether there were significant changes in settlement, preload, and compressive bending strength before and after abutment fixation depending on abutment materials, one-way ANOVA and Tukey's HSD post-hoc test was performed. RESULTS Group TA exhibited the smallest mean change in the combined length of the implant and abutment before and after fixation, and no difference was observed between groups T3 and T4 (P>.05). Group TA exhibited the highest preload and compressive bending strength values, followed by T4, then T3 (Pimplant systems. The strength of the abutment material was inversely correlated with settlement, and positively correlated with compressive bending strength. Preload was inversely proportional to the frictional coefficient of the abutment material. PMID:25551010
Albrecht, T; Kirsten, A; Kappert, H F; Fischer, H
The purpose of this study was to evaluate the fracture load of single zirconia abutment restorations using different veneering techniques and materials. The abutment restorations were divided into 6 groups with 20 samples each: test abutments (control group A), lithium disilicate ceramic crowns bonded on incisor abutments (group B), leucite ceramic crowns bonded on incisor abutments (group C), premolar abutments directly veneered with a fluor apatite ceramic (group D (layered) and group E (pressed)) and premolar abutments bonded with lithium disilicate ceramic crowns (group F). The fracture load of the restorations was evaluated using a universal testing machine. Half of each group was artificially aged (chewing simulation and thermocycling) before evaluating the fracture load with the exception of the test abutments. The fracture load of the test abutments was 705 ± 43N. Incisor abutments bonded with lithium disilicate or leucite ceramic crowns (groups B and C) showed fracture loads of about 580N. Premolar restorations directly veneered with fluor apatite ceramic (groups D and E) showed fracture loads of about 850N. Premolar restorations bonded with lithium disilicate ceramic crowns (group F) showed fracture loads of about 1850N. The artificial ageing showed no significant influence on the strength of the examined restorations. All ceramic crowns made of lithium disilicate glass-ceramic, adhesively bonded to premolar abutments showed the highest fracture loads in this study. However, all tested groups can withstand physiological bite forces. Copyright © 2010 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.
The U.S. Geological Survey, in cooperation with the South Carolina Department of Transportation, conducted a field investigation of abutment scour in South Carolina and used those data to develop envelope curves that define the upper bound of abutment scour. To expand on this previous work, an additional cooperative investigation was initiated to combine the South Carolina data with abutment scour data from other sources and evaluate upper bound patterns with this larger data set. To facilitate this analysis, 446 laboratory and 331 field measurements of abutment scour were compiled into a digital database. This extensive database was used to evaluate the South Carolina abutment scour envelope curves and to develop additional envelope curves that reflected the upper bound of abutment scour depth for the laboratory and field data. The envelope curves provide simple but useful supplementary tools for assessing the potential maximum abutment scour depth in the field setting.
Valley Fever is a disease caused by a fungus (or mold) called Coccidioides. The fungi live in the soil ... from person to person. Anyone can get Valley Fever. But it's most common among older adults, especially ...
Seetoh, Y L; Tan, Keson B; Chua, E K; Quek, H C; Nicholls, Jack I
Conical implant-abutment connections for platform switching have been recently introduced in implant systems. This study investigated the load fatigue performance of three conical abutment systems and their corresponding titanium and zirconia abutments. Regular-diameter implants of the Ankylos (AK), PrimaConnex (PC), and Straumann (ST) systems were tested with their corresponding titanium (Ti) and zirconia (Zr) abutments tightened to the recommended torque (n = 5 implant-abutment assemblies per group). A rotational load fatigue machine applied a sinusoidally varying tensile-compressive 21 N load to specimens at a 45-degree angle, producing an effective bending moment of 35 Ncm at a frequency of 10 Hz. The number of cycles to failure was recorded, with the upper limit set at 5 million cycles. Results were evaluated through analyses of variance. Except for the ST Zr group, which showed no failures in four samples and one failure just below the screw head, and the AK Ti group, in which one sample was preserved without fracture, all groups experienced failure of at least one of the components, whether the abutment screw only, the abutment, and/or the implant neck. There were significant differences between systems. There was no difference between systems for the Ti abutments, and the ST group was significantly different from the AK and PC groups for the Zr abutments. Ti conical abutments appear to have poorer load fatigue performance compared with earlier studies of external-hexagon connections. The load fatigue performance of Zr conical abutments varied and seemed to be highly system dependent. Many of the fractures in both the Ti and Zr abutment groups occurred within the implant, and retrieval would pose a significant clinical challenge. The clinician should weigh the mechanical, biologic, and esthetic considerations before selection of any implant system, connection type, or abutment material.
Cardoso, Mayra; Sangalli, Jorgiana; Koga-Ito, Cristiane Yumi; Ferreira, Leandro Lameirão; da Silva Sobrinho, Argemiro Soares; Nogueira, Lafayette
The influence of diamond-like carbon (DLC) films on bacterial leakage through the interface between abutments and dental implants of external hexagon (EH) and internal hexagon (IH) designs was evaluated. Film deposition was performed by plasma-enhanced chemical vapor deposition. Sets of implants and abutments (n = 30 per group, sets of 180 implants) were divided according to connection design and treatment of the abutment base: 1) no treatment (control); 2) DLC film deposition; and 3) Ag-DLC film deposition. Under sterile conditions, 1 μL Enterococcus faecalis was inoculated inside the implants, and abutments were tightened. The sets were tested for immediate external contamination, suspended in test tubes containing sterile culture broth, and followed for 5 days. Turbidity of the broth indicated bacterial leakage. At the end of the period, the abutments were removed and the internal content of the implants was collected with paper points and plated in Petri dishes. After 24-hour incubation, they were assessed for bacterial viability and colony-forming unit counting. Bacterial leakage was analyzed by χ(2) and Fisher exact tests (α = 5%). The percentage of bacterial leakage was 16.09% for EH implants and 80.71% for IH implants (P DLC and Ag-DLC films do not significantly reduce the frequency of bacterial leakage and bacteria load inside the implants.
Harel, N; Livne, S; Piek, D; Marku-Cohen, S; Ormianer, Z
Fixed implant supported single crowns and fixed dental prostheses (FDPs) have become an accepted treatment option for replacing and restoring missing teeth. Recent systematic reviews summarized excellent 5- and 10-year survival rates for both reconstruction types. In screw-retained restorations, the fastening screw provides a solid joint between the restoration and the implant abutment or between the restoration and the implant itself. With cement-retained prostheses, this restorative screw is eliminated for many reasons: esthetics, occlusal stability, and fabrication of passively fitting restorations. The purpose of this article is to review the variety of implant-abutments available for fabrication of fixed implant-supported restoration and compare between the various abutment forms (screw vs. cement retained).
Aminuddin Ab. Ghani; Reza Mohammadpour
Most of actual abutments in rivers are built on foundation, while there is limited number of study available on the effects of the foundation on the local scour. In this study, temporal variation of local scour around compound abutment was investigated experimentally under clear-water conditions. The results showed that a suitable level of foundation is able to decrease the scour depth and increase scour time during the flood events. The trend of temporal scour depth at compound pier and abut...
Takeuchi, C. S.; Sclater, J. G.; Grindlay, N. R.; Madsen, J. A.; Rommevaux-Jestin, C.
The ultra-slow spreading Southwest Indian Ridge (SWIR) separates the Antarctic and African plates. We present results from two surveys covering the SWIR between 26° and 27°30'E and between 32° and 35°E, lying on either side of the long-offset Andrew Bain transform fault. The objectives of the surveys were to characterize the segmentation of an ultra-slow spreading ridge on either side of a long-offset transform fault and to examine the structure of the individual segments. Four transform faults, the Du Toit, Andrew Bain, Marion, and Prince Edward, and one non-transform discontinuity bound four accretionary segments in the survey areas. Two segments lie northeast of the Andrew Bain (32°-35°E). Large central axial volcanoes, deep, broad mantle Bouguer anomaly (MBA) lows, and high magnetization intensities centered on the spreading axis result from high magmatic activity. Increased magmatism on the ridge axis is likely caused by high mantle temperatures produced by the close proximity of the Marion Plume, which abuts the northern end of the Andrew Bain. Two segments lie southwest of the Andrew Bain (26°-27°30'E). Discrepancies in the locations of the axial rift valley, central magnetization high, and an irregularly-shaped MBA low suggest complex accretionary processes at the western segment (~26°-27° E). The eastern segment (~27°-27°30'E), which abuts the southwest end of the Andrew Bain, shows a deep axial valley, MBA values which increase to the east, and nearly nonexistent magnetization intensity. These features are probably the result of amagmatic accretion caused by the transform edge effect of the Andrew Bain. A transition in the character of topography at 26°45'E suggests that the current segment configuration may not be temporally stable. High-relief (~1 km) ridge-trough structures south of the spreading axis may be the result of an episodic interplay between accretion, both magmatic and amagmatic, and tectonic extension.
Ristic, Ljubisa; Dakovic, Dragana; Postic, Srdjan; Lazic, Zoran; Bacevic, Miljana; Vucevic, Dragana
The grey-bluish discoloration of gingiva (known as "amalgam tattoo") does not appear only in the presence of amalgam restorations. It may also be seen in cases of teeth restored with cast dowels and porcelain-fused-to-metal (PFM) restorations. The aim of this article was to determine the clinical characteristics of abutment teeth with gingival discoloration. This research was conducted on 25 patients referred for cast dowel and PFM restorations. These restorations were manufactured from Ni-Cr alloys. Ninety days after cementing the fixed prosthodontic restorations, the abutment teeth (n = 61) were divided into a group with gingival discoloration (GD) (n = 25) and without gingival discoloration (NGD) (n = 36). The control group (CG) comprised the contralateral teeth (n = 61). Plaque index, gingival index, clinical attachment level, and probing depth were assessed before fabrication and also 90 days after cementation of the PFM restorations. The gingival index, clinical attachment level, and probing depths of the abutment teeth that had GD were statistically higher before restoration, in comparison with the abutment teeth in the NGD and control groups. Ninety days after cementation, the abutment teeth with GD had significantly lower gingival indexes and probing depths, compared to the abutment teeth in the NGD group. Both abutment teeth groups (GD and NGD) had significantly higher values of clinical attachment levels when compared to the control group. There were no statistically significant differences in plaque index values between the study groups. The results of this study indicated that impairment of periodontal status of abutment teeth seemed to be related to the presence of gingival discolorations. Therefore, fabrication of fixed prosthodontic restorations requires careful planning and abutment teeth preparation to minimize the occurrence of gingival discolorations. With careful preparation of abutment teeth for cast dowels and crown restorations it may be
Accurate estimation of the maximum possible depth of scour at bridge abutments is important in decision-making for the safe depth of burial of footings. Besides, investigation of the geometric features of scour holes around abutments provides useful information for the degree of scour counter-measure to be implemented ...
Experimental investigation of the 3D turbulent ﬂow ﬁeld around a 45° wing-wall abutment, resting on a rough rigid bed, is reported. The experiment was conducted ... The shear stresses acting on the bed around the abutment are estimated from the Reynolds stresses and velocity gradients. The data presented in this study ...
R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22
Kwan T F 1989 A study of abutment scour. Rep. No. 451, School of Engineering, University of. Auckland, Auckland, New Zealand. Kwan T F, Melville B W 1994 Local scour and flow measurements at bridge abutments. J. Hydraul. Res. 32: 661–673. Melville B W, Raudkivi R J 1977 Flow characteristics in local scour at bridge ...
Full Text Available Objectives: Microbial leakage through the implant-abutment (I-A interface results in bacterial colonization in two-piece implants. The aim of this study was to compare microleakage rates in three types of Replace abutments namely Snappy, GoldAdapt, and customized ceramic using radiotracing.Materials and Methods: Three groups, one for each abutment type, of five implants and one positive and one negative control were considered (a total of 17 regular body implants. A torque of 35 N/cm was applied to the abutments. The samples were immersed in thallium 201 radioisotope solution for 24 hours to let the radiotracers leak through the I-A interface. Then, gamma photons received from the radiotracers were counted using a gamma counter device. In the next phase, cyclic fatigue loading process was applied followed by the same steps of immersion in the radioactive solution and photon counting.Results: Rate of microleakage significantly increased (P≤0.05 in all three types of abutments (i.e. Snappy, GoldAdapt, and ceramic after cyclic loading. No statistically significant differences were observed between abutment types after cyclic loading.Conclusions: Microleakage significantly increases after cyclic loading in all three Replace abutments (GoldAdapt, Snappy, ceramic. Lowest microleakage before and after cyclic loading was observed in GoldAdapt followed by Snappy and ceramic.Keywords: Dental Implants; Dental Implant-Abutment Design; Thallium Chloride
R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22
When a wing-wall abutment is placed vertically on a rigid-bed rectangular channel by attach- ing it to one of the vertical sidewalls of the channel, the approaching turbulent boundary layer undergoes separation and rolles up to form the well-known primary vortex, which swept out by the side of the abutment. Limited research ...
Nagasawa, Yuko; Hibino, Yasushi; Nakajima, Hiroshi
This study was to examine the retentive force of crowns to implant abutments with commercial temporary cements. Six different temporary cements were investigated. Cast crowns were cemented to the abutments using each cement and their retentive forces to abutments were determined 7 or 28 days after cementing (n=10). The retentive force of the cements to abutments varied widely among the products [27-109 N (7-day), 18-80 N (28-days)]. The retentive force of all the cements was not reduced as the time elapsed, except for two products tested. The polycarboxylate cements and paste-mixing type eugenol-free cements revealed comparable retentive force after 28 days of storage. The powder-liquid type cements showed a positive correlation (pcement between the retentive force and compressive strength. Mechanical strength of temporary cements could not be a prominent predicting factor for retention of the crowns on the abutments.
Pandey, M.; Sharma, P. K.; Ahmad, Z.
At the time of floods, failure of bridges is the biggest disaster and mainly sub-structure (bridge abutments and piers) are responsible for this failure of bridges. It is very risky if these sub structures are not constructed after proper designing and analysis. Scour is a natural phenomenon in rivers or streams caused by the erosive action of the flowing water on the bed and banks. The abutment undermines due to river-bed erosion and scouring, which generally recognized as the main cause of abutment failure. Most of the previous studies conducted on scour around abutment have concerned with the prediction of the maximum scour depth (Lim, 1994; Melvill, 1992, 1997 and Dey and Barbhuiya, 2005). Dey and Barbhuiya (2005) proposed a relationship for computing maximum scour depth near an abutment, based on laboratory experiments, for computing maximum scour depth around vertical wall abutment, which was confined to their experimental data only. However, this relationship needs to be also verified by the other researchers data in order to support the reliability to the relationship and its wider applicability. In this study, controlled experimentations have been carried out on the scour near a vertical wall abutment. The collected data in this study along with data of the previous investigators have been carried out on the scour near vertical wall abutment. The collected data in this study along with data of the previous have been used to check the validity of the existing equation (Lim, 1994; Melvill, 1992, 1997 and Dey and Barbhuiya, 2005) of maximum scour depth around the vertical wall abutment. A new relationship is proposed to estimate the maximum scour depth around vertical wall abutment, it gives better results all relationships.
Full Text Available "nBackground and Aims: Nowadays, removable partial dentures are applied to patients who are not able to use dental implants or fixed prosthesis. Although based on the studies the users of removable partial dentures are in the risk of plaque accumulation and unacceptable changes such as gingivitis, periodontitis and mobility in abutment tooth. It is not clear whether the negative effects of removable partial dentures are more on the isolated teeth which are a kind of abutment adjacent to endentulous area in both sides. The purpose of this study was to investigate the clinical condition of isolated abutment teeth without splinting in comparison to control abutment from the aspects of B.O.P (bleeding on probing, mobility, pocket depth and gingivitis."nMaterials and Methods: In this cross-sectional study, the prepared questionnaires were filled out by 50 patients who received removable partial dentures in department of removable prosthodontics of dental school of Tehran University of Medical Sciences. The patients had isolated abutment tooth and did not have any systemic disease. The obtained data were analyzed. Using Wilcoxon, exact Fisher and Kruskal-Wallis test."nResults: B.O.P (P=0.004, pocket depth (P=0.035, and mobility (P<0.001 in isolated abutments were more than those in control abutments, but there were not significant differences in the degree of caries (P=0.083 and gingivitis (P=0.07."nConclusion: This study showed that clinical condition of isolated abutments is worse than that of control abutments. More attention should be paid to healthiness of isolated teeth without splinting and periodic follow ups should be done in these cases.
... loss Headache Valley fever Symptoms & causes Diagnosis & treatment Advertisement Mayo Clinic does not endorse companies or products. ... a Job Site Map About This Site Twitter Facebook Google YouTube Pinterest Mayo Clinic is a not- ...
Sailer, Irena; Asgeirsson, Asgeir G; Thoma, Daniel S; Fehmer, Vincent; Aspelund, Thor; Özcan, Mutlu; Pjetursson, Bjarni E
There is limited knowledge regarding the strength of zirconia abutments with internal and external implant abutment connections and zirconia abutments supported by a titanium resin base (Variobase, Straumann) for narrow diameter implants. To compare the fracture strength of narrow diameter abutments with different types of implant abutment connections after chewing simulation. Hundred and twenty identical customized abutments with different materials and implant abutment connections were fabricated for five groups: 1-piece zirconia abutment with internal connection (T1, Cares-abutment-Straumann BL-NC implant, Straumann Switzerland), 1-piece zirconia abutment with external hex connection (T2, Procera abutment-Branemark NP implant, Nobel Biocare, Sweden), 2-piece zirconia abutments with metallic insert for internal connection (T3, Procera abutment-Replace NP implant, Nobel Biocare), 2-piece zirconia abutment on titanium resin base (T4, LavaPlus abutment-VarioBase-Straumann BL-NC implant, 3M ESPE, Germany) and 1-piece titanium abutment with internal connection (C, Cares-abutment-Straumann BL-NC implant, Straumann, Switzerland). All implants had a narrow diameter ranging from 3.3 to 3.5 mm. Sixty un-restored abutments and 60 abutments restored with glass-ceramic crowns were tested. Mean bending moments were compared using ANOVA with p-values adjusted for multiple comparisons using Tukey's procedure. The mean bending moments were 521 ± 33 Ncm (T4), 404 ± 36 Ncm (C), 311 ± 106 Ncm (T1) 265 ± 22 Ncm (T3) and 225 ± 29 (T2) for un-restored abutments and 278 ± 84 Ncm (T4), 302 ± 170 Ncm (C), 190 ± 55 Ncm (T1) 80 ± 102 Ncm (T3) and 125 ± 57 (T2) for restored abutments. For un-restored abutments, C and T4 had similar mean bending moments, significantly higher than those of the three other groups (p < .05). Titanium abutments (C) had significantly higher bending moments than identical zirconia abutments (T1) (p < .05). Zirconia
da Fonte Porto Carreiro, Adriana; de Carvalho Dias, Kássia; Correia Lopes, Ana Lílian; Bastos Machado Resende, Camila Maria; Luz de Aquino Martins, Ana Rafaela
To evaluate the periodontal conditions and integrity of abutment and non-abutment teeth of patients evaluated 7 years after insertion of the removable partial denture (RPD). Twenty-two patients (17 women, 5 men) were assessed at the moment of denture insertion and 7 years later. The following items were verified in each assessment: bleeding on probing (BP), probing depth (PD), gingival recession (GR), and mobility (M), comparing direct and indirect abutment teeth, and the teeth not involved in the denture design. Tooth integrity was also evaluated and classified as intact when no caries or fractures were observed. The Kruskal-Wallis test was used to reveal statistical significance between the groups (p = 0.05) as well as the Bonferrroni-corrected Mann-Whitney test for post hoc comparison. The Wilcoxon test was used for evaluation within the group over time. Fisher's exact test was applied to cross data about abutment integrity. Statistically significant differences were found for GR (baseline, p < 0.001; 7 years, p < 0.001) and PD (baseline, p = 0.001; 7 years = 0.004) between the three groups at baseline and after 7 years of follow-up. Mean BP and M values increased from initial assessment to after 7 years of RPD use in every group, but no statistically significant difference was found between the groups. For abutment integrity, a statistically significant difference (p = 0.028) was observed, and the direct abutment exhibited more (33.3%) caries and fractures. RPDs generated more periodontal damage to direct abutments, since higher gingival recession probing depth indexes, and presence of caries and fractures were observed in comparison to indirect abutments and non-abutments. © 2016 by the American College of Prosthodontists.
The Iowa Department of Transportation has long recognized that approach slab pavements of integral abutment bridges are prone to settlement and cracking, which manifests as the "bump at the end of the bridge". A commonly recommended solution is to in...
Deterioration and necking of J-bars has been reportedly observed at the interface of the footing and stem wall during the demolition : of older retaining walls and bridge abutments. Similar deterioration has been reportedly observed between the pier ...
Integral abutment bridges, a type of jointless bridge, are the construction option of choice when designing highway bridges in many parts of the country. Rather than providing an expansion joint to separate the substructure from the superstructure to...
Integral abutment (IA) construction has become the preferred method over conventional construction for use with typical : highway bridges. However, the use of these structures is limited due to state mandated length and skew limitations. To : expand ...
Germana de Villa CAMARGOS
Full Text Available Abstract This study aimed to evaluate the influence of the type of prosthetic abutment associated to different implant connection on bone biomechanical behavior of immediately and delayed loaded implants. Computed tomography-based finite element models comprising a mandible with a single molar implant were created with different types of prosthetic abutment (UCLA or conical, implant connection (external hexagon, EH or internal hexagon, IH, and occlusal loading (axial or oblique, for both immediately and delayed loaded implants. Analysis of variance at 95%CI was used to evaluate the peak maximum principal stress and strain in bone after applying a 100 N occlusal load. The results showed that the type of prosthetic abutment influences bone stress/strain in only immediately loaded implants. Attachment of conical abutments to IH implants exhibited the best biomechanical behavior, with optimal distribution and dissipation of the load in peri-implant bone.
A new instrument (Photo-Electronic Erosion Pin, or PEEP) was examined in collecting field data and remotely monitoring bank erosion near bridge abutments during floods. The performance of PEEPs was evaluated through a detailed field study to determin...
Full Text Available Although the use of zirconia abutments for implant-supported restorations has gained momentum with the increasing demand for esthetics, little informed design rationale has been developed to characterize their fatigue behavior under different clinical scenarios. However, to prevent the zirconia from fracturing, the use of a titanium connection in bi-component aesthetic abutments has been suggested. Objective Mechanical testing of customized thin-walled titanium-zirconia abutments at the connection with the implant was performed in order to characterize the fatigue behavior and the failure modes for straight and angled abutments. Material and Methods Twenty custom-made bi-component abutments were tested according to ISO 14801:2007 either at a straight or a 25° angle inclination (n=10 each group. Fatigue was conducted at 15 Hz for 5 million cycles in dry conditions at 20°C±5°C. Mean values and standard deviations were calculated for each group. All comparisons were performed by t-tests assuming unequal variances. The level of statistical significance was set at p≤0.05. Failed samples were inspected in a polarized-light and then in a scanning electron microscope. Results Straight and angled abutments mean maximum load was 296.7 N and 1,145 N, the dynamic loading mean Fmax was 237.4 N and 240.7 N, respectively. No significant differences resulted between the straight and angled bi-component abutments in both static (p=0.253 and dynamic testing (p=0.135. A significant difference in the bending moment required for fracture was detected between the groups (p=0.01. Fractures in the angled group occurred mainly at the point of load application, whereas in the straight abutments, fractures were located coronally and close to the thinly designed areas at the cervical region. Conclusion Angled or straight thin-walled zirconia abutments presented similar Fmax under fatigue testing despite the different bending moments required for fracture. The main
Solá-Ruíz, María-Fernanda; Selva-Otaolaurruchi, Eduardo; Senent-Vicente, Gisela; González-de-Cossio, Inés; Amigó-Borrás, Vicente
To evaluate the vertical misfit between different brands of dental implants and prosthetic abutments, with or without mechanical torque, and to study their possible combination. Five different brands of implant were used in the study: Biofit (Castemaggiore, Italy), Bioner S.A. (Barcelona, Spain), 3i Biomet (Palm Beach, U.S.A.), BTI (Alava, Spain) and Nobel Biocare (Göteborg, Sweden), with standard 4.1 mm heads and external hexagons, and their respective machined prosthetic abutments. The implant-to-abutment fit/misfit was evaluated at four points (vestibular, lingual/palatine, mesial and distal) between implants and abutments of the same brand and different brands, with or without mechanical torque, using SEM micrographs at 5000X. Image analysis was performed using NIS-Elements software (Nikon Instruments Europe B.V.). Before applying torque, vertical misfit (microgaps) of the different combinations tested varied between 1.6 and 5.4 microns and after applying torque, between 0.9 and 5.9 microns, an overall average of 3.46 ± 2.96 microns. For manual assembly without the use of mechanical torque, the best results were obtained with the combination of the 3i implant and the BTI abutment. The Nobel implant and Nobel abutment, 3i-3i and BTI-BTI and the combination of 3i implant with BTI or Nobel abutment provided the best vertical fit when mechanical torque was applied. The vertical fits obtained were within the limits considered clinically acceptable. The application of mechanical torque improved outcomes. There is compatibility between implants and abutments of different brand and so their combination is a clinical possibility.
Integral abutment bridges provide bridge engineers an economical design alternative to traditional bridges with expansion joints owing to the benefits, arising from elimination of expensive joints installation and reduced maintenance cost. The superstructure for integral abutment bridges is cast integrally with abutments. Time-dependent effects of creep, shrinkage of concrete, relaxation of prestressing steel, temperature gradient, restraints provided by abutment foundation and backfill and statical indeterminacy of the structure introduce time-dependent variations in the redundant forces. An analytical model and numerical procedure to predict instantaneous linear behavior and non-linear time dependent long-term behavior of continuous composite superstructure are developed in which the redundant forces in the integral abutment bridges are derived considering the time-dependent effects. The redistributions of moments due to time-dependent effects have been considered in the analysis. The analysis includes nonlinearity due to cracking of the concrete, as well as the time-dependent deformations. American Concrete Institute (ACI) and American Association of State Highway and Transportation Officials (AASHTO) models for creep and shrinkage are considered in modeling the time dependent material behavior. The variations in the material property of the cross-section corresponding to the constituent materials are incorporated and age-adjusted effective modulus method with relaxation procedure is followed to include the creep behavior of concrete. The partial restraint provided by the abutment-pile-soil system is modeled using discrete spring stiffness as translational and rotational degrees of freedom. Numerical simulation of the behavior is carried out on continuous composite integral abutment bridges and the deformations and stresses due to time-dependent effects due to typical sustained loads are computed. The results from the analytical model are compared with the
Telleman, Gerdien; Raghoebar, Gerry M.; Vissink, Arjan; Meijer, Henny J. A.
A coded implant healing abutment makes an impression at the implant level no longer necessary. An impression is made of the healing abutment, which is placed onto the implant directly after implant placement. The codes embedded in the occlusal surface of the healing abutment provide essential
Dula, Linda J; Shala, Kujtim Sh; Pustina-Krasniqi, Teuta; Bicaj, Teuta; Ahmedi, Enis F
The aim of this study was to evaluate the influence of removable partial dentures (RPD) on the periodontal health of abutment and non-abutment teeth. A total 107 patients with RPD participated in this study. It was examined 138 RPD, they were 87 with clasp-retained and 51 were RPD with attachments. The following periodontal parameters were evaluated for abutment and non-abutment teeth, plaque index (PLI), calculus index (CI), bleeding on probing (BOP), probing depth (PD) (mm) and tooth mobility (TM) index. These clinical measurements were taken immediately before insertion the RPD, then one and 3 months after insertion. The level of significance was set at (P 0.05). With carefully planned prosthetic treatment and adequate maintenance of the oral and denture hygiene, we can prevent the periodontal diseases.
Katsuta, Yasuhiro; Watanabe, Fumihiko
Cyclic torsional loading tests were carried out in the laboratory using various implant systems, in order to clarify differences between the systems in loosening of abutment screws. Six samples from six commercially available abutment systems were used, giving a total of 36 samples. Four of the systems used internal connections, and two used external connections. The abutment screw for each system was tightened to a torque value specified by the manufacturer, and after 5 min, the loosening torque was measured using a digital torque meter. Measurements were taken twice, and a second measurement was taken as a reference value. A cyclic torsional loading test with 100,000 cycles was performed on the sample, and the loosening torque was again measured after the test. In conclusion, loosening of the abutment screw occurred as a result of cyclic torsional loading, and the degree of loosening varied with each implant system.
Integral abutment (IA) construction has become the preferred method over conventional construction for use with typical highway bridges. However, the use of these structures is limited due to state mandated length and skew limitations. To expand thei...
Delben, Juliana Aparecida; Barão, Valentim Adelino Ricardo; Dos Santos, Paulo Henrique; Assunção, Wirley Gonçalves
The effect of veneering materials on screw joint stability remains inconclusive. Thus, this study evaluated the preload maintenance of abutment screws of single crowns fabricated with different abutments and veneering materials. Sixty crowns were divided into five groups (n = 12): UCLA abutment in gold alloy with ceramic (group GC) and resin (group GR) veneering, UCLA abutment in titanium with ceramic (group TiC) and resin (group TiR) veneering, and zirconia abutment with ceramic veneering (group ZiC). Abutment screws made of gold were used with a 35 Ncm insertion torque. Detorque measurements were obtained initially and after mechanical cycling. Data were analyzed by ANOVA and Fisher's exact test at a significance level of 5%. For the initial detorque means (in Ncm), group TiC (21.4 ± 1.78) exhibited statistically lower torque maintenance than groups GC (23.9 ± 0.91), GR (24.1 ± 1.34), and TiR (23.2 ± 1.33) (p < 0.05, Fisher's exact test). Group ZiC (21.9 ± 2.68) exhibited significantly lower torque maintenance than groups GC, GR, and TiR (p < 0.05, Fisher's exact test). After mechanical cycling, there was a statistically significant difference between groups TiC (22.1 ± 1.86) and GR (23.8 ± 1.56); between groups ZiC (21.7 ± 2.02) and GR; and also between groups ZiC and TiR (23.6 ± 1.30) (p < 0.05, Fisher's exact test). Detorque reduction occurred regardless of abutment type and veneering material. More irregular surfaces in the hexagon area of the castable abutments were observed. The superiority of any veneering material concerning preload maintenance was not established. © 2013 by the American College of Prosthodontists.
Chowdhary, Ramesh; Kumari, Shail
Introduction Presence of gap at the implant-abutment interface, leads to microleakage and accumulation of bacteria which can affect the success of dental implants. Aim To evaluate the sealing capability of different implant connections against microleakage. Materials and Methods In January 2017 an electronic search of literature was performed, in Medline, EBSCO host and Pubmed data base. The search was focused on ability of different implant connections in preventing microleakage. The related titles and abstracts available in English were screened, and the articles that fulfilled the inclusion criteria were selected for full text reading. Results In this systematic review, literature search initially resulted in 78 articles among which 30 articles only fulfilled the criteria for inclusion and were finally included in the review. Almost all the studies showed that there was some amount of microleakage at abutment implant interface. Microleakage was very less in Morse taper implants in comparison to other implant connections. Majority of studies showed less microleakage in static loading conditions and microleakage increases in dynamic loading conditions. Conclusion In this systematic review maximum studies showed that there was some amount of microleakage at abutment implant interface. External hexagon implants failed completely to prevent microleakage in both static and dynamic loading conditions of implants. Internal hexagon implants mainly internal conical (Morse taper) implants are very promising in case of static loading and also showed less microleakage in dynamic loading conditions. Torque recommended by manufacturer should be followed strictly to get a better seal at abutment implant interface. Zirconia abutments are more to microleakage than Titanium abutments and there use should be discouraged. Zirconia abutments should be only restricted to cases where there was very high demand of aesthetics. PMID:28764310
Thoma, Daniel S; Gamper, Felix B; Sapata, Vítor M; Voce, Giuseppe; Hämmerle, Christoph H F; Sailer, Irena
Zirconia abutments are frequently used for implant-supported single crowns. Even though demonstrating esthetic benefits compared to metal abutments, zirconia abutments lead to an increased brightness of the peri-implant mucosa compared to natural teeth and are not ideal from an esthetic point of view. To test whether or not a fluorescent hybrid zirconia abutment offers superior esthetics compared to a non-fluorescent one-piece zirconia abutment based on spectrophotometric analysis. In 24 patients with 24 single-tooth implants, 2 types of reconstructions were fabricated: a directly veneered one-piece zirconia abutment/crown (control) and a directly veneered fluorescent hybrid zirconia abutment/crown (test). Spectrophotometric assessment was performed: prior to abutment insertion (WA), at abutment try-in (A), at the try-in of the final crowns (C). Color differences (ΔE) were assessed compared to the gingiva of natural teeth (T) and between the reconstructions. At abutment try-in, ΔE values were 8.49 ± 3.59 for A Control and 8.27 ± 4.03 for A Test compared to T. At crown insertion, ΔE values were 7.61 ± 4.03 for C Control and 8.32 ± 3.57 for C Test compared to T. The difference in ΔE values between A Control and A Test was 0.23 ± 2.54 (P = .37), whereas the difference in ΔE values between C Control and C Test was -0.66 ±3.45 (P = .48). For all cases with a mucosal thickness ≤2 mm, the comparison between C Control and C Test was significant in favor of the control group (P = .03). Both types of reconstructions were similar in terms of esthetics. Incases with a mucosal thickness of compared to the natural gingiva was more pronounced for the fluorescent hybrid zirconia reconstructions. © 2017 Wiley Periodicals, Inc.
Kitagawa, Tsuyoshi; Tanimoto, Yasuhiro; Odaki, Misako; Nemoto, Kimiya; Aida, Masahiro
The objective of this study was to investigate the influence of implant/abutment joint designs on abutment screw loosening in a dental implant system, using nonlinear dynamic analysis of the finite element method (FEM). This finite element simulation study used two dental implant systems: the Ankylos implant system (Degusa Dental, Hanau, German) with a taper joint (taper joint-type model), and the Bränemark implant system (Nobel Biocare, Gothenburg, Sweden) with an external hex joint (external hex joint-type model). The nonlinear dynamic analysis was performed using three-dimensional finite element analysis. In comparing the movement of the taper type-joint model and external hex type-joint model, it was found that the external hex type-joint model had greater movement than the taper type-joint model. The external hex joint-type model showed rotation movement, whereas the movement of the taper joint-type model showed no rotation. It was concluded that the nonlinear dynamic analysis used in this study clearly demonstrated the differences in rotation of components in dental implant systems with taper or external hex joints. Copyright (c) 2005 Wiley Periodicals, Inc.
Full Text Available Objectives: The objective was to test the hypothesis of no difference in implant treatment outcome after installation of implants with a scalloped implant-abutment connection compared to a flat implant-abutment connection. Material and Methods: A MEDLINE (PubMed, Embase and Cochrane library search in combination with a hand-search of relevant journals was conducted. No language or year of publication restriction was applied. Results: The search provided 298 titles. Three studies fulfilled the inclusion criteria. The included studies were characterized by low or moderate risk of bias. Survival of suprastructures has never been compared within the same study. High implant survival rate was reported in all the included studies. Significantly more peri-implant marginal bone loss, higher probing depth score, bleeding score and gingival score was observed around implants with a scalloped implant-abutment connection. There were no significant differences between the two treatment modalities regarding professional or patient-reported outcome measures. Meta-analysis disclosed a mean difference of peri-implant marginal bone loss of 1.56 mm (confidence interval: 0.87 to 2.25, indicating significant more bone loss around implants with a scalloped implant-abutment connection. Conclusions: A scalloped implant-abutment connection seems to be associated with higher peri-implant marginal bone loss compared to a flat implant-abutment connection. Therefore, the hypothesis of the present systematic review must be rejected. However, further long-term randomized controlled trials assessing implant treatment outcome with the two treatment modalities are needed before definite conclusions can be provided about the beneficial use of implants with a scalloped implant-abutment connection on preservation of the peri-implant marginal bone level.
Blum, Kai; Wiest, Wolfram; Fella, Christian; Balles, Andreas; Dittmann, Jonas; Rack, Alexander; Maier, Dominik; Thomann, Ralf; Spies, Benedikt Christopher; Kohal, Ralf Joachim; Zabler, Simon; Nelson, Katja
Based on the current lack of data and understanding of the wear behavior of dental two-piece implants, this study aims for evaluating the microgap formation and wear pattern of different implants in the course of cyclic loading. Several implant systems with different conical implant-abutment interfaces were purchased. The implants were first evaluated using synchrotron X-ray high-resolution radiography (SRX) and scanning electron microscopy (SEM). The implant-abutment assemblies were then subjected to cyclic loading at 98N and their microgap was evaluated after 100,000, 200,000 and 1 million cycles using SRX, synchrotron micro-tomography (μCT). Wear mechanisms of the implant-abutment connection (IAC) after 200,000 cycles and 1 million cycles were further characterized using SEM. All implants exhibit a microgap between the implant and abutment prior to loading. The gap size increased with cyclic loading with its changes being significantly higher within the first 200,000 cycles. Wear was seen in all implants regardless of their interface design. The wear pattern comprised adhesive wear and fretting. Wear behavior changed when a different mounting medium was used (brass vs. polymer). A micromotion of the abutment during cyclic loading can induce wear and wear particles in conical dental implant systems. This feature accompanied with the formation of a microgap at the IAC is highly relevant for the longevity of the implants. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.
Schoenbaum, Todd R; Chang, Yi-Yuan; Klokkevold, Perry R; Snowden, John S
In their stock form, some titanium provisional implant abutments are not ideally designed for use in immediate placement/immediate provisional restoration treatment. This is largely due to the apical flare design that applies excessive pressure to the peri-implant soft tissue complex and crestal bone. This appears to have the undesirable effect of increasing peri-implant bone resorption and severely impeding the potential for increases in gingival volume. This type of stock titanium abutment will therefore benefit significantly from recontouring. The subgingival portion of the abutment is recontoured from the flared stock shape to a straight or parallel design. This modification minimizes pressure on the surgical site and provides additional space around the subgingival portion of the provisional restoration, within which the gingiva has the potential to remodel and fill. This allows the potential formation of additional peri-implant gingival volume and a coronal maintenance or migration of the soft tissue complex. In order to minimize the "graying effect" of titanium abutments, the retentive portion is opaqued by the technician or clinician. These modifications will improve the potential outcomes for both the peri-implant gingiva and the provisional restoration. Narrowing the emergence profile of implant abutments for use in immediate implant provisional restorations appears to allow for creation of greater peri-implant volume. Thus resulting in increased esthetic potential and predictability of the peri-implant gingiva. © 2012 Wiley Periodicals, Inc.
Integral Abutment Bridges (IAB) are bridges without any joints within the bridge deck or between the : superstructure and the abutments. An IAB provides many advantages during construction and maintenance of : a bridge. Soil-structure interactions at...
Pinheiro Tannure, Ana Luiza; Cunha, Alfredo Gonçalves; Borges Junior, Luiz Antônio; da Silva Concílio, Laís Regiane; Claro Neves, Ana Christina
To evaluate the changes in the external-hexagon surface of the titanium (Ti) implant before and after mechanical cycling, when coupled with zirconia (Zr) abutments (A) manufactured by three computer-aided design/computer-aided manufacturing (CAD/CAM) systems (Neodent Digital, Zirkonzahn, and AmannGirrbach) and the ZrTi abutment manufactured by Neodent. Four groups were formed (n = 6): titanium implant with Zr AmannGirrbach abutment (AZrAG), with Zr Zirkonzahn abutment (AZrZ), with Zr Neodent abutment (AZrN), and with Zr abutment with infrastructure in Ti Neodent (AZrTiN). Standardized abutments were made from three identical abutments milled in wax. Images of the surface of each side of the hexagons of the implant were obtained by scanning electron microscopy, before and after mechanical cycling, to evaluate the parameters: (1) scratches in the hexagon face; (2) hexagon superior shoulder kneading; (3) hexagon shoulder wear; (4) alterations on the hexagon base; and (5) scratches on the hexagon top. The abutments were coupled with the implants, and Cr-Co crowns were cemented. The implant/abutment/crown assemblies were submitted to mechanical cycling (400 N, 8.0 Hz) for 1 million cycles. The observed changes were classified as follows: absence (0), mild (1), moderate (2), and severe (3). The results were analyzed using the Mann-Whitney, Kruskal-Wallis, and Dunn tests (P < .05). For parameter 1, a significant difference (P = .008) was observed between AZrZ and AZrAG, with more scratches in AZrZ; and between AZrN and AZrTiN (P = .006), with more scratches in AZrN. For parameter 2, a significant difference (P < .05) was observed between AZrZ and AZrAG and between AZrZ and AZrN, with greater kneading in AZrZ; among AZrN and AZrTiN, there was no significant difference (P = .103). For parameter 3, a significant difference (P < .05) was observed between AZrZ and the other groups of Zr, with more wear in AZrZ; between AZrN and AZrTiN, there was no significant difference (P
Fariba Saleh Saber
Full Text Available Background. Since the misfit of crown has an important role in clinical performance of implant-supported prostheses, and due to the impact of the settling effect on misfit, the aim of this study was to investigate the impact of torque forces on the total lengths of narrow and short implant abutments in different internal implant‒abutment connections. Methods. In four different implant‒abutment connections, 8 analog implants with a normal diameter (4 mm and narrow abutment (4.5 mm were selected from groups of internal hex, internal octagon, morse hex 6° and morse hex 11°. Each of them was mounted within plaster type IV, and 32 samples were obtained. Then, the amount of vertical displacement was measured by closing the impression copings and applying torques of 20 25 and 30 Ncm. This stage was repeated for the abutment. In the next stage, the resin pattern was built and measurements were performed after applying the torques mentioned. Finally, after making the frame, this stage was repeated, and the settling effect was statistically analyzed with ANOVA. Results. In the stages of impression coping, resin pattern and final prosthesis, HEXAGONE had significantly the highest and OCTAGONE had the lowest rates of settling, and the settling of morse hex 11° and 6° was between them. Conclusion. Octagon implant had significantly the lowest settling in various clinical and laboratory stages by applying different torques.
Aminuddin Ab. Ghani
Full Text Available Most of actual abutments in rivers are built on foundation, while there is limited number of study available on the effects of the foundation on the local scour. In this study, temporal variation of local scour around compound abutment was investigated experimentally under clear-water conditions. The results showed that a suitable level of foundation is able to decrease the scour depth and increase scour time during the flood events. The trend of temporal scour depth at compound pier and abutment is similar. The scour depth develops to top of foundation quickly, and then the foundation postpones the scour development (lag–time. Duration of lag–time depends on the foundation level, velocity ratio (U/Uc and foundation dimension. This study highlights that proper design of foundation level increases duration of scouring and provides enough time to treat bridge foundation after the flood events.
Bidra, Avinash S; Rungruanganunt, Patchanee
The clinical outcomes of anterior implant abutments are not well reported. Purpose of the Study To systematically review the existing literature to identify survival, mechanical, biological, and esthetic outcomes of anterior implant abutments. An electronic search was performed using PubMed/MEDLINE with specific search terms and predetermined criteria. After application of inclusion and exclusion criteria, the final list of articles was reviewed in-depth to meet the objectives of this review. Systematic application of inclusion and exclusion criteria resulted in identification of 27 studies that described outcomes of anterior implant abutments. Because of substantial heterogeneity of data, true survival, or cumulative survival of abutments could not be calculated. However, the mean failure of abutments was 1.15%, attributable to fractures restricted to ceramic abutments. Mechanical complications included abutment screw loosening, primarily restricted to external hex implants. Biological complications included fistulas and mucosal recession. Esthetic outcomes showed lesser gingival discoloration for zirconia abutments compared with metal abutments. Minimal anterior abutment fractures have been reported and are restricted to ceramic abutments. Studies using spectrophotometry showed lesser gingival discoloration with zirconia abutments, but there is no evidence for difference in patient's esthetic satisfaction between ceramic and metal abutments. For the anterior region, selection of an implant with internal connection and a customized metal abutment (titanium or cast metal) can have the least mechanical complications. Limited existing clinical data indicate reduced peri-implant mucosal discoloration from zirconia abutments, which may be preferable over metal abutments, in patients with thinner mucosal tissues or patients with high or gummy smiles. © 2013 Wiley Periodicals, Inc.
Fracture strength and failure mode of maxillary implant-supported provisional single crowns: a comparison of composite resin crowns fabricated directly over PEEK abutments and solid titanium abutments.
Santing, Hendrik Jacob; Meijer, Henny J A; Raghoebar, Gerry M; Özcan, Mutlu
Polyetheretherketone (PEEK) temporary abutments have been recently introduced for making implant-supported provisional single crowns. Little information is available in the dental literature on the durability of provisional implant-supported restorations. The objectives of this study were to evaluate the fracture strength of implant-supported composite resin crowns on PEEK and solid titanium temporary abutments, and to analyze the failure types. Three types of provisional abutments, RN synOcta Temporary Meso Abutment (PEEK; Straumann), RN synOcta Titanium Post for Temporary Restorations (Straumann), and Temporary Abutment Engaging NobRplRP (Nobel Biocare) were used, and provisional screw-retained crowns using composite resin (Solidex) were fabricated for four different locations in the maxilla. The specimens were tested in a universal testing machine at a crosshead speed of 1 mm/minute until fracture occurred. The failure types were analyzed and further categorized as irreparable (Type 1) or reparable (Type 2). No significant difference was found between different abutment types. Only for the position of the maxillary central incisor, composite resin crowns on PEEK temporary abutments showed significantly lower (p Provisional crowns on PEEK abutments showed similar fracture strength as titanium temporary abutments except for central incisors. Maxillary right central incisor composite resin crowns on PEEK temporary abutments fractured below the mean anterior masticatory loading forces reported to be approximately 206 N. © 2010 Wiley Periodicals, Inc.
Home; Journals; Sadhana; Volume 39; Issue 5. Live-bed scour experiments with 45° wing-wall abutments ... Keywords. Scour; bridge foundation; abutments; hydraulics; rivers. ... A design equation is proposed for estimating maximum scour depth at 45°wing-wall abutment under live-bed condition. The calculated values of ...
Broeke, S.M. van den; Baat, C. de
Fracture of the implant abutment screws is a complication which can render an implant useless. The prevalence of abutment screw fracture does not exceed 2.5% after 10 years. Causes are loosening of implant abutment screw, too few, too short or too narrow implants, implants not inserted perpendicular
Sui, Xinxin; Wei, Huasha; Wang, Dashan; Han, Yan; Deng, Jing; Wang, Yongliang; Wang, Junjun; Yang, Jianjun
The purpose of the study was to investigate the correlation between fit accuracy and fracture resistance of zirconia abutments, as well as its feasibility for clinical applications. Twenty self-made zirconia abutments were tested with 30 Osstem GSII implants. First, 10 Osstem GSII implants were cut into two parts along the long axis and assembled with the zirconia abutments. The microgaps between the implants and the zirconia abutments were measured under a scanning electron microscope. Second, the zirconia abutments were assembled with 20 un-cut implants and photographed before and after being fixed with a central screw of 30-Ncm torque. The dental films were measured by Digora for Windows 2.6 software. Then the fracture resistance of zirconia abutments was measured using the universal testing machine at 90°. All results were analyzed using SPSS13.0 software. The average internal-hexagon microgaps between the implants and zirconia abutments were 19.38±1.34μm. The average Morse taper microgap in the implant-abutment interface was 17.55±1.68μm. The dental film showed that the Morse taper gap in the implant-abutment interface disappeared after being fixed with a central screw of 30-Ncm torque, and the average moving distance of the zirconia abutments to the implants was 0.19±0.02mm. The average fracture resistance of zirconia abutments was 282.93±17.28N. The internal-hexagon microgap between the implants and zirconia abutments was negatively related to the fracture resistance of the abutments (r1=-0.97, pzirconia abutments. The fracture resistance of zirconia abutments can satisfy the clinical application. Copyright © 2014 Elsevier Ltd. All rights reserved.
Passively retained precision attachment partial dentures have been used successfully on natural tooth abutments since the 1920s. However, the dental profession has not advocated their use with implant abutments. When used in the passive manner that has proven successful on natural tooth abutments, precision attachment cases on implant abutments can be an excellent treatment option. This type of case has been used successfully for more than 17 years and offers tremendous advantages over the conventional overdenture approach to removal restorations on implant abutments.
Kupeyan, H K; Lang, B R
Selecting the abutment at second-stage implant surgery should combine the experience of both the surgeon and the restorative dentist to avoid complications during prosthetic reconstructions. If an inappropriate abutment is selected, the resultant removal of the abutment and replacement of it with a completely different one is both costly and inefficient. The availability of the healing abutment component has eliminated many of these problems. Making an impression at the implant level allows the dentist ample time to study the restorative needs before selecting the final abutment.
Kapos, Theodoros; Evans, Christopher
The aim of this systematic review was to compare implant prostheses fabricated by computer-assisted design and computer-assisted manufacturing (CAD/CAM) with conventionally fabricated implant prostheses when assessing esthetics, complications (biologic and mechanical), patient satisfaction, and economic factors. Electronic searches for clinical studies focusing on long-term follow-up were performed using the PubMed and Ovid search engines. Concentrating on the restorative aspect of the CAD/CAM technology applicable to implant dentistry, pertinent literature was divided into articles related to implant abutments, crowns, and frameworks. A total of 18 articles satisfied the inclusion criteria. Two articles reported on CAD/CAM crowns, six on abutments, and 10 on implant-supported CAD/CAM frameworks. The mean survival rate for CAD/CAM crowns was 98.85% and for CAD/CAM abutments 100%. The mean survival rate for CAD/CAM frameworks was 95.98%. Based on the current literature, CAD/CAM fabricated crowns, abutments, and frameworks demonstrate survival rates comparable to conventionally fabricated prostheses. Implant survival appears unaffected by fabrication technique. Since this technology encompasses several manufacturing variations, a new definition might be necessary to accurately define the processes under which the CAD/CAM restorations are fabricated. "Complete CAD/CAM product" where no or minimal manual intervention is employed could be a possible term.
provides useful information for the degree of scour counter-measure to be imple- mented against ... time-to-peak value of design flood hydrograph, smaller scour depths may be obtained, which reduce the total cost of ... where KyL is a factor accounting for the effects of flow depth and abutment length, KI is the flow intensity ...
provides useful information for the degree of scour counter-measure to be imple- mented against excessive scouring. Experiments have been performed to investi- gate time-dependent characteristics of scour holes around vertical wall abutments under clear water conditions with uniform bed materials. Temporal variations ...
Key words: Abutment teeth, apical periodontitis, endodontics, epidemiology, radiology. Date of Acceptance: 29‑Nov‑2014. Introduction. Extensive removal of enamel and dentin is required during the preparation of teeth for fixed partial dentures. This procedure may lead to irreversible damage of the dental pulp if not carried ...
da Silva, Lucas Hian; Ribeiro, Sebastião; Borges, Alexandre Luís Souto; Cesar, Paulo Francisco; Tango, Rubens Nisie
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.
Dudley, J E; Richards, L C; Abbott, J R
The cementation of crowns to dental implant abutments is an accepted form of crown retention that requires consideration of the properties of available cements within the applied clinical context. Dental luting agents are exposed to a number of stressors that may reduce crown retention in vivo, not the least of which is occlusal loading. This study investigated the influence of compressive cyclic loading on the physical retention of cast crown copings cemented to implant abutments. Cast crown copings were cemented to Straumann synOcta titanium implant abutments with three different readily used and available cements. Specimens were placed in a humidifier, thermocycled and subjected to one of four quantities of compressive cyclic loading. The uniaxial tensile force required to remove the cast crown copings was then recorded. The mean retention values for crown copings cemented with Panavia-F cement were statistically significantly greater than both KetacCem and TempBond non-eugenol cements at each compressive cyclic loading quantity. KetacCem and TempBond non-eugenol cements produced relatively low mean retention values that were not statistically significantly different at each quantity of compressive cyclic loading. Compressive cyclic loading had a statistically significant effect on Panavia-F specimens alone, but increased loading quantities produced no further statistically significant difference in mean retention. Within the limitations of the current in vitro conditions employed in this study, the retention of cast crown copings cemented to Straumann synOcta implant abutments with a resin, glass ionomer and temporary cement was significantly affected by cement type but not compressive cyclic loading. Resin cement is the cement of choice for the definitive non-retrievable cementation of cast crown copings to Straumann synOcta implant abutments out of the three cements tested.
Yilmaz, Burak; Salaita, Louai G; Seidt, Jeremy D; McGlumphy, Edwin A; Clelland, Nancy L
Various zirconia abutment designs are available to restore implant systems. Fracture resistance is one of the criteria involved in selecting among these options. The purpose of this in vitro study was to measure and compare load to failure for 5 zirconia abutments for an internally hexagon implant. Five 4.1×11.5-mm Zimmer tapered screw-vent implants were individually secured in a loading apparatus, and 3 specimens of each of the 5 different abutments (Zimmer Contour with a Ti ring, anatomic-contour Atlantis-Zr, anatomic-contour Inclusive-Zr, anatomic-contour Astra Tech ZirDesign, Legacy Straight Contoured abutment with Ti core) (N=15) were loaded at a 30-degree angle until the implant abutment complex failed. Data for load to failure were compared with analysis of variance and a Tukey-Kramer post hoc test (α=.05). The custom anatomic-contour abutment (Inclusive) showed the lowest load to fracture, and the stock anatomic-contour (AstraTech ZirDesign) the second lowest load to fracture. These were significantly lower than all other abutments (Pzirconia abutment with a titanium core-hexagon (Legacy Straight Contoured), which was significantly greater than all other abutments (Pzirconia abutments fractured at an average of 275 N compared with the average fracture load of 842 N for zirconia abutments with titanium component (Pzirconia abutment with a titanium ring and the zirconia abutment with a titanium core-hexagon (Legacy Straight Contoured) had significantly greater fracture resistance than that of any of the 1-piece anatomic-contour zirconia abutments tested. Copyright © 2015 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.
Alsahhaf, Abdulaziz; Spies, Benedikt Christopher; Vach, Kirstin; Kohal, Ralf-Joachim
To investigate the survival rate, fracture strength, bending moments, loading to fracture and fracture modes of different designs of zirconia abutments after dynamic loading with thermocycling, and compare these values to titanium abutments. A total of 80 abutment samples were divided into 5 test groups of 16 samples in each group. The study included the following groups, "Group 1" CAD/CAM produced all-zirconia abutments, "Group 2" titanium abutments, "Group 3" zirconia-abutments adhesively luted to a titanium base, "Group 4" prefabricated all-zirconia abutments and "Group 5" zirconia-abutments glass soldered to a titanium base. Half the number of samples in each group was exposed to 1.2 million loading cycles (5-years simulation) in the chewing simulator. The samples that survived the artificial aging were later tested for fracture strength in a universal testing machine. The remaining 8 samples of the group were directly tested for fracture strength. All samples exposed to the 5-years artificial aging survived except of six samples in one group (Group 1). The surviving samples were later fracture tested in the universal testing machine. The bending moments (Ncm) values were as follow: Exposed groups: "Group 1" 94.5Ncm; "Group 2" 599.2Ncm; "Group 3" 477.5Ncm; "Group 4" 314.4Ncm; "Group 5" 509.4Ncm. Non-exposed groups: "Group 1" 269.3Ncm; "Group 2" 474.2Ncm; "Group 3" 377.6Ncm; "Group 4" 265.4Ncm; "Group 5" 372.4Ncm. Except in Group 1, the values were higher in the exposed groups, although, statistically there was no difference (p>0.05). The one-piece ZrO2-abutment group (Group 1 and Group 4) exhibited lower values, while the two-piece ZrO2-abutment groups (Group 3 and Group 5) showed similar values and fracture modes like the titanium abutment group. The titanium abutment group showed the highest values of bending moments among all groups. The implant-abutment connection area appeared to influence the bending moment value and the fracture mode of the tested
Bo Kyun Sim
Full Text Available The prosthetic component of dental implant is attached on the abutment which is connected to the fixture with an abutment screw. The abutment screw fracture is not frequent; however, the retrieval of the fractured screw is not easy, and it poses complications. A retrieval kit was developed which utilizes screw removal drills to make a hole on the fractured screw that provides an engaging drill to unscrew it. To minimize this process, the abutment screw is modified with a prefabricated access hole for easy retrieval. This study aimed to introduce this modified design of the abutment screw, the concept of easy retrieval, and to compare the mechanical strengths of the conventional and hollow abutment screws by finite element analysis (FEA and mechanical test. In the FEA results, both types of abutment screws showed similar stress distribution in the single artificial tooth system. A maximum load difference of about 2% occurred in the vertical load by a mechanical test. This study showed that the hollow abutment screw may be an alternative to the conventional abutment screws because this is designed for easy retrieval and that both abutment screws showed no significant difference in the mechanical tests and in the FEA.
Polat, Beldan; İşeri, Mete; Orhan, Kadir Serkan; Yılmazer, Ayça Başkadem; Enver, Necati; Ceylan, Didem; Kara, Ahmet; Güldiken, Yahya; Çomoğlu, Şenol
To compare two different percutaneous bone-anchored hearing aid (BAHA) abutment systems regarding operation time, scar healing, quality of life, implant stability, audiologic results, and complications. The study involves a prospective multi-center clinical evaluation. Thirty-two consecutive patients who had undergone BAHA surgery from January 2011 to January 2013 in two tertiary centers were included in the study. The Glasgow Inventory Benefit Score was used to assess the patients at least 6 months after surgery. The operation time and complications were recorded. Implant stability quotient (ISQ) values were recorded using resonance frequency analysis. Holger's classification was used to evaluate skin reactions. The mean length of the operation was 39.2±4 min for standard abutment and 18.3±5.7 min for hydroxyapatite-coated abutment. ISQ scores were significantly better for standard abutment in all tests. The mean total Glasgow Inventory Benefit Score was 39.3±19 for the standard abutment and 46.3±24.5 for the hydroxyapatite-coated abutment groups, but there was no statistical significance between the two groups. There was no difference in audiological improvement between the two groups after surgery. Hydroxyapatite-coated abutment provided a shorter operation time that was significantly different from standard abutment. There were no significant differences between standard abutment and hydroxyapatite-coated abutment regarding audiologic improvement, quality of life, loading time, and complications.
Mühlemann, Sven; Truninger, Thomas C; Stawarczyk, Bogna; Hämmerle, Christoph H F; Sailer, Irena
To test the fracture load and fracture patterns of zirconia abutments restored with all-ceramic crowns after fatigue loading, exhibiting internal and external implant-abutment connections as compared to restored and internally fixed titanium abutments. A master abutment was used for the customization of 5 groups of zirconia abutments to a similar shape (test). The groups differed according to their implant-abutment connections: one-piece internal connection (BL; Straumann Bonelevel), two-piece internal connection (RS; Nobel Biocare ReplaceSelect), external connection (B; Branemark MkIII), two-piece internal connection (SP, Straumann StandardPlus) and one-piece internal connection (A; Astra Tech AB OsseoSpeed). Titanium abutments with internal implant-abutment connection (T; Straumann Bonelevel) served as control group. In each group, 12 abutments were fabricated, mounted to the respective implants and restored with glass-ceramic crowns. All samples were embedded in acrylic holders (ISO-Norm 14801). After aging by means of thermocycling in a chewing simulator, static load was applied until failure (ISO-Norm 14801). Fracture load was analyzed by calculating the bending moments. Values of all groups were compared with one-way ANOVA followed by Scheffé post hoc test (P-valuecrown occurred in the test groups. In groups BL and A, fractures were located in the internal part of the connection, whereas in groups RS and SP, a partial deformation of the implant components occurred and cracks and fractures of the zirconia abutment were detected. The differently connected zirconia abutments exhibited similar bending moments with the exception of one group. Hence, the type of connection only had a minor effect on the stability of restored zirconia abutments. In general, restored titanium abutments exhibited the highest bending moments. © 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.
Full Text Available Introduction: While using an implant-supported removable partial prosthesis, the implant abutments should be parallel to one another along the path of insertion. If the implants and their attachments are placed vertically on a similar occlusal plane, not only is the retention improved, the prosthesis will also be maintained for a longer period. Case Report: A 65-year-old male patient referred to the School of Dentistry in Mashhad, Iran with complaints of discomfort with the removable partial dentures for his lower mandible. Due to the lack of parallelism in the supporting implants, prefabricated ball abutment could not be used. As a result, a customized ball abutment was fabricated in order to correct the non-parallelism of the implants. Conclusion: Using UCLA abutments could be a cost-efficient approach for the correction of misaligned implant abutments in implant-supported overdentures.
Drago, Carl; Lazzara, Richard J
Dental implant treatments have changed dramatically since the introduction of osseointegration in the 1970s. Placement and restoration of dental implants now are considered to be a basic, important component of dental practices around the world. During the past several decades, there has been a significant increase in the number of dental implant manufacturers and implant restorative components available for clinicians and dental laboratory technicians treating partially edentulous patients. While the increase in components has improved the esthetic and functional results obtainable with dental implants, clinicians also have reported difficulties and confusion in treatment planning dental implant restorations for partially edentulous patients. This article introduces a protocol for implant abutment selection in partially edentulous patients undergoing dental implant treatment by describing a clinical/laboratory protocol for abutment selection in implant dentistry for implant surgeons, restorative dentists, and dental laboratory technicians.
Solow, Roger A
There is an overwhelming number of designs and components for dentists to choose from when treatment planning implant-supported restorations. The selection process can be simplified by establishing priorities on a site-by-site basis to facilitate a predictable, esthetic, and stable final result. Clinical considerations should include prosthetic support, periodontal stability, reparability, and oral hygiene, which often occur in concert. This article addresses the principles that guide implant abutment selection when treatment planning for fixed prosthodontics.
Sol?-Ru?z, Mar?a F.; Selva-Otaolaurruchi, Eduardo; Senent-Vicente, Gisela; Gonz?lez-de-Cossio, In?s; Amig?-Borr?s, Vicente
Objective: To evaluate the vertical misfit between different brands of dental implants and prosthetic abutments, with or without mechanical torque, and to study their possible combination. Study design: Five different brands of implant were used in the study: Biofit (Castemaggiore, Italy), Bioner S.A. (Barcelona, Spain), 3i Biomet (Palm Beach, U.S.A.), BTI (Alava, Spain) and Nobel Biocare (G?teborg, Sweden), with standard 4.1 mm heads and external hexagons, and their respective machined prost...
Cleide Gisele Ribeiro
Full Text Available The design and retentive properties of implant-abutment connectors affect the mechanical resistance of implants. A number of studies have been carried out to compare the efficacy of connecting mechanisms between abutment and fixture. Objectives: The aims of this study were: 1 to compare 3 implant-abutment interfaces (external hexagon, internal hexagon and cone-in-cone regarding the fatigue resistance of the prosthetic screw, 2 to evaluate the corresponding mode of failure, and 3 to compare the results of this study with data obtained in previous studies on Nobel Biocare and Straumann connectors. Materials and METHODS: In order to duplicate the alternating and multivectorial intraoral loading pattern, the specimens were submitted to the rotating cantilever beam test. The implants, abutments and restoration analogs were spun around their longitudinal axes while a perpendicular force was applied to the external end. The objective was to determine the force level at which 50% of the specimens survived 10(6 load cycles. The mean force levels at which 50% failed and the corresponding 95% confidence intervals were determined using the staircase procedure. RESULTS: The external hexagon interface presented better than the cone-in-cone and internal hexagon interfaces. There was no significant difference between the cone-in-cone and internal hex interfaces. Conclusion: Although internal connections present a more favorable design, this study did not show any advantage in terms of strength. The external hexagon connector used in this study yielded similar results to those obtained in a previous study with Nobel Biocare and Straumann systems. However, the internal connections (cone-in-cone and internal hexagon were mechanically inferior compared to previous results.
Late Pleistocene glaciers in the upper Wairau Valley deposited four groups of moraines inferred to represent one Waimean ice advance, two Otiran ice advances, and an advance of early Aranuian age. The Waimean and early Otiran glaciers advanced into Tarndale Valley, deposited terminal moraines, and shed outwash down both the Alma River and Travellers Valley. The middle Otiran glacier terminated in northern Tarndale Valley and shed outwash from the southern part of its terminus down the Alma River. The north side of the terminus abutted a large ice-dammed lake in the Wairau Gorge, and fan-deltas graded to an old shore level at an elevation of 1040 m. Well-preserved moraines at the mouths of four glaciated tributaries may be middle Otiran recessional, or late Otiran terminal moraines. The latest ice advance extended 11 km down the upper Wairau Valley and deposited a subdued moraine at Island Gully. The composite chronology of the latest glacial advance based on 10 radiocarbon ages suggests it occurred between about 9.5 and 10.2 ka. This age span is similar to that of early Aranuian glacial advances dated by other workers in the Southern Alps, and may reflect Younger Dryas cooling. (author). 22 refs., 10 figs., 3 tabs
Etxeberria, Marina; Abdulmajeed, Aous A; Escuin, Tomas; Vinas, Miguel; Lassila, Lippo V J; Närhi, Timo O
Fiber-reinforced composites (FRC) can potentially help in a physiologic stress transmission due to its excellent biomechanical matching with living tissues. Novel one-piece FRC implants and abutments with two different fiber orientations were loaded until failure to assess the load-bearing capacity, fracture patterns, and precision of fit. The one-piece FRC implants showed significantly higher load-bearing capacity compared to FRC abutments regardless of the fiber orientation (p < 0.001). For FRC abutments, bidirectional abutments showed significantly higher loads compared to unidirectional abutments (p < 0.001). The type of structure and fiber orientation are strong determinant factors of the load-bearing capacity of FRC implants and abutments.
Boff, Luís Leonildo; Oderich, Elisa; Cardoso, Antônio Carlos; Magne, Pascal
To evaluate the fatigue resistance and failure mode of composite resin and porcelain onlays and crowns bonded to premolar custom metal-composite resin premolar implant abutments. Sixty composite resin mesostructures were fabricated with computer assistance with two preparation designs (crown vs onlay) and bonded to a metal implant abutment. Following insertion into an implant with a tapered abutment interface (Titamax CM), each metal-composite resin abutment was restored with either composite resin (Paradigm MZ100) or ceramic (Paradigm C) (n = 15) and attached with adhesive resin (Optibond FL) and a preheated light-curing composite resin (Filtek Z100). Cyclic isometric chewing (5 Hz) was then simulated, starting with 5,000 cycles at a load of 50 N, followed by stages of 200, 400, 600, 800, 1,000, 1,200, and 1,400 N (25,000 cycles each). Samples were loaded until fracture or to a maximum of 180,000 cycles. The four groups were compared using life table survival analysis (log-rank test). Previously published data using zirconia abutments of the same design were included for comparison. Paradigm C and MZ100 specimens fractured at average loads of 1,133 N and 1,266 N, respectively. Survival rates ranged from 20% to 33.3% (ceramic crowns and onlays) to 60% (composite resin crowns and onlays) and were significantly different (pooled data for restorative material). There were no restoration failures, but there were adhesive failures at the connection between the abutment and the mesostructure. The survival of the metal-composite resin premolar abutments was inferior to that of identical zirconia abutments from a previous study (pooled data for abutment material). Composite resin onlays/crowns bonded to metal-composite resin premolar implant abutments presented higher survival rates than comparable ceramic onlays/crowns. Zirconia abutments outperformed the metal-composite resin premolar abutments.
Replacing an anterior tooth using a dental implant has long been a challenge for most clinicians. Implant abutment selection is a crucial aspect of maximizing esthetics, strength, and customization. The author has experienced significant success in this regard over a period of more than 7 years using a lithium-disilicate "H" ("Hybrid") abutment. In this case presentation, a procedure is described for providing these highly esthetic abutment-supported restorations, which may offer significant advantages over traditional options.
Kourtis, Stefanos G
Implant restorations must fulfill the functional and esthetic demands of the patient. The discrepancy in the diameters of an implant and a natural tooth often leads to compromise. The use of prefabricated abutments that can be individually modified offers certain advantages. Selection and modification of the abutment are simpler when a waxup of the restoration is used as a guideline. This article describes a laboratory technique in which the implant abutment is selected and modified according to the waxup of the restoration.
Wicks, Russell; Ahuja, Swati; Jain, Vinay
One of the most significant challenges in contemporary dental implant therapy involves managing the transition of the restoration from the implant through the soft tissues by means of an abutment. This article presents a practical technique to visualize if the selection of a custom-made abutment would be favored over the use of a manufactured standard abutment to receive crown restoration supported by a dental implant.
Karl, Matthias; Taylor, Thomas D
Cyclic loading may cause settling of abutments mounted on dental implants, potentially affecting screw joint stability and implant-abutment micromotion. It was the goal of this in vitro study to compare micromotion of implant-abutment assemblies before and after masticatory simulation. Six groups of abutments (n = 5) for a specific tissue-level implant system with an internal octagon were subject to micromotion measurements. The implant-abutment assemblies were loaded in a universal testing machine, and an apparatus and extensometers were used to record displacement. This was done twice, in the condition in which they were received from the abutment manufacturer and after simulated loading (100,000 cycles; 100 N). Statistical analysis was based on analysis of variance, two-sample t tests (Welch tests), and Pearson product moment correlation (α = .05). The mean values for micromotion ranged from 33.15 to 63.41 μm and from 30.03 to 42.40 μm before and after load cycling. The general trend toward reduced micromotion following load cycling was statistically significant only for CAD/CAM zirconia abutments (P = .036) and for one type of clone abutment (P = .012), with no significant correlation between values measured before and after cyclic loading (Pearson product moment correlation; P = .104). While significant differences in micromotion were found prior to load cycling, no significant difference among any of the abutment types tested could be observed afterward (P > .05 in all cases). A quantifiable settling effect at the implant-abutment interface seems to result from cyclic loading, leading to a decrease in micromotion. This effect seems to be more pronounced in low-quality abutments. For the implant system tested in this study, retightening of abutment screws is recommended after an initial period of clinical use.
Yang, Jianjun; Wang, Ke; Liu, Guangyuan; Wang, Dashan
Zirconia powder in nanometers can be fabricated into inter-joined abutment of dental implant system with the injection shaping technique. This study was to detect the resistance of inter-joined zirconia abutment with different angle loading for clinical applications. The inter-joined abutments were shaped with the technique of injection of zirconia powder in nanometers. Sixty Osstem GSII 5 × 10 mm implants were used with 30 zirconia abutments and 30 Osstem GSII titanium abutments for fixation using 40 N torque force. The loading applications included 90°, 30°, and 0° formed by the long axis of abutments and pressure head of universal test machine. The fracture resistances of zirconia and titanium abutments were documented and analyzed. The inter-joined zirconia abutments were assembled to the Osstem GSII implants successfully. In the 90° loading mode, the fracture resistance of zirconia abutment group and titanium abutment group were 301.5 ± 15.4 N and 736.4 ± 120.1 N, respectively. And those in the 30° groups were 434.7 ± 36.1 N and 1073.1 ± 74 N, correspondingly. Significant difference in the two groups was found using t-test and Wilcoxon test. No damage on the abutments of the two groups but S-shaped bending on the implants was found when the 0° loading was 1300-2000 N. Through the assembly of Zirconia abutments and implants, all the components presented sufficient resistance acquired for the clinical application under loadings with different angle. © 2012 John Wiley & Sons A/S.
Yunusov, A. V.; Kashapov, R. N.; Kashapov, L. N.; Statsenko, E. O.
The purpose of the research is to develop a method of manufacturing individual dental abutments for a variety of dental implants. System of industrial X-ray microtomography Phoenix V|tome|X S 240 has been applied for creation of highly accurate model of the dental abutment. Scanning of dental abutment and the optimization of model was produced. The program of milling the individual abutment with a standard conical neck of hexagon was produced for the five-axis milling machine imes - icore 450i from the materials titanium and zirconium oxide.
Güncü, M Bariş; Cakan, Umut; Canay, Senay
For fixed prostheses, retention is one of the most important factors for clinical success. It is unknown whether grooves that increase surface area of implant abutment while retaining the diameter and wall height provide greater uniaxial retention force. The purpose of this study was to determine the retention of 3 different cements on 2 implant abutments with different surface configurations. Thirty samples on 2 different abutments (a total of 60 crowns) with different margin and axial walls configuration and surface area were used. Metal crowns were fabricated on the abutment and cemented with 3 different (zinc-phosphate [ZP], glass ionomer [GI], or eugenol-free zinc oxide [ZO]) cements. After cementation, implant-abutment-casting assemblies were thermal cycled 1000 times with 1-minute dwell-time between 5°C and 55°C then subjected to tensile test with universal testing machine until decementation occurred. The mean force required to dislodge castings from abutment was determined. The luting agents influenced retention of castings on implant abutments, whereas different surface configurations and total surface area of the abutments did not influence the uniaxial retention forces. Among the cements tested, ZP exhibited higher values of retention, followed by GI and eugenol-free ZO. The increase in surface area of abutment did not result in improved retention. The present results suggest using ZP rather than GI and eugenol-free ZO in implant-supported crowns to provide higher retention.
de Campos, Tomie Nakakuki; Adachi, Lena Katekawa; Miashiro, Karen; Yoshida, Hideki; Shinkai, Rosemary Sadami; Neto, Pedro Tortamano; Frigerio, Maria Luiza Moreira Arantes
This study investigated whether surface topography affects the retentive strength of cemented full crowns, comparing the effects of standard machined, sandblasted, and grooved implant abutments. Five metallic crowns per abutment type were cast and cemented with zinc phosphate. After 24 hours, the specimens were submitted to a tensile test. The retentive strength of the cemented crowns was affected by abutment surface topography. The sandblasted and grooved surface groups had approximately 2.4 times greater mean uniaxial retentive strength than the machined surface group (P < .001). The retentive strength of the sandblasted and grooved abutments was similar, despite marked differences in surface profiles and roughness parameters.
Full Text Available Provisional cements are commonly used to facilitate retrievability of cement-retained fixed implant restorations; but compromised abutment preparation may affect the retention of implant-retained crowns.The purpose of this study was to investigate the effect of abutment design and type of luting agent on the retentive strength of cement-retained implant restorations.Two prefabricated abutments were attached to their corresponding analogs and embedded in an acrylic resin block. The first abutment (control group was left intact without any modifications. The screw access channel for the first abutment was completely filled with composite resin. In the second abutment, (test group the axial wall was partially removed to form an abutment with 3 walls. Wax models were made by CAD/CAM. Ten cast copings were fabricated for each abutment. The prepared copings were cemented on the abutments by Temp Bond luting agent under standardized conditions (n=20. The assemblies were stored in 100% humidity for one day at 37°C prior to testing. The cast crown was removed from the abutment using an Instron machine, and the peak removal force was recorded. Coping/abutment specimens were cleaned after testing, and the testing procedure was repeated for Dycal luting agent (n=20. Data were analyzed with two- way ANOVA (α=0.05.There was no significant difference in the mean transformed retention (Ln-R between intact abutments (4.90±0.37 and the abutments with 3 walls (4.83±0.25 using Dycal luting agent. However, in TempBond group, the mean transformed retention (Ln-R was significantly lower in the intact abutment (3.9±0.23 compared to the abutment with 3 walls (4.13±0.33, P=0.027.The retention of cement-retained implant restoration can be improved by the type of temporary cement used. The retention of cast crowns cemented to implant abutments with TempBond is influenced by the wall removal.
Rismanchian, Mansoor; Hatami, Mahnaz; Badrian, Hamid; Khalighinejad, Navid; Goroohi, Hossein
A microgap between implant and abutment can lead to mechanical and biological problems such as abutment screw fracture and peri-implantitis. The aim of this study was to evaluate microgap size and microbial leakage in the connection area of 4 different abutments to ITI implants. In this experimental study, 36 abutments in 4 groups (including Cast On, Castable, Solid, and Synocta abutments) connected to Straumann fixtures (with their inner part inoculated with bacterial suspension) and microbial leakage were assessed at different times. The size of the microgap in 4 randomized locations was then measured by scanning electron microscope. The data were analyzed by SPSS software and by 1-way variance statistical test, Kruskal-Wallis, and their supplementary tests (Mann-Whitney HSD and Tukey's; α = .05) at the next step. The effect of using different types of abutments was significant on the mean microgap size (P < .001) and on the mean number of leaked colonies (CFU/mL) through the connection area of the implant and abutment within the first 5 hours of the experiment (P = .012); however, it did not significantly influence microleakage at 24 hours, 48 hours, and 14 days (P = .145). Using Synocta abutments compared with Solid abutments will not provide us with more accommodation, and vice versa. Using Solid and Synocta abutments can significantly decrease the microgap size; however, Cast On abutments do not show a significant difference in terms of microgap compared with Castable abutments. Microleakage in the connection area is comparable for these 4 abutments.
Moris, Izabela Cristina Maurício; Faria, Adriana Cláudia Lapria; Ribeiro, Ricardo Faria; Rodrigues, Renata Cristina Silveira
The aim of this study was to analyze failure modes and misfit of abutments with reduced diameter for both cement and screw retentions after cyclic loading. Forty morse-taper abutment/implant sets of titanium were divided into four groups (N = 10): G4.8S-4.8 abutment with screw-retained crown; G4.8C-4.8 abutment with cemented crown; G3.8S-3.8 abutment with screw-retained crown; and G3.8C-3.8 abutment with cemented crown. Copings were waxed on castable cylinders and cast by oxygen gas flame and injected by centrifugation. After, esthetic veneering ceramic was pressed on these copings for obtaining metalloceramic crowns of upper canine. Cemented crowns were cemented on abutments with provisional cement (Temp Bond NE), and screw-retained crowns were tightened to their abutments with torque recommended by manufacturer (10 N cm). The misfit was measured using a stereomicroscope in a 10× magnification before and after cyclic loading (300,000 cycles). Tests were visually monitored, and failures (decementation, screw loosening and fractures) were registered. Misfit was analyzed by mixed linear model while failure modes by chi-square test (α = 0.05). Cyclic loading affected misfit of 3.8C (P ≤ 0.0001), 3.8S (P = 0.0055) and 4.8C (P = 0.0318), but not of 4.8S (P = 0.1243). No differences were noted between 3.8S with 4.8S before (P = 0.1550) and after (P = 0.9861) cyclic loading, but 3.8C was different from 4.8C only after (P = 0.0015) loading. Comparing different types of retentions at the same diameter abutment, significant difference was noted before and after cyclic loading for 3.8 and 4.8 abutments. Analyzing failure modes, retrievable failures were present at 3.8S and 3.8C groups, while irretrievable were only present at 3.8S. The cyclic loading decreased misfit of cemented and screw-retained crowns on reduced diameter abutments, and misfit of cemented crowns is greater than screw-retained ones. Abutments of reduced diameter failed more than
Siadat, Hakimeh; Belbasi, Simin; Alikhasi, Marzieh; Nazari, Vahideh; Beyabanaki, Elaheh
Improper seating of abutment on the implant is a common problem. This study investigated the effect of the type of implant/abutment interface on the complete seating of the abutments on the head of implants placed at different gingival depths. Three implant systems with three different connections including straight external hexagon, butt-joint internal tri-lobed, and conical internal hexagon were used. Two gingival thicknesses (2 and 7 mm) were created using pink baseplate wax around the straight abutments seated on the implants. After placing the implants in acrylic blocks, the wax was replaced with the gingival mask material to simulate the gingival drape around the implant heads. Afterwards, 15 prosthodontists were asked to hand-tighten the straight abutments in the corresponding implant bodies relying only on their tactile sense. At the final stage, the gingival mask was removed, and the seating quality of the abutments on implant bodies was assessed visually. The effect of implant connection and depth on abutment seating accuracy was analyzed using Kruskal-Wallis and multiple-comparison tests. No significant difference was found regarding the effect of either depth or connection design on the accuracy of the abutment seating (p > 0.05); however, pairwise comparison of the combined effect of the depth and connection design was significant (p = 0.009). Accuracy of abutment seating on the Nobel Active implants at both 2 and 7 mm depths were significantly better than Replace system with 7 mm depth (p = 0.027). The same results were obtained in comparison between Nobel Active system at both 2 and 7 mm depths with Branemark system with 7 mm depth (p = 0.006). An increase in implant placement depth meant a decrease in accuracy of the abutment seating. The internal conical connection design showed the best result in abutment positioning in deep implants as compared with external and internal butt-joint connection designs. © 2017 by the American College of
Xing, Rui; Tiainen, Hanna; Shabestari, Maziar; Lyngstadaas, Ståle P; Haugen, Håvard J; Witsø, Ingun L; Lönn-Stensrud, Jessica; Jugowiec, Dawid
Biofilm formation on dental abutment may lead to peri-implant mucositis and subsequent peri-implantitis. These cases are clinically treated with antibiotics such as doxycycline (Doxy). Here we used an electrochemical method of cathodic polarization to coat Doxy onto the outer surface of a dental abutment material. The Doxy-coated surface showed a burst release in phosphate-buffered saline during the first 24 h. However, a significant amount of Doxy remained on the surface for at least 2 weeks especially on a 5 mA–3 h sample with a higher Doxy amount, suggesting both an initial and a long-term bacteriostatic potential of the coated surface. Surface chemistry was analyzed by x-ray photoelectron spectroscopy and secondary ion mass spectrometry. Surface topography was evaluated by field emission scanning electron microscopy and blue-light profilometry. Longer polarization time from 1 h to 5 h and higher current density from 1 to 15 mA cm −2 resulted in a higher amount of Doxy on the surface. The surface was covered by a layer of Doxy less than 100 nm without significant changes in surface topography. The antibacterial property of the Doxy-coated surface was analyzed by biofilm and planktonic growth assays using Staphylococcus epidermidis. Doxy-coated samples reduced both biofilm accumulation and planktonic growth in broth culture, and also inhibited bacterial growth on agar plates. The antibacterial effect was stronger for samples of 5 mA–3 h coated with a higher amount of Doxy compared to that of 1 mA–1 h. Accordingly, an abutment surface coated with Doxy has potential for preventing bacterial colonization when exposed to the oral cavity. Doxy-coating could be a viable way to control peri-implant mucositis and prevent its progression into peri-implantitis. (paper)
Conclusion: Splinting a very weak abutment to an adjacent healthy tooth might not be beneficial. The acceptable crown to root ratio for fixed splinting a weak abutment to an adjacent normal tooth was around 1.65-2.
One of the major obstacles facing rapid bridge construction for typical span type bridges is the time required to construct bridge abutments and foundations. This can be remedied by using the controlled low strength materials (CLSM) bridge abutment. ...
Full Text Available Steel sheet piles are often used to support excavations for bridge foundations. When they are left in place in the permanent works, they have the potential to increase foundation bearing capacity and reduce displacements; but their presence is not usually taken into account in foundation design. In this article, the results of finite element analysis of a typical abutment foundation, with and without cover of sheet piles, are presented to demonstrate these effects. The structure described is located over the Więceminka river in the town of Kołobrzeg, Poland. It is a single-span road bridge with reinforced concrete slab.
It is very common to categorise people, especially in the advertising business. Also traditional marketing theory has taken in consumer segments as a favorite topic. Segmentation is closely related to the broader concept of classification. From a historical point of view, classification has its...... origin in other sciences as for example biology, anthropology etc. From an economic point of view, it is called segmentation when specific scientific techniques are used to classify consumers to different characteristic groupings. What is the purpose of segmentation? For example, to be able to obtain...... a basic understanding of grouping people. Advertising agencies may use segmentation totarget advertisements, while food companies may usesegmentation to develop products to various groups of consumers. MAPP has for example investigated the positioning of fish in relation to other food products...
van Geel, Nanja; Speeckaert, Reinhart
Segmental vitiligo is characterized by its early onset, rapid stabilization, and unilateral distribution. Recent evidence suggests that segmental and nonsegmental vitiligo could represent variants of the same disease spectrum. Observational studies with respect to its distribution pattern point to a possible role of cutaneous mosaicism, whereas the original stated dermatomal distribution seems to be a misnomer. Although the exact pathogenic mechanism behind the melanocyte destruction is still unknown, increasing evidence has been published on the autoimmune/inflammatory theory of segmental vitiligo. Copyright © 2016 Elsevier Inc. All rights reserved.
Eduardo Aloisio Fleck NEUMANN
Full Text Available Fractured abutment screws may be replaced; however, sometimes, the screw cannot be removed and the entire implant must be surgically removed and replaced. The aim of this study was to compare the fracture resistance of abutment retention screws made of titanium, polyetheretherketone (PEEK and 30% carbon fiber-reinforced PEEK, using an external hexagonal implant/UCLA-type abutment interface assembly. UCLA-type abutments were fixed to implants using titanium screws (Group 1, polyetheretherketone (PEEK screws (Group 2, and 30% carbon fiber-reinforced PEEK screws (Group 3. The assemblies were placed on a stainless steel holding apparatus to allow for loading at 45o off-axis, in a universal testing machine. A 200 N load (static load was applied at the central point of the abutment extremity, at a crosshead speed of 5 mm/minute, until failure. Data was analyzed by ANOVA and Tukey’s range test. The titanium screws had higher fracture resistance, compared with PEEK and 30% carbon fiber-reinforced PEEK screws (p 0.05. Finally, visual analysis of the fractions revealed that 100% of them occurred at the neck of the abutment screw, suggesting that this is the weakest point of this unit. PEEK abutment screws have lower fracture resistance, in comparison with titanium abutment screws.
Neumann, Eduardo Aloisio Fleck; Villar, Cristina Cunha; França, Fabiana Mantovani Gomes
Fractured abutment screws may be replaced; however, sometimes, the screw cannot be removed and the entire implant must be surgically removed and replaced. The aim of this study was to compare the fracture resistance of abutment retention screws made of titanium, polyetheretherketone (PEEK) and 30% carbon fiber-reinforced PEEK, using an external hexagonal implant/UCLA-type abutment interface assembly. UCLA-type abutments were fixed to implants using titanium screws (Group 1), polyetheretherketone (PEEK) screws (Group 2), and 30% carbon fiber-reinforced PEEK screws (Group 3). The assemblies were placed on a stainless steel holding apparatus to allow for loading at 45o off-axis, in a universal testing machine. A 200 N load (static load) was applied at the central point of the abutment extremity, at a crosshead speed of 5 mm/minute, until failure. Data was analyzed by ANOVA and Tukey's range test. The titanium screws had higher fracture resistance, compared with PEEK and 30% carbon fiber-reinforced PEEK screws (p 0.05). Finally, visual analysis of the fractions revealed that 100% of them occurred at the neck of the abutment screw, suggesting that this is the weakest point of this unit. PEEK abutment screws have lower fracture resistance, in comparison with titanium abutment screws.
Home; Journals; Sadhana; Volume 39; Issue 5. Live-bed scour experiments with 45° wing-wall ... Keywords. Scour; bridge foundation; abutments; hydraulics; rivers. ... A design equation is proposed for estimating maximum scour depth at 45°wing-wall abutment under live-bed condition. The calculated values of scour ...
van Brakel, Ralph; Meijer, Gert J.; Verhoeven, Jan Willem; Jansen, John; de Putter, Cornelis; Cune, Marco S.
Aim To compare the health of the soft tissues towards zirconia and titanium abutments in man, as observed using histological data. Material and Methods Twenty patients received two mandibular implants with either a zirconia or titanium abutment (split mouth study design, left-right randomization).
The armour-layer gradually increases the effective bed shear resistance, which restricts the development of scour hole. 4. Maximum equilibrium local scour depth around 45. ◦ wing-wall abutment. Maximum equilibrium local scour depth at 45. ◦ wing-wall abutment in non-cohesive bed sedi- ments depends on the variables ...
Ahmad Kutkut; Osama Abu-Hammad; Robert Frazer
Impression techniques for implant restorations can be implant level or abutment level impressions with open tray or closed tray techniques. Conventional implant-abutment level impression techniques are predictable for maximizing esthetic outcomes. Restoration of the implant traditionally requires the use of the metal or plastic impression copings, analogs, and laboratory components. Simplifying the dental implant restoration by reducing armamentarium through incorporating conventional techniq...
Vanessa Tavares de GOIS-SANTOS
Full Text Available Abstract Background The study of the phenomenon of fatigue is essential because implant failures usually are caused by this process. Purpose The objective of this study was to examine the fatigue resistance of straight and anatomical abutments joints that were submitted to cyclic loads. Material and method We used 37 Morse taper implants and 37 abutments, divided into two groups (n= 16: straight abutment, n= 21 anatomical abutment. The sets were submitted to cyclic loading (5 million using servo-hydraulic equipment. Three sets from each group were subjected to bending tests to determine the maximum load resistance, which served as the parameter for comparison of the cyclic tests. We evaluated number of cycles, load and bending moment. Result Of the 31 abutments cyclically tested, 17 (54.8% fractured in fewer than 5 million cycles; 8 (25.8% of these were straight abutments, and 9 (29% were anatomical. A total of 14 samples (45.2% resisted the cyclic loading. According to Fisher's exact test, there was no difference between groups as the fracture. Conclusion Despite of the straight abutments have higher average load and bending moment on the anatomical, both types of abutments showed similar performance as the fracture strength in vitro.
Fracture Strength and Failure Mode of Maxillary Implant-Supported Provisional Single Crowns : A Comparison of Composite Resin Crowns Fabricated Directly Over PEEK Abutments and Solid Titanium Abutments
Santing, H.J.; Meijer, Henny J.A.; Raghoebar, G.M.; Ozcan, M.
Background: Polyetheretherketone (PEEK) temporary abutments have been recently introduced for making implant-supported provisional single crowns. Little information is available in the dental literature on the durability of provisional implant-supported restorations. Purpose: The objectives of this
Full Text Available Impression techniques for implant restorations can be implant level or abutment level impressions with open tray or closed tray techniques. Conventional implant-abutment level impression techniques are predictable for maximizing esthetic outcomes. Restoration of the implant traditionally requires the use of the metal or plastic impression copings, analogs, and laboratory components. Simplifying the dental implant restoration by reducing armamentarium through incorporating conventional techniques used daily for crowns and bridges will allow more general dentists to restore implants in their practices. The demonstrated technique is useful when modifications to implant abutments are required to correct the angulation of malpositioned implants. This technique utilizes conventional crown and bridge impression techniques. As an added benefit, it reduces costs by utilizing techniques used daily for crowns and bridges. The aim of this report is to describe a simplified conventional impression technique for custom abutments and modified prefabricated solid abutments for definitive restorations.
Marcos Michelon Naconecy
Full Text Available OBJECTIVE: This study aimed to evaluate the bending moments, and compressive and tensile forces in implant-supported prostheses with three, four or five abutments. MATERIAL AND METHODS: Ten Pd-Ag frameworks were tested over two master models with: 1 parallel vertical implants, and 2 tilted distal implants. Strain gauges were fixed on the abutments of each master model to measure the deformation when a static load of 50 N was applied on the cantilever (15 mm. The deformation values were measured when the metallic frameworks were tested over three, four or five abutments, and transformed into force and bending moment values. Data were analyzed by ANOVA and Tukey's test for multiple comparisons at 5% level of significance. RESULTS: Abutment #1 (adjacent to the cantilever had the highest values of force and sagittal bending moment for all tests with three, four or five abutments. Independently from the number of abutments, axial force in abutment #1 was higher in the vertical model than in the tilted model. Total moment was higher with three abutments than with four or five abutments. Independently from the inclination of implants, the mean force with four or five abutments was lower than that with three abutments. CONCLUSION: The results suggest that in the set-ups with four or five abutments tilted distal implants reduced axial force and did not increase bending moments.
Naconecy, Marcos Michelon; Geremia, Tomás; Cervieri, André; Teixeira, Eduardo Rolim; Shinkai, Rosemary Sadami
This study aimed to evaluate the bending moments, and compressive and tensile forces in implant-supported prostheses with three, four or five abutments. Ten Pd-Ag frameworks were tested over two master models with: 1) parallel vertical implants, and 2) tilted distal implants. Strain gauges were fixed on the abutments of each master model to measure the deformation when a static load of 50 N was applied on the cantilever (15 mm). The deformation values were measured when the metallic frameworks were tested over three, four or five abutments, and transformed into force and bending moment values. Data were analyzed by ANOVA and Tukey's test for multiple comparisons at 5% level of significance. Abutment #1 (adjacent to the cantilever) had the highest values of force and sagittal bending moment for all tests with three, four or five abutments. Independently from the number of abutments, axial force in abutment #1 was higher in the vertical model than in the tilted model. Total moment was higher with three abutments than with four or five abutments. Independently from the inclination of implants, the mean force with four or five abutments was lower than that with three abutments. The results suggest that in the set-ups with four or five abutments tilted distal implants reduced axial force and did not increase bending moments.
Cano-Batalla, Jordi; Soliva-Garriga, Joan; Campillo-Funollet, Marc; Munoz-Viveros, Carlos A; Giner-Tarrida, Lluis
This study evaluated the effects of abutment height, airborne-particle abrasion, and type of cement on the tensile resistance to dislodgement of cement-retained implant restorations. Three groups of 12 standardized abutments each were prepared with different heights (4 mm, 5 mm, and 6 mm) using a milling machine. Crowns were cast in cobalt-chrome using the lost-wax technique, airborne particle-abraded using 50-Μm aluminum oxide, and cleaned with acetone. Restorations were cemented using a noneugenol acrylic urethane cement, a resin-modified glass ionomer, or a zinc oxide-noneugenol cement. A 5-kg load was applied for 10 minutes. Samples were kept at 37°C and 100% humidity overnight. A tensile force was applied to the crown using a testing machine at a crosshead speed of 5 mm/minute until failure occurred. Next, the abutments were airborne particle-abraded with 50-Μm aluminum oxide, and the cementation and testing procedures were repeated. The effects of cement, abutment height, and surface treatment were evaluated statistically. There were significant differences among the cements. The resin-modified glass ionomer provided the greatest retention in all the tested conditions, while the zinc oxide-noneugenol cement produced the lowest retention values. Significant differences were also detected between 4-mm and 6-mm abutments, with the 6-mm abutments being more retentive. No differences were found between 4-mm and 5-mm abutments or between 5-mm and 6-mm abutments. The effect of airborne-particle abrasion was also found to be significant. A maximum increase of 90 N in retention force was observed after airborne-particle abrasion for the 5-mm abutments cemented with the acrylic urethane cement. Cement, airborne-particle abrasion, and abutment height can significantly influence retention of implant-supported crowns. Different parameters, including those specific to the patient, should be considered in the selection of a luting agent.
Cohen, Omer; Gabay, Eran; Machtei, Eli E
One-piece dental implants are commonly used for the immediate restoration of missing teeth. In most cases, the clinician has to prepare the abutment intraorally to ensure a proper emergence profile and abutment angulation. However, this procedure might impair primary stability and thus potentially compromise osseointegration. The aim of this study was to determine the effect of abutment preparation on the primary stability of a one-piece implant system (UNO MIS). Implant stability was assessed by resonance frequency analysis with a novel custom-made external fixation device, validated previously, developed specifically for resonance frequency measurements of this implant. Thirty 3 × 13-mm implants were inserted in porcine jawbone with insertion torque of 15 Ncm (group A, 15 implants) or 30 Ncm (group B, 15 implants). Abutments were prepared by reducing the facial aspect of the implant abutment with a high-speed dental turbine (400,000 rpm) equipped with a medium-roughness diamond bur. Implant stability quotients (ISQs) were measured before and after abutment preparation. Mean ISQs measured in group A and group B before abutment preparation were very similar (58.2 ± 1.4 and 57.4 ± 0.9, respectively; P > .05). Following abutment preparation, three implants in group A lost primary stability. The mean ISQ value in group A was reduced from 58.2 ± 1.4 to 54.9 ± 7.9 following abutment preparation (P .05). Abutment preparation of a one-piece dental implant inserted with low insertion torque might impair implant primary stability.
Full Text Available Integral abutment bridges are becoming rather common, due to the durability problems of bearings and expansion joints. At the same time, among short- and medium-span bridges, multi-beam steel-concrete composite deck with hot-rolled girder is an economical and interesting alternative to traditional pre-stressed concrete solutions. The two concepts can be linked together to design integral steel-concrete composite bridges with the benefits of two typologies. The most critical aspect for these bridges is usually the joints between deck and piers or abutments. In this paper, an innovative beam-to-pier joint is proposed and a theoretical and experimental study is introduced and discussed. The analyzed connection is aimed at combining general ease of construction with a highly simplified assembly procedure and a good transmission of hogging and sagging moment at the supports in continuous beams. For this purpose, the traditional shear studs, used at the interface between steel beam and upper concrete slab, are also used at the ends of steel profiles welded horizontally to the end plates. To better understand the behaviour of this kind of joints and the roles played by different components, three large-scale specimens were tested and an FE model was implemented. The theoretical and experimental results confirmed the potential of the proposed connection for practical applications and indicated the way to improve its structural behaviour.
Ferrari, M; Mannocci, F; Vichi, A; Goracci, G
The study evaluated the bond strength values of a single-unit all-porcelain material luted with an adhesive-resin cement to different abutment substrates: amalgam, compomer, traditional glass ionomer cement, microhybrid resin composite, two resin composites for abutment build-up, gold, sandblasted gold, dentin and enamel. Syntac enamel-dentin bonding system, in combination with IPS-Empress porcelain material, was used. After thermal cycling, the samples were inserted into a Bencor jig device and sheared in a Controls testing machine. The statistical analysis of the differences between the bond strength values obtained was performed by ANOVA and the Student-Newman-Keuls multiple-comparison test. The type of failure at the interface was evaluated using scanning electron microscopy. The type of failure, such as adhesive, cohesive and adhesive-cohesive, was correlated with bond strength values. Enamel, dentin and the two resin composites for crown build-up showed the highest bond strength values, while amalgam and gold samples showed the lowest.
de Sá, Bruno Costa Martins; Andrighetto, Augusto Ricardo; Bernardes, Sergio Rocha; Tiossi, Rodrigo
This study tested the fracture strength of prosthetic abutments with different sizes and combinations to support a 5-implant milled framework with distal extension. Prosthetic abutments with different dimensions (4.8-mm diameter mini conical abutment and 3.5-mm diameter microconical abutment) were screwed to 5 threaded implants. The following groups were divided (n = 3): G1 with 5 miniconical abutments (standard size), G2 with 5 microconical abutments (small sized), G3 with a combination of 3 small sized abutments and 2 standard sized abutments, and G4 with a combination of 2 small sized abutments and 3 standard sized abutments. Standardized titanium frameworks for full-arch fixed dental prosthesis were milled with equidistant holes for each of the 5 implants and abutments. A loading point was selected at 18 mm away from both distal implants. A universal testing system was used for the fracture strength tests and load was applied at a crosshead speed of 0.5 mm/min on the previously described loading points until component fracture. Mean fracture strength for each group was statistically compared (α = 0.05). Prosthetic screws were the only fractured components for all tested groups. Mean fracture strength was: G1, 1130.22 N; G2, 1031.36 N; G3, 757.9 N; and G4 792.03 N (P prosthetic abutments and combinations that were tested provide adequate fracture strength for clinical use. However, the combination of standard and small diameter abutments leads to lower fracture strength compared with when only standard sized prosthetic abutments were used, irrespective of the abutment diameter (4.8- or 3.5-mm).
Coray, Rafaela; Zeltner, Marco; Özcan, Mutlu
The use of implants and their respective suprastructures to replace missing teeth has become a common therapeutic option in dentistry. Prior to their clinical application, all implant components have to demonstrate suitable durability in laboratory studies. Fatigue tests utilising cyclic loading typically simulate masticatory function in vitro. The objectives of this systematic review were to assess the loading conditions used for fatigue testing of implant abutments and to compare the fracture strength of different types of implant abutment and abutment-connection types after cyclic loading. Original scientific papers published in MEDLINE (PubMed) and Embase database in English between 01/01/1970 and 12/31/2014 on cyclic loading on implant abutments were included in this systematic review. The following MeSH terms, search terms and their combinations were used: "in vitro" or "ex vivo" or experimental or laboratory, "dental implants", "implants, experimental", "dental prosthesis, implant-supported", "fatigue", "dental abutments", "cyclic loading", "cyclic fatigue", "mechanical fatigue", "fatigue resistance", "bending moments", and "fracture". Two reviewers performed screening and data abstraction. Only the studies that reported, static fracture values before and after fatigue cycling of implant abutments, were included that allowed comparison of aging effect through cyclic loading. Data (N) were analyzed using a weighted linear regression analysis (α=0.05). The selection process resulted in the final sample of 7 studies. In general, loading conditions of the fatigue tests revealed heterogeneity in the sample but a meta-analysis could be performed for the following parameters: a) abutment material, b) implant-abutment connection, and (c) number of fatigue cycles. Mean fracture strength of titanium (508.9±334.6N) and for zirconia abutments (698.6±452.6N) did not show significant difference after cyclic loading (p>0.05). Internal implant-abutment connections
Full Text Available Conical crown-retained dentures (CCRD show a higher survival rate and greater patient satisfaction than transitional removable partial dentures during long-term follow-up. However, unsustainable denture retention force on supporting abutments after initial delivery and loss retention are frequently seen in long-term follow-up of clinical cases. The main causes are insufficient information concerning denture retention designs and the retention-tolerance of the supporting abutments. Monitoring by dental technicians of the quality of dental prostheses is critical. This case report describes an optimal method for CCRD construction that determines and distributes an optimal denture retention force on the supporting abutments to allow the patient to easily remove the denture while ensuring that the CCRD remains in place during physiologic activities. Oral rehabilitation with CCRD should consider the condition of the abutment periodontal support, the interarch occlusal relationship, supplemental fatigue of the terminal abutment, and patient's estimated bite force. The effects of friction on the abutment's inner crown were based on an optimal a angle. The dental laboratory used these measurements to fabricate a CCRD using a Koni-Meter to adjust the retention of the inner crown. This method protects the abutments and reduces the wear between the inner and outer crowns. The CCRD achieved good esthetic results and physiologic functions. Periodic long-term follow-up of the patient and CCRD after initial placement is recommended.
Full Text Available In order to analyze the causes of cracking in abutments subject to concrete shrinkage and temperature variation during the construction process and to determine factors affecting the mechanical properties of the abutment, nonlinear calculations capturing abutment behavior are conducted with Midas/FEA software. Using these calculations, the cracking mechanism is identified, and the influence of the evaluated factors is analyzed. It is concluded that the deformation between the pile cap and abutment backwall as constrained by a pile foundation when subjected to concrete shrinkage and temperature changes is the basic cause of abutment cracks during construction; these cracks form over the piles and develop upward. For a given reinforcement ratio, the distribution of horizontal crack-control steel using small, closely spaced bars is more beneficial. When pile-bearing capacity meets the standard, the width of the generated cracks tends to decrease with the decrease in the diameter of the piles. The existence of a postcast strip in the abutment backwall also contributes to the decrease in the depth of the crack. Finally, the impact of age difference between the pile cap concrete and abutment backwall concrete on cracking is inconsequential.
Bilhan, Hakan; Geckili, Onur; Mumcu, Emre
The anterior region is a challenge for most clinicians to achieve optimal esthetics with dental implants. The provisional crown is a key factor in the success of obtaining pink esthetics around restorations with single implants, by soft tissue and inter-proximal papilla shaping. Provisional abutments bring additional costs and make the treatment more expensive. Since one of the aims of the clinician is to reduce costs and find more economic ways to raise patient satisfaction, this paper describes a practical method for chair-side fabrication of non-occlusal loaded provisional crowns used by the authors for several years successfully. Twenty two patients (9 males, 13 females; mean age, 36,72 years) with one missing anterior tooth were treated by using the presented method. Metal definitive abutments instead of provisional abutments were used and provisional crowns were fabricated on the definitive abutments for all of the patients. The marginal fit was finished on a laboratory analogue and temporarily cemented to the abutments. The marginal adaptation of the crowns was evaluated radiographically. The patients were all satisfied with the final appearance and no complications occurred until the implants were loaded with permanent restorations. The use of the definitive abutments for provisional crowns instead of provisional abutments reduces the costs and the same results can be obtained.
Yamanishi, Yasufumi; Yamaguchi, Satoshi; Imazato, Satoshi; Nakano, Tamaki; Yatani, Hirofumi
Occlusal overloading is one of the causes of peri-implant bone resorption, and many studies on stress distribution in the peri-implant bone by three-dimensional finite element analysis (3D FEA) have been performed. However, the FEA models previously reported were simplified and far from representing what occurs in clinical situations. In this study, 3D FEA was conducted with simulation of the complex structure of dental implants, and the influences of neck design and connections with an abutment on peri-implant bone stress and abutment micromovement were investigated. Three types of two-piece implant CAD models were designed: external joint with a conical tapered neck (EJ), internal joint with a straight neck (IJ), and conical joint with a reverse conical neck (CJ). 3D FEA was performed with the setting of a "contact" condition at the component interface, and stress distribution in the peri-implant bone and abutment micromovement were analyzed. The shear stress was concentrated on the mesiodistal side of the cortical bone for EJ. EJ had the largest amount of abutment micromovement. While the von Mises and shear stresses around the implant neck were concentrated on the labial bone for IJ, they were distributed on the mesiodistal side of the cortical bone for CJ. CJ had the least amount of abutment micromovement. Implants with a conical joint with an abutment and reverse conical neck design may effectively control occlusal overloading on the labial bone and abutment micromovement. Copyright © 2012 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.
Apicella, Davide; Veltri, Mario; Balleri, Piero; Apicella, Antonio; Ferrari, Marco
The aim of the present study was to evaluate differences in the ultimate fracture resistance of titanium and zirconia abutments. Twenty titanium fixtures were embedded in 20 resin mandible section simulators to mimic osseointegrated implants in the premolar area. The embedded implants were then randomly divided into two groups. Afterwards, specimens in group A (n=10) were connected to titanium abutments (TiDesign™ 3.5/4.0, 5.5, 1.5 mm), while specimens in group B (n=10) were connected to zirconia abutments (ZirDesign ™ 3.5/4.0, 5.5, 1.5 mm). Both groups were loaded to failure in a dynamometric testing machine. Fractured samples were then analyzed by scanning electron microscopy (SEM). Group A showed a significantly higher fracture strength than that observed in group B. Group A failures were observed at the screw that connects the abutment with the implant while the abutment connection hexagons were plastically bent by the applied load. Group B failures were a result of abutment fractures. SEM analysis showed that in group A the screw failure was driven by crack nucleation, coalescence and propagation, while in group B, the SEM analysis of failed surfaces showed the conchoidal fracture profile characteristic of brittle materials. The strength of both tested systems is adequate to resist physiologic chewing forces in the premolar area. Conversely, the titanium and zirconia failure modes evaluated here occurred at unphysiological loads. In addition, because the abutments were tested without crowns, the presented data have limited direct transfer to the clinical situation. © 2010 John Wiley & Sons A/S.
Wadhwani, Chandur; Piñeyro, Alfonso; Hess, Timothy; Zhang, Hai; Chung, Kwok-Hung
To compare the effect of implant abutment modification on the amount of cement extruded at the crown-abutment margin and to evaluate the vertical discrepancy after cementation. Access openings of titanium abutments were modified with an opening (open) and placement of two vent holes 3 mm from the occlusal edge and 180 degrees apart (internal vent). Access openings were filled with resin material (closed) and used as controls. Each abutment was secured to an implant analog. Eugenol-free zinc oxide cement (TempBond NE) was selected to cement the cast crowns (n = 9) onto test abutments. The amount of cement extruded out of the margin was calculated, and vertical seating discrepancies were determined with a linear transducer device before and after cementation. Differences among groups were analyzed statistically. The mean amount of extruded cement ranged from 36% to 90% of the total cement placed within the crowns. The order, from least to greatest amount of excess cement extrusion at the margins, was internal vent, open, and closed; significant differences were observed between test groups. The net vertical discrepancies of tested specimens ranged from -7 μm to +6 μm (mean, 0 μm). No statistically significant differences in vertical discrepancy were found between the groups. Venting the hollow abutment resulted in the least amount of cement extrusion when compared to closing off the screw access channel or leaving it open. Within the limitations of this study, it may be concluded that the use of two, 0.75-mm radius vent holes placed 3 mm apical to the occlusal area of the abutment and 180 degrees apart will limit the amount of cement extruded into the gingival sulcus of implant-retained crowns.
Venkat, Gowtham; Krishnan, Murugesan; Srinivasan, Suganya; Balasubramanian, Muthukumar
Titanium has become the material of choice with greater applications in dental implants. The success of the dental implant does not only depend on the integration of the implant to the bone but also on the function and longevity of the superstructure. The clinical condition that demands long-term interim prosthesis is challenging owing to the decreased bond between the abutment and the veneering material. Hence, various surface treatments are done on the abutments to increase the bond strength. This study aimed to evaluate the bond strength between the abutment and the provisional veneering materials by surface treatments such as acid etching, laser etching, and sand blasting of the abutment. Forty titanium alloy abutments of 3 mm diameter and 11 mm height were grouped into four groups with ten samples. Groups A, B, C, and D are untreated abutments, sand blasted with 110 μm aluminum particles, etched with 1% hydrofluoric acid and 30% nitric acid, and laser etched with Nd: YAG laser, respectively. Provisional crowns were fabricated with bis-acrylic resin and cemented with noneugenol temporary luting cement. The shear bond strength was measured in universal testing machine using modified Shell-Nielsen shear test after the cemented samples were stored in water at 25°C for 24 h. Load was applied at a constant cross head speed of 5 mm/min until a sudden decrease in resistance indicative of bond failure was observed. The corresponding force values were recorded, and statistical analysis was done using one-way ANOVA and Newman-Keuls post hoc test. The laser-etched samples showed higher bond strength. Among the three surface treatments, laser etching showed the highest bond strength between titanium alloy implant abutment and provisional restorations. The sand-blasted surfaces demonstrated a significant difference in bond strength compared to laser-etched surfaces. The results of this study confirmed that a combination of surface treatments and bond agents enhances the
Fariba Saleh Saber
Full Text Available Background and aims. In contrast to prepared natural dentin abutments, little is known concerning factors influencing the retention of fixed prostheses cemented to implant abutments. The aim of this study was to investigate the effect of implant abutment height on the retention of single castings cemented to wide and narrow platform implant abutments. Materials and methods. Thirty-six parallel-sided abutments (Biohorizon Straight Abutment of narrow platform (NP and wide platform (WP sizes with their analogs were used. In each group of platform size, abutments were prepared with axial wall heights of 5, 4, 3, 2 mm (n=9. On the whole 72 castings were constructed, which incorporated an attachment to allow removal. Castings were cemented to abutments with TempBond®. A uniaxial tensile force was applied to the crown using an Instron machine until cement failure occurred. Analysis of variance of the models were fit to determine the effect of height of abutment of the restorations on the mean tensile strength (α=0.05. Results. The mean peak removal force for corresponding abutments was significantly different (P NP; (2 with alteration of axial wall height for NP: 5 mm > 4 mm > 3 mm = 2 mm and for WP: 5 mm > 4 mm = 3 mm = 2 mm. Conclusion. The retention of NP cement-retained restorations is influenced by the wall height but not in same manner as WP. Restorations of narrow-platform size with longer abutment exhibited higher tensile resistance to dislodgement.
Kim, Aram; Campbell, Stephen D; Viana, Marlos A G; Knoernschild, Kent L
The purpose of this study was to evaluate the effect of implant abutment material on peri-implant soft tissue color using intraoral spectrophotometric analysis and to compare the clinical outcomes with patient and clinician perception and satisfaction. Thirty patients and four prosthodontic faculty members participated. Abutments were zirconia, gold-hued titanium, and titanium. Peri-implant mucosa color of a single anterior implant restoration was compared to the patient's control tooth. Spectrophotometric analysis using SpectroShade TM Micro data determined the color difference (ΔE, ΔL*, Δa*, Δb*) between the midfacial peri-implant soft tissue for each abutment material and the marginal gingiva of the control tooth. Color difference values of the abutment groups were compared using ANOVA (α = 0.05). Patient and clinician satisfaction surveys were also conducted using a color-correcting light source. The results of each patient and clinician survey question were compared using chi-square analysis (α = 0.05). Pearson correlation analyses identified the relationship between the total color difference (ΔE) and the patient/clinician perception and satisfaction, as well as between ΔE and tissue thickness. Zirconia abutments displayed significantly smaller spectrophotometric gingival color difference (ΔE) compared to titanium and gold-hued titanium abutments (respectively, 3.98 ± 0.99; 7.22 ± 3.31; 5.65 ± 2.11; p esthetics than crown (white) esthetics (p < 0.05). Peri-implant mucosa with zirconia abutments demonstrated significantly lower mean color difference compared to titanium or gold-hued titanium abutments as measured spectrophotometrically; however, no statistical difference in patient or clinician perception/satisfaction among abutment materials was demonstrated. Patients were significantly more satisfied than clinicians. © 2015 by the American College of Prosthodontists.
Jaime, Ana Paula Gumieiro; de Vasconcellos, Diego Klee; Mesquita, Alfredo Mikail Melo; Kimpara, Estevão Tomomitsu; Bottino, Marco Antonio
Objectives: This study assessed the effect of cast rectifiers on the marginal misfit of cast UCLA abutments compared to premachined UCLA abutments. The influence of casting and porcelain baking on the marginal misfit of these components was also investigated. Methods: Two groups were analyzed: test group – 10 cast UCLA abutments, finished with cast rectifier and submitted to ceramic application; control group – 10 premachined UCLA abutments, cast with noble metal alloy and submitted to ceramic application. Vertical misfit measurements were performed under light microscopy. In the test group, measurements were performed before and after the use of cast rectifiers, and after ceramic application. In the control group, measurements were performed before and after casting, and after ceramic application. Data were submitted to statistical analysis by ANOVA and Tukey's test (α= 5%). Results: The use of cast rectifiers significantly reduced the marginal misfit of cast UCLA abutments (from 25.68μm to 14.83μm; p<0.05). After ceramic application, the rectified cylinders presented misfit values (16.18μm) similar to those of premachined components (14.3 μm). Casting of the premachined UCLA abutments altered the marginal misfit of these components (from 9.63 μm to 14.6 μm; p<0.05). There were no significant changes after porcelain baking, in both groups. Conclusion: The use of cast rectifiers reduced the vertical misfit of cast UCLA abutments. Even with carefully performed laboratory steps, changes at the implant interface of premachined UCLA abutments occurred. Ceramic application did not alter the marginal misfit values of UCLA abutments. PMID:19089125
Ana Paula Gumieiro Jaime
Full Text Available OBJECTIVES: This study assessed the effect of cast rectifiers on the marginal misfit of cast UCLA abutments compared to premachined UCLA abutments. The influence of casting and porcelain baking on the marginal misfit of these components was also investigated. METHODS: Two groups were analyzed: test group - 10 cast UCLA abutments, finished with cast rectifier and submitted to ceramic application; control group - 10 premachined UCLA abutments, cast with noble metal alloy and submitted to ceramic application. Vertical misfit measurements were performed under light microscopy. In the test group, measurements were performed before and after the use of cast rectifiers, and after ceramic application. In the control group, measurements were performed before and after casting, and after ceramic application. Data were submitted to statistical analysis by ANOVA and Tukey's test (a= 5%. RESULTS: The use of cast rectifiers significantly reduced the marginal misfit of cast UCLA abutments (from 25.68mm to 14.83mm; p<0.05. After ceramic application, the rectified cylinders presented misfit values (16.18mm similar to those of premachined components (14.3 mm. Casting of the premachined UCLA abutments altered the marginal misfit of these components (from 9.63 mm to 14.6 mm; p<0.05. There were no significant changes after porcelain baking, in both groups. CONCLUSION: The use of cast rectifiers reduced the vertical misfit of cast UCLA abutments. Even with carefully performed laboratory steps, changes at the implant interface of premachined UCLA abutments occurred. Ceramic application did not alter the marginal misfit values of UCLA abutments.
Dede, Doğu Ömür; Armağanci, Arzu; Ceylan, Gözlem; Celik, Ersan; Cankaya, Soner; Yilmaz, Burak
Ceramics are widely used for anterior restorations; however, clinical color reproduction still constitutes a challenge particularly when the ceramic crowns are used on titanium implant abutments. The purpose of this in vitro study was to investigate the effect of implant abutment material on the color of different ceramic material systems. Forty disks (11×1.5 mm, shade A2) were fabricated from medium-opacity (mo) and high-translucency (ht) lithium disilicate (IPS e.max) blocks, an aluminous ceramic (VITA In-Ceram Alumina), and a zirconia (Zirkonzahn) ceramic system. Disks were fabricated to represent 3 different implant abutments (zirconia, gold-palladium, and titanium) and dentin (composite resin, A2 shade) as background (11×2 mm). Disk-shaped composite resin specimens in A2 shade were fabricated to represent the cement layer. The color measurements of ceramic specimens were made on composite resin abutment materials using a spectrophotometer. CIELab color coordinates were recorded, and the color coordinates measured on composite resin background served as the control group. Color differences (ΔE 00 ) between the control and test groups were calculated. The data were analyzed with 2-way analysis of variance (ANOVA) and compared with the Tukey HSD test (α=.05). The ceramics system, abutment material, and their interaction were significant for ΔE 00 values (P2.25) were observed for lithium disilicate ceramics on titanium abutments (2.46-2.50). The ΔE 00 values of lithium disilicate ceramics for gold-palladium and titanium abutments were significantly higher than for other groups (P2.25) of an implant-supported lithium disilicate ceramic restoration may be clinically unacceptable if it is fabricated over a titanium abutment. Zirconia may be a more suitable abutment material for implant-supported ceramic restorations. Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.
Keener, Charles; Serpa, Laura; Pavlis, Terry L.
New geophysical and fault kinematic studies indicate that late Cenozoic basin development in the Mormon Point area of Death Valley, California, was accommodated by fault rotations. Three of six fault segments recognized at Mormon Point are now inactive and have been rotated to low dips during extension. The remaining three segments are now active and moderately to steeply dipping. From the geophysical data, one active segment appears to offset the low-angle faults in the subsurface of Death Valley.
Alexandre Wittcinski REGALIN
Full Text Available Abstract Purpose This study evaluated the torque maintenance of universal abutment retaining screws using different tightening techniques, and coated or uncoated screws. Material and method The screws were tightened to implants as following: Control – 32 Ncm torque; H20 – holding 32 Ncm torque for 20 s; R – 32 Ncm torque, repeated after 10 min (retorque; and H20+R – combining the two tightening techniques. Titanium and coated screws were also evaluated. Result Statistical analysis showed higher maintained torque for titanium screws (p<0.001. The H20+R technique showed the highest maintained torque (p=0.003, but the H20 technique’s maintained torque was similar. Conclusion Titanium screws associating the two tightening techniques can improve maintained torque.
Wentaschek, Stefan; Tomalla, Sven; Schmidtmann, Irene; Lehmann, Karl Martin
To examine the screw preload, coefficient of friction (COF), and tightening torque needed to overcome the thread friction of an implant-abutment-screw complex. In a customized load frame, 25 new implant-abutment-screw complexes including uncoated titanium alloy screws were torqued and untorqued 10 times each, applying 25 Ncm. Mean preload values decreased significantly from 209.8 N to 129.5 N according to the number of repetitions. The overall COF increased correspondingly. There was no comparable trend for the thread friction component. These results suggest that the application of a used implant-abutment-screw complex may be unfavorable for obtaining optimal screw preload.
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.
Fabiansen, Christian; Thybo, Søren
A case of fatal hemorrhagic Rift Valley fever during an epidemic in Kenya's North Eastern Province in January 2007 is described.......A case of fatal hemorrhagic Rift Valley fever during an epidemic in Kenya's North Eastern Province in January 2007 is described....
Full Text Available The aim of this study was to qualitatively evaluate the marginal vertical fit along two different implant-abutment interfaces: (1 a standard abutment on an implant and (2 a computer-aided-design/computer-aided-machine (CAD/CAM customized screw-retained crown on an implant. Four groups were compared: three customized screw-retained crowns with three different “tolerance” values (CAD-CAM 0, CAD-CAM +1, CAD-CAM −1 and a standard titanium abutment. Qualitative analysis was carried out using an optical microscope. Results showed a vertical gap significantly different from both CAD-CAM 0 and CAD-CAM −1, while no difference was found between standard abutment and CAD-CAM +1. The set tolerance in producing CAD/CAM screw-retained crowns plays a key role in the final fit.
Integral abutment (IA) construction has become the preferred method over conventional construction for use with typical highway bridges. However, the use of these structures is limited due to state mandated length and skew limitations. To expand thei...
Integral abutment (IA) construction has become the preferred method over conventional construction for use with typical highway bridges. However, the use of these structures is limited due to state mandated length and skew limitations. To expand thei...
The Illinois Department of Transportation (IDOT) has increasingly constructed integral abutment bridges (IABs) : over the past few decades, similar to those in many other states. Because the length and skew limitations : currently employed by IDOT ha...
Lorenzoni, Fabio C; Coelho, Paulo G; Bonfante, Gerson; Carvalho, Ricardo M; Silva, Nelson R F A; Suzuki, Marcelo; Silva, Thelma Lopes; Bonfante, Estevam A
To evaluate the sealing capability of external hexagon implant systems and assess the marginal fit, two groups (n = 10 each) were employed: SIN (Sistema de Implantes Nacional, Brazil) and Osseotite, (Biomet 3i, USA). Sealing capability was determined by placing 0.7 μL of 1% acid-red solution in the implant wells before the torque of their respective abutments. Specimens were then placed into 2.5 mL vials filled with 1.3 mL of distilled water with the implant-abutment interface submerged. Three samples of 100 μL water were collected at previously determinate times. The absorbance was measured with a spectrophotometer, and the data were analyzed by Two-way ANOVA (P implant-abutment interface of both groups. Gaps in the implant-abutment interface were observed along with leakage increased at the 144 hrs evaluation period.
Bruna, Ezio; Fabianelli, Andrea; Mastriforti, Giacomo; Papacchini, Federica
This study investigated the stability of titanium screws in implant-abutment connections by measuring the force necessary to induce unscrewing. A total of 60 implant-abutment couplings were assigned to two groups (n = 30 each). The sequence 10-20-32 Ncm was tested in Group 1; the sequence 10-20-32-32-32 Ncm was tested in Group 2. The force necessary to unscrew each abutment-implant sample was recorded and statistically analyzed. The significance level was set at P < .05. Significant differences were found between the two sequences. Group 2 required higher forces than Group 1 to unscrew. The stability of the implant-abutment joint may be improved by tightening with the sequence 10-20-32-32-32 Ncm.
The advantages of integral abutment bridges (IABs) include reduced maintenance costs and increased useful life spans. : However, improved procedures are necessary to account for the impacts of cyclic thermal displacements on IAB components, : includi...
Joda, Tim; Bürki, Alexander; Bethge, Stefan; Brägger, Urs; Zysset, Philippe
The objective of this study was to evaluate stiffness, strength, and failure modes of monolithic crowns produced using computer-aided design/computer-assisted manufacture, which are connected to diverse titanium and zirconia abutments on an implant system with tapered, internal connections. Twenty monolithic lithium disilicate (LS2) crowns were constructed and loaded on bone level-type implants in a universal testing machine under quasistatic conditions according to DIN ISO 14801. Comparative analysis included a 2 × 2 format: prefabricated titanium abutments using proprietary bonding bases (group A) vs nonproprietary bonding bases (group B), and customized zirconia abutments using proprietary Straumann CARES (group C) vs nonproprietary Astra Atlantis (group D) material. Stiffness and strength were assessed and calculated statistically with the Wilcoxon rank sum test. Cross-sections of each tested group were inspected microscopically. Loaded LS2 crowns, implants, and abutment screws in all tested specimens (groups A, B, C, and D) did not show any visible fractures. For an analysis of titanium abutments (groups A and B), stiffness and strength showed equally high stability. In contrast, proprietary and nonproprietary customized zirconia abutments exhibited statistically significant differences with a mean strength of 366 N (Astra) and 541 N (CARES) (P zirconia abutments (groups C and D) below the implant shoulder. Depending on the abutment design, prefabricated titanium abutment and proprietary customized zirconia implant-abutment connections in conjunction with monolithic LS2 crowns had the best results in this laboratory investigation.
Rudys Rodolfo de Jesus Tavarez
Full Text Available OBJECTIVES: The purpose of this in vitro study was to evaluate misfit alterations at the implant/abutment interface of external and internal connection implant systems when subjected to cyclic loading. MATERIAL AND METHODS: Standard metal crowns were fabricated for 5 groups (n=10 of implant/abutment assemblies: Group 1, external hexagon implant and UCLA cast-on premachined abutment; Group 2, internal hexagon implant and premachined abutment; Group 3, internal octagon implant and prefabricated abutment; Group 4, external hexagon implant and UCLA cast-on premachined abutment; and Group 5, external hexagon implant and Ceraone abutment. For groups 1, 2, 3 and 5, the crowns were cemented on the abutments and in group 4 crowns were screwed directly on the implant. The specimens were subjected to 500,000 cycles at 19.1 Hz of frequency and non-axial load of 133 N in a MTS 810 machine. The vertical misfit (μm at the implant/abutment interface was evaluated before (B and after (A application of the cyclic loading. Data were analyzed statistically by using two-away ANOVA and Tukey's post-hoc test (p<0.05. RESULTS: Before loading values showed no difference among groups 2 (4.33±3.13, 3 (4.79±3.43 and 5 (3.86±4.60; between groups 1 (12.88±6.43 and 4 (9.67±3.08, and among groups 2, 3 and 4. However, groups 1 and 4 were significantly different from groups 2, 3 and 5. After loading values of groups 1 (17.28±8.77 and 4 (17.78±10.99 were significantly different from those of groups 2 (4.83±4.50, 3 (8.07±4.31 and 5 (3.81±4.84. There was a significant increase in misfit values of groups 1, 3 and 4 after cyclic loading, but not for groups 2 and 5. CONCLUSIONS: The cyclic loading and type of implant/abutment connection may develop a role on the vertical misfit at the implant/abutment interface.
If yes . give date. D N/A 27. COMMENTS ~ APPROVED 0 DISAPPROVED I RB approved presentation of dental materials research w i th appropriate...The specimens were cemented to a titanium-base implant system, subjected to thermocycling and cyclic loading, and fractured in a material testing...zirconia abutment/lithium-disilicate crown. INTRODUCTION Dental implants and the use of esthetic abutments are widely practiced procedures for dentists
Alves da Cunha, Tiago de Morais; Correia de Araújo, Roberto Paulo; Barbosa da Rocha, Paulo Vicente; Pazos Amoedo, Rosa Maria
Although increase of misfit has been reported when associating implant and abutment from different manufacturers, Procera® (Nobel Biocare™, Göteborg, Sweden) custom abutment has been universally used in clinical practice. The purpose of this investigation was to compare the vertical gap of zirconia Procera abutment associated with implants from the same manufacturer (Nobel Biocare) and two other implant systems. Twenty-four zirconia Procera abutments were produced using computer-assisted design and manufacture (CAD/CAM) and paired with (1) eight MK Iii RP 4.1 × 10 mm implants (Nobel Biocare) - GNB group; (2) eight Try on, 4.1 × 10 mm implants (Sistema de Implantes, São Paulo, Brazil) - ES group; and (3) eight Master screw, 4.1 × 10 mm implants (Conexão Sistema de Prótese, São Paulo, Brazil) - EC group. A comparison of the vertical misfit at the implant-abutment interface was taken at six measuring sites on each sample using scanning electron microscopy with a magnification of 408×. One-way analysis of variance was used to test for differences, and Tukey's test was used for pairwise comparison of groups (α = 0.05). Significant differences relative to average misfit were found when Procera abutments were associated with other implant manufacturers. The ES group and EC group did not differ significantly, but both demonstrated significantly larger average misfit than the GNB group (p = .001). The average misfit was 5.7 µm ± 0.39, 9.53 µm ± 0.52 and 10.62 µm ± 2.16, respectively, for groups GNB, ES, and EC. The association of Procera zirconia abutment with other implant systems different from its manufacturer demonstrated significant alteration of vertical misfit at implant-abutment interface. © 2010 Wiley Periodicals, Inc.
de Morais Alves da Cunha, Tiago; de Araújo, Roberto Paulo Correia; da Rocha, Paulo Vicente Barbosa; Amoedo, Rosa Maria Pazos
Although increase of misfit has been reported when associating implant and abutment from different manufacturers, Procera custom abutment has been universally used in clinical practice. The purpose of this investigation was to compare the vertical gap of zirconia Procera® abutment associated with implants from the same manufacturer (Procera manufacturer) and two other implant systems. Twenty-four zirconia Procera abutments were produced using computer-assisted design and manufacture and paired with (a) eight MK III, RP 4.1 × 10 mm implants (Nobel Biocare™, Göteborg, Sweden) - GNB group (Nobel Biocare group); (b) eight Try on, 4.1 × 10 mm implants (Sistema de Implantes, São Paulo, Brazil) - ES group (SIN experimental group) ; and (c) eight Master screw, 4.1 × 10 mm implants (Conexão® Sistema de Prótese, São Paulo, Brazil) - EC group (Conexão experimental group). A comparison of the vertical misfit at the implant-abutment interface was taken at six measuring sites on each sample using scanning electron microscopy with a magnification of 408×. One-way analysis of variance was used to test for differences, and Tukey's test was used for pair-wise comparison of groups (α = 0.05). Significant differences relative to average misfit were found when Procera abutments were associated with other implant manufacturers. The ES group and EC group did not differ significantly, but both demonstrated significantly larger average misfit than the GNB group (p = .001). The average misfit was 5.7 µm ± 0.39, 9.53 µm ± 0.52, and 10.62 µm ± 2.16, respectively, for groups GNB, ES, and EC. The association of Procera zirconia abutment with other implant systems different from its manufacturer demonstrated significant alteration of vertical misfit at implant-abutment interface. © 2010 Wiley Periodicals, Inc.
Schmitt, Christian M; Nogueira-Filho, Getulio; Tenenbaum, Howard C; Lai, Jim Yuan; Brito, Carlos; Döring, Hendrik; Nonhoff, Jörg
In this systematic review, we aimed to compare conical versus nonconical implant-abutment connection systems in terms of their in vitro and in vivo performances. An electronic search was performed using PubMed, Embase, and Medline databases with the logical operators: "dental implant" AND "dental abutment" AND ("conical" OR "taper" OR "cone"). Names of the most common conical implant-abutment connection systems were used as additional key words to detect further data. The search was limited to articles published up to November 2012. Recent publications were also searched manually in order to find any relevant studies that might have been missed using the search criteria noted above. Fifty-two studies met the inclusion criteria and were included in this systematic review. As the data and methods, as well as types of implants used was so heterogeneous, this mitigated against the performance of meta-analysis. In vitro studies indicated that conical and nonconical abutments showed sufficient resistance to maximal bending forces and fatigue loading. However, conical abutments showed superiority in terms of seal performance, microgap formation, torque maintenance, and abutment stability. In vivo studies (human and animal) indicated that conical and nonconical systems are comparable in terms of implant success and survival rates with less marginal bone loss around conical connection implants in most cases. This review indicates that implant systems using a conical implant-abutment connection, provides better results in terms of abutment fit, stability, and seal performance. These design features could lead to improvements over time versus nonconical connection systems. © 2013 Wiley Periodicals, Inc.
Ishak, Muhammad Ikman; Shafi, Aisyah Ahmad; Rosli, M. U.; Khor, C. Y.; Zakaria, M. S.; Rahim, Wan Mohd Faizal Wan Abd; Jamalludin, Mohd Riduan
The success of dental implant surgery is majorly dependent on the stability of prosthesis to anchor to implant body as well as the integration of implant body to bone. The attachment between dental implant body and abutment plays a vital role in attributing to the stability of dental implant system. A good connection between implant body cavity to abutment may minimize the complications of abutment loosening and implant fractures as widely reported in clinical findings. The aim of this paper is to investigate the effect of different abutment-implant connections on stress dispersion within the abutment and implant bodies as well as displacement of implant body via three-dimensional (3-D) finite element analysis (FEA). A 3-D model of mandible was reconstructed from computed tomography (CT) image datasets using an image-processing software with the selected region of interest was the left side covering the second premolar, first molar and second molar regions. The bone was modelled as compact (cortical) and porous (cancellous) structures. Besides, three implant bodies and three generic models of abutment with different types of connections - tapered interference fit (TIF), tapered integrated screwed-in (TIS) and screw retention (SR) were created using computer-aided design (CAD) software and all models were then analysed via 3D FEA software. Occlusal forces of 114.6 N, 17.2 N and 23.4 N were applied in the axial, lingual and mesio-distal directions, respectively, on the top surface of first molar crown. All planes of the mandibular bone model were rigidly fixed. The result exhibited that abutment with TIS connection produced the most favourable stress and displacement outcomes as compared to other attachment types. This is due to the existence of integrated screw at the bottom portion of tapered abutment which increases the motion resistance.
Traini, Tonino; Di Iorio, Donato; Caputi, Sergio; Degidi, Marco; Iezzi, Giovanna; Piattelli, Adriano
This study investigates the use of thermomechanic abutment-to-implant coupling. Ten 3.5 x 1 mm commercially pure titanium Ankylos implants (Dentsply Friadent, Mannheim, Germany) and 10 standard abutment of titanium alloy Ti6Al4V were used in the present study. All fixtures were mounted on hold specimen provided of a 10-ohm electrical resistance to maintain the fixture at 37 degrees C +/- 3 degrees C during the entire test and to evaluate the influence of the coefficient of thermal expansion on joined conical abutment. The threading part of all abutments was cut off using a diamond disc. All abutment implants were coupled at 35 N using a universal testing machine (Lloyd 30K, Lloyd Instruments Ltd. Segensworth, UK). Five abutments were heated at 37 degrees C +/- 3 degrees C, whereas the reaming were cooled at 0 degrees C +/- 3 degrees C before connection. To measure the difference a pull-out test was performed. The results were statistically analyzed using unpaired t test at P < 0.05. The cooled specimens showed a result (mean +/- SD) of 421.6 +/- 55.20 N, whereas for heated specimens the result was 238.4 +/- 42.27 N. The difference was statistically significant (P = 0.001). The thermomechanic coupling significantly increases the performance of the conical joint.
Iglhaut, Gerhard; Schwarz, Frank; Winter, Robert R; Mihatovic, Ilja; Stimmelmayr, Michael; Schliephake, Henning
The soft tissues around dental implants are enlarged compared with the gingiva because of the longer junctional epithelium and the hemidesmosonal attachments are fewer, suggestive of a poorer quality attachment. Inflammatory infiltrates caused by bacterial colonization of the implant-abutment interface are thought to be one of the factors causing epithelial downgrowth and subsequent peri-implant bone loss. Gold alloys and dental ceramics as well as the contamination of the implant surface with amino alcohols, appear to promote epithelial downgrowth. Physical manipulaton of the abutment surfaces, including concave abutment designs, platform switching, and microgrooved surfaces are believed to inhibit epithelial downgrowth and minimizes bone loss at the implant shoulder. This paper reviews the factors that are believed to influence the migration of epithelial attachment the dental implant and abutment surfaces. Exploration of innovative computer-aided design/computer-aided manufacturing-based concepts such as "one abutment-one time" and their effect on epithelial downgrowth are discussed. Based on the review of current literature, the authors recommend inserting definitive abutments at the time of surgical uncovering. To implement this concept, registration of the implant position should to be taken at the time of surgical implant placement. © 2014 Wiley Periodicals, Inc.
Geringer, Alexander; Diebels, Stefan; Nothdurft, Frank P
To predict the clinical performance of zirconia abutments, it is crucial to examine the mechanical behavior of different dental implant-abutment connection configurations. The international standard protocol for dynamic fatigue tests of dental implants (ISO 14801) allows comparing these configurations using standardized superstructure geometries. However, from a mechanical point of view, the geometry of clinical crowns causes modified boundary conditions. The purpose of this finite element (FE) study was to evaluate the influence of the superstructure geometry on the maximum stress values of zirconia abutments with a conical implant-abutment connection. Geometry models of the experimental setup described in ISO 14801 were generated using CAD software following the reconstruction of computerized tomography scans from all relevant components. These models served as a basis for an FE simulation. To reduce the numerical complexity of the FE model, the interaction between loading stamp and superstructure geometry was taken into account by defining the boundary conditions with regard to the frictional force. The results of the FE simulations performed on standardized superstructure geometry and anatomically shaped crowns showed a strong influence of the superstructure geometry and related surface orientations on the mechanical behavior of the underlying zirconia abutments. In conclusion, ISO testing of zirconia abutments should be accompanied by load-bearing capacity testing under simulated clinical conditions to predict clinical performance.
Hansen, Allan Grutt; Bonde, Anders; Aagaard, Morten
This book is about using recent developments in the fields of data analytics and data visualization to frame new ways of identifying target groups in media communication. Based on a mixed-methods approach, the authors combine psychophysiological monitoring (galvanic skin response) with textual...... content analysis and audience segmentation in a single-source perspective. The aim is to explain and understand target groups in relation to, on the one hand, emotional response to commercials or other forms of audio-visual communication and, on the other hand, living preferences and personality traits...
Taiyeb-Ali, Tara B; Toh, Chooi Gait; Siar, Chong Huat; Seiz, Doris; Ong, Siew Tin
To compare the clinical soft tissue responses around implant tooth-supported 3-unit bridges using tapered abutments with those using butt-joint abutments. In a split-mouth design study, 8 mm Ankylos (Dentsply Friadent, Germany) implants were placed in the second mandibular molar region of 8 adult Macaca fascicularis monkeys about 1 month after extraction of all mandibular molars. After 3 months of submerged healing, 3-unit metal bridges were constructed. Clinical data was collected by the author who was blind to the abutment selections. Implants were clinically evaluated using Waite plaque index, sulcus bleeding index, probing pocket depth (PPD), probing attachment loss (PAL), and width of keratinized mucosa at baseline (BL) and 3-month and 6-month intervals. Stability of the implant was assessed using Periotest device at BL and after 6 months. At BL, all the clinical variables did not differ statistically between the tapered and the butt-joint groups except for PPD (P < 0.05), where the mean PPD was greater in the butt-joint group (2.75 ± 1.02 mm) as compared with the tapered group (1.97 ± 0.65 mm). At the 3-month assessment, there was no difference in all clinical variables. After 6-month loading, no significant difference between these 2 groups was detected in all these variables, with the exception of PAL (P = 0.05) where mean PAL was greater for implants with the butt-joint abutments (0.91 ± 0.86 mm) in comparison with the tapered abutments (0.50 ± 0.88 mm), and mean Periotest values (PTVs) that indicate the tapered-abutment implants (PTV = -4.5 ± 1.60) were more stable than butt-joint-abutment implants (PTV = -1.5 ± 3.59) with P < 0.05. The differences in these mucogingival responses between these 2 groups at BL (during seating of abutments, especially of butt-joint abutments) and after 6-month loading indicated enhanced peri-implant soft tissue stability around the tapered abutments of this system. There was also enhanced-PTV in the test group for
Tada, Sayaka; Ikebe, Kazunori; Matsuda, Ken-Ichi; Maeda, Yoshinobu
Predicting the tooth survival is such a great challenge for evidence-based dentistry. To prevent further tooth loss of partially edentulous patients, estimation of individualized risk and benefit for each residual tooth is important to the clinical decision-making. While there are several reports indicating a risk of losing the abutment teeth of RPDs, there are no existing reports exploring the cause of abutment loss by multifactorial analysis. The aim of this practice-based longitudinal study was to determine the prognostic factors affecting the survival period of RPD abutments using a multifactorial risk assessment. One hundred and forty-seven patients had been previously provided with a total of 236 new RPDs at the Osaka University Dental Hospital; the 856 abutments for these RPDs were analyzed. Survival of abutment teeth was estimated using the Kaplan-Meier method. Multivariate analysis was conducted by Cox's proportional hazard modelling. The 5-year survival rates were 86.6% for direct abutments and 93.1% for indirect abutments, compared with 95.8% survival in non-abutment teeth. The multivariate analysis showed that abutment survival was significantly associated with crown-root ratio (hazard ratio (HR): 3.13), root canal treatment (HR: 2.93), pocket depth (HR: 2.51), type of abutments (HR: 2.19) and occlusal support (HR: 1.90). From this practice-based longitudinal study, we concluded that RPD abutment teeth are more likely to be lost than other residual teeth. From the multifactorial risk factor assessment, several prognostic factors, such as occlusal support, crown-root ratio, root canal treatment, and pocket depth were suggested. These results could be used to estimate the individualized risk for the residual teeth, to predict the prognosis of RPD abutments and to facilitate an evidence-based clinical decision making. Copyright © 2013 Elsevier Ltd. All rights reserved.
de Medeiros, Rodrigo Antonio; Vechiato-Filho, Aljomar José; Pellizzer, Eduardo Piza; Mazaro, Jose Vitor Quinelli; dos Santos, Daniela Micheline; Goiato, Marcelo Coelho
The aim of this study is to evaluate through a literature review, the soft tissue response in contact with zirconia abutments, including case reports comparing prosthetics rehabilitations with zirconia and titanium abutments upto 3 years of follow-up as well as the factors that should be considered on implant's abutment selection. Metallic abutments can provide grayish color when in contact with thin soft tissues which may lead the implant prosthetic treatment to failure. In this context, the abutments of zirconia stand out because there is an excellent linking between esthetics and the health of peri-implant soft tissues. A consult of the published researches was made on the PubMed database from 2000 to September 2012. The including criteria were: literature reviews, clinical studies and case reports in English that focused on the response of the soft tissue in contact with zirconia implant abutments. The studies that were not in English and did not match the tackled issue were excluded. A total of 32 articles were found. According to the search strategy, just 16 articles were selected for this review. Three studies affirmed that zirconia abutments have an excellent soft tissue response; one study showed increased gingival recession with zirconia abutments and nine studies do not stand out any difference on biological behavior between titanium and zirconia abutments. Three studies affirmed that zirconia abutments provide natural gingival appearance, anatomic contour and greater esthetics. The use of zirconia abutments is recommended for anterior regions because of their greater optical properties and esthetic results and more studies should be performed and analyzed longitudinally regarding their biological response. The zirconia abutments have been established to be essential in order to achieve great esthetic results in cases of thin peri-implant soft tissues and in regions where the three-dimensional placement of implants is more superficial.
Gehrke, Peter; Johannson, Dirk; Fischer, Carsten; Stawarczyk, Bogna; Beuer, Florian
All-ceramic abutments are employed increasingly often in implant dentistry for esthetic reasons. In vitro stress testing is required to evaluate the suitability of these constructions, especially in load-bearing posterior regions. The purpose of the study was to assess and compare the fatigue and fracture resistance of one- and two-piece computer-aided design/computer-assisted manufacture (CAD/CAM) zirconia implant abutments with an internal-hex connection and prefabricated commercially available zirconia stock abutments. Twenty-one abutment-crown specimens were prepared for three test groups. Control group 1 (SZ) included specimens with unprepared stock zirconia abutments, test group 2 (OP) included one-piece CAD/CAM zirconia abutments, and test group 3 (TP) included two-piece CAD/CAM zirconia abutments. All 21 specimens underwent thermocycling and fatigue testing. Finally, all specimens were tested for fracture resistance with a universal testing machine. The maximum load was applied to the tapered occlusal area of each crown at a 30-degree angle and a crosshead speed of 0.5 mm/min until the implant-abutment connection failed. Kolmogorov-Smirnov, Shapiro-Wilk, and post-hoc Scheffé tests were used for statistical analysis. All abutments in groups SZ and OP fractured into two or more pieces after fracture resistance testing. None of the TP abutments displayed apparent disintegration, but failure was evidenced by bending of the retention screw. OP abutments (232.1 ± 29.8 N) and SZ abutments (251.8 ± 23.2 N) showed lower fracture loads than the TP abutments (291.4 ± 27.8 N). However, only the difference between the OP and TP groups was statistically significant. Further load-displacement analyses corroborated the higher mechanical stability of the TP abutments. Superior resistance was achieved for two-piece hybrid CAD/CAM zirconia abutments. These abutments might be clinically beneficial in high-load areas, such as premolar and molar regions.
Seyyed Mohammad Abrisham
Full Text Available Introduction: Surface roughness can increase the retention of castings by ridges and grooves that are microretentive. This study compared the retention of implant-supported crowns when used with 3 different surface roughness abutments and one temporary cement. Methods: Thirty solid abutments (ITI, 4 mm high, were divided into three groups randomly. In the first group, 10 abutments were roughened with sandblast (50-µm aluminum oxide and in the second group, 10 abutments were roughened with diamond bur. The third group had no surface treatment. Then, thirty implant fixture analogs (ITI were placed in the center of acrylic cylinders. After that a solid abutment was tightened on the each fixture analog with 35 N/cm force. Thirty base metal crowns were made on the 4 mm ITI abutment analogs using plastic coping. The prepared copings were cemented on the abutments by TempBond temporary cement and finally, crowns were pulled from the abutment in a universal test machine at a cross speed of 0.5cm/min. Results: The mean tensile strength in sandblasted, bur treated, and control group were 64.38±8, 91.37±7.19, and 58.61±1.93, respectively. Bur treated group showed higher tensile strength in comparison with two other groups. Conclusion: Surface modification of implant abutment by diamond bur may be an effective method to increase retention of crown when TempBond is used.
Full Text Available Introduction: Surface roughness can increase the retention of castings by ridges and grooves that are microretentive. This study compared the retention of implant-supported crowns when used with 3 different surface roughness abutments and one temporary cement. Methods: Thirty solid abutments (ITI, 4 mm high, were divided into three groups randomly. In the first group, 10 abutments were roughened with sandblast (50-µm aluminum oxide and in the second group, 10 abutments were roughened with diamond bur. The third group had no surface treatment. Then, thirty implant fixture analogs (ITI were placed in the center of acrylic cylinders. After that a solid abutment was tightened on the each fixture analog with 35 N/cm force. Thirty base metal crowns were made on the 4 mm ITI abutment analogs using plastic coping. The prepared copings were cemented on the abutments by TempBond temporary cement and finally, crowns were pulled from the abutment in a universal test machine at a cross speed of 0.5cm/min. Results: The mean tensile strength in sandblasted, bur treated, and control group were 64.38±8, 91.37±7.19, and 58.61±1.93, respectively. Bur treated group showed higher tensile strength in comparison with two other groups. Conclusion: Surface modification of implant abutment by diamond bur may be an effective method to increase retention of crown when TempBond is used.
Kortekaas, J; Oreshkova, N; van Keulen, L; Kant, J; Bosch, B J; Bouloy, M; Moulin, V; Goovaerts, D; Moormann, R J M
Rift Valley fever virus (RVFV) is a re-emerging zoonotic bunyavirus of the genus Phlebovirus. A natural isolate containing a large attenuating deletion in the small (S) genome segment previously yielded a highly effective vaccine virus, named Clone 13. The deletion in the S segment abrogates
Full Text Available Many dentists believe that the tooth need reinforcement provided by post before the definite restoration is placed. However, others suggest not to use post when posterior teeth especially molars, still have significant amount of tooth structure. Therefore, when endodontically treated molar is considered to be used as fixed denture abut-ment, clinicians must have proper knowledge about the impact of post placement. This literature will describe considerations regarding post placement in endodontically treated molar abutment in fixed partial dentures and their influence to the success rate. Previous studies implied the need of proper measurement of the amount of remaining tooth structure, the type of intracoronal reinforcement of the abutment, and the functional loads to ensure the success of fixed denture treatment. When planning definitive restorations for endodontically treated abutment teeth, some even suggest to use post and core to fulfill the need of reinforcement. On the contrary, others find that when a post is use in endodontically treated abutment teeth, the failure of custom made-tapered cast post and core is relatively high, whereas the use of amalgam or composite core in posterior teeth especially molars with adequate amount of tooth structure is sufficient due to post system’s limited influence on the suc-cess rate. Based on literature review, for cases with adequate tooth stucture, it can be concluded that the influ-ence of post placement in endodontically treated molar abutment to fixed partial dentures success rate is very limited.DOI: 10.14693/jdi.v18i2.64
Prado, Abraão M; Pereira, Jorge; Silva, Filipe S; Henriques, Bruno; Nascimento, Rubens M; Benfatti, Cesar A M; López-López, José; Souza, Júlio C M
The aim of this in vitro study was to evaluate the removal torque values on abutments and the morphological wear aspects of two different dental implant joints after immersion in a medium containing biofilm from human saliva. Twenty implant-abutment assemblies were divided into four groups in this study: (A) Morse taper free of medium containing biofilm, and (B) after contact with a medium containing biofilm from human saliva; (C) External Hexagon free of medium containing biofilm, and (D) after contact with medium containing biofilm from human saliva. The abutments were firstly torqued to the implants according to the manufacturer´s recommendations, using a handheld torque meter. Groups B and D were immersed into 24 well-plates containing 2 ml BHI medium with microorganisms for 72 h at 37 °C under microaerophilic conditions. After detorque evaluation, the abutments were removed and the implants were analyzed by scanning electron microscopy (SEM) and profilometry. On the detorque evaluation, the torque values decreased for the external hexagon implants and increased for the Morse taper implants. However, the values were lower when both implant-abutment assemblies were in contact with a medium containing biofilm from human saliva. The wear areas of contacting surfaces of the implants were identified by SEM. The highest average roughness values were recorded on the surfaces free of biofilm. The medium containing biofilm from human saliva affected the maintenance of the torque values on Morse taper and external hexagon abutments. Additionally, the removal of abutment altered the inner implant surfaces resulting in an increase of wear of the titanium-based connection.
Full Text Available Introduction: Titanium has become the material of choice with greater applications in dental implants. The success of the dental implant does not only depend on the integration of the implant to the bone but also on the function and longevity of the superstructure. The clinical condition that demands long-term interim prosthesis is challenging owing to the decreased bond between the abutment and the veneering material. Hence, various surface treatments are done on the abutments to increase the bond strength. Aim: This study aimed to evaluate the bond strength between the abutment and the provisional veneering materials by surface treatments such as acid etching, laser etching, and sand blasting of the abutment. Materials and Methods: Forty titanium alloy abutments of 3 mm diameter and 11 mm height were grouped into four groups with ten samples. Groups A, B, C, and D are untreated abutments, sand blasted with 110 μm aluminum particles, etched with 1% hydrofluoric acid and 30% nitric acid, and laser etched with Nd: YAG laser, respectively. Provisional crowns were fabricated with bis-acrylic resin and cemented with noneugenol temporary luting cement. The shear bond strength was measured in universal testing machine using modified Shell–Nielsen shear test after the cemented samples were stored in water at 25°C for 24 h. Load was applied at a constant cross head speed of 5 mm/min until a sudden decrease in resistance indicative of bond failure was observed. The corresponding force values were recorded, and statistical analysis was done using one-way ANOVA and Newman–Keuls post hoc test. Results: The laser-etched samples showed higher bond strength. Conclusion: Among the three surface treatments, laser etching showed the highest bond strength between titanium alloy implant abutment and provisional restorations. The sand-blasted surfaces demonstrated a significant difference in bond strength compared to laser-etched surfaces. The results of this
Vanlıoğlu, Burçin Akoğlu; Kahramanoğlu, Erkut; Yıldız, Coşkun; Ozkan, Yaşar; Kulak-Özkan, Yasemin
The aim of this study was to evaluate the treatment outcome of implants placed in the maxillary anterior segment. Patients were treated with bone-level implants (Straumann Bone Level Implant, Institut Straumann) that supported all-ceramic single crowns and were followed for 2 to 4 years. Titanium or ceramic abutments were used according to the quality of the soft tissue at each site. Esthetic parameters were recorded to assess treatment outcomes. Pink esthetic scores (PES) and white esthetic scores (WES) were used to evaluate the esthetic outcome of anterior single-tooth implant-supported crowns. Patient satisfaction was also evaluated by means of a questionnaire. Fifty-five implants were placed in 47 patients. At the recall examinations, all implants were confirmed to have successfully integrated and demonstrated healthy peri-implant soft tissues, as documented by generally accepted clinical parameters. Overall, the esthetic results were considered favorable, and there were no significant differences between restorations with ceramic or titanium abutments. WES values were slightly superior to PES values. None of the implants had mucosal recession. Objective and subjective evaluation of maxillary bone-level implants in the esthetic zone yielded satisfactory results. Pleasing esthetic outcomes and stable facial soft tissues were achieved.
Mattheos, N; Larsson, C; Ma, L; Fokas, G; Chronopoulos, V; Janda, M
The aim of this study was to investigate the micromorphological differences among three commercially available titanium abutments on Straumann implants. Furthermore, the possible impact of functional loading on the micromorphology and potential complications was investigated with the use of in vitro testing. Three groups of Titanium abutments (A: Straumann Variobase n = 5, B: EBI best Duo n = 5, and C: Implant Direct n = 5) were torqued on Straumann RN implants, as according to each of the manufacturer's instructions. The implant-abutment units were scanned with Micro-CT. Three units of each group were directly sliced in the microtome and photographed under different magnifications (10×-500×) through a Scanning Electron Microscope. Six units (two from each group) were restored with cement-retained crowns, subjected to 2000,000 load cycles with loads between 30 and 300 N at 2 Hz, examined through Micro-CT and finally sliced and photographed as described above. The micromorphology of each unit was studied, and the total length of tight contact (<3 μm) was calculated between the implant, abutment and screw contact areas. Major morphological differences were identified between the three units, as well as differences in the extent of tight contact in all areas examined. Despite the morphological differences, the 2M cycles of loading via in vitro test did not result in any noticeable complications although some changes in the micromorphology were observed. The examined implant-abutment units presented with major morphological differences. Two million cycles of in vitro loading did not appear to affect the stability of the units despite the micromorphological changes. These results need to be interpreted however under the limitations of the small sample size and the specific set-up of the in vitro testing. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.
Pereira, Jorge; Morsch, Carolina S; Henriques, Bruno; Nascimento, Rubens M; Benfatti, Cesar Am; Silva, Filipe S; López-López, José; Souza, Júlio Cm
The aim of this study was to evaluate the removal torque and in vitro biofilm penetration at Morse taper and hexagonal implant-abutment joints after fatigue tests. Sixty dental implants were divided into two groups: (1) Morse taper and (2) external hexagon implant-abutment systems. Fatigue tests on the implant-abutment assemblies were performed at a normal force (FN) of 50 N at 1.2 Hz for 500,000 cycles in growth medium containing human saliva for 72 hours. Removal torque mean values (n = 10) were measured after fatigue tests. Abutments were then immersed in 1% protease solution in order to detach the biofilms for optical density and colony-forming unit (CFU/cm²) analyses. Groups of implant-abutment assemblies (n = 8) were cross-sectioned at 90 degrees relative to the plane of the implant-abutment joints for the microgap measurement by field-emission guns scanning electron microscopy. Mean values of removal torque on abutments were significantly lower for both Morse taper (22.1 ± 0.5 μm) and external hexagon (21.1 ± 0.7 μm) abutments after fatigue tests than those recorded without fatigue tests (respectively, 24 ± 0.5 μm and 24.8 ± 0.6 μm) in biofilm medium for 72 hours (P = .04). Mean values of microgap size for the Morse taper joints were statistically signicantly lower without fatigue tests (1.7 ± 0.4 μm) than those recorded after fatigue tests (3.2 ± 0.8 μm). Also, mean values of microgap size for external hexagon joints free of fatigue were statistically signicantly lower (1.5 ± 0.4 μm) than those recorded after fatigue tests (8.1 ± 1.7 μm) (P joints were lower in comparison to those recorded at external hexagon implant-abutment joints after fatigue tests in a simulated oral environment for 72 hours.
Thulasidas, Shreedevi; Givan, Daniel A; Lemons, Jack E; O'Neal, Sandra Jean; Ramp, Lance C; Liu, Perng-Ru
To investigate the effects of abutment design to correct for implant angulation and aging on the fracture resistance of zirconia abutments. Greater understanding of the fracture strength of the zirconia abutments under various clinical conditions may lead to improvement of clinical protocols and possibly limit potential failures of implant prosthetics. Test specimens consisted of an implant-zirconia abutment-zirconia crown assembly with implant apex positioned at 0°, 20° to the facial (20F), and 20° to the lingual (20L) with respect to a constant crown contour. To keep the abutment design as the only variable, CAD/CAM technology was used to generate monolithic zirconia crowns identical both in external and internal dimensions and marginal contours to precisely fit all the abutments in an identical fashion. The monolithic zirconia abutments were designed to fit the constant crown contours and the internal connection of the implant at the three angulations. The customized abutments for the three implant angulations varied in emergence profile, screw hole location, and material thickness around the screw hole. Half the specimens from each group were subjected to steam autoclaving and thermocycling to simulate aging of the restorations in vivo. To mimic the off-axis loading of the central incisor, the specimens were loaded at the recommended cephalometric interincisal relationship of 135° between the long axis of the crown supported by the implant and the Instron force applicator simulating the mandibular incisor. The force applicator was positioned 2 mm from the incisal edge and loaded at a 1 mm/min crosshead speed. Data were evaluated by 2-way ANOVA (α = 0.05) and Tukey's HSD. The 20F group had the highest fracture values followed by the 0° group, and the 20L group had the lowest fracture values. Aging did not yield any significant difference in fracture force magnitudes. Within the limitations of this study, tilting the implant apex to the lingual
Morton, D; Stanford, C M; Aquilino, S A
Factors that affect transmission of strain from prostheses to bone may affect the long-term success of loaded implants. Current in vitro models are theoretically predictive (finite element modeling) or facsimile (photoelastic) in nature. A more clinically relevant in vitro model for strain evaluation should be investigated. This study attempted: (1) to validate a human cadaver bone model for vitro measurement of cortical bone strain, and (2) to evaluate the effect on cortical strain measurements of a resilient plastic component incorporated within a titanium implant in response to variable dynamic loading. Two IMZ (Interpore International) abutment alternatives were used: the titanium Abutment Complete and the polyoxymethylene Intra-mobile Element. The model system consisted of two implants placed in unfixed human cadaver ulna bone to simulate an implant bound edentulous region. Four biaxial rosette strain gauges simultaneously recorded cortical bone strain immediately mesial and distal to each implant. During experimentation a simulated prosthetic framework supported by either titanium or polyoxymethylene abutments was dynamically loaded 6 min from the terminal abutment along a cantilever extension. Cyclic nominal peak loads were applied with a materials testing machine at 20-N intervals from 20 to 200 N at a crosshead speed of 5 mm/minute. The protocol allowed frequency of load application to vary. A Newtonian linear correlation (r2 > or = 0.98) between load application and strain output was determined for each gauge position except for the terminal gauge located opposite the cantilever. Cortical strains recorded were within reported physiologic ranges involved in bone modeling and remodeling. Further, the polyoxymethylene abutment components did not result in reduction of peak microstrain at any gauge position. The Intra-mobile Element abutments, however, did increase the time required to complete 10 loading cycles when compared with the titanium Abutment
Blázquez-Hinarejos, Mónica; Ayuso-Montero, Raúl; Jané-Salas, Enric; López-López, José
Determine whether surface modified prosthetic abutments for dental implants influence connective tissue attachment to the implant-abutment system. A systematic review was conducted using the MEDLINE-PubMed database, with two independent reviewers filtering the titles and abstracts. Two reviewers assessed all potentially relevant articles. An assessment was carried out on the level of evidence of the research according to the guidelines of the Oxford Centre for Evidence-Based Medicine (OCEBM). After an initial search, 109 potentially relevant articles were found. After reading the titles and abstracts, 99 articles were excluded because the surface treatment was limited to the implant and not to the abutment, or because different materials were analysed instead of surface treatments; 28 were also duplicate articles. An additional 6 research studies were included that were of interest and were found by reading the references of the included articles. The studies included are: 7 in vitro studies, 5 experimental studies in animals, 2 clinical trials in humans and 2 clinical cases. Surface modification for prosthetic abutments on dental implants can achieve connective tissue attachment to the abutment; however, more studies should be conducted in humans to obtain more and better evidence of these results. Copyright © 2017 Elsevier Ltd. All rights reserved.
Basílio, Mariana de Almeida; Butignon, Luis Eduardo; Arioli Filho, João Neudenir
Different surface treatments have been developed in attempts to prevent the loosening of abutment screws. The aim of the current study was to compare the effectiveness of titanium alloy screws with tungsten-doped diamond-like carbon (W-DLC) coating and uncoated screws in providing stability to zirconia (ZrO2) ceramic abutments after cyclic loading. Twenty prefabricated ZrO2 ceramic abutments on their respective external-hex implants were divided into two groups of equal size according to the type of screw used: uncoated titanium alloy screw (Ti) or titanium alloy screw with W-DLC coating (W-DLC/Ti). The removal torque value (preload) of the abutment screw was measured before and after loading. Cyclic loading between 11 and 211 N was applied at an angle of 30 degrees to the long axis of the implants at a frequency of 15 Hz. A target of 0.5 X 106 cycles was defined. Group means were calculated and compared using analysis of variance and the F test (α = .05). Before cyclic loading, the preload for Ti screws was significantly higher than that for W-DLC/Ti screws (P = .021). After cyclic loading, there was no significant difference between them (P = .499). Under the studied conditions, it can be concluded that, after cyclic loading, both abutment screws presented a significant reduction in the mean retained preload and similar effectiveness in maintaining preload.
Kikuchi, Keisuke; Akiba, Norihisa; Sadr, Alireza; Sumi, Yasunori; Tagami, Junji; Minakuchi, Shunsuke
Vertical misfit of implant-abutment interface can affect the success of implant treatment; however, currently available modalities have limitations to detect these gaps. This study aimed to evaluate implant-abutment gaps in vitro using optical coherence tomography (OCT). Vertical misfit gaps sized 50, 100, 150, or 200 μm were created between external hexagonal implants and titanium abutments (Nobel Biocare, Göteborg, Sweden). A porcine gingival tissue slice, 0.5, 1.0, 1.5, or 2.0 mm in thickness, was placed on each implant-abutment interface. The gaps were evaluated by swept-source OCT at a center wavelength of 1330 nm (Panasonic Healthcare, Ehime, Japan) with beam angles of 90, 75 and 60 deg to the implant long-axis. The results suggested that while the measurements were precise, gap size and gingival thickness affected the sensitivity of detection. Gaps sized 100 μm and above could be detected with good accuracy under 0.5- or 1.0-mm-thick gingiva (GN). Around 70% of gaps sized 150 μm and above could be detected under 1.5-mm-thick GN. On the other hand, 80% of gaps under 2.0-mm-thick GN were not detected due to attenuation of near-infrared light through the soft tissue. OCT appeared as an effective tool for evaluating the misfit of implant-abutment under thin layers of soft tissue.
Lops, Diego; Bressan, Eriberto; Parpaiola, Andrea; Sbricoli, Luca; Cecchinato, Denis; Romeo, Eugenio
Aim of this study was to verify if the type of implant abutment manufacturing, stock or cad-cam, could influence the maintenance of stable gingival margins around single restorations in anterior areas. After 16 weeks of healing, implants (Osseospeed, Astra Tech Dental Implant) were positioned. Depending on the different fixture inclination and the thickness of buccal peri-implant soft tissue, abutment selection resulted in four groups: Group 1 (patients with zirconia ZirDesign(®) stock abutments), Group 2 (titanium stock TiDesign(®) abutments), Group 3 (zirconia cad-cam abutments), and Group 4 (titanium cad-cam abutments). The following parameters were assessed: buccal gingival margin modification (BGM). The modification of the implant gingival margin was followed at 1 and 2 years of follow-up. A computerized analysis was performed for measurements. Differences between soft tissue margin at baseline and after 2 years measured the gingival margin recession. A general linear model was used to evaluate each group in relation to gingival recession after two years. Tukey's post hoc test was used to compare the mean REC indexes of each group of abutments. Seventy-two healthy patients (39 males and 33 females; mean age of 46 years) scheduled for single gap rehabilitation in anterior areas were enrolled. A 100% of implant survival rate was observed after 24 months of function. One failure occurred due to fracture of a Zirconia cad-cam abutment. Moreover, two abutment screw unscrewing were observed. Both for zirconia and titanium stock abutments (Group 1 and 2), the mean recession of implant buccal soft tissue was of 0.3 mm (SD of 0.3 and 0.4 mm, respectively). Soft tissue mean recession of zirconia and titanium cad-cam abutments (Group 3 and 4) was of 0.1 and -0.3 mm, respectively (SD of 0.3 and 0.4 mm, respectively). REC values of cad-cam titanium abutments (Group 4) were significantly lower than that of Group 1 (-0.57 mm), Group 2 (-0.61 mm), and Group 3 (-0.40 mm
Kanno, Taro; Milleding, Percy; Wennerberg, Ann
Sintering porcelain on a ceramic abutment may change the microstructure and result in aging processes that influence the mechanical properties, internal strain, and the three-dimensional form of the abutment, thus causing a possible misfit between the abutment and the fixture. The aim was to investigate topography, microhardness, and precision of fit on yttrium-stabilized zirconia (Y-TZP) abutments before/after the sintering process. Ten Y-TZP abutment samples were ground to a shape used in the clinical situation and divided at random into two groups: before/after sintering. After the surface roughness was measured on all abutments, the abutments were connected to fixture replicas, embedded in resin, and cut in the longitudinal axis. Both sides of the cut samples were measured with respect to microhardness and minimum distance between fixture and abutment surface. t-Test, one-way analysis of variance, and Bonferroni multiple comparisons were used to investigate statistical significant differences. The surface roughness (S(a) and S(dr)) after sintering was significantly higher than before sintering. The total average values of microhardness after sintering were statistically lower than before sintering with a difference of 2%. The total distance between abutment/fixture before/after sintering demonstrated no statistically significant difference. Contact between abutment/fixture was most common at the top area of the fixture. A slight decrease of microhardness and contamination of porcelain particles immediately below the veneered part were found on the Y-TZP abutment after sintering. The sintering process did not affect the precision of fit.
Full Text Available Background and Aims: In response to esthetic demand and use of zirconia abutments; detection of implant-abutment connection misfit is so important. The purpose of this study was to evaluate the sensitivity and specificity of radiographic images in the detection of abutment-implant connection misfit in zirconia and titanium abutments of three different implant connections. Materials and Methods: One regular implant fixture of Branemark, Noble active and Replace systems were mount in acrylic models. Two pieces titanium and zirconium abutments were attached to the implants, once with correct adaptation and once with 0.5 mm spacer. Digital radiographic images were taken of 12 created states with zero degree vertical and horizontal inclination and evaluated by 10 specialists in implant treatment in two different time penods. Data were analyzed using Kappa analysis. Results: Interclass Correlation Coefficients (ICC of the agreement of answers in the first and second times were 97.4 and 97.5, respectively (P<0/001. Sensitivity of detecting gap in all groups was acceptable (95-100% except titanium abutment in Noble active which was the lowest value (35%. Specificity of all groups were acceptable (80-95% except zirconia abutments in Noble active and Replace with 45% and 30% values, respectively, and titanium abutments in Branemark had the highest value (95%. Conclusion: The sensitivity of radiographic images in detection of abutment-implant connection misfit only in Noble active with titanium abutment was not acceptable. Specificity of radiographic images in the absence of gap in titanium abutments was more favorable.
Van Weehaeghe, Manú; De Bruyn, Hugo; Vandeweghe, Stefan
An angulation of the implant connection could overcome the problems related to angulated abutments. This study compares conventional implants with angulated abutment to tilted implants with an angulated connection. Twenty patients were treated in the edentulous mandible. In the posterior jaw locations, one conventional tilted implant with angulated abutment and one angulated implant without abutment were placed. In the anterior jaw, two conventional implants were placed, one with and one without abutment. Implants were immediately loaded and 3 months later, the final bridge (PFM or monolithic zirconia) was placed. After a follow-up of 48 months, 17 patients were available for clinical examination. The mean overall marginal bone loss (MBL) was 1.26 mm. No significant differences in implant survival, MBL, periodontal indices, patients' satisfaction, or complications was found between implants restored on abutment or implant level, between the posteriorly located angulated implant nor angulated abutment, and between both anterior implants with or without abutment. The posterior implants demonstrated less MBL compared to the anterior implants (P implants restored with zirconia or PFM bridges (P = .294). Overall mean pocket depth was 2.83 mm. More plaque was found in the PFM group compared to the full-zirconia group, at the bridge (P = .042) and the implants (P = .029). There was no difference between both materials in pocket depth (P = .635) or bleeding (P = .821). One zirconia bridge fractured, two angulated abutment were replaced and four loose bridge screws connected to the angulated abutments had to be tightened. Patients were overall satisfied (4.74/5). An implant with angulated connection may results in a stronger connection but does not affect the marginal bone loss. No difference in MBL was seen between implants restored on abutment or implant level. Zirconia seems to reduce the amount of plaque. © 2017 Wiley Periodicals, Inc.
Gil, Mindy S; Ishikawa-Nagai, Shigemi; Elani, Hawazin W; Da Silva, John D; Kim, David M; Tarnow, Dennis; Schulze-Späte, Ulrike; Bittner, Nurit
The purpose of this prospective, randomized, controlled, multicenter clinical study was to analyze the optical effects of an anodized pink colored implant shoulder/abutment system in the peri-implant mucosa of immediately placed dental implants. Forty subjects with a restoratively hopeless tooth in the maxillary esthetic zone, were recruited and randomized to receive either a pink-neck implant, or a conventional gray implant. All patients received an immediate implant and immediate provisional and two identical CAD/CAM titanium abutments with different surface colors: pink and gray, and one zirconia all-ceramic crown. The color of the peri-implant mucosa was measured using a dental spectrophotometer and analyzed using CIELAB color system. The overall color difference between the peri-implant mucosa with a pink abutment and a gray abutment was ΔE = 4.22. Patients with gray implants presented a color change of ΔE = 3.86-4.17 with this abutment change, while patients with pink implants had a color change of ΔE = 3.84-4.69. The peri-implant mucosa with a pink abutment was significantly more red when compared with a gray abutment (P ≤ .01). When a pink abutment was used, there is a significant color change of the peri-implant mucosa that is above the detectable color threshold. Esthetic outcomes are important for the success of implant treatment of maxillary anterior implants. The phenomenon of the gray color of a dental implant and abutment shining through the peri-implant mucosa has been documented in the literature. The objective of this study was to assess the optical effect of an anodized pink-neck implant and a pink abutment on the color of peri-implant mucosa. This study demonstrates that using pink-neck implant and a pink abutment would contribute positively to the overall esthetic outcome for an anterior implant. © 2017 Wiley Periodicals, Inc.
Yuheng, Song; Hao, Yan
The technology of image segmentation is widely used in medical image processing, face recognition pedestrian detection, etc. The current image segmentation techniques include region-based segmentation, edge detection segmentation, segmentation based on clustering, segmentation based on weakly-supervised learning in CNN, etc. This paper analyzes and summarizes these algorithms of image segmentation, and compares the advantages and disadvantages of different algorithms. Finally, we make a predi...
Conclusion: Results from this study showed the platform switched abutment led to relative decrease in von Mises stress in transcortical section of bone compared to normal abutment under vertical and oblique forces in posterior mandible region.
Correia, André Ricardo Maia; da Silva Lobo, Fábio Daniel; Miranda, Mónica Célia Pereira; Framegas de Araújo, Filipe Miguel Soares; Santos Marques, Tiago Miguel
The purpose of this study was to evaluate whether the use of removable partial dentures affects the periodontal status of abutment teeth. An observational cross-sectional study was done on a sample of patients rehabilitated with removable partial dentures (2010 to 2013). At a recall appointment, a clinical examination was done to collect data related to the rehabilitation and periodontal status of the abutment teeth. Of 145 invited patients, 54 attended the requested follow-up appointment (37.2%). Mean patient age was 59.1 years, and the study population was 42.6% male and 57.4% female. The mean follow-up time for the prosthesis was 26 months. Abutment teeth had higher values in all periodontal variables (P removable partial dentures is affected by these rehabilitations. A recall program for these patients involving removable prosthodontics and periodontology appointments is mandatory.
Ortiz-Puigpelat, Octavi; Gargallo-Albiol, Jordi; Hernández-Alfaro, Federico; Cabratosa-Termes, Josep
The purpose of this retrospective case series was to report on the clinical performance of implant-assisted removable partial dentures (IARPDs) with Locator abutments in different partial edentulism situations, with a mean follow-up period of 28.6 months. Twelve consecutive patients were treated with IARPDs. A total of 24 implants were placed in the edentulous area. Minimum follow-up period was 12 months. Overall patient satisfaction, health of peri-implant tissues, survival of implants and abutments, and prosthetic complications were reported. Overall implant survival was 91.6%; two implants failed. No major complications were reported-only one IARPD metal framework broke. No Locator abutment loosening was reported. Within the limitations of this retrospective study, treatment with IARPDs can improve the patient's function, phonetics, and esthetics without the need for extensive bone regeneration surgeries and prosthodontic rehabilitations. However, well-designed prospective clinical studies on IARPDs are needed to support their long-term use.
Karunagaran, Sanjay; Markose, Sony; Paprocki, Gregory; Wicks, Russell
With an increase in the availability of implant restorative components, the selection of an appropriate implant abutment for a given clinical situation has become more challenging. This article describes a systematic protocol to help the practitioner more thoughtfully select abutments for single and multiple unit fixed implant prostheses. The article examines the evaluation, planning, design, and fabrication processes for the definitive restoration. It includes an assessment of a variety of factors, namely restorative space, soft and hard tissues, the location of the implant platform, the type of platform connection, platform switching indications, tissue collar heights, emergence profile, implant angulation, and finally the design and esthetic options for the final implant abutment. © 2014 by the American College of Prosthodontists.
Larrucea, Carlos; Conrado, Aparicio; Olivares, Denise; Padilla, Carlos; Barrera, Andrea; Lobos, Olga
In implant rehabilitation, a microspace is created at the abutment-implant interface (AII). Previous research has shown that oral microbiome can proliferate in this microspace and affect periimplant tissues, causing inflammation in peri-implant tissues. Preventing microbial leakages through the AII is therefore an important goal in implantology. To determine the presence of marginal bacterial microleakage at the AII according to the torque applied to the prosthetic implant in vitro. Twenty-five Ticare Inhex internal conical implants (MG Mozo-Grau, Valladolid, España) were connected to a prosthetic abutment using torques of implant adjustment as determined by micro-CT. The different torques applied to the abutment-implant system condition the bacterial leakage at the implant interface. No microleakage was observed at 20 and 30 N. © 2018 Wiley Periodicals, Inc.
Nader, Nabih; Aboulhosn, Maissa; Berberi, Antoine; Manal, Cordahi; Younes, Ronald
The periimplant bone level has been used as one of the criteria to assess the success of dental implants. It has been documented that the bone supporting two-piece implants undergoes resorption first following the second-stage surgery and later on further to abutment connection and delivery of the final prosthesis. The aim of this multicentric randomized clinical trial was to evaluate the crestal bone resorption around internal connection dental implants using a new surgical protocol that aims to respect the biological distance, relying on the benefit of a friction fit connection abutment (test group) compared with implants receiving conventional healing abutments at second-stage surgery (control group). A total of partially edentulous patients were consecutively treated at two private clinics, with two adjacent two-stage implants. Three months after the first surgery, one of the implants was randomly allocated to the control group and was uncovered using a healing abutment, while the other implant received a standard final abutment and was seated and tightened to 30 Ncm. At each step of the prosthetic try-in, the abutment in the test group was removed and then retightened to 30 Ncm. Horizontal bone changes were assessed using periapical radiographs immediately after implant placement and at 3 (second-stage surgery), 6, 9 and 12 months follow-up examinations. At 12 months follow-up, no implant failure was reported in both groups. In the control group, the mean periimplant bone resorption was 0.249 ± 0.362 at M3, 0.773 ± 0.413 at M6, 0.904 ± 0.36 at M9 and 1.047 ± 0.395 at M12. The test group revealed a statistically significant lower marginal bone loss of 20.88% at M3 (0.197 ± 0.262), 22.25% at M6 (0.601 ± 0.386), 24.23% at M9 (0.685 ± 0.341) and 19.2% at M9 (0.846 ± 0.454). The results revealed that bone loss increased over time, with the greatest change in bone loss occurring between 3 and 6 months. Alveolar bone loss was significantly greater in the
Galvão, Gustavo Holtz; Grossi, João Almeida; Zielak, João César; Giovanini, Allan Fernando; Furuse, Adilson Yoshio; Gonzaga, Carla Castiglia
This study aimed to compare, through photoelastic analysis, the distribution of stresses around narrow implants with external hexagon (EH) and Morse taper (MT) connections, when single crowns made with metal and ceramic abutments were used. Six photoelastic models were prepared, simulating the use of narrow EH and MT implants replacing a lateral incisor. These 2 groups received 3 different abutments: prefabricated metal abutments, customized metal abutments, and customized zirconia abutments. All crowns were identical and made with a leucite reinforced glass-ceramic. Vertical loads of 0 to 100 N were applied on the palatal surface of the crowns, and the photoelastic stress fringes developed in each model were captured in a high-definition video, and digital photographs were taken at 100 N. The abutment type and material influenced the stress distribution patterns around narrow implants with EH and MT connections. Stresses were generated mainly around the apical and lingual regions of the implants. For both connections, the prefabricated metal abutments presented better stress distribution around the implants when compared to customized metal and zirconia abutments because low stress levels were developed in smaller areas around the implants.
Neelima Sreekumar Menon; G P Surendra Kumar; K R Jnanadev; C L Satish Babu; Shilpa Shetty
Aim: The purpose of this in vitro study was to assess and compare the retention of zirconia copings luted with different luting agents onto zirconia and titanium abutments. Materials and Methods: Titanium and zirconia abutments were torqued at 35 N/cm onto implant analogs. The samples were divided into two groups: Group A consisted of four titanium abutments and 32 zirconia copings and Group B consisted of four zirconia abutments and 32 zirconia copings and four luting agents were used. T...
Full Text Available An impression technique called optical impression using intraoral scanner has attracted attention in digital dentistry. This study aimed to evaluate the accuracy of the optical impression, comparing a virtual model reproduced by an intraoral scanner to a working cast made by conventional silicone impression technique. Two implants were placed on a master model. Working casts made of plaster were fabricated from the master model by silicone impression. The distance between the ball abutments and the angulation between the healing abutments of 5 mm and 7 mm height at master model were measured using Computer Numerical Control Coordinate Measuring Machine (CNCCMM as control. Working casts were then measured using CNCCMM, and virtual models via stereo lithography data of master model were measured by a three-dimensional analyzing software. The distance between ball abutments of the master model was 9634.9 ± 1.2 μm. The mean values of trueness of the Lava COS and working casts were 64.5 μm and 22.5 μm, respectively, greater than that of control. The mean of precision values of the Lava COS and working casts were 15.6 μm and 13.5 μm, respectively. In the case of a 5-mm-height healing abutment, mean angulation error of the Lava COS was greater than that of the working cast, resulting in significant differences in trueness and precision. However, in the case of a 7-mm-height abutment, mean angulation errors of the Lava COS and the working cast were not significantly different in trueness and precision. Therefore, distance errors of the optical impression were slightly greater than those of conventional impression. Moreover, the trueness and precision of angulation error could be improved in the optical impression using longer healing abutments. In the near future, the development of information technology could enable improvement in the accuracy of the optical impression with intraoral scanners.
Odaira, Chikayuki; Kobayashi, Takuya; Kondo, Hisatomo
An impression technique called optical impression using intraoral scanner has attracted attention in digital dentistry. This study aimed to evaluate the accuracy of the optical impression, comparing a virtual model reproduced by an intraoral scanner to a working cast made by conventional silicone impression technique. Two implants were placed on a master model. Working casts made of plaster were fabricated from the master model by silicone impression. The distance between the ball abutments and the angulation between the healing abutments of 5 mm and 7 mm height at master model were measured using Computer Numerical Control Coordinate Measuring Machine (CNCCMM) as control. Working casts were then measured using CNCCMM, and virtual models via stereo lithography data of master model were measured by a three-dimensional analyzing software. The distance between ball abutments of the master model was 9634.9 ± 1.2 μm. The mean values of trueness of the Lava COS and working casts were 64.5 μm and 22.5 μm, respectively, greater than that of control. The mean of precision values of the Lava COS and working casts were 15.6 μm and 13.5 μm, respectively. In the case of a 5-mm-height healing abutment, mean angulation error of the Lava COS was greater than that of the working cast, resulting in significant differences in trueness and precision. However, in the case of a 7-mm-height abutment, mean angulation errors of the Lava COS and the working cast were not significantly different in trueness and precision. Therefore, distance errors of the optical impression were slightly greater than those of conventional impression. Moreover, the trueness and precision of angulation error could be improved in the optical impression using longer healing abutments. In the near future, the development of information technology could enable improvement in the accuracy of the optical impression with intraoral scanners. PMID:27706225
Cooper, Lyndon F; Stanford, Clark; Feine, Jocelyne; McGuire, Michael
Single-tooth implant restorations are commonly used to replace anterior maxillary teeth. The esthetic, functional, and biologic outcomes are, in part, a function of the abutment and crown. The purpose of this clinical study was to describe the implant, abutment, and crown survival and complication rates for CAD/CAM zirconia abutment and lithium disilicate crown restorations for single-tooth implants. As part of a broader prospective investigation that enrolled and treated 141 participants comparing tissue responses at the conical interface (CI; AstraTech OsseoSpeed), flat-to-flat interface (FI; NobelSpeedy), and platform-switch interface (PS; NanoTite Certain Prevail) of single-tooth implants, computer-aided design and computer-aided manufacturing (CAD/CAM) zirconia abutments (ATLANTIS Abutment) and cemented lithium disilicate (e.max) crowns were used in the restoration of all implants. After 2.4 years in function (3 years after implant placement), the implant, abutment, and crown of 110 participants were evaluated. Technical and biologic complications were recorded. Demographic results were tabulated as percentages with mean values and standard deviations. Abutment survival was calculated with the Kaplan-Meier method. After 2.4 years, no abutments or crowns had been lost. Abutment complications (screw loosening, screw fracture, fracture) were absent for all 3 implant groups. Crown complications were limited to 2 crowns debonding and 1 with excess cement (2.5%). Five biological complications (4.0%) were recorded. The overall complication rate was 6.5%. CAD/CAM zirconia abutments restored with cemented lithium disilicate crowns demonstrated high survival on 3 different implant-abutment interface designs. No abutment or abutment screw fracture occurred. The technical complications observed after 2.4 years were minor and reversible. The use of CAD/CAM zirconia abutments with cemented lithium disilicate crowns is associated with high technical and biologic success at 2
Alsiyabi, Abdullah S; Felton, David A; Cooper, Lyndon F
A critical factor that needs to be evaluated during the diagnosis and treatment planning phase for patients seeking an implant-tissue-supported overdenture or metal-resin implant fixed denture is the presence of adequate interarch distance. The amount of interarch distance is critical to the selection of appropriate implant abutments and attachments for both implant-tissue-supported overdentures and metal-resin implant fixed complete dentures. This clinical report describes a patient with complications related to the failure to diagnose inadequate interarch distance, and the methods used to resolve the patient's chief complaint. A guide for abutment-attachment selection using one commercially available implant system is given.
Papavassiliou, Harris; Kourtis, Stefanos; Katerelou, Julia; Chronopoulos, Vasillios
The detection of marginal gaps at the implant-abutment interface is a common clinical task in prosthodontic treatment. For the detection of the gap intraorally, especially under thick soft tissues the most common method is dental radiography. The objective of this experimental study was to investigate the accuracy of conservative dental radiography to detect marginal gaps at the implant-abutment interface. For these reasons radiographs were taken on internal and external hex implants with different experimental gaps and inclinations. The abutment (with a space created by plastic sheets 0.5 and 0.2 mm in thickness) was screwed on the implant, and the implant was placed into a box filled with silicone impression material. The X-ray film was placed parallel to the implant at the back of the box, the borders of the box were marked to the base and the box. A ruler of 10 cm was fixed at a long X-ray tube to ensure parallelism to the implant, X-ray film. Sets of radiographs were made at 0 degrees, 5 degrees, 10 degrees, 15 degrees, 20 degrees, 25 degrees, 30 degrees (to the abutment) and -5 degrees, -10 degrees, -15 degrees, -20 degrees, -25 degrees, -30 degrees (to the implant) degrees. The X-ray images were observed with visual examination, under magnification, and in higher magnification in a slide projector. The phenomenal and the true gap at the implant-abutment interface were calculated in order to determine the distortion. There were significant differences between the internal and external hex implants because of the different morphology of the implants. The detecting ability to diagnose a gap at the implant-abutment interface varied significantly with the angulation degree of the X-ray tube. At inclinations to the implant (- inclination) the gap diminished earlier than those inclinations to the prosthetic abutment (+ inclinations). In all examinations the gap was not detectable at angulations higher than 20 degrees. In visual examination at 25 degrees and 30
Yeung, Stephanie; Chee, Winston W L; Torbati, Arman
A clinical report is presented that describes the restoration of a severe anterior maxillary ridge defect and pneumatized sinuses with a rotation-path partial removable dental prosthesis and implant-supported abutments. Other treatment options were considered and rejected based on patient preferences and limitations, which included avoiding invasive surgeries. The principles of integrating fixed and removable prosthesis design were applied. However, the clasp design was modified to take into account the direct bone-to-implant contact of the abutments. An esthetic and functional outcome was obtained without any overly invasive surgery. Copyright © 2014 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.
Baker, Shaun; Centric, Aaron; Chennupati, Sri Kiran
Bone-anchored hearing devices are an accepted treatment option for hearing restoration in various types of hearing loss. Traditional devices have a percutaneous abutment for attachment of the sound processor that contributes to a high complication rate. Previously, our institution reported on the Sophono (Boulder, CO, USA) abutment-free system that produced similar audiologic results to devices with abutments. Recently, Cochlear Americas (Centennial, CO, USA) released an abutment-free bone-anchored hearing device, the BAHA Attract. In contrast to the Sophono implant, the BAHA Attract utilizes an osseointegrated implant. This study aims to demonstrate patient benefit abutment-free devices, compare the results of the two abutment-free devices, and examine complication rates. A retrospective chart review was conducted for the first eleven Sophono implanted patients and for the first six patients implanted with the BAHA Attract at our institution. Subsequently, we analyzed patient demographics, audiometric data, clinical course and outcomes. Average improvement for the BAHA Attract in pure-tone average (PTA) and speech reception threshold (SRT) was 41dB hearing level (dBHL) and 56dBHL, respectively. Considering all frequencies, the BAHA Attract mean improvement was 39dBHL (range 32-45dBHL). The Sophono average improvement in PTA and SRT was 38dBHL and 39dBHL, respectively. The mean improvement with Sophono for all frequencies was 34dBHL (range 24-43dBHL). Significant improvements in both pure-tone averages and speech reception threshold for both devices were achieved. In direct comparison of the two separate devices using the chi-square test, the PTA and SRT data between the two devices do not show a statistically significant difference (p-value 0.68 and 0.56, respectively). The complication rate for these abutment-free devices is lower than that of those featuring the transcutaneous abutment, although more studies are needed to further assess this potential advantage
This rare case report describes prosthodontic complications resulting from a dental implant was placed surgically more distally in the area of the missing mandibular first molar with a cantilever effect and a crest width of >12 mm in a 59-year-old patient who had a history of bruxism. Fracture of abutment is a common complication in implant was placed in area with high occlusal forces. Inability to remove the broken abutment may most often end up in discarding the implant. Adding one more dental implant mesially to the previously placed implant, improvisation of technique to remove the broken abutment without sacrificing the osseointegrated dental implant, fabrication with cemented custom-made abutment to replace the broken abutment for the first implant, and the use of the two implants to replace a single molar restoration proved reliable and logical treatment solutions to avoid these prosthodontic complications.
Full Text Available This rare case report describes prosthodontic complications resulting from a dental implant was placed surgically more distally in the area of the missing mandibular first molar with a cantilever effect and a crest width of >12 mm in a 59-year-old patient who had a history of bruxism. Fracture of abutment is a common complication in implant was placed in area with high occlusal forces. Inability to remove the broken abutment may most often end up in discarding the implant. Adding one more dental implant mesially to the previously placed implant, improvisation of technique to remove the broken abutment without sacrificing the osseointegrated dental implant, fabrication with cemented custom-made abutment to replace the broken abutment for the first implant, and the use of the two implants to replace a single molar restoration proved reliable and logical treatment solutions to avoid these prosthodontic complications.
Mao, Zhihong; Yi, Dake; Cao, Guo
The purpose of this study is to discuss the influence of sizes of abutments and fixation screws on immediately loaded dental implants in mandibular bones using nonlinear finite element methods. Abutments with three unilateral wall thicknesses and fixation screws with three diameters are analyzed to compare the stresses and deformations under a vertical or oblique force of 130 N. The nonlinearity due to friction contacts between the fixation screw, the abutment, the implant, and the bone is taken into account. The results showed that improper sizes of abutments and fixation screws would increase the stress and deformation of the dental implant system. If possible, the diameter of fixation screw should not be smaller than Φ1.0 mm, the diameter between Φ1.0 mm and Φ1.2 mm is acceptable. The fixation screw diameter preferably exceeds Φ1.4 mm. The unilateral wall thickness >0.5 mm is optimal selection for abutments.
Basílio, Mariana de Almeida; Abi-Rached, Filipe de Oliveira; Butignon, Luis Eduardo; Arioli Filho, João Neudenir
To evaluate the effectiveness of abutment screws coated with liquid Vaseline on the screw-joint stability of yttria-stabilized tetragonal zirconia (Y-TZP) abutment systems. Forty Y-TZP prefabricated abutments, 20 Neodent and 20 Bionnovation, were tightened to 20 Ncm on their respective external hexagon implants, and divided into four groups (n = 10) according to the screws: coated with Vaseline or uncoated. The removal torque (RT) value of the abutment screw was measured before and after loading. A cyclic loading (0.5 × 10 6 cycles; 15 Hz) between 11 and 211 N was applied. Means were compared using a repeated-measures ANOVA (α = 0.05). There was no significant difference between coated and uncoated screws (p = 0.822). Significant differences were found between the abutment systems (p implant restorations. © 2016 by the American College of Prosthodontists.
Chu, Chun-Ming; Huang, Heng-Li; Hsu, Jui-Ting; Fuh, Lih-Jyh
The aim of this study is to determine the effects of various designs of internal tapered abutment joints on the stress induced in peri-implant crestal bone by using the three-dimensional finite element method and statistical analyses. Thirty-six models with various internal tapered abutment-implant interface designs including different abutment diameters (3.0, 3.5, and 4.0 mm), connection depths (4, 6, and 8 mm), and tapers (2°, 4°, 6°, and 8°) were constructed. A force of 170 N was applied to the top surface of the abutment either vertically or 45° obliquely. The maximum von Mises bone-stress values in the crestal bone surrounding the implant were statistically analyzed using analysis of variance. In addition, patterns of bone stress around the implant were examined. The results demonstrate that a smaller abutment diameter and a longer abutment connection significantly reduced the bone stresses (P implant interfaced connection was more parallel, bone stresses under vertical loading were less (P = 0.0002), whereas the abutment taper did not show significant effects on bone stresses under oblique loading (P = 0.83). Bone stresses were mainly influenced by the abutment diameter, followed by the abutment connection depth and the abutment taper. For an internal tapered abutment design, it was suggested that a narrower and deeper abutment-implant interface produced the biomechanical advantage of reducing the stress concentration in the crestal region around an implant.
Lops, Diego; Bressan, Eriberto; Chiapasco, Matteo; Rossi, Alessandro; Romeo, Eugenio
To verify, in a medium-term follow-up, whether or not zirconia (Zr) abutments show similar survival outcomes as titanium (Ti) abutments in posterior areas. A two-stage surgical protocol was used. Each patient was followed for 5 years after the definitive prosthesis insertion. Clinical and radiographic parameters were assessed at the yearly follow-up visit, and prosthetic complications were recorded. Statistical analysis (Wilcoxon signed rank test) was used to compare any difference in biologic and radiographic parameters between implants and the natural contralateral teeth. Descriptive statistics were used to analyze the changes over time (from baseline to the last follow-up) of clinical and radiographic parameters. A total of 85 patients with a single posterior tooth gap were treated with 85 implants supporting 47 Ti and 38 Zr abutments, respectively. All-ceramic (38) and metal-ceramic (47) single crowns were fabricated. Four patients were classified as dropouts. Eighty-one implants supporting 44 Ti and 37 Zr abutments completed the 5-year follow-up examination. No implant, reconstruction, or abutment failures were recorded. Therefore, the prosthetic survival after 5 years of function was 100% for all the abutments and restorations. No significant differences in biologic and radiographic indexes were found between Ti and Zr abutments when compared with each other and with the natural teeth after 5 years. No significant marginal bone loss was found between the baseline and the last follow-up, both for Zr and Ti abutments. The medium-term survival of Zr abutments in posterior regions was comparable with that of Ti abutments. Long-term evaluations are needed to confirm this finding.
Vechiato-Filho, Aljomar José; Pesqueira, Aldiéris Alves; De Souza, Grace M; dos Santos, Daniela Micheline; Pellizzer, Eduardo Piza; Goiato, Marcelo Coelho
This systematic review aimed to evaluate whether the survival rate and predictability of zirconia abutments are similar to those of titanium abutments for single implant crowns in the posterior area. A systematic search of two databases (Medline/PubMed and Cochrane Library) was performed by two independent reviewers for articles published between January 2004 and July 2014. The electronic search was complemented by a hand search of the following journals from the same period: Journal of Periodontology, Clinical Oral Implants Research, International Journal of Prosthodontics, and International Journal of Oral and Maxillofacial Implants. Studies included were published in English, evaluated single implant crowns, and performed a mean observation ≥ 1 year. Any disagreement between the reviewers was solved by means of a discussion. Forest plot and funnel were used to compare zirconia and titanium abutments. The search strategy identified 669 studies. Of these, 11 studies were included and only 6 studies were selected for meta-analysis. The pooled results for fixed implant single crowns in posterior areas showed a 5-year success rate of 99.3% for zirconia abutments and 99.57% for titanium abutments. There was no statistical difference regarding veneer failure (P = .26). The pooled results of these studies showed that the mean bone loss was 0.38 ± 0.87 mm for zirconia and 0.2 ± 0.13 mm for titanium abutments. The use of zirconia abutments for single implant-fixed crowns in posterior regions is questionable due to the absence of long-term data. The short-term results of zirconia abutments regarding mechanical and biologic responses are similar to titanium abutments. Caution when using zirconia abutments in posterior regions is necessary until further clinical evidence shows favorable long-term results.
Quaresma, Sergio E T; Cury, Patricia R; Sendyk, Wilson R; Sendyk, Claudio
This study evaluates the influence of 2 commercially available dental implant systems on stress distribution in the prosthesis, abutment, implant, and supporting alveolar bone under simulated occlusal forces, employing a finite element analysis. The implants and abutments evaluated consisted of a stepped cylinder implant connected to a screw-retained, internal, hexagonal abutment (system 1) and a conical implant connected to a solid, internal, conical abutment (system 2). A porcelain-covered, silver-palladium alloy was used as a crown. In each case, a simulated, 100-N vertical load was applied to the buccal cusp. A finite element model was created based on the physical properties of each component, and the values of the von Mises stresses generated in the prosthesis, abutment, implant, and supporting alveolar bone were calculated. In the prostheses, the maximum von Mises stresses were concentrated at the points of load application in both systems, and they were greater in system 1 (148 N/mm2) than in system 2 (55 N/mm2). Stress was greater on the abutment of system 2 than of system 1 on both the buccal (342 N/mm2 x 294 N/mm2) and lingual (294 N/mm2 x 148 N/ mm2) faces. Stress in the cortical, alveolar bone crest was greater in system 1 than in system 2 (buccal: 99.5 N/mm2 x 55 N/mm2, lingual: 55 N/mm2 x 24.5 N/mm2, respectively). Within the limits of this investigation, the stepped cylinder implant connected to a screw-retained, internal hexagonal abutment produces greater stresses on the alveolar bone and prosthesis and lower stresses on the abutment complex. In contrast, the conical implant connected to a solid, internal, conical abutment furnishes lower stresses on the alveolar bone and prosthesis and greater stresses on the abutment.
Maule, R. William
Discusses prototype information infrastructure projects in northern California's Silicon Valley. The strategies of the public and private telecommunications carriers vying for backbone services and industries developing end-user infrastructure technologies via office networks, set-top box networks, Internet multimedia, and "smart homes"…
Dr. Duc Vugia, chief of the Infectious Diseases Branch in the California Department of Public Health, discusses Valley Fever. Created: 2/4/2014 by National Center for Emerging and Zoonotic Infectious Diseases (NCEZID). Date Released: 2/5/2014.
Harder, Sönke; Dimaczek, Birka; Açil, Yaha; Terheyden, Hendrik; Freitag-Wolf, Sandra; Kern, Matthias
Microleakage has been discussed as a major contributing factor for inflammatory reactions at the implant-abutment connection. In previous studies, the tightness against corpuscular bodies (viable bacteria) has been successfully investigated under static and dynamic conditions. The aim of this study was to investigate the tightness against endotoxins of two implant systems (AstraTech and Ankylos) with conical internal connections under static conditions. The inner parts of eight implants of each system were inoculated with endotoxin. Implants were screwed together with the respective abutments and stored under isostatic conditions in a supernatant of pyrogen-free water for 168 h. Supernatant samples were taken after 5 min, 24 h, 72 h, and 168 h, and endotoxin contamination was determined by the amebocyte-lysate test. Only one implant in the AstraTech group showed no sign of endotoxin contamination after 168 h, while the other implants showed contamination after varying storage times, respectively. The implants in the Ankylos group showed endotoxin contamination after only 5 min of storage in the supernatant solution. The tested internal conical implant-abutment connections appear to be unable to prevent endotoxin leakage. In average, Astra implants showed a higher tightness than Ankylos implants.
Medved, Mario; Truyen, Roel; Likar, Bostjan; Pernus, Franjo
Segmentation of colon CT images is the main factor that inhibits automation of virtual colonoscopy. There are two main reasons that make efficient colon segmentation difficult. First, besides the colon, the small bowel, lungs, and stomach are also gas-filled organs in the abdomen. Second, peristalsis or residual feces often obstruct the colon, so that it consists of multiple gas-filled segments. In virtual colonoscopy, it is very useful to automatically connect the centerlines of these segments into a single colon centerline. Unfortunately, in some cases this is a difficult task. In this study a novel method for automated colon segmentation and connection of colon segments' centerlines is proposed. The method successfully combines features of segments, such as centerline and thickness, with information on main colon segments. The results on twenty colon cases show that the method performs well in cases of small obstructions of the colon. Larger obstructions are mostly also resolved properly, especially if they do not appear in the sigmoid part of the colon. Obstructions in the sigmoid part of the colon sometimes cause improper classification of the small bowel segments. If a segment is too small, it is classified as the small bowel segment. However, such misclassifications have little impact on colon analysis.
Tselios, Nikolaos; Parel, Stephen M; Jones, John D
A patient underwent immediate implant placement and immediate provisional restoration with nonocclusal loading in the right central incisor area. A provisional custom abutment and a cemented provisional restoration were fabricated. At the impression appointment, an implant level impression was made and the provisional abutment was scanned for fabrication of the definitive custom abutment. This clinical report describes how CAD/CAM technology can facilitate the definitive restoration of immediately placed and loaded implants by allowing the fabrication of the definitive abutment as an exact duplicate of the provisional abutment.
Cançado Oliveira, Bruno Fernando; Valerio, Claudia Scigliano; Jansen, Wellington Corrêa; Zenóbio, Elton Gonçalves; Manzi, Flávio Ricardo
Misfit is a risk factor for rehabilitation with implants, and its detection is of fundamental importance to the success of treatment with implants. The use of appropriate radiographic imaging is key for a good prognosis. The aim of this study was to compare the efficacy of film and digital radiographs for the detection of misfit at the implant-abutment interface. Digital and conventional (manual and automatic processing) radiography was performed in seven test specimens, each one with a different vertical misfit between the abutment and the platform of the implant. Scanning electron microscopy was used to confirm the misfit and to measure it. Five dental radiologists independently and blindly evaluated the images. Cohen's kappa with linear weighting was calculated to determine interexaminer and intraexaminer concordance. Statistical analyses were performed using the Cochran's Q test and the receiver operating characteristic curve (ROC). Interexaminer analysis showed that the kappa value was equal to 0.74, whereas the average kappa value in the intraexaminer evaluation was 0.90. Digital imaging showed the largest area on the ROC graph, and conventional images with manual processing showed the smallest area. The images obtained through conventional radiography with both manual and automatic processing showed statistically significant differences from the measurement of the gold standard (P < .05). Digital imaging can be used to evaluate misfit at the implant-abutment interface. Conventional systems of radiographic imaging do not provide sufficient information to evaluate misfit at the implant-abutment interface.
Passos, Sheila Pestana; May, Liliana Gressler; Faria, Renata; Ozcan, Mutlu; Bottino, Marco Antonio
Microorganisms from the oral cavity may settle at the implant-abutment interface (IAI). As a result, tissue inflammation could occur around these structures. The databases MEDLINE/PubMed and PubMed Central were used to identify articles published from 1981 through 2012 related to the microbial
van Brakel, Ralph; Noordmans, Herke Jan; Frenken, Joost; de Roode, Rowland; de Wit, Gerard C.; Cune, Marco S.
Objectives: To determine the difference in light reflection of oral mucosa covering titanium (Ti) or zirconia (ZrO2) abutments as it relates to the thickness of the covering mucosa. Material and methods: Fifteen anterior implants (Astra Osseo speed (R)) in 11 patients were fitted with a Ti or a ZrO2
Streckbein, P; Streckbein, R G; Wilbrand, J F; Malik, C Y; Schaaf, H; Howaldt, H P; Flach, M
Micro-gaps and osseous overload in the implant-abutment connection are the most common causes of peri-implant bone resorption and implant failure. These undesirable events can be visualized on standardized three-dimensional finite element models and by radiographic methods. The present study investigated the influence of 7 available implant systems (Ankylos, Astra, Bego, Brånemark, Camlog, Straumann, and Xive) with different implant-abutment connections on bone overload and the appearance of micro-gaps in vitro. The individual geometries of the implants were transferred to three-dimensional finite element models. In a non-linear analysis considering the pre-loading of the occlusion screw, friction between the implant and abutment, the influence of the cone angle on bone strain, and the appearance of micro-gaps were determined. Increased bone strains were correlated with small (Ankylos) or a smaller cone angle (Bego). The results of our in silico study provide a solid basis for the reduction of peri-implant bone strain and micro-gaps in the implant-abutment connection to improve long-term stability.
Full Text Available The time-dependent behavior of the left bank abutment slope at Jinping I hydropower station has a major influence on the normal operation and long-term safety of the hydropower station. To solve this problem, a geomechanical model containing various faults and weak structural planes is established, and numerical simulation is conducted under normal water load condition using FLAC3D, incorporating creep model proposed based on thermodynamics with internal state variables theory. The creep deformations of the left bank abutment slope are obtained, and the changes of principal stresses and deformations of the dam body are analyzed. The long-term stability of the left bank abutment slope is evaluated according to the integral curves of energy dissipation rate in domain and its derivative with respect to time, and the non-equilibrium evolution rules and the characteristic time can also be determined using these curves. Numerical results show that the left bank abutment slope tends to be stable in a global sense, and the stress concentration is released. It is also indicated that more attention should be paid to some weak regions within the slope in the long-term deformation process.
Patil, Ratnadeep; den Hartog, Laurens; Dilbaghi, Anjali; de Jong, Bart; Kerdijk, Wouter; Cune, Marco S.
Objective: To evaluate the influence of abutment geometry on papillary fill in the esthetic zone in a delayed crown protocol. Materials and methods: Twenty-six subjects received two non-adjacent endosseous implants in the esthetic zone. Functional temporary crowns were installed 17-19 weeks later,
Patil, Ratnadeep C.; den Hartog, Laurens; van Heereveld, Christiaan; Jagdale, Aditi; Dilbaghi, Anjali; Cune, Marco S.
PURPOSE: To assess the response of soft tissues around two different abutment designs in healed sites in the esthetic zone. MATERIALS AND METHODS: Twenty-six subjects received two endosseous implants in healed, bilateral implant sites in the esthetic zone in the maxilla or the mandible. After 17 to
Full Text Available This paper aims to evaluate the impact interaction between the abutment and the girder subjected to nonuniform seismic excitation. An impact model based on tests is presented by taking material properties of the backfill of the abutment into consideration. The conditional simulation is performed to investigate the spatial variation of earthquake ground motions. A two-span continuous steel box girder bridge is taken as the example to analyze and assess the pounding interaction between the abutment and the girder. The detailed nonlinear finite element (FE model is established and the steel girder and the reinforced concrete piers are modeled by nonlinear fiber elements. The pounding element of the abutment is simulated by using a trilinear compression gap element. The elastic-perfectly plastic element is used to model the nonlinear rubber bearings. The comparisons of the pounding forces, the shear forces of the nonlinear bearings, the moments of reinforced concrete piers, and the axial pounding stresses of the steel girder are studied. The made observations indicate that the nonuniform excitation for multisupport bridge is imperative in the analysis and evaluation of the pounding effects of the bridges.
Bacchi, Atais; Regalin, Alexandre; Bhering, Claudia Lopes Brilhante; Alessandretti, Rodrigo; Spazzin, Aloisio Oro
The purpose of this study was to evaluate the influence of tightening technique and the screw coating on the loosening torque of screws used for Universal Abutment fixation after cyclic loading. Forty implants (Titamax Ti Cortical, HE, Neodent) (n=10) were submerged in acrylic resin and four tightening techniques for Universal Abutment fixation were evaluated: A - torque with 32 Ncm (control); B - torque with 32 Ncm holding the torque meter for 20 seconds; C - torque with 32 Ncm and retorque after 10 minutes; D - torque (32 Ncm) holding the torque meter for 20 seconds and retorque after 10 minutes as initially. Samples were divided into subgroups according to the screw used: conventional titanium screw or diamond like carbon-coated (DLC) screw. Metallic crowns were fabricated for each abutment. Samples were submitted to cyclic loading at 10(6) cycles and 130 N of force. Data were analyzed by two-way ANOVA and Tukey's test (5%). The tightening technique did not show significant influence on the loosening torque of screws (P=.509). Conventional titanium screws showed significant higher loosening torque values than DLC (P=.000). The use of conventional titanium screw is more important than the tightening techniques employed in this study to provide long-term stability to Universal Abutment screws.
Kurt, Murat; Güler, Ahmet Umut; Erkoçak, Ayça; Sanal, Fatma Ayşe
The aim of this technique report was to present a procedure for the fabrication of provisional restorations for ITI solid abutments using impression caps in the laboratory with a number of advantages over intraoral techniques. There may be no need for cementation, and elimination of cementation may assist tissue healing.
Conclusion: Misfit between the castable implant components can cause torque loss before and after cyclic loading. However, it is more appropriate to relate the results of this study to the screw loosening of the above mentioned abutments than judging their clinical performance.
Full Text Available This article describes a technique for repair of abutment tooth which fractured during removal of a provisional restoration before bisque trial. The technique uses plastic templates to fabricate new composite core foundation for the existing crowns. This technique helps the dentist to rebuild the core in a single appointment.
Raquel Rezende Martins de Barros
Full Text Available Aim: The presence of a microgap at the implant-abutment interface may permit bacterial contamination and lead to bone resorption, interfering with papillae formation. The present study evaluated adjacent implants with cement-retained abutments as an option to control such deleterious effects. Materials and methods Seven minipigs had their bilateral mandibular premolars previously extracted. After 8 weeks, four implants were installed in each hemi-mandible of each animal. The adjacent implants were randomly inserted on one side at the crestal bone level and on the other, 1.5 mm subcrestally. Immediately, a non-submerged healing and functional loading were provided with the abutments cementation and prostheses installation. Clinical examination and histomorphometry served to analyze the implant success. Results A total of 52 implants were evaluated at the end of the study. The subcrestal group achieved statistical better results when compared to the crestal group, clinically in papillae formation (1.97 x 1.57 mm and histomorphometrically in crestal bone remodeling (1.17 x 1.63 mm, bone density (52.39 x 45.22% and bone-implant contact (54.13 x 42.46%. Conclusion The subcrestal placement of cement-retained abutment implants showed better indexes of osseointegration and also improved papillae formation and crestal bone remodeling at the interimplant area after immediate loading, making them a promising option for the treatment of esthetic regions.
Centric, Aaron; Chennupati, Sri Kiran
Bone-anchored implantable hearing devices are widely accepted as a surgical option for certain types of hearing loss in both adults and children. Most commercially available devices involve a percutaneous abutment to which a sound processor attaches. The rate of complications with such bone conduction systems is greater than 20%. Most complications arise from the abutment. Recently, the Sophono (Boulder, CO) Alpha 1, an abutment-free system, has been introduced. We conducted a retrospective chart review of the first five patients who underwent implantation with the Sophono abutment-free bone conduction hearing system with the Alpha 1 processor at our institution and report here on these patients' pre- and postoperative audiometric data and clinical courses. Average improvement in pure-tone average was 32dB hearing loss and average improvement in speech response threshold was 28dB hearing loss. All patients were responding in the normal to mild hearing loss range in the operated ear after device activation. Average improvement across individual frequencies was between 17 and 37dB (SD 5.5-11dB). Our audiometric results to date are promising and have been consistent with published data on other bone-anchored hearing devices. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.
Full Text Available The borehole stress-meter was employed in this study to investigate the distribution of the side abutment stress in roadway subjected to dynamic pressure. The results demonstrate that the side abutment stress of the mining roadway reaches a peak value when the distance to the gob is 8 m and the distribution curve of the side abutment stress can be divided into three zones: stress rising zone, stress stabilizing zone, and stress decreasing zone. Further numerical investigation was carried out to study the effect of the coal mass strength, coal seam depth, immediate roof strength, and thickness on the distribution of the side abutment stress. Based on the research results, we determined the reasonable position of the mining roadway and the optimal width of the barrier pillar. The engineering application demonstrates that the retention of the barrier pillar with a width of 5 m along the gob as the haulage roadway for the next panel is feasible, which delivers favorable technological and economic benefits.
Samy, Abdallah M.; Peterson, A. Townsend; Hall, Matthew
Rift Valley Fever is an acute zoonotic viral disease caused by Rift Valley Fever virus (RVFV) that affects ruminants and humans in Sub-Saharan Africa and the Arabian Peninsula. We used phylogenetic analyses to understand the demographic history of RVFV populations, using sequence data from the three minigenomic segments of the virus. We used phylogeographic approaches to infer RVFV historical movement patterns across its geographic range, and to reconstruct transitions among host species. Res...
Liu, Yang; Wang, Jiawei
To review the influences and clinical implications of micro-gap and micro-motion of implant-abutment interface on marginal bone loss around the neck of implant. Literatures were searched based on the following Keywords: implant-abutment interface/implant-abutment connection/implant-abutment conjunction, microgap, micromotion/micromovement, microleakage, and current control methods available. The papers were then screened through titles, abstracts, and full texts. A total of 83 studies were included in the literature review. Two-piece implant systems are widely used in clinics. However, the production error and masticatory load result in the presence of microgap and micromotion between the implant and the abutment, which directly or indirectly causes microleakage and mechanical damage. Consequently, the degrees of microgap and micromotion further increase, and marginal bone absorption finally occurs. We summarize the influences of microgap and micromotion at the implant-abutment interface on marginal bone loss around the neck of the implant. We also recommend some feasible methods to reduce their effect. Clinicians and patients should pay more attention to the mechanisms as well as the control methods of microgap and micromotion. To reduce the corresponding detriment to the implant marginal bone, suitable Morse taper or hybrid connection implants and platform switching abutments should be selected, as well as other potential methods. Copyright © 2017 Elsevier Ltd. All rights reserved.
Rinke, Sven; Lattke, Anja; Eickholz, Peter; Kramer, Katharina; Ziebolz, Dirk
This study aimed to determine the survival rate and prevalence of biologic and technical complications associated with single-tooth implants with all-ceramic abutments in the anterior region. A total of 33 patients were restored with 50 anterior implants and temporarily luted all-ceramic crowns on prefabricated zirconia abutments. All of the patients subsequently received annual supportive maintenance; 27 patients (18 women, 22-74 years) with 42 implants participated in the final maintenance visit and were included in the study (follow-up 78.1 ± 27.0 months). The time-dependent survival rate (Kaplan-Meier) and the frequency of prosthetic complications (abutment fracture [AF], screw loosening [SL], fracture of veneering ceramics [VF], retention loss [RL]) and biologic complications (peri-implantitis) were calculated to determine the success rates. No implant loss (implant-related survival rate 100%) but one abutment fracture occurred throughout the entire observation period; therefore, the survival rate of the superstructures (in situ criterion) was 97.6% (95% confidence interval [CI] 0.930- 1.000) after 7 years. Eleven restorations were affected by prosthetic complications: RL (n = 4), VF (n = 5), and SL (n = 2). Peri-implantitis was diagnosed for two implants (probing depth > 5 mm, bleeding on probing [BOP]/suppuration, and bone loss > 3 mm) (implant-related peri-implantitis rate 4.8%). No restoration required replacement due to complications. The success rate (event-free restoration) was 75.9% (95% CI 0.636- 0.882) after 7 years. Considering the calculated survival rate, the application of all-ceramic zirconia implant abutments in the anterior region can be recommended as a reliable therapy in private practice. Fractures of veneering ceramics were the most common prosthetic complication.
Romanos, George E; May, Steffan; May, Dittmar
The present paper demonstrates a new technique and long-term results of a treatment concept that uses four implants placed in the anterior mandible that are connected to prefabricated telescopic abutments and immediately loaded with removable restorations. The present retrospective study included 488 implants (Ankylos, Dentsply) placed in 122 patients (mean age: 65.2 ± 9.8 years) with clinical and radiographic evaluation for a period of at least 1 year. Eighty-four implants were placed in fresh extraction sockets and combined in the restorations with implants placed in healed ridges. All implants were placed 2 mm subcrestally (based on chart documentation, measured from the midfacial bone level). The implants were connected immediately after surgery to conical prefabricated abutments (angle of 4 to 6 degrees) using a final torque of 15 Ncm. Secondary prefabricated copings that fit the abutments were placed over the abutments after abutment connection, and the complete denture of each patient was relined chairside with methyl methacrylate resin. The prosthetic restorations were to remain in place for 10 days to ensure that the implants remained immobile. After a mean of 79 ± 29.8 months (range, 17 to 129 months) only eight implants failed (1.6%). Twenty-one implants (4.3%) showed crestal bone loss greater than 2 mm relative to the implant position at the time of implant insertion. Therefore, the failure rate was 5.94% for the entire observation period. The success rate for the evaluated implants was 94.06%. The patients were satisfied with the stability of their prostheses, and no prosthetic or peri-implant problems were observed. These telescopic implant-supported restorations with immediate loading seem to be an alternative prosthetic solution for the edentulous patient, providing long-term implant stability.
Aloise, João Pedro; Curcio, Ricardo; Laporta, Marcia Zorello; Rossi, Liliane; da Silva, Adriana Madeira Alvares; Rapoport, Abrão
The aim of this study was to determine and compare the frequency of bacterial leakage of Streptococcus sanguinis biotype II along the implant-abutment interface between two systems of morse taper dental implants. Different methods of activation of the taper abutments were used: tapped-in (Bicon) and screwed-in (Ankylos). Twenty sterile assemblies were used and attached, 10 Bicon and 10 Ankylos implants, according to manufacturers' specifications. They were then totally immersed within 20 test tubes containing a sterile nutrient solution brain-heart infusion (BHI). The internal part of the 20 implants was previously inoculated with 0.1 microl of S. sanguinis II (ATCC 10557) and then connected to the respective abutments. The assemblies were incubated under anaerobic conditions for 14 days in an autoclave at 37 degrees C. They were monitored daily for solution cloudiness resultant from microbial leakage on the interface of the assemblies. For statistical analysis, the Fisher test was applied and significance was assigned at the 5% level. There was solution cloudiness, indicating the finding of bacterial growth inside two Bicon assemblies and two Ankylos assemblies 48 h after incubation. Microbial leakage was further substantiated by testing the suspension for the presence of Streptococcus sp. None of the sterility controls were contaminated. The frequency of bacterial leakage along the implant-abutment interface, with the two different morse taper implant systems, was 20% of the assemblies of each system. There were no statistical differences between them. Irrespective of which of the two morse taper implant connection systems of activation was analyzed, tapped-in (Bicon) or screwed-in (Ankylos), this in vitro experiment showed bacterial leakage along the implant-abutment interface.
Moris, Izabela Cristina Maurício; Faria, Adriana Cláudia Lapria; Ribeiro, Ricardo Faria; Fok, Alex Sui-Lun; Rodrigues, Renata Cristina Silveira
The use of zirconia abutments has increased because of aesthetics, but sometimes customization is necessary and its effect is unclear. This study evaluated the marginal fit and torque loss of customized and non-customized aesthetic zirconia abutments associated with Morse taper implants before and after thermomechanical cycling. Twenty-four implant/abutment/crown sets were divided into three groups (N = 8): Zr - non-customized zirconia abutments, Zrc - customized zirconia abutments, and Ti - titanium abutments. The ceramic crowns of the upper canines were made. All of the abutments were tightened with 15-N.cm torque, and the crowns were cemented on the abutments. The misfits and torque loss were measured before and after thermomechanical cycling. The marginal fit was evaluated in two planes throughout 10 different slices, 30 measurements for each face (i.e., buccal, palatal, mesial and distal) and 120 measurements for each sample. A load of 100N, a frequency of 2Hz and 1000,000 cycles with temperature variation of 5°-55°C were used for thermomechanical cycling. Thermomechanical cycling significantly decreased the marginal misfit only with the Zrc (p = 0.002), and the Ti was significantly different from the Zr and Zrc before and after thermomechanical cycling. Thermomechanical cycling did not affect the torque losses of the groups, but a significant difference between the Zr and Zrc (p = 0.0345) before cycling was noted. Customization of zirconia abutments does not significantly affect torque loss and marginal misfit after thermomechanical cycling suggesting that they can be safe for clinical utilization. Copyright © 2017 Elsevier Ltd. All rights reserved.
Ikegami, Tetsuro; Makino, Shinji
Rift Valley fever virus (RVFV), which belongs to the genus Phlebovirus, family Bunyaviridae, is a negative-stranded RNA virus carrying a tripartite RNA genome. RVFV is transmitted by mosquitoes and causes large outbreaks among ruminants and humans in Africa and the Arabian Peninsula. Human patients develop an acute febrile illness, followed by a fatal hemorrhagic fever, encephalitis or ocular diseases, whereas ruminants experience abortions during outbreak. Effective vaccination of both human...
Full Text Available The epigenetic valleys as part of the fluvial relief are of special geomorphologic significance. As ostensibly anomalous phenomena, they mirror the inconsistent fluvial relief, i.e. a phase of adjustment of longitudinal profiles of rivers. The subject of research in this paper involved some forms of the fluvial relief in the drainage basin of the Vardar River, in the Tikves Basin, which had some predispositions to be classified as an epigenetic valleys. The necessary geological-and-lithological and morphological parameters have shown that specific segments in the river valleys in Tikves are distinguished by special physiognomy, lithology and genesis, which correspond to epigenetic valleys and gorges. Thus arguments indicated in total ten created epigenetic valleys and gorges on the level of the Tikves Basin. Seven epigenetic occurrences were formed below the neogene level, whereas three of them were formed above the neogene level.
Zembic, Anja; Philipp, Alexander Otto Hermann; Hämmerle, Christoph Hans Franz; Wohlwend, Arnold; Sailer, Irena
Clinical studies on zirconia abutments report very good survival rates and biological and technical results, but few have an observation period of more than 5 years. The aim of this study was to assess the long-term performance of customized zirconia implant abutments supporting all-ceramic crowns. Twenty-seven patients receiving 54 single implants were included (25 incisors, 14 canines, 15 premolars in both jaws). Yttria-stabilized zirconia abutments were screwed to the implants with a defined torque. All-ceramic crowns were adhesively cemented onto the abutments. The implants, abutments, and crowns were clinically and radiographically examined after 11 years of use. Modified United States Public Health Service (USPHS) criteria were used to assess technical outcomes: fracture of abutment/crown framework/veneering ceramic, loosening of abutment screw/crown, marginal adaptation, anatomical form, occlusal wear, and abutment fit. The biological parameters were pocket probing depth, plaque control record, bleeding on probing, papilla index, and gingival/mucosal recession at implants and neighboring natural teeth. The cumulative success rate of abutments and crowns was calculated by the Kaplan-Meier method. The results of the USPHS criteria were analyzed descriptively. Sixteen patients with 31 zirconia abutments were examined at 11.3 (±0.9) years after implantation. No abutment or crown was lost. The cumulative success rate was 96.3% for abutments and 90.7% for crowns. Two abutment screws loosened, and three crowns exhibited minor chipping. There were no biological complications. Customized zirconia single implant abutments exhibited excellent long-term outcomes in anterior and premolar regions. © 2014 Wiley Periodicals, Inc.
Bressan, Eriberto; Venezze, Alvise Cenzi; Magaz, Vanessa Ruiz; Lops, Diego; Ghensi, Paolo
The conometric retention system was proposed and described as a predictable alternative to retain fixed implant-supported complete dentures and, more recently, to retain fixed partial restorations. Currently available studies describe a technique based on the Ankylos (Dentsply) implant system and stock conic coupling abutments. The purpose of this case series study is therefore to demonstrate the possibility of using Atlantis computer-aided design/computer-assisted manufacture technology to produce Conus abutments (Dentsply) and using the fixed conometric retention with other implant brands for which appropriate stock conic coupling abutments are not available.
Chaimattayompol, Nopsaran; Emtiaz, Shahram; Woloch, Michael M
Maintaining a fixed provisional prosthesis through all phases of complex implant prosthodontic therapy for a soon-to-be completely edentulous arch is a difficult task. This article focuses on the treatment phase in which teeth and/or transitional implants supporting a provisional fixed partial denture are removed. The described technique makes use of healing abutments to support a modified provisional fixed partial denture. This protocol ensures patient comfort and allows proper soft tissue healing before definitive implant abutment selection. It also eliminates the placement of interim implant abutments.
Saponaro, Paola C; Heshmati, Reza H; Lee, Damian J
When a screw fracture occurs on a cement-retained, implant-supported restoration, the abutment and restoration are completely separated from the implant's internal connection. Traditionally, an access hole is drilled through the crown to retrieve the broken screw, and the restoration can be placed again as a screw-retained restoration. This clinical report documents a patient whose broken abutment screw was retrieved from the restoration by burning off the cement and separating from the abutment without drilling an access hole. © 2014 by the American College of Prosthodontists.
Kappel, Stefanie; Eiffler, Constantin; Lorenzo-Bermejo, Justo; Stober, Thomas; Rammelsberg, Peter
To assess the frequency and amount of residual cement after attachment of monolithic zirconia crowns to standard and individualized ceramic abutments. Twenty patients (mean age 58.9 years at inclusion in the study; 30% male) were randomized to receive either a standard or an individualized abutment on a bone-level implant. Monolithic zirconia single crowns were attached to abutments by use of permanent glass-ionomer cement. Crowns were fabricated with an occlusal hole to enable unscrewing of the abutment-crown complex. Immediately after cementation, superstructures were removed and both the peri-implant soft tissue and the abutment-crown complex were photographed in a standardized manner, to detect residual cement. Photographs were analyzed using Corel Photo Paint X7, and residual cement-to-total abutment and residual cement-to-peri-implant soft tissue area ratios were calculated. Residual cement was observed for 9 of 10 (90%) individualized abutments, compared with 4 of 10 (40%) standard abutments (OR = 13.5, P = 0.049). Twenty-seven of 40 (68%) individualized abutment surfaces were affected, compared with 12 of 40 (30%) standard abutment surfaces. The probability of observing residual cement was approximately five times higher for the surfaces of individualized abutments than for those of standard abutments (P = 0.005). The mean amount of sulcus surface covered by cement was 1.17% (SD 2.85) for the individualized abutments and 3.78% (SD 7.40) for the standard abutments. The position of the margin significantly affected the amount of residual cement. Both individualized and standard all-ceramic abutments result in small amounts of subgingival residual cement on abutment and sulcus surfaces. However, use of individualized abutments does not guarantee complete avoidance of undetected cement rests. Undetected residual cement might be avoided by use of all-ceramic abutments with visible abutment shoulders. © 2015 John Wiley & Sons A/S. Published by John Wiley
Evaluation of the sealing capability of implants to titanium and zirconia abutments against Porphyromonas gingivalis, Prevotella intermedia, and Fusobacterium nucleatum under different screw torque values.
Smith, Nicole A; Turkyilmaz, Ilser
When evaluating long-term implant success, clinicians have always been concerned with the gap at the implant-abutment junction, where bacteria can accumulate and cause marginal bone loss. However, little information regarding bacterial leakage at the implant-abutment junction, or microgap, is available. The purpose of this study was to evaluate sealing at 2 different implant-abutment interfaces under different screw torque values. Twenty sterile zirconia abutments and 20 sterile titanium abutments were screwed into 40 sterile implants and placed in test tubes. The ability of a bacterial mixture of Prevotella intermedia, Porphyromonas gingivalis, and Fusobacterium nucleatum to leak through an implant-titanium abutment seal under 20 and 35 Ncm torque values and an implant-zirconia abutment seal under 20 and 35 Ncm torque values was evaluated daily until leakage was noted. Once a unit demonstrated leakage, a specimen was plated. After 4 days, the number of colonies on each plate was counted with an electronic colony counter. Plating was used to verify whether or not bacterial leakage occurred and when leakage first occurred. The implant-abutment units were removed and rinsed with phosphate buffered saline solution and evaluated with a stereomicroscope. The marginal gap between the implant and the abutment was measured and correlated with the amount of bacterial leakage. The data were analyzed with ANOVA. Bacterial leakage was noted in all specimens, regardless of material or screw torque value. With titanium abutments, changing the screw torque value from 20 to 35 Ncm did not significantly affect the amount of bacterial leakage. However, with zirconia abutments, changing the screw torque value from 20 to 35 Ncm was statistically significant (P<.017). Overall, the marginal gap noted was larger at the zirconia-abutment interface (5.25 ±1.99 μm) than the titanium-abutment interface (12.38 ±3.73 μm), irrespective of the screw torque value. Stereomicroscopy revealed a
Grandi, Tommaso; Guazzi, Paolo; Samarani, Rawad; Maghaireh, Hassan; Grandi, Giovanni
To compare immediately loaded post-extractive single implants using a definitive abutment versus provisional abutment later replaced by custom-made abutment. In two private clinics, 28 patients in need of one single post-extractive implant in the maxilla or mandible from the left second premolar to the right second premolar area were randomised shortly before tooth extraction to provisional abutment (PA) and definitive abutment (DA) groups. Three patients had to be excluded for buccal wall fracture after tooth extraction. In the PA group, implants were immediately restored using a platform-switched provisional titanium abutment and definitive platform-switched titanium abutments were used in the DA group. In both groups, a non-occluding provisional single crown was provided. Implants were definitively restored after 4 months. In the PA group, the abutment was removed and the impression was made directly on the implant platform. In the DA group an impression of the abutment was made using a retraction cord. Outcome measures were: implant failures; complications; and marginal peri-implant bone level changes. Patients were followed up to 1 year after loading. Twelve patients were randomised to the DA group and 13 patients to the PA group. At the 12-month follow-up, no implant failed. One biological complication occurred in the DA group and one mechanical complication occurred in the PA group. All complications were successfully treated. One year after loading, implants in the DA group lost an average of 0.11 mm (SD: 0.06) of periimplant bone and implants in PA group about 0.58 mm (SD: 0.11). At the 12-month follow-up, there was a statistically significant difference in bone level change between groups (mean difference: 0.48 mm, CI 95% 0.40; 0.55, P < 0.0001). Within the limits of this study, the non-removal of abutments placed at the time of surgery resulted in the maintenance of 0.5 mm more bone levels around immediately restored postextractive single implants than
Bertolini, Martinna de Mendonça e; Kempen, Juan; Lourenço, Eduardo José Veras; Telles, Daniel de Moraes
Well-placed dental implants are a prerequisite of functional and esthetically successful dental implant-supported crowns. The presence of soft tissue is essential for excellent esthetics because the dental implant or titanium abutment may become visible if the soft-tissue contour is not acceptable. This clinical report describes the use of a custom ceramic implant abutment designed with computer-aided design and computer-aided manufacturing (CAD/CAM) technology by milling a zirconia framework that was cemented extraorally to a prefabricated titanium abutment with a reduced diameter. This ceramic abutment has the strength and precise fit of a titanium interface and also the esthetic advantages of shaded custom-milled zirconia, with no visible metal. Copyright © 2014 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.
Kutkut, Ahmad; Abu-Hammad, Osama; Mitchell, Richard
Titanium and zirconia custom implant abutments are now commonly used for esthetic implant dentistry. Custom implant abutments allow the clinician to improve an implant's emergence profile, to customize cervical margins in accordance with the anatomy of the natural root, and to compensate for poor implant angulation. All of these are essential for optimum esthetic outcomes. Computer-aided design/computer-aided machining (CAD/CAM) technology allows the clinician to design custom implant abutment configurations and create natural-looking superstructures that are in harmony with the adjacent dentition and soft tissue. The CAD/CAM technique provides precise fit, reduces the cost of the procedure, and eliminates dimensional inaccuracies inherent in the conventional waxing and casting technique. The aim of this report is to describe a simplified technique for reconstructing emergence profiles during implant restoration using milled titanium and zirconia custom implant abutments. The results of 50 consecutive cases are reported.
Keeley, J.E.; Schoenherr, Allan A.
Grasslands are distributed throughout California from Oregon to Baja California Norte and from the coast to the desert (Brown 1982) (Figure 1). This review will focus on the dominant formation in cismontane California, a community referred to as Valley Grassland (Munz 1959). Today, Valley Grassland is dominated by non-native annual grasses in genera such as Avena (wild oat), Bromus (brome grass), and Hordeum (barley), and is often referred to as the California annual grassland. On localized sites, native perennial bunchgrasses such as Stipa pultra (purple needle grass) may dominate and such sites are interpreted to be remnants of the pristine valley grassland. In northwestern California a floristically distinct formation of the Valley Grassland, known as Coast Prairie (Munz 1959) or Northern Coastal Grassland (Holland and Keil 1989) is recognized. The dominant grasses include many native perennial bunchgrasses in genera such as Agrostis, Calamagrostis, Danthonia, Deschampsia, Festuca, Koeleria and Poa (Heady et al. 1977). Non-native annuals do not dominate, but on some sites non-native perennials like Anthoxanthum odoratum may colonize the native grassland (Foin and Hektner 1986). Elevationally, California's grasslands extend from sea level to at leas 1500 m. The upper boundary is vague because montane grassland formations are commonly referred to as meadows; a community which Munz (1959) does not recognize. Holland and Keil (1989) describe the montane meadow as an azonal community; that is, a community restricted not so much to a particular climatic zone but rather controlled by substrate characteristics. They consider poor soil-drainage an over-riding factor in the development of montane meadows and, in contrast to grasslands, meadows often remain green through the summer drought. Floristically, meadows are composed of graminoids; Cyperaceae, Juncaceae, and rhizomatous grasses such as Agropyron (wheat grass). Some bunchgrasses, such as Muhlenbergia rigens, are
Peixoto, Hugo Eduardo, E-mail: email@example.com [Implantology Team, Latin American Institute of Research and Education in Dentistry, Curitiba, Paraná (Brazil); Bordin, Dimorvan, E-mail: firstname.lastname@example.org [Department of Prosthodontics and Periodontology, Piracicaba Dental School, State University of Campinas, Limeira avenue, 901-Vila Rezende, Piracicaba, SP 13414-903 (Brazil); Del Bel Cury, Altair A., E-mail: email@example.com [Department of Prosthodontics and Periodontology, Piracicaba Dental School, State University of Campinas, Limeira avenue, 901-Vila Rezende, Piracicaba, SP 13414-903 (Brazil); Silva, Wander José da, E-mail: firstname.lastname@example.org [Department of Prosthodontics and Periodontology, Piracicaba Dental School, State University of Campinas, Limeira avenue, 901-Vila Rezende, Piracicaba, SP 13414-903 (Brazil); Faot, Fernanda, E-mail: email@example.com [Department of Restorative Dentistry, School of Dentistry, Federal University of Pelotas, Gonçalves Chaves, 457, 2nd floor, Pelotas, Rio Grande do Sul 96015-560 (Brazil)
Purpose: Evaluate the influence of abutment's material and geometry on stress distribution in a single implant-supported prosthesis. Materials and Methods: Three-dimensional models were made based on tomographic slices of the upper middle incisor area, in which a morse taper implant was positioned and a titanium (Ti) or zirconia (ZrN) universal abutments was installed. The commercially available geometry of titanium (T) and zirconia (Z) abutments were used to draw two models, TM1 and ZM1 respectively, which served as control groups. These models were compared with 2 experimental groups were the mechanical properties of Z were applied to the titanium abutment (TM2) and vice versa for the zirconia abutment (ZM2). Subsequently, loading was simulated in two steps, starting with a preload phase, calculated with the respective friction coefficients of each materials, followed by a combined preload and chewing force. The maximum von Mises stress was described. Data were analyzed by two-way ANOVA that considered material composition, geometry and loading (p < 0.05). Results: Titanium and zirconia abutments showed similar von Mises stresses in the mechanical part of the four models. The area with the highest concentration of stress was the screw thread, following by the screw body. The highest stress levels occurred in screw thread was observed during the preloading phase in the ZM1 model (931 MPa); and during the combined loading in the TM1 model (965 MPa). Statistically significant differences were observed for loading, the material × loading interaction, and the loading × geometry interaction (p < 0.05). Preloading contributed for 77.89% of the stress (p < 0.05). There were no statistically significant differences to the other factors (p > 0.05). Conclusion: The screw was the piece most intensely affected, mainly through the preload force, independent of the abutment's material. - Highlights: • The abutment's screw was the most impaired piece of the
Wang, Qing-Qing; Dai, Ruoxi; Cao, Chris Ying; Fang, Hui; Han, Min; Li, Quan-Li
This review aims to compare peri-implant tissue changes in terms of clinical and radiographic aspects of implant restoration protocol using one-time abutment to repeated abutment connection in platform switched implant. A structured search strategy was applied to three electronic databases, namely, Pubmed, Embase and Web of Science. Eight eligible studies, including seven randomised controlled studies and one controlled clinical study, were identified in accordance with inclusion/exclusion criteria. Outcome measures included peri-implant bone changes (mm), peri-implant soft tissue changes (mm), probing depth (mm) and postsurgical complications. Six studies were pooled for meta-analysis on bone tissue, three for soft tissue, two for probing depth and four for postsurgical complications. A total of 197 implants were placed in one-time abutment group, whereas 214 implants were included in repeated abutment group. The implant systems included Global implants, Ankylos, JDEvolution (JdentalCare), Straumann Bone level and Conelog-Screwline. One-time abutment group showed significantly better outcomes than repeated abutment group, as measured in the standardised differences in mean values (fixed- and random-effect model): vertical bone change (0.41, 3.23) in 6 months, (1.51, 14.81) in 12 months and (2.47, 2.47) in 3 years and soft tissue change (0.21, 0.23). No significant difference was observed in terms of probing depth and complications. Our meta-analysis revealed that implant restoration protocol using one-time abutment is superior to repeated abutment for platform switched implant because of less bone resorption and soft tissue shifts in former. However, future randomised clinical trials should be conducted to further confirm these findings because of the small samples and the limited quality of the original research.
Full Text Available This review aims to compare peri-implant tissue changes in terms of clinical and radiographic aspects of implant restoration protocol using one-time abutment to repeated abutment connection in platform switched implant.A structured search strategy was applied to three electronic databases, namely, Pubmed, Embase and Web of Science. Eight eligible studies, including seven randomised controlled studies and one controlled clinical study, were identified in accordance with inclusion/exclusion criteria. Outcome measures included peri-implant bone changes (mm, peri-implant soft tissue changes (mm, probing depth (mm and postsurgical complications.Six studies were pooled for meta-analysis on bone tissue, three for soft tissue, two for probing depth and four for postsurgical complications. A total of 197 implants were placed in one-time abutment group, whereas 214 implants were included in repeated abutment group. The implant systems included Global implants, Ankylos, JDEvolution (JdentalCare, Straumann Bone level and Conelog-Screwline. One-time abutment group showed significantly better outcomes than repeated abutment group, as measured in the standardised differences in mean values (fixed- and random-effect model: vertical bone change (0.41, 3.23 in 6 months, (1.51, 14.81 in 12 months and (2.47, 2.47 in 3 years and soft tissue change (0.21, 0.23. No significant difference was observed in terms of probing depth and complications.Our meta-analysis revealed that implant restoration protocol using one-time abutment is superior to repeated abutment for platform switched implant because of less bone resorption and soft tissue shifts in former. However, future randomised clinical trials should be conducted to further confirm these findings because of the small samples and the limited quality of the original research.
Garrana, Rhoodie; Mohangi, Govindrau; Malo, Paulo; Nobre, Miguel
Background. Endotoxin initiates osteoclastic activity resulting in bone loss. Endotoxin leakage through implant abutment connections negatively influences peri-implant bone levels. Objectives. (i) To determine if endotoxin can traverse different implant-abutment connection (IAC) designs; (ii) to quantify the amount of endotoxins traversing the IAC; (iii) to compare the in vitro comportments of different IACs. Materials and Methods. Twenty-seven IACs were inoculated with E. coli endotoxin. Six...
Keum, Eun-Cheol; Shin, Soo-Yeon
PURPOSE This study evaluated the effectiveness of various methods for removing provisional cement from implant abutments, and what effect these methods have on the retention of prosthesis during the definitive cementation. MATERIALS AND METHODS Forty implant fixture analogues and abutments were embedded in resin blocks. Forty cast crowns were fabricated and divided into 4 groups each containing 10 implants. Group A was cemented directly with the definitive cement (Cem-Implant). The remainder ...
Morgan, A. M.; Arvidson, R. E.; Duran Vinent, O.; Craddock, R. A.; Holo, S.; Gadal, C.; Blois, G.; Palucis, M. C.; Goudge, T. A.; Morgan, A. M.; Day, M.; Sullivan, R. J., Jr.; Umurhan, O. M.; Pähtz, T.; Birch, S.; Morgan, A. M.; Goudge, T. A.; Palucis, M. C.; Arvidson, R. E.; Duran Vinent, O.; Craddock, R. A.; Holo, S.; Blois, G.; Gadal, C.; Morgan, A. M.; Sullivan, R. J., Jr.; Day, M.; Arvidson, R. E.
Perseverance Valley, based on orbital observations from the Mars Reconnaisance Orbiter HiRISE image data, is a 180 m long, 20 m wide anastomosing shallow channel system superimposed on the Cape Byron rim segment of the 22 km diameter Noachian-age Endeavour Crater on Mars. Several impact craters are superimposed on the valley system, indicating antiquity, although the valley's high degree of preservation indicates that it formed after significant regional-scale fluvial erosion and diffusive smoothing of Endeavour and its rim segments. The valley cuts into the inner, eastern rim on a 10˚ to 15˚ slope, and starts at a local low area on the rim crest. A set of shallow channels, some lined with perimeter rocks, extends from the west to meet the entrance to the valley. The western rim tilts to the west 0.8˚ and thus the channels tilt away from the valley entrance. The Mars Rover Opportunity has explored the western shallow channels leading up to the entrance to the valley. As of this writing Opportunity is located on the southern side of the valley entrance, with the Athena Science Team waiting until after solar conjunction to command the rover to descend into the valley to search for geomorphic and sedimentologic evidence related to valley formation. Wind erosion along radial fractures extending into and down Cape Byron is a possibility. Debris flows are also under consideration, perhaps enabled by melting ice at the rim crest. Dry avalanches are unlikely due to the low slopes. A fluvial origin is a strong contender based on models that show it is possible to have had a western catchment present when the Burns formation hydrated sulfates were being emplaced, followed by self-compaction of these sediments that tilted the western plains away from the rim crest. The key to testing among the various hypotheses for formation of the valley and shallow channels leading into the entrance will be the detailed stereo and multispectral imaging observations Opportunity will make
Aradaib, Imadeldin E.; Erickson, Bobbie R.; Elageb, Rehab M.; Khristova, Marina L.; Carroll, Serena A.; Elkhidir, Isam M.; Karsany, Mubarak E.; Karrar, AbdelRahim E.; Elbashir, Mustafa I.
To elucidate whether Rift Valley fever virus (RVFV) diversity in Sudan resulted from multiple introductions or from acquired changes over time from 1 introduction event, we generated complete genome sequences from RVFV strains detected during the 2007 and 2010 outbreaks. Phylogenetic analyses of small, medium, and large RNA segment sequences indicated several genetic RVFV variants were circulating in Sudan, which all grouped into Kenya-1 or Kenya-2 sublineages from the 2006–2008 eastern Africa epizootic. Bayesian analysis of sequence differences estimated that diversity among the 2007 and 2010 Sudan RVFV variants shared a most recent common ancestor circa 1996. The data suggest multiple introductions of RVFV into Sudan as part of sweeping epizootics from eastern Africa. The sequences indicate recent movement of RVFV and support the need for surveillance to recognize when and where RVFV circulates between epidemics, which can make data from prediction tools easier to interpret and preventive measures easier to direct toward high-risk areas. PMID:23347790
Grammel, Jr., Leonard Paul (Inventor); Pennekamp, David Lance (Inventor); Winslow, Jr., Ralph Henry (Inventor)
An annular trapped vortex cavity assembly segment comprising includes a cavity forward wall, a cavity aft wall, and a cavity radially outer wall there between defining a cavity segment therein. A cavity opening extends between the forward and aft walls at a radially inner end of the assembly segment. Radially spaced apart pluralities of air injection first and second holes extend through the forward and aft walls respectively. The segment may include first and second expansion joint features at distal first and second ends respectively of the segment. The segment may include a forward subcomponent including the cavity forward wall attached to an aft subcomponent including the cavity aft wall. The forward and aft subcomponents include forward and aft portions of the cavity radially outer wall respectively. A ring of the segments may be circumferentially disposed about an axis to form an annular segmented vortex cavity assembly.
Wanninger, Andreas; Kristof, Alen; Brinkmann, Nora
Comparative molecular, developmental and morphogenetic analyses show that the three major segmented animal groups-Lophotrochozoa, Ecdysozoa and Vertebrata-use a wide range of ontogenetic pathways to establish metameric body organization. Even in the life history of a single specimen, different mechanisms may act on the level of gene expression, cell proliferation, tissue differentiation and organ system formation in individual segments. Accordingly, in some polychaete annelids the first three pairs of segmental peripheral neurons arise synchronously, while the metameric commissures of the ventral nervous system form in anterior-posterior progression. Contrary to traditional belief, loss of segmentation may have occurred more often than commonly assumed, as exemplified in the sipunculans, which show remnants of segmentation in larval stages but are unsegmented as adults. The developmental plasticity and potential evolutionary lability of segmentation nourishes the controversy of a segmented bilaterian ancestor versus multiple independent evolution of segmentation in respective metazoan lineages.
Zarrati, Simindokht; Heidari, Fatemeh; Kashani, Jamal
Objectives: This finite element method study aimed to compare the amount of stress on an isolated mandibular second premolar in two conventional reciprocal parallel interface designs of removable partial dentures (RPDs) and the same RPD abutment tooth (not isolated). Materials and Methods: A Kennedy Class 1, modification 1 RPD framework was simulated on a 3D model of mandible with three different designs: an isolated tooth with a mesial rest, an isolated tooth with mesial and distal rests and an abutment with a mesial rest (which was not isolated); 26 N occlusal forces were exerted bilaterally on the first molar sites. Stress on the abutment teeth was analyzed using Cosmos Works 2009 Software. Results: In all designs, the abutment tooth stress concentration was located in the buccal alveolar crest. In the first model, the von Mises stress distribution in the contact area of I-bar clasp and cervical portion of the tooth was 19 MPa and the maximum stress was 30 MPa. In the second model, the maximum von Mises stress distribution was 15 MPa in the cervical of the tooth. In the third model, the maximum von Mises stress was located in the cervical of the tooth and the distal proximal plate. Conclusion: We recommend using both mesial and distal rests on the distal abutment teeth of distal extension RPDs. The abutment of an extension base RPD, which is not isolated in presence of its neighboring more anterior tooth, may have a better biomechanical prognosis. PMID:26884772
Full Text Available To systematically measure and compare the stress distribution on the bone around an implant in the anterior maxilla using angled abutments by means of finite element analysis, three-dimensional finite element simplified patient-specific models and simplified models were created and analyzed. Systematically varied angled abutments were simulated, with angulation ranging from 0° to 60°. The materials in the current study were assumed to be homogenous, linearly elastic, and isotropic. Force of 100 N was applied to the central node on the top surface of the abutments to simulate the occlusal force. To simulate axial and oblique loading, the angle of loading was 0°, 15°, and 20° to the long axis of implant, respectively. There was the strong resemblance between the response curves for simplified patient-specific models and simplified models. Response curves under oblique loading were similar in both models. With abutments angulation increased, maximum von Mises stress firstly decreased to minimum point and then gradually increased to higher level. From a biomechanical point of view, favorable peri-implant stress levels could be induced by angled abutments under oblique loading if suitable angulation of abutments was selected.
Keum, Eun-Cheol; Shin, Soo-Yeon
This study evaluated the effectiveness of various methods for removing provisional cement from implant abutments, and what effect these methods have on the retention of prosthesis during the definitive cementation. Forty implant fixture analogues and abutments were embedded in resin blocks. Forty cast crowns were fabricated and divided into 4 groups each containing 10 implants. Group A was cemented directly with the definitive cement (Cem-Implant). The remainder were cemented with provisional cement (Temp-Bond NE), and classified according to the method for cleaning the abutments. Group B used a plastic curette and wet gauze, Group C used a rubber cup and pumice, and Group D used an airborne particle abrasion technique. The abutments were observed using a stereomicroscope after removing the provisional cement. The tensile bond strength was measured after the definitive cementation. Statistical analysis was performed using one-way analysis of variance test (α=.05). Group B clearly showed provisional cement remaining, whereas the other groups showed almost no cement. Groups A and B showed a relatively smooth surface. More roughness was observed in Group C, and apparent roughness was noted in Group D. The tensile bond strength tests revealed Group D to have significantly the highest tensile bond strength followed in order by Groups C, A and B. A plastic curette and wet gauze alone cannot effectively remove the residual provisional cement on the abutment. The definitive retention increased when the abutments were treated with rubber cup/pumice or airborne particle abraded to remove the provisional cement.
Rodríguez López, Marcelo
The work presented in this dissertation investigates music segmentation. In the field of Musicology, segmentation refers to a score analysis technique, whereby notated pieces or passages of these pieces are divided into “units” referred to as sections, periods, phrases, and so on. Segmentation
van Brakel, Ralph; Noordmans, Herke Jan; Frenken, Joost; de Roode, Rowland; de Wit, Gerard C; Cune, Marco S
To determine the difference in light reflection of oral mucosa covering titanium (Ti) or zirconia (ZrO(2)) abutments as it relates to the thickness of the covering mucosa. Fifteen anterior implants (Astra Osseo speed(®)) in 11 patients were fitted with a Ti or a ZrO(2) abutment (cross-over, within-subject comparison). Hyper-spectral images were taken with a camera fitted on a surgical microscope. High-resolution images with 70 nm interval between 440 and 720 nm were obtained within 30 s (1392 × 1024 pixels). Black- and white-point reference was used for spatial and spectral normalization as well as correction for motion during exposure. Reflection spectra were extracted from the image on a line mid-buccal of the implant, starting 1 mm above the soft tissue continuing up to 3 mm apically. Median soft tissue height is 2.3 mm (min: 1.2 mm and max: 3.1 mm). The buccal mucosa rapidly increases in the thickness, when moving apically. At 2.2 mm, thickness is 3 mm. No perceivable difference between the Ti and ZrO(2) abutment can be observed when the thickness of the mucosa is 2±0.1 mm (95% confidence interval) or more. It is expected that the difference in light reflection of soft tissue covering Ti or ZrO(2) abutments is no longer noticeable for the human eye when the mucosa thickness exceeds 2 mm. Haemoglobin peaks in the reflection spectrum can be observed and make hyper-spectral imaging a practical and useful tool for measuring soft tissue health. © 2011 John Wiley & Sons A/S.
To maximize esthetics in anterior implant restorations, the initial step in treatment planning should be determining the prosthesis's esthetic integration with the patient's smile in keeping with the patient's anatomical limitations. This article examines the role of the abutment in supporting both esthetics and technical success. Included are discussions regarding cemented versus screw-retained restorations, material selection for anterior tooth replacement, and design parameters.
Freitas, Amilcar Chagas; Rocha, Eduardo Passos; dos Santos, Paulo Henrique; de Almeida, Erika Oliveira; Anchieta, Rodolfo Bruniera
The aim of this study was to evaluate the influence of different Young moduli of the ceramic crown on the distribution of tensions in the region of the abutment-crown interface by making use of 2D finite element analysis. Two representative models of a sagittally sectioned maxilla were built through AutoCad program showing an implant in the region of the upper central incisor and were restored by means of IPS e.max Press or Procera AllCeram on zircon abutment. Numerical analysis (Ansys 10.0) was performed under 2 loading conditions (50 N): on the lingual face, at 45 degrees with the implant's long axis (L1) and perpendicular to the incisal edge (L2). The von Mises equivalent stress (σvM) and maximum principal stress (σmax) were obtained. It was noticed that, independent of the restoring system, the maximum σvM values were in the incisal region of the cementation interface for both loading conditions. The IPS e.max Press system showed higher σvM on the adhesive interface with higher L1 influence. The same behavior was also observed as regards the σmax variation. It was concluded that a restoring system with a lower Young modulus shows higher stress concentration on the abutment-crown interface when cemented on an abutment with a high Young modulus. Thus, IPS e.max Press system provides higher stress concentration in the resin cement layer than Procera AllCeram system, suggesting that the resin cement layer shows lower failure risk when the Procera crown is used.
Mehl, Christian; Harder, Sönke; Shahriari, Ahoo; Steiner, Martin; Kern, Matthias
To evaluate the influence of abutment height and thermocycling on the retrievability of cemented implant crowns. Ninety tapered titanium abutments (6 degree taper, 4.3 mm diameter, 8.5 mm height) were shortened to 2, 3, or 4 mm, respectively. Ninety crowns were designed and manufactured using CAD/CAM techniques and laser sintering a CoCr alloy. The crowns were cemented either with a glass-ionomer, a polycarboxylate, or a composite resin cement followed by 3-day storage in demineralized water without thermocycling or 150-day storage with 37,500 thermal cycles. The force (in N) and the number of attempts needed to remove the crowns using a universal testing machine (UTM) or a clinically used removal device (Coronaflex) were recorded. Statistical analysis at a level of significance of P ≤ .05 was conducted using the Kruskal-Wallis and Mann-Whitney U tests (Coronaflex) and three-way and two-way ANOVA, Tukey's HSD post hoc tests, and t tests (UTM). Regardless of whether the crowns were retrieved with Coronaflex or UTM, the crowns cemented with the glass-ionomer cement were significantly easier to retrieve followed by the polycarboxylate and the resin cement, both of which differed significantly from each other (P ≤ .001). With both retrieval methods, the cement, abutment height, and thermocycling were significantly influential (P ≤ .0001). Significant interactions could be found for retrieval with UTM between the abutment height and thermocycling, between the cement and thermocycling, and between all three factors (P ≤ .05). Glass-ionomer cement may be used for retrievable cementation of implant restorations, whereas polycarboxylate cement and especially composite resin cement should be used for a nonretrievable permanent cementation.
Bilhan, Hakan; Geckili, Onur; Mumcu, Emre
Purpose The anterior region is a challenge for most clinicians to achieve optimal esthetics with dental implants. The provisional crown is a key factor in the success of obtaining pink esthetics around restorations with single implants, by soft tissue and inter-proximal papilla shaping. Provisional abutments bring additional costs and make the treatment more expensive. Since one of the aims of the clinician is to reduce costs and find more economic ways to raise patient satisfaction, this pap...
El Haddad, E; Giannì, A B; Mancini, G E; Cura, F; Carinci, F
The aim of our study is to value the microbial contamination in the implant-abutment connections (IAC) of a Nobel Replace Conical Connection implant system [Nobel Biocare®, Vimercate (MB), Italy]. To identify the capability of the implant to protect the internal space from the external environment, the passage of genetically modified bacteria across IAC was evaluated. Four Nobel Replace Conical Connection implants (Nobel Biocare®, Vimercate (MB), Italy) were immerged in a bacterial culture for twenty-four hours and then bacteria amount was measured inside and outside IAC with Real-time PCR. Bacterial quantification was performed by Real-Time Polymerase Chain Reaction using the absolute quantification with the standard curve method. In all tested implants, bacteria were found in the inner side, with a median percentage of 10.9%. The analysis revealed that in both cases (internally and externally), bacteria grew for the first 48 hours but subsequently they started to dye, probably as a consequence of nutrient consumption. Moreover, the difference between outer and inner bacteria concentration was statistically significant at each time point. Implant's internal contamination shows that IAC is not sealing. The reported results are similar to those of previous studies carried out on different implant systems. Until now, no IAC has been proven to seal the gap between implant and abutment.
R.R.M. de Barros
Full Text Available Aim The nanomechanical evaluation can provide additional information about the dental implants osseointegration process. The aim of this study was to quantify elastic modulus and hardness of bone around cemented-retained abutment implants positioned at two different crestal bone levels. Materials and methods The mandibular premolars of 7 minipigs were extracted. After 8 weeks, 8 implants were inserted in each animal: crestally on one side of the mandible and subcrestally on the other (crestal and subcrestal groups. Functional loading were immediately provided with abutments cementation and prostheses installation. Eight weeks later, the animals euthanasia was performed and nanoindentation analyses were made at the most coronal newly formed bone region (coronal group, and below in the threaded region (threaded group of histologic sections. Results The comparisons between subcrestal and crestal groups did not achieve statistical relevance; however the elastic modulus and hardness levels were statistically different in the two regions of evaluation (coronal and threaded. Conclusions The crestal and subcrestal placement of cement-retained abutment implants did not affect differently the nanomechanical properties of the surrounding bone. However the different regions of newly formed bone (coronal and threaded groups were extremely different in both elastic modulus and hardness, probably reflecting their differences in bone composition and structure.
Dula, Linda J; Ahmedi, Enis F; Lila-Krasniqi, Zana D; Shala, Kujtim Sh
The aim of this retrospective study was to evaluate the effect of removable partial dentures in periodontal abutment teeth in relation to the type of denture support and design of RPD in a five-year worn period. Methods : A total of 64 patients with removable partial dentures (RPDs), participated in this study. It were examined ninety-one RPDs. There were seventy-five RPDs with clasp-retained and sixteenth were RPDs with attachments. There were 28 females and 36 males, aged between 40-64 years, 41 maxillary and 50 mandible RPDs. For each subjects the following data were collected: denture design, denture support, and Kennedy classification. Abutment teeth were assessed for plaque index (PI), calculus index (CI), blending on probing (BOP), probing depth (PD), gingival recession (GR), tooth mobility (TM). Level of significance was set at pdenture support of RPD, BOP, PD, PI, GR, CI and TM-index showed no statistically significant difference. Based on the denture design of RPD's, BOP, PD, PI, CI, and TM-index proved no statistically significant difference. Except GR-index according to denture design confirmed statistically significant difference in RPD with clasp pdentures and below the clasp arms in abutment teeth.
Full Text Available Background and Aims: Passive fit of prosthetic frameworks is a major concern in implant dentistry. Impression technique is one of the several variables that may affect the outcome of dental implants. The purpose of this study was to compare the three dimensional accuracy of direct and indirect abutment level implant impressions ofALL-ON-4 treatment plan.Materials and Methods: A reference acrylic resin model with four Branemark fixtures was made according to All-On-4 treatment plan. Multiunit abutments were screwed into the fixtures and two special trays were made for direct and indirect impression techniques. Ten direct and ten indirect impression techniques with respective impression transfers were made. Impressions were poured with stone and the positional accuracy of the abutment analogues in each dimension of x, y, and z axes and also angular displacement (Δθ were evaluated using a Coordinate Measuring Machine (CMM. Data were analyzed using T- test.Results: The results showed that direct impression technique was significantly more accurate than indirect technique (P<0.001.Conclusion: The results showed that the accuracy of direct impression technique was significantly more than that of indirect technique in Δθ and Δr coordinate and also Δx, Δy, Δz.
Kiliçarslan, Mehmet Ali; Özkan, Pelin; Uludag, Bülent; Mumcu, Emre
A common problem related to cemented single crowns is the internal misfit, which may cause inadequate retention, especially when seated on the implant abutment. The aim of this study was to compare the internal fit of Co-Cr crowns using a traditional lost-wax casting technique from laser-sintered Co-Cr alloy crowns. Twelve metallic crowns per each technique were fabricated. The effect of the thickness of cement, originated internal gap was evaluated. Crowns were cemented on the implant abutments with resin cement, and the internal fit of crowns was measured at five areas with an optical microscope. The data were analyzed, and the means were compared with a t-test (pcrowns obtained through the lost wax method (min. 65.50 ± 9.54 μm and max. 313.46 ± 48.12 μm). The fit of the metal crown likely varies with the fabrication technique. The use of techniques that enable the adjustment of crown parameters, such as the laser sintering technique, maintains the desired fit between casting and implant abutments. This study investigated which technique affects the internal fit of cemented implant-supported crowns, comparing the use of lost wax casting and laser-sintered metal dental alloys. The results of this study indicate that the use of laser-sintered crowns can improve for crown accuracy.
Vinícius Anéas RODRIGUES
Full Text Available Abstract Introduction The fit between abutment and implant is crucial to determine the longevity of implant-supported prostheses and the maintenance of peri-implant bones. Objective To evaluate the vertical misfit between different abutments in order to provide information to assist abutment selection. Material and method UCLA components (N=40 with anti-rotational system were divided as follows: components usinated in titanium (n=10 and plastic components cast proportionally in titanium (n=10, nickel-chromium-titanium-molybdenum (n=10 and nickel-chromium (n=10 alloys. All components were submitted to stereomicroscope analysis and were randomly selected for characterization by SEM. Result Data were analyzed using mean and standard deviation and subjected to ANOVA-one way, where the groups proved to statistically different (p=<0.05, followed by Tukey’s test. Conclusion The selection of material influences the value of vertical misfit. The group machined in Ti showed the lowest value while the group cast in Ni Cr showed the highest value of vertical misfit.
Park, Chan-Ik; Choe, Han-Cheol; Chung, Chae-Heon
Regardless of the type of performed restoration, in most cases, a screw connection is employed between the abutment and implant. For this reason, implant screw loosening has remained a problem in restorative practices. The purpose of this study was to compare the surface of coated/plated screws with titanium and gold alloy screws and to evaluate the physical properties of coated/plated material after scratch tests via FE-SEM (field emission scanning electron microscopy) investigation. GoldTite, titanium screws provided by 3i (Implant Innovation, USA) and TorqTite, titanium screws by Steri-Oss (Nobel Biocare, USA) and gold screws and titanium screws by AVANA (Osstem Implant, Korea) were selected for this study. The surface, crest, and root of the abutment screws were observed by FE-SEM. A micro-diamond needle was also prepared for the scratch test. Each abutment screw was fixed, and a scratch on the surface of the head region was made at constant load and thereafter the fine trace was observed with FE-SEM. The surface of GoldTite was smoother than that of other screws and it also had abundant ductility and malleability compared with titanium and gold screws. The scratch tests also revealed that teflon particles were exfoliated easily in the screw coated with teflon. The titanium screw had rough surface and low ductility. The clinical use of gold-plated screws is recommended as a means of preventing screw loosening.
Érica Dorigatti de Avila
Full Text Available When dental implants are malpositioned in relation to the adjacent teeth and alveolar bone or in an excessive buccal or lingual position, the final prosthesis rehabilitation impairs the peri-implant health of the gingival tissues and the aesthetics of the patient. Thus, the purpose of this case was to report and discuss a multidisciplinary protocol for the treatment of a compromised maxillary tooth in a patient with an abscess in his right central incisor due to an excessive buccal implant position. The patient presented with an implant-supported provisional restoration on his right maxillary central incisor and a traumatic injury in his left central incisor. The treatment protocol consisted in (i abutment substitution to compensate the incorrect angulation of the implant, (ii clinical crown lengthening, (iii atraumatic extraction of the left central incisor, and (iv immediate implant placement. Finally, (v a custom abutment was fabricated to obtain a harmonious gingival contour around the prosthetic crown. In conclusion, when implants are incorrectly positioned in relation to the adjacent teeth, associated with soft-tissue defects, the challenge to create a harmonious mucogingival contours may be achieved with an interdisciplinary approach and with the placement of an appropriate custom abutment.
Faot, Fernanda; Suzuki, Dalton; Senna, Plinio M; da Silva, Wander J; de Mattias Sartori, Ivete A
Cemented crowns are increasingly being used on dental implants instead of on screw-retained prostheses because of the reliability of internal Morse taper implant-abutment connections. However, there is a lack of information on the fit of metal ceramic and premachined alumina infrastructures. Therefore, the aim of this study was to evaluate the marginal and internal fits of different metal and alumina infrastructures cemented on universal post abutments. A total of 45 abutments (6 mm in height and 3.3 mm in diameter) were divided into five groups on the basis of their infrastructure material: cobalt-chromium (CoCr), nickel-chromium (NiCr), nickel-chromium-molybdenum-titanium (NiCrMoTi), gold (Au), and premachined alumina. The alumina group showed marginal overextension, and the Au group showed the highest discrepancy in marginal fit among the metal alloys. The CoCr and alumina groups showed the lowest discrepancies in internal fit. In conclusion, the alumina cylinders exhibited the best internal fit, despite their horizontal overextension. Among the metal alloys, CoCr exhibited the best fit at critical regions, such as the cervical and occlusal areas. © 2015 Eur J Oral Sci.
Renard, Yohann; de Mestier, Louis; Perez, Manuela; Avisse, Claude; Lévy, Philippe; Kianmanesh, Reza
Limited pancreatic resections are increasingly performed, but the rate of postoperative fistula is higher than after classical resections. Pancreatic segmentation, anatomically and radiologically identifiable, may theoretically help the surgeon removing selected anatomical portions with their own segmental pancreatic duct and thus might decrease the postoperative fistula rate. We aimed at systematically and comprehensively reviewing the previously proposed pancreatic segmentations and discuss their relevance and limitations. PubMed database was searched for articles investigating pancreatic segmentation, including human or animal anatomy, and cadaveric or surgical studies. Overall, 47/99 articles were selected and grouped into 4 main hypotheses of pancreatic segmentation methodology: anatomic, vascular, embryologic and lymphatic. The head, body and tail segments are gross description without distinct borders. The arterial territories defined vascular segments and isolate an isthmic paucivascular area. The embryological theory relied on the fusion plans of the embryological buds. The lymphatic drainage pathways defined the lymphatic segmentation. These theories had differences, but converged toward separating the head and body/tail parts, and the anterior from posterior and inferior parts of the pancreatic head. The rate of postoperative fistula was not decreased when surgical resection was performed following any of these segmentation theories; hence, none of them appeared relevant enough to guide pancreatic transections. Current pancreatic segmentation theories do not enable defining anatomical-surgical pancreatic segments. Other approaches should be explored, in particular focusing on pancreatic ducts, through pancreatic ducts reconstructions and embryologic 3D modelization.
Fabbri, Giacomo; Fradeani, Mauro; Dellificorelli, Gianluca; De Lorenzi, Marco; Zarone, Fernando; Sorrentino, Roberto
This multicenter retrospective clinical study aimed to evaluate the clinical performance of zirconia abutments in anterior and posterior regions, focusing on implant-abutment connections and restoration vertical height (RVH). Six experienced prosthodontists used 965 computer-aided design/computer-assisted manufacture zirconia abutments in 601 patients. Different surgical approaches were taken according to the needs of each patient. The final restorations were all-ceramic single crowns and short-span fixed dental prostheses. Screw-retained restorations were mainly used in anterior areas, whereas cemented prostheses were chosen in cases where the implant position was not ideal. Different types of implant-abutment connections were compared: external, internal with metal components, and internal full-zirconia conical connection. All the restorations were followed up for 4 to 10 years. Technical and biologic complications were assessed in relation to several biomechanical variables, such as RVH. Differences between groups were statistically analyzed, and longevity of abutments was evaluated according to Kaplan-Meier survival analysis. Zirconia abutments resulted in overall survival and success rates of 98.9% and 94.8%, respectively. External connections reported survival and success rates of 99.7% and 94.5%, internal metal connections 99.8% and 95.5%, and internal zirconia connections 93.1% and 93.1%, respectively. Overall complication rates of 1.14%, 3.42%, and 0.62% were reported for fractures, chipping, and unscrewing, respectively. The external connection showed the longest survival while the internal zirconia connection showed the highest fracture incidence over the observation period. The clinical risk limit of RVH was identified as 14 mm. Zirconia abutments showed satisfactory clinical performance in anterior and posterior regions after 4 to 10 years. RVH and connection type influenced the clinical longevity of restorations; in particular, internal connections
Weyhrauch, Michael; Igiel, Christopher; Scheller, Herbert; Weibrich, Gernot; Lehmann, Karl Martin
The fracture strengths of all-ceramic crowns cemented on titanium implant abutments may vary depending on crown materials and luting agents. The purpose of this study was to examine differences in fracture strength among crowns cemented on implant abutments using crowns made of seven different monolithic ceramic materials and five different luting agents. In total, 525 crowns (75 each of Vita Mark II, feldspathic ceramic [FSC]; Ivoclar Empress CAD, leucite-reinforced glass ceramic [LrGC]; Ivoclar e.max CAD, lithium disilicate [LiDS]; Vita Suprinity, presintered zirconia-reinforced lithium silicate ceramic [PSZirLS]; Vita Enamic, polymer-reinforced fine-structure feldspathic ceramic [PolyFSP], Lava Ultimate; resin nanoceramic [ResNC], Celtra Duo; fully crystallized zirconia-reinforced lithium silicate [FcZirLS]) were milled using a CAD/CAM system. The inner surfaces of the crowns were etched and silanized. Titanium implant abutments were fixed on implant analogs, and airborne-particle abrasion was used on their exterior specific adhesion surfaces (Al2O3, 50 μm). Then, the abutments were degreased and silanized. The crowns were cemented on the implant abutments using five luting agents (Multilink Implant, Variolink II, RelyX Unicem, GC FujiCEM, Panavia 2.0). After thermocycling for 5,000 cycles (5 to 55°C, 30 seconds dwell time), the crowns were subjected to fracture strength testing under static load using a universal testing machine. Statistical analyses were performed using analysis of variance (α = .0002) and the Bonferroni correction. No significant difference among the luting agents was found using the different all-ceramic materials. Ceramic materials LiDS, PSZirLS, PolyFSP, and ResNC showed significantly higher fracture strength values compared with FSC, FcZirLS, and LrGC. The PSZirLS especially showed significantly better results. Within the limitations of this study, fracture strength was not differentially affected by the various luting agents. However
Gehrke, Peter; Alius, Jochen; Fischer, Carsten; Erdelt, Kurt J; Beuer, Florian
The purpose of this study is to evaluate the retention of two-piece computer-aided design (CAD)/computer aided manufacturing (CAM) zirconia abutments after artificial aging under simulated oral conditions using three different types of resin-based luting agents. Twenty-one CAD/CAM-generated zirconia copings (CERCON Compartis, Degudent, Hanau, Germany) were bonded to a prefabricated secondary titanium implant insert (XiVE Ti-Base, Dentsply Friadent, Mannheim, Germany), using three different types of resin-based luting agents: group A: Panavia 21 (Kuraray Co, Kurashiki, Japan); group B: Multilink Implant (Ivoclar Vivadent, Schaan, Liechtenstein); and group C: SmartCem2 (Dentsply DeTrey, Konstanz, Germany). The bonding surfaces of the titanium inserts and the zirconia ceramic copings were air-abraded and cleaned in alcohol. All specimens were stored in distilled water for 60 days and subsequently thermal-cycled 15,000 times (5-55 °C). The dislodging force of the copings along the long axis of the implant/abutment complex was recorded using a universal testing machine with 2 mm/min crosshead speed. Data were analyzed descriptively and by performing the Kruskal-Wallis test. The mean retention values were 924.93 ± 363.31 N for Panavia 21, 878.05 ± 208.33 N for Multilink Implant, and 650.77 ± 174.92 N for SmartCem2. The Kruskal-Wallis test indicated no significant difference between the retention values of the tested luting agents (p = 0.1314). The failure modes of all tested two-piece abutments were completely adhesive, leaving the detached zirconia coping and titanium insert undamaged. The use of resin-based luting agents in combination with air abrasion of titanium inserts and zirconia copings led to a stable retention of two-piece CAD/CAM abutments. The bonding stability of the investigated luting agents exceeded the general limits of fracture resistance of two-piece zirconia abutments. A notable difference between the mean retention values of the tested bond
Mars Exploration Rover Opportunity has been exploring Mars for 12+ years, and is presently investigating the geology of a western rim segment of 22 kilometers diameter, Noachian- aged Endeavour crater. The Alpha Particle X-ray Spectrometer has determined the compositions of a pre-impact lithology, the Matijevic fm., and polymict impact breccias ejected from the crater, the Shoemaker fm. Opportunity is now investigating a region named Marathon Valley that cuts southwest-northeast through the central portion of the rim segment and provides a window into the lower stratigraphic record. (Geographic names used here are informal.) At the head of Marathon Valley, referred to here as Upper Marathon Valley, is a shallow, ovoid depression approximately 25×35 millimeters in size, named Spirit of Saint Louis. Layering inside Spirit of Saint Louis appears continuous with the Upper Marathon Valley rocks outside, indicating they are coeval. Spirit of Saint Louis is partly bounded by approximately 10-20 centimeters wide zone containing reddish altered rocks (red zone). Red zones also form prominent curvilinear features in Marathon Valley. Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) spectra provide evidence for a really extensive Fe-Mg smectite in the Marathon Valley region, indicating distinct styles of aqueous alteration. The CRISM detections of smectites are based on metal-OH absorptions at approximately 2.3 and 2.4 micron that are at least two times the background noise level.
He, Ling; Li, Deli; Zhang, Jiwu; Li, Xiucheng; Lu, Songhe; Tang, Zhihui
The aim of this study was to evaluate cross-sectional area of the abutments, strain distribution in the periimplant bone, stress in the abutments and dental root-analog implant by different abutment design under different loading conditions, through three-dimensional finite element analysis. Two three-dimensional finite element models were established. Two types of abutments, oval cross section abutment (OCSA) and circular cross section abutment (CCSA) were designed, keeping the size of the thinnest implant wall 0.75 mm. Two types of load were applied to the abutment in each model: 100 N vertical load (V), 100 N vertical/50 N horizontal load (VH). The biomechanical behaviors of abutments, implants, and periimplant bone were recorded. The cross-section area of OCSA is 36.5% larger than that of CCSA. In implants, the maximum von Mises stress value in OCSA design was 24.6% lower than that in CCSA design under V and under VH. In abutments, the maximum von Mises stress value in OCSA design was 40.0% lower than that in CCSA design under V, the maximum von Mises stress value in OCSA design was 12.2% lower than that in CCSA design under VH. The irregular design offers advantages over regular design.
Baker, V.R.; Gulick, V.C.
Work in progress on Hawaiian drainage evolution indicates an important potential for understanding drainage development on Mars. Similar to Mars, the Hawaiian valleys were initiated by surface runoff, subsequently enlarged by groundwater sapping, and eventually stabilized as aquifers were depleted. Quantitative geomorphic measurements were used to evaluate the following factors in Hawaiian drainage evolution: climate, stream processes, and time. In comparing regions of similar climate, drainage density shows a general increase with the age of the volcani island. With age and climate held constant, sapping dominated valleys, in contrast to runoff-dominated valleys, display the following: lower drainage densities, higher ratios of valley floor width to valley height, and more positive profile concavities. Studies of stream junction angles indicate increasing junction angles with time on the drier leeward sides of the major islands. The quantitative geomorphic studies and earlier field work yielded important insights for Martian geomorphology. The importance of ash mantling in controlling infiltration on Hawaii also seems to apply to Mars. The Hawaiian valley also have implications for the valley networks of Martian heavily cratered terrains
Sundh, Anders; Sjögren, Göran
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.
Canullo, Luigi; Peñarrocha-Oltra, David; Marchionni, Silvia; Bagán, Leticia; Micarelli, Costanza
Objectives: A randomized controlled trial was performed to assess soft tissue cell adhesion to implant titanium abutments subjected to different cleaning procedures and test if plasma cleaning can enhance cell adhesion at an early healing time. Study Design: Eighteen patients with osseointegrated and submerged implants were included. Before re-opening, 18 abutments were divided in 3 groups corresponding to different clinical conditions with different cleaning processes: no treatment (G1), laboratory customization and cleaning by steam (G2), cleaning by plasma of Argon (G3). Abutments were removed after 1 week and scanning electron microscopy was used to analyze cell adhesion to the abutment surface quantitatively (percentage of area occupied by cells) and qualitatively (aspect of adhered cells and presence of contaminants). Results: Mean percentages of area occupied by cells were 17.6 ± 22.7%, 16.5 ± 12.9% and 46.3 ± 27.9% for G1, G2 and G3 respectively. Differences were statistically significant between G1 and G3 (p=0.030), close to significance between G2 and G3 (p=0.056), and non-significant between G1 and G2 (p=0.530). The proportion of samples presenting adhered cells was homogeneous among the 3 groups (p-valor = 1.000). In all cases cells presented a flattened aspect; in 2 cases cells were less efficiently adhered and in 1 case cells presented filipodia. Three cases showed contamination with cocobacteria. Conclusions: Within the limits of the present study, plasma of Argon may enhance cell adhesion to titanium abutments, even at the early stage of soft tissue healing. Further studies with greater samples are necessary to confirm these findings. Key words:Connective tissue, dental abutments, randomized controlled trial, clinical research, glow discharged abutment, plasma cleaning. PMID:24121917
MGS MOC Release No. MOC2-418, 11 July 2003This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) high resolution image shows part of a dark-floored valley system in northern Newton Crater. The valley might have been originally formed by liquid water; the dark material is probably sand that has blown into the valley in more recent times. The picture was acquired earlier this week on July 6, 2003, and is located near 39.2oS, 157.9oW. The picture covers an area 2.3 km (1.4 mi) across; sunlight illuminates the scene from the upper left.
... 27 Alcohol, Tobacco Products and Firearms 1 2010-04-01 2010-04-01 false Lancaster Valley. 9.41... Lancaster Valley. (a) Name. The name of the viticultural area described in this section is “Lancaster Valley.” (b) Approved maps. The appropriate maps for determining the boundaries of the Lancaster Valley...
Özbek, Zühtü; Özkara, Emre; Yağmur, İpek; Arslantaş, Ali
Cervical adjacent segment disease; is the general name ofdisc pathologies that develop in adjacent levels after cervical surgery. If thecervical adjacent segment disease that do not require reoperation and it doesnot cause clinical signs is called radiological cervical adjacent segmentpathology, but those causing radiculopathy, myelopathy or instability is calledclinic cervical adjacent segment pathology. The incidence of cervical adjacentsegment disease in 10-year follow-up is 2.4% -2.9%. Wh...
Abstract: Adjacent segment disease (ASD) is defined as degeneration that develops at mobile segments above or below a fused spinal segment and usually develops after spinal fusion or other back surgeries. Nearly 5 decades ago, the medical findings related to ASD were usually released in case reports as a relatively unusual complication of lumbar or lumbosacral fusions. Since the initial reports, ASD has been found to occur more often than the earlier predictions for its prospect incidence. It...
Kim, Yongsik; Yamashita, Junro; Shotwell, Jeffrey L; Chong, Kok-Heng; Wang, Hom-Lay
In immediate implant loading, it is important to keep provisional restorations in place during early-phase healing. Current luting agents for provisional restorations may provide inadequate retention, creating a clinical challenge. This study compared the retention of provisional autopolymerizing acrylic resin implant-supported single restorations with combinations of different implant abutment surface conditions and provisional luting agents. Thirty solid titanium implant abutments (ITI), 4 mm high, were divided into 3 groups. Ten abutments were unaltered, 10 were airborne-particle abraded with 50-microm aluminum oxide, and 10 were roughened with a medium-roughness diamond rotary cutting instrument. Thirty implant analogs (ITI) were mounted in autopolymerizing acrylic resin blocks. A solid titanium implant abutment was placed in each implant analog and torqued to 35 N.cm. After fabrication of 4 provisional acrylic resin crowns for each abutment, provisional luting agents TempBond, TempBond NE, Life, and Zone were used to secure the provisional crowns to the respective abutments. All specimens were luted with one of the provisional luting agents for a given test. After ultrasonic cleaning of the abutments, another provisional crown was luted with another luting agent. All specimens were stored in 100% humidity environment for 1 day at 37 degrees C prior to testing. Each provisional acrylic resin crown was pulled from the abutment with a 500-kg load cell in a universal testing machine at a crosshead speed of 0.5 cm/minute, and tensile strength was recorded (N). Data were analyzed using analysis of variance (ANOVA) and the Scheffe test (alpha=.05). Tensile strength was significantly higher for Life and TempBond NE than for TempBond and Zone, regardless of the surface conditions (P=.0001). The result of the 2-way ANOVA indicated that a significant interaction existed between the provisional luting agents and surface conditions (P=.0039). TempBond NE showed
Gans, W. de.
This thesis is composed of five papers concerned with Late Quaternary geology and geomorphology of the Aa valley system. The correlation and chronostratigraphic position of the layers have been established by radiocarbon dating. (Auth.)
Blaffert, Thomas; Renisch, Steffen; Schadewaldt, Nicole; Schulz, Heinrich; Wiemker, Rafael
Prostate and cervix cancer diagnosis and treatment planning that is based on MR images benefit from superior soft tissue contrast compared to CT images. For these images an automatic delineation of the prostate or cervix and the organs at risk such as the bladder is highly desirable. This paper describes a method for bladder segmentation that is based on a watershed transform on high image gradient values and gray value valleys together with the classification of watershed regions into bladder contents and tissue by a graph cut algorithm. The obtained results are superior if compared to a simple region-after-region classification.
Pol, C W P; Raghoebar, G M; Kerdijk, W; Boven, G C; Cune, M S; Meijer, H J A
The purpose of the systematic review and meta-analysis was to compare the performance of 3-unit bridges on teeth with 3-unit bridges on implants, evaluating survival of the bridges, survival of the teeth or implants, condition of the hard and soft tissues surrounding the supports, complications and patient-reported outcome measures (PROM) after a mean observation period of at least 1 year. A literature search was conducted using a combination of the search terms: fixed partial denture and fixed dental prostheses (FDPs). An electronic search for data published until January 2017 was undertaken using the MEDLINE, EMBASE and Cochrane Library databases. Eligibility criteria included clinical human studies, either randomised or not, interventional or observational, which evaluated the results of 3-unit FDPs on either 2 implants or 2 abutment teeth. The search identified 1686 unique references. After applying eligibility criteria, 66 articles were included in the analysis. A total of 1973 3-unit FDPs were supported by teeth, and 765 were implant-supported. No significant differences were found either in the survival of the supporting abutments (P = .52; 99% vs 98.7% survival per year) or in the survival of the prostheses (P = .34; 96.4% vs 97.4% survival per year). Both treatments show an almost equally low complication rate, but there is a low level of reporting of hard and soft tissue conditions and PROM. It is concluded that implant-supported 3-unit FDPs seem to be a reliable treatment with survival rates not significantly different from the results of teeth-supported 3-unit FDPs. © 2017 John Wiley & Sons Ltd.
Pelosi, S; Chandrasekhar, S S
To review outcomes following implantation of an 8.5 mm bone-anchored hearing aid abutment, as regards post-operative management of scalp soft tissue overgrowth. Retrospective chart review of paediatric and adult patients implanted with bone-anchored hearing aids between 2003 and 2008 who subsequently underwent revision surgery for excessive soft tissue growth. A tertiary referral centre and a private otology and neurotology clinic. A total of 80 patients underwent bone-anchored hearing aid placement between 2003 and 2008. Of these patients, 14 had significant scalp soft tissue overgrowth unresponsive to first-line, nonsurgical local wound care. Fourteen patients underwent an average of 2.1 surgical procedures each for soft tissue overgrowth around their bone-anchored hearing aid abutment. The mean time between initial implantation and revision surgery was 13.6 months. Of these 14 patients, 11 were eventually fitted with an 8.5 mm abutment. Following placement of the longer abutment, only one patient required additional surgical reduction of soft tissue overgrowth (mean follow-up time 11.8 months). All patients were able to use their bone-anchored hearing aid. The 8.5 mm bone-anchored hearing aid abutment is successful in preventing the need for additional surgical intervention in the small but significant number of patients with post-implantation soft tissue overgrowth. Early consideration should be given to this option when first-line soft tissue care is inadequate.
Martínez-Rus, Francisco; Ferreiroa, Alberto; Özcan, Mutlu; Bartolomé, José F; Pradíes, Guillermo
To evaluate the fracture resistance of all-ceramic crowns cemented on titanium and zirconia implant abutments. Customized implant abutments for maxillary right central incisors made of titanium (Ti) and zirconia (Zr) (n=60, n=30 per group) were fabricated for an internal connection implant system. All-ceramic crowns were fabricated for their corresponding implant abutments using the following systems (n=10 per group): (1) monolithic computer-aided design/computer-assisted manufacture (CAD/CAM) lithium disilicate (MLD); (2) pressed lithium disilicate (PLD); (3) yttrium stabilized tetragonal zirconia polycrystal (YTZP). The frameworks of both PLD and YTZP systems were manually veneered with a fluorapatite-based ceramic. The crowns were adhesively cemented to their implant abutments and loaded to fracture in a universal testing machine (0.5 mm/minute). Data were analyzed using two-way analysis of variance (ANOVA) and Tukey's test (α=0.05). Both the abutment material (P=.0001) and the ceramic crown system (P=.028) significantly affected the results. Interaction terms were not significant (P=.598). Ti-MLD (558.5±35 N) showed the highest mean fracture resistance among all abutment-crown combinations (340.3±62-495.9±53 N) (Pcrown system showed significantly higher mean fracture resistance compared to manually veneered ones on both Ti and Zr abutments (Pcrown combinations failed only in the crowns without abutment fractures, Zr-YTZP combination failed exclusively in the abutment without crown fracture. Zr-MLD and Zr-PLD failed predominantly in both the abutment and the crown. Ti-YTZP showed only implant neck distortion. The highest fracture resistance was obtained with titanium abutments restored with MLD crowns, but the failure type was more favorable with Ti-YTZP combination.
Jeon, Jin-Hun; Lee, Kyung-Tak; Kim, Hae-Young; Kim, Ji-Hwan; Kim, Woong-Chul
The aim of this study was to evaluate the repeatability of the digitizing of silicon rubber impressions of abutment teeth by using a white light scanner and compare differences in repeatability between different abutment teeth types. Silicon rubber impressions of a canine, premolar, and molar tooth were each digitized 8 times using a white light scanner, and 3D surface models were created using the point clouds. The size of any discrepancy between each model and the corresponding reference tooth were measured, and the distribution of these values was analyzed by an inspection software (PowerInspect 2012, Delcamplc., Birmingham, UK). Absolute values of discrepancies were analyzed by the Kruskal-Wallis test and multiple comparisons (α=.05). The discrepancy between the impressions for the canine, premolar, and molar teeth were 6.3 µm (95% confidence interval [CI], 5.4-7.2), 6.4 µm (95% CI, 5.3-7.6), and 8.9 µm (95% CI, 8.2-9.5), respectively. The discrepancy of the molar tooth impression was significantly higher than that of other tooth types. The largest variation (as mean [SD]) in discrepancies was seen in the premolar tooth impression scans: 26.7 µm (95% CI, 19.7-33.8); followed by canine and molar teeth impressions, 16.3 µm (95% CI, 15.3-17.3), and 14.0 µm (95% CI, 12.3-15.7), respectively. The repeatability of the digitizing abutment teeth's silicon rubber impressions by using a white light scanner was improved compared to that with a laser scanner, showing only a low mean discrepancy between 6.3 µm and 8.9 µm, which was in an clinically acceptable range. Premolar impression with a long and narrow shape showed a significantly larger discrepancy than canine and molar impressions. Further work is needed to increase the digitizing performance of the white light scanner for deep and slender impressions.
Fauroux, Marie-Alix; Levallois, Bernard; Yachouh, Jacques; Torres, Jacques-Henri
The aim of this study was to evaluate, with a new gas flow technique, leakage at the implant/abutment junction in systems with four different connections. Five Branemark System, five One Morse, five Intra-lock System, and five Ankylos Plus implants and abutments were used. A hole was drilled in the apex of each implant to allow gas to flow through the connection from negative to atmospheric pressure. The gas flow was calculated (slope of pressure decrease, in hPa.s-1). Each connection was tested after both manual and key tightening. Statistical analysis was performed on a generalized linear model with repeated measurements. The significance level was set at α=.05. A global significant difference was observed between the various systems (P=.0001). After manual tightening, gas leakage was (Ln[hPa.s-1], means±standard deviations): One Morse: 0.20 (±1.70); Branemark System: -4.56 (±2.61); Intra-lock: -4.31 (±4.17); Ankylos Plus; -7.59 (±0.76). After key tightening, mean values were: One Morse: -2.51 (±2.72); Branemark System: -7.23 (±1.01); Intra-lock: -7.76 (±0.50); Ankylos Plus; -7.73 (±0.62). This study confirms that gas flow is an appropriate method to assess connection leakage. Ankylos Plus connection leakage was very low when the assembly was tightened manually. Among conical connection systems, low (Ankylos Plus) and high (One Morse) leakage was observed. This gas flow study suggests, therefore, that connection design is not the most important parameter for implant/abutment connection leakage.
Sasada, Yuya; Cochran, David L
Clinicians very often have seen marginal bone loss around dental implants at the crest level early on after implant placement and uncovering. Early clinical publications had suggested that this bone loss occurred during the first year of loading. Thus, numerous attempts have been made to minimize or eliminate such bone loss. However, the timing and reason for this bone loss are not always apparent. The objective of this study was to review the evidence regarding marginal bone loss around dental implants from the standpoint of biologic consequences to help understand marginal bone changes around dental implants. One hypothesis for the bone loss around these implants was related to the presence of bacteria in the interfaces between the implant and abutment connections. The literature was reviewed regarding the three major types of implant-abutment crestal connections, including butt-joint, platform-switched, and no interface (tissue-level or one-body). This review article revealed that 1.5 to 2.0 mm of bone loss occurred around bone-level, butt-joint connections when the interface was created because the microgap was wide enough for penetration and colonization of bacteria, and that this bone loss was not observed around implants with no interface because they did not have a contaminated interface at the bone crest. Many studies have shown an advantage in the amount of marginal bone resorption for implants with a platform-switched connection, and there appears to be a significantly different biologic reaction. Recent publications indicate that such contaminated implant-abutment connections might have an effect on peri-implantitis and failure over time.
Bittencourt, Thais Camargo; Ribeiro, Cleide Gisele; Devito, Karina Lopes; Ferreira, Cimara Fortes; Cagna, David Richard; Picorelli, Neuza Maria Souza
This prospective study evaluated peri-implant tissues around all-ceramic crowns fabricated using CAD/CAM technology. Twenty-five patients received pre-fabricated zirconia implant abutments with CAD/CAM zirconia copings in the esthetic zone. Implants were evaluated at baseline, and at 3 and 6 months in function. Radiographic analyzes showed stable bone crest around the implants. Esthetics were more favorable as time lapsed (p > 0.05). Bleeding Index was constant in all time intervals. Plaque index reduced from 3 to 6 months. The all-ceramic CAD/CAM crowns were clinically, radiographically and esthetically stable during the study period.
Segmented conjugated polymers, wherein the conjugation is randomly truncated by varying lengths of non-conjugated segments, form an interesting class of polymers as they not only represent systems of varying stiffness, but also ones where the backbone can be construed as being made up of chromophores of varying ...
Galeotti, Andrea; Moraga González, José
This paper explores the implications of market segmentation on firm competitiveness. In contrast to earlier work, here market segmentation is minimal in the sense that it is based on consumer attributes that are completely unrelated to tastes. We show that when the market is comprised by two
Once the market has been segmented into different segments or target markets, a customised marketing mix aimed ... restaurant managers need to understand what motivates consumers to dine out and to choose one ... Customers might consider food quality, price, promotions and recommendations, among other desirable ...
Conclusion: RPDs with an ARTR and both retainer types with a rigid design produced more strain distal to the abutting teeth. Using more than two abutting teeth did not improve the strain patterns of the tested RPDs. More strain was produced on the posterior edentulous ridges.
Balshi, Stephen F; Wolfinger, Glenn J; Balshi, Thomas J
The aim of this study is to demonstrate the accuracy and clinical precision of a guided surgery protocol by using traditional Brånemark System abutments in conjunction with a prefabricated all-acrylic provisional prosthesis that is immediately installed after implant placement. All presurgical methods in this treatment follow the standard NobelGuide protocol with the exception of the laboratory phase. Once the master cast is retroengineered from the surgical template, traditional Brånemark System abutments were secured onto the implant replicas (master cast) and an all-acrylic provisional prosthesis was constructed at the abutment level. The typical abutments used with this protocol, adjustable Guided Abutments, were not used. Twenty-three patients were treated in this pilot study. Via the surgical template, all implants were placed to the desired depth as planned in the virtual implant planning program. After the traditional Brånemark Abutments were installed, the provisional prosthesis was delivered and occlusion verified. The prosthesis fit was checked at abutment level clinically and radiographically. This report shows the extreme accuracy of this guided surgery protocol. If each step of this protocol is followed precisely, it is possible to deliver a prefabricated prosthesis built to traditional Brånemark System Abutments, which is extremely favorable for long-term patient and prosthesis management.
Koutayas, Spiridon-Oumvertos; Mitsias, Miltiadis; Wolfart, Stefan; Kern, Matthias
Zirconia implant abutments offer enhanced esthetics and promote biologic sealing; however, the effect of laboratory or intraoral preparation on the mechanical stability of zirconia has not been investigated. The purpose of the study was to evaluate the influence of the preparation mode and depth on the fracture strength of zirconia abutments restored with lithium disilicate crowns. To replace a maxillary central incisor (11.0 mm in height and 8.0 mm in width), 35 lithium disilicate crowns were cemented onto zirconia abutments on 4.5- ° - 15-mm titanium implants. Lithium disilicate implant crowns were divided into five study groups (n = 7) according to the abutment preparation mode (milling by the manufacturer or milling by the Celay System [Mikrona] [P]) and preparation depth (0.5 mm [A], 0.7 mm [B], or 0.9 mm [C]). All groups were subjected to quasi-static loading (S) at 135 degrees to the implant axis in a universal testing machine. Mean fracture strengths were: group SA, 384 ± 84 N (control); group SB, 294 ± 95 N; group SPB, 332 ± 80 N; group SC, 332 ± 52; group SPC, 381 ± 101 N. All specimens presented a typical fracture mode within the implant/abutment internal connection. Multiple regression analysis revealed that preparation depth up to 0.7 mm statistically influenced the fracture strength (P = .034), whereas the preparation mode did not seem to play an important role (P = .175). Regardless of preparation mode, circumferential preparation of zirconia abutments might negatively affect the fracture strength of adhesively cemented single implant lithium disilicate crowns.
Full Text Available Objectives: This finite element method study aimed to compare the amount of stress on an isolated mandibular second premolar in two conventional reciprocal parallel interface designs of removable partial dentures (RPDs and the same RPD abutment tooth (not isolated.Materials and Methods: A Kennedy Class 1, modification 1 RPD framework was simulated on a 3D model of mandible with three different designs: an isolated tooth with a mesial rest, an isolated tooth with mesial and distal rests and an abutment with a mesial rest (which was not isolated; 26 N occlusal forces were exerted bilaterally on the first molar sites. Stress on the abutment teeth was analyzed using Cosmos Works 2009 Software.Results: In all designs, the abutment tooth stress concentration was located in the buccal alveolar crest. In the first model, the von Mises stress distribution in the contact area of I-bar clasp and cervical portion of the tooth was 19 MPa and the maximum stress was 30 MPa. In the second model, the maximum von Mises stress distribution was 15 MPa in the cervical of the tooth. In the third model, the maximum von Mises stress was located in the cervical of the tooth and the distal proximal plate.Conclusion: We recommend using both mesial and distal rests on the distal abutment teeth of distal extension RPDs. The abutment of an extension base RPD, which is not isolated in presence of its neighboring more anterior tooth, may have a better biomechanical prognosis.
Nossair, Shereen Ahmed; Aboushelib, Moustafa N; Morsi, Tarek Salah
To evaluate the fracture mechanics of cemented versus fused CAD-on veneers on customized zirconia implant abutments. Forty-five identical customized CAD/CAM zirconia implant abutments (0.5 mm thick) were prepared and seated on short titanium implant abutments (Ti base). A second scan was made to fabricate 45 CAD-on veneers (IPS Empress CAD, A2). Fifteen CAD-on veneers were cemented on the zirconia abutments (Panavia F2.0). Another 15 were fused to the zirconia abutments using low-fusing glass, while manually layered veneers served as control (n = 15). The restorations were subjected to artificial aging (3.2 million cycles between 5 and 10 kg in a water bath at 37°C) before being axially loaded to failure. Fractured specimens were examined using scanning electron microscopy to detect fracture origin, location, and size of critical crack. Stress at failure was calculated using fractography principles (alpha = 0.05). Cemented CAD-on restorations demonstrated significantly higher (F = 72, p CAD-on and manually layered restorations. Fractographic analysis of fractured specimens indicated that cemented CAD-on veneers failed due to radial cracks originating from the veneer/resin interface. Branching of the critical crack was observed in the bulk of the veneer. Fused CAD-on veneers demonstrated cohesive fracture originating at the thickest part of the veneer ceramic, while manually layered veneers failed due to interfacial fracture at the zirconia/veneer interface. Within the limitations of this study, cemented CAD-on veneers on customized zirconia implant abutments demonstrated higher fracture than fused and manually layered veneers. © 2014 by the American College of Prosthodontists.
PURPOSE This study evaluated the effectiveness of various methods for removing provisional cement from implant abutments, and what effect these methods have on the retention of prosthesis during the definitive cementation. MATERIALS AND METHODS Forty implant fixture analogues and abutments were embedded in resin blocks. Forty cast crowns were fabricated and divided into 4 groups each containing 10 implants. Group A was cemented directly with the definitive cement (Cem-Implant). The remainder were cemented with provisional cement (Temp-Bond NE), and classified according to the method for cleaning the abutments. Group B used a plastic curette and wet gauze, Group C used a rubber cup and pumice, and Group D used an airborne particle abrasion technique. The abutments were observed using a stereomicroscope after removing the provisional cement. The tensile bond strength was measured after the definitive cementation. Statistical analysis was performed using one-way analysis of variance test (α=.05). RESULTS Group B clearly showed provisional cement remaining, whereas the other groups showed almost no cement. Groups A and B showed a relatively smooth surface. More roughness was observed in Group C, and apparent roughness was noted in Group D. The tensile bond strength tests revealed Group D to have significantly the highest tensile bond strength followed in order by Groups C, A and B. CONCLUSION A plastic curette and wet gauze alone cannot effectively remove the residual provisional cement on the abutment. The definitive retention increased when the abutments were treated with rubber cup/pumice or airborne particle abraded to remove the provisional cement. PMID:24049563
Ozkomur, Ahmet; Erbil, Mehmet; Akova, Tolga
The objectives of this study were to evaluate the galvanic corrosion behavior between titanium and nickel-chromium (Ni-Cr) alloy, to investigate the effect of diamondlike carbon (DLC) coating over titanium on galvanic corrosion behavior between titanium and Ni-Cr alloy, and to evaluate the effect of DLC coating over titanium abutments on the fit and integrity of prosthetic assemblies by scanning electron microcopy (SEM). Five Ni-Cr and 10 titanium disks with a diameter of 5 mm and thickness of 3 mm were prepared. DLC coating was applied to five titanium disks. Electrode samples were prepared, and open circuit potential measurements, galvanic current measurements over platinum electrodes, and potentiodynamic polarization tests were carried out. For the SEM evaluation, 20 Ni-Cr alloy and 10 gold alloy superstructures were cast and prepared over 30 abutments. DLC coating was applied to 10 of the abutments. Following the fixation of prosthetic assemblies, the samples were embedded in acrylic resin and cross sectioned longitudinally. Internal fit evaluations were carried out through examination of the SEM images. Titanium showed more noble and electrochemically stable properties than Ni-Cr alloy. DLC coating over the cathode electrode served as an insulating film layer over the surface and prevented galvanic coupling. Results of the SEM evaluations indicated that the DLC-coated and titanium abutments showed no statistically significant difference in fit. Hence, no adverse effects on the adaptation of prosthetic components were found with the application of DLC coating over abutment surfaces. DLC coating might serve as a galvanic corrosion barrier between titanium abutments and Ni-Cr superstructures.
This rare case report describes prosthodontic complications resulting from a dental implant was placed surgically more distally in the area of the missing mandibular first molar with a cantilever effect and a crest width of >12 mm in a 59-year-old patient who had a history of bruxism. Fracture of abutment is a common complication in implant was placed in area with high occlusal forces. Inability to remove the broken abutment may most often end up in discarding the implant. Adding one more den...
Kaleli, Necati; Sarac, Duygu; Külünk, Safak; Öztürk, Özgür
In recent years, the use of resin-matrix ceramics and polyetheretherketone (PEEK) abutments has been suggested to absorb excessive stresses on dental implants. However, only a few studies have evaluated the effect of these materials on stress distribution in implants and peripheral bone structure. The purpose of this finite element analysis was to evaluate the biomechanical behaviors of resin-matrix ceramics and PEEK customized abutments in terms of stress distribution in implants and peripheral bone. Three-dimensional (3D) models of a bone-level implant system and a titanium base abutment were created by using the standard tessellation language (STL) data of original implant components. An anatomic customized abutment and a maxillary right second premolar crown were then modeled over the titanium base abutment. A bone block representing the maxillary right premolar area was created, and the implant was placed in the bone block with 100% osseointegration. Six different models were created according to combinations of restoration materials (translucent zirconia [TZI], lithium disilicate glass ceramic [IPS], polymer-infiltrated hybrid ceramic [VTE]), and customized abutment materials (PEEK and zirconia). In each model, the implants were loaded vertically (200 N) and obliquely (100 N). The stress distribution in the crown, implant, and abutments was evaluated through the von Mises stress analysis, and the stress distribution in the peripheral bone was examined through the maximum and minimum principal stress analyses. The oblique load resulted in high stress values in the implant components, restorative crown, and cortical bone. Low stress values were observed in the VTE crowns. Zirconia customized abutments exhibited higher stress values than PEEK customized abutments. The stress distributions in the implant and peripheral bone were similar in all models. Changes in restoration and customized abutment material did not affect stress distribution in the implant and
Glauser, Roland; Sailer, Irena; Wohlwend, Arnold; Studer, Stephan; Schibli, Monica; Schärer, Peter
This prospective clinical study evaluated an experimental implant abutment made of densely sintered zirconia with respect to peri-implant hard and soft tissue reaction as well as fracture resistance over time. Twenty-seven consecutively treated patients with 54 single-tooth implants were included. Zirconia abutment ingots were individually shaped and set on the implants with gold screws. All-ceramic (Empress I) crowns were cemented using a composite cement. At the 1- and 4-year examinations, reconstructions were evaluated for technical problems (fracture of abutment or crown, loosening of abutment screw). Modified Plaque and simplified Gingival Indices were recorded at implants and neighboring teeth, and peri-implant bone levels were radiographically determined. All but 1 of the 27 patients with 53 restorations could be evaluated at 1 year, and 36 restorations in 18 patients were evaluated 4 years after abutment and crown insertion. The median observation period for the reconstructions was 49.2 months. No abutment fractures occurred. Abutment screw loosening was reported for 2 restorations at 8 months and 27 months, respectively. Mean Plaque Index was 0.4 (SD 0.6) at abutments and 0.5 (SD 0.6) at teeth; mean Gingival Index was 0.7 (SD 0.5) at abutments and 0.9 (SD 0.5) at teeth. Mean marginal bone loss measured 1.2 mm (SD 0.5) after 4 years of functional loading. Zirconia abutments offered sufficient stability to support implant-supported single-tooth reconstructions in anterior and premolar regions. The soft and hard tissue reaction toward zirconia was favorable.
Kunt, Göknil Ergün; Kökçü, Deniz; Ceylan, Gözlem; Yılmaz, Nergiz; Güler, Ahmet Umut
The purpose of this study was to investigate the effect of tooth supported (TSD) and toothtissue supported (TTSD) removable partial denture wearing on pulpal blood flow (PBF) of the abutment teeth by using Laser Doppler Flowmeter (LDF). Measurements were carried out on 60 teeth of 28 patients (28 teeth and 12 patients of TTSD group, 32 teeth and 16 patients of TSD group) who had not worn any type of removable partial dentures before, had no systemic problems and were non smokers. PBF values were recorded by LDF before insertion (day 0) and after insertion of dentures at day 1, day 7 and day 30. Statistical analysis was performed by student t test and covariance analyses of repeated measurements. In the group TTSD, the mean values of PBF decreased statistically significantly at day 1 after insertion when compared with PBF values before insertion (p<0,01). There was no statistically significant difference among PBF mean values on 1st, 7th and 30th day. However, in the group TSD, there was no statistically significant difference among PBF mean values before insertion and on 1st, 7th and 30th day. In other words, PBF mean values in group TSD continued without changing statistically significant on 1st, 7th and 30th day. TTSD wearing may show negative effect on the abutment teeth due to decreasing basal PBF. PMID:20001995
Göknil Ergün Kunt
Full Text Available The purpose of this study was to investigate the effect of tooth supported (TSD and toothtissue supported (TTSD removable partial denture wearing on pulpal blood flow (PBF of the abutment teeth by using Laser Doppler Flowmeter (LDF.Measurements were carried out on 60 teeth of 28 patients (28 teeth and 12 patients of TTSD group, 32 teeth and 16 patients of TSD group who had not worn any type of removable partial dentures before, had no systemic problems and were non smokers. PBF values were recorded by LDF before insertion (day 0 and after insertion of dentures at day 1, day 7 and day 30. Statistical analysis was performed by student t test and covariance analyses of repeated measurements.In the group TTSD, the mean values of PBF decreased statistically significantly at day 1 after insertion when compared with PBF values before insertion (p<0,01. There was no statistically significant difference among PBF mean values on 1st, 7th and 30th day. However, in the group TSD, there was no statistically significant difference among PBF mean values before insertion and on 1st, 7th and 30th day. In other words, PBF mean values in group TSD continued without changing statistically significant on 1st, 7th and 30th day.TTSD wearing may show negative effect on the abutment teeth due to decreasing basal PBF.
Michael Josef Kridanto Kamadjaja
Full Text Available Dental implants have been used for several decades. Patients of all ages have chosen dental implants to replace a single tooth or several teeth or to support partial or full dentures. This paper reports two cases of patients treated with dental implant as alternative to replace the missing teeth and connected with natural tooth as abutments in a fixed restoration with distal cantilever bridge. The underlining reasons that we decided to make such kind fixed prostheses are because of clinically imposible to put the implant on certain area and the patients asked for prostheses as optimum as possible, so the mastication function could return to the homeostasis condition. The benefit of these treatments are that prostheses could be made as optimum as possible with a more economic price, so the patients feel quite satisfied. The result shows that a few years after the treatments finished there is no any disadvantageous effect of connecting teeth to implants as abutments in fixed partial dentures and there is no sign of a harmful effect to the opposing teeth either.
Huacho, Patricia Milagros Maquera; Nogueira, Marianne N Marques; Basso, Fernanda G; Jafelicci Junior, Miguel; Francisconi, Renata S; Spolidorio, Denise M P
The aim of this study was to evaluate the surface free energy (SFE), wetting and surface properties as well as antimicrobial, adhesion and biocompatibility properties of diamond-like carbon (DLC)-coated surfaces. In addition, the leakage of Escherichia coli through the abutment-dental implant interface was also calculated. SFE was calculated from contact angle values; R a was measured before and after DLC coating. Antimicrobial and adhesion properties against E. coli and cytotoxicity of DLC with human keratinocytes (HaCaT) were evaluated. Further, the ability of DLC-coated surfaces to prevent the migration of E. coli into the external hexagonal implant interface was also evaluated. A sterile technique was used for the semi-quantitative polymerase chain reaction (semi-quantitative PCR). The surfaces showed slight decreases in cell viability (p0.05). It was concluded that DLC was shown to be a biocompatible material with mild cytotoxicity that did not show changes in R a, SFE, bacterial adhesion or antimicrobial properties and did not inhibit the infiltration of E. coli into the abutment-dental implant interface.
Full Text Available Background and Aims: Different mechanisms have been developed for connecting abutment to implant. One of the most popular mechanisms is Tapered Integrated Screw (TIS, which is a Tapered Interference Fit (TIF with a screw integrated at the bottom of that. The aim of this study was to investigate the mechanism of TIS and effective factors in employing TIS during design and implementation processes using an analytic method.Materials and Methods: Relevant equations were developed to predict tightening and loosening torques, contactpressure and preloads with and without bone tissue in this analysis. The efficiency is defined as the ratio of the loosening torque to the tightening torque. The effects of the change in elastic modulus and thickness of the bone on operation of this mechanism were investigated.Results: In this study, 14 independent parameters such as taper angle, friction coefficient, abutment and implantgeometry that are effective on performance of TIS mechanism were presented. The role of some factors was shown in the performance of ITI implant using sensitivity analysis.Conclusion: It was shown that friction coefficient, contact length, and implant radius play major roles on tightening and loosening torques and efficiency of the mechanism. Furthermore, the results revealed that the change in the elastic modulus and thickness of the bone influenced the efficiency of the mechanism less than 15%.
Full Text Available The use of dental implants to solve different problems in dentistry has been growing rapidly. The success rates of dental implants are also very important for patients. Depending on the bone level of patients, short dental implants are very popular and widely used by many dentists. Although many dentists are using short dental implants frequently, It can be guessed that there can be stability problems because of crown to implant ratios. In this study, it is aimed to find out the effects of dental implant and abutment lengths on stability of short dental implants. 3 different short dental implant design made with the use of Solidworks 2013. Abutment lengths were 3,5 mm, 4 mm, 4,5 mm, 5 mm and implant lengths were 5 mm, 6 mm, 7 mm for each model. Human mandible model is transferred from Computed Tomography. Then, each implant model is mounted to modeled mandible and Finite Element Analysis is performed for each model. In order to see the effects of implant number on stability, we performed same analysis by placing 4 implants to the mandible
Full Text Available Background: Peri-implant crestal bone must be stable for aesthetic reasons. Aim of this study was a histologic analysis of an implant with a platform switched implant-abutment connection. Materials and methods: A 32-year-old male patient participated in this study. The patient needed a bilateral mandibular restoration. Four implants were used, and were immediately restored and loaded the same day of insertion. After a 6 weeks healing period, one implant with platform-switched abutment was retrieved with trephine. Before retrieval the implant was osseointegrated and not mobile. On one side of the implant, a 1 mm resorption of the crestal bone was present. On the contrary, on the other side no bone resorption had occurred and about 1 mm of bone was present over the implant shoulder. Results: The bone-implant contact percentage was 65.1 ± 6.3 %. Platform- switching could help in maintaining the height of the peri-implant crestal bone.
Some aspects of chromosome condensation in mammalians -humans especially- were studied by means of cytogenetic techniques of chromosome banding. Two further approaches were adopted: a study of normal condensation as early as prophase, and an analysis of chromosome segmentation induced by physical (temperature and γ-rays) or chemical agents (base analogues, antibiotics, ...) in order to show out the factors liable to affect condensation. Here 'segmentation' means an abnormal chromosome condensation appearing systematically and being reproducible. The study of normal condensation was made possible by the development of a technique based on cell synchronization by thymidine and giving prophasic and prometaphasic cells. Besides, the possibility of inducing R-banding segmentations on these cells by BrdU (5-bromodeoxyuridine) allowed a much finer analysis of karyotypes. Another technique was developed using 5-ACR (5-azacytidine), it allowed to induce a segmentation similar to the one obtained using BrdU and identify heterochromatic areas rich in G-C bases pairs [fr
The Initialization Segment creates the starting description of the uranium market. The starting description includes the international boundaries of trade, the geologic provinces, resources, reserves, production, uranium demand forecasts, and existing market transactions. The Initialization Segment is designed to accept information of various degrees of detail, depending on what is known about each region. It must transform this information into a specific data structure required by the Market Segment of the model, filling in gaps in the information through a predetermined sequence of defaults and built in assumptions. A principal function of the Initialization Segment is to create diagnostic messages indicating any inconsistencies in data and explaining which assumptions were used to organize the data base. This permits the user to manipulate the data base until such time the user is satisfied that all the assumptions used are reasonable and that any inconsistencies are resolved in a satisfactory manner
The statistical characteristics of image speckle are reviewed. Existing segmentation techniques that have been used for speckle filtering, edge detection, and texture extraction are sumamrized. The relative effectiveness of each technique is briefly discussed.
Haralick, R. M.
The methodologies and capabilities of image segmentation techniques are reviewed. Single linkage schemes, hybrid linkage schemes, centroid linkage schemes, histogram mode seeking, spatial clustering, and split and merge schemes are addressed.
Zembic, Anja; Bösch, Adrian; Jung, Ronald E; Hämmerle, Christoph H F; Sailer, Irena
To test the survival rates, and the technical and biological complication rates of customized zirconia and titanium abutments 5 years after crown insertion. Twenty-two patients with 40 single implants in maxillary and mandibular canine and posterior regions were included. The implant sites were randomly assigned to zirconia abutments supporting all-ceramic crowns or titanium abutments supporting metal-ceramic crowns. Clinical examinations were performed at baseline, and at 6, 12, 36 and 60 months of follow-up. The abutments and reconstructions were examined for technical and/or biological complications. Probing pocket depth (PPD), plaque control record (PCR) and Bleeding on Probing (BOP) were assessed at abutments (test) and analogous contralateral teeth (control). Radiographs of the implants revealed the bone level (BL) on mesial (mBL) and distal sides (dBL). Data were statistically analyzed with nonparametric mixed models provided by Brunner and Langer and STATA (P zirconia and 10 titanium abutments were available at a mean follow-up of 5.6 years (range 4.5-6.3 years). No abutment fracture or loss of a reconstruction occurred. Hence, the survival rate was 100% for both. Survival of implants supporting zirconia abutments was 88.9% and 90% for implants supporting titanium abutments. Chipping of the veneering ceramic occurred at three metal-ceramic crowns supported by titanium abutments. No significant differences were found at the zirconia and titanium abutments for PPD (meanPPDZrO2 3.3 ± 0.6 mm, mPPDTi 3.6 ± 1.1 mm), PCR (mPCRZrO2 0.1 ± 0.3, mPCRTi 0.3 ± 0.2) and BOP (mBOPZrO2 0.5 ± 0.3, mBOPTi 0.6 ± 0.3). Moreover, the BL was similar at implants supporting zirconia and titanium abutments (mBLZrO2 1.8 ± 0.5, dBLZrO2 2.0 ± 0.8; mBLTi 2.0 ± 0.8, dBLTi 1.9 ± 0.8). There were no statistically or clinically relevant differences between the 5-year survival rates, and the technical and biological complication rates of zirconia and
Virk, Sohrab S; Niedermeier, Steven; Yu, Elizabeth; Khan, Safdar N
EDUCATIONAL OBJECTIVES As a result of reading this article, physicians should be able to: 1. Understand the forces that predispose adjacent cervical segments to degeneration. 2. Understand the challenges of radiographic evaluation in the diagnosis of cervical and lumbar adjacent segment disease. 3. Describe the changes in biomechanical forces applied to adjacent segments of lumbar vertebrae with fusion. 4. Know the risk factors for adjacent segment disease in spinal fusion. Adjacent segment disease (ASD) is a broad term encompassing many complications of spinal fusion, including listhesis, instability, herniated nucleus pulposus, stenosis, hypertrophic facet arthritis, scoliosis, and vertebral compression fracture. The area of the cervical spine where most fusions occur (C3-C7) is adjacent to a highly mobile upper cervical region, and this contributes to the biomechanical stress put on the adjacent cervical segments postfusion. Studies have shown that after fusion surgery, there is increased load on adjacent segments. Definitive treatment of ASD is a topic of continuing research, but in general, treatment choices are dictated by patient age and degree of debilitation. Investigators have also studied the risk factors associated with spinal fusion that may predispose certain patients to ASD postfusion, and these data are invaluable for properly counseling patients considering spinal fusion surgery. Biomechanical studies have confirmed the added stress on adjacent segments in the cervical and lumbar spine. The diagnosis of cervical ASD is complicated given the imprecise correlation of radiographic and clinical findings. Although radiological and clinical diagnoses do not always correlate, radiographs and clinical examination dictate how a patient with prolonged pain is treated. Options for both cervical and lumbar spine ASD include fusion and/or decompression. Current studies are encouraging regarding the adoption of arthroplasty in spinal surgery, but more long
Maričić Branko R.
Full Text Available Strategic planning of marketing activities is the basis of business success in modern business environment. Customers are not homogenous in their preferences and expectations. Formulating an adequate marketing strategy, focused on realization of company's strategic objectives, requires segmented approach to the market that appreciates differences in expectations and preferences of customers. One of significant activities in strategic planning of marketing activities is market segmentation. Strategic planning imposes a need to plan marketing activities according to strategically important segments on the long term basis. At the same time, there is a need to revise and adapt marketing activities on the short term basis. There are number of criteria based on which market segmentation is performed. The paper will consider effectiveness and efficiency of different market segmentation criteria based on empirical research of customer expectations and preferences. The analysis will include traditional criteria and criteria based on behavioral model. The research implications will be analyzed from the perspective of selection of the most adequate market segmentation criteria in strategic planning of marketing activities.
Patil, Ratnadeep; Gresnigt, Marco M M; Mahesh, Kavita; Dilbaghi, Anjali; Cune, Marco S
Purpose: To correlate patients' satisfaction and dentists' observations regarding two abutment designs used for single crowns in the esthetic zone: a divergent one (control) and a curved one (experimental), with special emphasis on muco-gingival esthetics. Materials and Methods: Twenty-six patients
A new bridge design and construction trend to help improve durability and rideability is to remove expansion joints over piers and abutments. One approach to achieve this is to make the deck continuous over the piers by means of a link slab while the...
A new bridge design and construction trend to help improve durability and rideability is to remove expansion : joints over piers and abutments. One approach to achieve this is to make the deck continuous over the piers by : means of a link slab while...
Grunder, Ueli; Spielmann, Hans-Peter; Snétivy, Daniel
The use of small-diameter implants is indicated when small missing teeth have to be replaced, especially in esthetic zones. Nevertheless, the small diameter can pose a limiting factor with respect to what materials can be used for the final crown. In most cases, full-ceramic crowns in combination with a ceramic abutment are usually the material of choice for final reconstructions. To date, based on mechanical considerations, a 3.5 mm implant diameter has been a contraindication for using ceramic abutments. The authors describe here the development, in vitro testing, and clinical use of a zirconium abutment with a 3.5 mm diameter. The advantages of this small-diameter zirconia abutment include a minimum platform height that offers optimal prosthetic flexibility, and an accurate transfer of the implant position on to the master model. Furthermore, a precise rotational orientation for single-tooth restorations, optimal mechanical stability, and optimal fatigue resistance can be achieved. The microgap is minimized and protection against overload is afforded. In the reported case, high patient satisfaction was achieved due also to an esthetically pleasing final result.
Erica Dorigatti de Avila
Full Text Available The aim of this review was to investigate the relationship between biofilm and peri-implant disease, with an emphasis on the types of implant abutment surfaces. Individuals with periodontal disease typically have a large amount of pathogenic microorganisms in the periodontal pocket. If the individuals lose their teeth, these microorganisms remain viable inside the mouth and can directly influence peri-implant microbiota. Metal implants offer a suitable solution, but similarly, these remaining bacteria can adhere on abutment implant surfaces, induce peri-implantitis causing potential destruction of the alveolar bone near to the implant threads and cause the subsequent loss of the implant. Studies have demonstrated differences in biofilm formation on dental materials and these variations can be associated with both physical and chemical characteristics of the surfaces. In the case of partially edentulous patients affected by periodontal disease, the ideal type of implant abutments utilized should be one that adheres the least or negligible amounts of periodontopathogenic bacteria. Therefore, it is of clinically relevance to know how the bacteria behave on different types of surfaces in order to develop new materials and/or new types of treatment surfaces, which will reduce or inhibit adhesion of pathogenic microorganisms, and, thus, restrict the use of the abutments with indication propensity for bacterial adhesion.
Scour around the foundations (piers and abutments) of a bridge due to river flow is often referred to as bridge scour. Bridge scour is a problem of national scope that has dramatic impacts on economics and safety of the traveling public. Bridge...
Glenn Hsuan-Chen Chang
Full Text Available Purpose: An integrated fixture mount/impression coping/ temporary abutment can provide many advantages for immediate loading of dental implants, such as simpler procedure, less chair time, cost reduction, and comfort for the patients. Materials and Methods: A newly designed dental implant fixture mount (DIFMA can be used as an impression coping for taking an immediate impression. An immediate load provisional prosthesis can then be fabricated shortly after implant placement to immediately load the implants. This fixture mount can also serve as a temporary abutment for immediate chair-side fabrication of provisional prosthesis. Two clinical cases are presented. Results: A clinical case utilizing the fixture mount abutment (DIFMA/implant assembly is presented. The precision of fitting between the impression copings and implants is secured with this system. The chair time for taking an immediate impression is greatly reduced. Less cost for the restoration is provided and patient comfort is delivered. Conclusions: More patient satisfaction can be conferred by employing the fixture mount in the process of immediate impression taking and as an immediate provisional abutment.
Chang, Glenn Hsuan-Chen; Tian, Chen; Hung, Yuen-Siang
Purpose: An integrated fixture mount/impression coping/ temporary abutment can provide many advantages for immediate loading of dental implants, such as simpler procedure, less chair time, cost reduction, and comfort for the patients. Materials and Methods: A newly designed dental implant fixture mount (DIFMA) can be used as an impression coping for taking an immediate impression. An immediate load provisional prosthesis can then be fabricated shortly after implant placement to immediately load the implants. This fixture mount can also serve as a temporary abutment for immediate chair-side fabrication of provisional prosthesis. Two clinical cases are presented. Results: A clinical case utilizing the fixture mount abutment (DIFMA)/implant assembly is presented. The precision of fitting between the impression copings and implants is secured with this system. The chair time for taking an immediate impression is greatly reduced. Less cost for the restoration is provided and patient comfort is delivered. Conclusions: More patient satisfaction can be conferred by employing the fixture mount in the process of immediate impression taking and as an immediate provisional abutment. PMID:22090763
... valley fever, but it is not contagious between animals and people. Valley fever in dogs is similar to valley ... Via Growth on Fomites. An Epidemic Involving Six Persons. Am Rev Respir Dis. ... aspects of coccidioidomycosis in animals and humans. Ann N Y Acad Sci. 2007 ...
Barwacz, Christopher A; Stanford, Clark M; Diehl, Ursula A; Qian, Fang; Cooper, Lyndon F; Feine, Jocelyne; McGuire, Michael
To objectively assess the influence that three different implant-abutment interface designs had on peri-implant mucosal esthetics at 1 year post-implant placement via the pink esthetic score (PES). Additionally, to demonstrate the novel employment of a tablet-based digital imaging format to reliably assess and score clinical images as part of a multicenter clinical trial according to PES criteria. Adult subjects (n = 141) with healed tooth-bound edentulous sites in the anterior maxilla as well as first premolar region were randomized to receive one of three different implant-abutment interface designs (conical interface = CI; flat-to-flat interface = FI; or platform switch interface = PS). Immediate provisionalization was performed with prefabricated titanium abutments, with definitive custom CAD/CAM zirconia abutments and all-ceramic cement-based crowns being delivered 12-week post-implant placement. Bilateral (anterior sites) or unilateral (premolar sites) digital clinical photographs were made at 1, 3, 6, and 12 months post-implant placement. Five calibrated faculty evaluators of different clinical backgrounds scored images during a 4-week timeframe on a standardized, tablet-based, digital imaging format. Six hundred and forty-nine clinical photographs were evaluated resulting in a total of 3245 sum PES values and 22,715 individual PES values. Faculty evaluator intra- and inter-rater reliability was found to be "strong" (ICC = 0.84) and "substantial" (ICC = 0.64), respectively, demonstrating repeatability of both the PES, evaluator calibration, and standardization of tablet-based scoring. All implant-abutment interface groups demonstrated significant improvements in mean sum PESs up to 1 year, with the largest improvement between restoration delivery and 6 months. No significant differences were found between groups in mean sum PESs both for individual study visits as well as for changes between study visits. No significant differences in mean
Alves, Célia C; Muñoz, Fernando; Cantalapiedra, António; Ramos, Isabel; Neves, Manuel; Blanco, Juan
The effect on the marginal peri-implant tissues following repeated platform switching abutment removal and subsequent reconnection was studied. Six adult female Beagle dogs were selected, and Pm3 and Pm4 teeth, both left and right sides, were extracted and the sites healed for 3 months. At this time, 24 bone level (BL) (Straumann, Basel, Switzerland) Ø 3.3/8 mm implants were placed, 2 in each side on Pm3 and Pm4 regions. In one side (control group), 12 bone level conical Ø 3.6 mm healing abutments and, on the other side (test group), 12 Narrow CrossFit (NC) multibase abutments (Straumann) , Basel, Switzerland) were connected at time of implant surgery. On test group, all prosthetic procedures were carried out direct to multibase abutment without disconnecting it, where in the control group, the multibase abutment was connected/disconnected five times (at 6/8/10/12/14 weeks) during prosthetic procedures. Twelve fixed metal bridges were delivered 14 weeks after implant placement. A cleaning/control appointment was scheduled 6 months after implant placement. The animals were sacrificed at 9 months of the study. Clinical parameters and peri-apical x-rays were registered in every visit. Histomorphometric analysis was carried out for the 24 implants. The distance from multibase abutment shoulder to the first bone implant contact (S-BIC) was defined as the primary histomorphometric parameter. Wilcoxon comparison paired test (n = 6) found no statistically significant differences (buccal P = 0.917; Lingual P = 0.463) between test and control groups both lingually and buccally for S-BIC distance. Only Pm3 buccal aBE-BC (distance from the apical end of the barrier epithelium to the first bone implant contact) (P = 0.046) parameter presented statistically significant differences between test and control groups. Control group presented 0.57 mm more recession than test group, being this difference statistically significant between the two groups (P < 0.001). It can be conclude
Full Text Available The objective of this study is implementation of system architecture for collecting and analysing data as well as visualizing results for hydrodynamic modelling of flood flows in river valleys using remote sensing methods, tree-dimensional geometry of spatial objects and GPU multithread processing. The proposed solution includes: spatial data acquisition segment, data processing and transformation, mathematical modelling of flow phenomena and results visualization. Data acquisition segment was based on aerial laser scanning supplemented by images in visible range. Vector data creation was based on automatic and semiautomatic algorithms of DTM and 3D spatial features modelling. Algorithms for buildings and vegetation geometry modelling were proposed or adopted from literature. The implementation of the framework was designed as modular software using open specifications and partially reusing open source projects. The database structure for gathering and sharing vector data, including flood modelling results, was created using PostgreSQL. For the internal structure of feature classes of spatial objects in a database, the CityGML standard was used. For the hydrodynamic modelling the solutions of Navier-Stokes equations in two-dimensional version was implemented. Visualization of geospatial data and flow model results was transferred to the client side application. This gave the independence from server hardware platform. A real-world case in Poland, which is a part of Widawa River valley near Wroclaw city, was selected to demonstrate the applicability of proposed system.
Biemond, G.J.E.; Feijen, Jan; Gaymans, R.J.
The tensile properties of segmented block copolymers with mono-disperse hard segments were studied with respect to the hard segment content (16–44 wt.%) and the temperature (20–110 °C). The copolymers were comprised of poly(tetramethylene oxide) segments with the molecular weights of 650–2,900 Da
Full Text Available The aim of the present study was to evaluate bone loss at implants connected to abutments coated with a soda-lime glass containing silver nanoparticles, subjected to experimental peri-implantitis. Also the aging and erosion of the coating in mouth was studied. Five beagle dogs were used in the experiments. Three implants were placed in each mandible quadrant: in 2 of them, Glass/n-Ag coated abutments were connected to implant platform, 1 was covered with a Ti-mechanized abutment. Experimental peri-implantitis was induced in all implants after the submarginal placement of cotton ligatures, and three months after animals were euthanatized. Thickness and morphology of coating was studied in abutment cross-sections by SEM. Histology and histo-morphometric studies were carried on in undecalfied ground slides. After the induced peri-implantitis: 1.The abutment coating shown losing of thickness and cracking. 2. The histometry showed a significant less bone loss in the implants with glass/n-Ag coated abutments. A more symmetric cone of bone resorption was observed in the coated group. There were no significant differences in the peri-implantitis histological characteristics between both groups of implants. Within the limits of this in-vivo study, it could be affirmed that abutments coated with biocide soda-lime-glass-silver nanoparticles can reduce bone loss in experimental peri-implantitis. This achievement makes this coating a suggestive material to control peri-implantitis development and progression.
Krejci, Ivo; Daher, René
The goal of this short communication is to present finite element analysis comparison of the stress distribution between CAD/CAM full crowns made of Lava Ultimate and of IPS e.max CAD, adhesively luted to natural teeth and to implant abutments with the shape of natural teeth. Six 3D models were prepared using a 3D content-creating software, based on a micro-CT scan of a human mandibular molar. The geometry of the full crown and of the abutment was the same for all models representing Lava Ultimate full crowns (L) and IPS e.max CAD full crowns (E) on three different abutments: prepared natural tooth (n), titanium abutment (t) and zirconia abutment (z). A static load of 400 N was applied on the vestibular and lingual cusps, and fixtures were applied to the base of the models. After running the static linear analysis, the post-processing data we analyzed. The stress values at the interface between the crown and the abutment of the Lt and Lz groups were significantly higher than the stress values at the same interface of all the other models. The high stress concentration in the adhesive at the interface between the crown and the abutment of the Lava Ultimate group on implants might be one of the factors contributing to the reported debondings of crowns.
Meijer, Henny J.A.; Kerdijk, Wouter; Raghoebar, Gerry M.; Cune, Marco
Abstract Background Single‐tooth replacement often requires a prefabricated dental implant and a customized crown. The benefits of individualization of the abutment remain unclear. Purpose This randomized controlled clinical trial aims to study potential benefits of individualization of zirconia implant abutments with respect to preservation of marginal bone level and several clinical and patient‐based outcome measures. Material and Methods Fifty participants with a missing premolar were included and randomly assigned to standard (ZirDesign, DentsplySirona Implants, Mölndal, Sweden) or computer aided design/computer aided manufacturing (CAD/CAM) customized (Atlantis, DentsplySirona Implants, Mölndal, Sweden) zirconia abutment therapy. Peri‐implant bone level (primary outcome), Plaque‐index, calculus formation, bleeding on probing, gingiva index, probing pocket depth, recession, appearance of soft tissues and patients' contentment were assessed shortly after placement and one year later. Results No implants were lost and no complications related to the abutments were observed. Statistically significant differences between stock and CAD/CAM customized zirconia abutments could not be demonstrated for any of the operationalized variables. Conclusion The use of a CAD/CAM customized zirconia abutment in single tooth replacement of a premolar is not associated with an improvement in clinical performance or patients' contentment when compared to the use of a stock zirconia abutment. PMID:27476829
Schepke, Ulf; Meijer, Henny J A; Kerdijk, Wouter; Raghoebar, Gerry M; Cune, Marco
Single-tooth replacement often requires a prefabricated dental implant and a customized crown. The benefits of individualization of the abutment remain unclear. This randomized controlled clinical trial aims to study potential benefits of individualization of zirconia implant abutments with respect to preservation of marginal bone level and several clinical and patient-based outcome measures. Fifty participants with a missing premolar were included and randomly assigned to standard (ZirDesign, DentsplySirona Implants, Mölndal, Sweden) or computer aided design/computer aided manufacturing (CAD/CAM) customized (Atlantis, DentsplySirona Implants, Mölndal, Sweden) zirconia abutment therapy. Peri-implant bone level (primary outcome), Plaque-index, calculus formation, bleeding on probing, gingiva index, probing pocket depth, recession, appearance of soft tissues and patients' contentment were assessed shortly after placement and one year later. No implants were lost and no complications related to the abutments were observed. Statistically significant differences between stock and CAD/CAM customized zirconia abutments could not be demonstrated for any of the operationalized variables. The use of a CAD/CAM customized zirconia abutment in single tooth replacement of a premolar is not associated with an improvement in clinical performance or patients' contentment when compared to the use of a stock zirconia abutment. © 2016 The Authors. Clinical Implant Dentistry and Related Research Published by Wiley Periodicals, Inc.
Richard J. Blakely
Full Text Available The tectonically active East Sierra Valley System (ESVS, which comprises the westernmost part of the Walker Lane-Eastern California Shear Zone, marks the boundary between the highly extended Basin and Range Province and the largely coherent Sierra Nevada-Great Valley microplate (SN-GVm, which is moving relatively NW. The recent history of the ESVS is characterized by oblique extension partitioned between NNW-striking normal and strike-slip faults oriented at an angle to the more northwesterly relative motion of the SN-GVm. Spatially variable extension and right-lateral shear have resulted in a longitudinally segmented valley system composed of diverse geomorphic and structural elements, including a discontinuous series of deep basins detected through analysis of isostatic gravity anomalies. Extension in the ESVS probably began in the middle Miocene in response to initial westward movement of the SN-GVm relative to the Colorado Plateau. At ca. 3–3.5 Ma, the SN-GVm became structurally separated from blocks directly to the east, resulting in significant basin-forming deformation in the ESVS. We propose a structural model that links high-angle normal faulting in the ESVS with coeval low-angle detachment faulting in adjacent areas to the east.
Stevens, Calvin H.; Stone, Paul; Blakely, Richard J.
The tectonically active East Sierra Valley System (ESVS), which comprises the westernmost part of the Walker Lane-Eastern California Shear Zone, marks the boundary between the highly extended Basin and Range Province and the largely coherent Sierra Nevada-Great Valley microplate (SN-GVm), which is moving relatively NW. The recent history of the ESVS is characterized by oblique extension partitioned between NNW-striking normal and strike-slip faults oriented at an angle to the more northwesterly relative motion of the SN-GVm. Spatially variable extension and right-lateral shear have resulted in a longitudinally segmented valley system composed of diverse geomorphic and structural elements, including a discontinuous series of deep basins detected through analysis of isostatic gravity anomalies. Extension in the ESVS probably began in the middle Miocene in response to initial westward movement of the SN-GVm relative to the Colorado Plateau. At ca. 3-3.5 Ma, the SN-GVm became structurally separated from blocks directly to the east, resulting in significant basin-forming deformation in the ESVS. We propose a structural model that links high-angle normal faulting in the ESVS with coeval low-angle detachment faulting in adjacent areas to the east.
Yankelovich, Daniel; Meer, David
In 1964, Daniel Yankelovich introduced in the pages of HBR the concept of nondemographic segmentation, by which he meant the classification of consumers according to criteria other than age, residence, income, and such. The predictive power of marketing studies based on demographics was no longer strong enough to serve as a basis for marketing strategy, he argued. Buying patterns had become far better guides to consumers' future purchases. In addition, properly constructed nondemographic segmentations could help companies determine which products to develop, which distribution channels to sell them in, how much to charge for them, and how to advertise them. But more than 40 years later, nondemographic segmentation has become just as unenlightening as demographic segmentation had been. Today, the technique is used almost exclusively to fulfill the needs of advertising, which it serves mainly by populating commercials with characters that viewers can identify with. It is true that psychographic types like "High-Tech Harry" and "Joe Six-Pack" may capture some truth about real people's lifestyles, attitudes, self-image, and aspirations. But they are no better than demographics at predicting purchase behavior. Thus they give corporate decision makers very little idea of how to keep customers or capture new ones. Now, Daniel Yankelovich returns to these pages, with consultant David Meer, to argue the case for a broad view of nondemographic segmentation. They describe the elements of a smart segmentation strategy, explaining how segmentations meant to strengthen brand identity differ from those capable of telling a company which markets it should enter and what goods to make. And they introduce their "gravity of decision spectrum", a tool that focuses on the form of consumer behavior that should be of the greatest interest to marketers--the importance that consumers place on a product or product category.
Hsu, Kuang-Wei; Shen, Yu-Fu; Wei, Pein-Chi
In addition to the original abutments provided by implant companies, compatible computer-aided design and computer-aided manufacturing (CAD-CAM) abutments are also available from different manufacturers. However, the combination of abutments and implant systems from different manufacturers may lead to mechanical problems between components. Little has been reported on the clinical performance of this treatment option. The purpose of this retrospective case series was to evaluate the outcome of compatible CAD-CAM titanium abutments (TiAs) for posterior single-implant tooth replacement (PSITR) up to 6 years after insertion. Eighty-one patients (34 men, 47 women) who received PSITR restored with compatible CAD-CAM TiAs and had a final recall examination between May 2014 and April 2015 were included in this study. Clinical and radiographic examinations were documented. Retrospective evaluation of the patient records was also performed. Correlations between bone-level changes and variables were calculated using the Spearman correlation. Implant and prosthesis survival rates were 100%. Twenty technical complications were observed, including 9 decementations of the crown, 6 screw loosenings, and 5 ceramic fractures. Periimplant mucositis was diagnosed in 36 patients (44.4%) and periimplantitis in 6 patients (7.4%). Correlation analysis showed a significant effect of the extent of periodontal bone loss of the remaining teeth on the marginal bone-level changes around implants (r=0.548, P<.001). Compatible CAD-CAM TiAs provide a viable treatment option for PSITR. However, in light of relatively high screw-loosening and decementation rates, choosing appropriate cements and abutment manufacturers is essential to improve the clinical performance of this treatment option. Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.
Cosgarea, Raluca; Gasparik, Cristina; Dudea, Diana; Culic, Bogdan; Dannewitz, Bettina; Sculean, Anton
To objectively determine the difference in colour between the peri-implant soft tissue at titanium and zirconia abutments. Eleven patients, each with two contralaterally inserted osteointegrated dental implants, were included in this study. The implants were restored either with titanium abutments and porcelain-fused-to-metal crowns, or with zirconia abutments and ceramic crowns. Prior and after crown cementation, multi-spectral images of the peri-implant soft tissues and the gingiva of the neighbouring teeth were taken with a colorimeter. The colour parameters L*, a*, b*, c* and the colour differences ΔE were calculated. Descriptive statistics, including non-parametric tests and correlation coefficients, were used for statistical analyses of the data. Compared to the gingiva of the neighbouring teeth, the peri-implant soft tissue around titanium and zirconia (test group), showed distinguishable ΔE both before and after crown cementation. Colour differences around titanium were statistically significant different (P = 0.01) only at 1 mm prior to crown cementation compared to zirconia. Compared to the gingiva of the neighbouring teeth, statistically significant (P crown cementation for both abutments; more significant differences were registered for titanium abutments. Tissue thickness correlated positively with c*-values for titanium at 1 mm and 2 mm from the gingival margin. Within their limits, the present data indicate that: (i) The peri-implant soft tissue around titanium and zirconia showed colour differences when compared to the soft tissue around natural teeth, and (ii) the peri-implant soft tissue around zirconia demonstrated a better colour match to the soft tissue at natural teeth than titanium. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.
Pihlaja, Juha; Näpänkangas, Ritva; Kuoppala, Ritva; Raustia, Aune
The mechanical properties of zirconia suggest that it might serve as a material for abutment crowns for partial removable dental prostheses (RDPs). Only limited clinical evidence is available for the use of ceramics as abutment crowns. The purpose of this retrospective clinical study was to evaluate the outcome of veneered zirconia single crowns in abutment teeth for RPDs in participants treated by predoctoral students. Thirty-seven veneered zirconia single crowns in 17 participants (9 men and 8 women; mean age 62.5 years) were prepared as abutment teeth for a clasp-retained RDP with a metal framework: 22 crowns with an occlusal rest seat and 15 crowns with both an occlusal rest seat and retentive clasps. The mean follow-up time was 4.2 years (2.9 to 5.4 years). In a clinical examination, the anatomic form of the crown, marginal fidelity (the border between the crown and the tooth was felt with an explorer), wear of the ceramic surface in the rest seat, and fracture of the veneering porcelain were examined and assessed as good, acceptable, or unacceptable. The retention and stability of the RDPs were recorded as good, moderate, or poor. The complications found were fracture of the veneering porcelain (11%) and fracture of the occlusal rest seat (3%). Wear of porcelain at the occlusal contact point was found in 24% of the zirconia single crowns. Wear of the ceramic surfaces of the rest seats for the RDPs was not found. The retention was good in all RDPs. The stability was good in 73% and moderate in 23% of the RDPs. Veneered zirconia single crowns are suitable in abutment teeth for RDPs with a metal framework. Fracture in the veneering porcelain remains a problem with veneered zirconia, although the zirconia surface in the rest seats for RDPs showed no wear. Copyright © 2015 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.
Shim, Hye Won; Yang, Byoung-Eun
To evaluate the cumulative survival rate (CSR) and mechanical complications of single-tooth Ankylos® implants. This was a retrospective clinical study that analyzed 450 single Ankylos® implants installed in 275 patients between December 2005 and December 2012. The main outcomes were survival results CSR and implant failure) and mechanical complications (screw loosening, fracture, and cumulative fracture rate [CFR]). The main outcomes were analyzed according to age, sex, implant length or diameter, bone graft, arch, and position. The 8-year CSR was 96.9%. Thirteen (2.9%) implants failed because of early osseointegration failure in 3, marginal bone loss in 6, and abutment fracture in 4. Screw loosening occurred in 10 implants (2.2%), and 10 abutment fractures occurred. All abutment fractures were located in the neck, and concurrent screw fractures were observed. The CSR and rate of screw loosening did not differ significantly according to factors. The CFR was higher in middle-aged patients (5.3% vs 0.0% in younger and older patients); for teeth in a molar position (5.8% vs 0.0% for premolar or 1.1% for anterior position); and for larger-diameter implants (4.5% for 4.5 mm and 6.7% for 5.5 mm diameter vs 0.5% for 3.5 mm diameter) (all Ptooth restoration in Koreans. However, relatively frequent abutment fractures (2.2%) were observed and some fractures resulted in implant failures. Middle-aged patients, the molar position, and a large implant diameter were associated with a high incidence of abutment fracture.
Nothdurft, Frank P; Nonhoff, Joerg; Pospiech, Peter R
Zirconia implant abutments have gained a much broader clinical use over the past few years. The aim of the present study was to assess the clinical performance of a pre-fabricated zirconium dioxide implant abutment for single-tooth replacement in the posterior region. Forty implants of the XiVE(®) S plus screw type (DENTSPLY Friadent, Mannheim, Germany) were inserted in the posterior region of 24 patients and provided with zirconium dioxide abutments (FRIADENT(®) CERCON(®) Abutment, DENTSPLY Friadent). The following parameters were used to document the state of soft tissue: modified plaque index, modified sulcus bleeding index and pocket depth. Mesial and distal bone levels were determined on radiographs during the prosthetic treatment and at the 36-month recall. Thirty-seven implants could be followed up after 36 months in function. One patient wearing two abutments was lost to follow-up. One abutment exhibited a rotational misfit after 2 years in function. A further abutment showed the same failure at the 36-months recall appointment. In the remaining 36 implants the soft and hard tissue parameters were indicative of a low inflammatory status. Compared to the baseline situation, a partly significant bone apposition could be observed. Chipping of parts of the veneering ceramic was registered in 22% of the remaining implant restorations. The use of zirconia abutments in this study lead to mainly healthy peri-implant hard and soft tissue conditions but, considering the observed failures after 3 years in function, clinical long-term results should be awaited before recommending full zirconia implant abutments in a posterior indication.
Magne, Pascal; Paranhos, Maria Paula Gandolfi; Burnett, Luiz Henrique; Magne, Michel; Belser, Urs Christoph
This study assessed the fatigue resistance and failure mode of type III porcelain and composite resin veneers bonded to custom zirconia implant abutments. Twenty-four standardized zirconia implant abutments were fabricated. Using the CEREC 3 machine, type III veneers of standardized shape were milled in ceramic Vita Mark II or in composite resin Paradigm MZ100. The intaglio surfaces of the restorations were hydrofluoric acid etched and silanated (Mark II) or airborne-particle abraded and silanated (MZ100). The fitting surface of the abutments was airborne-particle abraded, cleaned, and inserted into a bone level implant (BLI RC SLActive 10 mm). All veneers (n=24) were adhesively luted with a zirconia primer (Z-Prime Plus), adhesive resin (Optibond FL) and a pre-heated light-curing composite resin (Filtek Z100). Cyclic isometric chewing (5 Hz) was simulated, starting with a load of 40 N, followed by stages of 80, 120, 160, 200, 240, and 280 N (20,000 cycles each). Samples were loaded until fracture or to a maximum of 140,000 cycles. Groups were compared using the life table survival analysis (Logrank test at P=.05). Mark II and MZ100 specimens fractured at an average load of 216 N and 229 N (survival rate of 17% and 8%), respectively, with no difference in survival probability (P=.18). Among the fractured samples, 40% of the failures were at the abutment level for Mark II and 27% were at the abutment level for MZ100. No exclusive adhesive failures were observed. Type III Mark II and Paradigm MZ100 veneers showed similar fatigue resistance when bonded to custom non-retentive zirconia implant abutments. The bond was strong enough to induce abutment fractures. MZ100 presented a higher percentage of "friendly" failures, i.e. maintaining the restoration-abutment adhesive interface and the abutment itself intact. © 2010 John Wiley & Sons A/S.
Full text: 1. Presentations and status reports. T. Fukahori (JAEA) reported on the plans for the www interface layout. Discussions included which functions were needed for new RIPL-3 web pages. The results are summarized in next section. 2. Layout of the interfaces and retrieval tools and web. RIPL-3 home page will include some description about RIPL-3 and link to the Technical report in pdf-format. The web page for 'mass' segment contains same contents as RIPL-2 except the removal of the information about ground state deformation. The abundance data will be replaced by data from the new BNL wallet card (2005 version). The Q-value calculation tool will be also improved. The 'Nuclear Matter Density' will be renamed 'Nucleon Density Distribution'. 'Levels' segment will be same as before, and the deformation parameters for excited levels will be moved from 'optical' segment and given the name 'deformation'. 'Resonances' segment will be same as before - may be replaced with the new Mughabghab tables. 'Optical' segment will be same as before, and the deformation parameters for excited levels will be moved to 'optical' segment and given the name 'deformation'. The optical model calculation with ECIS and OPTMAN will be considered and double-folding calculation tool will possibly be provided. 'Densities' segment will be same as before, and the plotting programs will be checked. The 3-7 sets of combination of GC, BSFG, GSFM with/without enhancement factors will be given. 'Gamma' segment will be same as before, with addition of MLO and theoretical GDR calculation. 'Fission' segment will be same as before, and 'Exp.' will be renamed. New barrier evaluations will be added, for example, transition (2+) states. The fission spectrum calculation tool (codes and inputs) may be added. The fundamental format will be kept as before. For new items such as deformed 'nucleon density distribution', double-folding potential, evaluated fission barrier (extension into 3 or more) and fission
Joseph, E.; Aibinu, A. M.; Sadiq, B. A.; Bello Salau, H.; Salami, M. J. E.
Death as a result of scorpion sting has been a major public health problem in developing countries. Despite the high rate of death as a result of scorpion sting, little report exists in literature of intelligent device and system for automatic detection of scorpion. This paper proposed a digital image processing approach based on the floresencing characteristics of Scorpion under Ultra-violet (UV) light for automatic detection and identification of scorpion. The acquired UV-based images undergo pre-processing to equalize uneven illumination and colour space channel separation. The extracted channels are then segmented into two non-overlapping classes. It has been observed that simple thresholding of the green channel of the acquired RGB UV-based image is sufficient for segmenting Scorpion from other background components in the acquired image. Two approaches to image segmentation have also been proposed in this work, namely, the simple average segmentation technique and K-means image segmentation. The proposed algorithm has been tested on over 40 UV scorpion images obtained from different part of the world and results obtained show an average accuracy of 97.7% in correctly classifying the pixel into two non-overlapping clusters. The proposed 1system will eliminate the problem associated with some of the existing manual approaches presently in use for scorpion detection.
Cano, Jorge; Campo, Julián; Colmenero, César; Rodríguez-Vázquez, José Francisco
Loading in implant dentistry to accelerate prosthodontic treatment has been receiving increasing interest. The aim of this study was to investigate the effect of an early controlled lateral loading (after 7 days) on the establishment of osseointegration by means of resonance frequency analysis. Two groups of six beagle dogs each were used. Group I had implants without loading. Group II had implants loaded with a new prototype compression abutment that created controlled semi-static loading. Loaded implants showed slightly better stability after 5 weeks of healing, but the difference was not significant. We concluded that controlled loading is beneficial to maintain, and even improve, stability during the early critical healing period. Copyright © 2011 Elsevier Ltd. All rights reserved.
A provisional restoration in combination with an implant-retained restoration provides many of the same benefits as nonimplant-retained fixed restorations. Provisional restorations serve as a diagnostic tool to confirm esthetics, contours, accessibility for oral hygiene, and can be used to duplicate the definitive restoration. A provisional restoration allows for communication between the patient, dentist, and technician. The soft tissue around the implants can heal according to the contours of the provisional restoration. However, implant-retained treatment can require an extended period of osseointegration, and provisional treatment can be a challenge if a removable prosthesis is provided because adjustments of the denture may become necessary during healing. This article presents a case report that describes the simultaneous placement of implants with the connection of fixed provisional restorations to prefabricated plastic provisional abutments.
was to test the reliability and validity of six aesthetic parameters used at the Copenhagen Dental School to assess the aesthetic outcome of implant-supported restorations. The aims of study III and IV were to compare the influence of different abutment and crown materials on biological, biomechanical......To restore oral functions in patients with missing teeth, single-tooth implants are a well-documented treatment option. Along with high survival rates, aesthetic factors have become an important clinical outcome variable for evaluating treatment success of implant-supported restorations. Thus...... studies have reported on aesthetic, biological, biomechanical and patient-reported outcomes of implant-supported single-tooth restorations of various biomaterials. The aim of the present thesis was to investigate the clinical performance of zirconia-based implant-supported single-tooth restorations...
This book is an outcome of the research project “ECOBRIDGE – Demonstration of ECOnomical BRIDGE solutions based on innovative composite dowels and integrated abutments – RFCS – CT 2010-00024”, which has been co-funded by the Research Fund for Coal and Steel (R.F.C.S.) of the European Community. The main topics of the book are the following: design of integral bridges, innovative composite dowels for the shear transmission, construction of bridges, structural analysis of bridges and monitoring. The book joins the technical experience and the contributions of the involved research partners. The technical content of all the papers is present-day in the field of the design, construction and monitoring of innovative composite bridges. The efficient design and construction improve and consolidate the market position of steel construction and steel producing industry. In addition, the advanced forms of construction are contributing to savings in material and energy consumption for the structure during prod...
Galli, Fabio; Deflorian, Matteo; Testori, Tiziano
This article describes a simplified technique for relining provisional prostheses on natural abutments that can be applied to this specific type of tooth preparation with feather-edge finish line. Starting from a diagnostic wax-up, a provisional fixed restoration is constructed, containing all the correct structural information. This includes the controlled depth of the prosthetic margin into the gingival sulcus, the emergence profile, and the area from the emergence profile to the gingival third. Chair time is saved during the clinical procedures because the finishing and polishing steps are shortened, and the resulting provisional restoration is precise and highly biocompatible. This technique allows for a simple and quick relining and finishing procedure and for the delivery of an esthetic and biocompatible provisional restoration.
Davis, L. S.
Research into the role of cooperative, or relaxation, processes in image segmentation is surveyed. Cooperative processes can be employed at several levels of the segmentation process as a preprocessing enhancement step, during supervised or unsupervised pixel classification and, finally, for the interpretation of image segments based on segment properties and relations.
Yoon, Kyeong Han; Kim, Daehwan; Sohn, Seonghyang; Lee, Won Soo
Segmented heterochromia of scalp hair is characterized by the irregularly alternating segmentation of hair into dark and light bands and is known to be associated with iron deficiency anemia. The authors report the case of an 11-year-old boy with segmented heterochromia associated with iron deficiency anemia. After 11 months of iron replacement, the boy's segmented heterochromic hair recovered completely.
Zandparsa, Roya; Albosefi, Abdalah
The purpose of part II of this in vitro study was to compare the fracture load of two-piece zirconia custom abutments with different thicknesses and angulations. Forty zirconia custom abutments were divided into four groups as follows: group A1: 0.7 mm thickness and 0° angulations; group A2: 0.7 mm thickness and 15° angulations; group B1: 1 mm thickness and 0° angulations; group B2: 1 mm thickness and 15° angulations. As in part I, in all groups, implant replicas were mounted in self-cure acrylic jigs to support the abutments. The zirconia custom abutments were engaged in the implant replicas using a manual torque wrench. All jigs were secured and mounted in a metallic vice and subjected to shear stress till failure using a universal testing machine with a 0.5 mm/min crosshead speed with the force transferred to the lingual surface of the zirconia custom abutments 2 mm below the incisal edge. The test specimens used in this study did not include a crown. The universal testing machine was controlled via a computer software system, which also completed the stress-strain diagram and recorded the breaking fracture load. The fracture loads were recorded for comparison among the groups and subjected to statistical analysis (two-way ANOVA and Kolmogorov-Smirnov). The mean fracture load of zirconia custom abutments across the groups (A1 to B2) ranged from 432 ± 97 N to 746 ± 275 N. The angulated zirconia custom abutment exhibited the highest fracture load, which was statistically significant (p = 0.045). The thickness of the zirconia custom abutment also had a positive influence on the strength of the specimens (p = 0.005). In this study, the 15° angulated zirconia custom abutments showed the highest fracture load of those investigated. The 1 mm thick zirconia custom abutments also exhibited significantly higher fracture load compared to 0.7 mm abutments. The results of this in vitro study will help dental practitioners with their decision-making process in
Brozović, Juraj; Demoli, Nazif; Farkaš, Nina; Sušić, Mato; Alar, Zeljko; Gabrić Pandurić, Dragana
The aim of this study was to (i) obtain the force-related interferometric patterns of loaded dental implant-abutment assemblies differing in diameter and brand using digital holographic interferometry (DHI) and (ii) determine the influence of implant diameter on the extent of load-induced implant deformation by quantifying and comparing the obtained interferometric data. Experiments included five implant brands (Ankylos, Astra Tech, blueSKY, MIS and Straumann), each represented by a narrow and a wide diameter implant connected to a corresponding abutment. A quasi-Fourier setup with a 25mW helium-neon laser was used for interferometric measurements in the cervical 5mm of the implants. Holograms were recorded in two conditions per measurement: a 10N preloaded and a measuring-force loaded assembly, resulting with an interferogram. This procedure was repeated throughout the whole process of incremental axial loading, from 20N to 120N. Each measurement series was repeated three times for each assembly, with complete dismantling of the implant-loading device in between. Additional software analyses calculated deformation data. Deformations were presented as mean values±standard deviations. Statistical analysis was performed using linear mixed effects modeling in R's lme4 package. Implants exhibited linear deformation patterns. The wide diameter group had lower mean deformation values than the narrow diameter group. The diameter significantly affected the deformation throughout loading sessions. This study gained in vitro implant performance data, compared the deformations in implant bodies and numerically stated the biomechanical benefits of wider diameter implants. Copyright © 2013 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.
Scherg, Stefan; Karl, Matthias
Procera Implant Bridges (PIBs) do not engage supporting implant shoulders and are fixed using comparably long retention screws. The aim of this in vitro clinical study was to determine the detorque values in PIBs and conventionally fabricated fixed dental prostheses (FDPs). Two groups of screw-retained implant-supported three-unit FDPs (n=10) were fabricated by means of conventional casting or computer-aided design/computer-assisted manufacture to fit an in vitro situation with two implants. Following fixation, the restorations were subjected to masticatory simulation (100,000 cycles, 100 N) and subsequent detorquing of the retention screws. In the clinical part, a total of 10 patients received PIB restorations in the premolar/molar region that were detorqued after 2, 4, and 6 months. One-sample t tests adjusted for multiple testing by the Bonferroni-Holm method were applied for statistical analysis based on percentage detorque values (α=.05). 60% of the initial torque values were maintained in screws directly retaining restorations, while the abutment screws used in the conventional restorations showed detorque levels in the range of 80%. No significant difference in detorque levels between screws retaining PIBs and conventional FDPs could be detected (P=.5186). The abutment screws showed significantly greater detorque values compared with screws directly retaining restorations (P=.0002; P=.0000). In vivo, a significant increase in detorque values ranging from 21.64 Ncm after 2 months to 27.81 Ncm after 6 months was recorded. Prosthetic screws retaining implant-supported FDPs show torque loss during the initial period of service. Retightening reduces the amount of future torque loss.
Darós, Pollyana; Carneiro, Vinícius Cavalcanti; Siqueira, Amanda Pasolini; de-Azevedo-Vaz, Sergio Lins
A misfit or gap at the implant-abutment joint (IAJ) requires detection as it may compromise the health of the peri-implant tissue. However, which radiographic technique provides the most orthogonal relationship between the central beam and the implant/image receptor is unclear. The purpose of this in vitro study was to evaluate the diagnostic accuracy of 4 intraoral radiographic techniques on misfit detection at the IAJ. Twenty implants were placed in polyamide jaws, and customized dental implant abutments with a metal collar were installed. Different gaps were simulated by placing one or three 50-μm-thick polyester strips at the IAJ; the absence of the strip represented the control group (no gap). The 4 radiographic techniques were evaluated by using different film holders: a periapical with bisecting angle (PBA), a bitewing interproximal (BI), a periapical with standard paralleling (PSP), and a periapical with modified paralleling (PMP) holder (with a custom-made paralleling index). A total of 240 digital radiographs were evaluated by 4 clinicians experienced with dental implants. Differences were evaluated by using receiver operating characteristic (ROC) curves (Az) and Fisher tests (α=.05). Diagnostic values (sensitivity, specificity, accuracy, and positive and negative predictive values) were also obtained. The Kappa test was used to assess intra- and interevaluator reproducibility, which ranged from moderate to almost perfect. All diagnostic values, except specificity, were lower for the PBA technique for both the 50- and 150-μm gaps. Az values for the PBA technique were significantly lower than those obtained for the other 3 techniques (P<.05), which did not differ from each other. The 150-μm gaps were more easily detected than the 50-μm gaps only for PBA (P<.05). The BI, PSP, and PMP techniques detected misfits at the IAJ most accurately. The PBA technique is not recommended for this purpose. Copyright © 2017 Editorial Council for the Journal of
Full Text Available In this paper we present a method for segmentation of documents image with complex structure. This technique based on GLCM (Grey Level Co-occurrence Matrix used to segment this type of document in three regions namely, 'graphics', 'background' and 'text'. Very briefly, this method is to divide the document image, in block size chosen after a series of tests and then applying the co-occurrence matrix to each block in order to extract five textural parameters which are energy, entropy, the sum entropy, difference entropy and standard deviation. These parameters are then used to classify the image into three regions using the k-means algorithm; the last step of segmentation is obtained by grouping connected pixels. Two performance measurements are performed for both graphics and text zones; we have obtained a classification rate of 98.3% and a Misclassification rate of 1.79%.
This thesis aims to advance research in image segmentation by developing robust techniques for evaluating image segmentation algorithms. The key contributions of this work are as follows. First, we investigate the characteristics of existing measures for supervised evaluation of automatic image segmentation algorithms. We show which of these measures is most effective at distinguishing perceptually accurate image segmentation from inaccurate segmentation. We then apply these measures to evalu...
In “Connecting textual segments: A brief history of the web hyperlink” Niels Brügger investigates the history of one of the most fundamental features of the web: the hyperlink. Based on the argument that the web hyperlink is best understood if it is seen as another step in a much longer and broader...... history than just the years of the emergence of the web, the chapter traces the history of how segments of text have deliberately been connected to each other by the use of specific textual and media features, from clay tablets, manuscripts on parchment, and print, among others, to hyperlinks on stand...
Mittlefehldt, David W.; Gellert, Ralf; Yen, Albert S.; Ming, Douglas W.; Van Bommel, Scott; Farrand, William H.; Arvidson, Raymond E.; Rice, James W., Jr.
Mars Exploration Rover Opportunity has been exploring Meridiani Planum for 11+ years, and is presently investigating the geology of rim segments of 22 km diameter, Noachian-aged Endeavour crater. The Alpha Particle X-ray Spectrometer has determined the compositions of a pre-impact lithology and impact breccias representing ejecta from the crater. Opportunity is now investigating the head (higher elevation, western end) of Marathon Valley. This valley cuts eastward through the central portion of the Cape Tribulation rim segment and provides a window into the lower stratigraphic record of the rim. At the head of Marathon Valley is a shallow (few 10s of cm), ovoid depression approximately 27×36 m in size, named Spirit of Saint Louis, that is surrounded by approximately 20-30 cm wide zone of more reddish rocks (red zone). Opportunity has just entered a region of Marathon Valley that shows evidence for Fe-Mg smectite in Compact Reconnaissance Imaging Spectrometer for Mars spectra indicating areally extensive and distinct lithologic units and/or styles of aqueous alteration. Rocks at the head of Marathon Valley and within Spirit of Saint Louis are breccias (valley-head rocks). In some areas, layering inside Spirit of Saint Louis appears continuous with the rocks outside. The valley-head rocks are of similar, generally basaltic composition. The continuity in composition, texture and layering suggest the valley-head rocks are coeval breccias, likely from the Endeavour impact. These local breccias are similar in non-volatile-element composition to breccias investigated elsewhere on the rim. Rocks within the red zone are like those on either side in texture, but have higher Al, Si and Ge, and lower S, Mn, Fe, Ni and Zn as compared to rocks on either side. The valley-head rocks have higher S than most Endeavour rim breccias, while red zone rocks are like those latter breccias in S. Patches within the rocks outside Spirit of Saint Louis have higher Al, Si and Ge indicating
Insinga, Andrea Roberto; Bahl, Christian; Bjørk, Rasmus
We present a semi-analytical algorithm for magnet design problems, which calculates the optimal way to subdivide a given design region into uniformly magnetized segments.The availability of powerful rare-earth magnetic materials such as Nd-Fe-B has broadened the range of applications of permanent...
Bozzo, E.; Antonelli, A.; Argan, A.
we summarize the planned organization of the LOFT ground segment (GS), as established in the mission Yellow Book 1 . We describe the expected GS contributions from ESA and the LOFT consortium. A review is provided of the planned LOFT data products and the details of the data flow, archiving...
Wanninger, Andreas; Kristof, Alen; Brinkmann, Nora
Comparative molecular, developmental and morphogenetic analyses show that the three major segmented animal groups- Lophotrochozoa, Ecdysozoa and Vertebrata-use a wide range of ontogenetic pathways to establish metameric body organization. Even in the life history of a single specimen, different...
Haindl, Michal; Mikeš, Stanislav
Roč. 36, č. 4 (2014), s. 23-23 R&D Projects: GA ČR(CZ) GA14-10911S Institutional support: RVO:67985556 Keywords : unsupervised image segmentation Subject RIV: BD - Theory of Information http:// library .utia.cas.cz/separaty/2014/RO/haindl-0434412.pdf
Rees, Gareth; Greenway, Phil; Morray, Denise
An important challenge in mapping image-processing techniques onto applications is the lack of quantitative performance measures. From a systems engineering perspective these are essential if system level requirements are to be decomposed into sub-system requirements which can be understood in terms of algorithm selection and performance optimization. Nowhere in computer vision is this more evident than in the area of image segmentation. This is a vigorous and innovative research activity, but even after nearly two decades of progress, it remains almost impossible to answer the question 'what would the performance of this segmentation algorithm be under these new conditions?' To begin to address this shortcoming, we have devised a well-principled metric for assessing the relative performance of two segmentation algorithms. This allows meaningful objective comparisons to be made between their outputs. It also estimates the absolute performance of an algorithm given ground truth. Our approach is an information theoretic one. In this paper, we describe the theory and motivation of our method, and present practical results obtained from a range of state of the art segmentation methods. We demonstrate that it is possible to measure the objective performance of these algorithms, and to use the information so gained to provide clues about how their performance might be improved.
Dahl, Anders Bjorholm; Dahl, Vedrana Andersen
We propose a method for weakly supervised segmentation of natural images, which may contain both textured or non-textured regions. Our texture representation is based on a dictionary of image patches. To divide an image into separated regions with similar texture we use an implicit level sets...
Hajimiragha, Habib; Abolbashari, Mohammadreza; Nokar, Saeed; Abolbashari, AmirHossein; Abolbashari, Mehrdad
The present study was done to evaluate the effects of different types of abutments on the rate and distribution of stress on the bone surrounding the implant by dynamic finite element analysis method. In this study two ITI abutment models-one-piece and multi-piece-along with fixture, bone, and superstructure have been simulated with the help of company-made models. The maximum Von Mises stress (MVMS) was observed in the distobuccal area of the cortical bone near the crest of implant in two implant models. In the multi-piece abutment, MVMS was higher than the one-piece model (27.9 MPa and 23.3 MPa, respectively). Based on the results of this study, it can be concluded that type of abutment influences the stress distribution in the area surrounding the implant during dynamic loading.
teaching, outreach, and research in the science and art of joint special operations. JSOU provides education to the men and women of Special Operations... leftover guerrillas. One valley at a time, stability can spread. This persistent spreading of influence into for- mally controlled Taliban areas, one...world. To carry out some of these transactions, Al Qaeda operates in Malaysia, China , the Philippines, and Germany. 10 JSOU Report 06-6 History of the
Zembic, Anja; Sailer, Irena; Jung, Ronald Ernst; Hämmerle, Christoph Hans Franz
The aim was to test whether or not zirconia abutments exhibit the same survival and technical/biological outcome as titanium abutments. Twenty-two patients receiving 40 single-tooth implants in canine and posterior regions were included. The implant sites were randomly assigned to 20 zirconia and 20 titanium abutments. All-ceramic and metal-ceramic crowns were fabricated. At baseline, 6, 12 and 36 months, the reconstructions were examined for technical and biological problems. Probing pocket depth (PPD), plaque control record (PCR) and bleeding on probing (BOP) were assessed at abutments (test) and analogous contralateral teeth (control). Standardized radiographs of the implants were made and the bone level (BL) was measured referring to the implant shoulder on mesial (mBL) and distal sides (dBL). The difference of color (DeltaE) of the peri-implant mucosa and the gingiva of control teeth was assessed with a spectrophotometer. The data were statistically analyzed with Mann-Whitney Rank and Student's unpaired t-tests. Eighteen patients with 18 zirconia and 10 titanium abutments were examined at a mean follow-up of 36 months (range 31.5-53.3 months). No fracture of an abutment or loss of a reconstruction was found. Hence, both exhibited 100% survival. At two metal-ceramic crowns supported by titanium abutments chipping of the veneering ceramic occurred. No difference of the biological outcome of zirconia and titanium abutments was observed: PPD (meanPPD(ZrO(2)) 3.2 +/- 1 mm, mPPD(Ti) 3.4 +/- 0.5 mm), PCR (mPCR(ZrO(2)) 0.1 +/- 0.2, mPCR(Ti) 0.1 +/- 0.2) and BOP (mBOP(ZrO(2)) 0.4 +/- 0.4, mBOP(Ti) 0.2 +/- 0.3). Furthermore, the BL was similar at implants supporting zirconia and titanium abutments (mBL(ZrO(2)) 1.7 +/- 1, dBL(ZrO(2)) 1.6 +/- 1; mBL(Ti) 2 +/- 1, dBL(Ti) 2.1 +/- 1). Both, zirconia and titanium abutments induced a similar amount of discoloration of the mucosa compared with the gingiva at natural teeth (DeltaE(ZrO(2)) 9.3 +/- 3.8, DeltaE(Ti) 6.8 +/- 3.8). At
Sailer, Irena; Zembic, Anja; Jung, Ronald Ernst; Siegenthaler, David; Holderegger, Claudia; Hämmerle, Christoph Hans Franz
The aim of this study was to test whether or not customized zirconia abutments exhibit the same survival rates in canine and posterior regions as titanium abutments, and to compare the esthetic result of the two abutment types. Twenty-two patients with 40 implants in posterior regions were included and the implant sites were randomly assigned to 20 customized zirconia and 20 customized titanium abutments. All-ceramic (AC) and metal-ceramic (MC) crowns were fabricated. In all except two cases, the crowns were cemented on the abutments using resin or glass-ionomer cements. Two zirconia reconstructions were screw retained. At baseline, 6 and 12 months, the reconstructions were examined for technical and biological problems. Probing pocket depth (PPD), plaque (Pl) and bleeding on probing (BOP) were assessed and compared with natural control teeth. Furthermore, the difference of color (DeltaE) of the peri-implant mucosa and the gingiva of control teeth was evaluated by means of a spectrophotometer (Spectroshade). The data were analyzed with Student's unpaired t-test, ANOVA and regression analyses. Twenty patients with 19 zirconia and 12 titanium abutments were examined at a mean follow-up of 12.6+/-2.7 months. The survival rate for reconstructions and abutments was 100%. No technical or biological problems were found at the test and control sites. Two chippings (16.7%) occurred at crowns supported by titanium abutments. No difference was found regarding PPD (meanPPD(ZrO2) 3.4+/-0.7 mm, mPPD(Ti) 3.3+/-0.6 mm), Pl (mPl(ZrO2) 0.2+/-0.3, mPl(Ti) 0.1+/-1.8) and BOP (mBOP(ZrO2) 60+/-30%, mBOP(Ti) 30+/-40%) between the two groups. Both crowns on zirconia and titanium abutments induced a similar amount of discoloration of the soft tissue compared with the gingiva at natural teeth (DeltaE(ZrO2) 8.1+/-3.9, DeltaE(Ti) 7.8+/-4.3). At 1 year, zirconia abutments exhibited the same survival and a similar esthetic outcome as titanium abutments.
Manda, Mirianthi; Galanis, Christos; Venetsanos, Dimitrios; Provatidis, Christofer; Koidis, Petros
Insufficient coronal tooth structure may require restoration of endodontically treated (ET) teeth with cast posts and cores (CPCs). The prognosis for these teeth is a matter of scientific debate, especially if they serve as distal abutments in cantilever fixed dental prostheses (FDPs). The purpose of this study was to study stress field development in distal abutments in two types of FDPs with different pulp cavity conditions. The methodology involved the development of four digital models in which the right mandibular premolars were splinted via an FDP with: (1) no cantilever and a vital distal abutment, (2) no cantilever and an ET CPC distal abutment, (3) a single-unit cantilever and a vital distal abutment, and (4) a single-unit cantilever with an ET CPC distal abutment. The models were analyzed using a three-dimensional finite element program, and von Mises stress values and patterns were evaluated. The results revealed that although the stress distribution patterns in dentin were dissimilar, the von Mises stress values registered for the vital and ET CPC distal abutment were not considerably different. However, higher stress values were detected in the dentin area surrounding the post-gutta-percha interface after CPC placement. The addition of the cantilever resulted in a considerable increase in stress on the dental tissue structures. CPCs appear to create a risk of potential fracture that is initiated in the dentin at the apex of the post. The type of restoration appears to have a much more serious impact on the stress pattern developed in the distal abutment, and the addition of a cantilever appears to biomechanically compromise both biologic and restorative structures.
Wasiluk, Grzegorz; Chomik, Ewa; Gehrke, Peter; Pietruska, Małgorzata; Skurska, Anna; Pietruski, Jan
The aim of this study was to assess the frequency of cement residues after cementation of CAD/CAM monolithic zirconia crowns on customized CAD/CAM titanium abutments. Sixty premolars and molars were restored on Astra Tech Osseospeed TX ™ implants using single monolithic zirconia crowns fixed on two types of custom-made abutments: Atlantis ™ titanium or Atlantis ™ Gold Hue. Occlusal openings providing access to the abutment screws were designed for retrievability of the crown/abutment connection. After fixation with glass ionomer cement, the crown/abutment units were unscrewed to evaluate the presence of residual cement. Dichotomous assessment of the presence or absence of cement at the crown/abutment unit and peri-implant tissues was performed. Clinically undetected cement excess was visible on 44 of 60 restorations (73.3%). There was no interdependency between residual cement presence and implant location or diameter. However, a dependency between the presence of residual cement and the aspect of the abutment/crown connection could be noted. The majority of the residues were observed on the distal (17.9%) and mesial (15%) aspects. While on the palatal/lingual aspect, the cement was visible in 8.8%; only 3.4% of all surfaces displayed cement residues. Within the limitations of the study, it can be concluded that the use of customized CAD/CAM abutments do not guarantee avoidance of subgingival cement residues after crown cementation. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.
Lin, Wei-Shao; Harris, Bryan T; Zandinejad, Amirali; Morton, Dean
Preserving periodontally compromised abutments in patients who are actively undergoing oral and intravenous bisphosphonate treatment for osteoporosis provides an alternative to tooth extraction and dental implants, both of which put patients at risk for bisphosphonate-related osteonecrosis of the jaw. This case report describes how a CAD/CAM-fabricated cobalt-chromium telescopic prosthesis was placed on periodontally compromised abutments of a 74-year-old woman actively undergoing oral and intravenous bisphosphonate treatment for osteoporosis.
Butignon, Luis Eduardo; Basilio, Mariana de Almeida; Pereira, Rodrigo de Paula; Arioli Filho, Joao Neudenir
To evaluate the effectiveness of three types of abutments in the maintenance of screw joint preload before and after cyclic loading as well as to observe possible microdamage in the structure of the components using a scanning electron microscope (SEM). Forty-five external-hex implants were embedded in epoxy resin, received their respective abutments, and were randomly divided into three experimental groups (n = 15): (1) machined titanium (Ti) abutments; (2) pre-machined gold (Au) abutments; and (3) machined zirconia (ZrO(2)) abutments. The abutment screws were tightened according to the manufacturer's recommended torque. Initially, a static bending test was performed using five specimens of each group to determine the load applied in the cyclic loading test. Thus, 10 specimens of each group were used to measure the reverse torque value (preload) of the abutment screw before and after loading. A cyclic loading (0.5 × 10(6) cycles; 15 Hz) between 11 and 211 N was applied at an angle of 30 degrees to the long axis of the implants. The group means were compared using analysis of variance and the Tukey test (α = .05). The reverse torque analysis before cyclic loading showed no significant difference among the groups (P > .05). After cyclic loading, all preload means decreased significantly. The lowest decrease in preload was observed in the Ti group, whereas the highest decrease was observed in the ZrO(2) group, with a significant difference noted between them (P = .010). The Au group presented an intermediate decrease, with no significant difference compared to the other groups (P > .05). SEM images showed structural changes in the mating surfaces of the abutments after cyclic loading. The load application reduced the preload means significantly in all groups, and more significantly in the ZrO(2) group.
Lages, Frederico Santos; Willya Douglas-de-Oliveira, Dhelfeson; Ibelli, Guilherme Siqueira; Assaf, Fatimah; Queiroz, Thallita Pereira; Costa, Fernando Oliveira
Resonance frequency analysis (RFA) has become the main tool used to assess the osseointegration of dental implants. The objective of this study was to verify the relationship between the ISQ values with different prosthetic abutments and with the implant platform. The hypothesis was that ISQ values changes according to the abutment height. Twelve patients were included, whose contribution to the study was 31 dental implants (external hexagon connection implants, 4.1x10 mm). The temporary impl...
Yamanishi, Yasufumi; Yamaguchi, Satoshi; Imazato, Satoshi; Nakano, Tamaki; Yatani, Hirofumi
Occlusal overloading causes peri-implant bone resorption. Previous studies examined stress distribution in alveolar bone around commercial implants using three-dimensional (3D) finite element analysis. However, the commercial implants contained some different designs. The purpose of this study is to reveal the effect of the target design on peri-implant bone stress and abutment micromovement. Six 3D implant models were created for different implant-abutment joints: 1) internal joint model (IM); 2) external joint model (EM); 3) straight abutment (SA) shape; 4) tapered abutment (TA) shapes; 5) platform switching (PS) in the IM; and 6) modified TA neck design (reverse conical neck [RN]). A static load of 100 N was applied to the basal ridge surface of the abutment at a 45-degree oblique angle to the long axis of the implant. Both stress distribution in peri-implant bone and abutment micromovement in the SA and TA models were analyzed. Compressive stress concentrated on labial cortical bone and tensile stress on the palatal side in the EM and on the labial side in the IM. There was no difference in maximum principal stress distribution for SA and TA models. Tensile stress concentration was not apparent on labial cortical bone in the PS model (versus IM). Maximum principal stress concentrated more on peri-implant bone in the RN than in the TA model. The TA model exhibited less abutment micromovement than the SA model. This study reveals the effects of the design of specific components on peri-implant bone stress and abutment displacement after implant-supported single restoration in the anterior maxilla.
Nakata, Mitsuhiko; Tanimoto, Shunsuke; Ishida, Shuichi; Ohsumi, Michio; Hoshikuma, Jun-ichi
There is risk of bridge foundations to be damaged by liquefaction-induced lateral spreading of ground. Once bridge foundations have been damaged, it takes a lot of time for restoration. Therefore, it is important to assess the seismic behavior of the foundations on liquefiable ground appropriately. In this study, shaking table tests of models on a scale of 1/10 were conducted at the large scale shaking table in Public Works Research Institute, Japan, to investigate the seismic behavior of pile-supported bridge abutment on liquefiable ground. The shaking table tests were conducted for three types of model. Two are models of existing bridge which was built without design for liquefaction and the other is a model of bridge which was designed based on the current Japanese design specifications for highway bridges. As a result, the bending strains of piles of the abutment which were designed based on the current design specifications were less than those of the existing bridge.
Cakan, Umut; Cakan, Murat; Delilbasi, Cagri
The aim of this investigation was to measure the temperature increase due to heat transferred to the implant-bone interface when the abutment screw channel is accessed or a metal-ceramic crown is sectioned buccally with diamond or tungsten carbide bur using an air rotor, with or without irrigation. Cobalt-chromium copings were cemented onto straight titanium abutments. The temperature changes during removal of the copings were recorded over a period of 1 minute. The sectioning of coping with diamond bur and without water irrigation generated the highest temperature change at the cervical part of the implant. Both crown removal methods resulted in an increase in temperature at the implant-bone interface. However, this temperature change did not exceed 47°C, the potentially damaging threshold for bone reported in the literature.
Poulos, M. J.; Pierce, J. L.; McNamara, J. P.; Flores, A. N.; Benner, S. G.
Terrain aspect alters the spatial distribution of insolation across topography, driving eco-pedo-hydro-geomorphic feedbacks that can alter landform evolution and result in valley asymmetries for a suite of land surface characteristics (e.g. slope length and steepness, vegetation, soil properties, and drainage development). Asymmetric valleys serve as natural laboratories for studying how landscapes respond to climate perturbation. In the semi-arid montane granodioritic terrain of the Idaho batholith, Northern Rocky Mountains, USA, prior works indicate that reduced insolation on northern (pole-facing) aspects prolongs snow pack persistence, and is associated with thicker, finer-grained soils, that retain more water, prolong the growing season, support coniferous forest rather than sagebrush steppe ecosystems, stabilize slopes at steeper angles, and produce sparser drainage networks. We hypothesize that the primary drivers of valley asymmetry development are changes in the pedon-scale water-balance that coalesce to alter catchment-scale runoff and drainage development, and ultimately cause the divide between north and south-facing land surfaces to migrate northward. We explore this conceptual framework by coupling land surface analyses with statistical modeling to assess relationships and the relative importance of land surface characteristics. Throughout the Idaho batholith, we systematically mapped and tabulated various statistical measures of landforms, land cover, and hydroclimate within discrete valley segments (n=~10,000). We developed a random forest based statistical model to predict valley slope asymmetry based upon numerous measures (n>300) of landscape asymmetries. Preliminary results suggest that drainages are tightly coupled with hillslopes throughout the region, with drainage-network slope being one of the strongest predictors of land-surface-averaged slope asymmetry. When slope-related statistics are excluded, due to possible autocorrelation, valley
von Maltzahn, Nadine Freifrau; Holstermann, Jan; Kohorst, Philipp
The adhesive connection between titanium base and zirconia coping of two-part abutments may be responsible for the failure rate. A high mechanical stability between both components is essential for the long-term success. The aim of the present in-vitro study was to evaluate the influence of different surface modification techniques and resin-based luting agents on the retention forces between titanium and zirconia components in two-part implant abutments. A total of 120 abutments with a titanium base bonded to a zirconia coping were investigated. Two different resin-based luting agents (Panavia F 2.0 and RelyX Unicem) and six different surface modifications were used to fix these components, resulting in 12 test groups (n = 10). The surface of the test specimens was mechanically pretreated with aluminium oxide blasting in combination with application of two surface activating primers (Alloy Primer, Clearfil Ceramic Primer) or a tribological conditioning (Rocatec), respectively. All specimens underwent 10,000 thermal cycles between 5°C and 55°C in a moist environment. A pull-off test was then conducted to determine retention forces between the titanium and zirconia components, and statistical analysis was performed (two-way anova). Finally, fracture surfaces were analyzed by light and scanning electron microscopy. No significant differences were found between Panavia F 2.0 and RelyX Unicem. However, the retention forces were significantly influenced by the surface modification technique used (p zirconia copings were pretreated with aluminium oxide blasting, and with the application of Clearfil Ceramic Primer. Surface modification techniques crucially influence the retention forces between titanium and zirconia components in two-part implant abutments. All adhesion surfaces should be pretreated by sandblasting. Moreover, a phosphate-based primer serves to enhance long-term retention of the components. © 2015 Wiley Periodicals, Inc.
CLINICAL EVALUATION OF AN ACRYLIC PONTIC "ADHESIVELY" BONDED TO UNCUT ABUTMENT TEETH: 18 MONTH RESULTS by George T. Eden, CAPT, DC, USN and...prosthesis is as esthetieally pleasing, as effective, and as durable as the muco-adhesive partial denture it would presumably supplant. FINDINGS...temporary) partial dentures were previously constructed. ADMINISTRATIVE INFORMATION This investigation was conducted as part of Bureau of Medi- cine
Saponaro, Paola C; Lee, Damian J; McGlumphy, Edwin A
This clinical report describes the management of a fractured 1-piece zirconia stock abutment from an implant with an internal connection using a modified plastic periodontal probe. This minimally invasive approach allows for the retrieval of fractured prosthetic components without causing irreversible damage to the implant's platform or its internal threads and does not require special equipment or costly instruments. Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.
Chang, Glenn Hsuan-Chen; Tian, Chen; Hung, Yuen-Siang
Purpose: An integrated fixture mount/impression coping/ temporary abutment can provide many advantages for immediate loading of dental implants, such as simpler procedure, less chair time, cost reduction, and comfort for the patients. Materials and Methods: A newly designed dental implant fixture mount (DIFMA) can be used as an impression coping for taking an immediate impression. An immediate load provisional prosthesis can then be fabricated shortly after implant placement to immediately lo...
Hill, David P.; Bailey, Roy A.; Hendley, James W.; Stauffer, Peter H.; Marcaida, Mae
Scientists have monitored geologic unrest in the Long Valley, California, area since 1980. In that year, following a swarm of strong earthquakes, they discovered that the central part of the Long Valley Caldera had begun actively rising. Unrest in the area persists today. The U.S. Geological Survey (USGS) continues to provide the public and civil authorities with current information on the volcanic hazard at Long Valley and is prepared to give timely warnings of any impending eruption.
Full Text Available The control on foreign exchange imposed by Venezuela in 2003 constitute a natural experiment that allows researchers to observe the effects of exchange controls on stock market segmentation. This paper provides empirical evidence that although the Venezuelan capital market as a whole was highly segmented before the controls were imposed, the shares in the firm CANTV were, through their American Depositary Receipts (ADRs, partially integrated with the global market. Following the imposition of the exchange controls this integration was lost. Research also documents the spectacular and apparently contradictory rise experienced by the Caracas Stock Exchange during the serious economic crisis of 2003. It is argued that, as it happened in Argentina in 2002, the rise in share prices occurred because the depreciation of the Bolívar in the parallel currency market increased the local price of the stocks that had associated ADRs, which were negotiated in dollars.
Olson, R.E.; Thumim, A.D.
A scintillation counter, particularly for counting gamma ray photons, includes a massive lead radiation shield surrounding a sample-receiving zone. The shield is disassembleable into a plurality of segments to allow facile installation and removal of a photomultiplier tube assembly, the segments being so constructed as to prevent straight-line access of external radiation through the shield into radiation-responsive areas. Provisions are made for accurately aligning the photomultiplier tube with respect to one or more sample-transmitting bores extending through the shield to the sample receiving zone. A sample elevator, used in transporting samples into the zone, is designed to provide a maximum gamma-receiving aspect to maximize the gamma detecting efficiency. (U.S.)
Castilho, Anderson Almeida; Kojima, Alberto Noriyuki; Pereira, Sarina Maciel Braga; de Vasconcellos, Diego Klee; Itinoche, Marcos Koiti; Faria, Renata; Bottino, Marco Antonio
Objective: The purpose of this study was to compare the accuracy of two working cast fabrication techniques using strain- gauge analysis. Methods: Two working cast fabrication methods were evaluated. Based on a master model, 20 working casts were fabricated by means of an indirect impression technique using polyether after splinting the square transfer copings with acrylic resin. Specimens were assigned to 2 groups (n=10): Group A (GA): type IV dental stone was poured around the abutment analogs in the conventional way; Group B (GB), the dental stone was poured in two stages. Spacers were used over the abutment analogs (rubber tubes) and type IV dental stone was poured around the abutment analogs in the conventional way. After the stone had hardened completely, the spacers were removed and more stone was inserted in the spaces created. Six strain-gauges (Excel Ltd.), positioned in a cast bar, which was dimensionally accurate (perfect fit) to the master model, recorded the microstrains generated by each specimen. Data were analyzed statistically by the variance analysis (ANOVA) and Tukey's test (Î±= 5%). Results: The microstrain values (με) were (mean±SD): GA: 263.7±109.07με, and GB: 193.73±78.83με. Conclusion: There was no statistical difference between the two methods studied. PMID:19089137
Anderson Almeida Castilho
Full Text Available OBJECTIVE: The purpose of this study was to compare the accuracy of two working cast fabrication techniques using strain-gauge analysis. METHODS: Two working cast fabrication methods were evaluated. Based on a master model, 20 working casts were fabricated by means of an indirect impression technique using polyether after splinting the square transfer copings with acrylic resin. Specimens were assigned to 2 groups (n=10: Group A (GA: type IV dental stone was poured around the abutment analogs in the conventional way; Group B (GB, the dental stone was poured in two stages. Spacers were used over the abutment analogs (rubber tubes and type IV dental stone was poured around the abutment analogs in the conventional way. After the stone had hardened completely, the spacers were removed and more stone was inserted in the spaces created. Six strain-gauges (Excel Ltd., positioned in a cast bar, which was dimensionally accurate (perfect fit to the master model, recorded the microstrains generated by each specimen. Data were analyzed statistically by the variance analysis (ANOVA and Tukey's test (Î±= 5%. RESULTS: The microstrain values (µepsilon were (mean±SD: GA: 263.7±109.07µepsilon, and GB: 193.73±78.83µepsilon. CONCLUSION: There was no statistical difference between the two methods studied.
Zhou, Hao; Pei, Fu-Ping; Zhang, Ying; Zhou, Zhong-Biao; Xu, Wen-Liang; Wang, Zhi-Wei; Cao, Hua-Hua; Yang, Chuan
The origin and tectonic evolution of the early Paleozoic arc terranes abutting the northern margin of the North China Craton (NCC) are widely debated. This paper presents detrital zircon U-Pb and Hf isotopic data of early Paleozoic strata in the Zhangjiatun arc terrane of central Jilin Province, northeast (NE) China, and compares them with the Bainaimiao and Jiangyu arc terranes abutting the northern margin of the NCC. Detrital zircons from early Paleozoic strata in three arc terranes exhibit comparable age groupings of 539-430, 1250-577, and 2800-1600 Ma. The Paleoproterozoic to Neoarchean ages and Hf isotopic composition of the detrital zircons imply the existence of the Precambrian fragments beneath the arc terranes. Given the evidences from geology, igneous rocks, and detrital zircons, we proposed that the early Paleozoic arc terranes abutting the northern margin of the NCC are a united arc terrane including the exotic Precambrian fragments, and these fragments shared a common evolutionary history from Neoproterozoic to early-middle Paleozoic.
Hartlev, Jens; Kohberg, Peter; Ahlmann, Søren; Andersen, Niels T; Schou, Søren; Isidor, Flemming
To assess patient satisfaction and esthetic outcome after immediate placement and provisionalization of single-tooth implants involving a definitive individual abutment and a provisional crown followed by later placement of a definitive crown. In private practice, a single-tooth implant was placed immediately after tooth extraction in the esthetic zone of 54 patients. A definitive individual abutment and a provisional crown were mounted in the same visit. The definitive crown was placed after a mean period of 7 months. After a mean follow-up period of 33 months, the subjective and professional evaluation of the total implant treatment, peri-implant soft tissues, and implant crown were assessed on a 10-cm visual analog scale (VAS). The professional esthetic treatment outcome was also evaluated using pink esthetic score (PES), white esthetic score (WES), and total score of PES/WES. The evaluation of total implant treatment, peri-implant soft tissues, and implant crown demonstrated a significantly higher subjective than professional score for all 3 parameters (P provisionalization of single-tooth implants involving a definitive individual abutment and provisional crown followed by later placement of a definitive crown demonstrated high subjective and professional satisfaction. Generally, the professionals seem to be more critical than the patients. A strong correlation was observed between the professional VAS scores and the PES and WES scoring systems. © 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.
Hurley, I W; Brooks, A M; Reinehr, D P; Grant, G B; Gillies, W E
A series of 22 patients with crystals in the anterior segment of the eye was examined by specular microscopy. Of 10 patients with hypermature cataract and hyperrefringent bodies in the anterior chamber cholesterol crystals were identified in four patients and in six of the 10 in whom aspirate was obtained cholesterol crystals were demonstrated in three, two of these having shown crystals on specular microscopy. In 10 patients with intracorneal crystalline deposits, cholesterol crystals were f...
Kuratani, Shigeru; Schilling, Thomas
Classic theories of vertebrate head segmentation clearly exemplify the idealistic nature of comparative embryology prior to the 20th century. Comparative embryology aimed at recognizing the basic, primary structure that is shared by all vertebrates, either as an archetype or an ancestral developmental pattern. Modern evolutionary developmental (Evo-Devo) studies are also based on comparison, and therefore have a tendency to reduce complex embryonic anatomy into overly simplified patterns. Her...
Baker, V.R.; Partridge, J.B.
The equatorial heavily cratered uplands of Mars are dissected by two classes of small valleys that are intimately associated in compound networks. Pristine valleys with steep valley walls preferentially occupy downstream portions of compound basins. Degraded valleys with eroded walls are laterally more extensive and have higher drainage densities than pristine valleys. Morphometric and crater-counting studies indicate that relatively dense drainage networks were emplaced on Mars during the heavy bombardment about 4.0 b.y. ago. Over a period of approximately 10 8 years, these networks were degraded and subsequently invaded by headwardly extending pristine valleys. The pristine valleys locally reactivated the compound networks, probably through sapping processes dependent upon high water tables. Fluvial activity in the heavily cratered uplands generally ceased approximately 3.8--3.9 b.y. ago, coincident with the rapid decline in cratering rates. The relict compound valleys on Mars are morphometrically distinct from most terrestrial drainage systems. The differences might be caused by a Martian valley formation episode characterized by hyperaridity, by inadequate time for network growth, by very permeable rock types, or by a combination of factors
Raster of the Depth in meters of EPA-delimited Valleys in Region 1.Valleys (areas that are lower than their neighbors) were extracted from a Digital Elevation Model (USGS, 30m) by finding the local average elevation, subtracting the actual elevation from the average, and selecting areas where the actual elevation was below the average. The landscape was sampled at seven scales (circles of 1, 2, 4, 7, 11, 16, and 22 km radius) to take into account the diversity of valley shapes and sizes. Areas selected in at least four scales were designated as valleys.
Wells, V.K.; Chang, S.W.; Oliveira-Castro, J.M.; Pallister, J.
A segmentation approach is presented using both traditional demographic segmentation bases (age, social class/occupation, and working status) and a segmentation by benefits sought. The benefits sought in this case are utilitarian and informational reinforcement, variables developed from the Behavioral Perspective Model (BPM). Using data from 1,847 consumers and from a total of 76,682 individual purchases, brand choice and price and reinforcement responsiveness were assessed for each segment a...
Spinal segmental dysgenesis is a rare congenital spinal abnormality seen in neonates and infants, in which a segment of the spine and spinal cord fails to develop normally. The condition is segmental in nature, with vertebrae above and below the malformation. It is commonly associated with various abnormalities that ...
Discusses the advantages and limitations of market segmentation as strategy for the marketing of information services made available by nonprofit organizations, particularly libraries. Market segmentation is defined, a market grid for libraries is described, and the segmentation of information services is outlined. A 16-item reference list is…
Describes market segmentation and how the principles of segmentation can be applied to the adult education market. Indicates that applying segmentation techniques to adult education programs results in programs that are educationally and financially satisfying and serve an appropriate population. (JOW)
Jugdev, Jasvinder; Borzabadi-Farahani, Ali; Lynch, Edward
To assess the effect of airborne particle abrasion of metal implant abutments on tensile bond strength (TBS) of TempBond, Retrieve, and Premier implant cements. Specimens were designed to replicate a single metal implant crown cemented to both smooth and airborne particle-abraded Osteo-Ti implant abutments with zero degrees of taper. Twenty castings were fabricated and cemented to either a smooth surface abutment (SSA) or to an airborne particle-abraded abutment (AAA). TBS was measured with a 50-kg load and a crosshead speed of 0.5 cm/min in a universal testing machine. Each cement was tested 10 times on both abutment types. The mean TBS values (standard deviations, 95% confidence intervals) of SSAs for TempBond, Retrieve, and Premier cements were 115.89 N (26.44, 96.98-134.81), 134.43 N (36.95, 108.25-160.60), and 132.51 N (55.10, 93.09-171.93), respectively. The corresponding values for AAAs were 129.69 N (30.39, 107.95-151.43), 298.67 N (80.36, 241.19-356.16), and 361.17 N (133.23, 265.86-456.48), respectively. There was no significant difference in TBS among the dental cements when used with an SSA. Air abrasion of abutments did not increase the TBS of TempBond but significantly increased crown retention with Retrieve and Premier. For SSAs, all failures were adhesive on the abutment surface; for AAAs, mostly cohesive cement failures occurred. The retention of copings cemented with Retrieve or Premier to zero-degree-taper abutments was significantly increased after airborne particle abrasion of the abutments. However, this was not significant when TempBond was used. Airborne particle abrasion of abutments and the use of Retrieve or Premier can be recommended for nonretrievable prostheses. Although TempBond functioned similarly to the two other cements in SSAs, it is advisable to limit its use to provisional prostheses; its long-term performance needs to be assessed clinically.
Duquesne Light Company met the problem of accumulating low-level radioactive waste at its Beaver Valley nuclear plant with an aggressive program to reduce the quantity of contaminated material and demonstrate that the plant was improving its radiological protection. There was also an economic incentive to reduce low-level wastes. The imaginative campaign involved workers in the reduction effort through training and the adoption of practical approaches to reducing the amount of material exposed to radiation that include sorting trash by radiation level and a compacting system. 4 figures
Al-Abdullah, Khaled; Zandparsa, Roya; Finkelman, Matthew; Hirayama, Hiroshi
Fabricating implant definitive casts with CAD/CAM technology (Robocasts) from coded healing abutment impressions represents a simpler and innovative alternative to conventional implant impression techniques. However, information about the accuracy of the impressions and the resultant definitive casts is limited. The purpose of the study was to evaluate the accuracy of the Robocasts and compare them to those definitive casts fabricated with conventional implant impression techniques (open tray with splinted impression copings technique). A reference epoxy resin cast was fabricated and shaped to simulate a dental arch. Two regular platform implant replicas (Biomet 3i Certain, 4.1 mm diameter and 15 mm length) with internal connections were placed 10 mm apart with a 10-degree convergence for one side of the reference resin cast and a 30-degree convergence for the other. Coded healing abutments (Encode) were placed at 3 different heights above the level of the soft tissue replication material (approximately 1, 2, and 4 mm) and served as test groups (E1, E2, and E4), and open trays with splinted impression copings (OTSC) served as a control group. The control group was compared to the impressions of the coded healing abutments by using a standardized measurement protocol. Impressions were made for each group (n=18) and poured with vacuum mixed (100 g powder/20 mL water) Type IV dental stone. The vertical discrepancy (Z axis) between 2 prefabricated passively fitting titanium reference frameworks and the platforms of the implant replicas was measured with an optical comparator applying the 1 screw test. Data were analyzed with Kruskal-Wallis and post-hoc Mann-Whitney U tests, as well as the Wilcoxon signed-rank tests. The Bonferroni correction was used to account for multiple comparisons. The significance level (α) used in a given set of tests was equal to .05 divided by the number of tests performed in that set. The median vertical discrepancy of each coded healing
Zipprich, Holger; Miatke, Sven; Hmaidouch, Rim; Lauer, Hans-Christoph
This study aimed to test bacterial microleakage at the implant-abutment interface (IAI) before and after dynamic loading using a new chewing simulation. Fourteen implant systems (n = 5 samples of each) were divided into two groups: (1) systems with conical implant-abutment connections (IACs), and (2) systems with flat IACs. For collecting samples without abutment disconnection, channels (Ø = 0.3 mm) were drilled into implants perpendicularly to their axes, and stainless-steel cannulas were adhesively glued inside these channels to allow a sterilized rinsing solution to enter the implant interior and to exit with potential contaminants for testing. Implants were embedded in epoxy resin matrices, which were supported by titanium cylinders with lateral openings for inward and outward cannulas. Abutments were tightened and then provided with vertically adjustable, threaded titanium balls, which were cemented using composite cement. Specimens were immersed in a bacterial liquid and after a contact time of 15 minutes, the implant interior was rinsed prior to chewing simulation (0 N ≘ static seal testing). Specimens were exposed to a Frankfurt chewing simulator. Two hundred twenty force cycles per power level (110 in ± X-axis) were applied to simulate a daily masticatory load of 660 chewing cycles (equivalent to 1,200,000 cycles/5 years). The applied load was gradually increased from 0 N to a maximum load of 200 N in 25-N increments. The implant interior was rinsed to obtain samples before each new power level. All samples were tested using fluorescence microscopy; invading microorganisms could be counted and evaluated. No bacterial contamination was detected under static loading conditions in both groups. After loading, bacterial contamination was detected in one sample from one specimen in group 1 and in two samples from two specimens in group 2. Controlled dynamic loading applied in this study simulated a clinical situation and enabled time-dependent analysis
Go, Gyungchoon; Lee, Kyung-Jin; Kim, Young Keun
Recently, the switching of a perpendicularly magnetized ferromagnet (FM) by injecting an in-plane current into an attached non-magnet (NM) has become of emerging technological interest. This magnetization switching is attributed to the spin-orbit torque (SOT) originating from the strong spin-orbit coupling of the NM layer. However, the switching efficiency of the NM/FM structure itself may be insufficient for practical use, as for example, in spin transfer torque (STT)-based magnetic random access memory (MRAM) devices. Here we investigate spin torque in an NM/FM structure with an additional spin polarizer (SP) layer abutted to the NM layer. In addition to the SOT contribution, a spin-polarized current from the SP layer creates an extra spin chemical potential difference at the NM/FM interface and gives rise to a STT on the FM layer. We show that, using typical parameters including device width, thickness, spin diffusion length, and the spin Hall angle, the spin torque from the SP layer can be much larger than that from the spin Hall effect (SHE) of the NM.
Bressan, Eriberto; Tessarolo, Francesco; Sbricoli, Luca; Caola, Iole; Nollo, Giandomenico; Di Fiore, Adolfo
The study aimed at evaluating the effect of chlorhexidine (CHX) in preventing plaque biofilm (PB) formation on healing abutments (HAs) in patients rehabilitated with osseointegrated implants. Fifty HAs were placed in 34 voluntary patients 1 week after implant surgery (test group). After 7 days, a new set of 50 HAs was placed in the same implant sites and removed 1 week after (control group). During the 2 testing periods, patients were instructed to apply: CHX mouth rinsing twice daily and no brushing (test); no CHX mouth rinsing and no brushing (control). Scanning electron microscopy and image analysis were blindly used to objectively quantify PB amount on removed HAs. Median values and interquartile ranges of the percent ratio of titanium surface covered from PB were 0.9 (0.1-4.1) and 1.2 (0.1-11.6) for test and control groups, respectively (P = 0.0275). CHX mouth rinsing significantly limited plaque formation on HAs, being a valid contribution to mechanical brushing in early phases of plaque control on dental implants.
Full Text Available In this paper, by analyzing the effects of two different kinds of implant-abutment connection interfaces under the same working condition on the mechanical and fatigue performances of the implant system as well as on the surrounding bones, we intend to study such effects on the reliability of the implants and provide a theoretical basis for the design and clinical application of dental implant systems. For the purpose, we adopt a 3-D modeling method to establish the model, and use FEA (finite element analysis to carry out static mechanic and fatigue analysis on the implant system and its surrounding bones; then we make the two implant systems, and carry out fatigue tests on a dynamic fatigue testing machine to verify the FEA results. After comparing the results from the two different systems, we find that the stress distribution and fatigue safety factor of the system which has deeper axial matching of the taper connection are better than those of the other system, that is to say, between the two major elements of a implant system, the axial length of the connecting taper and the size of the hexagon, the former has greater effects than the latter. When the axial matching is deeper, the stress distribution of the implant system will be better, the fatigue safety factor will be higher, and the implant system will be more reliable.
Surpless, B.; Egger, A. E.
that an older structure, perhaps related to the Brothers fault system of the Oregon high lava plains, is the primary control for the formation of the Fandango Valley accommodation zone. Both the east- and west-dipping range-bounding fault systems exhibit a corrugated appearance in map view, potentially formed by the linkage of both left- and right-stepping en echelon normal fault segments by breaching faults. These en echelon faults strike nearly N-S, and the majority of the breaching faults are oriented approximately N60W. On the east side of the range, many tips of outboard en echelon faults extend into the Surprise Valley as Quaternary scarps. Where the Surprise Valley fault system is oriented N60E, fault tips at the range front have propagated into the range itself, creating fault-bound blocks. The observed relationships between fault segments are consistent with right-lateral motion along the Surprise Valley fault system, which may influence the orientation of the Fandango Valley accommodation zone. The complex evolution of the Surprise Valley fault system lends insight into the processes of extension at the northwestern corner of the Basin and Range province. In particular, the Quaternary fault scarps of the Surprise Valley system and the impressive relief across the fault system, combined with recent GPS and trench data, suggest that the historically quiescent Surprise Valley fault system could host both normal and right-oblique- slip earthquakes.
Crumpler, L. S.; Arvidson, R. E.; Mittlefehldt, D. W.; Jolliff, B. L.; Farrand, W. H.; Fox, V.; Golombek, M. P.
In its 12th year of exploration and 1600 sols since arrival at the rim of the 22 km-diameter Noachian Endeavour impact crater, Mars Exploration Rover Opportunity traversed from the summit of the western rim segment "Cape Tribulation" to "Marathon Valley", a shallow trough dissecting the rim and the site of strong orbital detection of smectites. In situ analysis of the exposures within Marathon Valley is establishing some of the geologic and geochemical controls on the aqueous alteration responsible for smectite detection known to occur in crater rims throughout Noachian terrains of Mars.
Padfield, Dirk; Ross, James
A large variety of image analysis tasks require the segmentation of various regions in an image. For example, segmentation is required to generate accurate models of brain pathology that are important components of modern diagnosis and therapy. While the manual delineation of such structures gives accurate information, the automatic segmentation of regions such as the brain and tumors from such images greatly enhances the speed and repeatability of quantifying such structures. The ubiquitous need for such algorithms has lead to a wide range of image segmentation algorithms with various assumptions, parameters, and robustness. The evaluation of such algorithms is an important step in determining their effectiveness. Therefore, rather than developing new segmentation algorithms, we here describe validation methods for segmentation algorithms. Using similarity metrics comparing the automatic to manual segmentations, we demonstrate methods for optimizing the parameter settings for individual cases and across a collection of datasets using the Design of Experiment framework. We then employ statistical analysis methods to compare the effectiveness of various algorithms. We investigate several region-growing algorithms from the Insight Toolkit and compare their accuracy to that of a separate statistical segmentation algorithm. The segmentation algorithms are used with their optimized parameters to automatically segment the brain and tumor regions in MRI images of 10 patients. The validation tools indicate that none of the ITK algorithms studied are able to outperform with statistical significance the statistical segmentation algorithm although they perform reasonably well considering their simplicity.
Brooks, William E.; Willett, Jason C.; Kent, Jonathan D.; Vasquez, Victor; Rosales, Teresa
Debris flows caused by El Niño events, earthquakes, and glacial releases have affected northern Perú for centuries. The Muralla Pircada, a northeast-trending, 2.5 km long stone wall east of the Santa Rita B archaeological site (Moche-Chimú) in the Chao Valley, is field evidence that ancient Andeans recognized and, more importantly, attempted to mitigate the effects of debris flows. The Muralla is upstream from the site and is perpendicular to local drainages. It is 1–2 m high, up to 5 m wide, and is comprised of intentionally-placed, well-sorted, well-rounded, 20–30 cm cobbles and boulders from nearby streams. Long axes of the stones are gently inclined and parallel local drainage. Case-and-fill construction was used with smaller cobbles and pebbles used as fill. Pre-Muralla debris flows are indicated by meter-sized, angular boulders that were incorporated in-place into construction of the dam and are now exposed in breeches in the dam. Post-Muralla debris flows in the Chao Valley are indicated by meter-sized, angular boulders that now abut the retention dam.
Rosentritt, Martin; Rembs, Andreas; Behr, Michael; Hahnel, Sebastian; Preis, Verena
To investigate the influence of the combination of patient-specific abutments and titanium adhesive bases on the long-term in vitro performance of anterior crowns. Ten systems of screw-retained implant and adhesive base combinations (n=8/group) were restored with zirconia or polyetherketone (PEEK) abutments and identical full-anatomical zirconia crowns. For simulating clinical anterior loading, implants were fixed at an angle of 135° and submitted to prolonged thermal cycling and mechanical loading (TC: 6×3000 cycles, 5°C/55°C; ML: 100N, 3.6×10(6) cycles) to cause and register fatigue failure. Failed restorations were examined by means of scanning electron microscopy. Surviving restorations were loaded to fracture. Data (mean±standard deviation) were statistically analyzed (ANOVA; Bonferroni; Kaplan-Meier-Log-Rank; α=0.05). Seven systems survived TCML without any failure. The other three systems showed loosening and fracturing of the screw (0.4-1.6×10(6) loadings) or debonding between base and abutment (0.002-3.4×10(6) loadings). None of the systems showed any fracture of the crown or failed bonding between abutment and crown. The Log-Rank test showed significant (p=0.000) differences. Fracture data significantly varied (ANOVA p=0.000) between the individual systems (minimum: 371N; maximum: 763N). Failures were mostly caused by bending or fracturing of the screw and in three cases by fracture of the abutment. Anterior implant-supported zirconia crowns on titanium adhesive bases and bonded patient-specific zirconia abutments provided good in vitro performance and high fracture resistance. Sufficient high torque moments and early re-screwing may be advised. Most adhesive base and abutment combinations may be appropriate for anterior application. Individual improvements may contribute to enduring success. Copyright © 2015 Elsevier Ltd. All rights reserved.
Aradya, Anupama; Kumar, U Krishna; Chowdhary, Ramesh
The study was designed to evaluate and compare stress distribution in transcortical section of bone with normal abutment and platform switched abutment under vertical and oblique forces in posterior mandible region. A three-dimensional finite element model was designed using ANSYS 13.0 software. The type of bone selection for the model was made of type II mandibular bone, having cortical bone thickness ranging from 0.595 mm to 1.515 mm with the crestal region measuring 1.5 mm surrounding dense trabecular bone. The implant will be modulated at 5 mm restorative platform and tapering down to 4.5 mm wide at the threads, 13 mm long with an abutment 3 mm in height. The models will be designed for two situations: (1) An implant with a 5 mm diameter abutment representing a standard platform in the posterior mandible region. (2) An implant with a 4.5 mm diameter abutment representing platform switching in the posterior mandible region. Force application was performed in both oblique and vertical conditions using 100 N as a representative masticatory force. For oblique loading, a force of 100 N was applied at 15° from the vertical axis. von Mises stress analysis was evaluated. The results of the study showed cortical stress in the conventional and platform switching model under oblique forces were 59.329 MPa and 39.952 MPa, respectively. Cortical stress in the conventional and platform switching model under vertical forces was 13.914 MPa and 12.793 MPa, respectively. Results from this study showed the platform switched abutment led to relative decrease in von Mises stress in transcortical section of bone compared to normal abutment under vertical and oblique forces in posterior mandible region.
Barwacz, Christopher A; Brogden, Kim A; Stanford, Clark M; Dawson, Deborah V; Recker, Erica N; Blanchette, Derek
Dental implant abutments are fundamental prosthetic components within dentistry that require optimal biocompatibility. The primary aim of this cross-sectional study was to preliminarily assess differences in the pro-inflammatory cytokine and bone metabolism mediator protein expression in the peri-implant crevicular fluid (PICF) adjacent to transmucosal abutments. Abutments were fabricated from either titanium or zirconia in patients previously receiving single-tooth implant therapy. All subjects sampled in this study had an identical implant system and implant-abutment connection. Participants (n = 46) had an average time of clinical function for 22 months (6.2-72.8 months, ±SD 17 months) and received a clinical and radiographic examination of the implant site at the time of PICF sampling using a paper strip-based sampling technique. Cytokine, chemokine, and bone metabolism mediator quantities (picograms/30 s) were determined using a commercial 22-multiplexed fluorescent bead-based immunoassay instrument. A total of 19 pro-inflammatory cytokines and seven bone metabolism mediators were evaluated. Multivariable analyses provided no evidence of a group (titanium or zirconia), gender, or age effect with regard to the expression of pro-inflammatory mediators evaluated. Significant (P = 0.022) differences were observed for the bone mediator leptin, with titanium abutments demonstrating significantly elevated levels in comparison with zirconia. Osteopontin demonstrated a significant (P = 0.0044) correlation with age of the subjects. No significant differences in pro-inflammatory cytokine or bone metabolism mediator profiles were observed biochemically, with the exception of leptin, for the abutment biomaterials of titanium or zirconia The molecular PICF findings support the observed clinical biocompatibility of both titanium and zirconia abutments. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.
Barwacz, Christopher A.; Brogden, Kim A.; Stanford, Clark M.; Dawson, Deborah V.; Recker, Erica N.; Blanchette, Derek
Objectives Dental implant abutments are fundamental prosthetic components within dentistry that require optimal biocompatibility. The primary aim of this cross-sectional study was to preliminarily assess differences in the pro-inflammatory cytokine and bone metabolism mediator protein expression in the peri-implant crevicular fluid adjacent to transmucosal abutments. Material and Methods Abutments were fabricated from either titanium or zirconia in patients previously receiving single-tooth implant therapy. All subjects sampled in this study had an identical implant system and implant-abutment connection. Participants (n=46) had an average time of clinical function for 22 months (6.2–72.8 months, ±SD 17.0 months) and received a clinical and radiographic exam of the implant site at the time of peri-implant crevicular fluid (PICF) sampling using a paper strip-based sampling technique. Cytokine, chemokine, and bone metabolism mediator quantities (picograms/30 s) were determined using a commercial 22-multiplexed fluorescent bead-based immunoassay instrument. A total of 19 pro-inflammatory cytokines and 7 bone metabolism mediators were evaluated. Results Multivariable analyses provided no evidence of a group (titanium or zirconia), gender, or age effect with regard to the expression of pro-inflammatory mediators evaluated. Significant (p=0.022) differences were observed for the bone-mediator leptin, with titanium abutments demonstrating significantly elevated levels in comparison to zirconia. Osteopontin demonstrated a significant (p=0.0044) correlation with age of the subjects. Conclusions No significant differences in pro-inflammatory cytokine or bone metabolism mediator profiles were observed biochemically, with the exception of leptin, for the abutment biomaterials of titanium or zirconia The molecular PICF findings support the observed clinical biocompatibility of both titanium and zirconia abutments. PMID:24417614
Nilsson, Andrée; Johansson, Lars-Åke; Lindh, Christina; Ekfeldt, Anders
Studies have reported an increased risk for fractures of zirconia abutments compared with titanium abutments. The aim of this study was to evaluate single-tooth implant restorations with one-piece yttria-stabilized internal zirconia abutments on narrow and regular diameter implants up to 6 years after insertion. This study comprises 52 consecutively treated patients, with a median age of 19 years. In total, 59 narrow (3.3 mm) and 10 regular (4.1 mm) diameter implants were installed. Sixty-five all-ceramic crowns were cemented on implant-supported one-piece internal zirconia abutments and 4 restorations were screw-retained. Thirty-five patients with 48 implant restorations participated in the final examination and another 14 patients with 16 implant restorations were possible to reach and could be interviewed. The implant survival was 100% but the survival rate for the implant-supported ceramic restorations was lower, 87.5%. Three crowns (4.7%) were remade for different reasons. Five restorations (7.8%) were remade due to fracture of the internal one-piece zirconia abutment. Four of these fractures occurred in 3.3 mm implant abutments. Narrow diameter implants offer an opportunity to restore small single-tooth edentulous gaps. For esthetical reasons the choice of an abutment in zirconia can be favorable, but at least with the used implant system, there seems to be an increased risk for fracture. Most patients were very satisfied with the esthetics and function of their implant restorations. © 2017 Wiley Periodicals, Inc.
Borie, Eduardo; Leal, Eduardo; Orsi, Iara Augusta; Salamanca, Carlos; Dias, Fernando José; Weber, Benjamin
The aim of this study was to analyze the influence of three different transmucosal heights of the abutments in single and multiple implant-supported prostheses through the finite element method. External hexagon implants, MicroUnit, and EsthetiCone abutments were scanned and placed in an edentulous maxillary model obtained from a tomography database. The simulations were divided into two groups: (1) one implant with 3.75 × 10 mm placed in the upper central incisor, simulating a single implant-supported fixed prosthesis with an EsthetiCone abutment; and (2) two implants with 3.75 × 10 mm placed in the upper lateral incisors with MicroUnit abutments, simulating a multiple implant-supported prosthesis. Subsequently, each group was subdivided into three models according to the transmucosal height (1, 2, and 3 mm). A static oblique load at an angle of 45 degrees to the long axis of the implant in palatal-buccal direction of 150 and 75 N was applied for multiple and single implant-supported prosthesis, respectively. The implants and abutments were assessed according to the equivalent Von Mises stress analyses while the bone and ceramics were analyzed through maximum and minimum principal stresses. The total deformation values increased in all models, while the transmucosal height was augmented. The transmucosal height of the abutments influences the stress values at the bone, ceramics, implants, and abutments of both the single and multiple implant-supported prostheses, with the transmucosal height of 1 mm showing the lowest stress values.
Gutmacher, Zvi; Levi, Guy; Blumenfeld, Israel; Machtei, Eli E
The advantages of platform switching using narrower abutments remain controversial. Many researchers suggest that platform switching can yield enhanced clinical results, while others remain skeptical. We hypothesize that the effectiveness of platform switching might be associated with the degree of reduction in size of the abutment. To radiographically and clinically examine a new abutment design created to move the implant-abutment interface farther medially. This was a prospective, randomized controlled clinical trial that included 27 patients (41 MIS Lance Plus® implants; MIS Implant Technologies, Karmiel, Israel). The patients' age ranged from 39 to 75 years. At the second stage of the surgery, the implants were randomly assigned to either the new platform switch Tulip abutment (TA) design or to the standard platform abutment (SA). Implant probing depth (IPD) and bleeding on probing (BOP) were recorded at baseline and after 12 months. Standardized periapical radiographs were taken (at baseline and at 12 months) and the marginal bone height measured. All implants were successfully integrated. The mean IPD at 1 year post-op was 2.91 mm for the SA group and 2.69 mm for the TA group (p > .05). Similarly, the BOP at 1 year was almost identical in both groups. The mean values of bone resorption at baseline were 0.98 ± 0.37 mm and 0.69 ± 0.20 for the TA and SA groups, respectively (p > .05). Bone loss (baseline to 12 months) was significantly greater in the SA group compared with the TA group. Use of the new TA, with its significantly downsized diameter, resulted in reduced bone loss at 1 year. Further research will be required to assess the long-term effect of this abutment on peri-implant health. © 2014 Wiley Periodicals, Inc.
Yuan, Yading; Chao, Ming; Sheu, Ren-Dih; Rosenzweig, Kenneth; Lo, Yeh-Chi
This work aims to develop a robust and efficient method to track the fuzzy borders between liver and the abutted organs where automatic liver segmentation usually suffers, and to investigate its applications in automatic liver segmentation on noncontrast-enhanced planning computed tomography (CT) images. In order to track the fuzzy liver-chestwall and liver-heart borders where oversegmentation is often found, a starting point and an ending point were first identified on the coronal view images; the fuzzy border was then determined as a geodesic curve constructed by minimizing the gradient-weighted path length between these two points near the fuzzy border. The minimization of path length was numerically solved by fast-marching method. The resultant fuzzy borders were incorporated into the authors' automatic segmentation scheme, in which the liver was initially estimated by a patient-specific adaptive thresholding and then refined by a geodesic active contour model. By using planning CT images of 15 liver patients treated with stereotactic body radiation therapy, the liver contours extracted by the proposed computerized scheme were compared with those manually delineated by a radiation oncologist. The proposed automatic liver segmentation method yielded an average Dice similarity coefficient of 0.930 ± 0.015, whereas it was 0.912 ± 0.020 if the fuzzy border tracking was not used. The application of fuzzy border tracking was found to significantly improve the segmentation performance. The mean liver volume obtained by the proposed method was 1727 cm(3), whereas it was 1719 cm(3) for manual-outlined volumes. The computer-generated liver volumes achieved excellent agreement with manual-outlined volumes with correlation coefficient of 0.98. The proposed method was shown to provide accurate segmentation for liver in the planning CT images where contrast agent is not applied. The authors' results also clearly demonstrated that the application of tracking the fuzzy
Chan, K. S.
We studied the valley dependent transport in graphene L junctions connecting an armchair lead and a zigzag lead. The junction can be used in valleytronic devices and circuits. Electrons injected from the armchair lead into the junction is not valley polarized, but they can become valley polarized in the zigzag lead. There are Fermi energies, where the current in the zigzag lead is highly valley polarized and the junction is an efficient generator of valley polarized current. The features of the valley polarized current depend sensitively on the widths of the two leads, as well as the number of dimers in the armchair lead, because this number has a sensitive effect on the band structure of the armchair lead. When an external potential is applied to the junction, the energy range with high valley polarization is enlarged enhancing its function as a generator of highly valley polarized current. The scaling behavior found in other graphene devices is also found in L junctions, which means that the results presented here can be extended to junctions with larger dimensions after appropriate scaling of the energy.
The inland valley in Africa are common landscapes that have favorable conditions for agricultural production. Compared to the surrounding uplands they are characterized by a relatively high and secure water availability and high soil fertility levels. Inland valleys thus have a high agricultural
Sow, Abdourahmane; Faye, Ousmane; Ba, Yamar; Ba, Hampathé; Diallo, Diawo; Faye, Oumar; Loucoubar, Cheikh; Boushab, Mohamed; Barry, Yahya; Diallo, Mawlouth; Sall, Amadou Alpha
After a period of heavy rainfall, an outbreak of Rift Valley fever occurred in southern Mauritania during September-November 2012. A total of 41 human cases were confirmed, including 13 deaths, and 12 Rift Valley fever virus strains were isolated. Moudjeria and Temchecket Departments were the most affected areas.
... viticultural area are four 1:24,000 Scale U.S.G.S. topography maps. They are titled: (1) St. Helena, CA 1960... Valley viticultural area, using landmarks and points of reference found on appropriate U.S.G.S. maps..., with a county road known locally as Chiles and Pope Valley Road; (5) Then in a southwesterly direction...
Westbrook, Cherie J.; Cooper, D.J.; Baker, B.W.
We examined how beaver dams affect key ecosystem processes, including pattern and process of sediment deposition, the composition and spatial pattern of vegetation, and nutrient loading and processing. We provide new evidence for the formation of heterogeneous beaver meadows on riverine system floodplains and terraces where dynamic flows are capable of breaching in-channel beaver dams. Our data show a 1.7-m high beaver dam triggered overbank flooding that drowned vegetation in areas deeply flooded, deposited nutrient-rich sediment in a spatially heterogeneous pattern on the floodplain and terrace, and scoured soils in other areas. The site quickly de-watered following the dam breach by high stream flows, protecting the deposited sediment from future re-mobilization by overbank floods. Bare sediment either exposed by scouring or deposited by the beaver flood was quickly colonized by a spatially heterogeneous plant community, forming a beaver meadow. Many willow and some aspen seedlings established in the more heavily disturbed areas, suggesting the site may succeed to a willow carr plant community suitable for future beaver re-occupation. We expand existing theory beyond the beaver pond to include terraces within valleys. This more fully explains how beavers can help drive the formation of alluvial valleys and their complex vegetation patterns as was first postulated by Ruedemann and Schoonmaker in 1938. ?? 2010 John Wiley & Sons, Ltd.
Hollensen, Christian; Højgaard, L.; Specht, L.
and evaluate the method. The method uses deformable registration on computed tomography(CT) to find anatomical symmetry deviations of Head & Neck squamous cell carcinoma and combining it with positron emission tomography (PET) images. The method allows the use anatomical and symmetrical information of CT scans...... segmentations on manual contours was evaluated using concordance index and sensitivity for the hypopharyngeal patients. The resulting concordance index and sensitivity was compared with the result of using a threshold of 3 SUV using a paired t-test. Results: The anatomical and symmetrical atlas was constructed...... and sensitivity of respectively 0.43±0.15 and 0.56±0.18 was acquired. It was compared to the concordance index of segmentation using absolute threshold of 3 SUV giving respectively 0.41±0.16 and 0.51±0.19 for concordance index and sensitivity yielding p-values of 0.33 and 0.01 for a paired t-test respectively....
Sherrod, Brian L.; Barnett, Elizabeth A.; Knepprath, Nichole; Foit, Franklin F.
In October 2009, two trenches excavated across an 11-kilometer-long scarp at Wenas Valley in central Washington exposed evidence for late Quaternary deformation. Lidar imagery of the Wenas Valley illuminated the west-northwest-trending, 2- to 8-meter-high scarp as it bisected alluvial fans developed at the mouths of canyons along the south side of Umtanum Ridge. The alignment of the scarp and aeromagnetic lineaments suggested that the scarp may be a product of and controlled by the same tectonic structure that produced the magnetic lineaments. Several large landslides mapped in the area demonstrated the potential for large mass-wasting events in the area. In order to test whether the scarp was the result of an earthquake-generated surface rupture or a landslide, trenches were excavated at Hessler Flats and McCabe Place. The profiles of bedrock and soil stratigraphy that underlie the scarp in each trench were photographed, mapped, and described, and a sequence of depositional and deformational events established for each trench. The McCabe Place trench exposed a sequence of volcaniclastic deposits overlain by soils and alluvial deposits separated by three unconformities. Six normal faults and two possible reverse faults deformed the exposed strata. Crosscutting relations indicated that up to five earthquakes occurred on a blind reverse fault, and a microprobe analysis of lapilli suggested that the earliest faulting occurred after 47,000 years before present. The Hessler Flat trench exposure revealed weathered bedrock that abuts loess and colluvium deposits and is overlain by soil, an upper sequence of loess, and colluvium. The latter two units bury a distinctive paloesol.
The theoretical part covers general market segmentation, namely the marketing importance of differences among consumers, the essence of market segmentation, its main conditions and the process of segmentation, which consists of four consecutive phases - defining the market, determining important criteria, uncovering segments and developing segment profiles. The segmentation criteria, segmentation approaches, methods and techniques for the process of market segmentation are also described in t...
Baj, A; Beltramini, G A; Bolzoni, A; Cura, F; Palmieri, A; Scarano, A; Ottria, L; Giannì, A B
Bacterial leakage at the implant-abutment connection of a two-piece implant system is considered the main cause of peri-implantitis. Prevention of bacterial leakage at the implant-abutment connection is mandatory for reducing inflammation process around implant neck and achieving bone stability. Micro-cavities at implant-abutment connection level can favour bacterial leakage, even in modern two-piece implant systems. The conical connection with an internal octagon (CCIO) is considered to be more stable mechanically and allows a more tight link between implant and abutment. As P. gingivalis and T. forsythia penetration might have clinical relevance, it was the purpose of this investigation to evaluate molecular leakage of these two bacteria in a new two-implant system with an internal conical implant-abutment connection with internal octagon (Shiner XT, FMD Falappa Medical Devices S.p.A. Rome, Italy). To verify the ability of the implant in protecting the internal space from the external environment, the passage of genetically modified Escherichia c oli across implant-abutment interface was evaluated. Four Shiner XT implants (FMD, Falappa Medical Devices®, Rome, Italy) were immerged in a bacterial culture for 24 h and bacteria amount was measured inside implant-abutment interface with Real-time PCR. Bacteria were detected inside all studied implants, with a median percentage of 6% for P. gingivalis and 5% for T. forsythia. Other comparable studies about the tightness of the tested implant system reported similar results. The gap size at the implant-abutment connection of CCIOs was measured by other authors discovering a gap size of 1–2μm of the AstraTech system and of 4μm for the Ankylos system. Bacterial leakage along implant-abutment connection of cylindrical and tapered implants, Shiner XT, (FMD Falappa Medical Devices S.p.A. Rome, Italy) showed better results compared to other implants. Additional studies are needed to explore the relationship in terms of
Microleakage may be a factor in the progression of peri-implant pathology. Microleakage in implant dentistry refers to the passage of bacteria, fluids, molecules or ions between the abutment-implant interface to and from the surrounding periodontal tissues. This creates a zone of inflammation and reservoir of bacteria at the implant-abutment interface. Bone loss typically occurs within the first year of abutment connection and then stabilizes. It has not yet been definitively proven that the occurrence of microleakage cannot contribute to future bone loss or impede the treatment of peri-implant disease. Therefore, strategies to reduce or eliminate microleakage are sought out. Recent evidence demonstrates that the type of implant abutment channel occluding material can affect the amount of microleakage in an in vitro study environment. Thus, we hypothesize that different abutment screw channel occluding materials will affect the amount of observed microleakage, vis-a-vis the correlation between the microflora found on the abutment screw channel occluding material those found in the peri-implant sulcus. Additional objectives include confirming the presence of microleakage in vivo and assessing any impact that different abutment screw channel occluding materials may have on the peri-implant microbiome. Finally, the present study provides an opportunity to further characterize the peri-implant microbiome. Eight fully edentulous patients restored with at dental implants supporting screw-retained fixed hybrid prostheses were included in the study. At the initial appointment (T1), the prostheses were removed and the implants and prostheses were cleaned. The prostheses were then inserted with polytetrafluoroethylene tape (PTFE, TeflonRTM), cotton, polyvinyl siloxane (PVS), or synthetic foam as the implant abutment channel occluding material and sealed over with composite resin. About six months later (T2), the prostheses were removed and the materials collected. Paper
Fetner, Michael; Fetner, Alan; Koutouzis, Theofilos; Clozza, Emanuele; Tovar, Nick; Sarendranath, Alvin; Coelho, Paulo G; Neiva, Kathleen; Janal, Malvin N; Neiva, Rodrigo
Implant design and the implant-abutment interface have been regarded as key influences on crestal bone maintenance over time. The aim of the present study was to determine crestal bone changes around implants placed at different depths in a dog model. Thirty-six two-piece dental implants with a medialized implant-abutment interface and Morse taper connection (Ankylos, Dentsply) were placed in edentulous areas bilaterally in six mongrel dogs. On each side of the mandible, three implants were placed randomly at the bone crest, 1.5 mm subcrestally, or 3.0 mm subcrestally. After 3 months, the final abutments were torqued into place. At 6 months, the animals were sacrificed and samples taken for microcomputed tomographic (micro-CT) and histologic evaluations. Micro-CT analysis revealed similar crestal or marginal bone loss among groups. Both subcrestal implant groups lost significantly less crestal and marginal bone than the equicrestal implants. Bone loss was greatest on the buccal of the implants, regardless of implant placement depth. Histologically, implants placed subcrestally were found to have bone in contact with the final abutment and on the implant platform. Implants with a centralized implant-abutment interface and Morse taper connection can be placed subcrestally without significant loss of crestal or marginal bone. Subcrestal placement of this implant system appears to be advantageous in maintaining bone height coronal to the implant platform.
Watabe, Y. [Port and Harbour Research Inst., Kanagawa (Japan); Takemura, J.; Kimura, T. [Tokyo Institute of Technology, Tokyo (Japan). Faculty of Engineering
When embankment is constructed behind a piled bridge abutment in soft clay deposits, long term behavior of ground stability and deformation of piled bridge abutment have been investigated by a series of centrifuge model tests and FEM. After a short term change during the construction of embankment, horizontal displacement of the bridge abutment and bending moment of piles increased with time due to undrained creep of soft clay ground. When ground consolidation was predominant after the sufficient time, they decreased to be stable. Influence of the undrained creep on the behavior of piled bridge abutment was reflected to an increase in the bending moment when the constraint of pile end was sufficiently large, and to an increase in the horizontal displacement when it was small. It was effective to improve the backfill lateral ground and to prevent the lateral flow of ground. For the three-dimensional FEM analysis using a modified Cam-clay model, undrained creep deformation of clay can not be considered. Accordingly, an increase in the long term horizontal displacement of bridge abutment after the construction of embankment can not be grasped. However, pulling-back of piles to the backfill side due to the local consolidation can be grasped. 20 refs., 15 figs., 4 tabs.
Huang, Yi-Chen; Lin, Chun-Li; Ko, Ellen Wen-Ching
The resistance form is a key factor for a successful crown fabrication. This in vitro study evaluates the effects of proximal grooves and abutment height on the resistance of single cast crowns in molars with inadequate resistance. Sixty extracted human molars were prepared to possess 20° of total occlusal convergence for single crown fabrication. All of the prepared teeth were divided into six groups and prepared according to three axial heights (2, 3, and 4 mm) with or without preparing a pair of proximal grooves. Alloy metal copings of 5% titanium were casted and cemented. A self-adhesive modified-resin cement was used for cementation. A lateral dislodgement test was performed with an increasing external force applied at a 45° angulation on a universal testing machine. The force required to dislodge the crown from the tooth or to break the core was recorded. Proximal grooves increased the dislodgement resistance in groups with an abutment height of 4 mm, whereas adding grooves made no significant differences in resistance in groups with abutment heights of 2 and 3 mm. The 2 mm groups exhibited worse performance than the other groups, whether they had proximal grooves or not. An abutment height of 3 mm provided adequate resistance for single cast crowns when self-adhesive modified-resin cement was used. Preparing a pair of proximal grooves on abutments shorter than 4 mm had no significant influence on the resistance.
Chen, Yifan; Liu, Hongchun; Meng, Yukun; Chao, Yonglie; Liu, Changhong
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.
Koutouzis, Theofilos; Gadalla, Hana; Lundgren, Tord
The aim of this study is to utilize an in vitro dynamic loading model to assess the potential risk of bacterial invasion into the Implant Abutment Interface (IAI) microgap of dental implants with sloped marginal design. Forty implants were divided into two groups (n = 20 per group) based on implant marginal design. Group 1 was comprised of implants with Morse-taper connection and conventional marginal design that connected to titanium abutments. Group 2 was comprised of implants with Morse-taper connection and sloped marginal design that connected to titanium abutments. The specimens were immersed in a bacterial solution of E. coli and loaded with 500,000 cycles of 160N using a chewing simulator. Following disconnection of fixtures and abutments, microbial samples were taken from the threaded portion of the abutment, plated and cultured under appropriate conditions. Ten out of twenty implants of Group 1 and eight out of twenty implants of Group 2 had IAI microgaps colonized by E. Coli. There was not a statistically significant difference in the mean number of E. Coli CFU detected between implants of Group 1 (mean 19.2, SD 23.6) and Group 2 (mean 12.5, SD18.9) (p > .05). The present study demonstrated that implants with a sloped marginal design exhibited similar risk for bacterial invasion into the IAI microgap under in vitro dynamic loading conditions compared to implants with conventional marginal design. © 2015 Wiley Periodicals, Inc.
Kilicarslan, Mehmet Ali; Ozkan, Pelin
A common problem with cemented crowns is inadequate retention at the crown-abutment interface. The aim of this study was to compare the retention of new laser-sintered cobalt-chromium alloy crowns to the retention of cobalt-chromium alloy crowns fabricated with a traditional casting technique with and without an alloy primer. Twenty-four metallic crowns per casting technique were fabricated, and surface roughness values were recorded with a profilometer. Alloy primer was applied to half the specimens, and all crowns were luted with resin cement. After 24 hours, specimens were subjected to tensile force application with a universal testing machine. The effect of the cement amount was evaluated with an analytic balance. The results were compared using the Kruskal-Wallis multiple-comparison test. The Spearman correlation was used to determine correlations between crown retention and cement weight. The laser-sintered crowns (2.72 μm) were rougher than conventionally cast crowns. The mean load to failure values were as follows: 455.10 ± 192.69 Ncm for conventional crowns, 565.52 ± 112.87 Ncm for conventional crowns with alloy primer, 534.78 ± 130.15 Ncm for laser-sintered crowns, and 678.60 ± 212.83 Ncm for laser-sintered crowns with alloy primer. Laser-sintered crowns (10.10 ± 2.15 mg) showed a significant difference in terms of cement weight compared with cast crowns. In addition, negative correlations were found for retention and cement weight between all groups, except for the laser-sintered group without alloy primer. Retentive forces were significantly higher for laser-sintered crowns than for conventionally cast crowns. An increase in the surface roughness and the application of alloy primers led to an increase in the adhesive bonding of resin cements to metal alloys. It was concluded that a reduction in cement weight improved retention.
Miho, Otoaki; Sato, Toru; Matsukubo, Takashi
The purpose of this study was to evaluate grinding efficiency in abutment teeth comprising both dentin and core composite resin in the axial plane. Grinding was performed over 5 runs at two loads (0.5 or 0.25 N) and two feed rates (1 or 2 mm/sec). The grinding surface was observed with a 3-D laser microscope. Tomographic images of the grinding surfaces captured perpendicular to the feed direction were also analyzed. Using a non-ground surface as a reference, areas comprising only dentin, both dentin and core composite resin, or only core composite resin were analyzed to determine the angle of the grinding surface. Composite resins were subjected to the Vickers hardness test and scanning electron microscopy. Data were statistically analyzed using a one-way analysis of variance and multiple comparison tests. Multiple regression analysis was performed for load, feed rate, and Vickers hardness of the build-up material depending on number of runs. When grinding was performed at a constant load and feed rate, a greater grinding angle was observed in areas comprising both dentin and composite resin or only composite resin than in areas consisting of dentin alone. A correlation was found between machinability and load or feed rate in areas comprising both dentin and composite resin or composite resin alone, with a particularly high correlation being observed between machinability and load. These results suggest that great caution should be exercised in a clinical setting when the boundary between the dentin and composite resin is to be ground, as the angle of the grinding surface changes when the rotating diamond point begins grinding the composite resin.
Schwitalla, Andreas Dominik; Zimmermann, Tycho; Spintig, Tobias; Abou-Emara, Mohamed; Lackmann, Justus; Müller, Wolf-Dieter; Houshmand, Alireza
Frequent reports attest to the various advantages of tapered implant/abutment interfaces (IAIs) compared to other types of interfaces. For this reason, a conical IAI was designed as part of the development of a PEEK (polyetheretherketone)-based dental implant. This IAI is equipped with an apically displaced anti-rotation lock with minimal space requirements in the form of an internal spline. The objective of this study was the determination of the average insertion torque (IT) at failure of this design, so as to determine its suitability for immediate loading, which requires a minimum IT of 32Ncm. 10 implants each made of unfilled PEEK, carbon fiber reinforced ("CFR") PEEK (> 50vol% continuous axially parallel fibers) as well as of titanium were produced and tested in a torque test bench. The average IT values at failure of the unfilled PEEK implants were measured at 22.6 ± 0.5Ncm and were significantly higher than those of the CFR-Implants (20.2 ± 2.5Ncm). The average IT values at failure of the titanium specimens were significantly higher (92.6 ± 2.3Ncm) than those of the two PEEK variants. PEEK- and CFR-PEEK-implants in the present form cannot adequately withstand the insertion force needed to achieve primary stability for immediate loading. Nevertheless, the achievable torque resilience of the two PEEK-variants may be sufficient for a two-stage implantation procedure. To improve the torque resistance of the PEEK implant material the development of a new manufacturing procedure is necessary which reinforces the PEEK base with continuous multi-directional carbon fibers as opposed to the axially parallel fibers of the tested PEEK compound. Copyright © 2017 Elsevier Ltd. All rights reserved.
Saleem S M
Full Text Available A random population of 618 people with epilepsy hailing from different parts of Kashmir valley was screened for photosensitivity both clinically and on a standard protocol of intermittent photic stimulation (IPS provoked EEG recordings. Six (0.9% patients with a mean age of 15+6.57 years were found to be photosensitive; five had generalized and one had absence seizures. The baseline EEG in all patients showed generalized epileptiform discharges. On IPS, similar EEG findings were obtained with a narrow range of stimulus frequency i.e. 7-12 cycles/sec. There appears to be a low prevalence of photo-sensitivity in our epileptic population, possibly related to genetic factors.
Cowan, Jr., Maynard; Marder, Barry M.
A segmented rail linear induction motor has a segmented rail consisting of a plurality of nonferrous electrically conductive segments aligned along a guideway. The motor further includes a carriage including at least one pair of opposed coils fastened to the carriage for moving the carriage. A power source applies an electric current to the coils to induce currents in the conductive surfaces to repel the coils from adjacent edges of the conductive surfaces.
Cowan, M. Jr.; Marder, B.M.
A segmented rail linear induction motor has a segmented rail consisting of a plurality of nonferrous electrically conductive segments aligned along a guideway. The motor further includes a carriage including at least one pair of opposed coils fastened to the carriage for moving the carriage. A power source applies an electric current to the coils to induce currents in the conductive surfaces to repel the coils from adjacent edges of the conductive surfaces. 6 figs.
Baldwin, Darryl Dean; Willi, Martin Leo; Fiveland, Scott Byron; Timmons, Kristine Ann
A segmented heat exchanger system for transferring heat energy from an exhaust fluid to a working fluid. The heat exchanger system may include a first heat exchanger for receiving incoming working fluid and the exhaust fluid. The working fluid and exhaust fluid may travel through at least a portion of the first heat exchanger in a parallel flow configuration. In addition, the heat exchanger system may include a second heat exchanger for receiving working fluid from the first heat exchanger and exhaust fluid from a third heat exchanger. The working fluid and exhaust fluid may travel through at least a portion of the second heat exchanger in a counter flow configuration. Furthermore, the heat exchanger system may include a third heat exchanger for receiving working fluid from the second heat exchanger and exhaust fluid from the first heat exchanger. The working fluid and exhaust fluid may travel through at least a portion of the third heat exchanger in a parallel flow configuration.
The purpose of the Market Segment of the EUREKA model is to simultaneously project uranium market prices, uranium supply and purchasing activities. The regional demands are extrinsic. However, annual forward contracting activities to meet these demands as well as inventory requirements are calculated. The annual price forecast is based on relatively short term, forward balances between available supply and desired purchases. The forecasted prices and extrapolated price trends determine decisions related to exploration and development, new production operations, and the operation of existing capacity. Purchasing and inventory requirements are also adjusted based on anticipated prices. The calculation proceeds one year at a time. Conditions calculated at the end of one year become the starting conditions for the calculation in the subsequent year
Full Text Available Accurate segmentation of medical images is a key step in contouring during radiotherapy planning. Computed topography (CT and Magnetic resonance (MR imaging are the most widely used radiographic techniques in diagnosis, clinical studies and treatment planning. This review provides details of automated segmentation methods, specifically discussed in the context of CT and MR images. The motive is to discuss the problems encountered in segmentation of CT and MR images, and the relative merits and limitations of methods currently available for segmentation of medical images.
Full Text Available This paper presents efficient and portable implementations of a useful image segmentation technique which makes use of the faster and a variant of the conventional connected components algorithm which we call parallel Components. In the Modern world majority of the doctors are need image segmentation as the service for various purposes and also they expect this system is run faster and secure. Usually Image segmentation Algorithms are not working faster. In spite of several ongoing researches in Conventional Segmentation and its Algorithms might not be able to run faster. So we propose a cluster computing environment for parallel image Segmentation to provide faster result. This paper is the real time implementation of Distributed Image Segmentation in Clustering of Nodes. We demonstrate the effectiveness and feasibility of our method on a set of Medical CT Scan Images. Our general framework is a single address space, distributed memory programming model. We use efficient techniques for distributing and coalescing data as well as efficient combinations of task and data parallelism. The image segmentation algorithm makes use of an efficient cluster process which uses a novel approach for parallel merging. Our experimental results are consistent with the theoretical analysis and practical results. It provides the faster execution time for segmentation, when compared with Conventional method. Our test data is different CT scan images from the Medical database. More efficient implementations of Image Segmentation will likely result in even faster execution times.
Lopes de Chaves E Mello Dias, Eduardo Cláudio; Sperandio, Marcelo; Napimoga, Marcelo Henrique
The aim of this study was to evaluate the microgap between the abutment and implant as well as the circularity of implant platforms and associating conformational errors with bacterial microleakage in tapered connection implant systems. Four brands of implants with a tapered abutment connection were tested. Bacterial leakage was assessed using 0.3 μL of Escherichia coli suspension inoculated into the abutment screw chamber of the implants, which were then torqued and incubated at 37°C for 14 days. All specimens used for the microbiologic experiment were then cut lengthwise, and the microgap was measured at three points on each side of the sample using scanning electron microscopy (up to 5,000× magnification). Microtomography was used to assess implant platform circularity to validate the microscopic findings qualitatively. Two samples from the Nobel Biocare system, four from the Ankylos (Dentsply) system, four from the Neodent (Straumann) system, and five from the Conexão system were positive for bacterial leakage, with no significant difference between groups. The Neodent system had the highest mean microgap values (5.84 ± 9.83 μm), followed by the Nobel Biocare systems (5.17 ± 4.10 μm), Ankylos (3.47 ± 3.28 μm), and Conexão (2.72 ± 3.19 μm), with no significant difference between systems. All systems showed conformational errors of circularity on microtomography images. The tapered connection systems evaluated herein were not able to halt bacterial leakage, nor were they free from conformational errors.
Nogueira, Lorenna Bastos Lima Verde; Moura, Carmem Dolores Vilarinho Soares; Francischone, Carlos Eduardo; Valente, Valdimar Silva; Alencar, Suyá Moura Mendes; Moura, Walter Leal; Soares Martins, Gregorio Antonio
To compare the fracture resistance before and after cyclic fatigue assays of ceramic crowns with customized zirconia abutments when screw retained and cemented onto implants. The sample of this study consisted of 40 ceramic crowns with zirconia infrastructure fixed onto external hexagonal implants. The crowns were distributed into two groups (n = 20): Screw-retained and cemented crowns. Half the crowns of each group (n = 10) underwent compression until fracture and the other half (n = 10) underwent cyclic fatigue and subsequent compression until fracture. The cyclic fatigue test was carried out using an electromechanical fatigue device (loads from 0 to 100 N, 2 Hz frequency, in distilled water, at 37 °C for a period of 1 million cycles). The compression test was carried out using a universal testing machine with a 0.5 mm/min speed and 5 KN load cell. After fracture, the crowns were classified according to the type of fracture. Student's t test (p crowns (before = 1068.31 N, after = 891.49 N; p > 0.05) nor that of the cemented crowns (before = 2117.78 N; after = 2094.81 N; p > 0.05); however, the mean fracture resistance of the cemented crowns was higher than that of the screw-retained crowns both before (p crowns cemented onto the customized zirconia abutments offered greater fracture resistance than ceramic crowns with customized zirconia abutments screw retained onto implants. The cyclic fatigue did not seem to influence the fracture resistance of these crowns, whether cemented or screw retained onto implants. Fracture of the veneering ceramic was the predominant failure in this study. © 2015 by the American College of Prosthodontists.
Toyoshima, Yusuke; Wakabayashi, Noriyuki
The primary objective of this study was to investigate the fracture resistance of experimental mini-implants with a reduced abutment height. The secondary objective was to assess the effects of implant diameter and bone level on the load limit, using finite element simulations. Two Ti-6A1-4V 1.8-mm-diameter implants were subjected to monotonic bending testing and fatigue tests incorporating 5 x 10(6) cycles (ISO 14801): a commercially available implant (c18), and an experimental implant with a reduced abutment height (e18). The load limit was estimated using the finite element models based on the maximum stress at failure in the experiments. For simulations, implants with increased diameters of 2.1 and 2.4 mm were also modeled, and the load limit was estimated for all models in a bone model. In the bending test, e18 revealed a higher mean load at yield stress than c18, and this was attributed to the reduced height of the former. An endurance limit of 140 N was detected for both c18 and e18 in the fatigue test, while the load limit of e18 was higher than that of c18. The estimated load limit increased as the implant diameter or the bone level increased, with the highest value of 510 N observed at a diameter of 2.4 mm. A higher load limit was evident in the experimental mini-implant with a reduced abutment height. The simulations indicated that the load limit increased with increased implant diameter and higher bone levels.
Bordin, Dimorvan; Coelho, Paulo G; Bergamo, Edmara T P; Bonfante, Estevam A; Witek, Lukasz; Del Bel Cury, Altair A
To characterize the mechanical properties of different coating methods of DLC (diamond-like carbon) onto dental implant abutment screws, and their effect on the probability of survival (reliability). Seventy-five abutment screws were allocated into three groups according to the coating method: control (no coating); UMS - DLC applied through unbalanced magnetron sputtering; RFPA-DLC applied through radio frequency plasma-activated (n=25/group). Twelve screws (n=4) were used to determine the hardness and Young's modulus (YM). A 3D finite element model composed of titanium substrate, DLC-layer and a counterpart were constructed. The deformation (μm) and shear stress (MPa) were calculated. The remaining screws of each group were torqued into external hexagon abutments and subjected to step-stress accelerated life-testing (SSALT) (n=21/group). The probability Weibull curves and reliability (probability survival) were calculated considering the mission of 100, 150 and 200N at 50,000 and 100,000 cycles. DLC-coated experimental groups evidenced higher hardness than control (p1 indicating that fatigue contributed to failure. High reliability was depicted at a mission of 100N. At 200N a significant decrease in reliability was detected for all groups (ranging from 39% to 66%). No significant difference was observed among groups regardless of mission. Screw fracture was the chief failure mode. DLC-coating have been used to improve titanium's mechanical properties and increase the reliability of dental implant-supported restorations. Copyright © 2018 The Academy of Dental Materials. Published by Elsevier Inc. All rights reserved.
Marisol C. Camacho
Full Text Available Purpose: The purpose of this study was to evaluate the behavior of mandibular canines acting as abutment teeth and indirect retainers of a Kennedy class II according to different designs: lingual rest and lingual rest associated with a reciprocal arm. Materials & methods: A resin cast with two simulated canine teeth was made in Ni-Cr alloy, representing a Kennedy class II mandibular arch. With the objective of simulating the resilience of the periodontal ligament, a polyurethane layer was added at the canine tooth's root. A metallic framework of Co-Cr alloy was fabricated with a T bar clasp and a lingual rest associated with a reciprocal arm. To obtain the second framework, the reciprocal arm was removed using a tungsten bur. Each framework was submitted to tensile force using a VersaTest machine. The magnitude and direction of canine movement during removal of the framework was measured using two dial gauges (mm. The axial tensile force required to remove the experimental framework (N was also evaluated. The data were compared using the paired t-test with 95% confidence intervals. Differences were considered significant at P < .05. Results: The mean retentive force of the modified design framework with the reciprocal arm was significantly higher (P < .0001 than that of the framework with the lingual rest. The abutment teeth showed movement in the lingual and mesial directions, and this movement was less when associated with the reciprocal arm design. Conclusion: The reciprocal arm in association with a lingual rest in the framework decreased the movement of the abutment teeth when analyzed in the bucco-lingual and mesio-distal directions and contributed to increased retention by friction. Keywords: Materials science, Dentistry, Engineering
Kim, Seung-Mi; Yoon, Ji-Young; Lee, Myung-Hyun; Oh, Nam-Sik
The purpose of this study was to investigate the effect of resin cements and primer on the retentive force of zirconia copings bonded to zirconia abutments with insufficient retention. Zirconia blocks (Lava, 3M ESPE, St. Paul, MN, USA) were obtained and forty sets of zirconia abutments and copings were fabricated using CAD/CAM technology. They were grouped into 4 categories as follows, depending on the types of resin cements used, and whether the primer is applied or not:Panavia F2.0 (P), Panavia F2.0 using Primer (PRIME Plus, Bisco Inc, Schaumburg, IL, USA) (PZ), Superbond C&B (S), and Superbond C&B using Primer (SZ). For each of the groups, the cementation was conducted. The specimens were kept in sterilized water (37℃) for 24 hours. Retentive forces were tested and measured, and a statistical analysis was carried out. The nature of failure was recorded. The means and standard deviations of retentive force in Newton for each group were 265.15 ± 35.04 N (P), 318.21 ± 22.24 N (PZ), 445.13 ± 78.54 N (S) and 508.21 ± 79.48 N (SZ). Superbond C&B groups (S & SZ) showed significantly higher retentive force than Panavia F2.0 groups (P & PZ). In Panavia F2.0 groups, the use of primer was found to contribute to the increase of retentive force. On the other hand, in Superbond C&B groups, the use of primer did not influence the retention forces. Adhesive failure was observed in all groups. This study suggests that cementation of the zirconia abutments and zirconia copings with Superbond C&B have a higher retentive force than Panavia F2.0. When using Panavia F2.0, the use of primer increases the retentive force.
Rytting, C. Anton; Brew, Chris; Fosler-Lussier, Eric
Most computational models of word segmentation are trained and tested on transcripts of speech, rather than the speech itself, and assume that speech is converted into a sequence of symbols prior to word segmentation. We present a way of representing speech corpora that avoids this assumption, and preserves acoustic variation present in speech. We…
Sia, Priscilla Kia Suan; Masri, Radi; Driscoll, Carl F; Romberg, Elaine
Currently, no guidelines exist to help in the selection of Locator abutments for implants at different heights. The purpose of this in vitro study was to evaluate the effect of the differential heights of pairs of Locator abutments on the retention of overdentures after 6 months of simulated function. In vitro testing was performed with 4 sets of average-sized edentulous mandible analogs with 2 implants placed in the canine positions. There were 10 specimens in each of the 4 groups, with a total sample size of 40. Four groups of 2 implant-retained overdentures were fabricated, with Locator attachments at different vertical levels with differences of 0, 2, 4, and 6 mm. The overdentures were subjected to simulated function for a period corresponding to 6 months of clinical service and then tested with a universal testing machine for changes in peak load-to-dislodgement. The data were analyzed using 1-way ANOVA followed by the Tukey honest significant differences test (α=.05). Varying the heights of Locator abutments had a statistically significant effect on the retentive values of the pink Locator attachments after 6 months of simulated function (F=7.342, P=.001). The peak load-to-dislodgement ranged from 32.3 N (95% confidence interval [CI]: 26.0 to 38.6) for group 0 mm to 53.6 N (95% CI: 46.3 to 60.8) for group 6 mm. When the difference in Locator abutment heights was 2 and 4 mm, the peak load was 37.1 N (95% CI: 32.3 to 42.0) and 41.9 N (95% CI: 31.2 to 52.7). Statistical analysis revealed that the retention of group 0 mm and group 2 mm was significantly lower than group 6 mm. The retention of group 4 mm was not significantly different from groups 0 mm, 2 mm, or 6 mm. Although significant differences were found among the groups, these differences were small and may not be clinically detectable. Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.
Hartlev, Jens; Kohberg, Peter; Ahlmann, Søren; Gotfredsen, Erik; Andersen, Niels Trolle; Isidor, Flemming; Schou, Søren
To assess with a mean follow-up period of 33 months (median: 31 month, range: 11-89 month) the treatment outcome after immediate placement and provisionalization of single-tooth oral implants involving a definitive individual abutment and a provisional crown followed by later placement of a definitive crown. 68 patients with 68 single-tooth implants in the esthetic zone were consecutively treated; 55 of these patients were included in the study. The treatment involved tooth extraction, implant placement, placement of a definitive individual abutment, and a provisional crown in the same visit in private practice. The definitive crown was placed after a mean period of 7 months. The primary outcome measures included implant survival, definitive implant crown survival, and overall treatment survival. The secondary outcome measures included probing depth, bleeding on probing, peri-implant marginal bone level, marginal bone level of the neighboring tooth surfaces, biological complications, and technical complications. Of the inserted implants 98% survived and of the definitive crowns mounted a survival of 100% was observed. Consequently, the overall treatment survival was 98%. The mean probing depth was 2.9 mm at implant level and 63% of the implants were characterized by no bleeding on probing. The mean peri-implant marginal bone level was 2 mm. A significant mean peri-implant marginal bone level gain of 0.5 mm was observed from implant placement to the follow-up (95% CI: 0.07-0.89 mm, P = 0.022). No significant changes of the marginal bone level at the neighboring tooth surfaces were seen. Four episodes of peri-implant inflammation were identified in three patients, while 46 incidents of loosening of the provisional crown occurred in 33 patients. One abutment screw loosened before placement of the definitive crown. Finally, loosening of four definitive crowns occurred in four patients. Immediate placement and provisionalization of single-tooth oral implants
Qin, Jia-nan; Lu, Yu-miao; Zhou, Xiao-yan
To study and evaluate the effect preventing dentine hypersensitiveness by using Fluor Protector or Green Or on the prepared vital pulp abutment teeth of PFM bridges. 118 cases, 246 prepared vital pulp abutment teeth, were randomly divided into three groups: Experimental Group A--treated with the Fluor Protector and temporary crown; Experimental Group B--treated with the Green Or and temporary crown, and Control Group--only using temporary crown. The results of desensitization in 3 groups were evaluated. F test was used for analysis (DSPV6.01). Significant differences were found between experimental Group A, B and the control group after 1 week (when cementing the PFM bridges); and also after 1 month (P0.05). The effect of preventing dental hypersensitiveness by using Fluor Protector or Green Or on the prepared vital pulp abutment teeth of PFM bridges is ideal. It is easy to use and worth being widely applied.
Fürhauser, Rudolf; Mailath-Pokorny, Georg; Haas, Robert; Busenlechner, Dieter; Watzek, Georg; Pommer, Bernhard
Implant esthetics may benefit from individualized zirconia abutments copying the emergence profile of the natural tooth and delivered within days after immediate implant insertion. To investigate the esthetic outcome of the Copy-Abutment technique using the Pink Esthetic Score (PES). A total of 77 patients with single-tooth implants in the anterior maxilla restored at the day of immediate implant placement using Copy-Abutments and provisional crowns were followed-up after 1 week, 1 month, 4 months, 6 months, 1, 2, 3, 4, and 5 years to assess implant esthetics. PES ranged between 7 and 14 (median: 13) and improved significantly between the 6 month and 1 year follow-up (p implants in the esthetic zone show satisfactory long-term esthetic outcomes. © 2016 Wiley Periodicals, Inc.
Mandelaris, George A; Vlk, Scott D
Parallel use of implant treatment planning software and cone-beam computed tomography (CBCT) can, using certain criteria, consolidate steps and streamline tooth replacement strategies. The authors describe such a case in the esthetic zone whereby flapless extraction and immediate implant placement using CT-guided surgery were performed simultaneously, with placement of a computer-aided design/computer-aided manufactured (CAD/CAM) patient-specific abutment and non-occlusal function provisional in a single visit (supporting the "one-abutment, one-time" concept). An over-retained primary cuspid in a periodontally healthy woman with well-controlled type-2 diabetes was replaced with an implant and CAD/CAM patient-specific abutment in the No. 11 position. A necessary implant-axis angle correction was customized using digital information from a CBCT scan and implant treatment planning software, without the need for site development or a conventional impression. This data integration and streamlined workflow enabled fabrication of a CAD/CAM patient-specific abutment before surgical treatment. The abutment remained in place from implant surgery to the prosthetic phase, with minimal soft-tissue changes, enabling preservation of pink esthetics and expediting treatment. The result was a preserved emergence profile in the presence of high esthetic demands. However, due to slight post-extraction soft-tissue changes, digital reformatting of the abutment was required when the final crown was fabricated, thus limiting the disruption of the biologic width to a one-time occurrence. The importance of case selection for this treatment protocol in the esthetic zone cannot be overemphasized. A thick crestal dentoalveolar bone phenotype (> 1 mm, approaching 2 mm in this case), broad zone of attached and keratinized gingiva (3 mm to 4 mm in this case), adequate peri-implant soft-tissue thickness (> 1 mm in this case), and high primary implant stability (ISQ = 80 in this case) were all
Rammelsberg, Peter; Bernhart, Gunda; Lorenzo Bermejo, Justo; Schmitter, Marc; Schwarz, Stefanie
Objective of this study was to evaluate the incidence of complications in dental implants and abutment teeth used for combined tooth-implant- and solely implant-supported double crown-retained removable dental prostheses (RDPs). Patients were selected from a prospective clinical study. Seventy-three RDPs retained by 234 implants and 107 abutment teeth were placed in 39 men and 22 women with a mean age of 65 years. Forty-five RDPs were located in the maxilla and 28 in the mandible. Thirty-four RDPs were solely implant-supported and 39 were combined tooth-implant-supported. Kaplan-Meier analysis was used to estimate success defined as survival without severe abutment-related complications, and Cox regression was used to isolate the most relevant prognostic risk factors. After a median observation period of 2.7 years for the RDPs, six implants failed and eleven implants were diagnosed with peri-implantitis. Four abutment teeth were extracted, and three abutment teeth showed severe complications requiring extended interventions. For both abutment teeth and implants, Kaplan-Meier analyses revealed a 5-year probability of success of 85% for solely implant-supported RDPs and 92% for combined tooth-implant-supported RDPs. Multiple Cox regression identified RDP location (P = 0.01), age (P = 0.01), and gender (P = 0.04) as prognostic risk factors for severe implant-related complications. Solely implant-supported RPDs showed a poorer prognosis, but the risk difference did not reach statistical significance. Preliminary data suggest that the combination of teeth and implants to support double crown-retained RDPs may result in a prognostic advantage. The present findings should be validated in independent studies. © 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.
Cai, He; Chen, Junyu; Li, Chunjie; Wang, Jian; Wan, Qianbing; Liang, Xing
The implant abutments, which had their own colour, might cause the discoloration of peri-implant mucosa. We aimed to appraise trails comparing the discoloration of peri-implant soft tissue around zirconia and titanium or golden abutments, the tints of which were vastly different. We included randomized controlled trials (RCTs), controlled clinical trials (CCTs), cohort studies with patients rehabilitated with zirconia, titanium or golden implant abutments, quantitatively comparing the discoloration of peri-implant soft tissue according to CIE-Lab colour scale. A systematic search was conducted in PubMed, EMBASE, CDSR, and CENTRAL databases without any restriction on September 23, 2017. "Grey" literatures were also searched. A manual search was carried out as well. Of 584 articles initially retrieved, eight were eligible for inclusion. After data extraction, meta-analyses with mean differences (MDs) and their 95% confidence intervals (CIs) were employed. Moreover, the risk of bias within or across studies was assessed by Cochrane Collaboration's tool for assessing risk, the Newcastle-Ottawa scale, funnel plots, or Egger's test. Four RCTs and four cohort studies were included. Soft-tissue discoloration around zirconia abutments was significantly less likely compared to that around titanium abutments (MD = -1.84; 95% CI = -3.62 to -0.07; P = 0.04 implant mucosa and natural teeth. Based on the present evidence, the "nature-like" zirconia abutments should be applied more often in the clinic. CRD42017075930. Copyright © 2018 Elsevier Ltd. All rights reserved.
Butkevica, Alena; Nathanson, Dan; Pober, Richard; Strating, Herman
Repeated tightening and loosening of the abutment screw may alter its mechanical and physical properties affecting the optimal torque and ultimate reliability of an implant/abutment connection. The purpose of this study was to evaluate the effect of repeated tightening and loosening of implant/abutment screws on the loosening torque of implant/abutment connections of commercially available implant systems. Seven different implant/abutment connections and their modifications were tested. The screws of each system were tightened according to the manufacturer's specifications. After 20 minutes the screws were loosened. This procedure was repeated ten times, and the differences between the 1st and 10th cycle were expressed as a percentage change RTq(%) and correlated with initial torque, the number of threads, the length of shank, and thread surface area employing Spearman's analysis. All systems showed significant differences in residual torque (RTq) value (p 0.05). All connections but group 3 (p = 1.000) showed a significant change from the initial torque (ITq) to the RTq values. The first successive RTq values increased in two connection groups 1 and 2. The remaining connections showed reduced RTq values ranging from -1.2 % (group 5) to -23.5% (group 6). The RTq values declined gradually with every repeated tightening in groups 1, 2, 3, 8, 9, 11, 12. In group 2, after the tenth tightening the RTq was still above the ITq value. Only length of shank demonstrated a correlation with the RTq(%) change over the successive tightening loosening cycles (p implant/abutment screws caused varying torque level changes among the different systems. These observations can probably be attributed to connection design. Limiting the number of tightening/loosening cycles in clinical and laboratory procedures is advisable for most of the implant systems tested. © 2016 by the American College of Prosthodontists.
... Surface Transportation Board Conecuh Valley Railway, LLC--Acquisition and Operation Exemption--Conecuh Valley Railroad Co., Inc. Conecuh Valley Railway, LLC (CVR), a noncarrier, has filed a verified notice of exemption under 49 CFR 1150.31 to acquire from Conecuh Valley Railroad Co., Inc. (COEH), and to operate...
Zhang, Xu-Long; Xu, Lei; Zhang, Jun
Electron edge states in gated bilayer graphene in the quantum valley Hall (QVH) effect regime can carry both charge and valley currents. We show that an interlayer potential splits the zero-energy level and opens a bulk gap, yielding counter-propagating edge modes with different valleys. A rich variety of valley current states can be obtained by tuning the applied boundary potential and lead to the QVH effect, as well as to the unbalanced QVH effect. A method to individually manipulate the edge states by the boundary potentials is proposed.
Ota, Mitsuhiko; Skarabela, Barbora
This study explores the possibility that early word segmentation is aided by infants' tendency to segment words with repeated syllables ("reduplication"). Twenty-four nine-month-olds were familiarized with passages containing one novel reduplicated word and one novel non-reduplicated word. Their central fixation times in response to…
The rationale behind marketing segmentation is to allow businesses to focus on their consumers' behaviors and purchasing patterns. If done effectively, marketing segmentation allows an organization to achieve its highest return on investment (ROI) in turn for its marketing and sales expenses. If an organization markets its products or services to…
Wyatt, Christopher L.; Ge, Yaorong; Vining, David J.
Virtual colonoscopy is a minimally invasive technique that enables detection of colorectal polyps and cancer. Normally, a patient's bowel is prepared with colonic lavage and gas insufflation prior to computed tomography (CT) scanning. An important step for 3D analysis of the image volume is segmentation of the colon. The high-contrast gas/tissue interface that exists in the colon lumen makes segmentation of the majority of the colon relatively easy; however, two factors inhibit automatic segmentation of the entire colon. First, the colon is not the only gas-filled organ in the data volume: lungs, small bowel, and stomach also meet this criteria. User-defined seed points placed in the colon lumen have previously been required to spatially isolate only the colon. Second, portions of the colon lumen may be obstructed by peristalsis, large masses, and/or residual feces. These complicating factors require increased user interaction during the segmentation process to isolate additional colon segments. To automate the segmentation of the colon, we have developed a method to locate seed points and segment the gas-filled lumen with no user supervision. We have also developed an automated approach to improve lumen segmentation by digitally removing residual contrast-enhanced fluid resulting from a new bowel preparation that liquefies and opacifies any residual feces.
Jinhee Jun; Gerard Kyle; Andrew Mowen
We examined the practical utility of segmenting potential visitors to Cleveland Metroparks using their constraint profiles. Our analysis identified three segments based on their scores on the dimensions of constraints: Other priorities--visitors who scored the highest on 'other priorities' dimension; Highly Constrained--visitors who scored relatively high on...
Wright, Peter H.
A concept-based introduction to market segmentation is provided in this instructional module for undergraduate and graduate transportation-related courses. The material can be used in many disciplines including engineering, business, marketing, and technology. The concept of market segmentation is primarily a transportation planning technique by…
Hofstede, ter F.
The primary objective of this thesis is to develop and validate new methodologies to improve the effectiveness of international segmentation strategies. The current status of international market segmentation research is reviewed in an introductory chapter, which provided a number of
Markarian, Roberto Adrian; Galles, Deborah Pedroso; Gomes França, Fabiana Mantovani
To measure the microgap between dental implants and custom abutments fabricated using different computer-aided design/computer-aided manufacture (CAD/CAM) methods before and after mechanical cycling. CAD software (Dental System, 3Shape) was used to design a custom abutment for a single-unit, screw-retained crown compatible with a 4.1-mm external hexagon dental implant. The resulting stereolithography file was sent for manufacturing using four CAD/CAM methods (n = 40): milling and sintering of zirconium dioxide (ZO group), cobalt-chromium (Co-Cr) sintered via selective laser melting (SLM group), fully sintered machined Co-Cr alloy (MM group), and machined and sintered agglutinated Co-Cr alloy powder (AM group). Prefabricated titanium abutments (TI group) were used as controls. Each abutment was placed on a dental implant measuring 4.1× 11 mm (SA411, SIN) inserted into an aluminum block. Measurements were taken using scanning electron microscopy (SEM) (×4,000) on four regions of the implant-abutment interface (IAI) and at a relative distance of 90 degrees from each other. The specimens were mechanically aged (1 million cycles, 2 Hz, 100 N, 37°C) and the IAI width was measured again using the same approach. Data were analyzed using two-way analysis of variance, followed by the Tukey test. After mechanical cycling, the best adaptation results were obtained from the TI (2.29 ± 1.13 μm), AM (3.58 ± 1.80 μm), and MM (1.89 ± 0.98 μm) groups. A significantly worse adaptation outcome was observed for the SLM (18.40 ± 20.78 μm) and ZO (10.42 ± 0.80 μm) groups. Mechanical cycling had a marked effect only on the AM specimens, which significantly increased the microgap at the IAI. Custom abutments fabricated using fully sintered machined Co-Cr alloy and machined and sintered agglutinated Co-Cr alloy powder demonstrated the best adaptation results at the IAI, similar to those obtained with commercial prefabricated titanium abutments after mechanical cycling. The
Anupama Aradya; U Krishna Kumar; Ramesh Chowdhary
Purpose of the Study: The study was designed to evaluate and compare stress distribution in transcortical section of bone with normal abutment and platform switched abutment under vertical and oblique forces in posterior mandible region. Materials and Methods: A three-dimensional finite element model was designed using ANSYS 13.0 software. The type of bone selection for the model was made of type II mandibular bone, having cortical bone thickness ranging from 0.595 mm to 1.515 mm with the...
Asmar, Mahmoud M.; Ulloa, Sergio E.
The possibility to effect valley splitting of an electronic current in graphene represents the essential component in the new field of valleytronics in such two-dimensional materials. Based on a symmetry analysis of the scattering matrix, we show that if the spatial distribution of multiple potential scatterers breaks mirror symmetry about the axis of incoming electrons, then a splitting of the current between two valleys is observed. This leads to the appearance of the valley Hall effect. We illustrate the effect of mirror-symmetry breaking in a minimal system of two symmetric impurities, demonstrating the splitting between valleys via the differential cross sections and nonvanishing skew parameter. We further discuss the role that these effects may play in transport experiments.
Whiteman, C.D.; Allwine, K.J.
Following a thorough analysis of meteorological data obtained from deep valleys of western Colorado, a modular air-pollution model has been developed to simulate the transport and diffusion of pollutants released from an elevated point source in a well-defined mountain valley during the nighttime and morning transition periods. This initial version of the model, named VALMET, operates on a valley cross section at an arbitrary distance down-valley from a continuous point source. The model has been constructed to include parameterizations of the major physical processes that act to disperse pollution during these time periods. The model has not been fully evaluated. Further testing, evaluations, and development of the model are needed. Priorities for further development and testing are provided.
Ettevõtluse Arendamise Sihtasutuse esinduse töölepanekust USAs Silicon Valleys räägib esinduse juht Andrus Viirg. Vt. ka: Eestlasi leidub San Franciscos omajagu; Muljetavaldav karjäär; USAga ammune tuttav
Ruus, Kertu, 1977-
Ilmunud ka: Delovõje Vedomosti 5. dets. lk. 4. Peaminister Andrus Ansip avas Eesti Ettevõtluse Sihtasutuse esinduse Silicon Valley pealinnas San Joses. Vt. samas: Ränioru kliima on tehnoloogiasõbralik; Andrus Viirg
This document outlines the strategy for evaluating the integrated freeway, arterial, and incident management system known as the Silicon Valley Smart Corridor (SVSC). Centered in San Jose, California, the SVSC is one of approximately 65 deployments o...
California Department of Resources — These burrowing owl observations were collected during the spring and early summer of 1976 in the Palo Verde Valley, eastern Riverside County, California. This is an...
Sorey, M.L.; Lewis, R.E.; Olmsted, F.H.
The geologic and hydrologic setting of the hydrothermal system are described. The geochemical and thermal characteristics of the system are presented. A mathematical model of the Long Valley caldera is analyzed. (MHR)
All-ceramic single-tooth implant reconstructions using modified zirconia abutments: a prospective randomized controlled clinical trial of the effect of pink veneering ceramic on the esthetic outcomes.
Büchi, Dominik L E; Sailer, Irena; Fehmer, Vincent; Hämmerle, Christoph H F; Thoma, Daniel S
The aim of this study was to test whether veneering of the submucosal part of zirconia abutments using pink veneering ceramic positively influences the color of the peri-implant mucosa. Single-tooth implants were restored with either white zirconia abutments (control group) or pink-veneered zirconia abutments and all-ceramic crowns. Esthetic outcome measurements included a spectrophotometric evaluation of the peri-implant mucosal color. Test and control groups induced a visible discoloration of the peri-implant mucosa after the insertion of the abutments and following cementation of the crowns compared to natural teeth. The calculated color differences were above the clinically visible threshold value and were more favorable for the control group, although not statistically significant. It is concluded that veneering of zirconia abutments with pink veneering ceramic failed to positively influence the esthetic outcome, mostly due to a decrease of the brightness compared with the control group.
Kongskov, Rasmus Dalgas
), the classical reconstruction methods suffer from their inability to handle limited and/ or corrupted data. Form any analysis tasks computationally demanding segmentation methods are used to automatically segment an object, after using a simple reconstruction method as a first step. In the literature, methods...... problem. The tests showed a clear improvement for realistic materials simulations and that the one-stage method was clearly more robust toward noise. The noise-robustness result could be a step toward making this method more applicable for lab-scale experiments. We have introduced a segmentation...... that completely combine reconstruction and segmentation have been suggested, but these are often non-convex and have very high computational demand. We propose to move the computational effort from the segmentation process to the reconstruction process, and instead design reconstruction methods...
Regional History Project, UCSC Library; Shikuma, Hiroshi; Jarrell, Randall
Mr. Shikuma is a prominent Nisei strawberry grower in the Pajaro Valley. In this volume he describes family life in the Japanese-American community in the Pajaro Valley during the first decades of the twentieth century. He conveys the texture of everyday family life, recalling details of housing, food preparation, education, religion, and his childhood responsibilities in a farming family. The second part of the volume describes the growth and development of strawberries as an import...
Mo, Arild; Hjortsjö, Carl; Olsen-Bergem, Heming; Jokstad, Asbjørn
The aim of this study was to present the clinical outcomes of patients with an edentulous maxilla treated with a removable prosthesis without palatal coverage retained by Locator abutments on three titanium implants. All the patients in a private dental clinic consecutively treated up to 6 years earlier were invited for a follow-up examination (n = 23). Two implants were placed bilaterally and one implant anteriorly in a tripod pattern. All patients underwent a clinical and radiological examination and completed questionnaires related to their experiences and satisfaction with the reconstructions. The prosthesis and implants were examined for adverse biological or technical aspects. Patient satisfaction and quality of life outcomes were collected using a self-reported Denture Satisfaction Scale and OHIP-20. Statistical analyses were limited to descriptive statistics. Twenty-one of 23 invited participants consented to participate. We report in this study the outcomes of the study participants who had received their implants more than 2 years ago (n = 12). None of their 36 implants gave any indications of mobility or tenderness upon percussion. Suppuration was observed on one implant. Probing around the implants caused no (53%) or minor bleeding (47%). The incidence of adverse biological and technical events was near non-existent. The rates of replacement of male attachments varied, as did any changes of male attachment retention force. All participants described the task of insertion and removal of the prosthesis as unproblematic. The marginal bone loss ranged between 0 and 5.3 mm. The OHIP-20 and the Denture Satisfaction Questionnaire scores were high. The results in this clinical study are positive and promising. Admittedly, the study design is purely retrospective and observational with a small participant cohort, so the technical solution of placing three implants in the edentulous maxilla to retain a removable prosthesis should be appraised further in
Gilja, Gordon; Valyrakis, Manousos; Michalis, Panagiotis; Bekić, Damir; Kuspilić, Neven; McKeogh, Eamon
Safety of bridges over watercourses can be compromised by flow characteristics and bridge hydraulics. Scour process around bridge foundations can develop rapidly during low-recurrence interval floods when structural elements are exposed to increased flows. Variations in riverbed geometry, as a result of sediment removal and deposition processes, can increase flood-induced hazard at bridge sites with catastrophic failures and destructive consequences for civil infrastructure. The quantification of flood induced hazard on bridge safety generally involves coupled hydrodynamic and sediment transport models (i.e. 2D numerical or physical models) for a range of hydrological events covering both high and low flows. Modelled boundary conditions are usually estimated for their probability of occurrence using frequency analysis of long-term recordings at gauging stations. At smaller rivers gauging station records are scarce, especially in upper courses of rivers where weirs, drops and rapids are common elements of river bathymetry. As a result, boundary conditions that accurately represent flow patterns on modelled river reach cannot be often reliably acquired. Sediment transport process is also more complicated to describe due to its complexity and dependence to local flow field making scour hazard assessment a particularly challenging issue. This study investigates the influence of flow characteristics to the development of scour and sedimentation processes around bridge abutments of a single span masonry arch bridge in south Ireland. The impact of downstream weirs on bridge hydraulics through variation of downstream model domain type is also considered in this study. The numerical model is established based on detailed bathymetry data surveyed along a rectangular grid of 50cm spacing. Acquired data also consist of riverbed morphology and water level variations which are monitored continuously on bridge site. The obtained data are then used to compare and calibrate
Bosman, A J; Kruyt, I J; Mylanus, E A M; Hol, M K S; Snik, A F M
Performance of an abutment-level superpower sound processor for bone-anchored hearing, the Ponto 3 SuperPower from Oticon Medical (BCD2), was compared to an earlier model from Oticon Medical (BCD1). A comparative study in which each patient serves as its own control. Tertiary clinic. Eighteen experienced BCD1 users with profound mixed hearing loss. Speech reception thresholds in noise; APHAB and SSQ questionnaires. In a group of 18 patients with severe mixed hearing loss, the performance of a recently introduced bone conduction device (BCD2) is evaluated relative to that of an earlier model (BCD1). Speech reception thresholds for the sentence-in-noise test in the speech and noise frontal condition are not significantly different (P > .05) for BCD1 and BCD2. Speech reception thresholds for frontal speech and three identical noise sources are 1.7 dB lower for BCD2 than for BCD1 (P .05). Scores for the speech, spatial and quality of hearing domains of the SSQ questionnaire are significantly higher (P < .01), that is more favourable, for BCD2 than for BCD1 with effect sizes of 1.22, 0.71 and 1.05, respectively. Scores for the SSQ-factors "speech understanding," "spatial," "clarity, separation and identification" and "listening effort and concentration" were all significantly higher (P < .05) for BCD2 than for BCD1, with effect sizes of 1.28, 0.64, 0.98 and 0.78, respectively. On a proprietary questionnaire, 16 patients indicate a preference for BCD2 over BCD1 for conversations in a small group and two patients have no preference for either device. In a large group, one patient prefers BCD1, six patients have no preference, and eleven patients prefer BCD2. When listening to music, all patients prefer BCD2 over BCD1, with a strong preference for BCD2 for seven patients. When asked for an overall preference, all patients prefer BCD2 over BCD1, with nine patients strongly preferring BCD2. The lower speech reception thresholds in noise with BCD2 relative to BCD1
Garrana, Rhoodie; Mohangi, Govindrau; Malo, Paulo; Nobre, Miguel
Background . Endotoxin initiates osteoclastic activity resulting in bone loss. Endotoxin leakage through implant abutment connections negatively influences peri-implant bone levels. Objectives . (i) To determine if endotoxin can traverse different implant-abutment connection (IAC) designs; (ii) to quantify the amount of endotoxins traversing the IAC; (iii) to compare the in vitro comportments of different IACs. Materials and Methods . Twenty-seven IACs were inoculated with E. coli endotoxin. Six of the twenty-seven IACs were external connections from one system (Southern Implants) and the remaining twenty-one IACs were made up of seven internal IAC types from four different implant companies (Straumann, Ankylos, and Neodent, Southern Implants). Results . Of the 27 IACs tested, all 6 external IACs leaked measurable amounts of endotoxin. Of the remaining 21 internal IACs, 9 IACs did not show measurable leakage whilst the remaining 12 IACs leaked varying amounts. The mean log endotoxin level was significantly higher for the external compared to internal types ( p = 0.015). Conclusion . Within the parameters of this study, we can conclude that endotoxin leakage is dependent on the design of the IAC. Straumann Synocta, Straumann Cross-fit, and Ankylos displayed the best performances of all IACs tested with undetectable leakage after 7 days. Each of these IACs incorporated a morse-like component in their design. Speculation still exists over the impact of IAC endotoxin leakage on peri-implant tissues in vivo; hence, further investigations are required to further explore this.
Alvarez-Arenal, Angel; Gonzalez-Gonzalez, Ignacio; Pinés-Hueso, Javier; deLlanos-Lanchares, Hector; del Rio Highsmith, Jaime
The aim of this study was to evaluate and compare the retention strength of three cements commonly used in implant-supported prostheses before and after compressive cyclic loading. The working model consisted of five solid abutments, 7 mm in height and with a 6-degree taper, screw retained to five implant analogs secured in a rectangular block of self-curing acrylic. On the abutments, 30 metal Cr-Ni alloy copings were cemented using three luting agents: glass ionomer, resin urethane-based, and compomer cement (n = 10). Two tensile tests were conducted with a universal testing machine, before and after 100,000 cycles of 100 N and 0.72 Hz compressive cyclic loading in a humid environment. Before applying the compressive load, the retention strength of the resin urethane-based cement was slightly higher than that of the compomer cement and 75% greater than the glass-ionomer cement. After compressive loading, the resin urethane-based cement showed the highest percentage of loss of retention (64.45%, compared with 50% for glass-ionomer and compomer cement). However, the glass-ionomer cement showed the lowest mean retentive strength with 50.35 N as opposed to 75.12 N for the compomer cement and 71.25 N for the resin urethane-based. Compressive cyclic loading significantly influences the retention strength of the luting agents tested. All three cements may favor the retrievability of the crowns.
Pabst, A M; Walter, C; Bell, A; Weyhrauch, M; Schmidtmann, I; Scheller, H; Lehmann, K M
This study investigated the influence of three CAD/CAM zirconia ceramics for implant-abutment manufacturing on cell viability, migration ability, and cytotoxicity of human gingival fibroblasts (HGF) and oral keratinocytes (HOK) in vitro. HGF and HOK were cultured on zirconia ceramic disks (VITA In-Ceram YZ, Ivoclar IPS e.max ZirCAD, Sirona inCoris ZI) and on control disks made of tissue culture polystyrene. Cell viability was analyzed by a MTT assay. Migration ability was detected by a scratch assay. A ToxiLight assay was used to analyze the influence of the tested zirconia ceramics on adenylate kinase (ADK) release and cytotoxicity. At MTT assay, HGF showed an increased cell viability compared to the control after 9 and 12 days for all ceramics (p each ≤0.0002) while HOK demonstrated a decreased cell viability after 9 and 12 days for all ceramics (p each ≤0.0003). At scratch assay, HGF exhibited for all ceramics decreased relative distances of the scratch wound compared to the control from 24 to 48 h (p each zirconia ceramics on HGF and HOK could be shown. The analyzed zirconia ceramics could influence oral soft-tissue cells that might affect the esthetic outcome after implant placement using CAD/CAM zirconia abutments.
Full Text Available X-ray micro-tomography (micro-CT is a miniaturized form of conventional computed axial tomography (CAT able to investigate small radio-opaque objects at a-few-microns high resolution, in a nondestructive, non-invasive, and tri-dimensional way. Compared to traditional optical and electron microscopy techniques, which provide two-dimensional images, this innovative investigation technology enables a sample tri-dimensional analysis without cutting, coating or exposing the object to any particular chemical treatment. X-ray micro-tomography matches ideal 3D microscopy features: the possibility of investigating an object in natural conditions and without any preparation or alteration; non-invasive, non-destructive, and sufficiently magnified 3D reconstruction; reliable measurement of numeric data of the internal structure (morphology, structure and ultra-structure. Hence, this technique has multi-fold applications in a wide range of fields, not only in medical and odontostomatologic areas, but also in biomedical engineering, materials science, biology, electronics, geology, archaeology, oil industry, and semi-conductors industry. This study shows possible applications of micro-CT in dental implantology to analyze 3D micro-features of dental implant to abutment interface. Indeed, implant-abutment misfit is known to increase mechanical stress on connection structures and surrounding bone tissue. This condition may cause not only screw preload loss or screw fracture, but also biological issues in peri-implant tissues.
Valente, Valdimar S; Francischone, Carlos E; Vilarinho Soares de Moura, C D; Francischone, C E; Silva, Antonio M; Ribeiro, Izabella S; Filho, E M Maia; Bandéca, Matheus C; Tonetto, Mateus R; de Jesus Tavarez, R R
This study evaluated the cervical fit of cemented metal-ceramic and In-Ceram implant-supported crowns, before and after the cementing procedure. Twenty crowns cemented on implant abutments are divided into two groups (n = 10): Group 1 -cemented metal-ceramic crowns and group 2 - cemented In-Ceram crowns. The marginal adaptations before and after cementation were evaluated in a comparison microscope with an error of 1 μm. All crowns were cemented with zinc phosphate cement. The cervical misalignment of cemented crowns before cementation (52.65 ± 11.83 and 85.73 ± 14.06 μm) was lower than that after cementation (66.80 ± 15.86 and 89.36 ± 22.66 μm). The cementing procedure interferes with the marginal fit of cemented crowns on implant abutments, with the prosthesis having better adaptation before cementation. Cemented metal-ceramic crowns exhibited better cervical adaptation than In-Ceram crowns cemented before and after the cementing procedure. The maintenance of gum health and the longevity of prosthetic restorations are closely related to the restoration's marginal integrity.
Zhu, Yuqing; Chen, Hui; Cen, Lian; Wang, Jun
The influence of abutment tooth position and adhesive point dimension on rigidity of wire-composite splints, used in dental trauma, was evaluated in vitro. A commercial artificial resin model was used. The central incisors served as injured teeth with increased mobility (degrees of loosening II tooth 21 and III tooth 11), whereas teeth 12/22 or teeth 13/23 served as non-injured teeth with physiological mobility. Horizontal and vertical tooth mobility before and after splinting was assessed, using a universal testing machine. Teeth were splinted with a wire-composite splint (0.8 mm). Four groups were assigned with respective abutment tooth position and adhesive point dimension: group 1 (13-11-21-23, 2 × 2 mm(2) ), group 2 (12-11-21-22, 2 × 2 mm(2) ), group 3 (12-11-21-22, 3 × 3 mm(2) ), group 4 (12-11-21-22, 4 × 4 mm(2) ). For each group, tooth mobility after splinting was significantly higher than the physiological tooth mobility (P 0.05) were found in tooth mobility after splinting. Significant differences were found in horizontal tooth mobility after splinting of tooth 11 between Group 2 and 3, Group 2 and 4 and Group 3 and 4, respectively (P vertical dimension for tooth 11 only between Group 2 and 4 (P vertical mobility in most cases. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.
Full Text Available Background. Endotoxin initiates osteoclastic activity resulting in bone loss. Endotoxin leakage through implant abutment connections negatively influences peri-implant bone levels. Objectives. (i To determine if endotoxin can traverse different implant-abutment connection (IAC designs; (ii to quantify the amount of endotoxins traversing the IAC; (iii to compare the in vitro comportments of different IACs. Materials and Methods. Twenty-seven IACs were inoculated with E. coli endotoxin. Six of the twenty-seven IACs were external connections from one system (Southern Implants and the remaining twenty-one IACs were made up of seven internal IAC types from four different implant companies (Straumann, Ankylos, and Neodent, Southern Implants. Results. Of the 27 IACs tested, all 6 external IACs leaked measurable amounts of endotoxin. Of the remaining 21 internal IACs, 9 IACs did not show measurable leakage whilst the remaining 12 IACs leaked varying amounts. The mean log endotoxin level was significantly higher for the external compared to internal types (p=0.015. Conclusion. Within the parameters of this study, we can conclude that endotoxin leakage is dependent on the design of the IAC. Straumann Synocta, Straumann Cross-fit, and Ankylos displayed the best performances of all IACs tested with undetectable leakage after 7 days. Each of these IACs incorporated a morse-like component in their design. Speculation still exists over the impact of IAC endotoxin leakage on peri-implant tissues in vivo; hence, further investigations are required to further explore this.
Cronin, V. S.; Ashburn, J. A.; Sverdrup, K. A.
The Truckee earthquake (9/12/1966, ML6.0) was a left-lateral event on a previously unrecognized NW-trending fault. The Prosser Creek and Boca Dams sustained damage, and the trace of the suspected causative fault passes near or through the site of the then-incomplete Stampede Dam. Another M6 earthquake occurred along the same general trend in 1948 with an epicenter in Dog Valley ~14 km to the NW of the 1966 epicenter. This trend is called the Dog Valley Fault (DVF), and its location on the ground surface is suggested by a prominent but broad zone of geomorphic lineaments near the cloud of aftershock epicenters determined for the 1966 event. Various ground effects of the 1966 event described by Kachadoorian et al. (1967) were located within this broad zone. The upper shoreface of reservoirs in the Truckee-Prosser-Martis basin are now exposed due to persistent drought. We have examined fault strands in a roadcut and exposed upper shoreface adjacent to the NE abutment of Stampede Dam. These are interpreted to be small-displacement splays associated with the DVF -- perhaps elements of the DVF damage zone. We have used the Seismo-Lineament Analysis Method (SLAM) to help us constrain the location of the DVF, based on earthquake focal mechanisms. Seismo-lineaments were computed, using recent revisions in the SLAM code (bearspace.baylor.edu/Vince_Cronin/www/SLAM/), for the 1966 main earthquake and for the better-recorded earthquakes of 7/3/1983 (M4) and 8/30/1992 (M3.2) that are inferred to have occurred along the DVF. Associated geomorphic analysis and some field reconnaissance identified a trend that might be associated with a fault, extending from the NW end of Prosser Creek Reservoir ~32° toward the Stampede Dam area. Triangle-strain analysis using horizontal velocities of local Plate Boundary Observatory GPS sites P146, P149, P150 and SLID indicates that the area rotates clockwise ~1-2°/Myr relative to the stable craton, as might be expected because the study area is
Full Text Available An 18-year old girl with segmental vitiligo involving the left side of the trunk and left upper limb with segmental morphea involving the right side of trunk and right upper limb without any deeper involvement is illustrated. There was no history of preceding drug intake, vaccination, trauma, radiation therapy, infection, or hormonal therapy. Family history of stable vitiligo in her brother and a history of type II diabetes mellitus in the father were elicited. Screening for autoimmune diseases and antithyroid antibody was negative. An autoimmune link explaining the co-occurrence has been proposed. Cutaneous mosiacism could explain the presence of both the pathologies in a segmental distribution.