In a previous study, the authors used a finite element analysis (FEA) to evaluate the stresses developed during the loading of an all‐ceramic, inlay supported fixed partial denture and compared it ...with the more traditional full crown supported prosthesis. To date there has been little research into correlating the responses of the numerical model against physical mechanical tests; such validation analysis is crucial if the results from the FEA are to be confidently relied upon. This study reports on the experimental methods used to compare with the FEA and thereby to validate the predictive fracture behaviour of the numerical model. This study also outlines the methods for manufacture and testing of the ceramic structure along with observations of the fracture tests. In addition the procedure used for developing the FEA model for the test system is outlined.
Abstract Zirconia is currently used as a framework material for posterior all-ceramic bridges. While the majority of research efforts have focused on the microstructure and corresponding mechanical ...properties of this material, clinical fractures appear to be largely associated with the appliance geometry. Objective The objective of this study was to estimate the maximum stress concentration posed by the connector geometry and to provide adjusted estimates of the minimum connector diameter that is required for achieving 20 years of function. Methods A simple quantitative description of the connector geometry in an all-ceramic 4-unit bridge design is used with published stress concentration factor charts to estimate the degree of stress concentration and the maximum stress. Results The magnitude of stress concentration estimated for clinically relevant connector geometries ranges from 2 to 3. Using previously published recommendations for connector designs, adjusted estimates for the minimum connector diameter required to achieve 20 years of clinical function are presented. Significance To prevent clinical fractures the minimum connector diameter in multi-unit bridges designs must account for the loads incurred during function and the extent of stress concentration posed by the connector geometry.
summary This study evaluated the fracture loads of three‐unit all‐ceramic bridges on implants; the core frameworks of the bridges were made of zirconium oxide. Three core framework designs were ...fabricated according to the design of the bars between the retainers: (i) straight, (ii) curved in the occlusal direction, or (iii) curved in the gingival direction. A static load was applied at the centre of the pontic, and the mean initial crack and final fracture loads were measured and compared. The core framework curved in the occlusal direction had the highest final fracture loads; there were significant differences (P < 0·05) in the mean final fracture load, whereas initial fracture load, which fractured of veneered porcelain, did not show significant differences among three designs. The all‐ceramic bridges on the implants made with Procera zirconium core frameworks had high final fracture load. The core framework design that curved in the occlusal direction helped the framework withstand the occlusal load, which results in reliable prostheses, especially in the molar region.
Purpose: The aim of the present study was to clarify the effects of the shape of the zirconium framework of implant‐supported, all‐ceramic fixed partial dentures (FPDs) on the fracture strength and ...fracture mode.
Materials and Methods: This study consisted of mechanical strength testing and 3D finite element analysis (FEA). The three framework shapes used in this study were: (1) conventional shape (control); (2) convex shape: 1.0‐mm curve in the direction of the occlusal surface; and (3) concave shape: 1.0‐mm curve in the direction of the gingival surface. Five frameworks were made for each condition (total: 15). A load (N) was applied until the FPD fractured. For FEA, a 3D model consisting of cortical bone, cancellous bone, implant bodies, and superstructure was constructed.
Results: The results of the mechanical strength test showed that fracture load was 916.0 ± 150.1 N for the conventional shape, 1690.5 ± 205.3 N for the convex shape, and 1515.5 ± 137.0 N for the concave shape. The mean final fracture load for the FPDs with frameworks was the highest for the convex shape; however, a critical crack in the veneer porcelain (736.5 ± 145.2 N) was confirmed during loading for the convex shape. Stress distribution maps for all conditions showed that tensile stress was generated at the veneer porcelain on the gingival side of the mesial and distal connectors of the pontic; however, there were differences in the maximum value and stress distribution within the framework.
Conclusion: The shape of the framework, particularly the shape of the pontic–connector interface, affects the stress distribution, fracture strength, and fracture mode of all‐ceramic FPDs, and stress concentration inside a framework may induce cracking of layering porcelain.
Objectives
The aim of this study is to systematically review all the clinical articles about all‐ceramic resin‐bonded fixed dental prosthesis (RBFDP) in the anterior region and assess their designs, ...clinical procedures, and survival rates. A systematic review was conducted after searching electronic databases PubMed/Medline and EBSCOhost Research Databases for articles published in English between 1987 and July 2017.
Materials and Methods
The inclusion criteria were selected as all clinical studies, original design clinical reports, and clinical reports (follow‐up time more than 1 year) as all clinical information in the literature are desired to be included in the present review.
Results
The initial electronic search generated 472 articles from PubMed/Medline and 464 articles from EBSCOhost Research Databases. After selection of the articles as per the inclusion criteria, a final sample of 29 original studies is decided as: 1 randomized controlled clinical trial, 4 clinical controlled trials, 4 prospective cohort studies, 2 retrospective cohort studies, 6 original design clinical reports, and 12 clinical reports. After evaluation of the selected articles, it is likely that cantilever design all‐ceramic RBFDPs are more successful than two retainer design in the anterior region; however, there is limited evidence for this result in the literature.
Conclusion
Well‐designed randomized controlled clinical trials with large sample size are still needed to achieve more accurate results about the clinical success rate of different RBFDPs designs in the anterior region.
Clinical significance
Indications, designs, abutment teeth preparation, provisionalization, try‐in, surface treatment options, and cementation of the all‐ceramic resin‐bonded fixed dental prostheses are described in this article. Clinical survival rates are also given in detail, so that clinicians can easily compare the current studies and give their own decision about all‐ceramic resin‐bonded fixed dental prostheses in the anterior region.
Yttria-stabilized zirconia (Y-TZP) ceramic is a high-performance material with excellent mechanical properties suitable for fixed partial dentures. The purpose of this study was to evaluate after ...fatigue testing, the effect of heat-treatment and veneering on the fracture resistance of frameworks manufactured using sintered and subsequently hot isostatic pressed yttrium oxide partially-stabilized zirconia (Denzir).
The specimens were subjected to dynamic loading in water. Thereafter, using a universal testing machine, the fracture resistance of three-unit fixed partial dentures was determined; (i) of the frameworks as delivered after machining, (ii) after the frameworks had been subjected to heat-treatment similar to veneering with a glass–ceramic (Eris) or a feldspar-based ceramic (Vita D) and (iii) after the frameworks had been veneered with these ceramics. In addition, the fracture resistance of frameworks as delivered after machining not subjected to dynamic loading in water was determined.
Cyclic loading in water did not significantly (
p>0.05) affect the fracture resistance. The load necessary to fracture the frameworks as delivered after machining was significantly (
p<0.001) higher than for the heat-treated and veneered specimens. No significant difference was seen between the specimens veneered with Eris and those veneered with Vita D (
p>0.05). For all but three specimens the fractures were located in the loading point and through one of the connectors.
Heat-treatment and veneering reduce fracture resistance of hot isostatic pressed zirconia. Nevertheless, the results obtained indicate that it is an interesting material for potential in all-ceramic restorations.
There has been limited use of ceramic materials for all-ceramic posterior bridges. Major reasons are the low strength, the strength scatter, and the time-dependent strength decrease of ceramics due ...to slow crack growth. The objective of this study was to predict the long-term failure probability and loading capability of all-ceramic bridges (Empress 1, Empress 2, In-Ceram Alumina, and ZrO2) by computational techniques. The lifetimes of different bridge model designs were predicted by means of the NASA post-processor CARES. Bridges made of zirconia showed a very high mechanical long-term reliability. Empress I and InCeram Alumina seem to be insufficient as posterior bridge materials based on this prediction. The lifetime of the all-ceramic bridges can be significantly increased by improving the design in the connector area. We conclude that computational techniques can help to judge a ceramic material and a specific ceramic bridge design with respect to mechanical reliability before clinical use.
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