The influence of veneering porcelain thickness of all-ceramic and metal ceramic crowns on failure resistance after cyclic loading
Section snippets
Material and methods
Two different coping designs based on the thickness of the incisal veneering porcelain were used (Fig. 1, Fig. 2; Table I). Each design was used for the 2 different systems (metal ceramic and all-ceramic), resulting in 4 experimental groups (n=10). The sample size was determined from a pilot study based on 2-way ANOVA (metal versus ceramic framework; long framework versus short framework), and a sample size of 6 in each combination (24 total) was deemed sufficient to have 90% power to detect
Results
Success, survival, and failure of the specimens under cyclic loading are summarized in Table II. Five specimens from the CL and CS groups were considered success, whereas only 1 from ML and none from MS were considered a success. According to the Fisher's exact test, the all-ceramic group showed significantly higher success (P=.003) and survival rates (P=.001) than those of the metal ceramic group after cyclic loading. The CL and CS groups had 3 and 1 failures, respectively, due to the presence
Discussion
For the present study, 2 null hypotheses were addressed for the testing of the ultimate failure load: (1) there would be no significant differences in the failure resistance between 2 different thicknesses of veneering porcelain in the individual crown systems, and (2) there would be no significant difference in the failure resistance between 2 different crown systems. The first null hypothesis was rejected for the metal ceramic system, but it was accepted for the all-ceramic system, which
Conclusions
Within the limitations of this study, the following conclusions were drawn:
- 1.
All-ceramic crowns tested showed significantly higher success and survival rates after the cyclic loading test than did metal ceramic crowns.
- 2.
Metal ceramic crowns showed significantly greater failure loads than the all-ceramic crowns following cyclic loading.
- 3.
The thickness of the incisal veneering porcelain affected the failure load of the metal ceramic crowns, but not that of the all-ceramic crowns. The metal
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2022, Journal of the Mechanical Behavior of Biomedical MaterialsCitation Excerpt :Thus, improvement of the ceramic fracture strength is an important issue, especially in posterior teeth, and the IDS technique proved to be effective in increasing the fracture strength of ultrathin occlusal veneers made of PICN. However, the extrapolation of the results must include the limitations of a laboratory study that does not reproduce the clinical scenario, such as the oral environment or masticatory biomechanics (Shirakura et al., 2009). The following limitations of the present study can be cited: a) a constant axial load, which does not occur clinically, was applied to the specimen until fracture; b) the cyclic mechanical loading corresponded to an axial load applied by a pneumatic piston in the occlusal central area of the restoration, not simulating the clinical reality in which forces are applied in different directions; c) the small sample size of the study; however, the statistical analysis could demonstrate significant differences in fracture strength for specimens with and without IDS.
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This study was partially supported by a Greater New York Academy of Prosthodontics Student Grant.