Source:Dental Materials
Author(s): Vinicius P. Fardin, Vitor Guarconi de Paula, Estevam A. Bonfante, Paulo G. Coelho, Gerson Bonfante
ObjectiveTo evaluate the fatigue life of zirconia-veneered and metal-ceramic crowns comprised by an even thickness or a modified framework design when loaded on marginal ridges.MethodsEighty marginal ridges were present after fabrication of forty molar crowns cemented onto composite-resin replicas and divided (n=20/each), in the following groups: metal-ceramic with even thickness (MCev) or with a modified framework design (MCm, lingual collar with proximal struts); porcelain-fused to zirconia with even thickness (PFZev) or with the modified framework design (PFZm). Each marginal ridge (mesial and distal) was subjected to cyclic loading separately with a lithium disilicate indenter for 106 cycles or until fracture. Kruskal–Wallis and Wilcoxon matched pair test (p<0.05) evaluated both marginal ridges. Every 125,000 cycles, the test was interrupted for damage inspection. Weibull distribution (90% confidence bounds) determined the probability of survival (reliability).ResultsWeibull 2-parameter contour-plot showed significantly higher fatigue life for PFZev compared to MC, and comparable with PFZm. A significant decrease in reliability was observed between groups from 625,000 until 106 cycles. Metal-ceramic groups presented significantly lower probability of survival at 106 cycles (MCev=0.66% and MCm=4.73%) compared to PFZm (23.41%) and PFZev (36.68%). Fractographic marks showed a consistent fracture origin and direction of crack propagation. Reliability was higher for porcelain-fused to zirconia than for metal ceramic crowns, regardless of framework design.SignificanceZirconia-veneered crowns presented decreased fracture rates compared to metal ceramics, even when loaded at marginal ridges, regardless of framework design.
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