Design effect on the fatigue life of crowns with zirconia intaglio

Abstract

The present study will evaluate the fatigue life of completely or partially porcelain / glaze covered crowns, determining their reliability with Weibull analysis. The null hypothesis is that there will be differences in the reliability of the types of crowns. Seventy-two intact molars will be used, which will be prepared for full crown and divided into three groups (n = 24): traditional zirconia infrastructure and full veneering coverage; modified restoration 1 - infrastructure in zirconia with partial coverage, (the exposed zirconia coated by a thin layer of glaze) and modified restoration 2 - totally in zirconia coated with glaze (Akzent Vita, Vita Zahnfabrik, Germany). Before undergoing the fatigue test, static test will be held in a universal testing machine to determine the fracture load. The fatigue load corresponds to 60% of the fracture load. Then, specimens will be mechanically cycled in a simulator of chewing cycles (CICLA 10), in which an applicator tip will apply 2.106 cycles at 2Hz. Every 200,000 cycles, the machine will be stopped and the crowns will be assessed for the presence of failures in a stereomicroscope (DiscoveryV20, Carl Zeiss, LLC, USA). If samples do not show any fatigue signs, the fatigue test will continue until they fail or until the end of the test. Specimens that do not fail will be considered "suspended" in the analysis, Results from this evaluation will be subjected to reliability analysis with the method of Weibull, with bilateral confidence interval of 95%. (AU)