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Fatigue life and failures modes of crowns made with a zirconia intaglio: design and type of surface treatment effects

Abstract

This study will evaluate the fatigue life of ceramic crowns with Zirconia intaglios covered either with veneering porcelain or glaze. Before cementation, the crowns will be submitted to one of the following internal treatments: primer, silicatization or vitrification. 144 molars will be prepared, randomly divided into de groups according to the type of restoration: traditional, with zirconia infrastructure (Vita In-Ceram® YZ, Vita Zahnfabrik, Alemanha) covered by feldspathic porcelain (Vita VM9, Vita Zahnfabrik, Alemanha), and modified (m), covered with porcelain on the buccal face and glazed on the other faces. The surface treatment subgroups will be primer (Clearfil Ceramic Primer, Kuraray, Osaka, Japão), silicatization (Cojet sand + ESPE SIL, 3M ESPE, St Paul, MN, EUA), vitrification (Vita Akzent glaze, Vita Zahnfabrik, Alemanha). The zircônia blocks will be machined and sintered in a furnace (ZYRcomat, Vita Zahnfabrik, Alemanha). The porcelain and glaze will be applied on the infrastructures according to the manufacturer recommendations. The crowns will have a maxilar first molar anatomy and will be treated internally and cemented to the teeth with RelyX ARC (3M ESPE, St Paul, MN, EUA). Three crowns from each group will be submitted to compression test in a universal testing machine (1mm/min) to determine the critical load for failure, which will serve as a basis for the fatigue load determination. The crowns will be cycled in a fatigue machine under a frequency of 2 Hz, until failure or until completion of 2.106 cycles. Every 200, 000 cycles the specimens will be inspected as to the presence of failure, in a stereomicroscopy. The fatigue data will be collected as a function of the number of cycles to failure and analyzed with Weibull distribution for determination of the survival probability (reliability) considering a two-sided 95% confidence interval. After fatigue, the specimens and the fractured specimens will be analyzed under stereomicroscopy, as well as under Scanning Electron Microscopy (SEM). (AU)

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VEICULO: TITULO (DATA)