The aim of this study is to investigate, by microscopy images and bond strength, the effect of hydrofluoric acid concentrations and previous thermal treatment to the etching procedure on a dental ceramic. Vitreous ceramic blocks of IPS e.max Press (Ivoclar Vivadent, Schaan, Liechtenstein) will be made and randomly assigned in 2 groups for acid concentrations: 5% IPS Etching Gel (Ivoclar Vivadent, Schaan, Liechtenstein) and 9.5% Porcelain Etch (Ultradent Products Inc., South Jordan, UT, USA). Next, the samples will be randomly divided in 4 subgroups: no thermal treatment; thermal treatment of ceramic; thermal treatment of hydrofluoric acid; thermal treratment ceramic + hydrofluoric acid. After etching steps, the ceramic will be fixed to a dual cure resin cement (Variolink II, Ivoclar VIvadent, Schaan, Liechtenstein) to microhybrid resin composite (Z250, 3M ESPE, St. Paul, MN, USA) and randomly assigned in subgroups according to the microtensile bond strength and aging protocols: 24 hours after cementation; thermal cycling; thermal/mechanical cycling; 12 months water storage. It will be analyzed the failure modes classified as: adhesive failure (Mode 1); cohesive failure in ceramic (Mode 2); cohesive failure in resin cement (Mode 3); mixed failure (Mode 4). Representative samples of each group and subgroups will be randomly chosen for superficial and interface analysis by scanning electron microscopy. The results of microtensile bond strength will be tabulated and submitted to analysis of variance (ANOVA) with split parcel and Tukey test with 5% level of significance.
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