The purpose of this study will to evaluate the effect of proanthocyanidin (PA) on the bond strength to enamel and dentin of a restorative system after dental bleaching. One hundred blocks of enamel/dentin will be obtained from bovine incisors. After planning and polishing the same, half (50) will be used to evaluate the adhesion to enamel and the other half in dentin. The 50 blocks of each substrate will be divided into 5 groups (n = 10): without bleaching and without PA (positive control), bleaching and without PA (negative control), bleaching and pre-treatment with 5 % solution of PA, bleaching and incorporation of 1 % of PA into primer of the adhesive system and, bleaching and incorporation of 2 % PA into primer of the adhesive system. Bleaching will be performed with 35 % hydrogen peroxide (Whiteness HP, FGM) according to the manufacturer's recommendation. After 24 h, only to adhesion on the dentin, it will be removed with abrasive paper and will be held to standardize the smear layer. So will be applied the three-step etch-and-rinse adhesive system (Adper Scotchbond Multipurpose, 3M ESPE) with different concentrations of PA (0, 1, or 2 %) with or without pre-treatment, then 2 pillars of composite resin will be made per sample with the composite type flow (Filtek Z350, 3M ESPE). The microshear test will be carried out using an universal testing machine (EZ Test, Shimadzu) and the fracture pattern will be observed using a stereomicroscope (Leica). Illustrative images of failure patterns are obtained in scanning electron microscopy (JSM 5600 LV, Jeol). The data will be collected, tabulated, and statistically analyzed by a statistical consultant.
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