In restorative treatment, bonding procedures represent essential part for the establishment of hybrid layer, whose longevity depends on factors related to the properties of employed materials and their interaction with dental substrates overtime. Studies have shown that dentin intrinsic proteolytic enzymes such as matrix metalloproteinases (MMPs) and cysteine cathepsins present in the dentin-pulp complex can be reactivated by the low pH in situations as dental caries or erosive process. The aim of this study is to evaluate the effect of an universal adhesive system (etch-and-rinse mode) on bonding to dentin in different conditions (artificial caries or erosion) and pretreated with proteolytic inhibitors. Ninety molars will be selected and prepared as flat surfaces treated with 600 sandpaper for 1 minute. The specimens will be randomly divided into three groups according to the substrate: CONT- with no simulations, CA- artificial caries simulation, E-artificial erosion simulation. Then, each of these groups will be redivided into three subgroups according to the pretreatment of dentin: A- treated with water; CHX-treated with chlorhexidine and E64- treated with E64 inhibitor. Therefore, they will consitute 9 groups (n = 10): CONT-A, CONT-CHX, CONT-E64, CA-A, CA-CHX, CA-E64, E-A, E-CHX, E-E64. All specimens will be restored with Single Bond ® Universal and composite resin Filtek Z250. The teeth will be cut to obtain sticks (area of approximately 0.64 mm2), which will be subjected to the test in the testing machine at 0.5 mm/min. The mode failures will be classified according to the analysis of interfaces by optical microscopy 40X. Data will be tested to verify normal distribution and homogeneity to be analyzed by ANOVA and multiple comparison tests (p <0.05).
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