The dentin pretreatment with cross-linking agents has provided better stabilization of the collagen and improved the durability of the tooth-restoration bond interface, which is the area most susceptible to degradation in the oral environment, so the inclusion of these agents in the adhesive system could contribute to greater clinical longevity of adhesive restorations. This study will evaluate the effect of proanthocyanidin (PA) included in an adhesive system on the degree of conversion (DC), on the nanohardness (NH), on the reduced elasticity modulus (Er), on bond strength (BS), on exposed collagen (EC) and on the gelatinolytic activity (CA). The occlusal surfaces of human molars will be flattened and the etch-and-rinse three-step adhesive system (Adper Scotchbond Multi-Purpose, 3M ESPE) will be applied according to manufacturer's specifications, with the primer of system containing concentrations of 0, 1, or 2 % PA. Then a block of composite resin (Filtek Z250, 3M ESPE) will be made. Slabs and slices will be obtained of the specimens. The DC (n = 5) of the hybrid layer and the adhesive will be obtained through the micro-Raman spectroscopy in situ. NH and Er (n = 5) tests of the dentin, the hybrid layer, and adhesive are performed in a nanoindenter. The BS (n = 7) will be obtained by microtensile test. The EC (n = 5) will be observed by Goldner's Trichrome staining for detection of collagen fibrils exposed. The CA (n = 5) of the dentin will be assessed by in situ zymography with a confocal microscope fluorescence laser scanning. The tests will be performed after 24 h and 12 months of storage. The data are recorded, tabulated, and statistically analyzed by a statistical consultant.
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