The longevity of the restoration in composite resin is a constant search for the Dentistry. The preservation of the structural integrity of the collagen keeps mechanical properties, chemical stability and resistance to degradation of resin/dentin interface, contributing to restoration durability. The matrix metalloproteinase (MMP) in the dentin, when activated participate of this tissue erosion process, exposing the organic matrix to decomposition. The digluconate chlorhexidine (DC) is a synthetic inhibitor of MMPs, extensively studied in adhesive dentistry, but this substance induces inflammatory reactions and tissue necrosis. The Epigallocatechin-3-gallate and the Chitosan are natural agents that exhibit properties antimicrobial, anti-inflammatory, mineralization, tissue regeneration, low toxicity, inhibition of MMPs of the dentin and protection of collagen fibers. However, the literature lacks scientific data that characterize the conduct of the physicochemical and biochemical properties of teeth treated with these agents in comparison to those treated with DC and conventional adhesive protocol. The aim of this study will be obtain data on these aspects, by the comparison between teeth treated with EGCG, CH, EGCG + CH, with those treated with DC and conventional adhesive protocol, by means of mechanical, chemical and biochemical tests: mechanical cycling, microtensile, microhardness, Fourier transform infrared spectroscopy, scanning electron microscopy and in situ zymography. For this, the dentin will receive the treatments according to the groups: GI) phosphoric acid - control; GII) phosphoric acid with DC; GIII) EGCG incorporated into phosphoric acid - experimental; GIV) CH incorporated into phosphoric acid - experimental; (GV) EGCG + CH incorporated into phosphoric acid - experimental.
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