This study will evaluate the resin-dentin bonds obtained with four surface pre-treatments (37% phosphoric acid, self-etching, 10-3 solution, or 1.4% nitric acid), different post-conditioning moisture levels, and two "universal" adhesive systems containing distinct solvents (alcohol or acetone-based) regarding matrix metalloproteinases (MMPs) activity, in situ degree of conversion, and stiffness of demineralized dentin matrix. Adhesives will be applied on moist (positive control groups) or dry (negative control and experimental groups) dentin after treatment with the tested conditioning agents for 15 s. For the self-etch groups, adhesives will be applied over sound dentin, following manufacturers' instructions. Dentin MMPs activity will be analyzed by in situ zymography (n=5) using a self-quenched fluorescein-conjugated gelatin. Dentin MMP-2 and -9 activity will also be analyzed by gelatin zymography of dentin powder extracts (n=4). In situ degree of conversion will be evaluated by means of micro-Raman spectroscopy (n=3). A three-point flexural strength test will be performed to assess the stiffness of the demineralized dentin matrix (n=10) for each of the tested conditioners. In situ zymography data will be analyzed descriptively, while data from the remaining tests will be checked for normality and equal variances, and, depending on their distribution, the adequate parametric or non-parametric tests will be applied.
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