Due to inherent characteristics of the dentin substrate and the adhesive systems, the production of a longitudinally stable resin-dentin bond still challenges the clinical procedures and the researches in the field. Among the mechanisms proposed to diminish the degradation of the hybrid layer over time there is the collagen biomodification. That procedure aims at increasing the mechanical properties of collagen which in turn would become more resistent to both hydrolitic and enzymatic degradation. The innactivation of matrix metalloproteinases has also been proven efficient as a hybrid layer anti-degradation mechanism. Therefore, the aim of this study will be to evaluate the effect of carbodiimide (EDC)-containing experimental primers on the total metalloproteinases (MMPs) activity. A hundred and twenty dentin specimens (1x1x6 mm)will be cut from 40 sound permanent teeth. Half of the specimens (n=60) will be used to determine MMPs activity. The occlusal surface will be etched with 35% phosphoric acid for 15s, followed by water rinse and removal of the excess water. Then, the specimens will be randomly divided into 6 treatment groups (n=10): deionized water (control), 0,5 mol/L EDC, experimental primer (50% HEMA in water), experimental primer with EDC, Schotchbond MP (SBMP) primer and SBMP primer containing EDC. Total MMPs activity will be determined after the treatments by means of a colorimetric assay (SenSolyte). The remaining 10 specimens of each group will be used to evaluate dentin collagen degradation. These specimens will be completely demineralized in 10% phosphoric acid for 18h. Dry mass and hydroxyproline release will be evaluated before the treatments (same mentioned above) and 7 days after artificial saliva storage. Data from total MMPs activity, dry mass loss and HYP release will be submitted to statistical tests chosen according to the data distribution of each dataset and hemocedasticity. All statistical tests will be considered using the level of significance of 5%.
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