The preservation of affected dentin during removal of carious tissue is a reality; however, the quality and longevity of the adhesive restorations performed on this substrate are still important challenges for Restorative Dentistry. The aim of this in vitro study is to evaluate the effect of selective removal of caries lesion with Er: YAG laser and biomodification with phosphorylated-chitosan nanoparticles (NanoPC) on micro-shear bond strength to affected dentin after 24h and 6 m of hydrolytic degradation. The sample will be composed of 92 sound human third molar. Dentin specimens will be submitted a microbiological method to produce dentin caries lesions. Selective removal of the caries lesion will be performed using the Er:YAG laser (250mJ/4Hz) or but at low-speed handpiece (conventional method). The teeth will be divided according to the dentin biomodification: without biomodification (control) or NanoPC for 1 min. Specimens will receive Single Bond Universal adhesive system (3M) and a teflox matrix with cylinder-shaped orifices (0.8 mm in diameter) will be adapted on the dentin surface. Increments of Filtek Z250 composite resin (3M) will be included with a periodontal probe. Specimens will be submitted to hydrolytic degradation for 24h or 6 months. Afterwards, they will be subjected to micro-shear bond strength (n=10) and analysis of adhesive interface by means of confocal laser scanning microscopy (n=3). The selection of statistical tests will be based on the characteristics of the data set for each variable. The statistical inferences will be made considering the significance level of 5%.
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