This study aims to evaluate the marginal adaptation, nanoleakage and microtensile bond strength of three photo-activated bulk-fill composites, comparing them with each other and with a traditional microhybrid composite, shortly after the restorative procedure and after being submitted to thermomechanical cycling . 56 healthy human molars will be selected and restored in a class I cavity, with a depth of 4 mm, by insertion into single increment, in the case of bulk-fill composites, and by incremental technique, for the microhybrid composite. All composites will be light-activated with LED 3rd generation device (Valo - Ultradent). For the analysis of marginal adaptation, replica of the teeth will be made in epoxy resin from occlusal surface impressions, in two times: 24 hours after the restorative procedure, and after the samples were submitted to thermomechanical cycling. The initial and final comparative analysis will be performed using scanning electron microscope (SEM). Then, new samples not submitted to thermomechanical cycling, in addition to the teeth already aged, will be submitted to the mechanical test of microtensile bond strength through beams obtained the buccal interface, and subsequently the fracture pattern will be evaluated using SEM . For nanoleakage analysis, fourteen beams of each group will be randomly separated to assess, also in SEM, infiltration of silver nitrate ions. Data will be statistically analyzed.
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