This study aims to evaluate in vitro the shear bond strength of a conventional glass ionomer cement to Er:YAG laser-irradiated dentin after the degradation of adhesive interface by thermocycling (TC) and water storage (WS). Fifteen bovine incisors will be selected, cleaned and roots will be removed. Each crown will be sectioned in mesio-distal and incise-cervical direction, resulting in 4 fragments per tooth and totaling 60 samples that will be individually embedded in acrylic resin and ground with decreasing grits (#320 a #600) of silicone carbide paper (SiC) to expose the dentin. Complementary grinding will be accomplished with a #1200-grit SiC paper for 30 seconds to standardize the smear layer. After receiving delimited bonding sites of 3-mm diameter, dentin surfaces will be randomly assigned to two groups, according to the method employed for cavity preparation: Er:YAG laser irradiation (Group I) or carbide bur (Group II). Samples will be fixed to a metallic device where conventional glass ionomer cement cylinders will be prepared. Subsequently, samples will be subdivided according to the period of water storage and thermocycling employed for simulating the adhesive interface degradation (n-15): A. 24 hours WS/ no thermocycling (baseline) and B. 6 months WS/ 12,000 TC. After the pre-determined period of each group, samples will be subjected to a shear bond strength test (50 Kgf at 0.5 mm/minute). Data will be statistically analyzed by the most appropriate method.
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