Nd:YAG/Er:YAG irradiation on bond strength of resin luting cement/dentin

Objectives: The aim of this study was to evaluate the bond strength of luting resin cement to a dentin surface treated by Nd:YAG or Er:YAG laser irradiation. Methods: Twenty-four extracted human molars with an exposed flat dentin surface were divided into three groups (n = 8): Group 1 (G1): dentin irradiated by an Nd:YAG (100mJ, 15 Hz, 1,5W); Group 2 (G2): dentin irradiated by an Er:YAG (60mJ, 10Hz, 250W); Group 3 (G3): control (untreated). After, the dentin surfaces were treated with phosforic acid 37%, Single Bond adhesive and luted with Enforce (Dentsply) to blocks made from composite resin W3D (Wilcos – 5X6X6) according to manufacturers' directions. The specimens formed by dentin, cement and composite resin of each groups were sectioned to obtain several bonded beams of ±1.0 mm² cross-sectional area. The microtensile test was accomplished in a universal testing machine (EMIC) at a crosshead speed of 0,5 mm/min. Results: Means and standard deviations of bond strengths (MPa) were: G1: 27.77(6.67); G2: 23.42(7.37); G3: 34.94(11.35). The results, after log transformation, were analyzed by one-way ANOVA (5%). The Tukeyxs test indicated there were significant statistical difference among the groups. G3 showed the higher bond strength and G2, the smallest. G1 showed intermediate values of bond strenght. Conclusions: Laser irradiation decreased the bond strength of resin luting cement to dentin.