Abstract: Objective：To investigate influence of thermalcycling on the bonding durability of two one-step products ［Adper Prompt (AP) and G-bond (GB)］ and one two-step self-etching adhesive ［Clearfil SE bond (SE)］ with dentin in vitro.  Methods:Forty-two extracted human molars were selected. The superficial dentin was exposed by grinding off the enamel. The teeth were randomly distributed into six groups with varied bonding protocols. The adhesives were applied to the dentin surface. Composite crowns were built up, then the samples were cut longitudinally into sticks with 1.0 mm×1.0 mm bon-ding area ［for microtensile bond strength (MTBS) testing］ or 1.0 mm thick slabs (for nanoleakage observation). Bonding performance was evaluated with or without thermalcyling. For the MTBS testing, the strength values were statistically analysed using One-Way ANOVA. Four slabs in each group were observed for nanoleakage by SEM with a backscattered electron detector.Results:Thermalcycling procedures affected MTBS. In the two onestep groups, the MTBS decreased significantly (P<0.05) after thermalcycling ［AP group from (19.06±1.50) MPa to (12.62±2.10) MPa; GB group from (17.75±1.10) MPa to (6.24±0.42)MPa］. But in SE groups, MTBS did not significantly affect ［(45.80±2.97) MPa compared with(40.60±5.76) MPa］. As a whole, one-step selfetching adhesives showed lower MTBS than two-step bonding system after aging.For AP and GB, continuous nanoleakage appearance was notable and more obvious than for SE. Conclusion:Thermalcycling can affect the bonding performance of self-etch adhesives including decrease of bond strength and nanoleakage pattern. One-step self-etch adhesives showed more obvious change compared with their two-step counterparts.

Key words: Dentin-bonding agents, Acid etching, dental, Temperature, Adhesiveness, Materials testing