Analysis of differential artificial ageing of the adhesive interface produced by a two-step etch-and-rinse adhesive

This study was performed to evaluate the effects of different in vitro ageing techniques on the dentine-bonded interface produced by a two-step etch-and-rinse adhesive. Composite build-ups were bonded to sectioned human molars using XP BOND and cut into non-trimmed dentine-composite beams for microtensile testing. Beams were assigned to one of the following storage conditions: (i) artificial saliva, 24 h (control); (ii) 10% sodium hypochlorite (NaOCl), 1 h; (iii) 10% NaOCl, 3 h; (iv) 60,000 thermal cycles, 2 months; (v) artificial saliva, 2 months; (vi) 60,000 thermal cycles, 6 months; and (vii) artificial saliva, 6 months. Beams were then pulled until failure and bond strength was calculated. Additional specimens were examined to investigate interfacial nanoleakage expression. NaOCl solution significantly reduced bonding compared with the control (group 2 = group 3 < group 1); and thermocycling reduced the bond strength in comparison to specimens stored for the same time-period in artificial saliva (group 4 < group 5; group 6 < group 7). Artificial ageing affected bond strength only after 6 months of storage (group 7 < group 5 = group 1). Increased nanoleakage was found under all ageing conditions in comparison with controls. NaOCl solution is a rapid and reliable in vitro ageing method for examining the durability of the adhesive interface produced by two-step etch-and-rinse adhesive systems.