Impact of adhesive application to wet and dry dentin on long-term resin-dentin bond strengths

This study compared the effects of moisture and rubbing action on the immediate and one-year microtensile bond strength (BS) of an ethanol/water-based adhesive system (Single Bond [SB]) and an acetone-based system (One Step [OS]) to dentin. A flat superficial dentin surface on 60 human molars was exposed by wet abrasion. Two coats of the adhesives were applied on either a dry (D) or rewetted surface (W) with no (NRA), slight (SRA) or vigorous rubbing action (VRA). After light curing (600mW/cm(2)/10 seconds), composite buildups were constructed incrementally and the specimens were stored in water (37 degrees C/24 hours). They were longitudinally sectioned in the "x" and "y" directions to obtain bonded sticks (0.8 mm(2)) to be tested in tension at 0.5 mm/minute. The sticks from each tooth were then divided, stored in water at 37 degrees C and tested immediately and after 12 months (12M) at 0.5 mm/minute. The bond strength values of sticks from the same hemi-tooth were averaged for statistical purposes. The prematurely debonded specimens were included in the hemi-tooth mean. The data from each adhesive was analyzed by three-way ANOVA and Tukey's multiple comparison tests (alpha=0.05). In the dry groups, high bond strength values were obtained under VRA. When the dentin was kept moist, both SRA and VRA provided high resin-dentin bond strength values. Reductions in bond strength values after one year of water storage were not observed for the SB adhesive or were less pronounced for the OS adhesive when it was vigorously rubbed onto the dentin surface.