Effects of Water Storage on Different Bonding Approaches

Objective: The aim of this study was to evaluate the effects of water storage on resin-dentin bond strengths [µTBS] formed by different adhesive bonding approaches. Methods: A flat superficial dentin surface the 24 human third molars were exposed and polished to create standardized smear layer. The teeth were randomly distributed into four different: 3 step total-etch (Adper™ Scotchbond™ Multi-Purpose, 3M ESPE - SBMP), and 2 step total-etch (Adper™ Single Bond 2, 3M ESPE - SB); 2 step self-etch (AdheSE, Ivoclar/Vivadent - AD); and 1 step self-etch (Adper™ Prompt™ L-Pop™, 3M ESPE - LP). Following the adhesive application (n=6 teeth), resin composite crowns was incrementally placed (Filtek™ Supreme XT - 3M ESPE) in order to obtain bonded sticks, with a cross-sectioned area of about 0.8 mm². The bonded sticks were randomly divided and assigned to be tested immediately [IM] (n=30) or after 6 months of water storage [6M](n=30). Results: Two-way ANOVA and Tukey's test showed that none of the adhesives showed degradation after 6 months, except SB, which was the one that achieved the highest µTBS either in the immediate time (49.13 MPa) and after 6 months (40.27 MPa). LP showed the lowest µTBS in both periods of evaluation (18.34 and 18.35 MPa). AD and SBMP showed intermediate performance. But the SB showed lower µTBS significantly after storage anyway showed high results. Conclusion: Although a significant degradation was only observed for SB, this was the adhesive that showed the highest µTBS after 6M of water storage. It seems that the microtensile test is not sensitive to detect degradation for adhesives with low immediate µTBS.