Effect of water storage on microtensile bond strength of a two-step self-etch adhesive and a two-step etch-and-rinse adhesive.

This study evaluated the effect of 24 h (1d) and one-year (1yr) water storage on the microtensile dentin bond strength of a two-step total-etch and a two-step self-etch adhesive system. Ten extracted human third molars were sectioned perpendicularly to their long axis to expose flat occlusal dentin surfaces. Teeth were divided into two groups (n=5) according to the adhesive used: a two-step etch-and-rinse adhesive (Adper Single Bond 2) and two-step self-etching adhesive (Adper Scotchbond SE). Composite resin (Z350) build-ups were incrementally constructed on the bonded surfaces. Specimens were sectioned into sticks (cross-sectional mean area 0.8 mm2) and after 1d and 1yr of storage in distilled water at 37 degrees C, the sticks were stressed to failure by microtensile test (1 mm/min). Interfacial observation of silver nanoleakage was performed using scanning electron microscopy (SEM). Data (MPa) were analyzed by two-way ANOVA and Bonferronis test (p = 0.05). SB2 showed the highest bond strength values after 1d of water storage. After 1yr, SB2 values significantly decreased and were similar to ASE, independently of water storage period. Both adhesives, independently of storage time, showed silver nitrate uptake within the hybrid layer and the adhesive layer One-year of water storage only affected the bond strength of the two-step etch-and-rinse adhesive.