Effect of Storage Time on Microtensile Bond Strength of Self-adhesive and Multi-step Resin Cements to Dentin

Objectives: The purpose of this study was to evaluate the effects of long-term storage on the microtensile bond strength (µTBS) to dentin of two self-adhesive and three multi-step resin cements.
Methods: Twenty-five extracted sound human molars were used (n=5). Two self-adhesive cements RelyX U100 (3M ESPE, U100) and seT PP (SDI, SET), and 3 multi-step resin cements, one using 2-step etch-and-rinse adhesive AllCem (FGM, ALC), and two conventional resin cements with self-etching primer Panavia F (Kuraray, PAN) and Multilink (Ivoclar Vivadent, MULT) were used. Restored teeth were serially sectioned into beams with a cross-sectional and were tested under tension at a crosshead speed of 1 mm/min. Specimens were subjected to the μTBS test after 24 h and 6 months of water storage. Fractured specimens were examined with a stereomicroscope (x40) and a scanning electron microscope (SEM). The µTBS were analyzed by Two-way ANOVA and Tukey test (α=0.05).
Results: The cross-product interaction was no statistically significant (p=0.284). ANOVA revealed a difference between the cements (p<0.0001) and storage (p=0.003). All multi-step resin cements ALC, MULT and PAN showed statistically similar bond strength values that were higher than those of the U100 and SET groups. The bond strength value of all resin cements decreases significantly after 6 months of storage. The majority of the failures were adhesive for all the groups tested.
Conclusions: The µTBS produced by the self-adhesive cements were significantly lower than those observed for multi-step luting agents. Regardless of the numbers of steps of resin cements, the storage time reduces µTBS values to dentin.