Effect of storage times and mechanical load cycling on dentin bond strength of conventional and self-adhesive resin luting cements

Abstract

The lack of long-term bond stability between resin cements and dentin may compromise the success of indirect restorations. The purpose of this study was to evaluate the effects of long-term storage in artificial saliva and mechanical load cycling on the microtensile bond strength of conventional and self-adhesive resin cements to dentin. The occlusal dentin surfaces of 128 human molars were exposed and flattened. The teeth were assigned to 16 groups (n=8) according to resin cement and invitro aging strategy. Two self-adhesive resin cements (RelyX Unicem and Clearfil SA Cement) and 2 conventional cementing systems (RelyX ARC and Clearfil Esthetic Cement) were used. Resin cements were applied to prepolymerized indirect resin disks, which were bonded to the dentin surfaces and light polymerized. The control groups were represented by immediate microtensile bond strength (24 hours) and aging methods were performed with mechanical load cycling or storage in artificial saliva (1 year and 2 years). Bonded beams were tested in tension until failure. Data (MPa) were analyzed by Proc Mixed for repeated measures and the Tukey-Kramer test (α=.05). The self-adhesive resin cements exhibited higher microtensile bond strength than conventional cementing systems for all conditions studied. The microtensile bond strength of RelyX ARC and self-adhesive resin cements did not decrease after storage in artificial saliva and mechanical load cycling. The Clearfil Esthetic Cement showed the lowest microtensile bond strength and a significant reduction after 2 years of storage in artificial saliva. The storage times and mechanical load cycling did not affect the microtensile bond strength of self-adhesives and RelyX ARC resin cements. The highest microtensile bond strength was obtained for self-adhesive resin cements, with no significant difference between them.