Effect of dentin surface conditions and curing mode of resin cement on the dentin bond strength for an indirect restoration

Abstract

Background: During the cementation of indirect restorations, the conditions of the dentin surface and dentin adhesive's curing technique that affect the adhesion between dentin and an indirect restoration are essential issues for clinicians. This study investigates the effects of dentin's wetness, roughness, and curing modes of resin cement on bond strength when using universal adhesives for the cementation of indirect restorations. Methods: Forty human teeth were divided into eight groups according to three experimental factors: 1) dentin's roughness achieved by 250-or 600-grit Silicon-carbide (SiC) paper (coarse or fine), 2) dentin wetness with an air-drying time (5-s or 10-s), and 3) Single Bond Universal adhesive's curing mode by co-curing with RelyX Ultimate resin cement or light-curing separately after applying the adhesive(co-curing or light-curing). After resin discs were cemented with RelyX Ultimate, the microtensile bond strength (μTBS) was measured (n = 15 each). The failure mode and adhesive layers were observed using stereoscopic and confocal laser scanning microscopy (CLSM). Results: The roughness of the dentin surface did not significantly affect the bond strength (p > 0.05), and the curing mode of dentin adhesive and the 5-s drying group of dentin had significant effects on bond strength (p < 0.05). Light-curing groups and 5-s drying groups showed significantly higher bond strength than co-curing groups (p < 0.05), and 10-s drying groups (p < 0.05), respectively. Conclusions: When using Single Bond Universal adhesive and RelyX Ultimate resin cement, the light curing mode, in which the adhesive and resin cement is light-cured, showed higher bond strength than the co-curing mode. The bond strength between the resin cement and dentin was improved in the 5-s drying groups than in the 10-s drying groups.