Are self-adhesive resin cements a valid alternative to conventional resin cements? A laboratory study of the long-term bond strength

ObjectivesThe aim of the study was to test whether or not the shear bond strengths of six self-adhesive resin cements to dentin and to glass-ceramic, 24 h and long-term-aged, are similar to the one of a conventional resin cement.MethodsHuman molars (N = 168, n = 12 per group) and silicabased glass-ceramic specimens (N = 168, n = 12 per group) were embedded in acrylic resin and randomly divided into 28 groups. The following resin cements were luted according to the manufacturers’ instructions: Clearfil SA (CSA), G-Cem (GCM), SmartCem2 (SMC), SpeedCEM (SPC), RelyX Unicem (RXU), RelyX Unicem2 (RXU2) and Panavia21 (control group, PAN). Shear bond strength was measured initially (24 h of water storage 37 °C) and after aging (24,000 thermal cycles, 5/55 °C). The failure types (adhesive, and cohesive) were evaluated after debonding. The shear bond strength values were analyzed using three-way and one-way ANOVA, followed by a post hoc Scheffé and two-sample Student's t-tests.ResultsRXU, RXU2 and GCM showed similar after 24 h and aged shear bond strength to dentin as the control group. CSA, SMC and SPC exhibited significantly lower values. Before aging, none of the bond strength values to glass-ceramic differed significantly from the other. After thermocycling, GCM showed higher results to glass-ceramic than CSA, SMC, RXU2 and the control group. Analyzing failure types after spontaneous debonding and shear bond test at dentin, solely adhesive failures were found, while at glass-ceramic only cohesive failures occurred.ConclusionNot all self-adhesive resin cements can be a valid alternative to conventional resin cements in order to bond silica-based glass-ceramics to human dentin.