Influence of the activation mode on long-term bond strength and endogenous enzymatic activity of dual-cure resin cements

Abstract

Abstract Objective To investigate the long-term microtensile bond strength (µTBS), interfacial nanoleakage expression (NL), and adhesive stability of dual-cure resin cements with/out light activation to dentin. Materials and methods Composite overlays ( N = 20) were luted to deep dentin surfaces with RelyX Ultimate (RXU, 3M) or Variolink EstheticDC (VAR, Ivoclar-Vivadent). A universal adhesive was used for bonding procedures (iBond universal, Heraeus Kulzer). The resin cements were either self-cured (SC; 1 h at 37 °C) or dual-cured (DC; 20s light-cure followed by 15 min self-cure at 37 °C). Specimens were submitted to µTBS immediately ( T 0 ) or after 1 year of laboratory storage ( T 12 ). The fracture pattern was evaluated using scanning electron microscopy (SEM). Data were statistically analyzed with two-way ANOVA/Tukey test. Further, the NL was quantified and analyzed (chi-square test) and in situ zymography was performed to evaluate the endogenous enzymatic activity within the hybrid layer (HL) at T 0 and T 12 (Mann–Whitney test) . The significance level for all statistical tests was set at p = 0.05. Results DC resulted in higher bond strength and decreased fluorescence at the adhesive interface, irrespective of the material and the storage period ( p < 0.05). Significantly lower bonding performances ( p < 0.05) and higher endogenous enzymatic activity ( p < 0.05) were observed within the HL at T 12 compared to T 0 in all tested groups. Conclusions Light-curing the dual-cure resin cements, more than the cement materials, accounted for good bonding performances and higher HL stability over time when used with a universal adhesive. Clinical significance The curing condition influences the bonding performances of dual-cure resin cements to dentin when used with a universal adhesive.

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