Bonding Durability of Dual-curing Composite Core Material with Different Self-etching Adhesive Systems in a Model Complete Vertical Root Fracture Reconstruction

Purpose: This study evaluated a dual-curing composite along with different dentin adhesive systems for 1 year under water storage, as a new bonding method of root fragments in complete vertical root fracture. Materials and Methods: Bovine root fragments were bonded with the dual-curing resin composite Clearfil DC Core Automix (DCA) and one of three adhesive systems: two-step self-etching adhesive Clearfil SE Bond (SE), one-step self-etching adhesive Tokuyama Bond Force (BF), one-step dual-curing self-etching adhesive Clearfil DC Bond (DC). Microtensile bond strength (µTBS)/ultimate tensile bond strength (UTS), FE-SEM ultramorphology of fracture modes, and adhesive dentin interface were observed after water storage for periods of up to one year. The data were analyzed with two-way ANOVA. Results: µTBS was influenced by "dentin adhesive system" (F = 324.455, p 0.001) and "length of water storage" (F = 8.470, p 0.001). SE yielded significantly higher µTBS, regardless of storage period (p 0.05) and maintained the initial µTBS without a significant change after 1 year of water storage (p > 0.05). From 24 h to 1 month, BF showed significantly higher bond strength than DC. UTS of DCA was influenced only by the curing mode of the material (F = 5.051, p = 0.027), but not by the length of water storage (F = 0.053, p > 0.05). Conclusion: Two-step self-etching adhesive systems and dual-curing composite core material can be considered as a suitable bonding method for complete root fractures. Keywords: root fracture, luting, self-etching adhesives, dual-curing composite, bonding