Influence of surface treatments on composite resin cores

Purpose/aim: This in vitro study aimed to evaluate the bond strength of resin cements to composite resin core submitted to different surface treatments, 24h and 6 months after the adhesive procedure, as well as the contact angle of the resin composite core. Materials and methods: Eighty-eight Filtek Z350 XT resin blocks were divided into 4 groups according to the surface treatments (no surface treatment – control group; etching with 37% phosphoric acid; etching with 37% phosphoric acid + silane; and etching 37% phosphoric acid + dental adhesive) (n = 22). RelyX ARC and RelyX U200 resin cements were used for the microtensile bonding analysis. After bonding, the specimens were sectioned into beams of approximately 1.0mm2 of area, and evaluated in two distinct periods (24h and 6 months) using a microtensile bonding test(n = 7). Images of representative specimens were obtained using a scanning electron microscope. The superficial wettability was analyzed by goniometer (n = 8). Data on bond strength were subjected to 3-way ANOVA and Tukey test. Contact angle data were subjected to Kruskal–Wallis test, followed by Bonferroni's test for comparing the groups (˛ = .05). Results: For both resin cements, the groups that received the application of phosphoric acid + adhesive had the lowest bond strength values after 6 months. The surface treatment of the composite resin core with phosphoric acid + silane showed lower contact angle values than other groups (P < .05). Conclusions: Phosphoric acid, with or without silane application, yielded more satisfactory bond strength and surface wettability of the composite resin core.