Ultrasonic activation enhances bond strength and epoxy resin-based sealer penetration after removal of calcium hydroxide intracanal dressing

Purpose To evaluate the effect of conventional endodontic irrigation (CEI), passive ultrasonic irrigation (PUI), and continuous ultrasonic irrigation (CUI) protocols for the removal of calcium hydroxide intracanal dressings containing either propylene glycol (PG) or methylcellulose (MC) on the adhesive interface with epoxy resin-based endodontic sealer. Materials and methods Sixty canine teeth were submitted to chemomechanical preparation and divided into two groups (n = 30) according to the intracanal dressing composition (ICD): PG or MC. After one week, each group was further divided into three subgroups (n = 10) according to the irrigation protocol used for dressing removal: CEI, PUI, or CUI. Root canals were obturated and sectioned at the cervical, middle, and apical thirds. Bond strength was evaluated using the push-out test, and tag formation was assessed by confocal laser scanning microscopy. The data were analyzed using two-way ANOVA and Tukey's test (P = 0.05). Results In the cervical and middle thirds, CUI-PG and CUI-MC showed the highest bond strength and tags extension values (P < 0.05), but similar each other (P > 0.05), while CEI-PG and CEI-MC showed the lowest values (P < 0.05). In the apical third, CEI protocols also showed the lowest bond strength and tags extension values (P < 0.05). Conclusion Ultrasonic irrigation protocols (PUI and CUI) significantly improved the bond strength and tag formation of the epoxy resin-based sealer at the dentin interface, regardless of the calcium hydroxide vehicle or root third.