Is An Oxygen Inhibited Layer Required for Bonding of Resin-Coated Gutta-Percha to a Methacrylate-Based Root Canal Sealer?

Removal of the oxygen inhibition layer from the surface of resin-coated gutta-percha cones during packaging has been hypothesized for their weak adhesion to a methacrylate-based root canal sealer, resulting in their frequent delamination from the sealer after root canal obturation. This study examined the feasibility of creating oxygen inhibition layers on resin-coated gutta-percha cones via the adjunctive application of a dual-cured dentin adhesive just before bonding. Composite cylinders were bonded with EndoREZ to flat, resin-coated gutta-percha disks and similar disks that were post-treated with Prime&Bond NT Dual Cure adhesive and stressed to failure using a modified microshear testing design. Although shear strengths for both groups were relatively low, a 5-fold increase in shear strength was observed after adhesive application, with complex interfacial failures instead of complete sealer delamination from the resin-coating. In-situ dentin adhesive application appears to have merits in enhancing the coupling of resin-coated gutta-percha to methacrylate sealers.