Purpose: To evaluate the effect of endodontic irrigation regimens and calcium hydroxide root canal sealer (Sealapex) on the microtensile bond strengths (μTBS) of dual-curing resin composite (Clearfil DC Core Automix) to the intrapulpal dentin. Materials and Methods: Forty standardized coronal-half root canal dentin specimens obtained from human premolars were divided into 4 groups: group A, no treatment (control); group B, Sealapex; group C, NaOCl/Sealapex; group D, EDTA/NaOCl/Sealapex. After 7 days of storage in 100% relative humidity, Sealapex was removed. Dentin surfaces were bonded with adhesives, either etch-and-rinse (Single Bond) or self-etching (Clearfil SE Bond), and built up with resin composite. The bonded specimens were trimmed into an hourglass shape with a 1-mm2 cross-sectional area for microtensile testing (n = 20). The μTBS to intrapulpal dentin was analyzed using two-way ANOVA and Dunnett’s TC test. Two teeth of each group were prepared for micromorphological analysis of dentin surface. Results: The root canal sealer with or without endodontic irrigation significantly affected the bond strengths of resin composite to intrapulpal dentin compared with the control group (p < 0.05). There were no significant differences in μTBS of each experimental group between etch-and-rinse and self-etching adhesives (p > 0.05). The dentin surface was covered with a mud-like material after sealer application for 7 days. Conclusion: The root canal sealer reduced the μTBS of dual-curing resin composite with etch-and-rinse and self-etching adhesive systems to intrapulpal dentin. Treatment with EDTA followed by NaOCl prior to obturation caused an additional reduction in μTBS of both adhesive systems to intrapulpal dentin.

Keywords: endodontic irrigation, root canal sealer, intrapulpal dentin, microtensile bond strength