The effects of endodontic substances and naturally reducing agents on the bond strength of epoxy resin-based sealer to root dentin

AIM: To evaluate the effects of sodium hypochlorite (NaOCl), chlorhexidine (CHX), and two naturally derived reducing agents on the bond strength of epoxy resin-based sealer to root dentin. MATERIALS AND METHODS: A total of 60 single-rooted human teeth were prepared using ProTaper (Dentsply Tulsa Dental Specialties, Johnson City, TN, USA) and an irrigation protocol including 5% NaOCl or 2% CHX gel, and ethylenediaminetetraacetic acid (EDTA), for smear layer removal. The following subgroups (n = 10) were also assessed according to the naturally derived reducing agent used: no agent (control group); grape seed extract (GSE); and green tea. Root canals were filled with gutta-percha and AH Plus (Dentsply DeTrey, Konstanz, Germany). Bond strength was measured using the push-out test, and statistical analyses were performed using ANOVA; failure patterns (modes) were classified as adhesive, cohesive, or mixed. The types of failure modes were evaluated using the Chi-squared test at α =0.05. RESULTS: The irrigation protocols demonstrated similar bond strength values (P > 0.05). However, the Chi-squared test revealed significant differences in failure mode among the groups (P < 0.05). An increase in the incidence of adhesive failures was observed for the NaOCl and EDTA groups. The other groups demonstrated a prevalence of mixed and cohesive failures. CONCLUSION: The irrigation protocols and use of naturally derived reducing agents had no effect on the bond strength of the resin-based sealer to dentin; however, improvement was evident in the adhesion quality of AH Plus to NaOCl-treated root dentin, due to the prevalence of cohesive failure.