Effect of irrigant neutralizing reducing agents on the compromised dislocation resistance of an epoxy resin and a methacrylate resin-based root canal sealer in vitro

Objectives: To determine the effect of two reducing agents (sodium ascorbate and sodium thiosulfate) on the dislocation resistance of a methacrylate and an epoxy resin based root canal sealer to sodium hypochlorite (NaOCl) treated root canal dentin. Materials and methods: Single rooted teeth (n = 60) were instrumented with rotary instruments with an irrigation protocol of 3% NaOCl, 17% EDTA and 3% NaOCl in a sequence. Samples were randomly divided into three groups (n = 20) based on the final treatment: group 1 (saline), group 2 (5% sodium thiosulfate), group 3 (10% sodium ascorbate). Samples were then randomly divided into two subgroups (n = 10) based on the root canal sealer: A (a methacrylate resin sealer; EndoREZ); B (an epoxy resin sealer; AH Plus). The dislocation resistance was assessed using the push out bond strength test. The data were statistically analyzed by three-way ANOVA and a pair-wise comparison was done using the Bonferroni adjustment (P = 0.05). Results: There was a significant interaction between the root thirds and the final treatment protocol for EndoREZ (P < 0.001) but not AH Plus (P > 0.05). The two experimental protocols significantly improved the adhesion (bond) strength of EndoREZ compared to saline (P < 0.05) with sodium thiosulfate producing significantly higher values than sodium ascorbate (P < 0.05). Both reducing agents did not improve the adhesion strength of AH Plus significantly when compared to the control (P > 0.05). Conclusions: The bond strength of the methacrylate resin sealer EndoREZ is improved by the use of sodium thiosulfate and sodium ascorbate after irrigation with NaOCl, but these reducing agents do not improve the bond strength of the epoxy resin sealer AH Plus. Root canal sealers are differentially influenced by irrigant neutralizing (reducing) agents.