Sodium Thiosulfate for Recovery of Bond Strength to Dentin Treated with Sodium Hypochlorite

• Sodium thiosulfate (Na2S2O3) is an antioxidant that has been used in medicine and as a neutralizing agent of NaOCl in microbiological analysis, showing potential to be used as reducing agents for NaOCl-treated dentin without damaging biological tissues.
• This study was 1 of the few evaluating the resin bond strength to dentin pulp chamber after the use of typical endodontic substances; it is also the first to assess the applicability of Na2S2O3 to recover the dentin bond strength lost with the use of these products.
• Depending on the concentration and time application, the use of Na2S2O3 can recover the bond strength to the NaOCl-treated dentin. The use of Na2S2O3 can significantly increase the bond strength of composite resin to NaOCl-treated dentin, allowing adhesive restorations to be immediately applied after endodontic treatment.

IntroductionThe aim of this study was to evaluate the efficacy of sodium thiosulfate (Na2S2O3) for restoring adhesion to pulp chamber dentin treated with sodium hypochlorite (NaOCl) and EDTA.MethodsSixty-three crowns of bovine incisors were cut to expose the dentin pulp chamber. The specimens were polished and randomly distributed into 9 groups (n = 7) according to the following protocols used: 0.9% sodium chloride for 30 minutes (negative control), 5.25% NaOCl for 30 minutes, 17% EDTA for 3 minutes, and 5.25% NaOCl for 1 minute (positive control). The other groups, after treatments with NaOCl and EDTA, were immersed in 0.5% or 5% Na2S2O3 for 1, 5, and 10 minutes or just immersed in an inert solution for 10 minutes (0.9% sodium chloride). After drying the specimens, Scotchbond Multi-Purpose (3M ESPE, St Paul, MN) was applied to the pulp chamber dentin followed by Filtek Z250 composite (3M ESPE). Six rectangular slabs were obtained from each specimen, and the dentin/resin interface was tested by using a universal testing machine. The resulting data were submitted to 1-way analysis of variance and the Duncan test (P = .05).ResultsThere was a significant decrease in bond strength regarding NaOCl and EDTA (P < .05). When 5% Na2S2O3 was used for 10 minutes, the bond strength was found to be statistically equal to the negative control and higher than the positive control (P < .05).ConclusionsThe use of Na2S2O3 can significantly increase the bond strength of composite resin to NaOCl/EDTA-treated dentin, allowing adhesive restorations to be immediately applied after endodontic treatment.