Antibacterial Efficacy of Sodium Thiosulfate Used as a Dental Irrigant Against Enterococcus faecalis: An In Vitro Evaluation

Abstract

Enterococcus faecalis is frequently implicated in endodontic treatment failures due to its significant resistance to antimicrobial agents and its ability to form biofilms within root canals. This bacterium can withstand harsh conditions characterized by limited nutrient availability and elevated alkaline pH, conditions commonly encountered in root-filled teeth. Consequently, it represents a key pathogen associated with resistant endodontic treatments. The objective of this study was to evaluate the antibacterial efficacy of a 5% sodium thiosulfate (STS) solution as a novel endodontic irrigant against E. faecalis. The antibacterial activity of STS was compared with 2.5% sodium hypochlorite (NaOCl) and their combined application. This in vitro investigation assessed the antibacterial efficacy of various irrigant solutions against extracted human teeth at 20, 40, and 60 minutes. Four experimental groups were established: a control group, one treated with 5% sodium thiosulfate, one treated with 2.5% sodium hypochlorite, and one treated with their combination. Fifty-six extracted, single-rooted, caries-free teeth were inoculated with E. faecalis to facilitate biofilm formation, and bacterial viability was assessed using the colony-forming unit (CFU/mL) technique. The results indicated that the combination of 5% sodium thiosulfate (STS) and sodium hypochlorite (NaOCl) significantly exhibited the highest antibacterial efficacy at the 40-minute interval based on the statistical ANOVA test followed by the Duncan Multiple Range test. The promising antibacterial efficacy of the combined treatment was comparable to that of NaOCl alone. This combined approach has the potential to mitigate the cytotoxic effects typically associated with NaOCl in clinical applications.