Synergistic antibacterial activity of chlorhexidine and hydrogen peroxide against Enterococcus faecalis

The aim of the present study was to compare the in vitro antibacterial activity of common root canal irrigants with a combination technique against intratubular Enterococcus faecalis. Seventy-five human single-rooted teeth were selected and their crowns and root-ends were removed to obtain specimens 5 mm in length. The specimens were contaminated with E. faecalis and divided into five experimental groups (n = 15). These groups were irrigated with 2% chlorhexidine (CHX), 3% hydrogen peroxide (H2O2), 5.25% sodium hypochlorite (NaOCl), CHX/H2O2 and sterile saline (control). Surface and deep dentinal chips were collected for each sample. After incubation, the numbers of colony-forming units (CFUs) were counted. The Kruskal-Wallis and Mann-Whitney U tests were used for statistical analysis (α = 0.05). In the surface dentin, CHX, NaOCl, and CHX/H2O2 had significantly higher antibacterial activity than H2O2 (P < 0.05). In the deep dentin, NaOCl and CHX/H2O2 had significantly higher antibacterial activity than CHX and H2O2 (P < 0.05). CHX/H2O2 had similar antibacterial effectiveness to NaOCl in both surface and deep dentinal tubules. This combination can be considered a potentially useful irrigant for root canal treatment.