Comparison of the In Vivo Antimicrobial Effectiveness of Sodium Hypochlorite and Chlorhexidine Used as Root Canal Irrigants: A Molecular Microbiology Study

Introduction: The purpose of this clinical study was to compare the antimicrobial effects of 2.5% sodium hypochlorite (NaOCl) and 0.12% chlorhexidine digluconate (CHX) when used as irrigants during treatment of teeth with apical periodontitis. Methods: Forty-seven single-rooted single-canal teeth with necrotic pulps and asymptomatic apical periodontitis were selected for this study according to stringent inclusion/exclusion criteria. Bacterial samples were taken at the baseline (Si) and after (52) chemomechanical preparation using 2.5% NaOCl (n = 30) or 0.12% CHX (n = 17) as the irrigant. Bacterial, archaeal, and fungal presence was evaluated by broad-range polymerase chain reaction (PCR), whereas bacterial identifications were performed by a closed-ended reverse-capture checkerboard approach targeting 28 candidate endodontic pathogens. Results: All Si samples were PCR positive for bacterial presence but negative for both archaea and fungi. Both NaOCl- and CHX-based protocols were significantly effective in reducing the bacterial levels and number of taxa. No significant differences were observed between them in all tested parameters including the incidence of negative PCR results in S2 (40% for NaOCl vs 47% for CHX, p = 0.8), reduction in the number of taxa per canal (p = 0.3), and reduction in the bacterial levels (p = 0.07). The most prevalent taxa in S2 samples from the NaOCl group were Propionibacterium acnes, Streptococcus species, Porphyromonas endodontalis, and Selenomonas sputigena. In the CHX group, the most prevalent taxa in 52 were Dialister invisus, Actinomyces israelii, Prevotella baroniae, Propionibacterium acidifaciens, and Streptococcus species. Conclusions: Treatment protocols using irrigation with either NaOCl or CHX succeded in significantly reducing the the number of bacterial taxa and their levels in infected root canals, with no significant difference between these substances. (J Endod 2011;37:143-150)