Chemomechanical reduction of the bacterial population in the root canal after instrumentation and irrigation with 1%, 2.5%, and 5.25% sodium hypochlorite

Given the importance of bacteria in the development of periradicular lesion s, the eradication of the root canal infection is paramount in endodontic t reatment. This study evaluated the in vitro intracanal bacterial reduction produced by instrumentation and irrigation with 1%, 2.5%, and 5.25% sodium hypochlorite (NaOCl) or saline solution. Root canals inoculated with Entero coccus faecalis were instrumented and irrigated with the solutions tested. Canals were sampled before and after preparation. After serial dilution, sa mples were plated onto Mitis salivarius agar, and the colony-forming units grown were counted. Inhibitory effects of the three NaOCl solutions on E. f aecalis were also evaluated by means of the agar diffusion test. All test s olutions significantly reduced the number of bacterial cells in the root ca nal (p < 0.05). There was no significant difference between the three NaOCl solutions tested (p > 0.05). Nonetheless, all NaOCl solutions were signifi cantly more effective than saline solution in reducing the number of bacter ial cells within the root canal (p < 0.05). The three NaOCl concentrations showed large zones of inhibition against E. faecalis. The results of this s tudy suggest that regular exchange and the use of large amounts of irrigant should maintain the antibacterial effectiveness of the NaOCl solution, com pensating for the effects of concentration.