In vitro evaluation of the antibacterial potential of benzalkonium chloride in root canals infected by Enterococcus faecalis

Objective To evaluate the antibacterial potential of benzalkonium chloride in root canals infected by Enterococcus faecalis (E.faecalis) . Methods Sixty-four human premolars extracted for orthodontics were prepared and inoculated with E.faecalis. Two teeth were selected respectively using random lottery method before and after inoculation, then split in to two halves along the mesiodistal axis. One half was processed with light microscopic (Brown & Brenn stain) to check the bacteria in dentinal tubules, and the other was observed with SEM to investigate the bacterial status in infected root canals. The rest of the teeth were randomly assigned to the following groups: 0.05% benzalkonium chloride, 0.1% benzalkonium chloride, 3% hydrogen peroxide, 2.5% sodium hypochlorite, 5.25% sodium hypochlorite, 0.9% sodium chloride for endodontic irrigation. Before and after irrigating, microbiological samples were collected from root canals for bacteriological culture, and colony forming units (CFU) were counted. The t-test was used to analyze the difference of bacterial counts in root canals before and after irrigation. The difference of bacterial descent among the six groups were analyzed by ANOVA. Bacterial status after irrigation was assessed with SEM. Results (1) E.faecalis was found to penetrate into the dentinal tubules about 250~ 1050 μm. In the infected root canal samples, E.faecalis was attached to the root canal wall to form a biofilm structure. (2) The number of E.faecalis in root canal in each group was effectively reduced excepted 0.9% sodium chloride group (P 0.05) . Root canal surfaces were cleaner in benzalkonium chloride and 5.25% sodium hypochlorite groups than 3% hydrogen peroxide group and 2.5% sodium hypochloritethe group with SEM observation. Conclusion It was suggested that benzalkonium chloride solution had potential antibacterial activity against E.faecalis when it was used for root canal irrigation. Key words: Enterococcus faecalis; Root canal irrigants; Benzalkonium compounds; Dental models