Evaluation of the Antimicrobial Efficacy of Alexidine as an Endodontic Irrigant against Enterococcus faecalis by Time-kill Assay – An In vitro Study

Aim: The aim of this study was to assess the time-dependent antimicrobial efficacy of three endodontic irrigants 1% chlorhexidine (CHX), 1% alexidine (ALX), and 5% sodium hypochlorite (NaOCl) against Enterococcus faecalis , a common pathogen in persistent root canal infections. Materials and Methods: The microdilution method was used to calculate the minimum inhibitory concentration (MIC) for the experimental irrigants against E. faecalis . For the time-kill assay (TKA), concentrations were set at double the MIC to ensure effective antimicrobial activity. Standardized inoculum of E. faecalis was exposed to the experimental irrigants (1% CHX, 1% ALX, and 5% NaOCl) and control (bacterial suspensions without any irrigant served as the control) group, and bacterial viability was assessed at 30, 60, 90, and 180 s using serial dilutions to measure log reductions in colony forming unit (CFU) counts. Results: The results of the TKA showed the lowest mean CFU for ALX (2.1 ± 3.28), followed by CHX (7.09 ± 0.030), NaOCl (7.13 ± 0.02), and the control (7.21 ± 0.135). The difference was statistically significant ( P < 0.0001). Conclusion: Hence, the authors conclude that ALX showed the highest antimicrobial activity and could serve as a valuable alternative to conventional irrigants, particularly in cases where rapid and effective bacterial eradication is crucial for successful treatment outcomes.