Reverse transcription quantitative polymerase chain reaction-based comparative analysis of the antibacterial activity of irrigation solutions and activation methods against Enterococcus faecalis

Purpose: This study evaluated the antibacterial efficacy against Enterococcus faecalis (E. faecalis) biofilm of three irrigants combined with three irrigation activation protocols. Methods: One hundred standardized and sterilized single-rooted human teeth were inoculated with E. faecalis for 21 days and randomly assigned to three main groups based on the irrigant used, namely, NaOCl, Dual Rinse-HEDP, and Chitosan (CS) (n = 30 each). Each group was then further divided into three subgroups (n = 10) according to the activation method employed, namely, standard needle irrigation (SNI), passive ultrasonic irrigation (PUI), and sonic activation (SA). Reverse transcription quantitative polymerase chain reaction (RT-qPCR) was used to analyze bacterial reduction. The results were analyzed using two-way ANOVA (P < 0.05). Results: As compared with the other irrigation solutions, antibacterial activity was highest for NaOCl (P = 0.009). Regarding activation methods, CS had greater efficacy when combined with SA, whereas Dual Rinse-HEDP showed no significant difference across activation protocols. NaOCl was the most effective irrigant overall, particularly when used with SNI and PUI. Conclusion: NaOCl remains the gold standard for E. faecalis reduction. However, the antibacterial performance of CS can be significantly improved with sonic activation. Dual Rinse-HEDP maintains a consistent but limited antibacterial effect regardless of activation technique.