Abstract
PURPOSE: This study evaluates the effectiveness of different sequences of irrigation using sodium hypochlorite (NaOCl) and ethylenediaminetetraacetic acid (EDTA) on root canal disinfection, measured through bacterial reduction. METHODS: A total of 48 mandibular molars were divided into two groups. Group A received irrigation with NaOCl followed by EDTA, while Group B received EDTA followed by NaOCl. Passive ultrasonic irrigation (PUI) was applied in both groups. Bacterial samples were collected at three stages: before chemomechanical preparation (S1), after preparation (S2), and after ultrasonic activation (S3). Quantitative PCR (qPCR) was used to assess bacterial load reduction. ANOVA was performed to determine statistical significance. RESULTS: Group A demonstrated a significant reduction in bacterial load at all stages, with an ANOVA F-statistic of 9.40 (P = 0.00023). Group B showed a less pronounced reduction, with an F-statistic of 14.99 (P = 0.0000031). Bacterial reduction was more effective when NaOCl was used first followed by EDTA. CONCLUSION: The sequence of irrigation influences the effectiveness of root canal disinfection. NaOCl followed by EDTA achieved greater bacterial reduction compared to the reverse sequence.