Influence of Adjuncts to Irrigation in the Disinfection of Large Root Canals

Introduction: The aims of this study were to evaluate the effectiveness of disinfection methods and determine the most promising irrigation protocol for regenerative endodontics in teeth with large root canals. Methods: Sterilized root samples with 0.8-mm wide apical foramen (n = 94) were prepared from human mandibular premolars. Ninety-two samples were infected with Enterococcus faecalis for 21 days and biofilm formation was verified using scanning electron microscopy (n = 2). The 90 infected samples were randomly assigned into 9 groups: no intervention (initial), 1.5% NaOCl irrigation (1.5 N), 2.5% NaOCl irrigation (2.5 N), 1.5 N + intermittent passive ultrasonic irrigation (PUI), 1.5 N + intermittent canal brushing with Navitip FX (NFX), 1.5 N + intermittent XP-endo Finisher (XPF), 1.5 N + circumferential filing (CF), 1.5 N + 1-min Self-adjusting File (SAF), and 1.5 N + mechanical instrumentation using #90-110 files (MI). Subsequently, the root canal walls were shaved for microbial analysis. The mean colony-forming units (CFUs) were determined and analyzed using 1-way analysis of variance. Results: The mean CFU count was lowest in the MI group (63.5 CFU/mL), followed by the NFX, XPF, SAF, 2.5 N, CF, PUI, 1.5 N, and initial groups. The remaining bacteria in the 1.5 N group was 3.6-fold higher than that of the PUI group; 4- to 5-fold higher than that of the 2.5 N, CF, and SAF groups; and 22-fold and 36-fold higher than that of the XPF and NFX groups, respectively. The 2.5 N and 1.5 N groups with adjunctive treatments, excluding the PUI group, had significantly fewer remaining bacteria compared with the 1.5 N group (P < .05). Conclusions: Performing various procedures supplemental to 1.5 N improved large root canal disinfection. Adjunctive NFX most effectively reduced the number of bacteria without dentin removal.