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

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. 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. 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