Comparative evaluation of Enterococcus faecalis counts in different tapers of rotary system and irrigation fluids: An ex vivo study

Background: Bacteria and their by‑products are etiological factors for the failure of endodontic treatment. Reduction of root canal bacterial contamination is one of the chief aims of root canal therapy. The aim of this study was to compare the effects of different rotary file tapers and two irrigation fluids on Enterococcus faecalis counts. Materials and Methods: In this ex vivo study Root canals of 72 human upper lateral incisors were enlarged to ISO #20 K‑file. Then, the samples were sterilized and inoculated with E. faecalis for 72 h, divided into six experimental groups and prepared with #30 Flexmaster files with 0.02, 0.04, and 0.06 tapers and two different irrigation solutions such as normal saline and sodium hypochlorite. The control group (n = 10) was subdivided into two groups with or without bacterial inoculation and no mechanical instrumentation. Cleaning efficacy was evaluated in terms of the reduction of colony forming units (CFUs). T‑test, ANOVA, Duncan, and Tukey tests were applied to the groups. A significant level of α = 0.05 was set for comparison between the groups. Results: The canals instrumented with 0.06 taper exhibited greater significant reduction in CFUs compared to canals instrumented with 0.04 and 0.02 taper (P < 0.05); 0.04 taper also resulted in greater significant reduction in CFUs than 0.02 taper (P < 0.05). In addition, no significant differences were observed in E. faecalis counts between the two irrigation fluids (P > 0.05). Conclusion: Under the conditions of this study, root canal preparation with greater taper resulted in canal cleanliness and better debridement.