In vitro reduction in Enterococcus faecalis count following root canal preparation with Neolix and XP shaper rotary files

Introduction: The main goal of root canal treatment is to decrease the count of intracanal microorganisms and their byproducts. This study aimed to assess the efficacy of Neolix and XP Shaper rotary files for the reduction of Enterococcus faecalis (E. faecalis) count in the root canal system. Materials and Methods: This in vitro, experimental study evaluated 58 single-rooted single-canal teeth. The teeth were randomly divided into two experimental groups (n = 25) for root canal instrumentation with Neolix and XP Shaper files and positive and negative control groups (n = 4). All teeth were primarily instrumented with #20 K-file and #2 and #3 Gates-Glidden drills. The smear layer was removed using 17% ethylenediaminetetraacetic acid and 5.25% sodium hypochlorite. The teeth were then autoclave sterilized and the root canals in all groups, except for the negative control, were inoculated with E. faecalis. All teeth were then CO2 incubated for 24 h. Primary samples were collected. Next, the root canals in Group 1 were instrumented with Neolix, while the root canals in Group 2 were instrumented with XP Shaper. Root canals in the positive control group were only rinsed with saline. Secondary samples were collected after instrumentation. The number of colonies formed on the blood-agar was counted before and after instrumentation. Results: The negative control group showed no bacterial growth. The positive control group showed a 14.11% reduction in bacterial count. The mean percentage of reduction in bacterial colony count was 92.92% and 87.79% in the Neolix and XP Shaper groups, respectively. The difference in this regard was significant between the two experimental groups with different apical sizes (Mann–Whitney test, P = 0.02). Conclusion: Both files caused a significant reduction in E. faecalis count. However, Neolix had a superior efficacy for canal cleaning compared with XP Shaper.