(PR038) Effects of Repeated Instrumentation on the Cutting Efficency and Transportation of Endodontic Rotary Files

Objective: This study investigates how the usage and sterilization of rotary nickel-titanium (NiTi) endodontic instruments impact their cutting efficiency and shaping ability during root canal therapy. The effects of the number of sterilization cycles remain unclear. The central hypothesis of this study is that there will be no significant changes in the cutting efficiency or transportation of NiTi files used in endodontics after undergoing sterilization and reuse, regardless of the number of cycles.

Methods: Rotary files were assessed across three different instrumentation techniques and two sterilization cycles, using three groups of ten J-shaped resin canals. Efficiency was evaluated by recording the actual cutting procedure time. To analyze transportation, images taken by a Nikon DSLR camera in a standardized setting were measured using Image J software. Appropriate statistical tests were employed, including the Kruskal-Wallis test for cutting efficiency and ANOVA for transportation analysis, with a significance threshold set at p < 0.05.

Results: Instrumentation time showed a non-significant decrease across cycles (χ²(2) = 3.88, p = 0.144), supporting the null hypothesis regarding cutting efficiency. However, the transportation analysis revealed significant differences between cycles (F=13.212, p < 0.001), indicating that file transportation was increasingly altered with repeated use and sterilization.

Conclusion: The findings suggest that while cutting efficiency remains relatively unaffected by reuse, the transportation of files deteriorates significantly, which could impact clinical outcomes. These insights are critical for making decisions about file reuse in endodontics and highlight the need for further research to assess the long-term effects of repeated sterilization on file.