Comparison of cyclic fatigue resistance of three different nickel-titanium rotary file systems in artificial canal

Introduction and Objective: Root canal preparation is one of the most crucial stages of root canal therapy, but also has the highest rate of complications. Among the factors that directly affect the success of root canal treatment are the inability to reach the length of the canal during the preparation process, and insufficient irrigation and shaping. Nickel-Titanium files (Ni-Ti), with their superior cutting capabilities and flexibility, have become popular in root canal shaping procedures in recent years. Besides, one of the biggest problems of Ni-Ti files is that especially curved root canals break due to cyclic fatigue that occurs as a result of repetitive tensile and compression forces that occur without any signs during shaping. This study aims to compare the resistance of rotary ProTaper Gold, TruNatomy, and Mtwo Ni-Ti rotary file systems to cyclic fatigue using a stainless steel artificial block. Materials and Methods Three different Ni-Ti rotary file systems, fifteen TruNatomy primes (26.04) (Dentsply, Maillefer, Ballaigues, Swiss) fifteen ProTaper Gold (25.06) F2 (Dentsply, Maillefer, Ballaigues, Swiss), fifteen Mtwo (25.06) (VDW GmbH, Munich, Germany) were used in our study. Group 1 was determined as ProTaper GOLD (PTG), Group 2 as MTwo, and Group 3 as TruNatomy (TN). The files were used under the manufacturer's instructions until they broke in the artificial canals made of stainless steel with a radius of curvature of 5 mm, a canal curvature of 60°, and a canal inner diameter of 1.5 mm By recording the time elapsed until the files was broken with a digital stopwatch, the time elapsed until the files were broken was recorded in seconds. Results: Descriptive statistics and analyzes were made using the R version 3.2.3 (2015-12-10), Copyright © 2015 The R Foundation for Statistical Computing free software computer package program. In this study, the compatibility of continuous variables with the assumption of normality was evaluated using the Shapiro-Wilk tests. Considering the parametric test conditions, differences between means of independent groups belonging to the variables were compared using One-Way Analysis of Variance (ANOVA), and Bonferroni tests were used for pairwise comparisons. Results for p<0.05 were considered significant (p=0.000). PTG was more resistant than Mtwo (p=0.000), PTG was more resistant than TN (p=0.048), and TN was more resistant than Mtwo (p=0.035). Group 1 (PTG) was observed to have the highest resistance to cyclic fatigue. Conclusion: Based on the data and statistical results we obtained in our study, it was determined that the most resistant file system was PTG against breakage as a result of cyclic fatigue (p=0.000, F=13.214). Keywords: Cyclic Fatigue, Rotary Motion, Kinematics, TruNatomy File, ProTaper File, Mtwo File