Evaluation of cyclic fracture strengths by changing the usage protocols of different glide path files

Aim: This study was aimed to evaluate the cyclic fatigue resistance of different glide-path files when the rpm changes in this in vitro study. Materials and Methods: In this study, 80 glide path files were used; 20 each of the Path File (16.02), Easy path (14.04), HyFlex EDM (15.03), and Trunatomy Glider (17.02). 40 files were used at the speed recommended by the manufacturer, and 40 files were used at 1000 rpm. The cyclic fatigue test was performed in artificial stainless steel canals with 60° curvature angle, 5 mm radius of curvature, and 1 mm canal inner diameter (n=10). The time until the breakage of the files was recorded simultaneously with the video recording system and the digital stopwatch. The number of cycle fracture (KKTS) was calculated by multiplying the time until the files were broken by rotation. The fracture length was determined with a digital microcaliper. 16 broken files were examined by scanning electron microscopy (SEM) to determine the fracture type of files (n=2). The data were evaluated with Mann Whitney U Test and Kruskal Wallis Analysis of Variance (p<0.05). Results: We observed that the files showed statistically significantly different cyclic fatigue resistance against each other in manufacturer's recommended usage speed and 1000 rpm speed and NCF comparisons (p<0.05). The cyclic fatigue resistance of the files was from high to low in terms of duration and NCF in both groups respectively; Easy path, Path File, Hyflex EDM, Trunatomy Glider. It was observed that all of the files were fractured in a shorter time at 1000 rpm compared to the usage speed recommended by the manufacturer. Path File was the only file whose NCF increased at 1000 rpm according to the manufacturer's recommended usage speed, and no statistically significant difference was observed in other files (p<0.005). Conclusion: As a result, the access file used at a higher speed than the manufacturer's instructions reduced the time to fractured, but did not affect the number of cycles until the fracture.