Effect of clinical use on the cyclic fatigue resistance of F1 ProTaper gold rotary files: In vitro study

Introduction: Nickel–titanium (NiTi) rotary files are widely used in endodontics. However, they have some drawbacks, such as file breakage due to torsional or cyclic fatigue. Given that NiTi rotary files can be clinically reused, this study assessed the cyclic fatigue resistance of F1 ProTaper Gold (PTG) files after several uses and compared them to the performance of unused files. Materials and Methods: Ninety maxillary molars with three separate roots were chosen. The main root canals were instrumented with PTG files. The PTG F1 files were categorized according to the number of instrumented teeth (one tooth, two teeth, and three teeth). Then, they were subjected to the cyclic fatigue resistance test using stainless steel artificial canals, wherein the file was rotated at 300 rpm until fracture took place. The number of cycles to fracture was determined, and the fractured surface was evaluated under a scanning electron microscope (SEM) to assess the topographic changes of the file’s fractured surface. Statistical analysis was performed using an analysis of variance test at a 5% significance level. Results: There was no significant difference in the cyclic fatigue resistance of PTG F1 rotary files after multiple clinical uses as compared to the new file ( P > 0.05), and the SEM analysis showed typical features of cyclic fatigue in all tested groups. Conclusion: The reuse of PTG F1 files up to three molar teeth proved to be safe, since the cyclic fatigue resistance was not negatively influenced in the tested files.