Effect of Sterilization on Cyclic Fatigue Resistance of Proflexendo Endodontic Rotary Files

Background: Proflexendo file (Nexen, Houston, TX, USA) is a recently developed, novel nickel-titanium rotary file. However, several physical properties of the Proflexendo system remain to be investigated. Objectives: The aim of this study was to determine the effect of sterilization on cyclic resistance of Proflexendo files. Material and Methods: A total of 120 unused Proflexendo rotary files (90 each of file sizes 90/0.04, 30/0.04 and 20/0.06) were used in this study. Each set of files was subdivided into four groups of ten files. Group 1 did not undergo any sterilization (control), Group 2 underwent two rounds (2x) of sterilization, Group 3 five rounds (5x) and Group 4 ten rounds (10x). Cyclic fatigue resistance was tested using an artificial canal with a 5-mm radius curve. Results: The nonsterilized size 30,9.04 files had the highest cycles to failure, followed by the nonsterilized size 40/0.04 and 20/0.06 files (P < 0.001). With increasing rounds of sterilization, cycles to failure reduced for sizes 40 (2x, 5x and 10x) and 30 (2x) files compared with nonsterilized sizes 40 (P < 0.05) and 30 files (P < 0.001), respectively. Conclusion: Under the conditions of the current study, the results provide preliminary evidence that autoclave sterilization of Proflexendo rotary files reduced their cyclic fatigue resistance, except for size 20 (2x and 5x) and 30 (10x) files, in which resistance increased. Single use of this file is recommended to reduce the risk of separation.