In vitro study on cyclic fatigue resistance of three types of nickel titanium files in preparation for bending root canals

Objective The purpose of this study was to investigate the differences in the anti cyclic fatigue performance of Woride KS (WKS), Proteper Gold (PTG), and Hyflex CM (HCM) nickel titanium instruments with different tip diameters in curved root canal models, and to provide reference for the targeted selection of suitable nickel titanium instruments in clinical preparation of curved root canals. Methods Three kinds of new nickel titanium files with 20# and 25# (0.20 mm and 0.25 mm) tip diameters were selected, including WKS (20/0.06), WKS (25/0.06), PTG (20/0.07), PTG (25/0.08), HCM (20/0.06), and HCM (25/0.06), each with 20 files. According to the recommended speed and torque of the motor, the anti cycle fatigue performance of the nickel titanium file was tested in 30° and 60° stainless steel root canal models. The time from rotation to fatigue fracture (TTF) of the nickel titanium file was recorded with a camera and timer, and the fragment length (FL) was measured and recorded with a Vernier scale. Results Comparison of TTF of the same type of file. ① WKS: the TTF of files with the same tip diameter in a 30° curved root canal was longer than 60° (P0.05); In a 30° curved root canal, the TTF of 20# nickel titanium files was longer than that of 25# nickel titanium files (P0.05). ③HCM: the TTF of files with the same tip diameter in a 30° curved root canal was longer than 60° (P0.05). The TTF of 25# WKS was longer than that of other files (P