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

Abstract

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<0.05); In a 60 ° curved root canal, the TTF of 20# HCM was longer than other files with the same tip diameter (P<0.05), and the TTF of 25# WKS was longer than HCM with the same tip diameter (P<0.05). The FL of 20# PTG, 25# PTG, and 20# HCM in the 30° curved root canal model is significantly longer than that of 60° (P<0.05), while there is no statistical difference in FL among 20# WKS, 25# WKS, and 25# HCM in the 30° and 60° curved root canal models. Conclusion The anti cyclic fatigue performance of WKS is significantly superior to PTG and HCM in a 30° curved root canal. In a 60° curved root canal, 20# HCM had a significant advantage in terms of anti cyclic fatigue performance compared to other files, while only 25# WKS had a significant advantage in anti cyclic fatigue performance compared to HCM.

Keywords

• nickel titanium instruments，
• anti cyclic fatigue，
• heat treatment，
• curvature，
• curved root canals，
• instrument separation，
• woride ks，
• hyflex cm，