Multiple Autoclave Cycle Effects on Cyclic Fatigue of Nickel-Titanium Rotary Files Produced by New Manufacturing Methods

Abstract

Introduction Novel nickel-titanium rotary files with proprietary manufacturing techniques have recently been marketed. The purpose of this study was to assess multiple autoclave cycle effects on cyclic fatigue of GT Series X files (Dentsply Tulsa Dental Specialties, Tulsa, OK) and Twisted Files (SybronEndo, Orange, CA) Methods A jig using a 5-mm radius curve with 90° of maximum file flexure was used to induce cyclic fatigue failure. Files ( n = 10) representing each experimental group (GT Series X 20/.04 and 20/.06; Twisted Files 25/.04 and 25/.06) were first tested to establish baseline mean cycles to failure (MCF). Experimental groups ( n = 20) were then cycled to 25% of the established baseline MCF and then autoclaved. Additional autoclaving was accomplished at 50% and 75% of MCF followed by continual testing until failure. Control groups ( n = 20) underwent the same procedures except autoclaving was not accomplished. Results The GT Series X (20/.04 and 20/.06) files showed no significant difference ( p = 0.918/ p = 0.096) in MCF for experimental versus control files. Twisted Files (25/.04) showed no significant difference ( p = 0.432) in MCF between experimental and control groups. However, the Twisted Files (25/.06) experimental group showed a significantly lower ( p = 0.0175) MCF compared with the controls. Conclusions Under the conditions of this evaluation, autoclave sterilization significantly decreased cyclic fatigue resistance of one of the four file groups tested. Repeated autoclaving significantly reduced the MCF of 25/.06 Twisted Files; however, 25/.04 Twisted Files and both GT Series X files tested were not significantly affected by the same conditions.