Torsional Properties of Stainless-Steel and Nickel-Titanium Files After Multiple Autoclave Sterilizations

Abstract

This study tested the hypothesis that multiple sterilizations of endodontic stainless-steel and nickel-titanium files will lead to a continuous decrease in the resistance of files to separation by torsion. One hundred stainless-steel and 100 nickel-titanium #30 K-type files were divided into 20 groups of 10 and sterilized in increments of 10 cycles, using a full cycle and a fast cycle autoclave. These files were tested by twisting each of them in a clockwise direction until fracture (torque g-cm). Samples of the fractured files were embedded in an epoxy resin and polished for Knoop hardness tests. In addition, the samples were chemically etched to reveal changes in microstructure. The findings of this study indicate that neither the number of sterilization cycles nor the type of autoclave sterilization used affects the torsional properties, hardness, and microstructure of stainless-steel and nickel-titanium files.

The effect of autoclave sterilization on the fracture resistance of ProTaper rotary files

“…(2) This result also contradicts our finding. We found that sterilization cycles tend to be safe for rotary instruments, as shown in the studies by Silvaggio & Hicks (7) and Mize et al (6) Similar with the study by Hilt et al, (22) this investigation showed that nor the number of cycles, neither the sterilization process could affect the torque, hardness and microstructure of NiTi alloy.…”

Comparison of Autoclaving Effects on Torsional Deformation and Fracture Resistance of Three Innovative Endodontic File Systems

“…In contrast, a significant decrease in torsional fracture resistance after heat sterilization has been reported for some NiTi files (15). Other authors found no significant change in NiTi torsional properties or numbers of cycles to fatigue failure after heat sterilization (16,17).…”

SEM Observations and Differential Scanning Calorimetric Studies of New and Sterilized Nickel-Titanium Rotary Endodontic Instruments

“…The effect of sterilization procedures on physical and mechanical properties of the NiTi files has not yet been adequately evaluated. Some authors reported that heat sterilization increase number of rotations-to-breakage of NiTi instruments (2,4), while others showed that had no consistent or significant effect (5)(6)(7)(8). Some researchers (9,10) found that heat sterilization leads to reduction of cutting efficiency of the NiTi files.…”