Abstract
Objective The purpose of this study was to evaluate the effect of repeated autoclave sterilization on the cyclic fatigue resistance of heat-treated NiTi rotary endodontic instruments. Materials and Methods Three NiTi rotary endodontic instruments (EdgeFile X7, EFX7 0.30/0.4; Vortex Blue, VB 0.30/0.4; and TRUShape, TS 0.30/0.6) were selected. Each group (n = 24 each) was divided into 2 subgroups (n = 12 each): sterilized instruments and nonsterilized instruments. The sterilized instruments were subjected to 10 cycles of autoclave sterilization. Twelve instruments from each different subgroups were tested for cyclic fatigue resistance, and the number of cycles to failure (NCF) was calculated. Means and standard deviations were calculated for each group, and data were statistically analyzed using the SPSS program (P < 0.05). Results Sterilized and nonsterilized EFX7 files showed the highest NCF compared with other file subgroups. Comparing the results between sterilized and nonsterilized instruments for each type of files, there was a statistically significant difference (P < 0.05) only between sterilized and nonsterilized EFX7 files (1198 versus 755 NCF). The other instruments did not show significant differences (P > 0.05) in the mean NCF as a result of sterilization cycles (VB, 606 versus 568 NCF; TS, 487 versus 442 NCF). Conclusion Repeated cycles of autoclave sterilization increased the NCF of the new heat-treated files, with EFX7 showing statistically significant superior results compared with other files tested.
Highlights
Chemomechanical cleaning and shaping is the most critical step of root canal treatment (RCT) [1,2,3,4]
(regardless of sterilized or not), the EFX7 group had the highest cyclic fatigue resistance followed by the Vortex Blue (VB) group and the TS group
Up to our best knowledge, there are no available studies in the literature evaluating the cyclic fatigue resistance of VB, EFX7, and TS instruments after repeated cycles of autoclave sterilization
Summary
Chemomechanical cleaning and shaping is the most critical step of root canal treatment (RCT) [1,2,3,4]. This important step, with the help of nickel-titanium (NiTi) rotary endodontic files, becomes faster and more predictable; there is an uneventful risk of instrument separation, and it is a well-reported challenge in endodontic literature [5,6,7,8]. NiTi rotary files might be used many times, and the repeated sterilization process by autoclave is necessary to prevent cross-contamination [17, 18]. A 2020 systematic review and meta-analysis study found that autoclave was the most effective method to sterilize endodontic instruments [19]
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