Effect of autoclaving on the cyclic fatigue resistance of nickel-titanium rotary instruments: An in vitro study

AIM: The aim of the study is to determine the effect of autoclaving on the cyclic fatigue resistance (CFR) in respect to three different rotary nickel-titanium (NiTi) systems. METHODS: Three rotary NiTi files with different manufacturing process were selected and arranged into three groups. Group 1: Neolix Neoniti files (n = 15), Group 2: Edge Files (n = 15), Group 3: NeoendoFlex files (n = 15). Each group was then subdivided into three subgroups containing 5 samples each based on the number of cycles of autoclaving (0, 1, 5 cycles). The instruments were subjected to autoclave without usage. The files of size 25, taper 6%, and 25 mm length were taken. After the autoclaving cycles, the files were rotated in cyclic fatigue testing device with simulated canal curvature of 60° until file separation. Time taken for the instrument separation (in minutes) was multiplied by the number of rotations per minute to attain the mean number of cycles to failure for every file. The obtained results were subjected to statistical analysis using two-way ANOVA and Newman–Keuls multiple post hoc procedures. RESULTS: Neolix Neoniti files exhibited the maximum CFR (98.80) than EdgeFiles (80.47) and Neoendo Flex files (41.80) (P = 0.0001). Reduction in CFR was observed with increase in the number of cycles of autoclaving (i.e., 0, 1, 5 cycles). CONCLUSION: Autoclaving has a negative influence on the CFR of the rotary NiTi files used. Neolix Neoniti files exhibited greater CFR than EdgeFiles and Neoendo Flex files.