Effect of Immersion in Disinfectants on Cyclic Fatigue Resistance of Nickel-Titanium Instruments: An in Vitro Study

Objectives: The current study aimed to assess the cyclic fatigue resistance of two nickel-titanium (NiTi) rotary files after immersion in 5% sodium hypochlorite (NaOCl) and Deconex. Materials and Methods: In this in vitro study, 90 new M3 Pro Gold size 25.06 and size F2 SP1 files were tested. Forty-five files of the same brand were randomly distributed into three groups (n=15) and submitted to the following immersion protocol for 5 minutes at room temperature: no immersion (control group), immersion in 5% NaOCl, and immersion in Deconex. The cyclic fatigue resistance of the files was then measured in a custom-made tester. Two-way ANOVA was applied to compare the cyclic fatigue resistance of SP1 and M3 NiTi rotary files based on the type of disinfectant solution. Post-hoc LSD test was used for pairwise comparisons and P<0.05 was considered significant. Results: Two-way ANOVA indicated a significant difference in the mean cyclic fatigue resistance of M3 and SP1 NiTi rotary files. The M3 files immersed in NaOCL displayed the lowest and the SP1 files immersed in Deconex showed the maximum cyclic fatigue resistance. The effect of type of disinfectant solution (P<0.001) and type of NiTi file (P<0.001) on cyclic fatigue resistance was statistically significant. Conclusion: The cyclic fatigue resistance of NiTi rotary instruments can be affected by immersion in disinfectants, and the specific type of file and disinfectant used will ultimately determine the extent of this impact.