The Cyclic Fatigue Resistance of Different Lengths of CM Gold Wire and CM Blue Wire NiTi Alloy Endodontic Rotary Files: An In Vitro Study

Abstract

Background: The objective of the present study was to measure and compare how the length of CM Gold Wire and CM Blue Wire NiTi alloy endodontic rotary files impacts their resistance to cyclic fatigue. Methods: A total of 40 sterile endodontic rotary files were chosen and allocated to the following study groups: (A) 25.06 CM Gold wire NiTi alloy endodontic rotary files, 31 mm in length (n = 10); (B) 25.06 CM Gold wire NiTi alloy endodontic rotary files, 25 mm in length (n = 10); (C) 25.06 CM Gold wire NiTi alloy endodontic rotary files, 21 mm in length (n = 10); and (D) 25.06 CM Blue wire NiTi alloy endodontic rotary files, 17 mm in length (n = 10). A specialized device was designed using artificial root canal systems made from stainless steel for the dynamic cyclic fatigue tests, with an apical diameter of 250 µm, curvature angle of 60°, radius of curvature of 5 mm, lengths of 31, 25, 21, and 17 mm, and a 6% taper. An individual operator determined failure of the endodontic rotary instrument through direct observation and the tests were filmed so as to precisely measure the exact time to failure. The results were analyzed using ANOVA and Weibull statistical analysis. Results: The results found statistically significant differences across all study groups (p < 0.05). Conclusions: Rotary file length is inversely proportional to the cyclic fatigue resistance of the 25.06 CM Gold wire NiTi alloy at 31 mm, 25 mm, and 21 mm in length and of the 25.06 CM Blue wire NiTi alloy 17 mm length endodontic rotary files, with a greater length contributing to lower resistance to cyclic fatigue.