Evaluation of bending test, cyclic fatigue, and buckling resistance test using rotary Nickel-Titanium files of three types: An in vitro study.

AIM: This study aimed to compare the bending resistance, cyclic fatigue resistance, and buckling resistance of three types of Nickel-Titanium (NiTi) rotary files. MATERIALS AND METHODS: Ninety NiTi files (size 25.06 or equivalent) were divided into three groups (n = 30). Endostar E3 Azure Basic, ProTaper Ultimate, and TruNatomy. Each group was subdivided (n = 10) for bending, cyclic fatigue, and buckling resistance tests. After microscopic inspection (Zumax OMS2350, China), fractured segments were measured with an electronic digital caliper (Adoric, Taiwan). Data were analyzed through one-way Analysis of Variance and Scheffé's post hoc test, with significance set at P < 0.05. RESULTS: Significant differences were found across all properties (P < 0.001). Endostar exhibited the highest bending resistance, followed by ProTaper Ultimate and TruNatomy. For buckling, ProTaper Ultimate demonstrated the greatest resistance, followed by Endostar and TruNatomy. In cyclic fatigue testing, TruNatomy achieved the highest number of cycles to fracture (NCF), while ProTaper Ultimate showed the lowest. CONCLUSION: Within the limitations of this study, TruNatomy proved to be the most flexible and fatigue-resistant system but exhibited the lowest buckling resistance. Conversely, ProTaper Ultimate demonstrated the highest buckling resistance but the lowest fatigue life, while Endostar offered balanced performance across all the parameters. These findings suggest that instrument selection should be tailored to specific canal anatomies and clinical requirements to optimize safety and minimize the risk of separation.