ABSTRACT Aim: Instruments manufactured from nickel–titanium (NiTi) have revolutionized endodontic practice due to their flexibility, shape memory, and cutting efficiency, making them ideal for navigating curved and complex root canals. Despite advancements in NiTi instrument design and metallurgy, cyclic fatigue – caused by repeated tension and compression in curved canals – remains a primary cause of file fracture. Heat-treated NiTi alloys and manufacturing innovations such as electric discharge machining (EDM) and surface modifications aim to enhance flexibility, reduce microcracks, and improve cyclic fatigue resistance. The present study focused on comparing the cyclic fatigue resistance performance of BlueShaper PRO with HyFlex EDM file. Methods: Forty-eight NiTi rotary instruments (24 – HyFlex EDM and 24 – BlueShaper PRO) in total were inspected for surface integrity and were evaluated in a precalibrated metal block simulating a 60° curvature and 5 mm radius canal. Files were rotated using a torque-controlled handpiece according to the manufacturer’s guidelines, and the number of cycles to failure (NCF) was tabulated. Results: Data analysis using the Mann–Whitney U test indicated that HyFlex EDM had a slightly higher mean NCF (17.0096) than BlueShaper PRO (16.4813). However, the difference showed no statistical significance. Conclusion: Within the limitations of the study, HyFlex EDM and BlueShaper PRO file systems showed comparable resistance to cyclic fatigue in curved root canals. Thermomechanical process plays a crucial role in improving the cyclic fatigue resistance of the NiTi files.
Hameed et al. (Fri,) studied this question.