Evaluation of the Cyclic Fatigue Resistance and Mode of Failure of XP-4D Rotary Files at Different Rotational Speeds and File Sizes: An In-Vitro Study v1

Repeated clinical use, sterilization, and exposure to irrigants can further deteriorate the surface and reduce fatigue resistance (Hamdy et al., 2023). When large or wide-taper files are used at high rotational speeds, the mechanical stress on the file increases considerably. If this is combined with reduced flexibility or compromised surface integrity, the chances of early failure rise significantly. Instrument separation during root canal treatment not only complicates access to the apical third but can also affect cleaning and shaping quality, leading to poorer treatment outcomes. Understanding how cyclic fatigue, failure pattern, interact under different operating conditions is therefore crucial for improving file design, alloy treatment, and safe clinical use.