Autoclave Sterilization Differentially Degrades Cyclic Fatigue Resistance in EdgeFile X7 and Fanta File Nickel-titanium Rotary Instruments

Background The effect of autoclave sterilization on the fatigue life of modern heat-treated Nickel-Titanium (NiTi) files is debated. This study quantifies this effect on two contemporary file systems. Objective To evaluate the impact of 0, 1, and 2 autoclave cycles on the cyclic fatigue resistance of EdgeFile X7 (FireWire™) and Fanta File (AF-H Wire). Methods A total of 84 new files (25/.06, n=14 per subgroup) were tested. After autoclaving (134°C, 18 min), files were rotated at 300 RPM in a standardized steel canal (60° curve, 5mm radius) until fracture. The Number of Cycles to Failure (NCF) was calculated and analyzed using two-way ANOVA. Fractured surfaces were examined with Scanning Electron Microscopy (SEM). Results A significant interaction between file type and sterilization was found ( p < 0.001). EdgeFile had higher initial NCF (2649 ± 348) but showed a greater fatigue reduction after two cycles (38.6% loss). Fanta File had a lower initial NCF (1353 ± 168) but was more resistant to degradation (19.5% loss). Both file type ( p < 0.001) and sterilization ( p < 0.001) were significant factors. SEM confirmed fatigue failure in all samples. Discussion A significant interaction effect revealed that while EdgeFile X7 offers higher initial durability, its alloy is more susceptible to thermal degradation compared to the more stable Fanta File. Consequently, the cumulative damage induced by sterilization suggests that reuse protocols must be strictly limited to minimize the risk of intracanal fracture. Conclusion Autoclave sterilization significantly degrades the fatigue resistance of both systems, but the effect is material-dependent. The initially more durable EdgeFile was more susceptible to damage than the Fanta File. This data supports limiting the reuse of these instruments to ensure patient safety.