Beyond the Curve: Evaluating Performance and Integrity of Modern NiTi Systems Under Repeated Use

Aim: In endodontic treatment, nickel-titanium (NiTi) instruments, revolutionized root canal instrumentation owing to their superior flexibility, resistance to torsional fatigue, and shape memory. Among contemporary NiTi systems, ProTaper Ultimate (PU) (Dentsply Sirona, Ballaigues, Switzerland) and Fanta AF Rising (AF-R) (Fanta Dental, Shanghai, China) are widely utilized, yet differ consid-erably in terms of their metallurgical composition, design, and clinical performance. Although both systems are commonly used in clinical practice, there is a paucity of comparative data evaluating their canal centering ability, apical transportation, post-sterilization performance, and structural integrity after multiple uses. This study aimed to compare the shaping performance, apical transportation, and structural integrity of two thermally treated NiTi rotary file systems (AF-R and PU) after repeated use and sterilization cycles in standardized simulated curved canals.Material and Methods: Sixty standardized resin blocks with 45° curvature were prepared using either AF-R or PU instruments. Each group was divided into 3 subgroups based on the number of uses and sterilizations (1st, 2nd, and 3rd cycle). Canal centering and transportation were evaluated at 5 reference levels using high-resolution digital overlays and ImageJ software. File deformation and separation were assessed under stereomicroscopy. Statistical analysis was performed using the Kruskal–Wallis and Bonferroni tests, with P < 0.05 considered statistically significant.Results: AF-R demonstrated significantly superior canal centering (P = 0.008) and lower apical transportation (P = 0.004) across all refer- ence levels and usage cycles. No file separations occurred in the AF-R group, whereas PU exhibited progressive deformation and a 6.7% separation rate by the third cycle. AF-R instruments retained their original shape and mechanical behavior after autoclave sterilization.Conclusion: AF-R exhibited enhanced shaping precision, structural durability, and resistance to apical transportation compared to PU, especially after multiple clinical uses and sterilization. These findings support its suitability for minimally invasive and cost-effec- tive endodontic practice, particularly in anatomically complex canals.