Evaluation of self-adjusting file (SAF) damage during root canal therapy. An in vitro study

Introduction
The complex anatomy of root canal systems poses significant challenges for clinicians. In curved canals, fracture of endodontic instruments often prevents retrieval, compromising effective cleaning and shaping. The Self-Adjusting File (SAF) system was developed to enable efficient root canal preparation while reducing the risk of instrument fracture. Aim of the research: To evaluate the incidence and nature of damage to SAF files during the preparation of human root canals.

Material and methods
Forty extracted human root canals were included. Preoperative radiographic assessment was performed. Canals were prepared following the manufacturer’s protocol using the SAF system, operated in four-minute cycles. After each cycle, file integrity was assessed under 5× magnification using an operating microscope.

Results
All forty SAF files exhibited damage. A total of 34 cracks, 3 separations, and 3 other deformations were observed. Specifically, 32 strut fractures, 5 junction point failures, and 3 beam deformations were recorded. Neither canal curvature nor cross-sectional morphology significantly influenced the type or frequency of damage. The number of instrumentation cycles did not affect the timing of initial damage.

Conclusions
In this study, canal curvature, cross-sectional shape, and instrumentation time did not significantly impact SAF file damage, which predominantly involved strut fractures. Importantly, instrumentation was completed in all cases despite file damage. These results suggest that the SAF system is a safe and effective tool for root canal preparation in anatomically complex canals.