Comparative Evaluation of Fracture Resistance of Teeth Instrumented by Self adjusting File, Protaper NEXT, and Hyflex EDM: An In vitro Study.

INTRODUCTION

The primary aim of endodontic treatment is to preserve the structural integrity of teeth while enhancing their resistance to fractures. Endodontically treated teeth are more susceptible to fractures due to the removal of tooth structure and radicular dentin. This study evaluates and compares the fracture resistance of teeth instrumented using three rotary file systems: self-adjusting file (SAF), ProTaper NEXT, and Hyflex EDM.

METHODOLOGY: Sixty extracted human mandibular premolars were randomly divided into four groups: Group I (control, uninstrumented), Group II (SAF), Group III (ProTaper NEXT), and Group IV (Hyflex EDM). Following instrumentation, root canals were obturated with gutta-percha and AH Plus sealer, except in the control group. Samples were embedded in acrylic resin, and fracture resistance was tested using a universal testing machine. Statistical analysis included analysis of variance and Tukey's post hoc tests to compare group differences.

RESULTS

The control group exhibited the highest fracture resistance (560.46 ± 125.0 N). Among the instrumented groups, SAF demonstrated the greatest fracture resistance (537.8 ± 126.3 N), followed by Hyflex EDM (440.7 ± 210.3 N), whereas ProTaper NEXT exhibited the lowest (379.93 ± 130.0 N). Significant differences were noted between groups (P < 0.001). SAF preserved dentinal integrity most effectively, whereas ProTaper NEXT induced more structural damage.

CONCLUSION

The SAF system, with its adaptive design and minimal dentin removal, was superior in preserving root strength. ProTaper NEXT, although efficient in shaping, increased fracture risk due to higher stress generation. Hyflex EDM offered intermediate outcomes, combining flexibility and reduced dentin damage.