A comparative evaluation of cyclic fatigue resistance of different endodontic Nickel-Titanium rotary files in a curved canal: an in-vitro study

Background. The objective of this study was to analyze the resistance ability to cyclic fatigue failure of ProTaper Universal files (PTU; size 25, 0.08 taper), ProTaper Gold files (PTG; size 25, 0.08 taper), and Hyflex CM files (HCM; size 25, 0.06 taper). Materials and methods. An overall number of 120 new instruments of PTU, PTG, and HCM were tested in a stainless steel block that replicated artificial root canal morphology with an angle of curving point (45°) and the radius of curvature (5mm). Forty files from each group were employed inside the canal until fracture. The timing of the instruments fracture was recorded by a digital stopwatch. The time to separation was analyzed and the figure of cycles to failure (NCF) of the rotary files was measured and registered. The obtained data was statistically analyzed. Results. All files suffered a fracture at a precise number of cycles. The highest resistance to breakage of the rotating files demonstrated a superior number of cycles to fatigue separation. The HCM and PTG files showed greater grades of NCF than PTU files with significant differences (P <0.05). The HCM and PTG groups recorded comparable standards of resistance to repeated fatigue inside the canal (P >0.05). On the contrary, PTU exhibited the smallest competence to fracture resistance among the other tested files. Conclusions. The present findings showed that the HCM files appeared to be proper for shaping complicated root canal system as HCM files illustrated a remarkable performance in fatigue resistance followed by PTG and PTU, respectively.