Cyclic Fatigue Resistance of One Curve, Hyflex EDM and Neolix NiTi Files in Simulated Curved Canals

Objectives: The aim was to evaluate the cyclic fatigue resistance of One curve (OC), Hyflex EDM (HEDM) and Neolix (NE) files in simulated curved canals.

Study Design: Forty-five NiTi files in three groups (n=15 files/group) of OC, HEDM and NE files, respectively tested in a custom-made cyclic fatigue testing device designed to have 60o curvature in a stainless-steel simulated canal with 5 mm radius of curvature. All files rotated until fracture occur to determine the time to fracture, number of cycles to fractures (NCF) and length of the fractured fragment. Scanning electron microscope (SEM) was used to examine the fracture surface topography of the broken instruments (n=2/group). ANOVA and Tukey test was used to statistically analyses the results at significance level at 95% confidence level.

Results: OC files needed more time to fracture compared to HEDM and NE files (p<0.05), respectively, However, there was no significant difference of NCF between HEDM and OC file (p>0.05). NE file has significantly lower NCF than that of HEDM and OC file (p<0.05), respectively. There was no significant difference between all files in the mean length of the fractured fragment (p>0.05). SEM images of NE showed more pores compared to OC and HEDM, however, OC revealed rougher fractured surface than that of HEDM and NE.

Conclusions: OC and HEDM showed comparable resistance to cyclic fatigue in simulated curved canals, despite metallurgical differences among those NiTi file systems. NE files showed the lowest resistance to cyclic fatigue compared to HEDM and OC file.