Effect of EDTA solution on corrosion fatigue of Ni-Ti files with different shapes.

This study aimed to evaluate the effect of EDTA solutions (3% and 10% EDTA•2Na) on corrosion fatigue of three Ni-Ti files with different shapes, in comparison with other solutions (6% NaClO, 3% H2O2, 0.9% NaCl and distilled water). Ni-Ti files were subjected to rotational bending in a bent glass tube (30° and 60° angles) filled with the solutions, and the number of rotations to failure was counted. At 30° bent angle, files in the two EDTA solutions showed significantly lower resistance than those in distilled water, but no significant difference was found between the two EDTA solutions. Fatigue resistance of two tested files in the two EDTA solutions was not significantly different from those in the other three solutions, whereas one file in EDTA solutions showed significantly lower resistance than that in 3% H2O2. At 60° bent angle, early failure within 1-2.5 min was observed for all tested files, and no significant difference was found among the six solutions. At both angles, significant differences in fatigue resistance were observed among the three tested files, which could be related to the difference in the cross-sectional shapes of the files.