Effect of reciprocation usage of nickel-titanium rotary files on the cyclic fatigue resistance.

The use of reciprocating motion for a nickel-titanium file has been claimed to increase its resistance to fatigue in comparison to continuous rotation. The purpose of this study was to investigate the effect using a reciprocating motion instead of continuous rotation for nickel-titanium files on their cyclic fatigue resistance. Cyclic fatigue tests simulating clinical use with ProTaper F2 and ProFile #25/.06 instruments were carried out in an artificial stainless-steel root canal with a 1.5 mm inner diameter, 5 mm radius and 60° angle of curvature. The instruments were driven using either continuous rotation or reciprocation until fracture. For the reciprocation, the rotation angles were set to 140° clockwise and 45° counterclockwise. The number of cycles to fracture was determined by measuring the time to fracture. Statistical analysis was performed using two-way anova. There were no significant differences in the fracture cycles due to the use of reciprocation or continuous rotation for either instrument. The results found using reciprocation were comparable to those found using continuous rotation with regard to the cyclic fatigue resistance of nickel-titanium rotary files.