Effect of movement kinematics on the cyclic fatigue resistance of nickel-titanium instruments

AimTo compare the cyclic fatigue resistance of new generation OneShape and WaveOne instruments when used with different kinematics. MethodologyAn artificial canal, made of stainless steel with an inner diameter of 1.5mm, a 60 degrees angle of curvature and a curvature radius of 3mm, was used for cyclic fatigue test of new generation OneShape and WaveOne instruments. Groups were as follows (n=20): 150 degrees-30 degrees, 210 degrees-30 degrees, 360 degrees-30 degrees and continuous rotation. The time to fracture was recorded in seconds, and the data were analysed statistically using a two-way anova and LSD tests (P=0.05). ResultsCyclic fatigue resistance was significantly affected by the movement kinematics (P<0.001). The cyclic fatigue resistance of the new generation OneShape instruments increased significantly when operated in various reciprocation motions (150 degrees CW-30 degrees CCW, 210 degrees CW-30 degrees CCW and 360 degrees CW-30 degrees CCW) compared with the continuous rotation mode. New generation OneShape instruments had significantly more resistance to fracture under cyclic loading than WaveOne instruments (P<0.001). ConclusionsWhen using new generation OneShape and WaveOne instruments, all the reciprocating motions (150 degrees CW-30 degrees CCW, 210 degrees CW-30 degrees CCW and 360 degrees CW-30 degrees CCW) resulted in extended fatigue life when compared with continuous rotation.