Cyclic fatigue analysis of Reciproc R25® instruments with different kinematics.

This study aimed to compare the cyclic fatigue resistance of Reciproc (R) instruments when used with different kinematics (150 degrees counterclockwise (CCW)-30 degrees clockwise (CW), 270 degrees CCW-30 degrees CW, 360 degrees CCW-30 degrees CW and continuous rotation). Various kinematics were tested in steel canals with a 3mm radius and a 60 degrees angle of curvature as follows (n=20): 150 degrees CCW-30 degrees CW, 270 degrees CCW-30 degrees CW, 360 degrees CCW-30 degrees CW and 360 degrees CCW (rotary motion). Reciproc R25 (R) instruments were used until fracture occurred. The time to fracture was recorded in seconds. The data were statistically analysed using a one-way analysis of variance and Tukey's post-hoc tests (P=.05). The cyclic fatigue resistance of Reciproc R25 (R) instruments used with various kinematics in decreasing order was as follows: 150 degrees CCW-30 degrees CW>270 degrees CCW-30 degrees CW=360 degrees CCW-30 degrees CW>360 degrees CCW rotary motion. The 150 degrees CCW-30 degrees CW reciprocating motion had the best performance in time to fracture. All reciprocating motions (150 degrees CCW-30 degrees CW, 270 degrees CCW-30 degrees CW and 360 degrees CCW-30 degrees CW) resulted in a longer mean duration to failure compared with the 360 degrees CCW rotary motion.