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

This study aimed to compare the cyclic fatigue resistance of Reciproc® instruments when used with different kinematics (150° counterclockwise (CCW)–30° clockwise (CW), 270° CCW–30° CW, 360° CCW–30° CW and continuous rotation). Various kinematics were tested in steel canals with a 3 mm radius and a 60° angle of curvature as follows (n = 20): 150° CCW–30° CW, 270° CCW–30° CW, 360° CCW–30° CW and 360° CCW (rotary motion). Reciproc R25® 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® instruments used with various kinematics in decreasing order was as follows: 150° CCW–30° CW > 270° CCW–30° CW = 360° CCW–30° CW > 360° CCW rotary motion. The 150° CCW–30° CW reciprocating motion had the best performance in time to fracture. All reciprocating motions (150° CCW–30° CW, 270° CCW–30° CW and 360° CCW–30° CW) resulted in a longer mean duration to failure compared with the 360° CCW rotary motion.