All instrument movements were associated with apically extruded debris. However, the 150° CCW-30° CW and 270° CCW-30° CW reciprocating motions were associated with less extrusion than continuous rotation.

Movement kinematics affected the amount of apically extruded debris when using Twisted File Adaptive instruments.

No abstract

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.

Within the limitations of the present study, the use of nano-hybrid composite, short fiber-reinforced composite, bulk-fill flowable composite, and glass ionomer cement as an intra-orifice barrier may be useful in reinforcing roots. MTA placement (MTA Angelus or Micro Mega MTA) did not significantly increase the fracture resistance of endodontically treated roots compared to the control groups, however Biodentine did.