Introduction: Ni-Ti instruments used in reciprocation reduce instrument
separation. Reciproc-Blue is a thermally-treated NiTi single reciprocating system
coated by an oxide layer caused by the thermomechanical process improving fatigue
resistance. Aim: To evaluate the effect of different kinematics on the cyclic fatigue
resistance of the Reciproc-Blue file and examine the influence of different canal
curvatures on its cyclic fatigue resistance. Method: Eighty new Reciproc-Blue files
divided into four groups (n=20) according to the reciprocation angles 150°CCW–
30°CW, 210°CCW–30°CW, 90°CCW–40°CW and 360°CCW(continuous-rotation),
each group was subdivided into two subgroups (n=10) according to the canal curvature
45°and 60°angles. All instruments were operated until the fracture occurred, Cyclic
fatigue resistance was determined by recording the time to fracture in seconds. Data
were statistically analyzed by applying ANOVA test followed by Post Hoc Tukey test at
95% significance level. Results: all reciprocating motions yielded a significant increase
in time to failure when compared to continuous rotation in both canal curvatures. There
was a significant difference in time to failure among all reciprocating groups in both
canal curvatures. All experimental groups revealed greater cyclic fatigue resistance
at 45°compared to 60°angles of curvature. There was no significant difference in
the length of the fractured fragment for all tested groups in both canal curvatures.
Conclusion: Movement kinematics has a significant influence on the cyclic fatigue
life of Reciproc-Blue instruments. Also, Increasing the angle of progression for each
reciprocation cycle decreases the cyclic fatigue resistance of NiTi instruments.