Influence of different angles of reciprocation on the cyclic fatigue of nickel-titanium endodontic instruments.

INTRODUCTION

The purpose of this study was to evaluate cyclic fatigue fracture resistance of engine-driven nickel-titanium (K3XF) instruments under reciprocating movement in various angles.

METHODS

Fifty K3XF size 40 taper 0.06 nickel-titanium instruments were divided randomly into 5 groups of 10 each. All instruments were subjected to cyclic fatigue tests. Instruments in groups 1-4 were tested by using different reciprocating motions, whereas instruments of group 5 (control group) were used in continuous rotation. All instruments were rotated or reciprocated until fracture occurred. Time to fracture was recorded, and data were statistically analyzed by using one-way analysis of variance, followed by Tukey honestly significant difference test for comparison between different groups.

RESULTS

All reciprocating groups (groups 1-4) showed a significant increase in time to failure when compared with group 5 (continuous rotation) (P < .05). Mean time was significantly higher in group 1, followed by group 2. No significant difference was found between groups 3 and 4 (P = .251). Increasing the clockwise angle of reciprocation and consequently increasing the angle of progression for each reciprocation cycle reduced the resistance to cyclic fatigue.

CONCLUSIONS

Movement kinematics (reciprocating movements in various angles) had a significant influence on the cyclic fatigue life of the tested nickel-titanium instruments.