Cyclic Fatigue Resistance of New Endodontic Files in Reciprocal vs. Rotational Motion

Objectives: To evaluate the flexural fatigue resistance of WaveOne Primary and Protaper NEXT X2 NiTi files used in reciprocating and rotation motions. Materials and methods: A 20 files, 25mm long for use in reciprocating [Group 1: WaveOne Primary, n=10] and continuous rotation [Group 2: Protaper NEXT X2, n=10] were selected. All instruments were operated in a static model for cyclic fatigue testing which was conducted in a device that allowed for a reproducible simulation of an instrument confined in a curved canal. The instruments were activated by a torque-controlled motor [X-smart plus, Dentspy Maillefer] using the preset program WaveOne ALL for the WaveOne instruments and the preset program for the Ppotaper NEXT X2 instruments. All instruments were rotated until fracture occurred. The number of cycles to failure [NCF] for each instrument was calculated. The length of the fractured file tip was mea- sured. NCF data were statistically analyzed by Student t -test. Results: The statistical analysis revealed a statistically significant differences [p<0.001] between two groups. WaveOne primary instruments were associated with a significantly greater NCF. Conclusions: The test results showed significantly increased cyclic fatigue resistance of the file with reciprocal motions compared to continuous rotation. No differences were found between the lengths of the fractured segment.