Effect of interrupted motion on the cyclic fatigue resistance of reciprocating nickel-titanium instruments.

AIM: To compare the cyclic fatigue resistances of WaveOne Gold (Denstply Sirona, Ballaigues, Switzerland), WaveOne (Dentsply Sirona) and Reciproc (VDW, Munich, Germany) in interrupted reciprocation.

METHODOLOGY: Three groups of 18 instruments each of WaveOne Gold Primary, WaveOne Primary and Reciproc R25 were subjected to cyclic fatigue tests in reciprocation and interrupted reciprocation. The instruments in group 1 were tested in reciprocation, whereas in groups 2 and 3, reciprocation was interrupted for 1 s in every 5 s and 10 s, respectively. Cyclic fatigue resistance was tested using dynamic test devices in stainless steel, curved canals (60°, r = 5 mm) until fracture, and the time to fracture values were recorded. The lengths of the fractured tips were also recorded, and fractured surfaces were examined with a scanning electron microscope (SEM). Data were evaluated by one-way analysis of variance and Tukey's tests.

RESULTS: The cyclic fatigue resistance of WaveOne Gold Primary was not affected by the interruptions (P > 0.05) and exhibited significantly greater cyclic fatigue resistance than WaveOne Primary and Reciproc R25 in all groups (P < 0.05). Interruptions reduced the cyclic fatigue resistance of WaveOne Primary and Reciproc R25 significantly (P < 0.05).

CONCLUSION: Interrupted reciprocation reduced the cyclic fatigue resistance of Reciproc R25 and WaveOne Primary. The cyclic fatigue resistance of WaveOne Gold Primary was greater than that of WaveOne Primary and was not dependent on the occurrence of interruptions.