Influence of static and dynamic cyclic fatigue tests on the lifespan of four reciprocating systems at different temperatures.

AIM: To compare the cyclic fatigue resistance of four reciprocating single-file systems within artificial stainless-steel canals at two temperatures using different kinematics. METHODOLOGY: A total of 240 instruments, Reciproc Blue, Reciproc, WaveOne Gold and WaveOne, (60 of each), were tested at room and intracanal temperature using both a static and a dynamic model (n = 15) in a stainless-steel artificial canal with an inner diameter of 1.5 mm, 60 degrees angle of curvature and 5 mm radius of curvature until fracture occurred. The time to fracture was measured in seconds using a digital chronometer, and data were analysed using one-way analysis of variance and Bonferroni tests. RESULTS: WaveOne instruments had significantly less fatigue resistance compared to that of other systems in all conditions (P < 0.05). Comparison of the results from the static and dynamic models at both temperatures revealed that fatigue resistance was significantly increased in the dynamic model for all the instrument systems (P < 0.05). Temperature did not influence the cyclic fatigue resistance results (P > 0.05). There were no significant differences in the mean length of the fractured fragments of the various instruments tested (P > 0.05). CONCLUSION: WaveOne files had a shorter cyclic fatigue life. The dynamic axial movement extended the cyclic fatigue life, but it did not have any influence on the comparison among the instruments tested in respect of the static test. Temperature did not significantly affect the cyclic fatigue of these nickel-titanium files.