Cyclic fatigue of ProTaper rotary nickel-titanium instruments in artificial canals with 2 different radii of curvature

Abstract

Objective: This study compared the cyclic fatigue resistance of ProTaper rotary nickel-titanium (NiTi) files in artificial canals with 2 different radii of curvature.

Study design: One hundred ProTaper rotary instruments were used in this study. Twenty files of each size (S1, S2, F1, F2, and F3) were tested. Cyclic fatigue testing was performed using a device that allowed the instruments to rotate freely inside stainless steel artificial canals with radii of curvature of 5 and 10 mm. The number of cycles to fracture was recorded for each file and the data were analyzed using a t-test.

Results: The 5-mm radius group had significantly fewer cycles to fracture than the 10-mm radius group for all file sizes. For sizes F2 and F3, the difference between the 5 and 10-mm radius groups was highly significant (P < .001). For the 10-mm group, the difference between S1 and F3 was significant (P < .05). For the more abrupt 5-mm radius group, the difference between S1-F2, S2-F2, and F1-F2 was statistically significant. The difference between S1-F3, S2-F3, and F1-F3 was highly significant (P < .001).

Conclusion: Cyclic fatigue resistance of ProTaper instruments was dependent on both instrument size and radius of curvature. Especially larger-size instruments should be used with great care in curved canals.