An in Vitro Cyclic Fatigue Analysis of Different Endodontic Nickel-titanium Rotary Instruments

Introduction: The study compared Twisted File (TF) with 3 traditionally manufactured systems to determine whether changes in the manufacturing process improved the cyclic fatigue resistance.

Methods: Four rotary file systems, (1) ProFile (PF), (2) Mtwo, (3) K3, and (4) TF, were tested in artificial canals with 45° and 90° angles of curvature. Ten instruments each of the 4 file systems were tested in both angles of curvature (n = 10). All instruments had identical size and taper (.06/0.25 tip diameter).

Results: A statistically significant difference (P < .05) was noted between TF and other nickel-titanium instruments in both 45° and 90° angles of curvature. TF showed the greatest mean number of cycles to failure. There was no statistical difference between PF and K3 (P > .05) in both canal curvatures; however, statistically significant difference (P < .05) was observed between Mtwo and the other 2 traditionally manufactured instruments. Mtwo showed the lowest mean number of cycles to failure.

Conclusions: Under the conditions of this study, size .06/0.25 TF was significantly more resistant to fatigue than the other 3 instrument systems produced with the traditional grinding process.