Abstract
Objective: This study sought to assess the effect of cryogenic treatment on cyclic fatigue of Neoniti and Reciproc nickel-titanium (NiTi) rotary files. This in vitro, experimental study was performed on 48 Neoniti and Reciproc NiTi rotary files (#25, 6% taper) in two subgroups with and without cryogenic treatment. The files in cryogenic subgroups were stored in liquid nitrogen chamber at -196°C for 24 h. Next, they were placed at room temperature (25°C) to gradually warm up. Stainless steel (SS) blocks were used to standardize the degree of rotation of the files. The SS blocks simulated a root canal with the negative pattern of gutta-percha with 0.08 taper, #25 tip size, and 45° canal curvature. Each endodontic file was rotated in this canal until fracture. The time until fracture was recorded by a digital chronometer. Time to fracture was used to calculate the number of rotations before file fracture as the cyclic fatigue scale. Results: The mean cyclic fatigue resistance of both Neoniti and Reciproc rotary files in cryogenic subgroups was significantly higher than that in non-cryogenic control subgroups (P<0.05). Cryogenic treatment can significantly increase the cyclic fatigue resistance of Neoniti and Reciproc NiTi rotary files.
In vitro comparison of cyclic fatigue resistance of TruNatomy in single and double curvature canals compared with different nickel-titanium rotary instruments