The effect of temperature change on the cyclic fatigue resistance of Three Rotary Nickel Titanium instruments with different Heat Treatment

Abstract

This study aimed to compare the cyclic fatigue resistance of three NiTi rotary systems (RaCe, 2Shape, M-pro) at the room and body temperatures. As well, the phase transformation of the tested instruments was investigated using differential scanning calorimetry Total of sixty files #25 .06 of these brands were selected for the study, Cyclic fatigue testing was done using a dynamic cyclic fatigue testing device along with a custom made artificial stainless-steel canal that had 60° and 3mm radius of curvature. There were three groups divided according to the file type (n=20). Each group was subdivided into 2 subgroups according to the temperature during the test: Subgroup 1 (room temperature 22 ± 0.5°C) and Subgroup 2 (body temperature 37 ± 0.5°C). Samples were rotated continuously in an axial motion until fracture in the artificial canals to simulate clinical conditions. Five test specimens of RaCe, 2Shape, and M-pro all of the size #25 .06 were investigated using differential scanning calorimetry. Results showed that generally, the 2Shape file showed the highest cyclic fatigue resistance followed by the M-pro file and the least fatigue resistance was the RaCe file. At room temperature, there was a highly significant difference between the three files. While at the body temperature the 2Shape file and the RaCe file were significantly different but there was no significant difference between the 2Shape and the M-pro.