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

Document Type : Original articles

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Ain Shams University

Abstract

Aim
This manuscript aimed to compare the cyclic fatigue resistance of the RaCe, 2Shape, and M-pro instruments at room (22°C) and body (37°C) temperatures and to investigate their phase transformation.
Materials and methods
A total of 60 files #25 .06 of the RaCe, 2Shape, and M-pro instruments were selected. A dynamic cyclic fatigue testing device with a custom-made stainless-steel canal was used that had 60° and 3mm radius of curvature. Files were divided into three groups (n=20). Each group was subdivided into 2 subgroups according to the temperature during the test: SubgroupA (room temperature 22±0.5°C) and SubgroupB (body temperature 37±0.5°C). Samples were rotated continuously in an axial motion until fracture occurred then number of cycles to fracture (NCF) was calculated. Five test specimens of each file type size 25/.06 were investigated using differential scanning calorimetry.
Results
The 2Shape file showed the highest cyclic fatigue resistance followed by the M-pro file and the least was the RaCe file. in subgroup A, there was a significant difference between the three files. in subgroup B, the 2Shape file and the RaCe file were significantly different but there was no significant difference between the 2Shape and the M-pro.
The rise in temperature was accompanied by a decrease in the cyclic fatigue resistance of the RaCe and the 2Shape files. While there was an insignificant decrease in the M-pro file.
Conclusion
The 2Shape has the highest cyclic fatigue resistance among the tested instruments. The environmental temperature plays a key role in the fatigue behavior.

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