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. 2023 Oct;73(5):680-684.
doi: 10.1016/j.identj.2022.12.007. Epub 2023 Jan 10.

Dynamic Cyclic Fatigue and Differential Scanning Calorimetry Analysis of R-Motion

Tarek Elsewify  1 , Hisham Elhalabi  2 , Bassem Eid  3
Affiliations

Dynamic Cyclic Fatigue and Differential Scanning Calorimetry Analysis of R-Motion

Tarek Elsewify et al. Int Dent J. 2023 Oct.

Abstract

Introduction: The aim of this study was to assess the dynamic cyclic fatigue resistance of an R-Motion file at simulated body temperature and document corresponding phase transformations compared to OneCurve and HyFlex EDM (HFEDM).

Methods: R-Motion (25/.06), OneCurve (25/.06), and HFEDM (25/.06) files were selected and divided into 3 groups (n = 9) according to the file type. Dynamic cyclic fatigue testing was done with a custom-made artificial stainless-steel canal that had a 90° angle of curvature and a 5-mm radius of curvature. Files were operated continuously at body temperature until fracture in the artificial canal. The time to fracture was calculated. Statistical analysis was performed, and significance was set at 5%. Phase transformation temperatures for 2 instruments of each group were analysed by differential scanning calorimetry (DSC) analysis.

Results: The highest mean time to fracture value was measured in the HFEDM group (277.84 ± 2.51), followed by the R-Motion group (115.09 ± 0.01), whilst the lowest value was found in the OneCurve group (44.28 ± 3.63). Post hoc pairwise comparisons were all statistically significant (P < .001). DSC heating curves show austinite start temperatures to be 33.94 °C and 43.32 °C and austinite finish temperatures to be 35.09 °C and 50 °C for R-Motion and HFEDM, respectively. DSC cooling curves show martensite start temperatures to be 27.54 °C and 44.52 °C and martensite finish temperatures to be 29.13 °C and 37.68 °C for R-Motion and HFEDM, respectively. DSC curves of OneCurve failed to demonstrate transformation temperatures within the tested heat range.

Conclusions: Crystalline arrangement of Ni and Ti atoms within the NiTi alloys greatly affects the dynamic cyclic fatigue resistance of the file.

Keywords: Austinite; Electric discharge machining; Martensite; Reciprocation; Rotation.

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Conflict of interest statement

Conflict of interest None disclosed.

Figures

Fig 1
Fig. 1
Custom-made dynamic cyclic fatigue-testing device used in a water bath at body temperature.
Fig 2
Fig. 2
Differential scanning calorimetry thermographs of the tested files. A, R-Motion file; B, OneCurve file; C, HyFlex EDM file.
See this image and copyright information in PMC

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