The effect of electro-thermal treatment of stainless steel arch wire on mechanical properties and cell proliferation
Published Online: Jul 20, 2021
Page range: 75 - 86
Received: Aug 01, 2019
Accepted: Feb 01, 2020
DOI: https://doi.org/10.21307/aoj-2020-010
© 2020 Yingzhi Gu et al., published by Sciendo
This work is licensed under the Creative Commons Attribution 4.0 International License.
Background
Electric resistance heat treatment may be performed on orthodontic arch wires, but it remains unclear whether this procedure reliably provides better mechanical properties or whether an austenite phase transition affords less cytotoxicity and less arch wire width change.
Methods
Stainless steel (SS) arch wires of 0.017 × 0.025 and 0.019 × 0.025 inches in size were heat-treated using a spot welder for eight seconds at power settings of 2, 4, 6 and 8. The surface morphology, coefficient of friction (COF), flexural modulus, cytotoxicity, austenitic content, colour change and arch width of the samples were subsequently analysed.
Results
The COF, flexural modulus and austenitic content of the orthodontic SS arch wires increased after heat treatment. SS wires appearing brownish-yellow and blue exhibited higher flexural moduli. The heat treatment of the SS wires did not significantly increase arch wire width or cause cytotoxicity.
Conclusions
Electric resistance heat treatment of SS arch wires is a feasible method to improve the flexural modulus without widening the arch wire and increasing cytotoxicity. The colour of the wire helps determine the heating status, and the maximum flexural modulus of the wires is obtained when the colour changes to brownish-yellow.