Investigation of Nitinol Alloys in Orthodontic Wires: Properties, Applications, and Mechanisms

مهندسی متالورژی و مواد

Article 5, Volume 36, Issue 1 - Serial Number 37, April 2025, Pages 61-88   

Document Type: Original Articles

DOI: 10.22067/jmme.2025.91160.1171

Authors

Mohammadreza Seyedi Golmahaleh¹; Soroush Parvizi^{* 2}; Zahra Alirezaei²

¹Faculty of Engineering and Materials Science, Sharif University of Technology. Tehran. Iran

²Department of Materials and Metallurgy, Shahid Rajaee Teacher Training University, Tehran, Iran

Abstract

Nitinol (NiTi), due to its unique properties such as shape memory effect, fatigue resistance, and high biocompatibility, has been extensively used in medical and engineering fields. One of the most significant applications of this alloy is in the production of orthodontic wires, which, due to their ability to apply constant and low-force pressure, enhance the treatment process and reduce its duration. However, several challenges, including nickel ion release and its impact on biocompatibility, chemical composition control, and manufacturing process optimization, still require further investigation. This study examines the effects of manufacturing processes, including induction melting and powder metallurgy, on the mechanical and phase properties of Nitinol wires. Additionally, the role of heat treatment and aging in structural modification and improvement of the superelastic property of this alloy has been analyzed. The investigations indicate that by precisely controlling the chemical composition and preventing titanium oxidation during production, the functional properties of Nitinol can be optimized. Furthermore, the application of protective coatings such as Ni-P-NiTi plays a significant role in reducing nickel ion release and increasing the corrosion resistance of this alloy. The results obtained from the evaluation of the restoring force of Nitinol wires indicate that aging at a temperature range of 400 to 450°C for less than 60 minutes improves superelasticity and enhances mechanical strength. Finally, the influence of environmental factors such as pH and temperature on the corrosion resistance of this alloy has been examined, and the results suggest that applying surface coatings can significantly reduce the corrosion rate.

Keywords

Nitinol; shape memory; superelasticity; biocompatibility; corrosion resistance; heat treatment; coating

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