Oxidized Ethylene Glycol/ZrO₂-coated NiTi Orthodontic Arch Wires: Surface Characterization and Electrochemical and Corrosion Studies

Background: Orthodontic arch wires, typically made of Nickel Titanium (NiTi), are widely utilized in dental procedures for correcting teeth misalignment and jaw issues due to their favorable mechanical attributes and cost-effectiveness. However, these NiTi wires are prone to corrosion in the oral environment, leading to diminished mechanical stability, compromised aesthetics, and potential health concerns for patients. Objective: There is a growing demand to augment the corrosion resistance and stability of orthodontic wires. Hence, this study aimed to address these issues. Herein, zirconium dioxide (ZrO2) and oxidized ethylene glycol (OEG) films were deposited onto NiTi wires to improve the corrosion resistance and stability. Methods: NiTi wires were modified by a two-step process involving electrodeposition of ZrO2 and oxidized ethylene glycol (OEG) film. The surface characterizations of coated material (OEG/ZrO2/NiTi) were carried out by using Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive X-ray Spectroscopy (EDS), and Electron Microprobe Analysis (EMap) to confirm the elemental composition of the coated NiTi wire. Results: The OEG/ZrO2/NiTi wire exhibited a potentiodynamic polarization resistance of 547037 Ω and higher stability than the bare NiTi wire (396421 Ω). The corrosion rate for OEG/ZrO2/NiTi wire was found to be 0.040 mm/year, which was comparatively lower than a bare NiTi wire (0.069 mm/year). Due to the formation of OEG/ZrO2 film, NiTi wire became electrically insulative and showed a higher impedance than bare NiTi wire. Conclusion: The bilayer coating of ZrO2 and OEG has proven to significantly improve the corrosion resistance and stability of the wires. Thus, these materials can be considered for coating orthodontic arch wires with improved corrosion stability.