The effect of Cu-doping on the corrosion behavior of NiTi alloy arch wires under simulated clinical conditions

Allergy to nickel based alloy arch wires, which is largely induced by corrosion behavior, can cause severe problems during the orthodontic treatment. However, no consensus has been reached in the comparison of anti-corrosion behavior between Nickel-Titanium (NiTi) and Copper Nickel-Titanium (CuNiTi) alloy arch wires. Herein, the anti-corrosion behavior of NiTi and CuNiTi arch wires was simultaneously studied in artificial saliva under loading stress to simulate clinical conditions. Scanning electron microscope (SEM) was utilized to detect the surface morphology and following x-ray diffraction (XRD), electrochemical impedance spectroscopy (EIS) as well as x-ray photoelectron spectroscopy (XPS) were used to evaluate the potential anti-corrosion tendency of the arch wires, implying that CuNiTi arch wire had more defects on the surface yet intriguingly less release of Ni compared with NiTi arch wire after test. Both groups of arch wires were more corroded when loaded with clinic-simulating stress, nevertheless, the doping of Cu element can reduce the release of Ni to some extent, which is conducive to lowering the probability of metal allergy and supplying meaningful instructions for the manufactories and orthodontists.