Effect of heat treatment conditions on the mechanical properties of Ti-6Mo-4Sn alloy for orthodontic wires.

β-titanium alloy is frequently used in nickel-free orthodontic wires for patients with a metal allergy. However, the Young's modulus of β-titanium alloy wires is lower than that of Co-Cr-Ni alloys, causing loss of anchorage and failure to prevent unwanted tooth movements. To improve its mechanical properties for use in anchorage appliances such as transpalatal arches, Ti-6Mo-4Sn alloy wire was heat-treated at 300, 400, 500 and 600 °C for 5 min, 30 min, and 4 h in this study. Tensile testing revealed that the wire heated at 500 °C/30 min had a Young's modulus of 75 GPa and a tensile strength of 1,650 MPa - the highest among all the heat treatment groups. Therefore, Ti-6Mo-4Sn alloy wire heat-treated at 500 °C/30 min yielded mechanical properties approximating those of wires currently used for retainers and transpalatal arches.