Torsional properties of commercial nickel-titanium wires during activationand deactivation

This study evaluated torsional moments on activation and deactivation in co mmercial, nickel-titanium wires that are intended for use in the initial ph ases of orthodontic treatment. Nine commercial, rectangular nickel-titanium wires (0.017 x 0.025 in) were tested in torsion. One wire was conventional nickel-titanium, and the others were superelastic nickel-titanium wires. T he specimens were tested in a torsiometer for rotations between 10 and 40 d egrees in activation and deactivation. Wires E27, RF and R had the highest moments during activation and deactivation, without evidence of the plateau typical of the superelastic effect. Plateaus of constant moment were obser ved for wires C27, C35, E35, MO, NS, and NI. Torsional moments varied among superelastic nickel-titanium wires, even with wires that had the same tran sition temperature range. Some superelastic wires had torsional moments tha t were comparable with conventional nickel-titanium wires.