Comparison of the elastic properties of nickel-titanium and beta titanium arch wires.

The elastic strength, stiffness, and range of two titanium alloys are compared as a function of wire configuration. From the four beta titanium and eight nickel-titanium sizes available, all arch wire permutations were evaluated both in bending and in torsion. Results show that the stiffnesses of the two alloy compositions overlap substantially, except for those wires with the lowest and the highest stiffnesses--that is, the 0.016 and 0.018 inch nickel-titanium and the 0.017 by 0.025 and 0.019 by 0.025 inch beta titanium arch wires, respectively. To conclude, both "variable-cross-section" and "variable-modulus" orthodontics are illustrated within the context of an equivalent wire stiffness chart which includes conventional stainless steel arch wires.