Beta titanium alloy wires are often used in orthodontic treatment for patients with Ni allergy. The purpose of this study was to compare the bending properties of beta titanium alloy wires with those of stainless steel and super-elastic Ni-Ti alloy wires. In this study, thirteen different commercial beta titanium alloy wires, one stainless steel wire, and one super-elastic Ni-Ti alloy wire (size: 0.016×0.022 inch) were examined using the three-point bending test. The specific characteristics we measured included the stiffness, active deflection range, load at 3-mm displacement, and apparent plastic deformation. Beta titanium alloy and α+β titanium alloy wires demonstrated various mechanical characteristics except for super-elasticity. The stiffness of beta titanium alloy was 30.0-54.5% that of stainless steel, and 74.1-134.2% that of super-elastic Ni-Ti alloy. The active deflection range of beta titanium alloy was 126.7-178.2% that of stainless steel. The load at 3-mm displacement of beta titanium alloy was 5.89-9.52 N, being 197.0-319.0% that of super-elastic Ni-Ti alloy. Plastic deformations ranged from 0.27-1.34 mm. As these mechanical properties vary markedly among beta titanium alloy wires from different manufacturers, understanding their specific properties is essential for clinical application.

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