Bending and torsional properties of commercial nickel-titanium orthodontic wires

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The aim of this study was to investigate the force delivery for a variety of types and sizes of commercially available nickel-titanium wires. The relationship of the magnitude of the force and the tooth displacement in a severe crowding case is discussed. Nine brands of nickel-titanium orthodontic wires in a variety of sizes were examined with a three-point bending test and a torsion test at 37℃. Most wires exhibited superelastic behavior for the three-point bending and torsion tests at 37℃. In the three-point bending test, the variation of the average load at 1.5mm deflection during unloading ranged from 0kgf for Copper Ni-Ti 40℃ with a 0.016×0.022 inch cross-section to 0.46kgf for ORTHO LINE with a 0.021×0.025 inch cross-section. The average torsion load at a rotation of 30°on deactivation varied from 0kgf-cm for Copper Ni-Ti 40℃ to 0.023kgf-cm for ORTHO LINE. The predicted torsional angles for the maxillary arch in the severe crowding case were smaller than expected and only three positions exceeded 20°. Considering the play between bracket slots and archwire, nickel-titanium orthodontic wires of the superelastic type may not exhibit superelastic properties for torsion in most clinical situations.
北海道医療大学の論文