Torsional properties of Ni–Ti orthodontic archwires

Commercially preformed edgewise Ni–Ti based archwires are used in orthodontic practice. Two commercially available products were tested in torsion in controlled conditions of moment and temperature, in equipment especially designed to simulate the environments in clinical use. The results are compared with the traditionally used stainless steel archwires. It is shown that by changing the martensitic transformation temperatures through variations of composition, a wide variety in the properties of the archwires can be obtained according to the necessity of the dentist.