The characteristics of super-elastic Ni-Ti wires in three-point bending. Part I: The effect of temperature.

The load-deflection behaviour of a number of commercially available superalloy nickel-titanium orthodontic wires has been examined in three-point bending over the temperature range 5-50 degrees C. The loading and unloading curves and plateau regions are found to be closely related to temperature with the stiffness decreasing quite dramatically over a narrow temperature range. The position of this range depends on the material being tested as there are marked differences due to the differing processing methods of the manufacturer. Force values at mouth temperature can differ by 600 per cent for wires of the same nominal diameter made by different manufacturers.