Comparison of deactivation forces between thermally activated nickel-titanium archwires.

OBJECTIVE: The aim of the present study was to investigate and compare load-deflection characteristics of commercially available thermally activated nickel-titanium archwires using a three-point bending test. MATERIALS AND METHODS: Sixty thermally activated 0.019×0.025-inch nickel-titanium archwires from six different manufacturers were investigated. The superelastic properties of these archwires were evaluated by conducting a three-point bending test under identical testing conditions. Forces generated at deactivation for a deflection of 0.5, 1, 2 and 3 mm at a temperature of 37° C were selected for statistical comparison of the data. The results of forces of deactivation at all deflections applied were compared by two-way analysis of variance and the Tukey test. RESULTS: Statistical differences (P<0.05) were found at all force levels during deactivations. The results showed that the range of forces displayed great variation in quantitative behaviour. None of the archwires showed permanent deformation after the three-point bending test. CONCLUSIONS: This study revealed significant differences in deactivation forces among the six types of thermally activated nickel-titanium archwires tested. NiTinol Termoativado (Aditek) and NeoSentalloy F200 (GAC) produced the least amount of force in all four deactivation categories.