Thermal Programming of Commercially Available Orthodontic NiTi Archwires

The shape of superelastic Nickel-Titanium (NiTi) archwires can be adjusted with thermal treatments using devices such as the Memory-Maker (TM) (Forestadent), which potentially affects their mechanical properties. The effect of such treatments on these mechanical properties was simulated by means of a laboratory furnace. Fourteen commercially available NiTi wires (0.018 '' x 0.025 '') were selected from the manufacturers American Orthodontics, Dentaurum, Forestadent, GAC, Ormco, Rocky Mountain Orthodontics and 3M Unitek. Specimens were heat treated using different combinations of annealing duration (1/5/10 min) and annealing temperature (250-800 degrees C) and investigated using angle measurements and three-point bending tests. Complete shape adaptation was found at distinct annealing durations/temperatures for each wire ranging between similar to 650-750 degrees C (1 min), similar to 550-700 degrees C (5 min) and similar to 450-650 degrees C (10 min), followed by a loss of superelastic properties shortly afterwards at similar to 750 degrees C (1 min), similar to 600-650 degrees C (5 min) and similar to 550-600 degrees C (10 min). Wire-specific working ranges (complete shaping without loss of superelasticity) were defined and a numerical score (e.g., stable forces) was developed for the three-point bending test. Overall, the wires Titanol Superelastic (Forestadent), Tensic (Dentaurum), FLI CuNiTi27 (Rocky Mountain Orthodontics) and Nitinol Classic (3M Unitek) proved to be the most user-friendly. Thermal shape adjustment requires wire-specific working ranges to allow complete shape acceptance and high scores in bending test performance to ensure permanence of the superelastic behaviour.

Automated summary

The shape of superelastic Nickel-Titanium archwires can be adjusted with thermal treatments, which have an effect on their mechanical properties. Different combinations of annealing duration and temperature determine the complete shape adaptation range and the temperature at which superelastic properties are lost. Forestadent's Titanol Superelastic, Dentaurum's Tensic, Rocky Mountain Orthodontics' FLI CuNiTi27, and 3M Unitek's Nitinol Classic are the most user-friendly wires.