Effect of Short-Term Ageing Treatment on Bending Force Behavior of Commercial Nickel-Titanium Archwire

Superelastic nickel-titanium (NiTi) archwires have become the preferred archwire for orthodontic alignment and the levelling stage due to their ability to exert a light force on teeth throughout a wide range of tooth movement. The magnitude and trend of the force exerted on the malposed tooth is influenced by the orthodontist's consideration of the size and geometry of the NiTi archwire during orthodontic therapy. In this work, a novel approach of a short-term ageing treatment was utilized to modify the magnitude and trend of the bending force of a commercial superelastic NiTi archwire. The bending behavior of the superelastic NiTi archwire was altered by subjecting it to different temperatures in an ageing treatment for 15 min. The bending behavior of the aged NiTi archwire was examined using a three-point and three-bracket setup. The commercial NiTi archwire's bending forces in both the three-point and three-bracket configurations were successfully altered by the 15 min ageing treatment. During unloading in the three-bracket arrangement, the NiTi archwires aged at 490 °C or 520 °C exhibited a lower magnitude and more consistent force compared to the NiTi archwires aged at 400 °C or 430 °C. Ageing the archwire for 15 min at 490 °C produced a suitable size of Ni₄Ti₃ precipitate, which makes the wire more flexible during bending and reduces the unloading force in the three-bracket bending configuration. The short-term aged NiTi archwire could be used to enhance the force delivery trend to the malposed tooth by lowering the amplitude of the force delivered and sustaining that force throughout the orthodontic treatment duration.