(NiTi) archwires when subjected to bending within a bracket model featuring different inter-bracket distances. The flexural behavior of commercial 0.016 × 0.022-inch NiTi archwires was modified by subjecting them to different ageing temperatures. The archwire with the lowest unloading force during bending in a three-point bending arrangement was chosen for force-deflection evaluation at various inter-bracket distances. The findings indicate that subjecting the commercial as-received NiTi archwires to an ageing treatment at a temperature of 490 °C effectively decreased the magnitude of the unloading force from 2.0 N to 1.3 N. It was also discovered that NiTi archwires displayed unloading force in the form of a slope over the deflection course when narrow inter bracket distances of 7.0 mm and 7.5 mm were used. The force slope exhibited a significant decrease and approached a nearly constant force trend when the inter-bracket distance was increased to 8.5 mm and 9.0 mm. The unloading force of 490 °C aged NiTi archwires exhibited a progressive increase from 1.7 N to 3.4 N as the spacing between the brackets was altered from 7.0 mm to 9.0 mm. The ageing treatment approach might be useful for reducing the bending force released by commercial rectangular NiTi archwires at different inter-bracket distance settings.
