Nickel Titanium Alloys As Orthodontic Appliances: A Review

Abstract

Nickel‑titanium (NiTi) alloys have become central in orthodontics, especially as archwires for initial alignment and levelling stages. Their unique properties—shape memory effect, superelasticity, relatively low modulus, and ability to deliver a relatively constant force over a long deflection—make them well suited to the demands of moving teeth with minimal trauma. However, there are also concerns: corrosion and ion release (especially nickel), hypersensitivity, changes in mechanical behaviour under different oral conditions, fatigue, and cost. This review synthesizes the literature on the material science, mechanical behaviour, biological interactions, clinical use, limitations, and emerging modifications of NiTi alloys in orthodontics