Nitinol wire is a shape memory alloy primarily composed of nickel and titanium, exhibiting unique properties such as superelasticity and thermal shape memory. Due to its sensitive phase transformation and high nickel content, traditional soldering or welding methods can alter its microstructure, leading to loss of superelastic properties and mechanical strength. Additionally, the high temperatures involved in soldering or welding often cause oxidation and degradation of Nitinol’s functional characteristics. In contrast, stainless steel, gold, and TMA wires maintain their properties better with conventional joining techniques. Therefore, joining Nitinol wire using soldering or welding is not recommended for clinical use to preserve its functionality and biocompatibility.

Reference: Contemporary Orthodontics, 6th Edition.