Nitinol wire exhibits shape memory properties due to its unique alloy composition of nickel and titanium. When deformed at a lower temperature, it can return to its original shape upon heating, a phenomenon known as the shape memory effect. This property allows for gentle and continuous force application during orthodontic treatment, improving tooth movement efficiency and patient comfort. Other wires like stainless steel lack this capability as they do not have the reversible phase transformation characteristic of nitinol. Thus, nitinol is the preferred material when shape memory is required in orthodontics.

Reference: Graber's Orthodontics, 7th Edition.