NiTi Wire Properties — MFDS Part 1 MCQ

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ModerateOrthodontic PrinciplesNiTi Wire PropertiesMFDS Part 1

During the initial alignment of a fixed appliance, a markedly displaced lateral incisor must be engaged. Which orthodontic wire material is most appropriate when a wide range of recoverable activation and a relatively constant unloading-force plateau are required?

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Correct answer: E — Nickel-titanium (NiTi) wire

Nickel-titanium is the best answer. Superelastic NiTi can undergo substantial deflection while remaining recoverable and can deliver comparatively moderate forces over an unloading plateau. These characteristics allow a small initial archwire to engage markedly displaced teeth during alignment. Stainless steel is stiffer and has a higher load-deflection rate, although multistranded stainless steel may sometimes be used initially. Beta-titanium has lower stiffness and greater springback than stainless steel but does not characteristically provide the superelastic unloading plateau described. Cobalt-chromium is generally relatively stiff unless specially heat-treated, while gold wires are obsolete in routine contemporary fixed-appliance treatment. The question therefore tests superelastic behaviour rather than an absolute, testing-method-dependent ranking of 'springback'.

Reference: Waters NE. Superelastic nickel-titanium wires. British Journal of Orthodontics. 1992;19(4):319-322. https://pubmed.ncbi.nlm.nih.gov/33023727/