US Patent 4,037,324
United States Patent and Trademark Office
University of Iowa Research Foundation (Iowa City, IA, US)
Orthodontic movement of malaligned teeth is performed by attaching to the teeth a wire which has properties useful in orthodontics. When the anticipated use of the wire involves torsional and flexural stresses, the wire is a single strand of a material having a higher elastic limit and a lower elastic modulus than an 18-8 stainless steel wire of identical cross-section. The invention also contemplates the use of wires which demonstrate a plastic memory which causes them to return to a preset shape or length after being deformed and then heated. For example, longitudinally shrinkable wires are either attached to teeth for closing the spaces therebetween or are used to draw a tooth toward a fixed reference member such as a rigid archwire spaced from the tooth. The mechanical memory of the wire may also tend to restore it to a preset shape upon heating in order to level or torque malposed teeth. The disclosed wires are formed of Nitinol alloy which is a known near-stoichiometric alloy of nickel and titanium. When the wire exerts tooth-moving forces by being subjected to torsional or flexural stresses, the alloy also includes cobalt substituted for nickel on an atom-for atom basis so that the composition is TiNi.935 Co.065.
Andreasen, George F. Method and system for orthodontic moving of teeth. US Patent 4,037,324 filed May 21, 1973 and issued July 26, 1977. https://ir.uiowa.edu/patents/10