The super-elastic Japanese NiTi alloy wire for use in orthodontics. Part III. Studies on the Japanese NiTi alloy coil springs.

Closed and open Japanese nickel titanium (NiTi) alloy coil springs were fabricated from the Japanese NiTi alloy wire. The closed coil springs were subjected to a tensile test and the open coil springs were subjected to a compression test to evaluate the mechanical properties. At the same time, a test with the commercially available steel coil springs also was done. It was clearly established that the Japanese NiTi alloy coil springs exhibited superior springback and super-elastic properties similar to the properties of the Japanese NiTi alloy arch wires. In addition, it was shown that the load value of super-elastic activity can be effectively controlled by changing the diameter of the wire, the size of lumen, the martensite transformation temperature, and the pitch of the open coil spring. The most important characteristic of the Japanese NiTi alloy coil springs is the ability to exert a very long range of constant light, continuous force. It is possible to use this coil selectively to obtain optimal tooth movement.