Orthodontic force production by closed coil springs.

The effects of wire size, lumen size, and wire type on the production of force by closed coil springs were determined. Force production was affected as follows: (1) Keeping the lumen size constant, an increase in wire size produced an increase in force. (2) Keeping the wire size constant, an increase in lumen size produced a decrease in force. (3) For a given wire size, force varied with different wire types. This study has shown that the current recommendations for the use of closed coil springs produce forces of greater magnitude than is necessary for orthodontic tooth movement. The clinician should take care to select the proper closed coil spring for specific clinical situations.