Elastic energy/stiffness ratios for selected orthodontic wires.

This investigation determined the ratio of the energy available for orthodontic tooth movement to the stiffness and flexibility of a given wire. Twenty-five specimens each of five brands of orthodontic wire were tested in tension in the as-received condition. Force versus elongation diagrams were obtained and then converted into stress-strain data. Mean values were determined for the yield strength and yield strain for each brand of wire. The modulus of elasticity (E), modulus of resilience (R), and elastic compliance (C) were then calculated. Two ratios were established by using the three mechanical properties: (1) the modulus of resilience/modulus of elasticity (R/E) ratio and (2) the modulus of resilience/elastic compliance (R/C) ratio. The results confirmed that the use of these two ratios in combination permitted one to differentiate among the various types of orthodontic wires, with respect to stored energy and its relationship to the stiffness or flexibility of the wire.