Variable-modulus orthodontics.

Traditionally, orthodontists have varied the size of the wire in order to produce a range of light to heavy forces. A new approach to force control in presented which allows wire size to remain relatively constant and the material of the wire is selected on the basis of clinical requirements. When the material instead of the cross section is varied, superior orientation should be achieved with fewer wires during tooth alignment, and bracket-wire play becomes independent of the forces needed. Since wire stiffness is determined by wire corss section and material, a simplified numbering system is described which aids clinicians in evaluating any orthodontic wire.