Two-couple orthodontic appliance systems: activations in the transverse dimension.

Partially bracketed arch wires can be activated in the transverse dimension to produce first-order rotations of the molars and constriction or expansion of intermolar width. A 2 x 6 arch wire is ideal for such activations because of the minimal side effects to the anterior teeth. As with other two-couple orthodontic appliance systems, symmetrical V-bends, asymmetrical V-bends and step bends are used to generate moments of the couples whose associated equilibrium forces can be used to produce desired tooth movement.