Two-couple orthodontic appliance systems utility arches: a two-couple intrusion arch

The utility arch is a two-couple intrusion arch wire used for control of anteriordeep overbite. It is similar to a one-couple intrusion arch in that it is commonly made with rectangular wire, attached to the teeth only at the molars and the incisors and is activated for incisor intrusion by a molar tip back bend. It differs from a one-couple intrusion arch by the insertion of the incisor segment into the incisor brackets. This results in a fixed point of application of the intrusion force anterior to the incisors and, therefore, incisor rotation by the moment of the force. In addition, insertion of the rectangular wire into the incisor brackets usually creates a third-order couple for incisor rotation. Depending on how it is used, the moment of this couple may be activated in either direction and the resulting associated equilibrium forces will either supplement or reduce the vertical equilibrium forces created by the activation bends at the molars.