Early treatment of Class III incisor relationship using the chincap appliance

Twenty-three patients (10 male, 13 female), with Class III relationships of the incisor teeth at the mixed dentition stage, were treated with the chincap appliance associated, where appropriate, with an upper removable appliance to procline upper incisors and to free the occlusion. Cephalometric analyses at the beginning and at the end of active treatment were compared with those in a carefully matched untreated control group selected from the Belfast Growth Study. At the beginning of treatment patients differed significantly from the controls in the SNB was larger, ANB was negative, Wits' analysis was negative, and the intermaxillary angle significantly reduced. The overjet was reversed, the lower incisors were ahead of A-Po, and the upper lip was far behind the E line. Significant changes brought about by the treatment were improvement in the Wits' relationship (but there was no significant change in the ANB angle), increases in the intermaxillary angle and lower facial height, improvement in the overjet, proclination of upper incisors and retroclination of lower incisors, backward movement of the lower incisors in relation to A-Po, and backward movement of the lower lip. The efficacy of the chincap appliance can be attributed to retroclination of lower incisors and downward movement of the mandible which may improve the jaw relationship without affecting the ANB angle. There were marked changes in the lip posture.