Craniofacial adaptations induced by chincup therapy in Class III patients

The purpose of the present study is to examine the effects of an orthopedic force produced by chincup treatment in patients with Class III malocclusio n, Anteroposterior maxillary and mandibular changes were examined as were c hanges in the vertical dimension. Further, the possibility of posterior dis placement of temporomandibular joints in treated Class III subjects was eva luated. Serial lateral headfilms of 22 young females (average age, 9 years) , who had received chincup therapy were compared with those of 20 skeletal Class III subjects of similar age who received no treatment during the inte rval studied. A computerized x-y coordinate program was applied to analyze the cephalometric landmarks and measurements. The treated group showed impr ovement of the skeletal Class III pattern associated with a slight increase (0.8 degrees per year) in SNA and a slight decrease (-0.7 degrees per year ) in SNB and also a decreased genial angle. The distance from the condyle t o the chin (Co-Gn or effective mandibular length) increased significantly l ess in the treated group in comparison with controls. Increases in lower an terior facial height were not different between the treated and untreated g roups, In addition, the cranial base angles N-S-Ba and N-S-Ar showed no sta tistical difference between groups, but these angles tended to increase wit h time in both groups. Basion and Articulare showed almost the same amount of backward and downward movement in both groups. The results of this study indicate that the primary effect of chincup therapy was in producing a red uction in mandibular growth increments during the period studied. Maxillary growth was not affected during treatment. Further, the results of this stu dy fail to support the hypothesis that chincup appliance significantly indu ces the posterior displacement of the glenoid fossa.