Growth characteristics of prognathic face with relapsed incisor reversed occlusion following chincap therapy

The purpose of this study was to investigate the difference in craniofacial growth and skeletal profile between relapsed and non-relapsed incisor reversed occlusion in treated skeletal class III patients following maximum pubertal growth. The sample consisted of 35 Japanese girls who had skeletal class III malocclusions before treatment. Chincap therapy was applied from the beginning of treatment and was continued until normal anterior bite was achieved. The sample was divided into two groups based on the status of anterior bite at the postpubertal period. The anterior bite of the relapsed group (n=17) bounced back to crossbite, while in non-relapsed group (n=18), normal anterior bite was maintained. The data were derived from lateral cephalometric head films, taken serially at ages 8, 10, 14 and 17 years. Facial diagrams were constructed using X-Y coordinates of representative cephalometric landmarks. The data were analyzed statistically. The results were as follows : 1. At 8 years of age, the skeletal profile showed significant differences in mandibular length, gonial angle and posterior cranial base length between the two groups. 2. The total incremental change in mandibular total length (Cd-Gn) and anterior facial height (N-Me) were significantly large in the relapsed group as compared to the non-relapsed group. 3. The incremental change in mandibular total length and anterior facial height were significantly large in the relapsed group during postpubertal growth period. 4. The total incremental change in posterior cranial base length (S-Ba) was significantly less in the relapsed group. In conclusion, the reasons for the relapsed occlusion in treated skeletal class III patients after maximum pubertal growth were attributed to insufficient compensatory growth of cranial base against an excessively growing mandible.