Cephalometric evaluation of structural characteristics of mandibular rotation in people with Class III malocclusion and mandibular prognathism.

AIM: Evaluation of structural characteristics of mandibular rotation in adults with Class III malocclusion, and investigation of possible correlation of specific skeletal structures - as described by Bjork - to each other and to the growth pattern of the craniofacial complex. DESIGN: Retrospective analysis. MATERIAL AND METHOD: The material consisted of lateral cephalometric radiographs from 36 adults, with a mean age of 28.5 years (range: 17-31 years), who were patients at the Department of Orthodontics of Aarhus University, Denmark. Fourteen of these patients were males with mean age of 26.3 years (range: 21-29 years) and 22 females with a mean age of 26 years (range: 19-28 years). All patients presented a Class III malocclusion with mandibular prognathism. MAIN OUTCOME MEASURES: All initial tracings of the lateral cephalometric radiographs were performed by the same examiner with emphasis on mandibular structural characteristics, as proposed by Bjork, i.e. inclination of condylar head, curvature of mandibular canal, shape of mandibular border and inclination and shape of the symphysis. Evaluation of these variables was performed jointly by two researchers. RESULTS: Significant correlation between the shape of mandibular border and the craniofacial growth pattern was observed both for the entire sample as well as and for males and females separately. Furthermore, a significant relationship between inclination of condylar head and curvature of mandibular canal was observed in women. A significant correlation between curvature of mandibular canal and shape of mandibular border, as well as between curvature of mandibular canal and craniofacial growth pattern was found in men too. CONCLUSIONS: The shape of mandibular border seems to constitute an important morphological structural feature of the mandible, due to its significant correlation to mandibular rotation and consequently to the craniofacial growth pattern. Therefore, this specific morphological characteristic significantly contributes to the prognosis of Class III malocclusion.