[Cephalometric analysis of the relationship between occlusal plane and sagittal position of the mandible]

To investigate the relationship between occlusal plane and sagittal position of the mandible by examining dental and skeletal morphologies of average angle patients for better understanding of etiologies and definitive clinical guidelines of mandibular malpositions.The lateral cephalograms of 114 female average angle patients with neutral maxillary positions were selected and divided into three groups according to sagittal mandibular positions (ANB angle). Twenty-five skeletal and dental measurements were compared. The correlations between skeletal and dental measurements were analyzed by rectilinear correlation.Cant of posterior occlusal plane (OP-P) and height of the upper second molar were significantly related to sagittal position of the mandible (P0.05). Height of the upper second molar was relatively inadequate and OP-P was sloped when the mandible was positioned posteriorly; conversely, height of the upper second molar was excessive and OP-P tended to be flat when the mandible was positioned anteriorly. Tooth axial inclinations were affected by sagittal position of the mandible. Maxillary teeth proclined distally and mandibular ones mesially for patients with retrognathia. On the other hand, maxillary teeth proclined mesially while mandibular ones distally for patients with prognathia.There was a definite relationship between cant of posterior occlusal plane and sagittal position of the mandible in average angle patients, consistent with the dental morphologies of different skeletal configurations. In treating malocclusions of sagittal discrepancy of mandible, the height of posterior teeth and cant of OP-P might be a primary concern.