The cephalometric study of facial types in Class II division 1 malocclusion

앵글 II급 1류 부정교합자의 안모유형에 관한 연구

This study was focused on the distribution of different facial types of the Class II division I malocclusion groups and skeletal characteristics of the each group and those that anteropsterior relationship of the maxilla and mandible calculated from the analysis of ANB angle and Wits appraisal was quite different from each other, as well. Cephalometric headplates of 140 persons of Class II division 1 malocclusion whose mean age was 11.2 years and 69 persons of normal occlusion whose mean age was 12.2 years were utilize as materials. Measurements were recorded, tabulated and statistically analyzed employing the tracings of the lateral cephalograms, then Class II division 1 malocclusion group was divided into 9 Types according to the angle of SNA and SNB for the anteroposterior relationship of the maxilla and mandible, another 9 Types according to the FH-NPog and SN-MP for the horisontal and vertical relationship, and the other 9 Types according to the ANB and Wits appraisal for intermaxillary relationship as well, with which was based on $Mean{\pm}$ 1SD of those of normal occlusion. The result allowed the following conclusion: 1. $37.1\%$ of population demonstrated maxilla within nounal range and retrognathic mandible to the cranial base, $30\%$ for both maxilla and mandible within normal range, $20\%$ for retrognathic maxilla and mandible and $12.9\%$ of the rest were ananged in Class II division 1 maloccusion groups. 2. Retrognathic mandible and hyperdivergent face accounted for $30.7\%$, mesognathic mandible and neutrodivergent face for $29.3\%$, mesognathic mandible and hyperdivergent face for $16.4\%$, retrognathic mandible and neutrodivergent face for $13.6\%$, mesognathic mandible and hypodivergent face for $10\%$ of population were computed in Class II division 1 malocclusion groups. 3. It was suggested that skeletal Class II malocclusion might be due to anomaly in size and shape of cranial base, underdevelopment of mandible, retropositioning of mandible, underdevelopment of posterior face against anterior face, or any combination of these factors. 4. Population with underdevelopment and / or retropositioning of the mandible showed hyperdivergent tendency of facia profile. 5. The ANB angle and Wits appraisal did not coincide the severity of anteroposterior dysplasia in $35.7\%$ of Class II division 1 malocclusion group each other, and this inconsistency was suggested to be related with mandibular rotation, inclination of cranial base, and anteroposterior position of the maxilla.