Cephalometric comparisons of Chinese and Caucasian surgical Class III patients.

Pretreatment cephalometric radiographs of 30 Chinese and 30 Caucasian surgical Class III patients were studied to determine if there were skeletal and soft tissue morphology differences between the groups. Nineteen hard tissue and 13 soft tissue measurements were traced and digitized. A two-sample t test was used to analyze sex and ethnic differences between groups. A significant difference between sexes was found in the linear skeletal measurements but not in the angular measurements for both ethnic groups. Ethnic differences were found in the anterior cranial base measurement, which was significantly shorter in the Chinese sample. In addition, a larger posterior cranial base, a smaller gonial angle, and an increase in mandibular length contributed to the increase in mandibular prognathism found in the Chinese sample. Few differences between sexes were found in the soft tissue measurements. However, ethnic differences were found in maxillary and mandibular soft tissue prognathism, upper and lower lip protrusion, and nasolabial angle, which reflected the more severe underlying skeletal disharmony in the Chinese sample. When the surgical samples were compared to a reference population, an increase in skeletal measurements was found with the Chinese sample in maxillary and mandibular prognathism and dentoalveolar protrusion. Soft tissue maxillary prognathism and upper lip protrusion were found to be smaller than the reference population in the Caucasian sample but greater in the Chinese sample.