Craniofacial morphological characteristics of Chinese adults with normal occlusion and different skeletal divergence

The aim of the present study was to examine the craniofacial morphologic characteristics of different vertical dysplasias in a population of Chinese adults with normal occlusion. Sixty-nine subjects (39 males and 30 females) were selected from 800 healthy students between 18 and 24 years of age. Lateral cephalograms were obtained and 27 hard and 10 soft tissue measurements were analysed. The subjects were then divided into three groups: high angle, low angle, or control according to the value of FH-MP. Intraclass correlation coefficient was determined for the repeated measurements. One-way analysis of variance was used to determine the differences between the groups. The results showed that the low-angle group had a larger cranial basis angle (N-S-Ar) and the high-angle group had a shorter maxilla (Ans-Ptm; P < 0.01). The high-angle group displayed vertical hyperdivergency with increased PP-OP, OP-MP, gonial, and lower gonial angles, whereas the low-angle group showed significant hypodivergence with decreased values for all variables (P < 0.01). The low-angle group displayed a more protrusive chin and the high-angle group a more retrusive chin (P < 0.01). Differences in dentoalveolar measurements in the divergent groups were mainly in the anterior region. Moreover, the low-angle group had a thicker and the high-angle group a thinner lower dentoalveolus (P < 0.01). For face height measurements, the main differences in the divergent groups were at the anterior lower third (P < 0.01). Soft tissue deviations were less obvious in the high-angle group and in general less significant than those of the hard tissues in both divergent groups. Significantly different morphological characteristics exist in Chinese adults with vertical dysplasia but normal occlusion. Major skeletal cephalometric changes were found for the lower facial third. The soft tissues showed a well-adapting mechanism of soft tissue coverage for the skeletal dysplasia.