Morphometric variations and growth of the profile of the face in Chinese boys aged 4-15 years.

Much research has been conducted on the morphological growth and development of Chinese children. However, very few facial measurements have been documented, especially of the sagittal plane of the face. Morphometric variations and growth of the sagittal plane of the face in children were analyzed using geometric morphometric method in this study. The studied sample consisted of 108 boys (4-15 years) from Huzhu County in Qinghai Province of China, which were divided into three groups: 4-6 years old, 7-11 years old and 12-15 years old. It was revealed that the landmark-groups of nose area were relatively long, indicating large variation in the direction of the nasal protuberance, which possibly reflected the vigorous growth of the children's nose. There were larger landmark-groups' variability ranges in children aged 7-11 years, which may be related to the rapid growth in this period. The average morphology of the sagittal plane of the face changed a lot with age, which was showed in the comparison of the averaged graph of three groups: (1) the proportion of the forehead to entire face became smaller; (2) the 7^th landmark extruded more noticeably; (3) the nose became protruding; (4) the position of the mouth was relatively getting more upward, and the angle formed between the upper lip and the lower lip increased, and the lower lip moved forward; (5) the chin protuberated. Principal Component Analysis (PCA) revealed significant differences in the main distribution areas between age group 4-6 years and 12-15 years, even though there was a lot of overlap in the three age groups. Allometric analysis showed that the sagittal plane of the face aged 4-6 years and 7-11 years changed in the following way as the size increased: the forehead became vertical and the upper lip turned to be smaller. Additionally, as the size increased in age group 12-15 years, the most prominent landmark of the forehead became more conspicuous, and the bridge of the nose got more upturned. These may reflect the common morphological features and growing development of the facial sagittal plane of Chinese children.