The cephalometric examination of facial bones with age gives much information about the growth rate, growth, direction and morphologic changes of facial bones.
Among the facial bones, mandible is important not only to several functions such as
mastication, pronunciation, and protection of larynx and pharynx, but also as a definitive factor of external appearance. The growth pattern and growth rate of mandible is known to be different from other facial bones or cranium
In this study, we reviewed 1423n cephalometric films of normal Korean with age range from 7 to 16 years. The three dimensional measurements of mandible are compared with those of other facial or cranial bones, and cephalometric angles were
measured and analyzed.
Comparing the data of age 16 with those of age 7, following results are obtained.
1. The growth of mandible width(Go-Go) is proportional to the growth of midfacial
width(Z-Z), and the go-Me-Go angle is increased by 7.0-7.8 degrees with age.
2. The mandibular depth(Go-Me) is increased by 9% more than the cranial base dopth(S-N).
3. The ratio of Ar-Me to Go-Ll is increased by 5-7t, and it means that the mandible grows in antero-inferior direction against to cranial base.
4. The ratio of ID-Me/ANS-Me is increased by 4-5% more with age, it means that the proportion of anterior mandibular height to the lower facial height is increased.
5. The S-Go/N-Me ratio is increased by 6.9-7.7% with age, and it means the posterior facial height was increased more than the anterior facial height.
6. In cephalometric angles, the gonial angle is reduced by 6.0-6.5%, the sella angle is
increased by 4.8-4.9%, and the sum of gonial and sella and articular angle remained the same with age. The reduction of gonial angle means that the growth of mandibular angle is directed to postero-inferior with age.
7. There is no difference between male and female in mandibular growth.
From these results, we can obtain the standard measurements of three dimensional length of mandble in growing Korean, and also compare the mandibular growth change with other craniofacial bones. These data give us abundant utility in
the
planning and evaluation of maxillofacial surgery.
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