Abstract
This study was undertaken to determine the objectively internal structure of bone during the course of growth and development of the mandible of children. The subjects consisted of 160 children with normal occlusion, from 3 to 6 years old, who came to the Department of Pedodontic, Attached Hospital, Kyushu Dental College as outpatients for examination. Their cortical bones at the mandibular basewere measured on panoramic radiographs.
The results were as follows:
1. The average thickness of the cortical bone at the mandibular base for boys was 2.43±0.42 mm for age 3,3.13±0.50 mm for age 4,3.25±0.40 mm for age 5, and 3.48±0.50 mm for age 6. For girls, the average was 2.44±0.45 mm for age 3,3.07±0.49 mm for age 4,3.14±0.38 mm for age 5, and 3.47±0.51mm for age 6.
2. The T-test showed no significant differences between boys and girls and between the right and left sides in the thickness of the cortical bone at the mandibular base. Between the two ages 3 and 4,3 and 5,3 and 6,4 and 6, and 5 and 6, the latter showed significantly greater values (p<0.01) than the former.
3. When modified by vertical magnification factor 1.34 in the panoramic radiographs at the mandibular second primary molar, the values for boys were 1.81±0.31 mm for age 3.2.34±0.37 mm for age 4,2.43±0.30 mm for age 5, and 2.60±0.37 mm for age 6. The values for girls were 1.82±0.34 mm for age 3,2.29±0.37 mm for age 4,2.34±0.28 mm for age 5, and 2.60±0.38mm for age 6.
4. The coefficient of the correlation between age and thickness of the cortical bone at the mandibular base was r=0.657. When thickness of the cortical bone at the mandibular base is shown on the Y-axis and age on the X-axis, the regression line was Y=0.358×+1.243.
