1993 Volume 31 Issue 3 Pages 404-411
As a means for determining the internal structure of bone tissue, there is bone mineral analysis from the clinical standpoint. There have been reports involving the radius, vertebrae lumbales and others. No reports involving the mandibular bone at the growth stage however have yet been made. For determining the internal structure of the jaw bones in childhood, sixty children, from six to eight years old, visiting the out-patieent ward, Department of Pedodontics, Attached Hospital, Kyushu Dental College, for examination and treatment and who had normal occlusion without dental caries or substantial tooth defects were selected as subjects and the bone mineral quantity in the mandibular bone was measured.
The results were as follows:
1. The results of the measurement of the bone mineral quantity by age showed an increasing tendency with age for both boys and girls. The average bone mineral quantities for boys were 3.45±0,41 mmAl for age six,3.96±0.61 mmAl for age seven, and 4.91±0.75 mmAl for age eight, and for girls were 3.16±0.41 mmAl for age six,3.76±0.51 mmAl for age seven, and 3.99±0.61 mmAl for age eight.
2. The results of the T-tests between the sexes and between the ages showed no significant difference between boys and girls from six to eight years old. In comparison of bone mineral quantities by age, between the ages of six and seven, the age of seven showed significantly greater values (p<0.01) than the age of six; between the ages of six and eight, the age of eight showed significantly greater values (p<0.01) than the age of six; but between the ages of seven and eight, no significant difference was seen.
3. The coefficient of the correlation between age and bone mineral quantity was r=0.646. The expression of the regression line, with age on the X-axis and bone mineral quantity on the Y-axis, was Y=0.503X-0.005.4. As basic examination items for reproducibility of measurement, coefficients of variation were obtained using skulls of the seven-year-old Indian children for (i) variation based on the focus, subject, and film position, and (ii) variation in bone mineral quantity based on the exposure dose of X-r0y irradiation. The value for (i) was 1.19% and for (ii) was 0.41% and it was confirmed that variations in measurement were small.
