Growth prediction of mandible by using a computed X-ray densitometry method

本研究的目的是用计算机X射线密度法(CXD)研究下颌骨生长发育与骨密度之间的关系。研究对象为6~19岁的199名女孩和68名男孩。使用的材料是用铝阶梯尺拍摄的系列手骨X光照片、头颅侧位片和站立高度数据。结果表明：1.女性女性Sigma GS/D峰值速度比D、L和身高晚2年左右，女性女性Sigma GS/D峰值速度比D、L和身高晚2年左右。青春期下颌总长的年生长量与立高、Sigma GS/D、D和L的年生长量呈显著正相关。面部类型与Sigma GS/D.值无相关性。青春期女生下颌总长年增量与Sigma GS/D、MCI、L呈显著负相关，而男生青春期仅Sigma GS/D呈显著负相关。但两者在青春期前均无相关性。以下颌骨的年生长量为判据变量，以CXD法的参数为预测变量进行多元回归分析，男生青春期末期的复相关系数应为0.7~0.9。应用多元回归方程时，女生下颌骨实际年生长量与预测值的误差为0.5~1.0 mm，男生为1.0~2.0 mm。说明CXD法得到的参数可用于评价个体青春期后期的骨骼成熟和下颌骨生长潜力。尤其是在男孩身上。

The purpose of this study was to examine the relationship between mandibular growth and the value of bone mineral density by using computed X-ray densitometry (CXD) method. All of subjects consisted of 199 girls and 68 boys aged from 6 to 19 years at initial stage. The materials used were serial hand bone X-rays taken with an aluminum step-wedge ruler, lateral cephalograms and standing height data. The following annual increments were obtained-Cd-Go, Go-Pog', Cd-Gn from cephalograms, SIGMA GS/D,GSmax, GSmin, MCI,D,d, L from second metacarpal image by using "Bonalyzer" (Teijin Ltd.).Results were as follows :1. It indicated that peak velocity of SIGMA GS/D was about 2-year later than that of D,L and standing height, and 1-year around menarche in girls.2. There were significantly positive correlation coefficients between annual increments of total mandibular length and that of standing height, SIGMA GS/D,D and L during puberty.3. It showed no correlation between facial type and value of SIGMA GS/D.4. In girls, it significantly showed negative correlation between annual increment of total mandibular lengh and three parameters (SIGMA GS/D,MCI and L) at initial stage, and in boys, only SIGMA GS/D showed negative correlation during puberty. But both of them, there was no correlation before puberal growth period.From multiple regression analysis with annual increments of mandible as criterion variable and paraneters of CXD method as predictor variables were applied, it should that multiple correlation coefficients was 0.7-0.9 in late adolescent period in boys.When multiple regression equation was applied, the error between true annual increments of mandible and predicted value were 0.5-1.0 mm in girls, and 1.0-2.0 mm in boys.Above all, it indicated that the parameters obtained by CXD method were useful for the evaluation of individual skeletal maturation and mandibular growth potentiality in later adolescent period, especially in boys.