Maki K, Miller A, Okano T, Shibasaki Y
Department of Orthodontics, Showa University, Tokyo, Japan.
J Bone Miner Res. 2000 Apr;15(4):700-9. doi: 10.1359/jbmr.2000.15.4.700.
Quantitative computed tomography (QCT) was completed in 34 subjects between the ages of 9 and 33 years with symmetrical mandibles in order to investigate the three-dimensional cortical bone mineral density (BMD) distribution in the mandible. The number and distribution of the pixels were determined at three levels: (1) representing the entire mandibular bone; (2) the cortical bone at 60% above the baseline defined as the segmentation level (around 1050 mg/cm3) and representative of only cortical bone; and (3) the highest mineralized cortical bone (>1250 mg/cm3). The geometrical distribution of the highest mineralized areas was evaluated by three-dimensional reconstruction of the images. The total number of pixels for the entire mandible increased significantly at each time point represented at four increasing ages groups (9-11 years of age, 12-14 years of age, 15-17 years of age, and >18 years of age). The male and female subjects had a similar total number of pixels for the entire mandible before the age of 11, but the male subjects showed a significantly larger total number of mandibular pixels after that age. Comparison of the number of pixels for pure cortical bone (60% segmentation level) and the highest mineralized cortical bone indicated a significant increase with maturation with the greatest change occurring between the 13-year and 16-year age groups. However, the ratio of cortical bone/total bone increased at a more rapid rate in the male subjects and reached a plateau by the 16-year age group, showing distinct differences in mineralization of the mandible between the sexes.
为了研究下颌骨的三维皮质骨矿物质密度（BMD）分布，对34名年龄在9至33岁之间、下颌骨对称的受试者进行了定量计算机断层扫描（QCT）。在三个层面确定像素的数量和分布：（1）代表整个下颌骨；（2）基线以上60%处的皮质骨，定义为分割水平（约1050mg/cm³），仅代表皮质骨；（3）矿化程度最高的皮质骨（>1250mg/cm³）。通过图像的三维重建评估矿化程度最高区域的几何分布。在四个递增年龄组（9至11岁、12至14岁、15至17岁和>18岁）所代表的每个时间点，整个下颌骨的像素总数均显著增加。11岁之前，男性和女性受试者整个下颌骨的像素总数相似，但11岁之后男性受试者的下颌骨像素总数显著更大。对纯皮质骨（60%分割水平）和矿化程度最高的皮质骨的像素数量进行比较，结果表明随着成熟度增加像素数量显著增加，最大变化发生在13岁至16岁年龄组之间。然而，男性受试者皮质骨/总骨的比例增加得更快，并在16岁年龄组达到平台期，显示出两性下颌骨矿化存在明显差异。
