Department of Legal Medicine, Nihon University School of Dentistry, 1-8-13, Kanda-Surugadai, Chiyoda-ku, Tokyo 101-8310, Japan.
Forensic Sci Int. 2010 Jul 15;200(1-3):35-40. doi: 10.1016/j.forsciint.2010.03.024. Epub 2010 Apr 9.
The dental pulp, like other parts of the body, shows age-related changes. The aim of this study was to develop an age estimation method based on the ratio of the three-dimensional volume of the pulp chamber compared to the total tooth. Pulp chamber volumes were calculated using microfocus X-ray computed tomography (SMX-130CT, Shimadzu, Co., Kyoto, Japan) of the three-dimensional digital radiographic images of teeth. The specimens used in this study were 50 lower first and 50 lower second premolar teeth without caries or other abnormalities, obtained from patients in six 10-year age groups (age range 20-78 years). Each specimen was imaged by a micro-CT to reconstruct the three-dimensional structure. Using the reconstructed images, the tooth and pulp volumes at four levels (crown area (L(1)); coronal one third (L(2)); midroot (L(3)), and apical one third of the root (L(4))) were measured. Mean values of the pulp-tooth volume ratio (PTVR(1-4)) were compared between the six age groups and these values were used as the variables for the multiple regression analysis. The coronal one third of the root (L(2)) showed the greatest ratio values, followed by L(3), L(4) and L(1) in all age groups. Morphological changes of the pulp cavity in different age groups were observed. PTVR gradually reduced in value with increasing age, with the steepest reduction occurring in the 20-50 age range, and most noticeably at the L(2) level. The coefficients of determination by multiple regression analysis for four variables were 0.635 for lower first and 0.703 for lower second premolars. Among the variables used for estimating age by this method, only PTVR(2) showed a significant correlation at P<0.001. To determine the variables with the most significant contribution and to optimize the models, stepwise regression method was applied with inclusion level at P<0.05. Only the variable of PTVR(2) contributed significantly to the fit for lower first premolar whereas the two variables of PTVR(1) and PTVR(2) for lower second premolars. The coefficients of determination for the chosen variables were 0.625 for lower first and 0.698 for lower second premolars. Pulp-tooth volume ratio is an age-dependent variable that can be used to estimate age with reasonable accuracy.
牙髓像身体的其他部分一样，会发生与年龄相关的变化。本研究的目的是开发一种基于牙髓腔三维体积与牙齿总容积之比的年龄估计方法。使用 Shimadzu 公司的微焦点 X 射线计算机断层扫描（SMX-130CT），对 50 颗下颌第一前磨牙和 50 颗下颌第二前磨牙的三维数字射线图像进行牙髓腔容积计算，这些牙齿没有龋齿或其他异常，来源于六个 10 岁年龄组（年龄范围 20-78 岁）的患者。每个标本都通过微 CT 成像来重建三维结构。使用重建图像，在四个水平（牙冠区域（L(1)）；冠三分之一（L(2)）；根中三分之一（L(3)）和根尖三分之一的根（L(4)））测量牙和牙髓的体积。比较六个年龄组之间的牙髓牙容积比（PTVR(1-4)）的平均值，并将这些值用作多元回归分析的变量。在所有年龄组中，根尖三分之一的根（L(2)）显示出最大的比值，其次是 L(3)、L(4)和 L(1)。观察到不同年龄组牙髓腔的形态变化。随着年龄的增长，PTVR 值逐渐降低，在 20-50 岁年龄范围下降最快，在 L(2)水平最明显。多元回归分析的四个变量的决定系数为下颌第一前磨牙 0.635，下颌第二前磨牙 0.703。在所使用的估计年龄的变量中，只有 PTVR(2)在 P<0.001 时显示出显著相关性。为了确定贡献最显著的变量并优化模型，应用逐步回归方法，纳入水平为 P<0.05。只有 PTVR(2)变量对下颌第一前磨牙的拟合有显著贡献，而 PTVR(1)和 PTVR(2)两个变量对下颌第二前磨牙有显著贡献。选择变量的决定系数为下颌第一前磨牙 0.625，下颌第二前磨牙 0.698。牙髓牙容积比是一个与年龄相关的变量，可以用于以合理的精度估计年龄。
