Smith R N, Karmo M, Russell J, Brook A H
School of Dental Sciences, University of Liverpool, Daulby Street, Liverpool L69 3GN, UK.
Arch Oral Biol. 2007 Nov;52(11):1037-42. doi: 10.1016/j.archoralbio.2007.04.017. Epub 2007 Jul 6.
To mathematically assess the curvature of upper anterior teeth along the facial axis of the clinical crown (FACC) line to provide information valuable for assessment of enamel growth.
Forty upper study models were chosen from the Orthodontic clinic at the Charles Clifford Dental Hospital, Sheffield, UK. The study model incisors and canines were sectioned longitudinally down the FACC line, using a Microslice II cutting machine. Images were captured that showed the proximal view of the tooth curvature from incisal edge/cusp tip to the gingival margin. The images were converted into silhouettes and saved as bitmap files. These were vectorised and converted to an outline of xy data points. The forty xy files were mathematically adjusted so the distance between incisal edge and gingival margin were of equal length. Non Rotational Principal Component Analysis (PCA) was then applied at 20 equal intervals along the curve of each xy file to describe the shape of the teeth.
Intra class correlation coefficient for intra-operator repeatability ranged from 0.821-0.998 showing good or excellent levels of reliability. PCA showed variation between tooth types.
The method proved reliable. All tooth types showed that the mid-point region had the greatest rise variable, indicating that the most-prominent point was central or incisal for central and lateral incisors. All were skewed towards the incisal end and had kurtosis at both ends. Central incisors showed least variability. Greater variability was seen within the incisal third than within the gingival third for all tooth types.
通过数学方法评估上前牙沿临床牙冠面部轴（FACC）线的曲率，以提供对釉质生长评估有价值的信息。
从英国谢菲尔德查尔斯·克利福德牙科医院正畸诊所选取40个上颌研究模型。使用Microslice II切割机沿FACC线纵向切割研究模型中的切牙和尖牙。拍摄从切缘/牙尖到牙龈缘的牙齿曲率近视图图像。将图像转换为轮廓并保存为位图文件。对这些文件进行矢量化处理并转换为xy数据点的轮廓。对40个xy文件进行数学调整，使切缘与牙龈缘之间的距离长度相等。然后在每个xy文件曲线的20个等间隔处应用非旋转主成分分析（PCA）来描述牙齿形状。
操作者内重复性的组内相关系数范围为0.821 - 0.998，显示出良好或极好的可靠性水平。PCA显示不同牙齿类型之间存在差异。
该方法被证明是可靠的。所有牙齿类型均显示中点区域的上升变量最大，表明中切牙和侧切牙最突出的点在中央或切端。所有牙齿都向切端倾斜，两端有峰度。中切牙的变异性最小。所有牙齿类型在切端三分之一内的变异性大于牙龈三分之一内的变异性。
