Department of Oral and Maxillofacial Surgery, University of Pécs, Pécs, Hungary.
Dentomaxillofac Radiol. 2013;42(8):20130160. doi: 10.1259/dmfr.20130160. Epub 2013 Jun 17.
Our aim was to examine the panoramic darkening of the root, which is a "high-risk" sign, using quantitative measurements of pixel grey values to determine different aetiological backgrounds, namely inferior alveolar nerve (IAN) exposure with or without groove formation of the third molar roots or thinning/fenestration of the lingual cortex (LCTF).
38 impacted third molars that had been surgically removed and had darkened roots on panoramic radiographs were included in this retrospective case-control study. 15 IAN exposure cases were selected for the case group, and 23 cases with proven lingual cortical thinning or fenestration were chosen for the control group. The mean pixel grey values of selected areas in the dark band (D) and control areas within the same roots (R) were determined with the ImageTool (University of Texas Health Science Center, San Antonio, TX) software. The differences in pixel values (R-D) of the IAN and LCTF groups were analysed using the Mann-Whitney U-test and Pearson's χ(2) test.
The medians of the R-D pixel values were 45.7 in the IAN group and 34.3 in the LCTF group, whereas the interquartile ranges were 12.0 (IAN) and 18.3 (LCTF) (p < 0.001). The R-D critical value at which the outcomes differed significantly was 38. If the differences in pixel grey values (R-D) were higher than 38, the chance of IAN exposure was approximately 32 times higher than the chance of LCTF (χ(2) test, p < 0.001; odds ratio, 32.0; 95% confidence interval, 3.5-293.1).
The pre-operative prediction of IAN exposure or lingual cortical thinning in cases with "darkening" is possible based on pixel grey measurements of digital panoramic radiographs.
本研究旨在通过对像素灰度值的定量测量，探讨全景片上根面黑化这一“高危”征象的不同病因背景，即下颌神经（IAN）暴露伴或不伴第三磨牙牙根的沟槽形成或舌侧皮质变薄/开窗，观察其与根面黑化的关系。
本回顾性病例对照研究纳入了 38 颗已行外科拔除且全景片显示根面黑化的埋伏第三磨牙。其中 15 例为 IAN 暴露病例，纳入病例组；23 例证实存在舌侧皮质变薄或开窗，纳入对照组。使用 ImageTool（德克萨斯大学健康科学中心，圣安东尼奥，TX）软件确定黑化带（D）和同一牙根内对照区（R）的选定区域的平均像素灰度值。采用 Mann-Whitney U 检验和 Pearson χ(2)检验分析 IAN 组和 LCTF 组的像素值（R-D）差异。
IAN 组的 R-D 像素中位数为 45.7，LCTF 组为 34.3，而四分位间距分别为 12.0（IAN）和 18.3（LCTF）（p<0.001）。R-D 像素值差异有统计学意义的临界值为 38。如果像素灰度值（R-D）的差异大于 38，则 IAN 暴露的可能性约为 LCTF 的 32 倍（χ(2)检验，p<0.001；优势比，32.0；95%置信区间，3.5-293.1）。
基于数字化全景片像素灰度测量值，可对“黑化”病例中 IAN 暴露或舌侧皮质变薄进行术前预测。
