The accuracy of 4 panoramic units in the projection of mesiodistal tooth angulations
The accuracy of 4 panoramic units in the projection of mesiodistal tooth angulations
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DOI：
10.1067/mod.2002.119435
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发表时间：
2002-02-01
影响因子：
3
通讯作者：
Major, PW
中科院分区：
文献类型：
--
作者：
Mckee, IW;Williamson, PC;Major, PW
本研究的目的是比较用牙型/颅骨测试装置测定的近远端牙齿角度与4个现代全景单元（OP 100, Cranex 3+, Orthophos, PM 2002 EC）的近远端牙齿角度图像。利用三维坐标测量机和定制的软件，构建了一种错位测试装置，确定了正畸弓丝与中远端牙的真实角度。一个人的头盖骨作为基质，用来固定印字器以便成像。每个全景单元对颅骨重复成像并重新定位5次。用定制软件对图像进行扫描和数字化，以确定图像的中远端角度。结果表明，4个全景单元的大部分图像角度与真实角度测量值有统计学差异。然而，在全景单元中注意到明确的趋势。对于上颌牙齿，图像显示前根更近，后根更远，造成犬齿和第一前臼齿之间的根分叉夸张的外观。对于下颌骨的牙齿，图像显示几乎所有的牙根都比实际位置更近，其中犬齿和第一前臼齿受到的影响最严重。相邻牙齿的角度差异最大的是下颌侧切牙和犬牙，相对根平行度被投影为根收敛。结论：临床评估中远端牙成角的全景x线摄影应非常谨慎，并了解其固有的图像畸变。
The purpose of this study was to compare the mesiodistal tooth angulations determined with a typodont/skull testing device with the images of mesiodistal tooth angulations from 4 contemporary panoramic units (OP 100, Cranex 3+, Orthophos, PM 2002 EC). A typodont testing device was constructed, and the true mesiodistal tooth angulations relative to an orthodontic archwire were determined with a 3-dimensional coordinate-measuring machine and custom-designed software. A human skull served as the matrix into which the typodont was fixed for imaging. The skull was repeatedly imaged and repositioned 5 times for each panoramic unit. The images were scanned and digitized with custom software to determine the image mesiodistal angulations. Results revealed that the majority of image angles from the 4 panoramic units were statistically significantly different from the true angle measurements. However, definite trends were noted among the panoramic units. For the maxillary teeth, the images projected the anterior roots more mesially and the posterior roots more distally, creating the appearance of exaggerated root divergence between the canine and the first premolar. For the mandibular teeth, the images projected almost all roots more mesially than they really were, with the canine and the first premolar the most severely affected. The largest angular difference for adjacent teeth occurred between the mandibular lateral incisor and the canine, with relative root parallelism projected as root convergence. It was concluded that the clinical assessment of mesiodistal tooth angulation with panoramic radiography should be approached with extreme caution and with an understanding of the inherent image distortions.