牙种植患者曲面体层片上颌骨失真度的评价

目的分析不同区域曲面体层x线影像的失真率大小以及失真率的矫正。方法采用胶片直接测量和间接数字化图像的计算机辅助测量两种方法，回顾性分析32例成功种植的47张曲面体层X线片资料。结果各区域的水平失真率有明显不同，以前牙区的绝对值及变化范围最大，从-7．9％到40．0％，均值25．7％；前磨牙区、磨牙区均值分别16．2％、17．7％。前牙区、前磨牙区、磨牙区垂直失真率均值分别为27．0％、23．8％、27．3％。间接数字化图像的计算机辅助测量值随扫描时所选择的dpi数值变化而呈正比的变化；其水平失真率均值为1．85％，垂直失真率均值为4．94％。用计算机软件测量得到的失真率比在胶片上直接测量小很多：二者水平和垂直失真率的差异平均为18．21％、21．09％。结论不同患者不同的颌骨部位，失真率不同。

The assessment of dental implant site on panoramic radiographs

Objective The aim was to quantily the vertical and horizontal distortion in panoramic radiographs in various implant regions of the jaws. Methods 47 panoramic images ,54 implants of 32 patients were selected from 137 images of 62 patients who had accepted dental implants. The length and diameter of each implant were measured by three observers with computer aided method and direct measurement, respectively. Results The mean ratios of horizontal and vertical distortion of panoramic radiographs were 25.7% and 27.0% ,16. 2% and 23.8% ,17.7%and 27.3%in the incisor,premolar and molar region,respec- tively. The ratio of horizontal distortion was the largest in incisor;egion with a maximum variation of 49%. Compared with the di- rect measurement,the horizontal and vertical distortions decrease greatly by a ratio of 18. 21% and 22.09% with computer aided method, respctivcly. Conclusion As far as individual person is concerned,distortion of panoramic radiograph is not the same in differcnt region. The use of a computer aided method to correct for distortion is more reliable.