全口曲面断层片上颌牙根端低密度影的原因分析与处理

The cause and prevention of the Low-density shadow in the upper dentition image of panoramic radiography

目的:解决全口曲面断层上颌牙体根端水平状大片低密度影现象,提高牙体影像清晰度。方法:使用法国产trphy曲面断层机,囑患者做下颌中切牙前伸错,挺胸低头,舌体上提,将上下颌中切牙牙根冠相对长轴线进入垂直断层域后进行投照。结果:发现上颌全牙列牙体或牙根部水平长条黑色低密度影的原因,是患者舌体小,口咽腔空容积大,降低了X射线阻射率,掩盖了上颌牙体根端影像。结论:采用下前牙错前伸,大低头、舌体上提摆位法,改变了X线穿过的路径,避开了口咽腔的低阻射区与上颌牙列根端影像的重叠,提高了全口牙曲面断层影像质量和临床诊断准确率。

Objective： To eliminate the panoramic radiography phenomena of level black shadow of low-density of the upper dentition, improve definition of the dental image. Methods： The Trphy panoramic radiography was employed, the patients were instructed to lower theire head, raise their tongue base, and protrud their mandible forward until the long axis line of incisors was loacted into the vertical fault domain before project began. Results： We found that small tongue and big pharynx could lower the radiation-resisting rate of x-ray, so cover the real image, which was the casue of the low-density shadow in the whole dentition image. Conclusions： Changing X-ray projecting route could avoid the low radiation-resisting zone and images overlap of upper dentition, and promote image quality and accuracy of clinical diagnosis.