参考桩钉修正曲面断层片垂直向的测量值

Amendatory measurements on panoramic radiographs using reference pins

背景:牙周病的诊断和治疗过程中常需测量牙槽骨高度和牙根长度,用曲面断层片对其进行定量测量的可靠性一直存在争议。目的:验证用参考桩钉修正曲面断层片垂直向测量值的可行性。方法:采用20例正畸患者的寄存模,在模型中的磨牙区、双尖牙区、尖牙区和切牙区嵌入5.00mm钢珠作为测量对象,并在与钢珠相应的位置放置10.0mm桩钉作参照物。拍摄模型的曲面断层片,测量钢珠影像垂直径,用桩钉校准和修正测量结果,比较钢珠影像测量值和真实值的差异。结果与结论:用单一部位的参照物和1组参照物的平均值来校准,不同区域和不同桩钉放置方法测量结果的失真率不同,部分区域的失真率≥5%。在测量区域相应的部位放置完全垂直于牙合平面的参考桩钉来修正测量值,可提高各区域测量结果的准确性,其失真率皆<1%,修正后的结果不受参照物的影响。而用贴在模型牙槽骨表面的参考桩钉来修正测量值,所得结果不理想。

BACKGROUND：The diagnosis and treatment of periodontal disease often requires measuring alveolar bone height and root length,but the validity of panoramic radiographs for quantitative measurement is still controversial. OBJECTIVE：To evaluate the reliability of vertical lineal measurement on panoramic radiographs by means of amendment with reference pins. METHODS：Permanent teeth of 20 orthodontic cases patients were selected. 5.00 mm steel balls were embedded in molar,premolar and incisor models as the measuring objects,and the reference pins of 10.0 mm length were placed on corresponding position with the ball as the reference standard. Panoramic radiographs of model were taken to measure the vertical diameter of ball images. The measurements were calibrated and corrected using reference pins. The variation between image measurements of steel balls on panoramic radiographs and their true values was compared. RESULTS AND CONCLUSION：When using single reference or average reference of several pins,the distortion rate of panoramic measurements varied on different regions and different placement of reference pins,more than 5% in some regions. The accuracy of the results could be improved using reference pins which were completely perpendicular to occlusal plane to amend the vertical lineal measurement on panoramic radiographs. Here,all distortion rates were less than 1%,and the amendatory results were independent of calibration methods. Whereas the amendatory results were not satisfactory when using reference pins attached the surface of the alveolar of models.