传统全景片和锥形束CT重建全景片测量牙轴近远中倾斜度的对比研究

Comparison of mesiodistal tooth angulations determined through traditional panoramic radiographs and cone beam CT panoramic images

目的比较传统全景片和锥形束CT(CBCT)重建全景片用于测量牙轴近远中倾斜度的准确性。方法收集15名个别正常志愿者的石膏模型,在模型上确定上下颌从左侧第一磨牙到右侧第一磨牙的牙体长轴和平面的标记点,制作放射显影装置,志愿者佩戴放射显影装置拍摄全景片和CBCT片。分别在石膏模型、全景片和CBCT重建全景片上测量牙轴近远中倾斜度。利用多元方差分析和Dunnett-t检验比较3种测量方法的差异。结果 3种测量方法间的差异有统计学意义(P=0.00)。与模型测量相比,全景片组中12个牙位有2个牙位(上下颌第二前磨牙)测量结果的差异有统计学意义(P=0.00),CBCT组12个牙位的差异均无统计学意义。结论评价牙轴近远中倾斜度时,传统全景片存在一定误差,CBCT重建全景片是一种更为有效的评价手段。

Objective To compare the accuracy of mesiodistal tooth angulation measurements by using traditional panoramic radiographs and cone beam CT （CBCT） panoramic images. Methods Plaster models of 15 volunteers with individual normal occlusions were collected. The functional occlusal plane and tooth long axis on the plaster models were marked from the right first molar to the left first molar in the upper and lower dental arches. A radiographic stent, which contains radiopaque markers near the functional occlusal plane and approximating the root axis, was fabricated for each model. Traditional panoramic radiographs and CBCT scan images were obtained from each patient, with the radiographic stent seated on the dentition. A panoramic image reconstruction was made from the CBCT volumetric data by using related software. The CBCT panoramic image data were oriented parallel to the maxillary or mandibular functional occlusal plane containing all the radiopaque markers when measuring the maxillary or mandibular teeth, respectively. The mesiodistal tooth angulations of the plaster model, traditional panoramic radiographs, and CBCT panoramic images were measured and compared. Multivariate analysis of variance and Dunnett-t test were performed to compare the differences among the three methods. Results The difference among the three methods was statistically significant （P=0.00）. Significant differences compared with the model measurement were found in two teeth （upper second premolar and lower second premolar） among twelve teeth （P=0.00） in traditional panoramic measurement. CBCT panoramic measurement was not significantly different to model measurement. Conclusion Traditional panoramic radiographs do not provide a more reliable measure of mesiodistal tooth angulation, whereas CBCT panoramic image is an effective tool for evaluating mesiodistal tooth angulation.