中文摘要：

目的比较锥形束CT（CBCT）和根尖片诊断根尖区牙根外吸收（根尖吸收）的准确性。方法选取160颗单根前磨牙，用以模r以4种不同程度的根尖吸收：无、轻度、中度、重度。模拟完成后，对所有牙齿拍摄CBCT和根尖片获取两组影像学资料。正畸医师通过对影像学资料的分析独立地评估所有牙齿根尖吸收程度。采用McNemar检验对比分析两种成像技术诊断不同程度根尖吸收的准确率。结果CBCT诊断无、轻度、中度、重度及总的根尖吸收的准确率分别为95．0％、97．5％、42．5％、87．5％和80．6％，而根尖片的准确率分别为85．0％、42．5％、70．0％、92．5％和72．5％，两种成像技术轻度、中度及总根尖吸收的诊断结果比较差异有统计学意义（P〈0．05）。结论相比于根尖片，CBCT对根尖吸收具有更高的检出率，但其对中度吸收的敏感性较低。在正畸临床中，CBCT可用于对根尖吸收进行早期诊断，从而为继续或修正当前的正畸治疗提供必要的参考意见。

英文摘要：

Objective To compare the accuracy of cone-beam computed tomography（CBCT） and periapical radiography in the diagnosis of simulated external apical root resorption（EARR）. Methods The study sample comprised 160 single-rooted premolars for simulating 4 degrees of EARR：no（intact teeth）, mild（cavity of 1.0 mm in diameter and depth in root surface）, moderate（ 1.0 mm root shortening） ,and severe（3.0 mm root shortening）. Two sets of radiographic images were acquired with CBCT and periapi- cal radiography. The severity for all resorption lesions were evaluated blindly by one calibrated examiner. The percentages of correct classification of each degree of EARR were compared between the two imaging techniques using McNemar test. Results With CBCT method, the percentages of correct classification of no, mild, moderate, severe and all EARR were 95.0 %, 97.5 %, 42.50%, 87.5% and 80. 6%, respectively with periapical radiography method, the percentages were 85.0%, 42.5%, 70.0%, 92. 5% and 72.5 % ,respectively. Significant differences were found between the two imaging techniques for evaluating mild, moderate, and all- EARR（P〈0.05）. Conclusion CBCT imaging is more reliable than periapical radiography for detecting EARR,whereas it is not sensitive to moderate root shortening. In orthodontic practices,CBCT could be applied to the early diagnosis of EARR, in order to help make the decision on continuation and modification of orthodontic treatment.