Chen Quan, Liu Deng-gao, Zhang Gang, Ma Xu-chen
Department of Oral and Maxillofacial Radiology, Peking University School and Hospital of Stomatology, Beijing 100081, China.
Zhonghua Kou Qiang Yi Xue Za Zhi. 2009 Apr;44(4):217-21.
To investigate the actual relationship between the impacted mandibular third molars (IMTM) and the mandibular canals on panoramic radiographs and cone beam computed tomography (CBCT).
A cross-sectional study design was used and panoramic radiographs of 390 patients (645 sides developed IMTM) were included in the present study. The relationship between the IMTM and the mandibular canal on panoramic radiographs was defined in three types: 'untouched', 'touching in point', and 'superimposition or line touching'. The IMTM superimposing and line touching with mandibular canals on panoramic radiographs were examined by CBCT.
The relationship types on panoramic radiographs were as follows: 'untouched' type 441 IMTM (68.4%), the type of 'touching in point' 149 IMTM (23.1%) and the type of 'superimposition and line touching' 55 IMTM (8.5%). CBCT showed that 25 (50%) of 50 IMTM of superimposition and line touching type impinged on the mandibular canals.
More than 90% of IMTM which do not have intimate relationship with the mandibular canals can be screened out by panoramic radiographs. The IMTM which belong to the line touching and superposition type on panoramic radiographs should be examined by CBCT.
通过全景X线片和锥形束计算机断层扫描（CBCT）研究下颌阻生第三磨牙（IMTM）与下颌管之间的实际关系。
采用横断面研究设计，本研究纳入了390例患者（645侧有IMTM）的全景X线片。全景X线片上IMTM与下颌管的关系分为三种类型：“未接触”、“点接触”和“重叠或线接触”。通过CBCT检查全景X线片上IMTM与下颌管的重叠及线接触情况。
全景X线片上的关系类型如下：“未接触”型441颗IMTM（68.4%），“点接触”型149颗IMTM（23.1%），“重叠及线接触”型55颗IMTM（8.5%）。CBCT显示，50颗重叠及线接触型IMTM中有25颗（50%）侵犯下颌管。
全景X线片可筛查出90%以上与下颌管无密切关系的IMTM。全景X线片上属于线接触和重叠型的IMTM应行CBCT检查。
