下颌管与下颌第三磨牙牙根相对位置关系的CBCT研究

Applied Anatomy of the Mandibular Third Molar and Mandibular Canal:Reliability of CBCT

目的:对曲面断层X线片提示下颌第三磨牙与下颌管关系密切的患者,应用锥形束计算机断层扫描(CBCT)进一步观察测量,为临床制定下颌第三磨牙拔除的手术方案及预防术后并发症做参考。方法:对曲面断层X线片显示下颌阻生第三磨牙(impacted mandibular third molar,IMTM)牙根与下颌管接触或部分重叠的患者168例(210)侧进一步行CBCT检查,观察下颌第三磨牙与下颌管的相对位置。结果:下颌管壁完整者93侧(44.3%),其中72侧(77.4%)下颌管位于IMTM牙根颊侧(1.95±0.95)mm;19侧(20.0%)在其正下方(2.61±1.37)mm;1侧(1.1%)位于其舌侧3.98mm;1侧(1.1%)位于牙根间。下颌管不完整者117侧。其中有较小范围缺损者(缺损最大径≤2mm)42侧(20.2%);而下颌管相对IMTM的位置,位于颊侧有23侧(54.8%),位于正下方14侧(33.3%),位于舌侧5侧(11.9%)。有较大范围缺损者(缺损最大径>2mm)75侧(36.1%);下颌管相对IMTM的位置,位于颊侧有20侧(26.7%),平均缺损最大径(6.42±2.45)mm,平均缺损面积(12.86±10.84)mm2;位于正下方43侧(57.3%),平均缺损最大径(7.90±2.87)mm,平均缺损面积(12.73±8.75)mm2;位于舌侧12侧(16.0%),平均缺损最大径(8.06±2.14)mm,平均缺损面积(21.40±11.84)mm2。结论:对于曲面断层片上提示IMTM与下颌管关系密切的患者,有必要进行CBCT检查,进一步了解其相对位置。

Objective： To investigate the real anatomical position of impacted mandibular third molar （IMTM） and mandibular canal （MC） in which showed overlapping images on orthopantomography. Methods： 168 patients with 210 IMTM touching or partially overlapping the MC on orthopantomographies, were further reexamined by CBCT. Software was used to measure and classify the images. SPSS 19.0 was used for statistical analysis. Results： 93 （44.3%） cases showed MC was complete, undisturbed and IMTM was in no contact with MC. Of which in 72 （77.4%） cases, IMTM root apex located at the buceal aspect of MC, and the average distance was （1.95±0.95） mm. In 19（20.0%） cases, IMTM root apex located at the inferior aspect, and the average distance was （2.61±1.37） mm. IMTM root apex located at the lingual aspect in 1 case and the distance was 3.98 ram, MC located at the interradicular space of IMTM in 1 case. 117 （55.7%） cases showed MC was incomplete and in contact with IMTM roots. 42 （20.2%） cases indicated a small bone defect （≤2mm）, 23（54.8%） of which was in the buccal aspect, 14（11.9%） was in the inferior aspect, and 5 was to the lingual aspect. 75（36.1%） cases indicated a larger bone defect （≥2mm）, 20 of which was located at IMTM＇s buccal aspect, the average diameter was （6.42±2.45） mm, and the average area was （12.86±10.84） mm2. 43 of which was located at IMTM＇s inferior aspect, the average diameter was （7.90±2.87） ram, and the average area was （12.73-±8.75） mm2; 12 of which was located at IMTM＇s inferior aspect , the average diameter was （8.06± 2.14） mm, and the average area was （21.40±11.84） mm2. Conclusion： A preoperative radiographic evaluation aims to identify the anatomical relationship of critical structures such as MC and IMTM, 3-D images obtained from CBCT are reliable.