锥形束CT与曲面断层片下颌神经管与牙槽骨嵴间距离的比较

目的：以锥形束CT（CBCT）下颌第一、第二磨牙牙槽骨嵴顶至下颌神经管上缘的垂直距离为基准,计算曲面断层片（OPG）上下颌第一、第二磨牙处垂直距离放大率,并检验其稳定性。方法：对50例一侧下颌第一、第二磨牙缺失患者同时拍摄CBCT与OPG,分别测量两种图像上下颌第一、第二磨牙区牙槽嵴顶至下颌神经管上缘距离,计算OPG下颌第一、第二磨牙处放大率,并利用频数分布图进行分析。结果：和CBCT相比,OPG下颌第一磨牙处垂直放大率平均为25.27%,下颌第二磨牙处垂直放大率平均为17.55%,两处放大率均较稳定。结论：OPG下颌第一磨牙处和第二磨牙处垂直放大率不同,但均较稳定,可从OPG粗略估算下颌神经管上缘与牙槽骨嵴间实际距离。

The comparative study of the distance between mandibular canal and alveolar bone crest in CBCT and orthpantomography

Objective： To calculate the vertical amplification ratios of OPG in the L1M area and the L2M area based on the distance between mandibular canal and alveolar bone crest in CBCT of first lower molar（L1M） area and second lower molar（L2M） area, and to examine the stability of the amplification ratios. Methods： Firty patients with one side L1M and L2M missing were selected, taking CBCT and OPG examinations simultaneouslys, to calculate the amplification ratios of OPG in the L1M area and the L2M area compared with CBCT, and to analyze the data by frequency pattern analysis. Results： The vertical amplification ratios of OPG in the L1M area and the L2M area were different（25.27% and 17.55%, respectively）, compared with CBCT, which were stable. Conclusion： It is feasible to estimate the distance between mandibular canal and alveolar bone crest in OPG clinically.