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Abstract: The purpose of this study was to demonstrate the feasibility of applying cone-beam computed tomography (CBCT) to observe dimensional changes in human alveolar bone continuously after tooth extraction. Sixty patients were selected from a CBCT database. Each patient had two CBCT scans (CBCT I and CBCT II), one taken before and one taken after implant surgery. A fixed anatomic reference point was used to orient the horizontal slice of the two scans. The alveolar ridge width was measured on the horizontal slice. In each series of CBCT I sagittal slices, the number of slices from the start point to the pulp center of the test tooth was recorded. The tooth length was measured on the sagittal slice. In each series of CBCT II slices, tooth length was measured on a sagittal slice selected based on the number of slices from the start point to the pulp center recorded in CBCT I. Intraobserver reliability, assessed by the intraclass correlation coefficient (ICC), was high. Paired sample t-tests of repeated measurements of both tooth length and alveolar bone width showed no statistically significant differences (P<0.05). This study has proved that projection differences among CBCT scans taken at different time points from one patient can be neglected without affecting the accuracy of millimeter scale measurements. CBCT is a reliable imaging tool for continuously observing dimensional changes in human alveolar bone.

锥形束计算机断层摄影定位观察人类拔牙后牙槽突外形变化规律的可行性研究

研究目的：探讨同一患者不同时期所拍的锥形束计算机断层摄影（CBCT）是否因每次拍摄时投照角度不可能完全一致而影响数据测量的准确性。
创新要点：提出了一种人类后牙拔除后观察牙槽突外形变化的准确、无创、科学的定位方法。
研究方法：选择首都医科大学附属北京口腔医院种植中心60名患者两份于上颌后牙种植前后拍摄的CBCT影像资料。以磨牙根分叉区三个牙根开始分开处（图像上显示为三根恰好融合的点）为基准点定位两次CBCT的起始水平断层。在第一次CBCT的起始水平断层上，连线牙列远端磨牙参照点即矢状断层起点与近端双尖牙的髓室中心进行矢状断层重建。若实验牙为第一磨牙，找到通过其腭根髓室中心的矢状断层；若实验牙为第二双尖牙，找到通过其髓室中心的矢状断层。记录由矢状断层起点到实验牙移动的层数N，在水平断层上测量实验牙牙槽骨宽度，在实验牙髓室中心的矢状断层上测量牙全长。在第二次CBCT中依据第一次记录的移动层数N定位矢状断层，在定位后的矢状断层上测量实验牙全长，在水平断层的相应定位处测量牙槽骨宽度。
重要结论：利用本研究提出的定位方法可以精准定位同一患者不同CBCT 影像资料中的同一断层，从而实现拔牙位点动态连续观察。

关键词：锥形束计算机断层摄影（CBCT）；牙槽突改建；拔牙位点

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