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Abstract: The purpose of this study was to apply cone-beam computed tomography (CBCT) to observe contour changes in human alveolar bone after tooth extraction of the maxillary central incisor and to provide original morphological evidence for aesthetic implant treatment in the maxillary anterior area. Forty patients were recruited into the study. Each patient had two CBCT scans (CBCT I and CBCT II), one taken before and one taken three months after tooth extraction of maxillary central incisor (test tooth T). A fixed anatomic reference point was used to orient the starting axial slice of the two scans. On three CBCT I axial slices, which represented the deep, middle, and shallow layers of the socket, labial and palatal alveolar bone widths of T were measured. The number of sagittal slices from the start point to the pulp centre of T was recorded. On three CBCT II axial slices, the pulp centres of extracted T were oriented according to the number of moved sagittal slices recorded in CBCT I. Labial and palatal alveolar bone widths at the oriented sites were measured. On the CBCT I axial slice which represented the middle layer of the socket, sagittal slices were reconstructed. Relevant distances of T on the sagittal slice were measured, as were the alveolar bone width and tooth length of the opposite central incisor. On the CBCT II axial slice, which represented the middle layer of the socket, relevant distances recorded in CBCT I were transferred on the sagittal slice. The height reduction of alveolar bone on labial and palatal sides was measured, as were the alveolar bone width and tooth length of the opposite central incisor at the oriented site. Intraobserver reliability assessed by intraclass correlation coefficients (ICCs) was high. Paired sample t-tests were performed. The alveolar bone width and tooth length of the opposite central incisor showed no statistical differences (P<0.05). The labial alveolar bone widths of T at the deep, middle, and shallow layers all showed statistical differences. However, no palatal alveolar bone widths showed any statistical differences. The width reduction of alveolar bone was 1.2, 1.6, and 2.7 mm at the deep, middle, and shallow layers, respectively. The height reduction of alveolar bone on labial and palatal sides of T both showed statistical differences, which was 1.9 and 1.1 mm, respectively.

人类上颌中切牙拔除后牙槽骨外形变化的研究

观察人类上颌中切牙拔除后牙槽骨外形改建的规律。 锥形束计算机断层摄影（CBCT）在口腔硬组织测量方面具有可靠性，在不同时期拍摄的影像中测量具有可重复性。本研究充分利用这一影像学工具观察人类上颌中切牙拔除后牙槽骨改建的规律。 选择40名患者上颌中切牙拔牙前和拔牙后三个月时拍摄的两份CBCT影像资料。在第一次CBCT中，选取中切牙拔牙窝深、中、浅三个水平断层进行矢状断层重建，分别记录矢状断层起点到拟拔除中切牙（实验牙T）牙髓中心移动的层数，并测量实验牙T处牙槽骨宽度，在中切牙拔牙窝中层测量腭平面相关垂直距离。在第二次CBCT的三个水平断层上，依据第一次记录的移动层数定位实验牙T，并在定位处测量牙槽骨宽度。在中切牙拔牙窝中层上转移第一次CBCT记录的腭平面相关距离，并测量唇腭侧牙槽嵴顶沿原牙根外形垂直吸收的距离。 上颌中切牙拔除后三个月，在拔牙窝的不同深度，唇侧的牙槽骨均有不同程度的水平骨吸收，越接近牙槽嵴顶处牙槽骨吸收越明显。唇腭侧牙槽嵴顶均有明显的垂直骨吸收，唇侧牙槽嵴顶的垂直骨吸收比腭侧明显。
锥形束计算机断层摄影（CBCT）；牙槽突外形；上颌中切牙

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