基于锥形束 CT 的强支抗内收上前牙病例牙根及牙槽骨的形态学分析

目的：借助锥形束CT(cone beam computed tomography，CBCT)资料，对成人强支抗内收上前牙病例的牙根及牙槽骨进行形态学分析，以全面了解大范围移动上前牙后，其牙根及牙槽骨的形态学变化。方法： 从就诊于北京大学口腔医院正畸科的患者中选取12例成人(18~40岁)上颌前突病例，在正畸治疗前后拍摄CBCT，利用转化头颅侧位片进行头影测量分析，通过构建治疗前后的矢状截面重叠图和三维重建图定性分析根周牙槽骨的相对变化规律，并定量测量治疗前后的牙根长度、唇腭侧不同水平牙槽骨厚度、唇腭侧及近远中牙槽骨高度。各项指标均由同一操作者重复测量3次取均值，并应用SPSS 17.0软件进行分析。结果： 12例中有6例切牙根周牙槽骨变化以唇侧骨厚度降低［根尖区牙槽骨厚度变化可达（-0.64±1.18） mm］、腭侧骨厚度增加［根尖区牙槽骨厚度变化可达(0.93±2.00) mm］、牙根少量吸收［（-0.95±0.79） mm］为特征，另6例的切牙根周牙槽骨变化以唇侧骨厚度增加［根尖区牙槽骨厚度变化可达（2.12±1.46） mm］、腭侧骨厚度降低［根尖区牙槽骨厚度变化可达（-2.88±0.58） mm］、牙根大量吸收［（-2.12±1.43） mm］为特征；12例尖牙治疗前后根周牙槽骨变化基本一致，唇侧骨厚度降低［根尖区牙槽骨厚度变化可达（-0.27±1.86） mm］，腭侧骨厚度有不同程度增加［根尖区牙槽骨厚度变化可达（6.40±6.00） mm］，牙根少量吸收［（-1.12±1.19） mm］；所有上前牙治疗后三维方向上牙槽骨高度均不同程度降低，腭侧最为显著。结论： 强支抗内收上前牙病例治疗后，切牙根尖移动量越大，牙根吸收量越大，牙根唇侧牙槽骨相对厚度增加、腭侧相对厚度减少，但整体厚度降低；治疗后上前牙牙槽骨高度普遍降低，并以腭侧最为明显。

Morphological analysis of roots and alveolar bone changes after upper anterior retraction with maximum anchorage based on cone-beam computed tomography

Objective:To investigate the remodeling of alveolar bone and the changes of roots after an-terior retraction with maximum anchorage by analyzing CBCT data from adult cases.Methods:The sam-ple comprised 48 incisors and 24 canines from 12 patients (18 to 40 years of age)with problems of ma-xillary protrusion or upper arch protrusion.CBCT scans were exposed before and after treatment,and la-teral cephalometric images as well as multiple planar reconstruction images were reconstructed.Tracing superimpositions of sagittal sections and three-dimensional reconstructions were done for qualitative analy-sis.For all maxillary anterior teeth,changes of root length,alveolar bone height and labial-palatal thick-nesses at different levels were evaluated.The average of measurements taken by the same tester in three times was processed by SPSS 17.0 statistical package.Results:In 6 of the 12 cases,alveolar thickness became thinner on labial side apical area:(-0.64 ±1.18)mm]while thicker on palatal side apical area:(0.93 ±2.0)mm]and the root length decreased(-0.95 ±0.79)mm].In the other 6 cases, the incisors’alveolar bone became thicker on labial side apical area:(2.12 ±1.46)mm]while thin-ner on palatal side apical area:(-2.88 ±0.58)mm]and the loss of root length was obvious(-2.12 ± 1.43)mm].In all the 12 cases,the canines’alveolar bone became thinner on labial side especially on the apical level (-0.27 ±1.86)mm]while greatly thicker on palatal side apical area:(6.40 ± 6.00)mm]and the root resorption was slight (-1.12 ±1.19)mm].For all the anterior teeth,the height of alveolar bone reduced around them after retraction.Conclusion:When the root apical moved more palatally,more root resorption would occur and the alveolar bone would get thicker on labial side but thinner on palatal side and thinner as a whole after anterior retraction with maximum anchorage.In the vertical direction,the height of the alveolar bone generally decreased on all sides and decreased the most on the palatal side.