Han Guangli, Huang Shengfu, Von den Hoff Johannes W, Zeng Xianglong, Kuijpers-Jagtman Anne Marie
Department of Orthodontics, School and Hospital of Stomatology, Wuhan University, People's Republic of China.
Angle Orthod. 2005 Nov;75(6):912-8. doi: 10.1043/0003-3219(2005)75[912:RRAOIA]2.0.CO;2.
The aim of this investigation was to compare root resorption in the same individual after application of continuous intrusive and extrusive forces. In nine patients (mean age 15.3 years), the maxillary first premolars were randomly intruded or extruded with a continuous force of 100 cN for eight weeks. Eleven maxillary first premolars from six randomly selected orthodontic patients served as controls. Root resorption was determined using scanning electron microscopy. Quantitative assessment of the percentage of resorbed area of the total root surface was performed on composite micrographs. The severity of root resorption was also assessed by visual scoring of the roots. Root resorption mainly occurred at the apical part of the roots in both experimental groups. A significant difference in root resorption was found between the intruded and the control teeth (P = .006) but not between the extruded and the control teeth. However, the mesial and distal root surfaces showed resorption on 5.78 +/- 3.86% of the root surface of the intruded teeth and 1.28 +/- 1.24% of the root surface of the extruded teeth, and this difference was significant (P = .004). In addition, a large individual variation was found. From this study, it can be concluded that intrusion of teeth causes about four times more root resorption than extrusion. Because the amount of root resorption due to intrusion or extrusion in the same patient is correlated, every clinician should be aware that the extrusion of teeth might also cause root resorption in susceptible patients.
本研究的目的是比较同一患者在施加持续侵入力和持续牵张力后牙根吸收的情况。在9名患者（平均年龄15.3岁）中，对上颌第一前磨牙随机施加100 cN的持续力，使其侵入或伸长8周。从6名随机选择的正畸患者中选取11颗上颌第一前磨牙作为对照。使用扫描电子显微镜确定牙根吸收情况。在合成显微照片上对牙根总表面积的吸收面积百分比进行定量评估。还通过对牙根进行视觉评分来评估牙根吸收的严重程度。两个实验组的牙根吸收主要发生在牙根的根尖部分。侵入组牙齿与对照组牙齿之间在牙根吸收方面存在显著差异（P = 0. .006），但伸长组牙齿与对照组牙齿之间无显著差异。然而，侵入组牙齿的近中根面和远中根面吸收面积占牙根表面积的5.78±3.86%，伸长组牙齿为1.28±1.24%，这种差异具有统计学意义（P = 0. .004）。此外，还发现个体差异较大。从本研究可以得出结论，牙齿侵入导致的牙根吸收比伸长大约多四倍。由于同一患者因侵入或伸长导致的牙根吸收量具有相关性，每位临床医生都应意识到，牙齿伸长在易感患者中也可能导致牙根吸收。
