Root resorption is closely related to orthodontic force and affects orthodontic treatment with high incidence; however, the mechanism governing this effect is unclear. Microcracks are associated with bone resorption and may also play an important role in root resorption. This study aimed to assess the occurrence of microcracks on the root surface induced by orthodontic force, analyze the association between force and microcrack development, and propose potential measures to reduce microcracks. Different loads (0.5, 1, or 2 N) were applied between the left first molar and anterior teeth for different durations (1, 3, 7, or 14 days) in a rabbit model. The first molar was dissected and its surface was examined using scanning electron microscopy (SEM), which revealed the presence of microcracks on the compressed side of the root apices. The number, width, and length of microcracks were all positively correlated with the load magnitude and duration. The breaking strength of the root apex was tested by using a digital force tester. In addition, a finite element (FE) model was used to analyze the stress at the root apices and the crack propagation on the root surfaces. FE analysis calculated that the regions of maximum stress at the root apices were consistent with the microcrack regions observed via SEM. These results imply that orthodontic force can directly induce the occurrence and development of microcrack, and may contribute to further root resorption. Therefore, an appropriate interval and direction of orthodontic force may help reduce microcracks and prevent root resorption.

牙根吸收与正畸力密切相关，并以高发生率影响正畸治疗。但是，控制这种作用的机制尚不清楚。微裂纹与骨吸收有关，并且在根吸收中也可能起重要作用。这项研究旨在评估正畸力引起的牙根表面微裂纹的发生，分析力与微裂纹发展之间的关系，并提出减少微裂纹的潜在措施。在兔子模型中，在左第一磨牙和前牙之间施加不同的载荷（0.5、1或2 N），持续时间不同（1、3、7、14天）。解剖第一磨牙，并使用扫描电子显微镜（SEM）检查其表面，结果显示在根尖的压缩侧存在微裂纹。号码，微裂纹的宽度和长度均与载荷大小和持续时间成正相关。通过使用数字力测试仪测试根尖的断裂强度。此外，使用有限元（FE）模型分析根尖处的应力和根表面的裂纹扩展。有限元分析计算出，根尖处的最大应力区域与通过SEM观察到的微裂纹区域一致。这些结果表明，正畸力可以直接引起微裂纹的发生和发展，并可能有助于进一步的牙根吸收。因此，适当的正畸力间隔和方向可以帮助减少微裂纹并防止牙根吸收。通过使用数字力测试仪测试根尖的断裂强度。此外，使用有限元（FE）模型分析根尖处的应力和根表面的裂纹扩展。有限元分析计算出，根尖处的最大应力区域与通过SEM观察到的微裂纹区域一致。这些结果表明，正畸力可以直接引起微裂纹的发生和发展，并可能有助于进一步的牙根吸收。因此，适当的正畸力间隔和方向可以帮助减少微裂纹并防止牙根吸收。通过使用数字力测试仪测试根尖的断裂强度。此外，使用有限元（FE）模型分析根尖处的应力和根表面的裂纹扩展。有限元分析计算出，根尖处的最大应力区域与通过SEM观察到的微裂纹区域一致。这些结果表明，正畸力可以直接引起微裂纹的发生和发展，并可能有助于进一步的牙根吸收。因此，适当的正畸力间隔和方向可以帮助减少微裂纹并防止牙根吸收。有限元分析计算出，根尖处的最大应力区域与通过SEM观察到的微裂纹区域一致。这些结果表明，正畸力可以直接引起微裂纹的发生和发展，并可能有助于进一步的牙根吸收。因此，适当的正畸力间隔和方向可以帮助减少微裂纹并防止牙根吸收。有限元分析计算出，根尖处的最大应力区域与通过SEM观察到的微裂纹区域一致。这些结果表明，正畸力可以直接引起微裂纹的发生和发展，并可能有助于进一步的牙根吸收。因此，适当的正畸力间隔和方向可以帮助减少微裂纹并防止牙根吸收。