The utilization of optimal orthodontic force is crucial to prevent undesirable side effects and ensure efficient tooth movement during orthodontic treatment. However, the sensitivity of existing detection techniques is not sufficient, and the criteria for evaluating optimal force have not been yet established. Here, by employing 3D finite element analysis methodology, we found that the apical distal region (A-D region) of mesial roots is particularly sensitive to orthodontic force in rats. Tartrate-resistant acidic phosphatase (TRAP)-positive osteoclasts began accumulating in the A-D region under the force of 40 grams (g), leading to alveolar bone resorption and tooth movement. When the force reached 80 g, TRAP-positive osteoclasts started appearing on the root surface in the A-D region. Additionally, micro-computed tomography revealed a significant root resorption at 80 g. Notably, the A-D region was identified as a major contributor to whole root resorption. It was determined that 40 g is the minimum effective force for tooth movement with minimal side effects according to the analysis of tooth movement, inclination, and hyalinization. These findings suggest that the A-D region with its changes on the root surface is an important consideration and sensitive indicator when evaluating orthodontic forces for a rat model. Collectively, our investigations into this region would aid in offering valuable implications for preventing and minimizing root resorption during patients’ orthodontic treatment.

利用最佳的正畸力对于防止不良副作用并确保正畸治疗期间牙齿有效移动至关重要。然而，现有检测技术的灵敏度不够，并且尚未建立评估最佳力的标准。在这里，通过采用3D有限元分析方法，我们发现大鼠近中根的根尖远端区域（AD区域）对正畸力特别敏感。抗酒石酸酸性磷酸酶（TRAP）阳性破骨细胞在40克（g）的作用力下开始在AD区域积聚，导致牙槽骨吸收和牙齿移动。当力达到 80 g 时，TRAP 阳性破骨细胞开始出现在 AD 区域的牙根表面。此外，微型计算机断层扫描显示在 80 g 下有显着的牙根吸收。值得注意的是，AD 区域被认为是整个牙根吸收的主要贡献者。通过对牙齿移动、倾斜和玻璃样变的分析，确定40g是牙齿移动的最小有效力，且副作用最小。这些发现表明，在评估大鼠模型的正畸力时，AD 区域及其牙根表面的变化是一个重要的考虑因素和敏感指标。总的来说，我们对该区域的研究将有助于为患者正畸治疗期间预防和最大程度地减少牙根吸收提供有价值的启示。