Department of Pharmacology, Nihon University School of Dentistry, 1-8-13 Kanda-Surugadai, Chiyoda-ku, Tokyo 101-8310, Japan; Department of Orthodontics, Nihon University School of Dentistry, 1-8-13 Kanda-Surugadai, Chiyoda-ku, Tokyo 101-8310, Japan.
Department of Pharmacology, Nihon University School of Dentistry, 1-8-13 Kanda-Surugadai, Chiyoda-ku, Tokyo 101-8310, Japan; Division of Oral and Craniomaxillofacial Research, Dental Research Center, Nihon University School of Dentistry, 1-8-13 Kanda-Surugadai, Chiyoda-ku, Tokyo 101-8310, Japan.
Brain Res. 2018 Nov 1;1698:62-69. doi: 10.1016/j.brainres.2018.06.022. Epub 2018 Jun 18.
During orthodontic treatment, binding teeth, may change the topographically organized representation of teeth in the cerebral cortex. To test the hypothesis that experimental tooth movement (ETM) changes the somatotopy of an individual tooth arrangement in the somatosensory cortex, we examined the spatiotemporal features of cortical excitatory propagation in response to mechanical stimulation of the maxillary incisor or molar using optical imaging in late adolescent rats without or with ETM. The ETM models consisted of 1d, 3d, and 7d ETM in which a closed-coil spring was ligated between the maxillary first molar and incisors. In controls, incisor and molar mechanical stimulation evoked excitation in the rostral and dorsocaudal regions of the primary somatosensory cortex (S1), respectively. In addition, the secondary somatosensory cortex and insular oral region (S2/IOR) were also activated. Incisor stimulation-induced excitatory regions in S1 of 3d and 7d ETM shifted without changing the maximum excitatory area or peak amplitude; the incisor stimulation-responding region moved toward the dorsocaudal region, which responded to molar stimulation in the control. This shift in excitatory region was not observed in 1d ETM. One day after removal of the coil spring that was attached for 6 days, the excitatory region shift in S1 was recovered to the control region. On the other hand, 1d ETM exhibited facilitation of the excitatory area and peak amplitude upon molar stimulation, and the facilitation of excitatory propagation disappeared in 3d and 7d ETM. These results may explain the clinical finding that abnormal sensation temporally occurs during orthodontic treatment.
在正畸治疗过程中，结扎牙齿可能会改变大脑皮层中牙齿的拓扑组织表现。为了验证实验性牙齿移动（ETM）是否会改变感觉皮层中单个牙齿排列的躯体分布的假设，我们使用光学成像技术，在没有 ETM 和有 ETM 的情况下，检查了青春期后期大鼠上颌切牙或磨牙机械刺激时皮质兴奋性传播的时空特征。ETM 模型包括 1d、3d 和 7d 的 ETM，其中在上颌第一磨牙和切牙之间结扎了一个闭线圈弹簧。在对照组中，切牙和磨牙的机械刺激分别在上颌初级体感皮层（S1）的头侧和背尾侧区域引起兴奋。此外，还激活了次级体感皮层和岛叶口腔区域（S2/IOR）。3d 和 7d ETM 的 S1 中切牙刺激诱导的兴奋性区域发生了移位，但最大兴奋性区域或峰值幅度没有变化；切牙刺激反应区域向背尾侧区域移动，而在对照组中，该区域对磨牙刺激有反应。在 1d ETM 中未观察到兴奋性区域的这种移位。在去除连接 6 天的线圈弹簧后的第 1 天，S1 中的兴奋性区域移位恢复到对照组区域。另一方面，1d ETM 在上颌磨牙刺激时表现出兴奋性区域和峰值幅度的增强，而 3d 和 7d ETM 中的兴奋性传播增强消失。这些结果可能解释了临床上在正畸治疗期间会出现暂时异常感觉的现象。
