Sood Mandeep, Lee Jye-Chang, Avivi-Arber Limor, Bhatt Poolak, Sessle Barry J
Graduate Program in Orthodontics and Collaborative Program in Neuroscience, Faculty of Dentistry, University of Toronto, Ontario, M5G 1G6, Canada.
Department of Oral Physiology, Faculty of Dentistry, University of Toronto, Ontario, M5G 1G6, Canada.
J Comp Neurol. 2015 Jul 1;523(10):1548-68. doi: 10.1002/cne.23753. Epub 2015 Mar 10.
Orthodontic tooth movement (OTM) causes transient pain and changes in the dental occlusion that may lead to altered somatosensory inputs and patterns of mastication. This study used intracortical microstimulation (ICMS) and electromyographic (EMG) recordings to test whether neuroplastic changes occur in the ICMS-defined motor representations of left and right anterior digastric (LAD, RAD), masseter, buccinator, and genioglossus (GG) muscles within the rat's face primary motor cortex (face-M1) and adjacent face primary somatosensory cortex (face-S1) during OTM. Analyses included any changes in the number of ICMS sites representing these muscles and in the onset latencies of ICMS-evoked responses in the muscles. Sprague-Dawley rats were divided into experimental (E), sham (S), and naive (N) groups; OTM was induced in the E group. Statistical analyses involved a mixed model repeated-measures analysis of variance (MMRM ANOVA). OTM resulted in significant neuroplastic changes in the number of positive sites in the E group for LAD, RAD, and GG muscles in face-M1 and face-S1 at days 1, 7, and 28 of continuous orthodontic force application, and in the number of sites in face-M1 from which ICMS could simultaneously evoke EMG responses in different combinations of LAD, RAD, and GG muscles. However, the onset latencies of ICMS-evoked responses were not significantly different between groups or between face-M1 and face-S1. The neuroplastic changes documented in this study may reflect adaptive sensorimotor changes in response to the altered environment in the oral cavity induced by OTM.
正畸牙齿移动（OTM）会引起短暂疼痛和牙合变化，这可能导致体感输入和咀嚼模式改变。本研究采用皮层内微刺激（ICMS）和肌电图（EMG）记录，以测试在OTM期间，大鼠面部初级运动皮层（面部M1）和相邻的面部初级体感皮层（面部S1）中，ICMS定义的左右前腹直肌（LAD、RAD）、咬肌、颊肌和颏舌肌（GG）肌肉的运动表征是否发生神经可塑性变化。分析内容包括代表这些肌肉的ICMS位点数量的任何变化以及ICMS诱发的肌肉反应的起始潜伏期变化。将Sprague-Dawley大鼠分为实验组（E）、假手术组（S）和未处理组（N）；对E组诱导OTM。统计分析采用混合模型重复测量方差分析（MMRM ANOVA）。在持续施加正畸力的第1天、第7天和第28天，OTM导致E组面部M1和面部S1中LAD、RAD和GG肌肉的阳性位点数量发生显著的神经可塑性变化，以及面部M1中ICMS能够同时诱发LAD、RAD和GG肌肉不同组合的EMG反应的位点数量发生变化。然而，ICMS诱发反应的起始潜伏期在各组之间以及面部M1和面部S1之间没有显著差异。本研究记录的神经可塑性变化可能反映了对OTM引起的口腔环境改变的适应性感觉运动变化。
