Changes of neuroplasticity in cortical motor control of human masseter muscle related to orthodontic treatment

• Published in: Journal of oral rehabilitation Vol. 49; no. 2; pp. 258 - 264
• Main Authors: Liu, Weicai, Cui, Congcong, Hu, Zhonglin, Li, Juan, Wang, Jijun
• Format: Journal Article
• Language: English
• Published: England Wiley Subscription Services, Inc 01.02.2022
• Subjects: Cerebral blood flow; corticomotor control; Dental occlusion; Electromyography; Evoked Potentials, Motor; Excitability; Humans; Ischemia; Magnetic fields; Masseter Muscle; Motor Cortex; Motor evoked potentials; motor learning; Motor task performance; Muscle, Skeletal; Neural plasticity; Neuronal Plasticity; neuroplasticity; Orthodontics; Somatosensory cortex; Statistical analysis; Transcranial Magnetic Stimulation; Variance analysis; transcranial magnetic stimulation; motor learning; corticomotor control; masseter muscle; neuroplasticity
• ISSN: 0305-182X; 1365-2842
• DOI: 10.1111/joor.13298

Background Orthodontic treatment is a common clinical method of malocclusion. Studies have found that neurons in the sensorimotor cortex of the brain undergo adaptive remodeling in response to changes in oral behavior or occlusion. Objective To explore whether orthodontic treatment could be sufficient to cause neuroplastic changes in the corticomotor excitability of the masseter muscle. Methods Fifteen Angle Class II malocclusion patients who were receiving orthodontic treatment participated in the study. Cortical excitability was assessed by electromyographic activity changes evoked by transcranial magnetic stimulation. Four orthodontic time points were recorded, including baseline, day 1, day 7, and day 30. Motor evoked potentials (MEPs) were recorded in the masseter muscle and the first dorsal interosseous muscle (FDI) serving as a control. The data were analysed by stimulus–response curves and corticomotor mapping. Statistical analyses involved repeated measures analysis of variance, two‐way ANOVA, and Tukey's post hoc tests. Results Motor evoked potentials (MEPs) of the masseter muscle were significantly decreased during orthodontic treatment compared with those of the baseline (p < .001). MEPs of the masseter muscle were dependent on session and stimulus intensity (p < .001), whereas MEPs of FDI were only dependent on stimulus intensity (p = .091). Finally, Tukey's post hoc tests demonstrated that MEPs of the masseter muscle on days 1 and 7, with 70%–90% stimulus intensities, were higher than those of baseline values (p < .001). Conclusions The present study suggested that orthodontic treatment can lead to neuroplastic changes in the corticomotor control of the masseter muscle, which may add to our understanding of the adaptive response of subjects to changes of oral environment during the orthodontic treatment. Stimulated the cerebral cortex of orthodontic patients by transcranial magnetic stimulation. Changes in the amplitude of the masseter muscles MEPs and cerebral motor cortex map suggested the transformations of neuroplasticity in cortex, it may reflect adaptive sensorimotor changes in response to the orthodontic treatment‐induced altered environment in the oral cavity.