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Study Objectives: This study aims to investigate whether the use of a mandibular advancement device (MAD) is associated with neuroplasticity in corticomotor control of tongue and jaw muscles. Methods: Eighteen healthy individuals participated in a randomized crossover study with 3 conditions for 2 weeks each: baseline, wearing an oral appliance (sham MAD), or MAD during sleep. The custom-made MAD was constructed by positioning the mandible to 50% of its maximal protrusion limit. Transcranial magnetic stimulation was applied to elicit motor-evoked potentials (MEPs). The MEPs were assessed by constructing stimulus-response curves at 4 stimulus intensities: 90%, 100%, 120%,and 160% of the motorthreshold from theright tongue andright masseter and thefirst dorsal interosseous muscles (control) at baseline, afterthe first and the second intervention. Results: There was a significant effect of condition and stimulus intensity both on the tongue and on masseter MEPs (P < .01). Tongue and masseter MEPs were significantly higher at 120% and 160% after the MAD compared with the oral appliance (P < .05). There were no effects of condition on first dorsal interosseous muscle MEPs (P = .855). Conclusions: The finding suggests that MAD induces neuroplasticity in the corticomotor pathway of the tongue and jaw muscles associated with the new jaw position. Further investigations are required in patients with obstructive sleep apnea to see whether this cortical neuroplasticity may contribute or perhaps predict treatment effects with MADs in obstructive sleep apnea.
Matsuzaki et al. (Tue,) studied this question.