The effect of mandibular advancement appliances on awake upper airway and masticatory muscle activity in patients with obstructive sleep apnoea.

Background: There is little understanding of how dental appliances, designed to posture the mandible forwards, act on pharyngeal airway dilatory and masticatory muscles in patients with obstructive sleep apnoea (OSA). This study evaluates, in a prospective cohort design, the effect of mandibular advancement splints (MAS) on awake genioglossus (GG), geniohyoid (GH) and masseter (M) muscle activity.

Methods: Fifty OSA patients received a custom-made removable Herbst MAS appliance, adjusted for maximum therapeutic benefit, as judged by subjective improvement. Awake electromyographic (EMG) activity was recorded at baseline and with the MAS in situ, by using bipolar surface electrodes in patients seated upright and in the natural head position. The lower splint was modified to facilitate the placement of the intra-oral bipolar surface electrodes used to record GG EMG activity.

Results: Significant increases in GG (P = 0.041), GH (P<0.001) and M (P<0.001) muscle activity accompanied placement of the MAS.

Conclusions: These findings support the contention of a physiological role, which may act to augment the anatomical action of MAS.