Effects of a mandibular advancement device on genioglossus in obstructive sleep apnoea hypopnea syndrome

Objective: To investigate effects of mandibular advancement device (MAD) therapy for obstructive sleep apnoea hypopnea syndrome (OSAHS) on the genioglossus contractile properties and fibre-type distribution. Materials and methods: Thirty 6-month old male New Zealand white rabbits were randomised into three groups: OSAHS, MAD, and controls. Rabbits in Group OSAHS and Group MAD were established as OSAHS models by injection, at a dose of 2ml hydrophilic polyacrylamide gel, via the submucous muscular layer of soft palate. Spiral computed tomography (CT) showed a significant reduced retropalatal upper airway, and apnoeas happened with an increase of Apnea Hypopnea Index (AHI) and a decrease of blood oxygen saturation during polysomnography (PSG), which indicated the OSAHS model developed successfully. OSAHS rabbits in Group MAD were fitted with a MAD made from self-curing composite resin, at 30 degrees to the upper incisors, and the mandible was guided forward 3 to 4mm. Further, spiral CT and PSG suggested MAD was effective. Rabbits in 3 groups were induced to sleep for 4–6 hours per day for 8 weeks, after which the genioglossus was removed, mounted in a tissue bath, and stimulated through platinum electrodes; maximal twitch tension, contraction time, half-relaxation time, force-frequency relationship, and fatigability were recorded. The percentage of Type I and Type II fibres was quantified. Results: The fatigability and percentage of Type II fibres of genioglossus increased in Group OSAHS compared with controls; this abnormality was corrected by MAD. Conclusion: MAD therapy for OSAHS could prevent genioglossus fatigue and abnormal fibre-type distribution of genioglossus in OSAHS.