The effect of long-term mandibular advancement on the hyoid bone and pharynx as it relates to the treatment of obstructive sleep apnoea.

A cephalometric analysis was carried out to determine the effects of long-term mandibular advancement on the hard and soft tissues of the upper airway and, in particular, the relationship of the hyoid bone to both the cranium and the cervical spine, following mandibular advancement. One hundred consecutively-treated patients (87 males and 13 females; mean age: 49.26 years; SD: 8.56; range: 33-74 years) diagnosed with obstructive sleep apnoea and/or habitual snoring were reviewed at 6-month intervals over 6 to 30 months of treatment with a mandibular advancement splint. Significant changes to both the oropharynx and velopharynx were observed. At 12 months, the posterior airway space had increased from 10.71 mm to 11.99 mm (mean difference: 1.28 mm). At 6 months, significant changes had occurred in the soft palate length and thickness: a mean reduction in length of 1.46 mm (p < 0.0001) and in thickness of 0.57 mm. No changes were observed in the hypopharynx: the position of the hyoid bone remained unchanged in relation to both the cranium and cervical spine in all linear and angular measurements. The author concludes that mandibular advancement with oral appliances should be considered as a treatment for life.