Obstructive sleep apnea patients with the oral appliance experience pharyngeal size and shape changes in three dimensions.

Pharyngeal size and shape differences between pre- and posttrials of a mandible-protruding oral appliance were investigated using cine computerized tomography (CT). Fourteen patients diagnosed with obstructive sleep apnea whose apnea-hypopnea index was higher than 5 and arousal index higher than 20 underwent a second overnight sleep study to evaluate the effectiveness of the oral appliance. Three-dimensional changes in pharyngeal shape measured on cross-sectional CT images during two respiratory cycles after oral appliance delivery were estimated by three variables: (1) lateral dimension, (2) anterior-posterior dimension, and (3) cross-sectional area at five vertical levels. Apnea indices improved significantly when the appliance was used. During apnea, measurements at retropalatal and retroglossal levels decreased most. However, the cross-sectional area of these levels appeared to increase significantly (P < .05) with the appliance in place during wakefulness. The oral appliance appears to enlarge the pharynx to a greater degree in the lateral than in the sagittal plane at the retropalatal and retroglossal levels of the pharynx, suggesting a mechanism for the effectiveness of oral appliances that protrude the mandible.