Cephalometric and physiologic predictors of the efficacy of an adjustable oral appliance for treating obstructive sleep apnea

The purpose of this study was to investigate whether any physiologic or cephalometric parameters could be used to predict the efficacy of an adjustable mandibular advancement appliance for treating obstructive sleep apnea (OSA). Forty-two male and 5 female patients with OSA were recruited on the basis of baseline polysomnography with a documented Apnea and Hypopnea Index (AHI) greater than 15 per hour. Repeat polysomnography was performed with the appliance in place. Baseline cephalometry was performed for each patient, and follow-up cephalometry was completed for 19 of the subjects. The subjects were divided into 3 groups on the basis of the degree of change in the AHI with oral appliance therapy: good response (> 75% decrease in AHI), moderate response (25% to 75% decrease in AHI), and poor response (< 25% decrease in AHI). Patients with a good response were younger and had smaller upper airways. In a linear regression analysis, the change in AHI (%) was associated with physiologic (age and body mass index), cephalometric (overjet, height of the maxillary molars, vertical height of the hyoid bone), and airway variables. However, changes in either overbite or overjet were not related to changes in any of the polysomnographic variables for the 19 subjects. A stepwise regression analysis revealed a better treatment response with the adjustable mandibular advancement appliance in patients who were younger and had a lower body mass index, a longer maxilla, a smaller oropharynx, a smaller overjet, less erupted maxillary molars, and a larger ratio of vertical airway length to the cross-sectional area of the soft palate.