The efficacy of a mandibular advancement splint in relation to cephalometric variables.

The efficacy of a titratable mandibular advancement splint (MAS) for the management of obstructive sleep apnea (OSA) was investigated in relation to supine cephalometric variables. Fourteen adults with diagnosed OSA were recruited following an initial polysomnogram. Supine cephalographic radiographs were taken at baseline and subjects wore the MAS nightly for 6 to 8 weeks. The polysomnogram and cephalogram were repeated with the MAS at maximal titration. The MAS resulted in complete or partial treatment response in all subjects as measured by the improvement in mean apnea/hypopnea index (AHI) (baseline AHI 34 +/- 22/hr, with MAS 10 +/- 5/hr; p = 0.001). The perpendicular distance between the hyoid bone and the mandibular plane (HYML) measured in awake subjects decreased with the MAS (baseline HYML 25.3 +/- 7.8 mm, with MAS 16.5 +/- 9.6 mm; p = 0.002). Baseline HYML was the only cephalometric variable associated with a successful clinical outcome. It was strongly linked to improvements in AHI (adjusted R(2) = 0.37, p = 0.012) and arousals (adjusted R(2) = 0.455, p = 0.005). We conclude that the MAS is an effective therapy for OSA and baseline HYML is an important predictor of improvement. Improvements in AHI may be explained by the MAS maintaining the new or existing relationship of the hyoid and its surrounding structures, thus preventing obstruction in the upper airway during sleep.