During sleep, the muscle tonus in the oropharyngeal space is lost, the tongue might fall back andthe volume of the pharynx decreases. Air cannot pass through as it would in the awake state and thus airflow limitations occur. The person asleep might compensate the flow limitation by breathing faster, which causes the soft tissue to vibrate (= snoring). Further narrowing of the airways can lead to obstructive apneas (complete airway collapse and stopping of airflow). First line therapy for obstructive sleep apnea (OSA) is positive airway pressure (PAP) that keeps the airways open with a pneumatic splint. Since PAP involves wearing a facial mask that applies air pressure into the airways, some patients cannot tolerate this therapy. These patients might be candidates for an alternative treatment approach with a mandibular advancement device (MAD).