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).

During sleep, the muscles in the oropharyngeal space relax, the tongue falls back and the volume of the pharynx decreases. Air cannot pass through as it would in the awake state and thus airflow limitations occur. Diminishing airflow can lead to snoring or to the airways collapsing completely (obstructive sleep apnea, OSA). Patients who suffer from OSA have trouble breathing during sleep and will have a disturbed sleep architecture as repeated airway closure causes wake reactions and arousals. This does not only lead to severe daytime sleepiness with high risk of causing car accidents, for instance, but also affects synaptic activity during sleep and the balance of blood gas levels. These factors can have a aggravating effect on blood pressure and worsen the prognosis for cardiovascular comorbidities. First line therapy for obstructive sleep apnea (OSA) is positive airway pressure (PAP) that keeps the airways open with a pneumatic splint. Positive airway pressure is being applied through a facial mask and some patients cannot tolerate this therapy or refuse it. An alternative treatment approach is by fitting an MAD that the patient wears during sleep. An MAD pushes the lower jar forward and thereby increases the volume of the upper airways, thus preventing them to close. Studies have shown good compliance with MAD therapy and benefits in terms of sleepiness and quality of life. The Narval registry study aims to investigate MAD usage in real life and reasons for non-compliance. The registry aims to record patient characteristics (e.g. comorbidities) and side effects that lead to a termination of therapy, but also how the costs for therapy are split between the patient and public or private health insurance providers and how this affects therapy initiation and usage.

Inclusion Criteria:

• Prescription of any mandibular advancement device
• Age ≥ 18 years
• Ability to understand the study information and information on usage of personal data
• Signed and dated informed consent

Exclusion Criteria:

• Patients with central sleep apnea (central AI > 5/hour)
• Patients with loose teeth and severe parodontitis
• Patients with completely missing teeth or removable tooth replacement, or with a teeth health insufficient to retain an MAD Patients with missing molars Patients with maximum protrusion of less than 5mm

Eligible for recruitment are male and female patients of ≥ 18 years who have been diagnosed with OSA and who are not eligible for PAP treatment (no tolerance of PAP therapy, therapy refusal for any reason). Patients who have been prescribed an MAD as treatment for OSA. Patients will be followed in their clinical routine treatment pathway.