Mechanism of action
Mandibular repositioning devices (MRDs) hold the lower jaw in a forward position during sleep. In doing so, they:
- Create an anterior movent of suprahyoid and genioglossus muscles. (The suprahyoid muscle widens the oesophagus during swallowing and the genioglossus muscle depresses and protrudes the tongue
- Decrease the gravitational effect of the tongue
- Stretch the soft palate
- Stabilize the mandible to the hyoid bone. (The hyoid bone attaches to the muscles of the floor of the mouth and the tongue above; to the larynx below; and to the epiglottis and pharynx behind. This results in an increase in lateral pharyngeal cross-sectional area upper airway muscle activity to prevent snoring and obstructive apneas).
With Narval CC, the posterior rotation axes are elevated, making the connecting rods parallel to a patient's jawline, and allowing the retention force to work along the occlusal plane. In their biomechanical simulation study, Cheze et al1 showed this articulation to create 10% less stress on the TMJ than a conventional compression-based device and to sustain mouth-closing and physiological breathing during sleep.
Clinical studies show that custom-made MRDs are effective in treating mild to moderate obstructive sleep apnea and snoring. They reduce symptoms that go with OSA too, like daytime sleepiness and fatigue. MRDs also help people with severe OSA who have not been able to adhere to continuous positive airway pressure (CPAP) treatment.
Indications for custom MRDs2
MRDs are the first line of treatment for mild to moderate OSA patients who:
- Do not adhere to PAP treatment
- Prefer MRDs over PAP treatment
- Fail behavioral treatment measures
- Are inappropriate candidates for or fail to comply with CPAP
MRDs are the second line of treatment for severe OSA (AHI > 30) after CPAP trial.