Introducing SomnoDent® MAS. It is a Mandibular Advanced Splint (MAS) that treats mild, moderate and severe OSA by moving the lower jaw slightly forward. This movement tightens the soft tissue and muscles of the upper airway, which prevents obstruction while you sleep. The SomnoDent® MAS also prevents the tissues of the upper airway from vibrating as air passes over them, which is the major cause of snoring.