The Mandibular Advancement Splint (MAS)?or?Mandibular Advancement Device (MAD)?is a sleep apnoea device that is worn on the teeth during sleep like an orthodontic appliance. Also known as an anti-snoring device, the splint is used to prevent the soft tissue from collapsing into the airway and disrupting normal breathing patterns. Scientific evidence shows that the device is effective in treating mild to moderate obstructive sleep apnoea and getting rid of snores.