An intraoral mandibular advancement device to treat sleep disorders in a user having an obstructed airway includes a maxillary appliance with a main body for removable attachment to the maxillary teeth; a protrusive element distending from the central portion of the main body; and retention means extending from the main body for retention of the device on the maxillary teeth during sleep. A mandibular appliance removably attaches to the mandibular anterior teeth and includes a lingual spacer that extends posteriorly from the mandibular anterior teeth. The anterior aspect of the protrusive element of the maxillary appliance contacts the posterior edge of the lingual space and thereby causes mandibular advancement.