An intra-oral device comprising an upper splint (7100), a lower splint (7200) and a pair of lateral connecting rods (7300). Each connecting rod has a first rod end (7310) that connects to the lower splint and a second rod end (7320) that connects to the upper splint. The connecting rods (7300) are configured to maintain the mandible in an advanced position relative to the maxilla. The upper splint (7100) includes at least one upper gutter portion (7110) that retains the upper splint on the maxilla. The lower splint (7200) includes at least one lower gutter portion (7210) that retains the lower splint on the mandible. The thickness of the at least one upper gutter portion and/or the at least one lower gutter portion may vary across the profile of the teeth.
