Abstract: An orthotic device (100) for retaining a patient's mandible in an advanced or protrusive position comprises an intraoral anterior mandibular abutment surface (125) for resisting mandibular retraction by abutting the gingiva covering the mandible and an extramaxillary anterior maxillary abutment surface (115) against which the intraoral anterior mandibular abutment surface (125) is braced. In order to resist rotation of the dental orthotic produced by the interaction of the intraoral anterior mandibular abutment surface and the extramaxillary anterior maxillary abutment surface, the orthotic device is provided with an intraoral posterior maxillary abutment surface (140). The relative positions of the maxillary and/or mandibular abutment surfaces may be adjusted to suit the requirements of the user.