Abstract: An upper tray for receiving the maxillary teeth and a lower tray for receiving the mandibular teeth. Upper bite pads carried by the upper tray and lower bite pads carried by the lower tray. The lower bite pads located anterior to the upper bite pads so that the lower bite pads are free to engage the maxillary occlusal surface of the upper tray, and the upper bite pads are free to engage the mandibular occlusal surface of the lower tray to maintain the occlusal surfaces of the trays in a predetermined spaced relationship. The upper and lower bite pads are arranged to abut each other for advancing the mandible and preventing posterior movement of the mandible while allowing limited vertical and lateral movement. The bite pads are releasably carried by the trays for interchanging different sizes of pads to customize the appliance to the needs of the user's mouth.