An intra-oral device for positioning oral tissues during medical treatment, for example, radiation treatment. The device includes upper and lower dental arch members configured to engage the maxillary and mandibular teeth or edentulous arch(es) of a patient, respectively. Moldable material is maintained within channels formed in the dental arch members by partially extruding the material through keyways formed in the arch members during the bite mold process. The upper and lower dental arch members are operatively coupled to provide a dental arch assembly. A protective element to displace or depress a patients tongue is secured at a suitable working position with respect to the dental arch assembly via a threaded strut adjustably coupled between the protective element and a support structure disposed between the dental arch members.
