Abstract: An intra-oral device for protecting oral tissues during radiation treatment is disclosed. In an embodiment, the device includes substantially a U-shaped upper member and lower members coupled to the upper member at their first and the second ends, and a substantially oval-shaped protective element disposed between the first ends of the upper and lower members and the second ends of the upper and lower members and movably coupled with one of the upper or lower members so as to provide for a three-dimensional spatial adjustment of the protective element between the first and second ends of the upper and lower members. The upper and lower members are configured to receive upper and lower teeth of a patient and the protective element is configured to engage a tongue of the patient so that the tongue is selectively positioned for treatment and/or diagnostic procedures.