A thin sheet of metal or resin forming part of an appliance. An expansion plate is an orthodontic appliance with an acrylic palatal plate, split in an antero-posterior direction into two halves separated by a screw which can be progressively rotated to provide lateral pressure on the teeth. A base plate forms part of an orthodontic or prosthetic appliance which is contoured to fit the mucosa and to which are attached teeth, springs, or clasps. Bite plate See bite. The cortical plate forms the superficial outer layer of bone. A lingual plate is a type of connector used in a lower removable partial denture to join the right and left sides; it lies lingual to the alveolar ridge behind the anterior teeth and extends across the gingival margins to the cingulum of each tooth. A palatal plate is a type of connector used to join the units of one side of a partial or complete denture with those located on the opposite side of the arch.