A rigid or flexible prefabricated device intended to overlay the occlusal surfaces of the teeth to maintain the position of displaced or moveable teeth, to treat clenching and bruxism and their sequelae, and to provide temporary relief from muscle or temporo-mandibular joint (TMJ) pain (e.g., from TMJ dysfunction). It is removable by the patient (e.g., during meals), and is typically made of standard, preformed materials that are not moulded, or intended to be moulded to a specific patient. This is a reusable device.