Musculoskeletal repositioning devices are described. The devices are worn in the mouth and cause the lower jaw of the wearer to move into an active optimal position that relieves stress on the temporomandibular joint, causing increased muscular strength and decreased muscular tension. The devices have ramps on their upper surfaces which contact the upper posterior teeth and lingual anatomy and cause the jaw to reposition from a passive bite position to an active optimal bite position. A casting device for forming a musculoskeletal repositioning device and a method for using the casting device are also described.