A method and system for preventing head injury by providing parallel alignmentof a jaw are disclosed. A method of preventing a head injury comprisesproviding a dental appliance (75) having a left body (76), a right body (77)and a lingual bar (80) engaging the left body (76) and the right body (77)；placing the dental appliance (75) over a plurality of teeth of a lower jaw(50) so the lower jaw (50) and a upper jaw (68) are approximately parallel；and absorbing a force applied to the lower jaw (50), wherein the dentalappliance (75) absorbs the force applied to the lower jaw (50) whilepreventing a condyle (57) of a mandible from transferring the force to atemporal bone (53).
