A thermoplastic mouthguard has a U-shaped base with top and bottom sides and upward inner lingual and outer labial walls forming a channel for the upper jaw teeth having posterior and anterior portions. Occlusal posterior pads are on the bottom side of the base along the posterior portions of the guard to space apart the anterior teeth of the lower jaw from the anterior portion of the bottom side of the U-shaped base and to lessen pressure and possible impact forces exerted at the temporomandibular joint. Occlusal impact chambers are located within the occlusal posterior pads for shock dissipation and absorption. Anteriorly directed ridges are located along the bottom of the impact surfaces of the occlusal posterior pads for custom fitting of the mouthguard and tending to move the lower jaw anteriorly when a force impact is imposed upon the lower jaw. An anterior impact brace is located along the anterior portion of the outer labial wall. A connecting tab may extend from the mouthguard for connecting the guard to a fastening point on the user. A rigid framework tray is provided for assisting in heating the mouthguard and positioning and aligning the mouthguard for custom formation to the user's mouth.
