Mouth guards include either an upper member fitting the interior and exterior surfaces of a user's upper dentition, or a lower member fitting similarly adjacent a user's lower dentition, or both. The lower member includes molar extensions projecting away from the lower member. The upper member includes upper molar extensions projecting away from the upper member and toward the lower molar extensions so that when the user bites or clenches, the upper right and lower right extensions impinge on one another, as do the molar upper left and lower left extensions. The upper and lower members have an anterior shape to form a gap ranging from about 5 to about 15 mm and sufficient for the user's tongue to extend into the gap. Methods of using the apparatus and kits as mouth guards.