Mouth guards are required on all levels of performance and meant to cut down on dental damages. Most boxing mouthguards only cover the upper row of teeth, as double guards are notably harder to breathe through. They are typically made of a hard plastic that is softened by boiling, molded to the mouth, and then cooled down to hold shape. If a boxer is punched in the mouth or jaw, a broken tooth can pose a serious choking hazard. Using a mouthguard helps to absorb some of the shock from a punch and reduces the risk of breaking teeth. The mouthguards themselves can sometimes also prove to be a choking hazard. When a boxer is knocked unconscious, one of the first things a referee will do after separating the boxers is to remove the unconscious boxer's mouthpiece.