mouth guard

A mouth guard is a shaped piece of plastic or rubber used to protect the teeth and gums from injury during contact sports activity, such as hockey or American football. Another kind of mouth guard, also called a sleep guard or bite guard, is used while sleeping to prevent the grinding of teeth or for other kinds of dental and orthodontic treatment. A mouth guard is worn inside the mouth, between the teeth, and so may only be visible when it is taken out, or the character's mouth is sufficiently open.