High Quality Content by WIKIPEDIA articles! A mouthguard is a protective device for the mouth that covers the teeth and gums to prevent and reduce injury to the teeth, arches, lips and gums. A mouthguard is most often used to prevent injury in contact sports, as a treatment for bruxism or TMD, or as part of certain dental procedures, such as tooth bleaching. Depending on application, it may also be called a mouth protector, mouth piece, gumshield, gumguard, nightguard, occlusal splint, bite splint, or bite plane.