Mouthguards protect the teeth from injury during contact sports. Most commonly used in boxing and football, mouth guards can also provide protection in a variety of other sports such as soccer, basketball, lacrosse, hockey, etc. Not only do they help prevent oral/facial injuries, mouthguards are currently being researched to decrease the rate of concussions. See sportsdentistry.com
to find out more information on theories of how mouth guards may help with concussions.