If physical contact is part of your martial arts training it's probably a good idea to get your hands on a mouth guard. No doubt you've assumed that it can help protect you from punches to the face, but you may not be aware of just how valuable wearing a mouth guard can be!
When fit snugly over the teeth a mouth guard puts a critical barrier between your opponent's attack and your mouth. Without it, a punch would smash into your lips and grind them into your teeth. If the attack is strong enough that impact can shatter a tooth directly. A good mouth guard will disperse the incoming energy and stop the upper shelf of teeth from grinding into the lower shelf.
Another symptom of strong strikes to the head is concussion. Through proper construction and close contact with the jaw, a pliable mouth guard will absorb a lot of the vibration that causes concussion, thus reducing the impact of the brain against the skull. This is by no means a fool-proof piece of protection, but when combined with headgear can make a significant difference.
Some other injuries that are reduced by mouth guard wear include: lacerations to the lips and cheeks, damage to the jaw joints, neck injury from sudden jaw movement, and fractures in facial bones.
Physical damage aside, wearing a properly fitted mouth guard can also increase the effectiveness of your airways and neuromuscular pathways. Proper intact of oxygen is critical during high intensity sports, and while wearing a mouth guard might seem inhibiting at first it can actually set your jaw in such a way as to promote good air intake.
Neuromuscular pathways refer to the amount of stress and tension in the body. The face and head hold a lot of tension in order to move quickly and powerfully on a moment's notice. Scientific investigations have revealed that when mouth guards properly align the jaw and provide "padding" they allow the face, neck, and head to relax, thus reducing stress and improving overall performance.