Though they may not prevent a concussion, it makes sense that they could theoretically decrease a hard impact to the jaw from radiating to the skull and lessen the blow. More importantly, mouthguards help prevent trauma to the teeth and face.

Do mouthguards significantly reduce the rate and severity of concussions?

Although mouth guards have been shown to be effective in preventing dental and oro-facial injury, there is currently no evidence that standard or fitted mouth guards decrease the rate or severity of concussions in athletes (85).

Do helmets and mouthguards prevent concussions?

Mouth guards do not appear to prevent concussions, but prevent other facial injuries in sports. Helmets prevent head injuries in sports and motorcycling; however, future research should assess concussion as an independent outcome.