All athletes playing a sport should wear a mouth guard, but you should be especially cautious when playing contact sports like football, hockey, or boxing. Mouth guards should also be worn when playing a sport where another athlete or ball could hit you in the face, like basketball, baseball, soccer, volleyball, or wrestling. There are several types of mouth guards available, but a custom mouth guard made by your dentist will provide the most comfort and protection.
References:
American Dental Association, Policy Statement on Orofacial Protectors. Transactions; 1995. p. 613.
ADA Council on Access P, Interprofessional R, Affairs ADACoS. Using mouthguards to reduce the incidence and severity of sports-related oral injuries. J Am Dent Assoc 2006;137(12):1712-20.