Mouthguards in sport activities : history, physical properties and injury prevention effectiveness.

Three systematic reviews were conducted on: (i) the history of mouthguard use in sports; (ii) mouthguard material and construction; and (iii) the effectiveness of mouthguards in preventing orofacial injuries and concussions. Retrieval databases and bibliographies were explored to find studies using specific key words for each topic. The first recorded use of mouthguards was by boxers, and in the 1920s professional boxing became the first sport to require mouthguards. Advocacy by the American Dental Association led to the mandating of mouthguards for US high school football in the 1962 season. Currently, the US National Collegiate Athletic Association requires mouthguards for four sports (ice hockey, lacrosse, field hockey and football). However, the American Dental Association recommends the use of mouthguards in 29 sports/exercise activities. Mouthguard properties measured in various studies included shock-absorbing capability, hardness, stiffness (indicative of protective capability), tensile strength, tear strength (indicative of durability) and water absorption. Materials used for mouthguards included: (i) polyvinylacetate-polyethylene or ethylene vinyl acetate (EVA) copolymer; (ii) polyvinylchloride; (iii) latex rubber; (iv) acrylic resin; and (v) polyurethane. Latex rubber was a popular material used in early mouthguards but it has lower shock absorbency, lower hardness and less tear and tensile strength than EVA or polyurethane. Among the more modern materials, none seems to stand out as superior to another since the characteristics of all the modern materials can be manipulated to provide a range of favourable characteristics. Impact studies have shown that compared with no mouthguard, mouthguards composed of many types of materials reduce the number of fractured teeth and head acceleration. In mouthguard design, consideration must be given to the nature of the collision (hard or soft objects) and characteristics of the mouth (e.g. brittle incisors, more rugged occusal surfaces of molars, soft gingiva). Laminates with different shock absorbing and stress distributing (stiffness) capability may be one way to accommodate these factors.Studies comparing mouthguard users with nonusers have examined different sports, employed a variety of study designs and used widely-varying injury case definitions. Prior to the 1980s, most studies exhibited relatively low methodological quality. Despite these issues, meta-analyses indicated that the risk of an orofacial sports injury was 1.6-1.9 times higher when a mouthguard was not worn. However, the evidence that mouthguards protect against concussion was inconsistent, and no conclusion regarding the effectiveness of mouthguards in preventing concussion can be drawn at present. Mouthguards should continue to be used in sport activities where there is significant risk of orofacial injury.