Athletes wear mouth guards primarily to prevent dental and facial injuries during contact and high-impact sports. The protection is substantial: a 2019 systematic review found that people who skipped mouth guards had more than twice the risk of orofacial injury, while mouth guard users were between 82% and 93% less likely to suffer dentofacial injuries overall.
How Mouth Guards Absorb and Spread Impact
A mouth guard works by doing two things at once when something hits your face. First, the resilient material absorbs some of the impact energy, acting as a shock absorber between the blow and your teeth. Second, it spreads that remaining force across a much larger surface area than the small point of contact where the hit actually landed. Think of it like snowshoes on soft ground: the same weight distributed over a wider area means less pressure in any one spot. By spreading the impact across the entire arch of teeth rather than concentrating it on one or two, the guard keeps the force on any individual tooth below the threshold where fractures and knockouts happen.
What Mouth Guards Actually Protect
The most obvious benefit is keeping teeth intact. A study of professional handball players found that those wearing mouth guards were 5.55 times less likely to suffer dental injuries, including tooth fractures and teeth being knocked out entirely. Among college basketball players, the dental injury rate was five times lower for those using custom-fitted guards compared to those going without.
But the protection extends well beyond teeth. A mouth guard acts as a physical barrier between your teeth and the soft tissue inside your mouth, preventing your lips, tongue, and inner cheeks from getting cut against sharp tooth edges during a collision. It also prevents your upper and lower teeth from slamming together violently, which can crack or chip teeth even without an external blow.
Jaw Joint Protection
One of the less obvious benefits involves the jaw joint, known as the TMJ. A mouth guard slightly increases the gap between your upper and lower teeth, which shifts the lower jaw downward and reduces the load on the joint itself. This cushioning effect protects the disc and ligaments inside the joint from compression injuries. For athletes in sports like boxing, football, or rugby, where blows to the chin can drive the lower jaw upward with tremendous force, this spacing can be the difference between a sore jaw and a serious joint injury that causes chronic pain.
Do Mouth Guards Prevent Concussions?
This is one of the most common claims about mouth guards, and the honest answer is: probably not. Multiple systematic reviews and meta-analyses have examined whether mouth guards reduce concussion risk, and the results are consistently inconclusive. One meta-analysis of five studies found no significant reduction in concussion risk. Another found a slight trend toward protection that didn’t reach statistical significance. A review focused specifically on rugby found limited evidence to support any concussion-preventing benefit.
The current scientific consensus, summarized by Public Health Ontario after reviewing the full body of evidence, is direct: “There is no scientific evidence to suggest that mouth guards are an effective mechanism to prevent concussion in sport.” Mouth guards clearly prevent dental and facial injuries, but concussion prevention shouldn’t be your reason for wearing one.
Custom-Fitted vs. Boil-and-Bite Guards
The three main types of mouth guards are stock (pre-formed, one size), boil-and-bite (softened in hot water and molded to your teeth at home), and custom-fitted (made from a dental impression of your mouth). Stock guards are the cheapest but fit poorly and offer the least protection. Most athletes end up choosing between boil-and-bite and custom options.
Engineering analysis comparing the two shows meaningful differences. Custom multilayered guards provided roughly 13% to 21% better protection for teeth, jawbone, and supporting ligaments compared to boil-and-bite models, depending on the type of impact. For lower teeth specifically, a boil-and-bite guard reduced stress by about 39%, while a custom guard reduced it by about 53%. The custom version also covers both upper and lower teeth in some designs, while most boil-and-bite guards only protect the upper arch.
The fit matters for a practical reason too. Boil-and-bite guards are known to cause discomfort, have poor retention (they shift around during play), and make it harder to talk. A guard that fits badly is one athletes tend to leave on the bench, which means zero protection when it counts.
The Trade-Off With Breathing and Performance
Mouth guards do partially obstruct the airway. All three types reduce the amount of air you can forcefully exhale in one second and your total lung capacity at rest. During intense exercise, this translates to a real, if small, performance cost. A study of amateur boxers found that wearing a boil-and-bite guard reduced peak oxygen uptake by about 4%, dropping it from 56.3 to 54.1 mL/kg/min. Twelve of the 13 boxers in the study performed worse with the guard in.
For most athletes, a 4% dip in aerobic capacity is a worthwhile trade for keeping their teeth. But it helps explain why fit matters so much. A bulky, poorly fitting guard restricts breathing more than a slim custom one, and the discomfort can be distracting during competition. If you play a sport where sustained cardio matters, investing in a well-fitted guard minimizes the breathing penalty while still delivering strong protection.
Which Sports Need Mouth Guards
Mouth guards are mandatory in several organized sports, including football, ice hockey, lacrosse, field hockey, and boxing. But dental organizations recommend them for a much wider range of activities. The American Dental Association has long advocated for mouth guard use in any sport where there’s a risk of contact with other players, equipment, or the ground. That includes basketball, soccer, martial arts, wrestling, skateboarding, mountain biking, and gymnastics.
Basketball is a good example of a sport where mouth guards aren’t required but clearly help. Despite being classified as a non-contact sport, elbows to the face during rebounds and drives to the basket make dental injuries common. The college basketball study showing a fivefold reduction in dental injuries among guard wearers underscores how much protection they offer even in sports where collisions aren’t the main point.