Fistic Medicine: The Importance of Mouthguards

By Matt Pitt May 23, 2010
Late on May 3, five days before his fight against Lyoto Machida, Mauricio “Shogun” Rua realized he had a problem. A big problem.

Frantic calls were placed to Las Vegas. Contact was made with his supplier. The lab verified they had Rua’s bio-statistics on file, a rush order was placed and within 48 hours the custom-made product was dispatched. To mitigate the risk of interception by Canadian customs, a UFC staffer snuck the package into Montreal sequestered in his luggage; before nightfall the delivery was made. The title fight could go on -- Rua had his mouthguard.

The importance of mouthguards has not been debated among fighters since 1927, when boxer Mike McTigue, well on his way to winning his bout for a shot at the heavyweight title, was stopped by a punch to the mouth that caused a fight-ending upper lip laceration. By that time mouthguards, known as gum shields, had been in existence for 40 years.

Originally made of gum rubber, the devices served to protect a fighter’s upper lip from being torn open from punches to the maxilla. These lip lacerations not only stopped fights, they led to scarring that affected speech and appearance. Nevertheless, until the 1927 Sharkey-McTigue bout, when their value was demonstrated inescapably, mouthguards were illegal in professional boxing. Ten years later they were required.

Over time, technology led to improved mouthguard design. Non-malleable mouthguards have been done away with: They were held in place by biting down, interfered with breathing and had the rare but troublesome tendency to fall into and block the airway of an unconscious fighter. Devices made of thermoplastic rubber -- the popular and cheap Boil and Bite models -- mark a substantial design improvement. They marginally conform to the upper teeth and fit the occlusal surface of the lower teeth, offering improvements in passive retention and mandible fixation. The drawbacks of these guards are that they may become too thin during the “bite” fitting process, and the thermoplastic material does not have ideal protective properties of cushioning and rigidity.

The current state-of-the-art in dental protection is a dentist-fit, custom-made mouthguard. These guards hold themselves in place on the maxillary teeth and have appropriate thickness anteriorly (4-6 mm) and along the occlusal surfaces (3-5 mm). Importantly, they are more comfortable to wear: The worst mouthguard is one left in the gear bag because the fighter views its use as a burden. A custom guard is more expensive, but not excessively so -- less than $100.

Advances in mouthguard technology have been matched, perhaps overtaken, by claims of their pluripotent utility. Over the past 30 years, published studies -- and Internet marketing come-on’s -- have claimed, with wildly disparate levels of certainty and supporting evidence, that mouthguards enhance strength, speed auditory and visual reaction times, improve balance, sharpen concentration, modulate the stress response, treat spinal injuries, improve endurance and mitigate the risks of concussion and chronic traumatic brain injury.

The majority of these reported benefits fall in the realm of bad science, ethically suspect marketing and outright myth. The fact that some of these exorbitant claims are used to promote $2,000 mouthguards does nothing to lower the threshold of disbelief. There are, however, two claims -- that mouthguard use might improve endurance and minimize brain injury -- that bear further scrutiny: They are supported by both legitimate proposed mechanisms and intriguing supportive science.

A recent study used CAT scans to show mouthguards produce significant widening of the oropharynx: an average diameter of 28.3 mm with guards, 25.9mm without. As resistance to fluid flow is proportional to the inverse fourth power of radius (Poiseuille's Equation), a widening of 2.4 mm represents -- theoretically -- an almost 40 percent decrease in airway resistance. Muscles of respiration require approximately 10 percent of a maximally active athlete’s oxygen demands, therefore a decrease in the work of breathing might translate into better endurance and faster recovery. Clinical studies designed to see this effect in vivo, measuring athlete’s blood lactate levels during exertion in the lab, have been ambiguous. At best the studies show use of a fitted guard does not decrease cardiovascular performance -- the winded fighter who spits his mouthguard out is not helping himself anymore than if he threw away his cup.

Science and research also suggest that modern mouthguards may protect the brain from injury. The only connection between the jaw and the cranium in which the brain resides are the temporomandibular joints, where the mandibular condyles sit in their cranial fossae, and the contact of lower mandibular teeth on upper maxillary teeth. A recent study in Dental Traumatology posits that mal-alignment of these condyles may increase transmission of punch force and skull torque. This may be the physiologic cause of “glass jaw syndrome” and, excitingly, the article suggests that the infamous glass jaw can be corrected by dental orthotics -- an extremely specialized form of mouthguard. The preliminary study is intriguing, but a larger study on dental orthotics is needed.

A more well-studied mechanism of brain protection involves the innate elasticity of rubber. Wearing even a simple mouthguard pulls the condyles out of place and separates the teeth; this insures that any force applied to the jaw is cushioned by the mouthguard before affecting skull and brain. The extent of this cushioning has been assessed in a number of studies using cadavers or models: They have shown decreases in cranial force after a blow to the jaw of as much as 50 percent.

The ideal in vivo confirmatory study -- taking a large cohort of football players and fighters at a young age, depriving them of mouthguards for many years and measuring the number and severity of injuries they sustain -- cannot ethically be done. The in vivo studies that have been done, often methodologically compromised, show intriguing evidence supporting the neuro-protective benefits of mouthguards. It bears explicit statement that none of the “higher end” mouthguards being marketed have demonstrated clinical superiority over the standard dental fit guard.

Certainly the UFC finds the data regarding the benefits of mouthguards convincing. For the last two years they have hired the FightDentist, Dr. Adam Persky, a world expert in the field, to make custom mouthguards for all of their fighters. For the known and potential benefit -- certainly when balanced against the risks -- the UFC’s money could not be better spent.

(Author's Note: In the Fistic Medicine article published April 29, I wrote, “Technique may trump muscle, but technique plus steroids trumps everything.” Unfortunately, this was, understandably, interpreted by many readers as a suggestion that Matt Hughes was a steroid user. The error is mine. No such implication was intended.)

Matt Pitt is a physician with degrees in biophysics and medicine. He is board-certified in emergency medicine and has post-graduate training in head injuries and multi-system trauma. To ask a question that could be answered in a future article, e-mail him at

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