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Athletic mouthguards have been a staple of sports for decades; they provide a vital role in preventing injuries to the teeth and jaws as well as reducing the incidence and severity of concussions. In the past few years, however, the emergence of “performance mouthguards” has flooded the sports scene. These enhanced products claim to do more than merely protect the wearer; indeed, by positioning the mandible (lower jaw) into a specific position, the mouthguard is said to open the airway to increase oxygen intake, to relax jaw muscles ostensibly to prevent those contracting muscles from “robbing” other parts of one’s body’s energy (which allegedly decreases muscular efficiency elsewhere), and to trigger hormonal changes (chiefly by diminishing cortisol, the “stress hormone”, release). Big names such as Under Armour®, as well as smaller niche companies, dental labs, and others are invested in this concept, and millions are spent by athletes each year trying to get that extra edge that will allow them to rise above their competition.

Whether or not they do what they claim is not the purpose of this post (spoiler alert: probably not, but the jury is still out), but to alert our readers of a technique that dentists and other providers of these mouthguards employ to “demonstrate” the effectiveness of these expensive hunks of acrylic. Known as muscle testing or Applied Kinesiology, the practitioner will have the athlete clench his or her teeth, then perform tests such as pressing down on an extended arm, pushing the person to test for balance, and so on. Then the athlete will place something between his or her teeth- the mouthguard, a pencil, or a stick- and the tests are repeated. LO! The balance and strength is improved!

This is not a new trick. It was invented in the 1960s by a chiropractor, and is used for a myriad of uses, for example allergy testing whereby a patient holds a vial of a suspected allergen in his or her hand and the muscles are tested as described above; if there is weakness, then there must be an allergy or sensitivity for that particular substance. And no, I’m not making that up or pulling your leg. Recently, it has been showcased in “proving” the effectiveness of the Power Balance bracelet, debunked so beautifully by Richard Saunders. And now, it is been used to show that muscle strength and balance is improved with the use of these mouthguards. The sad thing is that I know many many dentists who believe in this “technology”, and I can attest to their honesty and sincere desire to help their patients. So in an overwhelming majority of cases, this is not an issue of fraud and deception (except for self-deception). It is merely ignorance of how the placebo effect, operator bias, and suggestibility works.

As with most fad gizmos, celebrity endorsements and patient testimonials are the cornerstone of the marketing approach undertaken by the producers of these products. After all , who needs a study when all you need is Shaq telling you that a mouthguard improved his free throw percentage (from 12% to 16%?)? And in a marketing coup, here is a photo from 2011 of Bill Gates being muscle tested for a mouthguard:


While there are a few small, poorly done studies (example here) that purport to show, if not outright effectiveness then a glimmer of biological and physiological plausibility, most of the perceived benefits can be attributed to biases on the part of the operator and recipient. A good overview of the process by Stephen Barrett can be found here, along with several references.  Whether or not they eventually are shown to work, don’t rely on parlor tricks as evidence of effectiveness.

So, exercise caution when evaluating the claims of these so-called “performance mouthguards.” To be sure, the appliances themselves are of high quality and will do all the things a mouthguard is supposed to do, but they cost 1-2 orders of magnitude more, so buyer beware.