MOUTHGUARDS AND INJURY PREVENTION

Dental injuries are the most frequently incurred orofacial injuries from sports activities.² In addition to injuries to teeth that may result in pulpal injury and the need for endodontic treatment or loss of teeth, an impact to the base of the skull via a blow to the chin in a vertical direction may result in concussion. In both types of injuries, use of a mouthguard could have a significant preventive role. Heintz³ and Chapman⁴ confirmed that properly fabricated, custom-fitted mouthguards reduce the incidence of concussion as well as dental and mandibular jaw injuries. Masahiro et al⁵ reported that mouthguards relieve the stress concentrated on the anterior teeth in a frontal collision by absorbing and dispersing some of the shock energy, quickly stopping the vibration of the maxillary teeth.

Figure 1. Any trauma to the mandible can cause the condyles to be displaced upward within the glenoid fossa, thereby causing trauma to the base of the skull. A concussion can result. (Courtesy: International Academy for Sports Dentistry.)

Research from Bloorview MacMillan Children’s Center and the Hospital for Sick Children⁶ indicates that the various types of sports injuries create a need for sports-specific models of mouthguards, stating that the injuries associated with basketball (eg, elbows impacting the maxillary jaw, loosening a tooth) are different from baseball (eg, ball impacting the teeth) and different from horseback riding (eg, teeth driven up into the jaw from the impact of a fall). Based on how the mandibular condyle articulates within the glenoid fossa, these different types of trauma have different clinical implications, and different types of mouthguards may prevent or minimize resultant injuries (Figure 1).

Unfortunately, the public is largely uninformed about the serious consequences of sports trauma as well as methods of prevention. Trauma resulting from orofacial sports injuries can range from the considerable pain and expense in replacing a lost tooth to the greater impairment and cost resulting from a concussion that can end a sports career. Parents, athletes (professional and nonprofessional), coaches, and trainers largely minimize and deny these consequences, perhaps as a defensive mechanism to protect psychologically against the possibility of an injury. A survey by Karl⁷ reported that even in the National Hockey League, only 51.6% of NHL players wear a mouthguard. It is understandable that it may not be possible to force a professional athlete to wear a mouthguard, but it is unfortunate that owners and the league administration do not educate the players and then make mouthguards mandatory, as are protective helmets in hockey.

FUNCTIONS OF MOUTHGUARDS

In their book Textbook and Color Atlas of Traumatic Injuries to the Teeth, Andreasen and Andreasen⁸ list 8 basic mouthguard functions:

(1) Mouthguards prevent laceration and bruising during impact by acting as a buffer between the soft tissues of the lips and cheeks and the teeth.

(2) Mouthguards prevent tooth fractures or dislocations by cushioning the teeth from direct frontal blows while redistributing the forces of impact.

(3) Opposing teeth are protected from seismic contact with each other.

(4) The mandible is afforded elastic, recuperative support that can prevent fracture or damage to the unsupported angle of the lower jaw.

(5) Mouthguards help reduce neurologic injury by acting as shock absorbers between the upper and lower jaws. Without a mouthguard, the trauma of the jaws violently jarring together can distribute the impact from the condyles of the mandible against the base of the skull, resulting in concussion.

(6) Mouthguards can provide positive reinforcement in the prevention of neck injuries.⁹

(7) Mouthguards provide a psychologic benefit to athletes. Findings suggest athletes feel more confident and aggressive when they have the proper protection.¹⁰

(8) Mouthguards fill edentulous spaces and thereby help support adjacent teeth. This allows removable prostheses to be taken out during athletic competition.

Facts from the National Youth Sports Foundation for Safety^11,12

(1) An athlete is 60 times more likely to sustain damage to the teeth when not wearing a protective mouthguard. Mouthguards and faceguards prevent an estimated 200,000 high school and college football injuries.

(2) The cost of replanting a tooth and follow-up dental treatment is estimated to be approximately $5,000. Individ-uals who experience an avulsed tooth that is not properly preserved or replanted may face lifetime dental costs of $15,000 to $20,000 per tooth.

(3) Each athlete involved in a contact sport has about a 10% chance per season of an orofacial injury, or a 35% to 56% chance during his or her athletic career. Approximately one third of all dental injuries are sports related.

(4) Every year hospitals in the United States see thousands of cases of lost or damaged teeth as a result of sports injuries. Treating these injuries can cost thousands, even tens of thousands of dollars per individual.⁶

(5) The total cost to replace an avulsed tooth (complete displacement of the tooth out of its socket) can be 20 times more than the cost of a custom-fabricated mouthguard.¹³

Figure 2. Trauma to the mandibular teeth during athletic competition. Mouthguard was not worn.

(6) The ADA recommends wearing custom mouthguards for the following sports: acrobatics, basketball, boxing, field hockey, football, gymnastics, handball, ice hockey, lacrosse, martial arts, racquetball, roller hockey, rugby, shot-putting, skateboarding, skiing, skydiving, soccer, squash, surfing, volleyball, water polo, weight lifting, and wrestling. There are newer sports such as rollerblading, mountain biking, and skateboarding, or sports such as racquetball and gymnastics, in which wearing a mouthguard may prove beneficial. With their increased participation in sports, female athletes need the protection a mouthguard offers (Figure 2).

CONCUSSION

The most serious and life-threatening consequence of orofacial sports trauma is a concussion. During contact sports, blows of varying degrees are repeatedly delivered to the jaw and chin. The concussive vibration from these blows is conducted to the temporal bone of the skull, which contains cranial nerve trunks that exit the base of the brain and affect hearing, balance, and blood supply to the brain. The brain “floats” in cerebrospinal fluid and is protected by the skull. Unfor-tunately, the skull cannot protect or prevent the brain from incurring forces from a violent impact. The result is the chance of the brain rotating within the skull, causing a concussion.

Figure 3. Custom mouthguards help protect the teeth while at the same time aid in diffusing the impact to the jaws by separating the mandible from the maxilla. The resulting separation within the glenoid fossa decreases the chance of concussive effects to the base of the brain. (Courtesy: International Academy for Sports Dentistry.)

A properly fabricated mouthguard covers and protects all of the teeth, especially the posterior teeth, with a prescribed thickness to diffuse impact to the jaw. The mouthguard separates the mandible and maxilla, thereby buffering the transmission of concussive effect to the base of the brain^3,4 (Figure 3). The mouthguard also protects the anterior teeth from frontal blows by absorbing and dispersing the shock vibration that could cause severe damage to the maxillary anterior teeth.

Levels of Concussion

The American Academy of Neurology (AAN) categorizes concussions into 4 grades. Robert C. Cantu, MD,¹⁴ chief of neurosurgery service and director of service of sports medicine, Emerson Hospital, Concord, Mass, developed this system. Dr. Cantu has 30 years of experience as a neurosurgeon and football team physician.

Asymptomatic: no head-ache or dizziness and no impaired orientation, concentration, or memory during exertion.

Grade 1 (mild): no loss of consciousness (LOC); post-traumatic amnesia (PTA) less than 30 minutes.

Grade 2 (moderate): LOC less than 5 minutes or PTA greater than 30 minutes.

Grade 3 (severe): LOC greater than 5 minutes or PTA greater than 24 hours.

Consequences of Concussion

(Guidelines for Grades 1 to 3 According to AAN)

Although loss of consciousness is not a prerequisite of concussion, CT scanning should be performed, as this is the most sensitive and specific mode for identifying such injuries. Plain radiographs are not specific enough to determine the level of damage. For those people who are asymptomatic from the initial, minimal force with no intracranial hemorrhage, the long-term chance exists for subtle abnormalities in specific cognitive function.15

Grade 1 Concussion. Re-turn to play after 15 minutes if the athlete shows complete recovery (no symptoms at rest or with exertion). The injured player should be examined immediately and at 5-minute intervals until the symptoms disappear. A second Grade 1 concussion in the same game should result in the player leaving the game for its duration. Before the player can return to competition, the player should show no symptoms at rest and exertion for a week and should also receive a neurological exam.

Grade 2 Concussion. Not allowed to return to play again that day. The player should be examined at frequent intervals. A trained person should re-examine the player the following day. Before the player can return to competition, the player should show no symptoms at rest or exertion for a week and should receive a neurological exam. A second Grade 2 concussion requires no symptoms at rest or exertion for 2 weeks with a neurological examination.

Grade 3 Concussion. Taken by ambulance to the nearest emergency department if still unconscious or if worrisome signs are detected  such as a vacant stare, delayed verbal or motor responses, confusion or inability to focus, slurred speech pattern, or any loss of conciousness. A thorough neurological examination, including a CT scan, should be performed promptly with admission to the hospital on signs of pathology such as diffuse swelling of the brain, small subdural hema-toma, and/or elevated intracranial pressure, or if the player’s mental status remains abnormal. If a player experiences a Grade 3 concussion, that player should not return to play until there are no symptoms at rest or exertion for 2 weeks. The player should also receive a neurological examination. A second Grade 3 concussion requires rest for at least 1 month.

BASIC TYPES OF MOUTHGUARDS¹⁶

Mouthguards are available in 3 basic types:

Figure 4. Stock mouthguard.

(1) Stock. For sale in sporting goods and department stores, stock mouthguards are the least preferred type. These devices are the least expensive, least effective, and are only available in a limited number of sizes. For comfort, they are often modified by the athlete for better fit. This can negate their usefulness (Figure 4). Stock mouthguards have been shown to provide only a low level of protection.¹⁷ If the wearer is rendered unconscious, the mouthguard may become unseated and cause an airway obstruction.¹⁸ In 1997, Division III football players were wearing stock-grade mouthguards that did not provide support for posterior teeth. Further, athletes were buying these poor-quality appliances and trimming them to improve speech and breathing. It was noted that these athletes sustained concussions while wearing the mouthguards. As a result, the Academy for Sports Dentistry (now called the International Academy for Sports Dentistry) formulated a position statement defining a “properly fitted mouthguard” with adequate posterior support. That statement has helped to educate athletes and trainers/coaches regarding what is meant by a proper mouthguard.¹⁹

(2) Boil and bite. Most commonly used, these mouthguards do not provide the proper thickness, comfort, or critical protection of the posterior teeth. They are made of a thermoplastic material that when immersed in boiling water can be fit and formed in the mouth with the use of the lips, tongue, cheeks, and biting pressure. Often, because of the inaccurate fit, clenching pressure is required to obtain satisfactory retention (Figures 5 and 6).

Figure 7. Custom mouthguard in various colors.

(3) Custom made: Designed by a qualified dentist, these mouthguards provide comfort, correct thickness, and maximum protection of all teeth, including the posterior teeth (Figures 3 and 7). They are designed with consideration of the patient’s dental history, and may be designed for a particular sport and with full knowledge of any past history of concussion. For example, if the athlete plays a sport such as tennis, which does not entail a high degree of traumatic contact, then the design of the mouthguard can be constructed with a thinner layer of ethylene vinyl acetate (EVA). For a single-layer mouthguard (approximately 0.08 inches [2 mm]) thick, EVA is used in a vacuum machine. This type of mouthguard would be best suited for those who participate in noncontact sports. The dentist can fabricate them directly in-office or send them to the laboratory. Multiple-layer mouthguards (approximately 0.15 inches [4 mm] or thicker) are also constructed by pressure lamination. These types of mouthguards are made by using multiple sheets that are laminated upon one another over a cast of the athlete’s teeth using heat and high pressure. The pressure enhances the accuracy of the lamination process. These mouthguards are constructed by a dentist in-office or by a dental laboratory and are best suited for those who participate in heavy contact sports such as boxing.

SUGGESTIONS FOR INCREASING THE USE OF MOUTHGUARDS

It can be suggested that in order to increase the use of mouthguards during sports activities, professional athletes should serve as role models for young athletes, performing public service announcements promoting the use of properly fitting mouthguards. If the professional athlete suggests the use of this appliance, it would enhance the willingness of young athletes to follow that example. Professional athletes, team physicians, trainers, and team dentists should be advocates for the use of sports mouthguards.

Local dentists can also contribute by educating their communities, even by fabricating mouthguards for school teams at a low cost.

FUTURE RESEARCH

Study is underway at Ryerson University in Toronto to suggest new mouthguard designs based on analysis of the forces that can affect the jaws and teeth during sports contests. Using mathematical models and cadavers, the goal is to predict the stresses exerted on the jaws and teeth when protected by various experimental mouthguard designs. A crash “test jaw,” similar in principle to human-sized dummies used in the auto industry to test car safety, will be used in this research.⁶

CONCLUSION

Dental injuries are the most frequently occurring orofacial injuries in sports activities. Further, the most serious and life-threatening consequence of orofacial trauma is concussion. Not only do mouthguards protect teeth, but they also protect the head from blows to the jaw that can result in concussions and unconsciousness. This article has reviewed the indications for mouthguard use, the types of mouthguards, and benefits of mouthguard use.

References

1. Gutmann JL, Gutmann MS. Cause, incidence, and prevention of trauma to teeth. Dent Clin North Am. 1995;39:1-13.

2. Sports dentistry facts page. Facts from the National Youth Sports Foundation for Safety.  Available at: http://www.qualitydentistry.com/dental/sdentistry/s-dent.html. Accessed October 11, 2005.

3. Heintz WD. Mouth protection in sports. Phys Sportsmed. 1979;7(2):45-46.

4. Chapman PJ. Concussion in contact sports and importance of mouthguards in protection. Aust J Sci Med Sport. 1995;3:23-27.

5. Morikawa M, Taniguchi H, Ohyama T. Evaluation of athletic mouthguard through vibration test on maxillary teeth of human dry skull. J Med Dent Sci. 1998;45:9-18.

6. Researchers aim to build the perfect mouthguard. CTV.ca Web site. Available at: http://www.ctv.ca/servlet/ArticleNews/ story/CTVNews/1044827305696_40236505///?hub=Health. Accessed October 11, 2005.

7. Karl W. Can mouthguards prevent concussions? The Hockey News. 2003;56(21).

8. Andreasen JO, Andreason FM, et al. Textbook and Color Atlas of Traumatic Injuries to the Teeth. 3rd ed. Ames, Iowa: Blackwell Publishing; 1994:724.

9. Stuart MJ, Smith AM, Malo-Ortiguera SA, et al. A comparison of facial protection and the incidence of head, neck, and facial injuries in Junior A hockey players: a function of individual playing time. Am J Sports Med. 2002;30:39-44.

10. Zhang N, Wang Q, Pan K. The effect of mouthguard on strength of the musculus deltoideus [in Chinese]. Zhonghua Kou Qiang Yi Xue Za Zhi. 2001;36:348-350.

11. Sports Dentistry Facts. National Youth Sports Foundation for Safety fact sheet. Available at: http://www.qualitydentistry.com/dental/sdentistry/s-dent.html. Accessed November 3, 2005.

12. Dental Injury Fact Sheet. National Youth Sports Foundation for the Prevention of Athletic Injury Inc. Needham, Mass: 1992.

13. Superstitions: the source of NHL’s tooth woes? Academy of General Dentistry Web site. Available at: http://www.agd.org/consumer/topics/mouthguards/superstitions.asp. Accessed October 11, 2005.

14. Concussion. American Association of Neurological Surgeons Web site. Available at: http://www.neurosurgerytoday.org/what/patient_e/concussion.asp. Accessed October 11, 2005.

15. Ravdin, LD, et al. Assessment of cognitive recovery following sports-related head trauma in boxers. Clin J Sport Med. 2003;13(1):21-7.

16. Types of athletic mouthguards. Sports Dentistry Online Web site. Available at: http://www.sportsdentistry.com/mouthguards.html. Accessed October 11, 2005.

17. Padilla RR, Lee TK. Pressure-laminated athletic mouth guards: a step-by-step process. J Calif Dent Assoc. 1999;27:200-209.

18. Krakowka E. Mouthguards: an effective piece of equipment. Northeast Rehabilitation Health Network Web site. Available at: http://www.northeastrehab.com/Sports/mouthguards.htm. Accessed October 12, 2005.

19: Winters JE. Commentary: Role of Properly Fitted Mouthguards in Prevention of Sports-Related Concussion. Journal of Athletic Training Web site. Available at:  http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=162236&tools=bot. Accessed November 3, 2005.

Dr.Vastardis maintains an active general dental practice in Garden City, NY, with an emphasis on restorative, aesthetic, and implant dentistry. Dr.Vastardis graduated from Tufts University School of Dental Medicine. He is a member of The International Academy for Sports Dentistry. He can be reached at (516) 326-0770 or peter@gardencitydentistry.com.

Continuing Education Test No. 72.2

After reading this article, the individual will learn:

• the indications for using a mouthguard during athletic competition, and
• the types of mouthguards that are available for use.

1. How many teeth are lost each year in the United States due to sports injuries and trauma?
a. 1 million
b. 3 million
c. 5 million
d. 8 million

2. The following statement is FALSE:
a. Mouthguards help prevent laceration and bruising during impact.
b. Mouthguards cannot help prevent fracture or damage to the unsupport- ed angle of the lower jaw.
c. Mouthguards can help reduce neuro- logical injury.
d. Mouthguards provide a psychologic benefit to athletes.

3. Each athlete involved in a contact sport has approximately a ____ chance per season of an orofacial injury.
a. 5%
b. 10%
c. 15%
d. 35%

4. A concussion resulting in loss of conciousness of less than 5 minutes or post-traumatic amnesia greater than 30 minutes is classified as ____.
a. Grade 1
b. Grade 2
c. Grade 3
d. Grade 4

5. If a player experiences a Grade 3 concussion, he or she should not return to play until there are no symptoms at rest or exertion for ______.
a. 1 week
b. 2 weeks
c. 3 weeks
d. 4 weeks

6. The most commonly used type of mouthguard, but one that does not provide adequate protection, is _____.
a. boil and bite
b. stock
c. custom
d. All of the above provide adequate protection against injury.

7. The following type of mouthguard is best suited for those who participate in noncontact sports:
a. boil and bite.
b. stock.
c. multiple-layer custom mouthguard.
d. single-layer custom mouthguard.

8. An athlete is ________times more likely to sustain damage to the teeth when not wearing a protective mouthguard.
a. 20%
b. 40%
c. 60%
d. 75%

To submit Continuing Education answers, download the answer sheet in PDF format (click Download Now button below). Print the answer sheet, identify the article (this one is Test 72.2), place an X in the box corresponding to the answer you believe is correct, and mail to Dentistry Today Department of Continuing Education (complete address is on the answer sheet).

Concussions and traumatic brain injuries in sports are the consequence of transfer of the energy of an impact, including impact to the lower jaw, to the brain.1-4 As intraoral appliance design evolves beyond the role of protecting only the teeth and periodontal tissues to assume a role of risk reduction for brain and TMJ injury in sports, the dental professional must have a thorough understanding of the nature and consequences of lower jaw impacts.

UNDERSTANDING TRAUMATIC BRAIN INJURIES AND CONCUSSIONS

Brain injury from trauma in sports can be broadly classified into two categories:

• Diffuse brain injury including concussions
• Focal brain injury including hematoma, edema, and hemorrhage.5-7

Figure 1. Localized injury causing space occupying mass.	Figure 2. Coup injury on side of impact.
Figure 3. Contre-coup injury on opposite side of impact.	Figure 4. Limitation of standard design mouthguards.
Figure 5. Multidimensional protection of Jaw Joint Protector.
Figure 6. Test results compare the relative effectiveness of various mouthguards placed in an articulated headform subjected to the 60″ standard NOCSAE drop test. The helmet with articulated headform is dropped on the faceguard at an angle off of center to produce a difference between right and left TMJ/basal skull surface forces. The articulated headform was utilized in order to study the effectiveness of various mouthguards and intraoral appliances during standard NOCSAE 60″ drop test studies. The 60″ drop height generates a force equivalent to an abrupt stop from approximately 18 ft/sec impact velocity during sports. This acceleration is sufficient to cause bone fractures, TMJ pathology, and TBI. The single-arch custom-fabricated mouthguard (Custom) protected only slightly better than the over-the-counter product. In both cases, energy transfer to the jaw joint and base of skull sensors exceeded impact forces proscribed by the helmet standards by 40%. The jaw joint protector (Brain-Pad; WIPSS) redistributed those forces of head impact to the appliance and the mandibular and maxillary dental structures, resulting in a significant decrease (within proscribed standards) in the load force arriving at the TMJ and skull base sensors.

Diffuse Brain Injury and Concussions

A concussion (mild traumatic brain injury or mTBI)8 is a diffuse (widespread) injury of the brain resulting from the shaking effect of the brain within the skull as a result of trauma. Shear strain from rotational forces can cause stretching of the axons with subsequent loss of function. The cellular injury may be a mechanical disruption of the axons, or a functional disruption resulting from the effects of inflammation, pressure changes, and neurotoxin accumulation within surrounding tissue.7 Diffuse brain injury is not visible with computerized tomography (CT) or magnetic resonance imaging (MRI). Diagnosis is based on assessment of brain function by neuropsychological testing.6,7,9,10

Focal Brain Injury

Focal brain injuries are usually a result of direct trauma or blows to the skull, producing localized space occupying lesions (contusions, hematomas, hemorrhage, edema) (Figure 1). Focal injuries can be visualized with CT or by MRI.5,6 Neurological problems are a result of local cellular damage and shifting and compression of brain tissue due to the effects of a space occupying mass within the confines of the skull.11 The effects of focal injuries are often reversible with surgery, but can be lethal.5,6

PHYSIOLOGY OF TRAUMATIC BRAIN INJURY

The American Orthopedic Society for Sports Medicine states that following brain injury there is a general metabolic dysfunction within the brain, a decrease in the ability of the brain to regulate its blood flow, and an overall inability of the brain to re-establish a normal physiologic balance.11 Death of a neuron may result from lack of oxygen or glucose, or from the shearing forces or pressure effects of trauma. Following an injury to the brain, many cells may be functionally disrupted but mechanically intact. If the surrounding environment is favorable there is possibility of cell recovery; however, if it is unfavorable then cells may die.11 Trauma to the brain is therefore capable of bringing about serious and permanent brain injury.1,11

MECHANISMS OF ENERGY TRANSFER IN BRAIN INJURY

Mechanisms of brain injury involve a transfer of energy to the brain by various means6,7,9,12:

(1) Direct transfer of energy can be a result of impact forces to the head. With sufficient force, skull fracture with underlying focal injuries can occur (coup injury) (Figure 2). Differential acceleration of the brain and skull can result in a delayed and second collision of the brain (which is still in motion) with the inner table of the opposite side of the skull (contre-coup injury) (Figure 3). Often, these result in focal injuries including contusions, lacerations, and hematomas.

Reduction of risk from indirect transfers of energy is more dependent on the rules governing the sport in question.16 In contact sports involving high-speed collisions, deceleration injuries are inevitable.

UNDERSTANDING THE PROBLEMS THAT RESULT FROM LOWER JAW IMPACTS

Since the lower jaw forms a bilateral joint with the base of the skull at the glenoid fossa, blows to this mobile jaw may drive the jaw up and back, creating a transfer of energy from the lower jaw to the temporomandibular joint (TMJ) and base of the skull. Dr. Robert Cantu4 stated that blows to the chin, which acts as a lever, produce maximal forces. This fact has long been known in boxing, where the prime target for the opposing combatants has always been the chin. Stewart and Witzig19 have estimated that in athletes, over 90% of concussions resulting in unconsciousness are the result of blows to the lower jaw.

Although boxing serves as a prime example of the effects of direct blows to the lower jaw, even athletes wearing face shields and helmets are at risk of TMJ and traumatic brain injury from lower jaw impacts. Tim Walilko at the Wayne State School of Medicine demonstrated that the impact of a hockey puck traveling at 64 mph into a face shield is capable of creating enough energy transfer (shield – chin rest – lower jaw – TMJ – basal skull ) to create a 20% likelihood of mTBI.20

Standard National Operating Committee on Standards in Athletic Equipment (NOCSAE) football helmet drop test studies21 have shown that impact to the football helmet faceguard can displace the helmet and pull on the chin strap, causing a similar transfer of energy exceeding the pass/fail criteria set for helmets themselves.21,22 The ability of standard design mouthguards to protect against concussion has long been an area of debate. Barth has pointed out the theoretical and mathematical basis for a role of mouthguards in protecting the brain during lower jaw impacts if the mouthguard is fitted to provide vertical separation between the condyle and glenoid fossa. He also pointed out that the protective effect is limited to blows of a vertical nature only.23 Blows with a horizontal component are still capable of driving the lower jaw posteriorly, imparting impact energy at the TMJ area.17

Unfortunately, most blows to the lower jaw in sports arrive from the front and side,24-26 and carry a significant component of horizontal force. Additionally, little protection is available if the jaw is open during impact.27 Without the ability to lock the lower jaw into position, standard design mouthguards are capable of providing only unidimensional protection (Figure 4).

A prime determinant of the effectiveness of an appliance in reducing the risk of brain injury is the ability of the appliance to prevent displacement of the lower jaw during lower jaw impacts from any direction. When considering risk reduction for TMJ and brain injury in sports, we must begin to distinguish between the uni-dimensional protection afforded by standard design mouthguards and the multidimensional support provided by a new class of intraoral guard known as jaw joint protectors (Figure 5).

INTRAORAL GUARDS TO REDUCE LOWER JAW IMPACT TRAUMA

Classification of Mouthguards in Sports

Types of athletic mouthguards have traditionally been classified based on fabrication or design, as follows27:

Stock mouthguard cannot be custom sized and should not be used
Boil and bite can be custom sized by molding when soft after boiling
Custom made dentist prescribed and laboratory fabricated mouthguards.

Single-arch design covers only one arch of teeth (usually the maxillary)
Dual-arch design covers both the maxillary and mandibular arches.

APPLIANCE DESIGN REQUIREMENTS FOR MINIMIZATION OF CONCUSSION RISK

An intraoral appliance designed to protect the brain and jaw joint should have the following features:

(1) It must prevent posterior and superior displacement of the lower jaw during impact, by fixing the mandible into position. This can only be accomplished by a dual-arch appliance.17

AN INTRAORAL APPLIANCE TO REDUCE THE RISK OF CONCUSSION

The limitations of single-arch appliances during lower jaw impact have also been recognized by athletes and dental professionals. Boxers have utilized numerous dual-arch dentist-fabricated appliances in the past, and various manufacturers (Everlast, Shock Doc) have had versions of dual-arch appliances meant to address lower jaw impact. Control of anteroposterior positioning of the mandible to create a horizontal separation of the TMJ and skull was not specifically addressed by these appliances. Compliance of wear by athletes is limited when breathing is compromised28,29 or when an airway breathing space is not incorporated or inadequate.

Dr. E. Williams designed an appliance to address the issue of lower jaw impacts and repetitive trauma in boxers. The appliance was designed to overcome previous limitations of dual-arch appliances, and is now utilized and endorsed by most major boxing, martial arts, and contact sport organizations. It is marketed as a jaw joint protector (Brain-Pad, WIPSS Products Inc). The appliance can be boil- and bite-fitted by dentists, athletes, or parents for general application, although custom fit by dental professionals may be recommended in cases of malocclusion, orthodontic therapy, or other special circumstances.

(1) Dual-arch design with upper and lower bite channels to lock and hold the lower jaw into a down and forward position, creating a multidimensional safety space in the jaw joint area.

The increase in bulk of a dual-arch appliance may be an initial concern for athletes accustomed to standard single-arch designs, but even younger athletes quickly adapt to the appliance. The Brain-Pad is not recommended for patients with class III malocclusion.

CONCLUSION

Dentists must increase public awareness that without locking the lower jaw into position, the brain and TMJ are at risk during lower jaw impacts.

References

1. Cantu RC. Reflections on head injuries in sport and the concussion controversy. Clin J Sport Med. 1997;7:83-84.

Standard Testing Methodology specifications available from the American Society for Testing and Materials (ASTM), 100 Barr Harbor Drive, Conshohocken, PA, 19428-2959.

Dr. Gusenbauer is an oral and maxillofacial surgeon who maintains a private practice in Hamilton, Ontario, Canada. He is a diplomate, oral and maxillofacial surgery and anesthesia, a member of the Dental Staff at McMaster University Hospital and Hamilton General Hospital, and serves on the Regional Trauma duty roster.

Disclosure: Dr. Gusenbauer is a stockholder in WIPSS Products Inc and a medical consultant to the company.