7.2 The History of the Athletic Mouthguard

The history of the mouthguard is not easily defined, but it can be assumed that both athletes and warriors over the centuries have tried to protect themselves from facial and oral injury. Medieval helmets and ancient Samurai headgear indicate features that protected specific areas of the head and face. But as to the protection of the mouth specifically in both war and sport, little has been identified from the distant past.

The use of mouth protection in sports usually focuses on the sport of boxing starting in the late nineteenth century. However the first documentable mouth protector found was a simple latex device used in baseball in the United States in the 1870s [7]. George Wright, a star player on the Cincinnati Red Stockings, produced a 50 cent rubber guard which was clenched between the teeth. The Red Stockings catcher, Doug Allison, who also was one of the first catchers to use gloves to catch the ball, was possibly the first who used it. A catcher in those days was almost entirely unprotected and generally stood far behind the batter and caught the ball on the first bounce. As catchers inched closer to the batter, it became more important for them to protect themselves from injury. The mouthguard was used to some degree until the invention of the catcher’s mask in 1877 (patented in 1878) by the coach of the Harvard Law School baseball team, Winthrop Thayer, who created it to convince outfielder James Tyng to become his catcher. George Wright then developed the first commercial catcher’s mask. Thayer received a royalty for each one purchased [7].

The sport of boxing is where the development of a mouthguard can be more clearly documented. The use of mouth protectors was common in the late nineteenth century, but these “devices” were often “cotton, tape, sponge, and even pieces of wood” [8]. A wonderful paper in 1994 by Robert Reed gave several firsthand testimonies of the development of the first true mouthguards [9]. A London dentist, Woolf Krause, fashioned the first true mouthguard or “gum shield” in 1890 out of gutta-percha to protect the boxers primarily from lip lacerations. The participant needed to clench his teeth together to hold the guard in place.

Krause’s son Philip improved on this design by creating a guard out of vellum rubber. A professional boxer named Ted “Kid” Lewis first used Phillip’s mouthguard in 1913. The following is, in his own words, how he came to use a mouth protector:

“The earliest recording of a U.S. mouthguard-type device was in 1916 when Thomas Carlos, a Chicago Dentist, designed a mouthpiece for U.S. Olympian Dinnie O’Keefe” [8]. Mouthguards become prevalent following a 1927 boxing match between Mike McTigue and Jack Sharkey. McTigue was clearly winning the fight; however, a chipped tooth severely cut his lip and forced him to forfeit the match. From then on, mouthguards become commonplace for boxers and also opened the possibilities for mouthguard use to flourish [8].

Three years following the infamous McTigue/Sharkey fight, mouthguards found their way into dental literature. Dr. Clarence Mayer, who was a dentist and also a boxing inspector, wrote about how custom mouthguards could be created from impressions using wax and rubber. He also suggested using steel springs to reinforce the materials [8].

In 1947, a major breakthrough was made when Los Angeles dentist Rodney O. Lilyquist used transparent acrylic resin to form the first acrylic splint. This mouthguard was molded to fit over the upper and lower teeth and made for a much more unobtrusive object. During this time, dental injuries were responsible for around 24–50% of all American football injuries. The Journal of American Dental Association picked up Lilyquist’s technique, which led to nationwide recognition for him, and he became known as the father of the modern mouthguard [10, 11]. Dick Perry, a UCLA basketball player, was the first known athlete to use an acrylic mouthguard. Later on Frankie Albert, the quarterback for the San Francisco 49ers, was the first known professional non-boxing athlete to wear this type of mouthguard [12].

In the 1950s, latex rubber was the material most commonly used for athletic mouthguards, but William Godwin was also perfecting a vacuum forming process on casts of athletes’ teeth using ethylene vinyl acetate (EVA) originally obtained through the automobile manufacturing industry [13, 14]. In the late 1950s, Dr. A.G. Jacobs pioneered the use of a silicone lining material to allow athletes to make their own mouthguards. In the early 1960s, Dr. Jacobs developed the first “boil and bite” mouthguard of EVA that athletes could easily form for themselves [15]. This innovation was groundbreaking as it made a simple fitted mouthguard much more accessible to athletes and added greatly to the success of rule changes first to American-style football and then to other sports.

In the early 1950s, the American Dental Association (ADA) realized that there was a significant injury problem in American-style football. The helmet was first introduced in the 1920s to protect the skull from catastrophic injury. This early helmet afforded no facial protection and only with the development of a plastic helmet was the introduction of a face shield made a reality. The rigid plastic construction of the helmet made the physical attachment of rigid face shield possible. The ADA along with the American Association for Health, Physical Education, and Recreation issued a report in 1960 that found that when no face shield or mouthguard was worn, 50% of all high school football injuries occurred in or around the mouth [16].

As a result of this information, the National Alliance Football Rules Committee composed of the The National Federation of State High School Associations, the National Junior College Athletic Association, and the National Association of Intercollegiate Athletics, in 1962, mandated that players must wear a facemask and a mouthguard. Interestingly, the National Collegiate Athletic Association (NCAA) did not immediately adopt this rule, but after 11 years, in 1973, they also instituted the mandate. These initial rule changes resulted in dramatic improvements in injury rates within a very short time. It was reported that prior to the rule changes, there was an incidence of 2.26% dental injuries per every 100 football players. This number was reduced to 0.3% in 1966 [16].

Dental protection in ice hockey followed a similar pathway, albeit later, with a similar development of helmet introduction followed by face shields followed by dental protection [17]. The NCAA mandated mouthguard use for ice hockey in 1975, as did many other governing bodies of youth and amateur hockey. For the 2017–2018 ice hockey season the NCAA rescinded the mandatory mouthguard rule. In both ice hockey and American-style football, professional players are not required to wear mouthguards. Currently boxing is the only professional sports to require the use of mouthguards.

As of 2016 the NCAA requires mouth protection in football, men and women’s ice hockey (rescinded in 2017), men and women’s lacrosse, and women’s field hockey [18]. The NCAA is phasing in women’s rugby, and this sport, in all likelihood, will require mouthguards as well. The National Federation of State High School Associations recommends mandated use of mouthguards in those sports as well as for wrestling participants who are wearing orthodontic appliances [19]. The American Dental Association has “endorsed the preventive value of orofacial protectors, including helmets, faceguards and mouth protectors, for use by participants in sporting and recreational activities with some degree of injury risk and at all levels of competition.” In addition to the more common sporting activities such as basketball or baseball, the ADA’s list of sports for which they recommend mouth protection names many sports including activities such as skateboarding and nontraditional sports such as cheerleading [20]. Many other sports that are played internationally such as rugby, hurling, field hockey, martial arts, team handball, and many more have various mandates depending on the region and country in which the sports are played.

7.3 Types of Mouthguards

The athletic mouthguard can be characterized by type, material, and physical properties. Different sports and different athletes demand different particular characteristics of an adequate piece of safety equipment. In this section we will describe the mouthguard in various ways to enable dentists and athletes a way to decide which device is best for any specific circumstance.

The ASTM International is an organization whose mission is to develop and create voluntary “consensus standards” for industry and consumers. Its subcommittee F08 has written in standard F 697-00 (approved in 2006) that there are three types of “mouth protectors,” Type I, II, and III, with several subgroups (◘ Fig. 7.2) [5]. This classification is the most common and straightforward way to categorize mouthguards. These will be discussed in reverse order from the standard to explain them from simplest to more sophisticated.

7.3.1 Stock Type

This is by far the simplest type of mouth protector . It is usually a device that is supposed to be used directly from the package with no attempt made at fitting for the individual. The use of this type of device results in a very loose-fitting appliance where the athlete must clench his or her teeth together to keep the device in place. This obviously leads to unintelligible speech and difficulty in breathing through the mouth. It is also much more likely that the guard will be dislodged when the player is contacted during play (◘ Fig. 7.3).

These guards are usually designed for the upper arch, but often they are configured to cover both the upper and lower teeth. There are quite a few styles and shapes available and at best should be used only when an athlete can stop his activities often and when ongoing verbal communication is not important.

Most sports dentists do not recommend these devices, but supporters note a few benefits. They are convenient and can be used immediately without fitting. Orthodontists sometimes recommend these, as they do not restrict the ongoing movement of teeth during orthodontic treatment. They are generally inexpensive. They make easy “spare mouthguards” to be kept on hand in case someone has lost or destroyed their own guard.

Stock mouthguards should be used only in very specific circumstances and should not be thought to be an acceptable alternative for general use. They do not meet the basic requirements of a “properly fitted mouthguard” (◘ Fig. 7.1).

7.3.2 Mouth-Formed

This type is the most widely used mouthguard. They are accessible and cost-effective and come in a large variety of styles and designs to supposedly fill all needs. As it is defined, it is to be molded in the mouth and has two basic types: the shell-lined or the thermoformed type. The shell-lined type is one where a resilient material is mixed and placed in a dental arch-shaped shell and then it is placed in the mouth to set. This type has largely disappeared from use.

The more common type is the thermally formed group usually termed the “boil and bite” group, as that is how it is most often fitted. This type is readily accessible, and in recent years an almost limitless number of varieties have been marketed. They are generally affordable, and the creativity in their design and materials has led this to become a very significant industry in the sporting goods world. Athletes often gravitate toward these as they are conveniently obtained and can be fitted without the intervention of a dental professional. Boil and bite mouthguards come in a wide range of prices depending on the features of a particular guard with a price to literally match every budget.

The mouthguard is individually fitted usually by heating the device in hot water (or in a microwave oven) and then placing inside the mouth to form it to the teeth. Once it is in the mouth, the participant molds in with his or her fingers to mold the outer side of the guard by pushing on the cheek and lips, by sucking hard on it while placing the tongue firmly against it, and by biting on it to fit it to the lower teeth.

The huge variety of these types of mouthguards makes it hard to assess whether accomplishing a good fit is possible or not. The fit largely depends on the individual doing the fitting. Dentists know how difficult it is to learn the skill of taking a good dental impression, and this fitting of a mouth-formed guard can be compared to that. Therefore it is difficult to categorically state whether or not this type of mouthguard is acceptable (◘ Fig. 7.4).

Mouth-formed mouthguards may vary, but one particular mouthguard made of a unique material (a polyolefin polymer trade name Vistamaxx) applied for and received, in 2016, the American Dental Association’s Seal of Acceptance. At the time of this writing, this mouthguard is the only one to have ever been awarded this designation.

7.3.3 Custom-Fitted Mouthguards

These mouthguards are created by dental professionals fabricating specific materials over a cast of an athlete’s teeth. These guards are usually made for the maxillary teeth except in prognathic Class III-type occlusions. The internal adaptation achieved and the ability to create comfortable borders make these mouthguards the most comfortable and intimately fitted. Studies have shown that these guards are the most desirable to players [21] (◘ Fig. 7.5)

This type of mouthguard, most commonly, uses some type of ethylene vinyl acetate (EVA) that is heated and then formed over the dental cast. The two most common ways of forming these guards are to use a vacuum forming technique or a heat and pressure technique.

The advantages of the custom-fitted guard beyond the intimate fit are that (a) the guards are specific to the athlete, (b) they can be customized to suit the sport played and the athlete’s requirements, and (c) the device is not easily dislodged during play. Also, because a custom guard is tailored to the athlete, speech considerations and the ability to breathe without detriment are not affected in any critical way. A significant number of studies have been conducted measuring VO2 max levels of an athlete wearing a mouthguard versus one without. VO2 max refers to the maximum amount of oxygen an individual can utilize during intense or maximal exercise; the result has found that there is no physiological effect on breathing with a mouthguard in place and that any complaints by the athlete are probably psychological. However there are studies done with stock mouthguards that do show a reduction in VO2 max [22–24]. For sports that are defined by continuous play, that are highly aerobic, and those sports in which athletes play without break for extended periods of time, this type of guard is by far the most suitable. They are also the type usually preferred by athletes [21].

The major disadvantages of this type of guard are cost and accessibility. They tend to be significantly more expensive than retail guards. An impression of the athlete’s teeth needs to be taken. This is most commonly achieved at a dentist’s office, but there are products available which allow the purchaser to fabricate their own impression. This impression is then used by the dental professional to fabricate the guard, or it is sent to a professional dental laboratory for the fabrication of the mouthguard.

7.3.3.1 Vacuum-Formed Mouthguards

The vacuum-formed type of custom guard has been used since first investigated in the early 1960s [13, 14]. A sheet of mouthguard material was heated and placed over a dental cast. A vacuum then pulls the material down over the cast. Currently a more modern version of this technique is still used with more sophisticated machines. This technique can be used to create a well-fitted mouthguard, and the machine that is used in its fabrication tends to be less expensive than the machine used in the heat and pressure technique. While this technique can create a very acceptable mouthguard, it is difficult to laminate multiple sheets of mouthguard material in order to add strength and longevity. In addition, if only one sheet of material is used, as is the common practice, the guard tends to lose its shape after a certain period of time.

7.3.3.2 Heat-Pressure Laminated Mouthguards

The heat-pressure lamination technique takes advantage of a specific type of machine that heats a sheet of mouthguard material and then, with a special pressure chamber, pushes rather than pulls the sheet onto the cast. This creates a very exact and detailed impression of the cast onto the internal aspect of the guard. Because of this detail, the fit of this guard is very snug and intimate. In addition, this technique allows for the addition of multiple layers of material onto one another. Each layer is directly fused or laminated to the previous one. Customization of thickness in different parts of the guard is a distinct advantage. This lamination technique also gives the dental professional the ability to laminate a clear layer as the final layer. This clear layer allows mouthguards to be decorated and personalized with logos, names, and decorations. In the authors’ experience, it is not uncommon to see a laminated mouthguard last multiple seasons as compared to vacuum and boil and bite types that in most cases do not make it through one season of play.

7.4 Materials and Physical Properties of Mouthguards

The athletic mouthguard works to protect teeth and their supporting structures by both absorbing and distributing injurious forces that impact the mouth. Mouthguards have been and continue to be made of a large number of different materials all of which possess varying abilities to fulfill its protective function. The early use of gutta-percha and several different forms of rubber has been replaced by different plastics and newer materials of varying physical characteristics. Creative new materials are being developed every year as the mouthguard industry tries to stay innovative and to further meet the needs of athletes.

The most commonly used materials currently are some form of ethylene vinyl acetate (EVA) which has desirable handling characteristics as well as the proven ability to absorb and distribute injurious forces to the teeth and the supporting structures. This material is also the most widely studied material in the dental literature. In addition to this however, polyvinyl chloride, acrylic resin, polyurethane, polyolefin, latex rubber, and other polymeric and thermoformable materials have been used [25].

The properties a mouthguard must possess are a combination of measurable material features plus the ability to be fabricated easily. This must result in a comfortable piece of athletic equipment. The vast majority of studies that have evaluated mouthguards have done so by testing one or more of their physical characteristics in an in vitro setting. The most common tests have been impact tests of guards or the materials testing the absorption of impact forces as well as the distribution of forces [25].

Unfortunately, comfort, fit, and clinical efficacy cannot be evaluated in this way. There are no considerations in these impact tests to evaluate the ability of a mouthguard to stay in place at time of contact in order to protect the athlete. In addition, the comfort to the athlete of different mouthguards to one another cannot be measured in a laboratory setting.

7.4.1 Physical Properties

In his excellent systematic review of the literature of mouthguards, Knapik et al. list six properties that combine to define any particular mouthguard. These are shock-absorbing capability, hardness, stiffness, tear strength, tensile strength, and water absorption [25]. These are strictly material measurements and do not fully define the effectiveness of mouthguards.

Shock absorption is the ability of a material or a device to reduce the impact energy or force transmitted to the surface below the tested item. Shock absorption measurements have been achieved in two ways: A device can drop a load onto the material, or it can use a pendulum to swing an impacting force onto the material. The acceleration of the impacting force can be measured. The mass of the object can also be recorded, and then the force transmitted can be calculated.

The force absorption can then be measured in one of the two ways. Firstly, the rebound of the impacting object can be measured to see how much energy has been dissipated. Secondly and more directly, a force transducer can be placed under the tested device, and the force transmitted can be registered. Other methods such as material compression or the use of strain gauges have been used.

Hardness is defined as the “resistance of a material to penetration with a load applied.” This is measured with a device called a durometer, and the resulting measurement carries the name of the commercial durometer used (e.g., Shore A or Rex A). The values for hardness are rated from 0 to 100. A measure of 0 means the material was penetrated completely, and 100 means no penetration at all.

“Stiffness is related to hardness and as hardness increases so does stiffness” [25]. Low stiffness materials tend to deform with applied force, allowing most of the force to be centered under the impact. High stiffness materials tend to distribute forces over a larger area.

Tear strength indicates the ability of a material to resist tearing forces. A notched material of known thickness is pulled until it tears. It was stated that studies varied in this measurement due largely to the method used, so only those comparisons within individual studies should be used.

Tensile strength is the “pull force required to break a material of known size” [25]. Again a notched piece of material is pulled apart until it breaks.

Water absorption is the amount of water taken up by a material. These measurements are done by measuring the amount of water taken up after a material is submerged or by measuring the weight change of a material in water after a specific time and temperature.

Shock absorption, hardness, and stiffness have been used to indicate the potential protectiveness of a given mouthguard or material. Tear strength, tensile strength, and water absorption generally designate the durability of mouthguards. The last three are generally not investigated, but they are critical as many athletes chew or otherwise abuse their guards. Also water absorption can be an indication of the ability of a mouthguard to absorb saliva and thereby to absorb microorganisms [25].

7.5 Functions and Efficacy of the Athletic Mouthguard

The athletic mouthguard is designed to protect the player from a variety of orofacial injuries. In addition to the prevention of dental injuries, the mouthguard has also been said to have other benefits to present to the wearer. This section will list some of these functions and critically evaluate the mouthguard’s ability to achieve these goals.

7.5.1 Dental Protection

The athletic mouthguard’s main function is undoubtedly the protection of the teeth. This is also the one area where it can be said that there is reliable evidence to back up this claim. Knapik in his systematic review states that “risk ratios ranged from 1.6 to 1.9 for the different groups of studies examined” when looking at studies comparing mouthguard wearers versus no wearers [25]. This protective benefit is not overwhelming and does not match the dramatic effects of mouthguard wear that was reported in the early 1960s with football use, but it is an indication that, when evaluated critically, mouthguards do work to protect teeth.

Sigurdsson in a paper critically evaluating the literature behind claims of the effectiveness of mouthguards noted one study by LaBella et al. which “attempted to investigate prospectively or in real time” using college basketball players to compare wearers of mouthguards versus nonwearers [26]. This study looked at athletic exposures (either games or practices) of mouthguard wearers and showed a 0.12 per 1000 athletic exposure dental injury rate as compared to 0.67 per 1000 athletic exposures for nonwearers [27].

A common discussion is whether custom-fitted mouthguards are more protective than retail or boil and bite mouthguards. Knapik points out that while in vitro studies indicate a clear superiority of custom-fitted mouthguards, there are no clinical studies which support this claim [25]. At least one author has claimed that there is no difference between using a boil and bite mouthguard versus wearing no mouthguard at all, although these claims are based on questionable studies and questionable reading of the results [28].

One very large study from the US Army has shown that its introduction of boil and bite mouthguards into its basic training significantly reduced the number of dental injuries seen [29]. This paper reported a 1999 study at Fort Leonard Wood that showed a 74% reduction in dental injuries “during military combat training activities.” This led to the adoption of the use of mouth-formed mouthguards for basic trainees engaged in this training activity and to Army Regulation 600-63 which requires mouthguards during army military combat training. Therefore it does seem that boil and bite mouthguards do help decrease dental injuries. However due to the impracticality of fabricating custom-fitted mouthguards to large numbers of trainees, this study does not compare custom-fitted guards to retail products [29].

In a large-scale study using the HS RIO (High School Reporting Information Online) data collection system, Collins et al. showed that 22 players in this large collection of athletic exposures were injured when wearing a mouthguard. Within this group, 21 of the 22 were wearing store-bought mouthguards, and only 1 was wearing a custom-fitted mouthguard [3]. This finding is interesting, but it was not a purpose of the study and should be read with caution. It does however imply some superiority of custom guards to retail ones.

7.5.2 Soft Tissue Injuries

A good number of studies look at soft tissue injuries as a measurable orofacial injury. However, few studies have evaluated soft tissue injuries as an individual entity. Therefore there is no comprehensive data that specifically addresses the ability of mouthguards to protect soft tissue.

Historically and anecdotally boxers used the first athletic mouthguards to primarily avoid intraoral and perioral cuts and tears to lips and mucosa. As was previously mentioned, this was the primary reason that Ted “Kid” Lewis stated as the reason he both started and continued using his device. It was also the reason for the legalization of the use of mouthguards in boxing when Jack Sharkey unfairly lost a fight that he was winning as a result of a soft tissue cut which caused an excessive amount of bleeding.

In the study mentioned previously by LaBella et al., oral soft tissue injuries were specifically addressed. The findings showed a 0.69 versus 1.06 soft tissue injures per 1000 athletic exposures, but this difference was not significant [27].

It does appear that the protection against soft tissue injuries is a realistic expectation when using an athletic mouthguard, especially if undergoing traditional orthodontic treatment. This, however, is not a proven fact based on the dental literature.

7.5.3 Concussion Protection

Since the 1960s with the publication of the findings of Jack Stenger, there has been a widely held belief that the use of an athletic mouthguard can play a role in the reduction in the incidence and severity of concussions in sports [30]. This topic is covered elsewhere in this volume, and currently it is believed that there is a weak, if any, connection with mouthguards and concussions . Anecdotal, small studies and at least one clinical trial continue to implicate the mouthguard as a protective piece of equipment in the fight against concussions, but realistic proof has not been found.

7.5.4 Bone Protection

There are two papers that deal with the ability of mouthguards to protect against injuries to the bone. Following Stenger’s groundbreaking “case reports” of concussion protection , Hickey et al. looked to investigate this with cadavers and pressure sensors. In addition, he also examined bone deformation on the mandible of these cadavers when stuck with and without mouthguards. He showed a definite diminution of bone deformation when a mouthguard was in place [31].

Takeda et al. reproduced this work with an artificial bone system and found similar diminution of energy to the bone [32]. These two studies are both in vitro, and obviously a clinical study would be extremely difficult to accomplish. It does however appear that a resilient mouthguard should dampen the effect of a blow to the jaws if this specific force was received.

7.5.5 Temporomandibular Joint Protection

The Academy for Sports Dentistry makes a slide series available to its members from which to teach others about sports dentistry. In this series are a well-known two photograph set of a dry skull without a mouthguard in place and one with a guard [33]. These pictures are meant to demonstrate that with a guard the mandibular condyle is displaced downward and out of the glenoid fossa. This example has been used for years to imply that mouthguards have a protective effect on the temporomandibular joint.

Unfortunately the truth is not that simple. At least one expert in the treatment of TMD (temporomandibular joint dysfunction ) has stated that the most stable positions for the joint “are when the condyles are in their most superoanterior position in the articular fossa, resting against the posterior slopes of the articular with the discs properly interposed. The condyles assume this position when the elevator muscles are activated with no occlusal influences” [34], in other words, a fully occluded position. This would lead one to believe that a mouthguard that allows for a solid clenched “bite” might protect the TMJ but not simply by altering the position of the condyle.

Mark Roettger of the University of Minnesota, using a magnetic resonance imaging (MRI) system, evaluated the actual position of the condyle on a living volunteer (◘ Fig. 7.6a–c). He imaged the condyle with the subject fully occluded with no mouthguard, one that was 3 mm thick between the molars and one which was 5 mm thick. With the use of a reference line, one can see that the condyle actually seems to change very little. Dr. Roettger notes that “there is an increased recoil space and that the disc stays in its proper position.” He has also cautioned that this example is only one individual [49].

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