Abstract:
Disclosed is a dental appliance composed of a thermo-plastic polymer with low compressibility, high toughness, and high tensile strength, with a low softening point. The appliance has perforations that enable it to be easily custom-fitted by the user or a health professional. The appliance begins as a generally U-shaped, unformed dental tray that is significantly thinner than existing dental appliances. Once fitted, the dental appliance provides superior protection against damage to the enamel of the teeth and abrasion of the teeth due to bruxism or other mechanism leading to biomechanical wear of dental surfaces. The perforations facilitate the custom-fitting process by allowing the user to suck air through the perforations, thus applying a negative pressure between the material and the teeth while the material is still soft and pliable. This enables a user or health professional to within minutes create a final product that rivals the quality and fit of an appliance made by dental laboratories using dentist made impressions.

Description:
RELATED APPLICATIONS 
       [0001]    This application is claiming the benefit, under 35 U.S.C. §119(e), of the provisional application filed on May 15, 2012, under 35 U.S.C. §111(b), which was granted Ser. No.  61 / 647 , 093 , and is hereby incorporated by reference in its entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates generally to night grinding appliances. More particularly, the invention relates to custom-formable night-grinding dental appliances that are thin and have a multiplicity of strategically placed perforations. The perforations facilitate breathing and the flow of saliva while maximizing the protection of teeth with regard to bruxism or other mechanisms leading to biomechanical wear of dental surfaces. 
       BACKGROUND OF THE INVENTION 
       [0003]    Many dental patients suffer from temporomandibular joint disorder (TMD), a condition involving the improper functioning of the jaw and the temporomandibular joint. One of the conditions leading to TMD is bruxism, the subconscious clenching and grinding of teeth that typically occurs during sleep, but that may also occur while the patient is awake. In some cases of bruxism, the forces from jaw movements lead to tooth enamel damage, and over time the exerted excessive pressure can cause damage to the TMJ&#39;s articulating surfaces and lead to abrasion of the teeth surfaces. One of the treatments for bruxism is to insert custom-formed dental appliances, also known as “night grinding appliances”, or “bruxism protective device” or “mouth guards” to prevent direct contact of the occlusal surfaces of the teeth. 
         [0004]    Night grinding appliances or fitted mouth guards are typically prescribed by dentists and custom formed. Typically, the dentist first takes an impression of the patient&#39;s teeth, and a cast of the maxillary upper arch is fabricated. Then, a polymeric material, usually an acrylic material is molded over the cast while applying a vacuum. The resulting fitted mouth guard is then trimmed and polished. Alternatively, multiple layers of polymer are laminated together under pressure in an attempt to improve the physical properties of the protective layers. These custom-made fitted mouth guards tend to be very expensive, and require a visit to the dentist, and, in some cases, fabrication in a dental laboratory. 
         [0005]    Mouth guards for other uses, such as sports, do not provide protection against shear forces created by bruxism. Sports guards are developed to accommodate single, quick, large forces that are acting substantially normal to the tooth outer surface. Sports guards have no mechanism to contend with constant, low level shear forces from the user&#39;s own teeth. 
       SUMMARY OF THE INVENTION 
       [0006]    The invention is a generally U-shaped dental appliance made of polycaprolactone or other thermoplastic polymer with a low softening point. The appliance is substantially thinner than conventional dental trays and has strategically located perforations. The majority of the perforations are disposed primarily outside of an arc-shaped region associated with a user&#39;s bite line. The perforations facilitate breathing and unrestricted flow of saliva. The appliance can easily be heated to its softening point and custom-fitted by a dentist, other health professional, or even by the patient conforming exactly to the contours of the user&#39;s dentitions. 
         [0007]    The fitted dental appliance provides superior protection against damage to the enamel of the teeth and abrasion of the teeth due to bruxism or other mechanisms leading to biomechanical wear of dental surfaces. 
         [0008]    The appliance facilitates the custom-fitting process by allowing the user to suck air and saliva through the perforations, thus applying a negative pressure between the material and the teeth while the material is still soft and pliable. The result is within a short time a conformal fit around every tooth as the material hardens, thus enabling a user or health professional to create a final product that rivals the quality and fit of an appliance made by dental laboratories using dentist made impressions. 
         [0009]    The appliance has a periphery including a plurality of lobes and cusps to enhance custom fitting by allowing the softened material to envelop the teeth without buckling. 
         [0010]    After fitting to the patient&#39;s dentitions, the fitted appliance cools to ambient temperature and contracts slightly, thus conforming even better to the contours of the user&#39;s dentitions, and thereby preventing the appliance from getting dislodged or falling out during sleep. 
         [0011]    The appliance covers only the teeth and not the gum line on the labial side and the palate on the lingual side, in order to not cause discomfort, irritation of the gums, gagging, or inhibited breathing and saliva flow. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The features of the subject invention will be better understood in the context of the detailed description, in conjunction with the drawings. 
           [0013]      FIG. 1  is a scanning electron micrograph of an unformed tray taken at 8,000× magnification, showing the interwoven strands of the polymer imparting high abrasion resistance. 
           [0014]      FIG. 2  is a schematic illustration of an unformed tray with strategically placed perforations. 
           [0015]      FIG. 3  is a schematic cross section of two adjacent perforations before (a) and during (b) application of grinding forces, illustrating how the shape of the perforations changes during application of grinding forces. 
           [0016]      FIG. 4  shows a frontal view of the fitted appliance. 
           [0017]      FIG. 5  shows a bottom view of the fitted appliance depicting a lower surface of the appliance that is in contact with the dental surfaces. 
           [0018]      FIG. 6  shows another bottom view of the formed appliance. 
           [0019]      FIG. 7   a  depicts one embodiment of a formed appliance with circular perforations. 
           [0020]      FIG. 7   b  depicts another embodiment of a formed appliance with circular and teardrop perforations. 
           [0021]      FIG. 7   c  depicts another embodiment of a formed appliance with half moon and teardrop perforations. 
           [0022]      FIG. 7   d  depicts another embodiment of a formed appliance with half moon perforations. 
           [0023]      FIG. 8  shows one embodiment of the formed appliance on the dentitions of a user. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0024]    It is to be understood that the invention may assume various alternative orientations and step sequences, except where expressly specified to the contrary. It is also to be understood that the specific devices and processes illustrated in the attached drawings, and described in the following specification are simply exemplary embodiments of the inventive concepts defined in the appended claims. Hence, specific dimensions, directions or other physical characteristics relating to the embodiments. 
         [0025]    Turning now to  FIG. 4-6 , one embodiment of a mouth guard  10  is depicted. The mouth guard  10  has an inner upstanding wall  12  with an inner surface  14  and an outer surface  16 . The two surfaces  14 ,  16  are generally parallel one another. The guard  10  also has an outer upstanding wall  18  with an inner surface  20  and an outer surface  22 . The two surfaces  20 ,  22  are generally parallel one another. The inner upstanding wall  12  and the outer upstanding wall  18  are connected at their base portions with a U-shaped occlusal line portion  24  to form a U-shaped cross section. The walls  12 ,  18  of the guard  10  and the occlusal line portion  24  are unitarily formed as one piece. The occlusal line portion  24  is the part of the device that covers the bite line—the surface of the protected dentition that comes in contact with the surface of the dentition on the other jaw when the individual bites down during grinding or clenching. The occlusal line portion  24  can also be appreciated from  FIG. 8 . 
         [0026]    Although the guard  10  may have an upper edge portion  26  of the outer upstanding wall  18  that is relatively straight, in the preferred embodiment a number of small lobes and cusps are located in the outer upstanding wall  18 . The lobes and cusps are used to enhance the custom fitting process of the guard  10  to the user&#39;s teeth by allowing the softened guard material to adapt to any shape of the user&#39;s dentitions during the fitting process. As shown in  FIG. 4 , the upper edge portion  26  of the outer upstanding wall  18  is provided with at least one cusp. A first cusp  28  is provided between a right half  30  and a left half  32  on a centerline  34  at a forward portion  36  of the outer upstanding wall  18 . The guard  10  is symmetric about the centerline  34 . 
         [0027]    Preferably, a second cusp  38  is provided on the upper edge portion  26  of the outer upstanding wall  18  as well. In the depicted embodiment, the second cusp  38  is provided at a rearward portion  40  of the outer upstanding wall  18 . The second cusp  38  is positioned so that it is located between the user&#39;s incisors and molars (see also  FIG. 8 ). A lobe  42  formed between points  44  and  46 . Lobes  42  and cusps  28 ,  38  are not depicted on the inner upstanding wall  12  but they may be used on this wall  12  as well. 
         [0028]    A cusp  28 ,  38  is defined as an indentation of the wall  18  of the mouth guard  10 , and a lobe  42  is defined as a protruding portion of the wall  18  of the guard  10 . Without such cusps  28 ,  38  and lobes  42 , a guard  10  that has been softened to mold against a user&#39;s teeth tends to fold or buckle when the guard  10  is wrapped around teeth and gums during fitting. This is especially the case if the curvature and shape of the dentitions are uneven. If such folding occurs when the material hardens during the fitting process, the fitted mouth guard  10  may become uncomfortable to wear, irritating the inside of the lip, and compliance to wear it may decrease. Thanks to these cusps  28 ,  38  and lobes  42  the final result is a conformally fitted mouth guard  10  that has an outer upstanding wall  18  and an inner upstanding wall  12  both without folds and irregularities and that is extremely comfortable. Another effect of such cusps  28 ,  38  and lobes  42  is that shear forces to the fitted mouth guard  10 , as applied from the lower jaw during grinding, are dissipated away from the occlusal line portion  24 , and up towards these cusps  28 ,  38  and lobes  42 , thereby decreasing the negative effect of grinding on the dental surfaces. 
         [0029]    Multiphysics computer simulation analysis has shown that the cusps  28 ,  38 , representing singular points on the curvature of the fitted mouth guard  10 , act as zones where stresses in the material are concentrated and energy is dissipated, adsorbing and dissipating forces from high impact areas, i.e. the occlusal line portion  24 . When shear forces are applied to the fitted mouth guard  10  during grinding or clenching of teeth, a deformation wave front travels though the walls  12 ,  18  and crests at a cusp  28  and/or  38 . This directs the impact energy away from the dentition and concentrates it harmlessly in the cusp  28  and/or  38 . 
         [0030]    As shown in  FIGS. 3A ,  4 - 6 , a plurality of openings  48  are located in the inner upstanding wall outer surface  16 . The openings  48  connect with a plurality of perforations  50  extending through to the inner upstanding wall  12 . The perforations  50  connect with a plurality of exits  52  in the inner upstanding wall inner surface  14 . 
         [0031]    As also shown in  FIGS. 4-6 , a plurality of openings  54  are located in the outer upstanding wall outer surface  22 . The openings  54  connect with a plurality of perforations  56  extending through the outer upstanding wall  18 . The perforations  56  connect with to a plurality of exits  58  in the outer upstanding wall inner surface  20 . 
         [0032]    The strategically placed perforations  50 ,  56  in the guard  10  distribute the forces from clenched teeth more evenly and prevent abrasion of the teeth. The perforations  50 ,  56  increase the ability of the guard  10  to dissipate energy produced during grinding and clenching of teeth by redirecting the forces generated when teeth are clenched and dissipating the energy by temporarily distorting their shape. 
         [0033]    As shown in  FIGS. 3   a , and  4 - 6 , the openings  48 ,  54  and exits  52 ,  58  maybe circular in shape and the perforations  50 ,  56  may be cylindrical. The openings  48 ,  54 , exits  52 ,  58 , and perforations  50 ,  56  temporarily deform from circles into ovals in the region where a grinding and/or clenching force is applied, as schematically depicted in  FIG. 3   b.    
         [0034]      FIGS. 3   a  and  3   b , depict two openings  48 , exits  52  and corresponding perforations  50  in the inner upstanding wall  12 . A shear force  60 , which is applied during grinding, travels along the outer surface  16  (in this example) as a wave. The wave encounters a first perforation  64 , which becomes temporarily deformed by the wave. The wave deforms the first perforation  64 , which has a circular cross-section, into a perforation with an oval cross-section, which expends some of the energy of the wave. The guard  10  in which the perforation  64  is located maintains a constant volume. Thus, a second perforation  66 , which is proximate the first perforation  64 , gets compressed to account for the deformation of the first perforation  64 . The combination of perforation  64  deformation and the compression of an adjacent perforation  66  acts to absorb the laterally moving shear force in the guard  10 . The amount of compression of an adjacent perforation  66  is a function of the amount of deformation caused by the first perforation  64 . It can be appreciated that the deformation and compression occurs across many perforations simultaneously in the guard  10 . 
         [0035]    Based on the foregoing, it can be appreciated that a shear force generated at a rear portion  68  of the guard  10  can be dissipated before it reaches a forward portion  70  of the guard  10  thus causing no distortion in the forward portion  70  perforations. 
         [0036]    The perforations  50 ,  56  are placed in the walls  12 ,  18  to maximize the tensile strength of the guard  10  without exposing any of the protected dental surfaces to the unprotected teeth on the opposite jaw. The location of the perforations  50 ,  56  also optimizes saliva flow around the dentitions, which improves comfort. 
         [0037]    The perforations  50 ,  56  improve comfort, i.e. improve breathing and decrease drooling, i.e. the flow of saliva outside the mouth. Breathing is improved since the perforations  50 ,  56  allow the guard  10  to be thinner and thus take up less space in the mouth. Drooling is decreased since saliva can be sucked straight through the perforations  50 ,  56  in the guard  10 . Drooling is a common problem with conventional dental devices and a major reason for poor compliance to use them. The optimized saliva flow in the current invention that enables the user to suck saliva straight through the guard  10 , thus avoiding saliva accumulation around it, mimics the natural sucking and swallowing of saliva an individual does automatically during sleep. 
         [0038]    The perforations  50 ,  56  also improve the fitting procedure. The fitting procedure begins by taking the tray  72  depicted in  FIG. 2 . The tray  72  is heated, such as by hot water, microwave energy, or the like. Upon application of heat, the tray  72  becomes malleable. The heated tray  72  is put into the user&#39;s mouth and against the occlusal line of one set of teeth, such as the top set of teeth. 
         [0039]    The perforations  50 ,  56  allow the user to suck saliva and air through the perforations  50 ,  56  during the fitting process. This creates a slight vacuum between the softened guard  10  and the dentitions thus attracting the softened material to the dental surfaces and molding it perfectly around the contours of every tooth. The perforations  50 ,  56  allow the user to suck the softened appliance down onto the dental surface without having to apply any external mechanical pressure. The result is a perfect fit around every individual tooth, no matter the shape or relative location of an individual tooth. Upon cooling, the material retains the shape obtained during the molding process. This overcomes a major problem with conventional fitted mouth guards, where the user has to press the fingers onto the lips from the outside to form the softened fitted mouth guard to the teeth, with generally poor results. 
         [0040]    The perforations  50 ,  56  can be manufactured in a variety of shapes, sizes, and directions through the unformed tray  72 , but are typically in the range of 1-2 mm in diameter and shaped as cylindrical, straight, horizontal channels penetrating the walls  12 ,  18  of the formed guard  10 . The location, shape, and direction of these perforations  50 ,  56  may vary depending on demands on saliva flow, since saliva flow is not uniform throughout the oral cavity. For instance, the saliva flow is higher close to the ducts of the Parotid and submandibular saliva glands, located in the buccal mucosa and in the floor of the mouth. The location of these salivary glands ducts correspond to the rear portion  68  of the fitted guard  10  (Parotid glands) and the inner wall in the midline (Submandibular glands), and the perforations  50 ,  56  could be bigger in these locations to compensate for greater saliva flow. 
         [0041]    Since perforations  50 ,  56  have been proven to increase the ability of the material to dissipate energy produced during grinding and clenching of teeth by temporarily deforming the cylindrical shape of the perforations  50 ,  56 , a wide variety of the number of perforations  50 ,  56  and of their exact locations and directions in the material can be used. The present invention can be used on upper as well as lower teeth to improve protection. 
         [0042]    The location, size and shape of the perforations  50 ,  56  are arranged in special patterns that are optimized to dissipate the shear forces applied to the grinding guard by the teeth of the user suffering from bruxism. Enhanced absorption and dissipation of shear forces can be achieved by strategically placing perforations  50 ,  56  having complex shapes such as tear drop shapes or half-moon shapes, as illustrated in  FIG. 7   a - d.  In some cases, nonsymmetrical perforations, whose shapes are not symmetrical to the laterally traveling shear force wave, are preferable for their ability to absorb and dissipate shear forces. 
         [0043]    It is preferred that at least two perforations  50 ,  56  are located adjacent one another and that the perforations  50 ,  56  have different shapes. By way of example, a guard  10  might have a circular perforation directly adjacent a teardrop perforation. Preferably, adjacent means that the adjacent perforations are no more than 1-2 perforation diameters away from one another with no intervening structure. This close relationship of perforations is preferred because it allows them to be in force transmitting communication with one another. In one embodiment, the distance between perforations is less than approximately 3 mm and preferably between approximately 1-2 mm. 
         [0044]      FIG. 7   a  depicts one embodiment where two rows of perforations are provided. These perforations  56  are from the outer upstanding wall  18 . A first upper row  74  is above a second lower row  76  wherein the perforations  56  in the respective rows are laterally offset from one another and do not overlap. In this embodiment, the perforations  56  in both rows are circular/cylindrical. 
         [0045]      FIG. 7   b  depicts another embodiment where two rows of perforations are provided. A first upper row  74  is above a second lower row  76  wherein the perforations  56  in the respective rows are laterally offset from one another and do not overlap. The perforations in the first row  74  are circular/cylindrical  78 ; the perforations in the second row  76  are a teardrop shape  80 . 
         [0046]      FIG. 7   c  depicts another embodiment where two rows of perforations are provided. A first upper row  74  is above a second lower row  76  wherein the perforations  56  in the respective rows are laterally offset from one another and do not overlap. The perforations in the first row  74  are a combination of circular/cylindrical  78  and tear dropped shaped  80 ; the perforations in the second row  76  are a combination of half moon shape  82  and circular/cylindrical  78 . 
         [0047]      FIG. 7   d  depicts another embodiment where two rows of perforations are provided. A first upper row  74  is above a second lower row  76  wherein the perforations in the respective rows are laterally offset from one another and do not overlap. The perforations in the first row  74  are circular/cylindrical  78 ; the perforations in the second row  76  are a half moon shape  82 . 
         [0048]    Based on the foregoing, it can be appreciated that guards  10  can be highly customized to individual bruxism issues of a user. The location, size and shape of perforations can be tailored to the specific type and severity of bruxism experienced by a user. 
         [0049]    The shapes, sizes, and exact location of these perforations are determined by multiphysics computer simulations. These multiphysics computer simulations allow to determine the optimum pattern distribution and perforation shapes that allow the guard  10  to deform in such a way that the shear forces applied during grinding are directed into distortions of the perforation shapes in a lateral direction, thereby dissipating energy and protecting the underlying teeth. This permits the appliance to dissipate shear forces by deformation of selected perforations in grinding guard regions that experience shear forces, while maintaining the remaining perforations unaltered. This feature preserves the excellent fit of the grinding guard  10  even under severe bruxism conditions. It is important to note that this mechanism of energy dissipation is fundamentally different than the principles of operation of prior art mouth guards where cylindrical perforations were used to dissipate vertically applied compressive forces. Here, horizontal shear forces are redirected to change the shape of the perforations, a fundamentally different energy absorption mechanism made possible by the special shape of the perforations. 
         [0050]    Dental appliances  10  according to this invention are made from a material that is considerably tougher than conventional stock boil and bite appliances, typically made of ethyl vinyl acetate (EVA). The increased toughness of the material improves its ability to absorb energy and its resistance to damage when stressed during clenching and grinding of teeth. 
         [0051]    The material used in this invention is substantially less compressible than the materials used in conventional boil and bite appliances. Preferably, the material is substantially incompressible and substantially constant volume. By way of example, the material may be such as polycaprolactone or other thermoplastic polymers. According to a multiphysics computer simulation, the material in the current invention deforms only 1.4% under a static load of 2 MPa in comparison to 35% for EVA used in conventional appliances. The less a dental device compresses under impact the less it “caves in”. This means that the impact forces dissipate laterally over the device rather than being transferred through the material to the underlying teeth. Better dissipation of forces increases the protection of the dental surfaces. Since compression of the current invention is only 1/25 of conventional dental devices, the transferred forces to the teeth are just a fraction of those in conventional devices, and the degree of protection of the dental surfaces by the current invention is significantly better. Furthermore, less compression results in less permanent deformation of the material itself, which increases its durability. The decreased deformation maintains the excellent conformal fit of the appliance during clenching of teeth and prevents dislodging of the appliance from the dentitions. 
         [0052]    Conventional, EVA based appliances need to be about 4 mm thick to provide adequate protection. Thanks to the superior properties of the material in the current invention, a thickness of on average 1.6 mm (range 1.0-2.5 mm) is sufficient to provide adequate protection of the dentitions against abrasion during grinding of teeth. The thinner a night grinding fitted mouth guard  10  is the more comfortable it is, which in turn is important for compliance to use the guard. Bulkier dental device tend to cause gagging. Furthermore, a thinner fitted mouth guard  10  is easier to fit around individual teeth, especially when perforations and the pliability of the current material allows custom fitting to any surface. 
         [0053]    The unformed tray  72  may have a uniform thickness, however, when it is fitted the thickness of the appliance may vary. For example, the thickness of the fitted guard  10  may vary in different areas between 1.0 and 1.8 mm when the unformed tray thickness is approximately 1.6 mm. The varying thickness may occur in different areas of the unformed tray to provide increased comfort to the user. Furthermore, the unformed tray  72  may be deliberately made thicker in specific areas where dental abrasion is suspected to occur. This can be accomplished by starting from an unformed tray  72  that has regions of different thickness. For example, the material covering the bite line could be made thicker uniformly or only in specific areas, such as the molar region. 
         [0054]    In the preferred embodiments the appliance according to the invention is based on a thermo-plastic polymer with low compressibility. The polymer softens when heated to temperatures above 50° C., allowing it to be conformally fitted to the dentitions. The physical properties of this thermo-plastic polymer, such as compressibility, toughness, tensile strength, pliability, and melting point can be adjusted by synthesizing the polymer with different molecular weight distributions (with mean molecular weight in the range of 20,000-80,000), or by incorporating nano-particles and other materials like bentonite clay nanoparticles modified by surfactants such as Stepantex SP-90, to get additional benefits, e.g. increased tensile strength, lower melting temperature, etc. In the preferred embodiment, the polymer is highly abrasion resistant thanks to its structure that contains interwoven strands  84  of polymer, as shown in a magnified scanning electron microscope image ( FIG. 1 ). Since these strands  84  are interwoven and extend deep into the material, they will not easily be pulled out or removed from the material during grinding of teeth, thereby making the appliance more abrasion resistant. 
         [0055]    The shape of the unformed tray  72  facilitates the fitting of the softened material by being wide enough to cover all teeth and wrap around them, and by being narrow enough not to cause pressure on the teeth when the fitted mouth guard  10  cools off and contracts around the teeth. In contrast to athletic fitted mouth guards, night grinding fitted mouth guards are used for 6-10 hours straight, and therefore need to be extremely comfortable to guarantee compliance to use them during an entire night&#39;s sleep. The carefully designed shape, with cusps  28 ,  38  and lobes  42  prevents the material from folding when the soft material is molded up against the teeth. The width of the dental unformed tray has also been carefully designed to cover the curved occlusal line portion  24  with solid material without perforations and still allow the user to mold the material up on the inside and outside of each tooth. This design will make sure that the fitted device grips around the teeth and does not fall out during sleep, and at the same time not extend up to the gum line, which is uncomfortable, nor to the hard palate on the inside, which can create gagging. It extends back to the molars, just enough to avoid contact between lower and upper dentitions, but it is short enough to avoid unnecessary gagging. The thinness and the exact design of the unformed dental tray  72  and the location of the perforations  50 ,  56  allow the material to mold conformally around any uneven surface of the teeth.  FIG. 3  shows an example of a fitted appliance. 
         [0056]    Due to the ease with which the material can be formed and manipulated, the user can fit the mouth guard  10  on site or at home without assistance of health professionals. Fitting is superior due to the distinct properties of the polymer (thin and pliable at moderate temperatures), and to the design of the unformed dental tray  72  with strategically placed perforations  50 ,  56 , as described above, and lobes  42  and cusps  28 ,  38  as described above. These properties permit the user to place and fit the heated, softened material over the dentition through a rapid process wherein the material is sucked onto the teeth. In particular, the perforations  50 ,  56  enhance the effect of the suctioning by allowing the user to create a negative pressure between the teeth and the material, thus sucking the material down to every irregularity of the teeth. Thanks to the perforations  50 ,  56  in the guard  10 , the suctioning maneuver creates a minimal dead space between the material and the teeth, thus leading to a perfect, conformal fit. Without such perforations  50 ,  56 , conformal fitting cannot be done since not enough negative pressure can be built up between a solid material and the dentition. This is reflected in the instructions of conventional fitted mouth guards, where the user is directed to apply downward mechanical pressure on the material, from outside with the fingers, to force the material to come closer to the teeth. 
         [0057]    Polymer-based guard  10  according to this invention are inexpensive and disposable thereby improving oral hygiene. Users can move their jaws in any way without risking the guard  10  becoming dislodged. 
         [0058]    The guard  10  can be re-shaped to optimize fitting by re-heating to the softening point and repeating the fitting. The superior fit of the guard  10  also results in the need for less material on the inside of the teeth, which in turn reduces gagging and improves comfort. 
         [0059]    Users of the inventive guard  10  can breathe more easily. There is more room in the mouth since the guard  10  is considerably thinner than prior art dental appliances, and air can also move freely though the perforations. 
         [0060]    In accordance with the provisions of the patent statutes, the present invention has been described in what is considered to represent its preferred embodiments. However, it should be noted that the invention can be practiced otherwise than as specifically illustrated and described without departing from its spirit or scope.