Abstract:
A dental appliance is disclosed designed to protect a wearer&#39;s dentitions against injury from impacts suffered in sports or other activities that can cause chipping, fracturing, dislodging or evulsion of teeth. The appliance may be custom-fittable with at least one pocket having an energy absorbing fluid. The energy absorbing fluid be nanosuspensions of small particles in viscous fluids that can undergo shear thickening when the dental appliance is struck by an object. The appliance dampens and diffuses horizontal and axial forces and directs them away from dentitions thereby reducing the risk for dental injuries.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims priority to and the benefit of U.S. Provisional Application Ser. No. 61/992,298 filed on May 13, 2014, which is incorporated by reference herein. 
     
    
     FIELD OF THE INVENTION 
       [0002]    An adaptive mouth guard to protect the dentition of people engaged in various sports, dentistry, hospital, or military activities. The adaptive mouth guard has a thermoplastic polymer structure that incorporates a shear thickening fluid to absorb energy. 
       BACKGROUND OF THE INVENTION 
       [0003]    There is mounting evidence that the materials typically used in mouth guards do not provide adequate protection. Despite widespread use of mouth guards in sports, there are more than one million dental injuries per year, and dental injuries are the most common type of orofacial injuries in sports. 
         [0004]    According to the American Dental Association (ADA), the lifetime costs for treatment of serious dental injuries are $15,000-$20,000 per tooth. Individuals who damage a tooth end up with multiple visits to the dentist, with down stream periodontal disease or other dental problems often leading to the need for implants. This brings the annual cost for dental injuries in sports in the USA alone to $500 million. 
         [0005]    Dental injuries are also quite common in hospitals during transoral proceedures. By way of example, a transoral procedure may be such as, but not limited to, an intubation or a rigid or flexible endoscopic procedure. 
         [0006]    Dental injuries during transoral procedures affect approximately 1% of patients, which corresponds to 150,000 patients/year and an annual cost of $75 million. Furthermore, dental injuries during intubation are the leading reason for litigation against anesthesiologists. 
         [0007]    Inexpensive mouth guards tend to have a poor fit, leading to low compliance of mouth guard use. Professional-grade mouth guards require fitting by dentists, making the mouth guards very expensive; but even these professional-grade mouth guards tend to be bulky, and restrict breathing and verbal communication. 
         [0008]    Since typical mouth guards are so uncomfortable, athletes frequently take them out and put them back in. The repeated handling of saliva-coated mouth guards leads to contamination of mouth guards from hands and fingers with pathogens. 
         [0009]    Clearly, a better mouth guard is needed that is thin enough so that does not impede breathing and communication, and does not tempt athletes to frequently remove it, while providing a much higher degree of protection than the state-of-the-art. 
         [0010]    There are sports activities where high-velocity impact events occur that reach peak force very quickly, within milliseconds (e.g. getting hit by an ice hockey stick or puck). While in other sports such as skateboarding, a crash can lead to landing on the chin or cheek. The peak force resultant from such an impact will be lower, but applied over a larger area of the face. 
         [0011]    In medical applications, such as intubation of patients during surgery, the peak forces are reached even more slowly but maintained over extended time periods, i.e. by laryngoscopes and rigid endoscopes inserted into the patient&#39;s mouth and throat. Similarly, in bruxism (night time teeth grinding), the forces are applied primarily in specific locations within the dental region, in the rear of the mouth in the molar region. 
         [0012]    A variety of materials have been used for mouth guards, including polyvinylacetate-polyethylene or ethylene vinyl acetate copolymer (EVA), latex rubber, polyurethane, polyvinylchloride, and acrylic resin. The current paradigm in materials selection for commercially available, inexpensive mouth guards is based on the concept that soft materials, such as ethylene vinyl acetate (EVA), provide protection by cushioning the teeth upon impact. However, in order to achieve the required degree of protection, relatively thick layers of polymer have to be used, with typical thicknesses in the range of 4 mm since these materials are highly compressible and thus tend to “cave in” and deform under impact. These mouth guards also usually fit very poorly. 
         [0013]    Better fitting, professional-grade mouth guards can be made from harder acrylic resins. This usually requires a visit to the dentist, where impressions are taken, so that the mouth guard can be fabricated in a dental laboratory. This process is time consuming and costly, a major impediment to consumer acceptance. 
         [0014]    Conventional mouth guards require the users to bite down on the mouth guards to keep them in place. The approximately 4 mm thickness of conventional mouth guards makes it almost impossible to wear them on both the upper and lower teeth. Furthermore, since the mouth guards are so bulky, they hinder breathing and verbal communication. It is also almost impossible to drink with the mouth guard in place. 
         [0015]    For sports where very high impact energies and velocities may be encountered, and for clinical applications where high stresses are encountered when intubation laryngoscopes and endoscopic instruments inserted into the throat apply pressure on the teeth, it is necessary to develop a much stronger mouth guard that can more effectively dissipate the forces. 
       SUMMARY OF THE INVENTION 
       [0016]    A dental appliance may have one or more flaps and/or cusps. A bite line extends through the appliance for receiving dentition. A least one pocket for a shear thickening fluid is located in the appliance. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    The features of the device and method of using it will be better understood in the context of the detailed description in conjunction with the drawings in which: 
           [0018]      FIG. 1  depicts a top view of one embodiment of a dental appliance in a first condition; 
           [0019]      FIG. 2A  depicts a cross-section along line  2 - 2  from  FIG. 1 ; 
           [0020]      FIG. 2B  depicts an alternative embodiment to the cross-section depicted in  FIG. 2A ; 
           [0021]      FIG. 3A  is a top view of one embodiment of a pocket of a dental appliance; 
           [0022]      FIG. 3B  is a top view of another embodiment of a pocket of a dental appliance; 
           [0023]      FIG. 3C  is a top view of another embodiment of a pocket of a dental appliance; 
           [0024]      FIG. 3D  is a top view of another embodiment of a pocket of a dental appliance; 
           [0025]      FIG. 4  is a top view of another embodiment of a dental appliance; 
           [0026]      FIG. 5  is a top view of another embodiment of a dental appliance; 
           [0027]      FIG. 6  is a top view of another embodiment of a dental appliance; 
           [0028]      FIG. 7  is a sectional view through another embodiment of a dental appliance; 
           [0029]      FIG. 8  depicts a force being applied to the dental appliance of  FIG. 7 ; 
           [0030]      FIG. 9  depicts the dental appliance of  FIG. 1  installed on the dentition of a patient; 
           [0031]      FIG. 10  depicts another view of the dental appliance of  FIGS. 1 and 9  installed on the dentition of a patient; and 
           [0032]      FIG. 11  depicts the dental appliance of  FIG. 1  in a second condition. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0033]    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 disclosed are not to be considered as limiting, unless the claims expressly state otherwise. 
         [0034]    Turning now to  FIG. 1 , one embodiment of a dental appliance  10  is depicted. A preferred embodiment of the dental appliance  10  is shown in a flattened, first state. The appliance  10  is a one-piece, unitary and integrally formed sheet of material. In one embodiment, the appliance  10  may be 0.25 mm to 2 mm thick and fabricated from a polycaprolactone thermoplastic matrix material. Such a material is widely available, inexpensive and readily disposable when the appliance  10  is exhausted. 
         [0035]    The appliance  10  may be produced by injection molding, but other production methods are permissible. In one embodiment, the appliance  10  may be produced by 3-D printing. Alternatively, a portion of the appliance  10  may be injected molded and another portion produced by 3-D printing. 
         [0036]    The appliance  10  comprises a first front flap  12  and a second front flap  14 , which together are called a maxillary flap. A forward cusp  16  is located between the two flaps  12 ,  14 . The cusp  16  extends inwardly into the appliance  10  at least partially dividing the first front flap  12  and the second front flap  14 . The cusp  16  extends inwardly toward, but preferably does not reach, a bite line  18 . 
         [0037]    The bite line  18  is the line on the appliance  10  along which the incisal edges  20  of the incisors  22  and the tips of the occluding surfaces  24  of the posterior teeth  26  come in contact with the appliance  10 , as shown in  FIG. 9 . Together, these edges  20  and surfaces  24  are called crowns herein. The bite line  18  is generally arch-shaped to be complementary to the arrangement of teeth in a wearer&#39;s mouth. 
         [0038]    A first side cusp  28  further defines the first front flap  12 . The first side cusp  28  is located between the first front flap  12  and a first outer side flap  30 . The first side cusp  28  extends inwardly into the appliance  10  toward the bite line  18 . The first side cusp  28  may extend inwardly into the appliance  10  at the same depth as the forward cusp  16  or to a greater or lesser extent. 
         [0039]    A second side cusp  32  further defines the second front flap  14 . The second side cusp  32  is located between the second front flap  14  and a second outer side flap  34 . The second side cusp  32  extends inwardly into the appliance  10  toward the bite line  18 . The second side cusp  32  may extend inwardly into the appliance  10  at the same depth as the forward cusp  16  or to a greater or lesser extent. 
         [0040]    In the embodiment depicted in  FIG. 1 , a line of symmetry  36  extends from the forward cusp  16  to equally divide the appliance  10  into a first half  38  and a second half  40 , which are symmetric with one another. More particularly, the line of symmetry  36  results in a mirror image between the first half  38  and the second half  40 . It is permissible, however, for the first half  38  to be non-symmetrical with the second half  40 . 
         [0041]    A perimeter  42  defines the first front flap  12 , the second front flap  14 , and the side flaps  30 ,  34 . The perimeter  42  is preferably rounded, or curvilinear. This embodiment is envisioned to impose the least, if any, discomfort to the wearer of the dental appliance  10  since it has no sharp corners or edges to embed into the soft gum tissue  44 , as shown in  FIG. 10 . 
         [0042]    The appliance  10  has a first planar side  46  and a second planar side  48  in the first state. The second planar side  48  is opposite the first planar side  46 . The second planar side  48  may be parallel to the first planar side  46 . Therefore, in the depicted embodiment, the appliance  10  has a substantially constant thickness, except where otherwise noted in the discussion below. The appliance  10  may, however, not have a substantially constant thickness. 
         [0043]    For example, the entire thickness of the appliance  10  may be increased, or it may be increased in certain areas. 3-D printing may be used to increase the thickness of the appliance  10  to 1.6-3 mm by depositing a polycaprolactone matrix on top of an existing layer. 
         [0044]    The appliance  10  depicted in  FIG. 1  has a plurality of open spaces  50  on an inner portion  52  and an outer portion  54  of the bite line  18 . The open spaces  50  extend through the appliance  10  from the first side  46  to the second side  48 , as shown in  FIG. 7 . 
         [0045]    The open spaces  50  are depicted as cylindrical with circular cross-sections, however, it can be appreciated that other shapes, numbers, designs and/or orientations are permissible. It is preferred that regardless of the open spaces  50  selected, that the design selected is symmetrical about the line symmetry  36 , but it is not required. 
         [0046]      FIGS. 1 and 2A  depict one embodiment of a pocket  56  located within the appliance  10 . In the depicted embodiment, the pocket  56  is located between the first planar side  46  and the second planar side  48  of the appliance  10 . In  FIG. 1 , the pocket  56  is located between the bite line  18  and the outer perimeter  42 . The pocket  56  may be entirely encased within the appliance  10 , as depicted in  FIGS. 1 and 2A . 
         [0047]    In an alternative embodiment, a portion of the pocket, or the entire pocket, may be exposed.  FIG. 2B  depicts one portion  58  of the pocket  56  extending above the first planar side of the appliance  10 . While  FIG. 2B  depicts the portion  58  extending from the first planar side to be a fraction of the pocket  56 , larger portions of the pocket  56  can be exposed. Additionally, while  FIG. 2B  depicts a portion  58  of the pocket  56  extending from the first planar side  46 , it is possible for the pocket  56  to extend from the second planar side  48  lower surface while not extending from the first planar side  46  or for the pocket  56  to extend from both sides  46 ,  48 . Further yet, it is permissible for two or more portions  58  of the same pocket  56  to extend from the appliance  10  or for two or more portions of different pockets to extend from the appliance  10 . Each of the alternatives discussed above is not limited to the embodiments discussed so far, but applies equally to each embodiment discussed herein. 
         [0048]    In the embodiment depicted in  FIGS. 1 and 2A , the pocket  56  comprises a channel  60  extending transverse to the line of symmetry  36 . The channel  60  is depicted a having a circular cross section, but other cross sections are permissible. Further, while the figures depict the channel  60  having the same cross-section, the shape and size of the channel  60  can change along its course. 
         [0049]    The channel  60  preferably extends from the first front flap  12  to the second front flap  14 . The channel  60  has a first end portion  62  and a second end portion  64 . In the depicted embodiment, the first end portion  62  is connected to a first reservoir  66  and the second end portion  64  is connected to a second reservoir  68 . 
         [0050]    In  FIG. 1 , the reservoirs  66 ,  68  are depicted as spherical; however, other shapes and sizes are permissible. What is preferable is that the reservoirs  66 ,  68  are in fluid communication with the channel  60 , regardless of the shape of the channel  60  or the reservoirs  66 ,  68 . 
         [0051]      FIG. 1  depicts the reservoirs  66 ,  68  in the first front flap  12  and the second front flap  14  of the appliance  10 . More particularly, the reservoirs  66 ,  68  are symmetrically located with respect to one another and axially aligned with the channel  60 . As shown in  FIG. 7 , the reservoirs  66 ,  68  are centered on an axis  70  of the channel  60  so that the channel axis  70  bisects the reservoirs  66 ,  68 . 
         [0052]    While  FIG. 1  depicts two reservoirs  66 ,  68 , only a single reservoir can be used. Further yet, it is conceivable that no reservoir is required at all. It is also within the scope of the disclosure that the single or more than one reservoir can be located in a position other than at an end portion  62  or  64  of the channel  60 . By way of example, the reservoir might be located equally between the two end portions  62  or  64 , or at any other location between the two end portions  62 ,  64 . 
         [0053]      FIG. 3A  depicts an alternative pocket  56  design wherein the channel  60  is curved, such as in a convex shape. Reservoirs  66 ,  68  are located at the end portions  62 ,  64  of the convex shape. 
         [0054]      FIG. 3B  depicts yet another pocket  56  design wherein the channel  60  has a serpentine trajectory. Reservoirs  66 ,  68  are located at the end portions  62 ,  64  of the channel  60 . 
         [0055]      FIG. 3C  depicts a coiled channel  60  design. In this embodiment, the channel  60  begins at a central point  72  and extends radially outward from the central point  72  in a curlicue fashion so that one portion of the channel  60  is radially encircled by another portion of the channel  60 . A reservoir is located at the outermost end of the channel. 
         [0056]      FIG. 3D  depicts yet another design wherein the pocket comprises a first and second channel  74 ,  76  angled with respect to one another. The first and second channels  74 ,  76  may be substantially linear. The channels  74 ,  76  intersect one another at a point and are in fluid communication with one another. Reservoirs  66 ,  68  are located at the ends of the channels  74 ,  76  opposite the intersection point. 
         [0057]      FIG. 4  depicts another pocket design wherein the pocket  56  has a complementary shape to the outer perimeter  42  of the appliance  10 . More particularly, the pocket  56  has a first portion  78  located in the first front flap  12 . The first portion  78  is located inward from the outer perimeter  42  but tracks the shape of the outer perimeter  42 . More particularly, the first portion  78  has a convex shape. 
         [0058]    The pocket  56  also has a second portion  80  located in the second flap  14 . The second portion  80  is symmetric with the first portion  78 . The second portion  80  is located inward from the outer perimeter  42  but tracks the shape of the outer perimeter  42  also with a convex shape. 
         [0059]    Inboard portions  82 ,  84  of the first portion  78  and the second portion  80  angle radially inwardly into the appliance  10  and meet at the line of symmetry  36  of the appliance  10 . The inboard portions  82 ,  84  are complementary to the shape of the forward cusp  16 . 
         [0060]      FIG. 5  depicts another embodiment with four pockets. A first pocket  86  has a round cross-section and is located in the first front flap  12 . A second pocket  88  has a tubular cross section and is located in the first outer side flap  30 . The second pocket  88  extends along, but inboard of, the outer perimeter  42  of the first outer side flap  30 . The first and second pockets  86 ,  88  are located in the first side  38  of the appliance  10 . 
         [0061]    The second side  40  of the appliance  10  is symmetrical with the first side  38 . Namely, a third pocket  90  with a round cross section is provided in the second front flap  14 . A fourth pocket  92  with a tubular cross section is located in the second outer side flap  34  along, but inboard of, the outer perimeter  42 . 
         [0062]    In the embodiment depicted in  FIG. 5 , the pockets  86 ,  88 ,  90 ,  92  are not in fluid communication with one another. However, one or more of the pockets  86 ,  88 ,  90 ,  92  may be in fluid communication with one another. 
         [0063]      FIG. 6  depicts another embodiment wherein on the first side  38  of the appliance  10 , a first pocket  94  with a tubular cross section extends along, but inboard of, the outer perimeter  42  in the first outer side flap  30 . A second pocket  96  having a circular cross section is located adjacent the first side cusp  28 . A third pocket  98  is located inboard of the outer perimeter  42  in the first front flap  12 . The third pocket  98  may have a first portion  100  that curls radially inwardly into the appliance  10 . A second portion  102  of the third pocket  98  extends radially outward toward the outer perimeter  42  in an arch-shaped fashion. A third portion  104  of the third pocket  98  extends radially inwardly away from the outer perimeter  42  but in a complementary fashion to the outer perimeter  42  of the first front flap  12  and the forward cusp  16 . 
         [0064]    Radially inward from the forward cusp  16 , a fourth pocket  106  is provided. The fourth pocket  106  has a circular cross section. A fifth pocket  108  is provided radially inward of the fourth pocket  106 . The fifth pocket  108  has a circular cross section. 
         [0065]    The appliance  10  has a sixth pocket  110  as a mirror image to the third pocket  98 , a seventh pocket  112  as a mirror image to the second pocket  96  and an eighth pocket  114  as a mirror image to the first pocket  94 . The sixth  110 , seventh  112  and eighth  114  pockets are located on the second side  40  of the appliance  10 . 
         [0066]    In the embodiment depicted in  FIG. 6 , the pockets  94 - 114  are not in fluid communication with one another. However, one or more of the pockets  94 - 114  may be in fluid communication with one another. 
         [0067]    Turning now to  FIG. 7 , the open spaces  50  extending through the appliance  10  from the first planar side  46  to the second planar side  48  can be appreciated. The open spaces  50  are shown to have circular openings at the sides  46 ,  48 , however, other shapes of the open spaces  50  are permissible. Further, while  FIG. 7  depicts the open spaces  50  having all the same size and shape, it can be appreciated that the size and shape of the open spaces  50  can vary. Continuing with the depicted appliance  10  in  FIG. 7 , the open spaces  50  extend through the appliance  10  with a cylindrical cross section. The opens spaces  50  in  FIG. 7  are in in the condition where a force has not been applied to the appliance  10 . 
         [0068]    A fluid  116  is located in one or more of the pockets (for example pocket  56 ) of the various embodiments described above. The fluid  116  in the pockets may all be the same or it may be different. Preferably, if a fluid  116  is provided in a pocket is comprises an energy absorbing fluid. The energy absorbing fluid may be such as a shear thickening fluid comprised of a suspension of nanoparticles inside a polymer matrix. 
         [0069]    Colloidal suspensions of nanoparticles have a natural resistance to flow due to random collisions between the particles. A high velocity impact onto the appliance  10  that is filled with nanoparticles suspended in a fluid imposes shear forces on the particles. When the shear rate increases beyond a certain threshold value, the viscosity of the fluid increases suddenly due to hydrodynamic interactions between particles that lead to transient fluctuations in particle concentration and the formation of so-called hydroclusters. The viscosity increases in a matter of milliseconds after receiving a force and causes the appliance  10  to stiffen. 
         [0070]    Typical separation distances between particles in these hydroclusters are in the range of nanometers. The onset of shear thickening is related to the size of the submicron particles and their volume fraction in the suspension. The onset of shear thickening can be modified by changing not only the particle size, but also the particle surface structure and chemical functionality. Surface roughness plays an important role, and the surface of particles can be further modified by adsorption of ions, surfactants, and polymers. During the shear-thickening event, a significant amount of impact energy is dissipated as the fluid stiffens, and within a few seconds after the event, the fluid returns to its original liquid like state. 
         [0071]    The shear-thickening event consumes energy as the structure of the nanofluid changes, and the stiffening of the entire structure dissipates a significant amount of the impact energy without transmitting it to the user&#39;s dentition. Furthermore, the energy absorption can be tuned for a given range of impact energies by modification of the composition of nanofluids. The tuning of the nanofluid properties is based on the following principles: In the shear thickening range of Brownian suspensions, the slope of the viscosity-shear rate curve tends to increase as the solid particle volume fraction increases. The onset of shear thickening of a nanosuspension occurs at a universal value of the Peclet number, Pe: 
         [0000]    
       
         
           
             Pe 
             = 
             
               
                 
                   
                     η 
                     s 
                   
                    
                   γ 
                    
                   
                       
                   
                    
                   
                     a 
                     3 
                   
                 
                 
                   
                     k 
                     B 
                   
                    
                   T 
                 
               
               ∝ 
               
                 γ 
                  
                 
                     
                 
                  
                 
                   t 
                   D 
                 
               
             
           
         
       
     
         [0000]    where η s  is the viscosity of the suspending fluid, γ the shear rate, a the radius of the solid particles, k B  the Boltzmann constant, T the absolute temperature, and t D  the time for a particle to diffuse a distance equal to is radius a. From this, the critical shear rate for the onset of shear thickening can be deduced to be proportional to the inverse of the cube of the particle radius. 
         [0072]    Additional tuning of the properties can be achieved through electrostatic charges and deformations of the steric stabilizing layer that can become important when small particles are mixed into a fluid. Therefore, particles with long-ranged repulsive interparticle potentials are expected to be most shear thickening. This opens the opportunity to modify the repulsive interparticle potentials by chemically functionalizing the surface of the particles with epoxy groups, hydroxyl groups, carboxyl groups, or amino groups. By changing variables such as particle type, particle size, surface functional groups, and particle/fluid weight ratio, it is possible to tune the range where the mouth guard responds dynamically and stiffens up for a given sport or military or medical application, where very different ranges of impact energies and velocities of impacting objects are encountered. 
         [0073]    One embodiment uses non-Newtonian fluids that are chemically compatible with thermoplastic polymers, and incorporates the fluids into internal cavities or small channels in a thermoplastic polymer matrix. Non-Newtonian fluids are fluids whose viscosity (a measure of a fluids resistance to deformation by shear or tensile stresses) is dependent on the shear rate. Examples of such fluids are salt solutions, starch suspensions, and molten polymers. 
         [0074]    Another embodiment of the invention uses shear-thickening solid liquid suspensions that exhibit increased viscosity when exposed to shear forces. Examples of such solid/liquid suspensions are: 
         [0075]    a) submicron-size silicon oxide particles in USP grade polyethylene glycol (PEG); 
         [0076]    b) submicron-size colloidal silicon oxide particles in USP grade glycerin; 
         [0077]    c) silicon nanoparticles in USP grade glycerin; 
         [0078]    d) silicon nanoparticles in USP grade polyethylene glycol (PEG); 
         [0079]    e) silicon dioxide nanoparticle in singular or binary mixtures in polyethylene glycol (PEG 200 and PEG 400); 
         [0080]    f) silicon dioxide nanoparticles functionalized with linear hydrocarbons in singular or binary mixtures in polyethylene glycol (PEG 200 and PEG 400); 
         [0081]    g) silicon dioxide nanoparticles functionalized with silanes in singular or binary mixtures in polyethylene glycol (PEG 200 and PEG 400); 
         [0082]    h) bentonite or kaolin clay (Al 2 Si 2 O 7 ) particles in USP grade glycerin; 
         [0083]    i) bentonite or kaolin clay (Al 2 Si 2 O 7 ) particles in USP grade polyethylene glycol (PEG); 
         [0084]    j) polycaprolactone particles in USP grade polyethylene glycol (PEG); 
         [0085]    k) salt solutions; 
         [0086]    l) starch suspensions; and/or 
         [0087]    m) molten polymers. 
         [0088]    In addition to these examples, many other solid particle-liquid combinations can be used to achieve shear thickening behavior. Depending on the shear rate and the amount of shear force, these suspensions can stiffen and thereby increase the energy absorption ability of the mouth guards by diverting the impact energy into the fluid filled cavities and channels and directing the impact forces away from the dentition. When the shear stress is removed, the nanosuspension inside the appliance returns to its original, non-shear thickened state with lower viscosity, making the appliance again comfortable to wear. 
         [0089]    The pockets inside the thermoplastic polymer matrix are filled with nanosuspensions that are tuned to exhibit a maximum dynamic response at a given trigger impact force. Tunable response where impact energies of different magnitudes can be dissipated can be achieved by incorporating nanosuspensions formulated with nanoparticles functionalized with linear hydrocarbons or with silanes. A range of nanosuspensions may be used that undergo shear thickening in dynamic response to peak forces and shear rates analogous to an impact event characteristic to a given activity or anticipated force(s). 
         [0090]    The pockets may also be filled with force dampening fluids such as glycerin and polyethylene glycol that do not undergo shear thickening. 
         [0091]    A method of using the dental appliances described above to protect the dentition of a wearer follows. The following description will use the embodiment of  FIG. 1 , but it can be appreciated that the method is readily used with the other embodiments. 
         [0092]    The appliance  10  is initially in a first planar state  118 , as shown in  FIG. 1 . At room temperature, the appliance  10  is rigid. The appliance  10  may be heated such as by convection, conduction and/or radiation until it is pliable. Once pliable, the appliance  10  is located adjacent the dentition of a patient. In the preferred embodiment, the appliance  10  is located adjacent the maxilla (upper dentation) into a second, non-planar state  120  described below, and depicted in  FIGS. 9 ,  10  and  11 . Alternatively, the appliance  10  may be located adjacent the mandible (lower jaw), or a first sheet can be located adjacent the maxilla and a second sheet can be located adjacent the mandible. 
         [0093]    Continuing with the embodiment wherein the appliance  10  is located just adjacent the maxilla, the crowns of the dentition  20 ,  24  are positioned adjacent the bite line  18  on the appliance  10 . The appliance  10  is moved into contact with the dentition  20 ,  24  and then molded around the dentition  20 ,  24 . More particularly, the first and second front flaps  12 ,  14  are molded in front of the outward facing surfaces  122  of the dentition. Similarly, the outer side flaps  30 ,  34  are molded in front of the outward facing surface  122  of the dentition. Preferably, the first and second front flaps  12 ,  14 , and also the outer side flaps  30 ,  34 , are located vertically, or with a small angle variance from vertical (e.g. 10 degrees), from the bite line  18 . In other words, the flaps  12 ,  14 ,  30 ,  34  are located parallel, or approximately parallel, the outward facing surfaces  122 . The flaps  12 ,  14 ,  30 ,  34  are preferably located in this orientation because it minimizes the mobility of at least the central incisor teeth  22  when the tips of these teeth  22  are subjected to a force. 
         [0094]    The appliance  10  also comprises a first inner side flap  124  and a second inner side flap  126 . The flaps  124 ,  126  are bounded by the perimeter  42  and the bite line  18 . As shown in  FIG. 1 , the flaps  124 ,  126  are symmetrical across the line of symmetry  36 , but non-symmetrical flaps are permissible. 
         [0095]    The first inner side flap  124  and the second inner side flap  126  are molded upwardly so they are positioned behind rearward facing surfaces  128  of the dentition. The flaps  124 ,  126  are located vertically, or within a small angle variance from vertical (e.g. 10 degrees) from the bite line  18 . In other words, the flaps  124 ,  126  are located parallel, or approximately parallel, the rearward facing surfaces  128 . 
         [0096]    The upward location of the flaps  12 ,  14 ,  30 ,  34 ,  124 ,  126  effectively encases the outward and rearward surfaces  122 ,  128  of the maxilla dentition in a channel  130 , which can be appreciated from  FIGS. 9 and 11 . The channel  130  is curved along the bite line  18  so as to be complimentary to the wearer&#39;s dentition. The channel  130  protects the outward and inward facing surfaces  122 ,  128  as well as the incisal edges  20  and occluding surfaces  24  of many of the wearer&#39;s dentition. 
         [0097]    When the appliance  10  is fit onto the dentition of a wearer, the forward cusp  16  falls centrally between the two maxillary central incisor teeth  22 . When formed to the dentitions, the first and second front flaps  12 ,  14  cross over a maxillary teeth-gum intersection line  132  and extend over the soft gum tissue  44 , as shown in  FIG. 10 . It has been found that when the appliance  10  extends over the maxillary teeth-gum intersection line  132 , the appliance  10  more robustly can protect the dentition from being moved during force application. In one embodiment, the flaps  12 ,  14  extend beyond the teeth-gum intersection line  132  approximately 0.25 to 0.35 mm. While one range of extension is mentioned above, it can be appreciated that this dimension can be larger or smaller to cover more or less of the soft gum tissue  44 . 
         [0098]    The flaps  12 ,  14 ,  30 ,  34 ,  124 ,  126  can be manually manipulated to position them as described above. In addition, the wearer can draw air through the open spaces  50 . The vacuum created by the wearer by drawing the air through the spaces  50  pulls the pliable appliance  10  into conformal contact with the dentition. 
         [0099]    The manual manipulation and/or the vacuum applied to the appliance  10  causes an interior surface  134  of the appliance  10  to mold into intimate contact with the outward facing surfaces  122  and/or rearward facing surfaces  128  of the dentition. As the appliance  10  cools, it may shrink into further contact with the dentition. During cooling, the appliance  10  hardens into a shape that well adheres to the contours of every unique tooth. This adherence ensures the appliance  10  does not become dislodged. In addition, the adherence and thin dimension of the appliance  10  provides a clear, unobstructed view of the wearer&#39;s mouth, voice box and trachea. 
         [0100]    The open spaces  50  in the appliance  10  provide a conformal fit of the appliance  10  onto any dentition and enable a secure custom fit by changing in size and in shape in all or some when the appliance  10  is in the pliable condition. The secure, custom fits enables the appliance to remain fixed on the dentition. The open spaces  50  allow the softened thermo-polymer material to be formed into a three-dimensional shape without buckling, bunching, creasing, or bulging. 
         [0101]    If the appliance  10  has to be re-fitted after it has cooled and hardened, it can be warmed to its softening point and the fitting process can be repeated because its second state is only a semi-permanent state. 
         [0102]      FIG. 8  depicts two of the open spaces  50  of  FIG. 7  but subject to a force. The force deforms the open spaces  50  resulting in dissipation of the force. In  FIG. 8 , the open space  50  is deformed as a result of one kind of force from a circular cross-section to an oval cross-section. The shape change of the open spaces  50  expends some or all of the energy of the force traveling through the appliance  10 . 
         [0103]    In one example, because the appliance  10  maintains a constant volume, when a force encounters an open space  50 , the deformed open space  50  compresses the adjacent open spaces  50 . The combination of deformation and compression of the open spaces  50  results in force dissipation. 
         [0104]    One kind of force, such as caused by a shearing action, may travel through the appliance  10  in a wave or waves. The waves may travel along an outer surface of the appliance  10  and/or through the appliance  10 . 
         [0105]    Another kind of force is a force that is normal to the appliance  10 . The normal force can be applied substantially at once, it can be repeated, and/or it can increase or decrease in intensity. 
         [0106]    While  FIG. 8  depicts the two open spaces  50  both deformed to dissipate a force, it can be appreciated that only one or the other might be deformed. Further, while  FIG. 8  depicts the open spaces  50  deformed into oval cross-sections, they may be deformed into other shapes and/or the shapes do not have to match one another. 
         [0107]    The open spaces  50  are located in the appliance  10  to maximize tensile strength of the appliance  10  without exposing any of the protected dental surfaces to the unprotected teeth on the opposite jaw. The locations of the open spaces  50  also optimize saliva flow around the dentitions, which improves comfort. More particularly, saliva can be sucked through the open spaces  50 . The open spaces  50  also function to improve breathing by allowing the appliance  10  to be thinner and thus take up less space in the mouth. 
         [0108]    Based on the foregoing, it can be appreciated that the appliance material, the location of that material on the wearer&#39;s dentition as described herein, the open spaces, and/or plastic and/or elastic deformation effectively diminishes forces transmitted in the axial (normal) direction, as well as in the horizontal direction, with respect to the dental surfaces. 
         [0109]    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.