Abstract:
The invention involves a mouthguard to optimize breathing while providing protection from physical blows. A mouthguard can include a plurality of conduits running substantially anterior-to-posterior therethrough.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    Mouthguards are known for protecting the teeth, jaw, and head during activities involving the risk of encountering blows to the face or head, such as athletics. Such mouthguards conventionally employ a resilient material for separating the upper and lower jaws to reduce the potential for damage to a user upon impact. 
         [0002]    It is desirable to provide a substantial amount of cushioning between the upper and lower jaws, yet too much such material interferes with breathing and thereby may hamper the performance of a user. It is therefore a problem in the art to provide a mouthguard which provides a substantial amount of cushioning between the jaws so as to protect the teeth and jaws without obstructing breathing. 
         [0003]    It is with respect to these and other considerations that the present invention has been made. 
       SUMMARY OF THE INVENTION 
       [0004]    The invention provides a mouthguard to optimize breathing while providing optimal protection from physical blows. In one embodiment, the mouthguard includes an arch-shaped upper channel adapted to receive a user&#39;s maxillary teeth, said upper channel comprising upward facing walls disposed along the buccal and lingual surfaces of the user&#39;s maxillary teeth; an arch-shaped lower channel adapted to receive a user&#39;s mandibular teeth, said lower channel comprising downward facing walls disposed along the buccal and lingual surfaces of the user&#39;s mandibular teeth; and a connecting portion disposed along the interface between said upper channel and said lower channel, said connecting portion comprising a plurality of hollow, tubular conduits running substantially anterior-to-posterior therethrough. In some embodiments, the mouthguard includes a plurality of conduits running substantially radially outward therethrough. In some embodiments, the conduits have a median cross-sectional area between 0.1 cm 2  and 4 cm 2  (e.g., between 0.2 cm 2  and 3.5 cm 2 , 0.5 cm 2  and 3 cm 2 , 0.75 cm 2  and 2.5 cm 2 , 1 cm 2  and 2 cm 2 , or 1.5 cm 2 ). 
         [0005]    In some embodiments, the anterior surface comprises air conduits at a density of at least 2 per square inch, said conduits comprising between 25% and 80% of the total composite anterior surface area. 
         [0006]    In some embodiments, the upper channel has a greater stiffness along the superior-inferior axis than the connecting portion, and the lower channel has a greater stiffness along the superior-inferior axis than the connecting portion. 
         [0007]    In some embodiments, the stiffness increases with increasing compressive strain along the superior-inferior axis. 
         [0008]    In some embodiments, the maximum impact force along the superior-inferior axis is reduced by at least 50% relative to the maximum impact force of an input pulse. 
         [0009]    In some embodiments, connecting portion is a resilient polymer having an ASTM D2240 type A hardness no greater than 90 of a modulus of no greater than 500 MPa. 
         [0010]    In some embodiments, the mouthguard is integrally molded using a single material. In other embodiments, the upper channel and the lower channel are a different material than the connecting portion. In some embodiments, the upper channel and the lower channel are a thermoplastic polymer that softens when heated to between about 100 and 300 degrees Fahrenheit and stiffens when cooled. The mouthguard can have a heat-resistant mold (e.g., one or more pronged inserts) occupying the conduit space to preserve the structure of the connecting portion during heating. 
         [0011]    In some embodiments, one or more cross sections of the air conduits are round in shape. In other embodiments, one or more cross sections of the air conduits are oval in shape. In other embodiments, one or more cross sections of the air conduits are polygonal in shape. In some embodiments, one or more cross sections of the air conduits are hexagonal in shape. 
         [0012]    In some embodiments, the connecting portion can be compressed by a user&#39;s application of bite force along the superior-inferior axis to seal the air conduits to facilitate swallowing. For example, the connecting portion can be sealed by a user&#39;s application of between 5 N and 800 N (e.g., 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 150, 200, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, or 800 N) compressive bite force. 
         [0013]    In some embodiments, the buccal walls of the upper and lower channels widen the lateral span of a user&#39;s lips by at least 10% relative to said user&#39;s at-rest state, said widening operative to expose one or more lateral air conduits to the exterior air. 
         [0014]    In some embodiments, the interior and exterior surface of the material surrounding each conduit is rounded or contoured to reduce disruptions in the air flowing through the conduits. 
         [0015]    In another embodiment, the mouthguard has an arch-shaped upper channel adapted to receive a user&#39;s maxillary teeth, said upper channel comprising upward facing walls disposed along the buccal and lingual surfaces of the user&#39;s maxillary teeth; a first lower channel adapted to receive a user&#39;s left mandibular molars, said first lower channel comprising downward facing walls disposed along the buccal and lingual surfaces of the user&#39;s left mandibular molars; a second lower channel adapted to receive a user&#39;s right mandibular molars, said first lower channel comprising downward facing walls disposed along the buccal and lingual surfaces of the user&#39;s right mandibular molars; a first connecting portion disposed along the interface between the upper channel and the first lower channel; and a second connecting portion disposed along the interface between the upper channel and the second lower channel; wherein a compressive stress exerted on the mouthguard along a superior-inferior axis is not directly transmitted to a user&#39;s mandibular incisors. 
         [0016]    In some embodiments, the mouthguard does not contact the user&#39;s mandibular incisors during an at-rest state. In some embodiments, the connecting portion is further disposed along the underside of the upper channel and connects the first lower channel with the second lower channel. 
         [0017]    In some embodiments, the mouthguard serves to provide optimal realignment of the user&#39;s upper and lower jaws and temporomandibular joint (TMJ), to further reduce the impact force and resulting trauma that may result from direct force transmission through the jaw into the cranium. 
       Definitions 
       [0018]    As used herein, “modulus” refers to the amount of stress required to compress a material by a given quantity. The modulus is a material property intrinsic to the material, independent of its geometry. 
         [0019]    As used herein, “stiffness” refers to the amount of force required to compress an object by a given quantity. Thus, the stiffness of a structure is a function of 1) the geometric orientation of its components and 2) the modulus of its materials. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0020]      FIG. 1  is a top front perspective view of a mouthguard according to a first embodiment 10, illustrating an upper channel and a lower channel with a connecting portion; 
           [0021]      FIG. 2  is a font view of the mouthguard  10 , illustrating the homogeneous plurality of hexagonal conduits; 
           [0022]      FIG. 3  is a side view of the mouthguard  10 ; 
           [0023]      FIG. 4  is a top view of the mouthguard  10 ; 
           [0024]      FIG. 5  is a bottom view of the mouthguard  10 ; 
           [0025]      FIG. 6  is a cross section view taken along line A-A in  FIG. 2 ; 
           [0026]      FIG. 7  is a front view of a mouthguard according to a second embodiment 20 illustrating the heterogeneous plurality of polygonal conduits; 
           [0027]      FIG. 8  is a top front perspective view of the mouthguard  20 ; 
           [0028]      FIG. 9  is a cross section view taken along line B-B in  FIG. 7 ; 
           [0029]      FIG. 10  is an illustration of one embodiment of a removable mold. 
       
    
    
     DETAILED DESCRIPTION 
       [0030]    Embodiments are described more fully below with reference to the accompanying figures, which form a part hereof and show specific exemplary embodiments. Embodiments may be implemented in many different forms and should not be construed as being limited to the embodiments set forth herein. 
         [0031]    In one aspect, the mouthguard is generally arch-shaped (the arch shape being viewed from a top or bottom view) and comprises an upper teeth-receiving channel  11  and a lower teeth-receiving channel  12  with an impact-absorbing connecting portion  13  disposed along its interface, described in greater detail hereafter. 
         [0032]    Optionally, the upper channel  11  and lower channel  12  can comprise substantially parallel surfaces to accommodate the bite of a user. Alternatively, the surfaces can be non-parallel such that to accommodate the rotational articulation of the temporomandibular joint (TMJ). In this embodiment, best seen in  FIG. 6 , the surfaces can be at a suitable angle  14  to provide support to a user&#39;s slightly open mouth. Such angle can be between 1 degree and 30 degrees. 
         [0033]    Upper and lower channels each extend in an arch shape from one posterior molar region across the anterior region to the second posterior region, as best shown in  FIG. 4 . A lingual wall  15  projects upward from the medial surface of the upper channel to contact the lingual side of a user&#39;s maxillary teeth. Similarly, a lingual wall  16  projects downward from the medial surface of the lower channel to contact the lingual side of a user&#39;s mandibular teeth. Lingual walls are functional to prevent forward slippage of the mouthguard. A buccal wall  17  projects upward from the distal surface of the upper channel to contact the buccal side of a user&#39;s maxillary. Similarly, a buccal wall  18  projects downward from the distal surface of the lower channel to contact the buccal side of a user&#39;s mandibular teeth. Buccal walls are functional to stabilize the mouthguard and to prevent displacement into a user&#39;s mouth upon impact. Buccal and lingual walls may project sufficiently far vertically across the lingual faces of a user&#39;s teeth as is comfortable. As best shown in the side view  FIG. 6 , the buccal walls preferably protrude to a greater height than lingual walls, and preferably cover the majority of the buccal surfaces of a user&#39;s teeth (e.g., incisors, pre-molars, molars, or combinations thereof) for protection from lateral blows. 
         [0034]    Preferably, the upper channel  11  and lower channel  12  are formed from a deformable thermoplastic material to enable molding to a user&#39;s own teeth. The thermoplastic material softens when heated to a temperature greater than body temperature but less than about 100° F. and rigidly stiffens when cooled so that the device can be fitted in situ in the user&#39;s mouth. This process, known in the art as “boil and bite,” is performed as follows. When initially fitting the mouthguard, the mouthguard is heated in hot water or otherwise to a temperature greater than body temperature but less than about 100° F. in order to soften the channels. Once sufficiently warmed, the mouthguard is placed in the user&#39;s mouth. The user then bites down on the base so as to make teeth impressions in the upper and lower bite surfaces, while applying suction and pressure with the tongue, lips, and oral musculature. Thereafter, the device is removed from the mouth and cooled, at which point the device hardens to a rigid form which includes an impression of the user&#39;s teeth and the user is left with a custom-fit protective dental appliance. 
         [0035]    In some aspects, the connecting portion is a material that is resistant to heat-dependent softening, such that it retains its physical properties throughout the “boil and bite” process. 
         [0036]    Alternatively, the upper channel, lower channel, and connecting portion may be comprised of a single material, which may be concurrently or sequentially injection molded or otherwise molded into a unitary whole. In this case, if a “boil and bite” procedure is to be performed, the conduits can be pre-fitted with removable molds  19  that are resistant to heating, as depicted in  FIG. 10 . In this embodiment, the conduit configuration retains its structure during a “boil and bite” process by physical support by the molds. Preferably, the molds have one or more handles  20  by which they can be removed by a user after the “boil and bite” process. More preferably, the molds can be attached to one another to enhance the ease or uniformity of their removal. 
         [0037]    A connecting portion  13  is disposed along the interface between the upper and lower teeth-receiving channels. A plurality of conduits  21  extend perpendicularly through the anterior-posterior depth of the connecting portion to allow for flow of air in and out of the user&#39;s mouth. To minimize air resistance without decreasing bulk mechanical properties, the conduits may account for anywhere between 25% and 80% of the total anterior surface area of the mouthguard. Other factors influencing the optimal conduit surface area ratio comprise (1) the modulus of the connecting channel material, (2) the lateral width of the connecting channel, (3) the superior-inferior height of the connecting channel, (4) the anterior-posterior depth of the connecting channel, and (5) the sizes and geometries of individual conduits. 
         [0038]    The impact-absorbing connecting channel can be about 10-20 mm in lateral width, about 1.0-1.5 mm in anterior-posterior depth, and about 0.5-1.5 mm in superior-inferior height. Preferably, the connecting channel increases in superior-inferior height toward the central, anterior region  22  to position the mouthguard into the user&#39;s slightly opened mouth as most clearly seen in  FIG. 3 . The connecting channel is fabricated from a polymer material having a high resilience, with a modulus of less than 500 MPa (e.g., about 500, 400, 300, 200, 150, 100, 90, 80, 70, 60, 50, 40, 30, 20, or 10 MPa) as measured by a universal testing machine, or a ASTM D2240 type A hardness of less than 90 (e.g., about 90, 80, 70, 60, 50, 40, 30, or 20) as measured by a durometer. Preferably, the material enables the conduits of the connecting portion to be fully closed by the user upon application of between about 5 to 800 N bite force (e.g., 5-800, 10-400, 20-100, or 40-60 N), to facilitate swallowing. The bulk mechanical properties of the connecting portion, while influenced by the modulus of selected material, ultimately depend on the geometry of the conduits. For this reason, the presence of conduits may impart a lower superior-inferior stiffness to the connecting portion in comparison to the upper and lower channels, even when the complete mouthguard consists of a single material. Thus, a desired stiffness of the connecting portion, and furthermore, the complete mouthguard, can be obtained by optimizing the conduit array geometry. Methods for rational design of such geometries are well known in the art and include finite element methods (i.e. two-dimensional stiffness matrix derivation). The stiffness between the upper and lower bite surfaces influences the efficiency of shock absorption. Preferably, the stiffness is a non-linear function of bite-induced compressive strain, wherein the stiffness increases with increasing compressive strain. Preferably, the user applies a compressive force of between 5 N and 800 N to fully close the conduits, as measured using a universal testing machine or a gnathodynamometer. 
         [0039]      FIGS. 1-6  depict a preferred embodiment wherein the connecting channel comprises a plurality of equally sized hexagonal air conduits  21 . The conduits  21  are each of a sufficiently high density and wide diameter to prevent high-resistance airflow upon breathing. The hexagonal supports of the connecting channel are of sufficient density to optimally resist compressive bite force and lateral displacement of the mandible relative to the maxillae. 
         [0040]    As an alternative to the homogeneous hexagonal channel design of  FIGS. 1-6 , another embodiment of the mouthguard  23  has a connecting portion comprised of larger, heterogeneously shaped channels  24  as depicted in  FIGS. 7-9 . A connecting portion comprising large air conduits further reduces air resistance upon heavy breathing, while maintaining protection of incisors from direct lateral impact of acute blows. Additionally, fewer structural members  25  compared to  13  can enable conduit closure by a lesser compressive bite force. Lateral conduits  26  provide even further enhancement of air flow by guiding outside air from lateral space posteriomedially into the user&#39;s mouth upon inhalation, and in the opposite direction upon exhalation, as best seen in  FIG. 9 . Preferably, the mouthguard extends the lateral span of a user&#39;s lips to ensure the lateral openings are unimpeded. The optimal lateral extension depends on the user&#39;s specific anatomy and may range from 5% increase over a user&#39;s at rest state to 100% increase. By channeling air from lateral outside regions which is not accessible by unassisted breathing, the lateral conduits may enhance airflow beyond the natural capacity. By enhancing a user&#39;s breathing efficiency, lateral conduits may enable greater oxygen exchange and lead to greater pulmonary performance in high-endurance conditions. 
         [0041]    To create a more smoothly flowing breathing environment, the interior and/or exterior surface of the material surrounding each conduit can be rounded, contoured, or chamfered  27  to reduce disruptions in the air flowing through the conduits. This enables a more efficient transfer of air, similar to the transfer of air over the smoothed leading surface of an airplane wing, and reduces noise, whistling, and other system inefficiencies. 
         [0042]    Alternatively, the mouthguard of the present invention can have a single conduit for airflow. Having a single conduit reduces the quantity of physical obstruction in the user&#39;s mouth and, in particular, enables the user to speak unimpeded. In one aspect, the mouthguard can be arch-shaped (when viewed from the front) such that the mandibular incisors are not directly supported in a teeth-receiving channel, but the maxillary incisors can be. Bite forces can be transmitted from the incisors laterally to the points where upper and lower channels contact the molars and premolars of the upper and lower jaw, respectively. The single conduit, in this aspect, is laterally defined by the connecting portions at the interfaces between the left and the right molar regions and vertically defined by the upper channel at the incisor region and the user&#39;s mandibular incisors. 
         [0043]    Although the subject matter has been described in language specific to structural features and methodologies, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims. It is intended that the invention not be limited to the particular embodiments described and illustrated, but that the invention will include all embodiments falling within the scope of the claims.