Patent Publication Number: US-6036487-A

Title: Mouthguard blank and mouthguard

Description:
FIELD OF THE INVENTION 
     THIS INVENTION relates to an improved material for mouthguards and to a mouthguard made from that material. 
     BACKGROUND OF THE INVENTION 
     The invention will be described by way of example with reference to mouthguards intended to be used while taking part in body contact sports. It should be appreciated that this is by way of example only and that the mouthguard of the invention may be used for therapeutic purposes also. For example the mouthguard may be used for treating temporomandibular disorders or the like. 
     DISCLOSURE OF THE INVENTION 
     Mouthguards are typically made from plastics material such as an ethylene vinyl acetate copolymer (EVA) and fall into three specific categories. The mouthguards are either stock products premoulded and made in a variety of sizes, home or self mouldable to suit the physical characteristics of the user or custom moulded to suit the characteristics of the user. The stock mouthguards are typically the cheapest and least effective in use while the custom moulded and shaped mouthguards are the most expensive and effective in their impact absorbent properties. 
     Little has been done to improve upon the characteristics and properties of mouthguards to enhance their effectiveness in protecting the teeth, jawbone and intraoral tissues from injury while the wearer takes part in body contact sporting activities such as boxing, football and the like. 
     German patent specification 4011204 discloses a mouthguard material consisting of an EVA copolymer material, polycaprolactone and colorants and perfumes and PVA to reduce the softening point of the resultant mouthguard for ease of manipulation and shaping. 
     U.S. Pat. No. 4,920,984 relates to a mouthguard material which may be custom shaped or moulded employing a teeth impression cast pressed against softened thermoplastic sheet material which increases in thickness from one end to the other. 
     Australian patent specification 633269 discloses a mouthguard made from an EVA copolymer having a softening point higher than the normal temperature of an oral cavity but lower than the highest temperature that the oral cavity can endure so that the user may adapt the mouthguard to fit the mouth by biting onto it after it has been heated. The shaping procedure may be repeated if the shape or configuration of the teeth should change. 
     Earlier proposals as well as providing materials enabling custom or self shaping of the mouthguard have also suggested the use of other additives to the material of construction to enhance the characteristics of the material. For example, U.S. Pat. No. 4,044,762 suggested the inclusion of not greater than 5% sodium fluoride, stannous fluoride or sodium fluorosilicate in the material of construction to simultaneously provide prophylactic treatment of the teeth. 
     There has been little activity in the construction of mouthguards in an attempt at enhancing the impact absorption properties other than the change in thickness referred to in U.S. Pat. No. 4,920,984. 
     It is an object of the invention to provide an improved mouthguard material and a mouthguard made from that material which provides enhanced impact absorbent properties. 
     According to one aspect, the invention provides a mouthguard material made of orally acceptable plastics material, the mouthguard material having a plurality of enclosed cavities therein at spaced locations arranged in at least a substantial part of the material. 
     The enclosed cavities may be of any suitable size and shape. For example, the cavities may have irregular shapes or regular shapes such as spherical or cylindrical shapes. The cavities need not be regularly spaced. For example, the cavities may occur randomly spaced throughout the material. The cavities in the material need not all be the same size or shape. However, it is preferred that the cavities employed in the material all be similar in size and shape. 
     The enclosed cavities may be present as voids in the material. If desired, the cavities may be filled with gas or liquid to enhance the impact absorption characteristics of the material. In one embodiment, the cavities may be filled with a synthetic material different from the substance from which the mouthguard material is predominantly made. 
     It is preferred that the mouthguard material be made from an ethylene vinyl acetate copolymer (EVA) substitute or equivalent. Additives may be added to the EVA to provide special properties for the mouthguard material. Preferably a copolymer of ethylene and about 20% by weight vinyl acetate is employed. Colorants, perfumes and softening agents may also be added. 
     According to another aspect, the invention provides a mouthguard made of orally acceptable plastics material and having a plurality of enclosed cavities therein at spaced locations arranged over at least a substantial part of the mouthguard. 
     One way in which the cavities may be formed is by employing an inner layer of sheet material in which a plurality of spaced apertures are formed and an upper and a lower layer of sheet material bonded to opposed sides of the inner layer to thereby close off the apertures to form the enclosed cavities. Other ways of forming the cavities may also be employed. 
    
    
     DISCLOSURE OF THE DRAWINGS 
     Preferred aspects -of the invention are described with reference to the drawings in which: 
     FIG. 1 is a spectral analysis of a preferred material from which the mouthguard of the invention may be made; 
     FIG. 2 is a graph showing comparative test results for materials from which mouthguards according to the invention may be made and standard mouthguard material; 
     FIG. 3 is a plan view of a blank of material from which a mouthguard in accordance with the invention may be made; 
     FIG. 4 shows a perspective view of a mouthguard made from the blank of FIG. 3; 
     FIG. 5 is an exploded perspective view of a cast and the mouthguard shown in FIG. 4; and 
     FIG. 6 is a graph of a thermal gravimetric analysis of the material identified by FIG. 1. 
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a Perkin-Elmer spectral trace which identifies the preferred material from which mouthguards according to the invention may be made. The material is sold under the trade mark STAY-GUARD and is made by World Wide Dental Inc in Clearwater, Fla., United States of America. FIG. 6 shows a graph of a thermal gravimetric analysis of this material. The material is an ethylene vinyl acetate copolymer with 20% by weight vinyl acetate. 
     The mouthguard may be pre-moulded and thus be of the more basic type of mouthguard previously mentioned. Alternatively the mouthguard may be user mouldable to suit the physical characteristics of the user. In yet another alternative, the mouthguard material of the invention may be custom moulded using a cast or impression taken of the user&#39;s physical characteristics. 
     FIG. 2 is a graph showing impact results for the preferred EVA material identified by the spectral analysis shown in FIG. 1 but not having voids or cavities in accordance with the invention. The sample identified as standard is such an EVA material. 
     Sample 1 is made from the same EVA material but has enclosed cavities formed in it. The cavities have a size of 2×2 mm and are separated by 2 mm wide borders. Sample 2 once again is made of the preferred EVA material and the cavities are 2×2 mm in size and separated by 1.00 mm borders. Sample 3 is made from the preferred EVA material and has cavities 3×3 mm in size separated by 1 mm borders. 
     The samples tested had a nominal thickness of about 4 mm and were all of the same dimensions. A minimal wall thickness may be provided on opposite side faces of the material overlying the cavities. A known force was applied to each of the sample materials and the force transmitted through the samples is shown in the graph. Sample 3 provided the greatest impact absorbing properties. 
     FIG. 3 shows a blank of material from which a mouthguard in accordance with the invention may be made. The blank 10 is in the general shape necessary for a mouthguard and may either be premoulded into standard sizes or softened and moulded to conform to the shape required by a user. 
     Not all of the blank 10 is provided with enclosed cavities shown generally by the numeral 11. These cavities 11 are confined within a border 12 such that when moulded the area defined by the border 12 extends over the ends of the teeth of the user and substantially over both sides of the teeth. A peripheral zone 13 is free of cavities. 
     FIG. 4 is a perspective view of a mouthguard 15 made from the blank like that of FIG. 3. The mouthguard has an occlusal zone against which the teeth may bite, and outer or buccal wall and an inner or lingual wall. The view shown is above looking into the valley within which teeth are received by the mouthguard. The cast 16 shown in FIG. 5 has been used as a mould for forming the mouthguard 15 and depressions 17 into which teeth project area clearly visible. Portions of the zone 13 may be trimmed away as required or deemed necessary. 
     FIG. 5 shows a view of a cast on which a mouthguard may be formed. The cast 16 is representative of an upper set of teeth 18. A blank of material in accordance with the invention is moulded into a mouthguard 19. Enclosed cavities 20 extend over a portion of the guard 19 and at least cover or extend over the teeth when in use. In this embodiment the cavities extend in rows and columns over the occlusal zone and in rows and columns part way over the lingual and buccal walls. A palate portion 21 shown in this figure is trimmed in the finished mouthguard 15 shown in FIG. 4. Likewise the free edge 22 may be trimmed to suit to provide a recess 23 (see FIG. 4) to accommodate the frenum on the inner surface of the upper lip of the wearer of the guard.