Abstract:
A dental device has a U-shaped carrier with at least one channel for embracing an arch of teeth. The carrier has recessed insets in the channel. Discrete inserts carrying a beneficial agent can fit into the insets and release the agent gradually. When the device is used in a primarily therapeutic application, the inserts may be installed into all or less than all of the insets to form various insert patterns. Thus, different oral regions can be affected by different insert patterns. When the device is used as an athletic mouthguard, temporary blanks may be initially fitted in the insets, while a portion of the mouthguard is softened before an arch of teeth is pressed into the channel to make a custom impression. The inserts that are later installed in the insets possess different physical properties than the carrier and may be positioned and shaped to mechanically buffer teeth of the arch from mechanical shocks as well as release beneficial agents. The inserts may be replaced or refreshed to maintain the beneficial agent, which may be xylitol, remineralizing agents, moisturizing agents, desensitizing agents, flavoring agents, breath fresheners, chemical and biological indicators, nutraceuticals, antibiotics, probiotics, other medications and chemotherapeutics, or other agents.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a divisional of U.S. patent application Ser. No. ______, attorney docket number DIAMON 3.0-001 DIV DIV, filed Aug. 14, 2008 and entitled “THERAPEUTIC AND PROTECTIVE DENTAL DEVICE USEFUL AS AN INTRA-ORAL DELIVERY SYSTEM,” which is a divisional of U.S. application Ser. No. 12/001,571, filed Dec. 12, 2007, which is a divisional of U.S. application Ser. No. 10/138,821, filed May 6, 2002, the entire disclosures of which are hereby incorporated by reference herein. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to dental devices that are worn on an arch of teeth, and in particular, to devices that can deliver a beneficial agent to, and protect the teeth and soft tissues from mechanical, chemical and biologic injury. 
         [0004]    2. Description of Related Art 
         [0005]    Mouthguards are typically made from plastics materials such as an ethylene vinyl acetate copolymer (EVA). Other devices such as dentoalveolar trays, carriers and splints may be made of EVA or other biocompatible plastic material. There are several categories of mouthguards: Mouthguards that are stock pre-molded products and made in a variety of sizes, home or self-moldable to suit the physical characteristics of the user, or custom molded by a dentist or other professional to suit the characteristics of the user. Regarding physical protection, stock mouthguards are typically the cheapest and least effective in use while the custom molded and shaped mouthguards are the most expensive and effective in their impact absorbent properties. 
         [0006]    Athletes in many sports wear mouthguards for prolonged periods. It is common knowledge that when these athletes engage in strenuous physical activity, they lose and must replace significant amounts of fluids, nutrients and calories. In order to hydrate themselves, and replenish their energy, athletes must drink large quantities of fluids and eat foods that are very often cariogenic. These cariogenic fluids and materials cover the teeth, and when a mouthguard is inserted afterwards, the teeth are acted upon by cariogenic bacteria in an ideal environment, shielded from the buffering ability of saliva. In athletes, factors that serve to diminish salivary flow around the teeth include the general sympathetic tone of the nervous system, dehydration and shielding of the teeth by a mouthguard. Moreover, the elderly, patients suffering from a variety of autoimmune diseases, patients on a variety of medications and patients treated in the head region with external beam radiation may also suffer from reduced salivary flow. Whatever the cause, reduced salivary flow greatly increases the incidence of dental caries and periodontal disease. 
         [0007]    U.S. Pat. No. 4,920,984 relates to a mouthguard material that may be custom shaped or molded employing a teeth impression cast pressed against softened thermoplastic sheet material that increases in thickness from one end to the other. 
         [0008]    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. 
         [0009]    In FIG. 15 of U.S. Pat. No. 5,082,007 a gel or fluid capsule is contained between the upper and lower portions of a mouthguard. The nature of this gel is not described and appears to serve a mechanical, that is, a shock absorbing function. 
         [0010]    It is not only known to employ materials enabling custom or self shaping of mouthguards, it has been suggested that mouthguards use other additives in the material of construction to enhance the characteristics of the material. For example, in U.S. Pat. No. 4,044,762 an athletic mouthguard is formed from a mixture of a plastic resin (e.g., an ethylene vinyl acetate that can be heated and softened to form a custom-fitted impression) and a fluoride compound that protects the wearer&#39;s teeth. As an alternative, the reference suggests spraying or otherwise coating the surface of a mouthguard with a fluoride compound. This fluoride compound is gradually delivered while the mouthguard is worn. 
         [0011]    In FIGS. 7 and 8 of U.S. Pat. No. 5,323,787 a medicated pad is adhesively secured on the occlusal surface of a mouthpiece to treat the teeth and gums. The pad is saturated with a medicating substance in an intermediate layer of absorbent polymeric or fabric material, and that intermediate layer is overlaid with a non-porous outer layer. The pad can either be replaced or soaked to renew the medication. Specific medications are not discussed, although for other embodiments the mouthpiece is soaked in sterilizing (bactericides) and mouth-refreshing ingredients such as flavorings of the type used in conventional mouthwashes. 
         [0012]    German patent specification 401 1204 discloses a mouthguard material consisting of an EVA copolymer material, polycaprolactone and colorants and perfumes and PVA (polyvinyl acetate) to reduce the softening point of the resultant mouthguard for ease of manipulation and shaping. 
         [0013]    In U.S. Pat. No. 5,395,392 an infant&#39;s pacifier has a perforated mouth bulb containing a powder, syrup, or tablet with an agent such as monoclonal antibodies, fluorides, sorbitol, or xylite (xylitol). 
         [0014]    Xylitol is a naturally occurring sugar. It is a five-carbon polyalcohol, pentitol, which is widely distributed in nature. Most fruits, berries and plants contain xylitol. Xylitol is also an intermediate of mammalian carbohydrate metabolism. Our bodies produce up to 15 grams of xylitol from other food sources using established energy pathways. Xylitol use is known to reduce tooth decay rates both in high-risk groups (high caries prevalence, poor nutrition, and poor oral hygiene) and in low risk groups (low caries incidence using all current prevention recommendations). Sugar-free chewing gums and candies made with xylitol as the principal sweetener have already received official endorsements from numerous international dental associations. Studies using xylitol as either a sugar substitute or a small dietary addition have demonstrated a dramatic reduction in new tooth decay, along with arrest and even some reversal of existing dental caries. Xylitol provides additional protection that enhances all existing prevention methods. This xylitol effect is long lasting and possibly permanent. Low decay rates persist even years after the trials have been completed. 
         [0015]    For the anticariogenic activity of casein phosphopeptides, see U.S. Pat. Nos. 5,015,628; 5,834,427 (method of preparing casein phosphopeptides); and U.S. Pat. No. 5,981,475. For various remineralizing compositions, see U.S. Pat. Nos. 4,348,381; 5,562,895; 5,895,641; and 6,036,944. 
         [0016]    For various mouthguards and similar dental devices, see U.S. Pat. No. 4,554,154 (plastic that is chewable or usable as dental floss carries remineralizing, immunological, and anti-bacterial agents; e.g. sodium fluoride, chlorhexidine and lysozyme); U.S. Pat. No. 5,085,585 (U-shaped applicator is placed over teeth to apply medicaments to teeth and gum pockets); U.S. Pat. No. 5,194,003 (device that fits over teeth releases beneficial agents from a reservoir); U.S. Pat. No. 5,339,832 (composite mouthguard with integral shock-absorbing framework); U.S. Pat. No. 5,365,624 (mouthpieces with cleaning motors or gum cushioning material); and U.S. Pat. No. 6,012,919 (occlusal protector pad in an athlete&#39;s dental appliance has an upper layer of EVA and polycaprolactone). 
         [0017]    Certain hydrogels, particularly synthetic hydrogels, can act as carriers for drugs and other active agents. These hydrogels allow passage of the agent, in some cases acting as a membrane that allows agent passage. Covalently crosslinked hydrogels can incorporate a drug or other agent during the polymerization step; or the agent can be loaded from a solution. These types of hydrogels tend, however, to be weak when swollen by its water content. With thermoplastic (solvent soluble) hydrogels, an agent or drug can be compounded with the polymer during extrusion or injection molding; or by combining the agent with the polymer solution in a suitable solvent. See “Hypan® Hydrogels” published by Hymedix International, Inc. The Hypan® hydrogels can be obtained with varying degrees of hydrophilicity. They can also be obtained either as relatively hard, crystalline blocks, used for structural applications; or as meltable transient clusters that are highly swelling, and useful as emulsifiers, gelling agents, and drug carriers. Various other suppliers of hydrogel exist as well. 
         [0018]    For hydrogels with improved stability, see U.S. Pat. No. 5,346,935. See also U.S. Pat. No. 5,071,657 (transdermal administration of a medicinal agent dissolved in a nonflowable gel distributed in a microdisperse mode in a crosslinked silicone elastomer); U.S. Pat. No. 5,200,194 (oral osmotic device has a beneficial agent and hydrophilic support fibers inside a semi-permeable membrane); and U.S. Pat. No. 5,252,692 (hydrophilic acrylic copolymers). 
         [0019]    See also, U.S. Pat. No. 3,996,934 (bandage using microcapsules to deliver a drug); U.S. Pat. Nos. 5,366,935; 5,286,490 (transdermal patch delivers fluoride medication to treat osteoporosis or periodontal disease); and U.S. Pat. No. 5,925,372 (transdermal delivery system for ethanol soluble drugs). 
         [0020]    Thus, while prior art devices are capable of delivering an agent to surfaces within the oral cavity, they lack the ability to deliver agents to selected surfaces within the oral cavity, or to deliver one or more agents to different oral surfaces simultaneously. The present invention fulfills this long-felt need by being able to selectively deliver agents to specific oral surfaces, and to be able to deliver multiple agents to different surfaces using a single device, which device includes numerous insets for receiving agent-containing inserts therein. This agent delivery function can be performed either independently of, or in conjunction with, the protective functions of the present invention, which can also act as an athletic mouthguard. Further, the present invention provides a means to recharge the device with an agent once that agent has been depleted. 
       SUMMARY OF THE INVENTION 
       [0021]    In accordance with the illustrative embodiments demonstrating features and advantages of the present invention, there is provided a dental device having a U-shaped carrier with at least one channel for embracing an arch of teeth. The carrier has at least one recessed inset in the at least one channel. The dental device also has at least one discrete insert carrying a beneficial agent. This insert is adapted to fit into the inset and release the agent gradually. 
         [0022]    In accordance with another aspect of the invention, the foregoing dental device also includes at least one blank removably fitted into the at least one inset. 
         [0023]    In accordance with yet another aspect of the invention, a dental device has a U-shaped carrier with at least one channel for embracing an arch of teeth. The carrier has at least one recessed inset in the at least one channel. Also included is at least one discrete insert adapted to fit into the inset. The insert has a different physical character (e.g., softer) than the carrier and is positioned and shaped to mechanically buffer teeth of the arch from mechanical shocks. 
         [0024]    In accordance with still yet another aspect of the invention, a dental device that can mechanically buffer an arch of teeth from mechanical shocks has a U-shaped carrier with at least one channel for embracing the arch of teeth. Also included is a beneficial agent suffused through at least a portion of the carrier. The beneficial agent includes xylitol or sorbitol in one case, or a remineralizing agent in another case. 
         [0025]    In accordance with a further aspect of the invention, a method is provided that employs at least one insert and a U-shaped carrier having at least one channel with at least one recessed inset containing a blank. The method includes the step of softening at least a portion of the carrier along the channel. Another step is pressing an arch of teeth into the channel to make an impression. The method also includes the step of removing the blank from the at least one inset. Also included is the step of installing the at least one insert into the at least one inset. 
         [0026]    In accordance with yet a further aspect of the invention, a method employs (1) a plurality of inserts suffused with a beneficial agent and (2) a U-shaped carrier having at least one channel with a plurality of recessed insets. The method includes the step of installing selected ones of the inserts into less than all of the insets to from a first installed insert pattern. Another step is removing at least some of the inserts from the carrier. The method also includes the step of installing at least one of the inserts to form a second installed insert pattern. Thus, different oral regions can be affected by different insert patterns. 
         [0027]    In accordance with still yet a further aspect of the invention, a method employs a beneficial agent and an athletic mouthguard. The method includes the step of suffusing the beneficial agent into the mouthguard. Another step is wearing the mouthguard in an athletic event. 
         [0028]    In accordance with still yet a further aspect of the invention, there is provided a kit for preparing a dental device. The kit includes a dental device with at least one channel for embracing an arch of teeth. The dental device has a carrier with at least one recessed inset in the at least one channel. Also included is at least one discrete insert adapted to carry a beneficial agent. The insert is adapted to fit into the inset and release the agent gradually. Also included is at least one beneficial agent for incorporation into the at least one discrete insert. 
         [0029]    In accordance with still yet a further aspect of the invention, there is provided a dental device having a core inside a liquid-permeable shell. The shell has a shape suitable for chewing or teething. The core carries a beneficial agent and is adapted to release the agent gradually. 
         [0030]    Methods and devices in accordance with the foregoing can chemically and physically protect a person&#39;s teeth and gingiva. An oral device (“mouth-guard/carrier”) or method of the foregoing type can directly apply agents to the teeth and, in one embodiment, provide for the mechanical protection of the teeth from trauma as a mouthguard. This mouthguard/carrier preferably contains individual undercut insets adjacent to each tooth or groups of teeth into which will be placed therapeutic agents contained in, for example, a hydrogel vehicle as described hereinafter. The number of insets per tooth may vary, ranging from one to three (or more) to accommodate the lingual/palatal, buccal and occlusal surfaces. The agent included in a preferred embodiment is the naturally occurring sugar, xylitol, although other beneficial agents are contemplated as well; for example, remineralizing agents, moisturizing agents, desensitizing agents, flavoring agents, breath fresheners, chemical and biological indicators, nutraceuticals, antibiotics, probiotics, other medications and chemotherapeutics, etc. 
         [0031]    Two generalized embodiments are described. In one embodiment, the device provides an intra-oral device that serves as an athletic mouthguard, provides a novel means of enhanced shock absorption, and contains insets for agent-containing inserts to be described hereinafter. In some embodiments disposable inserts, containing agents to be described presently, are constructed primarily of hydrogels. The inserts are placed into the device and release the intended agents directly onto the surface of the teeth and/or gingiva. The novel shock absorption characteristics of the device result from the unique mechanical force-distributive and dissipating properties of the (e.g., hydrogel) inserts that are placed in the anterior region (generally from canine to canine) which serves an additional function of providing a novel additive cushioning property against mechanical trauma. 
         [0032]    In another embodiment, the steps include providing an intra-oral carrier made out of standard and typical dental appliance materials intended solely as a vehicle with insets for holding inserts that contain active agents to be described, and for positioning these proximate to the dentoalveolar tissues. The carrier in this other embodiment is not necessarily intended to provide mechanical protection for the teeth as in the other embodiment. 
         [0033]    Thus the present specification discloses an intra oral device that may or may not have mechanically protective features (i.e. function as a mouthguard, depending on embodiment), may be applied to the maxillary or mandibular arch and will serve to deliver intra-orally, chemicals, therapeutics, medications, pharmaceuticals, nutraceuticals, etc. covered by this application; specifically xylitol and other agents disclosed herein as exemplar applications of the agent delivery features of the present invention. 
         [0034]    In one embodiment, the carrier material, made of orally acceptable plastics material, has one or more insets arranged to maximize mechanical protection of the teeth and surface contact to facilitate agent delivery. To maintain the shape and retentive integrity of the insets, preferably, blanks will fill the insets and will require removal in order to insert the hydrogel inserts. These blanks will be particularly useful in a “boil and bite,” self-molding carrier or mouthguard. 
         [0035]    It is an object of one embodiment of the present invention to provide the ability to directly apply, in a timely fashion, agents to prevent and/or reverse the decalcification of teeth, that is potentiated by the use of a mouthguard, some transient physiologic states, as well as some medical conditions and/or procedures or medications of a person. 
         [0036]    It is a further object of the invention to provide an improved material (preferably, hydrogel inserts) that in conjunction with typical EVA mouthguard materials, or the like, provides enhanced impact absorbent properties. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0037]    The above brief description as well as other objects, features and advantages of the present invention will be more fully appreciated by reference to the following detailed description of presently preferred but nonetheless illustrative embodiments in accordance with the present invention when taken in conjunction with the accompanying drawings, wherein: 
           [0038]      FIG. 1  is a plan view of a dental device showing the open channel of a U-shaped carrier; 
           [0039]      FIG. 2  is a plan view showing the reverse side of the dental device of  FIG. 1 ; 
           [0040]      FIG. 3  is a detailed, cross-sectional view of a blank fitted into an undercut inset of the dental device of  FIG. 1 ; 
           [0041]      FIG. 4  is a detailed, cross-sectional view of an insert replacing the blank of  FIG. 3 ; 
           [0042]      FIG. 5  is a detailed, cross-sectional view of an insert that is an alternate to that of  FIG. 4 ; 
           [0043]      FIGS. 6A-6D  are front views of dental arches showing in phantom four different arrangements of inserts for devices of the type shown in  FIG. 1 ; 
           [0044]      FIGS. 7A-7E  are a cross-sectional views of the device of  FIG. 1  showing a sequence of steps performed when using that device; 
           [0045]      FIG. 8  is a perspective view of dental device that is an alternative to that of  FIGS. 1-7  and is useful as a teething device for an infant; and 
           [0046]      FIG. 9  is a cross-sectional view of the device of  FIG. 9 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0047]    Referring to  FIGS. 1 and 2 , a dental device is shown as a U-shaped carrier  10 . Carrier  10  has a channel  12  serving as a recess for receiving an arch of teeth A. In this embodiment the device has only a single channel  12  for receiving the arch of teeth A, but other embodiments may have channels on opposite sides for receiving two arches of teeth. The inside wall  12 A and outside wall  126  of channel  12  are referred to as a lingual/palatal surface and buccal/labial surface, respectively. An occlusal/incisal surface  12 C is located between surfaces  12 A and  12 B. Surfaces  12 A- 12 C are collectively referred to as surfaces  12 . 
         [0048]    A central insert  1   4 A is fitted into an inset in surface  12 B, in front of four incisors I and two canines C of arch A (this combination being referred to as the anterior six teeth). A pair of back inserts  14 B are also fitted into an inset in surface  12 B, each in front of a pair of premolars P. Another pair of back inserts  14 C are fitted into an inset in surface  12 B, each in front of a pair of molars M (or in some cases all molars). Inserts  14 A- 14 C are collectively referred to as inserts  14 . These inserts  14  are placed symmetrically on the buccal surfaces. 
         [0049]    The anterior insert  14 A extends from canine to canine and laps the incisal edge and extends at least to the cervical junction. The two posterior inserts  146  and  14 C are adjacent to the second premolar through the second molar teeth, extending at least to the cervical margins. This insert pattern is intended to act as mouthguard-carrier, but other patterns are contemplated, especially for embodiments that are primarily therapeutic. 
         [0050]    As explained further hereinafter, a greater or lesser number of inserts may be employed, and these inserts can be designed to cover a greater or lesser number of teeth. Also, this dental device may be initially shipped without inserts, in which case plastic blanks will be initially installed in the insets normally containing inserts  14 . 
         [0051]    Preferably, and as described further hereinafter, hydrogel inserts will be emplaced within the buccal/labial wall  12 B of the EVA plastic of carrier  10 . 
         [0052]    The intended material for carrier  10  may, for various embodiments, be any such material as is currently used in therapeutic dental carriers or sports mouthguards. Mouthguards are typically made from plastics materials such as an ethylene vinyl acetate copolymer (EVA). Additives may be added to the EVA itself to provide special properties for the mouthguard material. For example, a copolymer of ethylene and about 20% by weight vinyl acetate may be employed. In some embodiments of this device, flavoring and aromatic agents may be added to the polymer. Colorants, perfumes and softening agents may also be added as well. 
         [0053]    There are generally three categories: (1) Mouthguards that are stock pre-molded products and made in a variety of sizes. (2) Home or self-moldable to suit the physical characteristics of the user. (3) Custom molded by a dentist or other professional to suit the characteristics of the user. 
         [0054]    Typically, custom-made mouthguards are fabricated by a vacuum-forming or pressure-forming process whereby two or three laminar sheets of EVA are heat adapted to a mold. The number of lamina used and the thickness at any point will be determined by the intended use of the mouthguard/carrier, i.e. for therapeutics delivery only; or for delivery of therapeutics while worn as a protective mouthguard in sports related activities. 
         [0055]    The illustrated embodiment is the self-moldable type. Accordingly, the occlusal/incisal surfaces  12 C of the carrier  10  contain a chemically bonded low-temperature plastic layer  10 A that deforms on heating to the temperature of boiling water (approximately 100 degrees Celsius). The user then “bites” into the channel  12  of device  10  and causes the low-temperature plastic component  10 A to mold and conform to the user&#39;s dentoalveolar structures. The portion of the device  10  containing the insets intended to bear the hydrogel inserts  14 A- 14 C is not permanently deformable. (Note relatively stiff blanks may be placed in the insets in the outer wall surface  12 B of the EVA mouthguard/carrier  10  when an impression is made.) 
         [0056]    In some embodiments, the carrier need not have separate inserts fitted into recessed insets, since the carrier itself can deliver a beneficial agent. The polymer may contain agents, such as xylitol. In some embodiments the polymer may contain a remineralizing agent for restoring calcium in teeth. Several flavors and/or aromas may be available to provide a wide selection to the user. The purpose of this beneficial agent and additives is to: (1) Provide an incentive for use of the mouth guard. (2) Alert the user when other beneficial agents are exhausted. 
         [0057]    In some embodiments of the present invention, the carrier is not intended to provide mechanical protection as a mouthguard, but is intended solely as an agent delivery system and may be fabricated from orally acceptable plastics material and having multiple insets. In embodiments intended for primarily therapeutic application of active agents, there will be insets not only on the buccal/labial surface  1213 , but on the lingual/palatal surface  12 A as well (up to 32 for 16 teeth per arch, buccal and lingual surfaces). In any event the insets can receive hydrogel inserts for applying agents to the tissues in this vicinity. 
         [0058]    Referring to  FIG. 3 , during the manufacturing of the carrier  10 , the shape and integrity of insets  15  are maintained by insert-shaped blanks  18  comprising the same material as the carrier  10 . The blanks  18  would remain in place during any “boil and bite” type of customizing molding of stock mouthguard/carriers. The blanks  18  would be removed just prior to placement of the hydrogel inserts (see  FIG. 4 ). 
         [0059]    In the therapeutic carrier only embodiment, the blanks  18  may be left in place for certain sites where no therapy is intended. In this carrier embodiment, individualized insets  15  may be adjacent to each tooth or tooth region on the buccal and lingual surfaces for a maximum of 64 insets. 
         [0060]    Referring to  FIG. 4 , the innermost portion of previously mentioned surface  12 , which is adjacent to the teeth and dentoalveolar tissues, will preferably hold preformed standard shaped inserts  14 , formed of hydrogel vehicles suffused with intended beneficial agents. The walls of the insets  15  will be undercut to provide for a mechanical “snap-in” lock of the hydrogel material. Insert  14  is shown having a beveled edge  20  to accomplish this snap-in feature. 
         [0061]    Referring to  FIG. 5 , carrier  10  is shown fitted with an alternate insert  114 . A matrix  122  embedded within insert  114  is in the form of a plastic mesh that enhances the rigidity and structural integrity of insert  114 . Matrix  122  is shown spaced from the outer surfaces of inserts  114 , but in some embodiments the mesh may be a porous covering encapsulating the hydrogel carrying the beneficial agent. 
         [0062]    Referring to  FIG. 6A , an upper arch A of teeth is shown overlaid in phantom with a carrier  110  similar to previously mentioned carrier  10 . The teeth of arch A are marked as before. Again, center insert  14 A is shown covering four incisors I and the canines C. In this embodiment, back insert  1481  has been lengthened from that of  FIG. 2  to cover two premolars P and three molars M. This pattern and the pattern of  FIG. 2  would be most appropriate for embodiments acting as a mouthguard that mechanically buffers teeth from mechanical shocks, although nothing would prevent these embodiments being used primarily for therapeutic purposes. 
         [0063]    The cervical region of the teeth is that region where the teeth narrow down, or form a neck. This is normally found around cervical line N. In any event, the cervical region, as that term is used herein, is not intended to define a mathematically precise domain, but a region in the neighborhood of cervical line N. Directions extending away from the cervical region N across the crown of the teeth and toward the distal end of the teeth are indicated by direction arrow  16  and are referred to as a occlusal and incisal direction (or extending occlusally and incisally). 
         [0064]    In this embodiment, the purpose of the device is twofold, i.e. to serve as a shock-absorbing mouthguard and therapeutic carrier. There are 3 (in some cases 5) insets in the buccal/labial wall of the mouthguard/carrier  110  into which is placed agent-containing hydrogels  14 A and  14131 . The hydrogels serve a second role of shock absorption and cushioning in order to protect the teeth from damaging physical contact. 
         [0065]    Referring to the embodiment of  FIG. 6B , the purpose of the device is also twofold, i.e. to serve as a mouthguard, but primarily as a therapeutic carrier. There exist approximately 30 insets in the buccal/labial and lingual/palatal walls of the mouthguard/carrier into which are placed agent-containing inserts  14 ′ made of hydrogels. The inserts  14 ′ on opposites ides of the teeth will typically (but not necessarily) be in registry. The hydrogels will serve a second role of shock absorption and cushioning in order to protect the teeth from damaging physical contact, however, the primary role is to deliver agents to the teeth. The inserts  14 ′ are each positioned to span across a pair of adjacent teeth. For strictly therapeutic purposes, not all of the inserts  14 ′ will be installed but will be placed in a pattern appropriate for those teeth needing treatment. 
         [0066]    Referring to the embodiment of  FIG. 6C , the purpose of the device  10 ″ is as a therapeutic carrier to bring active agents to the periodontium, cervical areas and/or interproximal areas of the teeth. There exist one (up to three) insets located at the cervical margins N of the teeth on the buccal and lingual walls of the carrier  10 ″ into which is placed agent-containing, hydrogel inserts  14 ″. 
         [0067]    Referring to the embodiment of  FIG. 6D , the purpose of the device  10 ′″ is as a therapeutic carrier to bring active agents to the periodontium, cervical areas and/or interproximal areas of the teeth. There exist approximately 30 insets in the buccal/labial and lingual/palatal walls of the mouthguard/carrier into which are placed agent-containing hydrogels  14 ′″. 
         [0068]    Referring to  FIG. 7A , a cross-sectional view is given of mouthguard/carrier  10 , through a location intended for a central incisor. The mouthguard  10  is in this embodiment a generic “stock” shape, composed of standard mouthguard material such as an ethylene vinyl acetate copolymer (EVA) substitute or equivalent. 
         [0069]    In addition, there is an EVA blank  18  in the mouthguard/carrier&#39;s inset  15  intended to maintain the integrity of shape of the inset during a “boil and bite” heating process, to resist deformation. The boil and bite feature is provided herein by the moldable layer  10 A′ formed on surface  12 A of carrier  10 . Layer  10 A′ is chemically bonded to the EVA as a separate, low-temperature material attached to surfaces apart from the inset and strategically placed to conform to the dentoalveolar process and teeth of the user when the material is heated and the user “bites” into the mouthguard/carrier. 
         [0070]    As shown in  FIG. 7B , a user now “bites” into device  10  to make an impression on moldable layer  10 A′. Significantly, blank  18  provides a firm surface for teeth such as incisor I, so that a reliable impression can be made. 
         [0071]    Referring to  FIG. 7C , after the molding process, the EVA blank  18  is removed, but moldable layer  10 A′ maintains an impression of the teeth. As shown in  FIG. 7D , blank  18  will be replaced at an appropriate time with the agent-containing hydrogel insert  14 . 
         [0072]    Referring to  FIG. 7E , in use, the hydrogel  14  is in contact with the labial surface of the incisor I, as well as other teeth. The hydrogel  14  releases, over time and in appropriate quantities, the active agent. In addition, the hydrogel&#39;s mechanical properties enhance the shock-absorbing properties of the carrier  10  as a mouthguard. 
         [0073]    For embodiments having as their main purpose preventing and/or reversing cariogenic activity, inserts  14  will apply agents such as xylitol directly to the teeth. This beneficial agent allows the use of device  10  as a mouthguard, which would otherwise act to accelerate decalcification by shielding the teeth from the natural cleansing activity of the lips, cheeks and tongue and buffering action of the saliva. In addition, the vehicle intended to bring the active agents to the teeth (hydrogels  14 ) have unique physical properties that would be adjunctive in the dissipation of potentially harmful kinetic energy directed at the teeth is that the hydrogel acts as a diffusion barrier that allows the agents to be released over a period of hours. Efficacious drug levels are achieved near the device surfaces, but the agents dilute out quickly into body fluids as they move away from the device. Only extremely low systemic levels of the agents result because of the dilution. 
         [0074]    The preferred vehicle for agent delivery is a commercially available hydrogel, such as Hypan® hydrogel from Hymedix International, Inc., Dayton, N.J. This hydrogel is reported to be a hydrophilic acrylate derivative, with each polymer chain having several sequences of units with pendant hydrophilic groups (called soft blocks) and several sequences of pendant nitrile groups (referred to as hard blocks). The lengths of the blocks, and/or the nature of the side groups, as well as the overall hydrophilicity of the polymer, are varied depending upon production conditions. 
         [0075]    Other hydrogels and agent-releasing vehicles from various sources and suppliers are contemplated for other embodiments. The preferred vehicles will be able to contain, and slowly release at a biocompatible rate and concentration, chemicals known to promote dental health and enamel and dentinal recalcification, such as: (1) Complex of calcium casein peptone derived from milk (CPP) and amorphous calcium phosphate (ACP), or CPP-ACP. (2) Xylitol. (3) Fluoride containing compounds, such as: (a) Sodium Fluoride; (b) Stannous Fluoride. 
         [0076]    Other hydrogel materials which are contemplated by the present invention include compounds such as polyhydroxy ethyl methacrylate, chemically or physically crosslinked polyacrylamide, polyvinyl alcohols, poly(N-vinyl pyrolidone), polyethylene oxide, and hydrolyzed polyacrylonitrile. Polysaccharide-based hydrogels, such as covalent or chemically crosslinked polyvalent metal salts of alginates, pectines, carboxymethylcellulose, heparin and hyaluronic acid, as well as hydrogels containing chitin, chitosan, gellan, pullulan, and xanthan are also contemplated by the present invention. 
         [0077]    Other fluoride containing compounds that may be suitable for use with the present invention include inorganic fluoride salts such as soluble alkali metals; alkaline earth metals; and heavy metal salts, for example, potassium fluoride, ammonium fluoride; cuprous fluoride; zinc fluoride; stannic fluoride; barium fluoride; sodium fluorosilicate; ammonium fluorosilicate; sodium fluorozirconate; aluminum mono- and difluorophosphate, fluorinated sodium calcium pyrophosphate and sodium monofluorophosphate. Calcium fluoride; cobalt ammonium fluoride; zinc ammonium fluoride; and stannous ammonium fluoride can also be used. Then known amine fluorides are also suitable organic fluorides which are contemplated by the present invention. 
         [0078]    Also, the remineralizing or recalcifying agents envisioned herein may be various calcium salts such as calcium phosphate. A commercially available remineralizing agent is sold as Recaldent, although other remineralizing agents are contemplated. Other agents such as fluoride containing chemicals (e.g. stannous fluoride, sodium fluoride), xylitol may be used in combination. The chemical will be activated by saliva and released from the hydrogel material at a rate that will be non-toxic. 
         [0079]    Examples of remineralizing agents include calcium compounds such as: amorphous calcium phosphate; amorphous calcium phosphate fluoride; amorphous calcium carbonate phosphate fluoride, amorphous calcium carbonate phosphate; potassium oxalate. Other compounds from which calcium ions may be obtained include calcium chlorides; calcium nitrate; calcium acetate; calcium benzoate; calcium butyrate; calcium gluconate; calcium formate; calcium fumarate; calcium glycerophophoshate; calcium lactate; calcium isobutyrate; calcium malate; calcium maleate; calcium proprionate and calcium valerate, and mixtures thereof. 
         [0080]    Source of inorganic phosphorus for use in a remineralizing composition include mono- and dibasic calcium phosphate; dipotassium phosphate; monosodium phosphate; sodium metaphosphate; and alkali salts and ammonium salts of orthophosphoric acid, such as sodium, potassium or ammonium orthophosphate. 
         [0081]    A water soluble salt, such as monobasic calcium orthophosphate, can also be used, as a source of both calcium and phosphate ions for use as a remineralizing agent. 
         [0082]    The preferred vehicles will also be able to contain and gradually release agents suitable for treating periodontal disease, such as chlorhexidine, or various antibiotics. Chlorhexidine is most commonly used in the digluconate form, although other chlorhexidine containing compounds can be employed. Tetracycline, doxycycline, oxytetracycline, chloramphenicol, penicillin, amoxicillin, erythromycin, streptomycin, sulfonamides, aminoglycosides, cephalosporins, quinolones are among the antibiotics which can be employed in the present invention. Neomycin, kanamycin, amikacin, tobramycin and gentamycin are among the aminoglycoside antibiotics which can be used. Additional compounds can include antiviral agents, such as acyclovir or zidovudine; or antifungal agents, such as imidazoles or polyene antibiotics. Antibacterial agents such as benzethonium chloride, benzalkonium chloride, cetylpyridinium chloride, or dequalinium chloride are also contemplated. The preferred vehicles will also be able to appropriately deliver intraoral deodorants; and agents for improving the aesthetic appearance of teeth (whiteners), e.g., peroxide containing and peroxide generating compounds. It is also desirable to use a device that can flavor the carrier and therapeutic elements so as to provide an incentive to use the mouth guard, and alert the user that the protective elements are exhausted and may need to be replaced or recharged. 
         [0083]    The present invention contemplates inclusion of sweeteners and flavorings known to those skilled in the art. These agents can be selected from among those in the following list, which is intended for examples only, and not intended as any limitation:
       Sugar alcohols such as xylitol, sorbitol, mannitol, and mixtures thereof;   Water-soluble sweeteners, including monosaccharides, disaccharides and polysaccharides, such as xylose, ribose, glucose, mannose, galactose, fructose, sucrose, maltose, glycerine and partially hydrolyzed starch or corn syrup;   Artificial sweeteners such as aspartyl-phenylalanine methyl ester, acesulfame K, saccharin and sodium cyclamates.       
 
         [0087]    As stated above, xylitol is a preferred sweetener because of its known non-cariogenic actions; sorbitol may also be substituted therefor. 
         [0088]    The flavorings contemplated by the present invention include both natural and artificial flavors, and mint flavors such as spearmint and peppermint. Flavors such as wintergreen, anise and cinnamon are also included. Fruit flavors, including citrus flavors like orange, lemon and tangerine and other flavors, either individually or in blends thereof, are also included. These flavorings are generally utilized in concentrations that depend upon the individual flavor, and may range, for example only, in concentrations of approximately 0.05% to approximately 6% by weight of the final composition. 
         [0089]    In addition, colorants may be added to the compositions. Among the colorants are pigments which may comprise up to about 2% by weight of the composition. These colorants can include what are known to those skilled in the art as “FD &amp; C” and “D&amp;C” dyes, meaning dyes suitable for use in food, drug and cosmetic applications. It is preferred that the dyes utilized be water soluble. Some examples include a triphenylmethane dye, FD&amp;C Green #3, or a yellow dye designated D&amp;C Yellow #10. The Kirk-Othmer Encyclopedia of Chemical Technology, 3 rd  edition, volume 6, pages 361-495 contains a comprehensive listing of FD&amp;C colorants which may be useful in conjunction with the present invention, including their chemical structures, and whose contents are hereby incorporated by reference herein. 
         [0090]    In an embodiment of this device intended to serve as a mouthguard also, the hydrogel insert will be an integral component of the mouthguard and provide a mechanical barrier/cushion contributing to the cushioning and energy dissipative properties of the mouth guard. The hydrogel will have sufficient integrity of form to maintain its overall shape and to mechanically lock into the receptacle in the mouthguard. The integrity of form may be an intrinsic property of the hydrogel or may result from an encasement or framework that provides the necessary integrity of shape, yet allows an adequate diffusion of agent from the hydrogel. Indeed, the encasement may be desirable in order to control the rate of diffusion of the active agent. 
         [0091]    In any event, following the instructions for use, the device and the hydrogel vehicle will deliver preferably not more than 15 grams of xylitol per 24 hours. At this rate of drug delivery, xylitol is fairly safe. 
         [0092]    It is appreciated that various modifications may be implemented with respect to the above described, preferred embodiment. For example, the present invention may be distributed in the form of a kit, containing the dental device, one or more inserts, and a quantity of at least one beneficial agent which can then be incorporated into the insert of the dental device. 
         [0093]    Referring to  FIGS. 8 and 9 , the illustrated dental device  20  functions as an infant&#39;s teething device, although chewing by adult users are contemplated for some embodiments. While this device is shown as a ring or toroid, in other embodiments it may be shaped as a disk, a rod, or have various other shapes. In some embodiments the teething device may have a handle. In this embodiment the illustrated teething ring  20  has a toroidal core  22  made of a hydrogel as described above or a similar substance. 
         [0094]    Core  22  may be contained inside a liquid-permeable shell, shown in this embodiment as a plastic skin  24  that is perforated by a multiplicity of orifices  26 . These orifices may be arranged with a density of 10 to 1,000 orifices per square inch (1.6 to 160 orifices per square centimeter), although other embodiments may have a different density depending upon the desired permeability, skin strength, etc. The thickness of the skin  24  will vary with the strength of the skin&#39;s plastic material, balanced against the weakening effect of the orifices  26 . The skin should be thick enough to avoid rupture, but thin enough to allow adequate diffusion of the active agents contained in the hydrogel core  22 . For example, with a skin made of an EVA polymer, a skin thickness of 0.5 mm to 2.0 mm will operate satisfactorily, although in other embodiments the thickness may be outside this range. Furthermore, the distribution of orifices need not be uniform and may be more densely spaced in regions where the infant&#39;s gums or teeth engage the skin  24 . The orifices  26  may be formed with a roller (not shown) having a large number of small piercing pins. The sheet of plastic skin, before installation, may pass over this roller, or the roller may be rolled over the plastic skin. 
         [0095]    The skin  24  may be formed from an upper half  24 A and a lower half  24 B joined along an outer seam  26  and an inner seam  28 . These seams may be welded by heat sealing, by gluing, or by other fastening means. Also, some embodiments may have just an inner seam  28 , in which case the skin  24  will be one continuous piece with only one seam. Alternatively, the skin can be formed from more than two pieces. In some embodiments, the skin may be formed by spiral wrapping the skin around the toroidal shape. In still other embodiments, the skin may be molded in place either as a perforated surface or a continuous surface that is later perforated. 
         [0096]    Core  22  is encased in an optional scrim  30 , which will be a porous matrix such as a knit or woven fabric. Alternatively, scrim  30  may be a fibrous matrix that is readily penetrated by liquid, or a relatively impermeable sheet that is perforated by a number of holes to act as a permeable matrix. 
         [0097]    In use, the infant may chew on the teething ring  20  in the usual fashion. The core  22  will be deformed and the active agent contained therein will tend to diffuse through the orifices  26 . The core  22  can be suffused or impregnated with any one of the beneficial agents mentioned above, or any combination thereof. Also, in the instance of an infant&#39;s teething device, the beneficial agents may include substances appropriate for soothing the infant&#39;s gums. Such agents may be numbing agents or analgesics typically used to soothe the gums. 
         [0098]    Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.