DENTURE ADHESIVE LINER

Abstract: A denture adhesive liner contains a foamed, flexible, polymeric, self supporting layer that supports a denture adhesive and, optionally, a material for adhering the liner to a denture. The foamed self supporting layer helps provide better cushioning and a more effective gasket for the denture adhesive liner.

Description: Denture Adhesive Liner BACKGROUND OF THE INVENTION 1. Field of the Invention The invention is directed to denture adhesive liners and methods of making and using such liners. 2. Description of Related Art Dentures and dental plates function as a substitute for all or part of missing teeth ordinarily found in the mouth. While dentures are usually carefully fitted for the user, the fit can change over time, causing discomfort and slippage. To alleviate the discomfort and to control the slippage, a denture adhesive may be applied to the denture. Denture adhesives typically contain a material that forms a gasket between the denture and the gum line. Generally, the gasket-forming material is a water swellable gum or polymer. The gum or polymer hydrates and becomes tacky when introduced to the saliva in the oral cavity, thus holding the dentures in place. The constant flow of saliva in the oral cavity, however, can cause premature washing away of the gum or polymer, so oils and petrolatum are used in a denture adhesive to suspend the gum or polymer and so delay the washing away and increase the effective life of the gum or polymer. Denture adhesives are usually applied as a cream or paste to the dentures before wearing. These highly viscous materials may be unpleasant to work with and may not provide an even hold at all points in the denture. Pressure gradients may cause the denture adhesive to migrate away from areas where the gum or other oral tissue is uncomfortably close to the denture material, thus reducing any cushioning effect of the adhesive at precisely the point where it is most needed. An alternative to traditional denture adhesives is a denture liner, which is a fixed, usually self supporting, layer coated with at least one layer of an adhesive material. The self supporting layers used as denture liners in the prior art do not generally assist in the adhesive function. Rather, they hold the adhesive in place to limit or prevent migration of the adhesive, allowing an effective gasket to remain at the site selected by the user. Self supporting layers used in the prior art include plastic films, non-woven fabrics, woven fabrics, and paper. Each of these materials can provide mechanical strength to support denture adhesive liner products and may prevent or reduce migration of the denture adhesive away from problem areas. But, these self-supporting layer materials do little to enhance the strength of the gasket formed by the self supporting layer and the associated adhesive. In addition, they tend not to have the necessary flexibility and conformability required for fully comfortable denture adhesive products. The more inflexible the liner, of course, the greater the chance that the adhesives on the liner will fail to bond well to the irregular surfaces of the dentures and oral tissues. The gasket formed by the adhesive is correspondingly weaker and may fail entirely. An early denture adhesive liner patent, U.S. Patent No. 1,917,902 describes a gum tragacanth adhesive on a cotton gauze self supporting layer. U.S. Patent No. 4,503,116 discloses a two- layer self supporting layer with the layers being bound together by a thermoplastic mixture of a polyethylene oxide and sodium alginate. U.S. Patent No. 4,880,702 discloses a three-layer strip, with the outer layers containing an adhesive made from either a mix of polyethylene oxide and carboxymethyl cellulose or polyvinyl alcohol, and the inner self-supporting layer comprising microcrystalline wax, polyethylene oxide and carboxymethyl cellulose. U.S. Patent No. 5,158,825 is directed to a non-woven fabric impregnated with a mixture of polyvinyl acetate and sodium alginate or carboxymethyl cellulose. U.S. Patent No. 5,6568,586 and European Patent Application No. 788,341 are directed to compositions containing to 70% of one or more therapeutic agents which are suitable for mucosal or topical administration, but specifically excluding polyvinyl acetate as a suitable adhesive component. PCT application WO 97US11720 is directed to the use of a zinc Gantrez salt with a denture liner, with the self-supporting layer material being polyester or polypropylene or nylon, nonwoven fabrics or fleece, paper, plastic, leather, microcrystalline wax, synthetic fibers, natural fibers and mixtures thereof. There is still a strong need for a liner that is i) strong enough to withstand use in the oral environment, forming a good gasket between the denture and the oral mucosa and adhering well to both the denture and the oral mucosa, ii) nontoxic and organoleptically acceptable, and iii) conformable enough to provide a well-adhered gasket in use. SUMMARY OF THE INVENTION The invention provides a denture adhesive liner comprising a liner and at least one adhesive material. The liner is a foamed material and the adhesive is any of a number of acceptable adhesive materials. The invention further provides a method for making the denture adhesive liner by coating or otherwise incorporating at least one adhesive onto a foamed liner matrix. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic cross section of one embodiment of the denture liner of the invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS A cross section of the liner of the invention is shown in Figure 1. For ease of reference, the denture adhesive 1 is shown as laying on top of the foamed self supporting layer 2. A coating of material that adheres to denture material may be placed on one side 3 of the denture liner. The coating 3 is an optional, albeit preferred, feature of the invention. The coating 3 may be the same or different from the denture adhesive 1 and may be placed on the self supporting layer 2 in a separate manufacturing step from the denture adhesive 1. In an embodiment of the invention, a pressure sensitive adhesive is coated both on the bottom of the self supporting layer 2 and either on top of the denture adhesive 1 or blended with the denture adhesive to form the top layer of the liner. The self-supporting layer. The self-supporting layer 2 is characterized by its ability to maintain strength and provide integrity for the adhesive composition in the presence of water and/or saliva. This layer comprises a foamed material, preferably a polymeric foam. Foams, particularly polymeric foams, can be relatively rigid, inflexible materials, such as certain insulating or packing foams, or can be resilient, flexible materials such as foam rubber. The foam should be resilient and soft during use and may contain open cells, closed cells, but preferably a combination of open and closed cells. The foamed material may be cut or molded into various desired shapes, either before or after combining the foamed material with the adhesive. The foam may have any density, cell structure, cell size, cell geometry, and fraction of open cells desired to carry out the purposes of the invention. The foam should have enough thermal and environmental stability to remain intact in the mouth during ordinary use. The foam should be sufficiently cohesive so as not to crumble or separate during use and preferably acts to cushion any contact between the denture and the oral tissues. The foamed self-supporting layer 2 generally does not have adhesive properties of its own, especially pressure sensitive adhesive properties, because such adhesion would tend to collapse the foam. Of course, since a permanent attachment to the mouth or denture is not contemplated with a denture liner, any adhesive properties should not cause permanent bonding to oral tissues or to the denture material. The non-adhesive self supporting layer may include such materials as flexible foams made from any of the commonly used materials such as linear or network polymers, polyester, polypropylene foam rubber, polyvinyl halides, polyurethanes, polyisocyanurates, polyphenols, polystyrene, cellulose acetate, other cellulose esters and ethers, other low modulus thermoplastics, and mixtures thereof. Since the invention is intended for oral use, nontoxic materials are preferable and either pleasant tasting or tasteless materials are most preferred. Preferably, the self supporting layer 2 is manufactured with a "skin" on at least one side that inhibits penetration of the foam by either the denture adhesive material or by the pressure sensitive adhesive. Excessive penetration into the foam could collapse the foam, reducing the effectiveness of the invention. Adhesive Materials. In addition to the self supporting layer, the invention comprises at least one adhesive material at least on one surface of the self-supporting layer 2. In a preferred embodiment of the invention, the self-supporting layer has a skin on its surface so that the adhesive material may be placed on the surface of one side of the layer 2 without significant migration into the interior of the foamed material. Of course, the adhesive material may be coated on to both sides of the self-supporting layer 2, preferably on top of a denture adhesive material as set forth herein. The denture adhesive may comprise any known denture adhesive material compatible with the self supporting layer. Examples include, but are not limited to, polyvinyl alcohols, polyethylene oxides, karaya gum, methyl vinyl ether/maleic anhydride copolymers and hydrated derivatives thereof and partial salts thereof, either alone or in combination with an additive such as carboxymethyl cellulose or sodium alginate. The selection of an appropriate adhesive to combine with a particular self supporting layer is a matter of routine experimentation. As seen below in the examples, however, even closely related materials can have vastly different results in a denture liner. Coating Materials. One side of the liner may also comprise a pressure sensitive adhesive coating that adheres well to denture material, such as polybutenes, pressure sensitive silicone adhesives, polyacrylate ester pressure sensitive adhesives, tackified rubbers, natural polymers, and synthetic polymers. The optional coating material 3 for adhering the liner to the denture material may be coated on to the liner at any point in the process. Additional Components. In addition to the denture adhesive, the self-supporting layer and the pressure-sensitive adhesive, the liner may comprise any additional ingredients appropriate for administration to the oral cavity, including teeth. Antibacterial agents, such as Triclosan, may be incorporated into any layer of the liner, as may ingredients such as anti-inflammatories, desensitizing agents, anesthetics, antifungals, C. alb i cans treatments, fluorides, and combinations thereof. Fluorides are especially helpful when the liner is used with a partial denture or dental prosthesis. The invention may also comprise additional components found in denture adhesives, such as natural gums, synthetic polymeric gums, adhesive materials commonly employed in denture stable compositions, additional synthetic polymers, mucoadhesive polymers, hydrophilic polymers, flavors, sweeteners, colorants, preservatives, thickeners, and polyethylene glycol and vehicles such as liquid petrolatum, petrolatum, mineral oil, propylene glycol, and glycerin. The liner of the invention may also contain other items not found in traditional denture adhesives such as plasticizers, bioadhesives, and even therapeutic actives designed for mucosal or topical administration. Preparation. The denture liner may be made by preparing a denture adhesive formulation using techniques well known in the art and uniformly coating the adhesive material on the self-supporting layer 2 to form the denture liner. The liner may then be cut to the final desired shape. The denture adhesive (and the coating 3, if present) may be coated on the self supporting layer by any conventional coating techniques, such as by spraying (if the material is liquid or slurry or dissolved or suspended in a liquid such as water) or by sifting (if the denture adhesive is in powder form). If carrying out the coating process at elevated temperatures or pressures, penetration of the denture adhesive into, or through, the foamed self supporting layer is to be avoided. In use, the liner may be placed on problem areas of the dentures before insertion into the mouth. Preferably, the liner either has a pressure sensitive adhesive layer 3 on the bottom that adheres to the denture material or has sufficient amounts of denture adhesive on the bottom to adhere to the denture. The presence of the denture adhesive on the bottom will help maintain the position of the liner on the denture if the liner is moistened before placement. The self- supporting layer 2, preferably a thermoplastic flexible foam, imparts enough mechanical strength to the liner to enable the liner to be easily removed intact from both the denture and the oral tissues when the denture wearer wishes to remove the liner. The pressure sensitive adhesive side of the liner may be applied directly to a dry denture, leaving the denture adhesive side of the liner to adhere to the oral tissues. The highly compressible and conformable plastic foam self-supporting material 2 overcomes the deficiencies of prior art denture adhesive liners in that the adhesive-faced plastic foam, owing to its easy compressibility, provides an excellent gasket. In addition the ready deformability, the adhesive-faced plastic foam enables the adhesive facings to come into such intimate contact with the irregular surfaces of the dentures and the oral tissues that good bonding to both surfaces is achieved. Example 1 The polyethylene oxide film of Comparative Example 1 was laminated to one side of a 0.75 mm thick LDPE pressure sensitive adhesive double-faced foam tape. The PSA face was adhered to one side of a small denture and the denture was inserted into the mouth of a volunteer. The denture remained comfortably in the mouth of the volunteer for the three hour duration of the test and was then removed. Example 2 A thin film of polyvinyl alcohol (PVA) was laminated to one side of a 0.75 mm thick LDPE PSA double-faced flexible foam tape. The PSA face of the resulting denture adhesive liner was applied to a denture, which was then inserted into the mouth of a volunteer. The PVA film side of the liner bonded to the oral tissues, specifically the upper palate. When the denture was removed, the denture adhesive liner was easily removed intact from the denture without leaving any residue. The PVA film, however, did not bond as well to the palate as did the polyethylene oxide film used in Example 1. Example 3 A powder adhesive comprising 49.6% by weight of zinc, magnesium, and sodium partial salt of poly(methyl vinyl ether-co-maleic acid), 49.6% by weight of carboxymethyl cellulose, 0.4% by weight spray dried peppermint, and 0.4% by weight spray dried spearmint was applied to one PSA side of a double faced LDPE foam tape. The powdered adhesive was pushed into the PSA layer until the PSA layer would accept no more. The excess powder was shaken off, and the resulting liner PSA side was applied to the denture. The coated strip held the denture in the mouth of a volunteer for the 3-4 hours of the test and was then removed. The purpose of the above description is to illustrate some embodiments of the present invention without implying a limitation. It will be apparent to those skilled in the art that various modifications and variations may be made in the apparatus or procedure of the invention without departing from the scope or spirit of the invention.

Claims: CLAIMS: 1. A denture adhesive liner comprising: (a) a self-supporting layer (2) of a foamed material; and (b) a denture adhesive material (1) coated on at least a portion of at least one side of said self supporting layer. 2. The denture adhesive liner of claim 1, further comprising a coating material (3) for adhering said self-supporting, foamed liner material (1) to a denture, supported by said self- supporting, foamed liner material (1). 3. The denture adhesive liner of claim 1, wherein said self-supporting foamed liner material (1) comprises a flexible, partially closed cell, polymeric foam. 4. The denture adhesive liner of claim 1, wherein said denture adhesive material (2) comprises a polymeric material selected from the group consisting of a methyl vinyl ether/maleic anhydride copolymer, a methyl vinyl ether/maleic acid copolymer, partial salts thereof and mixtures thereof. 5. The denture adhesive liner of claim 2, wherein said coating material (3) comprises a pressure sensitive adhesive. 6. The denture adhesive liner of claim 2, further comprising at least one agent selected from the group consisting of anti-inflammatories, antibacterial agents, desensitizing agents, anesthetics, antifungals, C. albicans treatments, fluorides, and combinations thereof. 7. Use of a denture adhesive liner according to any of Claims 1- 9 in the stabilization of a denture and adhering it to a oral mucosa surface thereof. 8. A method for making a denture liner comprising the steps of: (a) providing a self-supporting, foamed, flexible material (1); and (b) adhering a denture adhesive (2) to at least a portion of at least one surface of said self- supporting foamed flexible material. 9. The method of claim 7, further comprising the step of coating at least one additional adhesive material (3) onto a second surface of said self-supporting foamed flexible material (1). AMENDED CLAIMS [received by the International Bureau on 31 March 2000 (31.03.00); original claims 1-9 replaced by amended claims 1-9 (2 pages)] 1. A denture adhesive liner comprising: (a) a denture adhesive material (1 ) coated on at least a portion of at least one side of (b) a self-supporting layer (2) of a foamed material able to maintain strength and provide integrity for the adhesive material (1) in the presence of water and/or saliva. 2. The denture adhesive liner of claim 1, further comprising a coating material (3) for adhering said self-supporting, foamed liner material (1) to a denture, supported by said self- supporting, foamed liner material (1). 3. The denture adhesive liner of claim 1, wherein said self-supporting foamed liner material (1) comprises a flexible, partially closed cell, polymeric foam. 4. The denture adhesive liner of claim 1 , wherein said denture adhesive material (2) comprises a polymeric material selected from the group consisting of a methyl vinyl ether/maleic anhydride copolymer, a methyl vinyl ether/maleic acid copolymer, partial salts thereof and mixtures thereof. 5. The denture adhesive liner of claim 2, wherein said coating material (3) comprises a pressure sensitive adhesive. 6. The denture adhesive liner of claim 2, further comprising at least one agent selected from the group consisting of anti-inflammatories, antibacterial agents, desensitizing agents, anesthetics, antifungals, C. albicans treatments, fluorides, and combinations thereof. 7. Use of a denture adhesive liner according to any of Claims 1 -6 in the stabilization of a denture and adhering it to a oral mucosa surface thereof. 8. A method for making a denture liner comprising the steps of: (a) adhering a denture adhesive (1) to at least a portion of at least one surface of (b) a self-supporting, foamed, flexible material (2); and, where desired. (c) cutting the product to a desired shape. 9. The method of claim 8, further comprising the step of coating at least one additional adhesive material (3) onto a second surface of said self-supporting foamed flexible material (1).

Inventors: GASMAN ROBERT CHARLES, GASMAN, ROBERT, CHARLES
Applicants: BLOCK DRUG CO, WHALLEY KEVIN, BLOCK DRUG COMPANY, INC., WHALLEY, KEVIN
Application year: 1999
Main classification: A61K6
IPC codes: A61C13, A61K6