MXPA97007819A - System in dispersible particles to insensibilize dien - Google Patents

Abstract

The present invention relates to a method for the treatment of hypersensitive teeth, by treating teeth with an oral composition comprising hectorite clay, especially Laponi clay.

Description

SYSTEM IN DISPERSIBLE PARTICLES TO INSENSIBILATE TEETH 1. Pirmp ß The invention The invention refers to? new desensitizers for hypersensitive teeth, and methods for manufacturing and using these desensitizers. 2. Description of the Related Art The de'ntinal hypersensitivity causes pain in the mouth of a patient when sf exposes a nerve of an affected tooth to certain external stimuli, including temperature and tactile stimuli l A possible source of dental hypersensitivity is that it overexposes the dentin of the affected teeth to stimuli due to an injury, illness, or for some other reason. Dentin generally contains channels, called tubules, that allow the transport of material and energy between the outside of the dentine and the inside of the tooth where the nerve resides. Exposure of these tubules to external stimuli can cause irritation of the nerve in a tooth, leading to discomfort. Although the exact mechanism of hypersensitivity remains under investigation, recent research has shown that pain triggered by air currents is related with the number of tubules exposed per unit area of dentin (Kontturi-Narhi, Dentin Hypersensitivity - Factors Related to the Occurrence of Pain Symptoms, Kuopio University Publications B. Dental Sciences 5). In accordance with the hydrodynamic theory of dentine sensitivity, the mechanical and thermal stimuli of the dentin surface free from the exposed layer induce minute movements of the intratubular fluid. These fluid movements induce pain that encodes nerve responses in the intradental nerves located near the dentine / pulp boundary. Recent research has reinforced the experimental evidence in support of this relationship (B. Matthews and N. Vongsavan Archs Oral Biol, 39 (Suppl.): 875-955, 1994). Dental hypersensitivity is generally treated either by treating the nerve in the tooth to make it less sensitive to stimuli, or by blocking or obstructing the tubules to prevent or limit the nerve's exposure to external stimuli, and to limit fluid movements triggered by the stimulus in the dentinal tubules. Treatments that directly affect the nerve, usually interfere with the balance of electrolytes near the nerve, to affect the outer membranes of the nerve, so that the nerve does not "turn on" as often or as strongly as a nerve. nerve not treated. Agents useful in the treatment of dental hypersensitivity in this manner include potassium nitrate, as set forth in U.S. Patent No. 3,863,006 to Hodosh issued on January 28, 1975, potassium chloride, as stipulated in US Pat. U.S. Patent No. 4,751,072, to Kim, issued June 14, 1988, potassium bicarbonate, as set forth in the United States Patent Number 4,631,185 to Kim issued December 23, 1986, and strontium chloride, as set forth in United States Patent No. 3,122,483 to Rosenthal, issued February 25, 1964. Tubule occlusion provides an alternative treatment method. Useful reported agents include polymeric agents such as Carbopol, as set forth in U.S. Patent No. 5,270,031, to Lim et al., Issued December 14, 1993, and certain polystyrene granules, as set forth in U.S. Patent No. 5,211,939 to Turesky et al., Issued May 18, 1993. Apatite may also be an agent against hypersensitivity. U.S. Patent Number 4,634,589 to Scheller, issued on 6 January 1987, and the Patent of the United States of America Number 4, 710,372, issued Io. December 1987, also by Scheller, disclose dentifrices for hypersensitive teeth, which contain apatite having an average particle size of less than 10 microns, and optionally a local anesthetic. Other soluble mineral salts are not permitted to exert an interference effect in these patents. Apatite reduces the diameter of the dentin channels. It has also been reported that montmorillonite clay as an insensitizing agent in United States Patent Number 4,992,258 to Mason, issued on February 12, 1991. Unfortunately, montmorillonite clay is not compatible with most of the agents of known fluoride, and therefore, has limited use. In addition, montmorillonite clay loses its ability to thicken a dentifrice, and has a reduced ability to block tubules in the presence of inorganic salts, such as potassium salts, so its use as a desensitizer is limited. Other types of clays have been used in dental applications, although not in an insensitizing capacity. With the advent of transparent gel toothpastes, hectorite clays have been used, especially Laponite clays, as thickeners for dentifrices, for example as reported in United States Patent Number 4,069,310 by Harrison, and in Mayes, B., "Synthetic Hectorite - A New Toothpaste Binder", International Journal of Cosmetic Science, 1, 329-340 (1979). Although in thickeners thickeners and binders are usually found at about 1 weight percent, the Harrison patent indicates that the thickener may be present in amounts up to 5 weight percent. Actually, the Mason patent discussed above, indicates that the laponite may be one of a number of thickeners used in the toothpaste, despite its teaching of montmorillonite clay as an insensitizer. The Patent of the United States of North America No. 4,474,750 to Gaffar et al., Issued October 2, 1984, discloses toothpaste, cream, or gel, wherein the thickening agent may be CP or SP laponite, in an amount up to about 10 percent by weight. weight. There is no description in the patent that Laponite is incorporated into an oral composition for the purpose of treating hypersensitive teeth. U.S. Patent No. 4,081,526 to Asakawa et al., Issued March 28, 1978, discloses dentifrice compositions that they comprise from 0.5 to 13 percent of a hectorite clay, such as Laponite, to remove the plaque from the teeth. In spite of the continuous work in the field of desensitizers, there remains in the art a strong felt need for a long time, of an effective tubular blocking agent which is compatible with fluorides and other conventional dentifrice ingredients. This agent should work well although it should not be of an unpleasant taste to be used. It must be stable for the shelf life typical of a toothpaste, and must be affordable.

SUMMARY OF THE INVENTION The main object of the present invention, therefore, is to provide an effective tubular blocking agent, which is compatible with fluorides and other conventional tooth ingredients, and which is also organoleptically acceptable. The additional objects and advantages of the invention will be stipulated in part in the following description, and in parts will be obvious from this description, or can be learned by practicing the invention. The objects and advantages of the invention can be realized and obtained by means of the instrumentalities and combinations particularly indicated in the attached claims. In order to achieve the above objects and in accordance with the purpose of the invention, as incorporated herein and amply described, the invention provides an insensitizing agent for hypersensitive teeth, which comprises a hectorite clay, such as Laponite clay. To further achieve the above objects, and in accordance with the purpose of the invention, the invention further provides a method for the treatment of hypersensitive teeth, by contacting the teeth with an insensitizing formulation comprising a therapeutic amount of a hectorite clay. , such as Laponite clay.

DESCRIPTION OF THE PREFERRED MODALITIES Reference will now be made in detail to the presently preferred embodiments of the invention. The invention comprises a composition for the treatment of hypersensitive teeth, such as a dentifrice (either a paste or a gel) or another appropriate oral vehicle. The composition comprises a hectorite clay in an amount and in a formulation sufficient to desensitize the teeth. Preferred hectorite clays include Laponite clays and are preferred especially treated hectorite clays, termed "synthetic" such as LAPONITE DR and LAPONITE DFR, both sold by Southern Clay Products Inc. These clays have been treated to make them suitable for dental purposes (as thickeners for clear gel dentifrices), and the LAPONITA DFR has been treated by adding fluorine to the clay to prevent the absorption of fluoride from dentifrice formulations. The additional preferred Laponite clays sold under the trade name LAP0NITAR are products of Laporte Industries Inc. Laponites are synthetic hectorite clays composed of magnesium, lithium, silica, oxygen, hydrogen, and sodium. Like other clays, the Laponites are composed in the dry state of platelets configured in piles. Each plate has a double layer of tetrahedral silica bonded with oxygen atoms. Between the two layers of silica, there is a sheet of cations composed of magnesium and lithium in a ratio of 5.3 to 0.7. These cations coordinate the internal row of oxygens bonded with silica and OH groups. The partial replacement of Magnesium (+2) with Lithium (+1) imparts a global negative charge to the silica surface. The presence of incompletely complexed cations, which are part of the central layer (Mg, Li), imparts a positive charge on the edges of the plate. Between the individual stacked platelets there are interchangeable cations such as sodium. When a Laponite clay is properly dispersed in water, these interchangeable cations direct the water into the spaces between the platelets by means of the osmotic forces. This inward flow in water volume forces the platelets to separate. When the Laponite clay is properly dispersed in water in the presence of low levels of electrolytes, the anionic silica faces and the cationic edges can be electrostatically attracted to each other. This leads to the formation of what is known as a house of cards structure. Tear tensions can easily alter this house of cards structure. This formation and alteration of the structure by means of tear stress, means that the Laponite clay dispersions have remarkable thixotropic properties that make them attractive as thickeners, especially for transparent gel dentifrices. However, it is important and unexpected, that the concentrations and chemical environmental conditions that favor the formation of structured gel with dispersions of Laponite clay, do not necessarily favor the effectiveness of desensitization. The Compositions in which Laponite clays are dispersed to prevent or hinder the formation of the gel structure, demonstrate superior performance in the ability to desensitize, as measured by tubule blocking experiments. These compositions typically use higher amounts of clay than those found with compositions that exhibit ideal gel structures. In addition, inorganic dispersants and organic polymeric dispersants improve the desensitization performance of Laponite clay. Laponite clay-containing compositions with these added dispersants have superior efficacy, exhibit pleasing organoleptic characteristics, and are compatible with fluoride and most other tooth ingredients. Lappishite clays treated with fluoride are preferred for their ability to coexist with fluoride in a dentifrice. Dentifrices and mixtures containing fluoride sources and hectorite clays or laponite clays treated with fluoride were examined for the bioavailability of fluoride, and toothpastes containing untreated hectorite clays reduced the availability of sodium fluoride, whereas Clay dentifrices of Fluoride-treated Laponite retained the bioavailability of total fluoride.

Preferably, the dentifrice formulation is in the form of a paste or a gel, comprising about 0.1 weight percent to about 25 weight percent clay. More preferably, the clay comprises from about 1 percent clay to about 20 weight percent of the clay, and more preferably from about 2 percent to about 15 percent. Clay can also be incorporated into other formulations for oral care, such as mouth rinses, as well as tooth formulations. The effectiveness for reducing the flow of the clay can be improved in a surprising manner by the addition of dispersants such as salts, thickeners, or other additives. Preferred salts include: potassium salts, strontium salts (especially preferred salts include insensitizing salts, such as potassium nitrate, potassium chloride, potassium bicarbonate, and strontium chloride), and pyrophosphate salts, especially tetrapyrophosphate salts of potassium and sodium, and potassium and sodium acid pyrophosphate salts. Preferred thickeners include polymeric thickeners, and cellulosic thickeners are especially preferred, including ionically modified cellulosic polymers, such as sodium carboxymethylcellulose, a product of Aqualon, and a cationically modified cellulosic polymer known as CELQUATR, a product of the National Starch and Chemical Company. When tested by itself, the CELQUATR polymer induced inconsistent reductions in dentin fluid induced by the polymer, measured using the technique stipulated in the examples. In contrast, when tested as part of a prototype dentifrice containing a hectorite clay, consistently high flow reductions were observed. Although the inventors do not wish to be bound by any theory, it appears that the hectorite clays, especially the Laponite clays, comprise a plurality of individual mineral platelets having positively charged shores and negatively charged flat faces. It appears that the modified cationically charged cellulose and other positively charged entities can interact with the anionic face of the clay, resulting in better dispersion of the clay, which leads to an appropriate particle size to penetrate the dentine tubules, and a modification of the electrochemical characteristics of the particle that results in a better electrostatic adhesion of the clay to the wall of the tubule. The aspects of clay chemistry are discussed in more detail in the article Mayes mentioned above, and in U.S. Patent Number 4,621,070 to Pinnavaia et al., Issued November 4, 1986. Oral rinses utilizing the clay may be in the form of oral solutions or dispersions. Oral rinses may contain flavors, colorants, and other conventional additives that have an organoleptic or therapeutic efficacy. Toothpastes made using hectorite clay will normally be water based, and will contain a humectant, such as glycerin, sorbitol or other sugar alcohol, propylene glycol, or polyethylene glycol. The toothpaste can be a paste or a gel. The gelling agent may be a carboxymethylcellulose, hydroxyethylcellulose, or alkali metal hydroxymethylcellulose, xanthan gum, viscarine, iota-carrageenan, gelatin, starch, glucose, sucrose, polyvinylpyrrolidone, polyvinyl alcohol, tragacanth gum, karaya gum, hydroxypropylcellulose, methylcellulose , and sodium alginate, and magnesium aluminum silicate gel. Preferred are agents that are compatible with fluoride. Additional agents useful in a dentifrice are polishing agents, such as precipitated silica, hydrated silica, and other known abrasive polishing agents, fluoride, detergents, coloring or bleaching agents. such as titanium dioxide, fragrances and flavorings. Additional therapeutic agents can also be added, such as tartar control agents, antibacterial agents such as Triclosan or chlorhexadine. A dentifrice according to the invention can be made by mixing the ingredients in any conventional manner, for example, by creating a gel with the water and the gelling agent, and then adding the water-soluble ingredients. Finally, a surfactant is added, and then the hydrophobic ingredients are added. The mixture is then packaged in a conventional dentifrice container, such as a tube, and applied to the surface of the teeth through conventional brushing, coating, painting, or other direct or indirect application technique. The benefits of the invention will be demonstrated in the following examples.

E.TEMPfrQS Test Procedures Dispersions of hectorite clays in water were tested with different ingredients and prototype dentifrices containing hectorite clays, using an in vitro model of sensitivity of the dentin first described by Pashley (J. Periodontology, Vol. 55, No. 9, page 522, September 1984). Patent of the United States of America Number 5, 270,031 of Lim et al., Issued on December 14, 1993, also describes this methodology. In this method, intact human molars free of caries or restorations, perpendicular to the long axis of the tooth, are sectioned with a metallurgical saw, in thin sections of approximately 0.4 to 0.6 millimeters thick. The sections containing dentin and are free of enamel, are retained for testing. Then these sections are recorded with a solution of EDTA (ethylenediaminetetraacetic acid), to remove the covered layer. The disc is mounted on a divided chamber device as reported in J. Dent. Research, 57: 187 (1978). This special leak test chamber is connected to a pressurized fluid reservoir containing a tissue culture fluid. By using a mixture of pressurized N2 and CO2 gas, the fluid can be maintained at a physiological pH. To further ensure accuracy, the discs are moistened with human saliva to approximately the intraoral condition. The apparatus includes a glass capillary tube mounted on a ruler or other measuring instrument. An air bubble is injected into the glass capillary tube. By measuring the Displacement of this bubble as a function of time, fluid flow through the dentine disc can be measured. (It has been reported that the fluid 'actually flows out of the dentine tubules from inside a normal human tooth). Following the measurement of the baseline fluid flow in the dentin disc, the experimental mixture or dentifrice is applied to the outer surface of the disc with a nylon brush. After a defined brushing period, the experimental material is rinsed, and the hydraulic conductance is measured after application. In this way, the ability of different experimental materials, both alone and in components of dentifrice systems, can be tested for their ability to obstruct the flow of fluid in the dentinal tubules. Then the percentage of flow reduction induced by brushing can be calculated with the experimental materials.

Examples 1-5 Combinations of clays were prepared Laponite with water and other specified ingredients, and were tested by reducing the flow using the method stipulated above. Each combination had the composition stipulated in Table 1, and had the flow reduction shown in Table 1. The examples show the good ability to reduce dentin fluid flow of hectorite clays, especially when the clay is associated with a dispersant, such as a polymeric dispersant or salts.

Table 1 Percentage of flow reduction with laponifrag combination of water Examples 6-13 The following dentifrice formulations were prepared in the following manner. In a suitable mixer, equipped with a vacuum system, such as a whip mixer for the laboratory scale, or a Koruma mixer for larger batches (pilot plant), the required amount of purified water is added. Key ingredients are added, such as sodium fluoride (or sodium MFP), potassium tetrapyrrophosphate, sodium triphosphate, potassium or strontium salts, as appropriate, to the mixer, followed by sodium saccharin, silicon dioxide , and LAPONITA DF. The above volume is mixed for approximately 10 to 30 minutes (under vacuum), followed by the addition of abrasives, gum premix (humectants and gums), flavoring, and detergents. A final mixture of 20 to 30 minutes is conducted under vacuum to deaerate the product.

Example 6 Ingredient Percentage in Weight Laponita DF 5.0 Sodium fluoride 0.24 Sorbitol solution 20.0 Glycerin 20.0 Silicon dioxide 1.0 Amorphous silica 10.0 Carboxymethylcellulose 1.5 Carbomer 0.1 Sodium saccharin 0.3 Titanium dioxide 0.5 Cocoamidopropylbetaine 5.0 Sodium triphosphate, anhydrous 1.0 Flavoring 1.5 C.S purified water up to 100.0 Example 7 Ingredient Percentage in Weight Laponita DF 8.0 Sodium Fluoride 0.32 Potassium Chloride 4.0 Hydrated silica 10.0 Hydroxyethylcellulose 1.5 Sodium saccharin 0.3 Sodium Lauryl Sulfate 1.5 Triclosan 0.3 Sorbitol solution 40.0 Flavoring 1.3 Purified water C.S up to 100.0 Example 8 Ingredient Percentage in Weight Laponita DF 6.0 Sodium MFP 0.8 Silicon dioxide 2.0 Calcium diphosphate dihydrate 30.0 Carboxymethylcellulose 1.0 Sodium saccharin 0.25 Titanium dioxide 0.5 Cocoamidopropylbetaine 7.0 Sodium cocometyl acid taurate 0.75 Sodium triphosphate, anhydrous 1.0 Sorbitol solution 10.0 Glycerin 25.0 Flavoring 1.2 C.S purified water up to 100.0 Example 9 Ingredient Percentage j in Weight Laponite DF 7. .5 Sodium MFP 0. .8 Silicon dioxide 1. .0 Calcium carbonate 15. .0 Carboxymethylcellulose 1. .0 Carbomer 0, .1 Sodium saccharine 0.3 Titanium dioxide 0.5 Sodium lauryl sulfate 1.5 Sodium diprophophosphate 0.3 Sorbitol solution 30.0 Glycerin 10.0 Flavor 1.3 Purified water C.S. up to 100.0 Example 10 Ingredient Percentage in Weight Laponita DF 5.0 Potassium Chloride 3.75 Sodium fluoride 0.24 Silicon dioxide 1.5 Amorphous silica 10.0 Carboxymethylcellulose 2.0 Carbomer 0.1 Sodium saccharine 0.35 Titanium oxide 0.5 Cocoamidopropylbetaine 6.0 Sodium cocometyl acid taurate 0.5 Potassium Tetrapyrophosphate 3.0 Triclosano 0.3 Flavor 1.3 Sorbitol solution 40 .0 Purified water C.S. up to 100.0 Example 11 Ingredient Percentage in Weight Laponita DF 5.0 Sodium fluoride 0.243 Potassium Tetrapyrophosphate 3.0 Potassium citrate 5.0 Hydrated silica 12.0 Hydroxyethylcellulose 1.4 Sodium saccharin 0.3 Sodium cocometyl acid taurate 1.5 Sodium triphosphate, anhydrous 0.5 Sorbitol solution 12.0 Glycerin 12.0 Flavoring 1.2 Purified water C.S.up to 100.0 Example 12 Ingredient Weight Percentage Laponite DF 5.0 Sodium Fluoride 0.243 Potassium Tetrapyrophosphate 3.0 Potassium Bicarbonate 3.0 Hydrated silica 12.0 Hydroxyethylcellulose 1.4 Sodium saccharin 0.3 Sodium cocometyl acid taurate 1.5 Sodium triphosphate, anhydrous 0.5 Sorbitol solution 12.0 Glycerin 12.0 Flavoring 1.2 Purified water C.S. up to 100.0 Example 13 Ingredient Weight Percentage Laponita DF 6.0 Sodium chloride hexahydrate 10.0 Silicon dioxide 1.0 Hydrated silica 12.0 Sodium saccharin 0.3 Titanium dioxide 1.0 Carboxymethylcellulose 1.5 Sodium cocometic acid taurate 1.2 Sorbitol solution 12.0 Glycerin 12.0 Flavoring 1.2 Purified water C.S. up to 100.0 Several of the dentifrice formulations described above were tested for their ability to reduce dentin fluid flow. The results of this test are stipulated in Table 2.

Table 2 Percentage of Flow Reduction for Selected Dentifrices The purpose of the foregoing 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 method of the invention, without departing from the scope or spirit of the invention.

Claims (16)

NOVELTY OF THE INVENTION Having described the above invention, it is considered as a novelty, and therefore, the content of the following is claimed as property: CLAIMS

1. In a composition for the treatment of hypersensitive teeth, comprising an effective desensitizing amount of an insensitizing agent and a carrier therefor, the improvement comprising the desensitizing agent which is hectorite clay.

2. The composition according to claim 1, characterized in that the clay is Laponite clay.

3. The composition according to claim 2, characterized in that the clay contains fluoride.

4. The composition according to claim 1, which further comprises a dispersant.

5. The composition according to claim 4, characterized in that the dispersant is a salt.

6. The composition according to claim 5, characterized in that the salt is an alkaline salt.

The composition according to claim 4, characterized in that the salt is selected from the group consisting of alkaline salts of pyrophosphates, nitrates, halides, citrates, carbonates, bicarbonates, and strontium salts and mixtures thereof. same.

8. The composition according to claim 4, characterized in that the dispersant is a cellulosic compound.

9. The composition according to claim 8, characterized in that the cellulosic compound is cationically modified.

10. The composition according to claim 9, characterized in that the cellulosic compound comprises a cationically modified cellulose.

11. The composition as claimed in claim 10, which further comprises a salt.

12. The composition according to claim 11, characterized in that the salt is an alkaline salt.

13. The composition according to claim 12, characterized in that the salt is selected from the group consisting of alkaline salts of pyrophosphates, nitrates, halides, citrates, carbonates, bicarbonates, and strontium salts and mixtures thereof.

14. A method for the treatment of a hypersensitive tooth, which comprises administering to this tooth a therapeutically effective amount of the composition according to claim 1.

15. A method for the treatment of a hypersensitive tooth, which comprises administering to the tooth a therapeutically effective amount of the composition as claimed in claim 4.

16. In the method for blocking, occluding, or sealing dentinal tubules in hypersensitive teeth, the improvement essentially consists of the step of blocking the hypersensitive tooth tubules with fluoride oral ointments or fluoride toothpaste or gels containing Laponite or fluoride-treated hectorite clay as the essential blocking agent of dentinal tubules of hypersensitive teeth.