Oral care composition

Abstract

A dentifrice composition comprising a rice hull isolated silica thickener and a mineral silica abrasive, in which the weight ratio of rice hull isolated silica to mineral silica abrasive is from 1:1 to 1:12.

Description

ORAL CARE COMPOSITIONField of the InventionThe present invention is concerned with oral care compositions having an improved flavour profile.Background of the InventionWO08 / 082757(Huber) W02007 / 078630(Huber) and WO 2007 / 078651 (Huber) disclose toothpaste compositions comprising rice silica as an abrasive.Toothpaste compositions comprising silica are well known, however there remains the need for toothpaste compositions with compositions with enhanced flavour properties.Description of the InventionAccordingly, the present invention relates to a dentifrice composition comprising rice hull isolated silica thickener and mineral silica abrasive in which the weight ratio of rice hull isolated silica to mineral silica abrasive is from 1:1 to 1:12.The invention also relates the use of rice hull isolated silica to improve the intensity of flavour and / or freshness of a dentifrice composition.A further aspect of the invention is a composition comprising rice hull isolated silica for use in a method of improving the intensity of flavour and / or freshness of a dentifrice as described in any previous claim.Detailed Description of the InventionExcept in the examples, or where otherwise explicitly indicated, all numbers in this description indicating amounts of material or conditions of reaction, physical properties of materials and / or use may optionally be understood as modified by the word “about”.All amounts are by weight of the composition, unless otherwise specified.It should be noted that in specifying any ranges of values, any upper value can be associated with any particular lower value.Where a feature is disclosed with respect to a particular aspect of the invention (for example a composition of the invention), such disclosure is also to be considered to apply to any other aspect of the invention (for example a method of the invention) mutatis mutandis.Any ingredients mentioned in this application that are natural or naturally isolated have been sourced from Europe.Unless stated specifically otherwise "Particle size" for the purpose of the present invention means D50 particle size. The D50 particle size of a particulate material is the particle size diameter at which 50 wt% of the particles are larger in diameter and 50 wt% are smaller in diameter. For the purpose of the present invention, particle sizes and distribution are measured using a laser diffraction particle size analyser such as those made by Malvern.The composition of the invention is in the form of a dentifrice, preferably a toothpaste. Such a composition is not intentionally swallowed for purposes of systemic administration of therapeutic agents, but is applied to the oral cavity, used to treat the oral cavity and then expectorated. Typically such a composition is used in conjunction with a cleaning implement such as a toothbrush, usually by applying it to the bristles of the toothbrush and then brushing the accessible surfaces of the oral cavity.The composition is a product which, during the normal course of usage, is not for the purpose of systemic administration or intentionally swallowed but is rather retained in the oral cavity for a time sufficient to contact substantially all of the dental surfaces and / or oral tissues for the purposes of oral activity.Preferably the toothpaste is in the form of an extrudable semi-solid such as a cream, paste or gel (or mixture thereof).A preferred aspect of the invention is a composition comprising rice hull silica for use in a method of improving the flavour of a mineral silica abrasive dentifrice compared with a composition which is nearly identical but omits the rice hull silica.The silica material isolated from rice hulls, may be obtained as described in U.S. 6,406,678. While the amount of silica contained in rice hulls may vary somewhat due to geographical region where it is grown, and the strain of rice, silica content of rice hulls is generally in the13-15 percent range of dry weight. The silica contained in most biogenic material, such as rice hulls, is substantially all of highly desirable amorphous form, but is bound in a biogenic matrix of many other impurities, particularly long chain hydrocarbons such as lignin and cellulose, but including many inorganic minerals such as calcium, magnesium, etc. and compounds thereof. The rice hull silicas involve the necessary separation of the silica from the other impurities found in the biogenic material, primarily the hydrocarbons thereof. Following removal of the hydrocarbons, removal of small quantities of inorganic minerals that remain may be easily substantially removed. The end product is a finely divided white powder of highly pure amorphous silica.The inventive rice hull isolated silicas are ready-to-use additives.The rice hull silica used in the present invention has the additional advantage that it is present at levels that thicken the product. Preferably the level of rice hull isolated silica is from 0.1 to 12 wt% of the total composition, more preferably from 1 to 10.0 wt%.In terms of the present application the thickening rice silica has an abrasivity (RDA) of less than 30., preferably it has a bulk density of less than 100 g / L and a linseed oil absorption of greater than 200 ml / 100g.Preferably the rice hull isolated silica has a particle size (D50) from 5 to 12 microns.The composition of the invention comprises a mineral silica based abrasive referred to herewith as silica abrasive. The preferred abrasive silicas used in the present invention is a silica with a low refractive index. It may be used as the sole abrasive silica, or in conjunction with a low level of other abrasive silicas, e.g. those according to EP 236070. The low refractive index silicas, used as abrasives in the present invention are preferably silicas with an apparent refractive index (R.l.) in the range of 1.41 - 1.47, preferably 1.435 - 1.445, preferably having a weight mean particle size of between 5 and 15 pm, a BET (nitrogen) surface area of between 10 and 100 m2 / g and an oil absorption of about 70 - 150 cm3 / 100 g, but abrasive silicas with a lower apparent refractive index may also be used. Typical examples of suitable low refractive index abrasive silicas (e.g. having an R.l. of between 1.435 and 1.445) are Tixosil 63 and 73 ex Rhone Poulenc; Sident 10 ex Degussa; Zeodent 113 ex Zeofinn; Zeodent 124 ex Evonik, Sorbosil AC 77 ex PQ Corporation (having an R.l. of approximately 1.440). The amount of these silicas in the composition generally ranges from 5 to 60 wt% b, usually from 6 to 40 wt% most preferably 7 to 30 wt%.It is preferable if the silica isolated from rice hull is 95wt% pure, preferably 98 wt%.Thickening silica from mineral sources, (that is not isolated from rice) is preferably present at levels of less 0.5wt% of the total composition, preferably less than0.1wt%.Compositions according to the invention have a weight ratio of rice hull isolated silica to mineral silica ratio of from 1 :1 to 1:12, preferably from 1 :1 to 1:10.A composition according to the invention will generally contain further ingredients to enhance performance and / or consumer acceptability, in addition to the ingredients specified above.In some embodiments, abrasives, for example calcium carbonate, calcium phosphate abrasive, e.g., tricalcium phosphate, hydroxyapatite or dicalcium phosphate dihydrate or calcium pyrophosphate, and / or silica abrasives, sodium metaphosphate, potassium metaphosphate, aluminum silicate, calcined alumina, or other siliceous materials, or combinations thereof are used. However in preferred embodiments it is absent.The dentifrice composition according to the invention may comprise sodium bicarbonate at a level from 0.1 wt% to 5 wt%, preferably 0.1 wt% to 1 wt% of the total composition.Compositions according to the invention may comprise a poyol such as propyleneglycol, xylitol, and lactitol. Glycerol is a preferred polyol, sorbitol is particularly preferred.Composition of the invention may comprise 0.5 to 5 wt% of the total composition of an antimicrobial quaternary ammonium material. Preferred antimicrobial quaternary ammonium material are cetylpyridinium chloride (CPC), CPC-claybenzalkonium chloride, tetradecylpyridinium chloride (TPC), N-tetradecyl-4-ethylpyridinium chloride (TDEPC). Particularly preferred is a cetylpyridium chloride clay complex.The composition may comprise a natural or synthetic thickener or gelling agent in proportions of about 0.10 to about 5% by weight depending on the material chosen. These proportions of thickeners in the dentifrice compositions of the present invention form an extrudable, shaperetaining product which can be squeezed from a tube onto a toothbrush and will not fall between the bristles of the brush but rather, will substantially maintain its shape thereon. Irish moss, iota-carrageenan, gum tragacanth, and polyvinylpyrrolidone. Sodium carboxymethylcellulose, hydroxyethyl cellulose (Natrosol®), xanthan gum, gum arabic etc. as well as syntheticpolymers such as polyacrylates and carboxyvinyl polymers such as Carbopol®; Xanthan gum and Carrageenan are preferred. A dentifrice composition according to any preceding claim which further comprises a polymeric thickener selected from carboxy methyl cellulose, xanthan, carrageenan or mixtures thereof, particularly preferred is carboxy methyl cellulose.Preferably the weight ratio of polymeric thickener to rice husk silica is from 1 : 1 to 1 : 15.Compositions according to the invention may comprise a polymeric deposition aid. Preferably the composition comprises acid anhydride polymers, particularly preferred are co-polymers of maleic anhydride with methyl vinylether, in which the anhydride moiety may be in a partially or fully hydrolysed or alcoholysed form. Preferred copolymers include Gantrez(R) polymers such as:Gantrez S-95: molecular weight 216,000; free acid;Gantrez S-96: molecular weight 700,000; free acid;Gantrez S-97: molecular weight 1,500,000; free acid; andGantrez MS-955: molecular weight 1 ,060,000; calcium / sodium salt.Particularly preferred co-polymers of maleic acid and methyl vinylether have a molecular weight of 1 ,000,000 or greater and an especially preferred material is Gantrez S-97.Compositions according to the invention may comprise a tooth whitening agent. The whitening agent preferably comprises a green and / or a blue pigment. In the context of the present invention a pigment is generally understood to be a shade / material which is insoluble in the relevant medium, at the relevant temperature. This is in contrast to dyes which are soluble. In the context of this invention, the "relevant medium" is human saliva, the liquid medium in which the composition is used, at the temperature of the oral cavity during brushing of the teeth, i.e. up to 37 Degrees C. As a reasonable approximation, the relevant medium may be considered to be water and the relevant temperature to be 25 Degrees C.Preferably the blue pigment is Pigment Blue 15, more preferably Pigment Blue 15:1 , 15:2, 15:3, 15:4, 15:5 or 15:6, most preferably 15:1. A preferred pigment is blue pigment is Phthalocyanine Blue Pigment, Cl No. 74160, blue covarine.The preferred Green pigment is Phthalocyanine Green, preferably Phthalocyanine Green CI- 74260.Preferably the total level of pigment in the composition is from 0.01 wt% to 3 wt, more preferably from 0.02 to 2 wt%.If the composition is a toothpaste it may be a dual phase paste, with the whitening pigments present in one phase.Compositions according to the invention may comprise water-soluble or sparingly water-soluble sources of metal salts. Preferred are zinc ions such as zinc chloride, zinc acetate, zinc gluconate, zinc sulphate, zinc fluoride, zinc citrate, zinc lactate, zinc oxide, zinc monoglycerolate, zinc tartrate, zinc pyrophosphate and zinc maleate; also preferred are stannous ions such as stannous fluoride and stannous chloride.Compositions according to the invention may comprise oral care enzyme systems such as hydrogen peroxide producing enzyme systems (e.g. the oxidoreductase enzyme glucose oxidase), amyloglucosidase, dextranase and / or mutanase, (optionally in the presence of zinc ion providing compounds and / or 8- hydroxyquinoline derivatives), lactoperoxidase, lactoferrin, lysozyme and mixtures thereof.Compositions of the invention may comprise fluoride sources such as sodium fluoride, stannous fluoride, sodium monofluorophosphate, zinc ammonium fluoride, tin ammonium fluoride, calcium fluoride, cobalt ammonium fluoride and mixtures thereof. Fluoride ion sources may be added to the compositions at a level of about 0.001 wt. percent to about 10 wt. percent, e.g., from about 0.003 wt. percent to about 5 wt. percent, 0.01 wt. percent to about 1 wt., or about 0.05 wt. percent. In some embodiment, the stannous fluoride is present in an amount of 0.1 wt. percent to 2 wt. percent (0.1 wt percent -0.6 wt. percent) of the total composition weight. Fluoride ion sources may be added to the compositions at a level of about 0.001 wt. percent to about 10 wt. percent, e.g., from about 0.003 wt. percent to about 5 wt. percent, 0.01 wt. percent to about 1 wt., or about 0.05 wt. percent. However, it is to be understood that the weights of fluoride salts to provide the appropriate level of fluoride ion will obviously vary based on the weight of the counter ion in the salt, and one of skill in the art may readily determine such amounts. In some embodiment, the fluoride source is a fluoride salt present in an amount of 0.1 wt. percent to 2 wt. percent (0.1 wt percent -0.6 wt. percent) of the total composition weight (e.g., sodium fluoride (e.g., about 0.32 wt. percent).Some embodiments of the invention are free from fluoride sources, that is the composition comprises less than 0.01 wt% of a fluoride source.In one embodiment a preferred class of oral care active for inclusion in the compositions of the invention includes agents for the remineralisation of teeth. The term “remineralisation” in the context of the present invention means the in situ generation of hydroxyapatite on teeth.A specific example of a suitable agent for the remineralisation of teeth is a mixture of a calcium source and a phosphate source which, when delivered to the teeth results in the in situ generation of hydroxyapatite on teeth.Illustrative examples of the types of calcium source that may be used in this context (hereinafter termed “remineralising calcium sources”) include, for example, calcium phosphate, calcium gluconate, calcium oxide, calcium lactate, calcium glycerophosphate, calcium carbonate, calcium hydroxide, calcium sulphate, calcium carboxymethyl cellulose, calcium alginate, calcium salts of citric acid, calcium silicate and mixtures thereof. Preferably the remineralising calcium source is calcium silicate.The amount of remineralising calcium source(s) (e.g. calcium silicate) in the composition of the invention typically ranges from 1 to 30%, preferably from 5 to 20% by total weight remineralising calcium source based on the total weight of the oral care composition.Illustrative examples of the types of phosphate source that may be used in this context (hereinafter termed “remineralising phosphate sources”) include, for example, monosodium dihydrogen phosphate, disodium hydrogen phosphate, sodium pyrophosphate, tetrasodium pyrophosphate, sodium tripolyphosphate, sodium hexametaphosphate, potassium dihydrogenphosphate, trisodium phosphate, tripotassium phosphate and mixtures thereof. Preferably the remineralising phosphate source is a mixture of trisodium phosphate and sodium dihydrogen phosphate.The amount of remineralising phosphate source(s) (e.g. trisodium phosphate and sodium dihydrogen phosphate) in the composition of this invention typically ranges from 2 to 15%, preferably from 4 to 10% by total weight remineralising phosphate source based on the total weight of the oral care composition.In some embodiments, the oral care compositions comprise an effective amount of one or more antibacterial agents, for example comprising an antibacterial agent selected from halogenated diphenyl ether (e.g. triclosan), triclosan monophosphate, herbal extracts and essential oils (e.g., rosemary extract, tea extract, magnolia extract, thymol, menthol, eucalyptol, geraniol, carvacrol,citral, hinokitol, magnolol, ursolic acid, ursic acid, catechol, methyl salicylate, epigallocatechin gallate, epigallocatechin, gallic acid, miswak extract, sea-buckthorn extract), bisguanide antiseptics (e.g., chlorhexidine, alexidine or octenidine), quaternary ammonium compounds (e.g., cetylpyridinium chloride (CPC), CPC-claybenzalkonium chloride, tetradecylpyridinium chloride (TPC), N-tetradecyl-4-ethylpyridinium chloride (TDEPC)), phenolic antiseptics, hexetidine furanones, bacteriocins, ethyllauroyl arginate, arginine bicarbonate, a Camellia extract, a flavonoid, a flavan, halogenated diphenyl ether, creatine, sanguinarine, povidone iodine, delmopinol, salifluor, metal ions (e.g., zinc salts, stannous salts, copper salts, iron salts), propolis and oxygenating agents (e.g., hydrogen peroxide, buffered sodium peroxyborate or peroxycarbonate), phthalic acid and its salts, monoperthalic acid and its salts and esters, ascorbyl stearate, oleoyl sarcosine, alkyl sulfate, dioctyl sulfosuccinate, salicylanilide, domiphen bromide, delmopinol, octapinol and other piperidino derivatives, nisin preparations, chlorite salts; parabens such as methylparaben or propylparaben and mixtures of any of the foregoing. One or more additional antibacterial or preservative agents may optionally be present in the composition in a total amount of from about 0.01 wt. percent to about 0.5 wt. percent, optionally about 0.05 wt. percent to about 0.1 wt. percent or about 0.3 percent, by total weight of the composition.In some embodiments, the oral care compositions also comprise at least one flavorant, useful for example to enhance taste of the composition. Any orally acceptable natural or synthetic flavorant can be used, including without limitation essential oils and various flavoring aldehydes, esters, alcohols, and similar materials, tea flavors, vanillin, sage, marjoram, parsley oil, spearmint oil, cinnamon oil, oil of Wintergreen, peppermint oil, clove oil, bay oil, anise oil, eucalyptus oil, citrus oils, fruit oils, sassafras and essences including those isolated from lemon, orange, lime, grapefruit, apricot, banana, grape, apple, strawberry, cherry, pineapple, etc., bean-and nut-derived flavors such as coffee, cocoa, cola, peanut, almond, etc., adsorbed and encapsulated flavorants and the like. Also encompassed within flavorants herein are ingredients that provide fragrance and / or other sensory effect in the mouth, including cooling or warming effects. Such ingredients illustratively include menthol, carvone, menthyl acetate, menthyl lactate, camphor, eucalyptus oil, eucalyptol, anethole, eugenol, cassia, oxanone, a-irisone, , thymol, linalool, benzaldehyde, cinnamaldehyde, N-ethyl-p-menthan-3-carboxamine, N, 2, 3- trimethyl-2- isopropylbutanamide, 3- (1-menthoxy) -propane-1, 2-diol, cinnamaldehyde glycerol acetal (CGA), menthone glycerol acetal (MGA) and the like. One or more flavorants are optionally present in a total amount of from about 0.01 wt. percent to about 5 wt. percent, for example, from about 0.03 wt. percent to about 2.5 wt. percent, optionally about 0.05 wt. percent to about 1.5 wt. percent, further optionally about 0.1 wt. percent to about 0.3 wt. percent and insome embodiments in various embodiments from about 0.01 wt. percent to about 1 wt. percent, from about 0.05 to about 2 percent, from about 0.1 percent to about 2.5 percent, and from about 0.1 to about 0.5 percent by total weight of the composition.In some embodiments, the oral care compositions comprise at least one sweetener, useful for example to enhance taste of the composition. Sweetening agents among those useful herein include dextrose, polydextrose, sucrose, maltose, dextrin, dried invert sugar, mannose, xylose, ribose, fructose, levulose, galactose, corn syrup, partially hydrolyzed starch, hydrogenated starch hydrolysate, ethanol, sorbitol, mannitol, xylitol, maltitol, isomalt, aspartame, neotame, saccharin and salts thereof (e.g. sodium saccharin), sucralose, dipeptide-based intense sweeteners, cyclamates, dihydrochalcones.One or more sweeteners are optionally present in a total amount depending strongly on the particular sweetener (s) selected, but typically 0.005 wt. percent to 5 wt. percent, by total weight of the composition, optionally 0.005 wt. percent to 0.2 wt. percent, further optionally 0.05 wt. percent to 0.1 wt. percent by total weight of the composition.

[0041] In some embodiments, the oral care compositions further comprise an agent that interferes with or prevents bacterial attachment, e.g., ethyl lauroyl arginiate (ELA), solbrol or chitosan, as well as plaque dispersing agents such as enzymes (papain, glucoamylase, etc.).Mixtures of any of the above described materials may also be used.The composition according the invention will comprise further ingredients which are common in the art, such as: antimicrobial agents, e.g. chlorhexidine, sanguinarine extract, metronidazole, quaternary ammonium compounds, such as cetylpyridinium chloride; cetylpyridium chloride clay complex bis- guanides, such as chlorhexidine digluconate, hexetidine, octenidine, alexidine; and halogenated bisphenolic compounds, such as 2,2' methylenebis-(4-chloro-6-bromophenol); anti-inflammatory agents such as ibuprofen, flurbiprofen, aspirin, indomethacin etc.; anti-caries agents such as sodium- and stannous fluoride, aminefluorides, sodium monofluorophosphate, sodium trimeta phosphate and casein; plaque buffers such as urea, calcium lactate, calcium glycerophosphate and strontium polyacrylates; vitamins such as Vitamins A, C, D, B (preferably B3) and E;plant extracts; plant-derivable antioxidants such as flavonoid, catechin, polyphenol, and tannin compounds and mixtures thereof; desensitising agents, e.g. potassium citrate, potassium chloride, potassium tartrate, potassium bicarbonate, potassium oxalate, potassium nitrate and strontium salts; anti-calculus agents, e.g. alkali-metal pyrophosphates, hypophosphite-containing polymers, organic phosphonates and phosphocitrates etc.; biomolecules, e.g. bacteriocins, antibodies, enzymes, etc.; flavours, e.g. peppermint and spearmint oils; proteinaceous materials such as collagen; preservatives; opacifying agents; hyaluronic acid; amino acids such as arginine; colouring agents; pH-adjusting agents; sweetening agents; mouth feel agents pharmaceutically acceptable carriers, e.g. starch, sucrose, water or water / alcohol systems etc.; surfactants, such as anionic, nonionic, cationic and zwitterionic or amphoteric surfactants; polymeric compounds which can enhance the delivery of active ingredients such as antimicrobial agents can also be included; buffers and salts to buffer the pH and ionic strength of the oral care composition; and other optional ingredients that may be included are e.g. bleaching agents such as peroxy compounds e.g. potassium peroxydiphosphate, effervescing systems such as sodium bicarbonate / citric acid systems, colour change systems, and so on.In the following non-limiting Examples, Examples according to the invention are illustrated by a number while comparative Examples are illustrated by a letter.ExamplesToothpaste compositions were prepared as described in Table 1.Table 1

Claims

CLAIMS1. A dentifrice composition comprising a rice hull isolated silica thickener and a mineral silica abrasive, in which the weight ratio of rice hull isolated silica to mineral silica abrasive is from 1:1 to 1 :12.

2. A dentifrice composition according to claim 1 in which the weight ratio of the weight ratio of rice hull isolated silica to silica abrasive is from 1 :1 to 1:10.

3. A dentifrice composition according to any preceding claim in which the level of rice hull isolated silica is from 1.0 to 15.0 wt% of the total composition.

4. A dentifrice composition according to any preceding claim in which the mineral silica abrasive has a weight mean particle size of between 5 and 15 pm.

5. A dentifrice composition according to any preceding claim in which the level of mineral silica abrasive is from 5.0 to 30wt% of the total composition.

6. A dentifrice composition according to any preceding claim in which the rice hull isolated silica has a particle size (D50) from 5 to 12 microns.

7. A dentifrice composition according to any preceding claim which further comprises a polymeric thickener selected from carboxy methyl cellulose., xanthan, carrageenan or mixtures thereof.

8. A dentifrice composition according to claim 7 in which the polymeric thickener is carboxy methyl cellulose.

9. A dentifrice composition according to any preceding claim in which the weight ratio of polymeric thickener to rice husk silica is from 1 :1 to 1:15.

10. A dentifrice composition according to any preceding claim in which further comprises a zinc salt.

11. A dentifrice composition according to claim 8 or 9 in which the weight ratio of polymeric thickener to rice husk silica is from 1 :1 to 1:8.

12. Use of rice hull isolated silica to improve the intensity of flavour of a dentifrice composition as described in any preceding claim.

13. Use of rice hull isolated silica to improve the freshness of a dentifrice composition as described in any one of claims 1 to 11.

14. A composition comprising rice hull isolated silica for use in a method of improving the freshness of a dentifrice as described in one of claims 1 to 11.

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