GB2412315A

GB2412315A - Peroxide tooth whitening composition

Info

Publication number: GB2412315A
Application number: GB0406392A
Authority: GB
Inventors: Jennifer Jane Gordon
Original assignee: Glaxo Group Ltd
Current assignee: Glaxo Group Ltd
Priority date: 2004-03-22
Filing date: 2004-03-22
Publication date: 2005-09-28
Also published as: GB0406392D0

Abstract

An oral care composition comprising a peroxide containing compound dispersed in an orally acceptable carrier, wherein the carrier comprises a humectant and a combination of bioadhesive agents consisting essentially of at least one natural gum and a silicate. Preferred peroxide sources include hydrogen peroxide, carbamide peroxide, calcium peroxide and percarbonates. Preferred humectants include glycerine, sorbitol, propylene glycol, glucose, sucrose and low molecular weight polyethylene glycols. Preferred gums include xanthan gum, carrageenan, alginates, gum karaya, guar gum, gum Arabic and pectins. Preferred silicates include synthetic layered silicates, sodium magnesium silicate, hydrated aluminium silicates and magnesium aluminium silicate. Compositions comprising carabamide peroxide, glycerine, xanthan gum and a layered silica are exemplified. Such compositions show excellent substantivity to the teeth as a result of a synergistic interation between the gelling agents.

Description

ORAL COMPOSITION

The present invention relates to an oral care composition containing a peroxide containing compound. Specifically the present invention relates to a stable tooth whitening composition comprising synergistic gelling agents. Said composition shows excellent substantivity to the teeth.

White teeth have long been considered cosmetically desirable. Unfortunately, teeth almost invariably become discoloured in the absence of intervention. The tooth structure which is generally responsible for presenting a stained appearance is the enamel layer. Several factors contribute to enamel discoloration, but the three main factors are believed to be: (i) formation of plaque and tartar matrices on the tooth surface which then entraps stains; (ii) ingestion of certain drugs during gestational tooth formation; and (iii) discoloration due to oral cavity traumatization following which blood break-down products seep into the mineralized area of the teeth during enamel formation.

Over-the-counter teeth whitening preparations have been developed to address the cosmetic preference of many to restore luster to tooth enamel discolored by surface entrapped materials. There are various approaches to enamel whitening currently in general use. One approach is a physical abrading of the stain to effect stain removal, however this can be seen as potentially harmful to the teeth. This mechanical process may therefore be supplemented or even replaced by a chemical process which may involve an oxidative or enzymatic step to effect stain removal.

The chemical process generally utilizes a tooth whitening or bleaching formulation applied to a stained tooth surface for a specified period, after which the formulation is removed. Oxidizing agents represent one of the most widely distributed and utilized active agents in commercially available tooth whitening or bleaching products. Peroxide-containing agents such as carbamide peroxide, hydrogen peroxide and calcium peroxide are the most commonly used oxidizing agents, and are typically formulated into a liquid, solution, gel or paste. However it is known that products containing such agents may lose their whitening efficacy with time and retaining these types of formulations in the oral cavity, particularly in contact with the teeth has proved a problem. Moreover low viscosities of aqueous peroxide solutions do not allow the peroxide whitening agent to remain in contact with the teeth for the necessary time period to effect substantive whitening because of constant flushing effects of salivary secretions. The prior art indicates that viscous formulations show good substantivity when used in the oral cavity. EP-B-1 161 198 (Procter & Gamble Company) disloses a tacky or sticky aqueous tooth whitening substance suitable for application to the oral cavity via a thin film strip. However there remains a need for alternatives that do not suffer the drawbacks encountered with known formulations. It has therefore become desirable to provide simple formulations that do not require extensive stabilization, that are easy to manufacture and have excellent substantivity when applied directly to the oral cavity.

It has since been shown that viscosity is not directly related to substantivity and it is possible for a highly viscous formulation to show poor substantivity. The present invention therefore shows that substantivity effects can be increased synergistically by combining certain gelling agents.

It is an object of the present invention to provide a composition that meets these requirements. According to the invention there is provided an oral care composition comprising a peroxide containing compound dispersed in an orally acceptable carrier, wherein the carrier comprises a humectant and a bioadhesive agent consisting essentially of at least one natural gum and a silicate.

Peroxide containing compounds used as whitening agents in the present invention include the following compounds and mixtures thereof: hydrogen peroxide e.g. as a or 35%w/w aqueous solution, carbamide peroxide, calcium peroxide and percarbonates.

Suitably the total amount of peroxide present in the liquid whitening composition of the invention is in the range of 1 to 40% w/w, preferably in the range 10 to 30%w/w, more preferably in the range 5 to 20%w/w.

A humectant is a key component of a composition of the invention. Suitable humectants include the following and mixtures thereof: glycerin, sorbitol, propylene glycol, sugars, such as glucose or sucrose, and low molecular weight polyethylene glycols (PEGs) i.e. in the range 200-600 e. g. PEG 200, 300, 400, and 600, available from Dow Chemicals USA, PO Box 1206, Midland MI48642. Glycerin is available from Albion Chemical Distributers, 215, Tunnel Ave., Greenwich, London SE10 OQW. Preferred humectants include glycerin and PEG's.

Suitably the humectant is present in an amount ranging from 30 to 95 %w/w, preferably in the range 50 to 75%w/w, more preferably from 40% to 60%w/w.

A combination of bioadhesive agents are included in a composition of the invention.

In the present invention the bioadhesive agents will exhibit excellent adhesive properties i.e. have a strong affinity for biological surfaces such as teeth.

The combination of bioadhesive agents will include a natural gum and a silicate material. Natural gums useful in the present invention include Xanthan Gum, Gum Karaya, Carragenan, Alginates, Guar Gum, Gum Arabic, Gum Ghatti, Locust Bean Gum, Tara Gum, Fenugreek Gum, Gum Tragacanth, Tamarind Gum, Gellan Gum, Succinoglucan Gum, Welan Gum, Rhamsan Gum, Aloe Polysaccharides, Chia Gum, Flaxseed Gum, Okra Gum, Psyllium Seed Gum, Quince Seed Gum, Curdlan, Pullulan, Pectins and mixtures thereof. Xanthan gum is also known by the tradname Keltrol and is available from Nutrasweet Kelco Co Ltd.,Penrhyn Road, Knowsley Industrial Estate, Prescot, Merseyside. L34 9HY, England. The preferred natural gum for use in the invention is either xanthan or karaya gum. The most preferred is xanthan.

The term silicate refers to both synthetic and natural silicates. Examples of synthetic silicates include Laponite, a layered silicate available from Rockwood Specialities Inc., Princeton, NJ, USA and Hectorite, sodium magnesium silicate, available from Sud-Chemie Inc., PO Box 32370, Louisville, KY, USA. Other suitable silicates include Bentonite, a natural hydrated aluminium silicate and magnesium aluminium silicate.

Most preferably the bioadhesive agents are a mixture of a natural gum ea. Xanthan gum and a synthetic silicate e.g.Laponite.

Suitably the total amount of bioadhesive agents present are in an amount ranging from 0.1 to 20% w/w, preferably from 0.5 to 15%w/w, more preferably 1 to 10%w/w.

The composition may also comprise water, preferably deionised water. Water is an optional ingredient but if present it may be from 15 to 60%w/w, preferably 20 to 40% by weight of the composition (including the contribution from the aqueous peroxide ingredients, if used in this form).

Alcohol may also be present in the compositions disclosed herein. Alcohol may be used as an additional carrier, will increase the stability of the composition and will allow easy application of the composition to the teeth. Once the composition is applied to the teeth the alcohol will rapidly evaporate leaving the active ingredients firmly adhered to the teeth. Suitably 96% (pharmaceutical grade) ethanol is used.

Suitably alcohol may be used in the range 1 to 70%w/w, prefereably 5 to 40%w/w and more preferably 7.5 to 20%w/w.

Additionally, compositions of the present invention will suitably contain acceptable additives or excipients conventional in the field of oral care products including for example chelating agents such as ethylenediaminetetraacetic acid and/or citric acid, antisensitivity agents such as potassium and strontium salts, colouring agents, a fluoride source such as sodium fluoride or sodium monoflurophosphate, flavouring agents and sweetening agents. The additives or excipients used in any given composition will be compatible both with each other and with the essential ingredients of the composition such that there is no interaction which would impair the performance of the active ingredients. All additives or excipients must of course be non-toxic and of sufficient purity to render them suitable for human use.

The oral care composition of the invention is a highly viscous liquid or gel that may be presented in any form that is suitable for application to the oral cavity. It may conveniently be applied to one or all of the teeth. On application to teeth, the composition forms a protective barrier which adheres firmly to the teeth and retains the components of the formulation in a matrix-type environment.

The composition adheres sufficiently to remain on the teeth for a period of time e.g. up to a few hours. Suitably the composition is applied at night time, allowing peroxide activity to take place during sleep periods. During use, the peroxide is released slowly from the gel, in an amount and at such a rate as required to effect stain removal. The gel may be removed from the user's teeth by any convenient means e.g. brushing and/or by rinsing with a mouthwash.

The term "painted onto the teeth" above is intended to encompass all manner of applying the whitening composition to the teeth and includes sponging, coating, daubing, spraying, wiping and rubbing. Preferably the composition is applied to the teeth with a soft applicator brush. Suitably the composition is housed in a container such as a bottle or tube, and the composition is applied with a soft applicator brush.

If the composition is to be supplied in a bottle and brush this may be provided in a kit form e.g. as may be used with a conventional nail varnish kit. Alternatively the composition may be housed in a dispensing device such as a pen with an applicator brush attached thereto e.g. generally of the type used with the Brite Smile To Go'M Whitening pen.

The whitening compositions of the present invention are prepared by adding and mixing the ingredients of the composition in a suitable vessel such as a stainless steel tank provided with a mixer. In the preparation of the composition the silicate was slowly added to the water to allow dispersion and full hydration. The humectant is then added to the mixture. The natural gum was then dispersed separately in a further carrier (if necessary) and added to the mixture in the vessel.

The mixture was mixed until homogeneity was achieved. The final whitening product prepared is then suitably packaged and stored as required.

Advantageously the composition of the invention is suitably prepared as a single or one component system i.e. it does not require segregation and then mixing of ingredients just prior to use. In a second aspect of the invention there is provided a kit of parts comprising an anhydrous liquid tooth whitening composition as hereinbefore described, a container for housing the composition and an applicator for applying the composition to teeth to be whitened.

In an alternative aspect there is provided a method of whitening teeth comprising: a. preparing a tooth whitening composition as hereinbefore described; b. painting the composition onto teeth to be whitened, suitably at night-time c. maintaining the composition in contact with the teeth for a plurality of hours per day.

d. repeating steps b and c for multiple days e.g. up to fourteen days, to thereby whiten the teeth.

The present invention is illustrated by the following examples but is not limited thereby.

Examples

I. A composition was prepared having the following ingredients: Ingredient %w/w Glycerin 20.00 Keltrol 2.00 Laponite 4.50 Hydrogen peroxide(30%) 12.00 Deionised water 49.00 Ethanol 12.5 Total 100.00 Keltrol is a tradename for Xanthan gum II. A composition was prepared having the following ingredients: Ingredient Owls Glycerin 70.00 Keltrol 2.00 Laponite 4.50 Carbamide peroxide 11.00 Ethanol 12.50 Total 100.00 *Keltrol is a tradename for Xanthan gum III. A composition was prepared having the following ingredients: Ingredient %w/w Glycerin 69.00 Keltrol 2.00 Laponite 4.50 Ethanol 12.50 Hydrogen peroxide (30%) 12.00 Total 100.00 *Keltrol is a tradename for Xanthan gum IV. A composition was prepared having the following ingredients: Ingredient %w/w Glycerin 74.00 Keltrol 1.00 Ethanol 13.00 Hydrogen peroxide (30%) 12.00 Total 100.00 *Keltrol is a tradename for Xanthan gum V. A composition was prepared having the following ingredients: Ingredient %w/w Glycerin 78.00 Keltrol 1.00 Laponite 9.00 Hydrogen peroxide (30%) 12.00 Total 100.00 *Keltrol is a tradename for Xanthan gum Determination of Gel Substantivity Method A thin layer of the test formulations coloured with erythrocin is applied to the tiles.

The tiles are mounted in the spray fermenter and sprayed with water at a rate of approximately lml/min for 30 minutes. The rate of flow is then increased to approximately 33ml/min. The substantivity is visually assessed (time for removal of formulation).

Results Formulation Composition %w/w Substantivity (mine) Peroxide | Water | Glycerin | Ethanol | Xanthan | Laponite Low | High 11 (carbarnide 70 12.5 4.5 30 12 peroxide) 11(carbamide 72.5 13 2 5 30 4 peroxide) 11(carbamide 70 12.5 2 4 5 30 21 peroxide) 11 (carbamide 72.5 13 2.5 30 12 peroxide) 12(30%H2O2) 0 69 12.5 2 4 5 30 20 1 2(30%H2O2) 0 72 12.5 1 2.5 30 10

Conclusion

Addition of xanthan to the system enhances the substantivity.

Determination of bleaching effect Method Stained Pellicle Cleaning Ratio (PCR) enamel blocks were hydrated for at least one hour in deionised water and then dried by vacuum for 20 minutes. L*a*b* measurements were then taken using a HunterLab Spectrocolorimeter and recorded for each PCR enamel block.

The blocks were then treated and placed into the spray fermenter. Tap water was used to spray onto the blocks at a rate of approximately [ml/minute for 30 minutes, followed by 330ml/minute for 30 minutes. After this time the enamel blocks were removed from the spray fermenter, rinsed by immersing in deionised water for approximately 2 minutes, dried under vacuum for 20 minutes and then the L*a*b* was remeasured.

Results A graph showing the change in L after 60 minutes treatment (hydrogen peroxide samples) is shown below in Figure 1.

Conclusion

The results indicate that after 60 minutes treatment the change in L was higher for the Laponite/xanthan combination (Example V) than for the xanthan formulation (Example IV) or the untreated control. -1D

Claims

Claims 1. An oral care composition comprising a peroxide contaning

compound dispersed in an orally acceptable carrier, wherein the carrier comprises a humectant and a combination of bioadhesive agents consisting essentially of at least one natural gum and a silicate.
2. An oral care composition according to claim 1 wherein the peroxide containing compound is selected from hydrogen peroxide, carbamide peroxide, calcium peroxide, percarbonates, and mixtures thereof.
3. An oral care composition according to claim 1 or claim 2 wherein the humectant is glycerin.
4. An oral care composition according to any one of claims 1 to 3 wherein the bioadhesive agents are selected from Xanthan Gum, Gum Karaya, Carragenan, Alginates, Guar Gum, Gum Arabic, Gum Ghatti, Locust Bean Gum, Tara Gum, Fenugreek Gum, Gum Tragacanth, Tamarind Gum, Gellan Gum, Succinoglucan Gum, Welan Gum, Rhamsan Gum, Aloe Polysaccharides, Chia Gum, Flaxseed Gum, Okra Gum, Psyllium Seed Gum, Quince Seed Gum, Curdlan, Pullulan, Pectins and mixtures thereof plus a carbomer homopolymer or copolymer.
5. A kit of parts comprising a tooth whitening composition according to any one of claims 1 to 4, a container for housing the composition and an applicator for applying the composition to teeth to be whitened.
6. A method of whitening teeth comprising: a. preparing a tooth whitening composition according to any one of claims 1 to 4; b. painting the composition onto teeth to be whitened; c. maintaining the composition in contact with the teeth for a plurality of hours per day; and then d. repeating steps b and c for multiple days to thereby whiten the teeth.