The present invention relates to an oral care composition that when used to brush the teeth mitigates staining.

White teeth are seen as cosmetically attractive, however the enamel of the teeth can stain, for instance when certain foods or drinks are consumed. Hence, there is a need for products that remove the staining of teeth.

WO2018060209 discloses compositions that whiten and mitigate tooth staining; the composition contains a whitening ingredient, a smectite clay and an acryl based polymer.

There remains the need for a composition that when used to clean the teeth whitens and mitigates tooth staining.

Description of the Invention

The present invention relates to an oral care composition comprising:

a) from 0.01 to 0.2 wt% of the total composition of charcoal; and

b) from 0.5 to 7 wt% of clay.

The invention further relates to the use of the above composition to cosmetically whiten the teeth.

A further aspect of the invention is the use the above compositionto remove stains from the teeth.

Detailed Description of the Invention

Compositions for use in the invention comprise charcoal. Preferably the charcoal has a total surface area (BET) of 900m ² /g to 1500m ² /g more preferably from 1 100 m ² /g to 1300 It is also preferred if the charcoal has a density from 250 kg/m ³ to 370kg/m ³ , more preferably from 300 kg/m ³ to 340 kg/m ³ . Preferably the charcoal has a D50 particle size from 2 microns to 40 microns, more preferably 5 to 30 microns. The level of charcoal is from 0.01 to 0.2 wt% of the total composition, more preferably from 0.02 to 0.01 wt% from 0.03 to 0.08 wt% of the composition.

Compositions for use in the invention comprise clay, preferably this is a 1 :1 layered silicate clay. Typically, the 1 :1 layered silicate clay are non-swelling clays. 1 :1 layered silicate clay includes kaolinite-serpentine group of clay. Kaolinite-serpentine group of clay includes subgroups of kaolinites and serpentines minerals. Serpentines are trioctahedral sheet minerals which has a tetrahedral sheet and an octahedral sheet having magnesium with minor amounts of aluminium and the species within this subgroup are preferably chrysotile, lizardite and antigorite.

Preferably the 1 :1 layered silicate clay is a kaolinites clay. Kaolinites have a

dioctahedral sheet and the species included within the kaolinites subgroup are kaolinite, dickite, nacrite and halloysite clay minerals, but not limited thereto. Kaolinite is particularly preferred in the disclosed invention.

Kaolinite, commonly known as kaolin clay, is a naturally occurring mineral. Kaolinite may be a calcined kaolin, highly purified calcined kaolin, colloidal kaolin, or hydrated kaolin, but not limited thereto. Preferred kaolinite have particle size distribution such that at least 98 wt percent of the particles have a particle size of 2 microns or less.

Preferably the kaolinite is a refined kaolin and further preferably the refined kaolin includes 38 wt percent AI203 and 45wt percent S102 and a maximum of 0.5 wt percent of Fe2C>3.

It is especially preferred if the clay is a hydrated aluminium silicate, with less than 0.025% of 53 micron or greater residues.

Preferably the weight ratio of charcoal to clay is from 1 :2.5 to 1 :700, more preferably from 1 :5 to 1 :500, most preferably from 1 : 10 to 1 :200.

In a particularly preferred embodiment the weight ratio of charcoal to clay is from 1 to 100 to 5 to 100. Compositions according to the invention may comprise a further 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 composition is free of dye.

In one preferred embodiment of the invention the whitening system comprises a combination of green and blue pigment, the weight ratio of green pigment to blue pigment is greater than 1 :2, preferably greater than 2:3 most preferably the weight ratio of green pigment to blue pigment is from 2:3 to 3:2.

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 preferably 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; and

Gantrez 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 of the invention are preferably toothpastes.

Compositions according to the invention, particularly toothpastes, preferably comprise particulate abrasive materials such as silicas, aluminas, calcium carbonates,

dicalciumphosphates, calcium pyrophosphates, hydroxyapatites, trimetaphosphates, insoluble hexametaphosphates and so on, including agglomerated particulate abrasive materials, usually in amounts between 3 and 60% by weight of the oral care composition.

Preferably the composition, particularly a toothpaste, comprises a silica based 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 mm, a BET (nitrogen) surface area of between 10 and 100 m ² /g and an oil absorption of about 70 - 150 cm ³ /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 Huber, Sorbosil AC 77 ex Crosfield Chemicals (having an R.l. of approximately 1.440). The amount of these silicas in the composition generally ranges from 5-60% by weight, usually 5-20% by weight.

The composition, particularly if a toothpaste preferably comprises an inorganic or a natural or synthetic thickener or gelling agent in proportions of about 0.10 to about 15% by weight depending on the material chosen. These proportions of thickeners in the dentifrice compositions of the present invention form an extrudable, shape-retaining 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. Suitable thickeners or gelling agents useful in the practice of the present invention include inorganic thickening silicas such as amorphous silicas available from Huber Corporation under the trade designation Zeodent 165, Irish moss, iota-carrageenan, gum tragacanth, and polyvinylpyrrolidone. In the context of the present invention silica is particularly preferred.

The toothpaste composition 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; 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 and E;

plant extracts;

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;

colouring agents;

pH-adjusting agents;

sweetening 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; Humectants such as glycerol, sorbitol, propyleneglycol, xylitol, lactitol etc.;

binders and thickeners such as sodium carboxymethyl-cellulose, hydroxyethyl cellulose (Natrosol®), xanthan gum, gum arabic etc. as well as synthetic polymers such as polyacrylates and carboxyvinyl polymers such as Carbopol®;

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.

Example of the invention will now be illustrated by the following non-limiting examples:

Examples

Examples were prepared using the base paste as in Table 1 and post dosing clay and charcoal to give test pastes summarised in Table 2.

Table 1 : Base Paste Formulation

Table 2: Test formulations summary

The test formulations were evaluated for their stain removal properties using the Ferric- Tannate (FT) in vitro stain model. The method in outline is as follows. Hydroxyapatite (HAP) discs were cleaned and polished using P1200 silicon carbide paper. The baseline (initial clean) colour was measured using a chromameter. Tannic acid (0.5% w/w) and Ammonium iron sulphate hexahydrate (0.5% w/w) solutions were prepared and mixed in the ratio of 1 :1 by volume to form the FT stain solution and used immediately. The FT stain solution was applied to the HAP discs using a small paintbrush and left to air dry. A further 3 to 4 coats of the stain were applied to each disc and allowed to dry. The colour of the discs was then remeasured (soiled).

The toothpastes were prepared as slurries in water 1 :2 toothpaste. Sixteen HAP discs were used per treatment group. A stained HAP disc was placed into each well of a brushing machine and 10ml of the toothpaste slurry was applied. The HAP discs were then brushed for 1 minute with a flat trim toothbrush at a brushing speed of 150 cycles per min and load of 185g. The HAP discs were removed from the well, rinsed with water, gently dried and the colour was remeasured (cleaned). The brushing with toothpaste for a further 1 minute was conducted in the first experiment.

The % stain removal was calculated for each HAP disc using the equation below and the mean % stain removal determined.

% stain removal = L*(cleaned) - L*(soiled) x100

L*(initial clean) - L*(soiled)

Table 3 and Table 4 demonstrate that compositions comprising clay are particularly effective at removing stains form the teeth. This can be enhanced with the addition of charcoal. Table 3: Mean % Stain removal after 1 and 2 minutes brushing (Test 1).

Statistical differences indicated by different letters (p<0.05, ANOVA, Tukey-Kramer)

Table 4: Mean % Stain removal after 1 minute brushinq (Test 2).

Statistical differences indicated by different letters (p<0.05, ANOVA, Tukey-Kramer)

The charcoal used had a total surface area (BET) of 1200m ² /g; density 320 kg/m ³ , and D50 particle size of approximately 23microns.