WO2020212361A1

WO2020212361A1 - Oral care compositions

Info

Publication number: WO2020212361A1
Application number: PCT/EP2020/060484
Authority: WO
Inventors: Adam John Limer; Alexander Thomas Ashcroft
Original assignee: Unilever Plc; Unilever N.V.; Conopco, Inc., D/B/A Unilever
Priority date: 2019-04-17
Filing date: 2020-04-14
Publication date: 2020-10-22

Abstract

A composition comprising polysaccharide and calcium carbonate for use in a method to decrease relative dentin abrasivity (RDA) without reducing cleaning efficiency.

Description

ORAL CARE COMPOSITIONS

Field of the Invention

The present invention relates to compositions for decreasing the abrasivity of a toothpaste without reducing cleaning efficiency.

Background and Prior Art

Abrasives for use in oral care compositions such as dentifrices, are required to be effective in removing extrinsic stains, dental plaque and food debris which builds up on the pellicle on the surface of teeth.

In general, the efficiency of physical removal of stain, plaque and food debris can be increased by using an abrasive having increased abrasivity, or by increasing the level of abrasive incorporated into the composition. However, both these approaches also increase the risk that tooth surfaces may be damaged.

WO2015/071023 discloses toothpastes having an aqueous continuous phase structured with a matrix of activated citrus fibre particle. The compositions have enhanced cleaning and lower abrasivity.

However, there is a continuing need for oral care compositions that demonstrate satisfactory levels of cleaning, yet, are not unduly abrasive and damaging to the teeth.

Summary of the Invention

The present invention provides a composition comprising polysaccharide and calcium carbonate for use in a low relative dentin abrasivity (RDA) method to clean the teeth.

A further aspect of the invention is the use of polysaccharide and calcium carbonate for the manufacture of a toothpaste for the low relative dentin abrasivity (RDA) cleaning of the teeth. Detailed Description of the Invention

The present invention comprises a polysaccharide. The polysaccharide reduces decrease relative dentin abrasivity (RDA) in a composition comprising calcium carbonate without reducing cleaning efficiency.

Suitable polysaccharides include natural gums such as carrageenan, gum karaya, guar gum, xanthan gum, gum arabic, and gum tragacanth.

Preferably the polysaccharide comprises an anionic heteropolysaccharide, more preferably the polysaccharide comprises a primary structure consisting of repeating pentasaccharide units pentasaccharide units and a glucuronic acid unit.

It is particularly preferred if the polysaccharide comprises an anionic

heteropolysaccharide, with a primary structure consisting of repeating pentasaccharide units and a glucuronic acid unit, for use in a method to decrease relative dentin abrasivity (RDA) without reducing cleaning efficiency. These repeating pentasaccharide units give xanthan gum its characteristic backbone, which consists of (1 4) b-D-glucopyranosyl units substituted at C-3 on every other glucose residue with a charged trisaccharide sidechain. The trisaccharide sidechain consists of a D-glucuronic acid unit between 2 D-mannose units. Slightly less than half (about 40%) of the terminal D-mannose residues contain a pyruvic acid residue linked via keto groups to the four and six positions, and the

D-mannose linked to the main chain mostly contains an acetyl group at position 0-6. Some side chains may be missing. The acetate and pyruvate contents are variable on the side chain, and depend on the bacterial strains and on the fermentation conditions used to produce the gum. Preferably the polysaccharide is xanthan gum.

Xanthan gum is a fermentation product prepared by action of the bacteria of the genus Xanthomonas upon carbohydrates. Four species of Xanthomonas, namely X.campestris, X. phaseoli, X.malvocearum and X.carotae are reported in the literature to be the most efficient gum producers.

Xanthan gum generally has a molecular weight of from 1 million to 50 million. Its viscosity generally ranges from 850 to 1 ,700 mPa.s (when measured at 25°C using a 1 % solution of the gum in 1 % KCI, on a viscometer of the Brookfield LV type, at 60 rpm using Spindle No. 3).

Xanthan gum is available from several commercial suppliers such as RT Vanderbilt Company and CP Kelco. Examples of suitable xanthan gums are Keltrol®, Keltrol® F, Keltrol® T, Keltrol® TF, Xantural® 180 and Vanzan® NF.

The amount of heteropolysccharide, in particular xanthan gum in the dentifrice preferably ranges from 0.01 to 0.9 wt% (by weight based on the total weight of the dentifrice), more preferably 0.05 to 0.5 wt%.

The composition for use in the invention comprises a particulate calcium carbonate composed of primary particles.

By“primary particles” is meant individual particles, defined as the smallest discrete particles that can be seen by electron microscopy analysis (such as, for example, individual crystals).

The primary particles may associate under certain conditions to form larger secondary structures such as aggregates or agglomerates.

In one present invention, a suitable source of particulate calcium carbonate as defined above includes crystalline calcium carbonates in which the individual crystals have a prismatic morphology and an average size of 2 microns or less.

The term“crystalline” (in the context of particulate calcium carbonate) generally means a particulate calcium carbonate in which at least 50% by weight, preferably at least 75% by weight, more preferably at least 90% by weight, most preferably more than 95% by weight and ideally more than 99% by weight of the calcium carbonate particles are in the form of crystals.

The term "crystal" means an essentially fully dense solid composed of atoms arranged in an orderly repetitive array bounded by plane surfaces which are the external expression of internal structure. Crystals may be identified and characterised by standard techniques known to those skilled in the art such as

X-ray diffraction.

Crystalline forms of calcium carbonate are available naturally, or may be synthetically produced in three particular crystalline morphologies, calcite, aragonite, and less commonly found, vaterite. The vaterite form of calcium carbonate is metastable and irreversibly transforms into calcite and aragonite. There are many different polymorphs (crystal habits) for each of these crystalline forms. The calcite crystalline morphology is the most commonly used crystal form of calcium carbonate. Over 300 crystalline forms of calcite have been reported in the literature.

References to a“prismatic crystal morphology” (in the context of crystalline calcium carbonates) generally denote a crystalline calcium carbonate in which at least 50% by weight, preferably at least 75% by weight, more preferably at least 90% by weight, most preferably more than 95% by weight and ideally more than 99% by weight of the crystals are prismatic crystals. Prismatic crystals have a set of faces with parallel edges that are parallel to the vertical or“c”-axis direction. There can be three, four, six, eight or even twelve faces that can form a prism. For the purposes of the present invention, preferred prismatic crystals have a generally uniform, typically generally hexagonal cross-sectional shape.

References to a“scalenohedral crystal morphology” (in the context of crystalline calcium carbonates) generally denote a crystalline calcium carbonate in which at least 50% by weight, preferably at least 75% by weight, more preferably at least 90% by weight, most preferably more than 95% by weight and ideally more than 99% by weight of the crystals are scalenohedral crystals. Scalenohedral crystals have a set of faces that are inclined to the vertical or“c”-axis direction, each of which are scalene triangles (i.e. triangles whose three sides are unequal in length). For the purposes of the present invention, preferred scalenohedral crystals have a trigonal scalenohedral shape, with twelve scalene triangle faces.

Reference to acicular” in this context refers to the shape of the crystals. Usually, crystals grow in three directions, length, width and height. Some crystals however, have one or two preferred growth directions. Acicular crystals have a preferred crystal growth in one direction. Examples are crystals in the form of needles, rods, fibres, whiskers or columns and the like. For the purposes of the present invention, preferred acicular crystals are rod-like or needle-like with a generally uniform, typically generally circular, cross-sectional shape.

Crystal shape may be determined by standard techniques known to those skilled in the art such as scanning electron microscopy (SEM). SEM is an imaging and analysis technique based on the detection of electrons and X-rays that are emitted from a material when irradiated by a scanning electron beam. Imaging allows the user to distinguish between primary particles and aggregates or agglomerates.

Usually, crystals grow in three directions, length, width and height. Some crystals however, have one or two preferred growth directions. For the purposes of the present invention, preferred prismatic calcium carbonate crystals have a ratio between the length and the width of the crystal (the so-called aspect ratio) ranging from about 1 :1 up to about 3:1 (length:width). The aspect ratio of a particle (e.g. a crystal) may typically be obtained from SEM photographs by averaging the ratio between the length and width of the particle, measured on at least 10 particles for 1 photograph.

Preferably the calcium carbonate for use in this invention has a prismatic, scalenohedral or acicular crystal morphology.

Preferably the calcium carbonate has an average particle size of 2 microns or less.

For the purposes of the present invention, preferred prismatic calcium carbonate crystals have an average size which is less than 2 microns and generally ranges from about 0.1 to 2 microns, with a preferred size ranging from about 0.2 to about 1.5, more preferably from about 0.3 to about 1 , most preferably from about 0.5 to 0.9 microns. Particle (e.g. crystal) size may be determined by standard techniques known to those skilled in the art such as sedimentation. Particle size values obtained from sedimentation techniques are normally expressed in terms of the equivalent spherical diameter (ESD), i.e. the diameter of a notional sphere having the same volume as the particle. The ESD value may be calculated based on the sedimentation rate of the particle in question as defined by Stokes' Law (Micromeritics SediGraph® 5100 Particle Size Analysis System Operator's Manual, V2.03, 1990). The sedimentation rate is measured using a finely collimated beam of low energy X-rays which pass through the sample cell to a detector. For a sample population of particles, the distribution of particle mass at various points in the cell affects the number of X-ray pulses reaching the detector. This X-ray pulse count is used to derive the particle size distribution expressed as the percent mass at given particle diameters. The median value of the ESD which can be derived from this distribution (i.e. the particular ESD value on the cumulative mass distribution curve at which 50 percent mass of the population has a higher ESD and 50 percent mass of the population has a lower ESD) is usually quoted as the average particle size of the sample population.

For the purposes of the present invention, preferred scalenohedral calcium carbonate crystals have an average size which is less than 2 microns and generally ranges from about 0.05 to about 1.5 microns, with a preferred size ranging from about 0.1 to about 1 micron, more preferably from about 0.15 to about 0.5 micron, most preferably from about 0.2 to 0.35 micron. A standard technique known to those skilled in the art for determining the average size of the individual crystals is air permeametry according to the Lea and Nurse method (standards NF X 11-601 and NF X 11 602). This analytical technique determines the average particle size by measuring the pressure drop across a packed powder bed using a water manometer. The pressure drop is a function of the

permeability of the packed bed. This is related to the surface area of the particles which is then transformed to an average size based upon the assumption that the particles are spherical. Average particle size (Dp) is obtained from the massic area (SM) derived from the Lea and Nurse method by making the assumptions that all the particles are spherical, non-porous and of equal diameter, and by neglecting contact surfaces between the particles. The relationship between Dp and SM is the following:

Dp=6/(pSM) where p is the specific mass of the calcium carbonate. The average particle size (Dp) obtained in this way represents the average equivalent spherical diameter, or average ESD, where equivalent spherical diameter (ESD) is defined as the diameter of a notional sphere having the same volume as the particle. For the purposes of the invention preferred acicular calcium carbonate is composed of a length of 2 microns or greater. Preferred acicular calcium carbonate crystals for use in the invention have a length ranging from 2 to 100 microns, more preferably from 10 to 30 microns and a width ranging from 0.1 to 4.0 microns, more preferably from 0.5 to 1.0 microns. A specific class of material suitable for use in the invention includes aragonite crystal form calcium carbonates such as those described for example in US 5,164,172.

The ratio between the length and the width of a crystal, the so-called aspect ratio, is higher than 1 :1 for preferred acicular crystals. The higher the aspect ratio, the longer the crystal. For the purposes of the present invention the aspect ratio is preferably at least 2.5:1 , more preferably at least 10: 1. For example the aspect ratio may typically range from 2.5:1 to 200:1 , and preferably ranges from 10:1 to 60:1 , more preferably from 20:1 to 30:1.

Preferred calcium carbonate crystals, in particular scalenohedral prismatic calcium carnonare generally have a BET specific surface area higher than or equal to

0.1 m2/g, preferably higher than or equal to 1 m2/g, more preferably higher than or equal to 3 m2/g and most preferably higher than or equal to 4 m2/g. The calcium carbonate particles according to the invention generally have a BET specific surface area lower than or equal to 30 m2/g, preferably lower than or equal to 25 m2/g, more preferably lower than or equal to 20 m2/g, and most preferably lower than or equal to 15 m2/g. The BET specific surface area is usually measured according to the standard ISO 9277 which specifies the determination of the overall specific external and internal surface area of disperse or porous solids by measuring the amount of physically adsorbed gas according to the Brunauer, Emmett and Teller (BET) method.

Crystalline forms of calcium carbonate suitable for use in the invention are available naturally, or may be produced by precipitation production technology. Typically, precipitated calcium carbonate is prepared by exposing calcium hydroxide slurry to a carbonation reaction. Control of the specific solution environment during the nucleation and growth of calcium carbonate governs the size and the shape of the crystals in the resulting precipitated calcium carbonate product. A commercially available source of particulate prismatic calcium carbonate suitable for use in the invention is ViCALity® ALBAFIL® Precipitated Calcium Carbonate (PCC), ex Specialty Minerals Inc., Bethlehem, Pa. 18017.

A commercially available source of particulate scalenohedral calcium carbonate suitable for use in the invention is SOCAL® S2E Precipitated Calcium Carbonate (PCC), ex Solvay S.A.

Suitable acicular crystal form calcium carbonates for use in the invention are

commercially available and include those marketed by Maruo Calcium Company Limited, Japan under the trade name WISCAL®.

Mixtures of any of the above described materials may also be used.

The level of calcium carbonate incorporated into the dentifrice generally ranges from 1 to 50 wt%, preferably from 2 to 30 wt%, more preferably from 3to 420 wt%, by weight based on the total weight of the composition (dentifrice).

Preferably the weight ratio of calcium carbonate to polysaccharide is from 130:1 to 5:1 , preferably 100:1 to 1o:1.

The oral care composition may take any product form suitable for application to the surface of the teeth preferably in a mixture with water. Examples of such product forms include solid forms, such as powders or discrete unit doses (for example pellets, pastilles, tablets and the like).

Preferably the composition is in the form of a dentifrice. The term "dentifrice" denotes an oral composition which is used to clean the surfaces of the oral cavity. 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. A dentifrice for use in the invention is suitably in the form of an extrudable semi-solid such as a cream, paste or gel (or mixture thereof).

Alternatively, a kit may be supplied to the consumer in which the anhydrous oral care composition as described above is packaged together with an independent aqueous activator.

The viscosity of the dentifrice generally ranges from 10,000 to 100,000 cps, and preferably ranges from 30,000 to 60,000 cps, (when measured at 25°C on a Brookfield viscometer).

The pH of the dentifrice generally ranges from 7 to 10.5, and preferably ranges from 8 to 9, when measured at 25° C using conventional pH sensitive electrodes.

Preferably the composition of the invention is anhydrous. The term“anhydrous” in the context of the present invention generally means that water is not deliberately added to the composition in any significant quantity. However, the term“anhydrous” does not mean that small amounts of water cannot be present, for example as a consequence of its association with hygroscopic raw materials. Accordingly, for the purposes of this invention, the term“anhydrous” generally means that water is present in an amount no greater than about 5 wt%, more preferably no greater than about 3 wt%, most preferably no greater than about 1 wt% (by weight based on the total weight of the composition).

A dentifrice for use in the invention will typically contain an anhydrous liquid continuous phase in an amount of from 40 to 99 wt%, by weight based on the total weight of the dentifrice.

Such an anhydrous liquid continuous phase will preferably comprise one or more organic polyols having 3 or more hydroxyl groups in the molecule (hereinafter termed“organic polyols”), with the amount of organic polyol generally ranging from 20 to 90 wt%, preferably from 35 to 90 wt%, more preferably from 45 to 80 wt% (by total weight organic polyol based on the total weight of the dentifrice). Preferred organic polyols having 3 or more hydroxyl groups in the molecule for use in the invention include glycerol, sorbitol, xylitol, mannitol, lactitol, maltitol, erythritol, and hydrogenated partially hydrolyzed polysaccharides. The most preferred organic polyol is glycerol. Mixtures of any of the above described materials may also be used.

The dentifrice for use in the invention is most preferably organic polyol-based. In the context of the present invention, the term“organic polyol-based” generally means that the dentifrice is not oil-based or water-based, but instead organic polyol (as defined above) forms a liquid continuous phase in which the particulate ingredients of the dentifrice (such as the acicular calcium carbonate) are dispersed. The dentifrice for use in the invention is ideally glycerol-based (i.e. glycerol forms a liquid continuous phase in which the particulate ingredients of the dentifrice are dispersed), and contains from 60 to 75 wt% glycerol (by weight based on the total weight of the dentifrice).

A composition, in particular dentifrice for use in the invention will also generally contain further ingredients to enhance performance and/or consumer acceptability.

For example, the composition (dentifrice) may suitably comprise one or more surfactants in an amount of from 0.2 to 5wt% (by weight based on the total weight of the oral care composition). Suitable surfactants include anionic surfactants, such as the sodium, magnesium, ammonium or ethanolamine salts of C8 to C18 alkyl sulphates (for example sodium lauryl sulphate), C8 to C18 alkyl sulphosuccinates (for example dioctyl sodium sulphosuccinate), C8 to C18 alkyl sulphoacetates (such as sodium lauryl sulphoacetate), C8 to C18 alkyl sarcosinates (such as sodium lauryl sarcosinate), C8 to C18 alkyl phosphates (which can optionally comprise up to 10 ethylene oxide and/or propylene oxide units) and sulphated monoglycerides. Other suitable surfactants include nonionic surfactants, such as optionally polyethoxylated fatty acid sorbitan esters, ethoxylated fatty acids, esters of polyethylene glycol, ethoxylates of fatty acid monoglycerides and diglycerides, and ethylene oxide/propylene oxide block polymers. Other suitable surfactants include amphoteric surfactants, such as betaines or sulphobetaines.

Preferred surfactants for use in the invention are selected from sodium lauryl sulfate, sodium lauryl sulfoacetate, cocamidopropyl betaine, sodium alpha olefin sulfonate, dioctyl sodium sulfosuccinate, sodium dodecyl benzene sulfonate and mixtures thereof.

Mixtures of any of the above described materials may also be used. A particularly 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.

Mixtures of any of the above described materials may also be used. The dentifrice may also include thickening agents to provide a desirable rheology and texture. Suitable thickening agents for use in this context may be selected from natural or synthetic organic thickeners or gelling agents. Examples of such materials include carboxyvinyl polymers (such as polyacrylic acids cross-linked with polyallyl sucrose or polyallyl pentaerythritol), hydroxyalkyl cellulose derivatives (such as hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxyethylpropyl cellulose, hydroxybutylmethyl cellulose and hydroxypropylmethyl cellulose), water soluble salts of cellulose ethers (such as sodium carboxymethyl cellulose and sodium carboxymethyl hydroxyethyl cellulose), starch and polyvinylpyrrolidone. Inorganic thickeners such as finely divided silicas, hectorites and colloidal magnesium aluminium silicates may also be used.

The amount of thickening agent incorporated into the dentifrice will depend on the particular agent (or agents) used, but generally ranges from about 0.05 to about 10 wt%, preferably from about 0.1 to about 2 wt%, by total weight thickening agent based on the total weight of the solid matrix. However, it is preferable if polysaccharides described as RDA mitigating agents are also used as thickeners, in particular we have found that the xanthan gum as described above is also an effective structurant for the composition of the invention. Accordingly, it is not generally necessary to include significant quantities of additional polymeric thickening agents. Preferably the level of such materials is no more than 0.5wt%, more preferably no more than 0.1 wt%, most preferably no more than 0.01wt%, ideally 0 wt% (by total weight additional polymeric thickening agents based on the total weight of the composition).

Good results have been observed when the anhydrous oral care composition comprises a polyol, and is preferably a glycerol-based dentifrice containing from 60 to 85 wt% glycerol (by weight based on the total weight of the dentifrice) and from 3 to 20 wt% acicular calcium carbonate (by weight based on the total weight of the dentifrice); and the weight ratio in the mixture ranges from 1 :2 to 1 :90, preferably from 1 :5 to 1 :70 (calcium carbonate: polyol preferably glycerol).

An oral care composition for use in the invention (such as the dentifrice as described above) may also contain further optional ingredients customary in the art such as anticalculus agents, buffers, flavouring agents, sweetening agents, colouring agents, opacifying agents, preservatives, antisensitivity agents, antimicrobial agents and the like. An aqueous activator suitable for use in the invention may also contain further optional ingredients customary in the art such as thickeners, anticalculus agents, buffers, flavouring agents, sweetening agents, colouring agents, opacifying agents, preservatives, antisensitivity agents, antimicrobial agents and the like.

The invention is further illustrated with reference to the following, non-limiting Examples:

EXAMPLES

The ingredients of the dentifrice formulations are shown in the table below. The pastes were prepared by mixing (in weight percent) the following ingredients under moderate shear until a homogeneous composition was obtained.

Numbered Examples represent formulations according to the invention. Lettered

Examples are comparative examples.

Purchased from a UK based chemical company The Pellicle Cleaning Ratio (PCR) was measured for each of the above formulations.

PCR was measured using a method based on that described by Pickles et al.

(International Dental Journal 55 (2005), pp. 197-202). This model uses enamel slabs cut from bovine central incisors, embedded in methacrylate resin. The enamel surfaces are smoothed by hand using an alumina paste on a glass block and lightly acid etched in order to facilitate stain accumulation and adherence. The enamel blocks are placed in an incubator set at a constant temperature of 50 degrees centigrade and slowly rotated to alternate between immersion in a staining broth (consisting of tea, coffee and mucin) and air drying. The broth is changed daily and after five days the slabs are removed and washed with distilled water to remove any loose debris. The stained slabs are then brushed in a mechanical brushing machine with distilled water to remove any loosely adhered stain. They are then dried and the L^* values (L*_stained) from the CIE L^*a^*b^* colour system are measured with a chroma meter in L^*a^*b^* mode. To assess cleaning performance, the stained specimens are then mounted in the mechanical brushing machine and the required load applied to each brush. The test composition is dispersed in an aqueous diluent to form a slurry (typically 38.5g test composition and 61.5g of distilled water) and the stained specimens brushed for a set number of brush strokes with 10ml of slurry. After brushing, the enamel slabs are rinsed with distilled water, dried and the L* values (U_mshed) are re-measured. In the final stage, all traces of stain are removed from the enamel slabs using flour of pumice, on a soft cloth using a grinder/polisher. The enamel slabs are then rinsed with distilled water, dried and the L^* values (L*_pumiced) are measured and recorded. The percentage of the stain removed by the test composition compared to full removal by pumice (hereinafter referred to as the pellicle cleaning ratio or PCR) may be calculated using the following equation:

PCR — [(L*brushed)-(L*stained)/ (L*pumiced)-(L*stained)] X 1 00.

The RDA was measured using the method for assessment of dentifrice abrasivity recommended by the American Dental Association (Journal of Dental Research 55(4) 563, 1976).

The PCR results after 800 brush strokes and RDA values are shown in the table below.

The examples of the invention show that the addition of xanthan gum leads to a significant reduction in RDA but not a significant reduction in PCR.

Claims

1. A composition comprising polysaccharide and calcium carbonate for use in a low relative dentin abrasivity (RDA) method to clean the teeth.

2. Use of polysaccharide and calcium carbonate for the manufacture of a toothpaste for the low relative dentin abrasivity (RDA) cleaning of the teeth.

3. A composition for use according to claim 1 in which the polysaccharide comprises an anionic heteropolysaccharide.

4. A composition for use according to claim 1 or claim 3 in which the polysaccharide comprises a primary structure consisting of repeating pentasaccharide units pentasaccharide units and a glucuronic acid unit.

5. A composition for use according to any preceding claim in which the

heteropolysaccharide is xanthan gum.

6. A composition for use according to any preceding claim which is anhydrous.

7. A composition for use according to any preceding claim in which the calcium

carbonate comprises primary particles which are acicular and which have a length of 2 microns or greater.

8. A composition for use according to any one of claims 1 to 6 in which the calcium carbonate comprise of scalenohedral calcium carbonate crystals have an average size which is less than 2 microns.

9. A composition for use according to any one of claims 1 to 6 in which the calcium carbonate comprise of prismatic calcium carbonate crystals have an average size which is less than 2 microns.

10. A composition for use according to any one of preceding claims, in which the anhydrous oral care composition is in the form of a dentifrice.

11. A composition for use according to claim 10, in which the dentifrice is glycerol- based, with a liquid continuous phase formed from glycerol, and contains from 60 to 75 wt% glycerol (by weight based on the total weight of the dentifrice).

12. A composition for use according to any preceding claim in which the weight ratio of calcium carbonate to polysaccharide is from 130:1 to 5:1.

13. A composition for use according to any preceding claim further comprising 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.