WO2019223960A1

WO2019223960A1 - Oral care composition

Info

Publication number: WO2019223960A1
Application number: PCT/EP2019/060928
Authority: WO
Inventors: Yajuan Li; Su YUAN
Original assignee: Unilever N.V.; Unilever Plc; Conopco, Inc., D/B/A Unilever
Priority date: 2018-05-21
Filing date: 2019-04-29
Publication date: 2019-11-28
Also published as: BR112020021667A2; PH12020551721A1; CL2020002995A1; CN112839625A; EP3773431A1

Abstract

An oral care composition is disclosed comprising from 1 to 20% by weight of particles having a refractive index of from 1.9 to 4.0, a pigment having a hue angle, h, in the CIELAB system of from 220 to 320 degrees, and a physiologically acceptable carrier, wherein the particles and the pigment are present in a weight ratio of rom 16:1 to 60:1

Description

ORAL CARE COMPOSITION

Field of the Invention

The present invention relates to oral care compositions such as tooth pastes, powders, gums, mouthwashes and the like. In particular, the present invention relates to oral care compositions comprising tooth whitening agents. The invention also relates to the use of such compositions for whitening of teeth of an individual.

Background of the Invention

The enamel layer of the tooth is naturally an opaque white or slightly off-white colour. However, this enamel layer can become stained or discoloured.

Many products we consume have a negative impact on our teeth and mouth. Many substances can stain or reduce the whiteness of one’s teeth, in particular, certain foods, tobacco products, and fluids such as tea and coffee. These staining and discolouring substances are often able to permeate the enamel layer. This problem occurs gradually over many years, but imparts a noticeable discoloration of the enamel of one’s teeth.

Consumers have always had a strong desire for whiter teeth and many individuals are dissatisfied with their current teeth colour. This desire for whiter teeth has given rise to a growing trend in the increased use of tooth whitening products which range from toothpastes to mouthwashes and chewing gums.

A variety of products are currently used for teeth whitening. Such products often comprise peroxides, abrasives or both in order to clean and whiten teeth. These types of products are often not desired since they can cause damage to teeth and gums if overused.

There is continuing need for more efficacious methods of whitening the teeth. The present inventors have now found unexpectedly that an oral care composition comprising particles with a high refractive index and certain pigments provides enhanced instant tooth whitening effect. Additional Information

WO 2016/099544 A1 (Colgate-Palmolive Company) discloses a tooth whitening oral care composition made by combining ingredients comprising flakes of a water soluble whitening film, a dye with a hue angle in the CIELAB system ranging from 200 to 320 degrees and an orally acceptable carrier vehicle.

EP 1 935 395 A1 (Unilever) discloses from 0.01 to 0.3% by weight of a pigment having a hue angle, h, in the CIELAB system of from 220 to 320 degrees, characterized in that the composition further comprises a soluble deposition aid for said pigment.

WO 2012/123241 A2 (Unilever) discloses an oral care composition suitable for delivering a temporary whitening effect to the surface of teeth, the composition comprising: a continuous phase comprising water or polyhydric alcohol or a mixture thereof; a particulate tooth surface whitening agent which is dispersed in the continuous phase, and a deposition aid for the particulate tooth surfaces whitening agent; characterised in that the deposition aid is a poly-(sulphonic acid) polymer. The particulate tooth whitening agent is a phthalocyanine blue pigment.

The additional information above does not describe an oral care composition comprising from 1 to 20% by weight of particles having a refractive index of from 1.9 to 4.0 and a pigment having a hue angle, h, in the CIELAB system of from 220 to 320 degrees, and wherein the particles and the pigment are present in a weight ratio of from 16:1 to 60:1.

Test and definitions

Dentifrice

“Dentifrice” for the purposes of the present invention means a paste, powder, liquid, gum or other preparation for cleaning the teeth or other surfaces in the oral cavity.

Tooth Paste

“Tooth paste” for the purpose of the present invention means a paste or gel dentifrice for use with a toothbrush. Especially preferred are tooth pastes suitable for cleaning teeth by brushing for about two minutes. Mouth Wash

“Mouth wash” for the purpose of the present invention means liquid dentifrice for use in rinsing the mouth. Especially preferred are mouth washes suitable for rinsing the mouth by swishing and/or gargling for about half a minute before expectorating.

Particle Size

“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.“Diameter”, as used herein, means the largest measurable distance on a particle in the event a well-defined sphere is not generated. For the purpose of the present invention, particle sizes and distribution are measured using Malvern Mastersizer 2000 and Malvern ZetaSizer Nano series.

Composite Particle

“Composite particle” for the purpose of the present invention means a particle comprising a first component core and a second component coating wherein the core and coating are composed of different materials.

Refractive Index

Refractive index is quoted at a temperature of 25°C and a wavelength of 589 nm. JDH

pH is quoted at atmospheric pressure and a temperature of 25°C. When referring to the pH of an oral care composition, this means the pH measured when 5 parts by weight of the composition is uniformly dispersed and/or dissolved in 20 parts by weight pure water at 25°C. In particular, the pH may be measured by manually mixing 5 g oral care composition with 20 ml. water for 30 s, then immediately testing the pH with indicator or a pH meter.

Solubility

“Soluble” and“insoluble”, as used herein, refers to the solubility of a source in water at 25°C and atmospheric pressure.“Soluble” means a source that dissolves in water to give a solution with a concentration of at least 0.1 moles per litre.“Insoluble” means a source that dissolves in water to give a solution with a concentration of less than 0.001 moles per litre.“Slightly soluble”, therefore, is defined to mean a source that dissolves in water to give a solution with a concentration of greater than 0.001 moles per litre and less than 0.1 moles per litre.

Viscosity

Viscosity of a tooth paste is the value taken at room temperature (25°C) with a Brookfield Viscometer, Spindle No.93/94 and at a speed of 5 rpm for 1 minute. Values are quoted in centipoises (cP=mPa.s) unless otherwise specified.

Miscellaneous

Except 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 final oral care composition, unless otherwise specified.

It should be noted that in specifying any ranges of values, any particular upper value can be associated with any particular lower value.

For the avoidance of doubt, the word“comprising” is intended to mean“including” but not necessarily“consisting of or“composed of”. In other words, the listed steps or options need not be exhaustive.

The disclosure of the invention as found herein is to be considered to cover all embodiments as found in the claims as being multiply dependent upon each other irrespective of the fact that claims may be found without multiple dependency or redundancy.

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.

Summary of the Invention

In a first aspect, the present invention is directed to an oral care composition comprising: a) from 1 to 20% by weight of particles having a refractive index of from 1.9 to 4.0; b) a pigment having a hue angle, h, in the CIELAB system of from 220 to 320 degrees; and

c) a physiologically acceptable carrier;

wherein the particles and the pigment are present in a weight ratio of from 16:1 to 60:1.

In a second aspect, the present invention is directed to a packaged oral care product comprising the oral care composition of the first aspect of this invention.

In a third aspect, the present invention is directed to a method of whitening teeth of an individual comprising the step of applying the oral care composition of any embodiment of the first aspect to at least one surface of the teeth of the individual.

All other aspects of the present invention will more readily become apparent upon considering the detailed description and examples which follow.

Detailed Description of the Invention

The composition of the present invention comprises particles having a refractive index of from 1.9 to 4.0. The particles are efficient for reflecting light and producing a white effect. The only limitation with respect to the particles that may be used in this invention is that the same is suitable for use in the mouth.

In order to provide more efficient whitening, it is preferable to use particles with even higher refractive index. Thus the particles preferably have a refractive index of at least 2.0, more preferably at least 2.2, even more preferably at least 2.4 and most preferably at least 2.5. The maximum refractive index of the particles is not particularly limited but preferably up to 4.0, more preferably up to 3.0. Preferably, the particles have a refractive index of from 2.0 to 3.0, more preferably from 2.2 to 3.0 and most preferably from 2.5 to 3.0.

Suitable materials to provide such a high refractive index are metal compounds and preferred are compounds where the metal is selected from zinc (Zn), titanium (Ti) or a mixture thereof. Preferably, the metal compound is (or at least comprises) a metal oxide such as titanium dioxide (T1O2), zinc oxide (ZnO) or a mixture thereof. In a preferred embodiment, the particles comprise metal oxides in an amount of at least 50% by weight of the particles and more preferably at least 70%, more preferably still from 80 to 100% and most preferably from 85 to 95%. In an especially preferred embodiment, the particles are at least 50% by weight titanium dioxide, and most preferably, from 60 to 100% by weight titanium dioxide, based on total weight of the particles and including all ranges subsumed therein. Most preferred, the particles are titanium dioxide.

In an especially preferred embodiment, the particles are composite particles. The refractive index of a composite particle comprising more than one material can be calculated based on the refractive indices and volume fractions of the constituents using effective medium theory, as is described for example in WO 2009/023353.

The composite particle comprises a first component core and a second component coating. Typically, the core of the composite particle comprises a material suitable to whiten teeth. Particularly suitable core materials are metal compounds and preferred are compounds where the metal is selected from zinc (Zn), titanium (Ti) or a mixture thereof. Preferably, the metal compound is (or at least comprises) a metal oxide such as titanium dioxide (T1O2), zinc oxide (ZnO) or a mixture thereof.

In a preferred embodiment, the core comprises metal oxides in an amount of at least 50% by weight of the core and more preferably at least 70%, more preferably still from 80 to 100% and most preferably from 85 to 95%. In an especially preferred embodiment, the core is at least 50% by weight titanium dioxide, and most preferably, from 60 to 100% by weight titanium dioxide, based on total weight of the first component core. In an especially preferred embodiment, the core of the composite particle is titanium dioxide.

The composite particle typically comprises the core in an amount of at least 50%, more preferably at least 70%, more preferably still from 80 to 99%, most preferably from 85% to 99% by weight of the composite particle, based on total weight of the composite particle and including all ranges subsumed therein.

The second component coating comprises material suitable to adhere to tooth enamel, dentin or both.“Adhere”, as used herein, includes bonding and/or effectively coupling to tooth surfaces as a result of the interaction between the elements in the coating and those in teeth.

Typically, the coating material comprises oxides and/or hydrated oxides. Illustrative yet non-limiting examples of the type of the coating material suitable for use in this invention include, for example, alumina (AI2O3), hydrated alumina (aluminium hydroxide), silica, hydrated silica, copper oxide, lanthanum oxide, nickel oxide, lead oxide, zinc oxide, magnesium oxide, mixtures thereof or the like. Especially preferred as the coating material is alumina.

In an especially preferred embodiment, the composite particles are titanium dioxide coated with alumina, which are available commercially, for example, from suppliers like Sachtleben under the trade name Hombitan AFDC 300.

Titanium dioxide coated with a mixture of 1 ) alumina and/or hydrated alumina and 2) silica and/or hydrated silica may also be suitable for use in this invention. Titanium dioxide coated with a mixture of hydrated alumina and silica are commercially available, for example, from suppliers like KOBO Products Inc under the trade name SIH-5 Ti02 R250. Titanium dioxide coated with a mixture of alumina and hydrated silica are made commercially available, for example, from Tayca Corporation under the trade name JR- 800.

The tooth enamel surfaces carry some negative charges. The composite particles may carry some positive charge when in contact with oral fluid due to the presence of metal oxides in the second component coating. Without wishing to be bound by theory, the present inventors believe that the positive charge of the composite particles allows for enhanced interaction with and deposition on tooth surfaces. In addition, the amphiphilicity surface of the composite particles also helps the retention of particles on tooth surfaces by enhancing their resistance to water rinsing.

Typically, the particles have a size from 10 nm to 10 microns, more preferably from 50 nm to 1 micron, more preferably still from 100 nm to 500 nm, most preferably from 150 nm to 350 nm. The oral care composition of the present invention comprises from 1 to 20%, preferably from 1 to 10%, more preferably from 1 to 8% and most preferably from 1 .5 to 5% by weight of the particles, based on the total weight of the oral care composition and including all ranges subsumed therein.

The pigment according to the invention is a shade/material which is insoluble in the relevant medium, at the relevant temperature. This is in contrast to dyes which are soluble. The term“relevant medium”, as used herein, refers to 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°C. The relevant medium may also be water and the relevant temperature to be 25°C. The only limitation with respect to the pigment is that the same is suitable for use in the mouth.

The pigment has a hue angle, h, in the CIELAB system of from 220 to 320 degrees, more preferably from 250 to 290 degrees. A detailed description of hue angels may be found on p57 of Colour Chemistry 3^rd edition by H. Zollinger published by Wiley-VCH. Preferably the pigment is violet or blue, more preferably the pigment is selected from one or more of those listed in the Colour Index International as pigment blue 1 through to pigment 83 and pigment violet 1 through to pigment violet 56. Other suitable pigments are pigment ultramarine blue and ultramarine violet. While the preferred pigment is blue or violet, the same effect may be achieved through mixing pigments outside of this hue angle range. For example, such a hue angle may also be obtained by mixing a red and green-blue pigment to yield a blue or violet shaded pigment.

It is particularly preferred that the pigment is a blue pigment. Some examples of blue pigments suitable for use in this invention include inorganic blue pigments such as iron blue (C.l. 77510) and ultramarine blue (C.l. 77007). A preferred class of blue pigments suitable for use in the invention are organic blue pigments such as phthalocyanine blue pigments. Phthalocyanines are organometallic compounds containing four symmetrically arranged isoindole rings connected in a 16-membered ring linking with alternate carbon and nitrogen atoms. Most phthalocyanines contains a central, coordinated metal ion such as copper. Copper phthalocyanines have the basis structure:

Phthalocyanine blue pigments exhibit more than one crystal modification, which differ in terms of coloristics. Methods have been developed to phase-stabilise the phthalocyanine pigment molecule in order to prevent conversion to a different crystal modification. An example is minor chemical modification of the molecule, for instance partial chlorination. Methods have also been developed to stabilise the phthalocyanine pigment molecule against flocculation during pigment application. An example is admixture of other agents to the molecule, such as surface active additives to the pigment molecule. The following pigments are illustrative phthalocyanine blue pigments preferably included in the composition according to the invention:

It is especially preferred that the pigment is phthalocyanine blue pigment selected from alpha copper phthalocyanines Pigment Blue 15, Pigment Blue 15:1 , Pigment 15:2 and mixtures thereof. Most preferably the pigment is Pigment Blue 15:1. A commercially available example is Cosmenyl Blue A4R from Clariant.

The pigment suitable for use in this invention may also be mixtures of any of the above described materials. The oral care composition of the present invention typically comprises from 0.001 to 1% by weight of the pigment, more preferably from 0.01 to 0.5%, and most preferably from 0.02 to 0.2%, based on the total weight of the oral care composition and including all ranges subsumed therein.

The oral care composition of the present invention is found to be effective in providing instant tooth whitening effect. Without wishing to be bound by theory, the present inventors believe that the tooth whitening is achieved by an increase in reflected light intensity (L^*) and a decrease in“yellowness” (b^*). L^* represents the overall light intensity that is reflected from the tested surface and b^* represents the light contribution from the yellow-blue. The particles with a refractive index of from 1.9 to 4.0 are light reflection materials, which increase the value of WIO (tooth whiteness index) by increasing the value of L^*. The pigment having a hue angle“h” in the CIELAB system of from 220 to 320 degrees is a light absorption material, which increase the value of WIO by reducing the value of b^*.

The weight ratio of the particles to the pigment in the oral care composition of the present invention ranges from 16:1 to 60:1 , more preferably from 20:1 to 50:1 , more preferably still from 20:1 to 45:1 , and most preferably from 20:1 to 30:1.

Preferably, the oral care composition has a pH from 4.0 to 10.0, more preferably from 5.0 to 9.0, and most preferably from 5.5 to 8.0.

The oral care composition of the present invention may also comprise high molecular weight polymers including Gantrez® type polymers, high molecular weight PEGs, and high molecular weight cellulose ethers. The high molecular weight polymers are incorporated into the composition at preferably from 0.01 to 10%, more preferably at from 0.02 to 5% and most preferably at from 0.05 to 3% by weight, based on total weight of the oral care composition.

The composition of the present invention is an oral care composition and typically comprises a physiologically acceptable carrier. The carrier preferably comprises at least surfactant, thickener, humectant or a combination thereof. Preferably the oral care composition comprises a surfactant. Preferably the composition comprises at least 0.01% surfactant by weight of the composition, more preferably at least 0.1% and most preferably from 0.5 to 7%. Suitable surfactants include anionic surfactants, such as the sodium, magnesium, ammonium or ethanolamine salts of Cs to Ci₈ alkyl sulphates (for example sodium lauryl sulphate), Cs to Cis alkyl sulphosuccinates (for example dioctyl sodium sulphosuccinate), Cs to Cis alkyl sulphoacetates (such as sodium lauryl sulphoacetate), Cs to Cis alkyl sarcosinates (such as sodium lauryl sarcosinate), Cs to Cis 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. Mixtures of any of the above described materials may also be used.

More preferably the surfactant comprises or is anionic surfactant. The preferred anionic surfactants are sodium lauryl sulphate and/or sodium dodecylbenzene sulfonate. Most preferably the surfactant is sodium lauryl sulphate, sodium coco sulfate, cocamidopropyl betaine, sodium methyl cocoyl taurate or mixtures thereof.

Thickener may also be used in this invention and is limited only to the extent that the same may be added to a composition suitable for use in the mouth. Illustrative examples of the types of thickeners that may be used in this invention include, sodium

carboxymethyl cellulose (SCMC), hydroxyl ethyl cellulose, methyl cellulose, ethyl cellulose, gum tragacanth, gum arabic, gum karaya, sodium alginate, carrageenan, guar, xanthan gum, Irish moss, starch, modified starch, silica based thickeners including silica aerogels, magnesium aluminum silicate (e.g., Veegum), Carbomers (cross-linked acrylates) and mixtures thereof.

Typically, xanthan gum and/or sodium carboxymethyl cellulose and/or a Carbomer is/are preferred. When a Carbomer is employed, those having a weight-average molecular weight of at least 700,000 are desired, and preferably, those having a molecular weight of at least 1 ,200,000, and most preferably, those having a molecular weight of at least about 2,500,000 are desired. Mixtures of Carbomers may also be used herein. In an especially preferred embodiment, the sodium carboxymethyl cellulose (SCMC) used is SCMC 9H. It has been described as a sodium salt of a cellulose derivative with carboxymethyl groups bound to hydroxy groups of glucopyranose backbone monomers and identified via CAS number 9004-32-4. The same is available from suppliers like Alfa Chem.

In another especially preferred embodiment, the thickener is xanthan gum.

In another especially preferred embodiment, the Carbomer is Synthalen PNC, Synthalen KP or a mixture thereof. It has been described as a high molecular weight and cross- linked polyacrylic acid and identified via CAS number 9063-87-0. These types of materials are available commercially from suppliers like Sigma.

Thickener typically makes up from 0.01 to about 10%, more preferably from 0.1 to 9%, and most preferably, from 0.1 to 5% by weight of the oral care composition, based on total weight of the composition and including all ranges subsumed therein.

When the oral care composition of this invention is a toothpaste or gel, the same typically has a viscosity from about 30,000 to 180,000 centipoise, and preferably, from 60,000 to 170,000 centipoise, and most preferably, from 65,000 to 165,000 centipoise.

Suitable humectants are preferably used in the oral care composition of the present invention and they include, for example, glycerin, sorbitol, propylene glycol, dipropylene glycol, diglycerol, triacetin, mineral oil, polyethylene glycol (preferably, PEG-400), alkane diols like butane diol and hexanediol, ethanol, pentylene glycol, or a mixture thereof. Glycerin, polyethylene glycol, sorbitol or mixtures thereof are the preferred humectants.

The humectant may be present in the range of from 10 to 90% by weight of the oral care composition. More preferably, the carrier humectant makes up from 25 to 80%, and most preferably, from 30 to 70% by weight of the composition, based on total weight of the composition and including all ranges subsumed therein.

The oral care composition of the present invention may contain a variety of other ingredients which are common in the art to enhance physical properties and performance, in addition to the particles and pigments which are included in the composition. These ingredients include antimicrobial agents, anti-inflammatory agents, anti-caries agents, plaque buffers, fluoride sources, vitamins, plant extracts, desensitizing agents, anti- calculus agents, biomolecules, flavors, proteinaceous materials, preservatives, opacifying agents, pH-adjusting agents, sweetening agents, particulate abrasive materials, polymeric compounds, buffers and salts to buffer the pH and ionic strength of the compositions, and mixtures thereof. Such ingredients typically and collectively make-up less than 20% by weight of the composition, and preferably, from 0.0 to 15% by weight, and most preferably, from 0.01 to 12% by weight of the composition, including all ranges subsumed therein.

The oral care composition of this invention can be used in a method of whitening the teeth of an individual comprising applying the composition to at least one surface of the teeth of the individual. The oral care composition of this invention may additionally or alternatively be for use as a medicament and/or used in the manufacture of a

medicament for providing an oral care benefit as described herein, such as for whitening the teeth of an individual. Alternatively and preferably, the use is non-therapeutic.

Typically, the composition will be packaged. In tooth paste or gel form, the composition may be packaged in a conventional plastic laminate, metal tube or a single compartment dispenser. The same may be applied to dental surfaces by any physical means, such as a toothbrush, fingertip or by an applicator directly to the sensitive area. In liquid mouthwash form the composition may be packaged in a bottle, sachet or other convenient container.

The composition can be effective even when used in an individual’s daily oral hygiene routine. For example, the composition may be brushed onto the teeth and/or be rinsed around the inside of the mouth of the individual. The composition may, for example, be contacted with the teeth for a time period of one second to 20 hours. More preferably from 1 s to 10 hours, more preferably still from 10 s to 1 hour and most preferably from 30 s to 5 minutes. The composition may be used daily, for example for use by an individual once, twice or three times per day.

The following examples are provided to facilitate an understanding of the present invention. The examples are not provided to limit the scope of the claims. Examples

Example 1

This example demonstrated the improvement of tooth whitening effect by using a combination of pigments and particles. All ingredients are expressed by weight percent of the total formulation.

Table 1 o

Os

a. Dispersion of C.l. 74160 (pigment blue 15:1 ) in water/glycerol under the trade name Cosmenyl Blue A4R from Clariant.

n b. Titanium dioxide coated with alumina under the trade name HOMBITAM AFDC300 from Sachtleben. H

e¾ c. Uncoated titanium dioxide under the trade name HOMBITAN AFDC from Sachtleben. O

o O o

Methods

To evaluate tooth whitening efficacy of the samples, the following in vitro test was performed. The WIO index is an index which has been optimized specifically for the evaluation of whiteness in teeth (as described in Journal of Dentistry, volume 36, Supplement 1 , 2008, pages 2 to 7). Changes in whiteness was calculated based on L^*, a^*, b^* values which were measured using DigiEye (VeriVide, England).

A polymer/glycerol solution (DAV diluent) was prepared by combining the ingredients in Table 2, and it was used to mimic the viscosity characteristics of saliva.

Table 2

The test sample was mixed with water and DAV diluent at a weight ratio of 1 :1 :1 to form a toothpaste slurry.

Bovine blocks were prepared and kept in deionized (Dl) water for complete hydration.

The baseline L^*, a^*, b^* of the bovine blocks was measured by DigiEye (VeriVide, England). Twelve bovine blocks were used for each sample. The bovine blocks were brushed for one minute with the toothpaste slurry on a WIRA^® brushing machine equipped with toothbrushes. The load of the tooth brushing was 175 g and the automatic brushing operated at a speed of 150 rpm. Thereafter the bovine blocks were rinsed three times each time with 20 ml. water by the brushing machine. After this step the L^*, a^*, b^* values of each bovine block were re-measured based on which the changes in WIO values (AWIO) from baseline were calculated and statistically analyzed.

Results

The results are summarized in Table 3 (error represents standard error for duplicate measurements). Table 3

The results clearly indicate that the weight ratio of the particles to the pigment is important. Samples 3, 4, 6, 7, 8 and 9 all showed significantly higher experimental AWIO values compared to calculated AWIO values (p<0.05), which reflects a synergistic improvement in tooth whitening efficacy. But for Samples 1 , 2 and 5, the experimental D\L/IO values were comparable to the calculated AWIO values, indicating no synergistic effect on tooth whitening was observed.

Claims

1. An oral care composition comprising:

a) from 1 to 20% by weight of particles having a refractive index of from 1.9 to 4.0;

b) a pigment having a hue angle, h, in the CIELAB system of from 220 to 320 degrees; and

c) a physiologically acceptable carrier;

2. The oral care composition according to claim 1 , wherein the pigment has a hue angle, h, in the CIELAB system of from 250 to 290 degrees.

3. The oral care composition according to claim 1 or claim 2, wherein the pigment is a blue pigment, preferably a phthalocyanine blue pigment.

4. The oral care composition according to claim 3, wherein the phthalocyanine blue pigment is selected from alpha copper phthalocyanines Pigment Blue 15, Pigment Blue 15:1 , Pigment Blue 15:2 and mixtures thereof, preferably Pigment Blue 15:1.

5. The oral care composition according to any of the preceding claims, wherein the particles has a refractive index ranging from 2.0 to 3.0, more preferably from 2.2 to 3.0.

6. The oral care composition according to any of the preceding claims, wherein the particles comprises a metal compound, preferably the metal is selected from zinc, titanium or a mixture thereof.

7. The oral care composition according to claim 6, wherein the metal compound is a metal oxide, preferably zinc oxide, titanium dioxide or a mixture thereof, more preferably titanium dioxide.

8. The oral care composition according to any of the preceding claims, wherein the particles are composite particles comprising a first component core comprising a metal compound, preferably the metal is selected from zinc, titanium or a mixture thereof, and a second component coating comprising alumina, hydrated alumina, silica, hydrated silica, copper oxide, lanthanum oxide, nickel oxide, lead oxide, magnesium oxide or a mixture thereof.

9. The oral care composition according to claim 8, wherein the metal compound is a metal oxide, preferably titanium dioxide, zinc oxide or a mixture thereof.

10. The oral care composition according to claim 8 or claim 9, wherein the first

component core of the composite particles is titanium dioxide.

1 1. The oral care composition according to any one of claims 8 to 10, wherein the composite particles are titanium dioxide coated with alumina.

12. The oral care composition according to any of the preceding claims, wherein the composition comprises from 1 to 10% by weight of the particles, preferably from 1% to 8%.

13. The oral care composition according to any of the preceding claims, wherein the particles and the pigment are present in a weight ratio of from 20:1 to 50:1 , more preferably from 20:1 to 45:1.

14. The oral care composition according to any of the preceding claims, wherein the particles have a particle size in the range from 10 nm to 10 microns, preferably from 50 nm to 1 micron.

15. A method of whitening teeth of an individual comprising the steps of applying the composition according to any of the preceding claims to at least one surface of the teeth of an individual.