CN112839625A

CN112839625A - Oral care compositions

Info

Publication number: CN112839625A
Application number: CN201980034029.2A
Authority: CN
Inventors: 李雅娟; 袁苏
Original assignee: Unilever NV
Current assignee: Unilever IP Holdings BV
Priority date: 2018-05-21
Filing date: 2019-04-29
Publication date: 2021-05-25
Also published as: CL2020002995A1; WO2019223960A1; EP3773431A1; BR112020021667A2; PH12020551721A1

Abstract

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

Description

Oral care compositions

Technical Field

The present invention relates to oral care compositions such as toothpastes, powders, gels, mouthwashes and the like. In particular, the present invention relates to oral care compositions comprising a tooth whitening agent. The invention also relates to the use of said composition for whitening the teeth of an individual.

Background

The enamel layer of the tooth itself is opaque white or slightly off-white. However, the enamel layer may be stained or discolored.

Many products we consume have a negative impact on our teeth and mouth. Many substances stain or reduce the whiteness of teeth, particularly certain foods, tobacco products, and liquids such as tea and coffee. These staining and discoloring substances are generally able to penetrate into the enamel layer. This problem occurs gradually over the years, but discolors the enamel of the human tooth significantly.

Consumers have a strong desire for whiter teeth at all times and many people are not satisfied with their current tooth color. The desire for whiter teeth has led to an increasing trend towards increased use of tooth whitening products, ranging from toothpaste to mouthwashes and chewing gums.

There are currently a variety of products used for tooth whitening. Such products typically contain peroxide, abrasives, or both to clean and whiten teeth. These types of products are generally undesirable because they can damage the teeth and gums if used excessively.

There is a continuing need for more effective methods of whitening teeth. The inventors of the present invention have now surprisingly found that oral care compositions comprising particles having a high refractive index and certain pigments provide enhanced immediate tooth whitening.

Additional information

WO 2016/099544 a1(Colgate-Palmolive company) discloses an oral care composition for whitening teeth, which is made by mixing in the CIELAB system ingredients of a sheet comprising a water-soluble whitening film, a dye processable sheet with a hue angle of 200 to 320 degrees in the CIELAB system, and an acceptable carrier solution.

EP 1935395 a1(Unilever) discloses 0.01 to 0.3% by weight of a pigment having a hue angle h in the CIELAB system of 220 to 320 degrees, characterized in that the composition further comprises a soluble deposition aid for the 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 a polyol or a mixture thereof; a particulate tooth surface whitening agent dispersed in the continuous phase, and a deposition aid for the particulate tooth surface whitening agent; characterized in that the deposition aid is a poly (sulfonic acid) polymer. The particulate tooth whitening agent is a phthalocyanine blue pigment.

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

Testing and defining

Dentifrice formulation

For the purposes of the present invention, "dentifrice" refers to a paste, powder, liquid, gel or other formulation used to clean teeth or other surfaces in the oral cavity.

Toothpaste tube

For purposes of the present invention, "toothpaste" refers to a toothpaste or gel dentifrice used with a toothbrush. Particularly preferred is a toothpaste suitable for cleaning teeth by brushing for about two minutes.

Mouthwash

For the purposes of the present invention, "mouthwash" refers to a liquid dentifrice used to rinse the mouth. Particularly preferred are mouthwashes suitable for washing the oral cavity by gargling and/or gargling for about half a minute prior to rinsing.

Particle size

For the purposes of the present invention, "particle size" refers to the D50 particle size. The D50 particle size of the granular material refers to the particle diameter at which 50 wt.% of the particles are larger in diameter and 50 wt.% are smaller in diameter. As used herein, "diameter" refers to the largest measurable distance on a particle without forming a well-defined sphere. For the purposes of the present invention, particle size and distribution were determined using a Malvern Mastersizer 2000 and Malvern Zetasizer Nano series.

Composite particles

For the purposes of the present invention, a "composite particle" refers to a particle comprising a core of a first component and a coating of a second component, wherein the core and the coating are composed of different materials.

Refractive index

The refractive index was used at a temperature of 25 ℃ and a wavelength of 589 nm.

pH value

The pH was used at atmospheric pressure and a temperature of 25 ℃. When referring to the pH of an oral care composition, this refers to the pH measured when 5 parts by weight of the composition is uniformly dispersed and/or dissolved in 20 parts by weight of pure water at 25 ℃. Specifically, the pH can be measured by manually mixing 5 grams of the oral care composition with 20mL of water for 30 seconds, and then immediately testing the pH with an indicator or pH meter.

Solubility in water

As used herein, "soluble" and "insoluble" refer to the solubility of the source in water at 25 ℃ and atmospheric pressure. "soluble" refers to a source that dissolves in water to give a solution having a concentration of at least 0.1 moles/liter. By "insoluble" is meant a source that dissolves in water to give a solution having a concentration of less than 0.001 moles/liter. Thus, "sparingly soluble" is defined to mean a source that is dissolved in water to give a solution at a concentration greater than 0.001 moles/liter and less than 0.1 moles/liter.

Viscosity of the oil

The viscosity of the toothpaste is the value obtained at room temperature (25 ℃ C.) using a Brookfield viscometer with spindle No.93/94 for 1 minute at 5 rpm. Unless otherwise stated, values are expressed in centipoise (cP ═ mPa · s).

Others

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 range 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 "consisting 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 interdependent embodiments found in the claims, irrespective of the fact that claims are found to be free of multiple dependencies or redundancies.

Where features are disclosed with respect to a particular aspect of the invention (e.g., a composition of the invention), the disclosure should also be viewed as applicable to any other aspect of the invention (e.g., a method of the invention).

Disclosure of Invention

In a first aspect, the present invention relates to an oral care composition comprising:

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

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

c) a physiologically acceptable carrier;

wherein the weight ratio of the particles to the pigment is from 16:1 to 60: 1.

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

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

All other aspects of the invention will become more apparent from consideration of the following detailed description and examples.

Detailed Description

The composition of the present invention comprises particles having a refractive index of 1.9 to 4.0. The particles are effective to reflect light and produce a white effect. The only limitation with respect to the particles useful in the present invention is that the particles are suitable for use in the oral cavity.

To provide more effective whitening, it is preferred to use particles with a 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, most preferably at least 2.5. The maximum refractive index of the particles is not particularly limited, but is preferably as high as 4.0, more preferably as high as 3.0. Preferably, the refractive index of the particles is from 2.0 to 3.0, more preferably from 2.2 to 3.0, most preferably from 2.5 to 3.0.

Suitable materials providing said high refractive index are metal compounds, and preferably compounds wherein the metal is selected from zinc (Zn), titanium (Ti) or mixtures thereof. Preferably, the metal compound is (or at least comprises) a metal oxide, such as titanium dioxide (TiO)₂) Zinc oxide (ZnO), or mixtures thereof.

In a preferred embodiment, the particles comprise metal oxide in an amount of at least 50%, more preferably at least 70%, more preferably from 80 to 100%, most preferably from 85 to 95% by weight of the particles. In a particularly preferred embodiment, the particles are at least 50 wt% titanium dioxide, most preferably from 60 to 100 wt% titanium dioxide, based on the total weight of the particles, and including all ranges subsumed therein. Most preferably, the particles are titanium dioxide.

In a particularly preferred embodiment, the particles are composite particles. The refractive index of a composite particle comprising more than one material may be calculated based on the refractive index and volume fraction of the components using effective medium theory, for example as described in WO 2009/023353.

The composite particle includes a first component core and a second component coating. Typically, the core of the composite particle comprises particles suitable for whitening teethA material. Particularly suitable core materials are metal compounds, and preferably compounds in which the metal is selected from zinc (Zn), titanium (Ti) or mixtures thereof. Preferably, the metal compound is (or at least comprises) a metal oxide, such as titanium dioxide (TiO)₂) Zinc oxide (ZnO), or mixtures thereof.

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

The composite particles typically comprise at least 50%, more preferably at least 70%, more preferably from 80 to 99%, most preferably from 85% to 99% of the core, including all ranges subsumed therein, based on the total weight of the composite particle.

The second component coating comprises a material suitable for adhering to enamel, dentin, or both. As used herein, "adhering" includes bonding and/or operatively coupling to the surface of the tooth due to interaction between elements in the coating and elements in the tooth.

Typically, the coating material comprises an oxide and/or a hydrated oxide. Illustrative, but non-limiting, examples of the types of coating materials suitable for use in the present invention include, for example, alumina (Al)₂O₃) Hydrated alumina (aluminum hydroxide), silica, hydrated silica, copper oxides, lanthanum oxide, nickel oxide, lead oxide, zinc oxide, magnesium oxide, mixtures thereof, and the like. Alumina is particularly preferred as the coating material.

In a particularly preferred embodiment, the composite particles are alumina coated titanium dioxide, which is commercially available, for example, under the trade name Hombitan AFDC300 from suppliers such as Sachtleben.

Titania 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 the present invention. Titanium dioxide coated with a mixture of hydrated alumina and silica is commercially available, for example, from suppliers such as KOBO Products Inc under the trade name SIH-5TiO 2R 250. Titanium dioxide coated with a mixture of alumina and hydrated silica is commercially available, for example, from Tayca Corporation under the trade name JR-800.

The enamel surface bears some negative charge. Due to the presence of the metal oxide in the second component coating, the composite particles may carry some positive charge when in contact with oral fluids. Without wishing to be bound by theory, the inventors believe that the positive charge of the composite particles allows for enhanced interaction with and deposition on the tooth surface. In addition, the amphiphilic surface of the composite particles also helps retain the particles on the tooth surface by enhancing the water-wash resistance of the particles.

Typically, the particles have a size of from 10nm to 10 microns, more preferably from 50nm to 1 micron, more preferably from 100nm to 500nm, most preferably from 150nm to 350 nm.

The oral care compositions of the present invention comprise from 1 to 20%, preferably from 1 to 10%, more preferably from 1 to 8%, most preferably from 1.5 to 5% by weight of the particles based on the total weight of the oral care composition, including all ranges subsumed therein.

The pigments of the present invention are shade (shade)/materials that are insoluble in the relevant medium at the relevant temperature. This is in contrast to soluble dyes. As used herein, the term "relevant medium" refers to human saliva, at the temperature of the oral cavity, i.e. up to 37 ℃, during tooth brushing, where the liquid medium of the composition is used. The relevant medium can also be water, the relevant temperature being 25 ℃. The only limitation with respect to the pigment is that the pigment is suitable for use in the oral cavity.

The pigment has a hue angle h in the CIELAB system of 220 to 320 degrees, more preferably 250 to 290 degrees. A detailed description of the hue angle can be found on page 57 of Color Chemistry, h.zollinger, published by Wiley-VCH. Preferably, the pigment is violet or blue, more preferably, the pigment is selected from one or more of the group consisting of pigment blue 1 to pigment 83 and pigment violet 1 to pigment violet 56 listed in the international color index. Other suitable pigments are the pigments ultramarine blue and ultramarine violet. When the preferred pigment is blue or violet, the same effect can be achieved by mixing pigments outside this hue angle range. This hue angle can also be obtained, for example, by mixing red and green-blue pigments to produce blue or violet colored pigments.

Particularly preferably, the pigment is a blue pigment. Some examples of blue pigments suitable for use in the present invention include inorganic blue pigments such as iron blue (c.i.77510) and ultramarine blue (c.i.77007). One preferred class of blue pigments suitable for use in the present invention are organic blue pigments, such as phthalocyanine blue pigments. Phthalocyanines are organometallic compounds containing four symmetrically arranged isoindole rings linked alternately in a 16-membered ring with carbon and nitrogen atoms. Most phthalocyanines contain a centrally coordinated metal ion, such as copper. Copper phthalocyanine has the following basic structure:

phthalocyanine blue pigments exhibit more than one crystal modification, which are not identical in color. To prevent conversion to different crystal modifications, methods have been developed to stabilize the molecular phase of phthalocyanine pigments. One example is minor chemical modification of the molecule, such as partial chlorination. Methods have also been developed to stabilize phthalocyanine pigment molecules against flocculation during pigment application. An example is the mixture of other agents with the molecule, such as the addition of surface active additives to the pigment molecule. The following pigments are exemplary phthalocyanine blue pigments preferably included in the composition according to the invention:

common name of C.I	C.I. component numbering	Crystal modification type	Amount of halogen atom
				Pigment blue 15	74160	α	--
Pigment blue 15:1	74160	α; phase-stable	0.5-1CI
				Pigment blue 15:2	74160	α; phase and flocculation stable	0.5-1CI
Pigment blue 15:3	74160	β	--
				Pigment blue 15:4	74160	Beta; flocculation-stable	--
Pigment blue 15:6	74160	ε	--
				Pigment (I)Blue 16	74100	Gamma; contains no metal	--

Particularly preferably, the pigment is a phthalocyanine blue pigment selected from the group consisting of alpha-copper phthalocyanine pigment blue 15, pigment blue 15:1, pigment blue 15:2, and mixtures thereof. Most preferably, the pigment is pigment blue 15: 1. A commercially available example is Cosmenyl Blue A4R from Clariant.

Pigments suitable for use in the present invention may also be mixtures of any of the above materials.

The oral care compositions of the present invention typically comprise from 0.001 to 1 weight%, more preferably from 0.01 to 0.5 weight%, most preferably from 0.02 to 0.2 weight% of a pigment, based on the total weight of the oral care composition, including all ranges subsumed therein.

The oral care compositions of the present invention were found to be effective in providing immediate tooth whitening effects. Without wishing to be bound by theory, the inventors believe that tooth whitening is achieved by increasing the reflected light intensity (L) and decreasing the "yellowness" (b). L denotes the total light intensity reflected from the test surface, b denotes the yellow-blue light contribution. Particles having a refractive index of 1.9 to 4.0 are light reflective materials which increase the value of WIO (tooth whiteness index) by increasing the value of L x. Pigments with a hue angle "h" of 220 to 320 degrees in the CIELAB system are light absorbing materials that increase the WIO value by decreasing the b value.

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

The pH of the oral care composition is preferably from 4.0 to 10.0, more preferably from 5.0 to 9.0, most preferably from 5.5 to 8.0.

The oral care compositions of the present invention may also comprise high molecular weight polymers, including

Type polymers, high molecular weight PEG, and high molecular weight cellulose ethers. The high molecular weight polymer is preferably incorporated into the oral care composition at from 0.01 to 10 weight%, more preferably from 0.02 to 5 weight%, most preferably from 0.05 to 3 weight%, based on the total weight of the composition.

The compositions of the present invention are oral care compositions and typically comprise a physiologically acceptable carrier. The carrier preferably comprises at least a surfactant, a thickener, a wetting agent, or a combination thereof.

Preferably, the oral care composition comprises a surfactant. Preferably, the composition comprises at least 0.01%, more preferably at least 0.1%, most preferably from 0.5 to 7% by weight of the composition of surfactant. Suitable surfactants include anionic surfactants, such as C₈To C₁₈Sodium, magnesium, ammonium or ethanolamine salts of alkyl sulfates (e.g. sodium lauryl sulfate), C₈To C₁₈Sodium, magnesium, ammonium or ethanolamine salts of alkyl sulfosuccinic acids (e.g. sodium dioctyl sulfosuccinate), C₈To C₁₈Sodium, magnesium, ammonium or ethanolamine salts of alkylsulfoacetic acids (e.g. sodium lauryl sulfoacetate), C₈To C₁₈Sodium, magnesium, ammonium or ethanolamine salts of alkyl sarcosines (e.g. sodium lauryl sarcosinate), C₈To C₁₈Sodium, magnesium, ammonium or ethanolamine salts of alkyl phosphates (which may optionally contain up to 10 ethylene oxide and/or propylene oxide units) and sulfated monoglycerides. Other suitable surfactants include nonionic surfactants such as optionally polyethoxylated sorbitan esters of fatty acids, ethoxylated fatty acids, esters of polyethylene glycol, ethoxylates of fatty acid mono-and diglycerides, and ethylene oxide/propylene oxide block polymers. Other suitable surfactants include amphoteric surfactants such as betaines or sulfobetaines. Mixtures of any of the above materials may also be used. More preferably, the surfactant comprises or is an anionic surfactant. A preferred anionic surfactant is sodium lauryl sulfateAnd/or sodium dodecylbenzenesulfonate. Most preferably, the surfactant is sodium lauryl sulfate, sodium coco sulfate, cocamidopropyl betaine, sodium methyl cocoyl taurate, or mixtures thereof.

Thickeners may also be used in the present invention and are limited only to the extent that they can be added to compositions suitable for use in the oral cavity. Illustrative examples of the types of thickeners that may be used in the present invention include sodium carboxymethylcellulose (SCMC), hydroxyethylcellulose, methylcellulose, ethylcellulose, tragacanth, acacia, carrageenan, sodium alginate, carrageenan, guar gum, xanthan gum, irish moss, starch, modified starch, silica-based thickeners including silica aerogel, magnesium aluminum silicate (e.g., Veegum), carbomers (cross-linked acrylates), and mixtures thereof.

In general, preference is given to xanthan gum and/or sodium carboxymethylcellulose and/or carbomers. When carbomers are used, it is desirable that they have a weight average molecular weight of at least 700,000, preferably at least 1,200,000, and most preferably at least about 2,500,000. Mixtures of carbomers may also be used herein.

In a particularly preferred embodiment, the sodium carboxymethylcellulose (SCMC) used is SCMC 9H. It is described as the sodium salt of a cellulose derivative having a carboxymethyl group bonded to the hydroxyl group of the glucopyranose backbone monomer and identified by CAS number 9004-32-4. It is commercially available from suppliers such as Alfa Chem.

In another particularly preferred embodiment, the thickening agent is xanthan gum.

In another particularly preferred embodiment, the carbomer is Synthalen PNC, Synthalen KP or a mixture thereof. It is described as a high molecular weight and crosslinked polyacrylic acid and is identified by CAS number 9063-87-0. These types of materials are commercially available from suppliers such as Sigma.

The thickening agent typically comprises from 0.01 to about 10 weight%, more preferably from 0.1 to 9 weight%, and most preferably from 0.1 to 5 weight% of the oral care composition, based on the total weight of the composition, including all ranges subsumed therein.

When the oral care composition of the present invention is a toothpaste or gel, the viscosity is typically from about 30,000 to 180,000 centipoise, 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 compositions of the present invention and they include, for example, glycerin, sorbitol, propylene glycol, dipropylene glycol, diglycerin, triacetin, mineral oil, polyethylene glycol (preferably PEG-400), alkane diols such as butylene glycol and hexylene glycol, ethanol, pentylene glycol, or mixtures thereof. Preferred humectants are glycerol, polyethylene glycol, sorbitol or mixtures thereof.

The humectant may be present in an amount of 10 to 90% by weight of the oral care composition. More preferably, the carrier wetting agent comprises from 25 to 80 weight percent, most preferably from 30 to 70 weight percent of the composition, based on the total weight of the composition, including all ranges subsumed therein.

The oral care compositions of the present invention may contain, in addition to the particles and pigments contained in the composition, a variety of other ingredients commonly used in the art to enhance physical properties and performance. These ingredients include antimicrobial agents, anti-inflammatory agents, anti-caries agents, plaque buffering agents, fluoride sources, vitamins, plant extracts, desensitizing agents, anti-calculus agents, biomolecules, flavoring agents, proteinaceous materials, preservatives, opacifiers, pH adjusters, sweeteners, particulate abrasives, polymeric compounds, buffers and salts for buffering the pH and ionic strength of the composition, and mixtures thereof. The ingredients typically and generally constitute less than 20% by weight of the composition, preferably from 0.0 to 15% by weight, and most preferably from 0.01 to 12% by weight, including all ranges subsumed therein.

The oral care compositions of the present invention may be used in a method of whitening an individual's teeth comprising applying the composition to at least one surface of the individual's teeth. The oral care compositions of the present invention may additionally or alternatively be used as medicaments and/or in the manufacture of medicaments to provide oral care benefits as described herein, for example for whitening of the teeth of an individual. Alternatively and preferably, the use is non-therapeutic.

Typically, the composition is packaged. The composition may be packaged in the form of a toothpaste or gel in a conventional plastic laminate, metal tube or single chamber dispenser. It can be applied to the tooth surface by any physical means, such as a toothbrush, a fingertip, or by direct application to the sensitive area through an applicator. The composition may be packaged in the form of a liquid mouthwash in a bottle, sachet, or other convenient container.

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

The following examples are provided to facilitate an understanding of the invention. This example is provided not to limit the scope of the claims.

Examples

Example 1

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

TABLE 1

a dispersion of c.i.74160 (pigment Blue 15:1) in water/glycerol, commercially available from Clariant under the trade name Cosmenyl Blue A4R;

b. titanium dioxide coated with alumina, available from Sachtleben under the trade name HOMBITAM AFDC 300;

c. uncoated titanium dioxide, available from Sachtleben under the trade name HOMBITAN AFDC.

Method

To evaluate the tooth whitening efficacy of the samples, the following in vitro tests were performed. The WIO index is an index specifically optimized for assessing tooth whiteness (as described in Journal of Dentistry, vol 36, Supplement 1,2008, p.2-7). The change in whiteness was calculated based on the values of L, a, b measured using DigiEye (VeriVide, england).

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

TABLE 2

Composition (I)	Amount per gram
		Glycerol	100
Sodium carboxymethylcellulose	10
		Formalin	2
Deionized water (Milli Q Water, Millipore, USA)	Equilibrate to 2L

The test samples were mixed with water and DAV diluent in a 1:1:1 weight ratio to form a toothpaste slurry.

Bovine blocks (Bovine blocks) were prepared and stored in Deionized (DI) water for complete hydration. The baseline L, a, b of bovine blocks were measured by DigiEye (VeriVide, england). Twelve bovine blocks were used for each sample. In thatWith a toothbrush

The cattle blocks were brushed with toothpaste slurry for one minute on a brushing machine. The brushing load was 175 grams and the automatic brushing was operated at 150 rpm. The bovine blocks were then rinsed 3 times with 20mL water each time using a toothbrushing machine. After this step, values of L, a, b are re-measured for each bovine block, and based on these values, the change in WIO values from baseline (Δ WIO) is calculated and statistically analyzed.

Results

The results are summarized in table 3 (error stands for standard error of repeated measurements).

TABLE 3

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

Claims

1. An oral care composition comprising:

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

c) a physiologically acceptable carrier;

wherein the weight ratio of the particles to the pigment is from 16:1 to 60: 1.

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

3. The oral care composition according to claim 1 or 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 the group consisting of alpha-copper phthalocyanine 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 one of the preceding claims, wherein the pigment has a refractive index of from 2.0 to 3.0, more preferably from 2.2 to 3.0.

6. The oral care composition according to any one of the preceding claims, wherein the particles comprise a metal compound, preferably the metal is selected from zinc, titanium or mixtures 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 one of the preceding claims, wherein the particle is a composite particle comprising a first component core and a second component coating, wherein the first component core comprises a metal compound, preferably the metal is selected from zinc, titanium or mixtures thereof, and the second component coating comprises alumina, hydrated alumina, silica, hydrated silica, copper oxide, lanthanum oxide, nickel oxide, lead oxide, magnesium oxide or mixtures 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 of claim 8 or 9, wherein the first component core of the composite particle is titanium dioxide.

11. The oral care composition according to one of claims 8 to 10, wherein the composite particle is alumina coated titanium dioxide.

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

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

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

15. A method of whitening an individual's teeth comprising the step of applying a composition according to one of the preceding claims to at least one surface of an individual's teeth.