Field of the Invention

The present invention relates to oral care compositions for remineralisation of teeth.

Background of the Invention

Dental caries or cavities are fairly common and in a general sense they are known as tooth decay. Dental caries is caused by demineralisation of the enamel.

Bacteria present in the buccal cavity break down food and produce acid. The acid erodes the enamel which eventually results in dental caries. The calcium and phosphate compounds which constitute the tooth enamel is a modified form of hydroxyapatite which is susceptible to acid attack. To a certain extent, saliva prevents the erosion of enamel by neutralizing these acids and the minerals in saliva deposit on the teeth to remineralize the enamel. As long as the rate of demineralization and the remineralisation are balanced, the teeth remain strong and healthy. Imbalance causes dental caries which occurs when more minerals are lost than can be replaced. Fluorides are known anti-caries agents. Fluorides help in slowing down

demineralisation by interacting with hydroxyapatite to form a stronger compound that is less susceptible to acid attack. Fluoride ions partially fluoridate hydroxyapatite and simultaneously repair the lattice irregularities to improve the remineralisation process. The effectiveness of fluoride depends upon the amount of fluoride ions available for deposition on the enamel. Therefore, it is desirable to increase or enhance the inherent anti caries action of fluorides so that the oral composition can do more remineralisation.

Toothpastes with fluoride are well known. US4455293 B (Harvey et al., 1984) discloses a stable dentifrice formulation having a polishing agent comprising alkali metal aluminosilicate and a stabilising amount of mono-fluorophosphate ion.

EP0102695 A2 (Advanced Research & Technology Institute, 1985) discloses that compositions containing calcined kaolins have better rheological properties. Compositions disclosed in this publication contain calcined kaolin, talc and titanium dioxide as primary ingredients. The compositions also contain a source of fluoride.

US4064231 A (Kao Corp, 1977) discloses a dentifrice composition comprising a water- soluble fluoride and 0.3 to 13 wt% montmorillonite or hectorite having a specific composition leads to reduction of the water-soluble fluoride concentration in the dentifrice with the passage of time.

US4122163 A (Advanced Research & Technology Institute, 1978) discloses new and more effective dentifrice preparations containing calcined kaolin (a 1 :1 clay) for abrasion and a source of fluoride. An example formulation contains Veegum® which is a 2:1 clay and trisodium citrate as the abrasive.

Fluorides tend to deactivate and be rendered unavailable by other ingredients in toothpaste, particularly the abrasives. Therefore, it is desirable that the performance of the source of fluoride ions, such as sodium monofluorophosphate, is improved to maximise the benefits.

Summary of the Invention

It is surprisingly found by the present inventors that a bipolar composite particle as disclosed hereinafter is able to increase or augment the efficacy of fluorides for more remineralisation of teeth.

According to a first aspect disclosed is a bipolar composite material comprising:

(i) a clay whose precursor is an asymmetric 1 :1 or 2:1 :1 clay particle, comprising alternating tetrahedral and octahedral sheets terminating with a tetrahedral sheet at one external surface plane and an octahedral sheet at another; and,

(ii) antimicrobial quaternary ammonium compound attached to a coordinating cation on one of said external surface planes,

in an oral care composition, further comprising at least one source of fluoride ions, for use in promoting remineralization of teeth.

According to a second aspect disclosed is a method of promoting remineralization of teeth by applying to said teeth an oral care composition comprising a bipolar composite material and further comprising at least one source of fluoride ions, wherein said material comprises: (i) a clay whose precursor is an asymmetric 1 :1 or 2:1 :1 clay particle, comprising alternating tetrahedral and octahedral sheets terminating with a tetrahedral sheet at one external surface plane and an octahedral sheet at another; and,

(ii) said ammonium compound attached to a coordinating cation on one of said

external surface planes.

According to a third aspect is disclosed use of a bipolar composite material comprising:

(i) a clay whose precursor is an asymmetric 1 :1 or 2:1 :1 clay particle, comprising alternating tetrahedral and octahedral sheets terminating with a tetrahedral sheet at one external surface plane and an octahedral sheet at another; and,

(ii) said ammonium compound attached to a coordinating cation on one of said

external surface planes.

in the manufacture of an oral care composition for promoting remineralisation of teeth, where said composition further comprises at least one source of fluoride ions.

These and other aspects, features and advantages will become apparent to those of ordinary skill in the art from a reading of the following detailed description and the appended claims. For the avoidance of doubt, any feature of one aspect of the present invention may be utilised in any other aspect of the invention. 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. It is noted that the examples given in the description below are intended to clarify the invention and are not intended to limit the invention to those examples per se. Similarly, all percentages are weight/weight percentages unless otherwise indicated. Except in the operating and comparative examples, or where otherwise explicitly indicated, all numbers in this description and claims indicating amounts of material or conditions of reaction, physical properties of materials and/or use are to be understood as modified by the word "about". Numerical ranges expressed in the format "from x to y" are understood to include x and y. When for a specific feature multiple preferred ranges are described in the format "from x to y", it is understood that all ranges combining the different endpoints are also contemplated.

All references to the term/expression wt% or % by weight, shall mean percentage by weight of the composition, except where indicated otherwise. Detailed Description of the Invention

The invention disclosed in this application discloses a non-obvious solution to the problem, whilst still retaining the essential functional and consumer-relevant attributes of the oral care compositions. The problem has been solved by identifying a new use of the antimicrobial particle. Compared to the solutions disclosed in prior art, the solution in the present invention lies in the inclusion of the bipolar composite material which acts as a carrier of the cationic antimicrobial agent. The composite material is based on an inert material which does not affect important properties of the oral care

compositions. In W014102032A1 , the Applicant has disclosed that the composite bipolar material is highly effective at controlling re-growth of bacteria, as well as at providing immediate control on the bacterial count.

It is preferred that median particle size (D50) of this material is 0.1 to 10 μηη, more preferably 0.4 to 1 μηη and most preferably 0.5 to 0.8 μηη. Without being bound by theory, it is believed that this makes more effective use of the antimicrobial agent, thereby providing opportunity for substantial reduction in dosage of the antibacterial agent. While conventional antibacterial agents need an optimised dosage of 0.2 to 0.5 wt%, the antibacterial agent, delivered in the form of the bipolar antibacterial material, is effective even at an (actual) dosage of 0.02 wt% of the oral care compostion, insofar as the antimicrobial effect is concerned.

Lower particle size also provides an effective mechanism for increased the loading of the antibacterial agent, if so desired. Particle size distribution (D50) is also known as the median diameter or the medium value of the particle size distribution, it is the value of the particle diameter at 50 percent in the cumulative distribution. For example, if D50 is 5.8 μηη, then 50 % of the particles in the sample are larger than 5.8 μηη and 50 percent smaller than 5.8 μηη. D50 is usually used to represent the particle size of group of particles. The D50 is the size in microns that splits the distribution with half above and half below this diameter.

It is preferred that in the bipolar composite material comprising a clay, the precursor of the clay is an asymmetric 1 :1 clay particle. Preferred 1 :1 clays include kaolinite and serpentine subgroups of minerals. The species included within the kaolinite subgroup include but are not limited to kaolinite, dickite, halloysite and nacrite. The species within the serpentine subgroup include but are not limited to chrysolite, lizardite, and amesite. Alternatively, it is also preferred that the precursor of the clay is an asymmetric 2:1 :1 clay particle. Preferred 2:1 :1 clays include chlorite group of minerals. The chlorite comprises tetrahedral-octahedral-tetrahedral sheets like 2:1 clays, with an extra weakly bound brucite like layer between tetrahedral layers. The tetrahedral sheet preferably comprises coordinating tetrahedral cations of silicon. The tetrahedral sheet may also include isomorphously substituted coordinating tetrahedral cations which are not silicon. Isomorphously substituted coordinating tetrahedral cations include, but are not limited to, cations of aluminum, iron or boron. It is preferred that the octahedral sheet has coordinating octahedral cations of aluminum. The octahedral sheet may also comprise isomorphously substituted coordinating octahedral cations which are not aluminium. Isomorphously substituted coordinating octahedral cations include cations of magnesium and iron. The antimicrobial agent is attached to the coordinating cations on the exterior side of one of the external surface planes. Accordingly, the antimicrobial agent is attached to coordinating cations on the exterior side of the tetrahedral sheet. Alternatively, the antimicrobial molecule is attached to the coordinating cations on the exterior side of the octahedral sheet. Coordinating cations on the exterior side of each of the tetrahedral and the octahedral surface sheets are attached to the antimicrobial agent, with the proviso that the antimicrobial agent attached to the coordinating cations on the exterior side of the tetrahedral surface sheet is not identical to the molecule attached to the coordinating cations on the exterior side of the octahedral surface sheet. The antimicrobial agent is preferably attached to the coordinating cations on the external surface of the octahedral surface plane and is not preferably attached to coordination cations of non-exterior tetrahedral or octahedral plane or on the interior side of the surface sheets.

It is preferred that the ratio of the clay: antimicrobial agent is from 1 :0.001 to 1 :1 , more preferably from 1 :0.001 and 1 :0.1 parts by weight of the bipolar composite material.

It is preferred that in the antimicrobial material, the antibacterial agent is attached to coordinating cations on the external surface of the octahedral surface plane.

It is preferred that oral care compositions of the invention comprise 0.1 to 10 wt% of the bipolar antimicrobial material, more preferably 0.5 to 5 wt% material. Preferably the quaternary ammonium compound is one or more of cetylpyridinium chloride (CPC), cetyltrimethylammonium chloride (CTAC), cetyltrimethylammonium bromide (CTAB), benzalkonium chloride (BKC), benzethonium chloride, cetrimide, quaternium, tetrabutyl ammonium bromide, undecylenamido propyltrimonium methosulphate, methylbenzethonium chloride, cetethyldimonium bromide,

cetromonium tosylate, cocotrimonium chloride, dodecylbenzyltrimonium chloride, lauryl isoquinolium bromide, laurylpyridinium chloride, dequalinium chloride or domiphen bromide. It is particularly preferred that the antimicrobial agent cetylpyridinium chloride (CPC). Without being bound by theory, it is believed that the primary activity is linked to the cationic charge of its amine group. Thus, cetylpyridinium chloride is attracted to and binds to negatively-charged protein moieties on the cell membrane or cell wall of the microorganism and to tooth surfaces which are also typically negatively charged. The resulting attachment to microorganisms disrupts the cell wall structure causing leakage of the intracellular fluids, eventually killing the associated microorganism. However, as disclosed earlier and in particular with reference to cetylpyridinium chloride, its tendency to stain the teeth has largely been responsible for the lack of popularity of oral compositions which contain for example and in particular, CPC.

It is particularly preferred that precursor of the clay is a 1 :1 clay particle. Further preferably the precursor of the clay is kaolinite. It is particularly preferred that the antimicrobial quaternary ammonium compound is cetyl pyridinium chloride. It is further particularly preferred that when the precursor of the clay is kaolinite, the antimicrobial quaternary ammonium compound is cetyl pyridinium chloride.

It is particularly preferred that the use in accordance with the invention is for non- therapeutic purpose. More particularly it is for cosmetic purpose. When teeth develop stains owing to prolonged use of such compositions comprising in particular, cetylpyridinium chloride, it is not a pathological state, but rather a bodily condition which is cosmetic or aesthetic in nature.

The description of preferred features applies mutatis mutandis to the other aspects of the invention. Oral care compositions

It is preferred that the oral care composition is a toothpaste. Alternatively, the oral care composition is a mouthwash. Other known forms include toothpowder, chewing gums and lozenges, strips and gels.

It is preferred that when the oral care composition according to the invention is a toothpaste, the toothpaste comprises at least one of calcium-based abrasive or silica- based abrasive. Toothpastes are also known as dentifrices. The term "dentifrice" generally denotes formulations which are used to clean the surfaces of the oral cavity. The dentifrice is an oral composition that 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, the dentifrice 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. Preferably the dentifrice is in the form of a paste or a gel (or a combination thereof).

An oral care composition according to the invention will usually contain a liquid continuous phase in an amount of from 40 to 99% by weight based on the total weight of the dentifrice. Such a liquid continuous phase will typically comprise a mixture of water and polyhydric alcohol in various relative amounts, with the amount of water generally ranging from 10 to 45% by weight (based on the total weight of the dentifrice) and the amount of polyhydric alcohol generally ranging from 30 to 70% by weight (based on the total weight of the dentifrice).

Humectants are generally included in toothpastes for a soft, supple mouth feel.

Humectants also reduce the tendency of toothpastes to lose moisture. Preferred toothpaste compositions contain 3.5 to 40 wt% humectants. Further preferred compositions have 10 to 40 wt%, more particularly 10 to 20 wt% humectants. A particularly preferred humectant is sorbitol, generally available as 70% aqueous solution. Other preferred humectants include glycerine, maltitol and xylitol. More preferred toothpastes contain glycerine and sorbitol for a lubricated mouth feel, but their cumulative levels should not exceed the disclosed upper limit. Lower humectant content provides an effective way to reduce the cost of the product. Source of fluoride

The oral care compositions of the invention comprise a source of fluoride. Prerefably the source of fluoride is stannous fluoride, sodium fluoride, potassium fluoride, sodium monofluorophosphate, sodium fluorosilicate, ammonium fluorosilicate, amine fluoride, ammonium fluoride, and combinations thereof. Preferably the source of fluoride is a soluble fluoride salt that provides a source of fluoride ions. Any orally acceptable fluoride salt or combination of salts may be used. It is particularly preferred that the source is sodium monofluorophosphate.

Depending on the application, the toothpaste composition in accordance with the present invention may include free fluoride ion in a range of 1 ,000 to 20,000 ppm by weight of the composition. Preferably free fluoride ion concentration in a toothpaste composition for general consumer use would typically range from 1000 to 15000 ppm by weight of the composition. Source of fluoride is preferably added to the composition of the disclosed invention at a level of about 0.01 wt% to 10 wt%, more preferably 0.03 to 5 wt%, still more preferably 0.1 to 2 wt% and most preferably from 0.15 to 1wt% of the composition. The weight of the source of fluoride which is typically a fluoride salt, to provide the appropriate levels of the free fluoride ion will vary depending on the weight of the counter ion in the salt.

An oral care composition according to the invention will generally contain further ingredients to enhance performance and/or consumer acceptability such as abrasive cleaning agent, binder or thickening agent, and surfactant.

For example, a dentifrice will usually comprise an abrasive cleaning agent in an amount of from 3 to 75% by weight based on the total weight of the dentifrice. Suitable abrasive cleaning agents include silica xerogels, hydrogels and aerogels and precipitated particulate silicas; calcium carbonate, dicalcium phosphate, tricalcium phosphate, calcined alumina, sodium and potassium metaphosphate, sodium and potassium pyrophosphates, sodium trimetaphosphate, sodium hexametaphosphate, particulate hydroxyapatite and mixtures thereof. Examples of abrasives include abrasive amorphous silica particles which have a weight mean particle size (d50) ranging from 3 to 15 microns. Preferred abrasive amorphous silica particles for use in the composition of the invention have a weight mean particle size in the range 3 to 6 microns. Preferably, the abrasive amorphous silica particles employed are precipitated silica. Suitable precipitated silicas for use as abrasive amorphous silica particles in the invention are commercially available and include those marketed by PQ Corporation under the trade names SORBOSIL® AC 43, AC77, AC35 and SORBOSIL® AC 33. Mixtures of any of the above described materials may also be used. The level of abrasive amorphous silica particles (as defined above) generally ranges from 0.05 to 5%, preferably from 0.1 to 3%, more preferably from 0.2 to 0.8%, by total weight abrasive amorphous silica particles (as defined above) based on the total weight of the composition. Preferably the compositions of the invention comprise calcium-based abrasive. A particularly preferred abrasive is fine ground natural chalk (FGNC). It is obtained from limestone or marble. FGNC may also be modified chemically or physically by coating during or after milling by heat treatment. Typical coating materials include magnesium stearate and oleate. The morphology of FGNC may also be modified during the milling process by using different milling techniques, for example, ball milling, air-classifier milling or spiral jet milling. FGNC can be used as the sole calcium containing abrasive. However, FGNC can also be used with other calcium containing abrasives to balance the abrasion. Other preferred calcium containing abrasives include dicalcium phosphate (DCP), calcium pyrophosphate and precipitated calcium carbonate (PCC). When a

combination of Calcium containing abrasives is used, it is preferred that FGNC is 35 to 100 %, more preferably 75 to 100 % and especially from 95 to 100 % of the total abrasive. In such cases, the balance, most preferably, is PCC.

Furthermore, the compositions of the invention preferably comprise a binder or thickening agent in an amount of from 0.5 to 10% by weight based on the total weight of the dentifrice. Suitable binders or thickening agents include carboxyvinyl polymers (such as polyacrylic acids cross-linked with polyallyl sucrose or polyallyl

pentaerythritol), hydroxyethyl cellulose, hydroxypropyl cellulose, water soluble salts of cellulose ethers (such as sodium carboxymethyl cellulose and sodium carboxymethyl hydroxyethyl cellulose), natural gums (such as carrageenan, gum karaya, guar gum, xanthan gum, gum arabic, and gum tragacanth), finely divided silicas, hectorites, colloidal magnesium aluminium silicates and mixtures thereof. Furthermore, the compositions of the invention preferably comprise a surfactant in an amount of from 0.2 to 10% by weight based on the total weight of the dentifrice.

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

Smectite clay

It is preferred that oral care compositions of the invention include a smectite clay which is in addition to the clay present by way of the bipolar antimicrobial material. Smectites constitute a group in the class of natural aluminosilicate minerals known as

phyllosilicates or layered silicates. Preferred smectite clay is selected from

montmorillonites (bentonites, hectorites and derivatives thereof); purified aluminium magnesium silicates (various grades are commercially available as VEEGUM ^(R) from R. T. Vanderbilt Company); purified sodium magnesium silicates (commercially available as LAPONITE ^(R) in various grades); organically modified smectites including tetra alkyl and/or trialkyl ammonium smectites (organically modified montmorillonite clays) such as quaternium-18 bentonite, quaternium-18 hectorite, stearalkonium bentonite and stearalkonium hectorite/ and mixtures thereof. Aluminium magnesium silicate clays are particularly preferred. An example is VEEGUM ^(R) HV. The clay tends to swell when exposed to water. Preferred toothpaste compositions contain 0.2 to 3 wt percent clay. More preferred compositions include 0.5 to 1 wt percent clay.

The smectite clay not only plays a role in sensory profile as is believed, but it also plays a role in thickening the composition, as the reduced content of thickening silica otherwise leads to a product with lower viscosity. Oral care compositions of the invention further preferably comprise a zinc salt, preferably zinc sulphate or zinc chloride, more preferably zinc sulphate heptahydrate. Preferably the level of zinc salt is from 0.05 to 1.0 wt% of the total composition more preferably from 0.1 to 0.5 wt%.

Compositions of the invention may comprise a preservative, a preferred preservative is sodium benzoate.

Preferably the level of preservative is from 0.1 to 1 wt% of the total composition. It is preferred that pH of the composition at 20 °C is from 4 to 10, more preferably 7 to 9.

The compositions of the invention may also comprise a deposition aid. The term "deposition aid" in the context of this invention generally means a material which further aids deposition of whitening agents from the composition. An example is polystyrene sulphonates. Another example is Gantrez® polymers.

The term "mouthwash" generally denotes liquid formulations which are used to rinse the surfaces of the oral cavity and provide the user with a sensation of oral cleanliness and refreshment. The mouthwash is an oral composition that 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.

A mouthwash composition will usually contain an aqueous continuous phase. The amount of water generally ranges from 70 to 99% by weight based on the total weight of the mouthwash.

A mouthwash composition according to the invention will generally contain further ingredients to enhance performance and/or consumer acceptability, such as the humectants and surfactants mentioned above for dentifrices. The amount of humectant generally ranges from 5 to 20% by weight based on the total weight of the mouthwash and the amount of surfactant generally ranges from 0.1 to 5% by weight based on the total weight of the mouthwash.

Compositions of the present invention (such as in particular dentifrices or

mouthwashes) may also contain further optional ingredients customary in the art such as fluoride ion sources, anticalculus agents, buffers, flavouring agents, sweetening agents, colouring agents, opacifying agents, preservatives, antisensitivity agents and antimicrobial agents.

Use of the composition in the context of this invention typically involves application of the composition to the oral cavity, for a recommended time, before being expectorated. The preferred time application time being from 10 to 60 seconds.

Various examples illustrative of the invention are presented as follows and are no way to be considered as limiting the scope of the invention.

Examples

Example 1 : Remineralisation Experiment 1

A toothpaste composition as detailed in Table 1 was prepared. Table 1

^* The bipolar composite material contained kaolinite and cetyl pyridinuim chloride in an amount which made the final amount of CPC to 0.045 wt% by weight of the total toothpaste composition. D50 of the material was 0.5 μηη. The material was made in accordance with Example 1 of US2012/0177712 A1 (Unilever).

As cetyl pyridinium chloride (CPC) is highly unstable and prone to react with sodium lauryl sulphate, no experiments could be carried out in a composition which contained inter alia, CPC but not in the form of the bipolar composite material

The toothpaste composition (inventive) of Table 1 was subject to a test to determine its efficacy towards remineralisation of teeth. For comparison, a marketed chalk-based toothpaste containing fluoride and arginine was also subjected to the same test. Enamel specimens obtained from human permanent teeth were used as the hard tissue test substrate. The teeth were sorted and cleaned. Selection of the tooth for further processing was based on the quality of the enamel and whether the particular tooth surface had sufficient size to obtain a large enough specimen to meet the study requirements. Tooth sections with white spots, cracks and other defects were rejected. The tooth sections were cut into 3 x 3 mm specimens using a low-speed saw. The teeth were stored in thymol during the sample preparation process. The 3 x 3 mm specimens were ground and polished to create flat surfaces to facilitate surface micro hardness testing using a polishing unit. The bottom side of the specimens was ground flat to a uniform thickness with 500-grit silicone carbide grinding paper. The topside of the specimen was ground using 1200-grit paper until most of the tooth surface was flattened. The specimens were serially polished using 4000-grit paper followed by 1 mm diamond polishing suspension. Specimens had at least 0.3 mm of enamel thickness. The specimens were sonicated in de-ionized water between each grinding/polishing step. As a final cleaning step, the polished specimens were sonicated in 2 % microliquid. The specimens were assessed with a magnification of 10X. To be accepted for the study the specimens were required to: not have any obvious cracks or other flaws in the enamel surface; b) have an evenly polished, high gloss enamel surface; c) have no contamination on the top surface from sticky wax or any other material.

Each specimen was mounted on an acrylic plate using wax. The sides of each specimen were covered with a varnish so that only the enamel surface was exposed. On the enamel surface, a sound reference area of approximately 3 mm x 1 mm was created on the specimens using acid-resistant, clear nail varnish.

Eighteen specimens per group were used for this study. Each group was composed of 3 subgroups of 6 specimens.

Initial Acid Demineralization Lesions were created for this study by controlling the demineralization time. To create the lesions enamel specimens were demineralized for nine days. The demineralization solution had the following composition and properties: 0.1 M lactic acid, 4.1 mM Ca (as CaC * 2H ₂ 0), 8 mM P0 ₄ (as KH ₂ P0 ₄ ) and 0.2% w/v Carbopol® 907 (BF Goodrich Co., USA), pH adjusted to 5.0 using KOH. Demineralization was performed at 37 °C. After demineralization, specimens were rinsed with deionized water and stored at 100% relative humidity at 4 °C until use. QLF Measurements - Lesion Baseline

The extent of fluorescence loss in the lesions was determined using QLF. All specimens were air-dried for at least 30 minutes before QLF measurements were performed using the QLF-D Biluminator 2 (Inspektor Research, the Netherlands). The clear nail varnish used to protect the sound enamel reference area was not removed, renewed or otherwise altered prior to basline QLF measurements (figure). Acquired QLF images were analyzed using the dedicated QLF Analysis software. AFbase values were recorded and at a threshold level of 5%, i.e. a minimum of 5% fluorescence loss between sound (i.e. the sound enamel area covered by nail varnish) and uncovered demineralized enamel (i.e. the experimental window). The distance between the camera and the surface of the specimen was kept constant throughout the experiment to facilitate repeat measurements. Only specimens whose AFbase value was within the range of mean AFbase ± 2xSD of all specimens were accepted into the study. Specimens were then balanced into treatment groups using AFbase and mounted on the end of an acrylic rod (1/4" diameter x 2" long) using cyanoacrylate (superglue).

Treatment Phase Saliva Collection A 50:50 (7.5 ml human + 7.5 ml mineral mix) mixture of pooled, human saliva and a mineral solution (2.20 g/L Gastric Mucin, 0.381 g/L NaCI, 0.213 g/L CaCI2-2H20, 0.738 g/L KH2P04, 1.1 14 g/L KCI) was used as the remineralization medium in all treatment regimens. Wax-stimulated saliva was collected from at least five individuals, pooled and refrigerated until use. Saliva samples were then warmed to room temperature and thoroughly mixed prior to distribution into 30 ml treatment beakers. Fresh saliva/mineral mix was used each day (changed during the acid challenge period).

Treatment Regimen

The cyclic treatment regimen consisted of a 4 hours/day acid challenge in the lesion forming solution and four, one-minute treatment periods.

Each group was prepared by adding 5 g of the toothpaste to 10 ml of fresh saliva in a beaker with a magnetic stirrer. A fresh treatment for each subgroup was prepared just prior to each treatment. All treatments were stirred at 350 rpm. After the treatments, the specimens were rinsed with running deionized water. All specimens were then placed back into saliva. The remaining time (-20 hours) the specimens were in the saliva mixture, remineralization system. The regimen was repeated for 20 days. The treatment schedule for this experiment is given in the table below: On the first day, this treatment was not given; the test began with one hour in saliva to permit pellicle development prior to any treatments.

Fluoride Analysis

At the end of the 20 day treatment regimen, the fluoride content of each enamel specimen was determined using the microdrill technique to a depth of 100 μηη. The diameter of the drill hole was determined. The enamel powder from the drill hole was collected, dissolved (20μΙ of HCI0 ₄ , 40μΙ Citrate/EDTA Buffer and 40μΙ Dl water) and analyzed for fluoride by comparison to a similarly prepared standard curve. Fluoride data was calculated as μg F/cm3: ^g F X dilution factor - volume of drilling).

QLF Measurements

After the pH Cycling phase, the lesions were analyzed as described above using QLF after 20 days of pH cycling yielding AFpost. Changes in fluorescence loss was calculated as AAF = AFbase - AFpost (indicative of remineralization if parameter

< 0, or further demineralization if > 0). The mean, SD, and SEM of each parameter for each group was calculated. Statistical analysis of the data was performed with a t-test using Sigma Plot (12.0) Software. All analyses were done with the

significance level set at below 0.05. The data is summarised in Table 2.

Table 2

The data in Table 2 indicates clearly that the composition in accordance with the invention is much better than the marketed toothpaste. This data therefore indicates that the bipolar composite particle when used in an oral care composition further comprising a source of fluoride ions, indeed promotes remineralization of teeth as demonstrated by the observed AAF values. Example 2: Remineralisation and Demineralisation (Experiment 2)

In this example, the compositions of Table 3 were compared against each other. Only the Composition 1 was inside the invention. The observations are also summarised in Table 3. Demineralisation

Labial surfaces of sound bovine incisors were ground flat and polished with alumina slurry. Four sections were cut from each tooth, and test regions were created on the polished surfaces by painting the rest of the tooth section with acid-resistant nail varnish to provide the teeth sample for the study. Micro-hardness of the prepared teeth sample were analysed and recorded. The teeth sample were subsequently washed with copious amounts of Milli-Q water and thereafter subjected to a pH-cycling regime as follows:

First the teeth sample was immersed for five minutes in toothpaste slurry. The toothpaste slurry was prepared by mixing one part of toothpaste composition with three parts of deionised water having 10 UI/mL alkaline phosphatase.

Next the teeth sample was immersed for one hour in an acidic buffer. The acidic buffer was prepared by mixing 50 mmol/L acetic acid and 1.5 mmol/L KH2P04; pH5.0.

After this, the teeth sample was immersed for one minute in a neutral buffer. The neutral buffer was prepared by mixing 20 mmol/L HEPES and 1 .5 mmol/L KH2PO4; pH 7. This cycle was repeated 12 times.

Teeth sample was washed after each step to thoroughly rinse off the active agents from the previous steps. Efficacy was assessed by micro-hardness analysis of the teeth sample, before and after pH-cycling.

Four readings were taken for each teeth sample and demineralisation expressed as a percentage reduction in hardness Remineralisation

Labial surfaces of sound bovine incisors were ground flat and polished with alumina slurry. Four sections were cut from each tooth, and regions were created on the polished surfaces by painting the rest of the tooth section with acid-resistant nail varnish to provide the teeth sample for the study.

The teeth sample was demineralised for 10 days in a gel system prepared from equal parts of 8 percent methyl cellulose and lactic acid, at 37 degrees centigrade and a pH 4.6. After demineralisation. each teeth sample was indented in order to obtain the Hardness Knoop value of the teeth sample. After lesion preparation, teeth sample were subjected to a pH-cycling regime as follows: First the teeth sample was immersed for 5 minutes in toothpaste slurry. The toothpaste slurry was prepared by mixing 1 part of toothpaste composition with 3 parts of deionised water having 10 UI/mL alkaline phosphatase. Next the teeth sample was immersed for 30 minutes in an acidic buffer. The acidic buffer was prepared by mixing 50 mmol/L acetic acid, 1.5 mmol/L calcium chloride dihydrate, 0.9 mmol/L potassium dihydrogen orthophosphate and 130 mmol/L potassium chloride, pH 5.0).

Thereafter the teeth sample was immersed for 10 minutes in a neutral buffer.

The neutral buffer was prepared by mixing 20 mmol/L HEPES, 1 .5 mmol/L calcium chloride dihydrate, 0.9 mmol/L potassium dihydrogen orthophosphate and 130 mmol/L potassium chloride, pH 7.0). Efficacy was assessed by micro-hardness analysis of the teeth sample, before and after the pH-cycling regime as described above. Four readings were taken for each teeth sample and the remineralisation was expressed as a percent of hardness Knoop (Hardness Knoop = HK) restored, as follow:

%HK Restored = (ΔΗΚ / HK Baseline) X 100 where ΔΗΚ was calculated as HK after - HK before treatment Table 3

^* Refer Note under Table 1

The data in Table 3 corroborates the observation recorded in Table 2. It can be seen that the use of a bipolar composite material as disclosed herein, in an oral care composition further comprising at least one source of fluoride ions clearly promotes remineralization of teeth.