Technical Field of the Invention

The present invention relates to tooth remineralization and/or the treatment of tooth hypersensitivity. In particular, the present invention relates to an oral care composition comprising bioactive ceramics and dihydrogen phosphate salts. This invention also relates to the use of such compositions for remineralizing and/or reducing sensitivity of teeth of an individual.

Background of the Invention

Teeth comprise dentin overlaid with an outer layer of enamel. Teeth are under constant attack from chemical and physical forces, including bacteria-derived acids and mechanical wear, resulting in demineralization and weakening of enamel and the underlying dentin.

Tooth hypersensitivity is a temporary induced pain sensation that affects up to 20% of the adult population. It is associated with tooth demineralization and the loss of either enamel or cementum to expose underlying dentin. The dentin of the tooth generally contains channels, called tubules, which provide for an osmotic flow between the inner pulp region of the tooth and the outer root surfaces. The cause of tooth hypersensitivity may be related to demineralization giving rise to increased exposure of tubules and permeability of the dentine. The most common causes of demineralization of the enamel or dentine are attrition, abrasion, gingival recession and erosion. When root surfaces are exposed, dentinal tubules are also exposed.

The currently accepted theory for tooth hypersensitivity is the hydrodynamic theory, based on the belief that open exposed dentinal tubules allow fluid flow through the tubules. This flow excites the nerve endings in the dental pulp. Clinical replica of sensitive teeth viewed in a SEM (scanning electron microscopy) reveal varying numbers of open or partially occluded dentinal tubules.

Efforts have been made over the years to treat tooth hypersensitivity. One approach is to reduce the excitability of the nerve in a sensitive tooth by using “nerve-depolarising agents” comprising strontium ions, potassium salts such as potassium nitrate, potassium bicarbonate, potassium chloride and the like. These nerve-depolarising agents function by interfering with neural transduction of the pain stimulus to make the nerve less sensitive.

Another approach is to use “tubule blocking agents” that fully or partially occlude tubules such as polystyrene beads, apatite, polyacrylic acid, mineral hectorite clay and the like. These tubule blocking agents function by physically blocking the exposed ends of the dentinal tubules, thereby reducing dentinal fluid movement and reducing the irritation associated with the shear stress described by the hydrodynamic theory.

Bioactive ceramics are used in bone repair applications and are being developed for tissue engineering applications. Such materials are called “bioactive” because interfacial bonds form between the material and surrounding tissues. For example, Ca-P ceramics, typically, hydroxyapatite (HAP) and b-tricalcium phosphate (b-TCP) ceramics are widely used for bone tissue replacement and regeneration due to their generally good biocompatibility and similar chemical composition with biological apatite in bone tissues. Other elements like magnesium (Mg) or silicon (Si) have been incorporated into Ca-P bioactive ceramics to enhance their bioactivity.

CN 1623952 A (Shanghai Institute of Ceramics, Chinese Academy of Sciences) discloses a preparation method and use of bredigite (Ca7MgSi4O16). The bioactive ceramic can be used as bone hard tissue repair and implant materials.

CN 102584203 A (Shanghai Institute of Ceramics, Chinese Academy of Sciences) discloses a preparation method of a bioactive ceramic material nagelschmidtite (Ca ₇ Si ₂ P ₂ O ₁₆ ) that can support adherence and proliferation of bone marrow stromal cells. Compared with traditional b-tricalcium phosphate ceramics, the bioactive ceramic can better promote osteogenic differentiation of the bone marrow stromal cells and has higher degradability.

A publication (C.Wu, J. Chang, W. Zhai, S. Ni, “A novel bioactive porous bredigite (Ca7MgSi4O16) scaffold with biomimetic apatite layer for bone tissue engineering”, J Mater Sci Mater Med, 2007, 18, pp. 857-864) discloses a novel bioactive, degradable and cytocompatible bredigite (Ca7MgSi4O16) scaffold with biomimetic apatite layer for bone tissue engineering. An oral care composition typically has a pH ranging from 5.5 to 10.0, more preferably from 6.0 to 10.0, which helps maintain a healthy mouth and protect the teeth. A lower pH may induce the enamel to demineralize and a higher pH may cause mucosa irritation. But a composition comprising bioactive ceramics usually has a pH too high to be used in mouth.

The present inventors have now found unexpectedly that bioactive ceramics or compositions comprising bioactive ceramics can be used to treat tooth hypersensitivity by occluding the open dentinal tubules and to remineralize teeth by rebuilding the enamel layer. The present inventors have further found that the pH of the oral care composition comprising bioactive ceramics can be reduced by incorporation of dihydrogen phosphate salts while the composition still maintains excellent tooth remineralization efficacy and/or tubule blockage efficacy to reduce tooth sensitivity. Besides, it has been further found that such compositions can provide enhanced tubule blockage efficacy when incorporate additional soluble calcium source.

Tests 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.

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.

Refractive Index

Refractive index is quoted at a temperature of 25°C and a wavelength of 589 nm. pH 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” for the purpose of the present invention means the solubility of a source (e.g., like calcium salts) 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.4 and at a speed of 5 rpm. Values are quoted in centipoises (cP=mPa.s) unless otherwise specified.

Remineralization

“Remineralization” for the purpose of the present invention means in situ (i.e. in the oral cavity) generation of calcium phosphate on teeth (including layers on teeth from 10 nm to 20 microns, and preferably from 75 nm to 10 microns, and most preferably, from 150 nm to 5 microns thick including all ranges subsumed therein) to reduce the likelihood of tooth sensitivity, tooth decay, regenerate enamel and/or improve the appearance of teeth by whitening through the generation of such new calcium phosphate.

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) a bioactive ceramic; b) a dihydrogen phosphate salt; and c) a physiologically acceptable carrier; wherein the bioactive ceramic is a Ca, Si and P-containing ceramic and wherein the pH of the composition ranges from 5.5 to 10.0.

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 for remineralizing and/or reducing sensitivity of 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 an individual. The method is preferably for non-therapeutic benefits. In a fourth aspect, the present invention is directed to non-therapeutic use of the oral care composition of any embodiment of the first aspect for remineralizing and/or reducing sensitivity of teeth of an individual.

In a fifth aspect, the present invention is directed to use of the oral care composition of any embodiment of the first aspect in the manufacture of a medicament in remineralizing and/or reducing sensitivity of an individual.

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

Detailed Description

Bioactive materials usually include ceramics, glasses and glass-ceramics, which can attach directly to bone tissue via a biologically active carbohydroxyapaptite layer that provides the interfacial bonding. Bioactive glasses have an amorphous structure, whereas glass-ceramics are crystallized glasses, consisting of a composite of a crystalline phase and a residual glassy phase. Bioactive ceramics have a fully crystalline structure.

Bioactive ceramics are an important subset of bioactive materials. Bioactive ceramics range in biocompatibility from the ceramic oxides, which are inert in the body, to the other extreme of resorbable materials, which are eventually replaced by the body after they have assisted repair.

It is reported that Si is located at active calcification sites in the bones and directly involves the mineralization process of bone growth. Due to its significant function in human bones, Si has been widely incorporated into calcium-phosphate based bioactive ceramics to enhance their bioactivity. Mg is also one of the most important elements in the human body which is closely associated with mineralization of calcined tissues and indirectly influences mineral metabolism. Bioactive ceramics, as used herein, refers to ceramic materials comprising calcium oxide (CaO), silicon dioxide (SiO ₂ ), magnesium oxide (MgO) or phosphorous oxide (P ₂ O ₅ ) which possess good biocompatibility and bioactivity. The bioactive ceramic suitable for use in this invention is Ca, Si, and P-containing ceramic. Illustrative yet non-limiting examples of the bioactive ceramic that may be used in this invention include, for example, nagelschmidtite (Ca7Si2P2O16), silicocarnotite (Ca ₅ SiP ₂ 01 ₂ ), mixtures thereof or the like. Particularly preferred is nagelschmidtite (Ca ₇ Si ₂ P ₂ 0 ₁₆ ). The bioactive ceramic may further comprise one or more elements selected from Zn, Cu, Sn, Na, Li, K, B, Sr, Ti, Al, N, Ag or F.

Bioactive ceramics are typically made by sol-gel process. Suitable preparation methods for bioactive ceramics are described, for example, in C. Wu, W. Fan, Jiang. C, M. Zhang, Y. Xiao, J. Am. Ceram. Soc., 2013, 96, 3, pp. 928-934, C.Wu, J. Chang, W. Zhai, S. Ni, J Mater Sci” Mater Med, 2007, 18, pp. 857-864, and W. Lu, W. Duan, Y. Guo, C. Ning, J Biomater. AppL, 2012, 26, pp. 637-650.

It is preferable that the bioactive ceramic is particulate which allows for maximum surface area for contact with dental tissue. Preferably the bioactive ceramic used in this invention has a particle size from 100 nm to 50 microns, preferably from 500 nm to 30 microns, more preferably from 700nm to 20 microns, most preferably from 1 micron to 15 microns.

A composition comprising the bioactive ceramic as described above is also included in the present invention. Preferably, the composition is an oral care composition. Typically, the oral care composition comprises from 0.1 to 80% by weight of the bioactive ceramic, more preferably from 0.2 to 50% and most preferably from 1 to 30%, based on total weight of the oral care composition and including all ranges subsumed therein.

To help maintain a healthy mouth and protect the teeth, an oral care composition typically has a pH ranging from 5.5 to 10.0, more preferably from 6.0 to 10.0. To obtain a pH within the acceptable range, dihydrogen phosphate salts are included in the oral care composition.

The dihydrogen phosphate salt that may be used in this invention is limited only to the extent that the same may be used in a composition suitable for use in the mouth. Illustrative examples of the phosphate source suitable for use in this invention include calcium dihydrogen phosphate, sodium dihydrogen phosphate, potassium dihydrogen phosphate, ammonium dihydrogen phosphate, mixtures thereof or the like. In a preferred embodiment, the phosphate source is calcium dihydrogen phosphate, sodium dihydrogen phosphate or mixtures thereof.

The dihydrogen phosphate salt is typically present in an amount of from 0.1 to 20%, more preferably from 0.2 to 15%, more preferably still from 0.5 to 10% and most preferably from 1 to 5%, based on total weight of the oral care composition and including all ranges subsumed therein.

The oral care composition preferably comprises the bioactive ceramic and the dihydrogen phosphate salt in a weight ratio from 1:5 to 20:1, more preferably from 1:3 to 15:1, most preferably from 1:1 to 10:1.

The oral care composition may further comprise a soluble calcium source which provides plenty of calcium ions in the mouth that may enhance the efficacy of tooth remineralization and/or dentinal tubule blockage. The soluble calcium source suitable for use in this invention is limited only to the extent that the same may be used in the mouth. Typical soluble calcium source includes, but not limited to, calcium chloride, calcium nitrate, calcium acetate, calcium lactate, calcium gluconate, calcium formate, calcium malate, calcium propionate, calcium butyrate, calcium bicarbonate, calcium glycerophosphate, calcium ascorbate, mixtures thereof or the like. In a preferred embodiment, the calcium source is calcium chloride, calcium nitrate or mixtures thereof.

The oral care composition of the present invention preferably comprises from 0.1 to 20% by weight of the soluble calcium source, more preferably from 0.5 to 15% and most preferably from 1 to 10%, based on total weight of the oral care composition and including all ranges subsumed therein.

The oral care composition preferably comprises the bioactive ceramic and the soluble calcium source in a weight ratio from 1:5 to 20:1, more preferably from 1:3 to 10:1, most preferably from 1:1 to 10:1.

The oral care composition may comprise other phosphate source in addition to the dihydrogen phosphate salt which is included in the composition. Non-limiting examples of other phosphate source includes trisodium phosphate, disodium hydrogen phosphate, ammonium phosphate, diammonium hydrogen phosphate, tripotassium phosphate, dipotassium hydrogen phosphate, mixtures thereof or the like.

If other phosphate source is present, it is preferable that the dihydrogen phosphate salt is at least 75% by weight of the phosphate source in the composition, more preferably from 80 to 100%, and most preferably from 95 to 100%, based on total weight of the phosphate source in the composition.

The oral care composition of the present invention 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 Ci ₈ 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 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.

In another 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.

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 60% by weight of the composition, based on total weight of the composition and including all ranges subsumed therein.

The oral care composition may further comprise benefit agents that are typically delivered to human teeth and/or the oral cavity including the gums to enhance or improve a characteristic of those dental tissues. The benefit agents are present in the oral care composition in addition to the bioactive ceramic and the dihydrogen phosphate salt that are included in the composition.

Typically the benefit agent is selected from optical agents, biomineralization agents, adsorbing agents, anti-microbial agents, gum health agents, desensitizing agents, anti calculus agents, freshness agents and mixtures thereof.

Optical agents may be selected from one or more of whitening agents and pearlescent agents. When the optical agent is a whitening agent, it is preferable that the whitening agent is a particulate whitening agent having a refractive index of from 1.9 to 4.0. 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), zirconium (Zr) or a mixture thereof. Preferably, the metal compound is (or at least comprises) a metal oxide such as titanium dioxide (TiO ₂ ), zinc oxide (ZnO), zirconium dioxide (ZrO2) or a mixture thereof. Preferably, the particulate whitening agent is a 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. Particularly suitable core materials are metal compounds and preferred are compounds where the metal is selected from zinc (Zn), titanium (Ti), zirconium (Zr) or a mixture thereof. Preferably, the metal compound is (or at least comprises) a metal oxide such as titanium dioxide (TiO ₂ ), zinc oxide (ZnO), zirconium dioxide (Zr0 ₂ ) or a mixture thereof. The second component coating comprises material suitable to adhere to tooth enamel, dentin or both. Typically the coating material comprises the element calcium, and optionally, other metals like potassium, sodium, aluminium, magnesium as well as mixtures thereof whereby such optional metals are provided as, for example, sulphates, lactates, oxides, carbonates or silicates. Optionally, the coating material may be aluminium oxide or silica. In a preferred embodiment, the second component coating can comprise, for example, calcium phosphate, calcium gluconate, calcium oxide, calcium lactate, calcium carbonate, calcium hydroxide, calcium sulphate, calcium carboxymethyl cellulose, calcium alginate, calcium salts of citric acid, calcium silicate, mixture thereof or the like. Calcium silicate is particularly preferred. In an especially preferred embodiment, the particulate whitening agent is titanium dioxide coated with calcium silicate.

In another preferred embodiment, the whitening agent is a dye or a pigment or a combination of the two. 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. Preferred pigment or dye for use in the present invention is violet or blue having a hue angle, h, in the CIELAB system of from 220 to 320 degrees, preferably from 250 to 290 degrees. When the whitening agent is a pigment, it is preferable that the pigment is violet or blue selected from one or more of those listed in the Colour Index International as pigment blue 1 through to pigment blue 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. A preferred class of blue pigments suitable for use in the invention are organic blue pigments such as phthalocyanine blue pigments. It is especially preferred that the pigment is phthalocyanine blue pigment selected from alpha copper phthalocyanines Pigment Blue 15, Pigment Blue 15:1, Pigment Blue 15:2,

Pigment Blue 15:3, Pigment Blue 15:4, Pigment Blue 15:6 and mixtures thereof. Most preferably the pigment is Pigment Blue 15:1. A commercially available example is Cosmenyl Blue A4R from Clariant. When the whitening agent is a dye, it is preferable that the dye is a blue dye, more preferably FD&C Blue 1 or Patent Blue V. In another preferred embodiment, the optical agent is a pearlescent agent. The term “pearlescent”, as used herein, means an agent in the form of particles which reflects and partially transmits the incident light. Suitable pearlescent agent for use in the present invention includes mica, bismuth oxychloride or mixtures thereof. Preferably the pearlescent agent is formed by coating one or more metal oxide layers onto natural or synthetic mica flakes. Examples of suitable mica include, for example, muscovite, phlogopite, fluorophlogopite, biotite or mixtures thereof. Examples of suitable metal oxides include, for example, Ti0 ₂ , Fe ₂ O3, TiFe ₂ O5, Fe ₃ O4, Cr ₂ O3, AI ₂ O3, Si0 ₂ , Zr0 ₂ , ZnO, SnO ₂ , CoO, C03O4, VO ₂ , V ₂ O ₃ , Sn(Sb)0 ₂ , titanium suboxides or mixtures thereof. One example of a preferred pearlescent agent is mica coated with Ti0 ₂ .

Biomineralization agents for tooth enamel remineralization may be selected from one or more of fluoride sources, biomolecules, proteinaceous materials, amorphous calcium phosphate, a-tricalcium phosphate, b-tricalcium phosphate, calcium silicate, calcium sulfate, calcium carbonate, calcium deficient hydroxyapatite

Caio-x(HP0 ₄ )x(PO ₄ ) ₆ -x(OH) ₂ -x, 0 £ x < 1), dicalcium phosphate (CaHPO4), dicalcium phosphate dihydrate (CaHPO ₄ -2H ₂ 0), hydroxyapatite (Ca10(PO4)6(OH) ₂ ), monocalcium phosphate monohydrate (Ca(H ₂ P0 ₄ ) ₂ H ₂ 0), octacalcium phosphate (Ca ₈ H ₂ (PO ₄ ) ₆ -5H ₂ 0) and tetracalcium phosphate (Ca ₄ (PO ₄ ) ₂ 0).

Adsorbing agents may be selected from one or more of boron nitride, porous silica, charcoal, layered silicate (e.g. montmorillonite, kaoline, clay), graphene and polymethyl methacrylate microsphere.

Anti-microbial agents may be selected from one or more of metal salts where the metal is selected from zinc, copper, silver or a mixture thereof, triclosan, triclosan monophosphate, triclocarban, curcumin, quaternary ammonium compounds, bisbiguanides and long chain tertiary amines, preferably zinc salts including zinc oxide, zinc chloride, zinc acetate, zinc ascorbate, zinc sulphate, zinc nitrate, zinc citrate, zinc lactate, zinc peroxide, zinc fluoride, zinc ammonium sulfate, zinc bromide, zinc iodide, zinc gluconate, zinc tartarate, zinc succinate, zinc formate, zinc phenol sulfonate, zinc salicylate, zinc glycerophosphate or a mixture thereof. Desensitizing agents may be selected from one or more of potassium citrate, potassium chloride, potassium tartrate, potassium bicarbonate, potassium oxalate, potassium nitrate and strontium salts.

Anti-calculus agents may be selected from one or more of alkali-metal pyrophosphates, hypophosphite-containing polymers, organic phosphonates and phosphocitrates.

Gum health agents may be selected from one or more of anti-inflammatory agents such as ibuprofen, flurbiprofen, aspirin and indomethacin, plaque buffers, biomolecules, proteinaceous materials, vitamins such as Vitamins A,C and E, plant extracts and curcumin.

Freshness agents may be flavours selected from one or more of peppermint, spearmint, menthol, flora oil, clove oil and citrus oil.

The benefit agent is preferably selected from optical agents, biomineralization agents and mixtures thereof. In an especially preferred embodiment, the benefit agent is an optical agent, especially a whitening agent.

The oral care composition of the present invention may comprise a single benefit agent or a mixture of two or more benefit agents. Typically, the benefit agent is present in an amount from 0.1 to 60%, and more preferably, from 0.3 to 40%, and most preferably from 0.5 to 30% by total weight of the oral care composition and including all ranges subsumed therein.

The oral care composition may further comprise abrasives. Preferred abrasives include silicas, aluminas, calcium carbonates, dicalcium phosphates, calcium pyrophosphates, hydroxyapatites, trimetaphosphates, insoluble hexametaphosphates or mixtures thereof, including agglomerated particulate abrasives. Calcium carbonate and silica are particularly preferred, especially silica. The abrasives may be present in the range of from 0.01 to 60%, more preferably from 0.1 to 30%, and most preferably from 1 to 15% by weight of the oral care 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. These ingredients include preservatives, pH-adjusting agents, sweetening agents, 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 for remineralizing and/or reducing sensitivity of teeth of an individual. Preferably, the method is non- therapeutic. The oral care composition of this invention may additionally be used for remineralizing and/or reducing sensitivity of teeth of an individual and/or used in the manufacture of a medicament in remineralizing and/or reducing sensitivity of an individual. Preferably, the use is non-therapeutic.

The oral care composition may be in any form common in the art, preferred forms are tooth pastes, gels, mouthwashes and whitening serums. 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. 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 was conducted to investigate pH and the blockage of dentinal tubules by using bioactive ceramic in combination with dihydrogen phosphate salts. All ingredients are expressed by weight percent of the total formulation and as level of active ingredient

TABLE 1 a

Methods pH Measurement 5 g sample was mixed with 20 ml_ de-ionised (Dl) for 30 seconds, and then immediately testing the pH with indicator or a pH meter within 3 mins. Brushing Protocol

To evaluate the blockage efficacy of dentinal tubules, the test sample was mixed with water at a ratio of 1 g to 2 mL water to make a slurry.

Human dentine discs were eroded by 6% citric acid for 2 mins, then they were treated with different slurries via brushing following the same protocol. Fourteen human dentine discs were separated into seven groups (n=2). The dentine discs were brushed with the slurry under a tooth brushing machine equipped with toothbrushes. The load of the tooth brushing was 170 g +/-5 g and the automatic brushing operated at a speed of 150 rpm. After brushing for 1 min, the dentine discs were soaked in toothpaste slurry for 1 min. Then the dentine discs were placed in 50 mL Dl water and agitated on a flatbed shaker at 150 rpm for 10 strokes. The discs were then soaked in simulated oral fluid (SOF) for at least 6 hours under the condition of a shaking water bath at 37°C and 60.0 rpm. After that, the dentine discs were brushed with the slurry by machine using the same procedure as in the first step. The brushing was repeated twice for one day, then the dentine discs were kept in SOF overnight (>12 hours) in a shaking water bath at 37°C to mimic oral environment. The dentine samples were characterized by scanning electron microscopy (SEM, Hitachi S-4800, Japan) after two days of brushing.

Simulated oral fluid was made by combining the ingredients in Table 2:

TABLE 2

Scoring Standard for Tubules Blockage

Regardless of the original shape of the dentine discs, a square (with a size of 4mm x 4mm) is selected and one image is captured under 50x magnification. Within this square, five spots (each with a size of 150 mm x 150 mm, one in the middle, and one in every corner) are selected and observed under 1000x magnification. The blockage of tubules is accessed following the standards described in Table 3. The measurement is carried out for the two dentine discs of each test group.

TABLE 3

Results pH values of the samples were measured after fresh preparation. The values were reported in Table 4.

TABLE 4

An oral care composition with a pH range from 5.5 to 10.0 is taken as acceptable. The results showed that samples 2 to 5 comprising dihydrogen phosphate salts had a pH value within the acceptable range while samples 6 and 7 comprising monohydrogen phosphate salts had a pH outside the acceptable range.

After two days of brushing, SEM images of the dentine discs were taken. The images were analyzed and scored. The results were reported in Table 5 (error represents standard error for duplicate measurements). TABLE 5 Sample 1 comprising only bioactive ceramics was used as control. The results showed that samples 3 and 5 comprising additional soluble calcium source like calcium chloride had much better tubule blockage efficacy compared to other samples.