FORM - 2 THE PATENTS ACT, 1970 (39 of 1970) & The Patents Rules, 2003 COMPLETE SPECIFICATION (See Section 10 and Rule 13) ORAL CARE PRODUCT HINDUSTAN UNILEVER LIMITED, a company incorporated under the Indian Companies Act, 1913 and having its registered office at 165/166, Backbay Reclamation, Mumbai -400 020, Maharashtra, India The following specification particularly describes the invention and the manner in which it is to be performed - 1 - ORAL CARE PRODUCT The present invention relates to an oral care product suitable for maintaining and/or enhancing the quality of 5 teeth. The product comprises an insoluble whitening agent and a dual composition delivery system for said whitening agent. The enamel layer of the tooth is naturally an opaque white 10 or slightly off-white colour; however, this enamel layer can become stained or discoloured. The enamel layer of the tooth is composed of hydroxyapatite mineral crystals that create a somewhat porous surface. It is believed that this porous nature of the enamel layer allows staining agents and 15 discolouring substances to permeate the enamel and discolour the tooth. Many substances can stain or reduce the whiteness of one's teeth; in particular, certain foods, tobacco products, and 20 fluids such as tea and coffee. These staining and discolouring substances are often able to permeate the enamel layer. This problem occurs gradually over many years, but imparts a noticeable discoloration of the enamel of one's teeth. 25 A variety of products are currently used for teeth whitening. Such products often comprise a peroxide compound (alone or on combination with enzymes). Such products may be used in the form of strips. Such products generally have 30 to be removed after a well defined time, the peroxide causing damage to the teeth and/or gums if left too long. A - 2 - particular problem with peroxide (and toothpastes comprising abrasive cleaners) is that it can roughen the surface of the teeth. 5 Certain prior art treatments are known to lead to the production of hydroxyapatite on the tooth surface. US 5,605,675 (Enamelon, 1997) discloses a process for remineralisation of dental enamel by application of a two-10 phase composition; one phase containing a water-soluble calcium compound and one phase containing a water soluble inorganic phosphate and a water-soluble fluorine compound. US 4,083,955 (F&G, 1978) discloses a process for 15 remineralisation of dental enamel by sequential application of two compositions, the first comprising calcium ions and second comprising phosphate ions, or vice versa. WO 04/017929 (Septodont ou Specialites Sepodont S.A., 2004) 20 discloses a preparation containing: an aqueous liquid part, a solid part comprising at least one silicate selected from tricalcium silicate and dicalcium silicate; calcium chloride and a water reducing agent, to be used to restore a mineralised substance, particularly in the dental field. 25 An object of the present invention is to deliver an insoluble whitening agent to the surface of the teeth, whilst simultaneously enabling the production of hydroxyapatite on the surface the teeth. - 3 - The present invention involves delivering a source of calcium ions to the surface of the teeth and ultimately converting the calcium ions into hydroxyapatite in situ by the simultaneous or sequential application of a source of 5 phosphate ions. The source of calcium ions and the source of phosphates ions are delivered from independent phases and their ability to interact prematurely is thereby minimised. The in situ generation of hydroxyapatite results in the 10 remineralisation of the teeth, potentially reducing the likelihood of tooth decay and improving the appearance of the teeth, in particular their whiteness, adding to the whitening effect produced by the deposition of the whitening agent. The teeth may also appear smoother and shinier as a 15 result. Since many "whitening" treatments result in a roughening of the tooth surface, the ability to whiten and yet reduce surface roughness is a particular benefit of the present invention. 20 The benefits delivered by the present invention are principally targeting at the enamel; however, it is also expected that any exposed dentin may also be beneficially affected. 25 In a first aspect of the present invention, there is provided an oral care product comprising a source of calcium ions, a source of phosphate ions, and an insoluble whitening agent for deposition onto the teeth, characterised in that the source of calcium ions and the source of phosphate ions 30 are physically separate prior to the use of the product. - 4 - In a second aspect of the present invention, there is provided a method of delivering an insoluble whitening agent to the teeth, said method comprising the application of the insoluble whitening agent in combination with a source or 5 calcium ions and a source of phosphate ions, characterised in that the source of calcium ions and the source of phosphate ions are applied from physically separate compositions. 10 In a third aspect of the present invention, there is provided a product according to the first aspect of the invention for use as a medicament. In a fourth aspect of the present invention, there is 15 provided the use of: 1. a source of calcium ions; 2. a physically independent source of phosphate ions, and 3. an insoluble whitening agent for deposition onto the teeth, 20 in the manufacture of an oral care product for use to improve tooth whiteness, and/or reduce tooth decay, and/or reduce sensitivity. Products according to the invention comprises an insoluble 25 whitening agent and a dual delivery system, said dual delivery system typically comprising a first composition comprising a source of calcium ions and second composition comprising a source of phosphate ions. 30 The insoluble whitening agent functions by being deposited onto the teeth and thereby changing their appearance. It is - 5 - believed that the deposition onto the teeth is aided by the dual delivery system, i.e. the application of calcium ions and phosphate ions from independent sources. Any insoluble whitening agent that functions in the above manner may be 5 used. Suitable insoluble whitening agents are particulate solids. They may comprise white particles or they may comprise blue particles; blue particles giving the teeth the appearance of 10 increased whiteness by decreasing the "yellowness" (b*) of the teeth. The insoluble whitening agent has been found to work synergistically with the dual delivery system to deliver enhanced whitening benefits. 15 ^Insoluble whitening particles" are insoluble in water at temperatures typically found in the oral cavity. Insoluble whitening particles typically have a solubility of less than 0.01 mol/L at 25°C. 20 The insoluble whitening particles preferably have an average particle size of from 200 nm to 300 nm, more preferably from 220 nm to 280 nm, and most preferably from 245 nm to 265 nm. Such particle sizes are preferred because they give the strongest light scattering of blue light (wavelength ca. 450 25 nm) and, as a result, the best whitening performance. Average particle size is on a number basis and may be calculated from image analysis of Scanning Electron Microscope (SEM) images taken in Secondary Electron Image (SEI) mode. - 6 - Insoluble whitening particles are preferably incorporated in the composition of which they are part at a level of from 0.01% to 5% and more preferably at from 0.03% to 2.5% by weight. 5 Insoluble whitening particles that are white particles are preferred, in particular titanium dioxide and zinc oxide. When used, such particles are preferably incorporated in the composition of which they are part at a level of from 0.1% 10 to 5%, more preferably 0.25% to 3% by weight, and most preferably at from 0.5 to 2.5% by weight. In the context of this invention, blue particles have a hue angle, h, in the CIELAB system of from 220 to 320 degrees, 15 preferably from 250 and 290 degrees. When used, such particles are preferably incorporated in the composition of which they are part at a level of from 0.01% to 0.3%, more preferably 0.02% to 0.1% by weight, and most preferably at from 0.03 to 0.08% by weight. The blue particles are blue 20 pigments, preferably Pigment Blue 15; more preferably Pigment Blue 15:1, 15:2, 15:3, 15:4, 15:5 or 15:6; most preferably Pigment Blue 15:1. A preferred source of calcium ions is an insoluble calcium 25 salt. In embodiments using such a source of calcium ions, it is believed that calcium is deposited onto the teeth before any premature interaction with phosphate in the saliva of the oral cavity csn occur. Having deposited on the tooth enamel and/or dentin, slow reaction with the 30 phosphate present in the saliva and, importantly, that added with the second composition, results in hydroxyapatite being - 7 - produced exactly where it is required and aiding the deposition of the insoluble whitening agent. Suitable insoluble calcium salts may be any salt capable of 5 delivery to the surface of the teeth when the composition is applied, other than a calcium phosphate, which is not a source of calcium ions in. accordance with this invention. Hence, calcium salts such as hydroxyapatite and fluoroapatite are not suitable insoluble calcium salts. ]0 A preferred insoluble calcium salt is calcium silicate (CS), present as the composite material calcium oxide-silica: CaO-Si02. The use of this insoluble calcium salt is preferred because of its excellent conversion to hydroxyapatite on the 15 tooth surface. Without wishing to be bound by theory, it is believed that the CS reacts with phosphate ions to form a calcium silicate-phosphate cement (CSPC) and that this material bonds strongly to the teeth and then gradually transforms into hydroxyapatite on the tooth surface. It is 20 believed that the high affinity of the CSPC for the tooth surface underlies the superior remineralisation and whitening benefits obtained. When CS is employed, its ratio of calcium to silicon (Ca:Si) 25 may be from 1:10 to 3:1. The Ca:Si ratio is preferably from 1:5 to 2:1, more preferably from 1:3 to 1:1, and most preferably it is about 1:2. The CS may comprise mono-calcium silicate, bi-calcium silicate, or tri-calcium silicate. Higher ratios of calcium to silicate are 30 preferred because such ratios are believed to enhance active bonding to the tooth surface and subsequent transformation - 8 - into hydroxyapatite; however, lower ratios axe preferred for ease of obtaining the desired pH {vide infra). Throughout this specification, ratios of calcium to silicon 5 (Ca:Si) should be understood to be atom ratios. Preferably, the insoluble calcium salt is a "biomaterial", by which is meant a material that is capable of bonding to human and/or animal tissue. It is especially preferred that 10 the biomaterial is able to bond to tooth enamel and/or tooth dentin. "Insoluble calcium salts" are insoluble in water at temperatures typically found in the oral cavity. Insoluble 15 calcium salts typically have a solubility of less than 0.01 mol/L at 25°C. Suitable insoluble calcium salts may be in a crystalline or amorphous state; preferably it is in an amorphous state; 20 more preferably it is in a mesoporous state, i.e. it is a material having pores with diameters from 1 to 50 microns. Mesoporous calcium silicate is particularly preferred and is abbreviated as MCS in this specification. 25 In one aspect of the invention, there is present MCS having an average pore size (diameter) of preferably from 0.4 to 4 nm, more preferably from 0.4 to 3.5 nm, and most preferably from 0.4 to 3 nm. 30 In another aspect of the invention, there is present MCS having an average pore size (diameter) of preferably from 2 - 9 - to 4 nm, more preferably from 2 to 3.5 run, and most preferably from 2 to 3 nm. In a further aspect of the invention, there is present MCS 5 having an average pore size (diameter) of preferably from 1 to 2.7 nm and more preferably from 1.35 to 2.45 nm. The pore size may be measured using any suitable method or means. For example, the pore size may be measured using BET 10 nitrogen sorption or mercury porosimetry techniques (particularly BET nitrogen sorption techniques). The content of the source of calcium ions is typically from 0.05 to 25%, particularly from 0.5 to 15%, and especially 15 from 2.5 to 10% by weight of the all the formulation components of the product as to be applied to the teeth. In terms of the specific composition of which it forms a part, the source of calcium ions is typically present at from 0.1 to 50%, particularly from 1 to 30%, and especially from 5 to 20 20% by weight. Preferably, the source of calcium ions is present in a composition that is substantially free of phosphate ions. By the term "substantially free" we mean that relative to 25 the weight of the calcium ions, the amount of phosphate ions is less than 2.5%, particularly less than 1%, more particularly less than 0.1%, and especially less than 0.01% by weight. It is possible to prepare calcium oxide-silica containing less than 0.005% by weight of phosphate ions by 30 using high purity starting materials, for example using calcium nitride supplied by China National Pharmaceutical - 10 - Group Corporation (SINOPHARM) , Beijing, which has a purity of greater than 99%. Preferably, the source of calcium ions is present in a 5 composition that is substantially free of fluoride ions. By the term "substantially free" we mean that relative to the weight of the calcium in the insoluble calcium salt, the amount of fluoride ions is less than 2.5%, particularly less than 1%, more particularly less than 0.1%, and especially 10 less than 0.01% by weight. Calcium silicate suitable for use in the present invention may be prepared by the methods described in our co-pending application PCT/EP2007/057556. 15 The source of calcium ions is preferably present in a composition having a pH of from 7 to 11, more preferably from 8 to 10.5, and most preferably from 9 to 10. Such compositions preferably comprise an acidic buffering, such 20 as citric acid. Such agents enable the composition to be formulated at the desired pH and are particularly desirably at higher Ca:Si ratios, for example 1:1 and greater and especially 2:1 and greater. 25 The source of phosphate ions used may be any source capable of delivering phosphate ions to the teeth. Preferably, the source is a water soluble salt {vide infra). Suitable water soluble salts include tri-sodium phosphate, di-sodium hydrogenphosphate, and sodium dihydrogenphosphate. - 11 - For the avoidance of doubt, the soured of phosphate ions is added to the oral cavity together witP the source of calcium ions. Whilst the saliva naturally present in the oral cavity provides a source of phosphate ions, this saliva 5 should not be considered a source of phosphate ions in accordance with the present invention.- The source of phosphate ions is preferably present in a composition at a concentration of from 1 mM to 100 mM, more 10 preferably 5 mM to 50 mM, and most preferably 10 mM to 40 Preferably, the source of phosphate ions is present in a composition that is substantially fre0 of calcium ions. By 15 the term "substantially free' we mean that relative to the weight of the phosphate ions, the amount of calcium ions is less than 2.5%, particularly less than 1%/ more particularly less than 0.1%, and especially less than 0.01% by weight. 20 The source of phosphate ions is preferably present in a composition comprising a source of fluoride ions. The source may be, for example, sodium fluoride or sodium monofluorophosphate. The level of fluoride ions present may be from 200 ppm to 10,000 ppm, preferably from 1000 ppm to 25 4000 ppm, and more preferably from 2000 ppm to 3000 ppm. The fluoride ions, particularly at the preferred concentrations, can aid the reaction between the insoluble calcium salt and the phosphate ions added from the second composition and present in the saliva. - 12 - The source of calcium ions and the source of the phosphate ions are typically kept physically separate from one another by having them in independent compositions. The delivery of these independent compositions to the teeth may be 5 sequential or simultaneous. In certain embodiments, for example dual phase toothpastes, the compositions are preferably delivered simultaneously. The means of delivery may involve a dual tube having a first 10 compartment for a first composition comprising the source of calcium ions and a second, independent compartment for a second composition comprising the source of phosphate ions. Such a dual tube typically has one of the compartments surrounding the other. Typically, the dual tube allows for 15 co-extrusion of the two compositions. The means of delivery may involve a single tube having first and second compositions as described above present as independent compositions within the same tube. In such 20 embodiments, the compositions or phases are extruded from the tube as one, such extrusion being termed "contact extrusion". In such embodiments, one the compositions may be present as stripes within the other composition. In preferred embodiments, one of the compositions is present as 25 a sheath, surrounding the other composition in the core. In particularly preferred embodiments, the core composition comprises the source of calcium ions and the sheath composition comprising a source of phosphate ions. 30 When two compositions are present as independent compositions within the same tube, the quantity of water - 13 - within each of the compositions is preferably less than 35%, more preferably less than 30%, and most preferably less than 25% by weight. In an especially preferred embodiment of this type, the first composition has less than 20% by weight 5 of water and the second composition has less than 25% by weight of water. It has been found that minimising the quantities of water reduces premature interaction of the calcium salt and source of phosphate ions. 10 In a preferred embodiment, the product according to the invention comprises a gel composition. Said gel composition preferably comprises the source or calcium ions; alternatively it may comprise the source of calcium ions. In certain embodiments, there are two independent gel 15 compositions, the first comprising the source or calcium ions and the second comprising the source of phosphate ions. Treatment with independent gel compositions typically involves mixing of the compositions on application and leaving the mixed composition in contact with the teeth. 20 Following such application, the mixed compositions are typically left on the teeth for from 10 minutes to 10 hours and more typically from 30 minutes to 8 hours. The application may be carried daily. The compositions may be applied from independently compartments of a dual 25 compartment tube or from independent phases of a product contained within a single container which is typically a tube. In certain embodiments, in particular those involving a gel 30 composition, the means of delivery may involve a tape, in particular an adhesive tape, onto which the source of - 14 - calcium ions and the source of phosphate ions are applied, prior to the strip being placed in contact with the teeth. Using this means of delivery, the compositions can be held in close contact with tooth surface, facilitating a high 5 concentration of calcium salt and/or source of phosphate ions close to the tooth surface. Much less of the composition(s) is/are lost into the saliva using this delivery means. 10 Gel compositions involve the use of a gel. The gel typically comprises a polymeric matrix, and is more typically a hydrogel (vide infra). Excluding any water present, the polymeric matrix is typically present at from 1 to 25% by weight of the composition(s) of which it is a 15 part. In the context of this invention, a vgel" is a colloidal system in which a porous network of interconnected nano-particles spans the volume of a liquid medium. In general, 20 gels are apparently solid, jelly-like materials. Both by weight and volume, gels are mostly liquid in composition and thus exhibit densities similar to liquids; however, they have the structural coherence of a solid. 25 The polymeric matrix material may be a hydrogel which, in the context of this invention, is an insoluble polymeric network containing an absorbed aqueous phase. Typically, the polymeric network is crosslinked. Typically, the content of other liquid components in the composition(s) 30 comprising the hydrogel is not more than 10% by weight. - 15 - Typically the content of water in the composition (s) comprising a hydrogel is from 80 to 99%. Monomers used to prepare hydrogels may be selected from 5 vinyl alcohol and acrylate, in particular sodium acrylate. Other monomers comprising an abundance of hydrophilic groups may also be used. Preferred hydrogels comprise a polysaccharide, 10 polyacrylamide, or polyacrylic acid. Suitable polysaccharides may be storage polysaccharides, such as starch or glycogen, or structural polysaccharides, such as cellulose or chitin. 15 Suitable polysaccharides may include saccharide units selected from one or more of the following: isomaltose, glucose, fructose, galactose, xylose, mannose, sorbose, arabinose, rhamnose, fucose, maltose, sucrose, lactose, 20 maltulose, ribose, lyxose, allose, altrose, gulose, idose, talose, trehalose, nigerose, kojibiose, and lactulose. Preferred hydrogels comprise one or more polysaccharides selected from the group consisting of: tamarind gum, guar 25 gum, locust bean gum. Tara, Fenugreek, Aloe, Chia, Flaxseed, Psyllium seed, quince seed, xanthan, gelIan, welan, rhamsan, dextran, curdlan, pullulan, scleroglucan, schizophyllan, chitin, hydroxyalkyl cellulose, arabinan, de-branched arabinan, arabinoxylan, galactan, pectic galactan, 30 galactomannan, glucomannan, lichenan, mannan, pachyman, rhamnogalacturonan, acacia gum, agar, alginates, - 16 - carrageenan, chitosan, clavan, hyaluronic acid, heparin, inulin, cellodextrins, cellulose, and cellulose derivatives. Particularly preferred hydrogels comprise polysaccharides 5 selected from the group consisting of: sodium alginate, hydroxypropyl alginate, gum carrageenan, gum grabic, guar gum, karaya gum, chitosan, pectin, and starch. Other preferred hydrogel forming components are the Carbopol 10 polymer, which are commercially available from Noveon. The compositions used in accordance with the invention may also comprise further ingredients which are common in the art, such as: 20 • antimicrobial agents, e.g. Triclosan, chlorhexidine, copper-, zinc- and stannous salts such as zinc citrate, zinc sulphate, zinc glycinate, sodium zinc citrate and stannous pyrophosphate, sanguinarine extract, metronidazole, quaternary ammonium compounds, such as cetylpyridinium chloride; bis-guanides, such as chlorhexidine digluconate, hexetidine, octenidine, alexidine; and halogenated bisphenolic compounds, such as 2,2' methylenebis-(4-chloro-6-bromophenol); • anti-inflammatory agents such as ibuprofen, flurbiprofen, aspirin, indomethacin etc. • anti-caries agents such as sodium trimetaphosphate and 30 casein - 11 - plaque buffers such as urea, calcium lactate, calcium glycerophosphate and strontium polyacrylates; vitamins such as Vitamins A, C and E; plant extracts; desensitising agents, e.g. potassium citrate, potassium chloride, potassium tartrate, potassium bicarbonate, potassium oxalate, and potassium nitrate; anti-calculus agents, e.g. alkali-metal pyrophosphates, hypophosphite-containing polymers, organic phosphonates and phosphocitrates etc.; biomolecules, e.g. bacteriocins, antibodies, enzymes, etc. ; flavours, e.g. peppermint and spearmint oils; proteinaceous materials such as collagen; preservatives; opacifying agents; colouring agents; pH-adjusting agents; sweetening agents; - 18 - pharmaceuticallly acceptable carriers, e.g. starch, sucrose, water or water/alcohol systems etc.; surfactants, such as anionic, nonionic, cationic and zwitterionic or amphoteric surfactants; particulate abrasive materials such as silicas, aluminas, calcium carbonates, dicalciumphosphates, calcium pyrophosphates, hydroxyapatites, trimetaphosphates, insoluble hexametaphosphates and s on, including agglomerated particulate abrasive materials, usually in amounts between 3 and 60% by weight of the oral care composition. humectants such as glycerol, sorbitol, propyleneglycol, xylitol, lactitol etc.; binders and thickeners such as sodium carboxymethyl-cellulose, xanthan gum, gum arable etc. as well as synthetic polymers such as polyacrylates and carboxyvinyl polymers such as Carbopol®; polymeric compounds which can enhance the delivery of active ingredients such as antimicrobial agents can also be included. Examples of such polymers are copolymers of polyvinylmethylether with maleic anhydride and other similar delivery enhancing polymers, e.g. those described in DE-A-3,942,643 (Colgate) ; - 19 - • buffers and salts to buffer the pH and ionic strength of the oral care composition; and 5 • other optional ingredients that may be included are e.g. bleaching agents such as pexoxy compounds e.g. potassium peroxydiphosphate, effervescing systems such as sodium bicarbonate/citric acid systems, colour change systems, and so on. 10 Summary of the Figures Fig. 1 Scanning electronic microscopy (SEM) image of human tooth enamel surface morphology of (a) 15 before treatment and (b) after treatment for two weeks with MCS-gel in phosphate-containing saliva in an 8 hours/day cycling treatment. Fig. 2 SEM image of cross section view of treated tooth. 20 A thin layer in 5 micron thickness has been formed (right bright area) on the original tooth enamel (left area). Fig. 3 Energy Dispersive X-ray (EDX) elemental analysis 25 of Ca and P scanned {left to right) across the dark line indicated on the SEM cross-sectional image of Fig. 2. The "distances" indicated are distances in microns. - 20 - Fig. 4 Raman spectrum of tooth surface before and after MCS-gel treatment in the presence of a phosphate containing composition. 5 Fig. 5a SEM image of a tooth surface prior to "etching" with phosphoric acid. Fig. 5b SEM image of a tooth surface after etching with phosphoric acid. 10 Fig. 6a Raman spectrum of phosphoric acid etched tooth surface. Fig. 6b Raman spectrum of phosphoric acid etched tooth 15 surface following treatment with MCS-gel composition and phosphate containing composition for one week. Fig. 7 SEM image of titanium dioxise raw material used in 20 Examples 14 and 15. Fig. 8 SEM image HAP disc treated with Example 14. Fig. 9 Energy dispersive spectrum (EDS) of HAP disc 25 treated with example 14. The following examples serve to illustrate the invention without limiting the invention to them. If not otherwise stated the percentages and parts are by weight. 30 - 21 - Examples Step I - Preparation of gel compositions comprising MC5 Homogeneous suspensions of fine powder MCS (Ca:Si = 1:2) in 5 distilled water were formed in a range of concentrations from approximately 0.5% to 5%, as indicated in Table 1, using ultra-sonification. Sodium alginate gel particles were then added with vigorous stirring. After about 5 to 15 minutes, uniform white gel suspensions resulted. The pH of 10 the gel suspensions were measured and are also indicated in Table 1. Table 1: MCS Compositions 1 2 3 4 MSC powder (g) 0.5 1.5 3 5 Water (g) 100 100 100 100 Sodium alginate (g) 5 5 5 5 pH 9.32 9.72 9.76 10.03 Further compositions were prepared as described above with the sodium alginate present at lg, 1.5g, and 3g. The viscosity of the resulting composition was found to be a function of the alginate level, being higher at the higher 20 alginate levels. - 22 - Step II - Application of the gel compositions comprising MC5 Extracted human teeth were cleaned using 75% alcohol and brushed using toothpaste to remove surface bacteria and 5 debris. The composition designated 4 in Table 1 was uniformly painted onto the teeth at a level of 1.0 g per six teeth. The teeth were then immersed in human saliva at 37°C. After eight hours, the gel■was .washed off with tap water and the teeth re-immersed again in the saliva at 37°C 10 for the rest of day. This treatment was continued for two weeks. The human saliva used was collected from many subjects. Its calcium concentration varied from 23 to 60 ppm and its 15 phosphorus concentration (present as phosphate ions) varied from 124 to 154 ppm. The surface morphology of the teeth was investigated using SEM before and after treatment. Figure 1(a) represents the 20 appearance before treatment and Figure 1(b) represents the appearance after treatment. It can be seen that before treatment the surface is smooth and after treatment certain new crystalline structures have grown out from the original smooth surface. At a magnification of 10,000, tiny 25 crystalline structures can be clearly seen, measuring about 100 nm. To quantify the amount of newly formed hydroxyapatite, the before and after treatment tooth samples were sectioned and 30 polished before being examined by SEM. The result is shown in Figure 2. It can be clearly seen that a thin coating - 23 - layer has been formed on the top of original enamel. The thickness of the layer varies from 2 to 10 microns, but seems to have a positive relation with the tooth surface roughness. Thus, it would appear that the treatment targets 5 those teeth in most need of repair. The chemical nature of the new crystalline material produced by the treatment was investigated by EDX elemental analysis (see Figure 3) and Raman spectroscopy (see Figure 4). 10 Figure 3 shows that the content of calcium and phosphorus in the newly formed hydroxyapatite is very similar to that in the original tooth enamel underneath. Figure 4 indicates that the chemical nature of the phosphate present in newly formed hydroxyapatite is essentially the same as that of the 15 untreated teeth, strongly suggesting that only "natural" hydroxyapatite has been added to the teeth. Hardness testing using nano-indentation 20 In this experiment, the mechanical properties of the regenerated enamel layer were investigated. Mechanical robustness is of crucial importance to the long term stability of the enamel and is essential for maintenance of teeth during biting and eating food. It is desired that the 25 enamel has a high level of mechanical hardness. Using the same procedures as described in "Step II" (vide supra), human tooth samples were first cleaned and then treated with Composition 5 and phosphate-containing saliva 30 on a daily basis for two weeks. On this occasion, however, an additional step was introduced: following the eight hour - 24 - immersion of painted teeth in saliva, the teeth were brushed for one minute with a chalk-containing toothpaste. They were then re-immersed in saliva as in the "Step II" procedure described above, 5 State of the art nano-indentation instrumentation was used to measure the hardness of the thin film of newly deposited film of hydroxyapatite on the surface of the teeth. Three treated tooth samples were measured and on each sample, nine 10 indentations were made. As shown in Table 3, the hardness of the remineralised layer is in the range of 5.4 and 5.7 GPa. This is very close to the hardness of the original enamel surface, also shown in Table 3. Another important mechanical parameter is Young's modulus, a basic value for a 15 material's elasticity. The higher the value, the stiffer the material is. It is desirable that the remineralisation layer is similar to the natural enamel. From the results indicated in Table 2, it is clear that the remineralised film has similar mechanical properties that that of the 20 original enamel. Table 2: mechanical properties of teeth before and after treatment Hardness (GPa) Young's modulus (GPa) Before treatment (Literature values) 5.0-6.0 95-120 After forming new enamel layer 5.4 -5.7 111-121 - 25 - Regeneration of damaged teeth To mimic the demineralization of teeth by many types of acidic fruit juice, human teeth were etched using 37 wt% 5 phosphoric acid for one minute. Images of the original teeth and the phosphoric acid etched teeth were taken by SEM. Fig. 5a represents a tooth surface before etching and Fig. 5b represents a tooth surface after etching. By treatment with Composition 5 (described below) and phosphate 10 containing saliva in the manner described above, it was found possible to cure the etching caused by the phosphoric acid within one week. Composition 5: MCS powder (0.5 g) added to water (10 g) and 15 dispersed as described above, then sodium alginate (0.3 g) added with vigorous stirring. A uniform gel was formed after about ten minutes stirring. The treated samples were found to have grown a significant 20 thickness of a new layer. The newly formed layer was characterized by Raman spectroscopy. Fig. 6a is the Raman spectrum of a tooth surface before treatment and Figure 6b is the Raman spectrum of a tooth surface after treatment. Table 3 indicates the position of the major peaks before and 25 after treatment. There is a peak at 961.42 cm*1 which corresponds to the major phosphate band. The after treatment sample gave an essentially identical Raman spectrum to the before treatment sample, including the location of the phosphate band at 961.42 cnf1. This implies 30 that the added material is identical to that originally present and is a somewhat surprising result. - 26 - Table 3: Raman peaks positions of human tooth enamel before and after treatment Band Position before treatment Position after treatment Vi P0„3" 961 961 v2 P043" ' 445 444 v3 PO43" 1072 1069 v4 P043" 579 579 The Raman bands Vlf V2f V3f and v* are characteristic of the crystallinity/perfection of the apatite crystal lattice. Example 6: dual phase gel product A product was prepared comprising two gel compositions: Gel 1 and Gel II. Details are given in Table 4. An MSC powder as described above under "step I" was incorporated into Gel I by the method disclosed under "step I". Gel II was prepared by adding sodium alginate to a solution of phosphate buffer and sodium fluoride. - 27 - Table 4: dual phase gel product MCS Powders (wt%) Alginate Powders