MXPA98008481A - Composition of tooth paste comprising an abrasive or additive based silicone and carbonate decalcio, compatible with fl - Google Patents

Abstract

A toothpaste composition is described, comprising at least one caries-preventing agent, with a base of compounds containing fluorine, and at least one silica, such a composition being characterized in that the silica is composed of particles containing a active dense silica protection and a calcium carbonate core. The use, as an abrasive or additive agent in toothpaste compositions, of the composite particles containing a calcium carbonate core and dense active silica protection, the protection optionally containing in the adsorbed state, an agent is also described. of stabilization of Ca2 + ions. The composite particles consist of a calcium carbonate core and a dense activated silica shield, containing in the adsorbed state at least one Ca ion stabilizing agent.

Description

COMPOSITION OF TOOTH PASTE COMPRISING A ABRASIVE OR ADDITIVE BASED ON SILICA AND CARBONATE OF CALCIUM, COMPATIBLE WITH FLUOR.

DESCRIPTION OF THE INVENTION The subject matter of the present invention are dentifrice compositions comprising, as an additive or abrasive agent compatible with fluorine, particles comprising a core of calcium carbonate and a dense active silica protection, optionally comprising, in the adsorbed state, an agent for stabilize Ca2 + ions. Another subject matter of the invention is the use, as an additive or abrasive agent for dentifrice compositions, of composite particles comprising a calcium carbonate core and a dense active silica protection, optionally, comprising in the adsorbed state, an agent for stabilize Ca2 + ions. A further subject matter of the invention is, as a novel industrial product, composite particles made of a calcium carbonate core and a dense active silica shield, comprising, in the adsorbed state, an agent for stabilizing Ca 2+ ions.

Silica and calcium carbonate are commonly used in dentifrice compositions as abrasive agents, helping through their mechanical action to the removal of dental plaque. Silica can also act as a thickener to confer specific rheological properties on the toothpaste. The dentifrice compositions contain several additive uses, in particular additives for the prevention of caries, in particular fluorides. The presence of fluorides has the problem of its compatibility with calcium-based abrasives (for example, calcium carbonate), which, due to its surface properties, may limit the ability of fluorides to exert their therapeutic effect. The Applicant Company has found that the composite particles of a silica shield and a calcium carbonate core are compatible with fluorine and thus are particularly advantageous in dentifrice compositions. The subject matter of the present invention in this manner is a dentifrice composition, comprising at least one agent for the prevention of caries, the agent is based on a fluorinated compound, and at least one silica, the composition is - characterized in that the silica is composed of particles comprising a dense active silica protection and a calcium carbonate core. The silica particles can exhibit an active silica (hydrated oxide) protection with a thickness of the order of 2 to 200 nm, preferably 5 to 50 nm, for a core size of calcium carbonate of the order of 20 nm at 30 μm, preferably of the order of 50 nm to 20 μm. Its BET specific surface is generally of the order of 1 to 100 m2 / g, preferably of the order of 1 to 40 m2 / g. Its RDA abrasion capacity can be of the order of 30 to 250, preferably of the order of 40 to 200. Its BET specific surface area is determined according to the B run-er method - Emme t -T e 11 er described in "The Journal of the American Chemical Society," Vol. 60, page 309, February 1938, which corresponds to Standard NFT 45007 (November 1987) The abrasion capacity RDA ("Abrasion of Radioactive Dentin") is measured according to the method described by JJ Hefferren in "Journal of Dental Research", vol 55 (4), page 563, 1976.

With respect to the calcium carbonate core, this can be precipitated carbonate (aragonite, c citation), natural ground carbonates, and the like. The core preferably exhibits a mean diameter in the range of 50 nm to 20 μm. The particles comprising a dense active silica protection and a calcium carbonate core can be prepared according to the conventional procedures through slow precipitation, on the calcium carbonate core, of active silica, from a solution of Aqueous alkali metal silicate with pH adjustment using an acid (US -A- 2, 885, 366). A particularly successful method for the preparation of particles of this type consists in the precipitation on calcium carbonate, of the active dense silica from an aqueous alkali metal M silicate solution, with a SiO2 / Na2O ratio of at least 2, preferably of the order of 2.5 to 4, with the adjustment of the pH using an acidifying agent, separation of formed silica sludge and drying of the recovered silica suspension, the operation of the formation of the silica sludge through precipitation it is carried out according to the following steps: a first step consisting of using an initial vessel residue with a pH of the order of 8 to 10 comprising water, calcium carbonate, an electrolyte salt of the alkali metal group, the amount of electrolyte present is at least about 0.4 moles, preferably in the order of 0.4 to 1.5 moles, of the alkali metal ion per liter of the recipient residue e, and optionally a pH regulator or basic agent at a temperature of the order of 80 to 98 ° C; a second stage consisting of the introduction, in such a container waste, of the alkali metal silicate in the form of an aqueous solution containing at least about 100 grams of SiO2 / liter, preferably of the order of 100 to 330 grams of SiO? / Liter, and the acidifying agent, under conditions such that the kinetics K of formation of the active silica, expressed in grams of s 1 liter / hour / g of calcium carbonate corresponds to the value K > 3 (A / 200) 2n preferably K > _ 4 (A / 200) 2n and more particularly K > _ 6 (A / 200) 2". N is equal to (T - 9 O) / 1 OA represents the specific surface, expressed in m? / G of carbonate that is coated, and T is the temperature in ° C. , the reaction mixture exhibits a substantially constant pH of the order of 8 to 10 and a temperature of the order of 80 to 98 ° C is maintained, until the desired amount of silica is formed, the selection of the silicate and the acidifying agent is The alkali metal silicate is advantageously a sodium or potassium silicate, generally used as an acidifying agent of an inorganic acid, such as sulfuric acid, nitric acid or hydrochloric acid. or an organic acid, such as acetic acid, formic acid or carbonic acid.This is preferably sulfuric acid.It can be used in dilute or concentrated form, preferably in the form of an aqueous solution exhibiting a concentration of the order of 60 to 400. g / 1. If it is á carbon dioxide, this can be introduced into the gaseous form.

The first stage consists in the separation of the initial container waste. The calcium carbonate is preferably introduced in the form of an aqueous dispersion. The amount of calcium carbonate, which can be used, is such that the residue of the container formed contains the order of 10% to 50% of its weight of calcium carbonate. Particular mention is made between the electrolytes of the salt of the starting silicate metal and the acidifying agent. Preferably this is sodium sulfate. However, sodium chloride, nitrate or acid carbonate may be preferred if the presence of residual sulfate ions is not desired. A pH regulator or basic agent may be employed in the initial vessel residue in order to measure the pH of such a vessel residue in the range of 8 to 10. This pH regulator or basic agent may be selected from alkali metal hydroxides. , such as sodium hydroxide, dissolved alkali metal silicates, alkali metal phosphates, alkali metal acid carbonates, and the like.

The obtained container residue is brought to a temperature of the order of [lagoon] 80 to 98 ° C. The second stage consists in adding the silicate solution and the acidifying agent simultaneously to the container residue, which is kept in agitation. The respective amounts of the alkali metal silicate and the acidifying agent are selected in order to obtain the kinetics K of the formation of the active silica mentioned above and in order to keep the pH of the reaction mixture at a substantially constant value of the order of 8 to 10 through the introduction of two reagents. These two solutions are introduced while maintaining the mixture at a temperature of the order of 80 to 98 ° C. The introduction of the silicate solution is interrupted when the desired amount of silica has been formed. The minimum desired amount of silica is that corresponding to a deposition of the order of 1 to 150 parts by weight of SiO2 per 100 parts by weight of calcium carbonate. This second stage usually lasts at least 30 minutes to 2 hours. The mixture obtained at the end of the second stage, after the interruption of the introduction of the reagents, is optionally left to mature for approximately 10 to 30 minutes under the same temperature conditions. In conclusion of the operations described above, a particulate sludge comprising active silica deposited on calcium carbonate is obtained, such sludge is subsequently separated (liquid / solid separation). This operation usually consists of a filtration (for example, separation through sedimentation, use of rotary vacuum filter, followed by water washing.) The suspension thus recovered (filter cake) is subsequently dried (furnace, blast furnace, atomization) The dentifrice composition forming the subject matter of the invention contains in the order of 5 to 40%, preferably in the order of 5 to 35% of its weight of silica composed of particles comprising a dense active silica protection and a calcium carbonate core and a flocked compound in an amount corresponding to a concentration of the order of 0.005 to 2%, preferably of the order of 0.1 to 1% by weight of fluorine in such composition. 1 o The compounds lloorado;. they are in particular monomeric acid salts, in particular those fluorides of sodium, sodium, lithium, calcium, aluminum and ammonium, or alkali metal fluorides, in particular sodium fluoride. An alternative form of the dentifrice composition forming the subject matter of the present invention consists of that dense silica protection of the particles comprising a dense active silica protection and a calcium carbonate core, which contains in the adsorbed state, by at least one agent to stabilize Ca + ions. Mention is made, among the stabilizing agents, of water-soluble phosphorus derivatives, such as alkali metal phosphates (pyrophosphates, or r t or f or s, t r ipo 1 i f or s f a t or s hexame t a ss of sodium, potassium or lithium). The amount of such a stabilizing agent may represent up to 2% of the mass of the particles comprising a dense active silica shield and a calcium carbonate core, expressed on a dry basis. Such particles can be obtained by treating the silica protection with an aqueous solution of the stabilizing agent, such treatment is carried out by adding the solution already to the silica sludge formed at the one of the precipitation stage, before the filtration, or the silica suspension (filter cake) obtained after filtering, before drying. Another embodiment consists in directly introducing the stabilizing agent into the dentifrice composition itself. The dentifrice compositions containing particles that comprise a calcium carbonate core and dense active silica protection containing, in the adsorbed state, at least one agent for stabilizing Ca2 + ions, in particular may contain, high the fluorinated compound, an alkali metal fluoride, such as sodium fluoride. The tooth structure which forms the subject matter of the invention may also contain anionic, nonionic, amphoteric and zwitterionic surfactants, in the proportion of about 0.1 to 10%, preferably about 1 to 5. %, of the weight of the composition. Mention may be made, by way of example, of anionic surfactants, such as hate alcohols, magnesium, ammonium or ethane] amine of C -C C alkyl sulphates, which may optionally contain up to 10 oxyethylene or oxypropylene units ( 1 auri 1 its 1 sodium diet, in particular) its 1-C8-C_8 alkyl acids (1 auri 1 its 1 fat or sodium carbonate, in particular). a 1 qu i 1 s u 1 f or s c c t i n s of C & - C _ 8 (dioctyl 1 its 1 sodium phosuccinate, in particular) C 8 -C 8 alkylsarcosinates (1 aui 1 sodium sarcosinate, in particular) at 1 qu i 1 f or C8-C? 8 fat, which can optionally contain up to 10 units of oxyethylene and / or oxypropylene at 1 qu and 1 terry box of 1 Cß-Cie, containing up to 10 oxyethylene and / or oxypropylene units. sulphated sulphonates, and the like, * nonionic surfactants, such as optionally polyethoxylated sorbitan fatty esters, ethoxylated fatty acids, polyethylene glycol esters, and the like * to anionic surfactants, such as betaine osu 1 f or etains - water, in the proportion of about 5 to 50%, preferably about 10 to 40% of the weight of the composition. humectants, in the proportion of about 10 to 85%, preferably 10 to 70% of the weight of the composition, humectants such as glycerol, sorbitol, polyethylene glycols, lactilol, xylitol and similar thickening agents, such as certain silicas used for this purpose (Tixosil .3 R, sold by Rh óne-Pou 1 ene, and similar) in the proportion of 5 to 15% by weight and / or polymers used alone or in combination such as xanthan gum, guar gum, cellulose derivatives (carboxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, and the like), crosslinked polyacrylates, such as Carbopol products "distributed by Goodrich, alginates or carrageenans, Viscarin", and the like, in the proportion of 0.1 to 5% by weight agents to stabilize ions of Ca '+, such as derivatives of water-soluble phosphors, such as alkali metal phosphates (pyrophosphates, or t of os fa ct, tri-polos os fatoso hexametaf osfatoe sodium, potassium or lithium) - other ingredients, such as : * other polishing abrasives, such as silica, precipitated calcium carbonate, magnesium carbonate, calcium phosphates, titanium oxide, zinc oxide, tin oxide, talc, kaolin, and the like * bactericidal, anti-microbial or anti-bacterial therapeutic agents plaque, such as zinc citrate, polyphosphates, guanidines, bi sb igua or its other cationic or therapeutic organic compounds * flavors (essence of anise seed, Chinese anise, mint, juniper, cinnamon, clove or rose), sweeteners, colorants (chlorophyll), preservatives, and the like. The dentifrice composition forming the subject matter of the invention can be provided in various forms (pastes, gels, creams), which are prepared using conventional methods. The compatibility of the particles comprising a protection of silica and a core of calcium carbonate (particles known as "abrasive" in the tests) with sodium monofluorosphosphate (MFP), on the one hand, and with sodium fluoride (NaF) On the other hand, it was measured using the following tests: Measurement of the Compatibility of MFP A suspension containing 20% by weight of abrasive was prepared by contacting 10 g of abrasive at 60 ° C in 40 g of a stock solution containing 625 ppm of MFP in a solvent selected from water, a mixture of s orbi t ol / ag ua 50/50, or a mixture of g 1 and ce 1 / a gua 35/65. The suspension and the control sample comprise the stock solution without the abrasive, they were maintained in magnetic stirring in an oven [pond] at 37 ° C for 4 weeks. The control sample and suspension were returned to room temperature and centrifuged. The supernatant was removed and then filtered, since it is the control solution. The quantitative determination through ionometry of the total soluble fluorine in the supernatant requires a previous hydrolysis treatment in an acid medium, which releases the fluorine ions present in the complex form in the MFP.

The hydrolysis was carried out by contacting 25 ml of the supernatant with 5 ml of 5N sulfuric acid and 20 ml of deionized water and placing it in an oven at 60 ° C for at least 5 hours. The compatibility of the abrasive, expressed in%, was defined by the ratio [C / C0] x 100. C representing the concentration of fluorine in the supernatant tested (after hydrolysis) and C0 the concentration of fluorine in the control (after hydrolysis). In addition, the concentration of the fluorine ion in the supernatant was measured before hydrolysis with acid, in order to gain access to the fluorine concentrations resulting from the hydrolysis of the MFP.

Quantitative determination of total soluble fluorine in toothpastes containing MFP 90 g of water at room temperature for 5 months were suspended in 10 g of toothpaste with the following composition: Composition% e n s or carboxymethyl cell ul 0. 8 sorbitol 1 8 sodium monofluorophosphate 0. 8 sodium saccharinate (sweetener) 0. 2 sodium benzoate (preservative) 0. 3 abrasive tested 4 0 Tixosil 43 (silica thickener) 5 1 au r i 1 s u 1 f a t sodium (30% aqueous solution) 4 flavor 0.8 deionized water 30.1 The suspension was centrifuged subsequently and the supernatant was filtered. The quantitative determination through ionometry of the total soluble fluorine in the supernatant requires a previous hydrolysis treatment in an acid medium, which releases the fluorine ions present in the complex form in the MFP. The hydrolysis was carried out by contacting 25 ml of supernatant with 5 ml of 5N sulfuric acid and 20 ml of deionized water and placing it in an oven at 60 ° C for at least 5 hours.

The concentration of the fluorine in the piobado supernatant was monitored after the hydrolysis as well as before the hydrolysis.

Compatibility measurement with respect to the Naf sodium fluoride The principle of the measurement is to leave the test abrasive in contact with a sodium fluoride solution of known concentration for 10 days at 37 ° C. The amount of fluoride present in the liquid medium obtained through centrifugation was measured by ionometry. - Procedure - The test silica was suspended at 20% in an aqueous NaF solution obtaining 625 ppm expressed as F ~ fluoride. The contact was maintained [lagoon] for 10 days at 37 ° C with shaking. The suspension was centrifuged. The supernatant was diluted 20 times with water. The concentration of F "was measured by ionometry and compared to the concentration in the initial solution, which was not in contact with the abrasive.The amount of F ~ not reacted in this way was determined.The result of the compatibility of NaF was expressed through (F "unreacted / F" starting) x 100 A second subject matter of the invention consists of the use, as an additive or abrasive agent in dentifrice compositions, of composite particles comprising a core of calcium carbonate and a dense active silica protection, optionally containing, in the adsorbed state, an agent for stabilizing Ca + ions.The characteristics of such particles, as well as a possible method of preparation, have already been mentioned above. from about 5 to 40%, preferably from about 5 to 35% of the weight of the compositions A final subject matter of the invention consists of, as Novel industrial oducts, composite particles made of a calcium carbonate core and dense activated silica protection, containing, in the adsorbed state, at least one agent to stabilize Ca 2+ ions. Mention may be made, among the stabilizing agents, of water-soluble phosphorus derivatives, such as alkali metal phosphates (pyrophosphates, or t or f or s, t rypo 1 i f or s f a t o s or h e x ame t a f or s of sodium, potassium or lithium).

The amount of such a stabilizing agent may represent up to 2% of the mass of the particles comprising a dense active silica protection and a calcium carbonate core, expressed on a dry basis. A method for preparing such composite particles has already been mentioned above. The following examples are given by way of illustration only.

Example 1 A container residue was prepared by introducing, to a 15 liter reactor, 3.5 liters of water, 0.68 mol / liter of the sodium container residue in the sodium chloride form, of 1150 g of precipitated calcium carbonate.

(Sturcal H, sold by Rhóne - P ou 1 e nc, exhibiting a particle size of 11 μm and a BET specific surface area of 4 m / g) and sodium silicate, with a SiO? / Na? O ratio of 3.5 (aqueous solution containing 130 g of SiO2 per liter), in an amount corresponding to a concentration of 4 g of SiO2 per liter of the container residue. The container residue, with a pH of 9, was brought to 90 ° C and kept stirring.

The following was introduced subsequently and simultaneously: an aqueous sodium silicate solution with an SiO / Na20 ratio of 3.5, the concentration of which is 130 g of S i O2 per liter of the solution, and an acid solution aqueous sulfuric containing 80 g of acid per liter, in order to form 230 g of silica in 90 minutes. After ripening for 30 minutes, the obtained sludge was filtered. The filter cake was washed with water and then dried in an oven at 80 ° C. Analysis of the product by electron microscope (TEM) showed that the thickness of the deposited silica layer is of the order of 20 nm. The BET surface [lagoon] of the final particles is 2.9 m2 / g. The addition kinetics of the sodium silicate was 0.134 g (SiO2) / h / g (CaCO3).

EXAMPLE 2 The abrasive prepared in Example 1 was tested for compatibility with MFP in solution in water and in mixtures of sorbitol / water and glycerol / water. The results obtained will be; presented in Table 1 and compared with those obtained with the same amount of Sturcal H (precipitated calcium carbonate, sold by Rh or ne-P ou 1 enc, exhibiting a particle size of 11 μm and a specific BET surface area of 4 m2 / g) as an abrasive agent.

EXAMPLE 3 The abrasive prepared in Example 1 was tested for compatibility with MFP in the dentifrice composition described above. The results obtained are presented in Table 1 and compared with those obtained with Sturcal H.

Example 4 A container residue was prepared through the introduction into a 15 liter, 3.5 liter water reactor, of 0.68 mol / liter of the sodium container residue in the sodium chloride form, of 1150 g of carbonate of precipitated calcium (Sturcal H, sold by Rhon e-Pou 1 enc, exhibiting a particle size of 11 μm and a specific surface area of BET of 4 m2 / g) and sodium silicate, with a SiO_ / Na20 ratio of 3.5 (aqueous solution containing 130 g of SiO2 per liter), in an amount corresponding to a concentration of 4 g of SiO2 per liter of the container residue. The container residue, with a pH of 9, was brought to 90 ° C and kept stirred. The following was introduced subsequently and simultaneously: - a solution of aqueous sodium silicate, with a SiO2 / Na2 ratio of 3.5, the yield of which is 130 g of SiO2 per liter of solution, and an acid solution aqueous sulfuric containing 80 g of acid per liter, in order to form 460 g of silica in 180 minutes. After ripening for 30 minutes, the obtained sludge was filtered. The filter cake was washed with water and then dried in an oven at 80 ° C. Analysis of the product by electron microscope (TEM) showed that the thickness of the deposited silica layer is of the order of 40 nm. The BET surface [lagoon] of the final particles is 2.4 m2 / g.

The addition kinetics of the sodium silicate was 0.134 g (SiO2) / h / g (CaCO3).

Example 5 The abrasive prepared in the Example. it was tested for compatibility with NaF. The results obtained are presented in Table 2 and compared with those obtained with the same amount of Sturcal H (precipitated calcium carbonate, sold by Rhóne-P ou 1 e nc, exhibiting a particle size of 11 μm and a specific surface area). of BET of 4 m2 / g) as an abrasive agent. Table 1 Table 2 Medium, water NaF compatibility in% E ff ective emp 1 or 4 88 Sturcal H 75

Claims (27)

1. A dentifrice composition comprising at least one agent for the prevention of caries, such agent is based on a fluorinated compound, and at least one silica, such composition is characterized in that the silica is composed of particles comprising an active silica protection dense and a core of calcium carbonate.

2. The dentifrice composition according to claim 1, characterized in that the silica particles exhibit a dense active silica protection with a thickness of the order of 2 to 200 nm, preferably of the order of 5 to 50 nm, for a core size of calcium carbonate of the order of 20 nm to 30 μm, preferably of the order of 50 nm to 20 μm.

3. The dentifrice composition according to claim 1, characterized in that the silica particles exhibit a specific surface area of BET of the order of 1 to 100 m2 / g, preferably of the order of 1 to 40 m2 / g.

. . The dental composition i i i IM < ) < . i < - u < i < I < > Which one of the re vindication! • i '< < d < n l t; , cdiactcp .ada orque las part .1 i ii l.i :. < J i: i] i < Do they exhibit an abrasion capacity of KD? d < 1 ci i-n d 30 to 250, preferably of the order of 200.

5. The dentifrice composition in accordance with any of the claimed claims on the subject (:, characterized in that the particles which are <i J dc> 11 dense active silica protection and a n e i <l <; Calcium carbonate can be obtained by precipitation over calcium carbonate from the active solution of an aqueous alkali metal silicate solution, with a SiO ratio of VNa_0 of at least 2, preferably of the order of 2.5 to 4, cn the pH adjustment using an age te -acidification, separation of the formed silica sludge and drying of the recovered silica suspension.

6. The dentifrice composition of Í < ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ following steps: a first step consisting in using an initial vessel residue with a pH of the order of 8 to 10 comprising water, calcium carbonate, an electrolyte salt of the alkali metal group, the amount of electrolyte present is at least about 0.4 moles, preferably of the order of 0.4 to 1.5 moles, of the alkali metal ion per liter of the container residue, and optionally a pH regulator or basic agent at a temperature of the order of 80 to 98 ° C; a second step consisting in the introduction, in the container waste, of the alkali metal silicate in the form of an aqueous solution containing at least about 100 grams of SiO2 / liter, preferably of the order of 100 to 330 grams of Si02 / liter, and the acidification agent, under conditions such that the kinetics K of formation of the active silica, expressed in grams of 1 ml / hour / g of calcium carbonate corresponds to the value K > 3. (A / 200) 2n preferably K > _ 4 (A / 200) 2n and more particularly K > _ 6 (A / 200) 2n. n is equal to (T-90) / 10 A represents the specific surface, expressed in m '/ g of carbonate to be coated. . and T is the temperature in ° C, the reaction mixture exhibits a substantially constant pH of the order of 8 to 10 and a temperature of. Order from 80 to 98 ° C, until the desired amount of silica is formed.

7. The dentifrice composition according to claim 5 or 6, characterized in that the alkali metal silicate is a sodium or potassium silicate.

8. The dentifrice composition according to any of claims 5 to 7, characterized in that the acidifying agent is selected from sulfuric acid, nitric acid, hydrochloric acid, acetic acid, formic acid or carbonic acid.

9. The dentifrice composition according to claim 8, characterized in that the acidifying agent is sulfuric acid.

10. The dentifrice composition according to any of claims 5 to 9, characterized in that the amount of calcium carbonate [lagoon] used is such that the formed container residue contains from 10 to 50% of its weight of calcium carbonate.

11. The dentifrice composition according to any of claims 5 to 10, characterized in that the calcium carbonate used exhibits a size of the order of 20 nm to 30 μm, preferably of the order of 50 nm to 20 μm.

12. The dentifrice composition according to any of claims 5 to 11, characterized in that the electrolyte is selected from sodium sulfate, sodium chloride, sodium nitrate or sodium acid carbonate.

13. The dentifrice composition according to any of claims 1 to 12, characterized in that it contains from 5 to 40% preferably from 5 to 35% of its weight of silica composed of particles comprising a dense active silica protection and a carbonate core of calcium and a fluorinated compound in an amount corresponding to a concentration of 0.005% to 2%, preferably of the order of 0.1 to 1. by weight of the fluorine in the composition.

14. The dentifrice composition according to any one of claims 1 to 13, characterized in that the fluorinated compound is a salt of mono f 1 or f or s or f or an alkali metal fluoride.

15. The dentifrice composition according to claim 14, characterized in that the fluorinated compound is a sodium, potassium, lithium, calcium, aluminum or ammonium salt of mono f 1 or r or f or r or sodium fluoride.

16. The dentifrice composition according to any of claims 1 to 15, characterized in that the dense silica protection of the particles contains, in the adsorbed state, at least one agent for stabilizing ions of

Ca 2 + 17. The dentifrice composition according to claim 16, characterized in that the agent for stabilizing the Ca ions is an alkali metal phosphate, preferably a sodium, potassium or lithium pyrophosphate, orthophosphate, tripolyphosphate or hexametaphosphate.

18. The dentifrice composition according to claim 16 or 17, characterized in that the agent for stabilizing the Ca2 + ions is adsorbed on the surface of the silica protection, treating the silica protection with an aqueous solution of the stabilizing agent, such treatment being It is done by adding the solution either to the silica sludge formed at the end of the precipitation stage, before the filtration, or to the silica suspension obtained after the filtration, before drying.

19. The dentifrice composition according to any of claims 1 to 18, characterized in that it also contains anionic, nonionic, amphoteric or zwitterionic surfactants in the proportion of about 0.1 to 10%, preferably about 1 to 5% of the weight of the co-position, water in a proportion of about 5 to 50%, preferably about 10 to 40% by weight of the composition, humectants in the proportion of about 10 to 85%, preferably 10 to 70%, of the weight of the composition, thickening agents in the proportion of 0.1 to 15% by weight, optionally at least one agent for stabilizing the Ca24 ions and other ingredients selected from other polishing abrasives, bactericidal therapeutic agents, antimicrobial agents or against plaque formation, flavorings, sweeteners, colorants or preservatives.

20. The tooth composition according to any of claims 1 to 19, characterized in that it is provided in the form of paste, gel or cream.

21. The use, as an additive or abrasive agent in dentifrice compositions, of composite particles comprising a calcium carbonate core and a dense active silica shield, optionally containing in the adsorbed state, an agent for stabilizing Ca 2+ ions.

22. The use according to claim 21, characterized in that the composite particles are as defined in any of claims 2 to 4, 16 or 17, or can be obtained according to any of claims 5 to 12, or 18.

23. The use according to the claim 21 or 22, characterized in that the composite particles are used in the proportion of approximately 5 to 40%, preferably 5 to 35% by weight of the dentifrice compositions.

24. The composite particles comprising a calcium carbonate core and a dense activated silica shield containing, in the adsorbed state, at least one agent to stabilize Ca 2+ ions

25. The composite particles according to claim 24, characterized in that the stabilizer is an alkali metal phosphate, preferably a sodium, potassium or lithium pyrophosphate, orthophosphate, tripolyphosphate or hexametaphosphate.

26. The composite particles according to claim 24 or 25, characterized in that the stabilizer can represent up to 2% of the mass of the composite particles.

27. The composite particles according to any of claims 24 to 26, characterized in that they can be obtained according to claim 18.