Dental Care

Remineralizing dental care preparation

Dental Care Abstract
A toothpaste containing typical components and a combination of silicas and dicalcium phosphate dihydrate (brushite) as its polishing component provides for particularly good restoration of the surface of teeth. This is achieved by controlled remineralization, particularly in scratch marks and dentinal canals. The effect can be enhanced by addition of magnesium ions and/or fluorophosphate ions.

Dental Care Claims
We claim:

1. In a toothpaste for restoring the surface of teeth containing a polishing agent, fluorine compounds, humectants, binders and water, the improvement which comprises: a polishing agent comprising silica and dicalcium phosphate dihydrate (brushite) in a ratio by weight of 10:1 to 1:1 and a water-soluble magnesium salt in an amount sufficient to provide 0.1 to 0.5% by weight magnesium.

2. The toothpaste as claimed in claim 1 containing a monofluorophosphate in an amount sufficient to provide 0.2 to 2.0% by weight (PO.sub.3 F.sup.-) as the fluorine compound.

3. The toothpaste as claimed in claim 1 containing magnesium monofluorophosphate as the fluorine compound.

4. The toothpaste as claimed in claim 1 containing a precipitated silica with an average particle size of 0.5 to 20 microns (.mu.) in an amount of 10 to 20% by weight and dicalcium phosphate dihydrate (brushite) in an amount of 1 to 5% by weight as the polishing agent.

5. The toothpaste of claim 1 containing monofluorophosphate in an amount sufficient to provide from 0.2 to 2.0% by weight PO.sub.3 F.sup.-.

6. The toothpaste as claimed in claim 1 containing magnesium monofluorophosphate.

7. The toothpaste of claim 1 containing a precipitated silica with an average particle size of 0.5 to 20 microns (.mu.) in an amount of 10 to 20% by weight and dicalcium phosphate dihydrate (brushite) in an amount of 1 to 5% by weight as the polishing agent.

8. The toothpaste of claim 1 containing a precipitated silica with an average particle size of 0.5 to 20 microns (.mu.) in an amount of 10 to 20% by weight and dicalcium phosphate dihydrate (brushite) in an amount of 1 to 5% by weight as the polishing agent.

9. The toothpaste of claim 3 containing a precipitated silica with an average particle size of 0.5 to 20 microns (.mu.) in an amount of 10 to 20% by weight and dicalcium phosphate dihydrate (brushite) in an amount of 1 to 5% by weight as the polishing agent.

10. The toothpaste of claim 1 comprising an optional additional polishing agent in a weight ratio of additional polishing agent to silica not greater than 15:100.

11. The toothpaste of claim 10 containing an additional polishing agent in a weight ratio of additional polishing agent to silica in the range of 1:100 to 15:100.

12. The toothpaste of claim 10 wherein the additional polishing agent comprises aluminum oxide.

13. In a method for remineralizing tooth enamel by a process in which a composition comprising a polishing agent containing silica and dicalcium phosphate in a ratio by weight of from 10:1 to 1:1, fluorine compounds, humectants, binders and water are applied to the surface of the teeth, the improvement which comprises: including in the composition a hydroxyl apatite crystal growth controlling amount of a water soluble magnesium salt.

14. The method of claim 13 wherein the amount of water soluble magnesium is sufficient to provide from 0.1 to 0.5 % by weight of magnesium.

15. The method of claim 13 wherein the polishing agent comprises silica and dicalcium phosphate dihydrate and an amount of an additional polishing agent in a weight ratio to the silica of less than 15:100.

16. The method of claim 14 wherein the polishing agent comprises silica and dicalcium phosphate dihydrate and an amount of an additional polishing agent in a weight ratio to the silica of less than 15:100.

Dental Care Description
This application is a 371 of PCT/EP93/02291 filed Oct. 28, 1993.

FIELD OF THE INVENTION

This invention relates to dental care preparations which have a restoring effect on the surface of teeth and to a process for restoring the surface of teeth.

BACKGROUND OF THE INVENTION

Dental care preparations are mainly used to remove food remains, dicoloration and firmly adhering bacterial coatings from the surface of teeth. In addition, attempts have been made to prevent dental diseases, such as caries or parodontosis, by incorporation of special additives, for example fluorine compounds or antimicrobial agents.

RELATED ART

Lesions in the dental enamel and open dentinal canals (so-called Tomes pits) are observed as one of the first signs of dental caries, being caused by dissolving processes under the influence of acid-forming bacteria. This damage to the dentinal substance is reflected, for example, in sensitivity in the necks of teeth to variations in temperature. Whereas additions of desensitizing agents can only control the painful symptoms, attempts have already been made to prevent the formation of the surface lesions in question by the incorporation of additives which reduce apatite solubility. Proposals have also recently been made to reduce existing damage by the use of remineralizing dental care preparations. Thus, Chow and Brown (J. Dent. Res., 54, (1975), 65-70) proposed the use of dicalcium phosphate dihydrate to remineralize the dentine. U.S. Pat. No. 4,097,588 describes a remineralizing mouthwash saturated with CaHPO.sub.4.2H.sub.2 O.

However, hitherto known efforts to restore the surface of teeth in this way have resulted in the uncontrolled growth of hydroxyl apatite crystals on the surface of the teeth which offers little resistance to further attacks on the surface of the teeth. Accordingly, the problem addressed by the present invention was to develop a toothpaste which would provide for controlled remineralization, particularly in scratch marks and dentinal canals, and would make these areas substantially level, so that the teeth would be left with a smooth continuous surface.

It has been found that this problem has been solved to a large extent by the combination of polishes according to the invention.

BRIEF SUMMARY OF THE INVENTION

The present invention relates to a toothpaste for restoring the surface of the teeth containing polishes, fluorine compounds, humectants, binders and water, characterized in that it contains a combination of silica and dicalcium phosphate dihydrate (brushite) in a ratio by weight of 10:1 to 1:1 as the polishing component. It has been found that regular brushing of the teeth with the toothpaste according to the invention results in the closure of dentinal canals so that the surface of the teeth is restored to a substantially smooth condition.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1: A scanning electron micrograph of human enamel, untreated

FIG. 2: A scanning electron micrograph of human dentine, untreated

FIG. 3: A scanning electron micrograph of human enamel, treated with comparison toothpaste C

FIG. 4: A scanning electron micrograph of human dentine, treated with comparison toothpaste C

FIG. 5: A scanning electron micrograph of human enamel treated with the toothpaste of Example 1. It can be seen that hydroxyl apatite has precipitated in the surface scratches.

FIG. 6: A scanning electron micrograph of human dentine treated with the toothpaste of Example 1. The substantial closure of the dentinal canals by precipitated hydroxyl apatite can clearly be seen.

DETAILED DESCRIPTION OF THE INVENTION

Any gel silicas, hydrogel silicas and precipitated silicas known as polishes are suitable for use as the silica polish. Gel silicas are obtained by reaction of sodium silicate solutions with strong aqueous mineral acids to form a hydrosol, ageing to form a hydrogel, washing and drying. If drying is carried out under moderate conditions to water contents of 15 to 35% by weight, the so-called hydrogel silicas known, for example, from U.S. Pat. No. 4,153,680 are obtained. Drying to water contents below 15% by weight results in irreversible shrinkage of the previously loosened structure of the hydrogel to the dense structure of the so-called xerogel. Xerogel silicas are described, for example, in U.S. Pat. No. 3,538,230.

A second particularly suitable group of silica polishes are the precipitated silicas. They are obtained by precipitation of silica by dilute alkali metal silicate solutions by addition of strong acids under conditions under which aggregation to the sol and gel cannot take place. Suitable processes for the production of precipitated silicas are described, for example, in DE-OS 25 22 486 and in DE-OS 31 14 493. The precipitated silica produced in accordance with DE-OS 31 14 493, which has a BET surface of 15 to 110 m.sup.2 /g, a particle size of 0.5 to 20.mu., at least 80% by weight of the primary particles being smaller than 5.mu., and a viscosity in a 30% glycerol/water (1:1) dispersion of 30 to 60 Pa.s (20.degree. C.), is particularly suitable and is used in a quantity of 10 to 20% by weight, based on the toothpaste as a whole.

In addition, particularly suitable precipitated silicas have rounded corners and edges and are commercially available under the trade name Sident.RTM.12 DS (DEGUSSA).

In order to obtain a sufficiently high percentage of silicas with an average particle size below 5.mu. and, more particularly, a percentage of at least 3% by weight, based on the toothpaste as a whole, of silicas having a primary particle size of 1 to 3.mu., the precipitated silica mentioned is preferably used in conjunction with an even finer type having a BET surface of 150 to 250. A suitable type of silica is, for example, Sipernat.RTM.22LS (DEGUSSA) which is used in a quantity of 1 to 5% by weight, based on the toothpaste as a whole.

To obtain a smooth tooth surface, it has proved to be of particular advantage for the toothpaste according to the invention to contain small quantities of freshly precipitated silica, i.e. silica produced in situ during production of the toothpaste. This is achieved, for example, by maintaining a pH value of 3 to 5 during production of the toothpaste, for example by addition of citric acid, and then increasing the pH value to 7-7.5 by addition of small quantities of an aqueous sodium silicate solution. The silica formed in situ in this way consists of extremely fine particles and makes up less than 0.1% of the weight of the toothpaste.

In addition to silica polishes, the toothpaste may also contain relatively small amounts of other kown polishes, for example aluminium oxide in the form of lightly calcined alumina containing .gamma.- and .alpha.-aluminium oxide. An aluminium oxide such as this is commercially available under the name of Poliertonerde P10 feinst (Giulini-Chemie). However, the ratio by weight of any additional polishing components such as these to the silica polish should be no higher than (1-15):100.

The second compulsory polishing component is dicalcium phosphate dihydrate (CaHPO.sub.4.2H.sub.2 O) which occurs in nature as brushite. Dicalcium phosphate dihydrate has long been used as a polish in toothpastes and is also commercially available in suitable particle sizes of 1 to 50.mu.. It is preferably used in a quantity of 1 to 5% by weight, based on the toothpaste as a whole.

The toothpastes according to the invention should contain no other polishing components which form calcium ions, for example chalk or other calcium phosphates.

By contrast, it has been found that magnesium ions have a favorable effect on the controlled crystal growth of the hydroxyl apatite growing in the tooth lesions, promote accelerated hardening of the dental enamel and therefore make a further contribution towards solving the problem addressed by the present invention. Accordingly, the present invention also relates to a toothpaste according to the invention which contains a water-soluble magnesium salt in a quantity corresponding to 0.1 to 0.5% by weight Mg. Suitable magnesium salts are any salts which are soluble in water at 20.degree. C. in a quantity of at least 0.5% by weight (expressed as Mg), for example MgSO.sub.4, MgCl.sub.2 and magnesium monofluorophosphate (MgPO.sub.3 F).

It has also been found that fluorophosphate ions have a favorable effect on the controlled crystal growth of the hydroxyl apatite. Accordingly, toothpastes according to the invention containing a monofluorophosphate in a quantity corresponding to 0.2 to 2.0% by weight (PO.sub.3 F.sup.-) as the fluorine compound are preferred. Alkali metal salts, for example, are suitable for this purpose. One example of a suitable alkali metal salt is the commercially available sodium monofluorophosphate. The preferred content of magnesium ions and fluorophosphate ions can be established with particular advantage by using magnesium monofluorophosphate as the fluorine compound.

A combination of humectants, binders and water is suitable as the carrier for the toothpastes according to the invention which makes it possible to establish a suitable consistency for dispensing from tubes, dispensing containers or flexible bottles on the basis of the combination of polishes according to the invention. Suitable humectants are, for example, glycerol, sorbitol, xylitol, propylene glycols, polyethylene glycols, particularly those having average molecular weights in the range from 200 to 800. Suitable consistency regulators (or binders) are, for example, natural and/or synthetic water-soluble polymers, such as alginates, carrageenates, tragacanth, starch and starch ethers, cellulose ethers, such as for example carboxymethyl cellulose (Na salt), hydroxyethyl cellulose, methyl hydroxypropyl cellulose, guar, acacia gum, agar agar, xanthan gum, carob bean flour, pectins, water-soluble carboxyvinyl polymers (for example Carbopol.RTM. types), polyvinyl alcohol, polyvinyl pyrrolidone, polyethylene glycols, particularly those having molecular weights in the range from 1,500 to 1,000,000.