WO2007122146A1

WO2007122146A1 - Toothpaste

Info

Publication number: WO2007122146A1
Application number: PCT/EP2007/053743
Authority: WO
Inventors: Nand Sanmukhdas Bijlani; Supesh Jain; Sharad Mukund Kilpady; Philip Christopher Waterfield
Original assignee: Unilever Plc; Unilever N.V.; Hindustan Unilever Limited
Priority date: 2006-04-26
Filing date: 2007-04-17
Publication date: 2007-11-01
Also published as: MX2008013710A; BRPI0710369A2; EP2010292A1

Abstract

A toothpaste composition comprising an abrasive calcium compound, a fluoride salt, alkali metal silicate and a salt selected from the class comprising alkali metal citrates.

Description

TOOTHPASTE

Technical Field

The invention relates to a toothpaste composition and more particularly a toothpaste having good fluoride and physical stability.

Background and prior art

Dentifrices generally contain an abrasive that helps in cleaning of the teeth. One class of commonly used abrasives include insoluble compounds of calcium, magnesium or aluminium e.g. alumina, calcium carbonate, dicalcium phosphate dehydrate. Of these, the toothpastes that contain calcium compound based abrasives are known as chalk-based toothpastes. Chalk based toothpaste are generally opaque. Another class of abrasives used commonly in toothpaste manufacturing are silicas. When carefully selected abrasive silicas are used in preparing dentifrices, gel type toothpastes can be prepared which have a transparent or translucent appearance. Various other additives have traditionally been added to toothpastes to provide many oral care benefits. Fluoride toothpastes have generally been very successful in providing anti-caries benefits.

It has been observed that the chemical stability of fluoride in chalk-based toothpastes is not very good. GB999857 (1965) describes a toothpaste comprising a substantially insoluble calcium or magnesium salt abrasive, a therapeutic amount of alkali metal fluoride and sufficient silica in water-soluble form preferably alkali metal silicate to provide a toothpaste having improved fluoride availability. The present inventors have found during the course of their extensive research directed to providing a chalk based toothpaste having enhanced fluoride stability that while alkali metal silicate provides improvement in the fluoride stability in these toothpastes, there are other problems related to product stability found associated with such formulations. The present inventors found that these toothpastes display syneresis on storage particularly at higher temperatures. Syneresis is a phenomenon wherein the flavour, water and other water-soluble components separate from the main semi-solid or paste phase. The present inventors have worked assiduously to solve this problem and have arrived at a solution that involves the inclusion of a selective class of salts that ensures that these toothpastes provide the necessary fluoride stability while having the desired phase stability on extended storage. The toothpaste compositions of the invention show enhanced physical stability over an extended period of storage without any separation of the liquid phase. When stored at different temperatures, the toothpaste composition exhibits the desired fluoride stability while product integrity and stability is improved. The compositions also exhibit high visual appeal on extended storage at low, ambient and high temperatures .

WO02030381 (Block Drug Co) describes an anhydrous composition for reducing dentinal hypersensitivity and remineralising exposed dentinal surface comprising a desensiting agent selected from an alkali metal salt where the alkali metal is strontium or potassium and the anion is bicarbonate, citrate, chloride, nitrate or acetate, a water soluble calcium salt and an incompatible ingredient selected from water soluble silicate, water-soluble phosphate salts and water soluble fluoride salts. This publication describes anhydrous compositions, which do not include chalk as an abrasive and therefore does not teach the solution to a problem encountered in stabilizing fluoride in these kinds of toothpastes.

Thus, although many salts, as described in the above prior art have been used in oral care compositions including toothpastes, none of the prior art disclose a solution to the problems encountered in stabilizing fluoride in chalk based tooth paste formulations while maintaining their physical stability over extended periods of storage.

It is thus an object of the present invention to provide for a toothpaste that exhibits enhanced fluoride stability as compared to prior art compositions.

It is another object of the present invention to provide for toothpaste that exhibits enhanced fluoride stability while maintaining the desired physical integrity during extended periods of storage.

Summary of the Invention

According to one aspect of the invention there is provided a toothpaste composition comprising an abrasive calcium compound, a fluoride salt, alkali metal silicate and a salt selected from the class comprising alkali metal citrates. - A -

It is particularly preferred that the fluoride salt is sodium mono fluoro phosphate. It is further particularly preferred that said salt is tri potassium citrate.

According to another aspect of the invention there is provided a process for preparing a toothpaste composition comprising an abrasive calcium compound, a fluoride salt, alkali metal silicate and a salt selected from the class comprising alkali metal citrates, said process comprising the steps of

(i) Mixing said salt in water and other optional ingredients like humectant to prepare a solution

(ii) Adding the abrasive calcium compound to said solution with mixing to prepare a uniform mixture (iϋ) Adding and mixing the alkali metal silicate followed by the fluoride salt to said mixture to prepare the toothpaste .

Detailed description of the invention The invention provides for a chalk based toothpaste composition having enhanced fluoride stability as well as enhanced physical stability on extended storage. The toothpaste composition of the invention comprises abrasive calcium compound, a fluoride salt, alkali metal silicate and a salt selected from the class comprising alkali metal citrates .

The abrasive calcium compound is chosen from fine ground natural chalk (FGNC) , precipitated calcium carbonate (PCC) or dicalcium phosphate dihydrate (DCPD) . Of these calcium compounds, FGNC & PCC is more preferred. Not only is FGNC a less expensive and more widely available abrasive, the improvement in fluoride stability and phase stability of the toothpaste is observed to be better in FGNC based toothpastes. The abrasive calcium compound is present in an amount in the range of 20 to 70 %, more preferably 25 to 50% by weight of the composition.

A fluoride salt is present in the toothpaste composition of the invention. Suitable fluoride salts are sodium fluoride, sodium mono fluoro phosphate or potassium fluoride, preferably sodium mono fluoro phosphate (SMFP) . The fluoride salts are preferably present in an amount in the range of 0.3% to 1.5% by weight of the toothpaste.

An alkali metal silicate is present in the toothpaste composition of the invention. The alkali metal may be sodium or potassium, preferably sodium. Thus sodium silicate is the most preferred alkali metal silicate, present in the toothpaste of the invention. Sodium silicate is generally available as a 10% to 40% aqueous solution, most common being 30% solutions. Sodium silicate is available as neutral sodium silicate or alkaline sodium silicate. Neutral sodium silicate is preferred in the toothpaste composition of the invention. Sodium with varying ratios of Na2θ: SiO2 is available. Sodium silicate with Na2U: SiO2 ratio in the range of 3.0 to 3.8 is preferred, more highly preferred range being 3.25 to 3.5. The alkali metal silicate is present in an amount in the range of 0.1 to 5.0% on dry weight basis with respect to the weight of the composition. Thus a 30% solution of sodium silicate is added to the composition in an amount in the range of 0.3 to 16.0%.

The salt is selected from the class comprising alkali metal citrates e.g. the salt could be mono, di or tri sodium or potassium citrate. Of these salts, tri potassium citrate is more preferred. It has been observed that any of these salts, when incorporated in the toothpaste of the invention, provides for excellent physical stability of the toothpaste. Further, when stored at extreme conditions of temperature from i.e. from 6 to 50 ⁰C, for extended periods of time of up to three months, incorporation of these salts also provides for very good surface properties like smoothness and ribbon stand-up.

The toothpaste of the present invention preferably comprises a flavor. The flavor may be peppermint, spearmint, menthol or combinations thereof. It has been observed in the past that the stability of such flavors in fluoride containing chalk-based toothpastes is poor. It has been surprisingly found that not only does the composition of the invention provide for fluoride stability in addition to physical stability of the toothpaste on storage, the flavor stability and impact is also better as compared to similar toothpastes of the prior art. The flavor is present in an amount in the range of 0.5 to 2% by weight of the composition.

The toothpaste also comprises other conventional ingredients e.g. a humectant. The preferred humectants are sorbitol, polyethylene glycol, xylitol, or glycerine. The humectant is present in an amount in the range of 5 to 40% on dry weight basis by weight of the composition. The toothpaste comprises water. The preferred amount of water is in the range of 10 to 50% by weight of the composition.

The toothpaste composition of the invention preferably has fluoride stability such that fluoride concentration after storage up to 50 ⁰C for three months is at least 80% of the initial fluoride concentration and the toothpaste displays no visible syneresis.

The compositions of the invention may also contain other ingredients such as sweetening agents, anti-microbial agents, binders, thickening agents, buffering agents, gloss enhancing agents, colours and preservatives.

The invention is now illustrated with the help of the following non-limiting examples.

Examples

In the following examples, Comparative examples are indicated by letters and examples according to the invention by number. The levels of components indicated are percentages by weight. Table 1: Compositions

The fluoride content [F] of the various toothpaste compositions indicated above were measured before and after storage using the following procedure.

Method of determination of fluoride content:

A portion of paste is boiled with dilute hydrochloric acid and any hydrolysable fluorine containing complexes are broken down to liberate fluoride ion. The fluoride ion activity is measured with a fluoride electrode. The fluoride electrode used was Orion 94 - 09 and the single junction reference electrode used was Orion 90 - 01. The quantity of fluoride ion present in the paste is calculated by comparison with a calibration curve prepared using the measured increase in fluoride ion activity produced by the addition of known amounts of fluoride ion. The linearity of response and the Nernst slope of the electrode are determined daily by a graphical standardisation method.

In a first series of tests, the compositions of Table 1 were stored at 40⁰C for three months. The fluoride content [F] in ppm and appearance/physical stability of the toothpastes were noted. The results are summarized in Table 2.

Table 2: Storage Stability of Compositions of Table 1

The invention thus provides for a chalk-based fluoride containing toothpaste that has high fluoride stability and good physical stability on extended storage as compared to toothpastes available in the prior art.

Compositions according to Table 3 were also prepared and placed on storage under various conditions for several months. Table 4 indicates the storage stabilities observed, the results illustrating the superior fluoride stability and superior flavor stability for compositions according to the invention. Table 3: Further Compositions

Claims

We Claim

1. A toothpaste composition comprising an abrasive calcium compound, a fluoride salt, alkali metal silicate and a salt selected from the class comprising alkali metal citrates .

2. A toothpaste composition as claimed in claim 1 wherein said salt is ;.ii potass:,uπ citrate.

3. A toothpaste composition as claimed in claim 1 or claim 2 wherein the abrasive calcium compound is chosen from fine ground natural chalk (FGNC) , precipitated calcium carbonate (PCC) or dicalcium phosphate dehydrate (DCPD) .

4. A toothpaste composition as claimed in claim 3 wherein the abrasive calcium compound is FGNC.

5. A toothpaste composition as claimed in any one of the preceding claims wherein the abrasive calcium compound is present in an amount in the range of 20 to 70 % by weight of the composition.

6. A toothpaste composition as claimed in any one of the preceding claims wherein the fluoride salt is sodium mono fluoro phosphate (SMFP) .

7. A toothpaste composition as claimed in any one of the preceding claims wherein the alkali metal silicate is sodium silicate.

8. A toothpaste composition as claimed in any one of the preceding claims wherein the sodium silicate is neutral sodium silicate having a Na2θ: SiC>2 ratio in the range of 3.0 to 3.8.

9. A toothpaste composition as claimed in any one of the preceding claims wherein the alkali metal silicate is present in an amount in the range of 0.1 to 5% on dry weight basis with respect to the weight of the composition.

10. A toothpaste composition as claimed in any one of the preceding claims comprising said salt in an amount in the range of 0.1 to 2% by weight of the composition.

11. A toothpaste composition as claimed in any one of the composition comprising a flavor.

12. A toothpaste composition as claimed in claim 11 wherein the flavor is peppermint, spearmint, menthol or combinations thereof.

13. A toothpaste composition as claimed in claim 11 or 12 wherein the flavor is present in an amount in the range of 0.5 to 2% by weight of the composition.

14. A toothpaste composition as claimed in any one of the preceding claims comprising a humectant.

15. A toothpaste composition as claimed in claim 14 wherein said humectant is chosen from sorbitol, polyethylene glycol, xylitol, or glycerine.

16. A toothpaste composition as claimed in claim 14 or 15 wherein the humectant is present in an amount in the range of 5 to 40% on dry weight basis by weight of the composition .

17. A toothpaste composition as claimed in any one of the preceding claims comprising water in an amount in the range of 10 to 50% by weight of the composition.

18. A toothpaste composition as claimed in any one of the preceding claims having a fluoride stability of at least 80% of the initial fluoride concentration and no visible synerisis after storage uoLo 50 °C for three months .

20. A process for preparing a toothpaste composition as claimed in any one of the preceding claims comprising the steps of

(i) mixing said salt in water and optionally the humectant to prepare a solution (ϋ) adding the abrasive calcium compound to said solution with mixing to prepare a uniform mixture (iii) adding and mixing the alkali metal silicate followed by the fluoride salt to said mixture to prepare the toothpaste.