Aqueous Solution Containing TiF.sub.4 and Chelating Agent

The present invention relates to an aqueous solution containing an anti-caries effective amount of TiF.sub.4.

Titanium tetrafluoride has been reported as providing greater reduction of enamel solubility and greater protection against animal caries than comparable levels of other fluorides, as well as forming a glaze on the teeth. Shresta et al., Enamel Dissolution: I. Effects of Various Agents and Titanium Tetrafluoride, J. Dent. Res. 51,1561-1566, 1972 and II. Action of Titanium Tetrafluoride, J. Dent. Res. 51, 1567-1571, 1972. In the patent literature, TiF.sub.4 is used in the form of a 1% aqueous solution having a pH of about 1.5, see, e.g. Mundorf et al., U.S. Pat. No. 3,751,568, but this highly acidic solution may result in marked irritation to the mouth unless carefully applied, and hence the use of TiF.sub.4 has been suggested for annual or semi-annual applications of a 1% aqueous solution of TiF.sub.4 by a dentist. Prior efforts to provide TiF.sub.4 in other than the highly acidic 1% solution have not been successful, because TiF.sub.4 is unstable in aqueous media at a pH above 3.0 and this coupled with its potential for irritation has prevented the use of TiF.sub.4 in consumer products.

The present invention now provides an aqueous solution comprising an anti-caries effective amount of TiF.sub.4 and an amount of a chelating agent effective to stabilize the TiF.sub.4. Since the TiF.sub.4 is stabilized by the chelating agent, the solution of the present invention has the required stability to be sold to the consumer using conventional over-the-counter channels of trade.

Furthermore, the aqueous solution of the present invention avoids the low pH at which conventional aqueous TiF.sub.4 solutions are employed, and hence the skin irritation arising from the prior art TiF.sub.4 solutions is also avoided. This is an important factor in a consumer product, since repeated use and lack of care would make skin irritations more pronounced. The consumer can now use the TiF.sub.4 -containing aqueous solution of the invention on a daily basis instead of being limited to annual treatments with TiF.sub.4 by a dentist.

In addition to the advantage of enhanced fluoride uptake, the solution of the invention also forms a protective glaze on the teeth in the form of an organo-metallic complex. when the amount of TiF.sub.4 is at least about 1.0% by weight, based on the total composition. This glaze renders the teeth more acid-resistant and may desensitize exposed dentin by sealing exposed dentin tubules. This latter effect may protect susceptible teeth against root caries.

The aqueous solution of the invention comprises a chelating agent to stabilize TiF.sub.4 in the aqueous solution and thereby prevent decomposition of the TiF.sub.4. A wide range of chelating agents may be used in the present invention, particularly those containing chelating hydroxy, carboxy and/or sulfonic acid groups, ethylenediaminetetraacetic acid, salicyclic acid, citric acid, 2,4 and 2,6-dihydroxybenzoic acids, dihydroxytartaric acid, nitrilotriacetic acid, tartaric acid, 4,5-dihydroxy-1,3-benzenedisulfonic acid, mandelic acid, malic acid, mellitic acids, oxalic acid and acetic acid. The acid groups may be in the form of the free acid or metal salt thereof. Alternatively, the chelating agent may be added in the form of a metal chelate, particularly a di- or trivalent metal chelate. Examples of such metal chelates include complexes of .beta.-diketones with aluminum and chromium, for example aluminium and chromium triacetylacetonates, and ethylene diamine tetraacetic acid complexes of zinc and copper. It is presently preferred to use tartaric acid or citric acid or their alkali metal salts, or other chelating agents containing both chelating hydroxy and carboxy groups.

The amount of the chelating agent will generally be from about 0.10 to about 15%, preferably from about 0.30 to about 6.0%, of the solution. It is presently preferred that the ratio of the chelating agent to the TiF.sub.4 be from about 1:1 to about 5:1 or more, preferably from about 2:1 to about 4:1.

The aqueous solution of the present invention also comprises an anti-caries effective amount of TiF.sub.4. Preferably, the solution will provide at least 250 ppm F to obtain an anti-caries effect and hence the amount of TiF.sub.4 in the solution will preferably be at least about 0.04%, such as from about 0.04 to about 2.5%, and most preferably from about 0.12 to about 1.0%.

One preferred embodiment of the invention provides from about 0.10 to about 0.30% of TiF.sub.4 and from about 0.10 to about 1.5% of said chelating agent, by weight based on the total composition.

Another preferred embodiment of the invention provides from about 1.0 to about 2.5% TiF.sub.4 and from about 1.0 to about 12.5% of said chelating agent, by weight based on the total composition.

The aqueous solution of the present invention may be used as an anti-caries dentifrice or mouthrinse, and may contain alcohol, humectants, such as glycerin, aqueous sorbitol, polyethylene glycol or polypropylene glycol and surfactants, including cationic, anionic and non-ionic surfactants. When present, it is suitable to use from about 6 to about 25% alcohol, from about 3 to about 15% humectant and from about 0.5 to about 2.5% surfactant.

Other materials may be added, such as soluble saccharin, flavoring oils (e.g. oils of spearmint, wintergreen, peppermint), coloring agents, menthol, chlorophyll compounds (e.g. sodium copper chlorophyllin), and anti-bacgerial agents (e.g. chlorhexidine). These materials, when present, will be in minor amounts, such as up to about 4%, e.g. from about 0.05 to about 3% in total.

The aqueous solution of the invention is prepared in the usual manner by dissolving the ingredients in water to form a solution. The pH of the solution will generally be from between about 3.5 and about 5.5. The aqueous solution whether formulated as a dentifrice or mouthrinse, is used in a conventional manner by placing a small portion in the mouth and swirling the solution into contact with the teeth and gums, after which the solution is expelled.

In a preferred embodiment of the invention, the TiF.sub.4 is admixed with an aqueous solution of the chelating agent to solubilize the TiF.sub.4, and then the remaining ingredients are combined with the mixture of TiF.sub.4 and the chelating agent.

The present invention is illustrated in terms of its preferred embodiments in the Examples that follow. In this specification and claims, all parts and percentages are by weight, unless otherwise stated.

The chelating agent was dissolved in water and the TiF.sub.4 was added and solubilized, after which sodium saccharin, flavor and dye were added. An aqueous solution of pH of 5.0 was obtained for use as an anti-caries dentifrice.

Following the procedure of Example 1, the above ingredients were combined to form a solution for use as an anti-caries mouthrinse. The aqueous solution had a pH of 5.0.

The TiF.sub.4 -containing composition of the present invention also has the unexpected advantage of providing greater uptake of fluoride in teeth than products using sodium fluoride or sodium monofluorophosphate. In addition, the composition of the present invention also provides increased titanium uptake as well.