Composition, comprising hydrofluoric acid, for inhibiting dental erosion

Abstract

The present invention relates to a composition, for inhibiting dental erosion, and the use thereof. The composition comprises an aqueous solution of hydrofluoric acid, in which the concentration of hydrofluoric acid is 0.05%-2.00% and the pH is between 2.5 and 4.5.

Claims

1. A composition with active agent for inhibiting dental erosion, the composition consisting essentially of hydrogen fluoride, and at least one of a humectant, a binder a thickening agent, an abrasive agent, a surfactant and a flavoring agent, wherein the hydrogen fluoride is the only fluoride present and is present in an aqueous solution at a concentration of 0.1-1% (w/v), the pH of the aqueous solution being between 2.5 and 4.5, and wherein the active agent is un-dissociated hydrogen fluoride.

2. The composition according to claim 1, wherein said abrasive agent is present and is selected from the group consisting of silica, xerogels, hydrogels and aerogels.

3. The composition according to claim 2, wherein said abrasive agent is silica in a concentration of 3-75% by weight.

4. The composition according to claim 1, wherein said humectant is present and is selected from the group consisting of cellulose, xanthan gum, sorbitol, glycerol, propylene glycol, polypropylene and polyethylene glycol.

5. The composition according to claim 1, wherein said binder and said thickening agent are present in a concentration of 0.5-10% by weight of the composition.

6. The composition according to claim 1, wherein said surfactant is present and is an anionic surfactant.

7. A composition for inhibiting dental erosion according to claim 1 in the form of a dentifrice.

8. A composition for inhibiting dental erosion according to claim 1 in the form of a gel.

9. A dentifrice with active agent for inhibiting dental erosion of teeth caused by organic acids, the dentifrice consisting essentially of a liquid phase that is 10-99% by weight of water and humectants, and hydrogen fluoride as the only fluoride present, wherein the hydrogen fluoride present at a concentration of 0.1-1% (w/v), wherein the pH of the dentifrice is between 2.8 and 4.5, and wherein the active agent is un-dissociated hydrogen fluoride.

10. The dentifrice according to claim 9, wherein said liquid phase comprises said humectant in a concentration of 10-90% by weight of the dentifrice.

11. A gel composition with active agent for inhibiting dental erosion, the gel composition consisting essentially of (a) 1-2% of a thickening agent; (b) optionally one or more of a sweetening agent and a flavoring agent; and (c) hydrogen fluoride as the only fluoride present at a concentration of 0.1-1% (w/v), wherein the pH of the aqueous solution is between 2.5 and 4.5, and wherein the active agent is un-dissociated hydrogen fluoride.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) FIG. 1 describes solubility reduction of teeth in aqueous solutions.

(2) FIG. 2 describes solubility reduction of enamel.

(3) FIG. 3 describes solubility reduction of dentine.

(4) FIG. 4 describes solubility reduction of cementum.

DETAILED DESCRIPTION

(5) Aqueous solutions of hydrofluoric acid (HF) are a weak acid which buffers between pH 3 and 4 and has a pK.sub.a of 3.45. The present invention is based on the observation that HF between pH 3 and pH 4 has unique properties by providing dental mineral tissues (i.e. enamel dentine and cementum) with a surface layer which forms immediately, and protects the mineralized tissues against erosive acids. This layer consists of calcium fluoride-like material which is particularly resistant against erosive acids. Possibly because it is formed under acidic condition. In the experiments concerning this effect we have used severe erosive challenges to ascertain that this was a clinically significant effect. The erosive challenge was 0.1M citric acid of pH 2.2, for 30 min., and human teeth were used. In vivo it is known that human saliva can neutralize acids, and that proteins adsorbed to teeth will protect the dental surfaces to some degree, against erosive acids. No attempts to mimic these protective forces were included, and it is believed that the experimental conditions used are more severe than most clinical challenges.

(6) Because of the buffering capacity of aqueous solutions of HF, the formation of the protective layer is formed at low pH, which appears to be favourable. It is furthermore believed that un-dissociated HF has the ability to come closer to the charged enamel surface than charged species of F. Un-dissociated HF can probably interact with the tooth surface by ionic exchange without, (or with a minimum of), free protons, which could etch and cause damage to the tooth surface. This concept would indicate that the region below the pK.sub.a is of particular significance for the unique effect of aqueous HF.

(7) The oral compositions of the present invention may contain orally acceptable ingredients in conventional amounts, depending upon the final form of the composition, i.e. whether a dentifrice a gel or a lozenge. A dentifrice will usually comprise an abrasive agent cleaning agent in an amount of from 3-75% by weight. Suitable abrasive cleaning agents are particulate aluminas, silica, xerogels, hydrogels and aerogels, and precipitated particulate silicas, calcium pyrophosphate, insoluble sodium metaphosphate, calcium carbonate, dicalcium orthophosphate and several others.

(8) Dentifrices usually contain liquid phase comprising water and humectants in amounts of 10-99% by weight. Typical humectants are sorbitol, glycerol, propylene glycol, polypropylene glycol and many others.

(9) A wide variety of thickening agents or binders are used in dentifrices including sodium carboxyl methyl cellulose, hydroxyethyl cellulose, finely devided silica, xanthan gum, Irish moss and synthetic hectorites. The amount of binders will usually range from 0.5-10% by weight of the dentifrice.

(10) A further conventional ingredient of a dentifrice is an organic surfactant. Anionic surfactant is usually preferred because of their good foaming properties. Sodium lauryl sulphate is usually chosen, but an alkyl aryl sulphates, especially sodium dodecyl benzene sulphonate can be used in the present invention.

(11) Various optional ingredient may be included of the invention including flavouring agents, sweetening agent such as sodium saccharin, and whitening agent such as titanium dioxide, anti-plaque agents, and agents for adjusting the pH of the dentifrice, which may range from 2.8-4.5. Such agents for acidification includes citric-, acetic- or maleic acids and their buffers. Weak inorganic acids such as phosphoric or fluoride acids, and strong acids as hydrochloric acid and its buffers.

(12) A gel for topical application according to the present invention may contain from 1% to 0.1% F.sup.−, depending on whether the gel is designed for weekly or daily use. The gel contain a thickening agent such as water soluble salts such as sodium carboxy methyl cellulose. Natural gums like gum arabic can also been used as thickeners in gels. The concentration of thickener is usually from 1-2%. A sweetening agent like xylitol or saccharin can be added in amounts of 5-10% or 0.2-0.3%, respectively, and a flavouring agent.

(13) A lozenge according to the present invention should contain 0.25 mg F and 100 mg of citric acid, and in addition 400 mg of xylitol, a flavouring agent and necessary constituents up to 0.6 g.

Experiment

(14) Extracted teeth were cleaned and pre-treated for 5 min with 0.01% HCl to eliminate differences in solubility between the individual teeth, and then treated with diluted hydrofluoric acid. The teeth (usually 6 parallels) were then exposed to 0.1M citric acid or 0.01% HCl for 30 min, and the release of calcium into the acid measured by atomic absorption. The teeth treated with hydrofluoric acid were compared with control teeth (usually 6) which were only exposed to water. The results are given in FIG. 1. It can be seen that treatment with 0.1% hydrochloric acid gave a solubility reduction of 20% of the control, whereas 1% hydrochloric acid gave a solubility reduction of close to 80%. Teeth treated with 0.4% of stannous fluoride was included for comparison. FIG. 1 shows the results of whole teeth treated with 0.01M HCl, whereas FIGS. 2, 3 and 4 shows the result of etching with 0.1% citric acid on enamel, dentine and cementum. Treatment with low concentrations of aqueous solutions of HF cause major reductions in solubility of the tooth samples. This example demonstrates that diluted hydrofluoric acid (0.1-1.0%) reduces the solubility of enamel (see FIG. 2), Dentine (see FIG. 3) and cementum (see FIG. 4) in 0.1M citric acid.

(15) The teeth were cut in two at the enamel cementum junction and the exposed dentine covered by acid resistant varnish. Dentin samples was made by removing enamel from tooth crowns and varnished as described above. The experiments were performed in 6 parallels. The tooth samples were first exposed to 0.1M citric acid for 30 min. The teeth were then washed in distilled water and dried, and then treated with the respective dilutions of hydrofluoric acid for 10 min. The teeth were individually treated and each tooth served as its own control. The teeth were again washed and dried and then treated with 0.1M citric acid for the second time.

(16) The solubility of the tooth samples was assessed by measuring the concentration of calcium in the citric acid. A reduction in calcium concentration between the first and second citric acid samples was assumed to be caused by the profylactic treatment with hydrofluoric acid dilutions.

(17) It can be seen from the figures that 0.1% of HF caused about 45% reduction in the solubility of enamel (FIG. 2), 80% reduction in dentine solubility (FIG. 3), and 95% reduction of cementum solubility (FIG. 4). 0.2% HF reduced the solubility 90%, 90% and 95% respectively.

(18) It can thus be seen that very low concentrations of HF have major effects on solubility. (0.1% HF represents 1 part of 40% HF in 399 parts of water and its application on teeth represents no health hazard.

Example 1

(19) A gel having the following composition was made:

(20) TABLE-US-00001 Ingredient % Silica thickener   50% Xanthan gum  0.1% Sodium saccharin 0.23% Xylitol   5% Cardemom oil   1% Hydrofluoric acid  0.3% Water ad  100%

Example 2

(21) A dentifrice having the following composition was made:

(22) TABLE-US-00002 Silica abrasive   60% Sorbitol syrup (70% sol)   25% Xanthan gum   1% Sodium saccharide 0.25% Sodium lauryl sulfate  1.0% Flavour (Cardedmom oil)  1.0% Hydrofluoric acid  0.1% Water add  100%

Example 3

(23) A toothpaste according to the present invention (%) Silica Abrasives: 56 Sorbitol (70% sol): 21 Sodium lauryl sulphate 1.5 Xanthan gum: 0.875 Titan dioxide: 0.5 HCl(37%): 0.15 F.sup.−: 0.15% Citric buffer pH 3.0, 0.1 M add 100