ORAL HYGIENE COMPOSITIONS

Abstract: An oral hygiene composition in the form of a dentifrice or mouthwash, comprising; (a) an aqueous solution containing hydrogen citrate ions and fluoride ions in a weight ratio from 10:1 to 500:1 and (b) an orally acceptable carrier, the concentration of hydrogen citrate ions in the composi­ tion being from 10⁻³ to 10⁻¹ M in a mouthwash, or from 4 x 10⁻³M to 4 x 10⁻¹M in a dentifrice, and the pH of the composition being less than 7.

Description: The present invention relates to oral hygiene compositions, and in particular to dentifices and mouth washes having improved anticaries effect. A variety of anticaries agents have hitherto been used in dentifrices and mouthwashes, including alkali metal fluorides and alkali metal monofluorophosphates. It has now been discovered that enhanced anticaries effect can be achieved when a combination of fluoride ions and hydrogen citrate ions is used within a specified weight ratio and below a certain pH threshold. In the past, oral hygiene compositions comprising a fluoride ion source and citrate have been disclosed. Thus, US 3 282 792 discloses compositions comprising stannous fluoride and a hydroxyl substituted aliphatic acid such as citric acid, the function of the latter being to maintain stannous ions in solution, to avoid formation of an insoluble precipitate. Us 3 227 617 discloses dentifrices comprising, as an abrasive, a mixture of an insoluble alkali metal metaphosphate and an insoluble calcium or magnesium polishing agent which is compatible with fluoride. Citric acid may be added as a buffer, to provide dentifrices with pHs in the range 5 to 6.5. EP 0 095 871 discloses oral hygiene compositions having a combination of potassium ions and citrate ions, for use as an antisensitivity system. A fluoride ion source may be added as an optional extra. In each case however there is no suggestion that hydrogen citrate may enhance the anticaries effect of fluoride ions. With reference to German patent application No. 3 526 654 (Lion Corporation), the applicant has voluntarily limited the scope of the present application and submitted separate claims for Germany. Accordingly the present invention provides for the use of hydrogen citrate ions and a source of fluoride ions in a weight ratio of from 10:1 to 500:1, for the manufacture of a mouthwash or a dentifrice for anti-caries therapy, such that in the mouthwash the concentration of hydrogen citrate ions is from 1 x 10⁻³ to 1 x 10⁻¹M and in the dentifrice the concentration of hydrogen citrate ions is from 4 x 10⁻³ to 4 x 10⁻¹M, with the fluoride ions provided by an alkali metal monofluorophosphate and/or an alkali metal fluoride, and the mouthwash or dentifrice having a pH of less than 7. The preferred weight ratio of hydrogen citrate ions to fluoride ions is from 50:1 to 250:1 Preferably, the hydrogen citrate ions are provided by a soluble alkali metal salt, such as disodium hydrogen citrate. Preferably, the fluoride ions are provided by an alkali metal monofluorophosphate and/or an alkali metal fluoride. Preferably, the concentration of hydrogen citrate ions is from 5 x 10⁻³M to 3 x 10⁻²M in a mouthwash, and from 2 X 10⁻²M to 1.2 X 10⁻¹M in a dentifrice. Preferably, the pH of the composition is from 4.0 to 5.0. The percentage by weight of citrate material in the compositions of the invention will, of course, depend on the molecular weight of the material. However, in general, a dentifrice composition of the invention will contain from 0.1% to 10% % by weight of alkali metal hydrogen citrate, preferably from 0.4% to 4.0%, and a mouthwash will contain from 0.025% to 2.5% by weight of alkali metal hydrogen citrate, preferably from 0.1% to 1.0% by weight of the composition. The preferrred alkali metal fluoride is sodium fluoride, and the preferred alkali metal monofluorophosphate is sodium monofluorophosphate. The composition of the invention preferably comprises from 100 ppm to 2500 ppm of fluoride ions in total. When the composition is a dentifrice, preferably from 10 to 90%, more preferably 40 to 80%, of the fluoride is provided by the alkali metal fluoride and the remainder is provided by the alkali metal monofluorophosphate. When the composition is a mouthwash, the fluoride may be provided entirely by alkali metal fluoride. A dentifrice composition according to the invention preferably includes a dentally acceptable abrasive in the orally acceptable carrier, and the choice of abrasive need only be limited by the necessity of keeping the pH of the final composition below 7. Calcium carbonate has been found to give a composition pH above 7, so is not suitable for use in the present invention. Examples of suitable abrasives are dicalcium phosphate, alumina, calcium pyrophosphate, pumice, methyl methacrylate and silica, the latter being particularly preferred. The silica abrasive can be a precipitated silica or a silica gel, such as the silica xerogels described in US Patent No. 3538230. Preferred silica xerogels are marketed under the trade name 'Syloid' by W.R. Grace and Company, Davison Chemical Division. Preferred precipitated silicas are those marketed under the tradename 'Zeodent' by the J.M. Huber Corporation. The amount of abrasive will be within conventional limits, and will normally vary from about 15% to 50% by weight of the composition. The compositions of the invention may optionally contain other agents known to enhance the anticaries effect of fluoride and monofluorphosphate, such as calcium glycerophosphate, this being incorporated in a weight ratio of up to 1:3, preferably 1:20 to 1:3, to the total weight of fluoride and/or monofluorophosphate salts. The composition of the invention may be presented in conventional toothpaste, dental cream and dental powder formulations, or as a conventional mouthwash formulation. Compositions according to the invention are able to reduce plaque growth and increase plaque pH thereby reducing acid formation and hence reducing the severity of attack on the tooth enamel. The increase in plaque pH is significantly enhanced by hydrogen citrate ions, as shown in the data section below. Compositions according to the present invention may be produced by admixture of the various ingredients and may contain the usual optional accessory ingredients such as detergents, dyes, sweetening agents, for example soluble saccharin, flavouring oils, for example oils of spearmint, wintergreen or peppermint, chloroform, colouring or whitening agents for example titanium dioxide, preservatives for example sodium benzoate, emulsifying agents, silicones, alcohol, menthol chlorophyll compounds for example sodium copper chlorophyllin, antibacterial agents, for example chlorhexidine, anti-plaque agents, anti-calculus agents, agents for sensitive dentine for example strontium salts or formaldehyde, and agents which enhance the anticaries activity of fluorides (e.g. calcium glycerophosphate). The compositions of the invention may, accordingly, be prepared by admixing hydrogen citrate and fluoride ion sources in an aqueous medium, and combining the resultant aqueous solution with an orally acceptable carrier at a temperature below the boiling point of water to produce a composition with a pH less than 7. In another aspect, the invention also provides a use in which the composition is a dentifrice and the abrasive is silica. In a further aspect, the invention provides a dentifrice in which the abrasive is selected from dicalcium phosphate, alumina, calcium pyrophosphate, pumice, methyl methacrylate and silica, and excluding dentifrices comprising dipotassium citrate and methyl methacrylate. The invention is illustrated by the following examples. Example 1 Mouthwash formula % w/w 70% sorbitol 5.00 Saccharin 0.003 Nipasept 0.1 Bromopol 0.01 Dyes (Blue No. 1) 0.001 (Yellow No. 10) 0.003 Flavours 0.05 Sodium fluoride 0.032 Sodium monofluorophosphate 0.1 Disodium hydrogen citrate 0.40 Water to 100% Example 2 Toothpaste in silica Base % w/w Zeodent 113 18.00 Sorbitol 50.00 Syloblanc 34 3.50 Glycerin 4.50 Carboxymethyl cellulose CMC 7MF 1.00 Flavour 0.60 15% Saccharin solution 1.20 Sodium monofluorophosphate 0.38 Sodium fluoride 0.11 Disodium hydrogen citrate 1.60 Nipagin Sodium 0.15 30% Empicol 4.00 Calcium glycerophosphate 0.07 Water 13.24 Natrosol 250H 1.50 0.1% FD ε C No 1 Dye 0.15 Example 3 Gel Formula Translucent %w/w Clear %w/w 70% Sorbitol Solution 50.00 65.00 PEG 300 3.00 3.00 Tixosil 53 BE 16.00 16.00 Aerosil 200 2.50 2.20 CMC 7M8 5XF 1.00 0.80 30% Sodium lauryl Sulphate 7.50 7.50 PVP K29-32 0.10 0.10 Butylated hydroxy toluene 0.10 0.10 Disodium hydrogen citrate. 0.60 0.60 Sodium monofluorophosphate 0.80 0.80 Calcium glycerophosphate 0.13 0.13 Flavour 0.90 0.90 Saccharin 0.20 0.20 0.2% F.D+C Blue No. 1 0.875 0.875 Water 16.295 1.795 Test Data 1. Effect on the pH of dental plaque 20 subjects were randomly allocated to a treatment and were allowed to use a test mouthwash or toothpaste for 1 week ad . lib . They then refrained from all oral hygiene measures for 24 hours. On the test day each subject refrained from eating or drinking for 1 hour prior to and during the test period. Each subject rinsed his mouth with 10 ml of a 3:1 slurry in water of the test toothpaste, or the test mouthwash. 30 minutes later plaque samples were collected from the molars and premolars and the mouth was then rinsed with 10ml of 10% w/v aqueous sucrose. Ten minutes later plaque samples were again taken from the molars and premolars. Each plaque sample, immediately following sampling, was suspended in 20µl physiological saline and the pH was measured using a microcombination electrode. The whole procedure was repeated on two further occasions. The results are presented in the Table. The results presented in Tables I and II show that the addition of disodium hydrogen citrate to both fluoride mouthwashes and dentifrices significantly reduced the plaque pH fall following a challenge with aqueous sucrose over and above that from the fluoride formulation alone. Therefore the addition of disodium hydrogen citrate to such formulations would appear to improve the ability of the formulation to reduce dental caries.

Claims: The use of hydrogen citrate ions and a source of fluoride ions in a weight ratio of from 10:1 to 500:1, for the manufacture of a mouthwash or a dentifrice for anticaries therapy, such that in the mouthwash the concentration of hydrogen citrate ions is from 1 x 10⁻³ to 1 x 10⁻¹M and in the dentifrice the concentration of hydrogen citrate ions is from 4 x 10⁻³ to 4 x 10⁻¹M, with the fluoride ions provided by an alkali metal monofluorophosphate and/or an alkali metal fluoride, and the mouthwash or dentifrice having a pH of less than 7. A use according to claim 1, in which hydrogen citrate ions are present in a concentration of from 5 x 10⁻³M to 3 x 10⁻²M in a mouthwash and from 2 x 10⁻²M to 1.2 x 10⁻¹M in a dentifrice. A use according to claim 1 or 2, in which the weight ratio of hydrogen citrate ions to fluoride ions is from 50:1 to 250:1. A use according to any one of claims 1 to 3, in which the source of hydrogen citrate ions comprises an alkali metal hydrogen citrate. A use according to claim 4, in which the percentage weight of alkali metal hydrogen citrate is from 0.1% to 10%, by weight of the composition when in the form of a dentifrice; or from 0.025% to 2.5% by weight of the composition when in the form of a mouthwash. A use according to claim 4 or 5 in which the alkali metal hydrogen citrate salt is disodium hydrogen citrate. A use according to any of claims 1 to 6 in which from 100 to 2500 ppm of fluoride ions are present in total. A use according to any of claims 1 to 7 in which the pH of the composition is from 4.0 to 5.0. A use according to any one of claims 1 to 8 in which the composition is a dentifrice and the abrasive is silica. A dentifrice comprising a source of fluoride ions provided by an alkali metal monofluorophosphate and/or an alkali metal fluoride; an orally acceptable carrier and an abrasive characterised in that the composition further comprises hydrogen citrate ions, present in a weight ratio of from 10:1 to 500:1 with respect the fluoride ions and in a concentration of from 4 x 10⁻³ to 4 x 10⁻¹M; the composition has a pH of less than 7; the abrasive is selected from dicalcium phosphate, alumina, calcium pyrophosphate, pumice, methyl methacrylate and silica, and excluding dentifrices comprising dipotassium citrate and methyl methacrylate. A mouthwash comprising a source of fluoride ions provided by an alkali metal monofluorophosphate and/or an alkali metal fluoride; an orally acceptable carrier and characterised in that the composition further comprises hydrogen citrate ions present in weight ratio of from 10:1 to 500:1 with respect the fluoride ions and in a concentration of from 1 x 10⁻³ to 1 x 10⁻¹M; and the composition has a pH of less than 7.

Inventors: DUKE, SUSAN ANN,SMITHKLINE BEECHAM CONSUMER BRANDS, READING, JULIAN PETER, SMITHKLINE BEECHAM
Applicants: BEECHAM GROUP PLC
Application year: 1986
Main classification: A61K7
IPC codes: A61K8, A61Q11