Oral hygiene compositions.

0001The present invention relates to oral hygiene compositions, and in particular to dentifrices and mouthwashes having improved anticaries effect.

0002A 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 oxalate ions is used within a specified weight ratio an pH range.

0003According to the present invention there is provided an oral hygiene composition comprising up to 7% by weight of the composition of alkali metal oxalate or alkaline earth metal oxalate from 20 to 1500 ppm of fluoride ions, and a dentally acceptable excipient, the composition having a pH of from 4 to 10.

0004The term alkali metal oxalate and/or alkaline earth metal oxalate as used herein includes mixtures of one or more alkali metal oxalates and/or alkaline earth metal oxalates. Suitable oxalates for use in compositions of the invention may include soluble and sparingly soluble oxalates such as sodium, potassium, lithium, calcium, magnesium, barium and strontium. Particularly preferred oxalates are sodium oxalate, potassium oxalate and calcium oxalate or mixtures thereof.

0005Preferably the alkali metal oxalate and/or alkaline earth metal oxalate is present in an amount of from 0.0025% to 7% by weight.

0006The fluoride ions may be provided by an alkali metal fluoride, such as sodium, potassium or lithium fluoride and the use of sodium fluoride is especially preferred. Other suitable fluorides include ammonium, stannous and zinc fluorides.

0007Alternatively, a monofluorophosphate may be used, preferably an alkali metal monofluorophosphate. Sodium monofluorophosphate, Na₂PO₃F, is especially preferred but the corresponding potassium and/or lithium salts can also be employed. The term 'monofluorophosphate' as used herein includes monofluoropolyphosphates, such as those of formulae Na₄P₃O₉F; K₄P₃O₉F; Na₃KP₃O₉F; (NH₄)₃NaP₃O₉F and Li₄P₃O₉F.

0008If desired, a mixture of ionic fluoride and monofluorophosphate may be employed. The total amount of fluoride and monofluorophosphate used is dependent to some extent on the type of composition, but it should be an effective, but non-toxic, amount. Typically the fluoride(s) is present in the oral hygiene composition in an amount to provide a total of from 0.025 to 0.25% of fluorine based on the weight of the oral hygiene composition. The preferred total fluoride level is from 0.05 to 0.15% by weight of the composition.

0009Preferably, the composition is in the form of a dentifrice, and in this form will usually include a dentally acceptable abrasive. Suitable abrasives are insoluble calcium salts such as calcium carbonate, dicalcium phosphate and calcium pyrophosphate; aluminia, silica and synthetic plastic resin particles.

0010The 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 trade name 'Zeodent' by the J.M. Huber Corporation.

0011The amount of abrasive will be within conventional limits, and will normally vary from 15% to 50% by weight of the composition.

0012The compositions of the invention may optionally contain other agents known to enhance the anticaries effect of fluoride and monofluorophosphate, such as calcium glycerophosphate, this being incorporated in a weight ratio of up to 1:13, preferably 1:20 to 1:3, to the total weight of fluoride and/or monofluorophosphate salts.

0013The composition of the invention may be presented in conventional dentifrice dental cream and dental powder formulations, or as a conventional mouthwash formulation.

0014The compositions of the invention will also usually contain surfactants, gelling agents and other excipients such as flavouring and colouring agents.

0015The surfactant is normally a water-soluble non-soap or synthetic organic detergent. Suitable sorfactants include the water-soluble salts of: higher fatty acid monoglyceride monosulphates (for example sodium hydrogenated coconut fatty acid monoglyceride monosulphate); higher alkyl sulphates (for example sodium lauryl sulphate); alkylarysulphonates (for example sodium dodecylbenzenesulphonates); and higher alkyl sulphoacetates (for example sodium lauryl sulphoacetate). There may also be used the saturated higher aliphatic acyl amides of lower aliphatic amino carboxylic acids having 12 to 16 carbon atoms in the acyl radical and in which the amino acid portion is derived from the lower aliphatic saturated mono-amino carboxylic acids having 2 to 6 carbon atoms, such as the fatty acid amides of glycine, sarcosine, alanine, 3-aminopropanoic acid and valine, particularly the N-lauroyl, myristoyl and palmitoyl sarcosinate compounds. Conventional non-ionic surfactants may also be included, if desired.

0016The surface-active materials are generally present in an amount of 0.05 to 15%, preferably 0.5 to 5% by weight of the composition.

0017The tooth powders and pastes are prepared in the usual manner. Thus, the ingredients can be mixed in the dry state or as slurries or solutions.

0018In general the liquid in the dental cream or paste will comprise chiefly water, glycerine, sorbitol and/or a glycol, including suitable mixtures thereof. Suitably, the glycol is propylene glycol or a polyethylene glycol. It is preferred to use also a gelling agent in dental creams such as natural or synthetic gums or gum-like materials, e.g. Irish Moss, gum tragacanth, sodium carboxymethylcellulose, polyvinylpyrrolidone or starch. Irish Moss and sodium carboxymethylcellulose are preferred gelling agents. The gum content is usually up to 10% and preferably 0.01 to 5% by weight of the preparation.

0019Other materials may be added, such as sweetening agents, for example soluble saccharine, flavouring oils (e.g. oils of spearmint, wintergreen, peppermint), chloroform, colouring or whitening agents (e.g. titanium dioxide), preservative (e.g. sodium benzoate), emulsifying agents silicones, alcohol, menthol, chlorophyllin), antibacterial agents (e.g. chlorhexidine), anti-plaque agents, anti-calculus agents and agents for sensitive dentine (e.g. strontium salts, formaldehyde).

0020The compositions of the invention may also be in the form of other oral hygiene compositions, for example, the ingredients may be incorporated in mouthwashes of the suspension type, or in compositions which will be chewed by the user, for example, chewing gum, tablets, pastilles and lozenges. These compositions will contain the conventional base materials together with suitable flavours and sweetening agents and may be formulated in known manner.

0021Oral hygiene compositions of the present invention have been found to inhibit glucose utilisation and lactate production by common oral microorganisms, and this appears to be the mechanism by which the improved anticaries effect of the compositions is achieved.

0022The compositions for the invention are illustrated by the following examples: <tables id="tabl0001" num="0001"><img file="EP0242977A2_D0001.tif" /></tables><tables id="tabl0002" num="0002"><img file="EP0242977A2_D0002.tif" /></tables>

EXAMPLE VI

0023A plaque pH study was carried out using mouthwash solutions according to the invention. Sixteen subjects were used each of which abstained from dental hygiene for 24 hours prior to the test and did not eat or drink for one hour before the test. Subjects each rinsed for 1 minute with 10ml of each of the 5 products under test.

0024Thirty minutes later plaque was sampled from the subjects molar and pre-molar teeth. The sample was mixed with 20 µl of saline and pH recorded. The subjects then rinsed for 1 minute with 10ml of a 10% w/v sucrose solution and 10 minutes later a further plaque sample was taken from the posterior teeth. The plaque pH was measured as described earlier.

0025Each subject used each product in a balanced randomised order, the study being double blind in nature.

0026Results are indicated below <tables id="tabl0003" num="0003"><img file="EP0242977A2_D0003.tif" /></tables>

0027The post challenge pH after rinsing with 25 ppm F and 0.1% Na oxalate was significantly greater than after rinsing with 25 ppm F.