This invention relates to an anti-plaque dentifrice, and in particular it relates to a dentifrice in the form of a non-abrasive gel containing active anti- plaque agents which maximises the recognised anti-plaque and anti-bacterial properties of the active components, and utilises the oral physiology in the mouth to assist in destroying dental plaque.

Dental plaque is the major cause of dental disease affecting both tooth and gum tissues. Therefore, its effective removal is critical to maintaining optimal oral health. Plaque consists of food breakdown products, food debris, and harmful pathogenic bacterial. In the presence of plaque, sugars create acids which cause loss of calcium from the tooth enamel eventually forming cavities. Due to the introduction of fluoride into community water supplies and toothpastes dental decay has been significantly reduced. Today, the major dental problem in all age groups is periodontal (gum) disease. It will increase markedly in the future because better dental care is resulting in more people keeping their teeth. Gum disease is initiated by the release of harmful toxin by-products from plaque. These result from the reaction between food breakdown products and the bacteria in the plaque. The toxins cause inflammation of the gum margins (gingivitis), and if the plaque is

retained it becomes calcified to form calculus. This calcification results from the deposition of calcium salts which are contained in the saliva reacting with plaque. If this process continues, infection follows and with it destruction of tooth support and bone, eventually resulting in tooth loss.

The most widely accepted method of removing plaque is with the use of a toothbrush assisted by a toothpaste. Prior to the present invention, it has always been the toothbrush alone which has determined how effectively plaque has been removed. The toothpaste assists the toothbrush through its detergent action. All conventional toothpastes are cosmetic products because the manufacturers believe a toothpaste must contain an abrasive which acts as a polishing agent. The basic composition of a conventional toothpaste then is the abrasive or polishing agent, a chemically inert carrier acting as a binder, a foaming agent, fluoride, flavouring, and the like. Usually, the composition also contains other additive(s) for which certain benefits are claimed.

As described above, to date it has been considered mandatory to incorporate an abrasive in any commercially available dentifrice, however, there are several reasons why an abrasive is not advised, especially in combination with a cationic anti-plaque agent. The use of abrasives is contraindicated with cationic agents because the commonly used dentifrice abrasives are anionic. They are therefore, ionically incompatible with the anti-plaque agent. Another reason why the use of abrasives is disadvantageous is that the dental pellicle - the protein layer coating the tooth surface - is part of the normal physiology of the mouth, and is a protective layer. The use of abrasives removes the pellicle, but it is reconstituted shortly afterwards by the salivary

proteins. Anti-plaque agents are attracted to the glycoproteins in the saliva, the soft tissues, and in the pellicle on the tooth surfaces. Accordingly, when the dental pellicle is not removed, there is enhancement of the anti-plaque activity of the anti-plaque agent.

The ability of quaternary ammonium compounds to inhibit the formation of dental plaque is well established. Similarly, it is also known that zinc salts can be used in compositions for inhibition of dental plaque. By way of example, U.S. Patent Specification No. 4,022,880 discloses an oral composition capable of retarding the development of plaque and dental calculus consisting essentially of zinc ions and an antibacterial agent such as a quaternary ammonium compound in an orally acceptable medium. Particular formulations of the oral composition disclosed in U.S. Patent Specification No. 4,022,880 include toothpastes incorporating abrasive polishing agents, typically in the range of from 40% to 50% by weight, or tooth powders incorporating such abrasive polishing agents in typical amounts of from 90% to 95%. Alternative formulations disclosed are mouthwash or rinse formulations in which the orally acceptable medium is water optionally containing ethanol.

It has now been discovered that a non-abrasive gel comprising a zinc salt (such as zinc chloride), a quaternary ammonium compound (such as cetyl pyridinium chloride - CPC) and a gelling agent is an effective anti- plaque dentifrice when used with a toothbrush, in the manner of a traditional toothpaste. The use of the toothbrush breaks up existing plaque mass, allowing for easier contact of the active anti-plaque agents with the retained plaque, hence increasing the performance and effectiveness of the anti-plaque agents.

Accordingly, the present invention provides a non- abrasive dentifrice gel which comprises an effective antibacterial amount of the combination of a zinc salt and a quaternary ammonium compound, and a gelling agent.

Clinical observation and dental research has demonstrated that the salivary concentrations of the anti-bacterial quaternary ammonium compounds remain high 4 to 6 hours after use. Also clinically, it has been observed that a "carry over" or additive effect after prolonged use can result in the tooth surface tending to repel dental plaque even though tooth brushing or a rinse has not been carried out. An advantage of the gel of the present invention over existing formulations is therefore, that by avoiding the use of an abrasive the anti-plaque and anti-bacterial activity of the quaternary ammonium compounds is potentiated, and by the addition of a zinc salt such as zinc chloride, which has recognised anti-staining and anti-calculus properties, the need for an abrasive can be avoided. It has also been observed that the zinc salt potentiates the quaternary ammonium compound, especially where this compound is cetyl pyridinium chloride.

In its own right, zinc chloride has been shown to be anti-bacterial, and reduce plaque and calculus formation. The reason for the increased effectiveness of CPC in combination with zinc chloride is unknown at present, but a suggested theory is that zinc chloride may retard the calcification of plaque allowing optimal activity of the recognised anti-plaque agent. Since the anti-calculus properties of zinc chloride continue to remain effective over long periods of use, this may be used to maintain the efficacy of CPC over greater periods of time.

The zinc salts which may be used in the gel composition of this invention include any water soluble zinc salt such as zinc chloride, zinc acetate, zinc sulphate, and the like. Other less soluble zinc salts such as zinc fluoride and zinc citrate may also be used. Preferably, the zinc salt is zinc chloride. The zinc salt may be included in the gel composition in an amount of from about 0.1 to 5% by weight. Preferably, zinc chloride is added in an amount of from 0.2 to 0.25% by weight, more preferably an amount of about 0.22% by weight.

Suitable quaternary ammonium compounds for inclusion in the gel composition of the present invention include (C _β .-^g) alkyl pyridinium chlorides and (C _β _i8) alkyl pyridinium bromides. Particularly preferred is cetyl pyridinium chloride (CPC) . The quaternary ammonium compound may be incorporated in the gel composition in amounts in the range of 0.01 to 0.5% by weight. Preferably, the gel composition includes CPC in an amount of 0.01 to 0.1% by weight, more preferably an amount of about 0.05% by weight.

The gel composition of this invention also includes a gelling agent. Preferably, this gelling agent is a non-ionic gelling or thickening agent such as the natural or synthetic gums including hydroxyethyl cellulose, hydroxymethyl cellulose, and the like. The gelling agent may be used in amounts in the range of 0.5 to 5% by weight. Preferably, the gelling agent is hydroxyethyl cellulose in an amount of 2 to 4% by weight, more preferably an amount of about 2.5 to 3% by weight.

The gel composition may also include suitable fluoride-providing compounds including, by way of example, soluble inorganic fluoride salts such as sodium or potassium fluoride and sodium monofluorphosphate.

Preferably, the fluoride-providing compound is incorporated in amounts of 0.005 to 2% by weight.

Preferably, the gel composition also incorporates a surfactant to enhance the foaming action of the quaternary ammonium compound. Suitable surfactants include the non-ionic surfactants and betaine surfactants such as cocoamidopropyl betaine, lauramidopropylbetaine and cocobetaine. The use of cocobetaine (Gafamox) is particularly preferred. The surfactant may be used in amounts of from 0.1 to 5% by weight, preferably from 0.2 to 0.5% by weight.

Other components which may be included in the gel compositions of this invention include humectants such as polyethylene glycol, sorbitol or glycerol, sweeteners such as saccharin, and colouring and flavouring agents. The gel composition may also include charged and uncharged polysaccharides and other polymers, particularly chitosan and alginates, which are used in food products and which are gel-forming agents. These can assist in binding the active anti-plaque agents such as zinc chloride and cetyl pyridinium chloride to the teeth by establishment of a polysaccharide or other polymer film layer to which the active agents will bind, thereby resulting in more effective antibacterial and anti-plaque performance.

As previously described, the gel composition of the present invention differs essentially from a traditional toothpaste formulation in that it is non- abrasive. Nevertheless, by applying it in a gel form on a toothbrush, the plaque massis broken up by the brushing action allowing easier penetration of the remaining plaque. A mouth rinse will not dislodge plaque as effectively as a gel applied with a toothbrush, even if the mouth rinse is agitated vigorously.

The following Example illustrates the non-abrasive dentifrice gel composition of the present invention, and the method of preparation thereof. It is to be understood, however, that this invention is not limited to the particular formulation set out in this Example.

EXAMPLE

An anti-plaque dentifrice gel composition is made up as follows:

Ingredient Amt♦ /kg

1. Cetylpyridinium chloride B.P. 0.5 g 2. Zinc chloride B.P. 2.2 g

3. Sodium fluoride B.P. 0.15 g

4. Sodium saccharin B.P. 0.5 g

5. Peppermint flavour

-(BBA07-7686, Bush Boake Allen) 83 ml 6. Hydroxyethylcellulose B.P.

-(Natrosol 250H) 28 g

7. Colouring agent -(Green Apple Colour 19-8723, Bush Boake Allen 30 g/1) 3 ml

8. Betaine surfactant -(Gafamox 35, GAF Australia) 2 g

9. Purified water B.P. to 1000 g

Items 1, 2, 3, 4, 5, 6 and 8 are dissolved in turn into the purified water, and then the hydroxyethylcellulose is added and stirred until the gel thickens. The resulting non-abrasive gel is used in the same way as a traditional toothpaste, that is by regular application to the teeth by brushing with a toothpaste.

It will be understood that the foregoing Example is included by way of illustration of the present invention only, and that variations may be made to the composition therein without departing from the spirit and scope of the invention.