GB2164255A - Stable antiplaque dentifrice - Google Patents

Abstract

A chemically and physically stable antiplaque dentifrice comprises an antiplaque quaternary ammonium compound, a betaine surfactant, a humectant system of glycerin and/or sorbitol and a nonionic gelling agent, and is prepared by a process which comprises the preparation of two separate gel phases, an oil gel phase and a water gel phase, combining the gel phases into a single gel, and adding a dental abrasive as the final step, or adding the abrasive to the water gel phase prior to the addition of the oil gel phase.

Description

SPECIFICATION Stable Antiplaque Dentifrice The present invention relates to the formulation of an antiplaque dentifrice with one or more of the following benefits: improved foaming, improved taste, solubilized active ingredient, improved fluoride stability, improved compatibility of all components, improved extrusion characteristics from various containers and increased cost effectiveness.

Until now it had been difficult to formulate a cosmetically acceptable antiplaque dentifrice consisting of a quaternary ammonium compound and a betaine surfactant with a humectant system of all glycerin or ail sorbitol. In addition, the use mixtures of glycerinlpolyethylene glycol or sorbitollpolyethylene glycol, where glycerin or sorbitol were present in excess of 10% by weight of the formulation, displayed marginal cosmetic stability. However, after extensive solubility tests on various mixtures of the components in a benzethonium chloride (BTC) dentifrice, a compatible system of water, BTC, betaine, salts and glycerin was found which was dependent upon the order of addition of these components.

Accordingly, it has been found that by using a specific process, stable formulations of an antiplaque dentifrice containing a quanternary ammonium compound and a betaine surfactant can be made with glycerin or sorbitol as the humectant. The essential feature in this process is the formation of two separate phases with the subsequent combination of these two phases to form the stable system. One of these phases contains the active quaternary ingredient (e.g. benzethonium chloride or cetyl pyridinium chloride) solubilized in the betaine surfactant (e.g. cocamidopropyl betaine) and a flavour, which is designated the oil gel phase. The second phase contains water, humectant, and nonionic gelling agent e.g.

hydroxyethylcellulose, and optionally sodium saccharin and fluorine-containing compound e.g. sodium monofluorophosphate, and is designated the water gel phase. The dental polishing agent may be added to the combined phases as a final step, or be added to the water gel phase prior to combining with the oil gel phase. The finished product has improved chemical and cosmetic stability and improved taste.

A conventional method of preparing antibacterial dentifrices containing a quaternary ammonium compound as the active material is disclosed in U.S. Patent No.4,118,476 and U.S. Patent No.4,188,372, and comprises the formation of a gel with humectant (glycerin, sorbitol, polyethylene glycol), thicknener (hydroxyethylcellulose), and sweetener, and adding thereto polishing agent, flavour, antibacterial agent, additional water, and lastly an antistain agent (a phosphono-containing compound or a mellitic acid-containing compound).

The prior art also discloses processes for stabilizing a dentifrice against precipitation and flocculation due to the incompatibility of an anti-bacterial agent and an alkali metal carboxyalkyl cellulose, as shown in U.S. Patent No. 3,842,168 and No. 3,843,779. The former patent utilizes the steps of adding the antibacterial agent dissolved in water to a non-aqueous blend of the carboxymethylcellulose, sodium saccharin and humectant and then adding the surfactant to form a gel, to which is added the polishing material and flavour as a final step. The latter patent adds the antibacterial agent separately or jointly with the surfactant to a mixture of glycerin, water, sodium saccharin, carboxymethylcellulose and surfactant, followed by the addition of a polishing material and flavour.The addition of the surfactant must precede or be simultaneous with the antibacterial addition in order to avoid precipitation in the dentifrice.

However, the prior art does not disclose a cosmetic and chemically stable antiplaque dentifrice containing, as the essential ingredients, a quaternary ammonium antiplaque compound, a zwitterionic betaine surfactant, a glycerin and/or sorbitoi humectant, and a nonionic gelling agent prepared by a novel process utilizing a specific sequence of steps, which comprises the formation of two separate gel phases, an oil gel phase consisting of the quaternary ammonium compound, betaine surfactant and flavour; and a water gel phase consisting of water, humectant and gelling agent; combining the two gel phases into a single parent gel, and adding a dental abrasive to the combined gel phase as a final step or to the water gel phase prior to the addition of the oil gel phase.

It has now been found that stable formulations of an antiplaque dentrifice containing a quaternary ammonium compound, and a betaine surfactant, can be made with glycerin or sorbitol as the humectant by utilizing a specific sequence of steps which comprises the formation of a separate oil gel phase of the quaternary ammonium compound, betaine and flavour, a separate water gel phase of humectant, nonionic gelling agent and water (which may preferably contain the salts, i.e. sodium saccharin and sodium monofluorophosphate or other fluoride salt), combining the oil and water gel phases to form a stable parent gel phase, and adding a dental abrasive as the final step. This process may be varied by adding the polishing agent to the water gel and then adding the oil gel to the water gel-abrasive mixture.This dentrifrice may be prepared at ambient temperature, i.e. each step in the total sequence of steps may be performed at ambient (room) temperature.

Accordingly, the present invention enables the provision of a stable antiplaque dentifrice based on quaternary active ingredients, and a betaine surfactant, with improved compatibility of all components, by the formation of two separate gel phases, which are combined to form a stable total gel system.

The present invention also enables the provision of a cosmetically and chemically stable antiplaque dentifrice containing glycerin and/or sorbitol as humectant which is compatible with the betaine and the quaternary active ingredients.

This invention further enables the provision of a stable antiplaque dentifrice containing a nonionic gum, such as hydroxyethylcellulose, as gelling agent to stabilize the betaine-quaternary system and to prevent deactivation of the quaternary active ingredient.

This invention still further enables the provision of a cosmetic (physical) and chemically stable antiplaque dentifrice also containing a fluoride-providing compound, without adversely affecting cosmetic stability of the dentifrice.

In accordance with the present invention, as embodied and broadly described herein, a novel stable antiplaque dentifrice of th is invention comprising a quaternary ammonium antiplaque compound, a zwitterionic betaine surfactant, flavour, and a humectantselected from glycerin, sorbitol and mixtures thereof, and a nonionic gelling agent is prepared at ambient temperature by a process which comprises the formation of two separate gel phases, an oil gel phase consisting of the quaternary ammonium antiplaque compound, the betaine and a flavour, and a water gel phase consisting of water, humectant and nonionic gelling agent; combining the two gel phases to form a single gel phase; and either adding a dental abrasive to the combined gel phase or adding the dental abrasive to the water gel phase prior to combining with the oil gel phase.However, it is essential that two separate gel phases be prepared prior to the addition steps.

The addition of salts such as fluorine-containing compound and/or sodium saccharin, which are preferred components, is made by dissolving in the formula amount of water prior to mixing the water with the humectant and gelling agent in the formation of the water gel phase.

Broadly, the invention relates to a process for preparing a dentifrice gel, the process comprising forming an oil gel phase of a quaternary ammonium antiplaque compound, a betaine surfactant and optionally a flavour and a water gel phase of water, a humectant which is glycerin and/or sorbitol and a nonionic gelling agent and combining the gel phases into a single gel. Dental abrasive may be added to the water gel phase, prior to the combination with the oil gel phase, or to the single gel formed by combining the gel phases, in the formation of a dentifrice from the dentifrice gel.

More specifically, the present invention relates to a process of preparing a cosmetic and chemically stable antiplaque dentrifice consisting essentially of the formation of two phases, an oil gel phase and a water gel phase comprising the following sequence of steps: a. dispersing the formula amount of a quaternary ammonium antiplaque agent in the formula amount of flavour, b. mixing the quaternary ammonium-flavour dispersion into the formula amount of betaine surfactant to form the oil gel phase, c. dispersing the formula amount of nonionic gelling agent in the formula amount of glycerin and/or sorbitol humectant, d. mixing the gelling agent-humectant dispersion with the formula amount of water to form the water gel phase.

e. combining the two gel phases to form a stable parent gel phase, f. adding the dental abrasive to the water gel phase or to the parent gel phase with mixing, and g. recovering a stable antiplaque dentifrice.

The oil gel phase is in the form of a viscous, translucent gel. The water gel phase is transparent. The stable parent gel phase resembles an emulsified system.

This process may be modified by adding and mixing the dental abrasive with the water gel phase, and then adding the oil gel phase to the mixture of dental abrasive and water gel phase.

Sodium saccharin and/or a fluorine-containing compound, which are optional but preferred additives, are dissolved in the formula amount of water prior to its addition to the humectant-gelling agent dispersion and the formation of the water gel phase.

The new formulation method of the instant invention using only glycerin and/or sorbitol humectant in a quaternary-betaine system provides chemical and cosmetic stability to the dentifrice as well as improved taste. The taste characteristics of a 20% containing-glycerin or sorbitol humectant, benzethonium chloride (BTC), betaine dentifrice are greatly improved when compared to a 20% polyethylene glycol (PEG 600) BTC dentifrice. The stability afforded by the glycerin and/or sorbitol humectant does not extend to other humectants such as polyethylene glycol. A precipitate has been observed in the 20% PEG 600 humectant gel phase of the BTC dentifrice. The precipitate was analysed using an l.R. spectrophotometric method and was found to comprise BTC, saccharin and betaine.

Fluoride stability studies on the BTC dentifrice have confirmed that a large part of monofluorophosphate (MFP) loss is due to hydrolysis in an all PEG 600 humectant system. Other phenomena (i.e. adsorption or insolubilization) may be responsible as well. A solubility problem with PEG 600 and monofluorophosphate (MFP) has been found. Stability studies of MFP in the BTC dentifrice indicate that hydrolysis of MFP occurs to a large extent in an all PEG 600 humectant system. However, an all glycerin humectant system in the BTC dentifrice displays much less loss of MFP. In fact an all glycerin humectant system meets the present requirement for MFP shelf life (more than 600 ppm total soluble fluoride, half of which is MFP) while an all PEG 600 humectant system does not (see Table I below).

TABLE I MFP Stability in BTC Dentifrice with 20% PEG 600 Humectant System and 20% Glycerin Humectant System pH Soluble F Humectant l+ 9w* I+ 3w 6w 9w* PEG 8.2 10.1 980 660 570 520 GLyc. 7.8 8.3 980 870 790 790 Humectant l+ 3w 6w 9w* I+ 3w 6w 9w* PEG 57 289 439 431 920 370 130 < 100 Glyc. 26 55 85 106 950 810 700 680 +initial value, *w=weeks.

This table clearly shows the poor stability of MFP in an all PEG 600 humectant and the very good stability of MFP in an all glycerin formulation.

HPLC (High Pressure Liquid Chromatography) analysis on both a glycerin and a sorbitol BTC dentifrice formulation was performed initially and after nine weeks accelerated ageing at 49"C. Two extraction methods for BTC (water and acetone) indicate no decrease in BTC recovery after accelerated ageing.

TABLE II HPLC Analysis on a Glycerin and a Sorbitol BTC Dentifrice Formulation Initially and after Nine Weeks Accelerated Ageing 49"C Initial Analysis Analysis AfterAgeing Water Acetone Water Acetone Humectant Extraction Extraction Extraction Extraction 20% Glycerin 0.42 0.54 0.47 0.52 20% Sorbitol 0.36 0.48 0.45 0.46 The glycerin and/or sorbitol humectant system constitutes about 1823% by weight of the dentifrice composition.

Cationic antibacterial materials are well known in the art. See, for instance, the section on "Quaternary Ammonium and Related Compounds" in the article on "Antiseptics and Disinfectants" in Kirk-Othmer Encyclopedia of Chemical Technology, 2nd edition (Vol.2, pp.632-635), incorporated herein by reference.

Cationic materials which possess antibacterial activity (i.e. are germicides) are used against bacteria and have been used in oral compositions to counter plaque formation caused by bacteria in the oral cavity.

Among the most common of these antibacterial antiplaque quaternary ammonium compounds is benzethonium chloride, also known as Hyamine 1622 ordiisobutylphenoxyethoxyethyl dimethyl benzyl ammonium chloride, and cetyl pyridinium chloride. In an oral preparation this material is highly effective in promoting oral hygiene by reducing formation of dental plaque and calculus, which is generally accompanied by a reduction in periodontal diseases. Other cationic antibacterial agents of this type are those mentioned, for instance, in U.S. Patent Nos. 2,984,639, 3,325,402, 3,431,208 and 3,703,583, and British Patent No. 1,319,396.

Other antibacterial antiplaque quaternary ammonium compounds include those in which one or two of the substituents on the quaternary nitrogen has a carbon chain length (typically alkyl group) of some 8 to 20, typically 10 to 18, carbon atoms while the remaining substituents have a lower number of carbon atoms (typically alkyl or benzyl group), such as 1 to 7 carbon atoms, typically methyl or ethyl groups. Dodecyl trimethyl ammonium bromide, benzyl dimethyl stearyl ammonium chloride, cetyl pyridinium chloride and quaternized 5-amino-1,3-bis (2-ethylhexyl)-5-methyl hexa hydro-pyrimidine are typical quaternary ammonium antibacterial agents.

The dentifrice formulation of present invention contains an effective amount of the antiplaque quaternary ammonium compound, preferably about 0.1-1% by weight of the composition.

The ability of quaternary ammonium compounds to inhibit the formation of dental plaque is well known. However, they are deactivated by the anionic surfactants such as sodium lauryl sulphate conventionally used in dentifrice formulations. The substitution of nonionic surfactants for the anionic surfactants eliminates the deactivation problem but results in products with poor foaming. However, the incorporation of betaine surfactants into antiplaque dental formulations based on quaternary active ingredients unexpectedly improves the foaming of these formulations without deactivating the quaternary antibacterial agents.

The betaine component of present dentifrice composition has the general formula:

wherein R1 is an alkyl group having 10 to about 20 carbon atoms, preferably 12 to 16 carbon atoms or the amido radical:

wherein R is an alkyl group having about 10 to 20 carbon atoms and a is the integer 1 to 3; R2 and R3 are each alkyl groups having 1 to 3 carbon atoms and preferably 1 carbon atom; R4 is an alkylene or hydroxyalkylene group having from 1 to 4 carbon atoms and, optionally, one hydroxyl group. Typical alkyldimethyl betaines include decyl betaine or 2-(N-decyl-N,N-dimethylammonio) acetate, coco betaine or 2-(N-coco-N,N-dimethylammonio) acetate myristyl betaine, palmityl betaine, lauryl betaine, cetyl betaine, stearyl betaine, etc. The amidobetaines similarly include cocoamidoethyl betaine, cocoamidopropyl betaine, lauramidopropyl betaine and the like.

The betaines, which are zwitterionic materials, function as a foaming agent in the quaternarycontaining dentifrice compositions. They act cationically over a wide pH range, but do not deactivate the quaternary antimicrobial activity.

In addition to the non-interference exhibited by the betaines with the quaternary activity, laboratory foam tests have shown that formulations containing both the quaternary ammonium compound (quat) and the betaine, foam 2-3 times better than the nonionic/quat formulations.

The zwitterionic betaines are completely compatible with the quaternary antimicrobial antiplaque agents, and impart detersive and improved foaming properties to the quaternary-containing dentifrice composition without deactivating the antimicrobial properties thereof. The amount of betaine effective in the production of improved foaming may be varied from about 35% by weight of the total formulation.

Cosmetic problems of stability is incurred with all zwitterionic-containing dentifrices, such as crimp leakage of flavour. The flavour oozes and is not solubilized in the zwitterionic surfactant. However, stability evaluations of present novel antiplaque dentifrices containing glycerin and/or sorbitol humectant indicate satisfactory flavour stability for nine weeks ageing at 49"C. The flavour ingredient which is an essential ingredient in a dentrifice constitutes about 0.52% by weight. Any suitable flavour may be employed.

Examples of suitable flavouring constituents are flavouring oils, e.g., oils of spearmint, peppermit, wintergreen, sassafras clove, sage, eucalyptus, marjoram, cinnamon, lemon, and orange, and methyl salicylate.

A sweetening material may also be employed as a complement to the flavouring material. Suitable sweetening agents are water soluble and include sucrose, lactose, maltose, sorbitol, sodium cyclamate and saccharin, in an amount of 0.010.5% by weight.

Another essential ingredient in present dentifrice is a gelling agent which is a nonionic gum, in an amount of about 0.1 .5% by weight. It has been found that large organic anionic molecules such as carboxymethylcellulose the potential to deactivate the quaternary antibacterial activity. Accordingly, hydroxyethylcellulose, which is a nonionic small organic molecule, effects a stable pituitous gel in the betaine-quat system of present invention, and is the preferred gelling agent. Other nonionic gelling agents may be used such as hydroxymethylcellulose, and the like.

The fluoride-providing compounds, which are preferably additional ingredients in present dentifrice, are characterised by their ability to release fluoride ions in water and by substantial freedom from reaction with other compounds of the dentifrice. Among these materials are inorganic fluoride salts, such as soluble alkali metal, alkaline earth metal and heavy metal salts, for example, sodium fluoride, potassium fluoride, ammonium fluoride, lead fluoride, a copper fluoride such as cuprous fluoride, zinc fluoride, a tin fluoride such as stannic fluoride or stannous chlorofluoride, barium fluoride, sodium fluorosilicate, ammonium fluorosilicate, sodium fluorozirconate, sodium monofluorophosphate, aluminium mono- and difluorophosphate, and fluorinated sodium calcium pyrophosphate. Alkali metal and tin fluorides such as sodium and stannous fluorides, sodium monofluorophosphate and mixtures thereof, are preferred.

The amount of the fluoride-providing compound is dependent to some extent upon the type of compound, its solubility, and the dentifrice, but it must be a nontoxic amount. In a solid oral preparation, such as a toothpaste or dental cream, an amount of such compounds which releases a maximum of 1 % by weight of the preparation is considered satisfactory. Any suitable minimum amount of such compound may be used, but it is preferable to employ sufficient compound to release from 0.005% to 1%, and preferably about 0.1% of fluoride ion. Typically, in the cases of alkali metal fluorides and stannous fluoride, this component is present in an amount up to 2% by weight, based on the weight of the preparation.In the case of sodium monofluorophosphate, the compound may be present in an amount up to 7.6% by weight, more typically 0.76%.

A dentifrice prepared in accordance with this invention, contains a dental abrasive. This may be a conventional water-insoluble polishing material or dental abrasive, in an amount from about 3565% by weight of the total formulation. Suitable examples of dental abrasives or polishing materials include sodium metaphosphate, potassium metaphosphate, tricalcium phosphate, dihydrated calcium phosphate, anhydrous dicalcium phosphate, calcium pyrophosphate, magnesium orthophosphate, trimagnesium phosphate, calcium carbonate, zirconium silicates, silica, bentonite, and mixtures thereof. The preferred abrasives are alumina-containing abrasives such as calcined alumina and hydrated alumina and mixtures thereof. The abrasive is added to the water gel phase or to the single gel after combining the oil gel and water gel phases.

The dentifrice of this invention may also contain conventional additional ingredients such as colouring or whitening agents, preservatives and ammoniated materials such as monoammonium glycyrrhizinate.

These additional ingredients may each be added to the dentifrice in minimal amounts of up to 5% by weight, and preferably up to 1%, provided they do not interfere with the foaming, antiplaque and stability properties of the finished product. The oil phase typically constitutes about 3.8% by weight of the dentifrice.

In the practice of this invention to promote oral hygiene, a dentifrice according to this invention may be applied regularly to dental enamel by brushing the teeth for 3090 seconds at least once daily.

The following examples are further illustrative of the nature of the present invention, but it is understood that the invention is not limited to them. The compositions are prepared in the usual manner and all amounts and proportions referred to herein and in the appended claims are by weight unless otherwise indicated.

Example 1 Glycerin Humectant Anti-Plaque Dentifrice Ingredients Water (deionized) 19.34 Sodium saccharin 0.30 Sodium monofluorophosphate 0.76 Hydroxyethylcellulose 1.10 Glycerin 20.00 Benzethonium chloride 0.50 Flavour 1.00 Cocamidopropyl betaine 5.00 Calcined alumina 10.00 Hydrated alumina 42.00 The benzethonium chloride is dispersed in the flavour and this dispersion is mixed into the betaine to form an oil gel. The sodium saccharin and sodium monofluorophosphate (MFP) are dissolved in the water.

Hydroxyethylcellulose is dispersed in the glycerin, and this mixture is added to the water-saccharin-MFP solution with stirring to form a water gel. The oil and water gels are mixed to form a stable parent gel. The calcined alumina and hydrated alumina are admixed with the parent gel to produce the finished dentifrice which is effected against plaque related bacteria while possessing excellent chemical and cosmetic stability as well as having sufficient foaming characteristics. This dentifrice is prepared at room temperature.

Example 2 Example 1 is repeated except that 20% sorbitol is substituted for the 20% glycerin. The resultant product is equally effective against plaque related bacteria and also possess excellent chemical and cosmetic stability and sufficient foaming properties.

MFP stability studies indicate that both the new glycerin and sorbitol dentifrices have an excellent MFP stability profile. Example 1 (20% glycerin) had an initial total soluble fluoride value of 990 ppm and an MFP as F value of 950 ppm. Example 2 (20% sorbitol) had an initial total soluble fluoride value and an MFP as F value of 1,020 ppm and 980 ppm respectively (see Table III).

Table Ill MFP Stability Profile of a New all Glycerin BTC Dentifrice and a New all Sorbitol BTC Dentifrice (Nine Weeks (w) Aging at 49"C) pH Soluble F lonic F MFP as Ex. Humectant I 9w 1 9w 1 9w I 9w 1 All Glycerin 7.8 8.0 990 820 43 94 950 730 2 All Sorbitol 7.6 7.7 1020 960 43 45 980 910 The pH profiles of both formulations showed only a slight increase after nine weeks ageing at 49"C.

After accelerated ageing, values for total soluble fluoride and MFP as F were 820 ppm and 730 ppm respectively for Example 1 and 960 ppm and 910 ppm respectively for Example 2.

Variations in the above formulations may be made. For example, other betaines such as lauramidopropyl betaine, cocobetaine and the like may be substituted for the cocoamidopropyl betaine in the examples. Similarly, other abrasives may be substituted for the specific abrasives in the examples.

Likewise, otherfluoride-containing compounds such as sodium fluoride, potassium fluoride, etc. may be substituted for the sodium monofluorophosphate in the specific examples. Likewise, cetyl pyridinium chloride or other quaternary ammonium antiplaque agents may be substituted for the benzethonium chloride. Also, sodium cyclamate may replace sodium saccharin.

It is understood that the foregoing detailed description is given merely by way of illustration and that variations may be made therein without departing from the spirit of the invention.

Claims (33)

1. A chemically and physically stable antiplaque dentifrice comprising an antiplaque quaternary ammonium compound, a betaine surfactant, a flavour, a humectant system of glycerin andlor sorbitol and a nonionic gelling agent, prepared by a process which comprises the preparation of two separate gel phases, an oil gel phase and a water gel phase, combining the gel phases into a single gel, and adding a dental abrasive to the single gel, or adding the abrasive to the water gel phase prior to the addition of the oil gel phase.

2. A dentifrice as claimed in Claim 1, wherein the abrasive is added as the final step.

3. A dentifrice as claimed in Claim 1 or 2, wherein the oil gel phase comprises the quaternary ammonium antiplaque compound, betaine surfactant and flavour; and the water gel phase comprises water, humectant and nonionic gelling agent.

4. A dentifrice as claimed in Claim 3, wherein a fluorine-containing compound is dissolved in the formula amount of water prior to the addition of the water to the humectant and gelling agent in the formation of the water gel phase.

5. A dentifrice as claimed in Claim 3 or 4, wherein a water-soluble sweetening material is dissolved in the formula amount of water prior to the addition of the water to the humectant and gelling agent in the formation of the water gel phase.

6. A dentifrice as claimed in Claim 5, wherein the sweetening material is sodium saccharin.

7. A dentifrice as claimed in any one of Claims 1 to 6, wherein the betaine content constitutes from 3 to 5% by weight of the formulation.

8. A dentifrice as claimed in any one of Claims 1 to 7, wherein the nonionic gelling agent is present in an amount of from 0.8 to 1.5% by weight.

9. A dentifrice as claimed in any one of Claims 1 to 8, wherein the nonionic gelling agent is hydroxyethylcellulose.

10. A dentifrice as claimed in any one of Claims 1 to 9, containing from 18 to 23% by weight of glycerin, sorbitol or a mixture thereof, as the humectant system.

11. A dentifrice as claimed in any one of Claims 1 to 10, containing from 35 to 65% by weight of a water-insoluble dental abrasive.

12. A dentifrice as claimed in Claim 11, wherein the dental abrasive is an alumina-containing abrasive.

13. A dentifrice as claimed in Claim 12, wherein the antiplaque agent is present in an amount of about 0.1 to 1% by weight.

14. A dentifrice as claimed in any one of Claims 1 to 13, wherein the antiplaque agent is benzethonium chloride.

15. A dentifrice as claimed in Claim 4, wherein the fluoride-providing compound is present in an amount sufficient to release from 0.Q05 to 1% by weight of fluoride ion to the dentifrice.

16. A dentifrice as claimed in Claim 4 or 15, wherein the fluoride-providing compound is sodium monofluorophosphate.

17. A dentifrice as claimed in any one of Claims 1 to 16, wherein the betaine is cocoamidopropyl betaine.

18. A dentifrice as claimed in any one of Claims 1 to 17, wherein the abrasive is a mixture of hydrated alumina and calcined alumina.

19. A dentifrice as claimed in any one of Claims 1 to 18, wherein the flavour constitutes from 0.5 to 2% by weight.

20. A dentifrice as claimed in Claim 6, wherein sodium saccharin constitutes from 0.01 to 0.5% by weight.

21. A process for preparing a dentifrice gel, the process comprising forming an oil gel phase of a quaternary ammonium antiplaque compound, a betaine surfactant and optionally a flavour and a water gel phase of water, a humectantwhich is glycerin and/or sorbitol and a nonionic gelling agent and combining the gel phases into a single gel.

22. A process for preparing a dentifrice comprising preparing a dentifrice gel by a process as claimed in Claim 21 and adding a dental abrasive to the water gel phase prior to the water gel phase being combined with the oil gel phase.

23. A process for preparing a dentifrice comprising preparing a dentifrice gel by a process as claimed in Claim 21 and adding a dental abrasive to the single gel formed by combining the gel phases.

24. A process as claimed in Claim 21, 22 or 23, wherein the water gel phase contains a sweetening material and/or a fluoride-containing compound.

25. A process as claimed in Claim 24, wherein the sweetening material comprises sodium saccharin.

26. A process as claimed in Claim 24, wherein the fluorine-containing compound comprises sodium monofluorophosphate.

27. A process of preparing a cosmetic and chemically stable antipiaque dentifrice consisting essentially of the formation of two phases, an oil gel phase and a water gel phase comprising the following sequence of steps: a. dispersing the formula amount of a quaternary ammonium antiplaque agent in the formula amount of a flavour, b. mixing the quaternary ammonium-flavour dispersion into the formula amount of a betaine surfactantto form the oil gel phase, c. dispersing the formula amount of a nonionic gelling agent in the formula amount of glycerin and/or sorbitol humectant, d. mixing said gelling agent-humectant dispersion with the formula amount of water to form the water gel phase, e. combining the two gel phases to form a stable parent gel phase, f. adding the dental abrasive to the water gel phase or to the parent gel phase with mixing, and g. recovering a stable antiplaque dentifrice.

28. A process as claimed in Claim 27, wherein a water-soluble sweetening material, a fluorinecontaining compound or both are dissolved in the formula amount of water prior to its addition to the humectant-gelling agent dispersion in the formation of the water gel phase.

29. A process according to Claim 28 wherein the sweetening material is sodium saccharin and the fluorine-containing compound is sodium monofluorophosphate.

30. A process according to any one of Claims 22 to 29, wherein the nonionic gelling agent is hydroxyethylcellulose.

31. A dentifrice as claimed in any one of Claims 1 to 20 whenever produced by a process as claimed in any one of Claims 21 to 30.

32. A dentifrice substantially as herein described with reference to any one of the examples.

33. A process for preparing a dentifrice gel or a dentifrice substantially as herein described with reference to any one of the examples.