Antibacterial Oral Composition

This invention relates to an antibacterial oral composition which promotes oral hygiene.

Cationic nitrogen-containing 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, second edition (Vol. 2, p. 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 anti-plaque quaternary ammonium compounds is benzethonium chloride, also known as Hyamine 1622 or diisobutylphenoxyethoxyethyl dimethyl benzyl ammonium 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 caries formation and periodontal diseases. Other cationic antibacterial agents of this type are those mentioned, for instance, in U.S. Pat. Nos. 2,984,639, 3,325,402, 3,431,208 and 3,703,583 and British Pat. 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, dodecyl dimethyl (2-phenoxyethyl) ammonium bromide, benzyl dimethyl stearyl ammonium chloride, cetyl pyridinium chloride and quaternized 5-amino-1,3-bis (2-ethyl-hexyl)-5-methyl hexa hydropyrimidine are exemplary of other typical quaternary ammonium antibacterial agents.

Other types of cationic antibacterial agents which are desirably incorporated in oral compositions to promote oral hygiene by reducing plaque formation are the amidines such as the substituted guanidines e.g. chlorhexidine and the corresponding compound, alexidine, having 2-ethylhexyl groups instead of chlorophenyl groups and other bis-biguanides such as those described in German patent application No. P 2,332,383 published Jan. 10, 1974, which sets forth the following formula: ##STR1## in which A and A' signify as the case may be either (1) a phenyl radical, which as substituent can contain up to 2 alkyl or alkoxy groups with 1 up to about 4C-atoms, a nitro group or a halogen atom, (2) an alkyl group which contains 1 to about 12C-atoms, or (3) alicyclic groups with 4 to about 12C-atoms, X and X' as the case may be may represent an alkylene radical with I-3C atoms, z and z' are as the case may be either zero or 1, R and R' as the case may be may represent either hydrogen, an alkyl radical with 1 to about 12C-atoms or an aralkyl radical with 7 to about 12C-atoms, n is a whole number of 2 to inclusively 12 and the polymethylene chain (CH.sub.2) can be interrupted by up to 5 ether, thioether, phenyl-or naphthyl groups; these are available as pharmaceutically suitable salts. Additional substituted guanidines are: N'-(4-chlorobenzyl)-N.sup.5 -(2,4-dichlorobenzyl) biguanide; p-chlorobenzyl biguanide, 4-chlorobenzhydryl guanylurea; N-3-lauroxypropyl-N.sup.5 -p-chlorobenzyl biguanide; 5,6-dichloro-2-guanidobenzimidazole; and N-p-chlorophenyl-N.sup.5 -laurylbiguanide.

The cationic tertiary amines also possess antibacterial and antiplaque activity. Such antibacterial agents include tertiary amines having one fatty alkyl group (typically 12 to 18 carbon atoms) and 2 poly(oxyethylene) groups attached to the nitrogen (typically containing a total of from 2 to 50 ethenoxy groups per molecule) and salts therefor with acids and compounds of the structure: ##STR2## where R is a fatty alkyl group containing 12 to 18 carbon atoms and x, y and z total 3 or higher, as well as salts thereof. Generally, cationic agents are preferred for their antiplaque effectiveness.

The antibacterial antiplaque compound is preferably one which has an antibacterial activity such that its phenol co-efficient is well over 50, more preferably well above 100, such as above about 200 or more for S, aureus; for instance the phenol coefficient (A.O.A.C.) of benzethonium chloride is given by the manufacturer as 410, for S. aureus. The cationic antibacterial agent will generally be a monomeric (or possibly dimeric) material molecular weight well below 2,000, such as less than 1,000. It is, however, within the broader scope of the invention to employ a polymeric cationic antibacterial agent. The cationic antibacterial is preferably supplied in the form of an orally acceptable salt thereof, such as the chloride, bromide, sulfate, alkyl sulfonate such as methyl sulfonate and ethyl sulfonate, phenylsulfonate, such as p-methylphenyl sulfonate, nitrate, acetate, gluconate, etc.

The nitrogen-containing cationic antibacterial agents (including the tertiary amine) antibacterial agents effectively promote oral hygiene, particularly by removing plaque. However, their use has been observed to lead to staining of dental surfaces or discoloration.

The reason for the formation of such dental stain has not been clearly established. However, human dental enamel contains a high proportion (about 95%) of hydroxyapatite (HAP) which includes CA.sup.+2 and PO.sub.4.sup.-3 ions. In the absence of dental plaque additional Ca.sup.+2 and PO.sub.4.sup.-3 particularly from saliva, can be deposited on the enamel and such deposits can include color bodies which ultimately stain the tooth enamel as a calcified deposit thereon. It can be that as the cationic (including the tertiary amine) antibacterial agents remove plaque they also denature protein from saliva in the oral environment and the denatured protein can then act as a nucleating agent which is deposited on and stains or discolors tooth enamel.

Previously employed additives which reduced dental staining by cationic antibacterial antiplaque agents also generally reduced the activity of antibacterial antiplaque agents such as bis-biguanido compounds, as by forming a precipitate with such agents.

It is an advantage of this invention that anti-nucleating additives, namely certain copolymer agents are provided which unexpectedly inhibit, i.e. prevent or remove, the staining of dental enamel caused by such cationic (including the tertiary amine) antibacterial agents without precipitating or substantially adversely affecting their antibacterial and antiplaque activity. In themselves (even in the absence of such antibacterial agents), these additives are effective to reduce formation of dental calculus without unduly decalcifying dental enamel*, in addition to effectively inhibiting gingivitus. However, not all anti-nucleating agents are effective to prevent staining by such antibacterial agents. Victamide (also known as Victamine C) which is a condensation product of ammonia with phosphoruspentoxide, actually increases staining even in the absence of such antibacterial agents.

In accordance with certain of its aspects, this invention relates to an oral composition comprising an orally acceptable vehicle, at least one cationic nitrogen-containing antibacterial antiplaque agent whose use has been observed to lead to staining of dental surfaces, and as anti-staining additive, an effective stain-inhibiting amount of a copolymer consisting essentially of:

(A) n units having the molecular configuration of units derived from glutamic acid,

(B) m units having the molecular configuration of units derived from alanine, and

(C) p units having the molecular configuration of units derived from tyrosine,

the ratio of (n+m):p ranging from about 5:1 to about 9.5:1 and the ratio of m:n ranging from 0:1 to about 0.6:1,

the molecular weight of the copolymer ranging from about 5,000 to about 150,000.

The afore-mentioned copolymers may be prepared in well known manner, as for example by the procedure disclosed in Chase and Williams "Immunochemistry", Vol. 2, pp 168, 169 (1978) Academic Press. In general, the copolymers are prepared by random copolymerization of the N-carboxyanhydries of glutamic acid, tyrosine and alanine in the required molar proportions in the form of a mixture in an organic solvent such as dioxane, benzene, dimethyl formamide or N-methyl pyrrolidone and in the presence of an initiator such as an organic amine (e.g. triethylamine) or sodium methoxide.

The (A) units in the copolymer may be depicted as having the structural formula: ##STR3## n being a numerical value representing the number of (A) units of glutamic acid in the copolymer.

The (B) units in the copolymer may be depicted as having the structural formula: ##STR4## m being a numerical value representing the number of (B) units of alamine in the copolymer.

The (C) units in the copolymer may be depicted as having the structural formula: ##STR5## p being a numerical value representing the number of (C) units of tyrosine in the copolymer.

As defined above, the ratio of (n+m):p ranges from about 5:1 to about 9.5:1, the ratio of m:n ranges from 0:1 to about 0.6:1, and the values of m, n and p are such that the copolymer has a molecular weight of about 5,000 to about 150,000, preferably about 17,000 to about 100,000.

Especially preferred copolymers are a two component copolymer containing glutamic (A) units and tyrosine (B) units in a ratio of about 9:1 and having a molecular weight of about 17,000 to about 21,000, and a three component copolymer containing glutamic (A) units, alanine (B) units and tyrosine (C) units in a ratio of about 6:3:1 and having a molecular weight of about 80,000 to about 100,000.

It will be understood that the free acid form of the copolymers employed herein may be converted to, and employed, in their equivalent salt form by treatment with any base containing an orally acceptable cation such as alkali metal (e.g. sodium or potassium), ammonium, C.sub.1-18 mono-, di- or tri-substituted ammonium (e.g. alkanol substituted such as mono-, di- or tri-ethanolammonium), organic amines, etc. It will also be understood that when referring to these copolymers as being water soluble such copolymers should be water soluble or readily water dispersible in the concentrations employed in conventional oral compositions such as mouthwashes, toothpastes and the like.

Bearing in mind that human saliva contains natural inhibitors of calcium and phosphate precipitation including glutamic acid and tyrosine, the instant copolymers are relatively safe to use even if ingested since they are readily hydrolyzed in the stomach by chymotyprin, a proteolytic enzyme known to hydrolyze tyrosine. In contrast, other non-hydrolyzable oral additives when absorbed in the G.I. tract could cause changes in the bone. These copolymers are additionally advantageous in being substantive to oral surfaces.

The concentration of these copolymer antistain additives in oral compositions can range widely, typically upward from about 0.01% by weight with no upper limit except as dictated by cost or incompatibility with the vehicle. Generally, concentrations of about 0.01% to about 10% and preferably about 0.5% to 5% by weight are utilized. Oral compositions which in the ordinary course of usage could be accidentally ingested preferably contain concentrations in the lower portions of the foregoing ranges.

Cationic nitrogen-containing antibacterial antiplaque agents which may be employed in the practice of this invention are described above. They are typically employed in amounts such that the oral product contains between about 0.001 and 15% by weight of the agent. Preferably for desired levels of antiplaque effect, the finished oral product contains about 0.01 to about 5%, and most preferably about 0.25 to 1.0% by weight of the antibacterial agent, referring to its free base form.

In certain highly preferred forms of the invention, the oral composition may be substantially liquid in character, such as a mouthwash or rinse. In such a preparation the vehicle is typically a water-alcohol mixture. Generally, the ratio of water to alcohol is in the range of from about 1:1 to about 20:1 preferably from 3:1 to 20:1 and most preferably about 17:3, by weight. The total amount of water alcohol mixture in this type of preparation is typically in the range of from about 70 to about 99.9% by weight of the preparation. The pH of such liquid and other preparations of the invention is generally in the range of from about 4.5 to about 9 and typically from about 5.5 to 8. The pH is preferably in the range of from about 6 to about 8.0. It is noteworthy that the compositions of the invention may be applied orally at a lower pH without substantially decalcifying dental enamel.

Such liquid oral preparations may also contain a surface active agent and/or a fluorine-providing compound.

In certain other desirable forms of this invention, the oral composition may be substantially solid or pasty in character, such as toothpowder, a dental tablet, a toothpaste or dental cream. The vehicle of such solid or pasty oral preparations contains polishing material. Examples of polishing materials are water-insoluble sodium metaphosphate, potassium metaphosphate, tricalcium phosphate, calcium pyrophosphate, magnesium orthophosphate, trimagnesium phosphate, calcium carbonate, alumina, hydrated alumina, aluminum silicate, zirconium silicates, bentonite, and mixtures thereof. Preferred polishing materials include complex amorphous alkali metal aluminosilicate, hydrated alumina, calcium dihydrogen phosphate.

Alumina, particularly the hydrated alumina sold by Alcoa as C333, which has an alumina content of 64.9% by weight, a silica content of 0.008%, a ferric oxide content of 0.003%, and a moisture content of 0.37%, at 100.degree. C., and which has a specific gravity of 2.42 and a particle size such that 100% of the particles are less than 50 microns and 84% of the particles are less than 20 microns, is particularly desirable.

When visually clear gels are employed, polishing agents comprising alkali metal aluminosilicate complexes are particularly useful, since they have refractive indices close to the refractive indices of gelling agent-liquid (including water and/or humectant) systems commonly used in dentifrices.

Many of the so-called "water-soluble" polishing materials are anionic in character and also include small amounts of soluble material. Thus, insoluble sodium metaphosphate may be formed in any suitable manner as illustrated in Thorpe's Dictionary of Applied Chemistry, Volume 9, Fourth Edition, pp. 510-511. The forms of insoluble sodium metaphosphate known as Madrell's salt and Kurrol's salt are further examples of suitable materials. These metaphosphate salts exhibit a minute solubility in water, and therefore are commonly referred to as insoluble metaphosphates. There is present therein a minor amount of soluble phosphate material as impurities, usually a few percent such as up to 4% by weight. The amount of soluble phosphate material, which is believed to include a soluble sodium trimetaphosphate in the case of insoluble metaphosphate, may be reduced by washing with water if desired. The insoluble alkali metal metaphosphate is typically employed in powder form of a particle size such that no more than about 1% of the material is larger than 37 microns.

The polishing material is generally present in amounts ranging from about 20 to about 99% by weight of the oral preparation. Preferably, it is present in amounts ranging from about 20 to about 75% in toothpaste, and from about 70 to about 99% in toothpowder.

In the preparation of toothpowders, it is usually sufficient to admix mechanically, e.g., by milling, the various solid ingredients in appropriate quantities and particle sizes.

In pasty oral preparations the above-defined combination of the antibacterial antiplaque agent and additive should be compatible with the other components of the preparation. Thus, in a toothpaste, the liquid vehicle may comprise water and humectant typically in an amount ranging from about 10 to about 90% by weight of the preparation. Glycerine, sorbitol, or polyethylene glycol may also be present as humectants or binders. Particularly advantageous liquid ingredients comprise mixtures of water, glycerine and sorbitol.

In clear gels where the refractive index is an important consideration, about 3-30% by weight of water, 0 to about 80% by weight of glycerine, and about 20-80% by weight of sorbitol is preferably employed. A gelling agent, such as natural or synthetic gums or gumlike materials, typically Irish moss, sodium carboxymethylcellulose, methyl cellulose, or hydroxyethyl cellulose, may be employed. Other gelling agents which may be employed include gum tragacanth, polyvinylpyrrolidone and starch. They are usually present in toothpaste in an amount up to about 10% by weight, preferably in the range of from about 0.5 to about 5%. The preferred gelling agents are methyl cellulose and hydroxyethyl cellulose. In a toothpaste or gel, the liquids and solids are proportioned to form a creamy or gelled mass which is extrudable from a pressurized container or from a collapsible, e.g., aluminum or lead, tube.

The solid or pasty oral preparation which typically has a pH measured on a 20% slurry of about 4.5 to 9, generally about 5.5 to about 8 and preferably about 6 to about 8.0 may also contain a surface active agent and/or a fluorine-providing compound.

It will be understood that, as is conventional, the oral preparations are to be sold or otherwise distributed in suitable labelled packages. Thus a jar of mouthrinse will have a label describing it, in substance, as a mouthrinse or mouthwash and having directions for its use; and a toothpaste will usually be in a collapsible tube, typically aluminum or lined lead, or other squeeze dispenser for metering out the contents, having a label describing it, in substance, as a toothpaste or dental cream.

In oral compositions such as mouthrinses and toothpastes, a surfactant is often present, e.g. to promote foaming. It will be understood that it is preferable to employ nonionic surfactants rather than their anionic counterparts. Examples of water-soluble nonionic surfactants are condensation products of ethylene oxide with various reactive hydrogen-containing compounds reactive therewith having long hydrophobic chains (e.g. aliphatic chains of about 12 to 20 carbon atoms), which condensation products ("ethoxamers") contain hydrophilic polyoxyethylene moieties, such as condensation products of ethylene oxide with fatty acids, fatty alcohols and fatty amides including alcohols such as sorbitan monostearate or polypropyleneoxide (that is Pluronic materials).

In certain forms of this invention a fluorine-providing compound is present in the oral preparation. These compounds may be slightly soluble in water or may be fully water-soluble. They are characterized by their ability to release fluoride ions in water and by substantial freedom from reaction with other compounds of the oral preparation. 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, Ca fluoride, a copper fluoride such as cuprous fluoride, zinc fluoride, a tin fluoride such as stannic fluoride or stannous chlorofluoride, barium fluoride, sodium fluorsilicate, ammonium fluorosilicate, sodium fluorozirconate, sodium monofluorophosphate, aluminum mono- and di-fluorophosphate, 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 fluorine-providing compound is dependent to some extent upon the type of compound, its solubility, and the type or oral preparation, but it must be a nontoxic amount. In a solid oral preparation, such as toothpaste or toothpowder, an amount of such compound which releases a maximum of about 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 about 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 about 2% by weight, based on the weight of the preparation, and preferably in the range of about 0.05 to 1%. In the case of sodium monofluorophosphate, the compound may be present in an amount up to 7.6% by weight, more typically about 0.76%.

In a liquid oral preparation such as a mouthwash, the fluorine-providing compound is typically present in an amount sufficient to release up to about 0.13%, preferably about 0.0013 to 0.1% and most preferably about 0.0013 to 0.05%, by weight, of fluoride ion.

Various other materials may be incorporated in the oral preparations of this invention. Examples are whitening agents, preservatives, silicones, chlorophyll compounds, and ammoniated material such as urea, diammonium phosphate, and mixtures thereof. These adjuvants, where present, are incorporated in the preparations in amounts which do not substantially adversely affect the properties and characteristics desired.

Any suitable flavoring or sweetening material may also be employed. Examples of suitable flavoring constituents are flavoring oils, e.g., oils of spearmint, peppermint, wintergreen, sassafras, clove, sage, eucalyptus, marjoram, cinnamon, lemon and orange, and methyl salicylate. Suitable sweetening agents include sucrose, lactose, maltose, sorbitol, sodium cyclamate, perillartine, APM* saccharin. Suitably, flavor and sweetening agents may together comprise from about 0.1 to 5% or more of the preparation.

In preparing the oral compositions of this invention comprising the above-defined combination of antibacterial agent and additive in an oral vehicle which typically includes water, it is highly preferred if not essential to add the additive after the other ingredients (except perhaps some of the water) are mixed or contacted with each other to avoid a tendency for said agent to be precipitated.

For instance, a mouthrinse or mouthwash may be prepared by mixing ethanol and water with flavoring oil, nonionic surfactant, humectant, cationic antibacterial antiplaque agent, such as benzethonium chloride or chlorohexidine, sweetener, color and then the above-defined additive, followed by additional water as desired.

A toothpaste may be prepared by forming a gel with humectant, gum or thickener such as hydroxyethyl cellulose, sweetener and adding thereto polishing agent, flavor, antibacterial agent, such as benzethonium chloride or chlorhexidine, additional water, and then the above-defined additive. If sodium carboxymethyl cellulose is employed as the gelling agent, the procedure of either U.S. Pat. No. 3,842,168 or U.S. Pat. No. 3,843,779, modified by the inclusion of the additive, is followed.

In the practice of this invention an oral composition according to this invention such as a mouthwash or toothpaste containing cationic nitrogen-containing antibacterial antiplaque agent in an amount effective to promote oral hygiene and the defined additive in an amount effective to reduce staining of dental surfaces otherwise resulting from the presence of the antibacterial antiplaque agent, is applied regularly to dental enamel, preferably from about 5 times per week to about 3 times daily, at a pH of about 4.5 to about 9, generally about 5.5 to about 8, preferably about 6 to 8.

The following specific examples are further illustrative of the nature of the present invention, but it is understood that the invention is not limited thereto. All amounts and proportions referred to herein and the appended claims are by weight unless otherwise indicated.

Table I below is illustrative of mouthwash formulations according to the invention and the antistaining activity of the instant copolymer additive therein. The tooth staining characteristics of the formulations are evaluated by slurrying hydroxyapatite (Biogel), a specific salivary protein, a carbonyl source (e.g. acetaldehyde), and a pH 7 phosphate buffer, with and without the mouthwash formulations being tested. The mixture is shaken at 37.degree. C. for 18 hours. The colored HAP powder is separated by filtration, dried and the color levels (in reflectance units) determined on a Gardner color difference meter.

The above results plainly establish that the copolymer additives of the present invention substantially reduce dental staining ordinarily produced by cationic quarternary ammonia antibacterial antiplaque agents as exemplified by CPC.

Further, in vitro tests establish that the antiplaque activity of Examples 2 and 3 are substantially equal, indicating that the copolymer additives of this invention do not significantly effect the antiplaque activity of CPC and the like.

Substitution of equivalent amounts of the following antibacterial antiplaque agents for the CPC employed in Examples 3 and 4 yield formulations also producing an unexpected reduction in dental staining.

The following formulations exemplify toothpastes with antiplaque activity and reduced staining.

This invention has been described with respect to preferred embodiments and it will be understood that modifications and variations thereof obvious to those skilled in the art are to be included within the spirit and purview of this application and the scope of the appended claims.