AU7636094A

AU7636094A - Baking soda toothpaste and tooth gel containing soluble pyrophosphate salts

Info

Publication number: AU7636094A
Application number: AU76360/94A
Authority: AU
Inventors: Todd W Domke; Anthony E. Winston
Original assignee: Church and Dwight Co Inc
Current assignee: Church and Dwight Co Inc
Priority date: 1993-08-30
Filing date: 1994-08-29
Publication date: 1995-03-22
Also published as: CA2170532A1; WO1995006455A1

Description

BAKING SODA TOOTHPASTE AND TOOTH GEL CONTAINING SOLUBLE PYROPHOSPHATE SALTS

The present invention relates to a dentifrice selected from the group consisting of a toothpaste and a tooth gel which contain baking soda and an alkali metal pyrophosphate salt. Calculus, or tartar as it is sometimes called, is the solid, hard mass of calcified material deposited on and adhering to the surfaces of the teeth. It is composed of inorganic salts which make the calculus hard and resistant to removal. Although not entirely understood, the general concept is that plaque, which is a sticky film of oral bacteria and their products, adheres to teeth and becomes calcified with the ultimate formation on the teeth of a hard mineral-like material consisting of calcium phosphates. Calculus is largely calcium phosphates, mainly hydroxyapatite with varying, but small, amounts of other inorganic salts.

As the mature calculus develops, it becomes visibly white or yellowish in color unless stained or discolored by some extraneous agent. In addition to being unsightly and undesirable from an aesthetic standpoint, the mature calculus deposits can be constant sources of irritation to the gingiva. Further, the calculus can promote and retain plaque accumulations. Plaque is recognized as a prime etiological agent involved in gingivitis and periodontal disease. Additionally, plaque is porous and can retain toxic bacterial end products which are also associated with periodontal disease.

Methods for chemically reducing or preventing calculus formation have been directed at affecting the process at any of several stages in its development. One approach is to develop agents which inhibit the formation of the crystalline calcium phosphate or hydroxyapatite. A wide variety of chemical and biological agents have been suggested to retard calculus formation or to remove calculus after it is formed. The chemical approach to calculus inhibition generally involves crystal growth inhibition which prevents the calculus from forming. Generally, once formed, mechanical removal by the dentist is necessary and is a routine dental office procedure.

The most widely used tartar control agents in dentifrices are sodium and potassium salts of pyrophosphoric acid. It is important that the pyrophosphate salt be in a readily available form so that the pyrophosphate ions (P₂C>₇ ^~ ) contact the enamel surfaces during use. The bioavailability of the ion is determined by the solubility of the salt both in the liquid vehicle of the dentifrice and in the water/expectorant mixture in which the dentifrice is dispersed during brushing of the teeth.

In a dentifrice containing sodium bicarbonate, i.e., baking soda, and the alkali metal salts of pyrophosphoric acid, the solubility of the pyrophosphate salt within the liquid vehicle of the dentifrice is greatly reduced. This suppression of solubility is due to the excess of sodium ions placed in solution by the sodium bicarbonate.

Therefore, there is a need to improve the solubility of alkali metal pyrophosphate salts within a baking soda toothpaste or a baking soda tooth gel.

The present invention provides a dentifrice in the form of a toothpaste or tooth gel.

The toothpaste comprises sodium bicarbonate, typically about 8-65%, preferably about 20-55%, most preferably 40- 50%; an effective amount of an alkali metal pyrophosphate salt as an anti-tartar agent; and an aqueous solution of sorbitol in an amount sufficient to dissolve at least about 50% of the pyrophosphate salt and to provide the desired consistency to the toothpaste, typically at least about 30- 70%, preferably about 40-60%. The tooth gel comprises sodium bicarbonate, typically about 5-50%, preferably about 10-40%, most preferably about 20-35%; an effective amount of an alkali metal pyrophosphate salt as an anti-tartar agent; and an aqueous solution of sorbitol in an amount sufficient to dissolve at least about 50% of the pyrophosphate salt and to provide the desired consistency to the tooth gel, typically at least about 30- 70%, preferably about 35-60%.

The pyrophosphate ion is more readily available because tetrasodium pyrophosphate is more soluble in the aqueous sorbitol solution used herein as the liquid vehicle than in the conventional aqueous liquid vehicles used in most toothpastes and tooth gels.

In a toothpaste and.a tooth gel, water is typically a desirable component. However, in the present toothpastes and tooth gels, water is not especially desirable and any additional water (i.e., water over and above that in the sorbitol solution) comprises only up to about 30%, preferably only up to 7%, of the composition. The sorbitol solution is the main liquid vehicle. The water used to dissolve the sorbitol is that amount which is effective to solubilize it. Typically, the sorbitol solution is a 70% aqueous solution.

In translucent gels, where the refractive index is an important consideration, it is preferred to use higher ratios of sorbitol or other humectant to water than in opaque pastes. For a gel the ratio of humectant to water is typically above 0.5 to 1, preferably above 1 to 1.

Optional, but preferred, components which are typically included in the toothpastes and tooth gels are organic thickeners and/or inorganic thickeners, surfactants, flavoring agents and/or sweetening agents, coloring agents and/or pigments, an anti-caries agent such as a soluble fluoride source, buffering agents such as alkali metal orthophosphates, phosphoric acid, alkali metal glycerophosphates, tartrates and citrates, and like components conventionally added to toothpastes and tooth gels. If desired, a secondary anti-calculus agent can be included. The optional components should not interfere with the solubility of the pyrophosphate in the aqueous sorbitol solution.

The present invention also provides a method of preventing tartar formation on dental enamel which comprises contacting the enamel surface in the mouth with a toothpaste or a tooth gel comprising sodium bicarbonate, an alkali metal pyrophosphate salt, and an aqueous sorbitol solution, with the amount of pyrophosphate salt dissolved in the toothpaste or the tooth gel being sufficient to provide about 0.5-4.0% pyrophosphate ions in the toothpaste or 0.5- 2% pyrophosphate ions in the tooth gel. The present invention further provides a method for increasing the solubility, in a sodium bicarbonate- containing dentifrice, of alkali metal pyrophosphate anti- calculus agents by adding an aqueous solution of sorbitol, as the liquid vehicle, to dissolve the sodium pyrophosphate salt formed in the presence of the sodium bicarbonate.

Suitable pyrophosphate salts which may be incorporated in the toothpastes and tooth gels of the present invention include mono-, di-, tri- or tetra-alkali metal pyrophosphates and mixtures thereof. The preferred pyrophosphate salts include disodium pyrophosphate (Na₂H₂P₂0₇) , tetrasodium pyrophosphate (Na₄P₂0₇) , tetrapotassium pyrophosphate (K₄P₂0₇) , and mixtures thereof. The pyrophosphates may be employed in their anhydrous as well as their hydrated forms. The levels of each of these salts used in the toothpastes are as follows (all are in the unhydrated form) : Na₂H₂P₂0₇ — about 1-10%, preferably about 1-5%, Na₄P₂0₇ — up to about 2%, and K₄P₂0₇ — up to about 6%. The levels of each of these salts used in the tooth gels are as follows (all are in the unhydrated form) : Na₂H₂P₂0₇ - 0- 12%, Na₄P₂0₇ - 1-10%, preferably 1-5%, K₄P₂0₇ - 0-6%. Although a particular pyrophosphate salt, e.g., disodium or tetrapotassium pyrophosphate, may be the pyrophosphate initially added to the toothpaste or the tooth gel, the actual pyrophosphate present in the toothpaste or tooth gel is dependent on both the final pH of the toothpaste or tooth gel and the salting-out effect of the sodium bicarbonate. Typically, the actual pyrophosphate is tetrasodium pyrophosphate. The quantity of dissolved pyrophosphate ion present in the toothpaste or tooth gel is dependent on the solubility, in the presence of sodium bicarbonate, of the particular alkali metal pyrophosphate salt used, in the amount of aqueous sorbitol solution and in the added water, if present, as well as the final pH of the toothpaste or tooth gel. The sodium bicarbonate particles may have a median particle size of about 5 to 200 microns, preferably about 10-150 microns, most preferably about 20-74 microns. The bicarbonate particles are incorporated in the toothpaste or tooth gel in varying amounts, depending upon the desired properties of the formulation. Higher levels of sodium bicarbonate, e.g., about 50-65%, allow it to be used as the sole abrasive. Such formulations remove plaque effectively, have a desirable low abrasivity, and provide an exceptionally clean feeling to the teeth and gums after brushing. Lower levels allow the incorporation of secondary abrasives and permit the formulation of clearer gels.

To improve clarity in tooth gels less sodium bicarbonate is used, typically about 10-35%, preferably about 20-30% and coarser bicarbonate crystals are chosen, preferably crystals having an average particle size of greater than 44 microns, most preferably greater than 74 microns. At very low concentrations the clarity of the tooth gel is increased. If a secondary abrasive is used in the tooth gel, the abrasive selected is one which will give a clear or translucent gel. When low levels of sodium bicarbonate are used in the toothpaste, it is desirable to add an opacifying agent such as titanium dioxide in an amount of up to about 5%, preferably about 0.1-1%. If one wishes to convert the present gels into an opaque toothpaste, one should add an opacifying agent such as titanium dioxide in an amount up to about 5%, preferably about 0.1-1%.

At very low levels, e.g., less than about 10%, the bicarbonate still enhances the clean feeling of the teeth and gums, but to a lesser degree than when high levels are used. It also provides effective buffering in the pH range of 7.5 to 9.5.

Suitable secondary humectants for use herein include glycerin, propylene glycol, polypropylene glycol, and/or polyethylene glycol and other conventional humectants. In addition to the above described required components, the toothpaste or tooth gel can contain a variety of conventionally used optional components.

Typically, the toothpastes and tooth gels contain a natural or synthetic organic thickener or gelling agent. In the toothpastes the amounts are up to about 2%, preferably about 0.1-2%. In the tooth gels the amounts are up to about 0.1-10%, preferably about 0.1-2%. Suitable organic thickeners include sodium carboxymethyl cellulose, starch, gum tragacanth, carrageenan, xanthan gum, polyacrylate salts, polyvinylpyrrolidone, hydroxyethylpropyl cellulose, hydroxybutylmethylcellulose, hydroxypropylmethylcellulose, or hydroxyethyl cellulose, which are usually used in amounts of about 0.1-2.0%. Inorganic thickeners such as hydrated silicas may also be used in amounts of up to about 10% or greater in the toothpastes or in amounts of about 0.5%-10% or greater in the tooth gel.

Conventional abrasives or polishing materials are useful herein as a secondary abrasive provided they do not interfere with the solubility of the pyrophosphate salt. Suitable water-insoluble abrasives for the toothpastes include sodium metaphosphate, potassium metaphosphate, calcium pyrophosphate, aluminum silicate, zirconium silicate, hydrated silica, hydrated alumina, bentonite, and/or the like. Preferred abrasive materials which may be admixed with the sodium bicarbonate include hydrated silica, silica gel, or colloidal silica and complex amorphous alkali metal aluminosilicates. Any of the foregoing water- insoluble abrasives may be present in the toothpaste in amounts of up to about 40%, preferably in amounts up to about 20%, which amount will depend upon the amount of sodium bicarbonate used.

Suitable water-insoluble abrasives for tooth gels include colloidal silica, hydrated silica, silica gel, hydrated alumina, complex amorphous alkali metal aluminosilicates and/or the like. When visually clear gels are employed, polishing agents of hydrated or colloidal silica, alkali metal aluminosilicate complexes, and alumina are particularly useful since they have refractive indices close to the refractive indices of the gelling agent-liquid systems commonly used in the gels. Any of the foregoing water-insoluble abrasives may be present in the tooth gel in amounts of up to about 30%, preferably in amounts up to about 15%, which amount will depend upon the amount of sodium bicarbonate used.

Organic surfactants are useful herein to achieve increased cleaning action, to assist thorough and complete dispersion of the anti-calculus agent throughout the oral cavity, and to improve the detergent and foaming properties of the toothpastes and tooth gels. Anionic, nonionic or ampholytic surfactants may be used, typically in amounts of about 0.1-3%.

Examples of suitable anionic surfactants are the water- soluble salts of the higher alkyl sulfates such as sodium lauryl sulfate or other C₈-C₁₈ alkyl sulfates, water-soluble salts of higher fatty acid monoglyceride monosulfates such as the sodium salt of the monosulfate monoglyceride of hydrogenated coconut oil fatty acids, alkyl aryl sulfonates such as sodium dodecyl benzene sulfonate, higher alkyl sulfoacetates, higher fatty acid esters of 1,2-dihydroxy propane sulfonate, and the substantially saturated higher aliphatic acyl amides of lower aliphatic amino carboxylic acids such as C₁₂-C₁₆ fatty acids, alkyl or acyl radicals, and the like. Examples of the last mentioned amides are N- lauroyl sarcosinate and the sodium, potassium, and ethanolamine salts of N-lauroyl, N-myristoyl, or N-palmitoyl sarcosinate which should be substantially free from soap or similar higher fatty acid materials.

Other suitable surfactants include non-ionic agents such as the condensates of sorbitan monostearate with ethylene oxide, the condensates of ethylene oxide with propylene oxide, or the condensates of propylene glycol (available under the trademark "Pluronics") . Other examples of water-soluble nonionic surfactants useful herein are the condensation products of ethylene oxide with various other compounds which are reactive therewith and have long hydrophobic chains (e.g., C₁₀-C₂₀ aliphatic chains) which condensation products ("ethoxamers") contain hydrophilic polyoxyethylene moieties, such as condensation products of polyethylene oxide with fatty acids, fatty alcohols, fatty amides, or polyhydric alcohols (e.g., sorbitan monostearate) . The various surfactants may be utilized alone or in admixture with one another. In toothpastes and tooth gels, the total amount used is preferably about 0.05%-5%, more preferably about 0.1%-2.0%.

Sweetening agents are also useful herein. They include saccharin, sucralose, dextrose, levulose, aspartame, D- tryptophan, dihydrochalcones, acesulfame, sodium cyclamate, and calcium cyclamate. They are generally used in amounts of up to about 2%. Also useful as sweetening agents are xylitol and mannitol in amounts of up to about 3% and 5%, respectively, in toothpastes and up to about 5% in tooth gels. Anti-microbial agents can be included in the toothpastes to help inhibit plaque formation and gingivitis or to reduce mouth odor. For example, cationic anti¬ microbial agents such as cetyl pyridinium chloride or benzothonium chloride can be used. Bis-biguanides are also effective. Such agents include chlorhexidine (1,6-bis [N⁵- p-chlorophenyl-N-biguanido] hexane) , and the soluble and insoluble salts thereof and related materials such as 1,2- bis (N⁵-p-trifluoromethylphenyl-N¹-biguanido) ethane which are described more fully in U.S. Pat. No. 3.937.807 (issued Feb. 10, 1976 to Haefale) , Belgian Pat. No. 843.244 (published Dec. 22, 1976) and Belgian Pat. No. 844.764 (published Jan. 31, 1977) . If present, the secondary anti¬ microbials generally comprise about 0.01-0.5% of the composition. When using cationic agents, it is generally necessary to avoid using anionic surfactants in the formulation. Non-ionic anti-microbials such as triclosan can be used. These materials have the advantage of not losing efficacy in the presence of anionic surfactants. Soluble complex phosphate salts other than the pyrophosphates may be used as secondary anti-calculus agents, e.g., tripolyphosphates and hexametaphosphates.

The toothpastes and tooth gels can include a water- soluble fluoride ion source which is effective both as a pyrophosphatase inhibitor and as an anti-caries agent. Suitable fluoride ion sources include inorganic fluoride salts such as soluble alkali metal or alkaline earth metal salts, e.g., sodium fluoride, potassium fluoride, sodium fluorosilicate, ammonium fluorosilicate, sodium fluorozirconate and sodium monofluorophosphate. Alkali metal fluorides such as sodium fluoride, sodium monofluorophosphate, and mixtures thereof are preferred. The amount of the soluble fluoride ion source in the dentifrice is dependent on the particular compounds used and the type of dentifrice, but it must be incorporated in an effective, but nontoxic amount, generally up to about 5.0%. Any suitable minimum amount of fluoride may be used, but it is preferable to employ a quantity sufficient to release about 50 to 3500 ppm, preferably about 850-1500 ppm, of fluoride ions. In the case of sodium fluoride, the fluoride ion source is present in an amount from 0.05-0.65%, preferably about 0.18-0.35%. In the case of sodium monofluorophosphate, the amount is about 0.2-2%, more typically about 0.65%-l.20%.

Various other materials may be incorporated in the toothpastes and tooth gels. Examples thereof are coloring and whitening agents, preservatives, silicones, and/or chlorophyll compounds. These adjuvants are incorporated in the toothpastes and tooth gels in amounts which do not substantially adversely affect the properties and characteristics desired and are selected and used in effective amounts, depending upon the particular adjuvant and the type of toothpaste or tooth gel involved.

The pH of the toothpastes and tooth gels herein range from 7.0 to 10.0, preferably from 7.5 to 9.0. The pH is preferably achieved through a proper balancing of the bicarbonate and other additives.

The toothpastes and tooth gels herein are made using conventional mixing techniques and used in a conventional manner. The following examples further illustrate the present invention, but it is understood that the invention is not limited thereto. All amounts and proportions referred to herein and in the appended claims are by weight and temperatures are in degree Celsius unless otherwise indicated.

Example l The following toothpaste containing about 1.3% pyrophosphate all in solution was prepared.

Sodium bicarbonate (mean 43.374 particle size < 35)

Tetrasodium pyrophosphate 2.000 Sodium fluoride 0.. 243

Sorbitol (70% aqueous solution) 40. , 100

Glycerin 4 . , 104

Polyethylene glycol (PEG-8) 1. , 000 Sodium carboxymethyl cellulose 0. , 700

(9M31F)

Distilled water 5. . 279

Sodium saccharin 1. . 000

Sodium lauryl sulfate 0. . 300 Sodium lauroyl sarcosinate 1. . 000

(30% solution)

Flavor 0. . 900

TOTAL 100. . 000

Example 2 The following tooth gel containing about 1.3% pyrophosphate ion all in solution was prepared.

Sodium bicarbonate (Grade 2) 31.354

Tetrasodium pyrophosphate 2.000

Sodium fluoride 0.243 Sorbitol (70% aqueous 40.100 solution)

Glycerin 4.104

Polyethylene glycol (PEG-8) 1.000

Sodium carboxymethyl cellulose 0.600 (9M8F)

Distilled water 5.279

Sodium saccharin 0.650

Thickening silica (Sylox 2) 4.500

Hydrated silica (Sylodent 700) 8.000 Sodium lauryl sulfate 0.500

Sodium lauroyl sarcosinate 1.670

(30% solution)

Flavor 0.950

TOTAL 100.000 Examples 3-6 The following are representative toothpastes.

3 4 5 6

Sodium bicarbonate 42.287 55.000 8.000 20.000

Tetrasodium 2.000 2.000 6.000 4.000 pyrophosphate

Tetrapotassium 0.000 0.000 0.000 3.000 pyrophosphate

Hydrated silica 0.000 0.000 0.000 4.300 abrasive

Thickening silica 0.000 0.000 0.000 3.000

Titanium dioxide 0.000 0.000 0.000 0.200

Calcium pyrophosphate 0.000 0.000 8.000 0.000

Sodium fluoride 0.243 0.243 0.243 0.243

Sorbitol (70% 40.100 40.100 40.100 40.100 solution)

Glycerin 5.000 5.000 5.000 5.000

Polyethylene glycol 0.000 0.000 1.000 1.000

(PEG-8) Sodium carboxymethyl 0.600 0.600 0.600 0.600 cellulose

Distilled water 6.000 5.279 5.279 10.000

Sodium saccharin 0.650 0.650 0.650 0.650

Sodium lauryl sulfate 0.500 0.500 0.500 0.500 Sodium lauroyl 1.670 1.670 1.670 1.670 sarcosinate (30% solution)

Flavor 0.950 0.950 0.950 0.950 TOTAL 100.00 100.00 100.00 100.00

0 0 0 0

Approximate % of 80% 50% 75% 55% pyrophosphate which is in solution

Examples 7-10

The following are representative tooth gels.

7 8 9 10

Sodium bicarbonate 25.000 50.000 5.000 12.000

Tetrasodium 2.000 1.000 6.000 4.000 pyrophosphate

Tetrapotassium 0.000 0.000 0.000 3.000 pyrophosphate

Sodium fluoride 0.243 0.243 0.243 0.000

Sodium 0.000 0.000 .000 0.780 monofluorophosphate

Sorbitol (70% aqueous 44.882 39.984 62.000 58.692 solution)

Glycerin 5.150 10.000 5.000 6.220

Polyethylene glycol 0.000 1.500 1.000 2.000 (PEG-8)

Sodium carboxymethyl 0.600 0.300 0.600 0.300 cellulose

Sodium saccharin 0.650 0.650 0.500 0.800

Hydrated silica 4.500 0.000 12.000 6.000 abrasive (Sylodent 700) Thickening silica 8.000 0.000 6.000 4.000 (Sylox 2)

Sodium lauryl sulfate 0.500 0.500 1.000 1.500

Sodium lauroyl 1.670 0.870 0.000 0.000 sarcosinate (30% solution)

Flavor 0.800 0.950 0.655 0.700

Color 0.005 0.003 0.002 0.008

TOTAL 100.00 100.00 100.00 100.00 0 0 0 0

Approximate % of 100% 100% 65% 60% pyrophosphate which is in solution

Examples 11-14

The following are additional representative toothpastes

11 12 13 14

Sodium bicarbonate 35.000 43.220 14.979 65.00 Tetrasodium 0.000 0.000 2.500 2.00 pyrophosphate

Tetrapotassium 3.400 5.000 0.000 0.00 pyrophosphate

Disodium dihydrogen 0.000 0.200 0.000 0.00 pyrophosphate

Hydrated silica 5.500 0.000 5.000 0.00 abrasive

Thickening silica 0.000 0.000 5.000 0.00 Titanium dioxide 0.100 0.000 0.500 0.00

Sodium fluoride 0.243 0.000 0.221 0.243

Sodium 0.000 0.780 0.000 0.00 monofluorophosphate Sorbitol (70% solution) 44.657 40.100 35.000 24.32

Xylitol 3.000 0.000 0.000 0.00

Mannitol 0.000 0.000 5.000 0.00

Glycerin 4.000 0.000 4.000 4.00

Polyethylene glycol 1.000 1.000 0.000 1.00 (PEG-8)

Sodium carboxymethyl 0.300 0.600 0.800 0.30 cellulose

Distilled water 0.000 6.000 25.000 0.00

Sodium saccharin 0.650 0.700 0.500 0.80 Sodium lauryl sulfate 1.200 0.300 0.800 0.33

Sodium lauroyl 0.000 1.000 0.000 1.00 sarcosinate (30% solution)

Flavor 0.950 1.100 0.700 1.00 TOTAL 100.000 100.000 100.000 100.00

Approximate % of 100% 70% 80% 75 pyrophosphate which is in solution Examples 15-18

The following are additional representative tooth gels.

15 16 17 18

Sodium bicarbonate 32.000 43.220 29.500 20.000

Tetrasodium 0.000 0.000 2.500 5.000 pyrophosphate

Tetrapotassium 3.400 5.000 0.000 0.000 pyrophosphate

Disodium dihydrogen 0.000 0.195 0.000 0.000 pyrophosphate

Sodium fluoride 0.243 0.000 0.243 0. .000

Sodium 0.000 0.780 0.000 0. .780 monofluorophosphate

Sorbitol (70% aqueous 43.157 40.100 40.000 42. .000 solution)

Xylitol 5.000 0.000 0.000 0. ,000

Mannitol 0.000 0.000 4.882 0. ,000 Glycerin 0.000 0.000 5.000 0. ,000

Polyethylene glycol 1.000 1.000 1.000 0. ,000 (PEG-8)

Sodium carboxymethyl 0.300 0.600 0.600 0.300 cellulose Distilled water 0.000 6.000 0.000 9.367

Sodium saccharin 0.646 0.700 0.650 0.800

Hydrated silica abrasive 4.100 0.000 4.500 4.000 (Sylodent 700) Thickening silica (Sylox 8.000 0.000 8.000 15.000 2)

Sodium lauryl sulfate 1.200 0.300 0.500 0.330

Sodium lauroyl 0.000 1.000 1.670 1.000 sarcosinate (30% solution)

Flavor 0.950 1.100 0.950 1.000

Color 0.004 0.005 0.005 0.003

TOTAL 100.00 100.00 100.00 100.000 0 0 0

Approximate % of 100% 55% 100% 50% pyrophosphate which is in solution

Example 19

This example shows the effect of sodium bicarbonate

(NaHC0₃) on the solubility of tetrasodium pyrophosphate.

Wt % of P₂0₇~⁴ in Solution

With Satura

Without NaHC0₂ NaHCO.

Distilled Water 4.03 1. .77

Glycerin 0.04 0. .12

70% Aqueous Sorbitol Solution 5.97 4. .18

18% Aqueous Mannitol Solution 2. .09

60% Aqueous Xylitol Solution 2. .44

The results show that, in the presence of sufficient sodium bicarbonate to saturate the water, the solubility of the pyrophosphate ion (P₂0₇~⁴) was suppressed from 4.03% to

1.77%. The results show that, in the absence of sodium bicarbonate, the pyrophosphate is more soluble in the 70% aqueous sorbitol solution than it is in the distilled water. While the presence of the bicarbonate in the aqueous sorbitol solution also suppressed the pyrophosphate solubility, the decrease was not as great as that observed with water. The pyrophosphate was not soluble in glycerin in either case. The results further show that other similar polyols, i.e., mannitol and xylitol, were not as effective as sorbitol, in increasing pyrophosphate solubility in the presence of bicarbonate.

Example 20 This example shows the solubility of tetrasodium pyrophosphate in various dentifrice solvent systems saturated with sodium bicarbonate. The percent solubility of the pyrophosphate ion (P₂0₇~⁴) is given as weight %.

Water* Glvcerin* 70% Sorbitol Wt. % Pn0 Solution

1 0 0 1.77

0 1 0 0.12

0 0 1 4.18

1/2 1/2 0 0.44

1/2 0 1/2 2.19

0 1/2 1/2 1.73

1/3 1/3 1/3 1.01

2/3 1/6 1/6 1.15

1/6 2/3 1/6 1.48

1/6 1/6 2/3 2.08

*Weight fraction of solvent system. The results show that the best solubility (4.18%) was in the 70% aqueous sorbitol solution and the worst solubilities were in solvent systems containing no aqueous sorbitol solution (0.12% for glycerin and 0.44% for a glycerin/water mixture) .

In addition to the levels and combinations of ingredients shown in these examples, others can be used which are consistent with the invention disclosed and claimed herein.

Claims

WHAT IS CLAIMED IS:

1. A toothpaste consisting essentially of: a. about 10-65% sodium bicarbonate; b. an alkali metal pyrophosphate salt in an amount effective as an anti-tartar agent, of which amount at least 50% is dissolved in the toothpaste; and c. an aqueous solution of sorbitol, as a main liquid vehicle, in an amount which is sufficient to dissolve at least about 50% of the amount of the alkali metal pyrophosphate salt added and to provide the desired consistency to the toothpaste.

2. The toothpaste of Claim 1, wherein the amount of the alkali metal pyrophosphate salt is sufficient to provide about 0.5-5% by weight of dissolved pyrophosphate ions.

3. The toothpaste of Claim 2, wherein the sodium bicarbonate is about 20-55%; wherein the pyrophosphate salt added is selected from the group consisting of tetrasodium pyrophosphate, disodium dihydrogen pyrophosphate, tetrapotassium pyrophosphate, and mixtures thereof; and wherein the aqueous sorbitol solution is about 70% aqueous.

4. The toothpaste of Claim 3, wherein the sodium bicarbonate is about 40-50%; wherein the pyrophosphate salt added is tetrasodium pyrophosphate present in an amount of about 1-10%, disodium dihydrogen pyrophosphate present in an effective amount of up to about 2%, or tetrapotassium pyrophosphate present in an effective amount of up to about 6%; and wherein the about 70% aqueous solution of sorbitol is about 30-70% of the toothpaste.

5. The toothpaste of Claim 4, wherein the about 70% aqueous solution of sorbitol is about 40-60% of the toothpaste and wherein the pyrophosphate salt added is tetrasodium pyrophosphate in an amount of about 1-5%.

6. The toothpaste of Claim 5, wherein the amount of pyrophosphate ions present in the toothpaste is about 0.5- 2%. 7. The toothpaste of Claim 2, further consisting essentially of: added water in an effective amount up to about 30%; a humectant other than sorbitol in an effective amount up to about 2%; a water-insoluble abrasive in an effective amount up to about 40%; an opacifying agent in an effective amount up to about 5%; an organic thickener in an effective amount up to about 2%; an inorganic thickener in an effective amount up to about 10%; an effective amount of a surfactant; an effective amount of a flavoring agent; a sweetening agent in an effective amount up to about 5% ; and/or an effective amount of an anti-caries agent. 8. The toothpaste of Claim 7, wherein the water is present in an effective amount up to about 6%; wherein the water-insoluble abrasive is calcium pyrophosphate present in an effective amount of up to about 8% or hydrated silica present in an effective amount of up to about 5.5%; the humectant is polyethylene glycol present in an effective amount of up to about 2%; wherein the opacifying agent is titanium dioxide; wherein the inorganic thickening agent is silica present in an effective amount of up to about 5%; wherein the surfactant is sodium lauryl sulfate present in an amount of about 0.3-1.4% and sodium lauroyl sarcosinate, as a 30% solution, present in an amount of about 1.

7%; wherein the amount of the flavoring agent is about 0.05-2%; wherein the sweetening agent is sodium saccharin present in an amount of about 0.5-0.

8%, xylitol present in an effective amount of up to about 3%, or mannitol present in an effective amount of up to about 5%; wherein the anti-caries agent is a fluoride source present in an amount sufficient to provide about 50-3500 ppm of fluoride ions and is selected from the group consisting of sodium fluoride and sodium monofluorophosphate.

9. A tooth gel consisting essentially of: a. about 10-50% sodium bicarbonate; b. an alkali metal pyrophosphate salt present in an amount which is effective as an anti-tartar agent, of which amount at least 50% is dissolved in the tooth gel; and c. an aqueous solution of sorbitol, as a main liquid vehicle, in an amount which is sufficient to dissolve at least about 50% of the amount of the alkali metal pyrophosphate salt added and to provide the desired con¬ sistency to the tooth gel.

10. The tooth gel of Claim 9, wherein the amount of the alkali metal pyrophosphate salt is sufficient to provide about 0.5-6% by weight of dissolved pyrophosphate ions.

11. The tooth gel of Claim 10, wherein the sodium bicarbonate is about 10-40%; wherein the pyrophosphate salt added is selected from the group consisting of tetrasodium pyrophosphate, disodium dihydrogen pyrophosphate, tetrapotassium pyrophosphate, and mixtures thereof; and wherein the aqueous sorbitol solution is an about 70% aqueous sorbitol solution.

12. The tooth gel of Claim 11, wherein the sodium bicarbonate is about 20-35%; wherein the pyrophosphate salt added is tetrasodium pyrophosphate present in an amount of about 1-10%, disodium dihydrogen pyrophosphate present in an effective amount of up to about 12%, or tetrapotassium pyrophosphate present in an effective amount of up to about 6%; and wherein the about 70% aqueous solution of sorbitol is about 30-70% of the tooth gel.

13. The tooth gel of Claim 12, wherein the about 70% aqueous solution of sorbitol is about 35-60%; wherein the added tetrasodium pyrophosphate is about 1-5%; and wherein the amount of pyrophosphate ions present in the tooth gel is about 0.5-2%.

14. The tooth gel of Claim 9, further consisting essentially of: added water in an effective amount up to about

10%; a water-insoluble abrasive in an effective amount up to about 20%; an organic thickener in an effective amount up to about 2%; an inorganic thickener in an effective amount up to about 15%; an effective amount of a surfactant; an effective amount of a flavoring agent; a sweetening agent in an effective amount up to about 5% ; and/or an effective amount of an anti-caries agent.

15. The tooth gel of Claim 14, wherein the water is present in an effective amount about 6%; wherein the humectant is polyethylene glycol present in an amount of about 1-2%; wherein the thickeners are carboxymethyl cellulose present in an amount of about 0.3-0.6% and/or silica present in an amount of about 10-20%; wherein the surfactant is sodium lauryl sulfate and/or sodium lauroyl sarcosinate present in an amount of up to about 1.7%; wherein the flavoring agent is present in an amount of about 0.05-2%; wherein the sweetening agent is sodium saccharin present in an amount of about 0.5-0.8%, xylitol present in an effective amount of up to about 5%, or mannitol present in an effective amount of up to about 5%; and wherein the anti-caries agent is a fluoride source present in an amount sufficient to provide about 50-3500 ppm of fluoride ions and is selected from the group consisting of sodium fluoride and sodium monofluorophosphate.

16. A method for preventing tartar formation on dental enamel which comprises contacting the enamel surface in the mouth with a dentifrice selected from the group consisting of a toothpaste and a tooth gel, which dentifrice consists essentially of sodium bicarbonate, an alkali metal pyrophosphate salt, and an aqueous sorbitol solution, with the amount of pyrophosphate salt dissolved in the toothpaste or the tooth gel being sufficient to provide about 0.5-2% pyrophosphate ions.

17. The method of Claim 16, wherein the sodium bicarbonate is present in an amount of about 10-65% in the toothpaste or about 10-50% in the tooth gel; wherein the pyrophosphate salt is selected from the group consisting of tetrasodium pyrophosphate, disodium dihydrogen pyrophosphate, tetrapotassium pyrophosphate, and mixtures thereof; and wherein the aqueous sorbitol solution is an about 70% solution present in an amount of about 30-70% of the toothpaste or the tooth gel.

18. A method of improving the solubility of an alkali metal pyrophosphate salt in a sodium bicarbonate-containing dentifrice, selected from the group consisting of a toothpaste and a tooth gel, by adding an aqueous solution of sorbitol, as a main liquid vehicle, to the toothpaste or the tooth gel to dissolve about 50% the pyrophosphate salt formed in the toothpaste or the tooth gel in the presence of the sodium bicarbonate.

19. The method of Claim 18, wherein the sodium bicarbonate is present in an amount of about 10-65% in the toothpaste or about 5-50% in the tooth gel; wherein the aqueous solution of sorbitol is a 70% aqueous solution used in an amount sufficient to dissolve at least 50% of the pyrophosphate salt added to the dentifrice; and wherein the pyrophosphate salt is selected from the group consisting of tetrasodium pyrophosphate, disodium dihydrogen pyrophosphate, and tetrapotassium pyrophosphate and mixtures thereof.

20. The method of Claim 19, wherein the amount of dissolved pyrophosphate is about 0.5-5% by weight.