GB1592660A - Dentrifrices - Google Patents

Description

(54) DENTIFRICES (71) We, COLGATE-PALMOLIVE COMPANY, a Corporation organised under the laws of the State of Delaware, United States of America, of 300 Park Avenue, New York, New York 10022, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to toothpaste dentifrices.

It has been difficult heretofore to provide dentifrices for use in the daily brushing and cleaning of teeth which provide a desirable balance of cleaning and polishing actions. This has been largely due to the difficulty in selecting suitable abrasives which will afford maximum removal of difficult stains and debris without damaging the enamel surfaces of the teeth.

The function of an abrasive substance in dentifrices is to remove various deposits, including pellicle film from the surface of the teeth. Pellicle film is a tightly adherent film which often contains brown or yellow pigments and imparts an unsightly appearance to the teeth. An advantageous abrasive material for incorporation into dentifrices should maximize film removal without causing undue abrasion of the hard tooth tissues. The typical soft abrasives used in dental compositions, such as dicalcium phosphate and calcium pyrophosphate, although not unduly abrasive to tooth tissue, are not as effective as hard abrasives in removing these undesirable deposits from the teeth. However, hard abrasives in dentifrices can present serious problems because their outstanding abrasive characteristics are likely to cause undue abrasion to the oral hard tissues (enamel, dentin and cementum).

It has now been found that the addition of a small amount, namely from 0.1% to 5%, preferably from 1% to 5%, by weight of certain calcium, magnesium or sodium salts to a dental abrasive system comprising certain proportions of a siliceous abrasive and the hard abrasive calcined alumina, with the pH of the dentifrice maintained above 7, effects a substantial reduction in the radioactive enamel abrasion value (REA) thereof. Therefore toothpastes can now be made containing a hard abrasive (heretofore undesirable because of the tendency to abrade tooth enamel) to give superior polishing and cleaning without encountering the problem of excess enamel abrasion. In addition to reduced REA values, other beneficial changes have been observed on highly polished human tooth enamel surfaces brushed with these dentifrices; namely, less grooving or scratching was seen under the microscope.

Thus, according to the present invention, a toothpaste having a pH maintained above 7 comprises an alkali metal or alkaline earth metal aluminosilicate as a siliceous abrasive in an amount of at least 10% and up to 70% by weight and flat flakes or crystals of alpha alumina as a calcined alumina abrasive having a particle size in the range from 1-15, preferably 1-10 microns in diameter in an amount of at least 7.5% and up to 20% by weight (such amount of the calcined alumina abrasive being sufficient to give the toothpaste, in the absence of the undermentioned salt, an REA of above 450) and a calcium, magnesium or sodium salt selected from the carbonates, bicarbonates, chlorides, phosphates, silicates and nitrates to an amount in the range from 0.1% to 5% by weight to reduce the REA of the toothpaste.

The actual pH of the toothpaste above 7, and the amount of the said salt within the said range, are preferably both chosen so that the REA of the toothpaste is reduced to below 450. Most commercial toothpastes presently on the market have an REA not exceeding 300, some as low as 50.

It has been found that the enamel abrasion as evidenced by REA of a dentifrice containing a siliceous abrasive and a calcined alumina abrasive is reduced by increasing the pH of the dentifrice as shown in TABLE 1, wherein the pH of a composition comprising 24% siliceous abrasive and 10% alumina abrasive was modified by the addition of HCI and NaOH. All percentages herein are by weight unless otherwise specified.

TABLE 1 pH additive REA RDA* 4 HCl 4855 714 5 HCI 2563 432 6 HCI 1200 338 6.6 unadjusted 891 353 7 NaOH 792 342 8 NaOH 656 348 9 NaOH 488 349 10 NaOH 434 346 * Radioactive Dentin Abrasion Value.

This table shows that the enamel abrasivity is sensitive to pH in the 5-10 range with the abrasivity decreasing as the pH increases, whereas the dentin abrasivity remains substantially the same within the pH range 6-10.

The effectiveness of reducing the enamel abrasivity by modifying the pH of a dentifrice containing a silicious abrasive and calcined alumina with and without 5% Cacti2 is shown in TABLE II wherein the abrasive was constituted by 10% alumina and 24% silicious abrasive.

TABLE II pH REA RDA none 5% CaCl2 none 5% Cacti2 5 1374 723 458 392 7 858 461 416 411 9 663 436 442 424 This table also shows the combined salt and pH effects on enamel abrasivity. The dentin abrasivity remains substantially unaffected.

TABLE III shows the combined effects of pH and various salt additives on the enamel abrasivity of a dentifrice comprising 24% hydrated silicious abrasive and 10% calcined alumina, using 5% salt. The pH's of the dentifrices were unadjusted.

TABLE III Salt REA RDA pH Salt Test 1 Test 2 Test 3 Test 1 Test 2 None (Control) 859 783 704 323 324 6.2 CaCO3 284 377 7.9 CaHPO4 2H2O 316 , 291 6.9 CaHPO4 anhy. 574 383 6.6 CaSiO3 234 - - 7.8 Cacti2 406 271 5.9 Ca(NO3)2 .589 267 5.7 Mg-SiO4 288 - - 8.1 MgCO3.Mg(OH)2 282 340 8.9 MgCl2 648 325 5.7 NaHCO3 342 309 8.3 NaOH to adjust pH 431 - - 8.2 Accordingly, it is desirable to adjust the pH of the dentifrice so as to obtain a further reduction in the enamel abrasivity thereof. This may be effected by the addition of suitable alkaline buffering agents or by the very presence of the calcium, magnesium or sodium salts heretofore referred to. pH adjustment can be obtained by the addition of appropriate amounts of, for example sodium hydroxide, sodium hydrogen phosphate, trisodium phosphate and sodium bicarbonate. Particlarly useful buffer systems include sodium carbonate-sodium bicarbonate; tetrasodium pyrophosphate; and a phosphate buffer system comprising Na2HPO4 and Na3PO4, wherem there Is selected the appropriate ratio of compounds to give the desired pH.

Of the salts found effective in reducing the REA, in general the calcium salts are more effective than the magnesium salts which are better than the sodium salts. Some of the anions are more effective than others, as shown in TABLE IV wherein dentifrices comprising 24% hydrated silicious abrasive and 10% calcined alumina and 5% sodium salt at pH 8 are evaluated.

TABLE IV Salt REA RDA Control 520 340 NaNO3 490 343 NaCl 453 333 NaHCO3 436 336 Na2HPO4 395 339 The magnesium silicate compound found particularly useful has a MgO : SiO2 ratio of 1:2.5 (indicated herein as Mg-SiO4).

Even amounts less than 1% of the additive salt have been found to reduce the abrasivity.

For example, to a composition comprising 20% siliceous abrasive and 10% calcined alumina, was added calcium chloride in mounts ranging from o.1% to 5.0% with the following results in enamel abrasion: TABLE V Enamel Abrasion REA Value Control (no additive) 763 0.1 CaCl2 600 0.3 CaCl2 510 0.5 Cacti2 499 1.0 CaCI2 475 5.0 Cacti2 394 Amounts in excess of 5% salt additive have been found to have no significant effect in decreasing the abrasivity of the composition below that attained by 5% of salt, as evidenced by the following results of tests wherein sodium bicarbonate was added to a composition comprising 10% calcined alumina and hydrated silicious abrasive.

TABLE VI % hydrated silicious abrasive % NaHCO3 REA pH (Control) 24 0 917 7.0 24 15 466 8.2 20 15 469 8.6 24 15 465 8.3 24 5 443 8.8 24 2 434 8.4 These results show that the additive concentration beyond 5% does not beneficially effect enamel abrasion to a significant extent.

Flaked calcined alumina is the preferred hard abrasive. This is defined as flat flakes of alpha-alumina crystals, of disc-like or plate-like configuration, the flakes having a mean (by weight) particle diameter of less than 7 microns (e.g. from 2 to 7 microns). Viewed under a scanning electron microscope, the flakes have sharp edges indicating that they have been fractured perpendicular to their flat parallel faces. Generally, the thickness of the flakes is less than 1/3 (e.g. about 1/3 to 1/10) of their diameter, and they are in the size range from 1/2 micron (or less) to 2 microns (e.g. about 1 micron). The flat alpha-alumina crystals and a process for preparing them are described in U.S. patent specification 3,121,623.

A calcined alumina product available commercially in U.S.A. as RC-152 DBM is very dense and highly stable. It has a mean particle size between about 1 and about 2 microns, typically about 1.6 microns. Its typical particle size distribution is as follows: Particle Diameter (microns) Percent of Particles Finer than corresponding diameter 10 about 100 5 about 95 3 about 85 2 about 75 1 about 25 0.5 about 5 Under an electron microscope the larger particles appear flat with sharp sides and the smaller particles appear as irregularly rounded in circular and oval shapes.

Crystalline alumina RC-152 DBM is ground from a coarser alumina commercially available in U.S.A. as RC-152. RC-152 has a crystal particle size such that 98% of the particles pass through a 200 mesh screen and 25% pass through a 100 mesh screen. Screen sizes herein are U.S. Sieve series.

The crystalline alpha lumina has been observed to be chemically % by weight ppm Al203 99.7 Na2O 0.04 SiO2 0.065 Fe2O3 0.024 TiO2 0.0016 MnO 0.0012 CaO 0.045 Cr203 0.00036 B203 0.001 F2 200 alpha phase alumina 90 The proportion of the calcined alumina hard abrasive in the dentifrice may be, for instance, above 7.5% and in the range from 7.5% to 20%, preferably 7.5% to 15%.

In addition to the calcined alumina abrasive, a sufficient amount of silicous abrasive as an additional dental abrasive is included. The silicious abrasive is soft by comparison, and has been conventionally employed in toothpastes. A silicious abrasive which is particularly useful is an amorphous alkali metal or alkaline earth metal aluminosilicate having a refractive index in the range from 1.44 to 1.47, and containing at least 70% silicious abrasive, up to 10% alumina, up to 20% moisture and up to 10% sodium oxide, the moisture content preferably being from 10% to 20%, measured by loss at 10000C and the typical content of sodium oxide being from 5% to 10%. When little alumina is present in the aluminosilicate, e.g. about 1% or less, the material can be a silica with combined alumina.

The silicious dental abrasive may have a particle size in the range from 2 to 40 microns and may also be present in the form of relatively large agglomerates (of the individual particles) of such size as to be visible to the naked eye by easily reduced to the fine impalpable particle size upon being subjected to tooth-brushing in the mouth. Such agglomerates may be agglomerated with or without a binding agent which may be water-soluble or water-insoluble.

For most purposes it is preferable that the silicious dental abrasive has a particle size less than 20 microns, to avoid any gritty feel.

The proportion of this additional silicious dental abrasive in the dentifrice is in the range from 10% to 70%, preferably from 10% to 50%, and is preferably such that if the calcined alumina abrasive were omitted from the detifrice, the RDA (radioactive dentin abrasion) would be in the range from 100 to 600, preferably from 100 to 450.

To make toothpastes or dental creams, the hard abrasive such as the flat flakes of alpha-alumina and the silicious abrasive are dispersed in a dental vehicle which preferably contains a liquid which is water and/or a humectant such as glycerine, sorbitol, xylitol, propylene glycol or polyethylene glycol 400, including suitable mixtures thereof. It is usually advantageous to use a mixture of water and one or two humectants. Polyethylene glycols of higher molecular weight, e.g. polyethylene glycol 600 may also be present. The total liquid content is generally well over 20% by weight of the vehicle (sorbitol, generally present in admixture with water, is considered as a liquid for this purpose). The preferred humectants are glycerine and sorbitol. Typically, the vehicle contains 0 to 80% of glycerine, up to 80% of sorbitol and from 5% to 80% of water.

The calcium, magnesium or sodium salt selected from the carbonates, bicarbonates, chlorides, phosphates, silicates and nitrates may be added directly to the dental vehicle containing the abrasives, or the abrasives may be pretreated with an aqueous solution of the salt and the pretreated abrasives added to a suitable dental vehicle. Insoluble salts are preferably added. directly to the vehicle along with the abrasives. Soluble salts can be dissolved in an aqueous medium and stirred with the abrasives (both hard and soft) for about five minutes. The solids are then isolated and washed with water. The salt-treated abrasive is then incorporated into a dental vehicle.

The vehicle usually also contains a thickening or gelling agent, such as a natural or synthetic gum or gum-like material, e.g. Irish Moss, gum tragacanth, alkali metal (e.g. Li, K or Na) carboxymethyl cellulose and hydroxymethyl carboxyethyl cellulose, polyvinyl pyrrolidone, starch, xylitol, water-soluble hydrophilic colloidal carboxyvinyl polymers such as those sold under the trade mark CARBOPOL as "Carbopol 934" and "Carbopol 940", hydroxyethyl cellulose, Indian gum, acacia gums, agar agar, locust bean. gum, synthetic inorganic complex silicate clavs sold under trade mark LAPONITE as "Laponite CP" and "Laponite SP" by Laporte Industries,,Ltd., and pectin or inorganic thickeners such as colloidal silica, e.g. synthetic finely divided silicas including those sold under the trade marks CAB-O-SIL, SYLOID, ZEOSYL and AEROSIL as "Cab-O-Sil M5", "Syloid 244", "Syloid 266", "Zeosyl 200" and "Aerosil D200". The solid portion of the vehicle is typically present in an amount up to 10% by weight of the toothpaste and preferably in the range from 0.5% to 8%.

Fine particles of thermoplastic resin may also be present, such as particles of solid polymer having a molecular weight above 1000 (preferably above 10,000, e.g. about 10,000 to 100,000 or more) and a mean diameter less than 50 microns (preferably.in the range from 0.5 to 50 microns, e.g. from 10 to 30 microns). The polymer particles may be prepared directly by emulsion or suspension polymerization or by grinding the polymer in bulk, and may be present in amount of up to 60% or even more of the dentifrices, e.g. in the range from 20% to 60%, such as from 30% to 50% in a toothpaste. Examples of thermoplastic resins are polymerized ethylenically unsaturated compounds, such as polyolefines (e.g.

polyethylene or polypropylene) or vinyl or vinylidene resins, such as polyvinyl chloride, polystyrene, vinyl chloride-vinyl acetate copolymers, styrene-butadiene copolymers, polyvinylidene chloride; polyamides such as Nylon (e.g. Nylon 6); and cellulosics such as cellulose acetate.

The toothpaste may also contain surface-active agents, e.g. to achieve increased prophylactic action, assist in achieving thorough and complete dispersion of the compositions throughout the oral cavity and render the compositions more cosmetically acceptable. The organic surface-active material may be anionic, nonionic, ampholytic or cationic in nature, and it is preferred to employ as the surface-active agent a detersive material which imparts to the composition detersive and foaming properties. Suitable types of such detergents are water-soluble salts of fatty acid monoglyceride monosulphates such as sodium salts of monosulphated monoglycerides hydrogenated coconut oil fatty acids, alkyl sulphates such as sodium lauryl sulphate, alkyl aryl sulphonates such as sodium dodecyl benzene sulphonate, alkyl sulphoacetates, fatty acid esters of 1, 2 hydroxy propane sulphonates, and substantially saturated higher aliphatic acyl amides of lower aliphatic amino carboxylic acid compounds, such as those having 12 to 16 carbons in the fatty acid alkyl or acyl radicals. Examples of the last-mentioned amides are N-lauroyl sarcosine, and the sodium, potassium, and ethanolamine salts of N-lauroyl, N-myristoyl or N-palmitoyl sarcosinates, which should be substantially free from soap or similar high fatty acid material which tends substantially to reduce the effect of these compounds. The use of these sarcosinate compounds in dentifrices of the present invention is particularly advantageous since these materials exhibit a prolonged and marked effect in the inhibition of acid in the oral cavity due to carbohydrates, in addition to exerting some reduction in the solubility of tooth enamel in acid solutions.

Other suitable surface-active materials include non-ionic agents such as condensates of one mole of sorbitan monostearate with approximately 60 moles of ethylene oxide, and condensates of ethylene oxide with propylene oxide condensates of propylene glycol (as sold under the trade mark PLURONIC). Cationic surface active germicides and anti-bacterial compounds such as di-isobutylphenoxyethyldimethyl benzyl ammonium chloride, benzyl dimethyl stearyl ammonium chloride, tertiary amines having one fatty alkyl group (of from 12 to 18 carbon atoms) and two (poly) oxyethylene groups attached to the nitrogen (typically containing a total of from 2 to 50 ethenoxy groups per molecule) and salts thereof with acids, and compounds of the structure:

where R is a fatty alkyl group containing from 12 to 18 carbon atoms, and x, y and z total 3 or higher, as well as salts thereof with mineral organic acids, may also be used. It is preferred that the total amount of surface-active material be from 0.05% to 5%, preferably from 1% to 3%, of the dentifrice.

Various other materials may be incorporated in the dentifrices of this invention.

Examples are colouring or whitening agents such as titanium dioxide, preservatives, silicones, chlorophyll compounds, and ammoniated materials such as urea, diammoniumphosphate and mixtures thereof. Each of these adjuvants may be typically incorporated in the dentifrices in amounts up to 5%.

The dentifrices may also contain antibacterial agents, e.g. in amounts from 0.01% to 5%.

Typical examples of such agents are guanidines, biguanides and amines such as: N1-(4-chlorobenzyl)-N5-2 ,4-(dichlorobenzyl) biguanide; p-chlorophenyl biguanide; 4-chlorobenzhydryl biguanide; 4-chlorobenzhydrylguanylurea; N1-3-lauroxypropyl-N5-p-chlorobenzylbiguanide; 1 ,6-di-p-chlorophenylbiguanidohexane; 1-(lauryldimethylammonium)-8-(p-chlorobenzyldimethyl-ammonium)octane dichloride; 5,6-dichloro-2-guanidinobenzimidazole; N1-p-chlorophenyl-N5-laurylbi uanide; 5-amino-1, 3-bis (2-ethylhexyl)-5-methylhexahydropyrimidine; and their non-toxic acid addition salts.

Benzethonium chloride and cetyl pyridinium chloride may also be used.

Suitable flavouring or sweetening sialagogues may be employed in formulating a flavour for the dentifrices. Examples of suitable flavouring constituents include the flavouring oils, e.g. oils of spearmint, peppermint, wintergreen, sassafras, clove, sage, eucalyptus, majoram, cinnamon, lemon and orange, as well as methyl salicylate. Suitable sweetening agents include sucrose, lactose, maltose, sorbitol, xylitol and saccharin. Suitably, the flavour and sweetening agent may together constitute from 0.01% to 5% or more of the dentifrice.

The dentifrice may be prepared by suitably mixing the ingredients. For instance, in making a toothpaste, a gelling agent such as sodium carboxymethyl cellulose or "Carbopol 934" and a preservative such as sodium benzoate, if employed, are dispersed with a humectant such as glycerine. Water may be present. Additional humectant and water, e.g.

as an aqueous 70% sorbitol solution, may then be mixed with the dispersion and a paste, gel or cream is formed. The abrasives, surface active agent and flavour are then added. The toothpaste is then thoroughly deaerated (e.g. in vacuo) and tubed.

Preferably the amount of water-insoluble flavouring oil is above 0;5% and below 2%.

Strongly flavoured toothpastes contain above 1% of such flavouring oil, e.g. from 1.2% to 1.5%.

The dentifrices have been found useful as prophylactic dental pastes applied professionally, for use on dentures and for daily use on the teeth.

The following Examples illustrate the invention.

Example 1 A toothpaste is prepared according to the following formulation: glycerine 25%; sodium carboxymethyl cellulose 1.4%; sodium benzoate 0.50%; sodium saccharin 0.20%; sodium alumino-silicate (silicious abrasive) 24.0%; titanium dioxide 0.4%; calcined alumina RC-152DBM 10.0%; sodium lauryl sulphate 1.5%; flavouring oil 1.00%; deionized water to 100%. This toothpaste has a pH of 7.1 and an REA value of 751.

In changing the pH of this dentifrice by the addition of appropriate acids or bases the following results are obtained; TABLE VII pH REA Control 7.1 751 4.5 2975 6.0 1141 8.1 603 9.3 506 Thus, it is apparent that the pH of the dentifrice has a considerable effect on its abrasivity, decreased abrasivity being obtained at alkaline pH.

REA represents the radioactive enamel abrasion value obtained by a technique described in the literature. A method for determining enamel abrasion values is as follows: Molar teeth are exposed to neutron radiation whereby a predetermined portion of phosphate content is converted to p32. Each enamel specimen is mounted in a self-curing polymer such as methyl methacrylate. The specimens are then placed in apparatus consisting of a means of stabilizing the enamel specimen, a tube to contain the diluted toothpaste and a toothbrush head under a tension of 150 grams. The enamel specimen is then subjected to 4500 reciprocal brush strokes over the cusped surface. A 2.0 ml aliquot is placed in a planchet, dried at room temperature, and the radioactivity (p32) determined using a conventional Geiger-Meuller detector. By comparing the radioactivity of the slurries of the experimental pastes to that obtained on each enamel specimen with a reference, calcium pyrophosphate powder which is arbitrarily assigned an enamel abrasion score of 500, the relative abrasiveness of the experimental pastes may be determined.

The RDA values may be determined using the dentin portions separated from human cuspids and subjecting the dentin to 1000 reciprocal brush strokes. This radioactive technique is more fully described in the literature; Stookey, C.K. and Muhler, J.C., J.

Dental Research 47 524-538 (1968).

Similarly to the REA values, the RDA values must not be high, in order to prevent or minimize oral hard tissue damage.

Examples 2, 3, and 4 Example 1 is repeated except that the silicious abrasive content is reduced to 20% and calcium carbonate is added in amounts of 1%, 3% and 5% while maintaining a pH of 8, with the following results: %CaCo3 pH REA RDA Example 2 1.0 8 437 359 Example 3 3.0 8 395 342 Example 4 5.0 8 375 371 The above results indicate that the addition of calcium carbonate in an amount as low as 1% and the maintenance of a pH of 8 effects a considerable reduction in the REA value, namely, from 751 of the control to 437. Increasing the amounts of calcium carbonate from 1% to 5% effects a greater reduction in enamel abrasivity.

Example 5 24% sodium alumino-silicate containing 89% to 91% silica, 0.8% to 1.2% alumina, 0.3% to 0.9% sodium oxide and about 10% water is substituted for the silicious abrasive in Example 4; and 8% of a calcined alumina sold under the name "Microgrit" (Microgrit is a Trade Mark) is substituted for the 10% calcined alumina in Example 4. The alpha alumina flakes of the "Microgrit" alumina have a mean particle diameter of about 4 microns, all the particles thereof having diameters less than 10 microns, from 85% to 95% have diameters less than 6.0 microns and from 30% to 35% have particle diameters less than 3.5 microns.

This toothpaste has a pH of 7.8, an REA value of 294 and an RDA value of 461.

Example 6 Example 5 is repeated except that the silicious abrasive content is reduced to 20%. The REA value of the dentifrice is 285 and the RDA value is 420. This toothpaste without the 5% CaCO3 has an REA value of 848 and RDA value of 367.

Example 7 Example 1 is repeated except that 5% NaHCO3 is added to the dentifrice. This toothpaste has a pH of 8.4, an REA value of 373, and an RDA value of 409.

Example 8 Example 1 is repeated except that the silicious abrasive content is reduced to 20%, the calcined alumina of Example 5 sold as "Microgrit" is substituted for the RC-152 brand, and 5% Mg-SiO4 is added. This toothpaste has a pH of 8.5, an REA value of 377 and an RDA value of 452. The toothpaste without the Mg-SiO4 has an REA value of 665 and a RDA value of 394.

Example 9 Example 8 is repeated except that the RC-152 brand of calcined alumina is substituted for the "Microgrit". This toothpaste has an REA value of 318 and an RDA value of 464.

Example 10 Example 8 is repeated except that 5% CaCO3 is substituted for the 5% Mg-SiO4. This toothpaste has an REA value of 349 and an RDA value of 519.

Example 11 Example 8 is repeated except that 5% NaHCO3 is substituted for the 5% Mg-SiO4.

REA = 311, RDA = 490.

Examples 12a and 12b a) - Example 10 is repeated except that the RC-152 calcined alumina is substituted for the "Microgrit" alumina.

REA = 307, RDA = 498, b) - A calcined alumina having a mean particle diameter of 5 microns (sold as "Diamex" DIAMEX is a Trade Mark) is substituted for the "Microgrit". The composition has a pH of 8, REA value of 451 and RDA value of 443.

Example 13 Example 1 is repeated except that "Microgrit" alumina is substituted for the RC-152 brand and sodium hydroxide is added until a pH of 9.6 is obtained.

REA = 367.

Examples 14, 15, 16 Example 1 is repeated except that the silicious content is reduced to 20% and calcium chloride is added in amounts of 1%, 3% and 5% and the pH is maintained at 8. The following results are obtained: % Cacti2 pH REA RDA Example 14 5.0 8 319 288 Example 15 3.0 8 349 294 Example 16 1.0 8 391 303 The aforementioned results show the reduction in abrasivity effected by the addition of the calcium chloride, with the degree of abrasivity decreasing as the amount of calcium chloride increases from 1 to 5% (control without the calcium chloride has an REA of 751).

The drop in REA is greater than that caused by merely raising the pH (REA of 603 at a pH 8 as shown in Example 1). By comparison with insoluble CaCO3, the soluble Cacti2 effects a greater REA reduction using the same concentration of salt.

Examples 17 and 18 Example 1 is repeated except that 1% and 3% Mg-SiO4 is added. Results: % Mg-SiO4 REA Example 17 1.0 588 Example 18 3.0 526 Although the REA is not reduced to the same extent as with the calcium salts, a significant reduction in abrasion is effected, the REA of the control being 751.

Example 19 Example 10 is repeated except that the silicious abrasive content is increased to 24%, REA value of 312, and an RDA value of 356. Without the 5% CaCO3, the REA value of 723 and the RDA value of 430 is obtained. The pH of the resultant composition is 8.0.

Example 20 Example 7 is repeated except that 5% CaCO3 is substituted for the 5% NaHCO3.

REA = 375, RDA = 353.

Example 21 Example 11 is repeated except that the RC-152 calcined alumina is used. The resultant toothpaste has a pH of 8.9 and an REA value of 367.

Example 22 20% of the sodium alumino-silicate of Example 5 is admixed with 10% "Microgrit" alumina and 5% calcium carbonate. The resultant dentifrice has a pH of 8, an REA value of 367 and an RDA value of 442. The composition without the calcium carbonate has a pH of 6.7, an REA value of 513, and an RDA value of 369.

It is also within the scope of the invention to use other calcined aluminas in admixture with the silicious abrasive. An example of another calcined alumina is a pulverised alpha-alumina of irregular shape and having a mean particle size of about 3 to about 4 microns (all the particles being less than 7 microns in their largest dimension).

Suitable alkaline agents and alkaline buffering agents may be added to modify further the above Example, inclusive of sodium hydroxide, sodium hydrogen phosphate, trisodium phosphate, sodum carbonate-sodium bicarbonate tetrasodium pyrophosphate and Na2HPO4-Na3PO4.

The particle diameters given in the Examples are determined by conventional methods.

Thus, the standard liquid sedimentation technique may be used. The calculation of particle diameter from the sedimentation data being made (as is conventional) on the basis of Stokes' Law disregarding the particular shape of the particles.

The term "toothpaste" as used herein embraces dental creams, including dental creams of pourable consistency.

WHAT WE CLAIM IS: 1. A toothpaste having a pH maintained above 7, comprising an alkali metal or alkaline earth metal aluminosilicate as a siliceous abrasive in an amount of at least 10% and up to 70% by weight, and flat flakes or crystals of alpha alumina as a calcined alumina abrasive having a particle size in the range from 1 to 15 microns in diameter in an amount of at least 7.5% and up to 20% by weight, and a calcium, magnesium or sodium salt selected from the carbonates, bicarbonates, chlorides, phosphates, silicates and nitrates in an amount of from 0.1% to 5% by weight to reduce the radioactive enamel abrasion value of the toothpaste.

2. A toothpaste as claimed in Claim 1, the pH of which is maintained above 7 by the inclusion therein of an additional alkaline agent.

3. A toothpaste as claimed in Claim 2 in which the additional alkaline agent is an alkaline buffering agent.

4. A toothpaste as claimed in any of the preceding claims in which the siliceous abrasive is an amorphous alumino-silicate having a mean particle size in the range from 2 to 40 microns.

5. A toothpaste as claimed in any of the preceding claims in which the siliceous abrasive is sodium aluminosilicate containing by weight, at least 70% silica, up to 10% alumina, from 10% to 20% water and up to 10% sodium hydroxide.

6. A toothpaste as claimed in any of the preceding claims in which the calcium, magnesium or sodium salt constitutes at least 1% by weight thereof.

7. A toothpaste as claimed in Claim 1 and substantially as described in any of the Examples 2 to 22.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (7)

**WARNING** start of CLMS field may overlap end of DESC **. The particle diameters given in the Examples are determined by conventional methods. Thus, the standard liquid sedimentation technique may be used. The calculation of particle diameter from the sedimentation data being made (as is conventional) on the basis of Stokes' Law disregarding the particular shape of the particles. The term "toothpaste" as used herein embraces dental creams, including dental creams of pourable consistency. WHAT WE CLAIM IS:

1. A toothpaste having a pH maintained above 7, comprising an alkali metal or alkaline earth metal aluminosilicate as a siliceous abrasive in an amount of at least 10% and up to 70% by weight, and flat flakes or crystals of alpha alumina as a calcined alumina abrasive having a particle size in the range from 1 to 15 microns in diameter in an amount of at least 7.5% and up to 20% by weight, and a calcium, magnesium or sodium salt selected from the carbonates, bicarbonates, chlorides, phosphates, silicates and nitrates in an amount of from 0.1% to 5% by weight to reduce the radioactive enamel abrasion value of the toothpaste.

2. A toothpaste as claimed in Claim 1, the pH of which is maintained above 7 by the inclusion therein of an additional alkaline agent.

3. A toothpaste as claimed in Claim 2 in which the additional alkaline agent is an alkaline buffering agent.

4. A toothpaste as claimed in any of the preceding claims in which the siliceous abrasive is an amorphous alumino-silicate having a mean particle size in the range from 2 to 40 microns.

5. A toothpaste as claimed in any of the preceding claims in which the siliceous abrasive is sodium aluminosilicate containing by weight, at least 70% silica, up to 10% alumina, from 10% to 20% water and up to 10% sodium hydroxide.

6. A toothpaste as claimed in any of the preceding claims in which the calcium, magnesium or sodium salt constitutes at least 1% by weight thereof.

7. A toothpaste as claimed in Claim 1 and substantially as described in any of the Examples 2 to 22.