ANTICALCULUS ORAL COMPOSTIONS

Abstract: The disclosure relates to a toothpaste for inhibiting the formation of dental calculus comprising an abrasive agent and an amount of tetrapyrophosphate salt sufficient to provide at least 2.5% P₂O₇⁴⁻, which toothpaste is characterised by having a pH of at least 7.6 which rises by at least 0.45 on dilution of the toothpaste with distilled carbon-dioxide free water in the proportion of 10g of toothpaste to 30ml of water.

Description: This invention relates to anticalculus oral compositions, more particularly anticalculus toothpastes containing a water-soluble pyrophosphate salt. It is well known that the soluble pyrophosphate salts have anticalculus activity. Patents and patent applications that have been published relating to anticalculus toothpastes comprising a soluble pyrophosphate salt include US-A-4 684 518, US-A-4 627 977, US-A-4 590 066, US-A-4 515 772, GB-A-2 182 244, EP-A-295 116, EP-A-251 591, EP-A-249 398, EP-A-236 827 and EP-A-236 290. The disclosures of these publications are included herein by reference. The present invention relates to an anticalculus toothpaste composition based on the use of a water-soluble pyrophosphate and which is particularly efficacious. The anticalculus toothpaste of the invention comprises an abrasive agent and an amount of pyrophosphate salt sufficient to provide at least 2.5% P₂O₇⁴⁻, and is characterised by having a pH, measured directly on the paste, of at least 7.6, preferably at least 8.0, which rises by at least 0.45, preferably at least 0.60, on dilution of the toothpaste with distilled carbon dioxide-free water in the proportion of 10g of toothpaste to 30ml of water. The pH value on dilution is determined in the following way. Toothpaste (10g) is added to a tall form 150ml glass beaker. Distilled carbon dioxide-free water (10ml) is added and by stirring for two minutes using a laboratory stirrer (such as a Heidolf mixer at 1500ppm) the toothpaste is thoroughly dispersed in the water. After one minute a further 10ml of the water is added and the mixture stirred again for two minutes. After 1 minute a final 10ml of the water is added and the mixture stirred for another two minutes. The pH of the toothpaste slurry is measured after one minute. All pH measurements are made at 20°C. This improved composition is based on our discovery that the effectiveness of a toothpaste in inhibiting the formation of dental calculus is enhanced by increased pH. The abrasive agent of the toothpaste is preferably a silica abrasive but may be any of those referred to in any of the publications referred to above. Silica abrasives are particularly compatible with soluble pyrophosphate anticalculus agents. Suitable silica abrasives are well known to those skilled in the art. These include silica xerogels such as Syloid 63 available from Grace, precipitated silicas such as Zeodent 119 from Huber, and bifunctional silicas such as Sident 15 from Degussa. Examples of other abrasives disclosed in the prior published patent specifications referred to above include beta phase calcium pyrophosphate, alumina, insoluble metaphosphate and thermosetting resins. The amount of abrasive will generally be from about 5% to about 50%, especially from 8% to 25%, bv weight of the toothpaste. We have found that some ingredients disclosed in prior art anticalculus compositions containing soluble pyrophosphates tend to give a toothpaste a pH of less than 7.6 and/or limit an increase in pH on dilution of the toothpaste to less than 0.45. Such ingredients include the humectant glycerol, polycarboxylic materials such as the Gantrez resins, and acid buffering components such as mono- and di-sodium phosphates. Therefore sorbitol is the preferred humectant and acidic polycarboxylic materials and acidic buffers are preferably absent. The pyrophosphate employed in the toothpaste of the invention preferably consists of tetrapotassium pyrophosphate or tetrasodium pyrophosphate or a mixture of tetrapotassium pyrophosphate and tetrasodium pyrophosphate. When employing a mixture of tetrapotassium pyrophosphate and tetrasodium pyrophosphate the weight of the tetrapotassium pyrophosphate preferably ranges from about 0.7% to about 4% by weight and the tetrasodium pyrophosphate from about 0.6% to about 7% by weight. The choice of such preferred amounts, while meeting the above condition regarding the minimum amount of pyrophosphate, is particularly advantageous in providing a level of pyrophosphate which gives a high degree of efficacy and yet avoids the use of levels of tetrapotassium pyrophosphate which may give an unsatisfactory salty taste, or levels of tetrasodium pyrophosphate which, due to its lower solubility, can give rise to an unacceptable grittiness. The preferred ratio of tetrapotassium pyrophosphate to tetrasodium pyrophosphate is from about 1.2:1 to 3.7:1 by weight. The desired pH of the composition is preferably achieved through an appropriate choice of the pyrophosphate material or by the addition of an alkaline agent. The acid pyrophosphates are not employed since they tend to give products having a lower pH. The toothpaste of the invention also preferably comprises a fluoride-ion source sufficient to supply from 50ppm to 3500ppm, preferably 500ppm to 2000ppm, of fluoride ions. It is well known that fluoride ions have an anticaries effect and can also inhibit hydrolysis of pyrophosphate by the pyrophosphatase enzyme. The fluoride-ion source is preferably sodium fluoride or sodium monofluorophosphate. The toothpaste of the invention will contain other common ingredients well known to those in the art, including an humectant, a binder or thickening agent, surfactant and flavouring agent. The preferred humectant of toothpastes according to the present invention is sorbitol, which is usually incorporated in the form of an approximately 70% by weight aqueous solution. However, other humectants may be used provided they do not substantially inhibit pH rise on dilution of the toothpaste with distilled carbon dioxide-free water as described above. The amount of the humectant will generally range from about 10% to about 85% by weight of the toothpaste. Preferred toothpastes of the invention are glycerol-free. Numerous binding or thickening agents have been indicated for use in toothpastes, preferred ones being sodium carboxymethylcellulose and xanthan gum. Others include natural gum binders such as gum tragacanth, gum karaya and gum arabic, Irish moss, alginates and carrageenans. Various forms of silica are also used for thickening toothpastes, e.g. fumed silicas, silica aerogels and precipitated silicas. Mixtures of binders or thickeners may be used. The amount of binder or thickener included in a toothpaste is generally between 0.1 and 10% by weight. It is usual to include a surfactant in a toothpaste and again the literature discloses a wide variety of suitable materials. Surfactants which have found wide use in practice are sodium lauryl sulphate, sodium dodecylbenzene sulphonate and sodium laurylsarcosinate. Other anionic surfactants may be used as well as other types such as cationic, amphoteric and non-ionic surfactants. Surfactants are usually present in an amount of from 0.5 to 5% by weight of the toothpaste. Flavours that are usually used in toothpastes are those based on oils of spearmint and peppermint. Examples of other flavouring materials used are menthol, clove, wintergreen, eucalyptus and aniseed. An amount of from 0.1% to 5% by weight of the toothpaste is a suitable amount of flavour to incorporate in a toothpaste. The toothpaste of the invention may include a wide variety of optional ingredients. These include an anti-plaque agent such as an antimicrobial compound for example chlorhexidine or 2,4,4′ -trichloro-2 ′-hydroxydiphenyl ether, or a copper salt (see EP-A-0 038 867); another anti-tartar ingredient such as zinc citrate or other zinc salt (see US-A-4 100 269); further thickening or structuring agents such as polyethylene glycol 1500; a sweetening agent such as saccharin; an opacifying agent, such as titanum dioxide; a preservative, such as formalin; or a colouring agent. The invention also relates to a method of preparing a toothpaste composition according to the invention which comprises mixing together the components in a conventional manner. For a fuller discussion of the formulation of toothpastes reference is made to Harry's Cosmeticology, Seventh Edition, 1982, Edited by J B Wilkinson and R J Moore, pages 609 to 617. The following Examples illustrate the invention. Percentages are by weight. Example 1 An anticalculus toothpaste of the following composition was prepared. The two pyrophosphate salts were present in a total amount corresponding to 3.3% P₂O₇⁴⁻. The toothpaste had a pH of 8.08. On dilution of 10g of the toothpaste with 30ml of distilled carbon dioxide-free water in the manner described above the pH rose to 8.72. The toothpaste retained a high level of available fluoride and pyrophosphate when stored for 3 months at 0°C, 20°C and 37°C. Example 2 An anticalculus toothpaste of the following composition was prepared. The two pyrophosphate salts were present in a total amount corresponding to 3.3% P₂O₇⁴⁻. The toothpaste had a pH of 8.04. On dilution of 10g of the toothpaste with 30ml of distilled carbon dioxide-free water in the manner described above the pH rose to 8.54. The toothpaste retained a high level of available fluoride and pyrophosphate when stored for 3 months at 0°C, 20°C and 37°C. Example 3 An anticalculus toothpaste of the following composition was prepared. The two pyrophosphate salts were present in a total amount corresponding to 3.3% P₂O₇⁴⁻. The toothpaste had a pH of 8.10. On dilution of 10g of the toothpaste with 30ml of distilled carbon dioxide-free water in the manner described above the pH rose to 8.73. The toothpaste retained a high level of avalaible fluoride, pyrophosphate and zinc ions when stored for 3 months at 0°C, 20°C and 37°C. Example 4 An anticalculus toothpaste of the following composition was prepared. The two pyrophosphate salts were present in a total amount corresponding to 3.3% P₂O₇⁴⁻. The toothpaste had a pH of 7.86. On dilution of 10g of the toothpaste with 30ml of distilled carbon dioxide free water in the manner described above the pH rose to 8.41. The toothpaste retained a high level of available fluoride, pyrophosphate and zinc ions when stored for 3 months at 0°C, 20°C and 37°C.

Claims: 1. A toothpaste for inhibiting the formation of dental calculus comprising an abrasive agent and an amount of tetrapyrophosphate salt sufficient to provide at least 2.5% P₂O₇⁴⁻,the toothpaste being characterised by having a pH of at least 7.6 which rises by at least 0.45 on dilution of the toothpaste with distilled carbon-dioxide free water in the proportion of 10g of toothpaste to 30ml of water. 2. A toothpaste as claimed in claim 1 which has a pH of at least 8.0. 3. A toothpaste as claimed in claim 1 or claim 2 wherein the pH of the toothpaste on dilution in the manner specified in claim 1 rises by at least 0.60. 4. A toothpaste as claimed in any of the preceding claims wherein the abrasive agent is silica. 5. A toothpaste as claimed in any of the preceding claims wherein the abrasive agent is present in an amount of 5 to 50% by weight. 6. A toothpaste as claimed in any of the preceding claims wherein the tetrapyrophosphate salt consists of a mixture of tetrapotassium pyrophosphate and tetrasodium pyrophosphate. 7. A toothpaste as claimed in claim 6 wherein the weight ratio of tetrapotassium pyrophosphate to tetrasodium pyrophosphate is 1.2:1 to 3.7:1. 8. A toothpaste as claimed in any of the preceding claims also comprising a fluoride-ion source sufficient to supply from 50ppm to 350ppm of fluoride ions. 9. A toothpaste as claimed in claim 8 wherein the fluoride-ion source is sodium fluoride. 10. A toothpaste as claimed in any of the preceding claims wherein the toothpaste is glycerol-free. 11. A method of preparing a composition as claimed in any one of claims 1 to 9 which comprises mixing together the components specified in the said claims.

Inventors: CARTER, PETER, CUMMINS, DIANE, JONES, DAVID ALAN KENNETH, LOWRY, MICHAEL RICHARD
Applicants: UNILEVER N.V., UNILEVER PLC
Application year: 1989
Main classification: A61K7
IPC codes: A61K8, A61P1, A61Q11, C01B25