Dentifrice comprising spherical silica and perlite particles

Abstract

The invention relates to a dentifrice composition with superior cleaning properties. The properties derive from a novel abrasive system.

Description

[0001] DENTIFRICE COMPRISING SPHERICAL SILICA AND PERLITE PARTICLES

[0002] Field of Invention

[0003] The invention relates to the field of dentifrice compositions. In particular to improving the cleaning power of dentifrice compositions.

[0004] Background to the invention

[0005] Insoluble ingredients known generally as abrasives are added to dentifrices to help with the actual removal of stains, plaque, and food particles. These components give the toothpaste the grit required to lift stubborn materials from the tooth surface.

[0006] The two abrasives that are most frequently used in toothpastes are silica and calcium carbonate.

[0007] The level of abrasion (and therefore the amount of abrasive added) of the dentifrice is always a careful balancing act. A high level of abrasion will clean the tooth surface effectively, but also risks causing excessive damage to the tooth enamel itself.

[0008] The designers of dentifrice are always looking to optimise this balance between improving cleaning power and tooth enamel protection.

[0009] Statements of the invention

[0010] In its broadest aspect the invention comprises a dentifrice composition comprising spherical silica particles and perlite particles and wherein the spherical silica particles comprise between about 0.1 % and about 4.0 % by weight, and perlite particles comprise between about 0.1 % by weight and about 5.0 % by weight; and further wherein the spherical silica particles comprise the following properties: a. a pore volume from about 0.03 mL / g to less than about 0.1 mL / g b. a mean particle size from about 1 pm to about 10 pm; c. a BET surface area of about 50 m2 / g or less; d. an oil absorption capacity of about 20 to about 50 mL / 100 g; and e. a water content of less than about 0.2 % by weight; and wherein the perlite particles have a d50 particle size of less than 50 pm.

[0011] In a further aspect the spherical silica particles comprise between about 0.2 % and 1.5 % by weight and the perlite particles between about 0.25 % by weight and about 2.0 % by weight of the dentifrice composition. In a further aspect the spherical silica particles comprise between about 0.25 % and about 1.0 % by weight and the perlite particles comprises between about 0.75 % and about 1.5 % by weight.

[0012] In a further aspect the composition further comprises at least one surfactant, and at least one humectant.

[0013] In a further aspect the composition further comprises a source of fluoride.

[0014] In a further aspect the composition comprises a further abrasive.

[0015] In a further aspect the composition comprises an anti-sensitivity agent.

[0016] In a further aspect the anti-sensitivity agent comprises one or more of, stannous fluoride, potassium nitrate or a bioglass.

[0017] In a further aspect composition further comprises: a. At least one humectant, 50 - 80 % by weight, b. At least one surfactant, 0.5 - 5 % by weight, c. At least one gelling polymer, 0.25 - 2 % by weight; and d. A source of fluoride.

[0018] In a further aspect the at least one humectant comprises glycerol and polyethylene glycol; and the gelling polymer comprises a carbomer.

[0019] In another aspect the composition further comprises: a. At least one humectant, 20 - 55 % by weight, b. Water, 15-45 % by weight, c. At least one surfactant, 0.5 - 5 % by weight; and d. A source of fluoride.

[0020] In a further aspect the at least one humectant comprises one or more of, sorbitol, glycerol, polyethylene glycol or mixtures thereof. In a further aspect the at least one surfactant comprises sodium lauryl sulphate, coco amido propyl betaine and sodium methyl cocyl taurate and mixtures thereof.

[0021] In a further aspect the composition comprises one or more minor ingredients comprising an opacifying agent, a pH modifier, preservative, a flavouring, a colourant or mixtures thereof, and wherein the minor ingredients comprise between 0.1 % and 5 % by weight of the composition.

[0022] In another aspect the invention comprises the use of a dentifrice composition according to any of aspects above, wherein the brush may be manual or electric, to clean teeth.

[0023] Detailed description of the invention

[0024] It has been surprisingly found that the combination of perlite and spherical silica provides a superior cleaning performance in dentifrice compositions in comparison with known commercial silica abrasives.

[0025] As used herein, the term "non-aqueous" means anhydrous or substantially free of water. The individual components of the dentifrice composition may contain limited amounts of water as long as the overall composition remains substantially free of water.

[0026] As used herein the term "dentifrice" includes any semi-solid preparation in the form of a paste, cream or gel for use in cleaning all or a portion of the oral cavity of an individual.

[0027] As used herein the term "oral cavity" means an individual's teeth and gums including all periodontal regions including teeth down to the gingival margins and / or the periodontal pockets.

[0028] A combination of perlite and spherical silica has been found to form a highly effective abrasive system for dentifrice compositions, combining excellent cleaning properties (As measured by PCR testing) with very low abrasion (as measured by RDA testing).

[0029] The combination specific combination gives rise to a dentifrice with superb cleaning power over other known abrasives (High PCR scores), combined with even less wear caused to tooth enamel (Low RDA scores) Perlite is an amorphous volcanic glass that has a relatively high water content, typically formed by the hydration of obsidian. It occurs naturally and has the unusual property of greatly expanding when heated sufficiently. It is a commercial product useful for its low density after processing.

[0030] Perlite has also been shown to make an effective dentifrice abrasive, see J Clin Dent2013;24(3):88-93.

[0031] A non-limiting commercial example of perlite particles that are suitable for use in the present invention include, ImerCare® PeriWhite 19 supplied by Imerys Filtration EMEA.

[0032] Preferably the perlite particles of the present invention have a pH (measured as a 10% slurry in water) between 6-8.

[0033] Preferably the perlite particles of the present invention have a BET surface area of at least 1.0 m2 / g more preferably at least 1.25 m2 / g and most preferably at least 1.50 m2 / g.

[0034] Preferably the oil absorption of the perlite particles of the present invention is at least about 100 %, preferably at least about 120 % and most preferably at least about 140 % by weight of the perlite.

[0035] Oil absorption may be measured by ISO 19246:2016.

[0036] Preferably the perlite comprises between about 0.75 % and about 2.5 %, more preferably between about 1.0 % and about 2.0 % and most preferably about 1.5 % by weight.

[0037] The perlite particles of the present invention have a d50 particle size of less than 50 pm, more preferably a d50 particle size of less than 30 pm, more preferably a d50 particle size of less than 20 pm.

[0038] Spherical silica has been shown to have good properties for dentifrice abrasives. See US 11,246,809 which is herein included by reference.

[0039] Non limiting examples of spherical silica that are suitable for use in the invention include NP-30® or NP-100 by Sunsphere and MFIL-GS® silica by Madhu PVT. Ltd.

[0040] The silica gel particles of use in the invention comprise a high degree of sphericity i.e. they are spherical or substantially spherical, for example as can be seen by scanning electron micrography, for example as shown in Example 4 herein. For the avoidance of doubt, substantially spherical silica gel particle means any particle where the whole particle is mostly rounded or elliptical in shape. Suitably the silica gel particles of use in the invention comprise a smooth or a substantially smooth surface.

[0041] Suitably at least 90% of the spherical silica gel particles are substantially spherical, more suitably 95 % of the spherical silica gel particles are essentially spherical, even more suitably 99 % of the spherical silica gel particles are essentially spherical.

[0042] Suitably the silica gel particles of use in the invention have a mean particle diameter in the range from 1 pm to 10 pm, more suitably from 3 pm to 8 pm. Suitably the particles are generally of a uniform size and have a narrow particle size distribution for example from 1pm to 15pm. Particle size may be determined by laser diffraction.

[0043] In one embodiment according to the invention silica gel particles of use in the invention are non- porous or virtually non-porous i.e. comprise a substantially or completely closed surface (beyond the limit of detection). Porosity may be determined by the method described by Ojeda, Phys. Chem. Chem. Phys 5, 1859-1866, 2003 or as described herein.

[0044] Suitably silica gel particles of use in the invention are relatively hard materials as compared to other precipitated silicas; as such they are more resistant to shearing stress and disintegrate less easily under shear. Suitably the compression strength (MPa) of a silica gel of use in the invention is in the range from 1800 to 2000, such as from 1850 to 1950. Compression strength may be determined by using a micro-compressive strength tester.

[0045] Suitably the silica gel particles of use in the invention have smaller BET surface area values as compared to those observed for known dental abrasives such as the precipitated silicas available commercially as Zeodent-103 and Zeodent-115. The silica gel particles of use in the invention have a BET surface area (m2 / g) of 50 or less. In one embodiment the silica gel particles have a BET surface area (m2 / g) of 40 or less. In one embodiment the silica gel particles have a BET surface area (m2 / g) of 30 or less. In one embodiment the silica gel particles have a BET surface area (m2 / g) of 20 or less. In one embodiment the silica gel particles have a BET surface area (m2 / g) of 10 or less. In one embodiment the silica gel particles have a BET surface area (m2 / g) of 5 or less. BET surface area measurements are determined by measuring the amount of nitrogen adsorbed on a surface, suitably as described in Brunaur et al., J. Am. Chem. Soc., 60, 309 (1938) or as demonstrated herein.

[0046] Suitably silica gel particles of use in the invention have a low oil absorption capacity as compared to those observed for known dental abrasives such as Zeodent -109 and Zeodent-119, reported to have oil absorption values (ml / lOOg) of 79.8 and 110.7 respectively and as reported in W02010 / 068433.

[0047] The silica gel particles of use in the invention have an oil absorption capacity (mL / lOOg) suitably of 20 to 50, more suitably of 35 or less, even more suitably in the range 25 to 35. Oil absorption may be measured according to the method described in U.S. Patent Application 2007 / 0001037A1, published 4thJanuary, 2007.

[0048] The dentifrice compositions of the present invention comprise spherical silica particles between about 0.1 % and about 4 % by weight, and perlite between about 0.1 % by weight and about 5.0 % by weight of the dentifrice composition.

[0049] Preferably the spherical silica comprises between about 0.2 % and about 2.0 %, more preferably between about 0.25 % and 1.0 % by weight of the dentifrice composition.

[0050] The spherical silica particles of the present invention have the following properties a. a pore volume from 0.03 mL / g to less than 0.1 mL / g b. a mean particle size from 1 pm to 10 pm; c. a BET surface area of 50 m2 / g or less; d. an oil absorption capacity of 20 to 50 mL / 100 g; and e. a water content of less than 0.2 % wt %.

[0051] Wherein the parameters, including water content, are measured prior to addition to a dentifrice composition.

[0052] Other dentifrice ingredients

[0053] Dentifrice compositions of the present invention may be aqueous or non- aqueous. A non-aqueous carrier useful in the present invention typically comprises a thickening agent and one or more formulation solvent(s). Optionally, a further dentally acceptable abrasive may be included in the non-aqueous carrier.

[0054] Advantageously, a thickening agent may be present in the formulation to give the product a rheology closer to that of a conventional dentifrice. Suitably the thickening agent comprises a carboxyvinyl polymer such as a carbomer. A carbomer comprises synthetic high molecular-weight cross-linked polymers of acrylic acid. The polymer chains formed of repeating units of acrylic acid may be crosslinked with, for example: allyl sucrose to provide a carbomer available commercially in one form as Carbopol™ 934; ethers of pentaerythritol to provide a carbomer available commercially in one form as Carbopol™ 974; or with divinyl glycol, available commercially in one form as Noveon™ AA-1. CarbopolTM polymers are manufactured by B.F. Goodrich Company.

[0055] In one embodiment the carboxyvinyl polymer comprises CarbopolTM 974. The carboxyvinyl polymer may be present in the range of from about 0.1 to about 7.5% by weight of the dentifrice composition. In one embodiment the carboxyvinyl polymer is present in an amount from about 0.3 to about 1.0 % by weight of the dentifrice composition.

[0056] The dentifrice composition according to the invention may contain at least one surfactant. The composition may comprise two or more surfactants.

[0057] Preferably the at least one surfactant comprises sodium lauryl sulphate (SLS), or cocoamidopropyl betaine (CAPB), or sodium cocyl glycinate or sodium methyl cocyl taurate and / or mixtures thereof.

[0058] The total amount of surfactant in the dentifrices of the present invention may comprise between about 0.1 % and about 15 % by weight, preferably between about 0.5 % and about 10 % by weight and most preferably between about 1.0 % and about 5.0 % by weight of the dentifrice composition.

[0059] The surfactants may comprise any known for use in the art for oral care use. The skilled person will be aware of many possible suitable surfactants.

[0060] The at least one surfactant may comprise sodium lauryl sulphate, coco amido propyl betaine, sodium cocyl glycinate and sodium methyl cocyl taurate and mixtures thereof. A composition according to the invention comprises may comprise a surfactant system. A surfactant system may comprise a first surfactant and a second surfactant. In certain embodiments the surfactant system consists of a first surfactant and a second surfactant wherein the second surfactant consists of a mixture of surfactants.

[0061] A suitable first surfactant belongs to the class of compounds known as betaines. Structurally, betaine compounds contain an anionic functional group such as a carboxylate functional group and a cationic functional group such as quaternary nitrogen functional group separated by a methylene moiety. They include n-alkyl betaines such as cetyl betaine and behenyl betaine, and n-alkylamido betaines such as cocoamidopropyl betaine. In one embodiment the betaine is cocoamidopropyl betaine, commercially available under the trade name Tego Betain. Suitably the betaine is present in an amount ranging from about 0.05 % to about 4 % by weight of the dentifrice composition, for example from about 0.2 % to about 2.0 % by weight of the dentifrice composition.

[0062] A second surfactant for use in the surfactant system of a composition according to the invention is selected from a taurate or a C10-20 alkyl sulphate surfactant. Taurate surfactants useful in the present invention are salts of fatty acid amides of N-methyl taurine. They conform generally to the structural formula:

[0063] RC(O)N(CH3)CH2CH2SO3l\ / l

[0064] Where RC(O)- represents a fatty acid radical and M represents sodium, potassium, ammonium or triethanolamine. Fatty acids having carbon chain lengths of from 10 to 20, including those derived from coconut, palm and tall oil are used. In one embodiment the fatty acid is derived from coconut. In one embodiment, sodium salts are used. In one embodiment the taurate is sodium methyl cocyl taurate. This taurate surfactant is sold under the trademark by Adinol CT by Croda.

[0065] The taurate surfactant may be present in an amount from about 0.1 % to about 10 % of the dentifrice composition. In one embodiment the taurate surfactant is present in an amount from about 0.1 % to about 5 % by weight of the non aqueous composition. In one embodiment the taurate surfactant is present in an amount from about 0.5 % to about 2.0 % by weight of the dentifrice composition.

[0066] Alkyl sulphate surfactants of use in the invention have the following structural formula: R1OSO3M

[0067] R1represents a fatty alcohol moiety and M represents sodium, potassium, ammonium or triethanolamine. Fatty alcohols having carbon chain lengths of from about 10 to about 20, including those derived from coconut, palm oil and tall oil. In one embodiment, the fatty alcohol is lauryl alcohol. In one embodiment, a sodium salt is used. In one embodiment the alkyl sulphate is sodium lauryl sulphate.

[0068] The alkyl sulphate surfactant may be present in an amount from about 0.1 % to about 10 % of the dentifrice composition. In one embodiment the alkyl sulphate surfactant may be present in an amount from about 0.1 % to about 5 % by weight of the dentifrice composition. In one embodiment the alkyl sulphate surfactant is present in an amount from about 0.5 % to about 2.0 % by weight of the dentifrice composition.

[0069] In certain embodiments, the surfactant system consists of a first surfactant which is a betaine, and a second surfactant which consists of a mixture of a taurate and a C10-20 alkyl sulphate surfactant as hereinabove described. In one embodiment the surfactant system consists of a first surfactant which is a betaine and second surfactant which consists of a mixture of sodium methyl cocyl taurate and sodium lauryl sulphate.

[0070] In one aspect a composition according to the invention comprises a dentifrice additive that is unstable or incompatible with an aqueous environment. An example of such an additive is a bioactive glass of the type disclosed in WO96 / 10985, WO 97 / 27158 and WO 99 / 13852.

[0071] In one embodiment the bioactive glass for use in the invention has a composition consisting of about 45 % by weight silicon dioxide, about 24.5 % by weight sodium oxide, about 6 % by weight phosphorus oxide, and about 24.5 % by weight calcium oxide. One such bioactive glass is available commercially under the trade name, NovaMin®, also known as 45S5 Bioglass®.

[0072] The bioactive glass is present in an amount ranging from about 1 % to about 20 % by weight of the dentifrice composition. In one embodiment, the bioactive glass is present in an amount from about 1 % to about 15 % by weight of the dentifrice composition. In an alternative embodiment, the bioactive glass in the dentifrice composition is present in an amount from about 1 % to about 10 % by weight of the dentifrice composition. In a further alternative embodiment, the bioactive glass is present in an amount from about 2 % to about 8 % by weight of the dentifrice composition.

[0073] Suitably a dentifrice composition according to the invention may further comprise an inorganic thickening agent such as a thickening silica. Suitably, the thickening agent is a thickening silica, for example, a colloidal hydrated silica, available commercially for example as Sident 22S or Syloid 244FP.

[0074] In one possible embodiment the thickening silica is present in the range of from about 0 % to about 15 %, suitably from about 5.0 % to about 15.0 % by weight of the dentifrice composition.

[0075] Suitable humectants for use in the present invention include glycerin, sorbitol, propylene glycol, polyethylene glycol or mixtures thereof. In one embodiment the humectant comprises glycerin. It is well known that commercially available glycerin may contain between 0.1 % -2.0 % by weight of water which is in association with the glycerin. Typically, this amount is < 0.5 % for example between 0.1- 0.5 % by weight of the glycerin. This small amount of water is bound to the glycerin and is therefore not available to the other ingredients. The skilled person would still consider a composition containing glycerin as being non-aqueous.

[0076] In one embodiment the humectant comprises polyethylene glycol. Suitably, the polyethylene glycol will be selected from PEG 300, PEG 400 and mixtures thereof. In one embodiment the polyethylene glycol comprises PEG 400.

[0077] In one embodiment the humectant comprises a mixture of glycerin and polyethylene glycol.

[0078] The formulation humectant is used to make the formulation up to 100 %, and suitably the total amount of solvent may be present in the range of from about 20 % to about 95 % by weight of the dentifrice composition.

[0079] Suitably the humectant comprises glycerin present from about 35 % to about 75 % by weight. In one embodiment the glycerin is present from about 50 % to about 70% by weight of the dentifrice composition. Suitably the humectant comprises polyethylene glycol present from about 0.1 % to about 40 % by weight of the dentifrice composition. In one embodiment the polyethylene glycol is present from about 15 % to about 25 % by weight of the dentifrice composition.

[0080] Suitably when the dentifrice comprises water, the humectant may comprise, sorbitol glycerine and polyethylene glycol.

[0081] In order to produce a composition that is smooth and does not show any signs of stickiness, use of a particular ratio of carboxyvinyl polymer to polyethylene glycol is desirable.

[0082] Advantageously, the ratio of carboxyvinyl polymer to polyethylene glycol is in the range of about 1:15 to about 1:30.

[0083] The dentifrice compositions of the present invention should not require additional abrasives.

[0084] However additionally dentally acceptable abrasive may optionally be added to the dentifrice composition. Suitable abrasives for use in the dentifrice composition include, for example, amorphous, gelled, precipitated or fumed silica, zinc orthophosphate, sodium bicarbonate (baking soda), plastic particles, , calcium carbonate, calcium pyrophosphate, insoluble metaphosphates or mixtures thereof.

[0085] The silica abrasive may be a natural amorphous silica, for instance diatomaceous earth; or a synthetic amorphous silica such as a precipitated silica. By way of example, silica abrasives include those marketed under the following trade names Zeodent, Sident, Sorbosil or Tixosil by Huber, Degussa, Ineos and Rhodia respectively.

[0086] Suitably a silica abrasive is present in an amount up to 25 % by weight of the total composition, for example from 2 % to 20 % by weight for example from 5 % to 15 % by weight of the total composition.

[0087] Generally, an amount of abrasive suitable for use in the non-aqueous or aqueous composition of the present invention will be empirically determined to provide an acceptable level of cleaning and polishing, in accordance with the techniques well known in the art.

[0088] Suitable sources of fluoride ions for use in the compositions of the present invention include an alkali metal fluoride such as sodium fluoride, an alkali metal monofluorophosphate such a sodium monofluorophosphate, stannous fluoride, or an amine fluoride in an amount to provide from 25 to 3500pm of fluoride ions, preferably from 100 to 1500ppm. Polyphosphates are known to help retard calculus formation and are examples of anticalculus agents suitable for use in the invention. A polyphosphate is generally understood to consist of two or more phosphate groups arranged primarily in a linear configuration, although some cyclic derivatives may be present. Polyphosphates of use in the invention include pyrophosphates, polyphosphates having three or more polyphosphate groups such as sodium tripolyphosphate, and polyphosphates having four or more polyphosphate groups such as tetrapolyphosphate and hexametaphosphate among others.

[0089] A dentifrice composition of the present invention may further comprise an alkali metal bicarbonate salt. The inclusion of such a salt in a dentifrice composition is beneficial for several reasons such as for providing good plaque removing capabilities, as well as for improving the whitening properties of dentifrices. Importantly bicarbonate salts provide a clean fresh feeling in the oral cavity after brushing and rinsing with water. Suitably the alkali bicarbonate is sodium bicarbonate.

[0090] A dentifrice composition of the present invention may comprise one or more active agents conventionally used in dentifrice compositions, for example, a fluoride source, a desensitising agent, an anti-bacterial agent, an anti-plaque agent, an anti-calculus agent, an oral malodour agent, an antiinflammatory agent, an anti-oxidant, an anti-fungal agent, a wound healing agent or a mixture of at least two thereof. Such agents may be included at levels to provide the desired therapeutic effect.

[0091] Examples of desensitising agents include a tubule blocking agent or a nerve desensitising agent and mixtures thereof, for example as described in W002 / 15809 (Block). Examples of desensitising agents include a strontium salt such as strontium chloride, strontium acetate or strontium nitrate or a potassium salt such as potassium citrate, potassium chloride, potassium bicarbonate, potassium gluconate and especially potassium nitrate.

[0092] A desensitising agent such as a potassium salt is generally present in an amount ranging from 2% to 8% by weight of the composition, for example 5 % by weight of the composition.

[0093] In another embodiment the desensitising agent comprises an arginine calcium carbonate salt. Suitably the arginine salt is present in an amount ranging from 0.5 % to 30 % by weight of the composition, such as from 1 % to 10 % by weight of the composition or from 1 % to 10 % by weight of the composition such as from 2 % to 8 % by weight of the composition.

[0094] In one embodiment the desensitising agent comprises a bioactive glass. Suitably the bioactive glass consists of 45 % by weight silicon dioxide, 24.5 % by weight sodium oxide, 6 % by weight phosphorus oxide, and 24.5 % by weight calcium oxide. One such bioactive glass is available commercially under the trade name, NOVAMIN, also known as 45S5 BIOGLASS.

[0095] Suitably the bioactive glass is present in an amount ranging from 1 % to 20 % by weight of the composition, such as from 1 % to 15 % by weight of the composition, or from 1 % to 10 % by weight of the composition, or from 2 % to 8 % by weight of the composition.

[0096] In one embodiment the desensitising agent comprises a stannous salt such as stannous chloride or stannous fluoride. Stannous salts, through hydrolysis and oxidation reactions, form insoluble metal salts that precipitate in dentinal tubules and on the dentine surface to provide effective relief from dentine hypersensitivity. Stannous salts also provide a benefit against dental erosion, dental caries and plaque / gingivitis.

[0097] Compositions of the invention may further comprise an anti erosion agent, for example a polymeric mineral surface-active agent as described in WO 04 / 054529 (Procter & Gamble).

[0098] Compositions of the present invention will contain additional formulating agents such as flavouring agents, sweetening agents, opacifying or colouring agents and preservatives, selected from those conventionally used in an oral hygiene composition art for such purposes.

[0099] In general, the optional agents may be used in a minor amount or proportion of the overall formulation. By way of example, such components are usually present in from about 0.001 to about 5% by weight of the dentifrice composition.

[0100] The dentifrice composition typically has a viscosity suitable for application to the oral cavity. The viscosity will vary depending on the type of dentifrice composition made and the ultimate use thereof. One of skill in the art can readily prepare compositions with suitable viscosities for use in the oral cavity from the teachings provided herein.

[0101] The compositions according to the present invention may be prepared by admixing the ingredients in the appropriate relative amounts in any order that is convenient.

[0102] The invention is further illustrated by the following Examples.

[0103] Results

[0104] To demonstrate the effectiveness of the novel abrasive system a comparison with a typical commercial toothpaste with a known silica abrasive was carried out. The tested formulas are on table 1.

[0105] Table 1

[0106] Example 1 is a commercial Sensodyne formulation.

[0107] Examples 2, 3 and 4 were modified versions of that commercial product with the commercial silica- based abrasive removed and replaced with the abrasive systems of the present invention.

[0108] Example 5 was a modified version of the base formula with the SnF2 removed and the commercial formula silica abrasive replaced with 1.5% Perlite only.

[0109] Previous work with the spherical silica alone (US 11,246,809 ) has produced the following comparative formulas

[0110]

[0111] Table 2

[0112] The six compositions were tested by known standard methods to compare their cleaning power and abrasion of the tooth surface. The results shown on table 3.

[0113] The three examples of the invention showed increased cleaning power over the commercial product in the Pellicle cleaning ratio test (PCR). And all three test samples also showed a dramatic drop in tooth wear over the three comparative formulations, the commercial product (example 1) , the perlite individually (example 5) and the silica individually (examples 6 and 7) in the radioactive dentine analysis test.

[0114] Table 3

[0115] Thus, the combination abrasive system of the present invention is clearly superior to the known silica systems in use currently. And to each component of the abrasive system individually.

[0116] The combination of perlite with the spherical silca provides a surprising boost to cleaning power while reducing wear to the tooth surface. The effect was not seen with the combination of regular commercial silica in combination with either perlite or the spherical silica.

[0117] Testing methods

[0118] Pellicle Cleaning Ratio Test (PCR) as a Measure of Stained Pellicle Removal from Bovine Enamel

[0119] Introduction

[0120] Previous studies (J. Dent. Res., 61:1236, 1982) have indicated that the results of the in-vitro PCR test with dentifrice slurries may be considered to be predictive of clinical findings with a reasonable degree of confidence.

[0121] Dentifrice formulations were assessed for their ability to remove pellicle stain from bovine enamel and compared with similar comparative formulations (not encompassed within the scope of the invention) containing alternative silica abrasive materials.

[0122] Methodology

[0123] Bovine, permanent, central incisors were cut to obtain labial enamel specimens approximately 8x8mm2. The enamel specimens were then embedded in an autopolymerizing methacrylate resin so that only the enamel surfaces were exposed. The enamel surfaces were then smoothed on a lapidary wheel and polished with flour of pumice and water, then sonicated to remove excess debris. They were then lightly etched (60 seconds in 0.12M HCI, 30 seconds in saturated NaCO3and 60 seconds in 1.0% phytic acid) to expedite stain accumulation and adherence. They were then placed on a rotating rod alternately exposing them to staining broth containing gastric mucin as a protein source and coffee, tea and FeCI36H2O as staining sources (i.e., 1.35g coffee, 1.35g tea, 0.02g Fe and 1.0 g mucin in 400ml) for a minimum of 10 days to ensure the specimens developed sufficient stain.

[0124] The amount of in vitro stain was graded photometrically (Minolta 2600d, colorimeter) using only the L value of the LAB scale. The area of the specimens measured was a %inch diameter circle in the centre of the enamel sample. Specimens with L value measurements between 30-38 (30 being more darkly stained) were used. On the basis of these measurements, the specimens were divided into groups of 16 specimens each, with each group having the same average baseline measurement.

[0125] The specimens were then mounted on a mechanical V-8 cross-brushing machine equipped with soft nylon-filament (Oral-B 40 Indicator) toothbrushes. Toothbrushes were conditioned by running the brushing machine for 1,000 strokes in deionised water. Tension on the enamel surface was adjusted to 150g. The dentifrices were used as slurries prepared by mixing 25g of dentifrice with 40ml of deionised water. The ADA reference material was prepared by mixing 10g of material and 50ml of a 0.5% CMC solution. The specimens were brushed for 800 double strokes. To minimise mechanical variables, one specimen per group was brushed on each of the eight brushing heads. Fresh slurries were used for each specimen brushed. Following brushing, specimens were rinsed, blotted dry, and measured again for stain as previously described.

[0126] The difference between the pre- and post-brushing stain measurements was determined and the mean and standard error calculated for the reference group. The cleaning ratio for the reference material group was assigned a value of 100. The mean decrement for the reference group was divided into 100 to obtain a constant value to multiple times each individual test decrement within the study. The individual cleaning ratio of each specimen was then calculated (decrement X constant). The mean and standard error mean (SEM) for each group (N=16) was then calculated using the individual cleaning ratios. The larger the value of the cleaning ratio, the greater the amount of stained pellicle removed.

[0127] Statistical analyses of the individual means were performed with a one-way analysis of variance (ANOVA) model using Sigma Stat (3.1) Software. Since the ANOVA indicates significant differences, the individual means were analysed by the Student Newman-Keuls (SNK) test.

[0128] RDA: Relative Dentine Abrasivity

[0129] The most used industry standard way of measuring how abrasive a toothpaste is. This procedure is described in ISO 11609 and ANSI / ADA Standard No. 130.

[0130] Each test is a result that is relative to the control and the lower the better.

[0131] Dentifrice formulations were assessed for their abrasivity (as determined by RDA) and compared as against similar comparative formulations

[0132] Methodology

[0133] The procedure used was the ISO / ADA recommended procedure for determination of dentifrice abrasivity. The dentin specimens (8) were placed in a neutron flux under the controlled conditions outlined by the ISO / ADA. The specimens were then mounted in methyl methacrylate so they would fit in a V-8 cross-brushing machine. The specimens were brushed for 1,500 strokes in a precondition run (since the teeth had been used previously) using a slurry consisting of 10g ISO / ADA reference material in 50ml of a 0.5% CMC glycerin solution. The brushes used were those specified by the ISO / ADA and had been used in a previous study. The brush tension was 150g. Following the precondition run, the test was performed using 150g and 1,500 strokes in a sandwich design in which each test material slurry (25g dentifrice / 40ml water) was flanked by reference material slurries (10g ADA reference / 50 ml 0.5% CMC).

[0134] A 1ml sample was removed from each reference material slurry, weighed (0.01g) and added to 4.5ml of scintillation cocktail. The samples were well mixed and immediately placed on the scintillation counter for radiation detection. Following counting, the net counts per minute (CPM) values were divided by the weight of the sample to calculate the net CPM / gram of slurry. The net CPM / g of the pre- and post-ADA reference material for each test slurry were then calculated and averaged to use in the calculation of the RDA for the test material. The ISO / ADA material was assigned a value of 100 and its ratio to the test material was calculated.

[0135] Statistical analyses were performed by a one-way ANOVA model using Sigma Stat Software (13.0). Since significant differences were indicated, the individual means were analysed by the Student Newman Keuls (SNK) test.

[0136] Silica and perlite particle testing methodology

[0137] Particle sizes may be determined by laser diffraction.

[0138] Oil absorption may be measured according to the method described in U.S. Patent Application 2007 / 0001037 Al, published 4th January, 2007.

[0139] Surface area and porosity analysis

[0140] The surface areas of the silica samples were measured by BET N2adsorption, isotherm plots were also measured to determine the pore size and volume.

[0141] Instrumentation:

[0142] Calculated Braun EmmetTeller (BET) specific surface areas from gas sorption (N2, 77 K) were measured on Micromeritics 3-Flex gas sorption analyser. All powder samples (400-700mg) were pre-degassed at 200°C for 8 hours under vacuum (10-3 mbar) in the oven and then degassed at 200 °C for 16 hours under dynamic high vacuum (10-6 mbar) in the 3-Flex analyser prior to analysis.

[0143] Specific surface area

[0144] Preconditioning: Heating at 300°C with N2flow 30mL / min for 30 minutes. Cooling at room temperature and 30 minutes in N2 Measurement of Nitrogen partial pressure: Multipoint measurement

[0145] Pore volume

[0146] Preconditioning: Heating at 300°C with N2 flow 30mL / min for 30 minutes. Cooling at room temperature and 30 minutes in Nj flow

[0147] Nitrogen pressure on measurement: O.IMPa

[0148] Operating procedure

[0149] 1). Fill 0.2g of sample to a sample tube and reduce the pressure to the region of measurement conditions.

[0150] 2) Close a valve of the sample tube and weigh it (A).

[0151] 3) Estimate weight difference between A and sample tube only (Blank).

[0152] 4) Start the measurement of the porosity.

[0153] 5) Specific surface area is calculated using next two equations.

[0154] [BET equation]

[0155] Pl i , c-i Pl

[0156] - — - F - X —

[0157] Vl(PO-Pl) VmC VmC P0

[0158] [Relational calculus between specific area and Vm]

Claims

Claims1. A dentifrice composition comprising spherical silica particles and perlite particles, wherein the spherical silica particles comprise between about 0.1 % and about 4.0 % by weight, and perlite particles comprise between about 0.1 % by weight and about 5.0 % by weight; and further wherein the spherical silica particles comprise the following properties: a. a pore volume from about 0.03 mL / g to less than about 0.1 mL / g b. a mean particle size from about 1 pm to about 10 pm; c. a BET surface area of about 50 m2 / g or less; d. an oil absorption capacity of about 20 to about 50 mL / 100 g; and e. a water content of less than about 0.2 % by weight; and wherein the perlite particles have a d50 particle size of less than 50 pm.

2. The dentifrice composition according to claim 1 wherein the spherical silica particles comprise between about 0.2 % and 1.5 % by weight and the perlite particles between about 0.25 % by weight and about 2.0 % by weight of the composition.

3. The dentifrice composition according to any of the previous claims wherein spherical silica particles comprise between about 0.25 % and about 1.0 % by weight and the perlite particles comprises between about 0.75 % and about 1.5 % by weight.

4. The dentifrice composition according to any of the previous claims wherein the composition further comprises at least one surfactant, and at least one humectant.

5. The dentifrice composition according to any of the previous claims wherein the composition further comprises a source of fluoride.

6. The dentifrice composition according to any of the previous claims wherein the composition comprises a further abrasive.

7. The dentifrice composition according to any of the previous claims wherein the composition comprises an anti-sensitivity agent.

8. The dentifrice composition according to any of the previous claims wherein the anti-sensitivity agent comprises one or more of, stannous fluoride, potassium nitrate or a bioglass.

9. The dentifrice composition according any of the previous claims wherein the composition further comprises: a. At least one humectant, 50 % - 80 % by weight, b. At least one surfactant, 0.5 % - 5 % by weight, c. At least one gelling polymer, 0.25 % - 2 % by weight; and d. A source of fluoride.

10. The dentifrice composition of claim 9 wherein the at least one humectant comprises glycerol and polyethylene glycol; and the gelling polymer comprises a carbomer.

11. The dentifrice composition according to any of claims 1 to 8, wherein the composition comprises: a. At least one humectant, 20 % - 55 % by weight, b. Water, 15 % - 45 % by weight, c. At least one surfactant, 0.5 % - 5 % by weight; and d. A source of fluoride.

12. The dentifrice according to claim 11 wherein the at least one humectant comprises one or more of, sorbitol, glycerol, polyethylene glycol or mixtures thereof.

13. The dentifrice composition according to any one of claims 9 to 12 wherein the at least one surfactant comprises one or more of sodium lauryl sulphate (SLS), cocoamidopropyl betaine (CAPB) and sodium methyl cocyl taurate and mixtures thereof.

14. The dentifrice composition according to any of the previous claims wherein the composition further comprises one or more minor ingredients; the minor ingredients comprising an opacifying agent, a pH modifier, preservative, a flavouring, a colourant or mixtures thereof, and wherein the minor ingredients comprise between 0.1 % and 5 % by weight of the composition.

15. The use of a dentifrice composition according to any of claims 1 to 14 in combination with a brush, wherein the brush may be manual or electric, to clean teeth.

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