BR112020003912B1 - SILICA OR SILICATE PARTICLES, COMPOSITION AND TOOTHPASTE COMPOSITION - Google Patents

Abstract

Spherical particles of silica and/or silicate having a median d50 particle size of 1 to 5 μm, a d95 particle size of less than 8 μm, an oil absorption of 40 to 100 cm3/100 g, a packing density of 0.32 to 0.96 g/cm3 (20 to 60 lb/ft3) and a sphericity factor (S80) of at least 0.9 are disclosed, as well as methods for producing such spherical particles, and dentifrice compositions containing the spherical particles.

Description

BACKGROUND OF THE INVENTION

[0001] Tooth sensitivity is a common problem for many people and is increasingly common in the aging population. The condition occurs as the protective layer of enamel on the teeth and/or gums regresses and exposes the dentin layer. Dentin is a much less mineralized material that is composed of mineral (hydroxyl apatite) and organic (collagen) content. The dentin layer is also porous, with round tubules that extend from the root of the tooth outward and allow the transfer of nutrients to different parts of the tooth. When these tubules are exposed to external stimuli such as heat, cold, or polysaccharides, it has been postulated that the fluid in the tubules changes pressure (due to expansion/contraction) and causes the pain associated with sensitive teeth. Potassium nitrate is commonly added to toothpaste formulations for sensitive teeth to act as a nerve blocking agent, where the potassium ions interfere with the tooth's ability to send pain signals to the brain. The conditions responsible for the pain are still present; however, pain is no longer felt after a sufficient concentration of potassium ions is increased in the region. Since it is recommended that potassium nitrate toothpastes not be used for a period of more than two continuous weeks, other sensitivity reducing agents are typically used alone or in conjunction with potassium nitrate. Remineralizing agents, which promote the formation of new hydroxyl apatite through precipitation of soluble calcium and phosphate ions that restore the enamel surface, can be used (e.g. Novamin bioglass-type materials). These materials introduce a unique set of formulation challenges, as the ingredients typically need to remain separated before application (double tube or hydrophobic formulation), and are not typically compatible with sodium fluoride (Ca ions).

[0002] Tubular occlusion techniques, in which a physical blockage of the tubule with a particle occurs, can also be used. Certain silica particles can occlude tubules, and their affinity toward hydroxyapatite can be modified with the addition of an adduct material. Typically, silica particles have to be air milled to achieve the proper particle size distribution that is required for fit in a tubule (e.g., 2-3 μm). The addition of these silica materials can be used for tubular occlusion, but such materials provide substantial viscosity build-up - functioning as a silica thickener - and do not provide significant cleaning. Lower structure silicas can be used, but problems with grinding, such as lower gloss levels and trace metal contamination (from grinding), can result in unacceptable attributes. The abrasive nature of these materials relative to enamel (as measured by REA) may tend to remove amorphous hydroxyapatite as new enamel is forming.

[0003] Therefore, it would be beneficial to provide silica materials with improved tubular occlusion performance, but still maintaining cleaning performance in a dentifrice composition. Consequently, the present invention is mainly aimed at these purposes.

SUMMARY OF THE INVENTION

[0004] This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify necessary or essential features of the claimed subject matter. This summary is also not intended to be used to limit the scope of the subject matter claimed.

[0005] Silica and/or silicate particles that can be used for tubular occlusion are disclosed and described in this document. According to one aspect of this invention, such silica and/or silicate particles may have (i) a d50 median particle size in a range of about 1 to about 5 μm, (ii) a d95 particle size of less than of or equal to about 8 μm, (iii) an oil absorption in a range of about 40 to about 100 cm3/100 g, (iv) a packing density in a range of about 0.32 to about of 0.96 g/cm3 (20 to about 60 lb/ft3), and (v) a sphericity factor (S80) of more than or equal to about 0.9. These silica and/or silicate particles have a spherical shape or morphology and can be produced using a continuous loop reactor process.

[0006] Also disclosed herein are dentifrice compositions containing spherical silica and/or silicate particles, typically in amounts in the range of 0.5-50% by weight, and methods of using the silica and/or silica particles and compositions. silicate.

[0007] Both the above summary and the following detailed description provide examples and are exemplary only. Consequently, the above summary and the following detailed description should not be considered as restrictive. Additionally, features or variations may be provided in addition to those set forth herein. For example, certain aspects may target various combinations and subcombinations of features described in the detailed description.

BRIEF DESCRIPTION OF FIGURES

[0008] FIG. 1 is a Scanning Electron Microscopy of the silica of Example 2A.

[0009] FIGS. 2A-2E are photographs illustrating the tooth preparation and sectioning process.

[0010] FIG. 3 is an optical microscope photograph of a mounted tooth section.

[0011] FIG. 4 is an optical microscope photograph of a mounted tooth section after brushing with the toothpaste formulation of Example 2B.

[0012] FIG. 5 is a Scanning Electron Microscopy of a mounted tooth section after brushing with the toothpaste formulation of Example 2B.

[0013] FIGS. 6A-6C are EDS mapping photographs of the dentin surface after brushing with the toothpaste formulations of Example 2B.

[0014] FIG. 7 is a Scanning Electron Microscopy of a mounted tooth section after brushing with the toothpaste formulation of Example 1B.

[0015] FIG. 8 is an EDS mapping photograph of the dentin surface after brushing with the toothpaste formulation of Example 1B.

DEFINITIONS

[0016] To more clearly define the terms used in this document, the following definitions are provided. Unless otherwise indicated, the following definitions are applicable to this disclosure. If a term is used in this disclosure but is not specifically defined herein, the definition in the IUPAC Compendium of Chemical Terminology, 2nd Edition (1997), may be applied, provided that definition does not conflict with any other applied disclosure or definition. herein or does not render undefined or unenforceable any claim to which that definition is applied. If any definition or usage provided by any document incorporated herein by reference conflicts with the definition or usage provided herein, the definition or usage provided herein controls.

[0017] In the present document, features of the matter are described in such a way that, within particular aspects, a combination of different features can be contemplated. For each aspect and each feature disclosed herein, all combinations that do not adversely affect the designs, compositions, processes or methods described herein are contemplated and may be changed, with or without explicit description of the particular combination. Accordingly, unless explicitly indicated otherwise, any aspect or feature disclosed herein may be combined to describe inventive designs, compositions, processes or methods consistent with the present disclosure.

[0018] Although compositions and methods are described herein as “comprising” various components or steps, the compositions and methods may also “consist essentially” or “consist” of the various components or steps, unless otherwise indicated. .

[0019] The terms “a”, “an”, “the” and “a” are intended to include several alternatives, for example, at least one, unless otherwise specified.

[0020] In general, groups of elements are indicated using the numbering scheme indicated in the version of the periodic table of elements published in Chemical and Engineering News, 63(5), 27, 1985. In some examples, a group of elements may be indicated using a common name assigned to the group; for example, alkali metals for Group 1 elements, alkaline earth metals for Group 2 elements, and so on.

[0021] Although any methods and materials similar or equivalent to those described herein may be used in practicing or testing the invention, typical methods and materials are described herein.

[0022] All publications and patents mentioned in this document are incorporated herein by reference for the purpose of describing and disclosing, for example, the constructs and methodologies that are described in the publications, which may be used in conjunction with the invention described in this document.

[0023] Various types of bands are disclosed in the present invention. When a range of any type is disclosed or claimed, the intent is to disclose or claim individually each possible number that such range could encompass to the greatest extent possible, including endpoints of the range, as well as any subranges and combinations of subranges covered therein. As a representative example, the BET surface area of silica and/or silicate particles may be in certain ranges in various aspects of this invention. By disclosing that the BET surface area can be in a range of about 25 to about 100 m2/g, the intention is to mention that the surface area can be any surface area within the range and e.g. , may be equal to about 25, about 30, about 40, about 50, about 60, about 70, about 80, about 90 or about 100 m2/g. Additionally, the surface area may be within any range from about 25 to about 100 m2/g (e.g., from about 45 to about 90 m2/g), and this also includes any combination of ranges between about from 25 to about 100 m2/g (for example, the surface area may be in a range of about 25 to about 50 m2/g or from about 70 to about 90 m2/g). Likewise, all other tracks disclosed in this document should be interpreted in a similar way to this example.

DETAILED DESCRIPTION OF THE INVENTION

[0024] Disclosed herein are generally spherical silica and/or silicate particles that may be characterized by (i) a median particle size d50 in a range of about 1 to about 5 μm, (ii) a size of d95 particle of less than or equal to about 8 μm, (iii) an oil absorption in a range of about 40 to about 100 cm3/100 g, (iv) a packing density in a range of about 0 .32 to about 0.96 g/cm3 (20 to about 60 lb/ft3), and (v) a sphericity factor (S80) of greater than or equal to about 0.9.

[0025] Methods of producing these spherical silica and/or silicate particles, dentifrice compositions containing the spherical particles and methods of treatment using the spherical particles and dentifrice compositions are also disclosed and described herein.

SPHERICAL SILICA / SILICATE PARTICLES

[0026] In accordance with aspects of the present invention, spherical silica and/or silicate particles with improved tubular occlusion may have the following characteristics: (i) a median particle size d50 in a range of about 1 to about 5 μm, (ii) a d95 particle size of less than or equal to about 8 μm, (iii) an oil absorption in a range of about 40 to about 100 cm3/100 g, (iv) a density of compaction in a range of about 0.32 to about 0.96 g/cm3 (20 to about 60 lb/ft3), and (v) a sphericity factor (S80) of greater than or equal to about 0 ,9. In further aspects, such silica and/or silicate particles according to the present invention may also be any of the characteristics or properties provided below, and in any combination.

[0027] In one aspect, the spherical silica and/or silicate particles may have a relatively small average particle size. Often, the median particle size (d50) and/or mean particle size (average) can be within a range of about 1 to about 5, from about 1 to about 4.5, from about 1 to about 4, from about 1.5 to about 5, from about 1.5 to about 4.5, or from about 1.5 to about 4 μm, and the like. In some aspects, the median particle size (d50) and/or mean particle size (mean) may be within a range of about 2 to about 5, of about 2 to about 4.5, of about from 2 to about 4, or from about 2.5 to about 3.8 μm. Other suitable ranges for median and mean particle sizes are readily apparent from this disclosure.

[0028] In one aspect, spherical silica and/or silicate particles may have a narrow particle size distribution, as demonstrated by particle size d95. Often, the d95 particle size may be less than or equal to about 8 μm, less than or equal to about 7.5 μm, less than or equal to about 7 μm, less than or equal to about 6 .5 μm, less than or equal to about 6 μm, or less than or equal to about 5.5 μm. The narrow particle size distribution can also be demonstrated in the weight percentage of the 325 mesh residue (amount retained on a 325 mesh sieve), which can generally be less than or equal to about 0.9% by weight. In some aspects, the 325 mesh residue may be less than or equal to about 0.7 wt %, less than or equal to about 0.5 wt %, less than or equal to about 0.3 % by weight, less than or equal to about 0.2% by weight, or less than or equal to about 0.1% by weight. Other suitable ranges for the d95 particle size and the 325 mesh residue are readily evident from this disclosure.

[0029] Generally, silica and/or silicate particles can have relatively low oil absorption, typically in a range of about 40 to about 100 cm3/100 g, or from about 45 to about 90 cm3/ 100 g, in some aspects of this invention. In other aspects, oil absorption may be in the range of about 50 to about 85 cm3/100 g, or from about 60 to about 80 cm3/100 g. Other suitable ranges for oil absorption are readily apparent from this disclosure.

[0030] Although without limitation, spherical silica and/or silicate particles may have a compaction density in a range of about 0.32 to about 0.96 g/cm3 (20 to about 60 lb/ft3) in an aspect of the invention. In another aspect, the compaction density may be in a range of about 0.4 to about 0.88 g/cm3 (25 to about 55 lb/ft3), from about 0.4 to about 0. 8 g/cm3 (25 to about 50 lb/ft3), or from about 0.48 to about 0.8 g/cm3 (30 to about 50 lb/ft3). In yet another aspect, the compaction density may be in the range of about 0.56 to about 0.96 g/cm3 (35 to about 45 lb/ft3). Other suitable ranges for packing density are readily apparent from this disclosure.

[0031] The sphericity of spherical silica and/or silicate particles can be quantified by a sphericity factor (S80), which is typically greater than or equal to about 0.85, greater than or equal to about 0, 88 or greater than or equal to about 0.9. The sphericity factor (S80) is determined as follows. An SEM image of the silica and/or silicate particle sample is magnified 20000 times, which is representative of the silica and/or silicate particle sample, and is imported into the photographic imaging software, and the contour of each particle (two-dimensionally) is plotted. Particles that are close to each other but not attached to each other should be considered separate particles for this analysis. The outlined particles are then filled with color, and the image is imported into particle characterization software (e.g., IMAGE-PRO PLUS available from Media Cybernetics, Inc., Bethesda, Md.) capable of determining the perimeter and particle area. The sphericity of the particles can then be calculated according to the equation, Sphericity = (perimeter)2 divided by (4π x area), where the perimeter is the software-measured perimeter derived from the contoured trace of the particles, and where the area is the area measured by software on the plotted perimeter of the particles.

[0032] The sphericity calculation is performed for each particle that completely fits into the SEM image. These values are then sorted by value, and the lowest 20% of these values are discarded. The remaining 80% of these values are averaged to obtain the sphericity factor (S80). Additional information about sphericity can be found in US Patents Nos. 8,945,517 and 8,609,068, incorporated herein by reference in their entirety.

[0033] In one aspect of this invention, spherical silica and/or silicate particles may have a sphericity factor (S80) greater than or equal to about 0.85, or greater than or equal to about 0.88, while, in another aspect, the sphericity factor (S80) may be greater than or equal to about 0.9. In yet another aspect, spherical silica and/or silicate particles may be characterized by a sphericity factor (S80) greater than or equal to about 0.92, and in yet another aspect, silica and/or silicate particles can be characterized by a sphericity factor (S80) greater than or equal to about 0.94. As one skilled in the art would readily recognize, a three-dimensional sphere (or two-dimensional circle) will have a sphericity factor (S80) equal to 1.

[0034] The spherical silica and/or silicate particles may have any suitable surface area, generally a BET surface area in the range of about 25 to about 100 m2/g. Often, the BET surface area can be within a range of from about 35 to about 95, from about 40 to about 90, or from about 45 to about 95 m2/g. In further aspects, the BET surface area may be in a range of about 20 to about 100, from about 20 to about 80, from about 50 to about 100, from about 60 to about 100, from about 40 to about 85, from about 50 to about 80, or from about 55 to about 80 m2/g, and the like. Other ranges suitable for the BET surface area are readily evident from this disclosure.

[0035] Additionally, spherical silica and/or silicate particles may be less abrasive, as demonstrated by an Einlehner abrasion value in the range of about 1 to about 15 mg lost/100000 revolutions. For example, the Einlehner abrasion value may be in a range of about 1 to about 10; alternatively, from about 2 to about 12; or alternatively, from about 2 to about 7 mg lost/100,000 revolutions. Other suitable ranges for the Einlehner abrasion value are readily evident from this disclosure.

[0036] In another aspect, spherical silica and/or silicate particles may have relatively low water absorption. For example, water absorption may be in a range of about 55 to about 115 cm3/100 g, from about 70 to about 100 cm3/100 g, or from about 65 to about 90 cm3/100 g . Other suitable ranges for water absorption are readily apparent from this disclosure.

[0037] In these and other aspects, any of the spherical silica and/or silicate particles may be amorphous, may be synthetic, or may be both amorphous and synthetic. Furthermore, spherical silica and/or silicate particles may comprise precipitated silica and/or silicate particles in particular aspects of this invention, although without limitation.

[0038] In one aspect of this invention, the spherical silica and/or silicate particles may comprise silica particles, while, in another aspect, the spherical silica and/or silicate particles may comprise silicate particles, and in yet another aspect , the spherical silica and/or silicate particles may comprise silica and silicate particles (e.g., a mixture of silica and silicate particles). When the spherical particles contain silicate particles, any suitable silicate material may be used, non-limiting examples thereof may include calcium silicate particles, magnesium silicate particles, sodium aluminosilicate particles (or other metal aluminosilicates). alkali), sodium magnesium aluminosilicate particles (or other alkali metal aluminosilicates modified by alkaline earth metal) and the like, as well as combinations thereof.

PROCESSES FOR PRODUCING SPHERICAL PARTICLES

[0039] The spherical silica and/or silicate particles disclosed herein are not limited to any particular synthetic procedure. However, to achieve the desired sphericity, a continuous loop reactor process can be used to form the spherical silica and/or silicate particles. This process and the associated reactor system (which may include a continuous loop of one or more looped reactor tubes) are described in US Patent Nos. 8,945,517 and 8,609,068, incorporated herein by reference in its entirety. In general, the continuous loop process involves (a) continuously supplying a mineral acid and an alkali metal silicate into a loop reaction zone comprising a stream of liquid medium, in which at least a portion of the mineral acid and the silicate alkali metal reacts to form a silica product (e.g., silica and/or silicate particles) in the liquid medium of the loop reaction zone; (b) continuously recirculate the liquid medium through the loop reaction zone; and (c) continuously discharging from the loop reaction zone a portion of the liquid medium comprising the silica product. Typically, the supply locations of the mineral acid and alkali metal silicate to the loop reaction zone are different, and the rate of total supply of acid and silicate is proportional to, and often equal to, the rate of discharge of the liquid medium that contains the silica product. All or substantially all of the contents within the loop reaction zone are recirculated, for example, at a rate in the range of about 50% by volume per minute (the recirculation rate per minute is half the total volume of the contents). at about 1000 volume % per minute (the recirculation rate per minute is ten times the total volume of the contents), or from about 75 volume % per minute to about 500 volume % per minute.

TOOTHPASTE COMPOSITIONS

[0040] Spherical silica and/or silicate particles can be used in any suitable composition and for any suitable end-use application. Often, silica and/or silicate particles can be used in oral care applications, such as in a dentifrice composition. The dentifrice composition may contain any suitable amount of the silica and/or silicate particles, such as from about 0.5 to about 50% by weight, from about 1 to about 50% by weight, from about 5 to about from 35% by weight, from about 10 to about 40% by weight or from about 10 to about 30% by weight, of the spherical silica and/or silicate particles. These weight percentages are based on the total weight of the toothpaste composition.

[0041] The dentifrice composition can be in any suitable form, such as a liquid, powder or paste. In addition to silica and/or silicate particles, the dentifrice composition may contain other ingredients or additives, non-limiting examples of which may include a humectant, a solvent, a binder, a therapeutic agent, a chelating agent, a thickener other than silica and/or silicate particles, a surfactant, an abrasive other than silica and/or silicate particles, a sweetening agent, a coloring agent, a flavoring agent, a preservative and the like, as well as any combination thereof.

[0042] Humectants serve to thicken or add “smooth mouth texture” to a toothpaste, as well as prevent the toothpaste from drying out. Suitable humectants include polyethylene glycol (in a variety of different molecular weights), propylene glycol, glycerin (glycerol), erythritol, xylitol, sorbitol, mannitol, lactitol and hydrogenated starch hydrolysates and mixtures thereof. In some formulations, humectants are present in an amount of about 20 to about 50% by weight, based on the weight of the dentifrice composition.

[0043] A solvent may be present in the toothpaste composition, in any suitable charge, and usually the solvent comprises water. When used, water is preferably deionized and free of impurities and may be present in the dentifrice in amounts of from 5 to about 70% by weight or from about 5 to about 35% by weight, based on the weight of the dentifrice composition.

[0044] Therapeutic agents can also be used in the compositions of this invention to provide the prevention and treatment of dental caries, periodontal disease and temperature sensitivity, for example. Suitable therapeutic agents may include, but are not limited to, fluoride sources such as sodium fluoride, sodium monofluorophosphate, potassium monofluorophosphate, stannous fluoride, potassium fluoride, sodium fluorosilicate, ammonium fluorosilicate and the like; condensed phosphates such as tetrasodium pyrophosphate, tetrapotassium pyrophosphate, disodium dihydrogen pyrophosphate, trisodium monohydrogen pyrophosphate; tripolyphosphates, hexametaphosphates, trimetaphosphates and pyrophosphates; antimicrobial agents such as triclosan, bisguanides such as alexidine, chlorhexidine and chlorhexidine gluconate; enzymes, such as papain, bromelain, glucoamylase, amylase, dextranase, mutanase, lipases, pectinase, tannase and proteases; quaternary ammonium compounds such as benzalkonium chloride (BZK), benzethonium chloride (BZT), cetylpyridinium chloride (CPC), and domiphene bromide; metal salts such as zinc citrate, zinc chloride and stannous fluoride; sanguinaria and sanguinarine extract; volatile oils such as eucalyptol, menthol, thymol and methyl salicylate; amine fluorides; peroxides and the like. Therapeutic agents can be used in dentifrice formulations individually or in combination, and at any therapeutically safe and effective level or dosage.

[0045] Thickening agents are useful in toothpaste compositions to provide a gelatinous structure that stabilizes the toothpaste against phase separation. Suitable thickening agents include silica thickeners; starch; starch glycerite; gums, such as karaya gum (sterculia gum), gum tragacanth, gum arabic, ghatti gum, acacia gum, xanthan gum, guar gum and cellulose gum; aluminum magnesium silicate (Veegum); carrageenan; sodium alginate; agar-agar; pectin; gelatin; cellulose compounds such as cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxymethyl cellulose, hydroxymethyl carboxypropyl cellulose, methyl cellulose, ethyl cellulose and sulfated cellulose; natural and synthetic clays, such as hectorite clays; and mixtures thereof. Typical levels of thickening or binding agents are up to about 15% by weight of a toothpaste or dentifrice composition.

[0046] Silica thickeners useful for use in a toothpaste composition, for example, include, as a non-limiting example, an amorphous precipitated silica, such as ZEODENT 165 silica. Other non-limiting silica thickeners include ZEODENT 153 silica products, 163 and/or 167 and ZEOFREE 177 and/or 265, all available from J. M. Huber Corporation.

[0047] Surfactants can be used in the dentifrice compositions of the invention to make the compositions more cosmetically acceptable. The surfactant is preferably a detersive material that gives the composition detersive and foaming properties. Suitable surfactants are safe and effective amounts of anionic, cationic, nonionic, zwitterionic, amphoteric and betaine surfactants such as sodium lauryl sulfate, sodium dodecyl benzene sulfonate, alkali metal or ammonium salts of lauroyl sarcosinate, myristoyl, palmitoyl sarcosinate, stearoyl sarcosinate and oleoyl sarcosinate, polyoxyethylene sorbitan monostearate, isostearate and laurate, sodium lauryl sulfoacetate, N-lauroyl sarcosine, the sodium, potassium and ethanolamine salts of N-lauroyl, N-myristoyl or N-palmitoyl sarcosine, alkyl phenol polyethylene oxide condensates, cocoamidopropyl betaine, lauramidopropyl betaine, palmityl betaine and the like. Sodium lauryl sulfate is a preferred surfactant. The surfactant is typically present in the compositions of the present invention in an amount of from about 0.1 to about 15% by weight, from about 0.3 to about 5% by weight, or from about 0.3 to about 2.5% by weight.

[0048] The disclosed silica and/or silicate particles can be used individually as the abrasive in the toothpaste composition, or as an additive or coabrasive with other abrasive materials discussed herein or known in the art. Therefore, any number of other conventional types of abrasive additives may be present in the dentifrice compositions of the invention. Other such abrasive particles include, for example, precipitated calcium carbonate (PCC), crushed calcium carbonate (GCC), chalk, bentonite, dicalcium phosphate or its dihydrate forms, silica gel (individually and of any structure ), precipitated silica, amorphous precipitated silica (individually and of any structure as well), perlite, titanium oxide, dicalcium phosphate, calcium pyrophosphate, alumina, hydrated alumina, calcined alumina, aluminum silicate, insoluble sodium metaphosphate, sodium metaphosphate insoluble potassium, insoluble magnesium carbonate, zirconium silicate, particulate thermosetting resins and other suitable abrasive materials. Such materials can be introduced into dentifrice compositions to customize the polishing characteristics of the target formulation.

[0049] Sweeteners can be added to the toothpaste composition (for example, toothpaste) to impart a pleasant taste to the product. Suitable sweeteners include saccharin (as sodium, potassium or calcium saccharin), cyclamate (as a sodium, potassium or calcium salt), acesulfame-K, thaumatin, neohesperidin dihydrochalcone, ammoniated glycyrrhizin, dextrose, levulose, sucrose, mannose and glucose.

[0050] Dyes can be added to improve the aesthetic appearance of the product. Suitable colorants include, without limitation, those colorants approved by appropriate regulatory bodies, such as the FDA and those listed in European Food and Pharmaceutical Directives and include pigments, such as TiO2, and colors, such as FD&C and D&C dyes.

[0051] Flavoring agents can also be added to toothpaste compositions. Suitable flavoring agents include, but are not limited to, wintergreen oil, peppermint oil, spearmint oil, sassafras oil and clove oil, cinnamon, anethole, menthol, thymol, eugenol, eucalyptol, lemon, orange and other such components. flavorings to add fruity notes, spicy notes, etc. These flavoring agents generally comprise mixtures of aldehydes, ketones, esters, phenols, aliphatic, aromatic and other acids and alcohols.

[0052] Preservatives can also be added to the compositions of the present invention to prevent bacterial growth. Suitable preservatives approved for use in oral compositions, such as methylparaben, propylparaben, and sodium benzoate, can be added in safe and effective amounts.

[0053] Other ingredients can be used in the toothpaste composition, such as desensitizing agents, healing agents, other cavity preventive agents, chelating/sequestering agents, vitamins, amino acids, proteins, other antiplaque/anticalculus agents, opacifiers, antibiotics, antienzymes, enzymes, pH control agents, oxidizing agents, antioxidants and the like.

METHODS OF USE

[0054] Any of the spherical silica and/or silicate particles and any of the compositions disclosed herein can be used in the treatment methods. For example, a method of reducing tooth sensitivity consistent with this invention may comprise placing any of the spherical particles (or any of the compositions) of silica and/or silicate disclosed herein in contact with a surface of the teeth of a mammal. Then, the silica and/or silicate particles (or compositions) can be applied, or delivered, to the mammalian tooth surface by brushing or any other suitable technique. Any suitable amount of the silica and/or silicate particles (or compositions) can be used and for any suitable period of time.

[0055] In another aspect, a method for occluding a dentinal tubule on a surface of a mammalian tooth consistent with this invention may comprise placing any of the spherical particles (or any of the compositions) of silica and/or silicate disclosed in the present document in contact with the surface of a mammal's tooth. As above, any suitable amount of the silica and/or silicate particles (or compositions) can be applied, or delivered, to the surface of a mammal's tooth by brushing or any other suitable technique and for any suitable period of time.

EXAMPLES

[0056] The invention is further illustrated by the following examples, which should not be interpreted in any way that imposes limitations on the scope of this invention. Various other aspects, modifications and equivalents thereof, after reading the description in the present document, may occur to a person skilled in the art without departing from the spirit of the present invention or the scope of the appended claims.

[0057] The BET surface areas disclosed in this document were determined on a Micromeritics TriStar II 3020 V1.03 using the BET nitrogen adsorption method of Brunaur et al., J. Am. Chem. Soc., 60, 309 (1938), and such a technique is well known to those skilled in the art.

[0058] The surface areas of CTAB disclosed in this document were determined by absorption of CTAB (cetyltrimethylammonium bromide) onto the silica surface, the excess was separated by centrifugation and the amount determined by titration with sodium lauryl sulfate using a surfactant electrode. Specifically, about 0.5 grams of the silica and/or silicate particles were placed in a 250 ml beaker with 100 ml of CTAB solution (5.5 g/l), mixed on an electric stir plate for 1 hour , then centrifuged for 30 min at 10000 RPM. One ml of 10% Triton X-100 was added to 5 ml of clear supernatant in a 100 ml beaker. The pH was adjusted to 3-3.5 with 0.1 N HCl and the specimen was titrated with 0.01 M sodium lauryl sulfate using a surfactant electrode (Brinkmann SUR1501-DL) to determine the end point.

[0059] The median particle size (d50) refers to the particle size for which 50% of the sample has a smaller size and 50% of the sample has a larger size. The median particle size (d50), mean particle size (mean) and d95 were determined using the laser diffraction method using a Horiba LA 300 instrument. The dried particles were transferred to the instrument for analysis.

[0060] For volumetric density and compaction density, 20 grams of the sample was placed in a 250 ml graduated cylinder with a flat rubber bottom. The initial volume was recorded and used to calculate the volumetric density by dividing it by the sample weight used. The cylinder was then placed in a tap density machine where it was rotated on a cam at 60 RPM. The cam is designed to raise and lower the cylinder a distance of 5715 cm once every second until the sample volume is constant, typically for 15 min. This final volume is recorded and used to calculate the compacted density by dividing it by the sample weight used.

[0061] The Einlehner abrasion value is a measure of the hardness/abrasivity of silica and/or silicate particles, and is described in detail in US Patent No. 6,616,916, incorporated herein by reference, and involves an Einlehner AT-1000 abrasion tester generally used as follows: (1) a Fourdrinier brass wire screen is weighed and exposed to the action of a 10% aqueous silica suspension for a fixed period of time; (2) the amount of abrasion is then determined as milligrams of brass lost from the Fourdrinier wire screen per 100000 revolutions (mg lost/100000 revolutions).

[0062] Oil absorption values were determined according to the rub-out method described in ASTM D281 using linseed oil (cm3 of oil absorbed per 100 g of particles). In general, a higher level of oil absorption indicates a particle with a higher level of large pore porosity, also described as larger structure.

[0063] Water absorption values were determined with a torque rheometer Absorptiometer “C” from CW Brabender Instruments, Inc. Approximately 1/3 of a cup of the silica sample was transferred to the mixing chamber of the Absorptiometer and mixed with 150RPM. Water was then added at a rate of 6 ml/min, and the torque required to mix the powder was recorded. As water is absorbed by the powder, the torque will reach a maximum as the powder changes from a fluidizer to a paste. The total volume of water added when maximum torque was reached was then standardized as the amount of water that could be absorbed per 100 g of powder. Since the powder was used on an as-received basis (not pre-dried), the free moisture value of the powder was used to calculate a “moisture-corrected water AbC value” by the following equation.

[0064] The Absorptiometer is commonly used to determine the carbon black oil number according to methods B and C of ASTM D 2414 and ASTM D 3493.

[0065] The pH values disclosed in this document (5% pH) were determined in an aqueous system containing 5% by weight of solids in deionized water using a pH meter.

[0066] The 325 mesh residue (% by weight) of the silica sample was measured using a North American Standard Sieve No. 325, with 44 microns or 0.0043 cm (0.0017 inch) openings (wire mesh stainless steel), weighing a 10.0 gram sample to the nearest 0.1 gram in the cup of a 1-quart Hamilton mixer (Model #30), adding approximately 170 ml of distilled or deionized water, and stirring the slurry for at least 7 min. The mixture was transferred to the 325 mesh screen and water was sprayed directly onto the screen at a pressure of 137.89 kPa (20 psig) for two minutes, with the spray head held at approximately 10.16 to 15. 24 cm (four to six inches) from the screen. The remaining residue was then transferred to a watch glass, dried in an oven at 150 °C for 15 min, then cooled and weighed on an analytical balance.

EXAMPLE 1A Irregular silica particles

[0067] Table I summarizes certain properties of comparative silica material 1A, which has an irregular and non-spherical particle morphology. Example 1A was a conventional silica material commercially available from Huber Engineered Materials.

EXAMPLE 2A Spherical Silica Particles

[0068] A continuous loop reactor process (see, for example, US Patent Nos. 8,945,517 and 8,609,068) was used to produce the silica particles of Example 2A, which have a spherical morphology and a distribution of narrower particle size (e.g. less 325 mesh residue in the final silica product). No grinding steps were used.

[0069] For Example 2A, 1.5 kg of precipitated silica, 1.34 kg of sodium sulfate, 11.1 l of sodium silicate (3.32 MR, 13.3%) and 20 l of water were added to the recirculation loop, followed by heating to 83 °C with recirculation at 80 l/min with the Silverson operating at 60 Hz (3485 RPM). Sodium silicate (3.32 MR, 13.3%) and sulfuric acid (11.4%) were added simultaneously to the loop at a silicate rate of 2.1 L/min and an acid rate sufficient to maintain a pH of 7.5. If necessary, the acid rate was adjusted accordingly to maintain pH. The acid and silicate were added under these conditions for 40 minutes to purge unwanted silica from the system before the desired material was collected. After 40 minutes, the collection vessel was emptied and its contents discarded. The silica product was then collected in a stirring vessel at 40 RPM while maintaining the temperature at approximately 80 °C. After the desired amount of product was collected, the addition of acid and silicate was stopped and the contents of the loop were circulated. The silica product in the collection vessel was adjusted to pH 6.0 by manually adding sulfuric acid and was then filtered and washed to a conductivity of ~1500 μS. The pH of the slurry was then readjusted to pH 6.0 with sulfuric acid and it was spray dried.

[0070] Table I summarizes certain properties of the silica particles produced in Example 2A, compared to the respective properties of Example 1A. Example 2A had a median d50 particle size of 3.1 μm, a d95 particle size of 6.0 μm, an oil absorption of 68 cm3/100 g, and a tap density of 0.64 g/cm3 (40 lb/ft3). FIG. 1 is a representative SEM image demonstrating the narrow particle size distribution and spherical particle morphology of Example 2A. The sphericity factor (S80) for Example 2A was greater than 0.9.

EXAMPLES 1B-2B Testing toothpaste formulations and tubular occlusion

[0071] Samples of silicas 1A-2A were used in toothpaste formulations 1B-2B as summarized in Table II. Since the volumetric density of the 3.1 μm spherical silica of Example 2A was about 6 times that of Example 1A, additional spherical silica was added to formulation 2B to keep the number of silica particles in the formulation approximately equal (5% in weight of 3.1 μm of spherical silica in Example 2B versus 0.8 wt% of the silica of

Example 1A in Example 1B).

[0072] For the tubular occlusion test, bovine incisors were obtained from a local slaughterhouse. Teeth were rinsed in water and sterilized in an autoclave, then rinsed in water to remove any remaining tissue and stored in isopropyl alcohol.

[0073] FIG. 2A shows a bovine incisor before sectioning. The incisal surface of the tooth was removed with a diamond cutting wheel on a Dremel tool (FIG. 2B). The sectioning was done by first cutting the proximal surfaces (FIG. 2C) and then the remaining tooth was cut lengthwise from the proximal surface towards the root, keeping it parallel to the labial surface of the tooth (FIG. 2D ). Finally, the tooth section was removed by cutting the labial surface in such a way that it meets the cut lengthwise (FIG. 2E).

[0074] The section of the tooth was placed with the enamel facing down in a Teflon mold measuring 1.9 cm x 1.27 cm x 1.27 cm (V' x V' x V'). Methacrylate resin (Yates Motloid, Chicago, IL) was mixed and poured into the mold containing the tooth section and cured for 35 minutes. The tooth embedded in resin was removed and then polished on a Unipol-810 Precision Polishing, Lapping and Precision Machine (MTI Corporation of Richmond, CA) with a diamond wheel with a roughness of 2000 at 150 rpm.

[0075] Polishing was carried out until the dentinal tubules were exposed. The polished sections were then placed in a 50 mM lactic acid solution containing 0.1 wt % polyacrylic acid for 30 minutes (as described by Karlinsky, et. al., Journal of Dentistry and Oral Hygiene, Vol. 3 (2 ) pages 22-29, February 2011, incorporated herein by reference in its entirety) to remove organic matter and to demineralize the dentin surface. After acid washing, samples were rinsed with deionized water for 20 seconds to remove any residual acid, followed by drying overnight at room temperature. After the mounted tooth sections were completely dry, they were marked and photographed at 100x with an optical microscope (see representative FIG. 3). The assembled tooth sections were placed in a UHMW Delrin retainer, and a Byk Gardner Model 5400 Abrasion Tester was used for the brushing studies. The abrasion tester has been modified to accept Oral-B toothbrushes.

[0076] First, the 3.1 μm spherical silica from Example 2A was evaluated. The toothpaste formulation of Example 2B was diluted for brushing studies 1:3 in a solution containing 1 wt % glycerin and 0.1 wt % Cekol 2000 (C.P. Kelco, Atlanta, GA). The toothpaste solution was mixed for 2 minutes with a Silverson model L4RT-A high shear mixer. The brushing machine was turned on and the toothpaste solution was pumped over the tooth sections at a rate of 15 ml/min with a Masterflex peristaltic pump. Brushing was suspended after 300 brush strokes, and tooth sections were rinsed with deionized water for 20 seconds to remove residual toothpaste. After drying at room temperature overnight, photographs were taken with an optical microscope at 100x magnification (see representative FIG. 4) to determine the impact of brushing with the toothpaste formulation (Example 2B) containing the particles 3.1 μm silica spheres (Example 2A).

[0077] From FIG. 4, it was unexpectedly found that the 3.1 μm spherical silica particles resided in the dentinal tubules - see the white regions of the image. FIG. 5 is a SEM image of the same dental dentin seen in FIGS. 3-4 after brushing with toothpaste formulation 2B, which contained 3.1 μm spherical silica. In the SEM micrograph of FIG. 5, it was unexpectedly observed that the majority of tubules were occluded with 3.1 μm spherical silica particles.

[0078] FIGS. 6A-6C illustrate the mapping by EDS (Electron Dispersive Spectroscopy, Oxford Instruments Inca with Penta FET) of the dentin surface after brushing with toothpaste formulation 2B, which contained 3.1 μm spherical silica (Example 2A). In FIG. 6A (phosphorus) and FIG. 6B (calcium), the black dots represent tubules in which phosphorus and calcium, respectively, are not present. In FIG. In Fig. 6C, the white dots indicate that silicon (from 3.1 μm spherical silica) now resides in the tubules.

[0079] For comparison, toothpaste formulation 1B, which contained the 3.3 μm silica of Example 1A - with a non-spherical and irregular particle morphology - was evaluated in the same way as toothpaste formulation 2B. Example 1A is a fine-particle silica product that has previously been shown to occlude dentinal tubules in some circumstances.

[0080] FIG. 7 is an SEM image of dental dentin after brushing with toothpaste formulation 1B, which contained 3.3 μm silica in a non-spherical and irregular shape. In contrast to the SEM micrograph of FIG. 5, it was observed that very few tubules were occluded with the silica particles of Example 1A, despite having approximately the same number of silica particles present in both toothpaste formulations. Clearly, the 1B toothpaste formulation resulted in minimal tubular occlusion and was not effective as the 2B toothpaste formulation.

[0081] The EDS mapping in FIG. 8 also demonstrates the less effective tubular occlusion of formulation 1B, where the white dots indicate the presence of silicon (compared to FIG. 6C). Furthermore, the broader particle size distribution of the silica of Example 1A is evident in FIGS, 7-8, in contrast to the narrow particle size distribution of Example 2A.

[0082] In summary, the results indicate that toothpaste formulation 2B (containing the 3.1 μm spherical silica particles from Example 2A) was surprisingly more likely to occlude dentinal tubules after brushing. Without being bound by theory, it is believed that the small particle size, narrow particle size distribution, and highly spherical particle morphology of the silica particles were significant factors that led to the increase in tubular occlusion. In contrast, toothpaste formulation 1B (containing the irregularly shaped, non-spherical 3.3 μm silica particles of Example 1A) was not nearly as effective in tubular occlusion, likely due to the non-spherical nature (pin analogy). square to round hole) and wider particle size distribution (higher percentage of large particle sizes). Furthermore, the silica of Example 2A can provide cleaning performance superior to that of the silica of Example 1A, at least due to the lower oil absorption value and the superior volumetric density and compaction properties. Table I. Examples 1A-2A. Table II. Examples 1B-2B - Toothpaste formulations (all values in % by weight).

Claims (21)

1. Silica or silicate particles, characterized by comprising: (i) a median particle size d50 in a range of 1 to 5 μm; (ii) a d95 particle size of less than or equal to 8 μm; (iii) an oil absorption in a range of 40 to 100 cm3/100 g; (iv) a compaction density in a range of 0.32 to 0.96 g/cm3 (20 to 60 lb/ft3); and (v) a sphericity factor (S80) of greater than or equal to 0.9. 2. Particles according to claim 1, characterized by the fact that the median particle size d50 is in a range of 1.5 to 4 μm. 3. Particles according to claim 1, characterized by the fact that the median particle size d50 is in a range of 2 to 4.5 μm. 4. Particles according to any one of claims 1 to 3, characterized by the fact that the particle size d95 is less than or equal to 6 μm. 5. Particles according to any one of claims 1 to 4, characterized in that the oil absorption is in a range of 60 to 80 cm3/100 g. 6. Particles according to any one of claims 1 to 5, characterized in that the compaction density is in a range of 0.56 to 0.8 g/cm3 (35 to 45 lb/ft3). 7. Particles according to any one of claims 1 to 6, the silica and/or silicate particles being further characterized by an Einlehner abrasion value in a range of 1 to 10 mg lost/100,000 revolutions. 8. Particles according to any one of claims 1 to 6, the silica and/or silicate particles being further characterized by an Einlehner abrasion value in a range of 2 to 7 mg lost/100,000 revolutions. 9. Particles according to any one of claims 1 to 8, the silica and/or silicate particles being further characterized by a BET surface area in a range of 40 to 90 m2/g. 10. Particles according to any one of claims 1 to 9, the silica and/or silicate particles being additionally characterized by a water absorption (AbC) in a range of 70 to 100 cm3/100 g. 11. Particles according to any one of claims 1 to 10, the silica and/or silicate particles being further characterized by a 325 mesh residue of less than or equal to 0.2% by weight. 12. Particles according to any one of claims 1 to 11, characterized by the fact that the sphericity factor (S80) is greater than or equal to 0.94. 13. Particles according to any one of claims 1 to 12, characterized in that they are precipitated silica and/or silicate particles. 14. Particles according to any one of claims 1 to 13, characterized by being amorphous. 15. Particles according to any one of claims 1 to 14, characterized in that they comprise precipitated silica particles. 16. Particles according to any one of claims 1 to 15, characterized in that they comprise sodium aluminosilicate particles, sodium magnesium aluminosilicate particles, calcium silicate particles, magnesium silicate particles or any combination thereof. 17. Composition, characterized by comprising silica and/or silicate particles, as defined in any one of claims 1 to 16. 18. Toothpaste composition, characterized by comprising silica and/or silicate particles, as defined in any one of claims 1 to 16. 19. Toothpaste composition, characterized in that it comprises from 0.5 to 50% by weight of silica and/or silicate particles, as defined in any one of claims 1 to 16. 20. Toothpaste composition, characterized by comprising 5 to 35% by weight of silica and/or silicate particles, as defined in any one of claims 1 to 19. 21. Toothpaste composition according to any one of claims 18 to 20, characterized in that it further comprises at least one of a humectant, a solvent, a binder, a therapeutic agent, a chelating agent, a thickener other than silica particles and/or silicate, a surfactant, an abrasive other than silica and/or silicate particles, a sweetening agent, a coloring agent, a flavoring agent and a preservative, or any combination thereof.