CA2220105A1 - Dentifrice compositions - Google Patents

Abstract

Oral compositions, such as oral gels and toothpastes, containing a novel abrasive. An amorphous silica abrasive composition comprising: a) a precipitated silica, said precipitated silica being a low structure precipitated silica having a narrow particle size range distribution of soft particles and having a mean value (MV) particle size ranging from 8 to 14 microns, an oil absorption ranging from 60 to 120 cc/100g, and a mercury intrusion (HGI) void volume of 1.0 to 4.0 cc/g; said precipitated silica, when formulated into a dentifrice, having a Pellicle Cleaning Ratio (PCR) of from 70 to 140 and a Radioactive Dentin Abrasion (RDA) value of from 60 to 130; and wherein the ratio of said PCR to said RDA is at least 1.1; and wherein, as the particle size in microns increases in said silica, the RDA value remains substantially constant; and b) a gel silica comprising particles, preferably having: i) a mean particle size of from 5 to 11 microns (s.d. < 9); ii) an Einlehner hardness of from 3 to 15 for abrasive to brass screen and from 8 to 20 for abrasive to polyester screen; iii) an oil absorption of from 60 ml/100 gm to 130 ml/100 gm; and iv) a radioactive dentin abrasion of from 80 to 200 wherein at least 70 % of all of said particles have a diameter of below 25 microns and wherein the pellicle cleaning ratio is from 90 to 135 and the radioactive dentin abrasion is from 60 to 100 with a pellicle cleaning ratio/radioactive dentin abrasion ratio of from 1.20 to 1.60 and wherein the ratio of precipitated silica to gel silica is from 90:10 to 60:40, respectively.

Description

CA 0222010~ 1997-10-31 WO 9~5/34592 PCT/lJ~96~0~496 DENTIFRICE COMPOSITIONS

TECHNICAL FIELD
5The present invention relates to denti~ice ~ompositions such as toothraete~, which provide improved oral cleaning.
BACKGROUND OF THE I~VENTION
A s~ti~f~ctory dentifrice composition should have a cosmetic effeet upon the lteeth, namely, keeping them light colored. It shou~d also clean and remo~te debris as l~ell, thereby aiding the prevention of tooth decay and promoting gingival health.
Abrasives aid in the removal of the tightly adherent pellicle film. This ~ m usually comprises a thin acellular, glycoprotein-mucoprotein coating which adhleres to the enamel within minutes a~Ler teeth are cleaned. The presence of various food pigrnents lodged within the film accounts for mos~ instances of teeth disc~loration.
]:deally, an abrasive should provide s~ticf~ctory removal (cleaning) of the pellicle film ~vith minim~l damage (abrasion) to oral tissue, i.e. tlle dentin and enamel.
Beyond the pellicle cleaning aspect, incorporating an antiplaque agent(s) provides additional benefits. The formation of dental plaque is the priman~ .source of clerltal caries, gingival and periodontal disease, and tooth loss. Plaque is a mixed rnatrix of bacteria, epithelial cells, leukocytes, macrophages and other oral: exudate 1'he bacteria associated with plaque can secrete enzymes and endotoxins ~A~hieh can ilTitate the gums and cause an infl~mm~tory gingivitis. As the gums blecome increasingly irritated by this process, they have a tendency to bleed, lose their toughness and resiliency, and separate from the teeth. This separation results in periodontal pockets leading in turn to fi~rther accumulation of debris, secretiorls, and more bacteria/toxins. This process eventually leads to destruction of both the hard and so~ tissue of the oral cavity.
The use of a variety of agents to clean the oral cavity and reduce plaq-le and mo~th malodor has been recognized for some time. Examples include: U.S. Patent 3~696~191, October t, 1972 to Weeks; U.S. Patent 3.991~177~ November 9, 1976 to ~,'idra et al.; U.S. Patent 4.058~595~ November 15, 1977 to Colodney; U.'i. Patent 4~115.546. to Vidra et al.; U.S. Patent 4.138.476. February 6, 1979 to Simonson et a~.; U.S. Patent 4.140.758~ February 20, 1979 to Vidra et al.; U.S. Patent 4.154.815.
~Iay 15, 1979 to Pader; U.S. Patent 4.737.359~ Ap,~il 12, 1988 to Eigen et al., U.S.
Patent 4.986.981. January 2~, 1991 to Glace et al.; U.S. Patent 4.992.420, February 12, 1991 to Nesser; U.S. Patent 5.000.939~ March 19, 1991 to Dring et al.; Kokai0'2/I05~898~ published April 18, 1990 to Kao Corporation; Kokai 03/128.313~ pub-CA 0222010~ 1997-10-31 lished May 31, 1991 to Nippon Kotai Kenkyu and Kokai 03/223.209~ published October 2, 1991 to Lion Corporation; U.S. Patent 4~652~444~ March 24, 1987 to Maurer; U.S. Patent 4~725~428~ February 16, 1988 to Miyahara et al.; U.S. Patent4~355~022. October 19, 1982 to Rabussay and PCT application WO 86/02831 published May 22, 1986 to Zetachron, Inc.
Abrasives are described in U.S. Patent 4~340~583~ July 20, 1982 to Wason, U.S. Patent 3~574~823~ April 13, 1971 to Roberts et al., EP Patent 535~943Al~ April 7, 1993, McKeown et al., and PCT Patent WO 92/02454~ February 20, 1992 to McKeown et al.
Moreover, various combinations of silicas have been described in the art.
Silica combinations invo1ving compositions of differing particle sizes and specific surface areas are disclosed in U.S. Patent 3~577~521 to Karlheinz Scheller et al., May 4, 1971 and U.S. Patent 4~618~488 to Maeyama et al., October 21, 1986, respectively. Similarly, U.S. Patents 5~110~574 to Reinhardt et al., May 5, 1992discloses combining precipitated thickener and polishing silicas to form silica compositions having oil absorption values of at least 200. Further examples of silica combinations include U.S. Patent 5~124~143 to Muhlemann, June 23, 1992 and U.S.
Patent 4~632~826 to Ploger et al., December 30, 1986.
While the prior art discloses a variety of silica compositions useful as dental 20 cleaning abrasives, there is still a need for additional compositions providing improved cleaning with minim~l abrasion. The present inventor has discovered amorphous silica abrasive compositions comprising precipitated and gel silicas providing improved dental cleaning with minim~l abrasion.
Accordingly, it is the object of the present invention to provide a precipitated2s silica and gel silica compositions providing improved pellicle cleaning without a corresponding increase in dentin or enamel abrasion. Another object of the present invention is to provide an improved method for the prevention or removal tooth stains. A further object of the present invention is to provide an improved method for the prevention or removal of plaque. These and other objects will become readily 30 appal enl from the disclosure which follows.
SUl\~MARY OF THE INVENTION
The present invention relates to amorphous silica abrasive compositions comprislng:
a. a precipitated silica, said precipitated silica being a low structure precipitated silica having a narrow particle size range distribution of soft particles and having a mean value (MV) particle size ranging from 8 to 14 microns, an oil absorption ranging from 60 to 120 cc/lOOg, CA 0222010~ 1997-10-31 WO 96/.34592 PCT/U~;9~6J05496 and a mercury intrusion (HGI) void volume of 1.0 to 4.0 cc/g;
said precipitated silica, when formulated into a dentifrice, having a Pellicle Cleaning Ratio (PCR) of from 70 to 140 and a R.adioactive Dentin Abrasion (RDA) value offrom 60 to 130;
S and wherein the ratio of said PCR to said RDA is at least 1.1;
and wherein, as the particle size in microns increases in saidl silica, the RDA value remains substantially constant; and b. a gel silica comprising particles wherein at least about 70% of all of said particles have a diameter of below 0 about 25 microns and wherein the pellicle cleaning ratio is from about 90 to about 135 and the radioactive dentin abrasion is from about 60 to about 100 with a pellicle cleaning ratio/radioactive dentin abrasion ratio of frcm about 1.20 to about 1.60 and wherein the ratio of precipitated silica to gel silica isfrom about 90:10 to about 60:40, respectively.
Preferably, the gel silica particles have:
i.) a mean particle size of from about 5 to about 11 microns (s.d. < ~);
ii.) an Einlehner hardness of from about 3 to about 15 for abrasive to brass screen and from about 8 to about 20 for abrasive to polyester screen;
iii.) an oil absorption of from about 60 ml/100 gm to about 130 ml/100 gm; and iv.) a radioactive dentin abrasion of from about 80 to about 200.
The present invention further relates to dentifrice compositions cont:3inin~
these abrasives and to a method of cleaning teeth reducing plaque, gingivitis and calculus using the above compositions.
All percentages and ratios herein are by weight unless otherwise specified.
PlCR and RDA are unitless. Additionally, all measurements are made at 25~C unless ol:herwise specified.
DETAILED DESCRIPTION OF THE TNVENTION
By "safe and effective amount," as used herein, means a sufficient a.mount to reduce stain and/or plaque/gingivitis without harming the tissues and structures of the oral cavity.
By the term "orally-acceptable carrier," as used herein, means a suitable vehicle which can be used to apply the present compositions to the oral cavity in a safe and effective manner.
The pH of the present herein described compositions range from about 4.0 to about 9.5, with the preferred pH being from about 6.5 to about 9.0 and the most CA 0222010~ 1997-10-31 plefellèd pH being 7.0 to about 9Ø
The escenti~1 as well as optional components of the compositions of the present invention are described in the following paragraphs.
Abrasive The precipil~ted silicas of the present invention provide unique Radioactive Dentin Abrasion (RDA) values in the dentifrice compositions of the present invention and are characterized by having a mean value particle size (MV) as measured on aMicrotrac Particle Analyzer, in the range of 8 to 14 microns and more preferablyfrom 8-10 microns. The mean value (MV) particle size takes into account skewed o particle sizes and speaks to distribution of the particle. Thus, as the mean particle size increases over the range of 8-14 microns as disclosêd herein, it would be expected that the RDA would also increase. However, the RDA of these silicas is relatively lower and remains relatively constant or increases at a slower rate. These silicas also have good fluoride compatibility.
Certain of these precipitated silicas can also be characterized as agglomerated or cohered silicas wherein subparticles are cohesively bound together during theprocess of acit~ tion and/or curing to form the agglomerated precipitated silicas having the mean particle size of 8 to 14 microns. Preferably greater than about 2%, more preferably greater than about 5%, even more preferably greater than about 10%
20 and most preferably greater than about 15% by weight of the precipitated silica particles of the present invention are made up of these agglomerates. Agglomeration is not a result of the addition of a binding agent to the process, but rather is a natural agglomeration caused by physical binding characteristics of the subparticles. It is theorized that during digestion and subsequent curing, the particles of silica become 2s more uniform in size by a process of cohesion of smaller particles and breaking apart of large agglomerates.
It is therefore theorized that when used in dentifrice formulations, the agglomerated particles break down during the brushing process when in contact with dentin or enamel so that the precipitated silica particles appear to be softer particles 30 when used in the dentifrice formulations. This property, when considered with the fact that thê precipitated silicas already possess lower RDA values than prior art silicas, provides dentifrice compositions with increased cleaning but lower abrasiveness. Therefore, a feature of the precipitated silicas of the invention is that they are agglomerated precipitated amorphous silicas of substantially uniform particle 35 size and having mean particles sizes of 8 to 14 microns, and more preferably from 8 to 10 microns, and which have reduced RDA values as compared to the prior art.
A feature of these precipitated silicas is the relationship of the mean particle CA 0222010~ 1997-10-31 WO 96l/34592 PCT~S'~6/~5496 $ize and exhibited RDA. The precipitated silica.s of the invention have a mean ~article size of 8-14 microns and also unexpectedly have a relatively lower abrasivity or hardness. This relatively lower abrasivity for a low structure silica is u~ique to the l~ie~ Led silicas ofthe invention.
The precipitated silicas of the invention are Low Structure silicas in accordance with the definitions set forth in the J. Soc. Cosmet. Chem. 2'J., 497-521 (August, 1978), and Pigment Handbook: Volume 1, Properties and Economics, 'iecond Edition, Edited by Peter A. Lewis, John Wiley & Sons, Inc., 19~,8, p. 139-~L 59. Further, the precipitated silicas may be characterized as having an oil absorption ranging from 60 to 120 cc/lOOg and preferably 80 to 100 cc/lOOg, morepreferably about 90 cc/lOOg. The silicas may also be characterized as having ~ BET
s;urface area in the range of 50 to 250 m2/g.
A further feature of the precipitated amorphous silicas of the inventi:on is theporosity as determined by mercury intrusion (HGI) void volume measurementC,. Thesilicas of this invention have mercury intrusion values in the range of 1.0 to 4.0 cc/g a.nd. preferably 1.5 to 2.5 cc/g. A further feature of the precipitated silicas of the vention resides in the pH which ranges from 4.0 to 8.5 and preferably fi-om 6.5 to .5~ as measured in a 5% aqueous slurry.
The Pellicle Cleaning Ratio (PCR) of the inventive silica, which is a measurement of the cleaning characteristics of a dentifrice, ranges from 70 to 140 and preferably from 100 to 130 for the precipitated silica of the invenl:ion. The Radioactive Dentin Abrasion (RDA) of the inventive silicas, which is a measurement of the abrasiveness of the precipitated silicas of the invention when incorpor,ated into a dentifrice, ranges from 60 to 130, preferably from 60 to 100, and more preferably fi-om 80 to 90.
The silicas of the invention may also be characterized as having a pour density r;mging from 12-16 Ib./ft3, a pack density ranging from 25-30 Ib./ft3 and medianaverage particle size ranging from 7.0 to 11Ø
These silicas, when incorporated into a dentifrice composition provide an irnproved PCR/RDA ratio. The PCR/RDA ratio is used to determine the relative ratio of cleaning and abrasion characteristics of a dentifrice fo~rmulation.
Cornmercially available dentifrice formulations generally have a PCR/RDA ratio in the range of 0.5 to below 1Ø The precipitated silicas used in the compositions of the present invention provide PCR to RDA ratios to dentifrice formulations of greater than 1, usually in the range of 1.1 to 1.9, but more preferably in the range 1.:2 to 1.9.
The precipiLated silicas of the invention are preferably characterized as s~mthetic hydrated amorphous silicas, also known as silicon dioxides or SiO2. This CA 0222010~ 1997-10-31 wo 96/34592 PCT/USg6/05496 definition is intptl~led to include gels and hybrids of silicas such as Geltates.
The RDA (Radioactive Dentin Abrasion) values are determined according to the method set forth by Hefferren, Journal of Dental Research~ July-August 1976,pp. 563-573, and described in the Wason U.S. Patent Nos. 4,340,583, 4,420,312 and 4,421,527, which publication and patents are incorporated herein by reference.
The PCR (Pellicle Cleaning Ratio) cleaning values are determined by a slightly modified version of the PCR test described in "In Vitro Removal of Stain With Dentifrice", G. K. Stookey, T.A. Burkhard and B. R. Schemerhorn, J. Dental Research, 61, 1236-9, 1982. Cleaning is ~sessed in vitro by use of the modified o pellicle cleaning ratio test. This test is identical to that described by Stookey et al.
with the following modifications: (1) a clear artificial pellicle film is applied to bovine chips prior to application of the stained film, (2) solution heating is used rather than radiative heating during film application, (3) the number of brush strokes is reduced to 200 strokes and (4) the slurry concentration is I part dentifrice to 3 parts water.
In the present specification, oil absorption is measured using the ASTM rub-out method D281. Surface area is determined by the BET nitrogen adsorption method of Brunaur et al., J. Am. Chem. Soc.~ 60, 309 (1938). To measure brightn.oss, fine powder materials that are pressed into a smooth surfaced pellet are evaluated using a Technidyne Brightimeter S-S/BC. This instrument has a dual beam optical system where the sample is illuminated at a angle of 45~, and the reflected light viewed at 0~. It conforms to TAPPI test methods T452 and T646, and ASTM
Standard D985. A series of filters direct to reflected light of desired wavelengths to a photocell where it is converted to an output voltage. This signal is amplified and then processed by an internal microcomputer for display and printout.
The average particle size (mean value and median or 50%) is measured using a Microtrac II apparatus, Leeds and Northrup. Specifically, a laser beam is projected through a transparent cell which contains a stream of moving particles suspended in a liquid. Lights rays which strike the particles are scattered through angles which are inversely proportional to their sizes. The photodetector array measures the quantity of light at several predetermined angles. Electrical signals proportional to themeasured light flux values are then processed by a microcomputer system to form a multi-channel histogram of the particle size distribution.
The pore volumes (mercury pore volume) are determined using an Autopore II 9220 Porosimeter (Micromeritics Corporation). This instrument measures the void volume and pore size distribution of various materials. Mercury is forced into the voids as a function of pressure and the volume of mercury intruded per gram of sample is calculated at each pressure setting. Total pore volume expressed herein CA 0222010~ 1997-10~31 WO 96t34592 PCT/U~96/OS496 rel)rese..l~ the cum~ tive volume of mercury intruded at pressures from v~cuum to ~iO,000 psi. Increments in volume (cc/g) at each pressure setting are plotted against the pore radius corresponding to the pressure setting increments. The pleak in the i~ltruded volume versus pore radius curve corresponds to the mode in the pore size 5 distribution. It identifies the most common pore size in the sample.
Bulk density is measured by measuring the volume in liters occupiecl by a ~;ven weight ofthe abrasive and is reported in pounds per cubic foot.
The silicas can be further characterized using a Einlehner At-1000 .~brader to measure the softness of the silicas in the following manner: A Fourdrinier wire screen is weighed and exposed to the action of a 10% aqueous silica suspem~,ion for a certain length of time. The amount of abrasion is then determined as rnilligrams~eight lost of the Fourdrinier wire screen per 100,000 revolutions Brass E inlehner (lBE) results are expressed in milligrams.
The silicas preferably possess a BE of less than about 7 and preferably 5 between 2 and 5.
These precipitated silicas are prepared by a. fresh water acidulation process ~rherein silica (silicon dioxide or SiO2) is precipitated by reaction of an alkali metal silicate and a mineral acid in aqueous solution. The alkali metal silicate rnay be any alka.li metal silicate, but sodium silicate is plt;felled. While any mineral acicl may be 20 used in the process, sulfuric acid is a prefe"~d reactant.
It is a feature of the invention that the process of preparation is a *esh waterpirocess, that is, no electrolyte such as alum, Na2SO4, or NaCI, is present dllring the reaction.
In the p,~felled process, an aqueous sodium silicate solution is provided 25 wherein the sodium silicate is present in a concentration of about 8.0 to 3S weight percent, preferably 8.0 to 15 weight percent. The Na2O:SiO2 ratio in the silicate solution should range from about I to 3.5:1 and preferably from 2.5 to 3.4:1. The sulfi~ric acid reactant will preferably have a concentration of about 6 to 35~~, in water, pre~erably about 9.0 to 15 weight percent.
In the pl~fel-ed procedure, a small portion of the sodium silicate solution is charged to a reactor for reaction with the sulfuric acid and the remaincler of the silic,ate. In the p- efel, ed embodiment, only about 1 to 5% of the total stoic:hiornetric amount of sodium silicate solution, preferably about 2%, should be initially placed in thie reactor to serve as initiating nuclei for the silica. This aqueous solution of sodium silicate is then preheated to a temperature in the range of about 80 to 90~C with agitation prior to the addition of the sulfuric acid and rern~inder of sodiurn silicate.
Agitation may be provided by conventional stirring of agitation equipment.

CA 0222010~ 1997-10-31 Thereafter with continued agitation, the remainder of the sodium silicate and sulfuric acid are separately slowly added to the reactor over a limited period of time. In the ple~.l~:d embodiment, the sodium silicate is metered into the reaction mixture at the rate of about 7 to 12 liters per minute and, more preferably, at the specific rate of 8.94 liters per minute. The sulfuric acid is metered into the reactor at the rate of about 1 to 4 liters per minute but more preferably at the rate of about 2.95 liters per minute.
The sodium silicate solution and sulfuric acid are metered into the sodium silicate solution in the reactor over an addition time of about 40 to 60 minutes, but 0 prc~relably over a 50 minute addition time. At the end of this addition time at which point the silica has precipitated, the sodium silicate solution addition is stopped but sulfilric acid addition is continued with agitation until a final pH of 5.0 to 5.8 is obtained in the reactor. At this stage, the silica has precipitated to provide a mixture of the precipitated silica and the reaction liquor.
After precipitation of the silica and lowering of the pH of the mixture, the reaction mixture is then subjected to digestion and curing. Digestion is carried out by raising the temperature of the mixture to a temperature of 90~ to 98~C, preferably about 95~ to 98~C, with continued agitation, over a residence time of about 5 minllte~S to an hour preferably about 10 to 30 minutes.
Thereafter, the product is cured by further raising the temperature of the mixture to a temperature in the range of about 100~C with continued agitation so as to boil the reaction mixture over a cure time of about one-half hour to about two hours, preferably about 30 minlltes to 80 minutec, more preferably about 1 hour.Digestion and curing procedures are critical features of the invention.
2s On completion of the reaction, the pH is again adjusted to about 5.0, and reaction mixture is filtered and washed with water to remove salts from the filter cake. The filter cake is then dried, preferably by conventional spray drying to produce a precipitated silica containing about 3 to 10% moisture. If necessary, the plecipilaled silica may be milled to desired particle size by adjusting milling 30 conditions. Because of the uniqueness of the process, milling conditions are easily adjusted to produce silica particles of desired mean values.
Preferred precipitated silica materials include those available from the J.M.
Huber Corporation under the tradename, "Zeodent", particularly the silica carrying the designation "Zeodent 128".
Precipitated silica suspensions are prepared in accordance with general methods described, for example, in prior U.S. Patents: 3.893~840, issued July 8,1975, to Wason; 3~988~162~ issued October 26, 1976, to Wason, 4~067.746, issued CA 0222010~ 1997-10-31 J~muary 10, 1978, to Wason; and 4~340.583. issued July 29, 1982, to Wason; all of which are herein incorporated by reference, varying reaction parameters to form pleci,~ ated silicas having BE values in the range of from about 1.5 mg to about 6.0 mg and PE values in the range of about 4 mg to about 12 mg, an RDA ranging from about 25 to about 90, and an oil absorption of from about 95mUlOOgm to about 1 151nl/lOOgm. Reaction parameters which affect the characteristics of the reslllt~nt si].ica include: the rate at which the various rea~t~nt.c are added; the levels of concentration of the various reactants; the reaction pH; the reaction temper,ature or the rate at which electrolytes are added. The formed suspension is subsequently o filtered, followed by a washing and drying of the filtered precipitate. The resl-lting precipitated silica is next milled to a particle size in which 70% of the partLcle size distribution is below 20 microns.
In a separate process, gel silicas are prepared in accordance with general me,thods described, for example, in prior U.S. Patents: 4~153.680. to Seybert, issued May 8, 1979; 4.303.641. to DeWolfII et al., issued December 1,1981 and 4.632.826.
to Ploger et al., issued December 30, 1986, varying reaction parameters to forrn gel silicas having BE values in the range of from about 3 mg to about 1~ mg and PE
values in the range of 8 mg to about 20 mg, an RDA ranging from about 80 to about 2CO, and an oil absorption offrom about 130ml/100gm to about 60ml/100gm. ~Once 20 folrmed, the gel silica is milled to a particle size in which 70% of the particle size distri,bution is below 20 microns.
The precipitated and gel silicas, next, are combined (e.g., by physical mixing) to form the amorphous silica compositions of the present invention. The n~slllt~nt amorphous silica composition can then be incorporated into suitable dentifrice 2s compositions.
In addition to the above described essenti~l components, the dentifrice compositions of the present invention can contain a variety of optional de:ntifrice redients some of which are described below. Optional ingredients incl~lde, for ex;ample, but are not limited to, adhesives, sudsing agents, flavoring ag~ents, 30 sweetening agents, additional antiplaque agents, abrasives, and colorin~; agents.
These and other optional components are further described in U. S . Patent 5.004.597~ April 2, 1991 to Majeti; U.S. Patent 4.885.155. December 5, 1989 to Parran, Jr. et al.; U.S. Patent 3.959.458. May 25, 1976 to Agricola et al. .mld U.S.
Patent 3.937.807. February 10, 1976 to Haefele, all being incorporated herein by35 reference.
The Pellicle Cleaning Ratio (PCR) of the inventive silica composition, which is a measurement of the cleaning characteristics of a dentifrice, ranges from 90 to 135 and preferably from 100 to 130 for the amorphous silica combination of the invention. The Radioactive Dentin Abrasion (RDA) of the inventive silicas, which is a measurement of the abrasiveness of the precipitated silica combination when incorporated into a dentifrice, ranges from 60 to 10, preferably from 80 to 90.
The amorphous silica combinations of the present invention, when incorporated into a dentifrice composition further provide an improved PCR/RDA
ritio. The PCR/RDA ratio is used to determine the relative ratio of cleaning andabrasion characteristics of a dentifrice formulation. Commercially available dentifrice formulations generally have a PCR/RDA ratio in the range of 0.5 to below 1Ø The amorphous silicas used in the compositions of the present invention provide PCR to RDA ratios to dentifrice formulations of greater than 1, usually in the range of 1.20 to 1.60, but more preferably in the range 1.25 to 1.50.
The abrasive, in the form of a precipitated silica and gel silica compositions of the present invention, when incorporated into the compositions described herein, is present at a level of from about 6% to about 70%, preferably from about 15% to about 35% when the dentifrice is a toothpaste. Higher levels, as high as 95%, may be used if the composition is a toothpowder.
The abrasive in the compositions described herein is present at a level of from about 6% to about 70%, preferably from about 15% to about 35% when the denti-frice is a toothpaste. Higher levels, as high as 95%, may be used if the composition is a toothpowder.
In addition to the above described essential components, the embodiments of this invention can contain a variety of optional dentifrice ingredients some of which are described below. Optional ingredients include, for example, but are not limited 2s to, adhesives, sudsing agents, flavoring agents, sweetening agents, additional anti-plaque agents, abrasives, and coloring agents. These and other optional components are further described in U.S. Patent No. 5~004.597, April 2, 1991 to Majeti; U.S.
Patent No. 4.885.155~ December 5, 1989 to Parran, Jr. et al.; U.S. Patent No.

3.959~458. May 25, 1976 to Agricola et al. and U.S. Patent No. 3 937.807. February 10, 1976 to Haefele, all being incorporated herein by reference.
PHARMACEUTICALLY ACCEPTABLE CARRIER
The carrier for the components of the present compositions can be any dentifrice vehicle suitable for use in the oral cavity. Such carriers include the usual components of toothpastes, tooth powders, prophylaxis pastes, lozenges, gums andthe like and are more fully described hereinafter. Toothpastes are the pl~felledsystems.
Surfactants:

CA 0222010~ 1997-10-31 WO 96134592 PCT/U~;96/0~;496 One of the preferred optional agents of the present invention is a sulfactant, preferably one selected from the group consisting of sarcosinate surf~ct~nts7 isethionate surf"ct~nt~ and taurate surfactants. Preferred for use herein are alkali m,etal or ammonium salts of these surfactants. Most preferred herein are the sodium 5and potassium salts of the following: lauroyl sarcosinate, myristoyl salrcosi~iate, palmitoyl sarcosinate, stearoyl sarcosinate and oleoyl sarcosinate.
This surfactant can be present in the compositions of the present in.vention from about 0.1% to about 2.5%, preferably from about 0.3% to about i'.'j% and most preferably from about 0.5% to about 2.0% by weight ofthe total compos,ition.
0Other suitable compatible surfactants can optionally be used along v,~ith the sarcosinate surfactant in the compositions of the present invention. Suitable optional su~ ct~ntc are described more fully in U.S. Patent 3.959.458~ May 25, 1976 to A~,ricola et al.; U.S. Patent 3.937.807, February 10, 1976 to Haefele; and U.S. Patent 4~()51,234~ September 27, 1988 to Gieske et al. These patents are incorpolated 15herein by reference.
Preferred anionic surfactants useful herein include the water-soluble salts of al-kyli sulfates having from 10 to 18 carbon atoms in the alkyl radical and the water-soluble salts of sulfonated monoglycerides of fatty acids having from 10 tO 18 carbon atoms. Sodium lauryl sulfate and sodium coconut monoglyceride sulfonates are 20examples of anionic surf~ct~ntc of this type. Mixtures of anionic surfact~,nt.c can also be Ut;1i7.o~
~rerell~zi ca~ionic surf~ct~nte usefui in the present invention can be broadry defined as derivatives of aliphatic quaternary ammonium compounds having orle long alkyl chain cont~ining from about 8 to 18 carbon atoms such as lauryl trimethylam-25monhlm chloride; cetyl pyridinium chloride; cetyl trimethylammonium bromide; di-is-obutylphenoxyethyl-dimethylbenzylammonium chloride; coconut alkyltrimethylam-monium nitrite; cetyl pyridinium fluoride; etc. Preferred compounds are the quater-nary ammonium fluorides described in U.S. Patent 3.535.421. October 20, 15~70, to Briner et al., herein incorporated by reference, where said quaternary ammlonium30fluorides have detergent properties. Certain cationic surf~ct~nts can also act as germicides in the compositions disclosed herein. Cationic surfactants such as chlor-hexadine, although suitable for use in the current invention, are not preferred due to theiir capacity to stain the oral cavity's hard tissues. Persons skilled in the art are aware of this possibility and should incorporate cationic surfactants only v~ h this O 35limi.tation in mind.
Preferred nonionic surfactants that can be used in the compositions of the present invention can be broadly defined as compounds produced by the condensa-CA 0222010~ 1997-10-31 tion of alkylene oxide groups (hydrophilic in nature) with an organic hydrophobic compound which may be aliphatic or alkylaromatic in nature. Examples of suitablenonionic surf~ct~ntc include the Pluronics, polyethylene oxide condensates of alkyl phenols, products derived from the condensation of ethylene oxide with the reaction product of propylene oxide and ethylene diamine, ethylene oxide conden~es of aliphatic alcohols, long chain tertiary amine oxides, long chain tertiary phosphine oxides, long chain dialkyl sulfoxides and mixtures of such materials.
Plefe.led zwitterionic synthetic surfactants useful in the present invention canbe broadly described as derivatives of aliphatic quaternary ammonium, phos-lo phomium, and sulfonium compounds, in which the aliphatic radicals can be straight chain or branched, and wherein one of the aliphatic substituents contains from about 8 to 18 carbon atoms and one contains an anionic water-solubilizing group, e.g.,carboxy, sulfonate, sulfate, phosphate or phosphonate.
Preferred betaine surfactants are disclosed in U.S. Patent 5,180,577 to Polefka et al., issued January 19, 1993. Typical alkyl dimethyl betaines include decyl betaine or 2-(N-decyl-N,N-dimethylammonio) acetate, coco betaine or 2-(N-coc-N, N-dimethyl ammonio) acetate, myristyl betaine, palmityl betaine, lauryl betaine, cetyl betaine, cetyl betaine, stearyl betaine, etc. The amidobetaines are exemplified by cocoamidoethyl betaine, cocoamidopropyl betaine, lauramidopropyl betaine and the20 like. The betaines of choice are preferably the cocoamidopropyl betaine and, more preferably, the lauramido propyl betaine.
Chelating agents:
Another preferred optional agent is a chelating agent selected from the group consisting of tartaric acid and pharrn~ceutically-acceptable salts thereof, citric acid 25 and alkali metal citrates and mixtures thereof. Chelating agents are able to complex calcium found in the cell walls of the bacteria. Chelating agents can also disrupt plaque by removing calcium from the calcium bridges which help hold this biomassintact. However, it is possible to use a chelating agent which has an affinity for c~ ium that is too high. This results in tooth demineralization and is contrary to the 30 objects and intentions of the present invention.
Sodium and potassium citrate are the preferred alkali metal citrates, with sodium citrate being the most prefe"ed. Also preferred is a citric acid/alkali metal citrate combination. Preferred herein are alkali metal salts of tartaric acid. Most preferred for use herein are disodium tartrate, dipotassium tartrate, sodium potassium 35 tartrate, sodium hydrogen tartrate and potassium hydrogen tartrate. The amounts of ~.hel~ting agent suitable for use in the present invention are about 0.1% to about 2.5%, preferably from about 0.5% to about 2.5% and more preferably from about CA 0222010~ 1997-10~31 WO 96/34592 PCT/US!~6/05496 l.0~/o to about 2.5%. The tartaric acid salt chelating agent can be used alone or in co~ inaLion with other optional chelating agents.
Other optional chelating agents can be used. Preferably these chel~tin~ agents have a calcium binding constant of about 10 1 to 105 provide improved cleaning with 5 reduced plaque and calculus formation.
Another group of agents suitable for use as chelating agents in the present irlvention are the soluble pyrophosphates. The yyrophosphate salts useld i.n thepresent compositions can be any of the alkali metal pyrophosphate salts. Specific s~lts include tetra alkali metal pyrophosphate, diallcali metal diacid pyrophosphate, - 10 trialkali metal monoacid pyrophosphate and mixtures thereof, wherein the alkali metals are preferably sodium or potassium. The salts are useful in both l:heir hy-dlrated and uinhydrated forms. An effective amount of pyrophosphate salt useful in the present composition is generally enough to provide at least 1.0% pyrolphosphate ion, preferably from about 1.5% to about 6%, more preferably from about 3.5% to abollt 6% of such ions. It is to be appreciated that the level of pyrophosphate ions is th.at capable of being provided to the composition (i.e., the theoretical amount at an a~)plol"iate pH) and that pyrophosphate forms other than P207-4 (e.g., (HP207-3)) may be present when a final product pH is established.
The pyrophosphate salts are described in more detail in Kirk & Othmer, l_ncv-clopedia of Chemical Technolo~2y. Second Edition, Volume 15, Interscience Publish-ers (1968), incorporated herein by reference.
Still another possible group of chelating agents suitable for use in the presentinverltion are the anionic polymeric polycarboxylates. Such materials are welll hlown in the art, being employed in the form of their free acids or partially or preferably fully neutralized water soluble alkali metal (e.g. potassium and preferably sodiuîn) or an~onium salts. Preferred are 1:4 to 4:1 copolymers of maleic anhydride or acid w~lth another polymerizable ethylenically unsaturated monomer, preferably methylvi]1yl ether (methoxyethylene) having a molecular weight (M.W.) of about i0,000 to about 1,000,000. These copolymers are available fi~r example as Gantrez AN 139 (~I.W. 500,000), AN 119 (M.W. 250,000) and preferably S-97 Pharmacelltical Grade (M.W. 70,000), of GAF Chemicals Corporation.
Other operative polymeric polycarboxylates include those such as the 1:1 copolymers of maleic anhydride with ethyl acrylate, hydroxyethyl methacrylate, N-vi-nyl-2-pyrollidone, or ethylene, the latter being available for example as Monsanto E~ No. 1103, M.W. 10,000 and EMA Grade 61, and 1:1 copolymers of acrylic acid with methyl or hydroxyethyl methacrylate, methyl or ethyl acrylate, isobutyl vinyl ether or N-vinyl-2-pyrrolidone.

CA 0222010~ 1997-10-31 WO 96134592 PCTrUS96/OS496 Additional operative polymeric polycarboxylates are disclosed in U.S. Patent 4.138.477, February 6, 1979 to Gaffar and U.S. Patent 4~183.914. January 15,1980to Gaffar et al. both patents are incorporated herein by reference, and include co-polyrners of maleic anhydride with styrene, isobutylene or ethyl vinyl ether, poly-s acrylic, polyitaconic and polymaleic acids, and sulfoacrylic oligomers of M.W. as lowas 1,000 available as Uniroyal ND-2.
Flavoring agents can also be added to dentifrice compositions. Suitable flavor-ing agents include oil of wintergreen, oil of peppermint, oil of spearmint, oil of sassafras, and oil of clove. Sweetening agents which can be used include aspartame, 10 ~ce.~l-lf~me7 saccharin, dextrose, levulose and sodium cyclamate. Flavoring and sweetçning agents are generally used in dentifrices at levels of from about 0.005% to about 2% by weight.
Dentifrice compositions can also contain emulsifying agents. Suitable emulsifying agents are those which are reasonably stable and foam throughout a wide 15 pH range, including non-soap anionic, nonionic, cationic, zwitterionic and amphoteric organic synthetic detergents. Many of these suitable surfactants are disclosed by Gieske et al, in U.S. Patent No. 4,051,234, September 27,1977, incorporated herein by reference.
It is common to have an additional water-soluble fluoride compound present in 20 dentifrices and other oral compositions in an amount sufficient to give a fluoride ion concenL~alion in the composition at 25~C, and/or when it is used of from about 0.0025% to about 5.0% by weight, preferably from about 0 005% to about 2.0% by weight, to provide additional anticaries effectiveness. A wide variety of fluoride ion-yielding materials can be employed as sources of soluble fluoride in the present25 compositions. Examples of suitable fluoride ion-yielding materials are found in U.S.
Patent No. 3.535~421, October 20, 1970 to Briner et al. and U.S. Patent No.
3~678~154, July 18, 1972 to Widder et al., both being incorporated herein by refer-ence. Re~.ese"1ali~e fluoride ion sources include: stannous fluoride, sodium fluo-ride, potassium fluoride, sodium monofluorophosphate and many others. Stannous 30 fluoride and sodium fluoride are particularly preferred, as well as mixtures thereof.
Water is also present in the toothpastes of this invention. Water employed in the preparation of commercially suitable toothpastes should preferably be deionized and free of organic impurities. Water generally comprises from about 10% to 50%,preferably from about 20% to 40%, by weight of the toothpaste compositions herein.
35 These amounts of water include the free water which is added plus that which is introduced with other materials such as with sorbitol.
In prepa~ g toothpastes, it is necessary to add some thickening material to CA 0222010~ 1997-10-31 WO 96134592 PCTAU'~.96/05496 provide a desirable conci~tenry. Preferred thickening agents are carboxyvinyl polymers, carrageenan, hydroxethyl cellulose and water soluble salts of cellulose ethers such as sodium carboxymethyl cellulose and sodium carboxymethyl hy-droxethyl cellulose. Natural gums such as gum karaya, xanthan gun, gum arabic, and S gum tr~ e~nth can also be used. Thickening agents in an amount from 0.5% to 5.()% by weight ofthe total composition can be used.
It is also desirable to include some humectant material in a toothpaste to keep it from hardening. Suitable humectants include glycerin, sorbitol, and other. edible polyhydric alcohols at a level of from about 15% to about 70%.
0 Also desirable for inclusion in the compositions of the present invention are other staMous salts such as stannous pyrophosphate and stannous gluconate and antimicrobials such as quaternary ammonium salts, such as cetyl pyridinium c;hloride and tetradecylethyl pyridinium chloride, bis-biquanide salts, copper bisgrlycinate, no:nionic anti microbial salts and flavor oils. Such agents are disclosed in U.,S. Patent 15 No. 2,946,725, July 26, 1960, to Norris et al. and U.S. Patent No. 4,051,234,September 27, 1977 to Gieske et al., incorporated herein by reference. Other optional components include buffering agents, bicarbonates, peroxides, nitrate salts such as sodium and potassium nitrate. These agents, if present, are included at levels of from about 0.01% to about 30%.
Other useful carriers include biphasic dentifrice formulations such as those disclosed in U.S. Patents 5,213,790, issued May 23, 1993, 5,145,666, issued September 8, 1992, and 5,281,410 issued January 25, 1994 all to Lukacovic et al.and in U. S. Patents 4,849,213 and 4,528,180 to Schaeffer the disclosures of which are incorporated by reference herein.
Suitable lozenge and chewing gum components are disclosed in U.S. Patent No. 4,083,955, April 11, 1978 to Grabenctettçr et al., incorporated herein by refer-enc:e.
The following examples further describe and demonstrate preferred embodi-memts; within the scope of the present invention. The examples are given solely for 30 illustration and are not to be construed as limitations of this invention as many variations are possible without departing from the spirit and scope thereof.
EXAMPLES
The following examples further describe and demonstrate preferred em-boclirnents within the scope of the present invention. The examples are given solely 35 for illustration, and are not to be construed as limitation of this invention as many variations thereof are possible without departing from its spirit and scope.
Example I

CA 0222010~ 1997-10-31 A dentifrice composition of the present invention contains the following com-ponents as described below.
Component Wgt %
Sorbitol 70% soln 24.200 s RO Water 24.757 Glycerin 7.000 Carboxymethyl Cellulose1 o.SoO
PEG 6 4.000 Sodium Fluoride 0.243 lo Sodium Saccharine 0.130 Monosodium Phosphate 0.415 Trisodium Phosphate 0.395 Sodium Tartrate 1.000 TiO2 0.500 Silica2 35 000 Sodium Lauroyl Sarcosinate (95% active) 1.060 Flavor 0.800 1 Supplied by Aqualon Company.
2The amorphous silica ingredient possesses the following characteristics: APS Mean Value= 8.3microns; oil absorption = 108cc/lOOg; BE = 2.6; PE = 9; PCR = 118;
RDA= 80.
The jacket temperature of a mixing tank is set to about 150~F (65~C) to about 160~F (71~C). The humectants and water are added to the mixing tank and agitation is started. When the temperature reaches approximately 120~F (50~C) fluoride, sweetening agents, buffering agents, chelant, coloring agents and tit~ninm dioxide are added. Thickening agents are added to the abrasive and the res~-ltin~
mixture is added to the mixing tank with high agitation. The surfactant is added to the combination and mixing is contin~ed The tank is cooled to 120~F (50~C) and the flavoring agents are added. Mixing is continued for approxil"dLely S minlltes The reclllting composition will have a pH of about 7.
Example II
A dentifrice composition of the present invention contains the following com-ponents as described below.
Component Wgt %
Sorbitol 70% soln 29.810 RO Water 24.757 Glycerin 7.000 WO 96~34592 PCT/US96105496 Carboxymethyl Cellulosel 0.750 PEG 6 4 ooo Sodium Fluoride 0.243 Sodium Saccharine 0.130 Monosodium Phosphate 0.415 Trisodium Phosphate 0.395 TiO2 0.500 Silica2 30 000 Sodium Lauryl Sulfate 1.200 lo Flavor 0. 800 1 S,upplied by Aqualon Company.
2T:he amorphous silica ingredient possesses the following characteristics~ , Mean Value= 8.3 microns; oil absorption = 108cc/lOOg; BE = 2.6; PE = 9; PCR = 118;
RDIA= 80.
Example III
A gum composition of the present invention contains the following com-ponerlts as described below.
Component Wei~ht %
Gum Base 30.000 30 parts Estergum 45 parts Coumorone Resin 15 parts Dry Latex Silical I~ ~~
Sugar 40.000 Corn Syrup 18.175 Sodium Lauroyl Sarcosinate O . 075 Sodium Tartrate 0.250 Flavor 1.500 lThe amorphous silica ingredient possesses the following characteristics. APS Mean Value= 8.2 microns; oil absorption = 106 cc/lOOg; BE = 3.3; PE = 10.

Claims (10)

WHAT IS CLAIMED IS:

1. An amorphous silica abrasive composition comprising:
a. a precipitated silica, said precipitated silica being a low structure precipitated silica having a narrow particle size range distribution of soft particles and having a mean value (MV) particle size ranging from 8 to 14 microns, an oil absorption ranging from 60 to 120 cc/100g, and a mercury intrusion (HGI) void volume of 1.0 to 4.0 cc/g;
said precipitated silica, when formulated into a dentifrice, having a Pellicle Cleaning Ratio (PCR) of from 70 to 140 and a Radioactive Dentin Abrasion (RDA) value of from 60 to 130;
and wherein the ratio of said PCR to said RDA is at least 1.1;
and wherein, as the particle size in microns increases in said silica, the RDA value remains substantially constant; and a gel silica comprising particles, preferably having:
i.) a mean particle size of from 5 to 11 microns (s.d. < 9);
ii.) an Einlehner hardness of from 3 to 15 for abrasive to brass screen and from 8 to 20 for abrasive to polyester screen;
iii.) an oil absorption of from 60 ml/100 gm to 130 ml/100 gm;
and iv.) a radioactive dentin abrasion of from 80 to 200 wherein at least 70% of all of said particles have a diameter of below 25 microns and wherein the pellicle cleaning ratio is from 90 to 135 and the radioactive dentin abrasion is from 60 to 100 with a pellicle cleaning ratio/radioactive dentin abrasion ratio of from 1.20 to 1.60 and wherein the ratio of precipitated silica to gel silica is from 90:10 to 60:40, respectively.

2. A dentifrice composition according to Claim 1 which further comprises a safe and effective amount of a dentifrice carrier and wherein said abrasive has an RDA, when formulated into a dentifrice formulation, ranging from 60 to 98, a BET surface area ranging from 50 to 250 m2/g, a pH of 5 percent water slurry ranging from 4.0 to 8.5 wherein said silica particles are of substantially uniform particle size with a very narrow distribution within the MV particle size of from 8 to 14 microns, and wherein smaller particles, preferably representing greater than 2%, more preferably greater than 5%, of the precipitated silica, are cohesively adhered to each other by physical binding tobe within said MV particle size.

3. A dentifrice composition according to any one of the preceding Claims, wherein said composition further comprising a fluoride ion source wherein the fluoride ion source is selected from the group consisting of sodium fluoride, stannous fluoride, sodium monofluorophosphate, potassium fluoride and mixtures thereof.

4. A dentifrice composition according to any one of the preceding Claims, which further comprises a surfactant selected from the group consisting of sarcosinate surfactants, isethionate surfactants and taurate surfactants.

5. A dentifrice composition according to any one of the preceding Claims, which further comprises from 0.1% to 2.5% of a chelating agent selected from the group consisting of tartaric acid and pharmaceutically-acceptable salts thereof, citric acid and alkali metal citrates and mixtures thereof.

6. A dentifrice composition according to any one of the preceding Claims, wherein said composition has a pH above 7 and wherein the surfactant is selected from the group consisting of sodium lauroyl sarcosinate, sodium decyl sarcosinate, sodium myristyl sarcosinate, sodium stearyl sarcosinate, sodium palmitoyl sarcosinate, sodium oleoyl sarcosinate and mixtures thereof.

7. A dentifrice composition according to any one of the preceding Claims, further comprising from 15% to 70% of a humectant selected from among the group consisting of glycerin, sorbitol, Propylene glycol and mixtures thereof.

8. A dentifrice composition according to any one of the preceding Claims, wherein the surfactant is a combination of sodium lauroyl sarcosinate and cocoamidopropyl betaine and the chelating agent is a combination of tartaric acid and sodium tartrate.

9. A dentifrice composition according to any one of the preceding Claims, in theform of a toothpaste, tooth powder, prophylaxis paste, lozenge, gum, or oral gel.

10. A process of manufacturing a dentifrice composition comprising the steps of:
a. precipitating a silica, wherein said silica is precipitated by the following steps:
i) providing an aqueous solution of sodium silicate having a concentration of 8.0 to 35 weight percent, and an Na2O:SiO2 ratio of 1 to 3.5:1;
ii) providing a sulfuric acid aqueous solution having a concentration of 6 to 35 percent;
iii) charging to a reactor 1 to 5 percent of the stoichiometric amount of said sodium silicate solution with agitation;
iv) heating said solution of said sodium silicate to a temperature in the range of 80 to 90°C;
v) slowly adding to said reactor, sulfuric acid and the remainder of said sodium silicate solution, said addition being conducted over a period of time wherein the sodium silicate is metered into the reaction mixture at the rate of 7 to 12 liters per minute and the sulfuric acid is metered into the reactor at the rate of 1 to 4 liters per minute;
vi) continuing the addition of sodium silicate and sulfuric acid to said reactor over an addition time of 40 to 60 minutes;
vii) stopping the sodium silicate solution addition but continuing the sulfuric acid solution addition with agitation until a final 1 pH of 5.0 to 5.8 is obtained in the reactor to provide a precipitated silica in the reaction liquor;
viii) raising the temperature of said reaction mixture to a temperature of 90° to 98°C for a time of 10 minutes to 1 hour while continuing agitation; and ix) curing the reaction mixture by boiling said mixture for a period of at least 30 minutes to two hours to cause formation of substantially uniform particle size precipitated silica;
x) cooling the reaction mixture and recovering the precipitated silica; and b. combining the precipitated silica of step a. with from 0.1% to 99% of an orally-acceptable dentifrice carrier.