CA1098830A - High fluoride compatibility dentifrice abrasives and compositions containing alkali earth metal treated amorphous silicon dioxide - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
Novel precipitated silicon dioxide abrasive compo-sitions which can be incorporated into therapeutic toothpaste compositions containing both soluble fluoride salts and soluble phosphate salts are disclosed. The abrasives comprise low structure precipitated silicon dioxides which have been reacted with about 10 to 300 parts per million alkaline earth metal ion, particularly calcium. Reaction with the alkaline earth metal ion minimizes abrasive interaction with the fluoride ion source in therapeutic toothpaste. Also provided are methods for preparation of the novel silicon dioxide abrasives and resulting toothpaste formulations containing such abrasives.

Description

3~
This invention relates to improved dentifrice abrasives.
More particularly, the present învention relates to novel, alkaline earth-treated, precipitated silica abrasives which are suitable for use in therapeutic toothpaste compositions contain-ing both soluble fluoride salts as enamel solubility reducing agents and soluble phosphate salts as dental pellicle film penetration agents. The invention further relates to methods for preparing these improved precipitated silica abrasives and to toothpastes containing the improved abrasives including tooth-paste embodiments which comprise both enamel solubility reducing agents (i.e. fluoride) and dental pellicle film penetration agents. Such toothpaste compositions exhibit both high fluoride compatibility and high cleaning performance.
This application is related to copending Canadian application 2a5,885 filed August 31, ~977.
The function of an abrasive substance in ~ormulations intended fox use in the oral cavity is to remove various deposits, including pellicle film, from the surface of the teeth. Pellicle film is tightly adherent and often contains brown or yellow pigments and thus imparts an unsightly appear-ance to the teeth. An advantageous toothpaste abrasive material should maximize film removal without causing undue abrasion to the hard tooth tissue. Dental researchers are continually con-cerned with developing toothpaste abrasives which demonstrate satisfactory levels of cleaning and which are not unduly abrasive and damaging to the oral tissue.

B

`. ,. . i ~ ::

In addition to abrasives, -therapeutic too-thpastes typically contain fluoride ion sources. The beneficial reduction in the in-cidence of dental caries resulting from the topical application to dental enamel surfaces of solutions containing fluoride ions is well known. Especially at solution pH's between about 4 and 8, Eluoride ions are believed to interact with enamel to reduce the acid solubility of such enamel. Enamel 50 treated with fluoride is more resistant to -the formation of den~al caries. Accordingly, therapeutic toothpaste compositions are formulated to provide fluoride ion availability in brushing solu-tions formed in the oral cavity during use.
It has been postulated that the e~fectiveness of fluoride -treatment in providing enamel antisolubility/anticariogenic bene-fits is dependent upon the amount of fluoride ion which is avail-able for uptake by the enamel bein~ treated. It is, of course, therefore desirable to formulate toothpaste compositions which provide maximum fluoride ion availability in brushing solu-tions formed therefrom. However, efforts to utilize such ionic fluoride anticariogenic agents in toothpastes suitable for home use have been unable to provide the theoretical maximum soluble fluoride because of the tendency for ionic fluoride to be inactivated and thereby rendered unavailable for enamel uptake. That is, -the tooth-pastes lose, upon storage (at rates which increase with tempera-ture), the capabili-ty of providing the theoretical ma~imum amount of soluble fluoride. E'or purposes of this invention, the "soluble fluoride" content of any given toothpaste composition refers to the ppm concentration of fluoride ion which is found in the super-natant sample centrifuged from 1:3 by weight slurry of the tooth-paste in water (1:3 = toothpaste:water).

~ ~98~3~
., Fluoride ion sources ~end to interact with toothpaste impurities and with such toothpaste componcnts as abra-sives/ bu~fers, etc. Such interaction diminishes the ~bility of the fluoride sourcé to provide "soluble fluoride"
upon use. The propensity of the toothpaste compositions herein to maintain their levels of soluble fluoride af ter storage is expressed here~na~ter as "toothpaste fluoride compatibility". Thus, the -toothpaste fluoride compatibility of a particular toothpaste composition is that percentage 10 - of the theoretical maximum amount of fluoride source that is actually measured as soluble fluoride after storage for a specified time and at a specified temperature (e~g. one week at 120F.~. Similarly, the propensity of such a den-tifrice component such as the abrasive to interact with the fluoride source to diminish the measured "soluble fluoride" level from the theoretical maximum amount of fluoride source (particularly in the presence of pellicle ; film penetration agents described in detail below~ is ~expressed as "abrasive fluoride compatibility". The test procedures used herein to determine "toothpaste fluoride compatibility" values and "abrasive fluoride compatibility"
~ .
values are described more fully hereinafter.
~;
` One toothpaste component which can pose special dif-~ .
ficulties in f~ormulating fluoride too~hpastes is a preci-pitated silica abrasive component. Precipitated silica abra-sives are desirable for use in toothpastes since they have desirably low dcntin abrasion values~ Certain prior art precipitatcd silica abrasives are ~enerally compatible with soluble ~luoride sourccs but have insufficiently hi~h , :, :;

- ~

a~rasivity to provide effective cleaninc3 performance.
Certain other prior art precipitated silica abrasives provide acceptable cleanincJ performance but llave low abra-sive fluoride compatibility as measured by the method here-inafter It is believed that no prlor art precipitated silica abrasives give both high"a~rasive fluoxide compa-tibility" as well as acceptable cleaning performance,(as indicated by s-tandard Radioactive Den~in Abrasion vaIues~
There is thus a clear need to ormulate precipi-tated silica abrasives which exhibit high "abrasive fluoride compatibi1ity" as well as acceptable cleaning performance.
According]y, it is an object of the presen-t invention to provide precipitated silica abrasives which eYhibit high "abrasive fluoride compatibility" as well as acceptable cleanlng performance.
Another dentifrice component which can be especially destructlve of soluble fluoride content in certain tooth-`: : :
paste composltions 1S soluble phosphate. Soluble phosphate salts, upon toothpaste use, serve to enhance the abili-ty , ~ :
o~ fluoride ions to penetrate dental pellicle film.
For this reason, soluble phosphate salts are deslrably included in fluoride toothpaste composi-tions. Ilo~ever, particularly in combination with silica dental abrasives, soluble ~hospha~te pellicle penetration agents tend to pro-mote loss of soluble fluoride in toothpastes containin~ these ma-terials and, thus, the toothpastes e~hibit low toothpaste fluoride coMpatibility values. Thcre is thus a clear need to formulate precipitated silica abrasives which provide high toothpaste fluoride compatibility when utilized in fluoride toothpastescontaining soluble phosphate salts as ; pellicle ~ilm pcnetra-tion agents.
..
- 5 _ 93~

There is thus a further need to provide fluoride toothpastes which can contain precipi-tated silica abrasives in combination with soluble phosphate salts. Accordingly, it is an object of the present invention to provide fluoride toothpaste compositions which contain soluble phosphate salts and precipitated silica abrasives and which nonetheless retain relatively high levels oL soluble fluoride even after periods of storaye.
It has been surprisingly discovered that the above objectives can be realized by the present invention which provides a nove~ precipitated siliaa abrasive which has been treated with an alkaline earth material, particularly cal;cium. By utilizing the instant den-tal abrasives, fluoride ; toothpastes- particularly those embodiments containiny ; 15 soluble phosphate~salts - can be realized which have high toothpaste ~fluoride compatibility and excellent cleaning performance.
: ~
; ~ It is of course well known that therapeutic tooth-~; pastecompositions contain calcium phosphate materials as ~0 abrasives~but these calcium materials are present inllarye amounts as described above and illustrated for example in U.5. Patents 3,624,199, issued November 30, 1971, Norfleet et al, and 3,864,471, issued February 4, 1975, Mills et al.
Toothpaste compgsitions are also known in the art which contain smal~ amounts of alkallne earth metal ions, such as calcium ions, and compositions of this type are illus-trated by U.S. Patent 3,991,177, issued November 9, 1976, Vidra et al. This patent discloses toothpaste compositions ~, .
~ ' .
-3~

which contain a s-tabilizer-activator for a dex-tranase enzyme agent with -the stabilizer-ac-tivator being a salt such as calciw-n chloride present in an amount of .001 -to 0.3 weight percent. rrhis composition can also contain therapeutic fluoride and the abrasive agel1t is calcium carbona-te.
Other prior art which cliscloses toothpaste cornposi~
tions containing alkaline earth me-tal compounds or ions include U.S. Patents 3,095l356, issued June 25, 1963l to Moss;
3l122l483, issued February 25l 1964, -to Rosenthal; 3,669,221, issued June 13, 1972 to Hase; 3/782/446/ issued January 1 1974l to Walter; 3,842,168, issued October lS, 1974, to Colodney; and 3,689/537/ issued September 5, 1972, to Kuder.
However, none of these prior art patents disclose thera~
peutic toothpaste compositions which contain as the abrasive agent a low structure precipitated silicon dioxide which contains about 10 to 300 par-ts per million of alkaline earth metal ion as described herein.

~''' . ~

98~3~

There is provided by the present invention a novel abrasive material for toothpaste compositions which comprises in its broadest embodiment, a precipitated silicon dioxide which is prepared from fresh water alkali metal silicate by acidulation. Such precipitated abrasives contain about 10-300 partsper million of alkaline earth metal ion, and are characteri~ed by an RDA value of at least 40, an oil absorption value of abou-t 70-95 ccs/100 gram, a pack density of about 0.24 to 0.55 grams per milliliter, a loss on ignition value of about 4 to 6% and a BET surface area of about 100 to 250 m /g, and preferably with an average particle size of about 5 to 15 microns. Also provided is a method for the preparation of the novel abrasives of this invention which in general comprises formation of a low structure precipitated silicon dioxide by the acidulation of certain fresh water sodium silicate solutions with a mineral acid and subsequent treatment of the resulting wet cake with the required amount of alkaline earth metal ions.
The present invention further relates to fluoride-containing toothpaste compositions which exhibit minimal loss of soluble fluoride upon storage at normal temperatures and which provide excellent cleaning performance. Such toothpaste ~- compositions comprise the amorphous, precipitated silica abrasives of the present invention, a source of fluoride ions, a binding agent, a humectant and water. Such toothpaste compositions provide a pH of from about 4.0 to 8.0 when slurried with water in a 3:1 water/composition weight ratio.
The amorphous, precipitated silica abrasives of the present invention comprise from about 6% to 3~ by weight of the toothpaste compositions.

-The fluoride ion source comprises from about 0.01~ to 3.0% by weight of the too thpas te compositions and can be any water-soluble material which yields fluoride ions in aqueous solution.
The binder comprises from about 0.2% to 2~ of the toothpaste composi tions .
The humectant comprises from about 3% to 55~ by weight of the toothpaste composition. The water in the toothpastes herein comprises from about 15% to 80~ by weight of composition~

::, ~f ,~
;' . . .
r ~L~3~
\

The present invention relates to novel, precipitated silicon dioxide dentifrice abrasives, methods for their preparation, and their incorporation into toothpastes to provide re~ulting compositions having excellent toothpaste fluoride compatibility values and excellent abrasivity values. The toothpaste compositions herein further essentially comprise a water-soluble fluoride ion source, a binding agent, and certain amounts of humectants and water. Each of these components as well as optional in~redients, composition use and composition preparation are described in detail as follows:
PRECIPITATED SILICA DENTAL ABRASIVE
The presen~ invention relates to low stxucture precipitated silicon dioxide materials which are suitable for use as dental abrasives. Such abrasives have ultimately associated therewith about 10 - 300 parts per million, preferably 10 - 100 parts per million, of alkaline earth metal, preferably calcium, based on the amount of recoverable dry material. This dental abrasive material is characterized further by generally having a percent abrasive fluoride compatibility in the range of at least 90%, a RDA of at least 40, perferably from about 70 to 120, a loss on ignition (hereinafter "LOI") in the range o 4 - 6~, a pack density in the range of about 0.24 to 0.55 grams per milliliter, an oil absorption in the range of about 70 - 95 cc/100 grams and a BET surface area in the range of about 100 -250 m /y with an average particle size in the range of 5 - lS
microns. When incorporated into a toothpaste, the dental abrasives herein provide high fluoride compatibility and excellent cleaning performance. The definition of low structure silicon dioxide materials is given in United States Patent No. 3,893,840, ; 30 mentioned above.

., ~; ~ . ', ~, ' : `' \
The dental abrasive materials of the present invention are precipitated silicon dioxides which are prepared by the 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; and 4,067,746 issued January 10, 1978. Abrasives produced by such methods are subsequently treated with alkaline earth metal ions in the manner described herein. In general, the process for preparation of the silicon dioxides comprises the acidulation of an aqueous alkali metal silicate solution preferably with a mineral acid to effect precipitation of silicon dioxide. The acid addition is continued to an acid pH and the resulting precipitated silicon dioxide is then removed such as by filtration, and washed to remove any by-product materials such as alkali metal sulfate, to provide a wet cake. The resulting wet cake is then reslurried in its own water or with additional water and thereafter is treated with the re-quired amount of alkaline earth metal ions in the form of a soluble salt to provide the abrasive materials of this invention.
The abrasive products of the present application are to be distinguished from the precipitated silicon dioxide composi-tions which have been treated with alkaline ear~h metal ions as disclosed in my U.S. Patent 4,159,280 issued June 26, 1979. The silicon dioxides treated with alkaline earth metals as disclosed in U.S. Patent 4,159,280 are abrasives which are useful or incorporation into toothpaste compositions so as to prevent corrosion of unlined aluminum toothpaste tubes. Such corrosion~

3~

inhibitin~ precipitated silicon dioxides as are described in U.S. Patent 4,159,280 are silicon dioxides prepared by a so called sulfate liquor method. In that me~hod, an electrolyte such as alkali metal sulfate is admixed with the alkali metal silicate liquor during acidulation with mineral acid as disclosed for example in my U.S. Patents 3,960,586 and 3,928,541. While the products of V.S. Patent 4,159,280 may be described as precipitated silicon dioxides having intimately admixed therewith an amount of alkaline earth metal ions which is within the range of that of the present invsntion, the abrasive products of the present invention have different characteristics from the silicon dioxides derived from the sulate-liquor method. The sulfate liquor silica materials, when utilized in certaln fluoride-containing toothpaste compositions, do not provide ~he superior fluoride compatibility values of the present invention. The superior fluoride compatibility values of the dental abrasives of this invention are achieved only with th~ silicon dioxides prepared from so-called fresh-water alkali metal silicate process as described herein.
The silicon dioxide abrasives of the present invention, are alkaline earth metal~treated precipitated silicon dioxides which are prepared from fresh water silicate solutions. Such a process does not make use of any electro-lyte such as sodium sulfate in preparation of the untreated precipitated silicon dioxide. Further, in the products of the present invention, it has been found that the pre-sence of alkaline earth metal ions intimately associated with the resulting silicon dioxide, must be present within a particular narrow range to provide the fluoride compati-bility necessary for use in the present invention. Thus, 3~

the abrasive products of the present invention have fluoride compatibility values of at least 90~, whereas those abrasives of the U.S. Patent 4,159,280 generally give cc,mpatibility values of 89% or below as determined by the toothpaste fluoride compatibility tests described in this application.
It is theorized that the improved fluoride compatibility of the instant dental abrasives is based on the manner in which the silanol groups therein are attached to the surface of the silicon dioxide product. Thus, in the fresh water silicate derived silicon dioxide of the present invention, the silanol groups on the surface of the material are believed to be more available than on the sulfate liquor silicate derived silicon dioxide as disclosed in my U.S. Patent 4,159,280. Further, the surface acidity of the fresh water silicon dioxides, due to the silanol groups, is higher than the corresponding acidity of the silicon dioxides derived from the sulfate liquor process.
Because the silanol groups are different in these two materials, the intrinsic surface acidity does not respond well to calcium treatment for fluoride compatibility in the sulfate liquor products. The products of U.S. Patent 4,159,280 also have higher abrasive values than the silicon dioxides of this application. Therefore, the instant abrasives are to be distinguished from the alkaline earth metal treated silicon dioxides disclosed in U.S. Patent 4,159,280.

!~
., ~

~' ' , " ~

The instant precipitated silicon dioxide abrasives are preferably prepared by charging an aqueous solution of an alkali metal silicate solution, preferably an alkali metal silicate having an SiO2 to X20 mole ratio of about 2.0 to 2.7 wherein X is an alkali metal, and most preferably a sodium silicate solution, to a reactor for acidulation. The aqueous sodium silicate solution is a fresh water solution having a sodium silicate concentration range of about 10 - 17 weight percent, and more preferably 12.5 to 15.5 weight percent, and a sodium silicate composition of Na2O-2.6 SiO2 for best results. The aqueous sodium silicate solution is then raised to a temperature of about 50 to 95C, preferably 77 to 91C, and with continuous agitation the solution is acidulated by the addition of an aqueous ~olution of a mineral acid having a concentration of about 10 - 20 weight percent at a substantially constant pH in the range of about 8.5 to 10.5.
The mineral acid is preferably sulfuric acid as sulfuric acid provides best results but as is known in the art ~See U.S.
Patents 3,988,162, 3,893,840 and 4,067,746), o~her acidulation agents such as nitric acid, phosphoric acid, hydrochloric acid, carbonic acid and the like can also be employed.
In the most preferred embodiment only a portion of the alkali metal silicate solution is charged to the reactor, brought to temperature under agitation, and the sulfuric acid and remainder of the alkali metal silicate 1,. - ' -solution simultaneously added to the initial silicatesolution at the reaction temperature. Preferably about 8 to 12 wt. % of the metal silicate is initially charged to the reactor. The remaining portion is then added with the sulfuric acid. The time period over which the alkali ~ metal silicate and sulfuric acid are added to the alkali ; metal silicate in the reactor can be predetermined and is generally based on the volume of the reactor and the difficulties in control of the temperature and agitation.
After completion of the addition of the alkali metal silicate solution, the acidulation agenb is continually adaed until the pH of the reaction slurry falls below about 6.0 and preferably to within the range of about 4.6 - 5Ø The resulting slurry is the precipitated silicon dioxide contained in the reaction medium.
After the pH of below 6.0 is reached, the slurry is then heated for a digestion period at a temperature of 10 to 30C above the reaction temperature and the reaction pH
again adjusted as necessary. The resulting slurry is then filtered and washed with additional water to remove any reaction by-product such as sodium sulfate which may be contained in the silicon dioxide product. The wet cake moisture o the resulting filter cake is in the range of about 60 - 66% and is a low structure material. The above reaction to this point is generally the same as disclosed in my prior Patents 3,893,840, 3,988,162 and 4,067,746, mentioned above, in the preparation of silicon dioxide prepared from fresh water alkali metal silicate.

3~

- In the process oE the presen~ i~vention, at the point of filtra-tion and ~ashing of the silicon dioxide wet cake, the material is then subjected to treatment with alkaline earth metal ions to produce the new abra-sive products of the present inventlon. In accordancewith the process oE the present invention, the wet washed filter cake is then reslurried in its own water or with the addition of fresh water at ambient temperature with agitation. While under agltation, this slurry is then treated with sufficient alkaline earth metal ions, pre-ferably calcium ions, in the form of a salt su~ficiently soluble to provide an amount of alkaline earth metal ions corresponding to about 10 to 300 parts per million, or .001 to .03 weight percent tbased on the weight of the dry recoverable silicon dioxide), of alkaline earth metal ions in-tirnately associated with the silicon dioxide.
, The alkaline earth metal ion added at this point ~ is preferably caIcium lon because of its readily availabil-; ity, low cost, and ease of incorporation into the silicon dioxide. The calcium ions can be incorporated into thè
silicon dioxide at this stage in any sufficiently water soluble form (ite., soluble in water to the extent of at least .07 g/100 cc H2O at 20C~) such as with solutions of calci~ nitrate,' calcium oxide, calcium hydxoxide, or calcium chloride. Lime or calcium hydroxide is preferred.
Also, solutions of oryanic salts such as calcium acetate, calcium formate, and the like can also be used. The cor-responding strontium and magnesium salts of the alkaline earth class can also be used. Food yrade sal~s should be used.

~i ~b'9 ~ ~3~

, ~
A:~ter t~eatmcnt wil~ll the al]:-lline earth met~l ion, '~ -. ~
the cake slurr~, is th~n ayitated vicJorously for 10-20 minut~s, preferably 15 minutes, -to provide the effective .
level o~ alkaline earth metal for treatment on~o the sur-ace Orc the silicon dio~ide abrasi~re. The resulting pro- ,~
duc~. is then cl.ried. Preferably dr~ing ls conduc-ted in a spray clryer at an inlet temperature o~ ~83C. and outlet temperature o~ 122C. as known :i.n ~he art, and sub.sequenl:ly milled to the desirecl dec;ree oE ~ineness.
TOOTHPP~S'rl'".S
Also provicled by the present. inven-tion-herein are therapeutic toothpastes containiny the instan-t novel precipitated sili.ca abrasives. In acldition to the instant abrasives, the toothpaste compositiolls o~ the present invention ~urther cornprise certain amounts o a ~ater-soluble fluori.de ion source, a hindi.ng acJent, a humectant and water. Each oE these adcliti.onal toothpaste components as well as optional toothpaste components are described in detai,l as ~ollows:
A. A ~
.. As indicated above, the instant precipitat_d silica abrasives are particularly suitable or incorporalion into fluoride-contai.nincJ therapeutic toothp,3s.te compositions.
Therapeutic toothpastes employin~J such abrasives provide satisactory tooth.cl.eaning perormarlc:e and also possess excellent abrasi.ve 1uoride compati.bll.i.t~ characteristics.
The instarlt toothpaste composi~ic)ns esc-,entially contain from about 6o to 35 %, preferahly from about 10% to 2.0~O/
by ~eight o~ -the, i.nstant preci.pi.tated silica abrasi,ves.

~ ' ' .

~ - ~.7 --3~

B. Fluoride IOII Source The instank therapeutic toothpaste compositions further contain from about 0.01% to 3%l preferably from about 0.1% to l.Q~, by weight of a water-soluble, fluorine-containing material which yields fluoride ions in aqueous solutions. Such fluoride ions combine with dental enamel and thereby reduce enamel solubility in acid. Application of fluoride ions to dental enamel serves to protect teeth against decay.
A wide variety of fluoride ion-yielding materials can be employed as souxces of soluble fluoride in the instant composi-tions. Examples of suitable fiuoride ion-yielding materials are found in Briner et al; U.S. Patent 3,535,421; issued October 20, 1970 and Widder et al; U.S. Patent 3,678,154; issued July 18~ 1972. Preferred fluoride ion sources for use herein include sodium fluoride (NaF), stannous fluoride (SnF2), potassium fluoride (KF), potassium stannous fluoride (SnF2-KF), indium fluoride (InF3), zinc fluoride (ZnF2), ammonium fluoride (NH4F), and stannous chlorofluoride ~SnClF). Sodium fluoride and stannous fluoride are particularly preferred as well as mixtures thereof.
Preerably the instant toothpaste compositions provide from about 50 ppm to 500 ppm, more preferably from about 100 to 400 ppm, of fluoride ions in the aqueous solutions which contact dental surfaces when the toothpastes o the present invention are used in the mouth. As described more fully hereinafter, such solutions are simulated by preparing 3:1 water/toothpaste slurries ~by weight) of the toothpaste compositions herein and by subsequently centrifuging such slurries to obtain an aqu~ous supernatant. The fluoride ion concentration in such a supernatant is taken as a measure of the "soluble fluoride" provided by any given fluoride tooth-paste composition.

'~''3 3~

C. Binder __ A binder is essentially employcd to prevent separ-ation of the liquid and solid phases in tlle toothpaste compositions herein. Such binder materials ~re well known in the toothpaste art. The most conventiollally used bin-ders are the seaweed colloids such as Caxrageenan (Irish moss or Viscarin ~ and derivatives of cellulose, such as sodium carboxymethyl cellulose and hydroxyethyl cellu~
lose. Another type of binder which is suitable for use herein is gums such as 1) vegetable gums, e~g., guar gums and

2) fermentation products e.g., xanthan ~-~. The binder component generally comprises from about 0.1% to 5~, pre-ferably 0.2%to 2% by weight of the toothpaste compositions he~ein. Since the natural and synthetic tlater dispersions of water binders are subject to microbial or mold attack, the toothpastes herein can optionally contain a relatively s~all amount of a preservativ~. Examples of preservatives typically employed are the esters of parahydroxyl benzoates.
Toothpaste binders are more fully described in }lager et al, U.S. Pa~ent 2,839,448, issued ~une 17, 1958;
and DiGiulio, 3,862,307, issued January ~1, 1975.

D~ ~lumectant Another essential component of the toothpaste com-positions here1h is a humectant. Suitable humectant ma-terials are also well known in the toothpaste art. The humectant ~erves to retain moisturç and thereby to keep ~le toothpaste compositions ~rom hardening upon exposure to air~ Cert2in humectants ~an also impart desirable sweetness or flavor to toothpaste composi-tions. The humec-tant generally comprises from about 5% to 55~, ~referably ~rom about 20~ to 36~, by weight of the tootllpaste compo ions herein. - 19

3~D

~uitable humec~ants for use in this invention in-~lude edible polyhydric alcohols such as qlycerine, sor-bitol, xylitol and propylene glycol~ Sorbitol i5 fre-~uently employed as a 70~ a~ueous solution known as ~orb~ ~0 Mixtures of glycerine and sorbitol are espe-cially preferred as th~ humectant component o the tooth-pa~te co~positions herein~
E~ Wa~er __ .
Wat~r is another essential element o the ooth~
pastes o~ thi~ invention. Water employed in the prepar-ation o~ commercially sui~able ~oothpastes ~hould be deionized and free o organic impurities. Water comprises ~ro~n about 1596 to 80%, pre~erably from about 15% to ~0%, by weight of thb toothpaste compositions herein.
Y. O~
In addition to the above described essential com~
ponents, the toothp~stes of this invention can contain , ~ariety of optional conventional toothpa~te ingredients.
Such optional inyredie~ts include (1) sudsing agents, ~o : ~2~ pellicle film penetration agents, ~3) 1avoring and sweetening agents, (4) anticalculus, antiplaque agen~s, and ~S) pigments and coloring agents.
1 ) Suds~
A preferred optional ingredient is a sudsing agcnt, Suitable sudsing agents are those which are rioason~bl.y stable and form suds throughout a widc p~l range , i . e ., non-soap anionic, nonionic ~ cationic t zwitterionic anc~
amphoteric organic synthetic detergents~ Sudsing ~gcnts of thcse t:ypes are described more fully in ~grico~ a ct al;
U.S. Pat~nt 3,95~,4587 issued ~ay 25, 1976 and in ll~efcle;
lJ.S. raten~ 3?~37~ 807; 1ssucd Fcbruary 10, 1976, ~ 20 -~ 3 ~

Anionic sudsing agents useful herei~ include the water-soluble salts of alkyl sulfates having from 8 ~o 18 carbon atoms in the alkyl radical and the water-soluble salts of sulfonated monoglycerides o~ fatty acids ha~ing from 10 to 18 carbon atoms~ Sodium lauryl sulate and sodium coconut monoglyceride sulfonates ar~ examples oP
anionic s~rfactants o~ th.is type. Mixtures o anionic ~urfactants can also be employed.
The nonionic sudsing agents which can be used in the toothpastes of the present invention can be broadly defined as compounds produced by th~ condensation of alkylene oxide groups thydroPhilic in na~ure) with an organic hydrophobic compound which may be alipha~ic or alkyl-aromatic in nature. Exampl s of suitable nonionic sudsiny agents include the Pluronics ,polyethylene oxide con~en-~at~s of alkyl phenols, products d~rived from the CGn-:densation of ethylene oxide with the reaction product of propylene oxide and ethylene diamine, ethy.l~ne oxide con~ensates of aliphatic a}cohols, long chain tertiary a~ine oxides, long chain tertiary phosphine oxides, long chain dialkyl sulfoxides and mixtures of such materials.
~ The zwitterionic synthe~ic sudsin~ agents useful in the toothpast~s of th~ present invention can be broadly described as de~ivatives of aliphatic quaternary ammonium phosphonium, and sulfonium compounds, in which the ali-p~atic radicals ~an be straight ch~in or branched, and wherein one of the aliphatic substituents contai.ns from ~bcut B to lB carbon atoms and one contains an ~nionic water-solubilizin~ gxoup~ e~., carboxyt sulfollate~ sulfate, phospha~e, or p~ospllonate.
2' -e . .. ~. .. ~ . .

33~
The cationic sudsingagents useful in the tooth-pastes of the present invention can be broadly defined as quaternary ammonium compounds having one long alkyl chain containing from about 8 to about 18 carbon atoms such as lauryl trimethylammonium chloride; cetyl pyridinium chloride; cetyl trimethylammonium bromide; di-isobutyl-phenoxyethoxyethyl-dimethyobenzylammonium chloride;
coconutalkyltrimethylammonium nitrite; cetyl pyridinium fluoride, etc. ~specially preferred are the quaternary ammonium fluorides described in U.S. Patent 3,535,421, Briner et al, issued October 20, ].970, where said quaternary ammonium fluorides have det~rgent properties. The cationic sudsing agents can also act as germicides in certain of the toothpastes herein.
The amphoteric sudsing agents useful in the present invention can be broadly described as derivatives of aliphatic secondary and tertiary amines in which the : aliphatic radical can be straight chain or branched and wherein one of the aliphatic substituents contains from about 8 to about 18 carbon atoms and one contains an anionic water-solubilizing group, e.g. carboxylate, sulfonate, sulfate, phosphate, or phosphonate.
The sudsing agent can be present in the toothpaste compositions o this invention in an amount from 0.1% to 6%
by weight of the total composition.

,~
,:

3~

~) Phosphate Pell_c.1e F'enetration ~ent ~he toothpaste cornpositio~s of the present inven-tion contain as a hiyhly preEerred op-tional component fro~ abou~ 5% to :1.2~, preferab.l.y from about 7% to ll~, by weight of a water soluble pllosphate "pellicle penetra-tion agent"~ Such soluble phosphate salts serve to promote transfer of fluoride ions through the naturally-occurring salivary pelli.cle film formed on the teeth. Fluoride-containin~ toothpas-tes which utilize the level.s of phos-phate salts prescribed herein demons-trate enhanced fluo-ride pellicle diffusion and dental enamel fluoride uptake in comparison with fluoride toothpastes which contain no such phosphate pellic].e penel:ration agents.
While rel.atively high levels of soluble phosphate salts can provide fluoride pellicle penetration benefits in fluoride toothpastes, the presence of such salts can also diminish the soluhle fluoride s-tability of such tooth-pastes during storage~ I~ has been surprisincJly discovered, however, that such soluble phosphate salts can be included : 20 in the sil1ca~containinq, fluoride toothpastes herein with especially beneficial fluori.de compatibili-ty results if the particular alkaliale earth metal treated precipi-tated silica abrasives herein are employed.

- ~3 ~

33~

Phosphate sal-ts optionally present in the toothpaste compositions herein are water-soluble. For purposes of this invention a "water-soluble" phosphate salt is one which is soluble in water -to the extent of at least 3.0 g/100 cc H2O at 20C.
The phosphates are those phosphorus compounds in the anions of which each atom of phosphorus is surrounded by four oxy~en atoms arran~ed at the corners of a tetrahedron. ~y shar-ing oxygen atoms between tetrahedra, chains, rings and branches polymers of interconnected PO4 tetrahedra can be realized.
Simple phosphates are orthophosphates. Polymeric phosphates include the polyphosphates such as the pyrophosphates and tripoly-phosphates. Ring phosphates are the metaphosphates.
Examples of suitable water-soluble polyphosphates for use herein include tetrapotassium pyrophosphate, tetrasodium pyro-phosphate, disodium pyrophosphate, sodium tripolyphosphate and potassium tripolyphosphate~ Examples oE suitable water-soluble metaphosphates include monopotassium metaphosphate, sodium tri-metaphosphate, sodium hexametaphosphate, and sodium heptameta-phosphate. Many of these water-soluble polyphosphates and meta-phosphates are utilized in the form of hydrated salts.
The most preferred phosphate salts for use in the presentinvention are the simple orthophosphate salts. Orthophosphate salts are derived from tribasic orthophosphoric acid of the formula H3PO4. Water soluble sodium, potassium and ammonium salts can be utilized.
There are about 10 different cr~lstalline sodium ortho-phosphate salts including the various hydrates. These include, p 2PO4, NaH2PO H2O, NaH2PO~-2H2O, Na H PO

2 4 2 ' 2HPO4 7H2O, ~a2HPO4 12 H2O, Na PO ~6H O
Na3PO4 8H2O, and mixtures thereof. Preferred sodium orthophos-phates include NaH2PO4 H2O, Na2HPO4 2H2O and mixtures thereof.

3~
"~
Especially preferred are mixtures of NaH2PO~H20 and Na2HPO~
21120 in a weight ratio of monosodium to disodium salt within the range of from about l:3 to l:5.
Potassium and ammonium orthophosphates can also be utilized as pellicle penetration agents herein. E~amples of such potassium and ammonium salts include KH2P04, K2HPO~, K ~1PO4 2H20, K2~PO4-6H20, K3PO4 3H2 ~ 3 ~ 2 3 (N114)H2PO4, (NH~)2HPO4, ~N~)3PO~ and mixtures of -these salts.
An especially preferred phosphate salt mixLure for use in thetoothpastes herein comprises a mixture of Na~l2PO~ H20 and HPO4 2H20 in a weight ratio of sodium to potassium salt with-in the range of from about l:3 to l:5.
The soluble phosphate salts of the present invention are commercially available materials. A more detailed description of such phosphate salts useful herein can be found in Kirk &
Othmer, En yc_oped a of Chemical Technology, Second Edition, Volume 15, Interscience Publishers, Inc. (1968), pp. 232-276.
Preferably the ins-tant toothpaste compositions provide from about 0.5 mole/lOOOg H20 to 2~0`moles/lOOOg H20 concentra-tions of phosphate salts in the aqueous solutions which contactdental surfaces when the toothpastes of the present invention are used in the mouth. Again, the supernatant from 3:l slurries of water and toothpaste are used to simulate such use solutions.
Additional pellicle film penetration agents can also optionally be added to the Eluoride containing toothpastes of the present invention. Such optical in~redients further enhance the fluoride pellicle penetration ~enefits provided by the phosphate salts herein. Such agents include, for ' , ~ ,i .

example, hydroxy acids and salts thereof such as citric acid, trisodium cikrate, malic acid and tartaric acid.
If present, such additional pellicle penetration agents comprise from about 0.2 to 5.0% by weight of the tooth-paste composition.
3) Flavoring A~nts Flavoring agents can also be added to the instant compositions. Suitable flavoring agents include oil of wintergreen, oil of peppermint, oil of spearmint, oil of sassafxas, and oil of clove. Sweetening agents which can be used include saccharin, dextrose, levulose, aspartame, D-tryptophan, acetosulpham, dihydrochalcones and sodium cyclamate~ Flavoring agents are generally used in tooth-pastes a~ levels of from about 0.01% to 2% by weight and sweetening agents at levels of from about 0.05% to about 3% by weight.

4) Ant plaque/Anticalculus A~ent Phosphorus-containing anticalculus agents and/or bis-piguanide antiplaque agents can also optionally be added to the toothpastes of this invention. Phosphorus-containing anticalculus agents such as disodium ethane-l-hydroxy-l, 1-diphosphonate and related materials are described more fully in McCune et al; U.S. Patent 3,488,419, issued January 6, 1970. Bis-biguanide antiplaque agents such as chlorhexidine (1,6-bis[M5-p-chlorophenyl-Ml-biguanido]hexane), the soluble and insoluble salts thereof and related materials such as 1,2-bis(N5-p-trifluoromethylphenyl-Nl-biguanido) ethane are described more fully in Haefele, U.S. Patent 3,934,002, issued January 20, 1976; Haefele, U.S. Patent 3,937,807, issued February 10, 1976; Procter ~ Gamble, Belgian Patent 843,244, published December 22, 1976 and Procter & Gambl~, Belgian Patent 844,764, published January 31, 19770 ~1383~
, ~ .~

If present, the optional anticalculus and/or anti-plaque agents generally comprise from about 0.01% to 2.S%
by weight of the toothpaste compositions herein.

5) ~ s and Coloring Agents, Misc.
A variety of other optional components well known in the art may be added to the toothpaste compositions herein to improve the usual aesthetics. These inclllde pigments, dyes, speckles and the like. When present, these optional components generally comprise ~rom about lG 0.001 to abou~ 2~ by weight of the toothpastes herein.

~ ~ .

~;
;
;

3~
c~MposIrrIoM PREP~I~TION
Toothpaste compositions o the present invention are prepared silnply by mixin~ together in any order and any conventional means the essential and optional components herein. O11Ce prepared, the compositions herein provide a pEI of from about 4~0 ko 8.0, preerably

6~5 to 7OSj when said compositions are slurricd with watex in a 3:1 weight ratio of water to composition.
Fluoride toothpastes providing pH values within the 4.0 to 8O0 range provide especially effective dental enamel antisolubility benefits compared to toothpastes with pH values outside this range Flavoring of toothpastes wi~hin this pH range is also comparatively easy.
(:~OMPOSITION USE
Toothpaste compositions o~ the present invention are used in conventional manner. 'rhe toothpaste compo-sitions or slurries thereof are brushed onto dental sur-faces and subsequently rinsed away.
During use of the toothpaste herein in conventional manner, pastes or slurries generally contact dental sur-aces ~or at least about 30 seconds. More pre~erably such pastes or slurries contact dental surfaces Eor at least about ~0 seconds.
.' , .................... . ..
,~ ..

~9~

The following examples are presentecl to illustrate the present invention but it is not to be considered as limitec'l ~hereto. In the ollowing examples, parts are by we.ic3ht unless otherwise indicated.

Into a 30,000 liter stainless steél reactc~r ja'cketed o.r steam heating was added 1794 liters o sodium silicate ~olution (3~78 percent Na2O, 9.53 percenk SiO2) of specific g.ravity 1~121 containing 42 grams of Na2O per liter~ The ; 10 reaction medium was heated to 88C~ ~ikh continuous agitationO
~t this point sulfuric, 10% concentration (specific gravi.ty 1.066) and sod]um silicate solution were added simultan-eousl~ to the reaction medium at the`rate oE 151.4 l/min~
a.ci.d and 351 l/min~ sodium silicate while maintaining the reaction temperature at 88C~ + l~C. These two solutions were added to the reaction medium for a predetermined lenstl o time. The silicate addltion was discon-tinued afker

7 minu-tes but the acid addition was continued until the slurry pH was between 4~8~5.0~ The reaction slurry was boiled at 100C~ for twenty minu-tes and the reac-tion p}l was adjusted again ko between 4.8-5Ø The resultinc3 si.lica slurry was filtered, and washed to remove most cf the reac-tion by-product'(sodium sulfate) and thc filtcr ca~e was dri.ed and the dry product milled tc the desi,red degree of 2~ fineness~ The dry silica was subjected to va.rious physical-' ehemical tests and the analysis o which are set forth hereinafter (See Table I). ~his example is prepara~ion of con~xol product to which no alkaline earth metal is addea.

., .

~ 2g ~

3g[~
, ~N~IILl 2 l~lto a 30,000 liter stainless steel reactor jac~eted fo~ am hea~ t3 ~Jas added 1734 liters of sodium si.licate solutio~ (3~7~ percent Na20, 9.53 pexcent SiO2) o speci-~;c gr~vi.t~ .l. containiIlcJ ~2 grams of Na20 per liter.
Tl~e rcac~io~l m~dium was h~ated to 8~C. with conti.nuous ~Igi~ation~ At this poin-t sulfuric, 10~ concentrati.on (spe-Ci~iG CJraVity 1~ 066) and soclium silica~e so1.u~ion were added silnultaneously to the re~ction mediulrl at the rate or lSlo 4 l/min. aci.d ~nd 351 l/minO sodium sili.cate while maintain-. ing ~he reaction temperature at 88C~ C~ These two so].utions were added ~o the reaction medium for a pred.eter-milled lel~gth o time~ The silicate additioll ~as discon~inued ater 47 rl~i.nutes bu~ the acid additi.on was continued until ~he slurry pH ~Jas between 4~8 - 5Ø The reaction s].urry was bo.iled al~ 100C. for t~lcnty minu-tes and the reacti.on pl~ was adjusted again to bet~een ~.8 ~ 5.0O Tlle resull:i.ncJ
~ silica slurry was iltered and washect to remove most o~ the : reaGtion by-product (sodium sulate).
qlhe washed filter cake ~as then reslurri~d without rater addi.tion at ambient temperature ~ith ac~itati.on.
While under ayitation, the slurr~ ~ras treated with 102 grarns o CodeY~ grade (U~SO p~lrity ood yrade) hydxatecl lime (calcium hydro~i.de) to p~ovi.de 25 pprn of calcium ion treat~
Tnent based on t~he total weiyht of clry recoverable sol;d product i.n the slurry form. ~fter treatment ~rith the - Galcium ion, the ca~e slurry was agitated vic~orously `or ~ l~ minutes to provide the e~fectivc lcvel. o calcium ion ;~ trca~entonto-~lle surace of the silicon dioxide abrasive.

~}le res-~llti.llg prod~ct is then spra~ dried al. an inlet tc~-peraturc of ~1~33Co and outlct temperaturc of 122C., millc~i alld char.actcri.~,cd or abrasi.vc ~In~ phy ;icc-l]. propcL-~
~i.cs i.ll tllc samc m~nncr a~; ~]~c al~L-asivc i.n l'.~;nltll?lC lo :: :

l~X~l~PLE. 3 i ~ , The me~hod o~ tllis example was the same as in Example 2 except the rate o:E adclit;.on of sulEuric acid was at the rate of 152.7 lit:ers per mi.nute and the calci.um addi~ion was 204 cjrams of calci.um hydroxide which provides 50 parts per mi.llion o~ calcium ion. The procluct was then charac- :
teri~edO

_X~lPL~ 4 ~ :
This e~ample was the same as E~ample 2 excep-t that 1~ the rate of addition of sul~uric acid was 166.5 llters per minute and the calcium addition compr.ised 408 grams of cal-~: cium hydroxide to provide 100 parts per million of calcium~ ,;
ion in the silicon dioxide. The product was then charac-~-: terized.
~; ':
P8~MPLE S .:
: In this example, a dentifrice silica abrasive was prepared by initially addiny 1420 ].iters o~ sodiurn silicate solution (~.09 percent Na2O, 10.31 percent sio2) of specifi.c gravity 1.131 containlng 46.3 grams of Na2O per liter to the 20 reactor as reaction medium. The reactor was heated to 91C.
wi,th continuous ayitation. At this point sulfuric acid, 126-concentration (specific gravity 1.08) and sodi~m silicate soluti,on were added simultaneously to the reaction medium at the ; rate o~ 162.7 .ljmin acid and 315.7 1/min sodium silicate while maintalniny the reaction temperature at 91 ~ 1C. The silicate addition was discontinued after ~7 minutes but the acid addition was conti.nlled until the slurry p~ was between ~1.6-q,8. The ~ Jl -- .

reac~ion slurr~ was boiled at 100C~ for twenty minutes and ~he reaction pl-l was adjusted again between 4.6-4.~. The resultiny silica slurry was filtered and washed to remove sodium sulfate by-produc t .
The washed fil-ter cake was theII reslurried without wa-ter addition at ambient temperature with agitation. While under agitatioII the slurry was treated wiLh 510 grams of Coclex grade (U.S. purity food grade) hydrated lime (calciurn hydroxide) to provide 125 ppm of calcium ion treatment based on the total weight of the dry recoverahle silicon dioxide abrasive present in the slurry form. After treatment with the calcium ion, the cake slurry was agitated vigorously for 15 minutes to provide the effective level of calci~n ion treatment onto the surface of the silicon dioxide abrasive. The resulting product was then spray dried at an inlet temperature of 483C. and an outle-t temperature of 122C., milled and then characterized. ;

EXA~lP~E 6 This example was the same as Example 5 except that 1608 liters of sodium silicate solution was initially charged to the reactor as reac-~ion medium and the acid ra~e was increased to 170.3 l/min but the sillcate rate was maintained at 315.7 l/min.
The washed fi.lter cake was treated with ~16 grams of calcium hydroxide to provide 200 parts per million of calcium ion ; treatment onto the sur~ace of silica abrasive. The product was ~, then characterized~

This example was the same as Example 2 except that the calciurn ion addition ~Jas 2,040 grams of calcium hydroxide to provide S00 parts per million o-F calciurn ions. The product was then characterized. ;
Ater preparation of the products of ExampleS 1 to 7 the~ ~ere characterized for physical properties and tlle results are set ~orth in tlle followillg Table I.

3~?

rl r I

o o a~
r-l ~
rl u~ O
~ O ~
w ~ o u-) ~g r l O E; ~ 1 r~ O
h O ~
~ -rl ~

~c tO

~ _ r l ~r ~ r l o l (~
U~ ~ ~ ~ ~ ~ ~ ~ ~ h r l m ~ 'I H

~ 'o ~ O
O ~
h .q ~
~¢ h `
~1 ~1 o I
~ ,_ ~ ~1 ~
- rl ~1 1~) ~ O ~1 1~ 0 ~ O
~ O O O O O O O ~ ,~

h O
H ¦ O ~ ~ o ~r r~
o~o (~
a '~ ~
~ * *
x o Z

83(;~
, , .

Several representative toothpastes of the present invelltlon ar~ set forth in the fo}.lowing examples that u~ilize the instant precipitated silica abrasives.
EX~MPLE 8 ~ toothpaste is formulated utiliziny the ~recipi-; . , tated silica abrasive of Exarnple 2 which has the follow-ing composition: .

mount ; Componen-t .(Wt. ~) Preci.pitated Silica Abrasive 160 0 (EY.ample 2) Sodi~n Fluoridc (~aF) .. 0.28 `, Sorbitol Solution (70%) 32.0 Glyceri.n . 130 0 Sodium Carrageenan 0.75 Monosodiurn Orthophosphate Monohydrate 2.15 (NaH2PO~ H20) Dlsodium Orthophosphate Dihydrate 8.34 ~H~04 2~12o) Sodium Alkyl Sulfate Solution (28.8%) 6.0 : Coconut Monoylyceride Sodi~ Sul~Eona-te 0.9 . Flavor 1.22 Sodi.um Saccharin 0.3 Color (F~G Blue #1 Solution 1%) 0~35 2S Ti-taniurn Dioxide (Tio2~ 005 Trisodi.urn Citrate Dihydrate 0.25 (C~;H5~1a307~ 2H20) Distilled Water'~ . . q'S' 100. 0 Total .

. , ~ 34 - ~~

831D .

~he above toothpaste compositi.on is prepared by ~dmi~ing the components thereof in the normal manner of too}hpas-~.e pxeparcltior~. Pxefe.rably, the water component is first added to a sultable conta:iner to which thereafter ' .is aclded ~ith moderate agitation, in order, the pellicle ~ilm penetratioII agents, the flavor, the humectant and ~he.reafter, the remaining components.
~ 3:1 weight slurry o the above freshly prepared composition with water (3:1 is water to composition) pro-duces a pH o about 7.1.
Such a toothpaste composition provides beneficial ~luoride treatment for dental tissue brushed therewith due to the high toothpaste fluoride compatibility. The tooth-paste also provides good cleaning and an RDA oE lOU. When s~ored for prolonged periods of time at 80Fr. such a toothpaste exhibits minim~l loss o soluble fluoride.
Toothpastesproviding substantially simi.lar ~luor-ide treatment benefits, toothpaste 1uoride compatibility, and cleaning per~ormance are realized when in the Example

8 composition, the sodium fluoride is replaced w:itll an ~qui~alent amount of stannous fluoride, sodium chlorofluor-i.del potassium fluoride, potassium stannous fluoxide, lndium ;~luori.de, ~inc fLuoride or ammonium fluoride.

3~

~ oo~llpastes providing substantially similar fluoride treatilletlt b~ne;.ts and substall~ially si.milar cleaning per-form~ce a:re reali~ed when, in the Example 8 composition, 1;hQ. phospllclte salt mixture is repl.aced with an equivalent C)Ill~ 0~ Na~l2Po~ aH2P04 H20~ MaH2P04~ 2H20~

'1~ 2~1P~ 2~I2lNa2HP04 71~120~Na3PO~'6H o ~ N~3Po~ g~i20; KH2P04~ K2HPO~r K2}~Po4D2}~20~

~ 4 I20l ~3P04 3H20- ~3P04-7H2or K3P0~ 9H20, (NH ) H PO
- ~Nil,~)2HPO~, tNH~)3PO~, other mixtures of NaH2PO~ O
and Na2IlPO~lo2H20 in monosodium to disodium weight ratios o~ rom about 1 3 to 1: 5, mixtures o~ NaH2P04 H20 and K2HP04 2H20 in sodium to potassium salt weight ratios o~ from about ].:3 to 1:5, tetrapotasslum pyrophosphate, tetrasodium pyro-~, .i phosphate, disodium pyrophosphate, sodium tripolyphospha.te~

; 15 po-tassium tripolyphosphate, monopotassium metaphosphate, ~ ~ sodium -trimetaphosphate, sodi.um hexametaphosphate or sodium ; . hep-tametaphosphate; provided such composi tions provide a 3-1 slurry pH of from 4.0 to 8Ø

.;

3~

F.X~PLF, 9 A high abrasive level toothpaste is for~ulated utilizing the p~eclpitated silica abrasive of ExaMple 3 which has the following compositionO
.
~mount Component (Vwt~%) Precipita~ed Sillca Abxasive 35.0 ~Example 3) 8Odium Fluoride ~NaF~ 0o22 Glycerin 5.0 . Sorbito]. Solution ~70%~ .20.0 Carboxymethyl Cellulose 10.7 D.S.) O.S
Magnesium Aluminum Silicate (Veegum Flakes) 0.3 Monosodium Orthophosphate Monohydrate 0.3 (Na~l2PO~ H2O) 0 3 Disodium Orthophosphate Dihydrate ~Na2~P04 2H2) Sodium Alkyl Sulfate Solution ~28.8%) ~-3 Coconut:Monoglyceride Sodium Sulonate 0.7 Flavor 0 9 Sodium 5accharin 0.2 Ti~anium Dioxide (TiO~) 0.5 Speckles 0.5 Distilled Water ~
Total - 100.0 ~ - 37 ~

3~

Toothpastes providirl~ subst~ntially ~imilar ~luoride ~.reatment beneits, toothpaste fluo.ride compatibility~
and cleaning performance are reali~.ed when in the Example

9 compositi.on, the preclpita.ted si.li.ca abrasive componen~
5 ; prepared as in Example 3 is replaced with an equivalent amount o~ abrasives prepared by Examples 2, 4j 5 and 6.
Toothpastes pro~iding substantially similar fluoride treatment benefits and substant.ially sirnilar cleaning performance are realized when, in the Example 9 composi-tion, the phosphate salt mixtuxe is replaced with an equi valent amount of NaH2PO~,NaH2PO~ H2O, NaH2PO4 2H2O, Na2HPO~Na2HPo4 2H2O,Na2HPO4 7H~O,Na3PO4 6EI20 Na3po4~8H2o~ KH2PO4,~ K2EIPO~r K2 ~ 2 K~PO~ 6H2O, K3PO4 3~2~ I~3PO4-7H2O~ K3PO4 9H2O~ (NH4) H2P4 ~N}i4)2ilPO4, (NH4)3PO~, other mixtures o Na}l2PO4 H2O
and Na2HPO4 2H2O in monosodi.~ to disodium weight ratios of rom about 1:3 to 1:5, mixtures of Na~PO,1 H2O and K~HPO~2H2O
in sodium to potassi.um salt weicJht ratios of from about 1:3 to 1:5, tetrapotassium pyrophospha-te, tetrasoclium pyrophosphate, disodium pyrophosphate, sodium -tripolyphos-phate, potassium tripolyphosphate, monopotassium metapilos-phate, sodium trimetaphosphate, sodium hexametaphosphate or sodium heptametaphosphate, pxovidecl such compositi.ons provide a ~:1 slurFy pE~ o~ from 4Øto 8Ø

, 3~
.

EX~MPLE 10 A clear toothpaste is formulated utilizing the precipitated silica abrasi.ve of Example 4 which has the following composition:

Amount Component ~Wt Precipitated SiLica Abrasive 20.0 (Example 4) Sodium Fluoride (NaF) ~24 ; : 10 Sorbitol Solutian (70~) 57.0 Glycerin , Sodium Carrageenan 0.5 Phosphoric Acid (85~) 0.10 Sodiu~:Alkyl Sulfate Solution (28.8%) ~0 Flavor Sodium Saccharin 0.2 Color (FD~C Blue ~1 Solution 1~) . 0.05 Distilled Water . ~ s.
' 100. 0 : !To~al , .
:

, .

.: , ~ .

~P~i8~
EXAMPLE ll ~ low abrasive level toothpaste is formulated util.izing the precipitated silica a~rasive of Example 3 which has the followiny composition:

Amount Component (Wt. ~) Precipitated Silica Abrasive 6.0 (Example 3) Stannous Fluoride (SnF2) 0.40 Sorbitol Solution ~70%) 51.0 Glycerin 25.6 Sodium Carboxymethyl Cellulose (.7 DS) l.0 Sorbitan Monoisostearate 2.00 Sodium Alkyl Sulfate Solu~ion (28.8%) 6.0 Flavor 1.20 Sodium Saccharin 0.28 Color ~FD ~ C Blue #l Solution 1%) 0.25 Pyrogenic Colloidal Silica (Aerosil~ 200V)* 5.00 Distilled Water q.s.
Total lO0.0 *Marketed by Degussa, Inc.

: . . . .

-3(P

Toothpclstesprovldiny subst.an-tially similar fluoxide treatment henefits, toothpaste fluoride compatibility and cleaning pexformance are reallzed when in the Example 10 composition, the precipita-ted silica abrasive component 5 prepared as in Ex~ple ~ is replaced with an equivalent amount o abrasives prepared by Examples 2, 3, 5 and 6!
A toothpaste providing substantially similar fluor-ide treatment benefits and an i,mproved anticalculus benefit is realized when the Example 10 composition additionally contains about 1.0% by weight of disodium ethane-l-hydroxy-l, l-diphosphonate.

~9~38~(~

TE:STI~G ~ND EVALOATION
The precipitated silica abrasives herein can be used - to prepare especi.ally desirable therapeutic toothpaste compositions conkaining soluble phosphate pellicle film penetration agents~ Such compositions provide both high abxasive-fluoride compatibility and yet have ~ood tooth- cleaning performance~ The ollowing tests and evaluation ' serve~ to demonstrate ~le excellent fluoride compatibility - provided by the precipitated silica dental abrasives herein - ~o in the -toothpaste composition of the presen-.,t inventionO
It is also shown hereinbelow that abrasives o~ the present : invention provide higher abrasive fluoride compatibility ., ~
than similarly prepared abrasives which have not been treated ,~ so as to contain the essential amounts of alkaline earth material~ The excellent cleaning performance of the -tooth-paste compositions herein is additionally demonstrated.
,: ~inally, it is shown herein that abrasives made from a sulfate liquor acidulation process --even though contain-: :- ing an al~aline earth material-- fail to provide the high 20 ~ fluoride compatibility values of the "resh water" preci-pitated silica abrasives provided herein.
. Abrasive Fluoride Cornpatibility .
Precipitated silica dental abrasives can be screened for their relative compatibility with fluoride materials by means o a 24 hr~ abrasive slurry test~ Such a test can be used to generate-data which c,an predict the avail-- ability o soluble fluoride in certain types of fluoride ~ ~h-pas~ after storage ovcr approximately a four~~eek period at 80l The 2~ hour abrasive slurry test i.s us~,d to ~'enerate fluoride compatib1lity values wllich are dc~incd as that per-t - centa~e of theoretical maximum availablc ~luoride which is - actu~lly mcasurcd a~tcr ~ hours as solublc ~luori.de by thc following tcst mc~hod. In this n~ctl~od (Orion ~ccif.ic , - 42 -Ion ~lectrode Method) a standaxd sodium fluoride stock solution containing 1624 ppm of fluoride is prepared by dissolving 2.80 yrams of soclium fluoride, 21.5 grams of Na}l2PO4 and 83.4 grams cf Na2HPO~ 2ll?0 in 672.5 grams of deionized distilled ~ater and stored in a polyethylene bottlc. Thirty (30) grams of this solution is then weighed out. Seven (7) grams of the silica abrasive being tested is then dispersed into the solution and contacted for 24 hours at a temperature of about 100~. (37.8C.). After 24 hours~ the precipitated silica abrasive/fluo~ide solu-tion is centri~uged for 20 minutes at 15000 rpm or until the supernatant is clear. Then 10 ml. of the supernatant is pipetted into a plastic vial. Thereafter, 10 ml. of EDTA/TT~AM solution is likewise pipetted into -the plastic vial. (The EDTA/THAM solution is a 0.2 molar in EDTA
(ethylene diaminetetraacetic ~ acid, disoclium salt) and 0.2 molar in TH~M (2~Amino-2-hydroxymethyl-1,2-propanediol) and ad~usted to pH 8.0 with sodium hydroxide.) ~ magnetic stirring bar is added and gentle stirring is initiated.
~o The fluoride ion concentration is determined by direct potentiometxy with the Orion fluoride electrode (Model 9S-09). Emf is converted to parts pex million (pp~n) fluoride in the supernatant by means of a logarithmic equation. The fluoride compatibility value is then cal-~5 culated by expr1~ssing the measured ppm soluble fluoride as a percentage of the theoretically available soluble fluoride.
Using this method, the relative abrasive fluoride compatibili~y values are determined for the several abrasives prepared according to Examples 1 through 7. The results of such evaluation are set forth in the follo~ing Table ~I.
~ 43 ~ ~91~133~

l`A L~ II
~brasive Fluoride Compatibility . Abrasive Calclum Treatment Fluoride .
Example No. (ppm) _ . Compatibi~
~ .
1 (control) 76 2 25 93~
3 50 94%
.
4 100 ' 93%
125 91% -.10 5 6 . 200 90~
8U~ :

.
' ' , - ~ . ,............................... ' ~ ; ' :

:, .
, ' ' , . .

.
.

' .

~ . .

: ~4 ,~

"
.
.. , I'he Table II data demonstrate that the precipitated silica abrasives herein containing particular amounts of an alkaline earth material provide markedly superior abra-sive fluoride compatibility in comparison with that provided by an al]caline earth-~ree abrasive material which is other-wise similarly prepared. Thus, precipitatecl silica abra-sives prepared as in Examples 2 through 6 should be suit-able for realizing toothpastes containincJ Eluoride and pellicle film penetration agents that demons~rate high abrasive fluori,de compatibility.
brasive Fluoride Compatibility in Toothpa,stes Preferred ,toothpastes herein containing precipitated silica abrasives and pellicle film penetration agents are evaluated for abrasive fluoride compatibility~ The tooth-pastes which are prepared for evaluation have the compo-sition of the toothpaste of Example 8 and differ onl~ in the variation of the abrasive component.
. To decermine fluoride compatibility values for the : - toothpastes tested; a soluble fluori.de determination method :~ 20 is used which is similar to the method descri~ed above for the determination of abrasive fluoride compati.bility values.
In this method, the toothpaste composi.-tions are stored for a spe,cified length o~ time in a lami.nate tube. rrllereater~
15.0 grams o~ the composition is placed in a lO0 ml n heaker and then 45.0 g~ams oE distilled water is added. The mixture then is sti.rred to form a slurry in which the tooth-paste is uniformly dispersed. The ~slurry i5 subsequently centriEuged ~or 20 minutes at lS,000 rpm or until th,~.super-natant is clear.

-- ~5 3~

Th~ supernatant is then treated as in the abrasive fluoride compat.ibility determination method described above. Solub.le fluoride concentration is similarly mea~
sured and an abrasive fluoride compatib.ility~value for each toothpaste is similarly calculated. The toothpaste fluoride compatibilit~ values of the respective toothpastes evaluated are shown in Table III. The abrasives evalllated are those prepared as described in Examples 1 through 7 above and characteri.zed in Table I aboveO

.

' .

' '' ' ". ' ..' ' ' , ' ' ~ . ' ' ''' ,' '- : , :

. " ' :' ' . ' ' ' ' " ' '' ' , " ' ' ' , ,.

.;

:

~' .

~98~3~

T~BLE III
Toothpaste Fluoride Compatihility Toothpaste Fl~ri~e Abrasive Calcium Treatmen-t Compatibility ! (Example No.) ~ pm) _ (1 wk. 80F.) ~_ .
1 ~Control) 0 76%
. 2 , 25 99%
3 5 0 9 8.~i ' ~ 100 99%`

6 . 200 94 , ' ~ . .

~ . .
`'' ' .

. ' .

.

3~

The Table III clata demonstrate that ~he pre~erred toothpastes herein whlch utilize the instant precipitated silica abrasives provide superior abrasive fluoride compati-bility values in comparison with that provided by a similar too-thpaste composition COntaininCJ the non-alkallne earth treated precipitated silica abrasive prepared by the method of-Example 1~ The data of Table III further demonstrate that the soluble fluoride avai.lability from the fluoride ion source material is not significantly diminished upon storage when the silica abrasives of the present invent~on .
ara employed in the preferred toothpastes herein.
Of course, it is to be recognized that the amount of available soluble fluoride in even the toothpas-te com-positions herein will decrease to some extent as a Eunction o inc.reasing time and temperature of storage. Thus, tooth-paste fluoride compatibility values for too-thpastes stored for longer periods or at more severe temperatures are gener-ally lower than those exemplified above.
Additional abrasive fIuoride ~ompatibili-ty dclta for several toothpastes demonstrating storage for longe.r periods ancl higher temperatures are shot~n in Table` IV o : . ~ 4~

9~3 E~
~Sl oo ~D I I I ~ I CO
." ..
~ ~ I .

~ ~ ~ o~o a) h ~ ' n ¦
~ ~ o H E~ 3 ~ o~ -C~ o~O

~ ,1 m g ~ ~

: : ~ ~

~ ~ ~

¦
' ~, .

o ` :
g _ ~ ._ .. .

31~33~

., The Table IV data.demonstra~e that the preferred ~oothpastes herein maintain their relatlvely high fluoride~
a~rasive compati.bility levels ~ven under prolonged stora~e or under severe storage conditlonsO
l Cleaning Performance :
, The dental cleaning ability of the silica ab'ra-sives herein can be estirnated by means o Radioactive Dentin Abraslon (RDA) testin~3. RDA values can be used to estimate the xelative cleaning perormance of various - abxasives fQr any given type of dentifr.ice abrasive.
Thu~, for precipitated silica abrasives, an RV~ value (measured by the method provided below) of at least 40, prefera~ly between 70 and 120, is needed to insure that;
the abrasive has su~icient abrasi.vity to be an ef~ec-tive dentifrice cleaner. Prior art precipitated si.lica abrasives which do exhibit high toothpaste fluoride com-patibility generally are poor cleaners for oral hyglene purposes as evidenced by low RDA values. The'alkaline -earth treated abrasives, however, provide both effective .

:20 tooth cleaning and high fluoride compatibility.' : ' Several commercial precipitated silica abrasives ; which demonstrate relatively high toothpaste 1uoride compatibility as measured herein are selec-tecl for evalua-tion for RDA values~ Testing is conducted within a standaxd 25~ toothpaste ma~rix having the composition of the tooth~aste of Ex~mple 8, which d.iffers only in the variation of the ' abrasive component.
The method which is employed for determining the ~DA
. ~alues for toothpastes that are tabulated in Table V is 3~' described below. This test method is described more full~
in the Journal of Dental 1~esearch, July - August, 1976, by ~Seferren, pp7 563-573. 'l~he specific steps for determi.n-ing RDA values are set ~o~h as follows-.

, . . ....

3~

A. Selection and preparation of teeth . _ Sound, single-rooted permanent teeth tlat are caries-free and vital at extraction are selected. Teeth are then scraped clean with a scalpel~ ~he crown and root tip of each too~h are removed using an abrasive disc so as to prepare a dentin sample 14 n~ long and at least 2 mm wide at the narrower end. Cut pieces of root ~dentin chips~ or, alternatively, an additional tooth,are also prepared to be later used in determining a correction factor for self~absorption o~ radiation.
B~ Irradiation of dentin . The prepared roots and dentin chips described in Step ~ are exposed to a neutron ~lux of 2 x 101 neutrons/
cm2 for three hours.
C Mountiny_of roots ~, .
After irradiation, the irradiated roots are embeded in a mount of cold-curing dental methacrylate resin and mounted onto a cross-brushing machine. Too~hbrushes used throughout the test are 50-Tuft, mediuml flat~ "Pepsodent"~
toothbrushes.
D. ~reconditionin~ the dentin surfaces Prior to initial test run, the freshly mounted, irradiated roots are brushed with a reference slur~^y (l~g calcium pyrophosphate ~ 50 ml of a O.5% CMC-10~
. glycerine solut~on) for 6,000 brush strokes. At tlle : beginniny of each subsequent dayls test run, t'~e roots are brushed for 1,0~0 strokes.
:.

~ 3 ~ . !
., "" ~. ' ' ., 3~

E. Test run Ater precondi-tioning, the dentin samples are then conditionecl wi.th the reference slurry (same slurry as in Step D) fox 1,500 brush strokes at the beginning, during and end of each test runO The test run consists of brush-. ing dentin samples or 1,500 brush strokes with a slurry of test product (25g denti.fri.ce -~ 40 ml deionized of distilled water).
F. Preparation o~ correction factors .The correction factors are prepared by dissolving the dentin chips or, alternati~ely, an additional tooth, from Step B in 5 ml~ conc. HCl brought to a volume of 250 ml. with distilled water. One ml~ of this solution is ~ added to test pastes and reference slurries which are pre-pared similarly to those in Step E, and then neutrallzed with 0~1 N NaOH.

Radioactive Tracer Countiny The radioactivity of the slurry sarnples (1.0 ml.) .
is determined with an I~tertechnique SL-30 liquid scintil-lation counter~ Alternate counting procedure: 3 ml. ali-quots of each slurry are transferred to stainless steel, flat-bottom 1 inch x 5/16 inch planchets and counted using Nuclear Chicago Geiger Counting System~
Calculations ~5 l`he radioactive dentin abrasion value (RD~) for a particular paste will be the ra-tio of the average cor-rected counts or that paste to the average count or the reference multiplied by 100. The reference abrasive is yiven an arbitrary dentin abrasion value o 100 units.
The results of such ~A value determination are set for-th in the following Table V.
, ' ' ' .
- 52 ~

3~
TABLE V
Radioactive Dentin Abrasion Values Toothpaste Fluoride Compatibility Abrasive RDA One Week (80UF) A. (Example No.) 1. Control 75~7 76%
2. 80~21 99%
3~ 67-8 98%
4. 80+1 99%
5. 103~5 97%
. 111-5 9~%
7. 56+4 90%
B. Commercial Precipitated S.ilica Products 8. Sident~ 3 1. 14~2 92%
9. Neosyl~ 2- 25-2 78%

10. QUSO~ G-30 3' 22-2 87%

11. Neosyl~ ET ' 26-4 84%

1. A precipitated silica marketed by Degussa, Inc. (N.Y.C.).
2. A precipitated silica marketed by Joseph Crosfield & Sons, Ltd. (London, England).
3. A precipitated silica marketed by Philadelphia Quartz Co~
(Valley Forge, Pa.).
4. A precipitated silica marketed by Joseph Cros~ield & Sons Ltd.

:~`
'' 3~

The Table V data demonstrate that commerclal pre-cipitated silica abrasives may well demonstrate high abrasive fluoride compatibility but are not sufficiently abrasive so as to be useful as dentifrice abrasives. Surprisingly, the instant novel precipitated silica abrasives provide outstand-ing abrasive fluoride compatibility yet simultaneously provide excellent RDA abrasivity values, which values can be used as an indicator of relative dental cleaning performance.
"Fresh Water" versus "Sulfate Li~uor" Abrasives As indicated hereinabove the abrasive products of the present invention are related to but distinctly different from the calcium treated silicas of U.S. Patent 4,159,280. To demonstrate such a difference, the following evaluation is made to compare the fluoride compatibility of the products of U.S. Patent 4,159,280 with that of the abrasive products of this invention. The "sulfate liquor" silicon dioxide materials tested are prepared in accordance with the process disclosed in U.S. Patent 4,159,280 and U.S~ Patent 3,960,586, issued June 1, 1976, by the following procedure- ;^
Dry sodium sulfate was added to 10.0 gallons of water in a 200 gallon reactor so that the sodium sulfate concentration in the reaction medium was 10%~ The pH of the reaction ~edium was then adjusted to 9.0 by the addi-tion of sodium silicate. The reaction temperature was 65C.
(150F). The sodium silicate solution had an SiO2/Na2O
mole ratio of 2.5 and a concentration of 2.0 pounds per gallon. Sodium silicate was added to the reaction medium for 4 minutes. At this point the sodium silicate addition was stopped and sulfuric acid of 11.4% of concentration was added to the reaction medium until the pH of 9.0 was reached.
At this point the sodium silicate solution and the sulfuric ._ 3~

acid solution were add~d simultarleously for a period oE
35 minute~. A-t -the end of the 35 minute period of silicate acl~i.tion, the silicate was discontinued and the acid addi-tion was continued until a slurry pH oi 5.5 was obtained.
The batch was digested at 77~C. for 20 minutes and the resulting wet cake recovered and washed.
The wet cake was then treated in the manner describ-d Eor Example 2 of this applica-~i.on, divided into six separate portions and t.reated respectively with 50, 100, 200, 400 and 800 parts per million of calci~n from aqueous solutions of calcium hydroxide. Each wet cake was then dried and processed as described for Example 2 and characterized in the following Table VI whexe the first ahrasive is a control in which no calcium was added. Table VI se-ts forth the resul-ts of such evaluation.

3~

TABLE VI
Abrasive Ca Addition Fluoride "Sulfate Liquor" Abrasive ~ppml Compatibility*
A O (control) 88 : C 1~0 , 8~

*Determined by test descrihed for rrable II.
As can be seen rom the Table VI data, the calcium treated "sulfate liquor" abrasives of U.S. Patent 4,159,280 provide abrasive fluoride compatibility values which are generally lower than those provided by the "fresh water"
silica abrasives of the present invention (See Table II).
Furthermore, the addition of an alkaline earth metal to abrasives made by the "sulate liquor" method does not result in a dramatic improvement in abrasive fluoride compatibility~ Conversely, as can be seen from a comparison of Table II, the addition of equivalent amounts of alkaline ear~h metal to the silica abrasives herein made by the "fresh water" method does result in dramatic improvements in abrasive fluoride compatibility.

~ 56 ~

Claims (24)

WHAT IS CLAIMED IS:

1. An abrasive composition comprising a preci-pitated amorphous silicon dioxide prepared from a fresh water alkali metal silicate solution by acidulation, which silicon dioxide has been intimately reacted with a salt of an alkaline earth metal so as to have present therein about 10 - 300 parts per million of alkaline earth metal ions in said amorphous silicon dioxide exhibiting a Radioactive Dentin Abrasion value of at least 40, a pack density of about 0.24 to 0.55 grams per milliliter, an oil absorption of about 70 - 95 ccs/100 grams, a BET sur-face area of about 100 - 250 m2/g, and a percent loss on ignition of about 4 - 6%.

2. A composition according to Claim 1 wherein said alkaline earth metal ions are selected from the group con-sisting of calcium, strontium and magnesium.

3. A composition according to Claim 1 wherein the amount of alkaline earth metal ion present ranges from about 10 - 100 ppm.

4. A composition according to Claim 1 wherein the alkaline earth metal is calcium ion.

5. A composition according to Claim 1 wherein said abrasive is prepared by preparation of an amorphous sili-con dioxide by precipitation through acidulation of a fresh water alkali metal silicate solution with a mineral acid, isolating a wet cake of said precipitated product, and reacting said wet cake with a solution of a salt of said alkaline earth metal.

6. A composition according to Claim 5 wherein the mineral acid is selected from the group consisting of sul-furic acid, phosphoric acid, nitric acid, hydrochloric acid and carbonic acid.

7. A composition according to Claim 6 wherein only a portion of the alkali metal silicate is initially charged to the reaction vessel, the remaining portion of the alkali metal silicate solution is simultaneously added with the mineral acid, and the silicate solution addition discontinued after a predetermined period of time, and wherein mineral acid is added to a pH of less than 6.0, and wherein the wet cake is isolated by filtration and washing.

8. A composition according to Claim 7 wherein the alkaline earth metal ion is calcium and is added in the form of a solution of a salt selected from the group con-sisting of calcium hydroxide, calcium oxide, calcium nitrate and calcium chloride.

9. A method for the production of a composition of Claim 1, which method comprises forming an aqueous solution of an alkali metal silicate having an SiO2 to X2O mole ratio of about 2.0 to 2.7, wherein X is alkali metal, at a reaction temperature in the range of about 77° to 91°C., acidulating with a mineral acid until precipitation of silicon dioxide is substantially complete, then continuing the mineral acid addition until the pH is 6.0 or less, digesting at a tem-perature 10 - 30°C. higher than the reaction temperature for a period of 10 - 30 minutes, filtering the resulting slurry and washing the solid product with fresh water, reslurrying the resulting wet cake in water and under agitation conditions, adding sufficient alkaline earth metal ion in the form of a sufficiently soluble alkaline earth metal salt in sufficient amount to add to said wet cake alkaline earth metal ions in the range of 10 - 300 parts per million based on the dry recoverable product in said slurry, agitating the resulting mixture to provide adherence of the effective level of said alkaline earth metal treatment on the surface of said silicon dioxide, drying and recovering the solid product.

10. A method according to Claim 9 wherein the mineral acid is selected from the group consisting of sulfuric acid, phosphoric acid, nitric acid, hydrochloric acid and carbonic acid.

11. A method according to Claim 10 wherein only a portion of the alkali metal silicate is initially acidulated by the mineral acid and the remaining portion is added to the alkali metal silicate solution simultaneously with the mineral acid.

12. A method according to Claim 10 wherein the alkaline earth metal ion is selected from the group consisting of cal-cium, strontium and magnesium.

13. A method according to Claim 10 wherein the alkaline earth metal ion is calcium and is added as a salt selected from the group consisting of calcium hydroxide, calcium oxide, calcium nitrate and calcium fluoride.

14. A method according to Claim 10 wherein the alkaline earth metal salt is reacted with the wet cake slurry at ambient temperature.

15. A method according to Claim 14 wherein the alka-line earth metal treated silicon dioxide is dried by spray drying.

16. A method according to Claim 10 wherein the alkali metal silicate is sodium silicate, the acidulating acid is sulfuric acid, the alkaline earth metal ion is added in the form of calcium hydroxide to provide a 10 - 100 parts per million of calcium ion intimately reacted with said silicon dioxide product.

17. A toothpaste composition, comprising:
A. from about 6% to 35% by weight of a precipitated silica abrasive material which is a precipitated amorphous silicon dioxide prepared from fresh water alkali silicate by acidulation, which has been intimately reacted with a solution of a salt of an alkaline earth metal so as to have present about 10 - 300 parts per million of alkaline earth metal ions in said amorphous silicon dioxide, said amorphous silicon dioxide exhibiting a Radio-active Dentin Abrasion value of at least 40, an average particle size of from about 5 to 15 microns in diameter, a pack density of about 0.24 to 0.55 grams per milliliter, an oil absorption of about 70 - 95 ccs/100 grams, a BET surface area of about 100 - 250 m2/g, and a percent loss on ignition of about 4 - 6%;

B. from about 0.01% to 3.0% by weight of a water-soluble, fluorine containing material which yields fluoride ions in aqueous solution;
C. from about 3% to 55% by weight of a humectant;
D. from about 0.2% to 2.0% by weight of a binding agent; and E. from about 15% to 80% by weight of water;
said composition providing a pH of from about 4 to 8 when slurried with water in a 3:1 water/composition weight ratio.

18. A toothpaste composition in accordance with Claim 17, which composition additionally contains from about 5% to 12% by weight of a water-soluble phosphate pellicle film penetration agent selected from the group consisting of orthophosphate salts, pyrophosphate salts, tripolyphosphate salts and metaphosphate salts.

19. A toothpaste composition in accordance with Claim 18 wherein A. the precipitated silica abrasive comprises from about 10% to 20% by weight of the composition;
B. the fluorine-containing material comprises from about 0.1% to 1.0% by weight of the composition;
C. the humectant comprises from about 20% to 35%
by weight of the composition;
D. the water component comprises from about 15%
to 40%; and E. the pH provided by a 3:1 water/composition slurry ranges from about 6.5 to 7.5.

20. A composition in accordance with Claim 19 which composition additionally contains from about .1% to 6% by weight of the composition of a sudsing agent; and wherein A. the fluorine-containing material is selected from the group consisting of sodium fluoride and stannous fluoride;
B. the phosphate pellicle film penetration agent is an orthophosphate salt; and C. the humectant is selected from the group con-sisting of glycerine, sorbitol, xylitol and mixtures thereof.

21. A composition in accordance with Claim 20 wherein A. the fluorine-containing material is sodium fluoride; and B. the sudsing agent is selected from the group consisting of:
1. the water-soluble salts of alkyl sulfates having from about 8 to 18 carbon atoms in the alkyl radical, 2. the water-soluble salts of sulfonated mono-glycerides of fatty acids having from about 8 to 18 carbon atoms in the fatty acid moiety;
and 3. mixtures thereof.

22. A composition in accordance with Claim 19 wherein the binding agent is carrageenan.

23. A composition in accordance with Claim 20 which composition additionally contains from about 0.2%
to 5% by weight of the toothpaste composition of a second pellicle film penetration agent selected from the group consisting of citric acid, trisodium citrate, malic acid and tartaric acid; and wherein A. the fluorine-containing material is sodium fluoride; and B. the phosphate pellicle film penetration agent is a mixture of sodium dihydrogen phosphate monohydrate and disodium hydrogen phosphate dihydrate in monosodium to disodium weight ratio of about 1:3 to 1:5.

24. A toothpaste composition in accordance with Claim 19 which contains an additional component selected from the group consisting of A. from about 0.01% to 2% by weight of a flavoring agent;
B. from about 0.05% to 3% by weight of a sweeten-ing agent;
C. from about 0.01% to 2.5% by weight of an anti-calculus agent which is disodium ethane-1 hydroxy-1, 10diphosphonate;
D. from about 0.01% to 2.5% by weight of a bis-biguanide antiplaque agent; and E. mixtures of these additional toothpaste compo-sition components.