CA1258235A - Sodium bicarbonate containing toothpaste - Google Patents

Abstract

SODIUM BICARBONATE CONTAINING TOOTHPASTE
Abstract of the Disclosure A toothpaste containing at least 60% sodium bicarbonate particles as the sole abrasive, at least 30%
of the sodium bicarbonate having particle sizes of less than 25 microns. Humectants, thickening agents, fluoridating agents, flavors, sweeteners and other conventional adjuvants may also be included in the toothpaste.

Description

~Z5~323~

SODIUM BICARBONATE CONTAINING TOOTHPASTE
Technical Field This invention relates to a sodium bicarbonate containing toothpaste. More particulaely, this invention 5 relates l:o a toothpaste containing sodium bicarbonate particles as the sole abrasive agent therein ~,~

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Back~round of the Invention Many different den~ifrice compositions are known for cleaning, whitening, and preserving ~he tee~h. Of thlese known dentifrices, many include high contents of water-insoluble abrasives which aid in removing plaque and retarding stain build-up on the teeth. ~owever, since the ul~imate goal of any oral hygiene regimen is preservation of the teeth, it is widely accepted that dentifrice connpositions should include the least abra~ive material necessary to remove plaque and stain.
The use o~ sodium bicarbonate as an abrasive in dentifrices has previously been proposed. ~hile sodium bicarbonate has been described in the literature as an ingredient of both tooth powders (see, for example, Danner U.S. Patent No. 1,082,681; Crowther U.S. Patent No.

2,024,146; Cabardo U.S. Patent No. 4,276,287; and Winston et al Canadian Patent Application Serial No. 445,902 filed January 23, 1984, owned by the assignee of this invention~
and toothpastes (see, for example, Januszewski et al U.S.
2~ Pat~ent No. 3,935,304; and Delaney et al U.S. Patents Nos.

3,935,305; 3,937,321; 3,937,803; 3,937,804; 3,943,240; and

4,1~50,022), prior to this date it has met with limited commercial success.
Tooth powders generally contain oniy abrasives, flavors, sweeteners, and surfactants. On the other hand, toothpastes generally contain, in addition to the abralsive material, humectants, thickeners and water, as well as surfactants, flavors, and sweeteners. 8Oth forms of dlentrifice may also contain additional ingredients for spec~ial functional or esthetic reasons, for example, fluoridating or coloring agents. In view of the distinct nature of tooth powder and toothpaste formulations and, particularly, the presence of humectants, thickeners and water in toothpastes but not tooth powders, an abrasive which is suitable for use in a tooth powder may not be suitable for use in a toothpaste and, conversely, an abrasive which is suitable in a toothpaste may not be suitable in a tooth powder.

~8~3~i In general, sodium bicarbonate is a desirable abrasive for denti~rice compositions because it is low in abrasion and imparts an exceptionally clean, fresh feel to the mouth. Sodium bicarbonate particles are relatively soft as compared to most conventional abrasive materials used in clentifrice compositions. Thus, the American Den-tal Association has recommended that if only a slight degree of abrasion is necessary to keep from staining, baking soda is usually a satisfactory abrasive. Accepted 10 Dental Therapeutics, pp.340-41 (38th Ed., 1979).
Hereto~ore, low abrasivity has been associated with poor stain removal properties. Secondary abrasives have, therefore, frequently been incorporated in sodium bicarbonate containing toothpaste formulations to enhance 15 their stain removal properties. See, for example, the aforesaid Delaney et al patents, which disclose incorporating secondary, insoluble abrasives such as sil-ica, chalk, alumina, zirconium silicate, or alumino sil-icates in amounts of 5-~5%, or more, of the toothpaste 20 formulations described therein. Similarly, Januszewski et al discloses a sodium bicarbona~e based toothpaste additionally comprising from 0.1 to 5.0% titaniu~ dioxide to enhance the polishing ability of the formulation.
The need for a secondary abrasive to improve the 25 polishing ability of a sodium bicarbonate based dentifrice may be ob~riated by increasing the level of sodium bicarbonal:e in the formulation. This can be effective in a tooth powder, where there is essentially no practical limit to t:he level of sodium bicarbonate which can be 30 incorporat:ed into the product. However, high levels of conventional bicarbonate abrasives in toothpaste formulations impart excessively high viscosities, and prevent mixing during manufacture. Additionally, the dispensibility of such compositions is unacceptable. At 35 the maximum possible levels (about 60-~5%) at which conventional bicarbonate abrasives can be utilized in toothpaste!s, while still maintaining an acceptable consistency, the polishing ability of the formulation is insufficient due to the mild abrasivity of this material.

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Thus, previous attempts to achieve acceptable cleaning power in a toothpaste formulation by incorporating therein high levels of sodium bicarbonate as the sole abrasive have been unsatis~actory.
To avoid ~he undesirable effects generally associated with high levels of abrasive, the amount o~
abrasive included in kno~ln toothpaste formulations is gen-erally limited to between 40 and 50%. See, for example, the Delaney et al patents mentioned above, and Crocker U.S. Patent No. 2,128,917 which discloses incorporating sodium bicarbonate passing a ~200 mesh sieve (74 microns) in an amount of up to 50~ of a toothpaste formulation.
Formulation stability is also a ~requent problem with sodium bicarbonate containing toothpastes. Sodium bicarbonate is unstable in aqueous solution and releases carbon dioxide gas. As a result, the pH of bicarbonate based toothpastes increases during the requisite degassing procedure. It is desirable that dentifrice compositions have a pH close to the neutral range (e.g., pH of 5-9) to avoid damaging sensitive oral tissues. Moreover, in fluoride containing formulations, an increased pH may cause reduced fluoride uptake by tooth enamel. See, for example, the aforesaid Delaney et al U.S. Patents No.
3,943,240 (column l, lines 32-3~) and No. 3,937,803 (col-umn 9, lines 15-21), which caution that degassing be dis-continued be~ore the pH of the composition increases by one pl~ unit, even though degassing may be incomplete.
Another problem encountered in ~ormulating a sodiuTn bicarbonate based toothpaste is that sodium bicarbonate is not always compatible with other abrasive materials in the ~ormulation. ~ee, for example, Delaney et al U.S. Patent No. 3,943,240 at column 2, lines 58-62.
Thus, it is among the objects o~ the present invenl:ion to provide a sodium bicarbonate based toothpaste 35 containing higher amounts o~ bicarbonate than in previous ~ormulations, which toothpaste is effective in removing plaque and retardins stain build-up on the teeth without deleterious abrasion o~ tooth enamel, cementum or dentin, and which toothpaste substantially overcomes the formulation problems previously encountered, such as poor dispensibility, consistency, stability, and increased p~
on degassing.
Other objects and advantages of the invention will be apparent from the following description of pre-ferred embodiments thereof.

~58~35 Disclosure of the Invention In accoedance with the present invention, a toothpaste is provided comprising sodium bicarbonate as the sole abrasive material in an amount of at least about 60% by weight of the formulation, and wherein at least about 30% by weight of the sodium bicarbonate is of a partic:le size less than 25 microns. Toothpaste formu]ations prepared in accordance with this invention provicle cleaning and stain removal properties comparable to the leading co~mercial toothpastes. The toothpaste hereof has the further advantage of being low in abrasion despit:e its high content of abrasive material, as well as possessing desirable consistency and texture. Also, the sodium bicarbonate toothpaste oE the invention is stable on storage, even at elevated temperatures. Unlike existing sodium bicarbonate toothpastes, the toothpaste of this invention has virtually no tendency to excessively increalse in pH on degassing.
It has now been found that, contrary to expecta-tion, higher levels of sodium bicarbonate -- e.g., from about 60-75% by weight -- can be incorporated in toothpastes if finer particle size baking soda is used.
Toothpaste formulations including such an abrasive, i.e., a bicalrbonate in which at least 30%, preferably from about 40 ~o 100%, of its particles have sizes of from about 5 to 25 microns, provide adequate stain removal without the addition of any fur~her abrasive. Moreover, the finer particle size bicarbonate abrasives employed herein do not adversqly affect slurry viscosity during toothpaste formu-lation. In fact, the viscosity decreases as particle size decreases. Thus, a sodium bicarbonate based toothpas~e incorporating the particular sized bicarbonate accGrding to this invention, exhibits both good cleaning properties and formulating and dispensing characteristics.
~ particularly significant advantage of the formulation of the invention is the ability to provide satisfactory stain removal propeeties without having to include a second abrasive therein. Surprisingly, the low abrasivity generally associated with sodium bicarbonate ~Z5~3~35 based toothpastes is not increased in toothpastesformulated according to the invention, even though stain removal properties are improved. Thus a ~urther, although unexp~ected advantage of the toothpaste o~ the present

5 invention is that, while providing adequate stain and plaque removal, i~ is generally lower in abrasivity than commercial dentifrices. Low abrasion to dental enamel and dentin is of considerable importance for maintaining and preserving the teeth.
A further, and surprising, advantage of the toothpaste of the invention is that, unlike sodium bicarbonate toothpaste formulations pceviously reported, the pH has no tendency to rise during degassing. In fact, no increase in pH of the present formulation is recorded, 15 even if degassing is continued for extended periods, e.g., 1 hour. Thus, unlike the toothpastes disclosed in the aforesaid Delaney et al patents, wherein degassing was discontinued prior to complete deaeration to avoid pH
increases of geeater than one pH unit, in preparing the 20 toothpaste of the present invention deaeration can proceed to completion.
The toothpaste formulation of the invention also includes at least a humectant and a thickener. Examples of humectants include glycerol, propylene glycol, 25 sorbitol, polyethylene glycols (generally of formula H(OC2H43nOH), and other materials known to those skilled in the art. The humectant may be present in the toothpaste in an amount of up to about 35%, preferably in an amount of about 8 to 25~, by weight of the toothpaste 30 formulation. Suitable thickeners include sodium carboxymethylcellulose, xanthan gum, methyl cellulose, hydroKyethyl cellulose, carrageen, gum karaya, gum tragacanth, gum arabic, colloidal complex magnesium alumi-num silicates (e.g. "Veegum", manufactured by ~.T.
35 Vanderbilt Co.3, and sodium alginate. The thickener is incorporated in the toothpaste in an amount of up to about 3~, pre~erably within the range of about 0.3 to l.5%l by weigh~t of the toothpaste.
The toothpastes of the present invention * Trade mark 2 ., S~3235 pre~erably contain other ingredients in addition to sodiu~
bicarbonate, a humectant, and a thickening agent. The toothpaste may thus contain water in an amount necessary to achieve formulation o~ the toothpaste, e.gO, ~rom about 0 to 25~ by weight. ~dditional ingredients may include surfactants, flavoring agents, sweeteners, and fluoridating agents, as recognized by those skilled in the art.
Suitable surfactants include anionic surfactants such as the sulfates of long chain (Cg - Cl8) alcohols e.~. sodium lauryl sulfate or sodium tridecyl sulfate, the sulfates or sulfonates of monoglycerides e.g. so~ium lauroyl glyceryl sulfate or sodium coconut monoglyceride su~fonate; the su~fonates o~ succinic esters e.g. sodium dioctyl sulfosuccinate; the alkyl sulEoacetates such as sodium laury~ sulfoacetate or sodium coconut su]foacetate;
the sa1ts o~ sulfoacetic acid amidified with amino ethyl long chain fatty acid esters such as sodium sulfoco]aurate: the amides ~ormed from higher ~atty acids with short chain amino acids such as sodium lauroyl sarcosinate or sodium methyl lauroyl tauride and soaps such as the sodium, potassium or triethanolamine salts of fatty acids. Simil~r]y non-ionic surfactants may be used such as the ethoxylated sugar esters of the higher fatty acids for examples ethoxylated sorbitan monostearate and ethoxylated glyco] monostearate. Also amphoteric surfactants such as the mono or dicarboxylated imidazoline derivatives of fatty acids such as sodium lauryl dicarboxy imidazoline or sodium coconut dicarboxy imidazoline may be used. Cationic surfactants may also be used in the inven-tion. These materials may impart significant antibacterial action to the product. Examples are benzyl dimethyl stearyl ammonium chlor;de and cetyl pyridinium chloride. The sur~actant(s) are present in the toothpaste in an almount of up to about ~.0~, preferably within the range of about 0.~% to 2.0%, by we;ght o~ the toothpaste.
The flavor of a sodium bicarbonate containing toothpaste is afected by the particle size o~ the sodium bicarbomate. Generally, the saltiness of the toothpaste 323~i increases as the partic]e size decreases. However, the effect of small particle size sodium bicarbonate in a toothpaste formulation is not as pronounced as in tooth powders. It is believed t~at the presence of the humectant and thickening aaents in the toothpaste ~ormu lation retard bicarbonate dissolution in tke mouth and thus reduce the adverse saltiness. It should, however, be understood that this hypothesis does not, in any way, limit the scope of the present invention.
Moreover, much of the saltiness can be masked by the addition of optional flavoring agents and/or sweeteners to the toothpaste formulation. Suitable flavoring agents include the flavoring oils, for example, peppertnint, spearm;nt, menthol, wintergreen, clove, cinnamon, lemon, orange, methy~salicylate, licorice, or eucalyptus. The flavoring aqent may be present in the toothpaste in an amount up to about 5.0%, preferably in an amount within the range of about 0.3 to 2.~% by weiqht of the toothpaste. Suitable sweeteners inc~ude sodium s~ccharin, sodium or calcium cyclamate, aspartame, and other ;weeteners known to those skilled in the art. The sweetener may be present in the toothpaste in an ~mount of up to about 5.0%, preferably about 0.3 to 2.~, by weight of the toothpaste. It should be noted tha~ humectants, e.g. sorbitol, may sweeten the formulation to some degree.
However, the amount of humectant peesent in the composition is not included in the range of sweetener set forth above.
The toothpastes of the present invention may additionally contain a fLuoridating agent to aid in preventing dental car;es. Many fluoridating agents suitable for use in dentrifrice compositions are known.
Among l:hese are sodium, potassium, lithium or ammonium fluorides, organic amine fluorides, monofluorophosphake salts such as sodium, potassium, lithium and ammonium monofluorophosphate, sodium fluorosilicate, sodium flu-orozirconate, and other materials well known to ~hose skillefl in the art. The fluoridating agents are present in an effective but non-toxic amount, e.g., in amounts of ~5 5i;~35 --1.0--up to about 2.0%, and preferably in an amount to provide a fluoride level equivalent to about lOOOppm of fluoride ion.

:~5~3Z35 _~ Best Mode ~or Carry_ng Out The Invention The preferred toothpaste formulations of the invention com~rise about 62.0 to 75.0% by weight o~ sodium bicarbonate, at 1east about 30~ of which has a particle size under 25 miceons, desirably about 5 to 25 microns.
Preferably, the fine particles comprise about 40.0 to lOO.O~ o~ the scdium bicarbonate included in the Eormu-lation. oe the remaining sodium bicarbonate content, about 65.0-lOO.O~ has a particle size of from 25 to 210 microns, preferably from about 25 to 88 microns.
It is particularly preferred to incorporate the fo110winq ingredients in the bicarbonate-con~ainin~
tootlhpaste of the invention:
% By Weiq~t sodium bicarbonate 62 - 76 Less than 5 microns 0 - 5 5 - 25 microns 3S - 100 25 - 8~ microns O - 60 humect~nt (preFerably ~lycerol or mixtures with polyethylene g1ycol of molecular weight 400 (e.g.
Carbowax 400) 8 ~ 25 thickener (pr~ferably sodium carboxy-methyl cellulose) 0.3 - 1.5 surfactant ~preferably sodium lauryl sul~ate and/or so~ium i lauroyl sarcosinate0.2 - 1.0 f1avorin~ agent 0.3 - 2.0 sweetener rpreferably saccharin)0.~ - 2.0 fluoridating a~ent (preferably sodium fluoride/
sodium monofluoro-phosphate) 0.22 - 0.7~
The prefeered toothpastes of the present inven-tion are prepare~ by first mixing the thickener with the ~`
* Trade mark l~S~Z35 humectallt. ~ water solution containing the sweetener, surfactant and fluoride is added to the thickener-humectant mixture. Then, the sodium bicarbonate is stirred into the mixture. Finally, the flavor oil is added. The composition is then deaerated under vacuum, e.g., at about 26-30 inches o~ mercury, the vacuum being released every few minutes to improve release o~ the trapped gases, and then reapplied. The deaeration process is generally com~]eted in about 20 minutes.
10 The ~ollowing examples illustrate particularly preferred emhodiments oE the toothpaste of the present invention. In the examples all parts and percentages are given by weight.
Examples 1-3 - Texture and Dispensing 15 Characteristics of Toothpastes Containing _ 62~ Sodium Bicarbonate Examples o~ the sodium bicarbon~te containing toothpaste of the invention were prepared from the ~ollow-inq formulation. The examples were compared with controls based on the same formulation but containing bicarbonate componemts having differing particle size distributions in order to show the effect o~ the bicarbonate particle size distribution on the texture and dispensing pressure of the resulting product.
Formu]ation I
Sodium bicarbonate 62.0 Water 18.13 Glycerine 17.l Carboxymethylcellulose 0.75 So~ium ~luoride 0.22 Sodium lauryl sulfate 0.3 Sodium ~auroyl sarcosinate 0.3 FJavor n . 7 Saccharin 0.5 100.0%
Dispensing pressure and texture were evaluated.
Dispensing pressure was determined by measuring the pres-35 sure re~uired to eject a 26mm strip of toothpaste through a 7mm orifice. Dispensing pressure of a toothpaste ~Z~i~f~3~

composition is of concern because it is directly related to the dispensing of the paste from the tube and onto a toothbrush. Texture was evalua~ed visually using the ~ollowing rating system: 1 -- very creamy smooth; 2 --creamy smooth, 3 -- creamy, slightly gritty; 4 -- dry, slightly gritty; 5 ~- dry, gritty.
Examples 1, 2 and 3 representing variations of Formulation I within the scope of the invention, were compared with Controls A and B~ which are variations of Formulation I containing sodium bicarbonate having dif-ferinq particle size distributions and "Crest" toothpaste(Control C~. It should be noted that control B contains the commercial grade of sodium bicarbonate (baking soda) available to consumers, i.e, grade 1. The results are sum-marized in Table I:

* Trade mark ~Z~l23S

COMPARATIVE TEXTURE AND DISPENSING
CHARACTERISTICS OF`TOOTHPASTES CONTAINING
62~ SODIUM 8ICARBONATE HAVING VARYING
PARTICLE SIZE DISTRIBUTIONS
CbNTROL EXAMPLE

("Crest")*
More than 149 microns 92.5 0.5 0 0 O
149-89 microns 6.5 19.5 013 0 45-88 micron3 1.0 50 1533 0 25-44 microns 0 18 4512 o ~es~ than 25 microns 0 12 4042 100 ~-Initial dispensing pre.~ure(lbs)S.25 2.37 3.12 2.0 2.25 2.50 Dispensing pressure~lbs.), after 3 weeks at 125~ 8.2 ~.75 3.50 3.1 3.6 3-0 Dispensing pressure(lbs.), after 9 weeks at 125F 23.1 6.0 4.0 3.8 3.8 3.3 Initial texture rating 5 4 1 1 3 Texture rating after 9 weekq at 125F 5 4 1 4 3 2 ~Contains 30dium fluorLde in a base o~ sorbitol (humectant), water, hydrat~d ~ilica (abrasive), trisodium phosphate (buffer), sodium lauryl qulfate (sur~ac~ant), flavor, titanium dioxide (to improve color, and as a second abrasive), sodium phosphate ~buffer), xanthan gum (thickenlng agen~), Carbomer*940 (an acrylic type of polymeric thickening/ emulsifying agent), sodium saccharin (sweetener) and FD&C Blue tl(colorant).

* tracle mark ~lZS~3Z35 The above comparisons demonstrate that when the level of smaller particle size sodium bicarbonate crystals is increased, the dispensing pressure is lower and the smoothness of the toothpaste is greater, than when larger 5 bicarbonate particles are employed in the formulation.
As can be seen from the data presented in Tabl.e I, Exam ples l, 2 and 3 prepared in accordance with the present invention had low dispensing pressures which were compara-b3.e with ~Crest~ (Control C). .~dditiona1ly, Exampl.es l, 2 10 and 3 ha~ acceptable creamy textures.
In contrast Control. A, incorporating coarse crystals of sodium bicarbonate, had an unacceptahly high dispensing pressure especiall.y on aging. Control B, a toothpaste prepared with a quantity of fine crystals of sodium bicarbonate, bel.ow the ].evel of the invention, had an initially acceptable ~ispensing pressure. However, on aging the dispensing pressure increased beyond an accepta-ble level. Both Control.s ~ and B had unacceptab~y dry textures.
Examples 4-5 Texture and Dispensing Characteristics of Toothpastes Containing 70% Sodium Bicarbonate .
- Further toothpastes were prepared, and dispensing pressure and texture comparisons performed, emp1Oy1ng compositions prepared from the following formulations cont~ining 75~ (Example 4) and 70% (Example 5) sodium bicarbonate, respectively: The results, which are set forth in Table II, show that even at sodium bicarbonate levels of 70~ and above, low dispensing pres-sures and acceptable consis~encies are obtained.

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-l6-TABLE IT
COMPARATIVE TEXTURE AND DISPENSING
C~RACTERISTICS OF TOOTHPASTES CONTAINTNG
70% AND 75~ SO~IUM BICARBONATE HAVING
VARYING PARTICLE SIZE DISTRIBUTIONS
. _ EXAMPLE

Sodium bicarbonate 75 70 Water 13.08 18.08 Glyceeine 9.38 9.38 Xanth~n gum 0.25 0.25 Carboxymethylcel]ulose 0.25 0.25 Sodium F~uoride 0.24 0.24 SoAium Laury1 Sulfate 0.3 0.3 Sodium Lauroyl Sarcosinate 0.3 0.3 F~avor 0.7 0.7 Saccharin 0.5 0.5 Particle size of bicarbonate used more than 149 microns 0 n 89-149 microns 12 11 45-88 miceons 30 29 25-44 microns 11 l0 Less than 25 microns 47 50 Initial dispensing pressure NT* 4.2 Dispensing pressure (lbs~) after l week at 125F 4.8 5.7 Dispensing pressure (lbs.~ after 3 weeks at 125F NT* 3.8 * NT - Not tested Examples 6-9 Stain Removal and Abrasive Properties of Toothpastes Containing 65 _ Sodium Bisarbon~te Tests were run to illustrate the stain remova]
and abra,sion properties of sodium bicarbonate based toothpastes. Examples 6 through 9 and Controls D, E and F
incorporated the ingredients specified in Formulation II
below. Examples 6 through 9 contain varying bicarbonate partic]e size distributions in accordance with the inven-0 t;on~The stain removal properties of the various toothpaste compositions were evaluate~ using a simulated stain removal test. Ceramic tiles were stained with con-centrated tea solution, and the stain was fixe~ by dipping the tiles in Perrous sulfate. A slurry of test product (2 parts! and water (1 part) was placed on each test tile and the tile was brushed in a Gardner straight line washabillty machine for 50 cycles. The tiles were then rinsed and dried. Stain removal was determined by 0 comparing the reflectance before and after brushing.
Examples 6 through 9 were compared with Controls D, ~ and F, and with "Crest" (Control C) for stain removal efficiency. The results are set forth below.
Formulation Il Sodium Bicarbonate 65 Water 16.53 Glycerine l5.60 Carboxymethylcellulose0.75 Sodium Fluoride 0.22 Sodium Lauryl ~Sulfate0.3G
Sodium Lauroyl Sarcosinate 0.30 Flavor 0.70 Saccharin 0.50 -lB-TA~LE III
COMPARATIVE STAIN REMOVAL AND ABRASIVE PROPERTIES OF
TOOTHPASTES CONTAINING 65% SODIUM 8ICARBONATE
HAVING VARYING PARTICLE SIZE DISTRIBUTIONS
CONTROL EXAMPLE
- E F ct 6 7 More than 149 microns 0.5 0 0.5 0 0 0 0 89 149 microns 1~.5 11 16.5 0 6 14 0 45-88 microns 50 35 43 15 16 34 0 25-44 microns 18 30 15 45 6 12 0 Less than 25 microns 12 24 25 40 72 40 100 Increase in Re:Electance ~Higher value equals 13.3~19.8* 22.7* 31.0 27.3 27.6 28.0 31.0 better stain ;removal) t ~Crestn * Worse performance than Control C, and Examples 6-9 ( 95% t'onfidence Level) Not significant1y different than Control C.

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I g The stain removal comparisons demonstrate that stain removal properties qenerally increase with an increase in the proportion of the sodium bicarbonate particles havin~ sizes less than 25 microns. Controls D, 5 E and F, all containing 25% or less sodium bicarbonate p3rticles sized below 25 microns, performed significantl.y poorer in the stain removal tests than Examples 6-9, and Control C.
Examples 10-14 Stain Removal Properties of Toothpastes Containin~ 62% Sodium 10 Bicarbonate and Incorporating Varying Water to ~umectant Ratios ~ nother stain removal comparison was performed to determine whether variations in the water to humectant ratio wou~d affect the stain removal properties of 15 toothpastes formulated in accordance with the invention.
Examp]es ln through 14 and Controls G, H and I incorpor-atefl the composition of Formulation III, set forth below.
Stain removal was evaluated as describe~ in Examples 6~9, above.
Formulation III
Sodium bicarbonate62.0 ~ater ~ Glycerine* 35.23 Carboxymethylcellulose 0.75 Sodium fluoride 0.22 Sodium lauryl Sulfate 0.3 Sodium lauroyl Sarcosinate 0.3 Flavor 0.70 Sacchari.n 0.50 100.00 * Ratios as set ~orth in Table IV.

~L2S~'~35 TABLE IV
COMPARATIVE STAIN REMOVAL PROPERTIES OF TOOTHPASTES CONTAINING
62~ SODI~M BICAR80NATE HAVING DIFFERENT PARTICLE SIZE
DIsTRr-B-u-TIoNs AND VARYING WATER TO HUMECTANT RATIOS
CONTROL EXAMPLE
r: .__ ._ _ _ _ _ _ __ __ _ ___ G H I C~~ 10 11 12 13 14 More than 149 microns92.5 0.5 0.S 0 0 0 0 0 89-149 microns6.519.5 19.5 13 0 13 13 0 45-88 microns1.0 50 50 33 0 33 33 o 25--44 micron~ 0 18 18 12 0 12 12 0 Less than 25 microns 0 12 12 42 100 42 42 100 Water/
Glycerine Rcltio 1.1/1 1.3/1 0.6/1.0 1.3/1.0 0.6/1.0 1.1/1.1 0.6/1.0 1.3/1.0 Increase in Reflectance 5.6* 14.7* 14.9~ 22.4 18.4 19.0 20.3 21.7 23.0 t "Crest~

* Significantly worse performance than Contro~ C and Examples 12-4 (~ 95~ Confidence Level) Not significantly different than Control C.

:~2~ 35 The above comparisons generally confirm that increasing the quantity of sodium bicaebonate particles under 25 microns in the composition improves stain removal. Thus, it is possible to formulate toothpastes having sodium bicarbonate as the sole abrasive, without sacriEicing the stain removal achieved by commercially availab:Le products such as "Crest". Additionally, Table IV demonstrates that varying the water to humectant ratio does no1: significantly affect stain removal. Examples 10-14, prepared in accordance with the invention, have stain removal properties equivalent to that of the "Crest"
control~
Examples 15-16 - Stain Removal Properties of Toothpastes Containing Varying Proportions of Sodium Bicarbonate . _ _ Comparisons of stain removal properties of toothpastes containing various total amounts of sodium bicarbonate show that if sodium bicarbonate is used as the sole abrasive high levels (65~ - Example 15; or 75% -Example 16) are required to obtain the desired cleaningcapacity.
Stain removal comparisons were performed in the manner previously described. The results, which are sum-marized in Table V, show that stain removal generally increases with a corres~onding increase in the a~ount o~
sodium bicarbonate, provided the requisite level of fine particle~s of baking soda is maintained. As shown, at least 60% sodium bicarbonate is necessary to achieve stain removal equivalent to the commercial dentifrice.
Moreover, and contrary to expectation, solely using sodium bicarbona~e particles under 25 microns in size, but at a total percentage of less than 60%, does not significantly improve stain removal properties. Thus, a sodium bicarbonate based toothpaste containing baking soda 35 as the sole abrasive only ac~ieves the stain removal per-formance of a commercial dentifrice, if at least 60 sodium bicarbonate, with greater than 30% of the bicarbonate particles being smaller than 25 microns is included in the formulation.

~58'~35 COMPARATIVE STAIN REMOVAL CHARACTERISTICS OF
TOOTHPASTES CONTAINING VARYING TOTAL
AMOUNTS OF SODIUM BICARBONATE
CONTROL EXAMPLE

Sodium Bicacbonate 40 40 50 65 75 Water + Glycerine (Ratio 1:1) 56.78 56.78 46.98 32.28 22.48 Carboxymethylcellulose 1.20 1.20 1.00 0.70 0.50 Sodium FluoLide 0.220.22 0.22 0.22 0.22 Sodium Lauryl Sulfate0.300.30 0.30 0.30 0.30 Sodium Laurc~yl Sarcosinate 0.30 0.30 0.30 0.30 0.30 Flavor 0.700.70 0.70 0.70 0.70 Saccharin 0.500.50 0.50 0.50 0.50 ~ PARTICLE SIZE DISTRIBUTION
_ OF BICARBONATES _SED _ ~ore than 144 microns 0 0 0 0 0 89-149 microns 0 14 14 14 14 45-88 miron~ 0 34 34 34 34 24-44 microns 0 12 12 12 12 Less than 25 microns 100 40 40 40 40 STAIN REMOVAL CHARACTERISTICS
J~ L Control C 15 16 ( Crest" ) Increase in Reflectance 15.4* 13.4* 16.8* 23.0 24.4 29.2*~
* Significantly poorer than Examples 15 and 16, and Control C
(> 92~ Confidence Level) Same as Control C ~"Crest~) ** Significantly better than Control C (nCrestn) (> 95~ Con~idence Level) ~25;~3235 Examples 17-18 - Abeasive Characteristics of Toothpastes Containing 62~ Sodium Bicarbonate, As ComDared With Commercial Toothpaste Formulations .. . .
The abra~ivity of Examples 17 and 18 was compared with the abrasive characteristics of Controls M, N and O. Examples 17 and lg, and Control M, were pre~
pared from Formulation I (set forth above), with Examples 17 alnd 18 containing a sodium bicarbonate particle size distribution according to the present invention. Controls C, ~l and O were commercial toothpastes (1Crest", ~imn*and "Colgaten); the latter two formulations contain calcium pyrophosphate as the abrasive therein.
In the abrasion studies, the test toothpastes were compared for relative enamel and dentin abrasivity using the method of J.J. Hef~erren ("A Laboratory Method for Assessment of Dentifrice Abrasivity," J.Dent.Research S5, 563-573, 1976). Relative enamel abrasivity was dete~rmined by abrading the crowns of freshly extracted irra,diated human ~eeth, using slurries of the test composition~. The enamel removed was quantitated by the level of radioactive phosphorus abraded into the slurry.
Similarly, relative dentin abrasivity was measured by abrading the roots o~ freshly extracted irradiated teeth, and determining the amount of radioactive dentin eemoved.
The results were al~o compared with that of a calcium pyrophosphate control.
Slurries of Examples 17 and 18 and Control M
were prepared using 25 grams of pas~e in 50 ml. water. A
lOg control slurry of calcium pyrophosphate in 50 ml. of 0.5% aqueous carboxymethylcellulose was given an arbiteary abrasivity value of 100.
The results demonstrate that there is no signif-icant difference in dentin or enamel abrasivity between the test toothpastes containing sodium bicarbonate levels in accordance wlth the invention (Examples 17 and 18) and that toothpaste (Control M) formulated with le~s than 30%
of the baking soda particles smaller than 25 micron~.
Al~o, as can be seen, the toothpast~ compositlons of ~he invention are significantly lower ln dentin abrasivity than ~he commercial products (Controls C, M and O), * Trade mark ., .

~l~5 !3'~35 COMPARATIVE ABRASIVE CaARACTERISTICS OF TOOTHPASTES CONTAINING
SODIUM BICARBONATES HAVING VARYING PARTICLE SIZE DISTRIBUTION, WITH COMMERCIAL CONTROL TOOTHPASTE FORMULATIONS
CONTROL EXAMPLE

(WCrestn) ("Aim")l (~Colgaten)2 More than 149 microns 0.5 0 0 89-149 microns 19.5 0 13 45-88 microns SO 15 33 25-44 microns 18 45 12 Less than 25 microns l2 40 42 Relative dentin abrasivity 7144~ 64 63 43* 46 Relative enamel abrasiv:ity 219~* 10 12** 10*~ 11**

* Lower abraYivity than controls C, N and 0. (> 95% Confidence Level) ** Lower abrasiYity than controls C and N. ( ~ 95~ Confidence Level) L Aim contains sodium monofluorophosphate in a base of sorbi~ol, hydrated silica, PEG 32, water, sodium lauryl sulfai:e, SD alcohol 38B, flavor, cellulose gum, sodium saccharin, sodium benzoate, FD&C Blue ~1, D&C Yellow ~10.
2 Colga~:e contains sodium monofluorophosphate in a ba~e of dicalcium phosphate dihydrate, water, glycerin, sodium laury:L sulfate, cellulose gum, flavor, sodium benzoate, tetro--sodium pyrophosphate, sodium saccharin.

~2S~'~3~

Examples 19-20 - Abrasive Characteristics of Toothpastes Containing 40~ and 100% Sodium Bicarbonate as Compared With "Crest"
~ . .
Two additional sodium bicarbonate based toothpastes prepared in accordance with the present inven~
tion were compared with "Crest", for relative abrasivity to enamel and dentin. These results show that a sodium bicarbonate toothpaste wherein all the sodium bicarbonate particles are smaller than 25 microns, has significantly lower abrasivity than "Crest".
Example 19 Example 20 Sodium bicarbonate 62 65 Water 18.l3 16.63 Glycerine 17.1 15.6 Carboxymethylcellulose 0.75 0.75 Sodium Fluoride 0.22 0.22 Sodium Lauryl Sulfate 0.3 0.3 Sodium Lauroyl Sarcosinate 0.3 0.3 Flavor 0.7 0.7 Saccharin 0.5 0.5 TABLE VII
ABRASIVE CHARACTERISTICS OF TOOTHPASTES
CONTAINING SODIUM ~ICARBbNATES HAVING
VARYING PARTICLE SIZE DISTRI~UTIONS, AS Cb~MPARED WIT~ "CREST'i _ CONTROL EXAMPL~ _ ("Crest") More than 149 microns 0 0 89-149 microns 0 14 10 45-88 micronS
22-24 microns 0 l2 Less than 25 mfcrons 100 40 Relative dentin abra~ivity 90 47* 47*
Relative enamel abrasivity 24 18 21 * Lower abra~ivity than control (~ 95~ Confidence Level) ~25~3Z35 Examples 21-23 - Degassing Characteristics of Toothpastes Containing Sodium Bicarbonates Having Varyin~ Particle Slze ~istributions .
As previously discussed, the toothpastes of this invention can be totally degassed without significant increase in pH. Tests were run comparing the pH, before and after degassing, of three toothpaste compositions of the invention. The results, which are summarized in Table VIII be:Low, show that there is no significant change in pH
after degassing has been completed.

~S~323S

TABLE VIII
COMPARISON OF pH BEFORE AND AFTER
DEGASSING OF FORMUL~TIONS CONTAINING
SODIUM BIC~RBONATES ~AVING THE PARTICLE SIZE
DISTRIBUTION OF T~E INVENTION
EXAMPLE

Sodium Bicarbonate 62 62 62 Water 19.91 18.13 16.78 Glycerine 15.32 17.1 18.54 Carboxymethylcellulose 0.75 0.75 0.75 Sodium Fluoride 0.22 0.22 0.22 Sodium Lauryl Sulfate 0.3 0.3 0.3 Sodium Lauroyl Sarcosinate 0.3 0.3 0.3 Flavor 0.7 0.7 0~7 Saccharin 0.5 0.5 0.5 Particle Size of bicarbonate used More than 149 microns 0 0 0 83-149 microns 13 0 13 45-88 miceons 33 0 33 25-44 microns 12 0 12 Less than 25 microns 42 100 42 pH before degassing 9.15 9.3 9.0 pH after degassing 8.9 8~9 9.1 ~2~

It will be understood that the preferred toothpaste compositions of the invention described herein are illustrative only, and should not be construed as limiting the present invention.
What is claimed is:

Claims (11)

Claims

1. In a toothpaste containing an abrasive, a humectant and a thickening agent, the improvement comprising sodium bicarbonate as the sole abrasive, the sodium bicarbonate being incorporated in the toothpaste in an amount of at least 60% by weight, and at least 30% by weight of the sodium bicarbonate having a particle size of less than 25 microns.

2. The toothpaste according to claim 1, wherein the humectant is selected from the group consisting of glycerol, propylene glycol, sorbitol and polyethylene glycols.

3. The toothpaste according to claim 1, wherein the thickening agent is selected from the group consisting of sodium carboxymethylcellulose, xanthan gum, methyl cellulose, hydroxyethyl cellulose, carrageen, gum karaya, gum tragacanth, gum arabic, and sodium alginate.

4. The toothpaste of claim 1, further comprising from 0.01 to 2.0% by weight of a fluoridating agent.

5. The toothpaste according to claim 1 further comprising a surfactant.

6. The toothpaste according to claim 1, further comprising from 0.3 to 5.0% by weight of a flavoring agent.

7. The toothpaste according to claim 1, further comprising from 0.3 to 5.0% by weight of a non-humectant sweetener.

8. A sodium bicarbonate based toothpaste comprising from 60 to 75% by weight sodium bicarbonate, at least 30% of said sodium bicarbonate having a particle size of less than 25 microns; from 5 to 25% by weight of a humectant; from 0.3 to 300% by weight of a thickener; from 0.3 to 5.0% by weight of a surfactant; from 0.3 to 5.0% by weight of a flavoring agent; from 0.3 to 5.0% by weight of a sweetener; and from 0.01 to 2.0% by weight of a fluoridating agent.

9. The toothpaste of claim 8, wherein from 25 to 100% of the sodium bicarbonate has a particle size of from 5 to 25 microns, and from 60 to 100% of the sodium bicarbonate has a particle size of from 25 to 210 microns.

10. The toothpaste of claim 8, wherein the humectant is selected from the group consisting of glycerol, propylene glycol, sorbitol, and polyethylene glycols.

11. The toothpaste of claim 8, wherein the thickener is selected from the group consisting of sodium carboxymethylcellulose, xanthan gum, methyl cellulose, hydroxyethyl cellulose, carrageen, gum karaya, gum tragacanth, gum arabic, and sodium alginate.