Sodium dihydrogen phosphate enhanced dentifrice composition

A sodium dihydrogen phosphate stannous fluoride containing dentifrice composition wherein the enamel penetration and effectiveness of the fluoride is enhanced by sodium dihydrogen phosphate causing the enamel crystalline latticework of the teeth to become activated and allowing the stannous fluoride to penetrate and remain in the tooth enamel for a sufficient period of time to render the enamel effectively resistant to the development of dental caries. The dentifrice also may include a carrier incorporating quantities of abrasive material for polishing, a sweetening agent, a flavoring agent and a foaming agent. Within the acid pH range of between 2 and 5 and preferably 3.5, the sodium dihydrogen phosphate compound alters the crystalline latticework of the enamel thus rendering it capable of inducing deep penetration of fluoride ions and, subsequent to fluoride penetration, a surface capping effect or sealing effect is developed by the stannous fluoride phosphate complex that is effectively resistant to the natural leaching effect of the oral fluids.

FIELD OF THE INVENTION 
This invention relates generally to dentifrice materials incorporating 
sodium dihydrogen phosphate for developing caries resistant tooth enamel 
and dentifrice compositions incorporating a system of fluoride treatment 
and, more specifically, concerns a dentifrice composition incorporating a 
quantity of sodium dihydrogen phosphate sufficient to cause substantial 
enhancement of the caries resistance typically afforded by stannous 
fluoride. Even more specifically, the present invention concerns the 
provision of a water free gel or paste carrier of pleasing appearance that 
incorporates stannous fluoride as the fluoride compound and sodium 
dihydrogen phosphate as the acid phosphate compound, in such proportions 
as to render the caries resistant quality of the stannous fluoride 
substantially more effective than if utilized in the absence of the acid 
phosphate compound. 
BACKGROUND OF THE INVENTION 
Topical fluoride treatment with fluoride solutions has been found quite 
effective in the prevention of dental caries. The most effective type of 
fluoride treatment is almost always conducted in a clinical environment 
because of the strong concentration of the fluoride solution that is 
applied to the teeth. Of course, clinical treatment of this nature 
severely limits access by the general public to this character of fluoride 
treatment. Accordingly, dentifrice preparations have been developed and 
marketed having low concentrations of various fluoride compounds and these 
preparations have gained widespread acceptance by the public. The 
anticaries effectiveness of dentifrice products has been materially 
enhanced by the development of anticaries agents, such as stannous 
fluoride, sodium monofluorophosphate sodium fluoride, etc. These 
anticaries agents, when incorporated in dentifrice products, provide 
topical fluoride treatment with daily dental hygiene. Tests have shown 
marked reduction in the occurrence of dental caries when the dentifrice 
utilized for daily dental hygiene includes a fluoride containing compound. 
It is desirable to enhance the effectiveness of fluoride compounds, 
especially stannous fluoride, for caries prevention without necessitating 
an increase in the concentration of the fluoride compounds in dentifrice 
products that are available to the general public. For example, it has 
been found that a concentration of stannous fluoride in the range of 
0.3%-0.5%, and preferably 0.4%, of a dentifrice composition yield good 
results from the standpoint of anticaries treatment. Increasing the 
concentration of fluoride compound in a dentifrice materially above the 
level of 0.4% may yield minimal increase in anticaries activity, but the 
risk of harmful concentrations becomes a matter for careful consideration. 
For that reason, it is desirable to maintain a concentration of a fluoride 
compound at about 0.4% of a dentifrice composition and to provide for an 
increase in the anticaries activity of the product by other suitable 
means. 
The enamel of the teeth is defined by a crystalline latticework of 
hydroxy-apatite that is effectively resistant to absorption of most 
materials that are ordinarily present in the oral environment. Fluoride 
containing dentifrice materials are capable of penetrating the crystalline 
latticework to a limited degree and therefore fluoride treatment of the 
teeth is effective for caries resistance only under circumstances where 
the solution applied to the teeth includes a strong concentration of 
fluoride. For example, prophylactic pastes and gels utliized in dental 
offices contain fluoride at about 10% solution. The maximum allowable 
fluoride concentration in dentifrice materials sold to the public is about 
0.4% solution and the fluoride effectiveness is therefore quite limited. 
It is desirable to provide a fluoride containing dentifrice material that 
is capable of accomplishing increased fluoride enhanced caries resistance 
without requiring concentration of fluoride in excess of 0.4% solution. 
It is well known that fluoride penetrating the outer surface portion of the 
crystalline latticework of the enamel tends to leach out quite rapidly. 
The leaching action begins as soon as the oral cavity is rinsed after 
brushing, removing the fluoro chemical environment introduced by the 
dentifrice. It is desirable first to accomplish opening or activation of 
the crystalline latticework of the enamel and then to provide a surface 
sealing or capping effect for the enamel to retard the normal leaching 
action of the oral fluid which would otherwise allow rapid dissipation of 
the fluoride from the enamel. This activity will allow the fluoride to be 
retained deeply within the latticework as long as possible so as to 
provide long term anticaries activity even though fluoride is utilized at 
or below the weak solution range allowed by governmental authority. 
Most dentifrice preparations have a pH in the neutral, slightly basic or 
slightly acid range. For example, known dentifrice materials having an 
acid pH do not exceed an acid pH of about 5. The primary reason for this 
is that decalcification begins to occur in the acid pH range and, since 
the enamel is eroded to some extent by the abrasive material during the 
brushing or scrubbing action of oral hygiene it is considered undesirable 
to cause further deterioration of the enamel by decalcification. It has 
been determined, however, that the enamel crystalline latticework begins 
to open or become active at an acid pH and tests indicate that crystalline 
latticework is able to accept deeper penetration of the fluoride as the 
latticework opens or becomes activated. Thus, it is desirable to 
accomplish opening or activation of the crystalline latticework by means 
of an acid pH to promote deep penetration of the fluoride into the 
crystalline latticework of the enamel without involving a pH significantly 
low that decalcification becomes a problem. 
In some cases it will not be desirable to utilize a fluoride for daily 
anticaries activity. In this limited case it is desirable to provide a 
dentifrice composition that is capable of reacting with the enamel to 
develop caries resistance. 
One of the important aspects of providing a dentifrice that has wide public 
acceptance is the appearance of the dentifrice material itself. Dentifrice 
material having a translucent, pleasantly colored appearance is, 
therefore, a desirable feature insofar as the material also provides 
optimum prevention of caries and is pleasing to the taste. 
Accordingly, it is a primary feature of the present invention to provide a 
novel dentifrice material that incorporates a fluoride compound for 
fluoride induced anticaries treatment of the teeth and further 
incorporates an acid phosphate compound that functions to enhance the 
anticaries prevention capability of the fluoride compound, without 
increasing the concentration of the fluoride compound in the dentifrice 
composition beyond the level of concentration allowed by governmental 
authority. 
It is also a feature of this invention to provide a novel dentifrice 
composition that incorporates a sufficient quantity of sodium dihydrogen 
phosphate to alter the crystalline latticework of the enamel causing 
material enhancement of the resistance of tooth enamel to the development 
of dental caries. 
It is a further feature of this invention to provide a novel dentifrice 
material which incorporates a sufficient quantity of sodium dihydrogen 
phosphate to alter the crystalline latticework of the enamel to render the 
enamel actively receptive to deep penetration of fluoride ions into the 
crystalline latticework. 
Among the several features of the invention is noted the contemplation of a 
novel dentifrice composition having an acid pH range within which deep 
penetration of fluoride ions is induced and a subsequent stannous capping 
effect is developed that effectively prevents leaching of the fluoride or 
phosphate ions from the enamel of the teeth. 
It is also a feature of this invention to provide a novel dentifrice 
composition incorporating sodium dihydrogen phosphate which reacts with 
the enamel structure of the teeth to develop an electrically stable 
fluorophosphate complex within the enamel that promotes long term 
stability of the caries inhibiting effect of stannous fluoride 
incorporated therewith. 
It is also a feature of the present invention to provide a novel dentifrice 
material that incorporates stannous fluoride as the fluoride compound, 
with sodium dihydrogen phosphate as the acid phosphate compound, the 
resulting combination of the stannous fluoride and acid phosphate causing 
enhanced fluoride treatment effectiveness of the stannous fluoride. 
It is another feature of this invention to provide a novel dentifrice 
material incorporating a fluoride compound and an acid phosphate compound 
in a water free gel carrier in order to prevent degradation of the 
fluoride compound. 
It is an even further feature of the present invention to provide a novel 
dentifrice composition wherein stannous fluoride and sodium dihydrogen 
phosphate are combined in substantially equal proportions by volume and, 
at which proportional combination, provide a dentifrice wherein the 
anticaries effectiveness of the fluoride and the phosphate compounds are 
materially enhanced. 
Another feature of this invention concerns the provision of a novel sodium 
dihydrogen phosphate containing dentifrice wherein the pH of the resulting 
dentifrice is in the range of between 2 and 5 and preferably about 3.5. 
It is also a feature of this invention to provide a novel fluoride 
containing dentifrice material that is of pleasing appearance in that it 
is in the form of a pleasingly colored translucent gel. 
It is also a feature of this invention to provide a dentifrice composition 
incorporating sodium dihydrogen phosphate in sufficient amount to alter 
the crystalline structure of the enemel and rendering such enamel 
resistant to caries. 
Another feature of this invention concerns the provision of stannous 
fluoride containing dentifrice material that may be provided with a 
water-free gel carrier for effective use in single tube delivery systems, 
or, as an alternative, may be provided in a water containing carrier when 
double tube delivery systems are to be employed. 
Other and further objects, features and advantages of this invention will 
become obvious to one skilled in the art upon an understanding of the 
illustrative embodiments about to be described, and various advantages, 
not referred to herein, will occur to one skilled in the art upon 
employment of the invention in practice. 
SUMMARY OF THE INVENTION 
In one form of the invention, a dentifrice composition is provided which 
incorporates in a water-free carrier a quantity of stannous fluoride 
compound having a concentration in said dentifrice in the range of from 
about 0.03% to about 0.5% by weight. For enhancement of the anticaries 
effectiveness of the fluoride containing compound, the composition also 
incorporates sodium dihydrogen phosphate, in proportional amounts by 
volume that render the pH of the dentifrice composition in the range from 
about 2 to about 5 and preferably about 3.5. The acid phosphate compound 
may preferably be of substantially equal proportions to the fluoride 
compound by volume when incorporated into the dentifrice material. Where 
the dentifrice material is to be incorporated into a single tube delivery 
system, a pleasingly colored, translucent, water-free gel carrier may be 
employed as the basic carrier for the dentifrice composition. The carrier 
may be in the form of a water free paste or gel if stannous fluoride is 
included. Other conventional dentifrice agents such as binders, abrasive 
materials, sweeteners, flavoring materials and foaming materials are also 
incorporated into the dentifrice to provide the various desired functions 
thereof. 
In the alternative, the acid phosphate compound, such as sodium dihydrogen 
phosphate, may be provided in a water-containing gel or paste carrier 
where a double compartment delivery tube system is employed. It is 
imperative that the fluoride containing compound, such as stannous 
fluoride, for example, be contained within a water-free carrier to prevent 
rapid ionization and oxidation thereof. An aqueous base may be employed 
only under circumstances where contact between the water and stannous 
fluoride cannot occur until the time of application in the oral 
environment. Where a water-free gel or paste carrier is employed, 
ionization of the stannous fluoride component is not initiated until 
contacted by the water of the saliva in the oral environment. Ionization 
of the stannous fluoride is completed in a period of a few minutes 
thereafter, but brushing of the teeth typically requires only one or two 
minutes time during which the topical anticaries treatment of the stannous 
fluoride compound is effectively manifested. By employing a two tube or 
two compartmented tube delivery system, the acid phosphate compound and 
the fluoride containing compound are brought into contact only at the time 
of delivery. Admixture of these compounds occurs only during brushing and 
therefore degradation of the fluoride containing compound is initiated 
only at the time of brushing. 
While the present invention is discussed herein primarily from the 
standpoint of the stannous fluoride and sodium dihydrogen phosphate 
constituents of the dentifrice composition, it is intended to be 
understood that in every case the dentifrice composition will also contain 
other desirable ingredients. For example, at least one of many available 
sweetening and flavoring agents will be employed as well as one of many 
suitable and commercially available abrasive agents for effective cleaning 
and polishing of the teeth. The present invention is discussed herein 
primarily as it relates to stannous fluoride and sodium dihydrogen 
phosphate as combined anticaries constituents. Although other fluoride 
compounds are enchanced to a degree by incorporation of sodium dihydrogen 
phosphate and other acid phosphates therewith, the enhancement of such 
fluoride compounds is minimal as compared to the caries resistance 
enhancement accomplished by appropriate combination of stannous fluoride 
and sodium dihydrogen phosphate. 
Briefly, preferred dentifrice compositions according to this invention 
comprise a caries inhibiting quantity of stannous fluoride, and a fluoride 
treatment enhancing quantity of sodium dihydrogen phosphate. Preferably, 
both the stannous fluoride compound and the sodium dihydrogen phosphate 
compound are dispersed in a carrier, which may be the same or different 
carrier as described elsewhere herein, it being necessary only that a 
water free carrier be employed when the dentifrice composition 
incorporates stannous fluoride. The stannous fluoride compound and the 
sodium dihydrogen phosphate compound are provided in such proportions that 
the pH of the resulting dentifrice composition is between 2 and 5, and 
preferably about 3.5. It has been determined that combination of stannous 
fluoride and sodium dihydrogen phosphate at approximately equal volumes in 
the dentifrice composition will yield a pH of approximately 3.5 and will 
result in optimum anticaries effectiveness of the resulting dentifrice 
composition. As used herein, the term "caries inhibiting quantity" means 
an amount of fluoride compound or acid phosphate compound and specifically 
sodium dihydrogen phosphate which inhibits or otherwise retards or 
eliminates the formation of caries in teeth. The term "fluoride enhancing 
quantity of sodium dihydrogen phosphate" means the quantity of acid 
phosphate compound that is capable of enhancing the tooth impregnating 
capacity of the stannous fluoride compound. 
The amount of sodium dihydrogen phosphate compound employed is preferably 
the same as the fluoride compound on a weight percentage basis, however, 
the amount of acid phosphate may reasonably vary more or less than the 
fluoride compound as is desired. 
The dentifrice material will also incorporate various inert materials that 
form the gel or paste carrier composition. The specific constituents of 
the various materials incorporated in each dentifrice composition will be 
set forth herein in conjunction with the various examples. Percentages are 
by weight unless otherwise specified. 
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT 
An example of a dentifrice material that embodies the present invention is 
identified by the following ingredients and within the limits by weight as 
set forth below. 
Fluoride component--Stannous fluoride: 0.03-0.5% 
Binder--Sodium carboxymethylcellulose: 10-75% 
Carrier--Glycerin: 5-50% 
Sweetening agent--Xylitol: 0.01-5% 
Flavoring agent--Spearmint oil: 0.01-5% 
Abrasive--Insoluble sodium metaphosphate: 10-75% 
Fluoride Enhancement--Sodium dihydrogen phosphate: 0.1-10% 
Foaming agent--Sodium lauryl sulfate: 1-10% 
The fluoride containing compound utilized is stannous fluoride in the range 
of from about 0.03% to 0.5% of the composition by weight. 
Where detergent materials are employed, such detergents may conveniently 
take the form identified in U.S. Pat. No. 3,970,747. Other detergents such 
as sodium lauryl sulfate may also be employed within the spirit and scope 
of this invention. 
The abrasive agent employed in the following examples is insoluble sodium 
metaphosphate. If translucence is desired, the insoluble sodium 
metaphosphate will have been pre-treated by tumbling to remove the sharp 
edges and corners of the crystalline particulate. This pre-treatment 
modifies the abrasive crystals to render the abrasive refractive rather 
than reflective, and thus promote the development of a translucent rather 
than opaque dentifrice gel. Other abrasive materials of light refractive 
crystalline form may also be utilized. For example, calcium pyrophosphate, 
bentonite, tricalcium phosphate and sodium aluminum silicate are only a 
few of the numerous abrasive materials that may be employed in accordance 
with the teachings of the invention. 
The preferred sweetening agent utilized is xylitol which provides a cooling 
effect in the oral cavity, as well as a humectant capability to retard 
drying, thus preventing the orifice of the tube from being easily plugged 
by hardened dentifrice. Other sweetening agents, such as saccharin, or 
natural sweetening agents, such as honey, may also be employed. 
The carrier in the examples is defined primarily by glycerin and a gelling 
agent such as carboxymethylcellulose. Other gelling agents, such as 
natural and synthetic gums and gum-like materials such as gum tragacanth, 
gum acacia, gelatin, sodium alginate, methyl cellulose, 
polyvinyl-pyrrolidone and the like may also be employed. 
The flavoring agent utilized in the examples is spearmint oil and cherry, 
but other flavoring agents may also be employed. Various artificial or 
natural flavoring agents are considered acceptable for the dentifrice 
composition. To provide a dentifrice material that is especially 
acceptable for use by children, various other fruit flavors, i.e. orange, 
lemon, lime, pineapple, cherry, etc. may be utilized, as well as 
chocolate. For adult dentifrice flavors, a mint taste, such as provided by 
spearmint oil, is considered practical. 
Stannous fluoride concentration may vary from about 0.03% to about 0.5%, 
but at ranges in excess of 0.4% care should be exercised to insure against 
the development of undesirable systemic effects. It is generally believed 
the fluoride concentrations exceeding 0.5% should be utilized only under 
prescription and under professional care and guidance. 
The sodium dihydrogen phosphate concentration is sufficient to establish 
the desired pH range of from about 2 to about 5 and preferably about 3.5. 
At a pH of about 3.5 the volume of sodium dihydrogen phosphate will 
substantially equal the volume of the stannous fluoride.

The following specific examples are further illustrative of the nature of 
the present invention, but it is to be understood that the invention is 
not limited thereto. The amounts and proportions in the examples are by 
weight, unless otherwise specified. 
EXAMPLE I 
Into a container was added 7.5 grams sodium carboxymethylcellulose and 
145.0 grams glycerin. The container was slowly heated to 105.degree. F. 
accompanied by continuous stirring. Stirring in a vacuum environment is 
preferable, if translucence is desired, to prevent incorporation of air 
bubbles within the gel. 1.5 grams of xylitol and 2.0 grams of spearmint 
oil flavoring agent and 0.5 grams coloring agent were added. 2.0 Grams of 
stannous fluoride, 1,400 grams insoluble sodium metaphosphate and 14.0 
grams sodium dihydrogen phosphate and 5.0 grams sodium lauryl sulfate were 
added during stirring as the container was allowed to cool. The resulting 
dentifrice composition was in the form of a pleasantly colored blue-green 
translucent gel. 
The general appearance of the product thus produced is pleasant and the 
product is also pleasant to the taste. When the teeth of the user are 
brushed with the dentifrice composition identified above, the taste is 
pleasant during use and a minty pleasant aftertaste remains in the oral 
cavity of the user for several minutes thereafter. In order to insure 
optimum fluoride absorption by the teeth of the user, the above 
composition was provided with equally measured volumes of stannous 
fluoride and sodium dihydrogen phosphate constituents at 0.4% of the 
dentifrice composition. 
The dentifrice composition of Example I was prepared in several embodiments 
through variation of the volume of sodium dihydrogen phospate and fluoride 
penetration tests were conducted on extracted human teeth. The tests 
indicated that as the pH of the dentifrice composition approaches basic or 
between 5 and 7, the fluoride penetration becomes minimal. As the pH 
becomes very acid, i.e. about 2 or greater, fluoride penetration is 
slightly increased from that of the 3.5 level, but decalcification becomes 
a definite problem. 
EXAMPLE II 
Into a container was added 7.5 grams sodium carboxymethylcellulose, 145.0 
grams glycerin and 700 grams insoluble sodium metaphosphate. The container 
was slowly heated to 105.degree. F. accompanied by continuous stirring. 
1.5 Grams of xylitol, 2.0 grams spearmint oil flavoring agent and 1.0 gram 
inert coloring agent were added to the heated gel composition. 2.0 Grams 
of stannous fluoride and 2.0 grams of sodium dihydrogen phosphate were 
added during stirring as the container was allowed to cool. This 
dentifrice composition was in the form of a pleasantly colored blue-green 
translucent gel and the pH of the composition was about 3.5. 
The cooled dentifrice composition was placed in a single tube type 
dentifrice delivery tube. The dentifrice composition was pleasant to the 
taste during brushing of the teeth and provided a pleasant aftertaste that 
remained for several minutes after use. 
The insoluble sodium metaphosphate constituent had been previously prepared 
by tumbling to round the corners and sharp edges of the crystalline form 
and to render it more light refractive than light reflective. 
The dentrifice of Example II was also modified by increased and decreased 
volumes of sodium dihydrogen phosphate with fluoride penetration results 
on human extracted teeth further indicating a pH range of between 2 and 5 
and preferably about 3.5 being considered optimum from the standpoint of 
fluoride penetration as opposed to decalcification in the acid environment 
of the dentifrice. 
EXAMPLE III 
Into a container was added 7.5 grams sodium caroxymethylcellulose, 145.0 
grams glycerin and 700 grams insoluble sodium metaphosphate. The container 
was slowely heated to a temperature of 105.degree. F. with continuous 
stirring during heating. 1.5 Grams of xylitol, 2.0 grams cherry flavoring 
agent and 1.0 gram inert coloring agent were added to the heated gel 
composition. 2.0 Grams of stannous fluoride, 2.0 grams sodium dihydrogen 
phosphate and 10.0 grams sodium lauryl sulfate were also added during 
stirring as the container was allowed to cool. This dentifrice composition 
was in the form of a red paste of pleasing color. The cooled dentifrice 
composition was placed into a single compartment type dentifrice delivery 
tube. During brushing with the dentifrice, the detergent constituent 
caused a pleasant foaming action to occur. The taste of the dentifrce was 
pleasing and a pleasant aftertaste remained in the oral cavity for several 
minutes thereafter. 
EXAMPLE IV 
A denfifrice composition was prepared incorporating a carrier fluid 
including 10.0 grams sodium carboxymethylcellulose and 75.0 grams glycerin 
to which was added 700.0 grams calcium pyrophosphate and 75.0 grams 
distilled water. These dentifrice constituents were slowly heated in a 
glass container to a temperature of 105.degree. F. with continuous 
stirring occurring during heating. 1.5 grams of xylitol, 2.0 grams cherry 
flavoring and 1.0 grams inert red coloring agent were added to the heated 
gel-paste composition. 4.0 Grams sodium dihydrogen phosphate and 10.0 
grams sodium lauryl sulfate were also added during stirring as the 
container was allowed to cool. The resulting sodium dihydrogen phosphate 
dentifrice was in the form of a red paste of pleasing color. 
Tests of the dentifrice composition of Example IV were conducted for 
determination of the activity of sodium dihydrogen phosphate on the enamel 
of teech without the presence of a fluoride containing compound. Varying 
amounts of sodium dihydrogen phosphate were incorporated into the basic 
dentifrice composition of Example IV and the effects of the dentifrice on 
the enamel of extracted teeth were observed. The tests indicate that the 
crystalline latticework of the enamel is altered and it is considered that 
the resulting crystalline form of the enamel is more electrically stable, 
and thus, the enamel is rendered more resistant to the development of 
caries. 
ACTIVITY OF THE FLUOROPHOSPHATE COMPLEX 
As mentioned above, the enamel of the teeth has been shown to define a 
latticework of minute crystals of hydroxy-apatite. Basically, the enamel 
latticework is defined by crystalline or prism-like microcrystals of a 
hydroxy-apatite, which is a form of calcium phosphate. These minute 
crystals of hydroxy-apatite have various ions associated therewith which 
complete the electrical stability of the crystal. Also, as mentioned 
above, application of a dentifrice material to the teeth having an acid pH 
below a nominal range causes the crystlline latticework of the enamel to 
open or become activated, thereby preparing the latticework for effective 
penetration of the fluoride incorporated within the dentifrice. When the 
sodium dihydrogen phosphate is applied to the teeth in conjunction with 
the stannous fluoride compound in the form of a dentifrice, the acid 
phosphate that is defined by the sodium dihydrogen phosphate opens up or 
activates the crystal latticework of the enamel and allows the prism-like 
microcrystals to accept the acid phosphate complex as well as the fluoride 
into the latticework much more readily than if the dentifrice contained 
stannous fluoride or sodium fluoride alone. The activity is characteristic 
of the joining relationship of ions such that the fluoride compound and 
the phosphate complex is in effect transmitted ionically deeply into the 
crystalline latticework. In effect, the sodium dihydrogen phosphate opens 
up the enamel hydroxy-apatite crystal and allows the fluoride phosphate 
complex to penetrate into the crystal and then pass from that crystal to 
other hydroxy-apatite crystals of the latticework in the nature of a chain 
reaction. Thus, there is provided a significantly deeper penetration of 
the fluoride compound when utilized in conjunction with the sodium 
dihydrogen phosphate than is ordinarily available through use of the 
fluoride compound alone. 
Through use of a dentifrice containing stannous fluoride and sodium 
dihydrogen phosphate within an appropriate pH range, there is provided a 
fluorophosphate hydroxy-apatite crystal that is electrically stable. The 
stannous fluoride or tin fluoride that is in the compound will then 
combine with the surface layer of the enamel and will cause a complete 
crystalline change at the surface of the enamel. This crystalline change, 
i.e. from a monoclinic prism-like configuration to a rhomboid shape, that 
is effected by the stannous fluoride develops a sealing or capping effect 
at the enamel surface and this sealing or capping effect effectively 
retards leaching of the fluorophosphate complex from the hydroxy-apatite 
latticework. In effect, when sodium dihydrogen phosphate is utilized in 
conjunction with a tin or stannous fluoride, a much greater penetration of 
the fluoride and the phosphate into the enamel crystalline latticework is 
developed as compared with the fluoride penetration or acid phosphate 
penetration when stannous fluoride and sodium dihydrogen phosphate are 
utilized alone. The stannous or tin portion of the compound then combines 
with the surface to provide a sealing or capping effect, to prevent the 
fluorophosphate from being rapidly leached back out of the enamel 
latticework. 
It should be noted that the sealing or capping effect established by the 
stannous fluoride complex is strictly a surface phenomenon. After the tin 
is worn away from the surface of the enamel crystalline latticework, the 
fluorophosphate complex then is capable of being leached out of the enamel 
latticework by the natural activities of the fluids contained within the 
oral environment. When fluoride containing dentifrice materials are 
utilized at the rather weak solution level allowed by governmental 
authority, even with the elevated degree of phosphate and fluoride 
penetration promoted by sodium dihydrogen phosphate enhancement, much of 
the fluoride can be leached out of the crystalline enamel latticework 
within a short period of time. By providing a stannous fluoride containing 
dentifrice and with the caries resistance activities promoted by the 
stannous fluoride being enhanced by the sodium dihydrogen phosphate, 
enhanced fluorophosphate treatment can be effected on a daily basis. Such 
daily fluorophosphate treatment provides the enamel crystalline 
latticework with greater fluorophosphate penetration into the enamel and 
retarded leaching of the fluorophosphate from the crystalline latticework 
on a daily basis. Moreover, on a daily basis the enamel surface is capped 
or sealed with a new microlayer of tin, thereby promoting effective 
retention of the fluorophosphate complex within the tooth structure and 
thus effectively promoting continuing resistance to the development of 
caries. 
It has been determined through tests that penetration of various other 
fluoride containing compounds is rendered more effective through the use 
of various other acid phosphate compounds and particularly sodium 
dihydrogen phosphate. Thus, when a dentifrice containing sodium fluoride 
is utilized rather than stannous fluoride in conjunction with sodium 
dihydrogen phosphate, for example, the result is an enhanced or increased 
penetration of the phosphate fluoride into the enamel latticework much 
more effectively than if the sodium fluoride were utilized alone in the 
dentifrice composition. Sodium dihydrogen phosphate has been found 
imminently more effective than any other acid phosphate because the sodium 
dihydrogen phosphate has the unusual characteristic of altering the 
crystalline latticework of the enamel, allowing the fluoride compound to 
penetrate more deeply into the crystalline latticework of the enamel. 
Although other acid phosphate compounds enhance penetration of other 
fluoride containing compounds to some limited degree, utilization of 
sodium dihydrogen phosphate as the acid phosphate compound has been found 
to be infinitely more effective. Sodium dihydrogen phosphate has the 
characteristic of being able to force the fluoride much more deeply into 
the crystalline latticework of the enamel because of the chain reaction 
that occurs between the ions in the enamel crystal. 
Unfortunately, the sodium fluoride does not provide a capping or sealing 
effect at the enamel surface and therefore there is no surface sealing 
phenomenon to retard natural oral fluid leaching of the fluorophosphate 
complex from the enamel latticework. Even though the teeth are brushed 
with a dentifrice containing sodium fluoride and sodium dihydrogen 
phosphate so that excellent penetration of the fluorophosphate is 
obtained, the lack of a capping of sealing activity such as occurs when 
stannous fluoride is employed will allow the fluorophosphate to very 
quickly be leached out of the enamel material, thereby rendering the 
enamel susceptible to caries activity. 
Sodium dihydrogen phosphate by itself when used solely as the caries 
inhibiting compound without any fluoride demonstrates more effective 
caries resistance potential than either stannous fluoride, sodium fluoride 
or sodium monofluorophosphate used alone or in combination with other acid 
phosphate compounds. It is theorized that the sodium dihydrogen phosphate 
within an acid pH between 2.0 and 5.0 and optimally at 3.5 causes the 
enamel or hydroxy-apatite crystal to be structurally modified to a 
crystalline form that is more electrically stabilized and thus more 
resistant to decalcification or crystalline breakdown. It is further 
theorized that certain electrically unstable ions within the crystalline 
latticework, such as carbonate ions, are displaced and replaced by the 
more electrically stable phosphate and acid phosphate ions. The resulting 
crystalline network is thus changed to a more electrically stable form 
that is effectively resistant to the development of caries. 
The tin or stannous fluoride, when utilized in conjunction with sodium 
dihydrogen phosphate, enhances the stability of the fluorophosphate within 
the hydroxy-apatite crystal. For this reason, it is preferred to utilize 
stannous fluoride in conjunction with sodium dihydrogen phosphate rather 
than to rely on the limited mechanism of activity provided by various 
fluoride containing compounds other than stannous fluoride. 
The acid pH range that is established by appropriate combination of sodium 
dihydrogen phosphate and stannous fluoride renders the ions within the 
hydroxy-apatite crystal latticework more active. The acid pH creates an 
effect that is somewhat like introducing heat in a chemical reaction for 
the purpose of speeding up the reaction. By providing an acid environment, 
the enamel latticework is activated so that the fluoride and phosphate 
reacts with the enamel in a much more rapid fashion. If the pH of the 
composition were basic, the hydroxy-apatite crystalline latticework will 
remain inactive and will, in effect, remain substantially sealed, thus 
retarding penetration of the fluoride into the enamel material. Tests 
indicate that penetration of the fluoride into the enamel will be minimal 
when the pH is basic. The dentifrice materials that are currently sold to 
the public typically employ a neutral or slightly acid environment, but 
the more basic pH levels of the dentifrice materials provide minimal 
enamel surface activities or reaction that enhance penetration of the 
fluoride complex into the crystalline latticework of the enamel. 
The pH of the dentifrice composition of the present invention is, 
relatively speaking, a more acid pH than exists in other dentifrice 
compositions that are available to the public. The pH range of this 
dentifrice composition is in the range of between 2 and 5 and preferably 
about 3.5. This particular range is more acid that any other presently 
available dentifrice. A dentifrice material that is very acid, such as in 
the pH range of 2 or 3, is vastly different as compared to a material 
having a pH in the range of 5 to 7, which is, of course, only slightly 
acid. The pH that is involved with the present invention is the ideal or 
optimum range for the mechanism of action of the sodium dihydrogen 
phosphate in combination with stannous fluoride for the purpose of 
achieving optimum penetration of the fluoride and phosphate compound into 
the enamel. 
Some of the acid phosphate prophylactic gels are pastes that are used in 
dental offices and are quite effective, have a pH in the range of from 
4-4.5. These prophylactic gels and pastes, however, as far as the 
anticaries activity is concerned, are well below the anticaries activity 
that is developed when sodium dihydrogen phosphate by itself or in 
conjunction with stannous fluoride is used. Sodium dihydrogen phosphate is 
the only acid phosphate that effectively enhances the penetration of all 
fluorides. All of the other phosphate compounds at some point interfere 
with the mechanism of fluoride compounds. For some reason that is 
surprising and not fully understood, only sodium dihydrogen phosphate 
enables the deep ion penetration characteristics that facilitate enhanced 
anticaries activity as compared to combinations of other fluoride and 
phosphate compounds. 
Tests are conducted utilizing sodium monohydrogen phosphate in order to 
determine possible penetration and anticaries treatment of teeth. It was 
determined without question that the sodium monohydrogen phosphate does 
not function nearly as well as the sodium dihydrogen phosphate. The sodium 
dihydrogen phosphate, when used at varying pH levels, was demonstrated to 
have optimum penetration without noticeable decalcification at a pH of 
about 3.5. As the pH of the dentifrice material becomes more basic, the 
mechanism of penetration activity is obviously less operative. In the pH 
range of about 5, penetration activity is nominal. As the pH of the 
dentifrice material becomes more acid as compared to the optimum pH of 
about 3.5, the penetration activity of the fluoride seems to increase 
slightly as compared to penetration at a pH of about 3.5. However, as the 
dentifrice material becomes more acid in character, the pH actually 
becomes a problem rather than an enhancement. At a pH of 2 or lower, 
decalcification of the enamel of the teeth proceeds rather rapidly so that 
the benefit of the phosphate or the fluoride versus decalcification 
becomes moot. 
The sodium or potassium acid phosphates seem to work well from the 
standpoint of penetration but, as compared to the penetration obtained by 
sodium dihydrogen phosphate with fluoride enhancement, the other acid 
phosphate compounds achieve only nominal ion penetration. As a matter of 
fact, the sodium dihydrogen phosphate is so superior in fluoride 
penetration enhancement as compared to the other acid phosphate materials 
such as sodium or potassium acid phosphate, that it is hardly fair to 
compare them from the standpoint of effectiveness. This is in distinct 
contrast, however, with the phosphoric acids, such as orthophosphoric 
acid, which is currently being used in some fluoride phosphate gel type 
prophylactic preparations for restricted use only in dental offices. These 
materials are definitely acid in character and they are not nearly as 
effective as sodium dihydrogen phosphate from the standpoint of fluoride 
penetration enhancement. Acid phosphate materials cover a wide range of 
materials but, at the present time, only sodium dihydrogen phosphate has 
been found to have these exceptional characteristics from the standpoint 
of fluoride penetration enhancement. 
An interesting phenomenon concerned with the employment of sodium 
dihydrogen phosphate in combination with stannous fluoride is the capping 
effect or surface phenomenon that occurs particularly with stannous 
fluoride and which does not occur when other fluoride compounds are 
employed. When sodium dihydrogen phosphate is employed in conjunction with 
stannous fluoride, there is obtained an imminently greater penetration 
than is obtained when other phosphate compounds are employed and then a 
capping or surface sealing effect occurs because of the particular pH of 
the composition. A low pH, optimally around 3.5, yields an effective 
penetration of the sodium dihydrogen phosphate fluorocomplex into or 
through the enamel latticework of the teeth. The particular chemical 
activity that occurs is that the fluoride replaces hydroxyl or OH ions. 
The pH of the composition is raised to the point where stannous fluoride 
then functions at the surface of the enamel to provide the surface 
phenomenon and then caps off or seals the enamel. If the pH of the 
composition is lowered to around a pH of 2, effective penetration of the 
enamel structure will occur but the capping or sealing effect caused by 
the tin becomes inneffective. The reason for this activity is that only so 
much fluoride penetration can occur, before calcium, carbonate or hydroxyl 
ion are released and decalcification or complete crystalline breakdown 
becomes a significant factor. If an excessive amount of calcium is 
released in the chemical activity, the enamel structure of the tooth is 
effectively being dissolved which, of course, is an undesirable 
phenomenon. So the reason for the mechanism of action of the sodium 
dihydrogen phosphate with stannous fluoride at an optimum pH range of 
about 3.5 is that the pH that allows for the penetration of the acid 
fluorophosphate complex within the enamel latticework. As soon as the pH 
on a microscopic level is raised to the point where stannous fluoride is 
effective and the crystals become electrically stable, then the capping or 
sealing effect becomes predominant and, in effect, a degree of fluoride 
penetration is prevented by the capping or sealing effect accomplished by 
the stannous fluoride. 
When sodium fluoride is utilized in conjunction with sodium dihydrogen 
phosphate in an acid environment, there is yielded effective fluoride 
penetration but there is no sealing and capping effect developed as occurs 
with stannous fluoride. As soon as the mechanism of action is ceased and 
the pH environment is changed, such as when the oral environment is rinsed 
after brushing, the fluorophosphate complex begins to be leached out of 
the tooth purely by the law of mass action. There occurs, therefore, a 
release of the fluoride mechanism in the absence of the capping effect 
offered by stannous fluoride and therefore the overall fluoride treatment 
and caries resistance is considered more ineffective as compared with that 
obtained by stannous fluoride and sodium dihydrogen phosphate. 
Since stannous fluoride is the preferred fluoride to use in conjunction 
with sodium dihydrogen phosphate and since stannous fluoride is unstable 
for long periods of time, such as would be necessary for storage in a tube 
on a shelf, in an aqueous medium, the combination of stannous fluoride 
with sodium dihydrogen phosphate in a nonreactive water-free carrier is 
necessary for practical storage and shelf life. The reason for the 
water-free carrier is to prevent the degradation of the stannous fluoride 
component and not the sodium dihydrogen phosphate part. 
In view of the foregoing, it is clear that the dentifrice composition of 
the present invention provides all of the features and improvements 
indicated hereinabove together with other features that are inherent from 
this disclosure. The invention may also take other forms within the spirit 
and scope of the appended claims: