Foamable fluoride compositions and method

A foamable fluoride composition, for use in dental therapy, is provided that contains water, dental fluoride, foaming agent and acidifying agent. An illustrative composition comprises water, sodium fluoride, hydrofluoric acid, ethoxylated polyoxypropylene adduct of propylene glycol and phosphoric acid. The foamable fluoride composition, which is packaged in a nonmetallic, acid resistant, aerosol container in combination with an aerosol propellant, is dispensed into the trough of a dental tray as a dense, stable, non-flowable foam which is superimposed about and into engagement with the teeth to be treated to thereby effect fluoride uptake by the dental enamel. The fluoride foam provides substantially the same fluoride uptake as a fluoride gel but this result is achieved by the fluoride foam with substantially less fluoride in the tray than that which is present in a corresponding tray containing a like volume of fluoride gel.

BACKGROUND OF THE INVENTION 
This invention relates to dental compositions and, more particularly, to 
foamable fluoride compositions which are adapted to provide stable foams 
for use in dental therapy. 
It is generally understood in the dental art that certain kinds of food 
decay are initiated by acid etching of the tooth enamel with the source of 
the acid being a metabolite resulting from bacterial and enzymatic action 
on food particles in the oral cavity. It is generally accepted that 
plaque--which is a soft accumulation on the tooth surfaces consisting of 
an organized structure of micro-organisms, proteinaceous and carbohydrate 
substances, epithelial cells, and food debris--is a contributory factor in 
the development of various pathological conditions of the teeth and soft 
tissue of the oral cavity. It has been suggested that the saccharolytic 
organisms of the oral cavity, which are associated with the plaque, cause 
decalcification beneath the plaque matrix through metabolic activity which 
results in the accumulation and localized concentration of organic acids. 
The etching and decalcification of the enamel may continue until the pulp 
chamber of the tooth is reached. 
Fluoride compounds have been incorporated into dental topicals and into 
consumables to provide an orally beneficial effect by reducing the 
dissolving action of acids on dental enamel. It has been reported that the 
fluoride combines with hydroxyapatite, the crystalline structure of the 
teeth, to produce a modified crystalline structure which is more resistant 
to acid attack. 
Diverse fluoride compounds have been disclosed in the prior art for use in 
dental care including, for example, sodium fluoride, sodium 
monofluorophosphate, stannous fluoride, fluoroalkyl phosphates, and 
quaternary ammonium fluorides. 
The fluorides can be incorporated into gels, rinses, toothpaste, tooth 
powder, chewing gum and the like for topical application. Fluoride 
treatment can also be undertaken through consumables such as fluoridated 
drinking water and fluoride tablets. Heretofore, fluoride gels have been 
used in dental practice to topically apply fluoride to the teeth. The 
fluoride gel is usually supplied as a thick gel in a plastic bottle from 
which it is dispensed into the trough of a plastic dental tray that is 
inserted into the mouth in juxtaposition to the teeth whereby the teeth 
engage the gel for about 1 to 4 minutes, as per the supplier's 
instructions. 
A typical fluoride gel contains water, a water soluble dental fluoride such 
as sodium fluoride, glycerol, an acidifying agent such as phosphoric acid, 
and a water soluble thickener such as carboxymethyl cellulose, polyvinyl 
alcohol, or xanthan gum. 
An illustrative fluoride gel formulation is as follows: 
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INGREDIENTS TS BY WEIGHT 
______________________________________ 
Water 85.5 
Sodium fluoride 2.7* 
Xanthan gum 3.2 
Glycerol 3.4 
Phosphoric acid (85%) 
4.1 
______________________________________ 
*Available fluoride 1.2 pts. by wt. 
The water soluble thickener is selected so as to provide a highly viscous 
and thick system for maintaining the gel in the tray and in positive 
contact with the teeth, since a thin gel would tend to flow away from the 
tooth surface and thereby reduce fluoride uptake by the tooth and, 
additionally, a thin gel could flow out of the tray and cause the patient 
to gag and choke. 
The acidifying agent is selected so as to provide the fluoride gel with a 
pH between about 3.0 and 4.5 which facilitates and enhances fluoride 
uptake by the teeth. 
There are several problems associated with the use of fluoride gels in 
dental therapy. One of the most vexing problems is that of viscosity. The 
fluoride gel must be thick enough so that it does not flow out of the 
dental tray while the tray is in the patient's mouth and, at the same 
time, the gel must be thin enough to be dispensed from a plastic bottle 
into the tray in preparation for the fluoride treatment. Because it is 
extremely difficult to formulate a fluoride gel that flows from a plastic 
dispensing bottle and yet remains stationary in the dental tray for up to 
4 minutes while in the mouth, the fluoride gels heretofore available had a 
tendency to flow while in the tray and cause patient gagging during the 
course of treatment. 
Another problem associated with fluoride gels is that of toxicity. 
Fluorides have a low concentration threshold for exerting toxic effects. 
It is reported that severe symptons can be manifested from the ingestion 
of less than one gram of sodium fluoride. Thus, the ingestion of any 
significant amount of fluoride gel can produce serious consequences. This 
risk is especially noteworthy because fluoride gels, which have been 
flavored to mask the acidic taste, are most often used to treat children 
and the flavoring can increase the chance of unintentionally swallowing a 
significant amount of the semi-fluid gel. 
A further problem associated with fluoride gels is the cost-effectiveness 
of the thick gel. In view of the high viscosity of the fluoride gels, the 
only fluoride which is available for uptake by the tooth is that which is 
in the immediate vicinity of the tooth surface. The remaining fluoride, 
which is the bulk of the fluoride in the tray, is unavailable for dental 
uptake because fluoride movement is restricted by the high viscosity of 
the gel. 
Accordingly, it would be advantageous to provide a tray-fluoride that is 
non-flowable and which requires substantially less fluoride in the tray to 
achieve the same fluoride uptake as a corresponding volume of fluoride 
gel. 
SUMMARY OF THE INVENTION 
In accordance with one aspect of this invention, there is provided a 
foamable fluoride composition comprising: 
(a) a water soluble dental fluoride in an amount to provide the composition 
with about 0.5 to about 5 wt.% available fluoride; 
(b) an orally compatible and acid stable foaming agent in an amount from 
about 4 to about 20 wt.%; 
(c) an orally compatible and acid stable foam-wall thickener in an amount 
from about 2 to about 20 wt.%; 
(d) an orally compatible acidifying agent in an amount to provide the 
composition with a pH from about 3.0 to about 4.5; and 
(e) water to 100 wt.%. 
In accordance with a second aspect of this invention, there is provided a 
method for treating teeth with a fluoride foam, which comprises: 
(a) dispensing a pressurized and foamable fluoride composition from an 
aerosol container into the trough of a dental tray to form a fluoride foam 
within the trough, wherein the foamable fluoride composition contains: a 
water soluble dental fluoride in an amount to provide the composition with 
about 0.5 to about 5 wt.% available fluoride; an orally compatible and 
acid stable foaming agent in an amount from about 4 to about 20 wt.%; an 
orally compatible and acid stable foam-wall thickener in an amount from 
about 2 to about 20 wt.%; an orally compatible acidifying agent in an 
amount to provide the composition with a pH from about 3.0 to about 4.5; 
and water to 100 wt.%; and 
(b) superimposing the trough of the dental tray and its fluoride foam 
content about and into engagement with the teeth to be treated to effect 
fluoride uptake by such teeth.

DETAILED DESCRIPTION 
The foamable fluoride compositions of this invention comprise aqueous 
solutions containing water soluble dental fluoride, foaming agent, 
foam-wall thickener, and acidifying agent. 
Illustrative water soluble dental fluorides which can be used in the 
practice of this invention include sodium fluoride, sodium 
monofluorophosphate, stannous fluoride, fluoroalkyl phosphate salts as 
described in U.S. Pat. No. 2,955,985 (Kuna, 1960) such as monammonium 
1,1,7 - trihydroperfluoroheptyl phosphate, quaternary ammonium fluorides 
as described in U.S. Pat. No. 3,124,512 (Schmidt et al., 1964) such as 
doceyltrimethyl-ammonium fluoride, and mixtures thereof. The dental 
fluoride is generally present in the foamable fluoride composition in an 
amount to provide the composition with about 0.5 to about 5 wt.% available 
fluoride and, preferably, in an amount to provide the composition with 
about 1.0 to about 2.5 wt.% available fluoride. Sodium fluoride is 
particularly well suited for use in fluoride foam therapy and, when so 
used, is generally present in the foamable fluoride composition in an 
amount from about 1.1 to about 11.1 wt.% and, preferably in an amount from 
about 2.2 to about 5.6 wt.%. 
Foaming agents which can be used in the practice of this invention to 
produce dense, stable, non-flowable foams are those which are orally 
compatible and acid stable and include, for example, sucrose monostearate, 
sucrose distearate, sodium lauryl sulfate and mixtures thereof. The 
foaming agent is generally present in the foamable fluoride composition in 
an amount from about 4 to about 20 wt.% and, preferably, in an amount from 
about 7 to about 13 wt.%. 
Foam-wall thickeners which can be used in the practice of this invention to 
produce foams having enhanced stability are those which are orally 
compatible and acid stable and include, for example, glycerol, sorbitol, 
hydrogenated starch hydrolysate (a polyol) available under the trademark 
Hystar TPF from Lonza, Inc., Fair Lawn, N.J. 07410 as a 70% solution, and 
mixtures thereof. The foam-wall thickener is generally present in the 
foamable fluoride composition in an amount from about 2 to about 20 wt.% 
and, preferably, in an amount from about 4 to about 15 wt.%. 
Acidifying agents which can be used in the practice of this invention to 
facilitate and enhance fluoride uptake by the tooth structure from the 
fluoride foam are those which are orally compatible and include, for 
example, phosphoric acid, citric acid and mixtures thereof. The acidifying 
agent is generally present in the foamable fluoride composition in an 
amount to provide the aqueous solution with a pH from about 3.0 to about 
4.5. 
The foamable fluoride compositions are prepared by blending dental 
fluoride, foaming agent, foam-wall thickener and acidifying agent with 
water under mild mixing conditions at ambient temperature. The resulting 
aqueous solution is added in a predetermined amount to an open-mouth 
aerosol container. An appropriate aerosol valve is fitted over the mouth 
of and secured to the container. The container is then charged through the 
aerosol valve with an aerosal propellant, such as propane, isobutane or a 
mixture thereof as, for example, a mixture of 4% propane and 96% 
isobutane, to an operating pressure of about 40 pounds per square inch 
gage. A dispensing actuator and spout assembly is then fitted onto the 
valve. 
In use, the aerosol container, with its pressurized and foamable fluoride 
composition, is shaken and rotated to align the dispensing spout with the 
trough of a dental tray and the actuator is pressed to dispense an amount 
of flouride foam that substantially fills the volume defined by the 
trough. The tray is then placed in a patient's mouth so as to superimpose 
the trough and its fluoride foam content about and into engagement with 
the teeth to be treated. The fluoride foam, which is dense, stable and 
non-flowable, is maintained in engagement with the teeth for about 1 to 4 
minutes to effect fluoride uptake by the teeth. 
______________________________________ 
INGREDIENTS TS BY WEIGHT 
______________________________________ 
Water 85.0 
Sodium fluoride 3.1 
Sucrose distearate 
4.0 
Glycerol 2.2 
Phosphoric acid (85%) 
5.0 
Flavor q.s. 
______________________________________ 
The above formulation has a pH of about 3.0 and produces a foam having 
excellent density and stability characteristics. 
______________________________________ 
INGREDIENTS TS BY WEIGHT 
______________________________________ 
Water 79.0 
Sodium fluoride 3.1 
Sucrose monostearate 
10.1 
Glycerol 2.2 
Phosphoric acid (85%) 
4.8 
Flavor q.s. 
______________________________________ 
The above formulation produces a foam which is lighter than the foam 
produced by Examples 1(a) through 1(c). 
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INGREDIENTS TS BY WEIGHT 
______________________________________ 
Water 85.0 
Sodium fluoride 3.1 
Sodium lauryl sulfate 
3.0 
Glycerol 3.2 
Phosphoric acid (85%) 
5.0 
Flavor q.s. 
______________________________________ 
The above formulation produces a dense foam but it does not last as long as 
the foams produced by Examples 1(a) through 1(c). 
______________________________________ 
INGREDIENTS TS BY WEIGHT 
______________________________________ 
Water 85.5 
Stannous fluoride 
5.0 
Sucrose monostearate 
3.0 
Glycerol 3.1 
Phosphoric acid (85%) 
4.0 
Flavor q.s. 
______________________________________ 
______________________________________ 
INGREDIENTS TS BY WEIGHT 
______________________________________ 
Water 71.5 
Dodecyl-trimethyl-ammonium fluoride 
12.5 
Sucrose monostearate 8.0 
Citric acid 8.0 
Flavor q.s. 
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EXAMPLE II 
A comparative study was undertaken to evaluate fluoride uptake by dental 
enamel from (a) the fluoride foam of this invention, (b) a commercial 
fluoride gel for professional use available under the trademark Nupro APF 
Gel, and (c) deionized water. 
The foamable fluoride precursor for the fluoride foam contained 3.1 wt.% 
sodium fluoride, 6.0 wt.% sucrose distearate, 2.0 wt.% glycerol, 4.0 wt.% 
phosphoric acid (85%), 1.0 wt.% cherry flavor and water to 100 wt.%. The 
fluoride precursor was added to an open-mouth aerosol container and the 
final aerosol dispensing package was completed and pressurized in a 
customary manner as hereinabove described. 
The results of the comparative study are set forth in the following table: 
TABLE I 
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FLUORIDE UPTAKE 
GROUP TREATMENT PPM DEPTH 
______________________________________ 
1 Deionized water 
374 .+-. 38 
1.16 .+-. 0.12 
2 Fluoride foam 4210 .+-. 332 
0.80 .+-. 0.07 
3 Nupro APF Gel 4333 .+-. 318 
1.08 .+-. 0.14 
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The comparative study shows that the fluoride uptake from the fluoride foam 
and from the fluoride gel is substantially the same. 
The weight ratio of fluoride gel to fluoride foam, on a like volume basis, 
is about 2.5 to 1. Accordingly, the weight of fluoride in a dental tray 
substantially filled with fluoride foam is somewhat less than one-half the 
weight of fluoride in a like tray substantially filled with fluoride gel, 
where the percent of fluoride in each system is substantially the same. 
Thus, the fluoride foam of this invention provides substantially the same 
fluoride uptake as fluoride gel but this result is achieved by the 
fluoride foam with significantly less fluoride in the tray which markedly 
reduces exposure to fluoride toxicity in fluoride-tray treatment. 
ALTERNATIVE EMBODIMENT 
In an alternative emobodiment, an orally stable and acid compatible 
nonionic surfactant in the form of a block copolymer of polyoxypropylene 
and polyoxyethylene can be employed as the foaming agent and, when so 
employed, a foam wall thickener such as glycerol or sorbitol is not 
required to obtain a foamable fluoride composition that produces a dense, 
stable, non-flowable foam. 
The block copolymer which can be utilized in this embodiment of the 
invention can be prepared by initially creating a hydrophobe of desired 
molecular weight through the controlled addition of propylene oxide to the 
two hydroxyl groups of propylene glycol and thereafter ethylene oxide is 
added to sandwich the hydrophobe between polyoxyethylene hydrophillic 
groups which are controlled by length to constitute a selected percentage 
(by weight) of the final molecule. The resulting block copolymer comprises 
an ethoxylated polyoxypropylene adduct of propylene glycol. In general, 
the block copolymers which can be used in this aspect of the invention 
have an average molecular weight from about 3,000 to about 15,000, with an 
intermediate average molecular weight being from about 6,000 to about 
15,000, and a preferred average molecular weight being from about 10,000 
to about 15,000. The ethoxylated portion of the block copolymer generally 
constitutes from about 30 to about 80 percent, by weight, of the molecule, 
with an intermediate percentage being from about 40 to about 80 percent, 
by weight, of the molecule, and a preferred percentage being from about 70 
to about 80 percent, by weight, of the molecule. A particularly preferred 
block copolymer is an ethoxylated polyoxypropylene adduct of propylene 
glycol wherein the composition has an average molecular weight of about 
12,600, the polyoxypropylene portion thereof has a molecular weight of 
about 4,000, and the ethoxylated portion thereof constitutes about 70 
percent, by weight, of the molecule. 
In this embodiment of the invention, the nonionic, block copolymer, foaming 
agent is generally present in the foamable fluoride composition in an 
amount from about 2.5 to about 11 wt.% and, preferably, in an amount from 
about 3.5 to about 8 wt.%. 
Block copolymer surfactants, which have the above described structural 
characteristics, are available from BASF Corporation, Chemicals Division, 
100 Cherry Hill Road, Parsippany, N.J. 07054. Functional properties of the 
block copolymers, including foaming characteristics, are extensively 
described in the BASF technical brochure entitled Pluronic & Tetronic 
Surfactants (1987). Specific examples of nonionic surfactants which are 
useful in the practice of this embodiment of the invention, and which 
comprise polyoxyethylene/polyoxypropylene block copolymers, are set forth 
in the following table: 
TABLE I 
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Proprietary Average Polyoxyethylene 
name mol. wt. wt. % HLB 
______________________________________ 
Pluronic L64 
2,900 40 12-18 
Pluronic P123 
5,750 30 7-12 
Pluronic F108 
14,600 80 &gt;24 
Pluronic F127 
12,600 70 18-23 
______________________________________ 
The following examples illustrate various ingredients and concentrations 
which can be used in the preparation of foamable fluoride compositions 
that incorporate block copolymer, nonionic surfactants as the foaming 
agent. 
______________________________________ 
Ingredients Parts by Weight 
______________________________________ 
Water 178.75 
Sodium Fluoride 4.71 
Phosphoric Acid 4.50 
Hydrofluoric Acid 
0.23 
Pluronic F127 11.25 
Sodium Saccharin 
0.27 
Flavor 0.50 
______________________________________ 
The above formulation produces a very stable, dense, non-flowable foam. 
EXAMPLE II 
______________________________________ 
Ingredients Parts by Weight 
______________________________________ 
Water 168.00 
Sodium Fluoride 4.71 
Phosphoric Acid 4.50 
Hydrofluoric Acid 
0.23 
Pluronic F127 21.00 
Sodium Saccharin 
0.27 
Flavor 0.50 
______________________________________ 
The above formulation produces a very stable, dense, non-flowable foam 
which, however, has a noticeable detergent taste. 
EXAMPLE III 
______________________________________ 
Ingredients Parts by Weight 
______________________________________ 
Water 184.00 
Sodium Fluoride 4.71 
Phosphoric Acid 4.50 
Hydrofluoric Acid 
0.23 
Pluronic F108 5.25 
Sodium Saccharin 
0.27 
Flavor 0.50 
______________________________________ 
The above formulation produces a fluoride foam having minimum foam 
stability for use as a tray material in dental therapeutics. 
As an adjunct to the water soluble fluoride, the fluoride foam compositions 
advantageously contain hydrofluoric acid in an amount from about 0.05 to 
about 0.20 wt.% and, preferably, in an amount from about 0.07 to 0 15 
wt.%. 
Heretofore, it has been common to package aerosol compositions in tin or 
aluminum containers having a coated inner surface which insulates the 
compositions from the metal surface. As long as the protective coating has 
no pin holes and is uniformly applied to the inner surface of the 
container, the coated containers can be used for holding diverse aerosol 
compositions, including acidic compositions. However, in normal 
production, a large number of the coated containers will have pin holes in 
the coating and/or thin coating areas. Since the foamable fluoride can 
have a pH of about 3.3 and can contain both phosphoric acid and 
hydrochloric acid, any defect in the protective coating can lead to an 
accelerated acidic attack on the metallic can which can result in leakage 
or explosion. 
In accordance with another aspect of this invention, it has been found that 
the acidic fluoride foam compositions can be advantageously packaged in 
aerosol containers comprising polyester resin such as polyethylene 
terephthalate, which containers are resistant to acidic reaction and, 
therefore, do not require a protective coating. By employing a 
polyethylene terephthalate bottle as the aerosol container for the acidic 
fluoride foam, the quality of the dispensed foam is substantially 
improved. 
The prior art discloses that liquid oral care preparations can be 
formulated with a fluoride composition such as sodium fluoride and with 
nonionic surfactants such as Pluronic surfactants. 
U.S. Pat. No. 4,137,303 (Gaffar, et al., 1979) discloses in an 
antibacterial antiplaque mouthwash which may also contain a surface active 
agent and/or a fluoride-providing compound. The patentees, in an 
illustrative embodiment, disclose a mouthwash formulation containing 
flavored alcohol, Pluronic F-108, glycerine, benzethonium chloride, sodium 
saacharin, a polyamine polyphosphonic compound and water, with the pH 
adjusted to 8.0. 
U.S. Pat. No. 4,601,898 (Stier, et al., 1986) discloses an anti-caries 
mouthrinse containing titanium tetrafluoride stabilized with a chelating 
agent such as citric acid and which can be further formulated with 
alcohol, a humectant such as glycerin or aqueous sorbitol, and surfactants 
including cationic, anionic and nonionic surfactants. The patentees, in an 
illustrative embodiment, disclose a mouthrinse formulation containing 
titanium tetrafluoride, sodium citrate, Pluronic F-127, flavor, dye, 
sodium saacharin and water. 
In contrast to the flowable liquid compositions of the prior art, the 
compositions and method of the alternative embodiment described herein 
provide a dense, stable, non-flowable fluoride foam which is adapted for 
use as a tray material for professional applications in dental 
therapeutics. 
The water soluble fluorides which can be used in the alternative embodiment 
include sodium fluoride, sodium monofluorophosphate and mixtures thereof 
in an amount to provide the composition with about 0.5 to about 5 wt.% 
available fluoride. The orally compatible acidifying agent which can be 
used in the alternative embodiment comprises phosphoric acid in an amount 
to provide the composition with a pH from about 3.0 to about 4.5. 
In view of the foregoing description and examples, it will become apparent 
to those of ordinary skill in the art that equivalent modifications 
thereof may be made without departing from the spirit and scope of this 
invention.