Note: Descriptions are shown in the official language in which they were submitted.
~3~315~
SODI~M BICARBONATE-CONTAINING TOOTH POWDER
Back~round Of The Inventisn
- Thi~ invention relates ts a sodium
bicarbonate-containing tooth powder. More particularly,
this invention relates to a sodium bicarbonate-containing
tooth powder wherein the sodium bicarbonate particles have
a median size within a specific range.
Many different dentifrice compositions are known for
cleaning, whitening, and preserving the teeth. Many of
these dentifrice compositions include a high content of
water-insoluble abrasives, such as dicalcium phosphate,
which aid in preventing pellicle and stain build-up on the
teeth. In ord~r to preserve the teeth as much as pos-
sible, it is widely accepted that the least abrasive mate-
rial necessary to remove plaque and stain should be used
in dentifrice compositions.
Baking soda particles are relatively soft as compared
to most conventional abrasive materials used in dentifrice
compositions. The American Dental Association has recom-
mended that "if only a slight degree of abrasion is neces-
sary to keep tee~h from staining, baking soda will usually
be found satisfactory. n Accepted Dental Therapeutics,
pp.340-341 t38th ed., 1979). Toothpaste formulations con-
taining sodium bicarbonate particles as a cleansing agent
for teeth have been previously disclosed. See, for
example, U.S. 3,943,240 (Delaney et al) and similar
patents which disclose a toothpaste composition containing
at least about 20~, preferably at least about 30~, sodium
bicarbonate particles. The size of the sodium bicarbonate
particles in the disclosed toothpaste compositions may
vary; but it is preferred that a major portion of the par-
ticles be above 0.01mm and below 0.4mm in diameter. U.S.
2,128,917 (Crocker) also discloses a sodium
bicarbonate-containing toothpaste. This patent discloses
that the sodium bicarbonate comprises close to 50% by
weight of the toothpaste and that the sodium-bicarbonate
particles may be sifted through a ~200 mesh sieve~
Most dentifrices formulated today are in the form of
- -i2`43~5Yi
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a pa~te~ gel or powder. Toothpastes and gels generally
contain, in addition to the abrasive material, humectants,
water, thickeners, surfactants, flavors and sweeteners.
Tooth powders generally contain only abrasives, flavor,
sweetener and sometimes a surfactant. Both types of pro-
ducts sometimes contain additional ingredients for special
functional or aesthetic reasons, for example, fluoridating
or coloring agents.
Toothpastes and gels have gained wider consumer
acceptance than powders since they tend to be more conven-
ient to use. However, powder formulations have certain
advantages over toothpastes. For example, humectants,
thickeners and water serve no useful purpose in the actual
cleaning of t~eth but are needed to provide stability to
the desired paste or gel form. Powders do no~ require
these ingredients.
One drawback of paste and gels is the cost of the
non-cleaning ingredients. Pastes and gels usually contain
20-50~ humectant and thickener, representing a dispropor-
tionate share (30-50%) of the cost of the finished tooth-
paste or gel. Tooth powders, which may contain up to 99%
useful abrasive materials, eliminate the need for the
costly (non-cleaning~ humectant and thickener ingredients.
A further drawback of pastes and gels is the diffi-
culty of ensuring that these products have the right con-
sistency, are stable and that the ingredients are compati-
ble. Tooth powders, in contrast, are much easier to
formulate.
In the case of pastes or gels containing sodium
bicarbonate as the abrasive material, stability of the
formulation is a frequent problem. Sodium bicarbonate is
unstable in an aqueous solution and releases carbon diox-
ide gas. See, e~g., U.S. 3,943,240 at column 1, lines
32-34. Also, sodium bicarbonate is not always compatible
with other abrasive materials in pastes and gels. See,
e .q., U. S . 3,943,2g0 at column 2, lines 5~-62. In con-
trast, sodium bicarbonate is stable as a dry powder and is
compatible in almost any proportion with most other dry
-~2~3~5~
--4--
ingredients. Thus, sodium bicarbonate containing tooth
powd~rs have decided advantages over sodium
bicarbonate-containiny toothpaste~ or gels.
In addition to the above advantages of a sodium
bicarbonate-containing too~h powder, it should be
mentioned that it i5 possible to formulate a tooth powder
having a much higher proportion of sodium bicarbonate than
is possible in tooth pastes or gels. Sodium bicarbonate
gives a clean, fresh feeling to the mouth. Sodium bicar-
bonate also helps to deodori e the oral cavity by neu-
tralizing acidic odors. Thus, it is desirable to maximize
the sodium bicarbonate content of a dentifrice. ~owever,
because of stability problems, it is difficultp if not
impossible, to provide more than about 60% sodium bicar-
bonate in a paste or gel and maintain the product in usa-
ble form. A tooth powder, however, may contain higher
levels of sodium bicarbonate.
Thus, it is desirable to provide a dentifrice in the
form of a tooth powder in which a major proportion of the
ingredients comprises sodium bicarbonate particles~
Several tooth powders containing sodium bicarbonate
particles have been previously described. ~.S. 1,082,681
~Danner), discloses a sodium bicarbonate-containing tooth
powder having a fineness of about ~3~ mesh sieve. U.S.
2,024,146 (Crowther) discloses a tooth powder comprising
less than 50% by weight of sodium bicarbonate. The tooth
powder passes through a ~40 mesh sieve. U.S. 4,276,287
(Cabardo, Jr.) discloses a periodontal powder comprising
less than 50% by weight of sodium bicarbonate. The fin-
eness of the sodium bicarbonate particles in this patent
is not disclosed. However, none of these patents
discloses a sodium bicarbonate-containiny tooth powder
within the scope of the present invention. In addition,
the multipurpose baking soda which is sold to the public,
and which often contains a sugyestion on the package that
it may be used for cleaning the teeth, contains sodium
bicarbonate particles having a median particle size in the
range of 44-73 microns.
- ~243g~3
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one major problem encountered in formulating a tooth
powder having a major proportion by weight of abrasive
particles, including sodium bicarbonate particles, i
reducing the abrasiveness of the tooth powder to accepta-
ble levels. Excessive abrasiveness can lead to los~ of
tooth enamel and erosion of exposed dentin9 Abrasiveness
is of particular concern in tooth powders since the con-
centration of abrasives is much higher than in pastes or
gels. Also, the ingredients present in the pastes and
gels often serve to moderate the abrasivity of the overall
formulation.
Another major problem encountered in formulating a
tooth powder containing sodium bicarbonate particles is
the salty taste of sodium bicarbonate. It has been found
that the salty flavor decreases and can be more readily
masked if coarser grades of sodium bicarbonate are used in
the tooth powder. In order to prepare a sodium
bicarbonate containing dentifrice which is not too salty,
the use of large sodium bicarbonate particles is indi-
cated. However, it is known that abrasiveness generally
increases with increasing particle size. See, for
example, Cosmetics Science and Technology, Vol. 1, pages
427, 428 (Wiley-Interscience, 2d Edition, 1972); Tainter,
M.L., and S. Epstein, 30 J.Am.Dent.Assoc. pages 1036-1045
(1943). Thus, with the higher levels of sodium bicarbon-
ate present as the principal abrasive in a tooth powder,
one would expect that a significant increase in the mean
particle size would increase the abrasivity.
It has now been found that, contrary to expectations,
a tooth powder containing a major portion by weight of
sodium bicarbonate particles can be formulated in which
the abrasiveness oF the sodium bicarbonate particles
decreases with increasing particle size. In accordance
with various aspects of the present invention, it i5 now
possible to formulate a sodium bicarbonate-containing
tooth powder which is effective in preventing pellicle and
stain build-up on the teeth, but is not so abrasive as to
deleteriously affec~ tooth enamel, cementum, or dentin.
~2~3~59
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In addition, the sodium bic:arbonate particles are
sufficiently coarse so that the tooth powder is not
exce sively salty but leaves the user with a fresh mouth
taste.
_mmary and Detailed Description Of The Invention
In accordance with the presen~ invention, a tooth powder
may be prepared comprising at least about 50~ by weight
of sodium bicarbonate particles, wherein the sodium bicar-
bonate particles have a median particle size within the
range of about 74 to about 210 microns. (As used herein,
the term "median" particle size is equivalent to the
"mean" particle size.) Preferably, the median size of the
sodium bicarbonate particles in the to~th powder is within
the range of about 74 to about 149 microns. It has sur- -
prisingly been found that such a tooth powder is lower in
abrasivity than tooth powders in which the median particle
size of sodium bicarbonate is less than 74 microns. In
addition, the sodium bicarbonate particles in a tooth pow-
der according to the present invention are sufficiently
coarse so that the tooth powder is not unduly salty.
The tooth powder of the present invention co~prises
at least about 50% by weight of sodium bicarbonate parti-
cles within the specified range. Preferably, the tooth
powder comprises about 75% to about 98% by weight of
sodium bicarbonate. Most preferably, the tooth powder
comprises about 90% to about 98% by weight of sodium
bicarbonate.
As mentioned previously, tooth powders may contain
other ingredients in addition to the sodium bicarbonate.
The tooth powder may contain from about 0 to about 50~ by
weight of additional abrasive materials. Since it is
desirable that the tooth powder be low in abrasivity, it
is preferred that the additional abrasive materials have
RDA's (radioactive dentin abrasion tests) in the range of
about 20 to about 100. Abrasive materials suitable for
the present invention are well known in the art and
include for example, dicalcium phosphate, chalk, silica,
alumina, zirconium silicate, and the like, or mixtures
3~35~
.
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thereo~. As also mentioned previously, sodium bicarbonate
a~ a dry ingredient of a tooth powder is compatible with
these additional abrasive material~.
The tooth powder of the present invention may also
include a suitable flavoring agent. Examples of suitable
flavoring agents include the flavorin~ oils, for example,
oils of spearmint, peppermint, wintergreen, sassafras,
clove, sage, eucalyptus, marjoram, cinnamon, lemon, and
orange, as well as sodium methylsalicylate. The flavoring
agent may be present in the tooth powder in an amount
within the range of about 0 to 2% by weight of the tooth
powder. A carrier for the flavoring a~ent may optionally
also be present in the tooth powder. Such carriers are
well known to those skilled in the art. Suitably, the car-
rier is present in an amount within the range of about 0
to 5% by weight of the tooth powder.
A sweetening agent may also optionally be included in
the tooth powder. Examples of suitable sweetening agents
include lactose, maltose, sorbitol, aspartame, and sac-
charin. The amount of sweetener present in the tooth pow-
der may suitably be within the range of about 0 to 3% by
weight. The flavoring and sweetening agents help to mask
the salty taste of the sodium bicarbonate.
An anti-caking agent, such as silica or tricalcium
phosphate, may be included in the present tooth powder.
Suitably the amount of anti-caking agent is within the
range of about 0 to 2~ by weight of the tooth powder.
An organic surface active agent may also be incorpor-
ated into the tooth powder. The surface active agent aids
in cleaning the teeth and also improves the foaming prop-
erties of the tooth powder. Suitable surface active
agents are well-known in the art and include, for example,
water-soluble salts of the higher alkyl sulfates, such as
sodium lauryl sulfate, water-soluble salts of sulfonated
monoglycerides of fatty acids, such as sodium coconut mon-
oglyceride sulfonate, salts of amides of higher fatty
acids with lower aliphatic amino acids, such as sodium
- lauryl sarcosinate, and the like. The surface active agent
~;~43~S~
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may be present in the tooth powder in amounts ranging from
about 0 to about 2% by weight.
The tooth powder of the present invention may
additionally contain a fluoridating agent to ald in pre~
venting dental caries. Many fluoridating agents suitable
for use in a dentifrice composition are known. ~mong
these are sodium, potassium, ammonium, lithium, and amine
fluorides, monofluorophosphate salts, such as sodium,
potassium, ammonium, and lithium MFP, and other flu-
oridating agents well known to those skilled in the art.
The fluoridating agents are present in an effective but
non-toxic amount, such as within the eange of about 0 to
2% by weight of the tooth powder. Preferably, the tooth
powder of the present invention will contain about 0 to
0.5% by weight of sodium fluoride or 0 to 1% by weight of
sodium MFP as the preferred fluoridating agent.
In a preferred form, the tooth powder of the present
invention contains between about 75 and about 98%, most
preferably between about 90 and about 98%, by weight of
sodium bicarbonate particles having a median particle size
within the range of about 74 to about 149 microns, and
about 0.22% by weight of sodium fluoride.
The following examples will serve to illustrate the
practices of the present invention.
Example 1
Tests were run to show the effect of the concen-
tration of sodium bicarbonate particles on the
abrasiveness of dentifrice compositions~ In runs l, 2 and
3 shown below, different amounts of multipurpose baking
soda having a median particle size within the range of
44-73 microns were mixed with 50 ml of water containing
0.5% of carboxymethyl cellulose (CMC) as a thickener. The
mixtures were sukjected to the well-known radioactive den-
tin abrasion (RDA) and the radioactive enamel abrasion
(REA) tests. The results are shown in Table I~ Table I
also shows the results when comparable RDA and REA tests
were performed on two commercial toothpastes which do not
contain sodium bicarbonate. Paste A (Crest with
4~3~59
g
fluoristat) contains hydrated silica as the dental
abrasive. Paste B (Colgate dental cream) contains dical-
cium phosphate as the dental abrasive.
Table I
Concentration RDA REA
Baking Soda lOg NaHCO3/50ml H20 25 16
Baking Soda 25g NaHC03/50ml H20 62 16
Baking Soda 50g NaHco3/5oml H20 6a 20
Paste A 25g/50ml H20 67 50
Paste B 25g/50ml ~2 46 14
As expected, the results in Table I show an increase
in abrasivity with increasing concentration of sodium
bicarbonate particles.
Example 2
A preferred tooth powder was formulated comprising
97.32% of sodium bicarbonate particles, wherein the median
size of the sodium bicarbonate particles was in the range
of 74-149 microns, 2% flavoring and saccharin, 0.22%
sod;um fluoride, and traces of other ingredients. The
tooth powder was mixed with 50 ml of water containing 0.5%
C~C and was tested as in Example 1 for abrasivity by the
RDA and REA tests at different concentrations. The
results are shown in Table II.
Table II
Concentration RDA REA
~aking Soda lOg NaHC03/50ml H20 21 16
Baking Soda 25g NaHC03/50ml H20 52 16
Baking Soda SOg NaHC03/50ml H20 5~ 13
These results, when compared to the results of Table
I, demonstrate that sodium bicarbonate particles having a
median particle size within the range of 74-149 microns
are less abrasive than sodium bicarbonate particles having
a median particle size within the range of 44-74 microns.
Example 3
¦ -35 The abrasivity of sodium bicarbonate particles of
¦ different sizes as compared to calcium pyrophosphate was
tested by the RDA test~ The results are shown in Table
'~
_ _ . . ..... . _ _ _ _ _ _ . _ ., _ . . , .. _ . . _ .. .
.: ~
s~
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Table III
Median Particle Average
Size _ RDA
Calcium pyrophosphate 100
Bakin9 Soda <4~ 39
8aking Soda 44-73~ 28
Baking Soda ~ 74~ 25
Baking Soda >149~ 22
The results show that sodium bicarbonate is much
lower in abrasivity than calcium pyrophosphate. The
results also show that the abrasivity of sodium bicarbon-
ate particles decreases as the median particle size
increases. Thus, a tooth powder low in abrasivity and low ,~
in salty flavor can be formulated which is comprised of a
major proportion by weight of sodium bicarbonate particles
having a median size within the specified range.
While the invention has been described by reference
to specific embodiments, this was for purposes of illus-
tration only and should not be construed to limit the
spirit or scope of the invention.
