Note: Descriptions are shown in the official language in which they were submitted.
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Title: A COMPOSITION FOR WHITENING TEETH AND METHOD OF
MAKING THE SAME
FIELD OF THE INVENTION
This invention relates generally to the field of oral care products,
and more particularly to oral care products that whiten teeth.
BACKGROUND OF THE INVENTION
Tooth whitening products are well known and are used to lighten
the color of teeth for aesthetic reasons. Many forms of whitening agents
or actives are used and are delivered in many types of products. Tooth
whitening actives are used in toothpastes or dentifrices, gels, both paint
on and tray=based systems, gums and strips, including strips having
backing layers, among other things.
A problem for such tooth whitening products is to provide a product
that, on the one hand has a long shelf life (and thus remains active and
effective for a considerable time) and one which is faster acting, so the
whitening step can be accomplished quickly without inconvenience to the
user. The more reactive the tooth whitening active the quicker the tooth
whitening occurs. Of course, a more reactive tooth whitening formulation
is typically less stable. Thus, more stable whitening compositions tend to
be slow acting, while faster acting compositions tend to be less stable.
What is desired is a tooth whitening composition having a tooth whitening
active which is both fast acting and relatively shelf stable over reasonable
shelf storage times.
Typically, tooth-whitening compositions will include a form of tooth
whitening active, such as a hydrogen peroxide or a hydrogen peroxide
precursor such as carbamide peroxide. When introduced to water, the
precursor dissociates into urea and hydrogen peroxide. Typically one or
more polymers or other substances are used in a viscous carrier such as
glycerin or glycol to prevent premature dissociation. Water typically forms
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a part of the composition and thickeners are used to control viscosity and
to prevent the water from separating out of the composition. The use of
such thickeners to help form the viscous gel leads to other problems for
the composition. For example, the use of such thickeners prevents the
active from migrating to the tooth surface. This is referred to as gel
blocking. Where the tooth whitening composition is used in a composition
that is brushed onto the teeth, such as a dentifrice, this is not so much of
a concern since the act of brushing will cause fresh active to be
introduced to the tooth surface. For paint on gels, tray-based systems
and aqueous-based strips, the inability of the active to move through the
thickened gel is a serious limitation.
U.S. Patents 5,614,174, 5,690, 913 and 5,599,525 to Colgate
Palmolive Company disclose a dentifrice with up to 9% water content
which includes either Xanthan or Sylodent 15, as a thickening agent. The
use of these compositions will both thicken the gel and make it more
difficult for the active to migrate through the gel to reach the tooth
surface.
However, for a dentifrice which is applied in the normal course by tooth
brushing, lack of mavement of the active through the thickened gel is not
a problem due to physical mixing and remixing of the composition and a
spreading of the composition onto the tooth surface introducing fresh
active during such brushing.
U.S. Patent 6,221,341 proposes another form of tooth whitening
agent, in which two separate chemicals are brought together, in the act of
applying the composition in the mouth which, through their interaction,
create the tooth whitening active. In the preferred example the
combination of a hydrogen peroxide precursor with glyceryl triacetate and
water creates peroxyacetic acid as the tooth whitening active. However,
this requires separate compartments in the dispensing container to keep
the components apart during storage and a form of dispenser that
ensures good mixing as the material leaves the container to ensure the
appropriate conditions occur to create the active. This requires a more
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complex and expensive form of container and compounds packaging
costs.
U.S. Patents 6,682,721 and 6,689,344 disclose a dry type tooth
whitening patch having peroxide as a tooth whitening agent. The patch is
a hydrophilic glass polymer that has a strong adhesion to the tooth.
However, a patch system is less convenient than a paint on gel.
What is desired is a tooth whitening composition that is both fast
acting (in a mater of minutes rather than hours) and yet which discloses a
high stability and long shelf life. Preferably such a composition includes a
stable hydrogen peroxide precursor, which is not likely to dissociate
before being placed in the mouth.
SUMMARY OF THE INVENTION
The present invention is directed, in one aspect, to a relative thick
or viscous anhydrous formulation for application directly to teeth to whiten
the same. The anhydrous formulation is preferably comprised of a polyol
carrier material such as glycerin into which a stabilized oxidizing agent
such as PVP hydrogen peroxide is mixed. Most preferably the PVP
hydrogen peroxide is cross linked which adds viscosity renders the PVP
substantially insoluble in water and yet provides a stable oxidizing agent
which remains reactive over time due to both its stability and the absence
of water in the formulation. The cross-linked PVP according to the
present invention shows goad mixing with the polyol. The cross-linked
PVP does not solubilize with the anhydrous polyol media. A surfactant is
also added to lower the surface tension of the water on the tooth surface
when the formulations of the present invention becomes hydrated from
the saliva on the tooth surface. This will lower the surface tension and will
further increase the migration of active to the tooth surface. . The
formulation according to the present invention demonstrates reasonable
shelf life, strong tooth whitening and rapid action, meaning that the
oxidizing agent is able to come to bear on the surfaces to be whitened in
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commercially effective concentrations over the course of a short,
generally less than ten minute and most preferably about five minute,
treatment.
Most preferable the cross-linked PVP hydrogen peroxide will be
sufficiently viscous so as to, in combination with the other ingredients,
cause the formulation to adhere to the teeth of a user.
Therefore according to a first aspect of the invention there is
provided a composition for whitening teeth comprising:
an anhydrous mixture of a polyoi carrier material, a stabilized
oxidizing agent, and a surfactant, said mixture having a viscosity sufficient
to adhere to moistened tooth enamel while being substantially free of
water soluble thickener, said anhydrous mixture being substantially shelf
stable due to the absence of water, and wherein said mixture when
applied to said moistened tooth enamel oxidizes organic compounds
without gel blocking.
According to a further aspect of the present invention there is
disclosed a method of whitening teeth comprising applying a formulation
comprised of an anhydrous mixture of a stabilized oxidizing agent, a
polyol carrier material and a surfactant to a tooth surface to be whitened,
letting the formulation remain on the teeth for an effective tooth whitening
period wherein the tooth whitening period is between four and six
minutes.
According to a further aspect of the present invention there is
provided a composition for whitening teeth comprising
an anhydrous mixture of a poiyoi carrier material and an oxidizing agent,
wherein said oxidizing agent does not substantially dissociate in said
anhydrous mixture until said mixture is applied to a moistened tooth
surface.
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DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The formulation made according to the present invention is an
anhydrous mixture of a poiyol carrier material, a stabilized active and a
surfactant. Other additives may also be used to improve the
characteristics of the formulation such as colorants, sweeteners, flavoring
agents, accelerants and the like, as discussed in more detail below. In
this specification the terms formulation and composition are used
interchangeably.
Turning first to the polyol, the preferred polyol is glycerin. Although
glycerin is referred to commercially as being anhydrous, in fact it may
contain trace amounts of water, typically less than 0.5%. Being a
humectant though it has an affinity for water and can absorb water from
air, for example during manufacturing. The present invention can tolerate
small amounts of water and for the purposes of this disclosure the term
anhydrous is intended to mean a water content of less than about 2% by
weight of the overall solution. Essentially the present invention requires
that there so little water present that the gel is not characterized as an
aqueous gel nor is an aqueous thickener required.
While the most preferred polyol is glycerin other polyols can also
be reasonably substituted. These include anhydrous or relatively
anhydrous polyols. Polyols may be defined a:r hydrocarbons, commonly
from carbohydrates, that have had some of their carbonyl groups reduced
to a primary or secondary hydroxyl groups) and be more simply defined
an organic compound having more than one hydroxyl (-OH) group per
molecule and alcohols. Examples of such polyols are glycerin, propylene
glycol, butylene glycol, and propylene glycol, and an alcohol, such as 200
proof anhydrous ethanol.
The polyol is included in the formulation of the present invention at
a concentration of about 10% to about 85% by weight.
Turning now to the whitening active, the most preferred form of
whitening active is a cross-linked polyvinylpyrrolidone hydrogen peroxide
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(PVP-H20). The cross-linking renders the material mostly water
insoluble, which helps to stabilize the mixture in the anhydrous
formulation even the presence of trace amounts of water. Other actives
include uncrosslinked anhydrous Polyvinylpyrrolidone hydrogen peroxide.
This may in some case be suitable but is less preferred for two reasons.
Firstly, it is less stable and so is more likely to have a reduced shelf life
and secondly, it tends to be less viscous meaning that it is harder to
achieve the desired viscosity with the uncross linked PVP H20.
The active is included in the formulation of the present invention at
a concentration of about 10 to 60% by weight. Most preferably the active
has a molecular weight of about 15 to 50. As will be appreciated by those
skilled in the art, about 20% (wlw) of PVPH202 is hydrogen peroxide, so
for example 15% to 50% PVP-H202 range is actually 3% to 10% H202.
The percentage of PVP-H2O2 as measured by concentration of H2O2 is
between 1 and 15% (wlw) and most preferably between 1 and 10% (wlw).
Surfactants are typically added reduce the surface tension. In
aqueous gel formulations of the prior art the presence of significant
concentrations of water results in a thin or fluid composition that requires
a thickener to achieve a workable viscosity. Low viscosity is to be
avoided because it affects the control over the location of the whitening
product in the mouth. For example if the gel is too runny the active will
run off the teeth, may spill out of a tray or otherwise becomes mobile and
thus is more likely to come into contact with sensitive gingival tissues. As
a result since surfactants reduce viscosity, aqueous based systems do
not include any surfactants.
According to the present invention surfactants are desirable to
reduce the viscosity of the anhydrous formulation of a mixture of stabilized
oxidizing agent and polyol that makes it easier to apply to the tooth
surface, encourages better mixing of the ingredients and permits the
active to more easily reach and therefore interact more quickly with
organics located on the tooth surface. After the formulation of the present
_ .. __. . ,
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invention comes in contact with the saliva it will lower the surface tension
to further increase the migration of active material in the invention. A
lower viscosity permits a better tooth whitening rate andlor efficacy of the
product via an increase in the migration of active ingredient to the tooth
surface.
Examples of suitable surfactants according to the present invention
are sodium dodecanyl sulfate (sodium lauryl suilfate) and sodium lauroyl
sarcosinate. According to the present invention the surtactant is included
in the formulation in an amount of about 0.1 to 5 % by weight.
The present invention also provides for the optional addition of
organoleptic ingredients. These ingredients contribute to the visual
appeal, taste and odor of a product. Examples of Organoleptic
ingredients according to the present invention include flavorants,
colorants, pigments, dyes~and sweeteners. Examples of sweeteners are
sucralose, sodium saccharin, potassium acesulfame. Examples of dyes
are those approved under the Food and Drug Cosmetics Act, and are
under the category of FD&C and D&C dyes (Food Drug and Cosmetic).
Examples are FD&C Red #4, FD&C Blue 1 and FD&C Yellow 5.
Pigments and colorants may add color andlor opacity to a product.
Examples of pigments and colorants are titanium dioxide, mica and the
lake equivalents of FD&C and D&C dyes.
Some common flavorants that may add both taste and odor to the
invention may include peppermint oil, spearmint oil, methyl salicylate and
menthol. According to the present invention the preferred formulation is
anhydrous, meaning the pH cannot be measured. However, when the
formulation comes in contact with the saliva on the tooth surface, then the
resulting mixture will have a certain pH. Depending upon the other
ingredients, it may be advisable to add one or more pH-adjusting agents
to the formulation to ensure that the tooth whitening formulation has an
optimal pH when moistened by saliva when placed on teeth in the mouth:
As well an alkaline agent can encourage the oxidation reaction so in one
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embodiment the present invention comprehends adding alkaline agent
such as Triethanolamine. The alkaline agent is preferably in a small
amount of less than 1 % by weight and most preferably about 0.5% by
weight of the total formulation.
While the primary embodiment of the present invention is as a
viscous formula to be applied directly to the teeth, in another aspect it can
be used as a foundation to a dentifrice formulation. In such an
embodiment it is preferred to add to the formulation silicas. Silicas and
hydrated silicas are added to act as abrasive agents and rheological
modifiers. Also, it can be used in a less viscous formulation in a pen-
based or brush on application.
Inorganic polyphosphate salts may also be added as anti-tartar
agents, such as sodium tripolyphosphate, sodium hexametaphosphate,
tetrapotassium pyrophosphate and tetrasodium pyrophosphate.
To prepare the formulations of the present invention the polyol i.e.
glycerin, the surfactant and the whitening active are dispersed in a
conventional mixer until the mixture becomes <~ homogeneous phase.
Then, into the homogeneous phase are added the remaining ingredients
such as flavoring or other organoleptic agents, anti tartar agents, and the
like. Thereafter the ingredients are further mixed until a homogenous
consistency is achieved. The desired viscosity is between 50,000 and
1,500,000 centipoises and more preferably between 300,000 and
1,200,000:
It will be understood by those skilled in the art that because the
formulations of the present invention are anhydrous, care must be taken
during manufacture to limit the exposure to potential sources of water,
such as humid air. As well, if the viscosity needs to be changed to
achieve the desired viscosity, this must be done without using water or
thickeners as is traditionally been the case for these types of
compositions.
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Example I
Table I below details various embodiments of the present made
following the above-described standard procedure. These embodiments
are depicted as formulations A to F on the Table. Table II below depicts
alternate embodiments of the present invention using PVP-H20 which is
not cross-linked. The present invention also comprehends mixtures of
cross-linked and uncross-linked PVP-H202 being combined with the
anhydrous polyol media, to combine lower viscosity with improved
stability. The method of preparation is generally the same, and different
formulations of this embodiment are shown as A to D in the table. Table
III below is a further embodiment of the present invention in which the
viscous formulation is used as a base for a dentifrice. In this embodiment
various other ingredients are added such as silica in the amounts shovun,
which also act to thicken the formulation.
Crosslinked PVP-H202
Formulations
Ingredient . A B C ~ E F
Crosslinked PVP-H202 21.0 21.0 21.0 21.0 21.0 30.0
Glycerin 62:'7 63.2 30.0 30.2 30.7 54.0
PEG-6 30.2 15.0 15.
0
Propylene Glycol 15.0 15.0
Etidronic Acid 0.5
Ethanol (200 Proof) 15.0 15.0 18.0 18.0 18.0 15.0
Alkaline Agent (e.g. Triethanolamine)0.5 0.5 0.5 0.5 0.5
,
Surtactant (e.g. Sodium Lauroyl0 0 0 0 0 0
3 3 3 3 3 5
Sarcosinate) . . . . . .
Total 100.0 100.0100.0 100.0100.0100.0
TABLE It
PVP-H202 Formulations
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Ingredient A B C D
,VP-H202 21.C1 32.5 21.0 21.0
Slycerin 62. 66.2 63.0
l'
'EG-6 62.7
thanol 15.0 15.0 15.0
'hosphoric Acid 0.5
tidronic Acid 0.'i 0.5 0.5
Alkaline Agent (e.g. Triethanolamine)0.5 0.5 0.5 0.5.
Surfactant (e.g. Sodium Lauroyl
0.3 0.3 0.3
Sarcosinate)
Total 100.0 100.0 100.0100.0
TABLE III
Crosslinked PVP-H202 Dentifrice~~ B C D
Formulations
Crosslinked PVP-H202 3.0() 5.00 5.00 5.00
Glycerin 64.7;T53.50 54.0056.OCD
Xylitol 4.00
PEG-18 10.00 10.0010.00
Sodium Saccharin 0.4c) 0.40
Flavor 0.50 0.50 0.50 0.50
Titanium Dioxide 1.50 1.50 1.50 1.50
Sodium Tripolyphosphate 3.00 3.00
Sodium Monofluorophosphate 0.83
Surfactant (e.g. Sodium Lauroyl1.00 1.00 1.00 1.00
Sarcosinate)
Abrasive Silica (Hydrated 20.00 20.00 25.0015.0()
Silica e.g.
Sylodent XWA 350)
Thickening Silica (Hydrated 5,00 5.00 3.00 7.00
Silica e.g.
Zeodent 165)
Total 100.00100.00100.00100.00
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Notes:
Sylodent XWA 350 is made by Grace
Davison
Zeodent 165 made by J.M. Huber
Corporation
stability further increased with the use
Example II
An experiment was conducted to test the whitening efficacy and to
test the safety of the formulation according to 1"able I of the present
invention. The test conducted compared the effect of the present
invention to other whitening products and one control product (i.e.
placebo). The test was conducted on a study population of 200 subjects,
male and female, who met predetermined inclusion and exclusion criteria..
Eight groups were identified with twenty-five subjects in each group. The
test was conducted on a single blind basis to optimize objectivity. Clinical
measurements were taken at the start, after three days for certain groups
and after two weeks for all groups. The clinical measurements included,
an oral soft tissue exam, a tooth shade exam, a modified gingival index
exam, a sensitivity questionnaire, and intraoral photographs were taken
for spectrophotometric analysis for changes in shade.
In this test two different groups were given variations of the Table I
present invention. In one group the subjects were to brush their teeth
normally with regular toothpaste and a regular soft bristled brush. Then
they placed a bead of formulation according to the present invention into
upper and lower customized mouth trays that were then placed in the
mouth. Contact of the formulation with the gums was to be avoided. Z'he
trays were left in place for five minutes then removed and excess gel was
brushed off with tap water. The teeth whitening regimen was repeated
_ .... _... _. _ . ; _.
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twice per day. In one group the teeth were also thoroughly brushed at
least twice per day. For the other group, everything was the same except
they did not also brush their teeth twice per day.
In the case of the one group the results of two specific teeth for
each subject that were measured at a baseline, and after two weeks,
showed a starting whiteness of 15.1+I-3.1 and a finishing whiteness of
12.0+l-3.3 for an average percentage increase of 21.8% +/-11.7%. For
the other group, the starting whiteness was measured at 14.0+I- 5.0 and
after two weeks was measured at 9.7+/-5.9 for a percentage increase of
35.0%+I-23.4%. Brushing immediately after application of the formulation
seems to reduce the effectiveness of the whitening treatment.
The conclusions drawn from the study are that the whitening
obtained with the present invention is similar to thase of other prior art
formulations, and in particular to Crest White Strips( which showed an
average increase of 42.3% +/- 22.4%), when following the protocols of the
study, except that instead of requiring tuvo thirty minute application periods
per day as does Crest White Strips in a two week treatment program the
present invention requires two five minute application periods per day.
The study further showed whitening occurred sooner in the present
invention and the data showed the formulation was safe to oral tissues.
In summary the present invention demonstrates effective whitening
in a short time due to the elimination of gel blocking which is typical for
prior art compositions which use water and thickeners to achieve the
desired viscosity. By providing an anhydrous formulation, in which the
viscosity is achieved by mixing the active with a polyal media, and which
coats the tooth surface well, through the help of a surfactant, the present
invention provides a tooth whitening composition which demonstrates
effective tooth whitening in short treatment session of less than ten
minutes and most preferably about five minute, at a time. Further the use
of a cross linked oxidizing agent which has both good viscosity and
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demonstrates improved stability provides an easy to use formulation
which has a long stable shelf life.
