Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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COMPOSITIONS AND METHODS FOR WHITENTi\ G
Al~'D DESENSITIZING TEETH
BACKGROUND
1. The Field of the Invention.
The present invention relates to compositions and methods for whitening and
desensitizing teeth. More particularly, the present invention encompasses
compositions
that include both a bleaching agent and a desensitizing agent. Such
compositions are
especially suitable for maximized tooth whitening and minimized tooth
sensitivity when
in prolonged contact with the teeth to be treated.
2. The Relevant Technoloav.
The natural color of teeth is opaque to translucent white or slightly off
white.
However, the use of certain foods and tobacco, the process of aging, diseases,
trauma,
medications, some congenital conditions, and environmental effects can cause
teeth to
become discolored. Because whiter teeth are considered to be aesthetically
superior to
stained or discolored teeth, there has been a large demand for dental
bleaching
compositions.
Typical tooth bleaching agents release active oxygen radicals. Such bleaching
agents include peroxides, such as hydrogen peroxide, percarbonates and
perborates of the
alkali and alkaline earth metals, or complex compounds containing hydrogen
peroxide.
Also, peroxide salts of the alkali or alkaline earth metals and peroxyacetic
acid
(CH3C=00-OH) are known to be useful in whitening teeth.
The most commonly used dental bleaching agent is carbamide peroxide
(CO(NH~yH20J, also called urea hydrogen peroxide, hydrogen peroxide carbamide,
and
perhydrol-urea. Carbamide peroxide has been used by dental clinicians for
several
decades as an oral antiseptic. Tooth bleaching was an observed side effect of
extended
contact time. Over-the-counter compositions of 10% carbamide peroxide are
available
as GLY-OXIDE~ by Marion Laboratories and PROXIGEL~ by Reed and Carnrick. A
sticky bleaching gel which is able to hold a comfortable-fitting dental tray
in position for
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an extended time period is available under the trademark OPALESCENCE from
Ultradent Products, Inc. in South Jordan, Utah.
Patients who have desired to have their teeth whitened have typically done so
by
applying a bleaching composition to the teeth by means of a dental tray for
repeated
treatments, or they have had to submit to conventional in-office bleaching
techniques that
required from 4 to 10 visits to the dental office before clinically
significant results were
achieved. Clinically significant results are quantifiable such as by measuring
gray scale,
L*, and as to yellowness or blueness, b*, in the CIE~ system of color
measurement or
by equivalent methods.
Although dental bleaching compositions are effective in removing stains and
superficial discoloration, they are often limited by the inherent translucence
of many
people's teeth. More precisely, teeth having more translucent enamel are
difficult to
whiten beyond a certain point since the yellowish or grayish tint of the
underlying dentin
is difficult to change by bleaching alone.
Another downside of tooth bleaching regimens is the tendency of tooth
bleaching
agents to cause increased sensitivity when applied to teeth over prolonged
periods of
time. Thus, attempts to further whiten a person's teeth, including prolonged
bleaching
of excessively translucent teeth, may result in increased tooth sensitivity,
which can
become quite severe for some people.
From the foregoing, it will be appreciated that what is needed in the art are
improved compositions and methods for whitening teeth, including improved
compositions and methods for whitening translucent teeth.
It will also be appreciated that what is also needed are improved compositions
and methods for whitening teeth which reduce tooth sensitivity, compared to
conventional dental bleaching compositions.
Such compositions and methods for bleaching, whitening teeth, while reducing
tooth sensitivity, are disclosed and claimed herein.
BRIEF SUMMARY OF THE INVENTION
The present invention generally relates to dental whitening compositions and
methods for whitening teeth. In addition, the present invention relates to
compositions
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and methods that result in reduced tooth sensitivity compared to conventional
dental
bleaching compositions. The compositions of the present invention include a
dental
bleaching agent in combination with potassium nitrate (KN03), which has
surprisingly
been found to both desensitizea teeth and enhance the whitening ability of the
dental
bleaching agent when included in smaller amounts (about 0.01 % to about 2% by
weight
of the dental bleaching composition). Whereas it was known that potassium
nitrate is
effective as an anesthetic in order to reduce tooth sensitivity, it was not
heretofore known
that potassium nitrate also enhances tooth whitening when used in a dental
composition
in combination with a bleaching agent.
The potassium nitrate and bleaching agent are typically dispersed in a liquid
or
gel Garner. In addition, the whitening compositions may include one or more
other dental
agents, such as an anticariogenic agent for reinforcing teeth against tooth
decay or an
antimicrobial agent for treating gum diseases. The most commonly used
anticariogenic
agents include fluoride salts, such as stannous or sodium fluoride, which can
also impart
antidemineralization or even remineralization properties to the tooth
whitening
compositions. Examples of preferred antimicrobial agents include
chlorohexidine,
tetracycline, cetyl pyridinium chloride, benzalkonium chloride, cetyl
pyridinium bromide,
methyl benzoate, and propyl benzoate.
The compositions are preferably substantially free of abrasives, as the
compositions are typically not scrubbed onto the teeth. When using abrasive
toothpastes,
people typically brush for less than 60 seconds, which is not enough time to
cause a
noticeable whitening effect. On the other hand, scrubbing teeth with an
abrasive material
for an extended period of time can be harmful to the tooth enamel. Therefore,
in order
to allow for extended bleaching, whitening and opacification of teeth, the
inventive
compositions will preferably not include substantial quantities of an
abrasive.
The compositions are preferably used with a dental tray that is thin-walled,
flexible and lightweight. Preferred dental trays should be adapted for maximum
comfort
and will exert little, if any, significant mechanical pressure onto the
person's teeth or
gums. When using a tray of this nature, the tooth whitening compositions of
the present
invention will preferably be sufficiently sticky, viscous and resistant to
dilution by saliva
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so as to act as a glue-like material and reliably adhere and retain the dental
tray over the
person's teeth for a desired time duration. Although such dental trays are
prefeu-ed, any
conventional dental trays may also be utilized. The inventive dental
compositions may
also be applied directly to a person's teeth without using a tray. In such
cases, higher
concentrations of the active bleaching agents will preferably be used in order
to speed up
the desired bleaching action.
Any component other than the active dental agents, such as the potassium
nitrate,
bleaching agent, antimicrobial agent and anticariogenic agent, shall comprise
the
"carner ". In the case where the dental composition is sticky and viscous, the
carrier will
constitute a sticky matrix material formed by combining a sufficient quantity
of a
tackifying agent, such as carboxypolymethylene, with one or more solvents,
such as
glycerin, polyethylene glycol, or water. Although the carrier is preferably
formed by
combining a tackifying agent and a solvent, the carrier may comprise a solvent
without
a tackifying agent in some embodiments. Preferred compositions, as described
hereinbelow, are relatively sticky and glue-like to enable a prefewed dental
tray to be held
and retained against a person's teeth. Preferred carriers are preferably safe
for oral use,
do not readily dissolve in saliva, and do not react with the active dental
agents.
In addition to carboxypolymethylene, examples of other suitable tackifying
agents, or thickening agents that can assist other tackifying agents, include
xanthan gum,
talha gum, tragacanth gum, carboxymethylcellulose, locust bean gum, guar gum,
Irish
moss gum, ghatti gum, furcelleran gum, carrageenan gum, arabic gum, alginic
acid gum,
agar gum, alginate gum, proteins, such as collagen, PEMULEN~, a proprietary
compound of B.F. Goodrich, POLYOX~, a mixture of polyethylene oxides having a
molecular weight of 100,000-8,000,000 and available from Union Carbide,
including
higher molecular weight polyethylene glycols, or any compositional or chemical
equivalents of the foregoing. PEMULEN~ is a propriety formula that includes a
significant quantity of a polyacrylic copolymer that has a slightly
hydrophobic end and
a strongly hydrophilic end.
In addition to glycerin, many other polyols may serve as suitable solvents.
The
solvent may also be water alone or in combination with a polyol. Glycerin is a
preferred
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solvent as it works well in forming a sticky gel with carboxypolymethylene.
Glycerin
also provides some flavor enhancement. A few possible substitutes for glycerin
include
propylene glycols, polypropylene glycol, polyethylene glycols, enyrthritol,
sorbitol,
mannitol, other polyols, and the like. In some embodiments polyols such as
glycerin,
5 lower molecular weight polyethylene glycols, polypropylene glycol, propylene
glycol, and
sorbitol may also be used without a tackifying agent.
As indicated hereinabove, one currently preferred sticky matrix material
includes
a mixture of carboxypolymethylene together with other suitable admixtures. The
term
"carboxypolymethylene" is used to denote a broad category of polymers,
particularly
copolymers of acrylic acid and polyallyl sucrose. Because carboxypolymethylene
that has
not been completely neutralized includes active carboxylic acid groups or
moieties,
carboxypolymethylene can be classified as a weak acid. When dispersed in
water,
carboxypolymethylene can have a pH as low as about 2.5.
Because highly acidic compositions can etch teeth, it is generally preferable
to
adjust the pH of dental compositions that include carboxypolymethylene or
other acids
to make them less acidic. Accordingly, it is preferable to adjust the pH of
the bleaching
compositions to within a range from about 4 to about 9, more preferably to
within a range
from about 5 to about 8. Because it is contemplated that the
carboxypolymethylene used
in the matrix material and the compositions of the present invention will be
mixed with
a base to raise the pH of the resulting dental composition, for purposes of
the
specification and the appended claims, the term "carboxypolymethylene" shall
include
carboxypolymethylene within compositions at any pH. Preferred bases used to
adjust the
pH of the dental compositions may include inorganic bases such as sodium
hydroxide or
ammonium hydroxide. Alternatively, the base may include an organic base such
as
triethanolamine or other organic amines.
Since peroxides may cause irntation and also greater sensitivity in teeth for
some
people, the simultaneous inclusion of potassium nitrate can offset the
potentially negative
effects of the peroxide. Accordingly, potassium nitrate can simultaneously
provide both
opacification and desensitization. Even though other desensitizing agents can
also be
used to desensitize teeth, including citric acid, citric acid salts, strontium
chloride, and
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the like, only potassium nitrate has been proven to also enhance tooth
whitening. Since
the present invention allows for prolonged contact via the use of an
appropriate tray
and/or a sticky composition, the potassium nitrate is preferably included in
an amount of
about 0.01 % to about 2% by weight of the dental composition, and more
preferably in an
amount of about 0.05% to about 1 % by weight. Surprisingly, dental bleaching
compositions that include only 0.5% potassium nitrate have been found to be
far superior
to compositions that include 3% potassium nitrate, both in enhancing whitening
and also
in desensitizing teeth.
In a preferred embodiment, the dental bleaching compositions within the scope
of the present invention will be sufficiently sticky and generally viscous
such that positive
pressure is needed to dispense them from the container; gravity is not
sufficient. Unlike
conventional low-viscosity compositions such as GLY-OXIDE (manufactured by
Marion
Laboratories) or PROXIGEL (manufactured by Reed and Carnick according to U.S.
Patent No. 3,657,413 to Rosenthal), preferred whitening compositions according
to the
present invention will be packaged within a syringe, squeezable tube, or other
similar
positive pressure dispensing device.
An improved dental tray that is thin-walled, flexible and lightweight for
holding
the dental composition adjacent to a person's teeth is preferably used in
combination with
sticky and viscous dental whitening compositions of the present invention. The
general
process for preparing such dental trays is as follows. First, an alginate
impression which
registers all teeth surfaces plus the gingival margin is made and a stone cast
is made of
the impression. Optional reservoirs can be prepared by building a layer of
rigid material
on the stone cast on specific teeth surfaces to be treated. A dental tray is
then vacuum
formed from the modified cast using a thin, flexible plastic sheet material.
Once formed,
the tray is preferably trimmed barely shy of the gingival margin on both the
buccal and
lingual surfaces of the person's teeth. The resulting tray provides a
comfortable fit of the
person's teeth, with optional reservoirs or spaces located where the rigid
material was
placed on the stone cast. The trays can optionally overlap the gums if desired
to provide
contact between the dental compositions and a person's gums. The trays of the
present
invention have greatly increased comfort and exert little or no significant
mechanical
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pressure on a person's teeth or gums. Instead, sticky dental compositions
within the
scope of the invention can act like a glue to hold the improved trays in
place.
The amount of tooth whitening obtained through the use of the inventive
compositions and methods is dependent primarily upon (1) the length of time
each day
the tray is worn; and (2) the number of days the tray is worn. The treatment
schedule may
be tailored to each person's lifestyle or response to the treatment and can be
performed
as often as a person desires to provide effective relief fi-om excessively
translucent teeth.
It has been found that treatment during sleep is a good treatment period since
there is less
mouth activity which causes less whitening composition to be pumped from the
tray.
In short, the desensitizing bleaching compositions according to the invention
include a dental bleaching agent (e.g., carbamide peroxide) in an amount so as
to effect
bleaching of a person's teeth, typically by maintaining the dental composition
in contact
with the person's teeth for at least about 15 minutes, more preferably for at
least about
1 hour. They also include potassium nitrate in an amount so as to both reduce
sensitivity
that may be caused by contacting the dental bleaching agent with a person's
teeth and
also to enhance the whitening effect of the dental bleaching agent. By means
of a
comparative study discussed below, the inventors discovered the surprising and
unexpected result that the desensitization and enhanced whitening properties
of
potassium nitrate are actually higher when included in lower concentrations
(e.g., 0.5%)
rather than at higher concentrations (e.g., 3%).
Moreover, the compositions of the present invention should be contrasted with
conventional desensitizing tooth paste compositions formulated with large
quantities of
abrasives (e.g., 20% or more by weight) and high concentrations of potassium
nitrate
(e.g., up 10% by weight) which are intended to contact the teeth during daily
brushing
(typically for 60 seconds or less). Such compositions are formulated to treat
past, rather
than prospective, tooth sensitivity. They do not treat sensitivity caused by
simultaneous
contact of the teeth with a dental bleaching agent, particularly since no
significant
bleaching and sensitization of a person's teeth are likely using peroxide-
containing
toothpastes due to the extremely short contact times.
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These and other features of the present invention will become more fully
apparent from the description as follows, or may be learned by the practice of
the
invention.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a perspective view of a stone cast of a person's teeth with a
coating
being applied to selected teeth surfaces.
Figure 2 is a perspective view of the stone cast of Figure 1 with a dental
tray
formed from the cast and trimmed below the gingival margin.
Figure 3 is a cross-sectional view taken along line 3-3 of Figure 2.
Figure 3A is an enlarged close-up view taken within the section line 3A-3A of
Figure 3.
Figure 4 is a cross-sectional view taken along line 4-4 of Figure 2.
Figure 5 is a perspective view of the bleaching composition being delivered
from
a syringe into a thin-walled, flexible dental tray.
Figure 6 is a perspective view of a thin-walled, flexible dental tray filled
with the
bleaching composition just before being positioned on a person's upper arch.
Figure 7 is a perspective view of a thin-walled, flexible dental tray filled
with the
bleaching composition positioned on a person's upper arch.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
As surr~narized above, the present invention generally relates to dental
bleaching
compositions and methods for bleaching and whitening teeth, while also
minimizing or
eliminating tooth sensitivity. At a minimum, the inventive compositions will
include a
dental bleaching agent and potassium nitrate, which acts as both a whitening
agent and
as a desensitizing agent. The bleaching agent and potassium nitrate are
delivered to the
teeth by means of a carrier, preferably a carrier that is a sticky matrix.
Although
potassium nitrate is known as an effective desensitizing agent when used in
toothpastes
at higher concentrations (e.~., 5% or more), it has surprisingly been found
that its
effectiveness as a desensitizing agent when used in combination with a dental
bleaching
agent actually increases when used in very low concentrations (e.g., about
0.01 % to about
2%). It also more effectively increases the tooth whitening effect of the
bleaching agent
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at such lower concentrations, which is also a surprising result. The
compositions
prefer°ably do not include an abrasive.
In a prefewed embodiment, the dental whitening compositions will be used in
conjunction with a thin, flexible, comfortable-fitting dental tray in order to
hold the
compositions against the person's teeth. Preferred dental trays will conform
to the size
and shape of a person's teeth and will exert little or no significant
mechanical pressure
onto the person's teeth and/or gums. This makes them more comfortable and
pleasant
to use compared to conventional dental trays. Nevertheless, the inventive
tooth
whitening compositions may certainly be used with conventional dental trays,
or with no
tray at all.
In the case where a thin, flexible dental tray is used, the potassium nitrate,
dental
bleaching agent and optional dental agents will preferably be dispersed in a
sticky matrix
material capable of exerting a glue-like action such that the whitening
composition can
adhere and retain the tray in place over a person's teeth without significant
mechanical
pressure by the tray. The tooth whitening/desensitizing compositions may
alternatively
be placed directly onto the person's teeth without a tray, or by means of
conventional
dental trays that are held in place by mechanical fit.
The amount of potassium nitrate that is included within the whitening
compositions of the present invention may vary depending on the duration that
the
composition will be in contact with the person's teeth. When used with dental
bleaching
compositions that are intended to come into prolonged contact with a person's
teeth, such
as dental regimens in which a person applies the composition on a daily basis
over an
extended period of time, the concentration of potassium nitrate is preferable
in a range
of about 0.01 % to about 2% by weight of the dental composition, more
preferably in a
range of about 0.05% to about 1 % by weight, and most preferably in an amount
of about
5% by weight. On the other hand, for one-time applications, particularly for
shorter
periods of time (r. e., one hour or less), the concentration of the potassium
nitrate can be
increased, even up to 10% or more.
For repeated and prolonged usage, lower concentrations of KI~T03 are better at
desensitizing, perhaps because KN03, while an anesthetic in lower dosages, may
become
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an irritant at higher dosages. Moreover, using lower concentrations of KNO,
also gives
the surprising result of enhancing the whitening effect of the bleaching
agent. KNOz is
believed to increase the opacity, and thereby decrease the translucence, of
tooth enamel.
In a preferred embodiment, the carrier will include a tackifying agent and a
5 solvent, which together yield a sticky matrix material, although a solvent
may be used
alone in some embodiments. The sticky matrix material will be sufficiently
sticky to
enable a preferred dental tray to be held and retained against a person's
teeth. Various
tackifying agents will be described hereinbelow.
Suitable sticky matrix materials are preferably safe for oral use and do not
10 inactivate the potassium nitrate. They are preferably viscous and do not
readily dissolve
in saliva. One currently preferred tackifying agent used to form a sticky and
viscous
matrix material is carboxypolymethylene. Carboxypolymethylene can be used to
form
a glue-like dental whitening composition that can itself act as an adhesive in
holding a
comfortable, non-self retaining dental tray against a person's teeth. The use
of
carboxypolyrnethylene, either alone or in combination with other tackifying
agents,
eliminates the need to use dental trays that are self retaining (i. e.,
typically trays that are
rigid, which mechanically interlock over a person's teeth or gums, and which
are intended
for use with less sticky compositions).
Carboxypolymethylene is a broad term that refers to vinyl polymers having
active carboxyl groups. Suitable carboxypolymethylene compositions may be
obtained
from B. F. Goodrich Company under the trade name CARBOPOL~. Another tradename
for carboxypolymethylene is CARBOMER~. In a commonly-sold form, carboxypoly-
methylene can have a pH as low as 2.5. As discussed below, the pH of
compositions
made with carboxypolymethylene can be raised to yield compositions that are
less acidic.
One currently preferred carboxypolymethylene resin is known by the tradename
CARBOPOL 934P. CARBOPOL 934P is a high purity pharmaceutical grade of
CARBOPOL 934, having an approximate molecular weight of about 3,000,000. In
addition to thickening and suspending, CARBOPOL 934P has been used in dry
tablets
to impart sustained release properties. Extensive toxicity studies have been
conducted
on CARBOPOL 934P, and a master file has been established with the Food and
Drug
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Administration. It is listed as CARBOMER 934P in the National Formulary. A
more
recently preferred carboxypolymethylene is CARBOPOL 974P NF, which has more
recently surpassed CARBOPOL 934P as the carboxypolymethylene of choice.
Although
CARBOPOL 974P NF is similar or identical in molecular weight compared to
CARBOPOL 934P, it is purified in a way that makes it more pharmaceutically
acceptable
material.
It is believed that other carboxypolymethylene resins, such as CARBOPOL 940,
may be substituted for CARBOPOL 934P or CARBOPOL 974P NF. CARBOPOL 934P
and CARBOPOL 974P NF are currently prefen-ed because they are obtainable in a
pharmaceutical grade.
The amount of carboxypolymethylene within the inventive dental whitening
compositions can vary depending on the desired level of stickiness and also
the identities
and amounts of the other components within the dental composition. In general,
the
dental whitening/desensitizing compositions of the present invention will
preferably
include carboxypolymethylene in a concentration in a range fi~om about 0.5% to
about
25% by weight of the dental whitening composition, more preferably in a range
from
about 2% to about 12% and most preferably in a range from about 3% to about
10%.
Where is it desired to increase the stickiness, viscosity and resistance to
dilution to saliva,
one may adjust the concentration of carboxypolymethylene to achieve a desired
level of
any or all of these properties. Increased stickiness assists in retaining the
preferred dental
trays against a person's teeth. Alternatively, compositions can be made less
adhesive and
tacky if desired, particularly is applied directly without a dental tray.
It should be understood, however, that the actual amount of
carboxypolymethylene is not critical for obtaining a sticky, viscous dental
composition.
For example, the sticky matrix material may include other tackifying
components that in
combination with, or in lieu of some or all of, the carboxypolymethylene will
yield a
dental whitening composition having the desired level of stickiness needed to
hold a
preferred, comfortable-fitting dental tray in place over a person's teeth.
Other synthetic
polymers and/or natural gums, proteins, or other gel-forming admixtures can be
used so
long as they yield a sticky dental whitening composition.
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In order to obtain good dispersion of the carboxypolymethylene resin within
the
dental whitening composition, it is recommended that the carboxypolymethylene
be
mixed with a suitable solvent before attempting to add other components that
are less
compatible with carboxypolymethylene, such as water. Examples of suitable
solvents for
use with carboxypolymethylene include glycerin, polyalkylene glycols, other
polyols, and
the like. Glycerin appears to enable larger quantities of carboxypolymethylene
to be
dispersed in water. It is preferable that the concentration of glycerin,
polyol, or like
substance utilized as a solvent in the dental whitening compositions be added
in a range
from about 15% to about 85% by weight of the dental whitening compositions,
more
preferably in a range from about 25% to about 75% by weight, and most
preferably in a
range from about 30% to about 65% by weight.
Glycerin, other polyols, and the like are inexpensive solvents that work well
in
forming a sticky gel with carboxypolymethylene. The glycerin also provides
some flavor
enhancement such that a bland, sweet flavor is perceived. A few possible
substitutes for
glycerin include propylene glycol, polypropylene glycol, polyethylene glycols,
sorbitol,
mannitol, eryrthritol, other polyols, stearyl alcohol and other alcohols, and
the like.
Ethylene glycol would also work but is disfavored since it is toxic. In
addition to acting
as a solvent for the tackifying and thickening agents, hydrophilic solvents
such as
glycerin, polyethylene glycols, polypropylene glycol, propylene glycol, and
sorbitol may
also be used as a suitable carrier without a tackifying agent.
Water may also be included as a solvent within the compositions of the present
invention, although more carboxypolymethylene or other tackifying agent must
generally
be included as more water is included in order to maintain the same level of
stickiness.
The amount of water included within the dental whitening compositions of the
present
invention is preferably in a range of about 0% to about 50% by weight of the
dental
whitening composition, more preferably in a range of about I % to about 45% by
weight
and most preferably in a range of about 2% to about 40% by weight . It will be
appreciated that the total quantity of water in the dental whitening
composition may come
from different sources. For instance, some constituents such as dental agents
and bases
discussed below may come as aqueous solutions.
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Because carboxypolymethylene is a polycarboxylic acid, it tends to lower the
pH
of the resulting dental whitening compositions significantly, down to a pH of
about 2.5
in some cases. Although measuring the pH in anhydrous compositions is
generally
meaningless, the theoretical pH becomes relevant when an anhydrous dental
composition
is applied to a person's teeth. which are bathed in water-containing saliva.
It appears,
based upon clinical and in vimo testing, that dental whitening compositions
with a pH
below about 5 are able to etch enamel. To avoid etching enamel, it is
preferable to add
a neutralizing agent, or more specifically, a base in order to raise the pH of
the inventive
dental whitening compositions to within a pH range of about 4 to about 9,
preferably to
within a range of about 5 to about 8, and most preferably a pH from about 6 to
about 7.
Inorganic and organic bases may be used to raise the pH, with the use of
concentrated aqueous sodium hydroxide (50% NaOH in water) being one currently
preferred embodiment. In addition to sodium hydroxides, other inorganic bases
may be
used such as potassium hydroxide and ammonium hydroxide. Examples of suitable
organic bases include alkyl amines such as triethanolamine, di-isopropanol
amine and
other similar amines. The amount of neutralizing agent or base to be included
will
generally depend on the desired pH and the amount of carboxypolymethylene in
the
dental whitening composition. Accordingly, neutralizing agents or bases are
preferably
included in a range from about 1 % to about 12% by weight of the dental
whitening
composition, more preferably in a range from about 2% to about 8% by weight
and most
preferably in a range from about 3% to about 7% by weight.
The term "carboxypolymethylene" shall be understood to include carboxypoly-
methylene resins regardless of the pH of the overall dental composition. In
other words,
the term "carboxypolymethylene" broadly includes resins that have been mixed
with a
base to raise the pH of the compositions. Moreover, the term
"carboxypolymethylene"
shall broadly include carboxypolymethylene resins that have reacted with,
formed
complexes with, or otherwise been altered in any way by other components
within the
dental whitening compositions of the present invention so long as the
carboxypolymethylene or mixture product thereof is able to impart the desired
level of
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stickiness and viscosity to the final dental whitening composition in
combination with
the other components within the dental whitening composition.
In addition to carboxypolymethylene, examples of other suitable tackifying and
thickening agents include gums such as xanthan gum, talha gum, tragacanth gum,
locust
bean gum, guar gum, Irish moss gum, ghatti gum, furcelleran gum, carrageenan
gum,
arabic gum, alginic acid gum, agar gum, and alginate gum, as well as proteins,
such as
collagen, or cellulosic ethers. Another suitable tackifying agent is sold as
PEMULEN R ,
a proprietary compound from B.F. Goodrich, or a compositional or chemical
equivalent
thereof. PEMULEN~ includes a significant quantity of a polyacrylic copolymer
that has
a slightly hydrophobic end and a strongly hydrophilic end. Additional examples
of
suitable tackifying agents include polyethylene oxides such as POLYOX~ sold by
Union
Carbide. These tackifying agents may be present in the same ranges as
discussed above
in relation to carboxypolymethylene.
Examples of suitable bleaching agents include aqueous hydrogen peroxide,
carbamide peroxide, benzoyl peroxide, glyceryl peroxide, percarbonates and
perborates
of alkali and alkaline earth metals (e.g., sodium perborate) and peroxyacetic
acid. A
significant advantage of using potassium nitrate as an opacifying agent in
combination
with a bleaching agent in a tooth whitening composition is that the potassium
nitrate
simultaneously decreases the sensitivity of the teeth that may result from the
use of the
bleaching agent. The bleaching agents are preferably included in a range from
about
0.5% to about 50% by weight of the dental whitening composition, more
preferably in
a range from about 1 % to about 30% by weight and most preferably in a range
from about
3% to about 20% by weight.
In order to preserve the stability of the dental whitening compositions, it is
often
preferable to include an ion scavenger such as EDTA, salts of EDTA such as
edetate
disodium, oxine EDTA, calcium disodium EDTA, and others. Additionally, ion
scavengers such as citric acid, succinic acid, adipic acid, nitrates and
phosphates of tin
and any other commonly-used chelating agents may be used. Ion scavengers are
preferably included in an amount in a range from about 0% to about 1 % by
weight of the
dental whitening composition, more preferably in a range from about 0.03% to
about
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IS
0.5% by weight and most preferably in a range from about 0.05% to about 0.2%
by
weight.
It may also be preferable to include other active dental agents to provide
other
types of dental and/or gum treatment. For example, in conjunction with dental
desensitization and/or opacification, it may be desired to provide an
anticariogenic
treatment. Preferred anticariogenic and antidemineralizing agents include
fluoride salts,
more particularly sodium monofluorophosphate, sodium fluoride, and stannous
fluoride.
Depending on the level of fluoride treatment desired, and depending on whether
or not
a composition is "over-the- counter" or "by prescription", the fluoride will
be included
in a range from about 0% to about I % by weight of the dental whitening
composition,
more preferably in a range from about 0.1 % to about 0.5% by weight.
Antimicrobial agents, e.g., for fighting gum disease, may be included in
conjunction with the potassium nitrate or other opacifying agent. Examples of
useful
antimicrobial agents include chlorohexidine, tetracycline, cetyl pyridinium
chloride,
benzalkonium chloride, cetyl pyridinium bromide, methyl benzoate, and propyl
benzoate.
The antimicrobial agents are preferably included in an amount in a range from
about 0%
to about 15% with the dental whitening composition, more preferably in a range
from
about 1 % to about 5% by weight.
As indicated hereinabove, the dental whitening compositions of the present
invention preferably do not include an abrasive. Abrasives only externally
treat a tooth;
however, it is believed that whitening and opacification of a tooth is
achieved by the
action of the bleaching agent and potassium nitrate internally within a tooth.
Not only
are abrasives unnecessary but inclusion of abrasives in the composition may be
undesirable in preferred embodiments where it is desired for the whitening
composition
to remain on the teeth for an extended period of time (i. e., greater than
about 3 minutes).
In any event, it is common experience that toothpastes become quickly diluted
by saliva
and will not persist in a paste-like form for more than a short period of time
(i.e., for
more than about a minute).
Other suitable tooth desensitizing agents that may be used in addition to
potassium nitrate according to the present invention include citric acid,
citric acid salts,
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16
strontium chloride, and the like, as well as other desensitizing agents known
in the art.
The amount of desensitizing agent included within the dental whitening
compositions of
the present invention may vary according to the concentration of the potassium
nitrate,
the desired strength and intended treatment times. Accordingly, if included at
all, the
other desensitizing agents will preferably be included in an amount in a range
from about
0.1% to about 10% by weight of the dental desensitizing composition, more
preferably
in a range from about 1 to about 7% by weight.
One currently preferred method of dispensing preferred sticky and viscous
dental whitening compositions within the scope of the present invention is by
means of
a syringe. Squeezable tubes and other similar dispensing devices may also be
used to
dispense the compositions. Upon dispensing, preferred dental whitening
compositions
are sufficiently viscous that they do not easily settle or spread once
dispensed, but will
generally remain as a single extruded strand or bead of dental whitening
composition.
Nevertheless, bottles, tubes or other dispensing means known in the art may be
used,
particularly where the whitening composition has lower viscosity, low
stickiness, and/or
does not include a thickening agent.
It is currently preferred to provide a unit dose of the dental whitening
compositions in a syringe or similar dispensing device. In this way, the
person can load
the precise amount of dental whitening composition onto the dental tray for
each
treatment period. By using such dispensing devices, the dentist is also able
to monitor
how many doses the person has received and used.
Although not required, sticky and viscous dental whitening compositions of the
present invention are preferably used to treat a person's teeth in conjunction
with dental
trays that exert little or no significant mechanical pressure onto a person's
teeth and
gums. The result is a more comfortable and pleasant feeling dental tray,
unlike prior ant
dental trays which are generally rigid and/or thick-walled such that they
exert sufficient
mechanical pressures onto the teeth and' or gums to be "self retaining".
In the general process for preparing preferred dental trays according to the
present invention, an alginate impression is made which registers all teeth
surfaces plus
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17
the gingival margin. Thereafter, a stone cast is made of the impression.
Excess stone can
be trimmed away for easy manipulation and foaming the dental tray.
Reference is now made to Figures I-4. In a prefen-ed method for forming a
dental tray, one or more reservoirs can be formed in the resultant dental tray
by applying
a thin coating 10 of a rigid material to the stone cast 12 corresponding to
teeth where it
is desired to provide more of the dental whitening composition. As depicted in
Figure
1, the coating 10 may be applied using a brush tipped applicator 14. The
coating may be
light curable for convenience. In those instances where the dental tray is to
be trimmed
below the gingival margin, the coating material will preferably be applied in
a manner
that is kept at a distance greater than about 1 mm from the gingival line 16
represented
on the stone cast, more preferably in a range from about 1.25 to about 1.5 mm
from the
gingival line 16.
The finished coating will have a thickness corresponding to the desired
reservoir
depth, which will commonly be about 0.5 mm. It is generally preferred that the
rigid
coating material not be applied over the stone cast corresponding to the
incisal edges 18
and occlusal edges 20 of the person's teeth. This because it is preferable for
the incisal
edges and occlusal edges of the person's actual teeth to contact the finished
tray in order
to prevent or reduce vertical movement of the tray during use, which movement
could act
as a pump that could express the dental whitening composition from the tray
and result
in the intake of saliva within the dental tray.
A dental tray 22 is then vacuum formed from the stone cast using conventional
techniques. The dental tray 22 is preferably constructed of a soft transparent
vinyl
material preferably having a preformed thickness in a range from about 0.2 mm
to about
1.5 mm, more preferably in a range from about 0.25 mm to about 1 mm. Soft
materials
yield dental trays that are more comfortable for the patient to wear. It will
be appreciated
that the final tray thickness may vary depending on the technique used to
prepare the tray,
as well as the size and shape of the person's teeth. Patients suspected of
being breuxers
or hard biters may require either a thicker or a harder material. Of course,
patients should
be counselled not to eat with trays in place or to bite firmly into them.
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Once foamed, the dental tray 22 is preferably trimmed barely shy of the
gingival
margin 16 of the person's teeth on both the buccal and lingual surfaces for
maximum
comfort. Enough tray material should be left to assure that the teeth will be
covered to
within about 1/4 mm to about 1/3 mm of the gingival border upon finishing and
beveling
of the tray periphery. It is also generally preferred to scallop up and around
the
interdental papilla so that the finished tray does not cover them. The tray
edges are
preferably smoothed so that the lip and tongue will not feel an edge
prominence. Slight
adjustments to the tray may be made by carefully heating and stretching the
tray material.
Reference is now made to Figures 5-7. Figure 5 depicts the dental
whitening/desensitizing composition 40 being deposited into a dental tray 50
from a
syringe 60. Figure 6 depicts dental tray 50 being inserted onto an arch 70 in
a patient's
mouth. Figure 7 depicts dental tray 50 in position on the teeth of arch 70.
The dental
composition may be deposited throughout the dental tray to contact the entire
arch or may
be deposited within a portion of the tray to only contact a portion of the
arch.
Additionally, the dental tray may be configured to only contact a portion of
an arch or
only a single tooth. While depositing the dental whitening composition into
dental tray
50 as shown in Figure 5 is the preferred method, the dental whitening
composition may
also alternatively be deposited directly onto the teeth and then tray 50 may
be positioned
on the teeth of arch 70.
From practice, it has been found that patients may experience less tooth
discomfort from tray pressures when using a tray with reservoirs built into
the tray as
described above. It is currently believed this is due to the fact that the
teeth are not held
as firmly by the tray, so "orthodontic" pressures experienced by teeth from
tray
discrepancies are minimized. The use of thin, soft tray materials minimize
mechanical
forces applied to teeth or gums compared to the harder or thicker plastics
known in the
art. Reservoirs, of course, can provide more of the dental whitening
composition against
the person's teeth and can also assist in seating the dental tray over the
person's teeth.
Although the aforementioned thin, flexible dental trays are preferred when
treating a person's teeth, it may be preferable in some cases to allow the
dental tray to
overlap the person's gums in the case where dental agents are included to
fight gum
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19
diseases. Of course, to the extent that the dental whitening compositions do
not imitate
the gums, the dental trays can always be constructed to overlap the gums.
Nevertheless, it has been found that where it is desired to treat a person's
teeth
rather than the gums, it is generally more comfortable for the patient if the
dental tray has
been trimmed to or below the gingival margin. Even in those cases where the
dental trays
will overlap the person's gums, the dental trays of the present invention
preferably will
not exert significant mechanical pressure onto the person's gums.
Accordingly, the dental whitening compositions will preferably have a
stickiness
such that they can reliably adhere and retain a dental tray over a person's
teeth for at least
about one hour without significant mechanical pressure from the dental tray,
more
preferably for at least about two hours, and most preferably for at least
about four hours.
Nevertheless, while the foregoing time durations are given in order to provide
an accurate
measurement of the stickiness of the dental whitening compositions of the
present
invention, they should not be taken to be a limitation as to the actual length
of time that
the patient may wish to use the inventive dental whitening compositions. While
a given
dental whitening composition may be able to retain the dental tray against a
person's
teeth for, e.g., 10 hours or more, that composition could certainly be used
within the
scope of the present invention for any desired time period, such as for 15
minutes, one
hour, or any desired time duration.
The desensitizing dental whitening compositions of the present invention may
be used at any time and for any duration by a person that desires to whiten
his or her
teeth. Although the dental whitening compositions of the present invention
facilitate the
use of flexible, thin-walled dental trays that are more comfortable to use
compared to
prior dental trays, the insertion of any dental tray within a person's mouth
will cause
some alteration of behavior and diminution of the freedom to use one's mouth.
Therefore, in order to maximize treatment time and reduce the inconvenience of
having
a dental tray lodged within a person's mouth, it is recommended to use the
dental trays
at night during a person's sleep.
It has been found that optimal results are achieved from cyclic exposure
periods
involving repeated exposures over several days or weeks. For example, the
treatment
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regime may alternatively entail exposure for a period of time such as an hour
without
further exposure until the subsequent day. For day use, it is recommended that
the
whitening compositions be applied for about 1 to 3 hours. The length of the
treatment
period during night use may vary with the sleep pattern of the particular
person and may
5 accordingly be between about 5 to 9 hours.
In order to more clearly illustrate the parameters of the inventive dental
whitening compositions within the scope of the present invention, the
following
examples are presented. The following examples are intended to be exemplary
and
should not be viewed as limiting to the scope of the invention.
10 EXAMPLE 1
A whitening composition within the scope of the invention was prepared by
combining the following ingredients in the following proportions, measured as
percentage by weight of the whitening composition:
15 CARBOPOL 974P NF 6.8%
Glycerin 48.45%
Polyethylene glycol 300 5.5%
Water 20.0%
Sodium hydroxide (50%) 5.4%
20 KN03 3.0%
Carbamide peroxide 10.5%
Disodium EDTA 0.1
NaF 0.25%
The CARBOPOL 974P NF was obtained from B.F. Goodrich Company in
Cleveland, Ohio. The CARBOPOL 974P NF was first combined with the glycerin and
polyethylene glycol 300 then mixed with the water. Mixing glycerin and
polyethylene
glycol 300 within the CARBOPOL 974P NF enabled it to be more easily mixed with
the
water. The KN03, carbamide peroxide and disodium EDTA were added to the
mixture,
after which the sodium hydroxide was blended into the homogeneous composition
in
order to raise the pH to an acceptable level. The sodium fluoride was then
added. The
resulting dental whitening composition was found to have opacifying,
bleaching,
desensitizing and anticariogenic properties, and was sufficiently sticky that
it could
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reliably hold and maintain a dental tray against a person's teeth without
significant
mechanical pressure being exemed by the tray onto a person's teeth and gums.
EXAMPLE 2
A preferred dental whitening composition within the scope of the present
invention was made according to the procedure of Example 1, except that the
ingredients
were combined in the following concentrations by weight percent:
CARBOPOL 974P NF 6.8%
Glycerin 35%
Polyethylene glycol 300 5.5%
Water 20%
Sodium hydroxide (50%) 5.8%
KN03 0.5%
Carbamide peroxide 10.5%
Disodium EDTA 0.3%
Peppermint Flavor 0.6%
Xylitol 15%
The resulting dental whitening/desensitizing composition was tested and found
to be surprisingly superior to test compositions similar to those of Example 1
that
included 3% potassium nitrate. Compared to tooth whitening/desensitizing
compositions
that included 3% potassium nitrate, the 0.5% formulation of Example 2
exhibited greatly
reduced tooth sensitivity. These included sensitivity to hot and cold, as well
as general
sensitivity of gums, tongue and throat. The 0.5% formulation of Example 2 also
showed
a dramatic increase in tooth whitening ability compared to a test composition
that
included no potassium nitrate, thus establishing the surprising result that
potassium
nitrate in minor concentrations greatly increases the whitening effect of the
dental
bleaching composition.
COMPARATIVE STUDY
The composition of Example 2 was the subject of a comparative study
comparing the desensitizing and bleaching ability of the composition of
Example 2 to
four other dental bleaching compositions. In the study, the five dental
compositions were
labeled as compositions A-E, respectively, with composition E being the
composition of
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Example 2. The dental bleaching compositions were applied using custom dental
trays
made to fit each patient. Compositions A-D were similar to the composition of
Example
2, except that they included differing amounts of carbamide peroxide and
potassium
nitrate and, in one case, a different sweetener:
Composition Carbamide Peroxide KN03 Sweetener
A 10% 0% Xylitol
B 10% 3% Xylitol
C 10% 3% Aspartame
D 15% 3% Xylitol
The results of the comparative study are set forth in Table 1.
Table 1
1 2 3 4 5 6 7 8 9
A 266 37 (13.9)40 (15) 2 (0.8)3 (1.1) 14 7 ~.4
B 294 51 ( 17.3)50 ( 14 (4. 3 ( 1 17 6 4.6
17) 8) )
C 279 65 (23.3)45 (16.1)4 (1.4)3 (1.1) 17 6 6.7
D 256 61 (23.9)70 (27.6)13 (5.1)2 (0.8) 18 2 7.5
E 216 14 (5.3) 4 (2.1) 0 (0) 0 (0) 7 11 8.6
Column 1 = Composition Tested
Column 2 = Total number of days used by all patients
in group
Column 3 = Number of days sensitive to hot or
cold (% of total days)
Column 4 = Number of days gums sensitive (% of
total days)
Column = Number of days tongue sensitive (%
5 of total days)
Column 6 = Number of days throat sensitive (%
of total days)
Column 7 = Number of patients reporting sensitivity
to anything
Column 8 = Number of patients reporting no sensitivity
to anything
Column 9 = Average number of shade tab changes
As clearly demonstrated by the data set forth in Table l, the comparative
study
showed a dramatic decrease for composition E in the number of days that
patients
experienced hot or cold sensitivity compared compositions A-D. Surprisingly,
even
though potassium nitrate was heretofore believed to be a desensitizing agent
at any
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23
concentration, when mixed with a dental bleaching agent at a concentration of
3%
(compositions B-D), it actually iiacreased patient tooth sensitivity compared
to
composition A, which included no potassium nitrate. This demonstrated that
potassium
nitrate, when blended with a dental bleaching agent and used , does not behave
as a
desensitizing agent but instead increases sensitivity at certain
concentrations (e.~. 3%).
Even more surprisingly, composition E resulted in an average Vita tab shade
change of
8.6, which was even more than any of compositions A-D, including composition
D,
which included approximately 50% more bleaching agent than composition E, thus
demonstrating the surprising result that including lower concentrations of
potassium
nitrate increases whitening of teeth compared to compositions that either
include no
potassium nitrate or those which include 3% potassium nitrate.
EXAMPLES 3-10
Dental whitening compositions within the scope of the present invention are
made according to Example 1, except that the concentration of KN03 is included
in the
following amounts: 0.01%, 0.05%, 0.1%, 0.3%, 0.75%, 1%, 1.5% and 2%. The
resulting
dental bleaching compositions exhibit superior bleaching with less sensitivity
compared
to dental bleaching compositions that include no potassium nitrate. The
resulting dental
bleaching compositions also exhibit superior bleaching with less sensitivity
compared to
dental bleaching compositions that include 3% or more potassium nitrate
blended with
10% or more carbamide peroxide.
EXAMPLE 11
Dental whitening compositions within the scope of the present invention are
made according to Example 2, except that at least a portion of the glycerin is
replaced by
propylene glycol.
EXAMPLE 12
Dental whitening compositions within the scope of the present invention are
made according to Example 2, except that the CARBOPOL 974 NF is included in
the
following amounts: 0%, 0.5%, 2%, 3%, 5%, 10% and 20%. The concentration of
NaOH
(50%) is adjusted accordingly to maintain approximately the same pH as in
Example 2.
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EXAMPLE 13
Dental whitening compositions within the scope of the present invention are
made according to Example 12, except that all or part of the CARBOPOL 974 NF
is
replaced by at least one of the following thickening agents: xanthan gum,
Irish moss gun,
ghatti gum, furcelleran gum, carrageenan gum, arabic gum, alginic acid gum,
agar gum,
alginate gum, a tackifying protein, or a cellulosic ether.
EXAMPLE 14
A dental whitening composition within the scope of the present invention is
made according to Example l, except that the ingredients are combined in the
following
concentrations by weight percent:
Glycerin 8 9
KN03 1
Carbamide peroxide 15%
The foregoing procedure results in a dental whitening composition having
similar opacifying and desensitizing capabilities compared to the composition
of
Example 2. However, the composition is less sticky than the composition of
Example
2 and has greater bleaching capability.
EXAMPLE 15
To any of the foregoing dental whitening compositions is added one or more of
the following antimicrobial agents for treatment of a patient's gums:
chlorohexidine,
tetracycline, cetyl pyridinium chloride, benzalkonium chloride, cetyl
pyridinium bromide,
methyl benzoate, and propyl benzoate. These compositions are preferably used
in
conjunction with a thin walled, flexible dental tray that overlaps the
person's gums in
order for the dental whitening compositions to contact the gums being treated.
EXAMPLE 16
To any of the foregoing dental whitening compositions which include a
bleaching agent and do not include a bleaching agent stabilizer, one of the
following
chelating agents may be added: EDTA, monosodium EDTA, citric acid, succinic
acid,
and adipic acid.
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From the foregoing, it will be appreciated that the present invention provides
compositions and methods for whitening teeth, including compositions and
methods for
opacifying excessively translucent teeth.
The present invention also provides compositions for whitening and opacifying
5 teeth which reduce tooth sensitivity compared to conventional dental
bleaching
compositions.
The present invention may be embodied in other specific forms without
departing from its spirit or essential characteristics. The described
embodiments are to
be considered in all respects only as illustrative and not restrictive. The
scope of the
10 invention is, therefore, indicated by the appended claims rather than by
the foregoing
description. All changes which come within the meaning and range of
equivalency of the
claims are to be embraced within their scope.
What is claimed is:
