Drug – bio-affecting and body treating compositions – Dentifrices – Oxygen or chlorine releasing compound containing
Reexamination Certificate
2001-04-10
2003-05-06
Rose, Shep K. (Department: 1614)
Drug, bio-affecting and body treating compositions
Dentifrices
Oxygen or chlorine releasing compound containing
C433S215000, C433S216000
Reexamination Certificate
active
06558654
ABSTRACT:
FIELD OF THE DISCLOSURE
The present invention relates to the field of dentistry, particularly to the whitening of teeth.
BACKGROUND
Over the last decade, one of the most prominent changes in dentistry has been the increased focus in aesthetic procedures. Teeth generally become more darkly pigmented with age and exposure to such materials as tea and coffee, and it has long been a goal of dentistry to provide a means to safely and effectively reverse this darkening process. Recently, in-office and at-home teeth whitening have been rapidly embraced.
One method for whitening teeth involves using oxidizing agents to bleach the undesired pigmentation. The active agents are usually weak solutions of hydrogen peroxide or carbamide peroxide, which is more stable than hydrogen peroxide. Generally, it is believed that there are only three primary variables that can be manipulated to control the rate of whitening.
The first variable is concentration of the peroxide. In order to make the procedure occur during a reasonable time span, concentrations of peroxide equivalent to at least 3 weight percent hydrogen peroxide are employed, with the concentrations going as high as 40 weight percent. The peroxide has been used in liquid, paste and gel forms, with the gel being the most popular. The second variable is exposure time, i.e., the time the tooth is exposed to the peroxide. The third variable is the pH of the peroxide mixture.
It is well known that tooth whiteners with higher pH are more effective than equally strong whiteners with lower pH. Unfortunately, increased pH also means decreased peroxide stability. It is for this reason that none of the present tooth whitening materials have a pH much above neutral, while the majority of them are actually acidic. The only exceptions to this rule are those materials that require addition of an alkalinity adjuster immediately prior to use, but this approach has little consumer or professional appeal because of the complex handling and preparation procedures.
Another barrier to achieving a desirable tooth whitening product is the lack of a good gelling material to use at the higher pH ranges. Virtually all of the current stable tooth-whitening gels use a carbomer matrix. Carbomer in its initial gelled form has a pH around 1 to 2. As the pH is raised, the carbomer begins to lose its viscosity and stability, such that it is only with great effort and skill that it can be made to remain useful above a neutral pH. For that matter, high concentrations of peroxide are also an anathema for the carbomer since it has some tendency to oxidize with strong agents.
These two factors combine in such a way that the only single-tube high-concentration peroxide gel product known by the present inventor to ever reach the marketplace (supplied by Ultradent of Salt Lake City, Utah) is sufficiently sensitive to destabilization by heat exposure that the manufacturer refuses to ship during certain weather conditions or over a weekend. Once received by the dentist, the material has to be refrigerated at all times, or again its potency is at risk. Yet, so significant is the need for such a product that even this unstable product is successful. However, the end user is left with a product that has unpredictable and unsatisfactory characteristics since its effectiveness can be completely destroyed by a common, uncontrollable event such as a slow shipment.
Manufacturers have long sought to stabilize their hydrogen peroxide in order to extend its service life. For more than a decade, almost all the large producers of hydrogen peroxide have produced various stabilized variations of their peroxide. For instance, one such stabilized hydrogen peroxide from Degussa became available several years ago but neither the Degussa product nor any other stabilized hydrogen peroxide has been embraced by the dental community. Doubtless this is because peroxide stability is only one part of the problem with the present whitening gels, and without the other part (the gel matrix material) in place there is no advantage of using this specialty product.
Thus, a need exists for a high pH, bleaching agent-containing gel or thickened composition that is available as a stable single-package or one-part premixed product. Over the years, many gel-forming materials have been used in an attempt to make a stable high peroxide concentration, high pH gel. None of these attempts have met with any success.
SUMMARY OF THE DISCLOSURE
According to one disclosed embodiment, an improved method for whitening at least one tooth has been discovered that includes contacting the tooth with a composition that includes a bleaching agent; a carrier; and an acrylate/&agr;, &bgr;-ethylenically unsaturated dicarboxylic acid or anhydride copolymer. In particular embodiments the acrylate/&agr;, &bgr;-ethylenically unsaturated dicarboxylic acid or anhydride copolymer is an acrylate itaconate copolymer. The acrylate/&agr;, &bgr;-ethylenically unsaturated dicarboxylic acid or anhydride copolymer (e.g., acrylate itaconate copolymer) serves as a rheology modifier that contributes unique characteristics to the whitening method and composition. In particular, the rheology modifier allows for the formulation of a stable high pH whitening gel or thickened composition that can be provided to the user in the form of a single-package or one-part premixed product.
The acrylate itaconate copolymer may be an alkali-swellable polymer that provides thickening to a composition when the pH of the composition is increased. Thus, according to a further disclosed embodiment there is provided a composition useful for whitening teeth that includes a bleaching agent; a carrier; an alkaline additive; and an acrylate itaconate copolymer.
According to one variant the rheology modifier can be prepared by polymerizing at least one (meth)acrylate or (meth)acrylic acid monomer with a surfactant monomer, the surfactant monomer being an esterification product of a nonionic surfactant reacted with itaconic acid. According to another variant the rheology modifier can be prepared by polymerizing (a) an acrylate monomer selected from a C
1
-C
6
alkyl ester of acrylic acid and a C
1
-C
6
alkyl ester of methacrylic acid; (b) a monomer selected from a vinyl-substituted heterocyclic compound containing at least one of a nitrogen or a sulfur atom, a (meth)acrylamide, a mono- or di-(C
1
-C
4
)alkylamino (C
1
-C
4
)alkyl (meth)acrylate and a mono or di-(C
1
-C
4
)alkylamino (C
1
-C
4
)alkyl (meth)acrylamide; and (c) a surfactant monomer.
The foregoing features and advantages will be come more apparent from the following detailed description of several embodiments.
DETAILED DESCRIPTION OF SEVERAL EMBODIMENTS
The bleaching agent is any material that has the ability to whiten teeth. Illustrative bleaching agents include an oxygen radical or hydrogen radical-generating compound such as metal ion free peroxides, organic peroxides, and metal ion containing peroxides. Specific, non-limiting examples of bleaching agents include carbamide peroxide, carbamyl peroxide, calcium peroxide, sodium percarbonate, perhydrol urea, urea peroxide, sodium perborate, calcium hydroxide, potassium chlorate, magnesium carbonate, hydrogen peroxide, materials that produce these compounds in situ, and combinations thereof.
The amount of bleaching agent in the composition may vary. For example, the bleaching agent could be present in an amount of about 3 to about 60 weight percent, based on the total amount of the bleaching agent and the carrier. If hydrogen peroxide is the bleaching agent, according to one particular embodiment, it may be present in about 3 to about 40 weight percent, especially about 7 to about 15 weight percent, based on the total amount of hydrogen peroxide and the carrier. If carbamide peroxide is the bleaching agent, according to one particular embodiment, it may be present in about 10 to about 60 weight percent, based on the total amount of hydrogen peroxide and the carrier. When using embodiments with a higher amount of bleaching agent (for example, about 30 to about 50 weig
Klarquist & Sparkman, LLP
Rose Shep K.
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