Drug – bio-affecting and body treating compositions – Dentifrices – Oxygen or chlorine releasing compound containing
Reexamination Certificate
2001-08-06
2003-01-07
Rose, Shep K. (Department: 1614)
Drug, bio-affecting and body treating compositions
Dentifrices
Oxygen or chlorine releasing compound containing
C433S215000, C433S216000, C222S137000
Reexamination Certificate
active
06503485
ABSTRACT:
BACKGROUND OF THE INVENTION
1 . Field of the Invention
This invention is in the field of compositions and methods for bleaching teeth. More particularly, the invention is in the field of compositions and methods for accelerated bleaching activity using a two-part bleaching system. A first part includes a stable concentrated dental bleaching agent at low pH and a second part includes a base dispersed within a stable gel that, when mixed with the first part, raises the pH of the mixed composition to an acceptable level and, optionally, in order to destabilize the dental bleaching agent and trigger the release of oxygen radicals to accelerate bleaching activity.
2. Review of the Relevant Technology
In the last decade there has been a proliferation of compositions and methods for bleaching teeth. Compositions for both in-office or at-home use typically include a peroxide bleaching agent, such as carbamide peroxide or aqueous hydrogen peroxide. Carbamide peroxide is a complex of urea and molecular hydrogen peroxide. On the other hand, hydrogen peroxide by itself only exists in aqueous form and is generally unstable except at relatively low pH (e.g. 2).
When formulating an appropriate bleaching composition there is inherently a trade-off between stability and reactivity. It is desirable for a bleaching composition to remain stable between the time when it is manufactured and when it is used to bleach a person's teeth. However, once placed on a person's teeth it is desirable for the composition to quickly break down and release active oxygen radicals capable of bleaching teeth. One way to obtain long-term stability is to keep the concentration of active bleaching agent relatively low. This, however, has the negative drawback of providing only minimal to modest bleaching activity.
Dental bleaching compositions that include higher concentrations of dental bleaching agent must generally be kept refrigerated to ensure long-term stability and/or kept at relatively low pH (e.g., 2 or less) where refrigeration cannot be guaranteed. In the case where it is desired to mass-produce a highly concentrated dental bleaching composition and then distribute it to many different locations, it is generally impossible to prevent at least a portion of such composition from becoming overheated at some point during shipping and handling. Unless such compositions are maintained at a low pH, their potency can be compromised if they are exposed to excessive heat during shipping. Accordingly, it has heretofore been difficult to manufacture and then distribute bleaching compositions at higher pH that include high concentrations of bleaching agent while avoiding at least partial breakdown of the bleaching agent.
Since highly acidic compositions can etch or otherwise damage teeth if maintained in contact with the teeth for more than a few minutes, it is typically desirable to neutralize an acidic bleaching composition prior to application to a patient's teeth. In the case where the composition to be applied to the patient's teeth is intended to have a generally aqueous, non-viscous consistency, neutralization of an acidic aqueous hydrogen peroxide solution by means of a base is straight forward. One simple neutralization method is to add aqueous sodium hydroxide to the aqueous hydrogen peroxide until the pH is raised to the desired level. Depending on the concentration of the hydrogen peroxide and the resulting pH, raising the pH can also have the desired benefit of at least partially destabilizing the hydrogen peroxide so as to accelerate the release of oxygen radicals responsible for bleaching teeth.
Besides sodium hydroxide, there are a variety of bases or buffers that have been used to neutralize the acidity of stable hydrogen peroxide compositions. U.S. Pat. Nos. 5,713,738 and 5,645,428 to Yarborough, for example, discloses the use of sodium carbonate, sodium bicarbonate, calcium carbonate, ammonium hydroxide, potassium hydroxide, or calcium hydroxide to raise the pH of aqueous bleaching compositions so as to accelerate bleaching activity. For purposes of disclosing bases for use in neutralizing acidic hydrogen peroxide compositions, the foregoing patents are incorporated herein by reference.
One of the challenges in manufacturing two-part bleaching systems having an acidic bleaching component and a strong basic component, which are mixed together by the dental practitioner, is the difficulty in obtaining stable gels. Gels are often desirable over runny compositions because they adhere much better to the patient's teeth compared to non-viscous liquids and stay in place rather than running off the teeth and onto surrounding soft oral tissues. Gels having a certain level of stickiness and viscosity are also desirable when using custom-fitting dental trays known in the art and exemplified by those disclosed in U.S. Pat. No. 5,376,006. For purposes of disclosing custom dental trays for bleaching teeth, the foregoing patent is incorporated herein by reference.
The ability to obtain a stable gel is particularly difficult where it is desired to use a polymeric tackifying agent such as carboxypolymethylene. Carboxypolymethylene is unable to maintain its desired stickiness and gelling capabilities over time when mixed with either concentrated acidic aqueous hydrogen peroxide solutions or strongly basic solutions used to neutralize the acidic hydrogen peroxide solution. Where it is desired to mass produce highly concentrated yet stable hydrogen peroxide bleaching compositions, it has heretofore been necessary to entirely replace carboxypolymethylene and like polymers with non-polymeric thickeners such as fumed silica in order to obtain stable gels.
In view of the foregoing, it would an advancement in the art to provide improved two-part dental bleaching systems and methods of manufacturing such systems in order to yield a mixed composition that is a stable gel containing a polymeric thickening agent. It would be a further advancement if such two-part systems could be manufactured so as to yield at least one component that could exist over time as a stable gel that includes a polymeric thickening agent. It would yet be an advancement to provide a concentrated low pH aqueous hydrogen peroxide bleaching composition in one part and a stable gel that included a polymeric thickening agent and strong base in another part for mixing with and at least partially neutralizing the acidic bleaching composition.
Such compositions and methods for providing multi-part dental bleaching systems that include at least one component that is a stable gel are disclosed and claimed herein.
SUMMARY AND OBJECTS OF THE INVENTION
The present invention relates to dental bleaching compositions and methods for manufacturing and using such compositions to bleach teeth. More particularly, the invention encompasses multi-part dental bleaching systems that comprise a first part (or composition) that includes a concentrated and stable dental bleaching agent and a second part (or composition) that includes a strong base dispersed within a stable gel that has good long-term stability.
The two-part systems are stable with respect to both bleaching potency and the maintenance of a gel have a desired range of stickiness and/or viscosity gel during transport and subsequent storage. Upon mixing the two parts together a bleaching gel composition having a desired bleaching potency can be formed. This allows the two-part composition to be manufactured and then shipped and stored as desired prior to mixing the parts together without any significant loss in bleaching potency and the breakdown of the gel that includes the strong base. The invention also encompasses methods of manufacturing the inventive multi-part dental bleaching systems, as well as methods for bleaching a person's teeth using such systems.
A first part or composition of the inventive dental bleaching system includes a dental bleaching agent. There are a variety of dental bleaching agents capable of releasing oxygen radicals. The most commonly used dental bleaching a
Rose Shep K.
Ultradent Products Inc.
Workman & Nydegger & Seeley
LandOfFree
Two-part dental bleaching systems having improved gel... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Two-part dental bleaching systems having improved gel..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Two-part dental bleaching systems having improved gel... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3047034