Drug – bio-affecting and body treating compositions – Dentifrices – Oxygen or chlorine releasing compound containing
Reexamination Certificate
2000-11-08
2002-09-10
Rose, Shep K. (Department: 1614)
Drug, bio-affecting and body treating compositions
Dentifrices
Oxygen or chlorine releasing compound containing
C424S049000
Reexamination Certificate
active
06447757
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to teeth whiteners, specifically to teeth whiteners having increased storage stability while having superior bleaching efficiency.
Teeth whiteners, also known as teeth bleaching agents, are in widespread use as a cosmetic means to enhance appearance and contribute to better oral health and hygiene in general. Particularly popular and effective among these agents are those whose chemistry is based on peroxides, of which hydrogen peroxide and carbamide peroxide (an adduct of hydrogen peroxide and urea) are most frequently employed. Such peroxides are characterized by a relative lack of stability which results in the generation of radical (atomic) oxygen, the chemical action of which is responsible for the desired whitening/bleaching effect of whitening agents containing such peroxides. The generation of atomic oxygen is highly undesirable during storage of peroxide-based teeth whitening agents because it reduces the potency of the agent in that some of the peroxide decomposes prior to the time of use. Thus, in their commercial form, whitening agents are formulated and/or stored in a manner designed to prevent and/or inhibit premature peroxide decomposition. Because contact with certain foreign objects, especially materials having highly developed surface areas, exposure to selected chemicals, and the presence of an elevated pH accelerate the decomposition process of said peroxides and the liberation of radical oxygen, attempts are made to avoid such conditions.
Stability of teeth whitening formulations, however, is in direct conflict with the purpose and objective of their applications, in that the best possible whitening effect in the shortest possible time of contact with the tooth surface is achieved when the composition, when placed in contact with the teeth, is very unstable as to evolve the radical oxygen in a reasonably short time. Consequently, teeth whitening formulations known in the art typically require multiple applications stretching over a period of weeks or even months, with each recommended application time usually being from two to eight hours.
To address this conflict between stability and efficacy, two component formulations have been recently developed to improve the stability of peroxide during storage. Such formulations allow for extended shelf life and more effective bleaching action, as the decomposition of peroxide (generation of radical oxygen) does not begin to occur at a significant rate until the two components are mixed.
In one type of two component system, the first component contains peroxide and is maintained at a low pH and is free of solid particles. Formulations based on carbamide peroxide are preferably water free as well to further enhance stability. The second component contains materials that stimulate the decomposition of peroxides, such as alkaline substances and insoluble particles having highly developed surface areas. The second part generally contains water in order to reduce tissue irritation caused by the desiccating effect of anhydrous and hydrophilic mediums used in the first part which would tend to draw water out of the mucosa and other oral tissues when placed in the mouth.
Of the two forms of peroxides commonly used in commercial teeth whiteners, hydrogen peroxide formulations are considered to be faster acting, while carbamide peroxide based formulations are considered to offer advantages in terms of greater storage stability, desirable formulation consistency and handling properties, and a lower risk of damage to soft tissues. Both hydrogen peroxide and carbamide peroxide-based formulations are more stable at low pH, preferably in the range of 3.0-4.5, with this effect being more pronounced in hydrogen peroxide formulations. Carbamide peroxide-based materials may, however, exhibit adequate stability even at neutral or near neutral pH. Because of these properties, formulations containing carbamide peroxide may be perceived as more desirable in terms of exhibiting greater compatibility with mucosa, having little or no detrimental effect on tooth enamel, and aiding in protecting the health of teeth in less than intact condition.
Carbamide peroxide formulations are, however, adequately stable only in environments containing little or no water. Examples of common commercial carriers for carbamide peroxide are glycerin and propylene glycol. While such carriers are considered nontoxic and convenient for their compatibility with desirable additives such as thickening agents, preservatives, flavors and therapeutics, their use may have some unwelcome side effects. The most common side effect is discomfort caused by the desiccating effect of these anhydrous (or near anhydrous) yet hydrophilic solvents/carriers on mucosa, as discussed above. This effect is especially pronounced when scarified or inflamed tissue is involved. Similar responses of discomfort may also be expected by those having leaching restorations or recessed gums.
The concentrations of peroxides in commercially available teeth bleaching formulations vary greatly, generally depending on factors such as recommended time of a single application, frequency and technique of application, and the identity of the intended user. This last factor is especially important, in that the concentration of peroxide will differ if the material is designed for professional use only, for application by the user/patient but under professional control, or if it is to be broadly available to the public for in-home, non-supervised use.
The concentration of peroxide (expressed as a percentage of H
2
O
2
) in formulations containing carbamide peroxide or hydrogen peroxide which are sold directly to the public is generally on the order of 3.4% by weight, which corresponds to approximately 10% carbamide peroxide. The concentration of H
2
O
2
in formulations designed for professional use is generally higher, and often lies in the 5-10% range.
To provide prolonged contact of whitening formulation with teeth while minimizing contact with mucosa which may cause irritation, the whitening material is usually placed on fabricated trays, preferably those which have been custom fit in a dentist's office to precisely conform to the patient's anatomy. The use of more highly concentrated H
2
O
2
formulations, which are generally faster acting, calls for special measures to protect the mucosa from contact with such inherently irritating compositions. In such cases, rubber dams or curable tissue coatings are routinely used to protect soft tissues.
Attempts have been made to accelerate the teeth bleaching processes without increasing the concentration of the peroxide by using heat-generating devices such as high intensity light emitting instruments or lasers. Because of the cost of necessary equipment and the greatly increased risk of tissue damage associated with these techniques, they are designed for use exclusively by a trained dental professional. The most effective of these techniques appear to be those using lasers, but such techniques also carry the highest risk of inflicting damage on the teeth and/or soft tissue. Furthermore, the treatment cost is considerably higher than when conventional methods are used.
SUMMARY OF THE INVENTION
Disclosed are new teeth whitening compositions comprising at least two components which are separated from one another during storage. The components are mixed shortly or immediately before their application to the teeth. In accordance with one aspect of the present invention, there is provided a teeth whitening composition comprising a first component, Part 1, comprising 5-40% by weight of at least one metal peroxide and a second component, Part 2, comprising at least one acid, wherein the Part 1 and Part 2 are mixed together shortly or immediately before application to form a material having a pH of about 4 to 11. In preferred embodiments, Part 1 comprises one or more peroxides of monovalent or bivalent metals, preferably zinc, sodium, calcium, magnesium, potassium, strontium, and combinations ther
Butler David V.
Noss Amy P.
Orlowski Jan A.
Knobbe Martens & Olson Bear LLP.
Rose Shep K.
Scientific Pharmaceuticals Inc.
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