Drug – bio-affecting and body treating compositions – Dentifrices
Reexamination Certificate
2000-12-21
2003-01-28
Rose, Shep K. (Department: 1614)
Drug, bio-affecting and body treating compositions
Dentifrices
C424S052000, C424S053000, C424S050000
Reexamination Certificate
active
06511654
ABSTRACT:
TECHNICAL FIELD
The instant invention is directed to a dentifrice (toothpaste, brushing gel, etc ... ). More specifically, the instant invention is directed to an anhydrous dentifrice that is thickened with cooked starch.
BACKGROUND ART
Dentifrices are used to clean, bleach, whiten, and otherwise treat the teeth and gums. Generally, the active ingredients in a dentifrice are contained within a carrier.
The carrier is either a paste (i.e., toothpaste) or a gel (i.e., brushing gels and bleaching gels). Each is dispensed through a tubular orifice onto a brushing device or, in some cases, onto a tray, stint or mouth guard. “Gels” are thickened by a gelling agent that hydrogen bonds a dispersion medium to produce a semisolid, transparent, jelly-like, material. In contrast, “pastes” are thickened by the addition of fillers. However, the line between gels and pastes is not always clear. Furthermore, sometimes dentifrices that are opaque and/or contain one or more abrasive fillers are labeled pastes, even if they exhibit gel-like properties. Therefore, in describing the present invention, the term “dentifrice” will be used to clearly indicate that both gels and pastes are embraced.
The efficacy of a dentifrice is directly proportional to the time the active ingredients contact the teeth and gums (a.k.a. “the residence time”). If the dentifrice disintegrates immediately upon contact with saliva, or brushing, then it will provide minimal benefit. In contrast, if the dentifrice does not readily disintegrate, it is much more effective.
Usually, the carrier for the active ingredients in the dentifrice contains water as the principal component. However, the use of water has several disadvantages. First, there are numerous beneficial materials that have limited solubility in, or even react with, aqueous systems. Second, water based dentifrices rapidly disintegrate in the presence of saliva since water is a principle component in saliva.
One method of improving residence time has been to utilize anhydrous compositions. These compositions often utilize oils or organic polyols as the principal carrier. Examples of anhydrous dentifrices include the following U.S. Pat. Nos. 3,939,261; 4,071,615; 4,132,771; 4,159,316; 4,170,635; 4,187,287; 4,582,701; 4,627,451; 4,812,306; 4,818,518; 5,670,137; and 5,747,005. These compositions suffer from a number of problems, one of the most common being a failure to provide adequate viscosity and tack.
The efficacy of a dentifrice is highly dependent upon obtaining an acceptable level of viscosity (flow resistance) and tack (adhesion). If the viscosity is too low, the composition is runny and hard to control. On the other hand, if the composition is too viscous it becomes difficult to expel from the tube. Similarly, if the composition is too tacky it leaves a stringy tail as it issues from the tube. But if the composition is not sufficiently tacky it fails to adequately adhere to the treated surfaces of the teeth and gums.
It is difficult to fine tune the viscosity of a dentifrice. This is especially true when the dentifrice exhibits gel-like qualities. This is because the degree of hydrogen bonding interaction between the gelling aid and the dispersion medium is complex and hard to manipulate. Furthermore, for reasons that are not fully understood, gels are susceptible to viscosity increases and decreases over time.
Starch is not a common ingredient in dentifrices. When starch is employed, it is generally as a filler rather than as a gelling agent. It is not believed that the benefits of using cooked starch as a gelling aid in dentifrices have been previously recognized.
U.S. Pat. Nos. 5,084,268 and 5,208,010 (“the Thaler patents”) describe an abrasive free hydrogen peroxide tooth whitening dentifrice composition that comprises a blend of corn starch, sorbitol, hydrogen peroxide, carbomer 940, flavor, sodium lauryl sulfate, sodium saccharin, potassium sorbate, and sodium benzoate in an aqueous base. The “[c]orn starch . . . functions as a gelling agent, a thickener, a filler and a binder.” A commercial product that is allegedly based on these patents is called “Booster” and is sold by Dental Concepts Inc. of Elmsford, N.Y.
The dentifrice described in the Thaler patents is water based-containing anywhere from 30.65% to 61.65%, by weight, water. As stated, water based dentifrices generally exhibit inferior residence time. Furthermore, the predominant gelling agent in the composition described in the Thaler patents is a carbomer even though the starch is described as both a filler and a gelling agent. In truth, the composition described in the Thaler patents utilize starch more as a filler. Based on prior experience with other formulations, it is believed that a combination of carbomer and starch means that the material will harden during storage. Finally, the Thaler patents fail to recognize that cooked starch provides far greater gelling action than uncooked starch and, therefore, far greater thickening action.
U.S. Pat. Nos. 4,812,306 and 5,004,596 (“the Cocherell patents”) describe a water free oil based dentifrice that comprises hydrogenated vegetable oils, flavoring oils, glycerin, cornstarch, inorganic salts, fluorides, saccharin or aspartame, and sodium lauryl sulfate. The cornstarch is added to thicken the mixture into a dough-like mass that is dried, ground, and mixed into the oil to form a cream or paste.
It is important to understand that the composition described in the Cocherell patents, although anhydrous, utilizes oils as the primary carrier rather than organic polyols. Glycerin, although present, makes up only 11.65%, by weight, of the composition whereas various oils make up more than 46% of the composition. Furthermore, although the composition employs starch as thickening agent, the thickening action obtained is no more than would be obtained using any solid filler. The Cocherell patents do not recognize that cooking increases the gelling action, and therefore the thickening action, of starch.
The closest prior art to the instant invention is U.S. patent application Ser. No.08/640,350 (“the '350 application”). This application describes some of Den-Mat Corporation's previous research in anhydrous, polyol based, dentifrices. The dentifrice described in the '350 application utilizes glycerin as a dispersion medium, carbomer (neutralized polyacrylic acid salt) as a gelling agent, peroxide as a bleaching agent, Citroxain® (a mixture of papain, citric acid and its salts, and hydrated alumina) for whitening, dicalcium phosphate as a mild abrasive filler, and uncooked starch thickeners. The dentifrice described in the '350 application demonstrates a number of desirable attributes—such as consistency, feel, cleaning, whitening, and bleaching capabilities. Unfortunately, the dentifrice also exhibits features that have proven to be undesirable. Paramount among the detrimental properties is a tendency to harden within the tube over a relatively short period of time (1 to 2 months) at rather moderate temperatures (~30° C.). The dentifrice also exhibits a tendency to evolve oxygen gas. Oxygen evolution starts immediately after the product is prepared. The formation of oxygen within the tube causes the product to self-extrude from open tubes and swell and/or rupture closed tubes.
Hardening can be slowed by adding more glycerin. However, this also causes a dramatic and undesirable reduction in viscosity. Furthermore, the use of additional glycerin only delays, and does not prevent, the onset of hardening. Dilution of the formulation does not improve the gas evolution problem.
Some, or all, of these problems can be prevented by eliminating one or more of the starch, dicalcium phosphate, or carbomer components. However, once again, such formulations do not possess desirable viscosity characteristics.
Thus there is still a need in the art for new and improved anhydrous dentifrice formulations. Such formulations should be stable, tacky, glossy, smooth flowing, thixotropic, and exhibit high residence time.
SUMMARY OF THE INVENTION
Th
Chadwick Thomas C.
Ibsen Robert
Matthews Alan
Pineda Rachel R.
Den-Mat Corporation
Dorsey & Whitney LLP
Rose Shep K.
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