Drug – bio-affecting and body treating compositions – Dentifrices
Reexamination Certificate
2000-06-05
2001-01-16
Rose, Shep K. (Department: 1614)
Drug, bio-affecting and body treating compositions
Dentifrices
Reexamination Certificate
active
06174515
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a gentle abrasive toothpaste containing calcined kaolin and a hydrating silica gel. More particularly, this invention relates to a toothpaste containing calcined kaolin as the sole abrasive therein, and having low abrasivity while maintaining desirable rheological properties.
The function of abrasives in toothpaste formulations for use in the oral cavity is to remove various deposits, including pellicle film, from the surface of the teeth. Pellicle film is tightly adherent and is partly responsible for the yellow or brownish discoloration of the teeth. A toothpaste therefore should be abrasive enough to maximize removal of this film and other undesired deposits without causing undue abrasion to the surface of the tooth. Dental research is continually concerned with developing toothpaste compositions that demonstrate satisfactory levels of cleaning and that are not unduly abrasive and damaging to the teeth.
U.S. Pat. No. 4,122,163 discloses a toothpaste using calcined kaolin as an abrasive. The kaolin is said to be predominantly of the gamma alumina or mullite form.
U.S. Pat. No. 4,414,199 discloses a toothpaste using calcined kaolin as an abrasive. The kaolin is at least 80% calcined to the mullite crystal form and has a particle size distribution such that more than 50% of the particles are between 1 to 10 microns and less than 5% exceed 10 microns. These toothpastes have a Radioactive Dentin Abrasion of about 124 as determined by the Radioactive Dentin Abrasion Index.
Merely reducing the level of kaolin in the toothpaste formulation results in lower abrasivity, but results in the need for increased levels of conventional thickeners such as gums or other solids such as alumina, calcium carbonate, calcium pyrophosphate, and dicalcium phosphate. An increased level of thickeners in the toothpaste formulation, however, imparts a greater degree of stringiness to the toothpaste and results in poor toothpaste break off properties (the ability of the toothpaste to cleanly come away from the tube when applied to a toothbrush).
Adding other solids such as calcium carbonate, calcium pyrophosphate, and dicalcium phosphate may provide a desirable rheology and break off properties, but they may reduce the availability of soluble fluoride ion because they react with fluoride. Moreover, these solids have inherently high abrasives qualities, which makes their use undesirable. Accordingly, it is a primary object of this invention to produce toothpaste compositions having reduced abrasivity, without sacrificing desirable rheological properties or fluoride availability.
SUMMARY OF THE INVENTION
The present invention relates to a fluoride toothpaste composition having low abrasivity. More specifically, the present invention relates to a toothpaste containing a novel combination of at least one nonabrasive silica and where the kaolin is the sole abrasive present in the toothpaste. Advantageously, the resulting toothpaste has a radioactive dentin abrasive (RDA) index of not more than 110.
The term “sole abrasive” as used in the detailed description and the appended claims means that the composition does not contain more than 5% of another abrasive material.
All percentages used in the detailed description and the appended claims refer to percent by weight unless specifically stated otherwise.
DETAILED DESCRIPTION OF THE INVENTION
The toothpaste composition of the present invention comprises a novel combination of kaolin with a nonabrasive silica gel, wherein the kaolin is the sole abrasive in the composition.
The toothpaste comprises from about 1% to about 50% by weight of kaolin, preferably from about 5% to about 20%, more preferably from about 8% to about 12%. In addition, the kaolin is the sole abrasive present in the toothpaste composition.
The toothpaste also includes at least one non-abrasive silica gel. The non-abrasive silica gel is incorporated into the toothpaste composition in an amount from about 1% to about 50% by weight, preferably from about 5% to about 20%, more preferably from about 10% to about 15%.
Within these ranges, it has been found that the desirable abrasive properties can be achieved when the ratio of the kaolin to the non-abrasive silica is in the range from about 40:1 to about 1:20, preferably from about 10:1 to about 1:3, more preferably from about 2:1 to about 1:2. Most preferably, the ratio of kaolin to hydrated silica is about 1:1.3.
The kaolin used in the toothpaste of the present invention is at least 80%, and most preferably, at least 90%, calcined to the mullite crystal form. Calcination to the mullite form occurs upon gradual heating of uncalcined kaolin to about 975° to about 990° C. Desirably, the kaolin is of a relatively pure grade. In addition, the kaolins useful in the present invention have a whiteness index of at least about 20 or below, and preferably about 13 or below. Suitable kaolins include those manufactured and sold under the trademarks Satintone Special from Englehard Minerals, Al-Silate-o from Freeport, and Optiwhite from Burgess Pigments. Of course, kaolins from other manufacturers may be suitable so long as it is calcined to a level of at least 80%. Kaolin manufacturers are identified in Soap & Cosmetics (December 1999), the relevant contents of which are incorporated herein by reference.
The non-abrasive silica gels used in the toothpaste of the present invention are the amorphous silicas also known as hydrated silica gels. The hydrated silica gels are those having a high silica (SiO
2
) content material, preferably at least 99% SiO
2
, and are substantially nonabrasive. The nonabrasive silica gel preferably has a radioactive dentin abrasion index of 25 or less, more preferably 20 or less. The suitable silica gel has an average particle size of about 8.0 to about 12.0 microns. Suitable nonabrasive gels are sold under the trademark Sylodent 15 from W. R. Grace and Huber-Zeodent 165.
The preferred silicas are those that are considered to be the “gel-type” as opposed to the precipitated or fumed type of silicas.
In addition to the above-described essential components, the toothpaste composition of the present invention can contain a variety of optional toothpaste ingredients, some of which are described below.
For example, the toothpaste may include a source of fluoride. A wide variety of fluoride containing materials can be used as a source of fluoride in the toothpaste compositions of the present invention. Examples of suitable fluoride containing materials are found in U.S. Pat. No. 3,535,421 and U.S. Pat. No. 3,678,154, both of which are incorporated herein by reference. Representative fluoride ion sources include: sodium fluoride, stannous fluoride, potassium fluoride, sodium monofluorophosphate amine fluorides and mixtures thereof. Sodium fluoride is particularly preferred.
The desired level of fluoride in the toothpaste composition is such that the composition contains about 0.1% fluoride by weight of the composition. The amount is the maximum allowed by the FDA in an over-the-counter fluoride toothpaste. Accordingly, sodium fluoride may be incorporated into the toothpaste composition in an amount of about 0.245% by weight of the composition. This will provide about 0.11% fluoride ion by weight of the composition.
Humectants may be incorporated in the toothpaste compositions of the present invention. Humectants are used to retain moisture in the toothpaste, particularly at the nozzle end of the tube where the toothpaste can be in prolonged contact with the air. Suitable humectants include glycerin, sorbitol, propylene glycol, other edible polyhydric alcohols, or mixtures thereof, which are admixed with a suitable humectant vehicle, such as water. Humectants are present in the toothpaste composition at a level of from about 15% to about 70%.
Water is also generally present in the toothpaste compositions of the present invention. Water used in the preparation of commercially suitable toothpastes should preferably be deionized and free of organic impurities. Water generally comprises abo
Amway Corporation
Brinks Hofer Gilson & Lione
Nichols G. Peter
Rose Shep K.
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