Drug – bio-affecting and body treating compositions – Dentifrices – Phosphate compound containing
Reexamination Certificate
2000-12-08
2002-11-12
Rose, Shep K. (Department: 1614)
Drug, bio-affecting and body treating compositions
Dentifrices
Phosphate compound containing
C424S049000, C424S052000
Reexamination Certificate
active
06479038
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to clear dentifrice gels comprising a tetrasodium pyrophosphate anticalculus agent.
BACKGROUND OF THE INVENTION
Dentifrices which are visually clear are appealing to consumers. Such products must also provide a functional benefit however. There are many dentifrice compositions which contain active agents to prevent the beginnings of gum disease, calculus build-up and cavities. The active agents of a dentifrice are those agents which inhibit the formation of calculus and prevent the accumulation of plaque bacteria and other micro-organisms which are responsible for halitosis, plaque, caries and gum diseases such as periodontitis and gingivitis.
Dental calculus, or tartar as it is sometimes called, is a deposit which forms on the surfaces of the teeth at the gingival margin. Supragingival calculus appears principally in the areas near the orifices of the salivary ducts; e.g., on the lingual surfaces of the lower anterior teeth and on the buccal surfaces of the upper first and second molars, and on the distal surfaces of the posterior molars.
Mature calculus consists of an inorganic portion which is largely calcium phosphate arranged in a hydroxyapatite crystal lattice structure similar to bone, enamel and dentine. An organic portion is also present and consists of desquamated epithelial cells, leukocytes, salivary sediment, food debris and various types of micro-organisms. As the mature calculus develops, it becomes visibly white or yellowish in colour unless stained or discoloured by some extraneous agent. This is undesirable from an aesthetic standpoint.
Mechanical removal of calculus periodically by the dentist is routine dental office procedure. A variety of chemical and biological agents have also been suggested to retard calculus formation or to remove calculus after it is formed. Pyrophosphate salts are chemical agents knows to have the ability to retard calculus formation as described, for example, in U.S. Pat. No. 4,999,184, to Parran, Jr. et al., issued Mar. 12, 1991, the disclosure of which is incorporated herein by reference in its entirety.
Tetrasodium pyrophosphate is one of the most useful pyrophosphate salts in this respect. However, due to its limited solubility it can be difficult to incorporate at highly effective levels. This is particularly true at high pH where the pyrophosphate anion is most effective as an anticalculus agent, or when the available water in the dentifrice is restricted. Furthermore, its use at substantial levels can introduce further formulation difficulties because of the ‘salt’ content that it introduces into the aqueous phase, potentially leading to salting out of surfactant and resulting cloudiness in an otherwise clear gel.
It is customary for a dentifrice product to incorporate a dental abrasive, for the purpose of cleaning and polishing the teeth. Silica dental abrasives, of various types are particularly useful because of their unique benefits of exceptional dental cleaning and polishing performance without unduly abrading tooth enamel or dentine.
The broad principles of formulating a clear gel are well known; the refractive indices of the various dentifrice components—typically a liquid vehicle comprising water and various humectants—and insoluble components such as the abrasive must be matched. This can present considerable problems however, unless compromises are to be made on the functionality of the dentifrice. Accordingly, there is a substantial amount of prior art in relation to the formulation of clear dentifrice gels.
Illustrative of the art is WO 96/38123 which relates to a clear gel dentifrice comprising a silica of refractive index (RI) 1.44 and a selected liquid vehicle. The document discloses water soluble polyphosphate salts, at levels of from 0.1 to 7%, as optional components and the examples include 2% tetrasodium pyrophosphate as an anticalculus component, along with 1.2% sodium lauryl sulphate surfactant. Nevertheless, the water content of the dentifrice compositions of W096/38123, from 27% up to 36%, is relatively high and there is no teaching of how to include moderate to high levels of tetrasodium pyrophosphate under the more demanding conditions of lower water content or high pH where a substantial portion of the tetrasodium pyrophosphate is likely to remain undissolved and where salting out effects are more critical.
U.S. Pat. No. 3,927,202 describes a clear gel dentifrice comprising an alkali metal phosphate salt, which can be tetrasodium pyrophosphate decahydrate, of RI 1.435 to 1.465 as a polishing agent, and a liquid humectant vehicle comprising no more free water than would dissolve about 30% by weight of the polishing agent at 40° C. The gels of U.S. Pat. No. 3,927,202 optionally comprise 0.5-20% silica abrasives of RI 1.44 to 1.47. Although the document discloses a broad range of surfactants the examples all incorporate sodium N-lauroyl sarcosinate which is a relatively poor foamer. In practice, it has been found that substitution of sodium alkyl sulphate into the tetrasodium pyrophosphate decahydrate examples of U.S. Pat. No. 3,927,202 gives opaque compositions.
It has now surprisingly been found that a dentifrice gel of excellent clarity, high anticalculus efficacy and good foaming can be formulated by selecting a silica dental abrasive with a RI matched to that of tetrasodium pyrophosphate decahydrate (1.45-1.46) and by incorporating sodium alkyl sulphate as a surfactant.
It has further surprisingly been found that a dentifrice gel of excellent clarity and with high anticalculus efficacy can be formulated by selecting a silica dental abrasive with a RI matched to that of tetrasodium pyrophosphate decahydrate (1.45-1.46), even when the anhydrous form of tetrasodium pyrophosphate, which has a RI of 1.425, is utilised. This is believed to be due to in situ hydration of the anhydrous form to the decahydrate. The use of anhydrous tetrasodium pyrophosphate allows greater formulation flexibility at the processing stage by freeing up water for the dissolution and/or hydration of other dentifrice components.
SUMMARY OF THE INVENTION
According to the present invention there is provided a visually clear, dentifrice gel comprising:
a) sufficient tetrasodium pyrophosphate to provide from 0.2% to 5% pyrophosphate anion;
b) a silica dental abrasive having a refractive index of from 1.445 to 1.47;
c) from 0.7% to 3% sodium alkyl sulphate; and
d) an aqueous liquid carrier.
The gel has excellent clarity, high anticalculus efficacy and good foaming.
According to a further aspect of the invention there is provided a process for making a visually clear, dentifrice gel comprising the step of adding anhydrous tetrasodium pyrophosphate to an aqueous carrier, the gel comprising:
a) a silica dental abrasive having a refractive index of from 1.445 to 1.47; and
b) an aqueous liquid carrier comprising less than 27% total water.
The use of anhydrous tetrasodium pyrophosphate allows greater formulation flexibility at the processing stage by freeing up water for the dissolution and/or hydration of other dentifrice components.
All percentages and ratios used herein are by weight of the total composition unless otherwise specified. All measurements are made at 25° C., unless otherwise specified.
DETAILED DESCRIPTION OF THE INVENTION
The term “gel”, as used herein, refers to a product having a consistency sufficient to maintain the undissolved particulates in stable suspension. Included within this scope are stiff gels and so-called “liquid” dentifrices, such as those described in U.S. Pat. No. 5,695,746. The clear gel dentifrice can be a single homogeneous product, but it can also form part of a multiphase product such as a deep or surface striped dentifrice or multiphase product stored in a dual compartment, wherein the entire product comprises other physically distinct components which may not be clear or otherwise conform to the clear gel compositions of the invention. The clear gel may also have dispersed within it small amounts of visible particulates e.g. coloured speckle,
Clark Karen F.
Hiland Emelyn L.
Rose Shep K.
Zea Betty J.
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