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OF THE INVENTION
1. Field of the Invention
The present invention relates to an oral care composition which contains a cationic antibacterial compound which composition is effective in retarding bacterial plaque accumulation on teeth and more particularly to a dentifrice composition containing a cationic antibacterial compound and a proteolytic enzyme which achieves plaque reduction with superior breath freshening characteristics.
2. The Prior Art
Halitosis, the technical term for bad breath, or Fetor ex Oris, is an undesirable condition. As a matter of fact, everyone, excluding the very young, occasionally has bad breath, with approximately 25% suffering on a regular basis and the problem tends to get worse and more frequent as one gets older. The problem seems to be evenly split between men and women. Bad breath results when proteins from the food we eat and saliva debris are broken down by bacteria. Even the cleanest mouth hosts millions of bacteria which have the potential to decompose these protein-containing particles left in the mouth. The tongue, with its fissures and large, bumpy surface area, retains considerable quantities of food and debris that support and protect a large bacterial population. Under low oxygen condition, this bacterial population forms foul smelling products, called volatile sulfur compounds (VSC)—such as hydrogen sulfide (“rotten eggs”) and methyl mercaptans (“skunk smell”) and other odorous and bad tasting compounds. Up to 80-90% of bad breath that originates in the mouth is by this mechanism.
Dental plaque or plaque bio-film is a soft deposit that forms on teeth and is comprised of an accumulation of bacteria and salivary as well as food by-products. Plaque adheres tenaciously at the points of irregularity or discontinuity, e.g., on rough calculus surfaces, at the gum line, on tongue surface and within crevices, and the like. Besides being unsightly, plaque is implicated in the occurrence of gingivitis and other forms of periodontal disease.
Bacteria thrive on the tongue. For the most part, the bacteria are a part of a protective bio-film that essentially renders them resistant to most treatments. Few people clean their tongue after brushing, even though it's been shown that as much as 50 percent of the mouth's bacteria can be found here. Additionally, for many people, brushing or scraping the tongue is difficult because of the gag reflex. Therefore, cleaning the tongue non-mechanically is highly desirable for those who are unable to do so with a mechanical device.
A wide variety of antibacterial agents have been suggested in the art to retard plaque formation and the oral infections and dental disease associated with plaque formation. For example, cationic antibacterial compounds such as cetyl pyridinium chloride are well known to the art for their antibacterial activity and have been used in oral compositions to counter plaque formation by bacterial accumulation in the oral cavity.
In spite of the extensive prior art relating to antibacterial dentifrice compositions, there is still a need in the art to formulate a dentifrice product capable of delivering an antibacterial agent having enhanced effect in the retardation of bacterial plaque accumulation on teeth, as well as on the tongue, without inhibiting the bioavailability of the antibacterial compound. The delivery of the antibacterial compound to the tongue will allow for effective control of bad breath.
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OF THE INVENTION
The present invention encompasses a dental composition containing in an orally acceptable vehicle a combination of an antibacterial compound, and a proteolytic enzyme whereby superior reduction of plaque accumulation is accompanied by enhanced malodor reduction.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In the practice of the present invention the dental composition containing the antibacterial agent and enzyme ingredients is formulated as a paste using a vehicle containing a safe and effective amount of the antibacterial and enzyme compounds.
Cationic antibacterial agents useful in the practice of the present invention are well known in the art and include both nonionic and cationic agents. See, for instance the section on “Quaternary Ammonium and Related Compounds” in the article on “Antiseptics and Disinfectants” in Kirk-Othmer Encyclopedia of Chemical Technology, 2nd edition (vol. 2, pp. 632-635), incorporated herein by reference. Cationic antibacterial compounds which possess antibacterial activity (i.e., are germicides) are used against bacteria and have been used in oral compositions to counter plaque formation caused by bacteria in the oral cavity.
Among the most common of these cationic antibacterial antiplaque quaternary ammonium compounds is benzethonium chloride, or diisobutylphenoxyethoxyethyl dimethyl benzyl ammonium chloride, and cetyl pyridinium chloride. In a dentifrice preparation this material is highly effective in promoting oral hygiene by reducing the formation of dental plaque and calculus, which is generally accompanied by a reduction in periodontal diseases.
Other cationic antibacterial quaternary ammonium compounds useful in the practice of the present invention include those in which one or two of the substituents on the quaternary nitrogen has a carbon chain length (typically alkyl group) of some 8 to 20, typically 10 to 18, carbon atoms while the remaining substituents have a lower number of carbon atoms (typically alkyl or benzyl group), such as 1 to 7 carbon atoms, typically methyl or ethyl groups. Dodecyl trimethyl ammonium bromide, benzyl dimethyl stearyl ammonium chloride, cetyl pyridinium chloride (CPC) and quaternized 5-amino-1,3-bis(2-ethylhexyl)-5-methyl hexa hydro-pyrimidine are typical quaternary ammonium antibacterial agents.
The antibacterial agent is included in the dentifrice at a concentration of about 0.10 to about 1.5% by weight and preferably about 0.3 to about 1.2% by weight.
Abrasives preferred for use the practice of the present invention include silica materials and particularly silica gels and precipitated amorphous silica having an oil absorption value of less than 100 cc/100 g silica and preferably in the range of from about 45 cc/100 g to less than about 70 cc/100 g silica. These silicas are colloidal particles having an average particle size ranging from about 3 microns to about 12 microns, and more preferably between about 5 to about 10 microns and a pH range from 4 to 10 preferably 6 to 9 when measured as a 5% by weight slurry.
Oil absorption values are measured using the ASTM Rub-Out Method D281. The low oil absorption silica abrasive is present in the oral are compositions of the present invention at a concentration of about 5 to about 40% by weight and preferably about 10 to about 30% by weight.
Low oil absorption silica abrasives particularly useful in the practice of the present invention are marketed under the trade designation Sylodent XWA by Davison Chemical Division of W.R. Grace & Co., Baltimore, Md. 21203. Sylodent 650 XWA, a silica hydrogel composed of particles of colloidal silica having a water content of 29% by weight averaging from about 7 to about 10 microns in diameter, and an oil absorption of less than 70 cc/100 g of silica is a preferred example of a low oil absorption silica abrasive useful in the practice of the present invention.
Another low oil absorption silica abrasive particularly useful in the practice of the present invention is marketed under the trade designation DP-105 by J.M. Huber Chemicals Division, Havre de Grace, Md. 21078 is a precipitated amorphous silica having an average particle size distribution from 5 to 12 microns and an oil absorption in the range of 50 to 70 cc/100 g.
Other abrasives which may be used in the practice of the present invention include precipitated silicas having a mean particle size of up to about 20 microns, such as Zeodent 115, marketed by J.M. Huber Chemicals Division, Havre de Grace, Md. 21078, or Sylodent 783 marketed by Davison Chemical Division of W.R. Grace & Company, sodium metaphosphate, potassium metaphosphate, tricalcium phosphate, dihydrated dicalcium phosphate, aluminum silicate, calcined alumina, bentonite or other siliceous materials, or combinations thereof.
The abrasive materials may be used individually as the sole abrasive in preparing the dental composition of the present invention or in combination with other known dentifrice abrasives. The total quantity of abrasive present in the dentifrice compositions of the present invention is at a level of from about 5% to about 60% by weight, preferably from about 10% to about 55% by weight when the dentifrice composition is a toothpaste.
The enzymes useful in the practice of the present invention include protein substances within the class of proteases, which breakdown or hydrolyze proteins (proteases). These proteolytic enzymes are obtained from natural sources or by the action of microorganisms having a nitrogen source and a carbon source. Examples of proteolylic enzymes useful in the practice of the present invention include papain, bromelain, chymotrypsin, ficin and alcalase.
Papain obtained from the milky latex of the Papaya tree is the proteolytic enzyme preferred for use in the practice of the present invention and is incorporated in the oral care composition of the present invention in an amount of about 0.1 to about 10% by weight and preferably about 0.5 to about 5% by weight, such papain having an activity of 150 to 300 MCU per milligram as determined by the Milk Clot Assay Test of the Biddle Sawyer Group (see J. Biol. Chem., vol. 121, pages 737-745).
An additional enzyme which may be formulated in combination with a protease enzyme such as papain is glucoamylase. Glucoamylase is a saccharifying glucoamylase of Aspergillus niger origin cultivated by fermentation. This enzyme can hydrolyze both the alpha-D-1,6 glucosidic branch points and the alpha-1,4 glucosidic bonds of glucosyl oligosaccharides. The product of this invention comprises about 0.001 to 2% of the carbohydrase and preferably about 0.01 to 0.55% by weight. Additional carbohydrases useful in accordance with this invention are glucoamylase, alpha and beta-amylase, dextranase and mutanase.
Other enzymes which may be used in the practice of the present invention include other carbohydrases such as alpha-amylase, beta-amylase, dextranase and mutanase and lipases such as plant lipase, gastric lipase, pancreatic lipase, pectinase, tannase lysozyme and serine proteases.
The lipase enzyme is derived from a select strain of Aspergillus niger, exhibiting random cleaving of the 1,3 positions of fats and oils. The enzyme has maximum lipolytic activity at pH 5.0 to 7.0 when assayed with olive oil. The enzyme has a measured activity of 120,000 lipase units per gram. The lipase may be included in the dentifrice composition at a concentration of about 0.010 to about 5.0% by weight and preferably about 0.02 to about 0.10% by weight.
The presence of tannase enzyme can be further beneficial in facilitating the breakdown of extrinsic stain. Tannase enzymes have been purified from Aspergillus niger and Aspergillus allianceus and are useful in the hydrolysis of tannins, known to discolor the tooth surface.
Other suitable enzymes which can comprise the present invention include lysozyme, derived from egg white, which contains a single polypeptide chain crosslinked by four disulfide bonds having a molecular weight of 14,600 daltons. The enzyme can exhibit antibacterial properties by facilitating the hydrolysis of bacterial cell walls cleaving the glycosidic bond between carbon number 1 of N-acetylmuramic acid and carbon number 4 of N-acetyl-D-glucosamine, which in vivo, these two carbohydrates are polymerized to form the cell wall polysaccharide. Additionally, pectinase, an enzyme that is present in most plants facilitates the hydrolysis of the polysaccharide pectin into sugars and galacturonic acid.
The orally-acceptable dentifrice vehicle used to prepare the dentifrice composition comprises a water-phase, containing a humectant therein. The humectant is preferably glycerin, sorbitol, xylitol, and/or propylene glycol of molecular weight in the range of 200 to 1,000; but, other humectants and mixtures thereof may also be employed. The humectant concentration typically totals about 5 to about 70% by weight of the oral composition. Reference hereto to sorbitol refers to the material typically commercially available as a 70% aqueous solution. Water is present typically in amount of at least about 10% by weight, and generally about 15 to 30% by weight of the oral composition. Water employed in the preparation of commercially suitable toothpastes should preferably be deionized and free of organic impurities. These amounts of water include the free water which is added plus that which is introduced with other materials such as with sorbitol.
The dentifrice compositions of the present invention can contain a variety of optional dentifrice ingredients. As described below, such optional ingredients can include, but are not limited to, thickening agents, surfactants, a source of fluoride ions, a synthetic anionic polycarboxylate, a flavoring agent, antitartar and coloring agents.