Drug – bio-affecting and body treating compositions – Dentifrices
Reexamination Certificate
2000-05-09
2001-09-18
Rose, Shep K. (Department: 1614)
Drug, bio-affecting and body treating compositions
Dentifrices
C051S308000, C423S335000, C423S339000
Reexamination Certificate
active
06290933
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to dentifrice compositions containing a silica abrasive, which provides improved oral cleaning and a safe level of abrasivity.
BACKGROUND OF THE INVENTION
Synthetically produced silicas play an important role as an ingredient in many of today's toothpaste formulations. Such silicas are relatively safe, nontoxic, ingredients which are compatible with other toothpaste ingredients, including glycerin, sorbitol (or xylitol), thickening agents, detergents, coloring and fragrance materials and optionally fluoride and other actives, whereby the silica acts as an abrasive to clean teeth, remove plaque and food debris.
As an abrasive, silicas debride and physically scrub the external surface of the teeth. This scrubbing action removes the organic film (i.e. the pellicle), formed of salivary proteins which covers the teeth and which is known to become stained and discolored by foods, such as coffee, tea and berries, as well as, by tobacco smoke, cationic antibacterials, and chromogenic bacteria. Such physical removal of the stained pellicle is a simple and effective means of removing the undesirable surface staining and discoloration which occurs daily. Further, such physical removal of the pellicle also removes plaque bacteria on the pellicle surface.
Synthetic silicas include both silica gels and precipitated silicas which are prepared by the neutralization of aqueous silicate solutions with a strong mineral acid. In the preparation of silica gel, a silica hydrogel is formed which is then typically washed to low salt content. The washed hydrogel may be milled to the desired size, or otherwise dried, ultimately to the point where its structure no longer changes as a result of shrinkage. When preparing such synthetic silicas, the objective is to obtain abrasives which provide maximal cleaning (i.e. removal of stained pellicle) with minimal damage to the tooth enamel and other oral tissue. Dental researchers are continually concerned with identifying synthetic silicas meeting these objectives.
U.S. Pat. No. 4,153,680 and GB Patent Application 2,038,303A both disclose the general use of silica hydrogels or hydrated silica gels as dentifrice polishing agents. U.S. Pat. No. 4,632,826 discloses the use of hydrated silica gels in combination with a weakly calcined alumina polish, to form a combination abrasive system. U.S. Pat. Nos. 4,943,429, 5,176,899 and 5,270,033 provide lists of alternative polishing agents, such lists including hydrated silica gels.
U.S. Pat. No. 5,939,051 discloses dentifrice compositions prepared with silica gels having low abrasion and high cleaning products. However, the silica gels have a low particle size distribution of from 2 to 4 microns in order to achieve the low abrasive properties. Manufacturing such small particle size silica gel is energy intensive and relatively costly.
U.S. Pat. Nos. 5,658,553 and 5,651,958 disclose dentifrice compositions containing a combination of precipitated silica and silica gels having high cleaning and low abrasion as indicated by their low radioactive dentin abrasion (RDA) values. Due to the low abrasive nature of the silicas described in U.S. Pat. Nos. 5,651,958 and 5,658,553 the composition inherently has limited cleaning ability.
RDA value is a dental art recognized method of determining the abrasiveness of dentifrice formulations and is determined according to the method recommended by the American Dental Association as set forth by Hefferren, Journal of Dental Research, Volume 55, Issue 4, July-August 1976, pp. 563-573, and described in the Wason U.S. Pat. Nos. 4,340,583, 4,420,312 and 4,421,527.
In spite of the extensive prior art relating to silica hydrogels and other abrasive compounds used to prepare dentifrice compositions for oral cleaning, there is still a need for additional compositions providing improved pellicle cleaning, improved removal of plaque and food debris, all with minimal abrasion of the tooth enamel and other oral tissue.
It is known in the dental art that increasing the RDA value of a dentifrice composition above 110 does not result in a corresponding increase in the cleaning performance of the dentifrice, as measured by Pellicle Cleaning Ratio (PCR), an in vitro method used to measure the efficacy of removing tea and coffee tooth stains relative to a standard. The PCR values referred to herein are obtained by a modification of the method described in “In Vitro Removal of Stain with Dentifrice”, G. K. Stookey, et al J. Dental Research, 61, 123-9, 1982. The modification of the PCR method used herein is described in U.S. Pat. No. 5,658,553 and 5,651,958. In this modification, a clear pellicle material is applied to a bovine tooth first, which is then stained with a combination of the pellicle material and tea, coffee and FeCl
3
whereas in the original method described by Stookey et al, both pellicle and stain are applied simultaneously.
It has now surprisingly been found that by the practice of the present invention the PCR value of a dentifrice composition can be made significantly higher than those reported in the prior art. In fact, PCR values from 150 to 300 can be achieved at RDA values from 110 to 200 when using the silica hydrogel abrasive of the present invention it being noted that RDA values of 110 to RDA of 250 (maximum allowable) are well within the acceptable abrasivity standards set by the US Federal Drug Administration as well as the American Dental Association, pursuant to the Federal Register (Anticaries Over-The-Counter Drug Products), vol. 45, No. 62, 1980, and vol. 60, No. 194, 1995.
SUMMARY OF THE INVENTION
In accordance with the present invention there is provided a dentifrice composition having superior cleaning functionality, which dentifrice composition, comprises:
(a) an orally acceptable dentifrice vehicle containing from about 5 to about 30% by weight silica hydrogel particles, the particles containing about 10 to about 35% by weight water having:
(i) a mean particle size from about 5 to about 12 microns;
(ii) an Einlehner hardness of from 1 to about 20;
(iii) an oil absorption value of from about 40 to less than 100 cc/100 g;
(iv) a BET surface area from 100 to 700 m
2
/g of silica,
the morphology of the particles being characterized by glass conchoidal fracture surfaces, whereby the dentifrice composition has an RDA of from 110 to 200, and a PCR of from about 150 to about 300.
Mean particle size is measured using a Malvern Particle Size Analyzer, Model Mastersizer S, Malvern Instruments, Inc., Southborough, Mass. 01772 wherein a helium-neon gas laser beam is projected through a transparent cell which contains the silica hydrogel particles suspended in an aqueous solution. Light rays which strike the particles are scattered through angles which are inversely proportional to the particle size. The photodetector array measures the quantity of light at several predetermined angles. Electrical signals proportional to the measured light flux values are then processed by a microcomputer system, against a scatter pattern predicted from theoretical particles as defined by the refractive indices of the sample and aqueous dispersant to determine the particle size distribution of the silica hydrogel.
Einlehner hardness value is obtained using Einlehner At-1000 Abrader to measure the softness of the silica hydrogel in the following manner: A Fourdrinier brass wire screen is weighed and exposed to the action of a 10% aqueous silica hydrogel suspension for a given number of revolutions. The hardness value is expressed as milligrams weight lost of the Fourdrinier wire screen per 100,000 revolutions.
BET surface area is determined by a BET nitrogen adsorption method described in Brunauer et al., J. Am. Chem. Soc., 60, 309 (1938). The BET measurement is preformed using an Accelerated Surface Area and Porosimetry Analyzer (ASAP 2400), by Micromeritics Instrument Corporation, Norcross, Georgia 30093. The sample is outgassed under vacuum at 350° C. for a minimum of 2 hours before measurement.
Oil absorption values are measured using the ASTM
Durga Gary A.
Prencipe Michael
Priolo Peter J.
Ren Peter
Colgate-Palmolive Company
Rose Shep K.
Shapiro Paul
LandOfFree
High cleaning dentifrice does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with High cleaning dentifrice, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and High cleaning dentifrice will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2451406