Patent Application
20170367943
Provided is an oral care product comprising an effective amount of a soluble and orally acceptable sulfate, e.g., sodium, potassium or ammonium bisulfate, in a buffered, electrically conductive medium, which product is useful in a method for in situ production of persulfate (S2O82−), and methods of making and using the same, for example for whitening the teeth, for oxidizing volatile sulfur compounds that give rise to halitosis, or for killing bacteria on the teeth.
Various products and procedures have been developed to whiten teeth. These products and procedures are either purchased and/or used directly by the consumer or are applied by a dentist or other professional.
Potassium persulfate (K2S2O8) has been proposed to whiten teeth, but due to the high reactivity of potassium persulfate in aqueous environments, it has poor compatibility with common ingredients used in oral care products, and, is therefore difficult to formulate into a stable product. Anhydrous and/or hydrophobic formulations may improve the stability of potassium persulfate, but may interfere with quick release of the persulfate from the formulation matrix, resulting in poor bleaching performance.
Electrochemical methods for treating teeth have been proposed in European Patent No. 1525857 and U.S. Pat. No. 7,775,795. Those references, however, do not discuss using persulfate to whiten teeth or the challenges associated with using it as such.
The present disclosure is directed to overcoming one or more problems set forth above and/or other problems of the prior art.
Provided is an oral care product comprising an effective amount of a soluble and orally acceptable sulfate, e.g., a bisulfate, e.g., sodium, potassium or ammonium bisulfate, in a buffered, electrically conductive medium, which product is useful in a method for in situ production of persulfate (S2O82−), and methods of making and using the same, for example for whitening the teeth, for oxidizing volatile sulfur compounds that give rise to halitosis, or for killing bacteria on the teeth. In some embodiments, the product further comprises a cathode and an anode which are electrically connectable to a voltage source, e.g., via a switch.
Also provided is a method for whitening the teeth, for oxidizing volatile sulfur compounds that give rise to halitosis, or for killing bacteria on the teeth, by applying an effective amount of an oral care composition comprising a an orally acceptable sulfate and/or bisulfate, e.g., potassium bisulfate (KHSO4), in a buffered, electrically conductive medium to the teeth, and (just before or during application) exposing the composition to an electric potential so as to facilitate in situ production of persulfate (S2O82−), e.g., potassium persulfate (K2S2O8).
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.
The following description of the preferred embodiments is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.
As used throughout, ranges are used as shorthand for describing each and every value that is within the range. Any value within the range can be selected as the terminus of the range. In addition, all references cited herein are hereby incorporated by referenced in their entireties. In the event of a conflict in a definition in the present disclosure and that of a cited reference, the present disclosure controls.
Unless otherwise specified, all percentages and amounts expressed herein and elsewhere in the specification should be understood to refer to percentages by weight. The amounts given are based on the active weight of the material.
The term “sulfate” as used herein, means a salt or mixture of salts formed or capable of being formed by reaction of sulfuric acid with a base. The term therefore includes bisulfate salts. In aqueous solutions, there may be an equilibrium between the fully deprotonated ion (sulfate or SO42−) and the partially deprotonated ion (bisulfate or HSO4), and both of these ions are capable of forming persulfate when exposed to an electrical potential in an aqueous medium. “Orally acceptable sulfate” refers to sulfates (including bisulfates) which are not toxic or harmful when administered as a component of an oral care product, at relevant concentrations, e.g., 10% or less. “Soluble sulfate” refers to sulfate salts (including bisulfates) which are soluble in aqueous solution at room temperature, e.g., having a solubility of at least 10 g per 100 mL water at 25° C. The term “soluble and orally acceptable sulfate” thus encompasses, for example, compounds such as NaHSO4, KHSO4, (NH4)HSO4, Mg(HSO4)2, Na2SO4, K2SO4, (NH4)2SO4, and MgSO4.
As used herein, “in situ” means that the persulfate is generated in the oral care product just before or during use and is not added as a separate ingredient.
As used herein, “effective amount” means an amount or concentration effective to perform the desired function when the product is used. Thus an effective amount of sulfate refers to an amount of a sulfate salt (e.g., selected from sodium bisulfate, potassium bisulfate, ammonium bisulfate, magnesium bisulfate, sodium sulfate, potassium sulfate, ammonium sulfate, magnesium sulfate, and mixtures thereof) which, when activated by an electrical current to form persulfate, provides persulfate in an amount or concentration effective to whiten the teeth.
In one embodiment, the activation of the sulfate to form persulfate is carried out just prior to use. For example, oral care product comprising an effective amount of a soluble and orally acceptable sulfate in a buffered, electrically conductive medium is dispensed into a container comprising electrodes, which are linked to a battery or other voltage source to provide an electrical current through the medium to generate persulfate.
If the oral care product is a mouthwash, it may for example be dispensed into the cap of the bottle, where the cap contains the electrodes on the inner surface. A mouthwash product may be poured into the cap, or it may be dispensed via a tube into the cap using a pump or squeezing mechanism, or it may be dispensed in a cap using a dosage system, e.g. by turning the bottle upside down to allow the mouthwash to flow into the cap, then turning the bottle right side up, so that the valve closes and the mouthwash portion to be activated is isolated in the cap chamber. Or the mouthwash may be dispensed into a container, and electricity provided by a toothbrush comprising electrodes or stirrer comprising electrodes, which can be inserted into the formulation to activate the persulfate formation just prior to use.
If the oral care product is a gel, it may for example be dispensed into a dental tray comprising electrodes and shaped to fit over the teeth, so that the persulfate can be generated in the tray just before the tray is applied to the teeth.
In another embodiment, the activation of the sulfate to form persulfate is carried out during use. For example, oral care product comprising an effective amount of a soluble and orally acceptable sulfate in a buffered, electrically conductive medium may be in the form of an aqueous gel which is tray comprising electrodes, which are linked to a battery or other voltage source to provide an electrical current through the medium to generate persulfate in situ, while the tray is in the mouth. Or the gel may be used like a toothpaste, and brushed using a toothbrush comprising electrodes which provide current to generate the persulfate in the mouth during brushing.
For example, in one embodiment, a toothbrush is used to activate the oral care product, the toothbrush comprising an effective amount of a soluble and orally acceptable sulfate in a buffered, electrically conductive medium is a powered toothbrush which includes a handle, a power source, a head including a cavity disposed at a distal end of the handle, a pair of electrodes disposed in the cavity and electrically connected to the power source, and a movable cleaning element connected to the head and movable relative to the cavity. The movable cleaning element includes a bristle support member disposed at least partially over the cavity, a plurality of bristles extending from the bristle support in a direction away from the cavity, and a ferromagnetic member. Application of an electrical current to the electrodes generates a magnetic field at the electrodes, which can be used (i) to move the ferromagnetic element, creating good distribution of the gel and also (ii) to generate the persulfate.
In another embodiment, a toothbrush comprising electrodes is used to activate the soluble and orally acceptable sulfate in a buffered, electrically conductive medium, wherein the toothbrush is as described in Colgate's U.S. Pat. No. 8,156,602, the entire contents of which are incorporated herein by reference.
In some embodiments, the polarity of the electrodes is altered at regular intervals during use. In the case of the above toothbrush, alternating the polarity of the electrodes during use changes the magnetic field so each electrode can alternately attract and repel the ferromagnetic member so as to move the movable cleaning element relative to the electrode. But more generally, alternating the polarity of the electrodes prevents accumulation of charged particles or ions on the electrodes, which could interfere with their effectiveness in generating persulfate.
In one embodiment therefore, the disclosure provides an oral care product (Product 1) comprising an effective amount of a soluble and orally acceptable sulfate in a buffered, electrically conductive medium, e.g.,
Further provided is a method (Method A) of providing an oral care composition comprising persulfate (S2O82−) comprising applying an electrical potential to an oral care composition comprising a soluble and orally acceptable sulfate in a buffered, electrically conductive medium, e.g.,
Further provided is a method (Method B) for whitening a tooth surface, or for oxidizing volatile sulfur compounds that give rise to halitosis, or for killing bacteria on a tooth surface, comprising
It is surprising that stable non-bleaching salts like sodium bisulfate can be made useful in methods of bleaching teeth, oxidizing volatile compounds and killing bacteria. Further provided therefore, is the use (Use A) of sulfate salt, e.g., selected from sodium bisulfate, potassium bisulfate, ammonium bisulfate, magnesium bisulfate, sodium sulfate, potassium sulfate, ammonium sulfate, magnesium sulfate, and mixtures thereof (for example in a formulation according to any of Product 1, et seq.) for whitening a tooth surface, or for oxidizing volatile sulfur compounds that give rise to halitosis, or for killing bacteria on a tooth surface, e.g., in accordance with any of Methods B, et seq.
Scheme 1 illustrates the electrochemical synthesis of potassium persulfate form potassium bisulfate.
Potassium bisulfate (HKSO4) at concentrations of 1-10%, by weight is dissolved in a phosphate buffer and the pH is adjusted as necessary for Lissamine Green bleaching experiments. An anode and cathode electrode is submersed in the reaction vessel and the generation of the potassium persulfate salt as a function of potassium bisulfate concentration, pH, voltage/current, and electrode material is monitored using Lissamine Green absorbance changes. The decrease of the absorbance (610 nm) of Lissamine Green over time is indicative of its bleaching by the persulfate produced. Alternatively, platinum electrodes are used and potassium bisulfate is added at 10% to distilled water, the reaction vessel is cooled to 4° C., and potassium persulfate powder is collected and confirmed with IR and XPS.
While the potassium persulfate has bleaching activity over a range of pH, the activity is greater at acidic pH.
Different electrodes, including carbon, platinum, iron, zinc, copper, and aluminum, are tested:
Although they all show the capability of producing the active, platinum, carbon, and iron are preferred. Zinc is also tested, but performs poorly. Two more electrodes—nickel and Boron Doped Diamond Electrodes—are tested using gels and perform very well.
The effect of voltage using different electrodes is assessed:
Effect at varying concentrations is also assessed:
Whitening efficacy on bovine teeth is assessed. Bovine teeth are brushed to achieve similar initial lightness values. The bovine teeth are placed in artificial saliva (composed up of 7.5 mL of Mucin solution and 7.5 mL of Saliva Buffer) for 10 minutes. Each sample is treated using electrochemistry treatment for 15-20 minutes in a phosphate-based buffer solution. The platinum electrodes are placed 2 mm from the bovine tooth surface. The electrode area is 1.2 cm×1.2 cm and the bovine teeth are roughly 0.5 cm×0.5 cm, and the applied bias is 4 volts. After treatment, the bovine teeth are rinsed with deionized water and the color (L*a*b* values) is measured with a spectrophotometer.
The spectrophotometer used is Spectroshade from MHT. The measurement scale is the CIE L*a*b* (CIELAB) scale developed by the International Commission on Illumination (CIE). CIELAB is an opponent color system based on the fact that retinal color stimuli are translated into distinctions between light and dark, red and green, and blue and yellow. CIELAB indicates these values with three axes: L*, a*, and b*. The L value indicates the lightness of a color, where L=0 is black and L=100 is white. ΔL=Ltreated−Linitial. Thus, a larger positive ΔL=whiter teeth. The a value ranges between +a=magenta and −a=green. The b value ranges between +b=yellow and −b=blue. The W value incorporates the L, a and b values to describe how close the measured color is to true white, where W*=(a2+b2+(L*−100)2)1/2. A larger negative ΔW value corresponds to greater whitening.
A comparison among 10% HKSO4 with no power applied (control); 10% HKSO4, activated with platinum electrodes at 4 volts (current ˜100 mA); and 4.5% H2O2 gel, in this assay is as follows (measurements for each treatment taken at approx. 20 minute intervals):
The generated persulfate is thus able to travel through the solution and bleach a stained bovine tooth significantly more quickly and completely than 4.5% H2O2 gel.
The bleaching of the stained bovine teeth using different electrodes is assessed.
The efficacy of sodium bisulfate solution vs. potassium bisulfate solution for whitening bovine teeth is about the same:
Sodium bisulfate is much more soluble than potassium bisulfate, and so is preferred for use in gel formulations. Different gel formulations are prepared and tested, and a citrate buffer was used instead. Gels are in the pH 5-6 range. Generally, gels have a composition such as:
Three particular candidate formulations are evaluated:
These gels are tested in the bovine staining assay:
Gels containing cross-linked PVP, carboxymethyl cellulose and gellan gum are also tested with varying degrees of success. The gels above contain persulfate with the sodium cation, but the potassium is also tested, with successful bleaching results.
In order to evaluate the effect of different electrode cleaning methods on the effectiveness of nickel electrodes, an experiment is conducted using cleaned nickel electrodes. One set of electrodes are cleaned by blasting with distilled water. The other set of electrodes are cleaned by blasting with a slurry of aluminum oxide powder in distilled water. Formulation 4 was used as the gel, and each treatment was conducted for about 20 minutes with a voltage of 4V and a current fluctuating between 20 and 30 mA. The pH of the formulation was 5. As shown in the table below, it is found that the alumina-cleaned electrodes perform much better than water-cleaned electrodes. It is believed this is due to the stripping of nickel oxide and other impurities from the surface of the nickel electrode, as well due to the creation of a microscopically rough surface which provides better electrical contact to the gel.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2015/066331 | 12/17/2015 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 62096578 | Dec 2014 | US |
