GB2409975A

GB2409975A - Tooth whitening composition

Info

Publication number: GB2409975A
Application number: GB0401112A
Authority: GB
Inventors: Jose Luis Velada
Original assignee: Glaxo Group Ltd
Current assignee: Glaxo Group Ltd
Priority date: 2004-01-19
Filing date: 2004-01-19
Publication date: 2005-07-20
Also published as: GB0401112D0

Abstract

An anhydrous liquid tooth whitening composition comprising a peroxide-containing compound and an orally acceptable carrier, wherein the carrier includes a polyethylene glycol having a molecular weight in the range 200 to 600 and a monohydric alcohol and a bioadhesive carbomer.

Description

TOOTH WHITENING COMPOSITION

The present invention relates to a tooth whitening composition for bleaching tooth enamel. Specifically the present invention relates to an anhydrous tooth whitening composition comprising a peroxide.

White teeth have long been considered cosmetically desirable. Unfortunately, teeth almost invariably become discoloured in the absence of intervention. The tooth structure which is generally responsible for presenting a stained appearance is the enamel layer. Several factors contribute to enamel discoloration, but the three main factors are believed to be: (i) formation of plaque and tartar matrices on the tooth surface which then entraps stains; (ii) ingestion of certain drugs during gestational tooth formation; and (iii) discoloration due to oral cavity traumatization following which blood break-down products seep into the mineralized area of the teeth during enamel formation. This invention is primarily concerned with the first factor of tooth discoloration, that is, the natural stain which accumulates on teeth.

Over-the-counter teeth whitening preparations have been developed to address the cosmetic preference of many to restore luster to tooth enamel discolored by surface entrapped materials. While all dentifrices and mouthwashes contain some cleaning and polishing agents, some enamel deposits become intractable to being fully removed by these agents under normal use conditions. For example, smokers often develop discolored enamel because the tars and particulate in exhaled cigarette smoke collect on the teeth. Further, a number of comestibles, such as tea, or some medicinal agents, can stain or discolor tooth enamel.

There are various approaches to enamel whitening currently in general use. One approach is a physical abrading of the stain to effect stain removal. Harsher abrasives, also known as polishing agents, than those used in typical non-whitening toothpaste preparations, are employed in this approach. Most, if not all of these preparations are toothpastes, gels or powder dentifrices. The mechanical process may be supplemented or even replaced by a chemical process which may involve an oxidative or enzymatic step to effect stain removal.

The chemical process generally utilizes a tooth whitening or bleaching formulation applied to a stained tooth surface for a specified period, after which the formulation is removed. Oxidizing agents represent one of the most widely distributed and utilized active agents in commercially available tooth whitening or bleaching products. Peroxide-containing agents such as carbamide peroxide, hydrogen peroxide and calcium peroxide are the most commonly used oxidizing agents, and are typically formulated into a liquid, solution, gel or paste. However it is known that products containing such agents may lose their whitening efficacy with time. In addition aqueous peroxide formulations may have only a brief period of efficacy when applied to teeth in the oral cavity because of rapid decomposition of peroxide on exposure to the enzyme, catalase, present in high concentrations in saliva.

Moreover low viscosities of aqueous peroxide solutions do not allow the peroxide whitening agent to remain in contact with teeth for the necessary time period to effect substantive whitening because of constant flushing effects of salivary secretions. WO 03/099246 (Colgate-Palmolive) aims to address these problems with the provision of an aqueous tooth whitening liquid composition comprising an orally acceptable vehicle comprising water and monohydric alcohol having dispersed therein a film forming combination of a poly(ethylene oxide) and a carbomer.

However there remains a need for alternatives that do not suffer drawbacks encountered with known formulations. Moreover it would be desirable to provide simple formulations that do not require extensive stabilization, that are easy to manufacture and are sufficiently substantive and robust to enable once-a-day application.

It is an object of the present invention to provide a composition that meets these requirements. This object is met according to the invention by the provision of an anhydrous liquid tooth whitening composition comprising a peroxide-containing compound and an orally acceptable carrier wherein the carrier includes a - 2 polyethylene glycol having a molecular weight in the range 200 to 600 and a monohydric alcohol and a bioadhesive carbomer.

The composition of the invention is essentially anhydrous. Water or an aqueous medium is not used as a carrier or vehicle in the composition. Whilst free water is not added to the composition, it will be understood that small amounts of water, i.e. less than 5%w/w, preferably less than 3%w/w, may be present as a result of being introduced with other materials e.g. by using a "stock" hydro gen peroxide aqueous solution such as a 30%w/w hydrogen peroxide solution.

The composition of the invention is suitably in the form of a gel that may conveniently be painted onto the teeth. Following its application, the composition dries in situ to form an adherent film which sticks firmly to the teeth. The gel is sufficiently strong and adherent to remain on the teeth for a period of time e.g. up to a few hours. Suitably the composition is applied at nighttime, allowing peroxide activity to take place during sleep periods. During use, the peroxide is released slowly from the gel, in an amount and at such a rate as required to effect stain removal. The gel may be removed from the user's teeth by any convenient means e.g. brushing and/or by rinsing with a mouthwash.

The term "painted onto the teeth" above is intended to encompass all manner of applying the whitening composition to teeth and includes sponging, coating, daubing, spraying, wiping and rubbing. The composition may be housed in a resealable container such as a tube or a bottle. Suitably the composition is applied to the teeth with a soft applicator brush. Preferably the composition is housed in a container such as a bottle, and the composition is applied with a soft applicator brush. The bottle and brush may be provided in kit form e.g. as may be used with a conventional nail varnish kit. Alternatively the composition may be housed in a dispensing device such as a pen with an applicator brush attached thereto e.g. generally of the type used with the Brite Smile To Go_ Whitening pen. - 3

Peroxide-containing compounds used as whitening agents in the present invention include the following compounds and mixtures thereof: hydrogen peroxide e.g. as a 30%w/w aqueous solution, carbamide peroxide, percarbonates and calcium peroxide.

Mixtures of different peroxide sources, as hereinabove described, may be used to provide variable peroxide release. For example both immediate and slow release peroxide may be achieved by using a combination of aqueous hydrogen peroxide and carbamide peroxide. Carbamide peroxide, and mixtures of carbamide peroxide with hydrogen peroxide (30% aqueous solution) are preferred.

Suitably the total amount of peroxide present in the liquid whitening composition of the invention is in the range of 1 to 30% w/w, preferably 2 to 20%w/w, even more preferably in the range 3 to 10%w/w.

A polyethylene glycol (PEG) having a molecular weight in the range 200 to 600 is present in the composition of the present invention. Examples of suitable PEGs include PEG 200, 300, 400 and 600, available from Dow Chemcals USA, PO Box 1206, Midland MI48642.

Suitably the polyethylene glycol is present in an amount ranging from 20 to 80%w/w, preferably in the range 30 to 70%w/w.

The composition of the invention further comprises a non-toxic volatile monohydric alcohol or any suitable mixture thereof. The presence of the volatile monohydric alcohol promotes the formation of a peroxide film by evaporation/diffusion of the alcohol from the composition when applied to a tooth surface in the oral cavity.

Examples of suitable non-toxic volatile monohydric alcohols include ethanol and isopropyl alcohol.

Suitably the volatile monohydric alcohol is present in an amount ranging from 5 to 40%w/w, preferably 10 to 30%w/w.

A bioadhesive carbomer is included in a composition of the invention. It has been found that specific carbomers function as bioadhesive agents and enhance substantivity (of a composition) to teeth. Carbomers are synthetic high molecular weight polymers of acrylic acid that are crosslinked with either allylsucrose or allyletheres of pentaerythritol. A suitable bioadhesive carbomer includes a carbomer sold under the trade name "Carbopol ", specifically Carbopol Ultrez 10_ available from Noveon Inc. 9911 Brecksville Road, Cleveland, Ohio 44141-3247.

This Carbopol may be characterized as having a viscosity of 15cPs when measured using a Brookfield RVT ?1 % weight, 20rpm, #1 spindle. Other suitable carbomers for use in the present invention include carbomer copolymers such as crosslinked copolymers of acrylic acid with alkylacrylate where the alkyl chain is C10-30 e.g. Pemulen TR1 and TR2, also available from Noveon Inc..

Suitably the bioadhesive carbomer is present in an amount ranging from 0. 5 to 30% w/w, preferably from 1 to 20%w/w.

Additionally, compositions of the present invention will suitably contain acceptable additives or excipients conventional in the field of oral care products including for example chelating agents such as ethylenediaminetetraacetic acid and/or citric acid, colouring agents, flavouring agents, a fluoride source such as sodium fluoride or sodium monofluorophosphate, an antisensitivity agent such as strontium or potassium salts e.,g strontium chloride, and sweetening agents. The additives or excipients used in any given composition will be compatible both with each other and with the essential ingredients of the composition such that there is no interaction which would impair the performance of the active ingredients. All additives or excipients must of course be non-toxic and of sufficient purity to render them suitable for human use.

The whitening compositions of the present invention are prepared by adding and mixing the ingredients of the composition in a suitable vessel such as a stainless steel tank provided with a mixer. In the preparation of the composition the ingredients are suitably added to the mixer in the following order: peroxide, chelating agents (if used), polyethylene glycol, bioadhesive carbomer and monohydric alcohol. The whitening composition prepared is then suitably packaged and stored as required.

Advantageously the composition of the invention is a suitably prepared in the form of a "single component" system i.e. all components of the whitening composition i.e. excipients and the peroxide-containing compound, are self-contained in a desired pre-mixed proportion. Accordingly there is no requirement for the components of the composition to be physically separated from each other prior to use in order to avoid any undesirable interactions, as may occur with some peroxide-containing formulations. In a second aspect of the invention there is provided a kit of parts comprising an anhydrous liquid tooth whitening composition as hereinbefore described, a container for housing the composition and an applicator for applying the composition to teeth to be whitened.

In an alternative aspect there is provided a method of whitening teeth comprising: a. preparing a tooth whitening composition as hereinbefore described; b. painting the composition onto teeth to be whitened, suitably at night-time; c. maintaining the composition in contact with the teeth for a plurality of hours per day; d. repeating steps b and c for multiple days e.g. up to fourteen days, to thereby whiten the teeth.

The present invention is illustrated by the following examples but is not limited thereby.

EXAMPLES

1. A whitening composition was prepared having the following ingredients: Ingredient % w/w PEG 400 66.00 Carbopol Ultrez 10 4.00 Ethanol l S.00 Carbamide peroxide 15.00 Total 100.00 s 2. A whitening composition was prepared having the following ingredients: Ingredient % w/w PEG 400 53.00 Pemulen TR2 4.00 Ethanol 25.00 Carbamide peroxide 18.00 Total 100.00 Determination of Bleaching Effects using Bovine Enamel Night Time Whitening Model

Introduction

The bleaching effects of the composition of Example 1 above was determined and lS compared to the bleaching effects observed with a commercially available preparation (a whitening product available as "C rest Night Effects").

Method Bovine teeth were used and L* (from the CIE 1976 L*a*b* colour space scale) was measured at the start of the experiment using a spectrocolorimeter. Formulations were applied to the teeth and these were placed into a container such that a liquid substantivity challenge was applied to the treated teeth. At the end of the treatment time the teeth were rinsed and dried and L* was remeasured using a spectrocolorimeter. This method was repeated for a number of days to mimic in- vivo nighttime use of the product. At the end of the experiment the overall change in L* i.e. AL was calculated.

Results SampleAL after 12hrs treatment

Example 1l 8.68

Crest Night EffectsI 5.67 Deionised water-1.24

Conclusions

The results indicate that change in 'L' after 12 hours treatment was comparable to that observed with a commercially available nighttime product. The results are illustrated graphically in Figure 1. - 8 In

Claims

1. An anhydrous liquid tooth whitening composition comprising a peroxide

containing compound and an orally acceptable carrier wherein the carrier includes a polyethylene glycol having a molecular weight in the range 200 to 600 and a monohydric alcohol and a bioadhesive carbomer.

2. An anhydrous liquid tooth whitening composition according to claim 1 wherein the peroxide is selected from carbamide peroxide, and mixtures of carbamide peroxide with hydrogen peroxide and/or a hydrogen peroxide complex with vinyl pyrrolidone.

3. An antydrous liquid tooth whitening composition according to claim 1 or claim 2 wherein the polyethylene glycol has a molecular weight of 400.

4. An anLydrous liquid tooth whitening composition according to any one of claims l to 3 wherein the monohydric alcohol is ethanol.

5. A kit of parts comprising an anhydrous liquid tooth whitening composition according to any one of claims 1 to 4, a container for housing the composition and an applicator for applying the composition to teeth to be whitened.

6. A method of whitening teeth comprising: a. preparing a tooth whitening composition according to any one of claims to 4; b. painting the composition onto teeth to be whitened; c. maintaining the composition in contact with the teeth for a plurality of hours per day; and then d. repeating steps b and c for multiple days to thereby whiten the teeth.