WO2013093743A1

WO2013093743A1 - Dental whitening device

Info

Publication number: WO2013093743A1
Application number: PCT/IB2012/057328
Authority: WO
Inventors: Peter Douglas Fairley; Nigel David Young; Bart Gottenbos
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2011-12-23
Filing date: 2012-12-14
Publication date: 2013-06-27

Abstract

A dental device (10, 40, 50, 60, 70) includes a carrier layer (12). Discrete first regions (30) of a whitening agent (24) are disposed on the carrier layer. Discrete second regions (32) of an activator (26) for the whitening agent are disposed on the carrier layer. The regions (30) of the whitening agent are spaced from the regions (32) of the activator. The device is suited to whitening teeth.

Description

DENTAL WHITENING DEVICE

The following relates to the dental cleaning arts, and related arts and more specifically concerns a dental device for applying a dental care agent, such as a whitening agent, to the teeth.

Tooth whitening agents are generally peroxide-based and the aim is generally to deliver the peroxide to the teeth in a sufficient amount to effect a color change in the surface of the teeth in an acceptable period of time without causing harm to the user. Various methods have been developed for applying tooth whitening agents to the teeth. For whitening teeth at home a whitening agent is held proximal to the tooth surface either by a custom- fitted dental tray or by an adhesive strip that is affixed to the teeth. In the former case, a gel containing the active reagent is injected into the dental tray prior placement in the mouth, and in the latter case, a whitening composition is deposited onto the surface of the adhesive strip.

Conventional tooth whitening formulations include a whitening agent to effect whitening of the teeth, such as hydrogen peroxide or carbamide peroxide. The whitening itself is performed by the free radicals that are generated following the breakdown of the peroxide. Even at a high concentration peroxide of 30%, the degree of whitening observed in a typical one hour treatment time is relatively small, and

consequently various methods of acceleration have been developed to activate the generate the free radicals in order to reduce this treatment time.

Methods for accelerating the whitening process include the use of chemical activators, such as chelators, transition metal salts, and those which have been used for the control of the pH. However, to maintain the shelf life of the active peroxide compound, it is desirable to prevent the combination of such activators with the active peroxide until such time as the whitening process is to be performed. One method for keeping the accelerator separate involves the use of a dual-barreled syringe (EP 1809382; US

7,060,256). Typically, the peroxide-based reagent is stored in one barrel and the other barrel stores the chemical activator. While such techniques are suited to forming gels used in dental trays, they are impractical for whitening strips used at home. The current invention provides a whitening device suitable used for home treatment in the form of a strip which enables the separation of the active reagents that are stored thereon until such time as they are needed.

An advantage arising from this separation is a reduction in treatment time without a reduction in reagent shelf life.

In accordance with one aspect of the invention, a dental device includes a carrier layer. Discrete first regions of a whitening agent are disposed on the carrier layer. Discrete second regions of an activator for the whitening agent disposed on the carrier layer. The first regions of the whitening agent are spaced from the second regions of the activator.

In accordance with another aspect of the invention, a method for whitening teeth includes applying a dental device to the teeth, the device including a flexible carrier layer, discrete first regions of a whitening agent disposed on the carrier layer, and discrete second regions of an activator for the whitening agent disposed on the carrier layer. The first regions of the whitening agent are spaced from the second regions of the activator. The method includes maintaining the device in contact with the teeth for sufficient time for the activator to activate the whitening agent and for a dental bleaching agent derived from the whitening agent to whiten the teeth.

The invention may take form in various components and arrangements of components, and in various process operations and arrangements of process operations. The drawings are only for the purpose of illustrating preferred embodiments and are not to be construed as limiting the invention.

FIGURE 1 diagrammatically shows a top view of a first embodiment of a dental whitening device with active peroxide regions interspersed with chemical activator regions as disclosed herein.

FIGURE 2 diagrammatically shows an enlarged side sectional view of a portion of the dental whitening device of FIGURE 1.

FIGURE 3 diagrammatically shows a top view of a second embodiment of a dental whitening device with topical layering of active peroxide regions and chemical activator regions as disclosed herein.

diagrammatically shows an enlarged side sectional view of a portion of the embodiment of the dental whitening device shown in FIGURE 3.

diagrammatically shows a top view of a third embodiment of a dental whitening device with topical layering of active peroxide regions and chemical activator regions as disclosed herein.

diagrammatically shows an enlarged side sectional view of a portion of the embodiment of the dental whitening device shown in FIGURE 5.

diagrammatically shows a side sectional view of a fourth embodiment of a dental whitening device with active peroxide regions interspersed with chemical activator regions as disclosed herein.

diagrammatically shows a side sectional view of a fifth embodiment of a dental whitening device with active peroxide regions interspersed with chemical activator regions as disclosed herein.

In various embodiments disclosed herein, a tooth whitening device is in the form of flexible adhesive strip upon which an active whitening agent is deposited, and which makes contact with the tooth surface during the whitening process. The active whitening agent and its activator are selectively deposited on the strip in separate regions such that they are not in direct contact with one another during the storage state, and such that they only become mixed together in the saliva from the moist tooth when they are in use.

With reference to FIGURES 1 and 2, a dental whitening device 10 (or "whitening strip") in accordance with a first embodiment is shown. The device includes a carrier layer 12, which includes a support layer 14 and an optional adhesive layer 16. Whitening reagents 18 are disposed on one side 20 of the carrier layer 12. The carrier layer may 12 be substantially impermeable to water, to avoid leaching of the reagents to the surrounding soft tissue. In some embodiments, the carrier material may dissolve or disintegrate over time in the mouth. The exemplary carrier layer 12 is in the form of a strip. It is flexible so as to wrap around a person's teeth and to be worn over the person's teeth during use. The support layer 14 of carrier layer 12, which can include two or more layers, may be formed from any suitable support material, such as polymeric materials, e.g., plastic or rubber, metal, paper, woven and non-woven fabrics, and combinations thereof. As examples of materials for forming the support layer 14, polymeric materials such as polyolefins (e.g., polyethylene and polypropylene) polyesters (e.g., polyvinyl acetate and polyethylene terephthalate), metalized plastic films (e.g., MYLAR™), fluoropolymers (e.g., TEFLON™), and combinations thereof may be used.

The carrier layer 12 may be from about 0.001-1 mm in thickness and of suitable dimensions to substantially cover a surface of a tooth or teeth to be treated, such as from 0.5-2 cm in width and 1-14 cm in length.

Any suitable adhesive which is acceptable for use in the mouth may be employed as the adhesive layer 16. The adhesive may be adapted to be activated with water, so that it becomes more sticky and adhesive when moistened with saliva or water. As examples, polyvinylpyrrolidone (PVP) or carboxymethylcellulose may be used as the adhesive layer. In some embodiments, the support layer 14 is formed of an adhesive material, so an extra adhesive layer is not needed.

The whitening reagents 18 include a whitening (bleaching) agent 24 and an activator 26 for the whitening agent, which are kept separate from each other on the same side 20 of the carrier material 12.

Exemplary whitening agents 24 are solid at ambient conditions and include carbamide peroxide, which is an adduct of urea and hydrogen peroxide (CH₄N₂O-H₂O₂). This material releases hydrogen peroxide on contact with water. Other example whitening agents include alkali metal percarbonates, sodium perborate, potassium persulfate, calcium peroxide, zinc peroxide, magnesium peroxide, strontium peroxide, other hydrogen peroxide complexes, sodium chlorite, combinations thereof, and the like.

The whitening agent can be present at up to 99 wt. %, based on the total weight of the device 10. For example, the whitening agent is at least 0.5 wt. %, or at least 2% of the total weight of the device. Exemplary activators 26 include transition and/or alkaline earth metals and their ions, typically as salts. Exemplary transition metal salts, are disclosed for example, in US 2006/0099155. Non- limiting examples of suitable metals and metal ions which can be used as activators herein include magnesium, iron, titanium, cobalt, nickel, copper, platinum, tin, zinc, manganese, chromium, aluminum, silver, and combinations thereof. In particular, the transition metal may be a transition metal with an atomic number of from 21 to 30. Magnesium and/or iron ions are particularly suitable. The anions for the transition metals may include gluconates, sulfates, nitrates, acetates and mixtures thereof.

For example, transition metal compounds may participate in either a Fenton reaction or a photoFenton reaction, in which a lower oxidative state transition metal, such as Fe(II), may react with peroxides such as hydrogen peroxide, either thermally or upon exposure to light, to facilitate the dissociation of peroxide into active whitening species such as hydroxyl radicals, perhydroxy anions or superoxide radicals. The lower oxidation state of the transition metal is regenerated in the whitening action.

The transition metal/compound, or other activator, can be present in a fairly small amount. For example, the activator can be present at from 0.01 wt.% to 4 wt.% of the whitening strip, more for example, from about 0.03 wt.% to 2 wt. %.

Another type of whitening agent activator includes enzymes capable of catalyzing the decomposition of hydrogen peroxide, particularly enzymes containing transition metals, such as iron. Examples of such enzymes include peroxidases and catalases.

Chelators may also be present as activators, such as those described in EP 1314419. Suitable chelators include ethylene diamine tetraacetic acid (EDTA) and its salts, diethylene triamine pentaacetic acid, citric acid and its salts, gluconic acid and its salts, alkali metal pyrophosphates, alkali metal polyphosphates and combinations thereof. Citric acid, sodium acid pyrophosphate and disodium EDTA are examples. When a small amount of a transition metal compound is present, such chelators can act as a catalyzing agent for the peroxide.

Other activators 26 include those for the control of the pH. Examples of these are given in WO2003/032857.

Some activators 26 are photo-activators which respond to electromagnetic wavelengths in appropriate ranges of the electromagnetic spectrum. Exemplary photo- activators include transition metal complexes, keto acids, riboflavin, pteridines, algal pigments, cyanocobalamin, thiamin, biotin, and aromatic ketones. Some photo-activators include one or more promoters of photo-Fenton reactions, such as metal salts, e.g., ferrous sulfate, ferrous gluconate, potassium iodide, and photosensitizers which absorb light energy, such as erythrosine B or carotene.

Photo-bleaching with application of UV or visible may occur on tooth surfaces by different pathways. In one, the staining on the tooth may undergo

photoreaction directly if the absorption spectrum of the colored chromagen it contains overlaps with the spectrum of incoming radiation (i.e., the color of the stain fades with exposure to light). In another, UV or light energy may be absorbed by photo-activators in the device that then chemically react with tooth surface chromagens resulting in an

"indirect" photo-bleaching.

The activators 26 are deposited on the strip such that they are kept separate from the active whitening agent 24 until use. As an example, FIGURES 1 and 2 show the whitening agent 24 distributed in discrete regions 30 ("first regions") on the carrier layer, here illustrated as substantially circular regions of approximately the same size and shape which form an array. For example the first regions 30 may be arranged in rows and columns to for an nxm array, where n and m are each at least 2, such as at least 3, and m may be at least 6 or at least 10, or at least 50. Each whitening device 10 may include at least 20 or at least 50 such regions 30. The regions 30 may be, on average, for example, up to 5 mm in diameter, such as at least 10 nm, or at least 20 nm, or at least 0.01 mm in diameter and in one embodiment, up to 1 mm, or up to 0.1 mm, or up to 200 nm, in diameter. Each of these dimensions may be average dimensions rather than a diameter, if the regions are not circular. The regions can include whitening agent, e.g., carbamide peroxide, at a concentration of at least 10 wt. %, or at least 20 wt. %, such up to 100 wt. %, or up to 60 wt. %, or up to 50 wt. %. For example, at about 20 wt.%. carbamide peroxide, the hydrogen peroxide concentration per region is about 6%.

The activator 24 also defines discrete regions 32 ("second regions") on the carrier layer 12, here shown as circular regions which form an array. For example the second regions 32 may be arranged in rows and columns to for an nxm array, as for the regions 30, but offset from the regions 30. The regions 32 may be, on average, for example, up to 5 mm in diameter, such as at least 10 nm, or at least 20 nm, or at least 0.01 mm in diameter and in one embodiment, up to 1 mm, or up to 0.1 mm, or up to 200 nm, in diameter/average dimension. Each whitening device 10 may include at least 20 or at least 50 such regions 32. The first and second regions 30 and 32 need not be identical in size but can be of relative sizes that are based on a desired ratio of the active agent to activator.

The activator may be present in each region 32 at from 0.1-100 wt. %, such as at least 1 wt. %, or at least 10 wt. %. In some embodiments, different activators may be applied in different regions 32. For example a first set of regions includes a first type of activator and a second set of regions 32 includes a second type of activator, but not the first type.

One or both of regions 30 and 32 may also include other ingredients, such as one or more desensitizing agents, antibacterial agents, fluoridating agents, vitamin supplements, anti-staining agents, and anti-plaque agents and mixtures thereof.

The regions 30 and 32 are interspersed on the carrier layer 12. For example, each region 30 has at its nearest neighbor at least one region 32 and/or each region 32 has as its nearest neighbor, at least one region 30. In particular each region 30 is spaced from its nearest neighbor (except at the periphery of the strip) by at least one region 32, and vice versa. The regions 30, 32, however, are not in direct contact with each other. For example, each region 30 may be spaced from its nearest region 32, for example, by a distance d of at least ¼ a diameter of the regions 30, and/or by a distance d of at least 0.2 mm.

The exemplary device 10 can be used for at-home tooth whitening where the adhesive-backed strip is affixed to the teeth, and from which the active whitening reagents 18 diffuse into the teeth in order to effect whitening. The chemical activator 26 reduces the duration of the whitening treatment, as compared with a device without the activator. The arrangement of activator regions 32 and whitening agent regions 30 enables these reagents to be kept separate until the whitening process is desired to take place. In use, moisture on the teeth allows the activator 26 to interact with the tooth whitening agent 24, accelerating tooth whitening. For example, when the strip 10 comes into contact with moisture on the tooth, the whitening agent dissolves in the moisture and diffuses into the tooth.

In the storage state, shown in FIGURES 1 and 2, the lifetime of the whitening agent(s) is preserved by preventing contact between the two reagents and their subsequent reaction. When in contact with the tooth, the reagents dissolve into the saliva, react together and subsequently diffuse into the tooth and perform the accelerated whitening reaction.

FIGURES 3 and 4 show a second embodiment of a whitening device 40, where similar elements are accorded the same numbers and new elements are accorded new numerals. The device 40 may be similarly formed to device 10, except as noted. In this embodiment, the regions 30, 32 of peroxide and chemical activator reagents are deposited on top of one another and are separated by a spacing layer 42 formed of a water soluble or water decomposable material, which can be substantially chemically inert towards the reagents 18. In one embodiment, the spacing layer 42 can be water soluble and can be formed from suitable biocompatible film forming material. An exemplary inert material for forming layer 42 is agarose, and chemically modified forms thereof (e.g., formed by introduction of methacrylate side-groups). Other suitable materials for forming the layer include water-soluble fibrin, water soluble chitosan, water soluble collagen, water soluble alginates, gelatin, silica gel, glycerol, and combinations thereof.

Layer 42 may also include other ingredients, such as dental care agents, e.g., one or more of: desensitizing agents, e.g., K 0₃, antibacterial agents, such as

chlorhexidine gluconate, fluoridating/remineralizing agents, such as NaF, vitamin supplements, anti-staining agents, anti-plaque agents, and mixtures thereof. In some embodiments, one or more of these dental care agents may additionally or alternatively be included in regions 30 and/or 32 or elsewhere in the device of any of the embodiments disclosed herein.

The regions 32 may be, on average, for example, up to 5 mm in diameter, such as at least 10 nm, or at least 20 nm, or at least 0.01 mm in diameter and in one embodiment, up to 1 mm, or up to 0.1 mm, or up to 200 nm, in diameter/average dimension. The regions 42 are each at least slightly larger than the respective region 30 to completely cover the region 32 and encapsulate it. The regions 32 can be slightly larger than regions 42 and 30, although they can be the same size or smaller. As for the embodiment of FIGURES 1 and 2, they can be deposited by screen printing or other printing techniques.

In this embodiment, the device may be formed by topically depositing regions 30 of the active whitening agent 24, which can be peroxide-based, as for the embodiment of FIGURES 1 and, and separating this from chemical activator 26 using inert layer 42. Upon contact with moisture, in particular the moisture on the tooth when the device is placed in the mouth, the agarose layer 42 dissolves, thereby permitting the active peroxide and chemical activator to mix and subsequently perform the whitening process.

As for the embodiment of FIGURE 1, the regions 30 and 32 and optionally also layer 42, are each arranged in nxm arrays, but in this case, the arrays may be superimposed. While in the illustrated device 40, layer 30 is closer to the carrier layer 12 than the layer 32 (deposited first), in other embodiments, the arrangement may be reversed.

FIGURES 5 and 6 show a third embodiment of a whitening device 50, where similar elements are accorded the same numbers and new elements are accorded new numerals. The device 50 may be similarly formed to device 40, except as noted. A layer 52 containing a dental care agent is disposed over the other layers 30, 42, and 32. This embodiment uses the layered nature of isolation to permit an initial dental care agent in layer 52 to be diffused into the tooth prior to the aforementioned layers. For example, in one treatment, it is desirable to permit a photo-activator (such as one or more of the photo- activators described above) in layer 52 initially to diffuse deep into the teeth, and then to permit the diffusion of the reactive whitening reagents 18. The deposition process and structures shown in FIGURES 5 and 5 permit such a sequential process in which an initial photo-activator can be diffused into the tooth prior to other reagents.

As for the embodiment of FIGURE 1, the regions 30 and 32 and optionally also layers 42 and 52, are each arranged in nxm arrays, but in this case, the arrays may be superimposed. While in the illustrated device 50, layer 30 is closer to the carrier layer 12 than the layer 32 (deposited first), in other embodiments, the arrangement may be reversed.

To form the device 10, 40, 50, regions 30 of the active whitening agent 24 are laterally deposited on the carrier layer 12 and interspersed (in the case of device 10) or superimposed (in the case of devices 40 and 50) with regions 32 of chemical activator 26. The desired ratio of dissolved reagents can be controlled by varying the relative sizes and/or densities of the two regions 30, 32. The regions 30, 32, 42 may be deposited in a screen printing process, but other printing techniques, such as inkjet printing, are also contemplated. For example, each component is dissolved or dispersed in a suitable solvent/dispersant and separately applied to the carrier. Carbamide peroxide, for example, is soluble in glycerol. Agarose may be dissolved in water. Activators may be soluble or dispersible in water or in an organic solvent. FIGURE 7 shows another embodiment of a whitening device 60, where similar elements are accorded the same numbers and new elements are accorded new numerals. The device 60 may be similarly formed to device 10, except as noted. In this embodiment, the whitening agent 24 and chemical activator 26 are spaced from each other by layer 42 which surrounds each region 30. In particular, the layer 42 forms a shell around a core region 30 formed of the whitening agent 24. The result is an encapsulated particle 62 which may be small enough to be considered a microparticle. The particles 62 may be arranged in an nxm array on the carrier layer 12, or randomly or otherwise arranged on the carrier. The chemical activator 26 may be deposited on the carrier layer 12 in an nxm array as in the embodiment of FIGURES 1 and 2, or may be randomly or uniformly distributed on the carrier. Another embodiment of a whitening device 70, shown in FIGURE 8, can be similarly configured to the device of FIGURE 7. In this embodiment, the chemical activator 26 forms a layer 32 of the microparticle which is spaced from the core 30 by the layer 42, e.g., layer 32 is an outermost layer of the microparticle 62. The microparticles can be dry, solid particles of up to 200 micrometers (μηι) in diameter, on average, or up to 100 μιη in diameter (or average dimension). The layer 32 and core 30 may be present in a weight ratio of from 1 :99 to 99: 1, e.g., from 10:90 to 90: 10, or from 30:70 to 70:30.

In the embodiments of FIGURES 7 and 8, the layer 42 can comprise a hydrophobic material 64 and a release rate modifier 66 in contact with the hydrophobic material, which modifies the rate of release of bleaching agent 24 from the microparticle particle. The hydrophobic material can comprise a waxy solid. The release rate modifier can be selected from the group consisting of polyethylene glycol, silica, water-soluble alkali metal salts, and combinations thereof.

The hydrophobic material, such as a wax, in this embodiment, serves as a matrix which adheres to the teeth (and to the carrier layer 12, in the embodiment of FIGURE 7). The release rate modifier is dispersed in the hydrophobic material. The integrity of the hydrophobic material is disrupted when the release rate modifier comes into contact with water. A ratio of the release rate modifier to hydrophobic material can be tailored to provide a slower or faster release rate of the hydrogen peroxide.

The hydrophobic material 64 used to form the layer 42 may be a waxy solid, i.e., is solid at ambient temperature (25°C) and may be a solid at higher temperatures. The hydrophobic material may be primarily (greater than 50%) or entirely formed from a waxy solid. Exemplary waxes suitable to use as the hydrophobic material include hydrocarbon waxes that are substantially or entirely unsaturated, such as paraffin wax, and the like. Exemplary paraffin waxes are mixtures of higher alkanes of the general formula C„H_2n+2, where typically, 20 < n < 50. They are solid at ambient temperatures and melt-processable.

The release rate modifier 66 used for forming the layer 42 may be a material which is insoluble or substantially insoluble in the hydrophobic material such that it forms discrete regions where it is of high concentration in the hydrophobic material (or a separate layer). The release rate modifier may be more hydrophilic than the hydrophobic material. Exemplary release rate modifiers include hydrophilic organic polymers which are capable of hydrogen bonding and that are solid at ambient temperatures (25°C), and hydrophilic and/or water soluble powders. The release rate modifier may be present in the

microparticles 62 in a total concentration of from 0.001 wt. % to 30 wt. %. Examples of hydrophilic powders include anhydrous inorganic particles, such as silicon dioxide, e.g., hydrophilic silica and silica nanopowders. Exemplary water-soluble powders include water-soluble acids and salts thereof, such as anhydrous phosphate salts, e.g., sodium polyphosphate, sodium tripolyphosphate, sodium pyrophosphate; anhydrous citric acid and salts thereof, such as alkali metals salts, e.g., sodium citrate; anhydrous sodium sulfate, anhydrous magnesium salts, such as magnesium sulfate and magnesium chloride.

Combinations of such release rate modifiers may be employed. The hydrophilic and/or water soluble powders, such as silica, may have an average size of, for example, 1-100 nanometers (nm), e.g., 5-20 nm. Hydrophilic fumed silica may be obtained under the tradename AEROSIL™ from Evonik Industries with a specific surface area (measured by the BET method) in the range of 90-300 m²/g. As an example, AEROSIL™ 200 has a specific surface area of 200 m²/g.

Hydrophilic organic polymers which are useful as release rate modifiers include polyalkylene glycols, such as polyethylene glycol and polypropylene glycol, and esters thereof, polyamide compounds (e.g., polyvinylpyrrolidone), poly( vinyl acetate), poly( vinyl alcohol), poly(acrylic acid), polyacrylamide, polyoxylglycerides, such as lauroyl, oleoyl, and stearoyl polyoxylglycerides, which are mixtures of monoesters, diesters, and triesters of glycerol and monoesters and diesters of polyethylene glycols (e.g., lauroyl macrogolglycerides), and ethylene oxide derivatives thereof, poloxamers, which are triblock copolymers having a central hydrophobic block of poly(propylene oxide) and two side blocks of poly(ethylene oxide) (e.g., poloxamer 188, which has a melting point 52°C), and derivatives thereof, and mixtures thereof. The hydrophilic polymer can have a weight average molecular weight of at least 300.

Exemplary polyethylene glycols (PEG) for the release rate modifier have a molecular weight of 300 daltons to 50,000 daltons, e.g., 600-35000, or 1000 to 5,000 daltons. As examples PEG 1000 (melting point 37-40°C), PEG 1500 (melting point 44- 48°C), PEG 2000 (melting point 49-52°C), combinations thereof, and the like may be used.

A ratio of the hydrophobic material to release rate modifier in the particles may be, for example, from 1 :99 to 99: 1 , expressed by weight, such as from 5 :95 to 95 :5 or from 10:90 to 90: 10. For example, the ratio of hydrophobic material: release rate modifier may be about 30:70 to 70:30, for example, in the case of PEG. For hydrophilic and/or water soluble powders, the ratio may be higher, such as at least about 85: 15.

The particles 62 generally have a low water content, such as less than 5 wt. %, or less than 1 wt. %, or less than 0.2 wt. % of the particles is made up of water.

Particles 62 can be formed by any suitable encapsulation method, such as spray cooling, precipitation, and the like. Spray cooling/chilling methods can be used where the molten hydrophobic material containing the core material is sprayed into a cold chamber or onto a cooled surface and allowed to solidify. For example, small particles of carbamide peroxide, or other bleaching agent, are combined with a molten mixture of wax and release rate modifier, e.g., PEG. The mixture is sprayed through a nozzle into a fluid at a sufficiently low temperature to solidify the mixture as microparticles. For example, carbon dioxide at low temperature may be used as the cooling fluid. Other encapsulation techniques are disclosed in MICROENCAPSULATION: Methods and Industrial

Applications, Edited by Benita and Simon (Marcel Dekker, Inc., 1996).

The particles 62 may be deposited on the carrier layer 12, for example, before they are completely solid.

A method for whitening teeth may include applying (e.g., adhesively mounting) the device of any one of FIGURES 1-8 to the teeth of a person for sufficient time for the activator to activate (e.g., to react with or catalyze decomposition of) the whitening agent and for the device to release a bleaching agent, such as hydrogen peroxide, onto the surface of the teeth, to effect whitening. For example, the device may be applied to the teeth for from 30 minutes to 12 hours, or longer. The procedure may be repeated at intervals to increase the whitening effect or to re-whiten the teeth when they become stained. In one embodiment, electromagnetic radiation, such as visible light (e.g., in the blue or violet region of the spectrum from 400 to 500 nm) and/or UV light (e.g., at wavelengths of 10-300 or 300-400 nanometers), may be applied from a suitably positioned light source to the device and/or teeth to accelerate the whitening treatment (by speeding up the conversion of hydrogen peroxide to active free radicals which effect whitening) and/or to activate photo-activators in the device. For example, the device may be configured to release the bleaching agent first and allow this to contact the teeth, for example, over a period of 10-60 minutes, followed by the release of the activators and photo-activators. Light may be applied through the strip at this stage, for example, for 5 to 30 minutes. In this embodiment, the carrier layer 12 is transmissive to at least a portion of the light in the applied wavelength range. Alternatively or additionally, light may be applied after the strip (i.e., carrier layer 12) is removed, for example, for 5 to 30 minutes. It is also contemplated that the bleaching agent and activator(s) may be released together and light applied from the start of the treatment, or shortly thereafter.

The exemplary method is suited to at-home or professional use.

Except where otherwise explicitly indicated, all numerical quantities in this description specifying amounts of materials, reaction conditions, molecular weights, number of carbon atoms, and the like, are to be understood as modified by the word "about." Unless otherwise indicated, each chemical or composition referred to herein should be interpreted as being a commercial grade material which may contain the isomers, by-products, derivatives, and other such materials which are normally understood to be present in the commercial grade. It is to be understood that the upper and lower amount, range, and ratio limits set forth herein may be independently combined. Similarly, the ranges and amounts for each element of the invention may be used together with ranges or amounts for any of the other elements. As used herein any member of a genus (or list) may be excluded from the claims.

The invention has been described with reference to the preferred embodiments. Obviously, modifications and alterations will occur to others upon reading and understanding the preceding detailed description. It is intended that the invention be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.

Claims

CLAIMS: Having described the preferred embodiments, the invention is now claimed to be:

1. A dental device (10, 40, 50, 60, 70) comprising:

a carrier layer (12);

discrete first regions (30) of a whitening agent (24) disposed on the carrier layer; discrete second regions (32) of an activator (26) for the whitening agent disposed on the carrier layer; the first regions (30) of the whitening agent being spaced from the second regions (32) of the activator.

2. The dental device (40, 50, 60, 70) of claim 1, wherein each first region is spaced from a respective second region by a spacing layer (42).

3. The dental device (40, 50) of claim 2, wherein the spacing layer is water soluble and is formed from a water soluble film forming material selected from the group consisting of agarose and chemically modified forms thereof, water-soluble fibrin, water soluble chitosan, water soluble collagen, water soluble alginates, glycerol, gelatin, silica gel, and combinations thereof.

4. The dental device (60, 70) of claim 2, wherein the spacing layer is water decomposable and is formed from a hydrophobic material (64) and a release rate modifier (66), dispersed in the hydrophobic material, which modifies the release of whitening agent from the first region.

5. The dental device (60, 70) of claim 4, wherein the hydrophobic material comprises a hydrocarbon wax.

6. The dental device (60, 70) of claim 4 or 5, wherein the release rate modifier is selected from the group consisting of polyethylene glycol, silica, water-soluble alkali metal salts, and combinations thereof.

7. The dental device (60, 70) of any one of claims 2-6, wherein the spacing layer encapsulates a respective first region or a respective second region.

8. The dental device (10, 40, 50, 60, 70) of any one of claims 1-7, wherein at least one of the regions of the whitening agent and the regions of the activator each define an nxm array, where n and m are at least 2.

9. The dental device (10, 40, 50, 60, 70) of claims 8, wherein where at least one of n and m is at least 10.

10. The dental device (40, 50, 60, 70) of claim 8 or 9, wherein the nxm arrays are superimposed on each other.

11. The dental device (10) of claim 8 or 9, wherein the nxm arrays are offset from each other.

12. The dental device (10) of claim 11, wherein each first region is spaced from its nearest neighboring second region by a distance of at least one of:

¼ a diameter of the first region; and

at least 0.2 mm.

13. The dental device (10, 40, 50) of any one of claims 1-12, wherein the first and second regions are formed by printing.

14. The dental device of any one of claims 1-13, wherein the first and second regions have an average diameter of up to 1 mm.

15. The dental device of claim 14, wherein the first regions have an average diameter of up to 100 μιη.

16. The dental device of any one of claims 1-15, wherein in the activator is selected from the group consisting of transition metals, transition metal salts, alkaline earth metals, alkaline earth metal salts, enzymes capable of catalyzing the decomposition of hydrogen peroxide, chelators, pH controllers, photo-activators, and combinations thereof.

17. A method for whitening teeth comprising:

applying the dental device of any one of claims 1-16 to the teeth for sufficient time for the activator to activate the whitening agent.

18. A method for forming the dental device of any one of claims 1-16, comprising:

disposing the first and second regions on the carrier by printing.

19. The method of claim 18, further comprising:

disposing a spacing layer (42) on the carrier by printing.

20. A method for whitening teeth comprising:

applying a dental device (10, 40, 50, 60, 70) to the teeth, the device including a flexible carrier layer, discrete first regions (30) of a whitening agent (24) disposed on the carrier layer, and discrete second regions (32) of an activator (26) for the whitening agent disposed on the carrier layer, the first regions (30) of the whitening agent being spaced from the second regions (32) of the activator; and

maintaining the device in contact with the teeth for sufficient time for the activator to activate the whitening agent and for a dental bleaching agent derived from the whitening agent to whiten the teeth.

21. The method of claim 20, wherein each first region is spaced from a respective second region by a spacing layer (42).

22. The method of claim 20 or 21, further comprising applying electromagnetic radiation in a wavelength of 300-500 nm to the dental device or teeth after applying the dental device to the teeth.