AU2010235870A1 - Apparatus and method for the cosmetic treatment of discoloured teeth - Google Patents

Description

/ ustralian Patents Act 1990 - Regulation 3.2 ORIGINAL COMPLETE SPECIFICATION STANDARD PATENT Invention Title Apparatus and method for the cosmetic treatment of discoloured teeth The following statement is a full description of this invention, including the best method of performing it known to me/us: P1/00/0i1 5102 Asclepion Laser Technologies GmbH PAT 9097/008 The invention relates to an apparatus with which teeth in a person's mouth are irradiated for dental whitening by means of a photothermally activable bleaching gel. Such an apparatus comprises light generating means for generating the light needed for irradiating the teeth, cooling means for cooling the light generating means, light distribution means through which the light generated by the light generating means can be irradiated in a defined region for simultaneous irradiation of many teeth, means for controlling the light dose directed at the teeth, and adapting means for positioning the apparatus with reference to the teeth in the mouth. The invention also relates to a method for the cosmetic whitening of teeth. A number of apparatuses and methods for dental whitening are described in prior art, including such for home use and such that are, as a rule, used professionally by dentists. Professional teeth whitening takes advantage of the bleaching action of peroxide compounds or other bleaching substances like perborates. The substance, at first inactive, is brought into contact with the structure to be bleached, i.e. the tooth surface facing out of the mouth, and then activated. Such substances applicable for bleaching are described, e.g., in US 6,387,353, WO 02/22097 or US 6,846,182 B1. Activation is effected by heat, which can be generated either directly - e.g. by means of heating resistors - or indirectly by means of a high-frequency alternating field, or light, or a combination of these methods. Examples of indirect heating are described, e.g., in US 7,320,595, where heating is accomplished by means of electrical, electrophoretic or electromagnetic alternating fields, or in US 2003/0157456 Al, where light is used. The mode of action of such peroxide-based bleaching agents is that they oxidize discoloured organic components formed or deposited on the teeth in the course of time. The discolorations are due either to chromogens in food ingredients and/or tobacco, or to chromogens without a function that have formed or deposited in the organic matrix of the dental enamel or the dentin with increasing age. These unwelcome colour changes are caused by the absorption of light at unsaturated chemical donor bonds of the chromogens. In the presence of peroxides, these unsaturated C=C electron donor bonds are extremely unstable and will decay and decompose, possible decomposition products being alcohols, carboxylic acids and, under extreme conditions, carbon dioxide and water. It is important to know that these reaction mechanisms of 2 Asclepion Laser Technologies GmbH PAT 9097/008 peroxides per se will not in any case lead to a damage of dental enamel or dentin, whether by demineralizations or etching, to mention just the most important risks. Quite the reverse, peroxides are completely unreactive to hydroxyl apatite, the mineral component of bones and teeth. Hydrogen peroxide with the chemical formula H 2 0 2 can decompose into HO, 02, 020, HOO~ or H0 2 0 radicals or ions. These decomposition products of hydrogen peroxide make up the active bleaching substance, which has an oxidizing and breaking effect on the pigments in the tooth, thus causing a brightening. H 2 0 2 is a weak acid which liberates more free oxygen radicals (00) than perhydroxyl radicals (H0 2 0); with pH levels of more than 9.5, however, it releases more perhydroxyl radicals than oxygen ones. The action of the perhydroxyl radical is stronger than that of the oxygen radical; oxygen liberation can be accelerated by heat, light (in the presence of suitable catalyzers) or by an increase in pH. Photothermal heating by activation with light has advantages compared to photothermal excitation directly with heat, because, in the first-named method, heat is generated in the gel only. With the tooth having too high a temperature, it becomes unresponsive to further bleaching treatment. Besides the use of bleaching agents, mechanical methods are known of course, such as the removal of material by means of abrasion or polishing agents and ultrasonic treatments: among professional users, though, bleaching by means of a gel using hydrogen peroxide is the method of choice. In addition to H 2 0 2 , the gel is provided with a pigment that serves as a target for light absorption. The absorption of the light energy causes the bleaching gel to heat up and thus to activate the hydrogen peroxide in the gel. If the gel contains a red pigment, for example, this means that the absorption of light having the wavelength of the complementary colour, i.e. green, is particularly high. With common methods and arrangements, the means used for light generation are lasers, individual light-emitting diodes (LEDs), and UV and white-light lamps. All these light sources, however, have some disadvantage or several of them, which make bleaching inefficient and laborious. WO 02/22097 describes a method which uses a gel to which a pigment as, for example, rhodamine has been added, and a laser for irradiating the pigment, so that the pigment absorbs the laser light and converts it into heat. Laser wavelengths and pigment are selected to ensure that the laser light can be absorbed by the pigment. One may use, e.g., a laser wavelength of 532 nm, this is within the range in which rhodamine absorbs light. The laser produces a very 3 Asclepion Laser Technologies GmbH PAT 9097/008 narrow band of light; rhodamine has its absorption maximum at a wavelength of 555 nm, so that the absorption is not particularly efficient in this case. As laser light sources are rather expensive, lasers of less than optimum output power are used as a rule, so that the teeth have to be treated one after the other. For this purpose, they are illuminated through a fibre-optic light guide. Because of the highly divergent beam exiting from the fibre end, the power density per unit area varies greatly with the distance between the fibre end and the tooth. The beam distribution and the power density per unit area also depend on the bending of the fibres, so that the method is not readily reproducible. Uniform treatment with defined power densities per unit area is impossible that way, so that the operator needs to be present throughout the treatment. As the treatment is applied to each tooth in succession, it is also possible that bleaching agent already applied but still inactive will, prior to activation, diffuse into an untreated tooth and thus become ineffective. Increasing the laser output, on the other hand, to enable simultaneous treatment of many teeth, would require high-power lasers, which would not only make the apparatus used much more expensive but also substantially increase the risk of lasting damage, e.g., to the eyes, in case of inexpert treatment. US 2007/0015112 Al describes an apparatus for dental bleaching in which gel heating for activation can be effected via heat supply and/or light. The apparatus is designed in the manner of a toothbrush, so that it can well be used at home, save that the bleaching agent may only be used in a low concentration, as a rule. This apparatus is unsuitable for professional use. US 7,320,595 B2 describes an arrangement for dental bleaching in which the apparatus inserted into the mouth follows the curvature of the dentition. Gel heating is effected mainly by electrophoresis, supplemented by a few LEDs feeding additional light into the gel for heating. US 2005/002613 A2 and US 2004/0110111 Al also describe apparatuses for home use, which are inserted into the person's mouth. One of these apparatuses has a structure of cells containing the bleaching agent. At the same time, the apparatus - which is intended for one time use - contains a phosphorescent light source that is activated once to activate the bleaching ingredients. The light source is activated before the apparatus is inserted into the mouth. Various other apparatuses known on the market use, e.g., UV lamps, white-light lamps or common LEDs for illumination. The company of Britesmile, for example, markets an arrangement in which between 400 and 500 white-light LEDs are arranged along an arc, and in which only a blue share in the range between 400 and 420 nm is filtered out to activate the 4 Asclepion Laser Technologies GmbH PAT 9097/008 previously applied gel. Treatment takes an hour, and gel has to be applied several times. Due to the great number of LEDs, the arrangement is rather big, so that it has to be positioned outside the mouth. Furthermore, the light of the LEDs is very bright, so that the person being treated must wear some eye protection means. Because of the great number of LEDs needed for achieving the power density that is necessary for gel activation, excessive cooling is required, which is implemented by air cooling here. Given the divergence of the light beams emitted, the power density per unit area greatly varies with the distance, so that the treatment is not exactly reproducible, as a rule; a variation of the distance between the illuminating arrangement and the teeth by a few millimetres may lead to substantially differing results. The use of blue LEDs, as for example in an apparatus made by Whitesmile, is more efficient. Here, an illuminator also arranged outside the mouth contains an arcuate arrangement of several LEDs, part of which emitting light of a blue wavelength range, and the rest emitting light of a cyan wavelength range, making up a wavelength range between 480 and 510 nm altogether. At a total output of 30 watts, the power density per unit area is 2500 mW/cm. This apparatus, too, is arranged outside the mouth, so that the person being treated needs protective wear. Here again, a substantial portion of power is lost; moreover, the arrangement suffers from the distance variation described and needs extensive air cooling. Given the arrangement outside the mouth and the variation of power density from distance due to the great divergence of the LED beams, here again the reproducibility of results cannot be guaranteed, so that the persons treated need operator attendance throughout. The invention therefore addresses the problem to improve, compared to prior art, an apparatus of the nature described above, especially with the aim to make the arrangement capable of achieving reproducible results, so that, in principle, treatment is possible without operator attendance. As an added goal, the apparatus is to be small enough to be placed into the mouth, with irritating noise and outgoing air flows during treatment to be suppressed as well as possible. In an apparatus of the kind described at the beginning, this problem is solved in such a way that the light generating means comprise at least one array of high-power light-emitting diodes (HPLEDs) arranged to form an emission surface, the high-power diodes being designed to emit light in emission wavelength ranges with a half-peak width of up to 100 nm each, and the emission wavelength ranges overlapping with an absorption wavelength range containing wavelengths with which the bleaching gel can be activated, and that the light distribution means comprise a light exit surface which directs the light at the teeth, this light exit surface having a 5 Asclepion Laser Technologies GmbH PAT 9097/008 curvature that essentially follows the curvature of the dentition, so that, with the apparatus inserted in the mouth, the light exit surface is, on average, at equal distances from the teeth to be irradiated. Here, distance means the shortest distance between the surface of a tooth and the light exit surface. The invented apparatus offers several advantages at once. As it uses at least one array of high power light-emitting diodes as a light source, e.g., 4x4, 5x5 or 6x6 light-emitting diodes, which are arranged to form an emission surface, it is relatively unproblematic to achieve the necessary power density per unit area of approximately 200 mW/cm2 required for activating the bleaching gel. As each of the high-power light-emitting diodes itself has a high output of 2.5 watts, compared to about 50 mW delivered by normal light-emitting diodes, only few light-emitting diodes are required to achieve the power density. The emission wavelength ranges of the diodes, which due to manufacturing tolerances may slightly vary in position by up to about 10 nm from diode to diode, have - with half-peak widths up to 100 nm each - a characteristic that is more on the narrow-band side. Also, the emission wavelength ranges are selected so as to overlap with an absorption wavelength range containing wavelengths with which the bleaching gel can be activated. Thanks to these two settings, the light emitted by the light-emitting diodes can be used for activating the bleaching gel with very high efficiency, because, on the one hand, only a small wavelength range is used, and on the other, its position is selected so that a large portion of the light emitted in this wavelength range is absorbed. In addition, the bleaching gel may be marked, e.g., with a pigment the hue of which is essentially, i.e. within a range of a few tens of nm, complementary to the wavelength centroid - the wavelength at which the intensity of the emitted light is maximum. So if, for example, green light is used for irradiation, the bleaching gel is preferably marked with a red pigment. In prior art with apparatuses arranged outside the mouth power, densities per unit area of up to 2500 mW/cm2 have to be obtained because a large portion of the light does not hit the bleaching gel to be activated but is scattered elsewhere, with the greater distance to the teeth on top of that; whereas the invented apparatus can manage with power densities per unit area of only 200 mW/cm', i.e. approximately one tenth. One of the reasons is the closeness of the arrangement to the teeth, i.e. the design of the light exit surface at which the light generated by the light generating means is directed and which radiates it on to the teeth. The curvature of the light exit surface follows the curvature of the dentition, i.e., with the apparatus inserted into the mouth, the light exit surface is, on average, spaced at equal distances to the teeth to be irradiated, or strictly, speaking, to the surfaces of the teeth to be irradiated, i.e., the outward looking surfaces that are visible to other persons if the mouth is open. Other than common 6 Asclepion Laser Technologies GmbH PAT 9097/008 irradiation apparatuses for professional use - and for this use only - the invented apparatus is intended at least partially to be put into the mouth of the person to be treated. This is possible only because narrow-band high-power light-emitting diodes are used the emission characteristics of which are matched to the pigment or pigments added to the bleaching gel. As the size of the light exit surface can also be adapted to the dentition, the light is used highly efficiently; there is no irradiation of areas not supposed to be treated; accordingly, heat generation is low, and the person being treated is not exposed to glare and therefore needs no protective eyewear. The high-power LEDs themselves are strong heat generators, though, so that efficient cooling is necessary, especially for a compact design that permits the apparatus to be taken into the mouth. As an advantage, however, the heat of the LEDs is generated outside the mouth. In prior art, LED cooling is commonly provided by thermoelectric and/or air cooling devices (cooling of apparatuses designed for home use is not needed or not provided, as a rule), whereas the invented apparatus is preferably provided with a water cooling system with at least one inlet and at least one outlet. The flow rate of the water can be monitored by means of a temperature sensor, for example. This type of cooling certainly requires additional measures such as the water inlets and outlets mentioned, which have to be integrated into the apparatus; but as this type of cooling is highly efficient and quiet, this extra expenditure is quite justifiable. In particular, the person under treatment is rot troubled by a noise source in close proximity. Contrary to this, apparatuses described in prior art are cooled only through air coolers, as a rule ventilating fans, which can simply be operated by electric power that is needed anyhow. In a preferred embodiment of the invention, the half-peak width of the emission wavelength ranges is between 30 nm and 50 nm. If the overlap between the emission wavelength ranges and the absorption wavelength range is appropriately adapted, the efficiency is increased further. Alternatively or in addition, the characteristics of the HPLEDs can be set so that the wavelength centroids of the emission wavelength ranges lie in a range of 30 nm about a wavelength in which the activation of the bleaching agent is maximum. This also leads to an increase in efficiency. In a particularly preferred embodiment of the invention, the light generating means comprise three arrays of high-power light-emitting diodes, in which the emission surface of each array is tilted relative to the emission surfaces of each of the other arrays by a tilt angle that is specific for the respective other array. In interaction with the light distribution means and especially with the light exit surface, it is thus possible to adapt the intensity distribution of the light radiated 7 Asclepion Laser Technologies GmbH PAT 9097/008 from the light exit surface to different requirements. The geometric centroids of the arrays preferably lie on a common line; the array in the middle can then be used for illuminating the region of the anterior teeth, for example. The two arrays arranged on the right and the left, then, are tilted relative to the middle array, e.g. by tilt angles of equal amount but different sign. In interaction with, and depending on, the light distribution means yet to be described, then, shallow tilt angles will direct the light rays mainly at the posterior teeth region, while steep tilt angles will direct them at the region of the anterior or canine teeth, for example. Other arrangements in which steep outward tilt angles Will direct the light at the posterior teeth region are feasible as well. Whereas the middle array faces the incisor teeth, the two outer arrays - the line on which the arrays lie is situated in the plane of occlusion - are directed outward by the said tilt angle, the light being deflected accordingly by the light distribution means. It is quite possible to provide means by which the tilt angles can be varied, so that the apparatus can be adapted to different requirements by variation of the intensity distribution. The light distribution means preferably comprise light guiding channels corresponding to the number of arrays, with light entry surfaces which are preferably arranged in parallel with the emission surfaces in order to capture the light emitted by the LEDs as completely as possible. For the same reason, the light entry surfaces are arranged as close to the emission surfaces as possible. Also for the same reason, the light entry surfaces have diameters in the order of magnitude of the LED arrays, provided that they are of round shape. Channel configurations with edges, i.e. of angular shape, are feasible as well; for light transmission and distribution with the lowest possible loss, however, round channels are preferable. The light guiding channels may, for example, be made of a material that is predominantly transparent to the emission wavelength ranges. In the simplest case, then, they are designed as simple glass rods. These glass rods may then be provided, e.g., with a reflective coating, which prevents light from exiting through the circumferential surfaces of the channels. It is also possible to do without the glass rods; in the simplest case, then, the light guiding channels consist of small hollow glass tubes, which are preferably provided with the inward-acting reflective coating mentioned before. The light guiding channels are followed by a light distribution space, which is bounded by one or several bounding faces on those sides to which no light is to be radiated, and the light exit surface through which the light is to be exited and which is arranged at a distance from the light guiding channels. As a rule, therefore, the light exit surface is situated facing the light guiding channels; these also bound the light distribution space. Regarding the design of the bounding 8 Asclepion Laser Technologies GmbH PAT 9097/008 faces, it should be minded that these should not have any more edges than necessary, so as to keep light losses as low as possible. To deflect the light to the light exit surface, the lateral bounding faces preferably reflect the light back into the light distribution space. Consequently, light entering the light distribution space via the light guiding channels can leave that space via the light exit surface only, apart from photons scattered back into the light guiding channels. The reflecting bounding faces of the light distributor are preferably designed in such a way that they direct at least part of the light reflected by the tooth surfaces back towards the dental arch. In this way, this light can be made available for activating the bleaching process again. If the bounding faces were not made reflective, still a major part of the light would be directed out via the light exit surface, but a minor part would either exit through the bounding faces or, if they were provided with an opaque coating, would be absorbed by this coating. The light distribution space and the bounding faces are designed especially in tune with the tilt angles of the arrays of HPLEDs, or with the position of the light guiding channels. If the light coming from the arrays is deflected out via the light guiding channels, a suitably curved design of the bounding faces can direct the light at the respective tooth regions. The light distribution space may also be filled, e.g., with some material that is transparent to the emission wavelength ranges. This may, for example, be the same material as that used for the light guiding channels, so that the distribution space and the channels can be manufactured as a single piece. A major portion of the light will then be totally reflected by the bounding faces facing the light distribution space. For improved light yield, the transparent material at the bounding faces may be provided with a coating that reflects light back into the light distribution space. In an alternative embodiment that can be manufactured at less cost, though, the light distribution space is designed as a hollow space. The bounding faces are then formed by a suitable partial enclosure made, e.g., of plastic. Here again, the insides facing the light distribution space may be provided with a reflective coating. Care must be taken to ensure that the light exit surface remains transparent. The enclosure may, for example, be made of some transparent plastic and be partially provided with a reflective coating. It is further feasible to do without any material light exit surface; this surface can then be defined as the plane through which the light leaves the light distribution space without passing any interface. On the other hand, a material light exit surface offers the advantage that the regions lying behind it are protected against soiling and other extraneous influences.

9 Asclepion Laser Technologies GmbH PAT 9097/008 Even if the light distribution space is designed as a hollow space, the light guiding channels may be filled with the transparent material mentioned above; they can, however be designed as hollow spaces as well. The adapting means are used to position the apparatus with reference to the teeth. In prior art this means that the lighting system is set up at a more or less fixed distance in front of the person to be treated, or arrested in a fixed position in front of the patient's mouth, with the patient's head being fixed by a rest, as a rule. However, since the invented apparatus is partially inserted into the mouth, special adapting means must be provided that prevent the apparatus from getting displaced during treatment. Preferably, therefore, the adapting means feature biting rests on which the person bites during treatment so that the position of the apparatus in the mouth, once defined, is retained for the duration of the treatment. In a specially preferred embodiment, the adapting means also feature ports for connecting suction lines through which saliva can be sucked off during treatment. With available prior-art apparatuses for professional teeth whitening, the light output is constant and setting of the power to be applied is only possible by varying the operating period, whereas the invented apparatus, in a preferred embodiment, features means with which the light output on a time average can be varied via pulse width modulation. This permits, for example, constant treatment times with different light outputs as required. In a particularly preferred embodiment of the invention, the apparatus is built up of modules that can be taken apart and assembled by an operator without any mechanical aids. A design consisting of three modules has proved practical. The first module is a basic body that is designed as a handling piece and can, e.g., be inserted into a suitable holder outside the mouth. Integrated in this basic body are, among other items, the light generating means and the cooling means. In proper use, the basic body is outside the mouth, so that the heat generated cannot lead to any undesirable heating of the oral cavity or the teeth. The second module is an attachment body, i.e. a body attached to the basic body, which comprises at least part of the light distribution means. The light guiding channels, for example, may be part of the basic body. The light distribution space with the light exit surface, in particular, is part of the attachment body. The light guiding channels can also be designed as part of the attachment body, so that the latter comprises the complete light distribution means. A third module is an adapter that comprises the adapting means; alternatively, however, this third module may be permanently joined to the attachment body.

10 Asclepion Laser Technologies GmbH PAT 9097/008 This modular design has the advantage that components whose manufacture and maintenance are more complex, such as light generating means and water cooling system, are all integrated in the basic body, and both the attachment body and the adapter can be designed as wearing parts. This is advantageous insofar as the apparatus needs to be disinfected after every use. Same as the treatment itself, disinfection may impair the quality of the light exit surface, e.g., make it dull in the course of time. One must reckon that a replacement will be necessary after about ten treatment sessions. The modular design prevents laborious dismantling of the entire apparatus before certain parts can be replaced. . The invented apparatus is further provided with means for controlling the light dose applied to the teeth. The light dose is adapted, for example, by varying the light output on a time average via pulse width modulation. Alternatively, the light dose can be adjusted by varying the irradiation period. The invention also relates to a method for cosmetic teeth whitening. With this method, in a first step, a passive bleaching gel that contains chromophores and can be activated photochemically is applied to the teeth to be treated. The chromophores are capable of absorbing light of wavelengths of an appropriate absorption wavelength range. The teeth to be treated are then illuminated simultaneously with light emitted by a light source and exiting from a light exit surface from which the teeth have essentially equal distances, the light having wavelengths of an emission wavelength range the half-peak width of which is not greater than 100 nm and which overlaps at least partially with the absorption wavelength range. In this way, the light efficiently excites the chromophores, which then convert the absorbed energy to heat, so that, as a consequence, hydrogen peroxide (H 2 0 2 ) contained in the bleaching gel is decomposed. The decomposition products of the hydrogen peroxide oxidize the pigments contained in the tooth and thus bleach the tooth. The method can be carried out, e.g., with an apparatus as described above. The light sources preferably used are high-power light-emitting diodes (HPLEDs). Before the application of the bleaching gel, a passivating gel can be applied to the gums. Furthermore, a cheek and lip spreader can be inserted into the mouth to keep it permanently open during treatment. After treatment and cleaning, another bleaching gel having a hydrogen peroxide concentration lower than the bleaching gel used first and also containing fluorine can be applied to the teeth, so that the teeth are sealed during another irradiation. Whereas the 11 Asclepion Laser Technologies GmbH PAT 9097/008 bleaching gel used first has a concentration of, for example, 35% H 2 0 2 , the concentration of the bleaching gel used for sealing need only be about 10%. Once the chromophores have been activated and completely bleached, no further hydrogen peroxide can be decomposed, so that the treatment automatically ends even though light irradiation continues. Because of its wavelength, however, this light does not cause any heating of the teeth that might lead to undesirable passivation against further bleaching. Optionally, however, the apparatus can be switched off automatically when, e.g., sensors detect that the chromophores in the bleaching gel are completely bleached. It also comes in the scope of the invented method to automatically terminate the activation of the bleaching agent when the chromophores in the bleaching gel are completely bleached. It is understood that the scope of the present invention allows for the characteristics mentioned above and those yet to be explained below to be used not only in the combinations described but also in different combinations or individually. Below, the invention will be explained by an example and with reference to the accompanying drawings, which also show features essential to the invention. Fig.1 is a total view of an irradiation apparatus, Fig.2 shows a handling piece with attachment body and adapter, Fig.3 shows light generating means in detail, Fig.4 shows an attachment body in detail, and Fig.5 shows an adapter in detail. Fig.1 shows an apparatus with which teeth in a person's mouth are irradiated for teeth whitening by means of a photochemically activable bleaching gel applied on the teeth. The apparatus is made up of several parts. A handling piece 1, which is gripped by the operator when he inserts the apparatus into the mouth of a person to be treated, and which is at the same time designed to be held in an appropriately adapted holder during treatment, contains the central technical means for generating light to irradiate the teeth wi th, and the means for cooling the light generating means. A hose 2 is connected to the rear end of the handling piece 1, i.e. in the direction away from the person being treated. This hose contains the electrical and possibly data lines for controlling the treatment process, but also the inlets and outlets of the cooling means, which in the present example are designed for water cooling. The treatment process is controlled, e.g., via the light dose directed at the teeth, which is defined by the light output and 12 Asclepion Laser Technologies GmbH PAT 9097/008 the irradiation period. At the other end of the handling piece 1, i.e. facing the person being treated, there is fitted an attachment body 3. Integrated in this attachment body 3 are at least part of the light distribution means by which the light generated by the light generating means can be radiated to a defined area for simultaneous irradiation of many teeth. Fitted to this attachment body 3, in turn, is an adapter 4, which comprises the adapting or positioning means for positioning the apparatus with reference to the teeth. The apparatus may be of modular design, which means that the handling piece 1, the attachment body 3 and the adapter 4 can be taken apart and assembled by an operator without any mechanical aids: where desirable, hose 2 can also be separated from the handling piece 1 in this way. This facilitates especially the change of attachment body 3 and adapter 4, which may be necessary, for example, if attachment bodies 3 and adapters 4 are available for different mouth sizes or if one of these two components has to be replaced because of wear or rules of hygiene. Alternatively, of course, it is also possible to have such an apparatus whose components are joined not only by force and friction, but also by form closure and can be separated only by the slackening or removal of screws, for example. In the detail illustration of Fig.2, the hose has been left out and the handling piece 1 is shown in an opened state. The technical elements are arranged essentially in the area where the handling piece 1 flares out. A major portion of the space is occupied by the water cooling system, which comprises a heat exchanger 5 and an LED cooler 6. The water inlets and outlets are not shown. The motor that drives the water flow is housed outside the apparatus in an external unit that can be arranged remotely from the person being treated. The cooling system is, therefore, an extremely quiet one; in addition, it is highly efficient and requires little space compared to cooling systems based on ventilating fans, even though the configuration is more complex. Connected to the LED cooler 6 are arra ys 7 of high-power light-emitting diodes arranged to form an emission surface. The high-power diodes are designed to emit light in emission wavelength ranges with a half-peak width of up to 100 nm each; the emission wavelength ranges of the light-emitting diodes, which may vary in a range of up to 10 nm due to manufacturing tolerances, overlap with an absorption wavelength range containing wavelengths with which the bleaching gel can be activated. At least one such array 7 of high-power light emitting diodes is needed; however, the irradiation result and the light distribution can be improved considerably if, for example, three such arrays are used. The light distribution means comprise, corresponding to the number of arrays 7, light guiding channels 8 with light entry surfaces 9, which are preferably arranged in parallel with the 13 Asclepion Laser Technologies GmbH PAT 9097/008 emission surfaces. The diameters of the light guiding channels 8 correspond in size to the size of the arrays 7 and are preferably slightly greater than those so as to capture also light radiated laterally by the arrays due to the design of the LEDs and to direct it at a light distribution space. The light generating means including the light guiding channels 8 are shown in somewhat greater detail in Fig.3. In the present example, the light guiding channels 8 are designed as solid glass bodies preferably provided with a coating whose inside reflects light; however, they may also be designed as hollow bodies. Shown here are three arrays 7 of high-power light emitting diodes; the emission surface of each of the arrays 7 is tilted relative to the emission surfaces of each of the other arrays 7 by a tilt angle that is specific for the respective other array 7. From the tilt angle setting in interaction with the light distribution means, there results a certain margin for setting the light intensity on the light exit surface 11. Whereas the tilt angle for the middle array 7 is 0 and this array essentially illuminates the anterior teeth region due to the configuration of the light distribution means, the two outer arrays 7 are tilted relative to the middle array 7 by tilt angles of equal amounts. A steeper tilt angle would lead to increased illumination of the anterior teeth region up to the canines, due to reflections at the bounding faces; with flatter tilt angles, the light is guided back to the sides of the light distribution space and thus directed at the posterior (lateral) teeth. Via the light entry channels 8, the light is guided into a light distribution space in the attachment body 3, which is bounded by one or several bounding faces 10 and a light exit surface 11. The light exit surface 11 is arranged at a distance from the light guiding channels 8. The attachment body 3 with the light distribution means but without the light guiding channels 8 is shown in greater detail in Fig.4. This body is designed essentially as a hollow body; its walls form the bounding faces 10 and the light exit surface 11. The light exit surface 11 directs the light at the teeth. It has a curvature which essentially follows the curvature of the dentition, so that, with the apparatus taken into the mouth, the light exit surface 11 is, on average, equally distant from the teeth to be irradiated. The bounding faces 10 and the light exit surface 11 enclose a cavity 2, which is provided with entry apertures 13 for the light guiding channels 8 at its rear end. The light distribution space may also be filled with some material that is transparent to the emission wavelength ranges, but this is more complex to manufacture. The insides of the bounding faces 10, i.e. the sides looking into the light distribution space, are reflective to deflect light to the light exit surface. In this way, the light output made available by the arrays 7 can be utilized to the maximum possible extent.

14 Asclepion Laser Technologies GmbH PAT 9097/008 Thanks to the use of high-power light-emitting diodes with optimized cooling, it is possible to design the apparatus compact enough to be inserted into the mouth of a person whose teeth are to be whitened. For greatest possible efficiency it is of advantage if the emission wavelength ranges of the high-power LEDs are matched to the absorption wavelength range of a pigment added to the bleaching gel, or vice versa, so that the two ranges overlap. A high level of efficiency can be achieved if the half-peak width of the emission wavelength ranges is about 30 nm to 50 nm, and if, in addition or alternatively, also the wavelength centroids of the emission wavelength ranges are within a range of 30 nm about an absorption wavelength of the pigment contained in the bleaching gel, at which absorption is maximum. Because of this efficient utilization, a relatively low power density per unit area, namely 200 mW/cm 2 , is sufficient to activate the pigment in the bleaching gel, with the result that the bleaching gel is heated up and hydrogen peroxide contained in it is decomposed into radicals. These then get the bleaching process going; but as soon as all of the pigment is completely bleached, further gel heating stops because the power density per unit area is not sufficient any longer, especially if the emission wavelength range is selected in the green or blue portion of the colour spectrum. The bleaching process is then stopped automatically. At its rear end, the attachment body 3 further has means by which it can be joined to the basic body 1. These comprise a retaining ring 14, which may be made, e.g., of some hard rubber and has an interference (oversize) fit on a mating peripheral groove in the basic body 1 so that a force-closed connection can be made. This can, in addition, be reinforced by magnetic coupling, for example, with magnets integrated in the basic body 1 and magnetisable metal elements provided in suitable fixtures 15. At the end facing the person being treated, the attachment body 3 is further provided with connecting pieces 16 which can be plugged into corresponding apertures 17 of the adapter 4 for a force-closed connection of the attachment body with the adapter 4. The adapter 4 is shown in detail in Fig. 5; preferably, it is also made of some elastic material. The adapter 4 features adapting means with biting rests 18, on which the person being treated bites, so that a permanent, defined position of the apparatus in the mouth is maintained. The adapter 4 is further provided with an elastic joint 19, which permits adaptation to different mouth sizes within a limited scope. In this way it is also possible to use one and the same adapter 4 for different sizes of the attachment body 3. For this purpose the adapter 4 has several apertures 17 arranged side by side. The dimensions should not be too large lest the adapter in the patient's mouth become a source of intolerable irritation.

15 Asclepion Laser Technologies GmbH PAT 9097/008 The adapter 4 further has ports 20 for the connection of suction lines (not shown), through which saliva, naturally excreted during treatment, can be sucked off the person's mouth. Compared to the apparatuses known in prior art, the apparatus described herein has several advantages. Because of the efficient light utilization and efficient cooling it is possible to place it into the patient's mouth, which so far has been possible only with apparatuses intended for home use, which, however, are considerably inferior in efficiency and with which the treatment not only takes longer but also produces results that are less satisfactory. Thanks to the water cooling system, the apparatus operates with very low noise, and due to its modular design the effort involved in changing the attachment body 3 or the adapter 4 can be kept within reasonable limits. To perform the cosmetic whitening of teeth, a first step is to apply a passivating gel to the gums in order to protect it against contact with the bleaching agent. In addition, a cheek and lip spreader is inserted into the mouth to keep it open throughout the treatment and to prevent displacement of the apparatus. Next, a passive bleaching gel that contains chromophores and is photochemically activable is applied onto the teeth to be treated. The chromophores are designed to absorb light of wavelengths from a specified absorption wavelength range. Then the apparatus is inserted into the mouth, with the person to be treated biting on the biting rests 18 of the adapter 4; thus, the light exit surface 11 is fixed in such a way that it is, essentially and on average, spaced at equal distances to the teeth to be treated. As the light exit surface 11 follows the curvature of the dentition and is placed in the mouth, the lateral (posterior) teeth are also directly irradiated with light, which has not been possible so far by means of professional teeth whitening equipment in prior art. Thus, the teeth to be treated are illuminated simultaneously and essentially at equal distances from a light exit surface through which light emitted by a light source exits. The light source used consists of the arrays of high power light-emitting diodes mentioned before. The emission characteristics of the light-emitting diodes and the absorption characteristic of the chromophores are matched in such a way that the light emitted by the high-power light-emitting diodes has wavelengths from an emission wavelength range that at least partially overlaps with the absorption wavelength range, so that the light excites the chromophores. The chromophores convert the absorbed light energy into heat and thus decompose hydrogen peroxide contained in the bleaching gel. The decomposition products of the hydrogen peroxide oxidize pigments contained in the tooth, thereby bleaching it. One should take care to keep the emission characteristic of the high-power 16 Asclepion Laser Technologies GmbH PAT 9097/008 light-emitting diodes as narrow as possible, with a half-peak width not exceeding 100 nm but preferably between 30 nm and 50 nm, to achieve the completest possible absorption of the light by the chromophores. This prevents the teeth from being heated, which would be a disadvantage for any follow-up treatment. Preferably, though not exclusively, the light-emitting diodes emit light in the visible spectral range between 400 nm and 800 nm. Light of this spectral range partially penetrates the tooth. In this way, bleaching agent that has been applied to the teeth's occlusal surfaces and has, e.g., seeped into fissures, can also be activated. The treatment, which as a rule can be completed within 20 minutes for all teeth, proceeds without needing constant operator attendance. Irradiation is stopped automatically as soon as the chromophores in the bleaching gel are completely bleached. No further light is absorbed then. This can be detected, e.g., by means of sensors, so the apparatus switches off and sends a signal, which can be transmitted to the operator. This may be an optical or sound signal. As an option after subsequent cleaning, a bleaching gel having a lower concentration of hydrogen peroxide than the bleaching gel used first and also containing fluorine can be applied to the teeth, so that the teeth will be sealed under another irradiation.

17 Asclepion Laser Technologies GmbH PAT 9097/008 List of References 1 handling piece 2 hose 3 attachment body 4 adapter 5 heatexchanger 6 LED cooler 7 array of high-power light-emitting diodes 8 light guiding channels 9 light entry surface 10 bounding face 11 light exit surface 12 hollow space 13 entry aperture 14 retaining ring 15 fixtures 16 connecting piece 17 aperture 18 biting rest 19 joint 20 port Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps. The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates. The reference numerals in the following claims do not in any way limit the scope of the respective claims.

Claims (19)

1. An apparatus with which teeth in a person's mouth are irradiated for dental whitening by means of a photothermally activable bleaching gel applied to the teeth, comprising - light generating means that generate light for irradiating the teeth, - cooling means for cooling the light generating means, - means for controlling the light dose directed at the teeth, - light distribution means, through which the light generated by the light generating means can be radiated in a defined area for simultaneous irradiation of many teeth, - adapting means for positioning the apparatus with reference to the teeth, - characterized in that - the light generating means comprise at least one array (7) of high-power light-emitting diodes arranged to form an emission surface, with the high-power diodes being designed for emitting light in emission wavelength ranges with a half-peak width of up to 100 nm each, and with the emission wavelength ranges overlapping with an absorption wavelength range containing wavelengths with which the bleaching gel can be activated, and - the light distribution means comprise a light exit surface (11), from which the light is directed to the teeth, and which has a curvature that essentially follows the curvature of the dentition. so that, with the apparatus inserted in the mouth, the light exit surface (11) is spaced, on average, at equal distances to the teeth to be irradiated.

2. An apparatus as claimed in Claim 1, characterized in that the half-peak width of the emission wavelength ranges is at 30 nm to 50 nm and/or the wavelength centroid of the emission wavelength ranges lies in a range of 30 nm about the wavelength that causes maximum activation of the bleaching agent.

3. An apparatus as claimed in Claim 1 or 2, characterized in that the light generating means comprise three arrays (7) of high-power light-emitting diodes, with the emission surface of each of the arrays being tilted relative to the emission surfaces of each of the other arrays by a tilt angle that is specific for the respective other array.

4. An apparatus as claimed in any one of the previous claims, characterized in that the high power diodes emit in a wavelength range of 400 nm to 800 nm. 19 Asclepion Laser Technologies GmbH PAT 9097/008

5. An apparatus as claimed in any one of the previous claims, characterized in that several teeth of the upper or lower teeth, or both, are intended to be irradiated simultaneously, with an irradiated area of 5 cm 2 to 40 cm 2 , preferably 15 cm 2 to 20 cm2.

6. An apparatus as claimed in any one of the previous claims, characterized in that the light distribution means comprise - light guiding channels (8) corresponding to the number of arrays (7), having light entry surfaces (9) that are preferably arranged in parallel with the emission surfaces and have diameters in the order of magnitude of the arrays, and - a light distribution space interfaced with the light guiding channels that is bounded by one or several bounding faces (10) and the light exit surface (11), which is arranged at a distance from the light guiding channels (8).

7. An apparatus as claimed in Claim 6, characterized in that the bounding faces (10) are designed to be reflective for the purpose of deflecting light to the light exit surface (11), and/or that the light distribution space is designed as a hollow space (12) or else filled with a material that is transparent to the emission wavelength ranges.

8. An apparatus as claimed in Claim 6 or 7, characterized in that, for the purpose of deflecting light to the light exit surface (11), the bounding faces (10) are designed in such a way that light reflected by the tooth surfaces is completely or partially directed back toward the tooth surface

9. An apparatus as claimed in any one of the previous claims, characterized in that the cooling means comprise a water cooling system with at least one inlet and at least one outlet.

10. An apparatus as claimed in any one of the previous claims, characterized in that the adapting means are provided with biting rests (18) on which the person bites during treatment so that a specified position of the apparatus in the mouth is maintained for the duration of the treatment.

11. An apparatus as claimed in any one of the previous claims, characterized in that the adapting means are provided with ports (20) for connecting suction lines for sucking off saliva. 20 Asclepion Laser Technologies GmbH PAT 9097/008

12. An apparatus as claimed in any one of the previous claims, characterized in that the light output, on a time average, can be varied by means of pulse width modulation in order to adapt the light dose in that way.

13. An apparatus as claimed in any one of the previous claims, characterized in that the light dose can be set by varying the irradiation period

14. An apparatus as claimed in any one of the previous claims, characterized in that it is built up of modules that can be taken apart and assembled by an operator without any mechanical aids, comprising (i) a basic body designed as a handling piece (1) comprising the light generating means and the cooling means, (ii) an attachment body (3) designed as an attachment to the basic body and comprising at least part of the light distribution means, and (iii) an adapter (4) comprising the adapting means

15. A method for the cosmetic whitening of teeth, in which - a passive bleaching gel that contains chromophores and is photochemically activable is applied to the teeth to be treated, with the chromophores absorbing light of wavelengths from an absorption wavelength range, - the teeth to be treated are illuminated simultaneously and essentially at equal distances from a light exit surface, through which light emitted by a light source exits, the light having wavelengths from an emission wavelength range the half-peak width of which is not greater than 100 nm and which overlaps at least partially with the absorption wavelength range, - so that the tight excites the chromophores, which convert the absorbed energy into heat and thus decompose H 2 0 2 contained in the bleaching gel, with the decomposition products oxidizing pigments contained in the tooth and thus bleaching the tooth.

16. A method as claimed in Claim 15, characterized in that, before the application of the bleaching gel, a passivating gel is applied to the gums and/or a cheek and lip spreader is inserted into the mouth to keep it permanently open during treatment.

17. A method as claimed in Claim 15 or 16, characterized in that, after the irradiation and a cleaning process, another bleaching gel is applied to the teeth that has a lower concentration of H 2 0 2 than that of the bleaching gel used first, and also has some fluorine content, so that the teeth will be sealed during another irradiation. 21 Asclepion Laser Technologies GmbH PAT 9097/008

18. A method as claimed in any one of Claims 15 to 17, characterized in that the irradiation is stopped automatically as soon as the chromophores in the bleaching gel are completely bleached.

19. A method as claimed in any one of Claims 15 to 18, characterized in that the activation of the bleaching agent is stopped automatically provided that the chromophores in the bleaching gel are completely bleached.