Abstract:
A light application unit for a combined photodynamic diagnosis and photodynamic therapy of non-malignant diseases of a parodontium and a tooth of a living being having administered a pharmaceutical preparation allowing said photodynamic diagnosis and said photodynamic therapy comprises a light source, a focusing unit for focusing light emitted by said light source, at least one element arrangeable in a light beam path of said light, and at least one wave guide for transmitting said light from said light source to a distal emitting end, said wave guide is configured rigidly in at least a distal handling end section thereof and being curved in a distal end section.

Description:
[0001]    This is a continuation of pending International Application PCT/EP99/04242 filed on Jun. 18, 1999 which designates the U.S.  
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    The invention relates to a light application unit for combined photodynamic diagnosis (PDD) and/or photodynamic therapy (PDT) of diseases of the parodontium and the teeth.  
           [0003]    The invention further relates to the use of 5-amino levulinic acid or a derivative thereof for producing a pharmaceutical preparation for photodynamic diagnosis and/or photodynamic therapy of diseases of the parodontium and the teeth.  
           [0004]    The invention still further relates to an apparatus for applying the pharmaceutical preparation to the parodontium.  
           [0005]    The use of 5-amino levulinic acid for photodynamic diagnosis (PDD) for the detection of bladder carcinoma is known from the article “Endo World” URO No. 17/1-D, 1997 of Karl Storz GmbH &amp; Co., Tuttlingen, Germany and Karl Storz Endoscopy, USA. As is disclosed there, certain photo-sensitizers together with a special light can be used to detect malignant or other types of tissue (photodynamic diagnosis, PDD) and to destroy such tissue (photodynamic therapy, PDT). The phenomenon is observed in malignant tissue, healthy tissue does not show this phenomenon.  
           [0006]    This phenomenon is based on the properties of 5-amino levulinic acid and consequently the induced formation of photo-sensitive protoporphyrine IX (PPIX). 5-amino levulinic acid is a precursor of the photo-sensitizer protoporphyrine IX, so that the amount of protoporphyrine IX is increased by administration of this precursor. The precursor does not become enriched and transform into PPIX in healthy tissue.  
           [0007]    The precursor to the photo-sensitizer is applied by installation, flushing, inhalation, orally or topically. This tissue can be excited to become fluorescent with a corresponding light application system and this fluorescence is observed, which makes possible the photodynamic diagnosis (PDD). Furthermore it has been found that a photo-toxic effect occurs induced by PPIX, which opens up the possibility of photodynamic therapy (PDT).  
           [0008]    The German patent applications DE 197 21 454 and DE 196 39 653 disclose apparatus for photodynamic diagnosis using fluorescence induced by 5-amino levulinic acid in biological tissue in vivo.  
           [0009]    The object of the present invention is to expand the utilization of 5-amino levulinic acid and optionally derivatives thereof and to provide the corresponding apparatus.  
         SUMMARY OF THE INVENTION  
         [0010]    According to the present invention, the object is achieved in that 5-amino levulinic acid or a derivative thereof is used for preparing a pharmaceutical preparation for photodynamic diagnosis and/or photodynamic therapy of non-malignant diseases of the parodontium (tooth support system) and the teeth.  
           [0011]    The object is further achieved with a light application unit for combined photodynamic diagnosis and/or photodynamic therapy of non-malignant diseases of the parodontium and the teeth making use of such pharmaceutical preparations. The application unit comprises a light source for generating light at least in the visible region, a focusing unit for focusing the light and at least one wave guide for transmitting the light from the light source to a distal, emitting end of the wave guide. The application unit further comprises at least one element disposed in the light beam with which the spectral properties of the light source can be altered. The wave guide is formed to be rigid at least in a distal region for handling and comprises a curved section at the distal end section.  
           [0012]    An apparatus for applying the pharmaceutical preparation comprises at least two chambers, one chamber containing the 5-amino levulinic acid or a derivative thereof and the other second chamber a carrier substance for the compounds contained in the first chamber. Further, a mechanism is provided for connecting the two chambers and mixing the compounds contained in the two chambers shortly before application. A canula is also provided for supplying the so-formed pharmaceutical preparation to a tissue region of the parodontium or to the teeth.  
           [0013]    Dental diseases, such as caries or parodontopathies, represent some of the most widely known diseases. Current treatment methods of parodontitis are based on the one hand on an instrumental, purely mechanical or ultrasound cleaning of the gums or the edges of the gums or the surface of the teeth or pockets in the gums. On the other hand, methods are used based on washing or purging the inflamed tissue with anti-bacterial chemical substances, with the purpose of destroying the bacteria which cause the inflammation.  
           [0014]    Affected or non-affected tissue areas are sometimes only difficult to differentiate. For serious inflammation or rapidly developing parodontopathies, a high systemic dosis of antibiotics is the only possibility of containing the disease, because the deeper lying bacteria in the parodontal soft tissue cannot be or only be partially inactivated by mechanical or ultrasound cleaning and flushing. Such antibiotic treatment however have a number of side effects, i.e. destruction of the intestinal flora or development of resistance, so that these therapies are not satisfactory.  
           [0015]    Caries are also caused by bacteria, mostly as the consequence of tooth demineralization from monosaccharides.  
           [0016]    It has now surprisingly been found that both a photodynamic diagnosis and a photodynamic therapy of non-malignant diseases of the parodontium or the teeth can be carried out successfully using 5-amino levulinic acid or derivatives thereof. This is surprising because a number of different agents or germs are responsible for diseases of the parodontium or the teeth. Even so, a reliable photodynamic diagnosis can be carried out using 5-amino levulinic acid or derivatives thereof and of even greater significance, a successful photodynamic therapy can be carried out.  
           [0017]    By configuring the light application unit with the above-mentioned features, the light can be directly applied to the parodontium or the teeth via the curved distal section of the wave guide, in particular also to the gum pockets between the gums and the teeth which arise in such diseases of the parodontium.  
           [0018]    The 5-amino levulinic acid or derivatives thereof can be applied, as is known, orally, parenteral, systemic, however also topically, where the gum pockets can be used to apply the pharmaceutical preparation. Namely, the preparation can remain there, so that the 5-amino levulinic acid or its derivatives can penetrate into the corresponding regions of the tissue. The apparatus for application thus comprises a suitable canula for this purpose.  
           [0019]    In further embodiments of the present invention, the 5-amino levulinic acid or one of its derivatives is used for producing a pharmaceutical preparation for photodynamic diagnosis and/or photodynamic therapy of parodontitis, parodontopathies, caries, surface bacteria on the tissue of the parodontium or bacteria located in the tissue of the parodontium. These are the most frequently occurring indications for afflictions of the teeth, which all can be diagnosed and also treated therapeutically using 5-amino levulinic acid or one of its derivatives.  
           [0020]    Parodontopathies are inflammatory (&gt;90%) degenerative (up to 4%) and hyperplastic (about 1%) diseases of the marginal parodontium multifactorial aethiology. Parodontitis is understood as an inflammation of the parodontium. Parodontosis is a degenerative form of parodontopathy with shrinkage of the marginal parodontium caused by primary regressive, noninflammatory processes under the formation of pockets and the loosening of the teeth.  
           [0021]    Depending on the progression and type of bacterial affliction, the bacteria is located on the surface of the tissue of the parodontium or has penetrated into the tissue. The photodynamic diagnosis now possible allows a localization of the afflicted areas in a first step and thus opens up thus the possibility of subsequently treating these areas in a direct photodynamic therapy.  
           [0022]    In a further configuration of the present invention, the 5-amino levulinic acid or one of its derivatives is used in a carrier substance, selected from the group consisting of hydrogels, in particular alginate gel, an oil and water emulsion or a buffer solution having a pH of 5 to 6.  
           [0023]    These substances are very compatible and allow a topical application, such that the precursor of the photo-sensitizer can be held on location with the carrier substance sufficiently long, where it can then diffuse into the tissue or in the afflicted area. This procedure may require several hours, so that the danger exists that the precursor is washed away by saliva in the mouth. The carrier substance in the form of the above embodiment prevents such a washing by saliva. An oral administration is also possible or a systemic administration, which makes a local application of the precursor with the carrier unnecessary.  
           [0024]    In a further embodiment of the present invention, an ester is employed as a derivative of the 5-amino levulinic acid. The use of esters has the advantage that they are chemically more stable than the 5-amino levulinic acid itself. It should be considered that not only saliva but also various enzymes are always present in the mouth, which could lead to rapid dissociation reactions of the 5-amino levulinic acid. A further advantage of an ester is that it provides a substantially higher penetration into the tissue due to better lipophylic properties than does the 5-amino levulinic acid. In the area of dental care, this offers the possibility of a rapid diagnosis and/or therapy after application of the precursor to the photosensitizer. For example, the patient can be diagnosed after application within a relatively short waiting time. In addition, substantially lower concentrations of esters can be used because of the faster penetration, so that possible side effects can be reduced or suppressed. For example, where an acid concentration of 160-200 mmol would be used, in comparison a concentration of 4-16 mmol of hexyl ester would be sufficient.  
           [0025]    A further more important advantage of esters, in particular methyl ester, ethyl ester and particularly significant hexyl ester, is that they produce a substantially stronger and more homogeneous fluorescence. For example, the hexyl ester of 5-amino levulinic acid causes a fluorescence 50 times stronger than the acid. In addition, the hexyl ester has a higher tissue penetration compared to the acid by a factor of 2. This then opens the way in the special area of dental care that a patient comes into the dental clinic, the pharmaceutical preparation containing the precursor for the photo-sensitizer is applied and the diagnosis is made or a therapy is begun after only a short time. This also considerably simplifies the practical use or the acceptance by patients, the so-called compliance.  
           [0026]    In a further embodiment of the present invention, the carrier substance and the precursor of the photo-sensitizer are mixed shortly before application. This feature is of advantage especially when the ester is used as a chemically stable substance. The two components, precursor as such and the carrier substance, can be stablely stored over longer periods and a suitable mixture is prepared shortly before application, which is then applied.  
           [0027]    The apparatus for administration comprises two chambers for this purpose, in which these substances are received, and a mechanism for mixing the two substances just before application. The mixture can then be supplied directly to the location on the parodontium or on the teeth via the canula.  
           [0028]    The precursor, e.g. 5-amino levulinic acid, and the carrier substance, e.g. alginate, can be contained as powder in one chamber. A buffer solution can be contained in the second chamber. The pharmaceutical preparation resulting from mixing has the form of a gel.  
           [0029]    An advantageous embodiment of the light application unit comprises two wave guides. The feature has a considerable advantage that one wave guide can be inserted into the tooth pocket between the tooth and the gum tissue and a further guide can be placed from the outside onto the gum. The excitation light can be specifically directed from two sides onto the afflicted area of the gum. In particular, when the bacteria has already deeply penetrated into the gum, the two-sided irradiation of the afflicted area is optimal, in particular for photodynamic therapy, so that successful therapy can be achieved after short intensive irradiation times.  
           [0030]    In a further embodiment of the present invention, the two wave guides run adjacently, wherein an emitting end face of one wave guide extends beyond the emitting end face of the other guide in distal direction. This embodiment has the advantage that the further extending wave guide can initially be directly inserted into a pocket between the gum and the tooth and then the other wave guide can be placed from the outside onto the gum. Or, if the pocket is not deep, precisely the opposite. The further extending guide can be placed over a large surface area on the outside of the gum and the shorter guide inserted only into the relatively small pocket.  
           [0031]    In a further embodiment of the present invention, one wave guide is axially shiftable relative to the other wave guide. The feature has the advantage that the mentioned handling is improved in its variability. This allows the dentist an optimal adaptation to the respective conditions and an optimal adaptation to the geometry to the parodontium of the patient, in particular in anomalous situations and problematic dispositions of the teeth.  
           [0032]    In a further embodiment of the present invention, the shiftable wave guide is fed through a tubular channel. The feature has the advantage that the shiftable and sometimes relatively thin wave guide can be exactly guided over a long distance, whose movement can be reliably controlled.  
           [0033]    In a further embodiment of the present invention, the tubular channel is configured for supplying media. This feature has the considerable advantage that flushing or suctioning or relieving a gas can be performed through the channel to support the therapy. Cool compressed air contributes to the subjective relief of pain in PDT. An acceleration of the PDT effect is produced by supplying oxygen. It is also possible to administer the pharmaceutical preparation containing the precursor through this channel.  
           [0034]    In a further embodiment of the present invention, the element arranged in the light beam is a filter. In particular, various filters can be disposed in the light path. One of the filters transmits in the region of the excitation spectrum of the employed photo-sensitizer, thus induces fluorescence excitation in the inflamed tissue for photodynamic diagnosis. When the second filter transmits at least in the region of fluorescence emission, it then is used in photodynamic therapy of the tissue, especially in the region of the inflamed tissue.  
           [0035]    In a further embodiment of the present invention, a third filter is provided which can be mounted in the optical path of the operator to the location on the parodontium being treated, which blocks fluorescence excitation light, however passes the fluorescence emissions. This feature has the advantage that the operating person can simply detect the fluorescence which characterizes the tissue.  
           [0036]    In a further embodiment of the present invention, a wave guide is configured as a plurality of light transmitting individual fibers. The feature has the advantage that the light can be transmitted through the curvature without problem. The active diameter of the individual fibers lies in the range of 20 to 400 μm. By melt-fusing the individual fibers to a type of glass rod, a sufficiently rigid structure is formed, so that no additional mantle is necessary. In addition, a sufficient biocompatibility is achieved and the structure can be sterilized for example in an autoclave.  
           [0037]    In a further embodiment of the present invention, the wave guide consists of a single light transmitting fiber. This feature has advantages in construction. Optionally, for handling purposes this wave guide must be reinforced with a mantle tube to achieve sufficient rigidity.  
           [0038]    The individual fiber has an active diameter in the range of about 200 to about 2000 μm. This small calibration wave guide has the advantage that irradiation can take place directly in the tooth pocket. The optical fiber can be a glass fiber, synthetic fiber, quartz fiber or also a liquid wave guide.  
           [0039]    In a further embodiment of the present invention, a further wave guide is provided which transmits light from the irradiated area in the proximal direction. This further wave guide can be part of a multi-fiber wave guide, which actually transmits light in the distal direction. This feature has the advantage that the return light can be used for detection of the fluorescence and thus also used for dosing in the PDT procedure. The determination of light intensity decay from the photo-sensitizer can be used in the PDD mode for dosing or for time control in the PDT procedure.  
           [0040]    Depending on the configuration of the wave guide, not only light but also an entire image can be returned with appropriate individual fibers, which is then supplied to a image detection or image processing system, for example a miniaturized CCD camera.  
           [0041]    In a further embodiment of the present invention, the light guided from the proximal end by the further wave guide is supplied to an evaluation unit. The evaluation unit is preferably a spectral analysis unit, a camera or a spectrally selective, sensitive photo element. This feature has the advantage that the returned light or image can be detected and quantified by a corresponding evaluation unit and for example the local information on the light decay process can be monitored. With this, the photodynamic treatment can be controlled and calculated.  
           [0042]    In a further embodiment of the present invention, the wave guide is provided with a spacer at the distal end. The feature has the advantage that a constant radiation intensity can be achieved, thus providing a better dosing in the photodynamic therapy.  
           [0043]    In a further embodiment of the present invention, the wave guide comprises a diffuser at the distal end. The diffuser can be configured as a spherical convex expansion of the distal end of the wave guide, or the diffuser can be formed as a light permeable material with properties for controlling optical transmission. Alternatively, the diffuser can be configured as an inflatable balloon, arranged at the distal end of the wave guide, which can be inflated via a channel.  
           [0044]    This feature has the advantage that the relatively colminated light directly emitted from the relatively small face of the end of the wave guide can be uniformly distributed over a larger area, so that uniform treatment conditions are established for example in the entire tooth pocket in which such a wave guide is inserted.  
           [0045]    In a further embodiment of the present invention, an ultrasound transmission element is provided through which ultrasound can be transmitted to the distal end. The feature has the advantage that the parallel application of ultrasound (e.g. 20 KHz to 3 MHz) can lead to an enhancement of the effect in photodynamic therapy and therefore to a more rapid inactivation of bacteria. It has been found that the penetration depth of the precursor of the photo-sensitizer is increased with the ultrasound effect and thus the desired depth effect in the treatment is improved.  
           [0046]    In a further embodiment of the present invention, an ultrasound excitation unit is provided which is coupled to the ultrasound element. The feature has the advantage that the light application unit itself is also designed for ultrasound generation.  
           [0047]    In a further embodiment of the present invention, the wave guide is configured as an ultrasound transmission element. The feature has the advantage that both light and ultrasound are transmitted in constructively simple manner, namely with one and the same element, namely the wave guide. For example, a piezo-electric drive can be attached to the wave guide, in particular a quartz wave guide.  
           [0048]    In a further embodiment of the present invention, the light source has a large blue component in the range of about 400 nm (±20 nm). The feature has the advantage that one lies in the excitation range for fluorescence of the protoporphyrine IX produced by the precursor, thus one is especially adapted to this range.  
           [0049]    In a further embodiment of the present invention, the light source comprises a xenon discharge lamp. The feature has the advantage that the light source provides a large blue component, a high radiation intensity and a relatively small focal spot. With this, a greater light penetration depth is possible in therapy.  
           [0050]    In a further embodiment of the present invention, the light application unit comprises a housing with a pistol-like handle, from which a tubular section extends in which the wave guide is disposed. The feature has the advantage that handling is possible with one hand in ergonomic manner.  
           [0051]    In a further embodiment of the present invention, the tubular section can be coupled to the housing and is removable from the housing. The feature has the advantage that different wave guides, i.e. different dimensions such as diameter, length and curvature can be simply coupled depending on the application.  
           [0052]    An additional advantage is when the wave guide and the tubular section are formed to be conical in at least one section, namely to the distal end, where a tampered distal tip of the wave guide is formed, which can be better guided to the parodontium. The cone also causes a type of focusing and an increased distal irradiation angle with the effect of a more homogeneous illumination.  
           [0053]    In a further embodiment of the present invention, the third filter is mounted on the tube section and preferably arranged there to be shiftable and pivotal. The feature has the advantage that a simple and flexible positioning of the observation filter can be carried out to provide favorable observation and visual conditions for the respective handling position.  
           [0054]    In a further embodiment of the present invention, a canula is provided through which a pharmaceutical preparation can be administered. The feature has the advantage that the unit provided for light application is configured as a multi-functional device, i.e. can also be employed for administration of the pharmaceutical preparation.  
           [0055]    It will be understood that the above-mentioned features and those to be described below are applicable not only in the given combinations, but also in other combinations or taken alone without departing from the scope of the present invention.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0056]    The invention is described in more detail below in terms of selected embodiments in conjunction with the appended drawings.  
         [0057]    [0057]FIG. 1 shows a highly schematical side view of a light application unit according to the invention.  
         [0058]    [0058]FIG. 2 shows a greatly simplified schematic side view of a further variation with an ultrasound generation unit.  
         [0059]    [0059]FIG. 3 shows a variation of a removable tube section of the light application unit.  
         [0060]    [0060]FIG. 4 shows an illustration corresponding to that of FIG. 3 of a further variation of a tube section for applying the pharmaceutical preparation.  
         [0061]    [0061]FIG. 5 shows a light application unit during a photodynamic therapy on a parodontium.  
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0062]    A light application unit is shown in FIG. 1 and indicated with the numeral  10 . The light application unit  10  comprises a housing  12  from which a pistol-like handle  14  projects at an angle at the proximal end. A tube section  16  extends from the housing  12  at the end opposing the handle  16 , which goes over into a curved section  18  at the distal end, which is slightly conically tampered toward its distal end  19 .  
         [0063]    The housing  12  includes a light source  20  and a focusing unit  22  which focuses light from the light source  20  onto the proximal end  21  of a first wave guide  23 . Depending on the configuration of the light application unit  10 , the light source  20  is powered by an energy source arranged in the housing  12  or is connected to an external energy source via a cable.  
         [0064]    The first wave guide  23  itself is a bundled glass fiber formed of a plurality of individual glass fibers adhered to one another. The bundled glass fibers form a rigid body in a distal region for handling, said region extends within the tube section. The first wave guide  23  fills the inner space of the tube section  16 . The conical tamper towards the distal end  19  for emitting excitation light provides a type of focusing and also an increase in the irradiation angle toward the distal end, which leads to a more homogeneous illumination.  
         [0065]    A second wave guide  24  is arranged in a channel  26  provided in the interior of the tube section  16 . The second wave guide  24  can also be composed of a rigid but elastic bundle of individual fibers or be one individual rigid but elastic fiber. A connector  28  extends from the channel  26  through which the channel  26  can be supplied with further media for example oxygen or a fluid. These media are passed through the free lumen between the second wave guide  24  and the inner side of the channel  26 . A proximal end  27  of the second wave guide  24  lies in the focal range of the focusing unit and light is introduced there into this wave guide.  
         [0066]    The second wave guide  24  is provided with a hump  30  in the straight section of the tube section  16 , under which a compression spring  32  is arranged. The top of the hump  30  lies at the underside of a button  34 , which is disposed in a housing, not described in detail here. The opposite side of the spring  32  is supported on the outer side of the tube section  16 .  
         [0067]    At the distal end, the second wave guide  24  extends beyond the channel  26 . Light is emitted from the outer end  25  of the second wave guide  24 , which has been introduced into the proximal end of the second wave guide  24  via the focusing unit  22 . When the button  34  is depressed, the hump  30  becomes flatter and consequently the second wave guide  24  is pushed further out of the tube section  16 . When the button  34  is released, the spring  32  urges the button  34  upwardly and the second wave guide  24  is retracted.  
         [0068]    A coupling is indicated schematically with the numeral  36  through which the tube section  16  is coupled to the housing  12 . The coupling  36  normally consists of a bayonet coupling. Thus it is possible to remove the tube section  16  from the housing  12  and to recouple this section or another tube section in a simple release and coupling procedure, as will be described below. The coupling can also be provided as a plug coupling or as a screw coupling.  
         [0069]    Elements  38  are arranged in the housing which can be disposed in the beam path between the light source  20  and the wave guides  23 ,  24 . These elements comprise a first filter  40  as well as a second filter  42  which can be rotated into and out of the beam path by a mechanism, not discussed in more detail.  
         [0070]    The first filter  40  is configured such that it transmits in the region of the excitation spectrum of the photo-sensitizer. The second filter  42  is configured such that it transmits in the region of fluorescence emission of the photo-sensitizer. In the illustrated mode, the first filter  40  is in place and passes substantially only the fluorescence excitation light. In this position, the light application unit  10  operates particularly for photodynamic diagnosis.  
         [0071]    A third filter  46  is arranged on the underside in the illustration of FIG. 1 on the outside of the tube section  16  via a support  44 . The third filter  46  is pivotal and also shiftable in the longitudinal direction of the tube section  16  via the support  44 .  
         [0072]    This third filter  46  is to be placed between the eye  48  of the person handling the light application unit  10  and the area irradiated by the wave guide  23 . This third filter  46  is configured such that the excitation light passing through the first filter  40  and through the wave guide  23  is blocked, the fluorescence light however is transmitted through the filter  46 , where a detection of the fluorescence of the irradiated area characterizing the tissue is possible.  
         [0073]    In the variation of the light application unit illustrated in FIG. 2, the same reference numerals are used for the same components as in FIG. 1. An ultrasound excitation unit  50  is provided at the proximal end region of the second wave guide  24 , which surrounds this part of the wave guide  24 . The wave guide  24  in this case provides light transmission from the the light source  20 , and also transmission of ultrasound coupled into the proximal end of the wave guide  24 . In this case, the second wave guide  24  in advantageous manner consists of quartz glass.  
         [0074]    As mentioned above, the tube section  16  is removable in a simple procedure from the housing  12  via the coupling  36  and can be reconnected thereto. In the variation of the tube section  16  shown in FIG. 3, a diffuser  52  is arranged at the outer distal end of the second wave guide  24 . This diffuser  52  provides a uniform distribution of the light exiting from the relatively small end side surface, so that a uniform radiation is achieved about a large region.  
         [0075]    When the diffuser  52  is formed to be relatively stiff, it can also serve as a spacer  54 . In one embodiment, the diffuser  52  is formed as a balloon  53  in communication with the channel  26  so that a medium can be supplied to inflate the balloon, thereby generating a relatively large radiation surface on site.  
         [0076]    In the variation in FIG. 4, the tube section  16  comprises a canula  56  at its center being connected at the proximal end with a container  58 . The container  58  comprises a first chamber  62  and a second chamber  64 . 5-amino levulinic acid or one of its derivatives is contained in the first chamber  62 , for example hexyl ester and the alginate gel, each in powder form. A carrier substance, for example a buffer solution is contained in the second chamber  64 . A mechanism  65  serves to mix the substances contained in the two chambers  62 ,  64  and then inject the mixture into the canula  56 . The buffer solution provides a pH of 5-6. The alginate gel represents a carrier substance after mixing.  
         [0077]    When the tube section  16  illustrated in FIG. 4 is coupled to the housing  12 , the light application unit  10  can also be used as an apparatus  60  for administering the photo-sensitizer. If this is not desired, this apparatus can be configured as a separate apparatus for administering the pharmaceutical preparation. The mechanism  65  then is formed for example as a plunger which destroys the separating wall  63  between the chamber  62 ,  63  and mixes their contents and then injects the same through the canula  56 .  
         [0078]    A use of a light application unit  10  for therapy is indicated in FIG. 5, where a variation is shown with the first wave guide  23  configured as a multi-fiber wave guide with a part, i.e. a few optical fibers are used to transmit light from the distal end to the proximal end. This wave guide  66  is connected to an evaluation unit  74  arranged in the handle  14 , which can also be arranged externally, where a corresponding light transmitting connection can be provided.  
         [0079]    A portion of the human parodontium  80  is shown in FIG. 5. It includes a tooth  82  having a nerve  86  located in the interior  84  of the tooth. The lower end of the tooth  82  sits in the jawbone  88  and is surrounded by the gums  90 . In the course of a disease, a pocket  92  has formed between the outer side of the tooth  82  and the gums  90 .  
         [0080]    A mixture of 5-amino levuline acid hexyl ester and alginate gel has been previously applied into this pocket  92  and the waiting time is about two hours. The alginate gel resulted from the alginate powder and the buffer solution. In the meantime, the precursor of the photo-sensitizer has penetrated into the interior region  94  of the gums due to the high penetration speed and the high penetration depth of the ester. This has led to an accumulation of the photo-sensitizer protoporphyrine IX in the afflicted region.  
         [0081]    The light application unit  10  is then placed against the parodontium  80 , such that the shiftable second wave guide  24  or its distal end extending from the tube section  16  is inserted into the pocket  92 . This procedure is simplified through the shifting capability. The first wave guide  23  directs light to the outer side of the gums  90 . Subsequently, the light source  20  is activated, which preferably is a xenon discharge lamp emitting in the blue region. The second filter  42  transmits in the region of this excitation spectrum of the photo-sensitizer and this light is passed via the first wave guide  23  and the second wave guide  24  to the parodontium  80 . The interior region  94  undergoes an optimal therapeutic treatment due to the two-sided radiation. A few of the wave guides  66  of the first wave guide  23  transmits fluorescence light emitted by the photo-sensitizer from the distal end back to the proximal end. These wave guides  66  are connected to an evaluation unit  74 .  
         [0082]    During the therapy, this evaluation unit  74  detects the decay of fluorescence emission and thus the course of the destruction of the afflicted tissue through the photodynamic therapy. Filters are provided to filter out the excitation light which is also returned, the filters only transmitting fluorescence light.  
         [0083]    In FIG. 5, a region of the tooth  82  afflicted with caries is indicated with the numeral  96 . As can be seen, this region  96  can also be diagnosed as well as subjected to therapy with the light application unit  10 . The described light application unit is also utilizable in principle for other photo-sensitizers which show the same phenomenon on the parodontium and the teeth.