Abstract:
Oral hygiene apparatus for destroying sensitized oral bacteria, comprising: 
     an incoherent light source; and 
     a light directing member, adapted for directing light from light source and onto at least part of a surface of at least one tooth within an oral cavity.

Description:
RELATED APPLICATION 
     This application is a continuation of PCT Application No. PCT/IL99/00030, filed Jan. 17, 1999, which designated the US. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to the field of oral hygiene and more particularly to devices and methods for selective photo-thermal destruction of oral bacteria. 
     BACKGROUND OF THE INVENTION 
     Various forms of periodontal disease in humans are caused by oral bacteria. Oral bacteria create plaque, a sticky, colorless film of bacteria that constantly forms on the surface of teeth and may lead to periodontal diseases. Plaque, if allowed to stay on the tooth&#39;s surface will eventually lead to gingival irritation also known as gingivitis, which may be accompanied by gum swelling, bleeding and by fibrous enlargement of the gingiva. 
     The plaque forming bacteria create toxins which irritate the gums and result in breakdown of the attachment of gum tissues to teeth. Over time, these toxins can destroy gum tissues, allowing the infection to progress to bone loss. 
     Plaque that is not timely removed can combine with other materials and harden into a rough, porous deposit called calculus or scale. If the plaque and scale builds up and are not removed by professional cleaning, the gums will start to move away from the teeth. This is the start of periodontal gum disease. Pockets form between the teeth and gums. If the gums are allowed deteriorate further, the gums recede and the bone and other supporting tissues around the teeth start deteriorating and the teeth may eventually become loose. 
     Calculus on the tooth&#39;s surface, above the gum-line, does not contribute to periodontal diseases. However, calculus on the root surface, below the gums, makes removal of new plaque and bacteria more difficult. Unlike plaque, which can be removed by tooth brushing, calculus must be removed by a dentist or dental hygienist. 
     Prevention and treatment of periodontal gum disease must be based to a large extent on the control of bacterial plaque. This requires a considerable effort on the patient&#39;s part. In addition, routine professional oral hygiene techniques, through professional cleaning of the teeth and frequent reassessment of the patient&#39;s periodontal tissues to provide early detection and treatment of new or reoccurring abnormalities or of destruction of supporting periodontal tissues. 
     By far the most important aspect of controlling periodontal diseases is the practicing of daily oral hygiene techniques that needs to be initiated at pre-adolescence and carried on for the rest of the patient&#39;s life. Daily maintenance schedules ideally require full patient&#39;s compliance with instructions and an ideal tooth cleaning technique. Far too often, token attempts at dental bacterial control are inadequate and unsuccessful in one or more sites of the dentition leading to inflammatory changes at these sites and further loss of periodontal attachment. 
     Products sold for the prevention of periodontal diseases include toothpaste, mouth rinsing solutions, Manual toothbrushes, dental floss and powered toothbrushes and oral irrigators. 
     Chemical antibacterial agents are increasingly being used in prophylactic and therapeutic regimes for plaque-related diseases. As these agents can be rendered ineffective by the development of resistance in the target organisms there is a need to develop alternative anti-microbial treatments. Light from high-power lasers is known to be bactericidal and investigations have shown that it is effective against organisms implicated in carries and inflammatory periodontal diseases. However, the adverse effects of such light on dental hard tissues argues against its use solely as an antibacterial agent. 
     U.S. Pat. No. 4,784,135 to Blum et al. discloses a method for treating tooth decay, by far UV radiation generated by an argon fluoride (ArF) laser, which is based on ablative photo-decomposition of organic biological material. No staining of the material is disclosed. 
     U.S. Pat. No. 5,658,148 to Neuberger et al. discloses a method and a device for cleaning teeth by a low power diode laser applying the principle of photodynamic therapy. This method is based on using a photosensitizer compound. The photosensitizer compound produces singlet oxygen upon irradiation by the laser light. The singlet oxygen thus produced destroys oral bacteria. 
     U.S. Pat. No. 5,611,793 to Wilson discloses a method of disinfecting or sterilizing tissues, wounds or lesions of the oral cavity. The method comprises applying a photosensitizing compound to the tissues and irradiating the tissues with laser light at a wavelength absorbed by the photosensitizing compound. The helium-neon laser or the gallium aluminum arsenide diode laser used by Wilson are expensive and may not be suitable for home use. 
     There is a widely recognized need for a simple, inexpensive and selective method for killing oral bacteria which is suitable for home use. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of some preferred embodiments of the present invention to provide a device and method for destroying oral bacteria. 
     An aspect of some preferred embodiments of the present invention involves the pre-staining of the bacteria using bacterial selective dyes or stains. 
     An aspect of some preferred embodiments of the present invention involves the use of incoherent broad band light for irradiating the preferably pre-stained bacteria. 
     As aspect of some preferred embodiments of the invention involves a dentifrice containing a bacterial stain. This dentifrice is preferably used to stain the bacteria during normal brushing so that they can be destroyed. 
     There is thus provided, in accordance with a preferred embodiment of the invention, oral hygiene apparatus for destroying sensitized oral bacteria, comprising: 
     an incoherent light source; and 
     a light directing member, adapted for directing light from said light source onto at least part of a surface of at least one tooth within an oral cavity. 
     Preferably, the light directing member comprises a light guide removably coupled to a housing containing the light source. 
     Preferably, the light directing member comprises a reflective layer coating light passage. Preferably, the reflective layer coated light passage comprises a hollow passage whose radial extent is defined by a light reflecting surface. 
     In a preferred embodiment of the invention, the light guide comprises an elongated member, having at least one peripheral surface uncoated by a reflecting material, said light guide directing light entering it at one end by internal reflection from said at least one peripheral surface to a second end. 
     In a preferred embodiment of the invention, the incoherent light source includes a lamp, a reflector which directs at least part of the light produced by said lamp to said light directing member. Preferably, the lamp is an arc discharge lamp or a flash lamp. Preferably, reflector is a parabolic reflector, a spherical reflector, a quasi-spherical reflector or an ellipsoidal reflector. 
     In a preferred embodiment of the invention the light source further includes at lease one lens disposed between said flash lamp and said light directing member for directing light onto said light directing member. 
     Preferably, the apparatus includes at least one filter which passes light to which said bacteria has been sensitized. Preferably, the at least one filter substantially blocks light at wavelengths at which oxyhemoglobin absorbs substantial energy. 
     In a preferred embodiment of the invention, the light is directed to said tooth surface from an exit port of the light directing member. 
     In a preferred embodiment of the invention, the apparatus a tooth brush like member adjacent to or surrounding said exit port. Preferably, the tooth brush like member comprises a plurality of bristle like members arranged peripherally around said exit port to enable said light exiting said port to reach said at least part of a surface of at least one tooth within said oral cavity while teeth are being brushed by said tooth brush like member. 
     In a preferred embodiment of the invention the apparatus includes a plurality of bristles coupled to said light directing member such that a first end of said plurality of bristles is optically coupled to said second end of said light guide and a second end of each of said plurality of bristles extends out of said terminal part for directing at least part of said light onto said at least part of said surface of said at least one tooth within said oral cavity. 
     In a preferred embodiment of the invention the apparatus includes a dental floss like member optically coupled to said incoherent light source which member emits said light along its length. 
     In a preferred embodiment of the invention the apparatus includes a power source that powers the incoherent light source and a controller that controls said light source. Preferably, the power source is a battery and said incoherent light source, said battery and said controller are mounted within a common housing. 
     In a preferred embodiment of the invention, the light directing member is easily separated from the light source and wherein the light directing member is disposable. 
     In a preferred embodiment of the invention, the light source is a pulsed light source. 
     There is further provided, in accordance with a preferred embodiment of the invention, a method for selective photothermal destruction of bacteria, the method comprising: 
     selectively staining at least some bacteria by application of a suitable selective bacterial stain; and 
     exposing at least some of said stained bacteria after said step of selectively staining to incoherent light, to photothermally coagulate said bacteria. 
     Preferably the incoherent light is band limited to exclude a portion of said light having wavelengths which are substantially absorbed by oxyhemoglobin. Preferably, the incoherent broad band light is pulsed. 
     In a preferred embodiment of the invention, the pulsed incoherent broad band light has a frequency of pulsing in the range of 0.5-50 pulses per second, a pulse duration in the range of 0.1-10 milliseconds and an energy density in the range of 0.1-10 joule/cm 2 . 
     Preferably, the selective bacterial stain has at least one substantial light absorption peak which has no substantial overlap with the major peaks of light absorption of oxyhemoglobin. 
     Preferably, exposing comprises: 
     generating at least one pulse of light to exclude a substantial portion of said at least one pulse of light, said portion having wavelengths which are substantially absorbed by oxyhemoglobin, to convert said at least one pulse of light into at least one band-limited light pulse; and 
     directing said at least one band-limited light pulse onto said bacteria to photothermally coagulate said bacteria. 
     In a preferred embodiment of the invention, the bacteria are oral bacteria. Preferably, the bacteria are situated in the oral cavity. 
     There is further provided, in accordance with a preferred embodiment of the invention, a dentifrice including a stain for bacteria in a concentration sufficient to stain at least some bacteria remaining in the mouth after tooth brushing with the dentifrice. Preferably, bacteria stained with said stain have a substantial absorption peak at a wavelength for which oxyhemoglobin does not have such an absorption peak. Preferably, the stain comprises E-127 (Erythrosin-B), preferably in a weight percentage of 0.1%-1%. 
     There is further provided, in accordance with a preferred embodiment of the invention, an oral hygiene kit comprising: 
     a dentifrice according to the invention; and 
     an oral hygiene apparatus comprising: 
     an light source which generates radiation which is absorbed by the stain; and 
     a light directing member, adapted for directing light from said light source onto at least part of a surface of at least one tooth within an oral cavity. 
     Preferably, the oral hygiene apparatus is constructed according to the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be more clearly understood by the following description of preferred embodiments thereof, herein described, by way of example only, with reference to the accompanying drawings, in which like components are designated by like reference numerals wherein: 
     FIG. 1 is a schematic graph illustrating the absorption spectrum of an aqueous solution erythrosin B; 
     FIG. 2 is a schematic graph illustrating the absorption spectrum of the commercially available stain PLAK CHEK™; 
     FIG. 3 is a schematic part block diagram part cross sectional view of a device for selective photothermal destruction of oral bacteria, in accordance with a preferred embodiment of the present invention; 
     FIG. 4 is a schematic cross sectional view of a hand held part of a device for selective photothermal destruction of oral bacteria, in accordance with another preferred embodiment of the present invention; 
     FIG. 5A is a schematic part block diagram part cross sectional view of a device for selective photothermal destruction of oral bacteria having a light source optically coupled to a hand held part by an optical fiber bundle, in accordance with yet another preferred embodiment of the present invention; 
     FIG. 5B is an isometric view of a system for selective photothermal destruction of oral bacteria including the device of FIG. 5A and a plurality of the light directing members of the type illustrated in FIG. 3; 
     FIG. 6 is an isometric view of a light directing member attachable to the handle of the devices of FIGS. 3,  4  and  5 A- 5 B; 
     FIG. 7 is a cross sectional view of the light directing member of FIG. 6 taken along the lines VII—VII; 
     FIG. 8 is a side view of a toothbrush like light delivery member attachable to the handle of the devices of FIGS. 3,  4  and  5 , in accordance with another preferred embodiment of the present invention; 
     FIG. 9 is a schematic cross sectional view of a toothbrush like light directing member attachable to the handle of the devices of FIGS. 3,  4  and  5 , and having transparent bristles optically coupled to a light guide included within the light directing member; and 
     FIG. 10 is a schematic cross sectional view of a light directing member attachable to the handle of the devices of FIGS. 3,  4  and  5 , and having a light scattering dental floss member optically coupled to a light guide included within the light directing member. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Preferred embodiments of the present invention are based on the use of incoherent broad band light for the selective photothermal destruction of selectively stained oral bacteria within dental plaque. The bacteria are stained preferably by applying a liquid or paste like formulation containing a bacterial selective dye within the oral cavity preferably followed by rinsing the oral cavity to wash out excess dye. The bacteria within the dental plaque are thus selectively stained by the dye. 
     The inventors of the present invention have noticed that when irradiated with broad band incoherent light, the stained bacteria within the plaque absorb more light than nearby non stained tissues, leading to a temperature increase of the stained bacteria and to their destruction by coagulation. However, broad band light including light having wavelengths in the range substantially absorbable by oxyhemoglobin may be absorbed by the oxyhemoglobin contained within red blood cells of the blood included in blood vessels. This may lead to undesired photothermal coagulation of blood vessels within the oral cavity. To prevent such undesired blood vessel coagulation the broad band light is preferably filtered to exclude a substantial portion of the light having wavelengths which are substantially absorbed by oxyhemoglobin. Thus the filtered light is band limited. The main absorption peak of oxyhemoglobin is at a wavelength of 418 nm with an absorption bandwidth of approximately 60 nm around this main peak. Oxyhemoglobin also has secondary absorption peaks at 542 nm and 577 nm with an overall bandwidth of approximately 100 nm around these peaks. 
     Optimally, band limiting of the broad band light is coupled with the selection of specifically selected stains or dyes which selectively stain bacteria within dental plaque and which have at least one major absorption peak at least a portion of which has no substantial overlap with the major peaks of light absorption of oxyhemoglobin. When the broadband irradiation is filtered to exclude the absorption peaks of the oxyhemoglobin, the stains or dyes absorb enough light energy from the band limited light irradiating them to ensure efficient photothermal destruction of the stained bacteria, without damage to the oxyhemoglobin. 
     An example of such a dye suitable for selective photothermal destruction of oral plaque forming bacteria is the topical solution of erythrosin B, commercially available from TRISA AG, Switzerland. The oral bacteria may be stained by putting 3-5 drops of the topical solution of erythrosin B under the tongue and rinsing the teeth with the dye solution for approximately 30 seconds, followed by washing the mouth. The surfaces of the teeth that have bacterial plaque on them are thus stained red. 
     Reference is now made to FIG. 1 which is a schematic graph illustrating the absorption spectrum of an aqueous solution of erythrosin B. The horizontal axis represents the wavelength in nanometers and the vertical axis represents the absorbance in arbitrary units. The curve labeled  1  represents the absorption spectrum of erythrosin B. The curve has a main absorption peak  2  at a wavelength of approximately 542 nm and a secondary absorption peak  3  at a wavelength of approximately 638 nm. 
     It is noted that the main absorption peak  2  is within the absorption region of oxyhemoglobin. However, peak  3  is outside the absorbance peaks of oxyhemoglobin. 
     Another example of a dye suitable for selective photothermal destruction of oral plaque forming bacteria is PLAK-CHEK™, commercially available from Clairol Inc., Conn. USA. The staining method is similar to the method described for erythrosin B hereinabove. 
     Reference is now made to FIG. 2 which is a schematic graph illustrating the absorption spectrum of the commercially available stain PLAK-CHEK™. 
     The horizontal axis represents the wavelength in nanometers and the vertical axis represents the absorbance in arbitrary units. The curve labeled  4  represents the absorption spectrum of the PLAK-CHEK™ solution. The curve has a main absorbance peak  5  at a wavelength of approximately 494 nm. The main absorbance peak  5  has a bandwidth of approximately 40 nm. Thus, PLAK-CHEK™ may be a better stain than erythrosin B since its main absorption peak  5  does not substantially overlap the absorption peak of oxyhemoglobin. 
     It is noted that, since both of the staining dyes disclosed hereinabove have a relatively broad bandwidth of absorption, using a non coherent light source having a suitably broad bandwidth corresponding to the full bandwidth of the main absorption peak of the dye is preferable to using a narrow bandwidth laser. Thus, such a narrow bandwidth laser will be less efficient for photothermal heating of these dyes than a non coherent light source. 
     Reference is now made to FIG. 3 which is a schematic part block diagram part cross sectional view of a device for selective photothermal destruction of oral bacteria, in accordance with a preferred embodiment of the present invention. Device  10  includes a handle  11  having a housing  12 . Housing  12  is preferably formed of a thermally and electrically insulating material such as plastic or the like. Device  10  also includes an incoherent light source  14  and a controller unit  16  preferably disposed within housing  12  and attached thereto. Incoherent light source  14  preferably includes a reflector  15  and a lamp  20  disposed within the reflector. Reflector  15  is preferably reflective and is made from a reflective metal shell such as aluminum or any other suitable highly reflective metal. Alternatively, reflector  15  is formed of plastic or any other suitable material coated, on its internal surface, by a light reflecting coating. The reflector or reflecting surface faces lamp  20  and reflects light produced by the lamp. Lamp  20  is preferably electrically connected to controller unit  16  by suitable isolated electrically conductive wires  27 . Device  10  further preferably includes a power supply  18  that supplies electrical power to lamp  20  and to the controller unit  16 . Power supply  18  is preferably suitably connected to controller unit  16  by a power cable  37  entering housing  12 . Alternatively power supply may be attached to the housing. 
     Power supply  18  may be a direct current (DC) source such as a disposable or a rechargeable battery or any other suitable type of battery. Alternatively, power supply  18  can be an alternating current (AC) operated power supply suitably connected to the mains. 
     Reflector  15  is preferably shaped as an ellipsoidal reflector and has an opening  17  at it&#39;s end which is attached to housing  12 . Ellipsoidal reflector  15  has two focal points. Lamp  20  is preferably disposed in the region of the focal point which is distal from opening  17 . However, lamp  20  may also be disposed at other regions within reflector  15 . Alternatively, opening  17  may be centered about the right focus of the ellipsoid to improve the coupling of the light into the opening. Alternatively or additionally, the reflector may have a different shape that couples the light generated by the lamp into the opening. Alternatively, the reflector may have other shapes such as parabolic, quasi-parabolic, spherical, quasi spherical, quasi-ellipsoidal reflectors or any other suitable shape. 
     Light source  14  further preferably includes one or more filters  21  and  23  situated between lamp  20  and opening  17  which filters the light produced by the lamp  20  to produce band limited light. 
     In a preferred embodiment of the invention lamp  20  is an arc discharge lamp such as a flash lamp or any other lamp suitable for producing incoherent broad band light having an energy density sufficient for performing photothermolysis of dye stained bacteria. Preferably, lamp  20  is a xenon flash lamp that has a peak of light emission in the visible part of the spectrum at around 500 nanometers. One suitable lamp is xenon flash lamp model G5109 commercially available from The Electronic Goldmine, Ariz., USA. 
     When a xenon flash lamp is used and system  10  is designed for use in conjunction with the PLACK CHEK™ stain, filter  21  preferably transmits all wavelengths above 450 nm and blocks all wavelengths below 450 nm and filter  23  preferably transmits all wavelengths below 500 nm and blocks all wavelengths above 500 nm. For example, filters  21  and  23  can be the filters having catalog numbers 450FH-90-25 and 500FL07-25, respectively, commercially available from Andover Corporation, N.H., USA. 
     Filters  21  and  23  filter the broad band light produced by the xenon lamp to produce incoherent light which is band limited with a bandwidth of approximately 50 nm including the approximate wavelength range of 450-500 nm. This band of wavelengths is outside the absorption bands of oxyhemoglobin and within the main absorption band of the stain. 
     It is noted that, while the non-limiting examples of filters  21  and  23  disclosed hereinabove are suitable for use in a device designed for being used in conjunction with PLACK CHEK™, other different types of filters having similar absorbance ranges can also be used. 
     It is further that, if other selective bacterial stains or dyes which are different from the stain PLACK CHEK™ are used, filters  21  and  23  are preferably chosen to pass wavelengths which match the absorbance of the particular stain or dye. 
     It is still further that, while the filtering of the light of lamp  20  is disclosed as being performed by two distinct filters  21  and  23 , it is also possible to use a single optical filter having appropriate band limiting characteristics. 
     In another example, if the device  10  is used the dye erythrosin B, a single filter can be used to replace filters  21  and  23 . The single filter preferably absorbs all the wavelengths below 600 nm and transmit all wavelength above 600 nm. A suitable filter for use with erythrosin B is the filter having a catalog number 600FH90-25 commercially available from Andover Corporation, N.H., USA. 
     Controller unit  16  controls the energizing of flash lamp  20 . Controller unit  16  includes standard electronic circuitry needed to operate the flash lamp  20  such as a triggering unit, a capacitor unit and electronic timing circuitry for timing the frequency of flashing of the lamp  20 . A suitable electronic circuit that can be used to construct as the controller unit  16  is the Personal Safety Strobe, Catalogue Number 61-2506, commercially available form Radio Shack, a division of Tandy Corporation, Tex., USA The Personal Safety Strobe circuitry is preferably modified by electrically connecting an electrolytic capacitor having a capacitance of 120 microfarad (rated as 330 volts) in parallel with the capacitor already included in the Personal Safety Probe. The flashing frequency of the modified Personal Safety Strobe is approximately 1 Hz. 
     It is noted that, The particular circuitry disclosed hereinabove is given by way of example only and that many other types of circuitry known in the art can be used to implement controller unit  16 . 
     Device  10  preferably includes an on-off switch  19  attached to the housing  12  and suitably connected to the controller  16  for starting and stopping the operation of the controller  16 . The switch  19  can be any suitable type of switch. It is noted that, while the switch  19  of FIG. 3 is attached to the housing  12 , the switch may be attached to the housing  12  or to the power supply or to any other suitable part of the device. 
     Device  10  further preferably includes a light directing member  22  attached to handle  11  for directing light from the incoherent light source  14  into the oral cavity of a user. In a preferred embodiment of the invention, light directing member  22  of the device  10  is an elongated member made of a thermally insulating material such as plastic or the like. Light directing member  22  has a proximal end  24  preferably detachably attached to housing  12  and a distal end  26  extending distally of the housing  12 . 
     In one preferred embodiment of the invention, light directing member  22  has a hollow passage  30  passing therethrough. Hollow passage  30  has an opening  17  at proximal end  24  of member  22  to receive light from light source  14  and a second opening  25  at distal end  26  of member  22 . Opening  25  is preferably closed by an optical window  34  which seals opening  25 . Optical window  34  is preferably made from a material which is substantially transparent to the band limited light which passes through filters  21  and  23 . For example optical window  34  can be made from a suitable glass or a suitable plastic material or the like. Alternatively, one or both of filters  21  and  23  can be omitted from the light source and placed within the light guide or as a replacement for or as part of window  34 . 
     Optical window  34  prevents any material such as saliva or other liquids or solid materials present in the oral cavity from entering and accumulating in passage  30  and partially or fully blocking the path of the light produced by light source  14  from entering the oral cavity. 
     It is noted that, while the light directing member preferably includes optical window  34 , other embodiments of the present invention are possible which do not include an optical window and opening  25  is uncovered. 
     Light directing member  22  preferably further includes a layer  32  of light reflecting material attached to the internal surface of passage  30 . Layer  32  is preferably made of a light reflecting material such as aluminum or any other metal or material having suitable light reflecting properties. Layer  32  may be formed by deposition thereof on the internal surface of passage  30  or by any other suitable forming or attaching method such as, for example vapor deposition or electroplating methods may be used. 
     Light reflecting layer  32  forms a light guide which guides the light produced by light source  14  and directs it onto the surfaces of teeth  36  within the oral cavity of the user. 
     In other preferred embodiments of the invention, the light guide may be any other type of suitable light guide as known in the art. For example, it may be a solid plastic rod coated on its outside with a light reflective coating or cladding. Alternatively, the light may be reflected from the outer surface of the guide by total internal reflection. Other suitable light guides will occur to persons of skill in the art. 
     Preferably, passage  30  has a circular cross-section. However, the passage  30  may also have an oval cross-section or any other cross section suitable for use in a light guide. 
     Light directing member  22  further preferably includes a tooth brush member  28  extending from end  26  of light directing member  22 . Tooth brush member  28  preferably includes a plurality of bristles  29  for brushing teeth. 
     It is noted that, while the tooth brush like member  28  is a physical extension of the end  26  of the light directing member  22 , it can also be formed as a separate part (not shown) which can be attached to the end  26  by gluing or fusing or by any other suitable attachment means. 
     When device  10  is used for photothermal destruction of oral bacteria, a user first selectively stains plaque bacteria by using a bacterial selective stain or dye such as PLAK-CHECK™ as described above. The user then holds housing  12  in his hand, switches switch  19  to the “on” position to commence the flashing of flash lamp  20  of light source  14 , and inserts brush member  28  into his oral cavity. The user then brushes his teeth using brush member  28 . Preferably, flash lamp  20 , is flashed at a flashing rate of approximately 1 Hz to 10 Hz, but flashing rates in the range of approximately 0.5-50 Hz may be used. Typically, each light flash has a duration of 0.1 to 10 msec and irradiates the teeth  36  with incoherent band limited light having an energy density of approximately 0.1-10 Joule/cm 2 , thereby heating stained bacteria to the temperature of coagulation. Using energy densities within this range, even a single flash can effectively cause photothermal heating and coagulation of selectively stained plaque bacteria. 
     Light rays produced by flash lamp  20  such as light ray  13  are reflected by reflector  15 , directed towards filters  21  and  23  to be filtered thereby. The filtered light rays are directed within the light guide by multiple reflections from the reflecting layer  32  to exit from the exit  25 . The filtered light rays are directed towards the surface of teeth  36  for coagulating stained plaque bacteria by photothermal heating. 
     The frequency of flashing of the lamp  20  by the electronic timer circuitry may be factory preset so as to take into account the typical parameters of the movements of the brush member  28  over the teeth during brushing of teeth by the user and to provide a sufficient irradiation of the surfaces of the teeth within the oral cavity of the user for efficient photothermal destruction of dental plaque bacteria. 
     After the user finishes the photothermal coagulation procedure, the user switches off the flashing of the flash lamp  20  by switching the switch  19  to the “off” position. If desired, the user may then apply a tooth paste to the bristles  29  of the tooth brush like member  28  and proceed to brush his teeth normally. 
     Alternatively, the person first brushes his teeth normally, using ordinary toothpaste or other dentifrice. The bacteria is then stained and the above irradiation procedure is performed. 
     Alternatively, a toothpaste incorporating a stain as described herein is used for ordinary brushing with the brush member. This brushing will be operative to clean the teeth and to stain any remaining bacteria. The mouth and the toothbrush are then preferably rinsed and the irradiation procedure, as described herein, is performed. In a preferred embodiment of the invention, E-127 red food coloring (Erythrosin-B) in a concentration of 0.1%-1% can be used as the stain. Other suitable stains can also be used. 
     As may be noted, light directing member  22  and brush member  28  are preferably detachable from handle  11 . Thus, a separate directing member may be used for each person using the device. Furthermore, the brush may be replaced from time to time as it becomes used. 
     Reference is now made to FIG. 4 which is a schematic cross sectional view of a handle  41  of a device for selective photothermal destruction of oral bacteria, in accordance with another preferred embodiment of the present invention. Handle  41  includes a housing  42  having a recessed opening  58  therein. Handle  41  further includes a controller unit  16  attached to a power supply (not shown) by a suitable power cable  57 . Handle  41  also includes switch  19  suitably connected to the controller  16  as disclosed with respect to FIG.  3 . Switch  19  is used to turn controller  16  on and off as disclosed for device  10  of FIG.  3 . Handle  41  further includes a reflector  44  to reflect light from a lamp  50  to an opening  58 . Handle  41  preferably also includes a lens  55  situated between filter  23  and opening  58 . 
     Lamp  50  is similar to lamp  20  of FIG.  3  and is electrically connected to the controller  16  by a conducting wires (not shown for the sake of clarity of illustration). Reflector  44  is made of a light reflecting material such as polished aluminum or any other suitable reflecting material. Alternatively, the reflector  44  may be made of a preferably thermally insulating material such as plastic or the like which is plated or coated by a light reflecting layer made of a suitable reflecting metal such as aluminum, silver or the like. Reflector  44  is preferably a parabolic reflector but can also have a quasi-parabolic, spherical or quasi-spherical shape or any other suitable shape. Light rays  56  produced by the lamp  50  are reflected by the reflector  44 , filtered by the filters  21  and  23  as described above and focused by the lens  55  at a point  59  within opening  58 . 
     Handle  41  can be attached to light directing member  22  of FIG. 3 by inserting end  24  of member  22  into opening  58  of handle  41 . When switch  19  is switched on, the light produced by lamp  50  and focused at point  59  enters into passage  30  and is directed by the light guide formed from the reflecting layer  32  to exit from the optical window  34  as disclosed above. 
     Reference is now made to FIG. 5A which is a schematic part block diagram/part cross sectional view of a device  71  for selective photothermal destruction of oral bacteria. Device  71  has a light source optically coupled to a hand held part by an optical fiber bundle  67 , in accordance with yet another preferred embodiment of the present invention. 
     Device  71  includes a handle  61  and a base  77 . Handle  61  includes a housing  62  having a recessed opening  68  therein. Handle  61  and the base  77  are optically coupled by flexible optical fiber bundle  67  passing through housing  62  of handle  61  and attached thereto. Base  77  preferably includes a housing  72 , a light source  74 , a power supply  18  and controller  16  electrically connected to light source  74  to control the energizing of light source  74  by power supply  18 . Base  77  also may include a control panel (not shown in FIG. 5A) suitably connected to controller  16  for activation of the controller. 
     Light source  74  preferably includes a lamp  70  similar to lamp  20  of FIG.  2  and electrically connected to controller  16 . Light source  74  preferably also includes a reflector  75  which includes filters  21  and  23  attached thereto as disclosed above. Reflector  75  is made of a light reflective material or is constructed from a thermally insulated material coated with a light reflecting layer as disclosed above. The reflected  75  may be ellipsoidal but may also have other shapes as disclosed above. Optical fiber bundle  67  has a first end  67 A and a second end  67 B. Light source  74  is optically coupled to first end  67 A, by the structure shown or by other suitable means known in the art. Optical fiber bundle  67  passes within housing  62  of handle  61  and end  67 B of optical fiber bundle  67  is attached to housing  62  at recessed opening  68  in such a way that it can be optically coupled to the light guide of light directing member  22  of FIG.  3 . Thus, light produced by light source  74  enters first end  67 A and is directed by the individual optical fibers within optical fiber bundle  67  to exit at second end  67 B. 
     It is noted that end  67 B of optical fiber bundle  67  can also be optically coupled to various types of light directing members which are constructed differently from light directing member  22  of FIG. 3 some of which are disclosed below. 
     Reference is now made to FIG. 5B which is an isometric view of a system  80  for selective photothermal destruction of oral bacteria including the device of FIG. 5A and a plurality of the light directing members of the type illustrated in FIG.  3 . 
     FIG. 5B illustrates base  77  which includes a control panel  73  for activation of controller unit  16  by the user. Base  77  is suitably formed to house handle  61  while it is not being used. Base  77  is also suitably formed to house a plurality of light directing members  22  each of which may be attached to handle  61  for use by a different individual for his own personal use. Optical fiber bundle  67  may be conveniently wound around a member  67  for storage. 
     Reference is now made to FIGS. 6 and 7. FIG. 6 is an isometric view of a light directing member  82 , in accordance with a preferred embodiment of the invention, attachable to the handle of the devices of FIGS. 3,  4  and  5 A- 5 B. FIG. 7 is a cross sectional view of the light directing member of FIG. 6 taken along the lines VII—VII. 
     Light directing member  82  is an elongated member having a proximal end  84  and a distal end  86 . Proximal end  84  can preferably be detachably attached to any of handles  11 ,  41  and  61  of FIGS. 3,  4  and  5 , respectively. Distal end  86  is insertable into the oral cavity of the user (not shown). 
     Turning to FIG. 7, the light directing member  82  includes a hollow member  83  preferably made from a thermally insulating and light opaque material such as opaque plastic or the like. Light directing member  82  further includes a light guide  85  having a first end  85 A and a second end  85 B. First end  85 A of light guide  85  is attached to hollow member  83  at proximal end  84  of light directing member  82  and second end  85 B of light guide  85  is attached to hollow member  83  at distal end  86  of light directing member  82 . Light guide  85  is preferably separated from hollow member  83  by an air gap  87 . Preferably, first end  85 A of light guide  85  terminates in a flat surface  89 A which is suitable for being optically coupled to a light source such as light source  14  of FIG. 3 or to second end  67 B of optical fiber bundle  67  of FIG.  5 A. Second end  85 B of light guide  85  terminates in a flat surface  89 B which is suitable for directing the light entering light guide  85  onto the oral cavity of a user. 
     Light guide  85  is optimally made from a material which is transparent to the bandwidth of the band limited light which is being used for photothermally coagulating the oral bacteria. The transparent material forming light guide  85  has an index of refraction which is higher than the index of refraction of air. A light ray  81  which enters light guide  85  at surface  89 A is guided by multiple reflection along light guide  85  towards end  85 B of light guide  85  where it exits through surface  89 B. 
     Preferably, light guide  85  is shaped as a rod having a generally circular cross-section and is made from clear polymethylmetacrylate (PMMA), glass or any other optically suitable transparent material. However, light guide  85  may have other different shapes and cross-sections which are suitable for implementing a light guide. 
     Reference is now made to FIG. 8 which is a side view of a toothbrush like light delivery member  92  attached to the handle of the device of FIGS. 3,  4  and  5 , in accordance with another preferred embodiment of the present invention. Light directing member  92  is similar to light directing member  82  of FIG.  6  and includes a light guide  83 . 
     However, in contrast to hollow member  83  of FIG. 6, hollow member  93  of light directing member  92  includes a lip  94  extending therefrom and surrounding surface  89 B. A plurality of bristles  95  are attached to lip  94  and extend from lip  94  in a direction is generally perpendicular to the surface of the  94  forming a tooth brush like member  97  at the end of light directing member  92 . When the light directing member  92  is attached to a handle such as, for example, handle  11  or  41  or  61  of FIGS. 3,  4  and  5 A, respectively, and teeth within the oral cavity of a user are brushed by tooth brush like member  97 , the light which exits from surface  89 B is not blocked by bristles  95  and illuminates part of the surface of the teeth which lie underneath tooth brush like member  97 . 
     It is noted that, while light can be directed onto the surfaces of teeth as discussed hereinabove for the light directing members  22 ,  82  and  92 , other methods for directing light can be used. 
     For example, FIG. 9, to which reference is now made, is a schematic cross sectional view of a toothbrush like light directing member  102  attachable to the handle of the devices of FIGS. 3,  4  and  5 . Member  102  has transparent bristles  109  optically coupled to a light guide included within the light directing member. Light directing member  102  is an elongated member having a proximal end  104  and a distal end  106 . Proximal end  104  can be detachably attached to any of Handles  11 ,  41  and  61  of FIGS. 3,  4  and  5 , respectively. Distal end  106  is insertable into the oral cavity of a user. 
     light directing member  102  preferably includes a hollow member  103  preferably made from a thermally insulating and light opaque material such as opaque plastic or the like. Light directing member  102  further includes a light guide  85  as described above. Light directing member  102  further preferably includes a terminal part  109 . Terminal part  109  preferably includes a plate  107  made of a thermally insulating and preferably light opaque material such as plastic or the like. Terminal part  109  preferably has a plurality of holes  108  passing therethrough. 
     Terminal part  109  further includes a plurality of transparent bristles  105 . Each of the bristles  105  has a first end  105 A and a second end  105 B. Bristles  105  are attached to plane  107 . First end  105 A of each of the bristles  105  is inserted into a hole  108  and glued to or frictionally held within the hole. First end  105 A of each of bristles  105  is optically coupled to light guide  85  at surface  89 B thereof by abutting surface  89 B or by being glued to surface  89 B using a suitable optically transparent glue. 
     Second end  105 B of each of bristles  105  extends distally from plate  107  in a direction generally perpendicular to a surface  107 A thereof. Bristles  106  are preferably made from a flexible material which is transparent to the bandwidth of the band limited light which is being used for photothermally coagulating the oral bacteria. For example, bristles  105  can be made form nylon or from any other suitably transparent flexible plastic. Light from surface  89 B enters first end  105 A and is guided within each bristle  105 , light exiting ends  105 B of bristles  105  irradiates the surfaces of the teeth and may photothermally coagulate selectively stained bacteria within plaque covering the surfaces of the teeth. 
     While all the preferred embodiments of the present invention disclosed hereinabove are useful in photothermally coagulating bacteria within plaque deposited on the more accessible surfaces of teeth, plaque on tooth surfaces which are less accessible to irradiation may need a treatment using another technique of irradiation. 
     For example, FIG. 10 to which reference is now made is a schematic cross sectional view of a light directing member  112  in accordance with a preferred embodiment of the invention. It is preferably attachable to the hand held part of the devices of FIGS. 3,  4  and  5  and has a light scattering dental floss like member  120  optically coupled to a light guide  115  included within a hollow cavity member  113  within the light directing member. Light directing member  112  has a proximal end  114  and a distal end  116 . Light guide  115  has a first end  115 A at proximal end  114  of light directing member  112  and a second narrowing end  115 B at distal end. 
     Light directing member  112  includes a terminal part  119  extending from distal end  116 . Terminal part  119  includes a floss holding member  117  holding light scattering dental floss like member  120  having a first part  120 A and a second part  120 B. Floss like member  120  is preferably made from a flexible transparent material such as nylon or any other type of suitably transparent flexible plastic. First part  120 A and a second part  120 B. Floss like member  120  is preferably made from a flexible transparent material such as nylon or any other type of suitably transparent flexible plastic. First part  120 A is attached to and optically coupled to the second end  115 B of the light guide  115 . The optical coupling my be performed by a glue having suitable optical properties or, alternatively, floss like member  120  can be an extension of narrowing end  115 B of light guide  115 . Second part  120 B of floss like member  120  is attached to floss holding member  117  such that floss like member is suitably held for flossing. 
     Floss like member  120  is constructed to scatter light which enters it from light guide  115 . The scattering of light may be caused by small light reflecting particles which are embedded in the transparent plastic material forming the floss like member  120 . However, other methods of inducing light scattering may also be used such as, for example, forming a plurality of closely spaced grooves or indentations on the outer surface of the floss like member. 
     After selective staining of plaque bacteria as disclosed above, a user inserts the floss like member  120  between the teeth as he would with ordinary floss. The light scattered from floss like member  120  irradiates the plaque on the surfaces of the teeth that are not accessible by regular brushing and performs photothermal coagulation of selectively stained plaque bacteria positioned at these inaccessible surfaces, while normal flossing is performed 
     It is noted that each of the handles  11 ,  41  and  61  can be attached to any of the light directing members  22 ,  82 ,  92 ,  102  and  112  of FIGS. 3,  7 ,  8 ,  9  and  10 , respectively 
     It is further noted that, while any of the light directing members  22 ,  82 ,  92 ,  102  and  112  of FIGS. 3,  7 ,  8 ,  9  and  10 , respectively, may be made for extended used, they may also be made to be disposable. Furthermore, while various features and forms of features have been shown in the various preferred embodiments, many of these features and variations may be present in other preferred embodiments of the invention. Furthermore, some preferred embodiments of the invention may omit some features shown in the preferred embodiments. 
     It will be appreciated by those skilled in the art that many variations of the preferred embodiments of the present invention can be made which are within the scope and spirit of the present invention. As used herein, the words “comprise” or “include” or their conjugates mean “including but not necessarily limited to.”