Patent Description:
<CIT> refers to an endodontic instrument for dental root canal filling using an elongated shank, which has a sealing plug at its end. Energy is fed via an optical fiber to the plug, so that it melts.

<CIT> refers to a method and apparatus for filling a cavity. To achieve this, an optical fiber is used, which is made of a low melting point composition, so that energy transmitted by laser radiation acts to melt the fiber to completely fill and seal a tooth or bone cavity.

An object of the present invention is to provide a device to close a canal so it can be filled with a low viscous material without the risk that the material penetrates over the apex.

The object is archieved by a device according to the invention. Such device is defined in the appended independent claim <NUM>.

The closure element is melted through the laser radiation transmitted through the light guide.

The invention provides a closure element, which is secured to one free end of a light guide conducting a laser beam, the light guide with the closure element is introduced into the canal, that the closure element is positioned in the region of the canal to be sealed and after positioning of the closure element energy is introduced, the closure element melts and/or softens and remains in this position in the canal and seals it tightly.

According to a further proposal it is provided that a sealing material is used that melts and/or foams through the introduction of heat energy and forms a closed-pore canal seal after cooling, in particular that sodium hydrogen carbonate enveloped by gutta percha material is used as the sealing material.

According to a further proposal it is provided that a material that comprises a first component and a second component which react with one another in a volume-expanding manner is used as sealing material.

According to a further proposal it is provided that a material is used as a closure element that comprises an in particular volume-scattering core material and an expanding material that envelops it.

According to a further proposal it is provided that an Er:YAG laser, Er:YSGG laser or CTE laser is used as the laser.

According to a further proposal it is provided that the laser is operated with a pulse duration between <NUM> and <NUM>, preferably between <NUM> and <NUM>, and especially preferably between <NUM> and <NUM>.

According to a further proposal it is provided that a laser beam is used that has a pulse energy exiting from the light guide between <NUM> mJ and <NUM> mJ, in particular between <NUM> mJ and <NUM> mJ.

The present invention can be better understood and its advantages appreciated by those skilled in the art by referencing to the accompanying drawings. Although the drawings illustrate certain details of certain embodiments, the invention disclosed herein is not limited to only the embodiments so illustrated.

In the following, the invention will be explained on the basis of the cleaning of a canal, such canal being a root canal, however, without limiting the invention. Rather, the teaching according to the invention can be applied in all cases where particularly canals with small diameters are to be cleaned and/or closed as is for example the case with medical instruments, as explained in the introduction. But it is to be mentioned that the cleaning is not a part of the invention itself.

The described method steps are not covered by the claimed invention.

In case of a traditional root canal treatment, the pulp chamber is opened, the pulp tissue removed and the root canals are enlarged with mechanical files until a conical shape of the root canal is achieved. The canal is manually flushed with cleaning fluids via syringes. Then the canal is filled with a sealer and conical gutta-percha points are plugged and condensed into the canal to achieve a dense root canal filling.

For this procedure canal enlargement is necessary to create a conical shape of the canal consistent with the conical shape of the Gutta-percha points filling the canal. The material loss weakens the tooth; the procedure is time consuming, bears the danger of over-instrumentation and file fracture. The success rate ranges from below70% to <NUM>% depending on who is doing the treatment.

An easier, less time consuming and technique sensitive procedure could help to raise the average success rate and increase the comfort for the patient.

A procedure without enlarging the root canal would avoid above mentioned disadvantages. However it creates new challenges. Not enlarging the canal results in irregular shaped root canals like a cave. Therefore traditional root canal cleaning and filling is not possible, because conically shaped Guttapercha points cannot be inserted in such an unshaped root canal. A new filling technology is required.

Laser assisted root canal procedures use steam bubbles generated by laser energy to cleanse root canals which are already enlarged with mechanical files to a conical shape typically to size #<NUM> or more. The steam bubble expansion and contraction causes water motion in the vicinity of the bubbles, which then cleanse the root canal walls.

Fotona, Biolase and KaVo sell or have sold dental laser systems which can be used for such an endodontic treatment. These lasers offer a wide range of dental indications up to drilling of cavities. The pulse repetition rate of these devices is typically limited to ~ <NUM> and they offer pulse energies up to 1J, which is necessary for cavity preparation. For endodontic treatment pulse energy below 50mJ is sufficient in combination with <NUM> or pulse repetition rate (<NPL>); <NPL>)) and the use of conical shape fiber tips (<NPL>).

These traditional flash lamp pumped Er:YAG / YSGG laser have an energy conversion efficiency of ~<NUM>% resulting in a large power supply and a bulky device with fluid cooling. This leads to a high price and thus very limited number of users.

Additionally these lasers are class <NUM> devices, the regulatory environment needs some efforts in a dental practice to comply with. A laser safety area must be declared and protected, a laser safety officer must be trained and nominated and DDS, assistant and patient need to wear eye protection goggles.

The actual laser assisted endodontic root canal procedure uses pulse energies in the range <NUM> - <NUM> mJ pulse energy, which is above the ablation threshold of dentin. Therefore generating a wrong pathway (via falsa) is possible, when protruding the laser fiber into the root canal.

In a protocol provided by DiVito (<NPL>) the laser applicator is placed in the pulp chamber and not protruded into the root canals. Even without the need for protruding the laser applicator into the root canal the procedure requires pretreatment of the root canals to size #<NUM> or #<NUM>. The laser energy generates fluid movement in the pulp chamber, which extends into the root canals partially. In favor of the method no fiber must be protruded into the canal. However disadvantages are inconsistent results, depending on the canal geometry and splashing of corrosive cleaning fluids out of the pulp chamber even out of the mouth of the patient can be observed due to relative high pulse energies of <NUM> - 30mJ.

Recent technology improvement enabled the design of diode pumped Er:YAG / YSGG lasers.

A diode pumped Er:YAG / Er:YSGG laser developed specifically for endodontic treatment offers a smaller device and more economical solution. This laser system is based on laser system developed by Pantec. (<CIT>, Bragangna, Heinrich, Pantec Biosolutions AG) Main reason is an improved efficiency of the conversion of electrical energy into light energy. This allows using a much smaller power supply and reducing the cooling efforts.

A higher pulse repetition rate (up to <NUM> compared to <NUM>) allows decreasing the pulse energy below the ablation threshold of dentin. This is important, because it avoids the formation of a "via falsa" (penetrating the root canal wall into the periodontium), which is a significant complication in endodontic treatment.

Totally unexpected, pulse energies in the range of <NUM>,<NUM> - 4mJ in combination with pulse repetition rates between <NUM> and <NUM> preferably <NUM> - <NUM> allow in combination with effective cleaning fluids efficient cleaning of root canals. The low pulse energy avoids splashing of the cleaning fluids, minimizes the vibration of the tooth during treatment and avoids a root canal wall perforation by the laser fiber during treatment, because the laser energy density is below the ablation threshold of dentin.

The root canal treatment with the claimed device starts like the traditional procedure with opening the pulp chamber, removing the pulp tissue in the pulp chamber, searching for the canal entrances and slightly enlarging the entrances, followed by path finding with file size up to size #<NUM> which created a pathway with at least <NUM> diameter at the apex and more diameter more coronal, which is necessary to protrude a laser fiber with same or smaller diameter close to the apex.

No further canal enlargement is required. This saves significant working time and increases the patient comfort.

The pulp chamber and the root canals are filled with cleaning fluid either manually with a syringe or automatically from fluid containers of the device and the laser fiber is inserted in to the root canal until <NUM> before the apex.

The laser radiation in a wavelength range <NUM> - <NUM> is strongly absorbed by fluids containing water and creates steam bubbles by vaporization in the fluid and causes hydrodynamic motion of the water in the root canal. This fluid motion cleanses the canal. The laser is activated and the laser fiber is moved up and down the root canal. Cleaning consists of removing vital and non-vital pulp tissue, bacteria and pus as well as opening the dentinal tubules. The main cleaning area is ~ <NUM> - <NUM> around the fiber tip and some less efficient "far distance" cleaning effects in the whole root canal, mainly caused by resonance phenomena as interaction between the root canal geometry and acoustic waves caused by steam bubble formation and collapse.

After cleaning, the canal with one fluid the canal is dried either conventionally with paper points or with laser energy (or both combined) to remove the cleaning fluid from the canal. Additionally compressed air can be used exiting the applicator supporting the drying process. Then optionally further cleaning fluids are filled into the root canals sequentially (Manually with syringes or automatically with the device) and the treatment is repeated. Finally the canal is dried again.

Possible cleaning fluids can be water, comprising NaOCl (<NUM> - <NUM>%), EDTA (<NUM> - <NUM>%), and H<NUM>O<NUM> (<NUM> - <NUM>%) or mixtures thereof.

<CIT>, Biolase inc. , Netchitailo V. , Boutoussov, D. Verdaasdonk, R. Pressure wave root canal cleaning system) report on cleaning improvement with laser energies, typically larger than 5mJ per pulse by adding gas bubbles to the cleaning fluid.

In contrary to Verdaasdonk's, disclosure cleaning with low pulse energies in the proposed range is less efficient, if the fluid contains gas bubbles before treatment. Best results are obtained with fluids without addition of gas bubbles or even degassed fluids.

To decide, whether a root canal is clean and dry enough and free of bacteria, a cleanliness check of the root canal can be done. Spectroscopic / fluorescent methods can be used guiding illumination / excitation light in the laser fiber into the root canal and collecting remitted light from the bacteria, debris and canal wall with same fiber. This can be done simultaneously to the laser cleaning. Bacteria emit fluorescence signatures in the visible wavelength range (especially <NUM> - <NUM>) when excited with UV light (e.g. <NUM>) or in the near infrared range (e.g. <NUM> -<NUM>), when excited with red light <NUM> - <NUM>. Excitation in the visible range is preferable, because auto-fluorescence of dentin has a strong emission in the green spectral area around <NUM>.

Alternatively electrical impedance spectroscopy can be applied for canal diagnostics.

In case bacteria remain after cleaning in the root canal bacteria can be reduced by a specific temperature treatment using high repetition rate laser energy or/ and a PDT procedure can be added to the treatment.

A pre-requisite for thermal killing of bacteria is a strong absorption of the laser radiation at the root canal surface. Diode lasers with emission wavelength between <NUM> and <NUM> used today for this purpose do not have a strong absorption in dentin, therefore are not ideal in part even dangerous, since the temperature rise in the periodontium and inside the root canal are nearly equal.

<NUM> - <NUM> wavelength e.g. of the proposed diode pumped Er:YAG laser device is much better adapted to the task.

Therefore, low power Er:YAG laser radiation in the order of <NUM>. 5W with <NUM> - <NUM> pulse repetition rate is fully sufficient to reach local peak temperatures on the root canal wall well above <NUM> for killing bacteria and keeping the periodontal temperatures well below critical <NUM>.

For PDT various protocols are available (e.g. Helbo, Dentofex, Wilson). For this treatment fluids like Methylen Blue or Toluidin Blue are applied into the root canal and the appropriate light is coupled into the light pass down into the root canal. For Methylen Blue <NUM> with around <NUM> mW are required and <NUM> with ~ 100mW for Toluidin Blue. The advantage over traditional PDT procedures is the simultaneous delivery of Er:YAG / Er:YSGG laser energy to agitate the PDT fluid by laser energy, rapidly inducing steam bubbles,causing adjacent fluid motion, and heating the PDT fluid. This allows a much more intense contact of the fluids with the bacteria and increases the penetration depth into the dentinal tubules compared to PDT without agitation or agitation with ultrasound. Filling not enlarged canals <NUM> as root canals requires a new approach capable of covering irregular root canal space without voids. This is possible with a low viscosity obturation material. The risk is however a penetration of the filling material over the apex.

An apical "plug" placed in the apical region before filling the canal with the low viscosity material can prevent this. Conventional solutions for placing an apical plug are disclosed already (e.g. <CIT>) but require however a canal preparation according to ISO and cannot be applied to irregular canals. Further they do not disclose the use of a laser system to place the plug.

In case of a small apex with a diameter in the order of laser fiber (<NUM> - <NUM>) a plug <NUM> is attached axially to the laser fiber <NUM> (<FIG>). The connection material <NUM> between the fiber tip <NUM> and the plug <NUM> improves the adhesion between plug material and the fiber tip <NUM>.

The plug material may be pre-heated before insertion in an external furnace actually used to pre-heat Thermafil obturators.

The plug material may be covered additionally with a sealer prior to insertion in the root canal <NUM>. The sealer may be composed as disclosed in <CIT>.

The laser fiber <NUM> with the plug <NUM> is protruded in the root canal <NUM> and pushed with slight pressure in position. At appropriate working length (length to apex - <NUM>) the laser is activated and the plug <NUM> or the connection material <NUM> begins to melt at the connection to the laser fiber <NUM>. The plug <NUM> can be slightly vertically condensed with the laser fiber <NUM>. That will hold the plug <NUM> in position while removing the laser fiber <NUM>. In the next step the low viscosity material is filled into the canal. This material can be e.g. a root canal filling material as disclosed in <CIT>, Dentsply intl.

To improve the coverage of the root canal wall in recesses and not directly accessible areas the low viscosity filling material can be subjected to laser radiation, which is absorbed by the material and create steam bubbles, which accelerate the material against the root canal wall. Finally a material with same or higher viscosity (e.g. according to <CIT>) is filled into the canal to obturate the remaining canal volume. Lateral and / or vertical condensation may be applied.

In case of a direct connection of the gutta-percha to the laser fiber <NUM> the gutta-percha formulation must have a stable connection to the laser fiber <NUM> at storage and during insertion into the canal <NUM> at room temperatures and must melt in between <NUM> and <NUM>. Gutta-percha has an absorption coefficient high enough to deposit enough energy in a few <NUM>th of micrometers, which ensures a very local heating of the interface to the laser fiber.

In case a connection material is used the connection material <NUM> must melt in between <NUM> and <NUM> and attach sufficiently to the laser fiber <NUM> and the plug material. The absorption coefficient at the laser wavelength must be high enough to deposit sufficient energy in a few <NUM>th of micrometers to melt the connection material with a power of less than 2W, preferably below 100mW within <NUM> - <NUM> seconds. The material melts between <NUM> and <NUM>, which insures shelf stability and keeps the temperatures in the apical region low enough during the heat application.

Alternatively the gutta-percha plug may be attached to an applicator which is heated electrically. A tiny SMD resistors (EIA01005, <NUM>,<NUM> x <NUM> x <NUM>,<NUM>) or semiconductor material at the tip of a plastic applicator feeded by <NUM> copper wires with less than <NUM> total diameter can be used.

In case of a wide apex <NUM> much wider than the fiber diameter e.g. <NUM>,<NUM> - <NUM> the above described approach would fail.

For such a situation a material is needed that can expand the volume "on demand" (like popcorn or polyurethane foam). The base material could be attached again to the laser fiber <NUM> protruded in position at the apex <NUM> and then the expansion is initiated by either laser energy converted to heat by absorption or UV light, but with a plug <NUM> comprising an expandable material <NUM>. The plug material <NUM> must expand at temperatures lower than the melting temperature of the connection material. After expansion of the plug material <NUM> and after some second of cooling to allow the plug material <NUM> to get harder, the laser power is increased for a short time duration e.g. <NUM> - <NUM> seconds to finally melt the connection material and remove the fiber tip <NUM> from the canal <NUM> without the danger of displacing the plug <NUM> from its apical position during removal.

Ideally the expansion of the plug material <NUM> is directed towards the canal wall. To achieve this, the expandable material must be placed on the side of a volume scattering material attached to the fiber tip <NUM> with a connection material. After expansion this volume scattering material <NUM> will remain in the canal <NUM> as part of the plug <NUM>. To separate the plug from the fiber tip, the connection material is heated with Er:YAG laser radiation. In this case the connection material must be transparent for radiation in the visible range, which is scattered by volume scattering part <NUM> of the plug <NUM> into the expandable plug material <NUM> to heat the expandable plug material <NUM>.

The plug material can be a dental composite material. The connection material can be a translucent (in the visible wavelength range) resin softening at less than <NUM>.

The plug <NUM> with the middle part of the scattering material <NUM> and the expandable material <NUM> surrounding the core is depicted in <FIG>.

Another option is attaching a material component A as expandable plug material to the laser fiber and a second Material B is applied to the first material just before insertion into the root canal, which starts a reaction with volume expansion. The laser energy would then only be used to melt the connection of the plug material and the laser fiber, which has kept the plug material in the correct position before it fixes itself to root canal wall by expansion.

A material with an expansion factor of <NUM> can fill the gap between a #<NUM> (<NUM> diameter) plug and an apex diameter of #<NUM> (<NUM> diameter). An expansion factor of <NUM> can fill the gap to an apex diameter of #<NUM> (<NUM>).

In case a fiber tip with larger diameter can be inserted without canal enlargement, which is often the case in anterior teeth a material with an expansion factor of <NUM> could fill the gap between a #<NUM> (<NUM> diameter) plug and an apex diameter of #<NUM> (<NUM> diameter). An expansion factor of <NUM> could fill the gap in this example to an apex diameter of #<NUM> (<NUM>).

Example for an expandable material: A mix of Natriumhydrogencarbonat (sodium bicarbonate) + guttapercha particles. When heat is applied via the optical fiber tip the following reaction <NUM> NaHCO<NUM> → Na<NUM>CO<NUM> + CO<NUM> ↑ + H<NUM>O releases CO<NUM> and forms a foam with the melted Guttapercha particles.

To keep the pH in physiological range an acid (e.g. Citric acid) may be added which will produce additional foam in a moist environment Alternatively any biocompatible foaming agent in combination with Guttapercha including the disclosure in <CIT> and <CIT>, Dentsply intl. can be used.

Small sodium bicarbonate particles may be encapsulated in gutta-percha to create a closed bubble foam.

Examples of different kind of plugs, plug materials, connection materials, and expandable materials are specified in Table I.

A device according to the invention is shown in principle in <FIG>. The device comprises a desktop device <NUM> with a touch screen <NUM> and a housing with integrated cooling elements <NUM>. The housing is connected to the turbine connector of a dental unit <NUM> (connector <NUM>) to have supply with water and compressed air.

The desktop housing is connected to a handpiece <NUM> with a delivery system <NUM>.

The handpiece <NUM> is connected to the delivery system <NUM> via a rotation coupling. A fiber tip <NUM> can be connected to the handpiece and disposable containers <NUM> with cleaning fluid can be attached and removed from the handpiece. The housing is connected with the handpiece <NUM> via a connecting line <NUM>.

The portable desktop device <NUM> comprises a laser as energy source. The laser radiation is transmitted with a delivery system together with water and compressed air and optionally cleaning fluids to the handpiece <NUM> with detachable fiber tip <NUM>.

The energy source is a Diode pumped ER:YAG - (Wavelength <NUM>), Er:YSGG - (Wavelength <NUM>) or CTE Laser (wavelength <NUM>). The pulse length is between <NUM> - <NUM>, preferably <NUM> - <NUM>, most preferably <NUM> - <NUM>. The pulse energy is between <NUM>,<NUM> - <NUM> mJ, preferably <NUM> - 10mJ at the distal end of the applicator. This requires around the double pulse energy at cavity exit. The average power is between <NUM>,<NUM> - 10W preferably <NUM> - 3W and the peak power is < 600W at cavity exit.

Further the device is equipped with light sources for aiming beam and apical plug heating and optional for bacteria detection and for PDT.

The aiming beam is coupled through the Er:YAG rod from the <NUM>% reflection mirror side and the other light source for apical plug heating and PDT is coupled into the light path with a dichroitic beam combiner. High power LEDs or laser diodes e.g. ADL-63V0ANP (Laser Components) may be used. The laser diode may be operated in parallel to the MID IR laser and is simultaneously transmitted to the handpiece. For fluorescence excitation (bacteria detection, canal cleanliness detection) cw or pulsed laser diodes in the range <NUM> - <NUM> are used.

The device uses preferably air cooling for laser cavity and electronics.

A schematic depiction of the laser system is shown in <FIG> which is self-explaining.

Especially, the invention is characterized by a diode pumped Er:YAG- / Er:YSGG/ CTE:YAG laser providing a cleanliness check of the canal as root canal via the same optical fiber used for the canal cleaning with the following excitation / detection wavelength ranges for bacteria fluorescence detection.

Further, the invention is characterized by a diode pumped Er:YAG- / Er:YSGG / CTE:YAG laser providing a cleanliness check of the canal as root canal via a metallization layer on the optical fiber tip used for the root canal cleaning using electrical impedance spectroscopy.

In addition, the invention is characterized by a diode pumped Er:YAG- / Er:YSGG / CTE:YAG laser providing energy (<NUM>. 05W - 3W with <NUM> - <NUM> pulse repetition rate ) into the canal as root canal via a fiber optic tip to heat the root canal inner surface via radiation absorption up to a <NUM> vicinity to temperatures lethal for bacteria reaching local peak temperatures on the root canal wall well above <NUM> and keeping the periodontal temperatures well below critical <NUM>.

A further feature of the invention is a diode pumped Er:YAG- / Er:YSGG / CTE:YAG laser providing an additional light source emitting at <NUM> with around <NUM> - <NUM> mW and/or <NUM> with <NUM> - <NUM> mW to simultaneously initiate PDT with fluids like Methylen Blue or Toluidin Blue and agitate the PDT fluid by laser energy with rapidly induced steam bubbles and adjacent fluid motion and heat.

Water and compressed air are provided by plugging a dental turbine connector in a socket of the device. The device may have further exchangeable containers <NUM> for different cleaning fluids (sterile water, NaOCl, EDTA), if these containers <NUM> are not positioned directly at the handpiece <NUM>. These cleaning fluid containers are pressurized by the compressed air of the dental chair provided by the dental turbine connector <NUM>.

The fluid flow from these containers <NUM> to the handpiece <NUM> is controlled with electromagnetic valves operated via the µC (embedded micro-controller). Controlling the laser parameters and the sequencing of the cleaning fluids, laser assisted drying and compressed air allows a fully automated cleaning process canal by canal (TABLE II). The dentist needs just to press a start button and then move gently the fiber in the canal up and down until a ready sign appears (LED or Beep). Then the fiber <NUM> is inserted in the next canal and the procedure is repeated.

The laser parameters used when cleaning a canal are specified in TABLE III.

Mechanisms are provided to ensure that the laser can only operate, if the laser fiber <NUM> is placed in the root canal <NUM> to reduce laser safety risks.

When the fiber tip <NUM> is inserted into the root canal <NUM> the light received through the fiber <NUM> is far less compared to the fiber <NUM> being in ambient light. A detector in the laser system measures the light coming back from the fiber tip <NUM> and detects the absolute light level and the change in light level (first derivative). This detection can be done independently from any micro-controller or detection software. It is based on fixed wired hardware with a fail-safe design, which disables the laser system in case of a hardware fault in the detection unit.

The electronics further can detect the change of reflection of light emitted into the fiber delivery system (e.g. the aiming beam) when the refraction index difference changes while immersing the fiber tip <NUM> into the fluid contained in the root canal. The light of the aiming beam is amplitude modulated to differentiate the signal from the ambient light.

Another method to detect the fiber tip <NUM> position inside a root canal <NUM> is to metallize the surface of the fiber <NUM>, inject a measurement current (AC) into the electrode(s) <NUM>, <NUM> and measure the impedance change during insertion of the fiber into the root canal <NUM>. The fiber <NUM> may be fully metallized as one electrode in combination with a counter electrode held by the patient or attached to the mouth of the patient (lip clip). A preferred solution is, however, a dual electrode concept, i.e. a first and a second electrode <NUM>, <NUM>, avoiding a counter electrode. Unambiguous connection is guaranteed by indexing the fiber tip.

Metallization layer may consist of a full coating of the optical fiber except the conical part of the fiber tip or may be a structured layer forming one or more electrodes on the same outer fiber surface.

A metallized tip configuration enables further "Canal is still wet" detection preferably with a dual electrode metallized fiber tip (see <FIG>).

A wet canal has a significantly higher relative permittivity constant compared to a dry canal. H<NUM>O: <IMG>: <NUM> - <NUM> and <IMG>: <NUM> - <NUM> compared to dentin <IMG>: <NUM>-<NUM> and <IMG>: <NUM>,<NUM> - <NUM>. This can be utilized to determine the degree of humidity of the root canal. Measurement is done with a single frequency or multiple single frequencies or a sweep over a frequency band, which can be in the range <NUM> to <NUM>, preferably <NUM> - <NUM>. A hydrophobic coating is applied in the area of the electrode to avoid direct not reversible wetting of the electrodes.

Using the canal humidity detection in combination with a laser based canal drying procedure, by applying laser energy with <NUM>,<NUM> - 1W with <NUM> - <NUM> pulse repetition rate allows a feedback controlled canal drying procedure.

Further impedance spectroscopy can be used for bacteria detection in the root canal <NUM> and length measurement during cleaning the canal <NUM>. A special variant of impedance spectroscopy offered by NuMed (Patent <CIT>) analyzing the harmonics generated by bacteria cell walls, can be integrated into the proposed cleaning device and allow bacteria detection in the root canal.

Using the metallized fiber <NUM>, root canal length measurement with impedance measurements can be performed simultaneously with cleaning to indicate the correct position of the fiber tip <NUM> during treatment and not to exceed the apex <NUM>.

To differentiate an upper jaw from a lower jaw treatment an inertial sensor e.g. is used (MEMs device e.g. Kionix KXTF9). This is important, since the fluid refill rate is different treating upper or lower jaw cases.

Further this inertial platform provides data for the movement direction of the fiber tip <NUM> (into - or out of the root canal <NUM>). This is important to switch off the laser when pushing the fiber tip <NUM> into the root canal <NUM>, in case an application requires an energy density above the ablation threshold.

Further the motion information provided by the motion sensor can be used to detect whether the dentist is continuously moving the fiber in the canal and remind the dentist with warning information, if he stops the movement during treatment and reduce or switch off the laser power.

Additionally the inertial platform data can be used to crosscheck with the fiber position data provided from the impedance based fiber position measurement.

The delivery system <NUM> connects the portable desktop device <NUM> with the handpiece <NUM> similar to a dental drill handpiece.

To avoid torque on the light guide the handpiece <NUM> is connected to the delivery system <NUM> with free rotation with low friction around the longitudinal axis.

The laser radiation is transported via a GeO, sapphire, ZrF<NUM> or any other light guide capable transmitting radiation (up to 50mJ, up to 5W Avg. power, 500W peak power) in the wavelength range <NUM> - <NUM> and additionally <NUM> - <NUM> to the handpiece. The core diameter of the light guide fiber is between <NUM> and <NUM>, preferably <NUM> - <NUM>. The light guide end surfaces are protected against moisture and may be coated with an anti-reflective material.

Compressed air and water available at the dental unit of the dental chair, connected to the device is guided through the delivery system together with the light guide.

Optional further cleaning fluids from exchangeable containers plugged in the device can be transported in the delivery system to the handpiece.

Electrical wires provide data and power transport between handpiece and desktop unit. To keep the number of wires and connectors low, a SPI- or I<NUM>C-bus system is used.

A bending protection insures that the fiber <NUM> is not bended beyond the allowed bending radius for oscillating bending.

The delivery system <NUM> is detachable from device in case of a need for repair and the handpiece <NUM> can be detached from the delivery system <NUM> routinely for cleaning/ sterilization.

<FIG> is a schematic depiction of the delivery system <NUM> which is self-explaining.

As an alternative to the placement of the motion sensor in the handpiece the sensor can be placed in the most distal part of the delivery system. This would avoid sterilization cycles to be applied to the sensor chip. Then however a rotation position detection between handpiece and delivery system must be added.

The handpiece <NUM> is connected with the delivery system <NUM> with a rotational coupling <NUM>, which allows to deliver water (line <NUM>) and pressurized air (line <NUM>) to the handpiece <NUM>. Air and water are delivered to the front section of the handpiece <NUM> and are applied towards the fiber <NUM> with nozzles <NUM>. The laser radiation is supplied from the delivery system <NUM> with an optical fiber <NUM>, via a protection window <NUM>, a lens <NUM>, and a deflection mirror <NUM> to the fiber <NUM>. Fluid containers <NUM> are snapped on the handpiece <NUM>. A motion sensor <NUM> is placed in the front section of the delivery system <NUM> and can detect in combination with a rotation encoder <NUM> the motion of the fiber tip <NUM> (see also <FIG>).

In the handheld applicator a removable, disposable fiber <NUM> can be plugged in under an angle in the order <NUM> - <NUM>° to main direction of the handpiece <NUM>. This fiber tip <NUM> is introduced into the root canal.

The handpiece <NUM> is comparable to a small dental handpiece, ideally contra-angle. The handpiece <NUM> is rotatable around longitudinal axis.

The laser beam deflection into attachable fiber <NUM> by ~<NUM>° is performed with the flat mirror <NUM> and a separate focusing element or a focusing mirror.

The disposable fiber <NUM> is connected to the handpiece <NUM> with a connector allowing unique positioning with an indexing connection to allow at least <NUM> electrical connections unambiguously being connected to contacts in the handpiece <NUM>.

In a simple version of the handpiece <NUM> only water and air are available for the treatment directly out of the handpiece <NUM>. Other cleaning fluids are applied manually with a syringe into the root canals <NUM>.

Pressurized air and water may form a mist. <NUM> -<NUM>/min water and <NUM> - <NUM>/min air are used to form the mist.

A fluid beam is directed towards the last <NUM>/<NUM> of fiber <NUM> with angle ca. <NUM> - <NUM>° from fiber <NUM> longitudinal axis. The water speed at exit of the handpiece is larger than <NUM>,<NUM>/s.

A Start/Stop button may be integrated in the handpiece.

A schematic depiction of the handpiece <NUM> with its components is shown in <FIG>, which is self-explaining.

In a variant of the handpiece <NUM> disposable fluid containers <NUM> / (also called cartridges) for NaOCl and EDTA are directly attached to applicator. The cartridge <NUM> has a fluid guidance close to the fiber <NUM> (see <FIG>). A direct placement at the handpiece <NUM> is possible since the treatment requires only small amounts of fluid in the order of <NUM>-<NUM> per fluid. Main objective is to keep the partially corrosive fluids separate from the handpiece <NUM>, delivery system <NUM> and desktop device <NUM>. Further objective is to avoid dripping before and after usage. An inexpensive solution to achieve these objectives is the separation of an electromagnetic valve <NUM> into the excitation part with the magnetic coil <NUM> and a part of the ferromagnetic core <NUM> in the handpiece <NUM> and a ferromagnetic material as valve <NUM> opener as part of the exit valve in the disposable cartridge <NUM>. The cartridge <NUM> is set under air pressure when placing the cartridge <NUM> in the handpiece <NUM>. A flexible membrane or a piston <NUM> may separate the fluid from the air inlet. For more details, see <FIG>.

The fiber material must allow the transmission of a wavelength range from <NUM> to <NUM> with reasonable loss and cost. OH reduced silica fibers are an acceptable compromise with ~<NUM>% attenuation over <NUM> length at <NUM> (including Fresnel reflection). The fiber <NUM> is a disposable surviving <NUM>-<NUM> root canals with moderate degradation. The end <NUM> of the fiber <NUM> is conically shaped without protection layer or metallization. Alternatively the fiber <NUM> can be hemispherical. The fiber <NUM> has an outer diameter of <NUM> - <NUM> and a core diameter of <NUM> - <NUM>. The length of the fiber <NUM> is between <NUM> - <NUM>. A molded plastic part connects the fiber <NUM> with the handpiece. The fiber <NUM> may have an additional coating to improve fracture resistance and may have a surface metallization to allow measuring the insertion length in the root canal, to determine the distance to the apex during treatment. The contact surfaces of the electrodes contact to connectors in the coupling to the handpiece <NUM>. The coupling part to the handpieces <NUM> allows only <NUM><NUM>° rotated positions to allow for unambiguous connection of the two electrodes. The electrodes <NUM>, <NUM> may be covered with a hydrophobic layer. Further details of the fiber <NUM> with its tip can be learned from <FIG>.

A software controls the laser parameters, air and water flow and in the extended handpiece <NUM> variant the flow of up to two additional cleaning fluids.

Sequencer programs are available for the following applications:.

The Cleaning/drying program provides a sequence of cleaning and drying steps (see TABLE II). The parameters can be program individually and stored as "Preferred treatment programs".

Bacteria detection is a program to detect remaining bacteria and/or bacteria residuals in the root canal via fluorescence detection.

Thermal bacteria reduction is a program to heat the inner root canal surface locally in a clear defined way. Pulse repetition rates preferably between <NUM> and <NUM> are used in combination with low pulse energies (<NUM>,<NUM> - 1mJ) to generate locally temperatures on the inner root surface and within a few <NUM>th of µm in the root canal wall high enough to kill remaining bacteria. No fluids are used in this program. Fiber motion is monitored by the motion detector to avoid any risk of local over-heating.

The aPDT program combines the traditional aPDT sequence known e.g. from Helbo with the laser generated steam bubbles to create motion in the aPDT dye fluid to enhance the contact and fluid exchange along the root canal wall. Instead of a cleaning fluid container an aPDT dye is inserted in the handpiece. After the aPDT the Dye is washed out the root canal automatically by flushing with water with support of laser generated steam bubbles.

For an irregular, not shaped root canal <NUM> a different obturation strategy is required. To support such an obturation method the device offers the following programs:
The apical plug placement program is used in combination with a fiber with attached gutta-percha plug. With the laser heat is applied to partially melt the plug in apical position and detach it from the fiber tip.

The obturation support program is used to accelerate a low viscosity obturation material placed over the apical plug in the root canal against the root canal wall to enhance the dense coverage of the whole root canal wall with obturation material. For that purpose transient steam bubbles are generated in the root canal filling material. The applied heat can further reduce the viscosity during the application additionally enabling the obturation material to creep in any niche of the canal.

The invention provides an automated control of the laser parameters and the sequencing of the cleaning fluids, laser assisted drying and compressed air, which allows a fully automated cleaning process.

Claim 1:
A device for sealing of a circumferentially closed canal (<NUM>), comprising a laser, a light guide (<NUM>) connected to the laser and conducting a laser beam, and a closure element (<NUM>) secured to a free end (<NUM>) of the light guide, wherein the closure element is connected to the free end of the light guide by means of a connection material (<NUM>),
characterized in that
the enclosure element (<NUM>, <NUM>) comprises an expandable material; and the material of the closure element expands at temperatures lower than the melting temperature of the connection material.