CA2231421A1 - Apparatus and method for laser vaporization of hard tissue - Google Patents

Abstract

This invention is an apparatus and method for vaporizing any one of hard tissue and deposits (36) on hard tissue (52). A scanner (22) substantially continuously scans a target area and directs a pulsed laser (20) beam during the scanning so as to vaporize portions of the target area to form a vaporized target area of a desired size and shape. Non-limiting examples of applications include those for performing a stapedectomy, drilling in teeth, vaporizing of plaque, and caries.

Description

W O 97/10768 PCT~L~6.'~A~35 APPARATUS AND MErHOD FOR LASER VAPORlZA~iON OF HARD TISSUE

FIELD OF THE INVENT~ON
The present invention reiates to apparatus and method for laser vaporization of hard tissue and deposits on hard tissue, such as teeth and bones, with a laser scanner in general and more particularly with a laser scanner and a pulsed laserbeam.

BACKGROUND OF lHE INVENTION
Teeth cleaning conventionally involves mechanical instruments that vibrate or pick at deposits to remove the deposits, such as plaque between teeth and gums. Some discomfort is felt during this mechanical cleaning technique. In dentistry, mechanical drills are used to make holes in teeth and even the sound of their motors may cause concern or anxiety to the patient. A local anaesthetic isusually needed because the drilling procedure is painful. Mechanical vibrations,mechanical contact of the drill with the tooth and irritative noise are the maindisadvantages of mechanical drills.
One alternative to mechanical drilling is the use of a laser for ablating hard tissue or for ablating deposits on hard tissue. In the prior art, the use of Erbium based lasers (Er:YAG and ER:YSSG) and CO2 laser is described.
Examples of U.S. patents describing the use of Erbium based lasers for dental application include U.S. Patents Nos. 5,342,198 to V~csiii~is et al., 5,458,594 to Mueller et al., 5,401,171 to Paghdiwala, 5,267,856 to Wolbarsht et al.
and 5,199,870 to Steiner et al.
The use of a pulsed CO2 laser to ablate hard tissue is described in an article 2~ entitled Hard Tissue ablation with pulsed CO2 lasers by Thomas Ertl and Gerhard Muller, published in SPIE journal, volume 1880 pp. 176 - 181, 1993. The use of aCO2 laser to melt and anneal teeth enamel in order to prevent caries is described in an article entitled MultiPle puise irradiation of dental hard tissues at CO~ laser W O 97/10768 PCTnL96/00099 wavelength by D. Fried et al. published in SPIE Vol. 2394 pp. 41 - 50, 1995 and in an article entitled Time-dePendent reflection and surface temperatures during co2 laser irradiation of dental hard tissue with 100-us ~ulses published in the sameSPIE volume by W. Seka et al. on pp. 51 - 66.
One drawback of prior art use of lasers in hard tissue applications is that in order to provide a laser beam having enough energy density to ablate the hard tissue or the deposits on the hard tissue one has to provide a laser beam havinga spot size on the order of tens of microns or few hundred microns which is an order of magnitude or more smaller than the size of the target area to be ablated.
For example, in dentistry, while the size required for holes drilled in the teeth is on the order of millimeters, the spot size of the ablating laser is one to two orders of magnitude smaller.
Also, with a focused laser beam as described in the prior art, the laser has to be applied in relatively short pulses and delivered in a low repetition rate in order to avoid undesirable thermal damage, such as cracking of enamel and dentin or thermal damage to the pulp.
Generally speaking, the drawbacks associated with the use of mechanical instruments and lasers for hard tissue dental application are found in other hard tissue applications, such as in the ablation of bones. For example, in stapedectomy, the use of a defocussed laser beam or a rosette of focussed laser beams as described for example in an article entitled Lasers for osteosclerosis -which one if any and why by S. George Lesinski, published in Lasers in Surgery and Medicine, volume 10, pp. 448 - 457, 1990, results in excessive thermal damage including carbonization of adjacent tissues.
Another drawback associated with the use of prior art lasers for hard tissue applications, as well as of mechanical drilling, is the limited sizes and shapes in which the target area of the hard tissue can be ablated.
Also, with the methods described in the prior art for ablating hard tissue the laser apparatus must be relatively big in order to provide the high energy density required for hard tissue ablation relatively to soft tissue ablation.

W O 97/10768 PCT~L96/00099 SUMMARY OF lHE INVENrlON
It is therefore an object of the present invention to provide an apparatus which includes a laser and a scanner for vaporizing hard tissue and deposits on hard tissue in any desired size and shape, in a rapid manner and substantially without thermal damage to the adjacent tissues.
It is also an object of the present invention to provide a method for vaporizinga target area of a hard tissue or of a deposit on a hard tissue of any desired size and shape substantially without causing thermal damage to adjacent tissues.
It is a further object of the present invention to provide an apparatus for vaporizing hard tissue and deposits on hard tissue which is relatively small andinexpensive. By providing a focused beam on the order of 100 microns, the energy density required for hard tissue vaporization is provided. By providing ascanner to scan the focussed beam over a target area, vaporization of a target area of any size and shape, typically an order of magnitude or more than the spot size of the laser beam is attained.
According to an aspect of the present invention, a SilkTouchTM flashscanner, manufactured and sold by Laser Industries Ud. of Tel Aviv, Israel, previously used with various types of lasers to radiate soft tissue, is used with lasers operative in accordance with the present invention to form a sequence of micro-holes which when taken together provide a large, clean, char-free vaporized target area of any desired size and shape in the hard tissue while substantially avoiding thermal damage to adjacent tissues.
Flashscanners suitable for making any desired pattern, such as a spiral or a lissajous pattern, are exemplified in the following disclosures: The pending U.S.
Patent Application Serial No. 08/358,386, (the '386 application) entitled METHODAND APPARATUS FOR APPLYING A LASER BEAM TO A WORKING SURFACE, PARTICULARLY FOR ABLATING TISSUE, and filed December 19, 1994, which is incorporated herein by reference, and U.S. Patent No. 5,411,~02 (the '502 patent), entitled SYSTEM FOR CAUSING ABLATION OF IRRADIATED MATERIAL OF
LIVING TISSUE WHILE NOT CAUSING DAMAGE BELOW A PREDETERMINED

W O 97/10768 PCT~L96/00099 DEPTH, issued to Eliezer Zair on May 2, 1995, which is incorporated herein by reference.
According to one aspect of the present invention, there is provided a method for vaporizing any one of hard tissue and deposits on hard tissue. The method includes the steps of substantially continuously scanning a target area, the target area being any of hard tissue and deposits on hard tissue and directing a pulsedlaser beam during the scanning so as to vaporize portions of the target area, thereby forming a vaporized target area of a desired size, preferably between 0.5 and 6 millimeters and any desired shape. For example, the shape of the target area are circular, elliptic, squared, rectangular or in the shape of a slit.
The method may include the step of focussing the laser beam to provide an energy density sufficient to vaporize each the portion of the target area.
Further, the method may include the step of selecting a scanning speed for the scanning and providing a maximal repetition rate for the pulses of the pulsed laser beam in accordance to the scanning speed.
Still further, the method may include the step of repeating the steps of scanning and directing to complete a plurality of passes of the target area until a desired overall penetration is attained.
In the preferred embodiment, the method also includes the step of cooling the vicinity the target area, thereby avoiding thermal damage to adjacent tissue or char.
In accordance with a preferred embodiment of the present invention, the step of directing includes the step of directing the laser beam in a rate that results in the laser beam dwelling at each of the regions for a duration that is less than that which would cause thermal damage to adjacent tissue or char.
According to a further aspect of the present invention, there is provides an apparatus for vaporizing any one of hard tissue and deposits on hard tissue. Theapparatus includes a laser, preferably a CO2 laser, for generating a pulsed laser beam and a scanner for substantially continuously scanning a target area, the W O 97/10768 PCT~L9G/000~5 target area being any of hard tissue and deposits on hard tissue and for directing a pulsed laser beam during the scanning so as to vaporize portions of the targetarea, thereby forming a vaporized target area of a desired size and shape.
The apparatus may generate a focussed laser beam which provides an energy density sufficient to vaporize each the portion of the target area.
The apparatus also includes a control unit for selecting a scanning speed for the scanning and for providing a maximal repetition rate for the pulses of the pulsed laser beam in accordance to the scanning speed.
In a preferred embodiment for drilling in teeth the CO2 laser operates with a 0 wavelength of 9.3 to 11.2 microns, preferably in the 9.6 micron band, the pulse frequency is 1 - 1000 Hz, preferably below 200 Hz, each pulse has a pulse duration of less then 100 microseconds and the spot size of the beam is between 100 - 300microns.

CA 0223l42l l998-03-09 W O 97/10768 PCT~L96/00099 BRIEF DESCRIPTION OF THE DRAWINGS
For a better understanding of the present invention, reference is made to the following description and accompanying drawings, while the scope of the invention is set forth in the appended claims.
Fig. 1 A is a schematic illustration of an apparatus for performing a stapedectomy, constructed and operative in accordance with a preferred embodiment of the present invention;
Fig. 1 B is a schematic illustration of an apparatus for teeth vaporization and for vaporizing deposits on teeth, constructed and operative in accordance with apreferred embodiment of the present invention;
Fig. 2A is a schematic representation of a spiral pattern formed from a sequence of micro-holes being formed by employing the apparatus of Fig. 1A or Fig. 1B in accordance with a preferred method of the present invention;
Fig. 2B is a schematic representation of a larger hole formed after completion of the spiral pattern of Fig. 2A;
Fig. 3A is a schematic representation of a rectangular pattern formed from a sequence of micro-holes being formed by employing the apparatus of Fig. 1A or Fig. 1 B in accordance with another preferred embodiment of the present invention;
Fig. 3B is a schematic representation of a larger rectangular hole formed after completion of the rectangular pattern of Fig. 2A; and Fig. 4 is a schematic representation of a tooth being drilled in accordance with a preferred method of the present invention and further illustrates the vaporization of plaque in accordance with another preferred embodiment of the present invention.

W O 97/10768 PCT~L96/00099 DESCRIPTION OF THE PREFERRED EMBODIMENT
Fig. 1A illustrates an apparatus, generally referenced 1, constructed and operative according to one preferred embodiment of the present invention.
Apparatus 1 which is particularly suitable for performing stapedectomy comprisesa micromanipulator 10, a flashscanner 12, an articulated arm 14, a surgical microscope 16 and a laser 18 generating a laser beam 20 which is preferably but not necessarily a pulsed laser beam.
The flashscanner 12 has movable vibrating or rotating mirrors 22 which operate to provide the scanned pattern. Preferably, the flashscanner 12 is the one 0 disclosed in the '386 application and '502 patent in conjunction with a laser having an articulated arm. However, the present invention is not limited to the scanners of the '386 application and the '502. Rather, according to the present inventionany suitable scanner, such as the one described in U.S. Patent 5,546,214 to Black et al. may be used.
The micromanipulator 10 includes a dichroic mirror 26 whose relative position therewithin is changed in response to movement of an adjustment handle 28. The surgical microscope 16 is arranged to permit viewing through the dichroic mirror 26 from the surgical microscope 16.
In a preferred embodiment, the laser 18 is a CO2 laser, which is pulsed during scanning. In an alternative embodiment the CO2 laser is a continuous working CO2 laser. In both embodiments laser 18 provides laser beams 20 in a wavelength between 9.3 and 11.2 microns, preferably in the 10.6 micron band and most preferably in the 9.6 micron band. The 9.6 micron band is preferred due to the higher absorption of this band by Hydroxyapatite which is a main component 2~ of human hard tissue.
Fig.1 B illustrates an alternative apparatus to the apparatus of Fig.1 A having a configuration which is particular suitable for applications related to teeth, non limiting examples being vaporizing enamel and dentin so as to form a hole of anydesired size and shape in the teeth 52 or for vaporizing plaque and caries from the surface of teeth 52 as described in detail hereinbelow. Fig. 1 B illustrates W O 97/10768 PCT~L~G~n33 apparatus 1 having similar elements and referred to by similar reference numerals without the surgical microscope 16 since for dental applications surgical microscope 16 is often not required. The apparatus of Fig. 1 B forms a hand piece held by the dentist.
In practice, the physician 30 looks through the surgical microscope 16 (Fig.
1A) and positions the dichroic mirror 26 with the handle 28 until the laser beam 20 strikes the stapes bone 32 of the middle ear 34 (Fig. 1A) or looks directly on the target area (Fig. 1 B) while the laser beam strikes the desired location on teeth 52 (Fig. 1 B) in the desired target area 36, about which a pattern 38 will be scanned by the laser beam which vaporize hard tissue. The laser beam 20 is initially a visible pilot laser beam which helps the physician 30 in aiming the treatment laser beamto a striking location.
After the striking location is determined, the surgical vaporization within the pattern 38 on the hard tissue may commence, such as in the target area 36 of thestapes bone 32 (Fig. 1A) or the teeth 52 (Fig. 1 B). Figs. 2A and 2B illustrate the formation of a hole 40, whose size is about 600 microns in diameter to accommodate implantation of a prosthesis (not shown). This hole 40 is formed through repeating the scan of the surgical vaporization pattern 38 as many timesas needed until a desired penetration is attained.
For dental applications, various sizes and shapes of the target area are required according to the dental procedure involved. In this case, rounded holes, such as hole 40 (Fig. 2B), are typically 1 - 5 millimeters in diameter and holes of other shapes, such as the hole 41 of Fig. 3B which may also be formed by a spiral pattern (Fig. 3A) are generally of similar sizes.
The flashscanner 12 is first set to sweep the target area 34 to generate the surgical vaporization pattern 38 in the form of a spiral. A focused laser beam 20 of a single pulse then sweeps the pattern 38 in a spiral from spot to spot to form micro-holes 42 in sequence on the target area 36. After completion of the pattern 38, the single large hole 40 develops, made from the combination of all the micro-holes 42, with minimal char and minimal tissue damage outside the target area 36.

W O 97/10768 PCT~L96/00099 By sweeping the pattern again repeatedly with pulses, the large hole 40 increases its depth.
Typical operating modes of the laser with flashscanner include superficial vaporization of large surfaces, e.g., plaque, carries and laser drilling of a deeper hole in hard tissue such as teeth and bones. In either mode, the laser is preferably a CO2 laser that is pulsed during scanning.
It will be appreciated that the use of the scanner as described above is advantageous in many respect for hard tissue vaporization. The use of the scanner in addition to the use of a relatively low energy laser while vaporizing larger 0 target areas allows heat dissipation between consecutive firing on the same location of the target area so as to avoid cracks in the teeth and thermal damage to adjacent tissue.
It will also be appreciated that the use of the scanner enables the use of a higher pulse frequency than would be possible without the scanner so as to more rapidly drill in the hard tissue substantially without causing thermal damage toadjacent tissue. Moreover, the use of the scanner allows for the use of a laser having relatively low energy per pulse and high repetition rate so as to substantially avoid thermal damage to adjacent tissue. Nonlimiting operational parameters are described hereinbelow for exemplary applications.
In accordance with a preferred embodiment of the present invention, a repetitively pulsed CO2 laser 18 is used in conjunction with the flashscanner 12 to provide a sequence of micro-holes 42 which combine to form a large, clean, char-free rounded hole 40 (Fig. 2B) or a rectangular hole 41 (Fig. 3B). A particular feature of the present invention is that the apparatus of Figs. 1A and 1B are operative to vaporize a target area of any desired size and shape. In the nonlimiting example of Figs. 2A and 2B the sequence of micro-holes 42 is spiral and the resulting hole in the hard tissue 40 is rounded. In another nonlimiting example illustrated in Figs. 3A and 3B, the sequence is also spiral and the resulting hole 41 in the hard tissue is rectangular. Other patterns, such as a lissajous patterri may also be followed to provide holes of similar or different shapes.

W O 97110768 PCTnL96/00099 In accordance with a further preferred embodiment of the present invention, the repetition rate of the pulsed laser and the scanning rate are synchronized to achieve full surface coverage and depth homogeneity. As should be appreciated, the advantage in combining a pulsed mode and a flashscanner stems form the ability of a focused pulsed beam to achieve extremely clean vaporization.
Typical parameters for use in stapedectomy operations to drill a 0.6 millimeter diameter hole in each scan period with 1 millimeter depth include a focal spot size of 100 microns to 300 microns, a power level of 10 to 30 watts, a laser energy per pulse of 20 to 50 millijoules, a repetition rate of approximately 5000 Hertz, a pulse duration of less than 1 millisecond and a scanning period time of 0.2 seconds to 1 second. Increasing the scan duration time increases the hole depth.The focal length of the micromanipulator may be between 250 to 310 millimeters.
With a focused beam, each beam scan of a pattern may generate a 50 micron crater depth with a 500- 700 micron diameter spot size after a 0.2 secondduration per scan pass. It is preferable to wait between scan passes to look at the result before continuing the cycle. The laser may be fired for up to one second continuously or stopped after each of five scan passes (for a total of one second of exposure to laser radiation). Thus, instead of using one large pulse to drill the desired hole, the flashscanner may be used to make successive smaller holes which, when taken together, result in the same size hole as is made by theone large pulse. The difference lies in that with the flashscanner, the hole maybe of any desired size and shape and the rate in which the process is completed is faster.
Fig. 4 depicts further applications of the invention in the treatment of caries 50 in a tooth 52, and the vaporization of plaque 54 between the tooth 52 and gum56. While Fig. 4 illustrates the above mentioned dental applications, the present invention is directed to any dental application in which vaporization of teeth is required, such as cavity preparation, etching for preparing teeth surfaces for composite material bonding and any other dental procedure where vaporization of dentin or enamel is required in restorative dentistry.
-CA 0223l42l l998-03-09 WO 97/10768 P ~ ~L96~0~99 For plaque vaporization, or drilling in teeth, the power level may be about 1 to 21 watts, preferably 3 - 8 watts; the scanning period may be about 0.1 to 0.3seconds, preferably 0.2 seconds; the spot size diameter preferably may be about 0.2 millimeters. The scanning diameter is preferably 0.5 mm to 6 mm in any desired shape, such as circular, elliptical, rectangular, squared or in the form of a slit. The focal length may be about 100 millimeters and the laser may be operated in the superpulse mode at energy levels of 20 - 80 millijoules.
In the superpulse mode, the pulse frequency for drilling in teeth is preferably between 1 - 1000 Hz and the pulse duration is preferably below 200 microseconds.
0 In the superpulse mode the scanner can be either synchronized with thelaser beam triggering control or can be completely independent of the laser.
However, the scanning frequency and the pulse repetition frequency should be slightly different in order to avoid a situation where the laser keeps drilling at the same point.
For dental drilling, the smallest typical scan diameter is about 1 millimeter.
Operational parameters for vaporizing a hole of 2 ."illi",elers in diameter, 3 millimeters deep may be as follows: the putse frequency is 120 - 180 Hz, the pulse duration is about 60 microseconds, the spot size of the foc~ssed CO2 beam is 200microns, the duration of each scan is 0.2 seconds and 5 microns of hard tissue are being vaporized in each scan. This results in a drilling rate of 25 microns per second and in a total scanning time of 2 minutes to attain the 3 millimeters depth.
For caries treatment, cleaning the teeth of decay is the intended goal rather than drilling, the diameter of the scanning hole beam or spot size may be from about 0.2 millimeters to 1 millimeter, but its size is dependent upon the size of the decayed area. The remaining parameters are the same as for plaque vaporization but the number of scanning cycles is significantly lower. The hole formed is filled with conventional filling material to prevent the further accumulation of matter that leads to decay.
If according to an alternative embodiment of the present invention the CO2 laser is continuous working for superficial vaporization of large surfaces, the CA 0223l42l l998-03-09 W O 97/10768 PCT~L96/00099 operative parameters include about a 40 Watt power ievel, about a one millisecond flashscanner dwelling time on single spots with about a 100 - 300 micron focal spot size and about a 0.1 - 0.3 second scanning duration for superficial vaporization of a single, approximately 50 micron, layer of plaque that has about a 2-6 millimeter diameter. This permits the cleaning of deposits on teeth or vaporization of bones, among other applications. Instead of continuous working, the CO2 laser may be pulsed and used for the same purpose (e.g., set at superpulse, SharpulseTM, SurgipulseTM, UltrapulserM as exemplary settings).
If the CO2 laser is continuous working for laser drilling of a deeper hole, such0 as caries, in hard tissue, the operative parameters include a power level ranging form 30 watts to 150 watts, about a 0.3 millisecond dwelling time on tissue withabout a 100 - 300 micron focal spot size and about a 0.2 to 1 second scan pulse duration. Each scan may vaporize a hole with a 0.5 millimeter to 2 millimeter diameter but multiple scan cycles are necessary to drill holes to a depth of 1 to 3 millimeters.
In each of these applications, the physician or dentist must first identify where the laser radiation is to strike. This is done through visual inspection, preferably with the aid of a visible pilot laser beam. Thereafter, the CO2 laser is fired to complete one full scan and is repeated until the desired overall depth is attained. After each scan, the results can be observed.
For dental work, difficult to reach areas of the teeth can be reached by directing the laser beam at the dentist's mirror used to view the backside of teeth if necessary to deflect the beam off the mirror and onto the difficult to reach area of the teeth. Since the dwelling time for the laser scan pass is so short, the entire dental procedure can be completed quickly.
According to the present invention, the vicinity of the target area is cooled by suitable cooling means, such as by a spray of water, so as to ensure that thevaporization of the hard tissue performed by the laser will be completed substantially without thermal damage to adjacent tissues.

W O 97/10768 PCT~L~6 A particular feature of the present invention is that cooiing is used for avoiding substantial thermal damage and not for enhancing the effect of hard tissue vaporization. In a nonlimiting experiment, using the same operation parameters described above for drilling a 2 millimeters in diameter and 3 millimeters deep hole in a teeth (120 - 180 Hz pulse frequency; 60 microseconds pulse duration; 200 microns spot size; 0.2 seconds single scan time; 2 minutes total scanning time),similar results with respect to the hole formed were attained with and without water cooling, where the only difference was that, without water cooling, undesirable thermal damage was observed.
While the foregoing description and drawings represent the preferred embodiments of the present invention, it will be understood that various changesand modifications may be made without departing from the spirit and scope of thepresent invention. For example, while the preferred embodiment of the present invention has been described with respect to the use of a CO2 laser, it will be appreciated that the scanner may also operate with an Erbium based laser, such as an ER:YAG laser.

Claims (38)

WHAT IS CLAIMED IS:

1. A method for vaporizing any one of hard tissue and deposits on hard tissue comprising the steps of:
a. substantially continuously scanning a target area, the target area being any of hard tissue and deposits on hard tissue; and b. directing a pulsed laser beam during said scanning so as to vaporize portions of said target area, thereby forming a vaporized target area of a desired size and shape.

2. A method according to claim 1 and further comprising the step of focussing said laser beam to provide an energy density sufficient to vaporize each said portion of said target area.

3. A method according to any of claims 1 - 2 and further comprising the step of selecting a scanning speed for said scanning and providing a maximal repetition rate for the pulses of said pulsed laser beam in accordance to said scanning speed.

4. A method according to any of claims 1 - 3 and further comprising the step of repeating said steps of scanning and directing to complete a plurality of passes of the target area until a desired overall penetration is attained.

5. A method according to any of claims 1 - 4 and further comprising the step of cooling the vicinity the target area, thereby avoiding thermal damage to adjacent tissue or char.

6. A method according to any of the previous claims and wherein the shape of said target area is circular, elliptic, squared, rectangular or in the shape of a slit.

7. A method according to any of the previous claims and wherein the size of said target area is between 0.5 mm - 6 mm.

8. A method according to any of claims 5 - 7, wherein said hard tissue is a stapes bone and said steps of scanning, directing and repeating are carried out while performing a stapedectomy for implantation of a prosthesis to restore hearing loss.

9. A method according to any of claims 5 - 7, wherein said hard tissue is a tooth and said steps of scanning directing and repeating are carried out as medical treatment of said tooth.

10. A method according to any of claims 5 - 7, wherein said deposit is plaque or caries and said steps of scanning, directing and repeating are carried out as part of a dental procedure to vaporize the plaque or caries.

11. A method according to any of the previous claims and wherein said step of scanning includes viewing and adjusting a relative position of the dichroic mirror with respect to the laser beam based on the viewing so that the laser beam deflects off the dichroic mirror to strike the target area.

12. A method according to claim 11, further comprising the step of firing a visible pilot laser beam to strike the target area, the viewing including watching where the visible pilot laser beam strikes the target area, the adjusting including adjusting the relative position of the dichroic mirror based on said watching.

13. A method according to any of claims 11 - 12 and wherein said step of viewing includes viewing through a surgical microscope and then through a dichroic mirror within a micromanipulator to see the target area.

14. A method according to any of the previous claims and further comprising the step of generating the laser beam with a CO2 laser.

15. A method according to claim 14 wherein said CO2 laser operates with a wavelength of 9.3 to 11.2 microns.

16. A method according to claim 15 wherein said CO2 laser operates in the 9.6 micron band.

17. A method according to claim 14 wherein said pulses have a pulse frequency of 1 - 1000 Hz.

18. A method according to claim 17 wherein said pulse frequency is below 200 Hz.

19. A method according to claim 14 wherein each pulse has a pulse duration of less then 100 microseconds.

20. A method according to claim 14 wherein the spot size of said laser beam is between 100 - 300 microns.

21. Apparatus for vaporizing any one of hard tissue and deposits on hard tissue comprising:
a. a laser for generating a pulsed laser beam; and b. a scanner for substantially continuously scanning a target area, the target area being any of hard tissue and deposits on hard tissue and for directing a pulsed laser beam during said scanning so as to vaporize portions of said target area, thereby forming a vaporized target area of a desired size and shape.

22. Apparatus according to claim 21 and wherein said pulsed laser beam is a focussed laser beam providing an energy density sufficient to vaporize each said portion of said target area.

23. Apparatus according to any of claims 21 - 22 and further comprising a control unit for selecting a scanning speed for said scanning and for providing a maximal repetition rate for the pulses of said pulsed laser beam in accordance to said scanning speed.

24. Apparatus according to any of claims 21 - 23 and further comprising means for cooling the vicinity of the target area.

25. Apparatus according to any of claims 21 - 24 and wherein said control unit is operative to repeat said scanning and directing to complete a plurality of passes of the target area until a desired overall penetration is attained.

26. Apparatus according to any of claims 21 - 25 and wherein the shape of said target area is circular, elliptic, squared, rectangular or in the shape of a slit.

27. Apparatus according to any of claims 21 - 26 and wherein the size of said target area is between 0.5 mm - 6 mm.

28. Apparatus according to any of claims 21 - 27 and wherein said laser is a CO2 laser.

29. Apparatus according to claim 28 wherein said CO2 laser operates with a wavelength of 9.3 to 11.2 microns.

30. Apparatus according to claim 29 wherein said CO2 laser operates in the 9.6 micron band.

31. Apparatus according to claim 28 wherein said pulses have a pulse frequency of 1 - 1000 Hz.

32. Apparatus according to claim 31 wherein said pulse frequency is below 200 Hz.

33. Apparatus according to claim 28 wherein each pulse has a pulse duration of less then 100 microseconds.

34. Apparatus according to claim 28 wherein the spot size of said laser beam is between 100 - 300 microns.

35. A method according to any of claims 1 - 20 substantially as described hereinabove.

36. A method according to any of claims 1 - 20 substantially as illustrated in any of the drawings.

37. Apparatus according to any of claims 21 - 34 substantially as described hereinabove.

38. Apparatus according to any of claims 21 - 34 substantially as illustrated in any of the drawings.