JPH06292680A - Elimination of vital tissue using recess by vapor - Google Patents

Abstract

PURPOSE: To effectively exsect a living tissue utilizing a highly controllable technique by controlling shift of irradiation energy to the living tissue to a minimum. CONSTITUTION: A laser irradiation beam 8 of a wavelength having water absorption coefficient corresponding to a laser irradiation beam of approx. 2.4-2.9 micron meter wavelength, is irradiated by an optical fiber 6 to a water film 2 covering the material to be removed. The initial energy of the irradiated laser beam 8 deforms the material to be removed into a destructible state, to which the laser beam 8 is further irradiated and the deformed material is destroyed and removed by the laser energy of the second irradiation. The destruction is effected by a shock wave which is formed in the water film 2 and generated from the cavity of the water film, yielded by the second laser irradiation energy.

Description

Detailed Description of the Invention

CROSS REFERENCE TO RELATED APPLICATION This is a continuation-in-part application of US Ser. No. 08 / 025,549, filed March 3,1993.

[0002]

FIELD OF THE INVENTION The present invention relates to a method and apparatus for removing obstructive substances in hard and soft tissues and blood vessels of the body. The invention particularly relates to the use of laser irradiation for carrying out such removal operations.

[0003]

BACKGROUND OF THE INVENTION Although laser irradiation energy actually has the effect of cutting or puncturing, the use of this laser irradiation energy for the removal of living tissue has been used in many studies over the last few decades. It has become the subject. These studies have revealed that various types of tissue can be cut by focused irradiation with lasers having many different wavelengths. Typical lasers that have been used for this purpose include ruby lasers that generate a wavelength of 0.694 μm, Nd: Y which has a standard wavelength of 1.06 μm but can also generate a wavelength of 0.532 μm.
AG laser, Er-Y generating a wavelength of 2.49 μm
AG laser and CO ₂ generating a wavelength of 10.6 μm
Includes laser.

The most common technique for cutting tissue by laser irradiation is to select a wavelength that is well absorbed by either the tissue components or water taken up in the tissue and by Focusing the laser so that the water absorbs it well is included. The irradiation parameters are selected by whether the power density of the laser absorbed in the tissue is sufficient to destroy the tissue. All methods of this type have the effect of heating the tissue adjacent to the area where the destruction occurs, so that the area of interface with the removed tissue may be damaged and even necrotic.
To reduce damage problems when cutting tooth tissue 1
US Patent No. 5, issued to applicant on June 4, 992
No. 020,995, intensively irradiating a tissue site that cuts a wavelength that is very well absorbed by hydroxyapatite as compared with water, cutting the irradiation site so that the irradiation site is sufficiently small, A method of applying the contained cooling liquid to an irradiation site is disclosed. This technique has made great advances in safety in cutting, but since the tissue to be cut absorbs laser irradiation energy in this method,
The tissue is heated to some extent.

[0005]

Here, another technique of cutting by utilizing laser irradiation is disclosed in US Pat. No. 5,116,227 issued to the applicant on May 26, 1992. ing. In the technique disclosed in this patent, a pulsed laser irradiation is directed into a liquid medium that fills the passage, concentrating the energy in each pulse in the liquid. The laser irradiation pulse forms a depression (cavitation) in the liquid, and the mechanical force of the depression acts so as to destroy the substance on the passage wall.
In this method, the laser irradiation energy is concentrated in the liquid and all the force needed to destroy the material of the passage walls is generated by the mechanical depression of the liquid. The cutting action achieved by this technique is effective in enlarging the passage and removing deposits on the passage walls. However, since the force due to the depression is dispersed throughout the passage, the effect generated in this way is not so directional.

The present invention has been made in view of the above problems, and the purpose thereof is as follows.

[0007] That is, the object of the present invention is to effectively remove living tissue by a method significantly improved from the prior art.

Another object of the present invention is to effectively remove living tissue in a highly controllable manner while minimizing the transfer of irradiation energy to the living tissue itself.

Another object of the present invention is to effectively remove tissue by laser irradiation generated by inputting a low level power to an interlocked laser.

[0010]

The above and other objects are achieved by the method according to the present invention. That is, about 2.
Between 4 μm and 2.9 μm (less than 2.9 μm)
Position the contact surface between the tissue surface and the water film on the part of the material that generates and removes the film of water that contacts the tissue by generating the laser irradiation beam of the wavelength that has the absorption coefficient of water corresponding to the laser irradiation beam of By introducing a laser irradiation beam into the water film, it is irradiated toward the contact surface with the substance to be removed, and the energy density is concentrated near the contact face to reduce the energy required to destroy the substance. As the first energy modifies the substance to be removed, the second energy is absorbed by the film of water and the water produces sufficient mechanical action to destroy the minimal substance modified by the first energy. Including that,
The above and other objects are achieved by a method of removing a substance from a living tissue having a surface.

The present invention is particularly suitable for living hard tissues, ie calcified or calcium-containing tissues including bone, enamel, dentin, cementum.

The material manipulation of the present invention can also be used to remove living soft tissue, including pulp, root tissue, gingiva and any other soft tissue found in the body. Furthermore, the method according to the invention can also be used for the removal of substances such as clots or plaques that form occlusions in blood vessels.

Specifically, according to the invention of claim 1 of the present application,
In a method for removing a substance from a biological tissue having a surface, a beam generating step of generating a laser irradiation beam having a wavelength having a water absorption coefficient corresponding to laser irradiation having a wavelength of about 2.4 μm or more and 2.9 μm or less, A water film forming step of forming a water film in contact with the tissue, the water film forming step of forming the film so that the contact surface between the tissue surface and the water film is located at the site of the substance to be removed, The laser irradiation beam generated in the beam generating step is directed to the water film and the contact surface with the substance to be removed, and the first laser irradiation energy causes the substance to be removed to concentrate the power density on the contact surface and destroy the substance. The material modified by this first energy is absorbed into the water film, and the second energy is absorbed by the water film. Causing the water to come into contact with the substance to generate a mechanical action sufficient to minimally destroy the substance.

The method according to claim 2 is characterized in that, in the method according to claim 1, the step of forming the water film is spraying water on the tissue surface.

A third aspect of the present invention is the method according to the first aspect, wherein the water film has a thickness of about several μm to 100 μm.

A method according to a fourth aspect is the method according to the first aspect, wherein the laser irradiation beam is a continuous irradiation pulse.

The method of claim 5 is characterized in that, in the method of claim 4, the average output level of the beam of the laser irradiation is about 0.1 to 40 W.

The method of claim 6 is the method of claim 5, wherein the average output level of the laser irradiation beam is about 0.1 to 5 W.

The method of claim 7 is the method of claim 5, wherein the area of the beam of the laser irradiation is 200 mm in diameter.
It is characterized by being the same as the area of a circle of μm to 500 μm.

The method of claim 8 is the method of claim 7, wherein the diameter of the circle is 300 μm to 400 μm.

A method according to claim 9 is the method according to claim 1, wherein the laser irradiation beam is about 10 ns to 10 ns.
It is characterized by a series of irradiation pulses with a duration of ms.

The method of claim 10 is the method of claim 9, wherein the irradiation pulse is about 100 ms to 800 ms.
Is characterized by having a duration of.

The method of claim 11 is the method of claim 9 wherein the irradiation pulse has a repetition rate of 10 to 30 pps.

A method according to claim 12 is the method according to claim 1, wherein the laser irradiation is about 2.65 μm to 2.8.
It is characterized by having a wavelength of 5 μm.

The method of claim 13 is the method of claim 12, wherein the laser irradiation is about 2.7 μm to 2.8.
It has a wavelength of μm.

A method according to claim 14 is the method according to claim 13, wherein the laser irradiation is about 2.71 μm-2.
It has a wavelength of 78 μm.

[0027]

In the method for removing a substance from a living tissue having a surface according to the present invention having the above-mentioned structure, a water film is formed on the tissue surface where the substance to be removed exists. The contact surface (boundary) between the water film and the tissue surface (the tissue surface where the substance to be removed exists)
Then, a laser irradiation beam having a wavelength having an absorption coefficient of water (corresponding to a laser irradiation beam having a wavelength of about 2.4 μm to 2.9 μm) is irradiated. By this, about 2.4μ
A laser irradiation beam having a wavelength having a water absorption coefficient corresponding to the laser irradiation beam having a wavelength of m to 2.9 μm is irradiated toward the water film 2 at the site where the removal substance is present.

When the laser irradiation beam is irradiated, the first laser irradiation energy modifies the material to be removed so that the material is easily destroyed. Then, by continuing to irradiate the modified material with the laser irradiation beam, a dent (cavitation) occurs in the water film, and further a physical force (for example, a shock wave) is generated from the dent, As a result, this physical force destroys and removes the material being modified. Therefore, according to the method of the present invention, hard tissue can be cut hygienically and effectively.

The method according to claim 1 most effectively produces the above action. The method according to claim 2 suitably forms the water film according to the method of the present invention. The method according to claim 3 provides a water film that effectively generates physical force by the water film of the present invention. The method according to claims 4 to 14 provides a laser irradiation beam which can effectively deliver the first and second laser irradiation energy.

[0030]

The present invention will be described in detail with reference to the drawings.

The mechanism for removing various substances, including substances that form blockages in living soft tissues and hard tissues and blood vessels by destroying them, is a pulse of concentrated laser irradiation having a wavelength that is properly absorbed only by a liquid. It is based on the tissue modification and the mechanical action of the fluid caused by. When such irradiation pulses are introduced into the coating of liquid with sufficient energy density for each pulse, each pulse at least produces vaporized liquid in the already formed micropores. This vaporization creates a pressure that causes sufficient microexplosion to destroy the material in which the micropores reside. Dimples are also formed in the liquid coating and / or in the micropores in the material to be destroyed, which creates shock waves that contribute to the destruction of the material. The action in the tissue to be severed is almost entirely mechanical, with very little heat being generated in or transferred to the tissue. A more detailed description of this effect is provided below with reference to FIGS.

1-3, the water coating 2 is held on the surface of the body 4 of the material to be cleaved by any suitable method so that there is no contact surface between the coating 2 and the surface of the body 4. Exists. The output end of the optical fiber 6 is installed so that a beam 8 of laser irradiation is introduced into the coating 2 and hits a cut site on the surface of the body 4. The output end of the optical fiber 6 may be in contact with the coating 2 or may be separated from the coating 2 by several hundred μm. This distance mainly depends on the size of the target spot near the contact surface and the irradiation power level, and
It also depends to some extent on the physical limitations of the size and shape of the laser device.

FIG. 1 illustrates the first step in a sequence of operations for removing increased amounts of material from body 4.
The irradiation beam 8 is applied to the surface of the body 4 to be cut through the coating 2. A dose of beam energy is absorbed in the surface area 12 of the body 4, modifying the tissue so that the body material at that location is more easily destroyed by mechanical forces. In the case of biological hard tissue, it changes into a crystal structure of hard tissue similar to carbonization, which increases the absorption coefficient of energy and decreases its mechanical strength. In the case of occlusion in living soft tissue and blood, disruption of protein field linkage is likely to occur. It should be emphasized that all of these changes are very local and do not spread to areas that are not removed. Therefore, the substance remaining after the removing operation is virtually not damaged by heat.

In FIG. 2, the liquid is absorbed in the micropores formed in the region 12 of the body 4, and a single irradiation energy is absorbed by the liquid in the micropores to cause vaporization.

This vaporization causes a minute explosion in the micropores. As a result, a depression 14 is formed in the surface area of the body 4, as shown in FIG.

In particular, when the radiation is properly absorbed only by the coating 2, the following additional effects may occur. In this case, one dose of energy forms bubbles 12 containing the trapped gas, as shown in FIG. This bubble forms a curved gas-liquid contact surface, which causes the lens in the beam 8 on illumination to be defocused or diverged. As a result, the surface of the body 4 in contact with the bubbles 12 is cooled and suddenly imploded, and a shock wave is generated, which is an effect due to the depression. This shock wave is mainly
It acts on the increased area of the body 4, which has been modified to destroy it. The destroyed material is removed, but preferably,
This destructive substance is automatically carried out from the cutting site by the continuous flow of the coating film 2 constituting the same. as a result,
As shown in FIG. 3, a recess (rec) is formed in the surface area of the body 4.
ess) 14 is formed.

The duration of the above series of operations depends on the thickness and flow rate of the coating 2, the material of the body 4 and the power density of the beam 8. When the various parameters are set appropriately, the series of operations ends in units of 5 μs.

After reaching the stage shown in FIG. 3, if the laser beam 8 is continuously irradiated, a series of operations are repeated. If the fibers 6 are held in place, the depressions 14 in the body 4 will be deeper and even wider. When the fiber 6 is moved along the surface of the body 4, the depression is extended in the moving direction.

Laser irradiation is preferably provided in the form of a continuous pulse. This is because it prevents the rise of heat in the body and at relatively low power input levels it is possible to generate laser irradiation with the required power density.

The presently preferred liquid is water. Because it is rich in water, has good compatibility with living organisms, and
This is because laser irradiation of a wavelength that produces a desired interaction with water is well known. Therefore, the following description is limited to the use of water. However, it should be understood that other liquids can be used in the practice of the invention.

If the wavelength and power density of the laser irradiation are not properly selected, the irradiation pulse will not have the desired effect. When water is sprayed on a substance which is irradiated by a certain kind of laser which is easily absorbed by water, such as an Er: YAG laser, it is difficult to control the irradiation so as to obtain the expected effects of the present invention. Since water absorbs energy, the effect of the cutting action due to heat that should be generated by such laser irradiation is reduced.

Further, according to an experiment using an Er: YAG laser, since this laser has a particularly strong exothermic effect due to the interaction with the hard tissue, when cutting the enamel of the tooth, the enamel is destroyed and the dentin is destroyed. It has been found that it may cause damage to the pulp tissue by giving unacceptable heat to the. When water is sprayed onto the tissue that is irradiated with the Er: YAG laser pulse, much of the laser irradiation is absorbed by the water and does not produce the effect envisioned by the present invention. And
The absorption of energy by water reduces the thermal cutting effect of Er: YAG laser irradiation.

The water coating used to carry out the invention is a few microns (μm) to 100 μm thick. The coating can be made by spraying on the tissue surface to remove air / water. The thickness of the coating is based on experience
The thickness can be adjusted to produce the desired cutting action.

By the method described by way of example, the laser employed in the practice of the invention is a solid-state laser constituted by a rod of YA10 (3) host material containing only dispersed activator ions such as Er ^3+. (For example, depending on the host material, about 5% to 50%
Ratio of atoms). According to another example, the host material may be, for example, a ratio of about 5% to 50% atomic E
It may be YSGG containing dispersed activator ions such as r ³⁺ or dispersed sensitizer ions such as Cr ^{3+ with} a ratio of about 0.5% to 3% atoms. This material is capable of producing laser radiation with a wavelength of 2.78 μm. Laser irradiation with a wavelength of 2.71 μm has similar absorption characteristics to laser irradiation with a wavelength of 2.78 μm, and thus produces the same effect. 199
SOLID filed by Levy et al. On May 21, 2013
As described in co-pending application No. 08,064,456 entitled STATE LASER FOR HARD TISSUE MEDICAL TREATMENT, these laser-generated materials exhibit high energy conversion efficiency.

The wavelengths that cause desirable vaporization in the water film are 1.06 μm; 1.54 μm; 2.71 μm.
m; and 2.78 μm are known. The first two wavelengths can be generated by a Nd: YAG laser and the latter two wavelengths can be generated by a YSGG-YAG laser. Furthermore, 0.7 μm laser irradiation generated by an alexandrite laser and 180 nm laser irradiation generated by an excimer laser also produce the desired effect.

On the basis of the known absorption properties, the removal operation according to the invention can be most easily controlled by laser irradiation with a wavelength between about 2.4 μm and 2.88 μm, but about 2.65 μm to 2. Preferably between 0.85 μm,
Most preferred is between about 2.7 μm and 2.8 μm.

The duration of the irradiation pulse employed in the practice of the present invention is between 10 ns and 10 ms, and 100
A duration of ˜800 μs is preferred. The pulse repetition rate is 1-1000 pps, preferably between 10-30 pps.

The average laser irradiation output power is 0.1 to 4
It is between 0w and preferably between 0.1 and 5w.

The laser can be applied to the surface of the body 4 in the form of spots having a diameter of 200 μm to 500 μm, preferably 300 μm to 400 μm. Since the irradiation beam hardly diffuses until it reaches the contact surface between the water film 2 and the body 4, a desired spot size can be set by a predetermined diameter of the fiber 6. To form the desired spot size, the ends of the fibers 6 are effectively in contact with or very close to the coating (eg, a few μm to a few hundred μm).
m).

To cite one non-limiting example of the method according to the invention, a laser irradiation of 2.78 μm wavelength with the above mentioned spot size and repetition rate is generated with an output power of 2W. When this laser irradiation is applied to the surface of the body 4 of living body hard tissue through the pulse coating 2,
Hard tissue is hygienically and effectively cut. When the same laser irradiation is performed in the absence of a water film, no cutting occurs but carbonization and modification of the crystal structure of the tissue are caused. The tissue may be bone, enamel, dentin, cementum or other calcified tissue.

The method according to the invention can be carried out both with conventional silica fibers, which provide fibers of considerably shorter length, and with wavelengths which are illuminated sufficiently effectively.

The air / water used can be injected by means of a spray unit or, conventionally, an ilrigator incorporated in the dental handpiece for the purpose of injecting a debris removal spray. To achieve the objects of the invention, water is supplied at a pressure of 1 psi and air is supplied at 10 p
It may be injected at a pressure of si. The same parameters can be used to cut enamel, dentin, or cementum of teeth, bone, or metal posts or fillings in the oral cavity. These parameters can also be used for cutting root tissue such as apicectomy.

The laser output irradiation average power for forming the depression may be 0.5 to 3 W. It has been found that excellent results are obtained at power levels in this range. The depth of the cut can be adjusted in advance by adjusting the power setting.

Irradiation of wavelengths between 2.7 μm and 2.8 μm is combined with wavelengths suitable for cutting soft tissue, for example 0.532 μm or 1.06 μm, for a wide range of operations in a single device. You can also

While the above description refers to specific embodiments of the present invention, it is understood that many changes can be made without departing from the spirit of the invention. The appended claims are intended to show that these modifications fall within the true scope and spirit of the invention.

As such, the embodiments disclosed herein are for the purpose of illustrating all details and are not intended to be limiting. The scope of the present invention is set forth in the appended claims rather than in the above description, and it is therefore intended to cover all changes in the meaning and range equivalent to those of the claims. .

[0057]

Industrial Applicability As described above, according to the method of the present invention, a living hard tissue containing bone, enamel, dentin, cementum or other calcified tissue is hygienically and effectively cut. can do.

[Brief description of drawings]

FIG. 1 is a view showing one of the steps for explaining a series of steps of a substance removing operation according to the present invention.

FIG. 2 is a view showing one of the steps for explaining a series of steps of a substance removing operation according to the present invention.

FIG. 3 is a view showing one of the steps for explaining a series of steps of a substance removing operation according to the present invention.

[Explanation of symbols]

 2 Water coating 4 Body 6 Optical fiber 8 Beam 12 area, bubble 14 Dimple

Claims (14)

[Claims] 1. A beam generating step of generating a laser irradiation beam having a wavelength having a water absorption coefficient corresponding to laser irradiation having a wavelength of about 2.4 μm or more and 2.9 μm or less, and forming a water film in contact with tissue. A water film forming step of forming a water film so that the contact surface between the tissue surface and the water film is located at the part of the substance to be removed, and the laser generated in the beam generating step. Direct the irradiation beam to the water film and to the contact surface with the substance to be removed, and the first laser irradiation energy removes the substance to be removed.
By modifying the power density to concentrate on the contact surface to reduce the energy required to destroy the material, the material modified by this first energy is absorbed into the water film by the second energy. Generating a mechanical action sufficient to minimally destroy the substance by water in contact with the substance, the method for removing the substance from a biological tissue having a surface. 2. The method according to claim 1, wherein the step of forming the water film is spraying water on the tissue surface. 3. The thickness of the water film is about several μm to 100 μm.
The method of claim 1, wherein m is m. 4. The method according to claim 1, wherein the beam of laser irradiation is a series of irradiation pulses. 5. The method of claim 4, wherein the average power level of the beam of laser irradiation is about 0.1-40 W. 6. The average output level of the beam of the laser irradiation is about 0.1 to 5 W.
The method described. 7. The method according to claim 5, wherein the area of the beam of the laser irradiation is the same as the area of a circle having a diameter of 200 μm to 500 μm. 8. The diameter of the circle is 300 μm to 400 μm.
The method of claim 7, wherein: 9. The laser irradiation beam is about 10 ns.
Method according to claim 1, characterized in that it is a sequence of irradiation pulses with a duration of -10 ms. 10. The irradiation pulse is about 100 ms to 80 ms.
Method according to claim 9, characterized in that it has a duration of 0 ms. 11. The method of claim 9, wherein the irradiation pulse has a repetition rate of 10 to 30 pps. 12. The laser irradiation is from about 2.65 μm.
2. Has a wavelength of 2.85 μm.
The method described. 13. The laser irradiation is from about 2.7 μm.
13. Having a wavelength of 2.8 [mu] m.
The method described. 14. The laser irradiation is from about 2.71 μm.
2. A wavelength of 2.78 μm.
3. The method described in 3.