WO1995024111A1

WO1995024111A1 - Local heat treatment device and corresponding treatment method

Info

Publication number: WO1995024111A1
Application number: PCT/FR1994/000244
Authority: WO
Inventors: François Lhuisset
Original assignee: Societe D'exploitation Dentaire
Priority date: 1992-12-21
Filing date: 1994-03-04
Publication date: 1995-09-08

Abstract

A local heat treatment device with a low-impedance input and a high-impedance output. The device comprises a step-up transformer (13) within a handpiece (21) for supplying power to a single active electrode.

Description

"L OCAL ISE HEAT TREATMENT DEVICE AND CORRESPONDING TREATMENT METHOD"

The invention relates to a local heat treatment device and to a corresponding treatment method.

The invention is particularly useful for odontological applications, in particular for clinical endodontics and surgical endodontics, and in particular endocanal vaporization of intracanal air and parietal organic matter.

Currently known devices for the Nd-YAG laser type are used for this purpose, for example of the commercial type produced under the name "Laser Endo Technic" by the French company "Société Endotechnic France". These known devices on the one hand, are dangerous for the environment and require the wearing of special protective glasses and, on the other hand, do not allow because of the unlimited range of the laser beam to regulate the depth of penetration or treatment.

The document US 4,839,492 (BOUCHIER and LHUISSET), the content of which is considered to be incorporated in the present description, relates to a process for cutting or treating material, in particular living tissue by means of a plasma of ionized gas, as well as a device corresponding to plasma for implementing said process.

This known biactive bipolar device comprises a handle comprising at least two spaced electrodes subjected to differences in electric potential capable of producing an electric arc between said electrodes, and means for passing at least one fluid flow in the space corresponding to said electric arc. . The potential differences are differences in alternating potential at medium or high frequency. The ends of the electrodes are substantially wire or tip shaped and their respective directions form an acute angle. A potential-boosting transformer is incorporated in the handle to produce said alternating potential differences, while the fluid flows emerge inside said acute angle or along at least one of said electrodes.

This known device is, for example, part of a set of the commercial type sold under the name "Sopha biotron" by the French company "Sopha Bioconcept" and includes a programmable and controllable power supply capable of delivering successive pulses of duration. reduced on the order of ten milliseconds to several seconds, to supply a device with two active electrodes in form of a two-conductor cable at an alternating voltage between 100 V and 500 V at high frequency of the order of 1 MHz of wire.

This known device is satisfactory, but nevertheless has several drawbacks:

. due to the presence of two active electrodes, the space occupied by the plasma and the electrodes is relatively large: this characteristic prevents any local intervention in a space of corresponding size inside a dental canal,

. because the handpiece of this known device supplied by a medium voltage contains a voltage step-up transformer to produce between the active electrodes a high ignition voltage of the order of several thousand volts, losses occur capacitive electrics which generate slight plasma instabilities between the two active electrodes. These instabilities that are admissible for surgery or coagulation of soft tissues are not admissible for localized odontological applications.

The object of the invention is to remedy the abovementioned drawbacks, so as to heat treat hard and locally hard tissue, in particular teeth. plumped or to be plumped, under improved economic and security conditions.

The subject of the invention is a local heat treatment device, of the type with gas supply and with electric supply at low impedance at an alternating voltage less than 500 V and at high impedance output at a high voltage higher than 1000 V, characterized in that the device comprises a step-up transformer inside a handpiece for supplying a single active electrode, and in that said active electrode is inside a tubular gas supply channel, so as to generate a microscopic ball of plasma to heat treat a localized space. The term “microscopic ball” is understood to mean a ball of plasma which can be written into a sphere of diameter less than one millimeter.

According to other characteristics of the invention: The single active electrode is made of a flexible refractory metal and the tubular channel is made of a flexible insulating material resistant to a temperature above 150 ^° C.

The tubular gas supply channel is at least partially rigid and has a hook shape.

Said single active electrode is included in a treatment head detachable from a handpiece constituting the main body of the device.

The treatment head further comprises an electrode which is not active and does not project beyond the treatment head. The non-active electrode is included in a tip made of material that insulates the treatment head.

Said step-up transformer comprises a core of ferrite or similar magnetic material with high resistivity, the primary circuit of the transformer surrounds said core in a compact conformation, and the secondary circuit of the transformer surrounds said core in a con gura ion deployed of contiguous and non-overlapping turns, located at a distance greater than a predetermined distance from said primary circuit and from the outer casing of the handpiece. The subject of the invention is also a method of using a device according to one of claims 1 to 7, characterized in that the method comprises the following steps:

- place the active electrode in the immediate vicinity of a soft tissue surrounded by hard tissue,

- switch on the gas supply and the electric supply,

- lower the active electrode to a chosen depth, so as to evaporate the soft tissue throughout the descent of the active electrode.

According to a preferred embodiment of the invention, said chosen depth is less than or equal to a predetermined depth, preferably less than 30 m. The invention will be better understood thanks to the description which follows, given by way of example and not in imitation with regard to the appended drawings in which:

FIG. 1 schematically represents a device of the prior art. FIG. 2 schematically represents a view in longitudinal section of a device according to the invention.

Figure 3 schematically shows an enlarged partial sectional view of a device according to the invention.

Figures 4 to 6 schematically represent several embodiments of transformer for device according to the invention.

With reference to FIG. 1, a known assembly comprises a power supply contained in a housing 1, a bipolar connector 2 for supplying a device 4 under an alternating voltage by an inductive cable 3 bipolar between 100 and 400 V at a frequency of the order of MHz.

The device 4 configured to be held in the hand contains a step-up transformer for supplying, in accordance with the teaching of American patent US Pat. No. 4,839,492 (BOUCHIER and LHUISSET) two active electrodes 6 and 7 generating a plasma 8 in the form of a point the two electrodes 6 and 7.

With reference to FIG. 2, a device 10 according to the invention is supplied by two conductors 11 and 12 connected to a power supply unit, not shown, similar to that of FIG. 1.

The conductors 11 and 12 are connected to a step-up transformer 13 so as to produce an alternating high voltage between 1000 and 6000 V at a frequency between several hundreds of kHz and several MHz between two output conductors 14 and 15, according to a so-called "floating bipolar" configuration due to the fact that none of the conductors 14 and 15 is directly connected to earth.

The conductors 14 and 15 have a small section and its fixed to a rigid structure in a configuration minimizing the capacities between the conductors and the operator. The conductors 14 and 15 are advantageously sheathed by insulating tubes. Other tubes 16 and 17 are provided for supplying a cooling gas G and plasma generator.

The conductors 14 and 15 are contained in this example directly in the tubes 16, 17 for supplying cooling gas G and plasma generator. The tubes 16, 17 are made of relatively rigid insulating material, refractory or not, such as alumina, silica, polytet afluoroethylene (PTFE), a plastic material of the silicone type or the like. The assembly is, after assembly of the aforementioned electrical components, molded in one end in sil icone 18 and covered with two i-coqu i 11 es 19, 20 in self-extinguishing insulating plastic material of the sil icone type or equivalent with a low dielectric constant, before being inserted into an external handpiece 21 made of insulating plastic material, self-extinguishing and having good mechanical rigidity, such as for example polyethylene terephthalate or polybutylene terephthal ate. The handpiece 21 is screwed or fitted hermetically with an insulating plug or endpiece 22 containing an insulating sleeve 23 made of rubber or material integral with the power cord not shown.

Preferably, the conductors 11 and 12 supplying the primary winding of the transformer 13 have a small diameter, less than 0.3 mm; the conductors 14 and 15 of the output of the secondary winding of the transformer 13 have a diameter less than or equal to 0.15 mm; and the transformer 13 is of the ferrite magnetic circuit type substantially in the form of a torus, so as to separate the corresponding windings by a geometric distance greater than one centimeter and so as to avoid significant capacitive couplings between the two windings and the instabilities. resulting plasma.

The invention allows, thanks to this arrangement, to significantly reduce the capacitive losses of the device according to the invention, which are approximately ten times lower than the capacitive losses of the devices of the prior art. Thanks to this significant reduction in capacitive losses, the device according to the invention ensures the operation under improved stability conditions of the head with two active electrodes of the prior art, but also allows the use of a monoelectrode head. of reduced dimensions according to the invention, symbolized by dotted lines. The device according to the invention may advantageously contain a means of lighting, not shown, for the treatment or surgical operation area, comprising for example at least one optical fiber to conduct the light and an end tip suitable for directing the light. towards the area to be lit.

With reference to FIG. 3, a treatment head 30 is pluggable onto the device of FIG. 2 by means of two male conductors 31, 32 of stainless steel or the like intended to be plugged in with corresponding female housings to ensure electrical continuity and the alternating high voltage supply of two electrodes 33, 34.

The electrode 33 is not active and does not exceed the tip made of insulating material 35 of the ceramic or similar kind, while the electrode 34 constituted by a fine wire of refractory metal such as tungsten is fitted in electrical continuity with the end 32a of the conductor 32 in a tubular sleeve 36 of insulating material. The tubular sleeve 36 is made relatively rigid by the fact that it surrounds a hook-shaped stainless steel tube.

The tubular sleeve 36 having the shape of a hook is connected to a flexible insulating tube 37 made of fine, non-combustible material of the polyimide or pol ytetraf1 uoroethylene type, into which a pressurized gas is preferably introduced, by known means. a neutral gas such as nitrogen, argon or carbon dioxide, or simply air. The flexible tube 37 is joined to the relatively rigid tubular sleeve 36 by means of an alumina fixing ring 38 or by direct insertion of the flexible tube 37 into the tubular sleeve 36.

The head 30 of the device connected to the handpiece and supplied with gas and at high voltage by the latter, is shown in the treatment position on a tooth 39. The flexible tube 37 is engaged rogress ely in the channel of the tooth 40 to the lower end or to the vicinity of the apex of the tooth.

Throughout the descent of the active electrode 34 inside the tooth, the plasma microbubble formed at the head of the active electrode instantly evaporates the soft parts inside the tooth 39 without damaging the hard tissues or heating up. the area to be treated due to weak conduction currents through the tooth to be treated or another area of the patient's body.

Thus, thanks to the invention, surgical or localized treatment operations requiring great geometric precision are carried out according to a controllable depth of penetration, unlike the techniques of the prior art in which the use of a laser only made possible control of energy consumed, but not the depth of intervention.

With reference to FIGS. 4 to 6, three different electrical embodiments of the invention each comprise a low impedance electrical supply of a step-up transformer for supplying high voltage to an active electrode for heat treatment, surgical intervention or analogous operation.

In FIG. 4, the primary circuit 100 of a step-up transformer capable of being mounted in a device in FIG. 2 is formed by continuous winding in a configuration of around twenty turns 101 conductive contiguous around an assembly of three magnetic cores 102, 103, 104 stacked on top of each other. The secondary circuit 105 of the transformer is formed by winding from one to several hundred contiguous but not overlapping turns 106 around the assembly of toroids 102 to 104 mentioned above.

The secondary winding is carried out so as to separate the incoming conductors and the primary winding turns from the outgoing conductors and the secondary winding turns of a distance greater than a predetermined distance, preferably greater than one hundred i met re.

In an advantageous embodiment, the material constituting the toroids is a high resistivity ferrite, for example of the 4C6 type marketed by the French company "RADIO TECHNIQUE COMPELEC", while the diameter of the primary conductor is of the order two tenths of a millimeter and the diameter of the secondary conductor of the order of tenths of a millimeter and that the winding of the secondary conductor is made so as to cover an area less than that of a half-torus, located in position diametrically opposite to that of the primary winding 100. After completion of the two primary and secondary windings, the entire transformer is coated with an insulator of the polyurethane type or the like with possible interposition of protections in Mylar (registered trademark) or in polyimide such as Kapton (registered trademark): this insulation is known to specialists and will not be described in more detail. lée.

In FIG. 5, the primary circuit 110 of rectangular shape constituted by the winding picked up of contiguous conductive turns 111 is supported by an insulating support, so as to present a branch coaxial with the axis of the ferrite toroid 112, two lateral branches and an outer branch spaced from the torus 112 by a distance of the order of a centimeter.

In this configuration, the secondary circuit 113 is advantageously wound on a surface smaller than that corresponding to three-quarters of a toroid, located in a position diametrically opposite that of the plane inside the primary winding 110.

This arrangement has the advantage that the secondary circuit has a greater number of contiguous and non-overlapping secondary turns 114, which which allows to obtain a higher transformation ratio than in the case of FIG. 4.

In FIG. 6, a transformer of elongated shape comprises a primary circuit 120 constituted by the winding of two collected parts 121, 122 each comprising a dozen primary conductive turns at the ends of a cylinder A of insulating material, so as to separate the two parts 121, 122 of a predetermined distance greater than the diameter of the cylinder A of insulating material.

The connection terminals 123, 124 of the supply conductors are situated on the same side of the primary circuit, an insulating passage 125 being provided for the protection of the straight conductor connecting terminal 124 to the end winding 122.

Inside the primary circuit 120, a secondary circuit 130 shown before complete introduction is also constituted by winding, on an insulating cylinder B, conductive turns in two thicknesses separated by a thick sheet 131 of insulating material of the polyimide type or the like. , so that the output terminals 132, 133 of the secondary circuit are located opposite the terminals 123, 124 of the primary circuit.

The secondary circuit 130, covered with a thermo-retractable material 134 before being placed inside the primary circuit 120 in which it is kept spaced apart by end flanges 135, 136, contains a cylindrical bar 137 of elongated ferrite and placed coaxially with the axis 138 common to the cylind indre A of the primary circuit 120, to the cyl indre B of the primary circuit 130.

According to the invention, the arrangements of the transformers of FIGS. 4 to 6 do not produce any noticeable capacitive effect at high frequencies of the order of MHz between the device of the invention and the hand of the operator or the surgeon, nor disturbances. likely to result. To reinforce this effect, the secondary circuit of a transformer according to the invention is advantageously distant from the external envelope of the handpiece by a predetermined distance greater than three thousand 1 i meters.

It follows that the microscopic plasma ball obtained by the invention by means of a single active electrode during operation in bipolar mode has stability and geometrical dimensions suitable for allowing its use for surgical, medical operations or other operations requiring high precision if one.

Although described with reference to particular embod ies, the invention is in no way imitated therein, but on the contrary covers any form realization and any variant of realization in the context and in the spirit of the invention. invention, in which a device with low impedance input and high impedance output has a single active electrode in bipolar mode for generating a microscopic ball of plasma at a high voltage greater than 1000 V and at a frequency close to MHz.

Claims

SELL IC _. AT _. IOjNS

1) Isized local heat treatment device, of the gas supply and electrical supply type with low impedance at an alternating voltage lower than 500 V and with high impedance output at a high voltage higher than 1000 V, characterized in that that the device comprises a transformer (13, fig 4-5-6) step-up voltage inside a handpiece (21) to imitate a single active electrode (34), and in that said active electrode (34) is inside a tubular channel (36, 37) for supplying gas, so as to generate a microscopic ball of plasma for heat treatment of a localized space. 2) Device according to claim 1, characterized in that the single active electrode (34) is made of a flexible refractory metal and in that the tubular channel (37) is made of a flexible insulating material resistant to a temperature higher than 150 ° C. 3) Device according to claim 1 or claim 2, characterized in that the tubular gas supply channel (36) is at least partially rigid and has the shape of a hook.

4) Device according to one of the preceding claims, characterized in that said active electrode

(34) unique is included in a treatment head (30) detachable from a handpiece (21) constituting the main body of the device.

5) Device according to claim 4, characterized in that the treatment head (30) further comprises an electrode (33) not active and not protruding from the head of t rai te ent (30).

6) Device according to claim 5, characterized in that the non-active electrode (33) is included in a tip (35) made of material insulating the treatment head (30). 7) Device according to any one of the preceding claims, characterized in that said transformer (13, fig 4-5-6) voltage booster comprises a ferrite core (102, 103, 104, 112, 137) or magnetic material analogous to high resistivity, in that the primary circuit (100, 110, 120) of the transformer surrounds said core (102, 104, 112, 137) in a compact conformation, and in that the secondary circuit (105, 113, 130 ) of the transformer surrounds said core (102, 104, 112, 137) according to a deployed configuration of contiguous (106, 114) and non-overlapping turns, located at a distance greater than a predetermined distance from said primary circuit (100, 110, 120) and the outer casing of the handpiece (21). 8) Method for using a device according to one of claims 1 to 7, characterized in that the method comprises the following steps:

- place the active electrode (34) in the immediate vicinity of a soft tissue surrounded by hard tissue (39), - switch on the gas supply and the electrical supply,

- lower the active electrode (34) to a chosen depth, so as to evaporate the soft tissues throughout the descent of the active electrode (34). 9 -A method according to claim 8 characterized in that said chosen depth is ^" less than or equal to a predetermined depth, preferably less than 30 mm.