US3812858A

US3812858A - Dental electrosurgical unit

Info

Publication number: US3812858A
Application number: US00300181A
Authority: US
Inventors: M Oringer
Original assignee: Sybron Corp
Current assignee: MDT Corp; Raytheon Co
Priority date: 1972-10-24
Filing date: 1972-10-24
Publication date: 1974-05-28
Anticipated expiration: 1991-05-28
Also published as: JPS4973883A; FR2203649B3; DE2353013A1; CA1012211A; FR2203649A1

Abstract

Disclosed is a dental electrosurgical apparatus having means to automatically regulate the proper amount of power needed to cut soft tissues of the body, a timing device to regulate and repeatedly interrupt the period of active current flow and a regulator means that cuts off current flow when the patient is not in contact with the inactive electrode.

Description

United tates Oringer tet 1 [54] DENTAL ELECTROSURGICAL UNIT 3,478,744 11/1969 Leiter 128/303.17 X 3,516,413 6/1970 McDonald et a1. 128/422 1751 lnvemo" Maul'lce Jules 0mg", New York 3,675,655 7/1972 Sinner 1. l28/303.17 x 3,731,188 5/1973 Ellman 128 303114 1 Assignooz Sybron Corporation, Rochester, FOREIGN PATENTS OR APPLICATIONS N'Y' 1,146,989 4/1963 Germany l28/303.14 [22] Filed; a 24, 1972 1,178,528 9/1964 Germany 128/303.17

[21] APP! 300,181 Primary Examiner-Channing L. Pace Attorney, Agent, or Firm-Theodore B. Roessel; Roger [52] US. Cl 128/303.14, 128/422, 128/423 Aceto; Charles C, Krawczyk [51] Int. Cl. A6lb 17/38, A61n 3/04 [58] Field of Search..... 128/303.14, 303.16, 303.17, 57 BS CT l28/303'l8 423 Disclosed is a dental electrosurgical apparatus having means to automatically regulate the proper amount of [56] References cued power needed to cut soft tissues of the body, a timing UNITED STATES PATENTS device to regulate and repeatedly interrupt the period 1,695,485 12/1928 Payer 128/422 of active current flow and a regulator means that cuts 1,841,968 LOWl'y off current flow when the patient is not in ontact 3,058,470 10/1962 Seeliger et a1. 128/422 x the inactive electrode, 3,127,895 4/1964 Kendall et a1.... 128/422 3,241,557 3/1966 Kazumi Masaki 128/422 7 Claims, 1 Drawlng Figure DUTY ,32 CYCLE TIMER IO 1 i l 22 12 l J 1 2O 18 |6 '4 R F A {an 'S w R F REGULATOR hJ GENERATOR ALARM Z so PATENTEBI Y 2 um RF GENERATOR DUTY CYCLE TIMER ALARM RF REGULATOR 1 DENTAL ELECTROSURGICAL UNIT BACKGROUND OF THE INVENTION The present invention relates generally to electrosurgical devices and more particularly to a dental electrosurgical device which greatly minimizes the danger to the patient of an electrosurgical procedure in the oral cavity.

Much of the danger of oral electrosurgery can be attributed to the physical characteristics of the oral tissue. For example, the gingival mucosa is exceedingly thin and is attached to periosteum which is in turn attached to viable bone that usually contains vital teeth. Such tissue is very thin and highly vulnerable to penetration by the electrosurgical heat and consequently very easily damaged. Thus, any electrosurgical procedure or treatment involving gingival tissue requires extremely precise electrosurgical techniques to avoid destructive damage to this tissue and underlying structures by heat penetration. For example, if insufficient power is used and the tissue cells in the path of the RF current are not volatilized as would occur in an efficient, safe cleavage of tissue, the organic content of the tissue cells are merely coagulated causing extensive destruction. On the other hand, excessive power causes charring and burning of the tissue which results in unnecessary and undesired tissue and bone destruction.

Tissue is also destroyed if the active electrode is applied too slowly. In this respect, a slow application of the electrode to the relatively thin gingival tissues allows the heat being generated to penetrate laterally far beyond the point of contact so that the heat penetrating through the tissue is likely to cause severe damage to the underlying tissue, bone and tooth structures. This same penetration of heat can occur if the electrode is repeatedly applied to the tissue without intervening intervals sufficient to permit the heat to dissipate. Thus, even though the electrode is used rapidly enough for each contact the continued repetition results in an accumulation of retained heat in the tissues that may penetrate and destroy the underlying structures.

For proper control and efficiency of the cutting and colagulating currents used in dental electrosurgery a dispersive or inactive electrode must be applied to the patients body. The RF current then enters the patients body through the active electrode and passes out of the body through the inactive electrode and back directly to the power source. Should the patient inadvertently lose contact with the inactive electrode or if the operator forgets to employ it, the subsequent loss of precise control and cutting efficiency is likely to cause damage to the patient.

These drawbacks and other dangers inherent in existing dental electrosurgical units are overcome in the present invention which provides for an automatic regulation of the power delivered to active electrode in direct proportion to the changes in resistance in the tissue being operated upon. In addition, the present invention has a duty timer which continuously interrupts the flow of current during the operating procedure. The interruption of the cutting current prevents heat build-up and instead allows sufficient time between applications of RF current to permit dissipation of the heat generated during the surgical procedure thereby reducing the danger of possible injury to the patient. Also, the timer makes the electrosurgical apparatus safer in the hands of a novice or an inexperienced electrosurgical practioner. In this respect, the interruption of the cutting current will automatically compensate for any tendency on the part of the novice to keep the electrode in contact with the tissue for periods of time sufficient to allow the penetration and build-up of heat resulting in unnecessary destruction of tissue. The present invention also employs an alarm means to cut off current flow whenever the patient has lost contact with the inactive electrode.

SUMMARY OF THE INVENTION I The present invention may be characterized in one aspect thereof by the provision of a dental electrosurgical unit having a power regulator acting responsive to the changes in the resistance of the patient tissue through which the RF current is passed to automatically increase or decrease the power applied to the active electrode in direct proportion to the tissue resistance; a timing device for regulating the period of active current flow and repeatedly interrupting flow of RF current into the patient tissue; and safety means for terminating the flow of RF current to the patient when the patient is not in contact with the indifferent electrode.

OBJECTS OF THE INVENTION One object of the present invention is to provide a dental electrosurgical apparatus having a power regulator which varies the electrosurgical RF power in direct proportion to the resistance of the tissue being operating upon.

Another object of the present invention is to provide a dental electrosurgical apparatus wherein the flow of RF current to the tissue being operating upon is intermittent.

A further object of the present invention is to provide a dental electrosurgical unit wherein the flow of RF current is cycled on and off during the operation procedure with the off cycle being longer than the on cycle.

A still further object of the present invention is to provide a dental electrosurgical apparatus having means to automatically terminate current flow when the patient is not in contact with an indifferent electrode.

The yet further object of the present invention, is to provide a dental electrosurgical apparatus which minimizes the possibility of burn injury to the patient even when used by a novice operator.

These and other objects and advantages and characterizing features of the present will become more apparent upon consideration of the following detailed description thereof when taken in connection with the accompanying drawing depicting the same.

DESCRIPTION OF THE DRAWINGS The sole FIGURE is a schematic representation of the electrosurgical equipment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings, the sole FIGURE shows the dental electrosurgical apparatus of the present invention generally indicated at 10. The apparatus includes an RF generator 12 of the type well-known in the art. It is sufficient for purposes of the present invention merely to say that such an RF generator suitable for purposes of dental electrosurgery should produce an RF signal on the order of 1.75 MHz and approximately 90 watts of power.

The generator has an outlet 14 for delivering the RF current in series through a conductor 16, a control switch 18 and a duty cycle timer switch 20 to a power regulator 22. The function of the power regulator will be set out herein below.

From power regulator 22, the RF current passes in series to the active electrode 24. The active electrode is, in turn manipulated by the operator for cutting or coagulating the patient tissue schematically illustrated at 26. RF current from the active electrode passes through the patient into a indifferent or inactive patient electrode 28 and then back through line 30 to the RF generator.

The usual practice in oral electrosurgery is for the operator to select in his judgement an appropriate power requirement and then adjust the RF generator accordingly. The power output of the generator then remains constant throughout the operative procedure. Various devices are used in the prior art to maintain the power output constant, for example, the RF current can be monitored and appropriate electronics provided to square the current in order to obtain an approximation of the power. This I value is then used to either increase or decrease the output of the RF generator in order to keep the power relatively constant. However, such devices ignore the resistance value of the tissue being operated upon and the electrosurgical expertise of the user. For example, as the thickness of the oral tissue varies, the resistance will also vary. Consequently, if the power applied is kept constant, the current density in the thinner tissue will be greater than the current density in the thicker tissue. As set out herein above, the gingival tissue is exceedingly thin and highly vulnerable to penetration by heat so that using the same power to cut through the thin tissue as ,is used to cut through thicker tissue could result in serious damage to gingival tissue and to the underlying peristum.

in the present invention, power regulator 22 is of the type which increases or decreases the RF current being applied to activeelectrode 24 in direct proportion to the increase or decrease in resistance of the tissue being operating upon. Accordingly, once the initial power requirement is set at the RF generator, the RF current applied to the active electrode will automatically increase when the resistance of the patient tissue increases and decrease when the resistance of the patient tissue decreases. Such power regulator devices are well within the skill of the art and may be, for example, a constant voltage device which will increase or decrease the current in direct proportion to the resistance being encountered.

As set out herein above, the RF current to power regulator 22 passes first through a cycle timer switch 20. The switch is operated by a duty cycle timer 32 which repeatedly opens and closes switch 20 during the operation of the electrosurgical device. Preferably the duty cycle timer 32 is programmed to close the switch for between 0.5 and 1.0 seconds and then to open the switch for a period ranging from 2.5 to seconds. This one second on, five seconds off cycle of operation, for example, will permit a sufficient interval between the application of RF current to allow a dissipation of heat. Such an arrangement greatly reduces the possibility of injury to the patient caused by keeping the active electrode in contact with the patient for relatively long periods of time or applying the electrode to the tissue repeatedly without a sufficient intervening interval to permit the heat to dissipate. I

in operating the device thus far described, the operator simply closes switch 18 which may be, for example, a foot switch. With switch 18 closed, the operator manipulates active electrode 24 and performs the electrosurgical procedure. With the active electrode in contact with the patient, the RF current flows from generator 12 in series through conductor 16, switches 18 and 20 power regulator 22, through the active electrode 24 to the patient and then from the patient through the inactive electrode 28 and back to the generator through return lines 30. During the operating procedure, duty cycle timer 32 operates to repeatedly open and close switch 20 in a programmed cycle designed to close the switch for 0.5 to 1.0 seconds and open the switch for about 2.5 to 5 seconds. The power regulator 22 in turn acts responsive to any increase or decrease in the resistance of the patient tissue to increase or decrease respectively the power being delivered to the active electrode 24. In this manner, the device thus far decribed will greatly reduce the possibility of burn damage to the oral tissue by reducing the RF current being utilized during the procedure and by discontinuing the application of the current for a time interval sufficient to permit dissipation of the heat generated during the operating procedure.

While the dental electrosurgical device may operate even though the patient is not in contact with the inactive electrode 28, best results and consistently efficient operation are achieved when the patient is in contact with the inactive electrode 28. This allows RF current to radiate through the patients body and return directly to the generator. To insure that the RF current is not applied to the patient unless he is in contact with the inactive electrode 28, the present invention employs an alarm system which includes an alarm device 34 connected on one hand through line 36 to the inactive electrode and on the other hand, through a line 38 to a switch 40 in line 16. Alarm device 34 may be any suitable electronic regulator for sounding an alarm and opening switch 40 whenever the patient is not in contact with the inactive electrode. For example, the alarm device 34 could include means to detect RF power flowing through the inactive electrode. With this arrangement, the alarm will sound and switch 40 will open whenever switches 20 and 22 are closed and no power is detected flowing through the inactive electrode. For proper function of course, alarm 34 should function only when both switches 18 and 20 are closed. Otherwise, the alarm would sound each time either switch is open and no RF power is flowing through the patient. For this reason alarm 34 is shown connected by a line 42 to line 16 between switch 20 and power regulator 22.

Various modifications in the arrangement shown should be readily apparant. For example, the function of

switches

18 and 20 could be incorporated into a single switch structure. in such a construction, alarm 34 could be connected to this switch for making the alarm sensitive to RF power flow through the inactive electrode only when the single switch structure is closed.

Thus, it should be appreciated that the present invention accomplishes its intended objects in providing a dental electrosurgical device which greatly minimizes the risk of injury to the patient. Having an electrosurgical unit which incorporates a power regulating device for varying the power output in direct proportion to the resistance of the patient tissue insures that excessive or inadequate power is not applied to the patient. Providing a duty cycle timer insures a periodic interruption of the RF current greatly reduces the possibility of excessive tissue destruction caused by heat build up and retention in the tissue.

Having thus described the invention in detail, what is claimed as new is:

1. In a dental electrosurgical unit including an RF power source, an active electrode for applying power from said source to a patient, and an inactive electrode for completing the circuit from the patient back to the RF power source, the improvement comprising:

a. circuit means connecting said RF power source to said active and inactive electrodes so that the output power thereof is a function of the patient tissue resistance through which said RF power passes; and

b. timer means periodically interrupting the delivery of RF power from said RF power source to said active electrode throughout the operating procedure in a timed cycle to control the time duration during which incisions can be made with the active electrode, wherein said timer means interrupts the flow of RF power to said active electrode for a period of time to allow the dissipation of heat from the tissue prior to the subsequent application of additional RF power by said active electrode, so that excessive heat damage to the tissue is prevented.

2. A dental electrosurgical unit as set forth in claim 1 wherein said circuit means connects a RF power regulator in series with the RF power source, a switch means is connected in series between said RF power source and said RF power regulator, and said timer means operates to cycle said switch means on and off throughout the operating procedure with the ofF portion of the cycle wherein the delivery of RF power to said active electrode is interrupted, is longer than the on portion of the cycle.

3. A dental electrosurgical unit as set forth in claim 2 wherein said timer means cycles said switch to permit delivery of RF power to said active electrode for between 0.5 and 1 second and thereafter interrupts the delivery of RF power to said active electrode for between 2.5 and 5.0 seconds.

4. A dental electrosurgical unit as set forth in claim 2 including alarm means operable when RF power is being delivered to said active electrode forsensing flow of RF power through said inactive electrode and terminating flow to said active electrode when flow of RF power through said inactive electrode is not sensed.

5. A dental electrosurgical unit as set forth in claim 4 wherein said alarm means is operatively connected to a switch located in series between said RF power source and RF power regulator.

6. A dental electrosurgical method comprising the steps of:

a. applying RF power to the patient tissue through an active electrode;

b. increasing and decreasing said power applied to the patient tissue as a function of the resistance of the tissue being operated on; and

c. periodically cycling te flow of RF power to the tissue on and off in a timed cycle throughout the operating procedure to limit the time duration during which incisions can be made to the patient tissue so that the tissue is allowed to dissipate heat between incisions to prevent excessive heat damage to the tissue.

7. A method as set forth in claim 6 wherein the flow of RF power is cycled on for between 0.5 and 1.0 seconds and is cycled off for between 2.5 and 5 seconds throughout the operating procedure.

Claims

1. In a dental electrosurgical unit including an RF power source, an active electrode for applying power from said source to a patient, and an inactive electrode for completing the circuit from the patient back to the RF power source, the improvement comprising: a. circuit means connecting said RF power source to said active and inactive electrodes so that the output power thereof is a function of the patient tissue resistance through which said RF power passes; and b. timer means periodically interrupting the delivery of RF power from said RF power source to said active electrode throughout the operating procedure in a timed cycle tO control the time duration during which incisions can be made with the active electrode, wherein said timer means interrupts the flow of RF power to said active electrode for a period of time to allow the dissipation of heat from the tissue prior to the subsequent application of additional RF power by said active electrode, so that excessive heat damage to the tissue is prevented.

2. A dental electrosurgical unit as set forth in claim 1 wherein said circuit means connects a RF power regulator in series with the RF power source, a switch means is connected in series between said RF power source and said RF power regulator, and said timer means operates to cycle said switch means ''''on'''' and ''''off'''' throughout the operating procedure with the ''''off'''' portion of the cycle wherein the delivery of RF power to said active electrode is interrupted, is longer than the ''''on'''' portion of the cycle.

4. A dental electrosurgical unit as set forth in claim 2 including alarm means operable when RF power is being delivered to said active electrode for sensing flow of RF power through said inactive electrode and terminating flow to said active electrode when flow of RF power through said inactive electrode is not sensed.

6. A dental electrosurgical method comprising the steps of: a. applying RF power to the patient tissue through an active electrode; b. increasing and decreasing said power applied to the patient tissue as a function of the resistance of the tissue being operated on; and c. periodically cycling te flow of RF power to the tissue on and off in a timed cycle throughout the operating procedure to limit the time duration during which incisions can be made to the patient tissue so that the tissue is allowed to dissipate heat between incisions to prevent excessive heat damage to the tissue.