Introduction to Electrosurgery
Electrosurgery is the passage of radio frequency or the high-frequency electrical current through the tissue to create a desired clinical effect on the tissue. This high-frequency energy is used to cut or coagulate the tissue. Application of high-frequency electrical current causes tissue to literally vaporize as the electrode passes through the tissue and capillaries on either side of the incision wall are sealed as the tissue shrinks. Hence, the term “Bloodless Surgery” is used to designate this procedure. The electrosurgical units are frequently used during surgical periodontal therapy. Follow-ing is the description of various aspects of electrosurgery in periodontal therapy.
The initial application of electricity in dentistry and medicine started with the application of spark gap generators (Hyfrecators) (in 1907) 1 and cautery units (in 1909) 2. Dr. William T Bovie 3 along with a neurosurgeon, Harvey W Cushing, MD, is credited for inventing the electrosurgical unit. The first use of the electrosurgical generator in an operating room was on October 1, 1926, at Peter Bent, Brigham Hospital in Boston, Massachusetts. Later on, with the …….. Contents available in the book …….. Contents available in the book …….. Contents available in the book …….. Contents available in the book ……..
Principles of Electrosurgery
When radiofrequency electrical current is applied to the tissue, the electromagnetic energy is converted in the cells, first to kinetic energy then to thermal energy. The desired effect in the tissue is determined by a number of electrical properties as well as factors such as tissue exposure time and the size and shape of the surface of the electrode near to or in contact with the target tissue. This whole procedure requires the creation of an electrical circuit that includes two electrodes, the patient, the electrosurgical unit, and the connecting wires. There are two kinds of instruments, bipolar and unipolar.
Bipolar instruments have both electrodes mounted on the device, usually located on or near the distal end, so that only the tissue located between the two electrodes is included in the circuit. In unipolar instruments only one electrode is mounted on the device and the entire patient is interposed between this “active electrode” and a large dispersive electrode that is also attached to the electrosurgical unit, but located relatively distant from the target tissue, typically on the thigh or back. The amount of energy delivered to the tissue during the procedure depends on inherent properties of electrical current which are current (I), voltage (V), and impedance or resistance (R).
Electrosurgery unit is composed of two electrodes 4, a passive electrode which acts as an antenna to draw the radio-signals back to the electrosurgery unit and an active electrode which is the cutting tip of the electrosurgery unit.
As already stated, passive electrode acts as an antenna to draw the radio-frequency electrical current back to the electro-surgery unit. There are several types of passive electrodes available. These include metallic plate, coated/ insulated passive electrodes, metallic wristband, metallic hand-held rod and Perma-ground.
Active electrodes are used for doing tissue cutting or coagulation. They are designed in various forms according to the function for which they are going to be utilized. Needle-like active electrodes are used for the cutting of the tissue, whereas, electrodes with a greater surface area at the tip are used for coagulation.
The physics of waveforms and lateral heat production in electrosurgery
Waveforms and their properties:
The waveform is the quality of the current wave which is passed through the tissue. There are basically four waveforms used in electrosurgery. These are: fully rectified filtered, fully rectified, partially rectified and fulguration waveform. The choice of waveform selected during a surgical procedure depends on (1) the required surgical effect, i.e., whether the tissue separation or hemostasis is required, and (2) the proximity of bone to the surgical site. Following is the brief description of the properties and clinical application of different waveforms,
Fully rectified filtered waveform:
It is a pure continuous flow of high-frequency energy where filtration results in a continuous non-pulsating flow of current which provides micro-smooth cutting. In this type of waveform, the lateral heat production is least. It is the only waveform that allows cutting in close proximity to bone due to the minimum amount of lateral …….. Contents available in the book …….. Contents available in the book …….. Contents available in the book …….. Contents available in the book ……..
The applications for the filtered waveform include the following,
- Biopsy procedure: With this waveform, no coagulation is produced, thus providing a clean cut of the specimen for the pathologist’s diagnosis.
- Incision and drainage.
- Grafting procedures.
- Mucogingival or osseous surgery.
- Implant flaps.
Fully rectified waveform:
This kind of waveform produces cutting with simultaneous hemostasis. It is produced by electronic titration. The tissue separation made is excellent with a little lateral heat production. The fully rectified waveform does create shrinkage and additional lateral heat and therefore should not be used in close proximity to the bone. On an oscilloscope, this waveform is demonstrated as a full-wave modulated signal.
- Gingivectomy/ gingivoplasty like procedures.
- Palatal stripping of the hyperplastic palate.
- Epulis removal and ridge re-contour.
- Periocoronal flap removal.
- Removal of tissue, exposing gingival margin during crown lengthening.
- Removal of tissue around anterior composite for visibility and elimination of ‘pink- composite’.
- Removing interproximal tissue for ease of matrix placement and elimination of overhanging margins.
- Removing tissue around fractured facings and crowns for ease of facing reconstruction.
- Removing tissue to facilitate placement of bonded bridge.
Partially rectified waveform:
It is an intermittent flow of the high-frequency current which is excellent in producing hemostasis of the soft tissue. Due to waveform characteristics, a large amount of lateral heat and tissue shrinkage is produced with this waveform. Therefore, it is not used for coagulation in close proximity to the bone or when performing osseous surgery.
The applications of the partially rectified waveform include the following:
- Coagulation of the soft tissue.
- Desensitizing dentin and cementum from cervical erosion.
It is a half-wave current that has a dehydrating effect on the tissue with the greatest amount of lateral heat production. It is mainly used for coagulation and destruction of cyst remnants only and can be used near the bone as electrodes do not touch the tissue. Electrosurgical fulguration coagulates and chars the tissue over a wide area. It utilizes sparking with the coagulation waveform of electrical current. It results in the creation of a coagulum rather than cellular vaporization. To overcome the high impedance of air, the …….. Contents available in the book …….. Contents available in the book …….. Contents available in the book …….. Contents available in the book ……..
- The applications of the fulguration waveform are as follows:
- Hemostasis involving the osseous surgery.
- Removal and destruction of any cyst remnants from biopsy and apicoectomy.
- Destruction or enucleation of any fistulous tracks.
- Coagulation of any pinpoint pulpal exposure.
The resistance of the tissue to electrical wave produces a certain amount of heat. This heat is called as lateral heat. The quality of the wave and lateral heat production are related to each other. The following formula is applicable to the amount of lateral heat production,
Lateral heat = T + AC + EF + CS / TI
LH = Lateral Heat.
T = Time.
AC = Amplitude of Current.
EF = Electrode Form.
CS = Current Selection.
TI = Tissue Impedance.
The lateral heat production is different for different waveforms. The waveform is chosen according to the desired effect of the tissue. The faster the active electrode is passed over the tissue, the lesser is the lateral heat produced. The active electrode must not remain in contact with tissue for more than 1 to 2 seconds at a time.
One study evaluated generation of lateral heat by various waveforms by measuring the rise in tissue temperature. They found temperature rises of 5 to 86o F dependent on the type of current, time of current application and the distance from the electrode 5. Another study demonstrated that lateral heat production adjacent to a fine wire needle electrode emitting fully rectified-filtered current was dependent on the time of incision 6. The authors of this study demonstrated a waiting period of minimum 8 seconds between subsequent incisions in the same area to avoid the adverse effects of lateral heat …….. Contents available in the book …….. Contents available in the book …….. Contents available in the book …….. Contents available in the book ……..
According to Krejci et al. 8 following clinical procedures should be employed during electrosurgery,
- A fully rectified filtered waveform at high frequency should be used to create intraoral incisions.
- The smallest electrode should be used to make an incision at a minimum rate of 7 mm/s.
- Between two successive electrode applications at the same site, a cooling period of 8 seconds should be allowed. This waiting period should be increased to up to 15 seconds if a loop electrode is used, such as for excisional procedures.
- Care should be taken not to contact the cemental surface of the tooth as well as regions where connective tissue reattachment is desired.
- While working in proximity to the bone care should be taken not to let excessive lateral heat production which can cause bone necrosis.
- The contact of the active electrode to metallic restorations should be less than 0.4 seconds to avoid any kind of pulp damage.
- The fulguration waveform should only be used to control bleeding if all other clinical procedures have been tried. This is because the use of fulguration waveform is associated with delayed healing response.
Wound healing following electrosurgery
The manner in which tissue heals following electrosurgery is a function of the lateral thermal damage and attendant tissue necrosis caused by the application of electrical energy. Higher current densities and decreased duration of exposure cause less damage, and lower current densities and longer exposure cause more. The histological effects of electrosurgery vary depending on the power output 11 and frequency 12 of the electrosurgery unit, the waveform selected 13 and the size and shape of the active electrode 14. It has been shown that electro-surgery units with lower frequency produce greater tissue alteration as compared to high-frequency electrosurgery units 11.
One study compared postoperative wound healing with electrosurgery unit and scalpel. Results demonstrated that healing after using electrosurgery unit was delayed as compared to a scalpel. The wound with electrosurgery showed more inflammation and tissue destruction. Otherwise, the osteoblastic activity was same in both the cases, which shows …….. Contents available in the book …….. Contents available in the book …….. Contents available in the book …….. Contents available in the book ……..
Advantages and disadvantages of electrosurgery
- The incision made in the tissue is clean with little or no bleeding.
- A clear view of the surgical site is provided.
- Can be used in difficult to reach areas.
- Healing discomfort and scar formation are minimal.
- Chair time of the surgical procedure, as well as operator fatigue, are reduced.
- Soft tissue planing can be done.
- The technique is pressureless and precise.
- The cost for electrosurgery unit is high.
- The bad odor of tissue burning is present if high-volume suction is not used.
- Cannot be used on patients with poorly shielded pace-makers.
- It cannot be used near inflammable gasses.
The use of electrosurgery in dentistry is increasing as more refined electrosurgical units are being introduced, specifically for dental usage. Regardless of the electrosurgery technique used, some degree of lateral thermal damage will always exist, although its extent can be limited to minute areas. But, it must be clear that electrosurgery can never completely replace the scalpel. Clinicians can combine the advantages of both of them and deliver the best results to the patient.
References are available in the hard-copy of the website.