Laser, Electrosurgery and their Applications in Periodontics
by Dinh X. Bui, D.D.S., M.S.

Laser, Electrosurgery and their Applications in Periodontics
by Dinh X. Bui, D.D.S., M.S.

Replacement of the conventional “steel” cut has been the subject of many investigations. It started with the d’Arsonval discover in 1891 of the high frequency current, that is current oscillating at 10,000 cps or more, can be passed through living tissue without producing a nervous or muscular response. In 1908, the first electronic scalpel was initiated when DeForest devised the first vacuum tube high frequency apparatus. The prototype of the instrument used today was developed in 1923 by Wyeth, and was capable of cutting tissue with little penetration, allowing primary healing, as the thin layer of dehydrated tissue on each side of incision was absorbed. Today, there is four different types of electrical current used; they are, electrodesiccation, fulguration, electrocoagulation, and electrosection or acusection. On the other hand, the use of laser has been new for dentistry, even though surgical lasers have been used in medicine for over a decade in the surgical specialties of Otolaryngology, dermatology, plastic surgery, gynecology, opthalmology, neurosurgery, urology, thoracic, and cardiovascular surgery, gastrointestinal surgery, orthopedics, and most recently in oral and maxillofacial surgery. Four type of laser has been developed for medical applications: CO2, Neodymium/YAG (yttrium-aluminum-garnet), argon, and ruby. The lasers are named according to the material used for the lasing medium. This paper discuss the history, rationale, histological study of wound healing in usage of electrosurgical and laser technology.

Four types of currents in electrosurgery indicates four clinical applications. Electrodessication is the monoterminal technique (only active electrode is used) using the low voltage, dehydrating current. The operator has no control over the amount of tissue destruction (a characteristic of low voltage current). Electrofulguration is a monoterminal technique which also used a dehydrating current, only that the active electrode does not touch the tissue but rather brought near the tissue surface to produce the sparks which produce an eschar. The operator thus can control the penetrating destruction of heat. Electrocoagulation, on the other hand, is the biterminal technique utilizing the partially rectified or fully modified rectified concentrated current to coagulate the organic content of the tissue without penetrating deeply the adjacent tissue. Similarly, the electrosection is also a biterminal technique which utilized the fully rectified high frequency current to create incision without accompanying coagulation. The best unit used today utilizes the fully rectified and filtered current produced a precise, undamped current for both incision and coagulation.

Electrosurgery can be used to perform gingivectomy and gingivoplasty. Although at the initial stages the cold knife gives a cleaner wound and a more rapid healing, in later stages, both modalities appeared to be good. However, extra caution must be carried out to avoid contact with the bone since irreparable damages will occur. The only advantage of electrosurgery today is the coagulation to reduce bleeding and resulting in a clean field with better visibility for the surgery.

Several studies has investigated electrosurgery effects on the periodontal tissue in creating incision or coagulation. Pope in 1968 found that repair following electrosurgery persists for much longer time compared to the scalpel surgery healing. The experiment is carried out on the four adult mongrel dogs with the fully rectified current of undamped waveform. This is a split mouth design, with electrosurgery procedure on the left side of the mouth and the scalpel surgery on the right side of the mouth. The results indicated that there is more severe and greater degree of bone injury, indicated by a larger number of osteoclast and osteoblasts in the area. The duration of complete repair was retarded as compared to that of the scalpel surgery.

Glickman and Imbert in 1970 compare the effect of gingival resection with electrosurgery and periodontal knives. Again four adult dogs was used in a split mouth design. Electrosurgery with a filtered, fully rectified current of undamped waveform was used on the right side, whereas the scalpel surgery was carried out on the left sides. Two types of laceration were evaluated, the deep and the shallow resection. In the shallow resection, there is more granulation tissue an more bleeding in the first two weeks after the surgery in the case of electrosurgery. Both techniques presented the similar microscopic appearances in the wound area after six and 12 weeks and the underlying bone at that time was unaltered. In the area of deep resection, after six weeks, the electrosurgery side showed gingival inflammation, recession, and bone height destruction in all areas. Bone necrosis and sequestration was found in the maxillary molar area, ulceraton of gingiva, and the pronounced destruction of buccal alveolar plate. On the knife treated side, the well form gingival sulcus obtained with slight recession, and gingival inflammation in the connective tissue with reduction in bone height is minimal. The conclusion of the experiment is that electrosurgery when performed with deep resection can result in extensive gingival recession, bone necrosis, and furcation involvement an the tooth mobility when used close to the bone. Such damage did not occur followed the use of peridontal knives.

In 1976, Sozio conducted a control electrosurgical currents and wound healing to examine the tissue healing at one to six months in order to see whether the electrosurgical wound healed as completely as the blade would. Three incisions were made on guinea pigs, one with the blade, one with filtered current, and one with the nonfiltered current. Histological data were collected at immediately postop, 24 hours, 48 hours, four days, seven days, 14 days, one month, and six months. Scalpel wounds demonstrated more rapid healing in early stages than the electrosurgical counterparts.

Wilhemsen et. al. in 1976 found that the gingival electrosurgery can result in permanent periodontal damage which includes the burning of cementum, loss of connective tissue attachment, and significant recession of gingival margin. Maness et. al. in 1978 evaluates the effects of varying frequency and waveform of electrosurgical device on wound healing. The histologic analysis showed that the machine with the full wave rectification and lowest frequency of operation produced greater tissue alteration than the full wave rectified with higher frequencies. The continuous output waveform produced less tissue alteration than the modulated type at the same frequency of operation. A band of coagulation necrosis 5Omicrons wide along the margin of incision is found.

Kenneth Nixon, Adkins, and David Keys investigates histologically the reaction of alveolar bone after gingival incision by electrosurgery using undamped fully rectified current on 25 guinea pigs and found that at 12 hours post op there is more soft tissue necrosis, more extensive inflammatory reaction, and greater destruction of the periosteum after electrosurgery. Necrosis of bone seen extensively at 48 hours. By 96 hours, the electrosurgical tissue were still lined with coagulum, but repair of the scalpel wounds had begun.

Nevertheless, clinical researches on human subject has revealed more encouraging results. Malone et al. compared the initial incision of the tissue and the postoperative healing and reveal that the healing was comparable to the scalpel in the 2.5mm depth cut. Thus he concluded that the electrosurgery is the safe and effective method. Aremband and Bryan Wade study of wound healing in gingivectomy with electrosurgery and knives in 27 patients reveals that there is no observable difference between the two modalities following a 3 week post op period. Pain was insignificant and experienced equally in both modalities. Cytological evaluation revealed no difference in epithelial cell maturity in both modalities. Histological examination revealed difference in both connective tissue and epithelial maturation between individuals, but not between the sides subjected to different types of surgical modalities. Periodontal knives does result in less gingival fluid exudate in the third week post-surgery.

In short, electrosurgery is only recommended for soft shallow excision of the tissue. Its use near the bone is contraindicated for reason of necrosis and retarded wound healing. On the other hand, laser surgery introduced a promising technology that would combine the rapid healing of the scalpel surgery and the minimal bleeding of electrosurgery. Laser unique characteristic lies in the fact that the laser light is emitted at a specific wavelength of energy and travels in a predictable pattern. The laser energy is produced in a laser cavity which consist of an active medium (the source of laser energy which can be solid, liquid, or gas), the incident energy source (stimulate the atoms of active medium), and the optical resonator (redirect the escaping incoherent photons of active medium into the directional, monochromatic, coherent form of light). When the concentrated energy of lasers is absorbed by tissue, a rapid thermal effect results in vaporization and carbonisation of the tissue.

There are two techniques in laser that are commonly used: excision or vaporization. Excision is prefered because it allows histologic confirmation of the diagnosis and indicates whether the lesion has been completely removed. Vaporisation has the risk of leaving behind the small fragment of the tissue, especially in the area of thick epithelium, of which the deeper layer may not be completely eradicated. Biological and clinical studies have shown that the wounds produce by C02 laser results in minimal damage to adjacent tissue and minimal inflammation. No dressing is required, and the laser area should be left exposed in the mouth. Skin graft of the laser wound is uneccessary as reported in various studies. The acute inflammatory reaction is delayed and minimal, and few myofibroblasts are present in the base of the wound during healing. These cells are the effectors of wound contraction and thus there is little contraction following removal of oral mucosa with laser. There is minimal scarring, resulting in little duration or restriction in movement of the soft tissues. There is less bleeding with laser as compared to the scalpel cut, since the blood vessels of .5mm or less in diameter are sealed spontaneously, thus aided to the surgeon visibility and precision during the surgery. However, laser surgery does have some disadvantage. The mild postoperative discomfort usually delayed up to one or two weeks. Epithelial regeneration is delayed, and the wounds take a longer time to reepithelialize than following conventional surgery. Another disadvantage is the high cost of equipment. This delayed of wound healing is thought to be the result of the lack of wound contraction and thus failure of the area to reduce in size. The procedure usually will take longer time especially in gingivoplasty where abundant of tissue removal is required.

An evaluation by Dr. J.W. Frame in using CO2 laser to eradicate 130 pathologic lesions of the oral tissue reveals that following laser treatment, the acute inflammatory reaction is minimal and its onset is delayed. There is little swelling, edema, and no airway distress. Healing is generally excellent, and because of the limited contraction and scarring that occurs, there is little restriction in mobility of the soft tissue or interference with oral function. Comparing to the scalpel incision, however, it does not possess any greater ability than the scalpel to cure these conditions.

A comparison of carbon dioxide laser and conventional scalpel excision in wound healing in the rat abdomen by Robert B. Shira (1990) indicated that there was a minimal inflammatory response around the laser wounds while there was a fairly brisk inflammatory reaction around the scalpel wound initially after 1 days. Both the scalpel and the laser wound were fully epithelialized clinically by 14 days. Histologically, there also was a relative absence of inflammatory response around the laser wound with minimal cell destruction. At a cellular level, the wound in both cases epithelialized at day 7. There is a precise thermo-destruction of tissue 190 micrometer around the laser beam and an area of thermo-damage, which is reversible, for another 500 micrometer beyond. Tissue temperature in laser measured to be up to 140 degree Celsius. The sealing and lymphatic and blood vessel by laser resulted in minimal extravasation of fluids and ultimately minimal inflammatory response. In contrast the scalpel wound allow extravasation of blood and lymph fluid, resulting in more swelling and more inflammatory response, which takes longer to resolve. Laser thus can be a recommended technique for soft tissue oral and maxillofacial surgical procedure.

Laser curettage is another area that has been promoted as a revolutionary procedure in periodontics. Its rationale includes its ability to vaporize not only the subgingival bacterial flora but also the necrotic gingival tissue, thus maximizing the healing potential of the site. (Myers, 1989). The technique involved the laser fiber (a glass fiber 200 to 300 micrometer in diameter) is inserted to the known depth of the periodontal pocket, being oriented parallel to the root surface. The laser is activated and the fiber slowly withdrawn using a sweeping motion. The process is repeated, using the overlapping insertion points to attempt to achieve a coverage of root surface. Energy usage are of typical range of 1-2 W, 20Hz pulse frequency, pulse energy 62.5-lOOmJ/pulse. Irradiation time is about 1-2 minutes per tooth or 3 seconds per mm2 area of root surface. In the review article by Laurence Walshin 1993, laser curettage is found to be not sufficient for removal of calculus. Lin et al. in 1992 in a clinical study demonstrated that laser curettage was less effective than scaling for removal of calculus. Dr. Walsh also disputed the claim that laser can be used in conjunction with conventional root planing technique to facilitate the removal of subgingival calculus. There is heat penetration into the tooth structure during the laser procedure, thus damage both the cementum and the dentin. The result is the peeling of the cementum an exposure of underlying dentin and dentinal tubule when laser treatment was followed by root planing. Laser curettage is not faster, especially in achieving the smooth surface as obtained by the conventional hand instrumented root planing. There is no evidence that the periodontal pocket environment was detoxified or made sterile by the laser curettage. While Nd:YAG lasers are capable of ablating small quantities of tissue, the absorption characteristics of this laser wavelength are not well suited to tissue ablation. The poor absorption of this wavelength in moisture environment results in penetration of energy into tissue, producing destructive thermal change and little vaporization of tissue. Laser curettage is not recommended as an effective treatment for aggression of the periodontal disease, since the ultimate etiology of periodontal disease is plaque control. In vitro study has indicated that the laser treatment inhibited fibroblast reattachment to the Nd:YAG laser treated tooth surface. Nd:YAG laser induced physical and chemical changes to root surface and reduce the biocompatibility of the root surface. Laser curettage thus are found to damage the teeth (charring, carbonisation, peeling of cementum, pulpal injury) and soft tissue. The lased enamel surface is rough, crazed, or cratered. The lased enamel is also softer with significant ultrastructural changes which consists of different shape and larger size of crystal and loss of prismatic structure.(Ferreira et. als. 1989) There is no data to evaulate the bacterial recolonization of the sites treated by laser curettage as compare to the site treated by conventional method of scaling and root planing. In short, Dr. Walsh recommended further investigation and studies are required prior to adopted the laser curettage technique as of long term therapeutic benefit. The weight of evidence available at present time does not support the value of the technique as an alternative to the conventional approach.

In evaluating the usage of laser as the mean in treating gingival hyperplasia, various reports with encouraging results have been published. Dr. Halter, Kirshner, and Susanin in 1992 published case study of laser surgery application for the immunosuppressive gingival hyperplasia. Since patient is immunocompromise, the possible danger of excessive bleeding and slow healing from conventional surgery prompted the consideration of laser for tissue removal. Bleeding was not excessive, less tissue trauma and healing is more rapid than the scalpel or electrosurgery. S. Barak and I. Kaplan in 1988 also published case report of the use of CO2 laser in the excision of gingival hyperplasia caused by nifedipine. The advantage lies in the hemostatic and sterilizing effect while post operative edema and pain is negligible. The advantage included debulking without bleeding, simultaneous sterilization, minimal postoperative pain which is particularly important in elder patient. There was no sign of recurring gingival hyperplasia after one year of follow up. Robert Pick, Bernard Pecaro, and Charles Silberman in 1985 also published the case report of C02 laser usage to perform gingivectomy in 12 patients. One of these cases involved hemophilliac patient, which expectedly will have bleeding problem. Again, the results is encouraging. The surgery is bloodless since the laser beam coagulate the blood vessels of .5mm or smaller. Surgical time thus is reduced due to better visibility. There is instant sterilization of the area, therefore decreasing bacteremia. There is noncontact surgery, thus no mechanical trauma to the surgical site. Histologic studies have shown that the thermal effects of laser energy in the adjacent nontarget tissue consists of three layers; the inner thin zone of carbonized tissue, the zone of dessicated and destroyed tissue, and the outer zone of edematous, possible reversibly damaged tissue. The width of the three zones is less than .5mm They also mentioned the disadvantage of the laser included the hospitalization and the cost of equipment. Delay in healing when use of CO2 laser in skin, subcutaneous, fascial, and muscular tissue is expected since superb coagulation of very small vessels and lymphatics occurs. Another disadvantage is loss of tactile feedback in using the instrument. Nevertheless, they recommended laser use in hyperplastic condition, bloodless incision, partial thickness dissections, and for the removal of soft tissue grafts from the palate leaving a dry wound, thus avoiding any postoperative bleeding complications.

According to the American Academy of Periodontology, the research, science, and therapy committee in 1992 indicated that the only periodontal use supported by researches is gingivectomy utilizing CO2 laser. There is abundant evidence confirming markedly less bleeding, particularly of highly vascular oral tissues, with laser surgery. Postoperative pain seem to be reduced in laser surgery due to the protein coagulum that is formed on the wound surface, acting as a biologic dressing and sealing the ends of the sensory nerves. Precaution of eye injury is noted since the laser beam may reflected from the mirrors or retractors and reflected toward the eye. Patient throat and delicate oral tissue must be protected by wet gauze packs from accidental impact. The AAP research committee dismissed the use of laser as root curettage instrument. Cost effectiveness is poor since laser technology is far more expensive than the conventional scalpel usage.
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Reference

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