The application of the laser as a surgical method is comparable to that of the scalpel, and it has become an important component of modern clinical dentistry. The different effects of certain laser systems can apply for the removal of soft tissue tumors, soft tissue cysts, and precancerous lesions, such as leukoplakia. Frenectomies, pre‐prosthetic surgical procedures, like vestibuloplasties, treatment of gingival hyperplasia, and removal of vascular benign tumors or malformations are other clinical indications.
Exact knowledge of the benefits of the laser light and the effects of the respective wavelength on biological structures are essential for the achievement of an optimum effect (see also Chapter 1). Only under these requirements is it possible to achieve a positive effect of the laser beam on the tissue and to accomplish excellent wound healing without complications.
The indications of the lasers in oral surgery vary from the common excision, biopsies, and coagulation of blood vessels to the complicated therapy of the removal of precancerous lesions and the treatment of vascular tumors and peri‐implantitis, which indeed seems to be very promising for the future (see also Chapter 6).
This chapter intends to provide an overview about the application of various laser wavelengths with different clinical indications for the surgically oriented clinician.
In oral soft tissue surgery, the most used and accepted laser systems at the moment are the CO2, the Nd:YAG, and the diode lasers. The argon ion, the Ho:YAG and the Er:YAG lasers can be also applied under special circumstances and depending on the clinical indication.
3.2 Basic Principles
The power and energy density in laser therapy must be defined precisely. A vaporized, a necrotic zone, and a zone of reversible thermal changes may be generated by the effect of the laser beam on the tissues.
In comparison to Nd:YAG, diode, or argon lasers, there is a stronger absorption of CO2 laser beams from fair and slightly inflamed tissues. Due to the effect that granulation tissue contains a high number of blood vessels and capillaries, the high hemoglobin tissue content leads to a higher absorption of the Nd:YAG laser beam.
This means that with the same beam’s energy, on the one hand we achieve quicker surgical excision in the inflamed area, and on the other hand, we have less risk of a pronounced tissue necrosis and/or bone dehiscence in cases of incautious or uncontrolled work using this laser wavelength. From the physical point of view, a slow application will result in a drastic increase of the respective energy density, which is dependent on the entire irradiation period and must be controlled at every surgical intervention.
3.3 Excision Biopsies
Several laser systems are used today in order to excise biopsies, especially the CO2, the diode, and/or the Nd:YAG pulsed laser. The incision occurs according to the surgical principles considering that thermal effects occur in variable degree in each case. A focus diameter of 0.2 mm generates a zone of thermal impact, which amounts to 50–200 μm with the CO2, and 500 μm–3 mm with the Nd:YAG laser (deep penetration into the tissue for the Nd:YAG laser) (Figure 3.1).
When the handpiece is focused and vertically applied on the tissue, a distinct marking appears, due to thermal damage (carbonization). This represents the “incision line.” The tissue elevation starts from the peripheral area of this marking and is directed in the depth of the lesion, until the tissue can be lifted easily from its base (Figure 3.2).
At this point, the handpiece is held perpendicular or in a slightly tilted direction to the tissue in order to separate the pathological tissue from the healthy basis. In cases of use of a diode laser, initiation of the fiber before surgery using an articulated paper (black or blue color) or a cork concentrating the maximum energy in the fiber tip is fundamental to control the peripheral thermal damage. The simultaneous coagulation allows a bloodless incision and excision (Table 3.1).
The lesion after removal with the laser must be referred to an oral, maxillofacial pathologist with the explanation of “laser excision,” in order to better illustrate the potential thermal effects and to avoid misdiagnosis. Only after histopathological confirmation of the diagnosis, can the complete excision of the lesion be performed, dependent on the laser wavelength and the type of lesion using a focused or defocused mode. The decrease of the distance between handpiece and tissue under constant power changes modifies the focus and therefore the power density, influencing cutting depth. In contrast to that, the increase of the distance of the handpiece decreases the power density and provides as a result the tissue ablation, so‐called vaporization, without distinctive thermal damage. This is of clinical significance in the removal of wide lesions, such as leukoplakia, lichen planus, or other pathological lesions.
Table 3.1 Operation mode and clinical procedure.
|Type of Procedure||Mode of Operation||Operative Mode||Applicator|
|Excision/incision||Focused beam||CW or pulsed||Angled|
|Ablation||Defocused beam||CW or pulsed||90°|
Suturing and special postoperative surgical measures are usually not necessary. Directly after excision of a lesion with the CO2 laser, a superficial irradiation of the tissue to create a small, coagulated zone (using the defocused beam) is clinically recommended (Figure 3.3) because this may significantly reduce postoperative pain and protect the wound from infection (wound dressing).
3.4 Removal of Benign Soft Tissue Tumors
In clinical practice, the surgically oriented dentist and/or specialist is confronted with small or big, stalked and superficial soft tissue tumors. The most frequent benign tumors of the oral cavity are the following:
- pyogenic granulomas
The most frequent wide tumors or soft tissue pathologies of the oral cavity are papillomatosis (especially in the palate), symmetric fibromas, vascular lesions and malformations, precancerous lesions (i.e. leukoplakia as well as oral lichen planus) (see also Figure 3.4). The surgical removal of papillomatosis of the palate, as well as the symmetrical fibromas and denture‐related fibromas, is often indicated in oral surgery from the pre‐prosthetic perspective. In comparison to the scalpel, the surgical laser permits the removal of such abnormalities with particular advantages for patients and surgeons.
3.4.1 Surgical Protocol for Removal of Small Tumors
In general, the incision design is similar to the conventional surgical method, but in comparison to that, there is only a small number of instruments necessary (Figure 3.5).
After a topical or local anesthesia, a wedge‐shaped excision will be performed with the laser handpiece. For the removal of the tissue, the handpiece is used in a focused mode. After the removal of a soft tissue tumor, the margins of the adjacent tissues should be ablated in order to achieve smooth excision margins. Afterwards the entire wound should be coagulated using a defocused beam and lower power settings (Table 3.2).
The noncontact CO2 laser is used with straight or angulated handpieces based on the location of the lesion. The articulated arm with the integrated glass mirror system is associated with some loss of power. This effect may lead to a local overheating at the end of the handpiece, particularly in cases of longer lasting surgical interventions. During surgical procedures under local (or general) anesthesia, there is a small risk of tissue overheating in the adjacent healthy tissues. For this reason, a periodical checking of the fiber condition is absolutely necessary to avoid complications (Figure 3.6).
In case of the Nd:YAG or diode laser application, the blood vessels and/or capillaries will be coagulated with a defocused (noncontact) beam. The risk of secondary bleeding, postsurgical discomfort, and edema is in general significantly reduced. The carbonized surface, which is formed directly after surgery can protect against an infection, and after three to four days there are no pathological changes of the mucosa to be observed. After the formation of a temporary thick fibrin layer (Figure 3.7), the healing is completed within three to four weeks.
Table 3.2 Chronological order in laser surgical procedures.
|Medical/dental history (update)|
|Clinical examination/informed consent|
|Anesthesia (topical and/or local)|
|Laser safety measures – test firing|
|Excision||Focused beam (CW or pulsed)|
|Marginal ablation||Defocused beam (CW or pulsed)|
|Coagulation||Defocused beam (pulsed/low power)|
The use of lasers with glass fibers, like diode and Nd:YAG lasers, provide an easier control of the tissue irradiation, since dentists, in general, feel comfortable having contact with the tissue in routine clinical dentistry.
Therefore, excisions can be performed when the glass fiber is in contact with the tissue, compared to other laser wavelengths like the CO2 laser or the Er:YAG laser, where a noncontact handpiece provides tissue removal.
However, knowledge of the penetration depth of the laser light within the tissue should be considered during incision. When a glass fiber of 300 μm in diameter is applied, a continuous contact with the tissue should be avoided in order to provide possible cooling of the tissue (thermal relaxation effect).
During the surgical procedure with the laser, surgical forceps should hold the soft tissue tumor, which is excised from the base with the laser glass fiber. The blood‐free surgical area permits an optically accessible treating of the tissue, whereas carbonization is not so pronounced in comparison to irradiation with the CO2 laser. Suturing is not necessary, and a soft/liquid diet is recommended for the first two to three postoperative days to avoid removal of the superficial wound layer. Local tissue irritation, as for example by a toothbrush, should be avoided particularly during the first three days (stage of a fibrin layer deposition), so that postoperative bleeding, associated with pain and wound healing problems, is avoided. For preventive antibacterial purposes, rinsing with chlorhexidine or other mouth rinses is advised.
Depending on the clinical indication of laser use, different parameters and power settings are recommended by the manufacturers. Clinical experience shows that a power up to 3.0 W (for the Nd:YAG laser) is good enough for use in private practice. The pulse frequency may vary between 40 and 100 Hz. High power settings or slow movement of the glass fiber under irradiation may lead to wound healing complications resulting in scar tissue formation or necrosis (Figure 3.8).
When the CO2 laser is used, a continuous beam or pulsed mode with short pulse duration and high‐pulse energy is recommended. During excisions, the handpiece is applied without tissue contact, with an average output power of 4–6 W. There is a variety of ceramic or metal tips with different diameters (e.g. 0.4 or 0.8 mm), which can be used in the handpiece for small focal spots in order to create precise incisions and excellent coagulation.
3.4.2 Surgical Protocol for Removal of Larger Soft Tissue Tumors
The most common larger soft tissue tumors and wide lesions in the oral cavity are fibroepithelial hyperplasia of the palate, and, in general hyperplasia, symmetric fibromas, granulomas, lipomas, hemangiomas, and last but not least adenomas. The removal of vascular lesions and malformations as well as precancerous lesions will be separately dealt within this chapter. Depending on the size of the lesion, a combination therapy of tumor excision with a scalpel and subsequent laser coagulation is sometimes recommended. Large fibromas or symmetrical fibromas can be excised today conventionally, and advanced bleeding can be controlled using the laser.
The CO2 laser in a continuous mode and with no contact to the tissue is mainly used for the treatment of wide (flat) pathologies of the oral soft tissue causing burning symptoms (e.g. oral lichen planus). A power of 6–10 W permits a quick ablation or vaporization of the pathological tissue when the laser is applied in a defocused mode. A small incision biopsy is necessary before the complete tissue is removed in layers (ablation). The decision of whether vaporization or excision of the lesion is indicated will be taken intraoperatively; however, it depends on the size and thickness of the lesion.
Erythematous pathological alterations localized at the palate (the so‐called fibroepithelial hyperplasia of the palate) is often associated with a poorly fitting prosthesis and secondary Candida superinfection. The tissue can be removed in layers with a CO2 laser in defocused mode, continuous beam, and a power of approx. 6–10 W. A sample incision biopsy of a clinically suspicious area must be carried out before complete ablation. For a better determination of the depth extension of the lesion, the carbonized tissue is continuously wiped away with wet gauze or cotton swabs. After that, a rinsing with hydrogen peroxide solution (3%) is very helpful. The prosthesis of the patient is then soft relined for the first two to three weeks, and the final relining will be performed at a later time.
Sachs and Borden (1981) were the first who treated such clinical recurrent lesions of the palate using the CO2 laser without observing any recurrences.
Some clinical applications of the CO2, diode, and Nd:YAG lasers in surgical treatment of benign soft tissue tumors are demonstrated in the following clinical cases.
3.5 Removal of Drug‐Induced Gingival Hyperplasias and Epulides
3.5.1 Removal of Drug‐Induced Gingival Hyperplasias
A gingival hyperplasia can be caused by systemic treatment with diphenylhydantoin‐containing drugs (e.g. for epilepsy), cyclosporine‐A (for immunosuppression after organ transplantations), calcium antagonists (for control of hypertension), and in particular nifedipine, but also diltiazem and amlodipine. A possible cause is the dysfunctional collagen degradation as a result of a limited functional ability of the fibroblasts (Scully et al. 1996).
The gingival hyperplasia has, as a result, difficulties in plaque control and, if combined with insufficient oral hygiene, can lead to inflammatory reactions and further bone loss. The therapy of choice is the removal of the hyperplastic tissues. This is possible, according to the size of the hyperplasias, either with the CO2 laser (Pick et al. 1985) alone, or in combination with Kirkland and Orban gingivectomy knives.
Initially, a measurement of the probing pocket depth with the Kaplan marking forceps allows determining the incision line. Two to three millimeters submarginal of this line, the incision will be initiated with the laser (see Figure in chapter 5) in the focused mode. Because of the strong carbonization and the resulting hemostasis, the incision line is usually visible. For small‐sized hyperplasias, the power of 4–6 W (CO2 laser beam, CW) is sufficient for excellent cutting and coagulation. At the same time, the antimicrobial effect of the laser beam leads to a distinctive bacteria reduction in the entire surgical field (Pick et al. 1985; Pick 1993). For more extensive gingival hyperplasias, the excision is carried out in combination with conventional gingivectomy knives, in order to shorten the surgical procedure.
To protect the tooth surfaces, it is recommended (Neiburger and Miserendino 1988; Sievers et al. 1993) that metal matrix or special flat instruments (e.g. spatula, gingivectomy knives) be used, which can be placed within the periodontal pockets during excision. In order to control the potential risk of overheating due to the reflection of the laser beam from the metallic surfaces, other options have been recommended. Since the CO2 laser beam is highly absorbed by wet surfaces, the use of a glycerin solution (or Vaseline®) over the tooth surface for further protection of the surrounding structures is strongly recommended.
After gingivectomy, the patients can be followed up in a strict recall program only when gingivoplasties can be successfully carried out with the help of a defocused laser beam, especially for medically compromised patients. The final hemostasis of the entire surgical area controls the bleeding and postoperative discomfort. The use of a periodontal pack (e.g. Coe‐Pak, Peripak®) is not actually required. After approximately one week, new capillaries and blood vessels are formed. Two weeks after surgery wound healing is usually completed. If the medication can be substituted by another drug, no recurrences are expected. If a substitution is not possible, the regular application of the laser is of importance especially during whole periodontal maintenance appointments. From the clinical experience, three‐ to four‐month intervals are recommended, where only topical anesthesia small, localized gingivectomies or gingivoplasties can be carried out.
3.5.2 Removal of Epulides
A frequent application of laser is performed for surgical removal of gingival epulides. As with the external gingivectomy, these lesions of the oral cavity can also be excised with the focused laser beam of CO2, Nd:YAG, diode, or the Er:YAG laser. At the moment, there are no longitudinal studies to determine the long‐term results after the removal of such tumors with different laser systems. The frequent recurrence after the removal of an epulis, without radical osteotomy of the adjacent bone and the extraction of the affected tooth, is given in the literature as between 5 and 70.6% (Giansanti and Waldron 1969; Eversole and Rovin 1972; Anderson et al. 1973; Benkert et al. 1982; Lee et al. 1986; Macleod and Soames 1987; Katsikeris et al. 1988; Mighell et al. 1995). A study of Gaspar and Szabo (1991) reported a recurrence rate of about only 7.9% after five years, if after the tumor excision with the CO2 ‐laser, an additional bone curettage and osseous decortication is carried out (Gaspar and Szabo 1991).