Diode Laser (805-1064 nm)

Many manufacturers produce diode lasers, delivering wavelengths in the range of 805 to 1064 nm. They are compact and portable in design and are relatively inexpensive surgical units, with efficient and reliable benefits for use in soft tissue oral surgical procedures. Diode lasers can be used in continuous-wave or gated-pulse modes, in contact or out of contact with tissue. The 980-nm diode laser has significantly higher absorption in water, which makes it cut more optically than thermally, with an optical penetration of less than 300 microns (µ, µm). Romanos and Nentwig⁴ found that the 980 nm diode laser produced a more precise incision margin compared with other laser wavelengths. In addition to various soft tissue oral surgical procedures, 980-nm diode lasers have become as popular as CO₂ lasers in the treatment of periimplantitis because they offer a bactericidal effect without causing implant surface alterations⁵ (see Chapter 7).

Neodymium:YAG Laser (1064 nm)

The Nd:YAG laser’s active medium is a crystal of yttrium, aluminum, and garnet doped with neodymium ions.⁶ By functioning in the near-infrared part of the spectrum at 1064 nm, the Nd:YAG laser exhibits minimal surface tissue absorption and maximal penetration; this allows for coagulation of tissue in depth.⁷ The optical delivery is free-running but must be in the “pulsed” mode because of Nd:YAG’s ability to penetrate deeply into soft tissues. Romanos⁸ believed that most procedures could be performed without local anesthesia because the pulse duration is shorter than the time required to initiate a nerve action potential.

Comparing Nd:YAG laser surgery to conventional scalpel surgery, White et al.⁹ concluded that the laser could be used successfully for intraoral soft tissue applications without anesthesia and with minimal bleeding. When the procedure involves significant ablation or resection of tissue, local anesthesia is necessary for patient comfort.⁷

As with the diode lasers, the Nd:YAG laser can be used in a contact (excision) and a noncontact (coagulation) mode. These properties have led to its use in a variety of maxillofacial procedures, including coagulation of angiomatous lesions, hemostasis in bleeding disorders, arthroscopic surgery of the temporomandibular joint (TMJ), resections in vascular tissues (in combination with CO₂ wavelength), and palliation of advanced neoplasms.¹⁰ The Nd:YAG laser has demonstrated some benefit with minimally invasive periodontal therapies, including sulcular debridement and bacterial decontamination, resulting in potential new attachment of gingival tissues, regeneration of supporting bone, and regrowth of periodontal ligament¹¹ (see Chapters 3 to 5).

Erbium Lasers (2780-2940 nm)

The erbium family of lasers, including two similar wavelengths, has gained popularity in dental implant surgery because of several properties. The erbium lasers are free-running pulsed lasers with thermal effects that interact solely with the surface layers of soft and hard tissue.¹² The beams are reflected by polished metal surfaces such as titanium, so they have no adverse effects on dental implants.¹³ Application of the erbium lasers in dental implant surgery has been advocated for the preparation of hard tissue, second-stage surgery, revision of soft tissue, and treatment of periimplantitis.^14–16

Although the erbium lasers are capable of osseous surgery, such as crown lengthening, harvesting autogenous bone grafts, and sectioning teeth, these procedures require more time than traditional methods. For this reason, oral surgeons, who spend much of their time treating osseous tissue, have not embraced erbium laser technology.

Carbon Dioxide Laser (10,600 NM)

The CO₂ laser has become the workhorse for intraoral soft tissue surgery. The emitted wavelength of 10,600 nm has ideal absorption by soft tissue because soft tissue is composed of 90% water, and CO₂ has excellent absorption in water. Cellular rupture occurs from the photothermal effect when intracellular water absorbs the energy from the CO₂ laser. The cellular vaporization is the basis for the CO₂ laser to function as a surgical tool.³ The wavelength allows for absorption into soft tissue, very quickly generating heat conducted into the surrounding tissue, and creates a very narrow zone of thermal necrosis approximately 500 µ or less.¹⁷ Lateral thermal damage of such a small area is an excellent advantage of CO₂ laser use, because it results in coagulation of vessels up to 500 µ in diameter and is clinically manifested by hemostasis and sealing of the lymphatics, which has been found to reduce postsurgical bacteremia compared with other methods of incision.¹⁸

The learning curve tends to be slightly higher with the CO₂ laser because it is the only soft tissue laser used without direct tissue contact. The delivery system is either an articulated arm or a hollow waveguide. The hollow waveguide requires the use of higher power because significant laser energy is absorbed internally by the laser delivery system. These delivery systems are acceptable when one has direct vision in the confines of the oral cavity. However, when performing endoscopic and microscopic surgical procedures in which clinicians are challenged by limited visibility of an area, a flexible core system can provide a needed advantage. Development of the BeamPath fiber allows laser energy to be transmitted by an innovative photonic band-gap omnidirectional dielectric mirror lining, which guides the light through a flexible hollow core.¹⁹

The CO₂ laser energy can be transmitted in several different modes, including continuous, chopped/gated pulse, and various “superspeed” and “ultraspeed” modes. Lasers are generally perceived as a continuous beam of light. Dispersion of CO₂ laser energy in this manner is associated with a continuous wave. Continuous-wave (CW) CO₂ lasers were the forefront of technology in the 1970s and proved to be successful in medicine. However, the constant emission of laser energy delivered very high energy densities, causing unnecessary injury to the soft tissues. As this technology progressed, a shutter was integrated into CW lasers, causing interruption (gating, or chopping) of the continuous wave. These units delivered fluences of approximately 1200 to 1500 mJ/cm² of energy density. This development limited the use of these lasers in microsurgical applications. Newer laser technology can also operate in a pulsed-wave (PW) mode, meaning the energy bursts on and off very quickly. PW laser energy creates an instant burst of light energy, achieving a greater peak power than the CW mode.

Superpulsed CO₂ lasers were designed to regulate the energy density transmitted to soft tissue. By changing the radiofrequency of the pumping mechanism in the laser, the pulsewidth and speed of transmission could now be predetermined. The superpulsed mode of transmitting CO₂ energy improved the working speed of pulses to 400 to 800 microseconds and decreased the energy density to 180 to 300 mJ/cm² on soft tissue. A direct result of the decreased energy density was less carbonization and charring, which resulted in a more consistent healing process in soft tissue procedures.

The next generation of technology currently on the market can create pulses of 20 to 80 milliseconds while generating a peak power of 320 W. However, the smaller beamwidth reduces the energy density transferred to the tissues. This technology can produce an extremely thin incision at depths of up to 4 to 5 mm in a single pass without carbonization or tissue damage. Many superficial soft tissue procedures using this technology generally do not require injectable anesthetics because of the minimal absorption depth of 0.10 mm, reducing lateral thermal damage and frequently resulting in minimal or no bleeding, discomfort, or swelling during the surgery and postoperative period.

Benefits

The benefits of using lasers in oral surgical procedures are significant, both for the dental surgeon and the patient. Laser light is monochromatic, coherent, and collimated; therefore it delivers a precise burst of energy to the targeted area. Laser energy incises tissue more efficiently than the scalpel, generates complete vaporization, and coagulates blood vessels. For contouring procedures, the laser is perhaps the surgical instrument of choice because of its ability to sculpt soft tissues by selective ablation.

The hemostatic effect created when the laser’s energy interacts with the soft tissue eliminates excessive bleeding, a factor that has traditionally discouraged dentists from performing surgery, and creates a clean surgical field, allowing increased precision and accuracy and greatly improving visualization of the surgical site, making laser surgery as straightforward as other dental procedures.

Examined histologically, laser wounds have been found to contain a significantly lower number of myofibroblasts.²⁰ This results in less wound contracture or scarring and, ultimately, improved healing.^21,22 Mobility to the dynamic tissues (lips, tongue, floor of mouth, soft palate) is attained more readily postsurgically. As a result of improved healing and hemostasis, intraoral laser wounds can often be left without sutures, healing by secondary intention, except when cosmesis is a concern.

With laser technology, the patient typically experiences less postoperative swelling and pain.^23,24 A compromised airway during oral surgery is less of a concern, partly because of the decreased swelling. Although not always predictable, the decreased postoperative pain can be managed with over-the-counter (OTC) nonnarcotic oral analgesics (e.g., ibuprofen) for most laser procedures. The physiology of this effect is still unknown but most likely correlates with decreased tissue trauma and an alteration of neural transmission.⁷

Because the patient has a painless surgical experience with minimal postoperative complications, many procedures are performed on an outpatient basis. Patients can often return to work within 1 day or even immediately after surgery.

Drawbacks

Despite the laser’s many advantages, when determining the appropriate treatment for a patient, the clinician also must consider its drawbacks. Although the healing process following laser surgery is generally marked by decreased scarring and increased function, some have found that the speed of healing is slightly prolonged compared with other types of wounds.²⁵ This delay in healing is undoubtedly caused by the sealing of blood vessels and lymphatics and subsequent need for neovascularization in healing. Typical intraoral healing after laser surgery may take as long as 2 weeks for wounds that would otherwise take 7 to 10 days. If sutures are indicated, delayed healing times must be taken into account when considering suture removal, to prevent premature dehiscence of the wound.²⁴

Nonsutured CO₂ laser wounds heal forming a fibrinous coagulum that functions as a biological dressing. Because of the slow epithelialization of CO₂ laser wounds, the fibrinous coagulum may be present beyond 2 weeks.²³ A clinician new to lasers should not confuse this healing process for infection and unnecessarily perform a wound debridement or prescribe antibiotics when there is no indication. Unlike postsurgical healing after conventional techniques, an increase in pain 4 to 7 days postoperatively may occur, which can normally be controlled with minimal oral analgesics (e.g., ibuprofen). The clinical appearance and anticipated discomfort after laser surgery should be discussed with patients to avoid confusion or perceived complications.²⁴

Virtually all laser wavelengths used for surgery to vaporize, coagulate, or cut tissue may produce particulate debris called laser plume. Clinicians, assistants, and patients may be at risk from exposure to laser plume. Laser plume may contain carcinogens, irritants, dusts, viruses, and bacterial spores, depending on the procedure. It may also contain carbon monoxide, polyaromatic hydrocarbons, various toxic gases, and chemicals such as formaldehyde, hydrogen cyanide, and benzene. There are currently no known potential chronic health effects from long-term exposure to laser plume. The literature on infectious transmission of laser plumes in medicine is equivocal. Several studies of patients positive for human papillomavirus type 2 (HPV-2) deoxyribonucleic acid (DNA), revealed no viable viral particles in the laser plume.^26–31 Other studies have shown HPV DNA in the plume of laser-vaporized tissue.^32–35 None of the studies reviewed involved treatment within the oral cavity. A review of the literature reveals no cases of any dental personnel becoming ill as a result of inhaling laser plume. In any case, contaminants generated by lasers can and should be controlled by ventilation, safe work practices, and personal protective equipment.

Biopsy Procedure

Every patient requires a screening for cancer, which is accomplished by performing a thorough oral, head, and neck examination. Oral examinations can be made more efficient by inspecting high-risk sites, where 90% of oral squamous cell cancers arise: floor of the mouth, ventrolateral aspect of the tongue, and the soft palate complex.³⁹ Many screening and detection aids can be used as adjunctive tools to identify precancerous and cancerous tissues early and before they become visible to the naked eye, expediting diagnosis and improving the patient’s prognosis. Oh and Laskin⁴⁰ noted accentuation of some lesions when patients used acetic rinse, but there was no significant improvement in detection. Also, examination with the chemiluminescent ViziLite system produced reflections that made visualization more difficult.

When cellular changes are detected, the downfall of all adjunctive techniques is that a surgical biopsy procedure remains necessary to obtain a diagnosis.^41–43 Biopsy is the process of removing a sample of tissue from a patient for diagnostic examination. The procedure is required to determine the underlying process within the tissues that is causing changes in their clinical appearance. The diagnosis obtained ranges from “normalcy” to an inflammatory process, and “systemic disease” to a benign or malignant neoplasm. Ultimately, an accurate diagnosis guides the clinician in determining the necessary treatment. The five intraoral biopsy techniques are aspiration biopsy, cytological biopsy, brush biopsy, excision biopsy, and incision biopsy.

The brush biopsy technique has improved the sensitivity (92.3%) and specificity (94.3%) for detection of oral squamous cell carcinoma or dysplasia when tested on visually identified lesions.^44–46 Note that brush biopsies in particular should be used only as a screening tool, and atypical cell identification or positive results from such biopsies require an additional step implementing a surgical procedure to confirm a diagnosis.⁴⁷

Formulating a definitive diagnosis generally requires the acquisition of a tissue specimen histologically representative of the lesion, using one of the two surgical biopsy techniques. Until recently, most surgical biopsies have been performed with “cold steel,” the scalpel. The disadvantage of using a scalpel is that patients frequently experience significant intraoperative and postoperative sequelae.

The preferred modality for the intraoral surgical biopsy is the laser, for several reasons. The laser’s hemostatic nature creates a blood-free surgical field compared to the scalpel. This is critical when treating vascular lesions or patients who tend to bleed excessively; the laser minimizes blood loss. Other advantages of using a laser are reduced surgery time (superior precision of incision) and unparalleled visualization of the surgical site (lack of blood in surgical field). Decreasing the length of surgery reduces tissue manipulation and potential wound contamination. The laser’s thermal effect produces minimal lateral thermal necrosis but provokes enough response to attain a bactericidal effect. Patients are comfortable during the procedure with minimal local anesthesia. After laser surgery, patients quickly return to their daily routine, experiencing no bleeding or swelling. Discomfort is usually minimal and generally can be treated with OTC nonnarcotic analgesics such as ibuprofen. Surgical biopsies with a laser can often be performed on a patient’s initial visit, accelerating the diagnostic process and expediting treatment.

Excision Technique

Excision technique requires the removal of the entire lesion with at least 2 to 3 mm of peripheral margin (Figure 6-5, A-C). This technique is preferred for oral lesions 1 cm or less and for minor, solid, and exophytic lesions. Localized discrete lesions such as fibroma, papilloma, mucocele, and pyogenic granuloma are most often excised with a laser.

FIGURE 6-5 • Excision biopsy technique. A, View of presenting lesion shows surrounding anatomy. B and C, Outlining the planned incision with a marking pen or with the laser at a lower power setting allows for greater control with incision placement. D, Ideal hemostasis within surgical defect. E, Photographic documentation of specimen. F, One-week postoperative view.

When surgeons perform their first laser biopsy, they should take slightly wider margins than they would take with a blade, to decrease the possibility of thermal necrosis (a beginner’s mistake in biopsy technique) at the incision margins.³⁸

When an excision biopsy is confirmed to contain a positive margin of disease, this procedure is classified as an “incision” biopsy. Additional treatment is then required to eradicate the disease.