Laser Method of Action Posted on 14 Dec 01:58

Written by Lori Trost, DMD and Karen Kaiser, RDH

Oral surgery procedures that require the removal of soft tissue can be achieved by vaporization (ablation) and/or cutting (incision, excision, or dissection) with the diode laser. Some of these soft-tissue applications include but are not limited to gingivectomy, frenectomy, hemorrhagic lesion removal, gingival sculpting techniques associated with implant recovering or therapy, and subgingival curettage. The advantages for laser soft-tissue oral surgery include improved hemostasis, reduced intraoperative and postoperative pain/discomfort, decreased postoperative swelling, eliminated need for sutures, reduced bacterial count at the wound site, reduced operator time, and versatility. Because of its versatility, this laser may be a useful alternative for soft-tissue oral surgery compared to traditional periodontal surgery.4 The disadvantages or limitations of laser surgery compared to incisions made by scalpel include slower tissue cutting, delayed healing, and reduced surgical precision.

 

Method of action

Lasers emit a precise beam of concentrated light energy. This light is unique in that it is comprised of a single wavelength, expressed in nanometers or one billionth of a meter, measured crest to crest in the wave. The wavelength generated is based on the active medium present in the laser device and can be a solid (Nd:YAG, diode, Er:YAG) or gas (CO2 or Argon). The diode laser is considered a solid, with a semiconductor chip embedded with crystals, making the device smaller and lighter. The active medium determines the wavelength, varying by the makeup of the crystals.

The diode wavelengths are in the near infrared spectrum, typically from 800 nm to 980 nm. The wavelength determines the absorption characteristic in biologic tissues. Absorption of laser light by biologic tissue determines efficiency of surgical removal. The various components of the biologic tissue determine whether laser light will be absorbed. Diode lasers are well-absorbed by hemoglobin and pigmented tissue and, to a lesser degree, by water. Different wavelengths are absorbed by soft tissue at varying rates, depending on the type of soft tissue.Keratinized tissues, containing less blood, require the use of lasers with higher wavelengths or the use of more power in general. The practitioner must match the wavelength to the specific tissue, because specific wavelengths provide great precision, minimizing potential risk of lateral tissue damage.

Interaction of the laser with tissue is a photo-thermal event, in which light is transformed into heat. When the laser beam penetrates tissue and is absorbed, a designated amount of energy is removed per unit of time, with a resultant temperature rise. Coagulation begins at over 50°C, with protein denaturation at 60°C. At temperatures 100°C to 200°C, vaporization of water occurs. (Note: Water is the chief component of soft tissue.) Laser surgery is achieved by the process of ablation, removing this tissue by converting it to a gaseous state or plume. The plume is considered to be a biohazard and should be removed with high-volume evacuation.

The power output utilized by the soft-tissue diode laser is typically between .and 10 watts or joules per second, in a continuous output or a pulsed power. Diode lasers use optical fibers to deliver the laser beam. These fibers, made up of primarily quartz, can deliver light through bends and curves, therefore allowing access to difficult intraoral sites. A pencil-size handpiece glides over the fiber and locks into place. Most treatment uses direct contact with the tissue and allows the operator to experience tactile feedback similar to a scalpel or mechanical instrument.