by Donald J. Colluzzi, DDS, FACD
Around 1975, medical surgeons began using a new device that complemented and, in some cases, replaced the scalpel. That instrument was a laser. During the 1980s, a carbon dioxide model was a common component in the operating suite. In 1989, the first laser specifically designed for dental use became available. Today, there are two dozen indications for use with various dental laser devices and the clinical applications continue to increase, making the laser one of dentistry’s most exciting advances with unique patient benefits. This article will present some fundamentals of lasers, laser-tissue interaction, laser features, advantages of lasers, and practice integration.
A laser produces light that is distinguished from ordinary light by two properties: 1) it is a single color, also known as monochromaticism; 2) the light waves are all coherent, which means that each wave is identical in physical size and shape. This monochromatic, coherent wave of light energy emerges from the laser device as a uniquely efficient source of energy.
Lasers are generically named for the material contained within the center of the device, called an optical cavity. The core of the cavity is comprised of chemical elements, molecules, or compounds, and is called the active medium, which can be a container of gas, a crystal, or a solid-state semiconductor. One currently available dental laser uses carbon dioxide as a gaseous active medium. The other devices are either solid-state semiconductor wafers made with multiple layers of metals such as gallium, aluminum, indium and arsenic, or solid rods of garnet crystal grown with various combinations of yttrium, aluminum, scandium and gallium, that are doped with the elements of chromium, neodymium, or erbium. For simplicity, the semiconductor lasers are called diodes, and the crystal lasers are designated with acronyms such as Nd:YAG, Er,Cr:YSGG, or Er:YAG. Of course, individual manufacturers create trademarked model names such as Waterlase, VersaWave, or AquaLite.
The active medium’s stimulation generates a specific color (or wavelength) of light. These wavelengths are in the form of nonionizing radiation, which is to be distinguished from ionizing radiation that is mutagenic to cellular DNA components. A few lasers emit visible light - the caries detecting systems, for example; but nearly all the surgical lasers produce invisible infrared beams.
Each wavelength has a somewhat unique effect on dental structures because of the specific absorption of that particular laser energy in the tissue. Some lasers are only absorbed by blood and tissue pigments, while others are only absorbed by water as well as “hard” tissue, such as enamel, dentin, and bone. More specifically, the wavelengths can be categorized into three groups:
- Diode and Nd:YAG wavelengths target the pigments in soft tissue and pathogens such as Porphyromonas gingivalis, as well as inflammatory and vascularized tissue.
- Carbon dioxide lasers also easily interact with free water molecules in soft tissue, as well as vaporize the intracellular water of pathogens.
- Erbium lasers (Er,Cr:YSGG and Er:YAG) are sometimes called “all tissue” instruments because of their excellent absorption in both apatite crystals and the water of soft and hard tissue.
Lasers produce light energy that can be absorbed by a target tissue, and this absorption process produces a thermal reaction in that tissue. Depending on the instrument’s parameters and the optical properties of the tissue, the temperature will rise and various effects will occur. In general, most nonsporulating bacteria, including anaerobes, are readily deactivated at temperatures of 50 degrees C. The inflammatory soft tissue present in periodontal disease can be removed with a temperature of 60 degrees C; moreover, hemostasis can also be achieved within the same heat parameters. Laser excisional or incisional surgery is accomplished at 100 degrees C, where vaporization of intra- and extracellular water causes ablation, or removal of biological tissue. At this temperature, the aqueous component of tooth structure and bone also boils; thus cavity preparation, calculus removal, and osseous contouring can proceed.
There are significant differences in the depth of penetration of the laser beam. Diode and Nd:YAG energy can penetrate a few millimeters into the tissue and carbon dioxide’s radiation will travel about 0.5 millimeters; however, the erbium wavelengths are absorbed on the surface of the tissue with a depth as little as 5 microns.
There are two basic emission modes for dental lasers - continuous-wave and free-running pulsed. Continuous-wave means that energy is emitted constantly for as long as the laser is activated. Carbon dioxide and diode lasers operate in this manner. A gated pulsed laser is a variation of continuous-wave and is accomplished with an electronically controlled mechanical shutter. This “gating” helps to minimize some of the undesirable residual thermal damage associated with continuous-wave devices. Free-running pulse mode is produced by a flash lamp, where true pulses - on the order of a few ten-thousandths of a second - emanate from the instrument. Nd:YAG, Er:YAG, as well as Er,Cr:YSGG devices operate as free-running pulsed lasers.
Flexible, small-diameter glass fibers are used to deliver diode and Nd:YAG laser energy. These bare fibers are usually used in contact with the tissue. Erbium and carbon dioxide devices use a more rigid glass fiber, semiflexible hollow wave-guides, or rigid sectional articulated arms to deliver the laser energy to the surgical site. Some of these systems employ additional small quartz or sapphire tips, which attach to the operating handpiece, and other systems are used without contacting the tissue. In addition, the erbium family of dental lasers uses a water spray for hard-tissue procedures; the water is typically switched off for soft-tissue surgery.
Advantages and limitations of lasers
One of the main benefits for using dental lasers is the ability to precisely interact with and, in some cases, remove a few cell layers at a time. Erbium lasers can have some selectivity in removing diseased tooth structure because carious lesions have a much higher water content than healthy tissue. Studies have shown other advantages over conventional high-speed handpiece interaction on the tooth surface, such as the elimination of micro-fractures and a reported lowering of pulpal temperature as the preparation proceeds. Osseous tissue removal and contouring can also proceed easily with reported faster healing. Moreover, it has been demonstrated that the lased enamel has a good potential for bonded restorations as long as they are subsequently etched with acid.
Lasers also allow the clinician to reduce the amount of bacteria and other pathogens in the surgical field and in the cavity preparation and, in the case of soft-tissue procedures, achieve very good hemostasis with a reduced need for sutures and surgical packing. Several manuscripts point out that postoperative scar formation is minimized: since the laser incision is more broad and irregular than that of a scalpel, the healing tissue better blends with the surrounding structures. Periodontally diseased tissue can be disinfected and detoxified. Lasers can be successfully and safely used on a wide range of the population, such as children and pregnant women, unlike some prescribed and/or sulcularly delivered drugs. Unlike with those medications, the patient will not experience allergic reactions, bacterial resistance, or untoward side effects when the laser is used.
With good control of bleeding, visualization of the surgical field is greatly improved, and many laser procedures can be performed with less injectable anesthesia. In those situations, additional treatment may be performed in the same appointment. Furthermore, initial postoperative discomfort and swelling are reduced because of the sealing of nerves and lymphatics.
There are some disadvantages to the current dental lasers, which only emit energy from the tip of the delivery system. In that sense, they are all “end cutting,” which usually means a modification of the practitioner’s clinical technique. Although they are useful for caries removal and tooth preparation, the erbium family of lasers is unable to remove gold and vitreous porcelain, and has only a small interaction with amalgam. Of course, that fact is also an advantage when treating a recurrent carious lesion adjacent to a veneer or crown, for example, since there will be no interaction with the restorative material. However, most composite restorations can be ablated.
In some cases, the delivery system can be more cumbersome than an air rotor or electric handpiece, and accessibility to the treatment area could be limited. The clinician must carefully observe and monitor the rate of tissue removal to prevent overheating and lateral thermal damage. For enamel removal, the laser is not as fast as a rotary bur, although it can be more conservative by not removing as much healthy tooth structure. The initial investment for some devices must be considered, as well as required supplies and maintenance. The instruments range in size from a paperback novel to a large dental cart, so space can become a factor. All units operate at line voltage and the erbium lasers require an additional compressed air supply.
Training and continuing education are essential, and most manufacturers provide good support. The Academy of Laser Dentistry (ALD) offers a Standard Proficiency Course that educates the practitioner at a reasonable beginning competency. Several journals and a few textbooks are readily available for descriptions of clinical procedures and research.
The return on investment for a laser instrument could be analyzed in four ways -
1) Several procedures will be made easier and simpler. Disinfecting an aphthous or herpetic ulcer will not only relieve the patient’s discomfort, it will prevent the rescheduling of the appointment because of the presence of the lesion. Tissue retraction for subgingival crown or implant restorations can be performed quickly with excellent hemostasis, ensuring an accurate impression. Laser clinicians report an average savings of 10 minutes of appointment time as well as the elimination of a majority of cords and medicaments. Soft-tissue surgeries are much easier to manage with excellent control of bleeding, and redundant or excessive gingival tissue around carious lesions can easily be contoured for access to the preparation, as well as improvement of the physiologic contour.
2) Procedures that were formerly referred can be treated in the practice according to the clinician’s experience, training, and confidence. Removal of fibrous tissue or commonly occurring fibromas is straightforward; suspicious lesions can be easily biopsied and analyzed for pathology. Revising frenum attachments to prevent or correct periodontal defects are also simply performed with laser energy; a mandibular lingual “tongue tie” procedure offers almost instant correction for a patient with speech or other oral difficulties. Tissue contouring during orthodontic treatment can prevent more serious disease if left untreated, and epuli and other ridge abnormalities of removable prosthodontic patients can be eliminated. An operculectomy can proceed with no damage to the erupting tooth.
3) A laser may provide the clinician opportunities to provide new treatments previously not available. Esthetic crown lengthening involving both gingival and osseous tissue removal can be done with precision and predictability. Preparing ovate pontic sites can result in more natural-looking fixed prosthodontic treatment, and uncovering a tooth for bonding of an orthodontic bracket could expedite treatment time.
4) In some cases, multiple procedures can be accomplished during the same appointment because of time saved in bleeding control or by reducing the use of injectable anesthetics. For example, recontouring the gingival tissue during restoration of cervical carious lesions, or treating additional carious lesions in another quadrant, can increase the efficiency and profitability of the operatory time and provide better patient care.
The attitude and involvement of the office team are critical to successful integration of a dental laser into the practice. The clinician should make educational opportunities available to all personnel and, clearly, they should experience laser procedures on themselves so their personal testimonies can be credible and enthusiastic.
Patients expect a fair fee for dental care, although a major equipment purchase usually necessitates an upward adjustment in the fee schedule. The majority of laser clinicians simply increase their overall charges incrementally; only a few practitioners add a surcharge.
Marketing for the dental laser should be straightforward. Many dental patients are aware of the use of lasers for other health-care needs, and some may have even received treatment with these devices. These same patients will appreciate the dental office’s desire to provide new technology, which in turn will increase the number of referral patients who also want modern treatment.
Laser use in dentistry has expanded and improved some treatment options for clinicians who have adopted the technology. As with all dental materials and instruments, the practitioner must use clinical experience, receive proper training, become very familiar with the operating manual, and proceed within the scope of his or her practice. The potential purchaser should carefully analyze the style and type of the practice to decide how useful the device would be. Moreover, attending introductory courses, seminars, and presentations, such as those offered at the Academy of Laser Dentistry’s Annual Conference, or at various State and National Scientific Sessions, are essential before buying.
Because of the varied composition of human tissue and the differing ways that laser energy is absorbed, there is no one perfect laser. However, all of our patients continue to agree that the dental laser is a wonderful instrument.
Donald J Coluzzi, DDS, is a 1970 graduate of the University of Southern California School of Dentistry. He recently retired after 35 years of general dental practice in Redwood City, Calif. He is an associate professor at the University of California San Francisco School of Dentistry Department of Preventive and Restorative Dental Sciences. He is past president of the Academy of Laser Dentistry and holds Advanced Proficiency certificates on Nd:YAG and Er:YAG wavelengths. He may be reached at email@example.com.
Disclosure: Dr. Coluzzi is a lecturer for HOYA ConBio. He receives honoraria for those services.