Laser Dentistry - Fresno, CA

Lasers are now part of our lives in many ways. They are in our computer printers and compact disc players, they record prices at the supermarket check-out, they light up rock concerts, and they guide weapons and measure distances between planets. Lasers have also revolutionized many surgical procedures, minimizing bleeding, swelling, scarring, and pain. And now they're beginning to blaze a new trail in dentistry. The potential benefits of laser use in dentistry include procedures done on soft tissues of the mouth. Because laser techniques cause less pain than traditional methods, they are also likely to reduce the fear that many people have of the dentist. At the very least, lasers in some dental applications would eliminate the noise of the instruments that to some patients are nearly as disturbing as the physical discomfort. However, it may be quite a while before you can have your cavities drilled or root canals cleaned with a painless flash of a laser. "FDA has cleared for marketing certain lasers for soft tissue use, such as gingivectomies [removing excess gum tissue], but not for hard tissues," says Gregory Singleton, D.D.S., senior dental officer in the Center for Devices and Radiological Health at FDA. The hard tissues include tooth and root, while soft tissues of the mouth refer to the gums, the ligaments and fibers that bind tooth to socket, and the tissue supporting the tongue. So far, lasers seem to be living up to their promise in the latter area. "For soft tissue surgery, lots of patients report less postoperative pain. There are sealed off nerve endings, so recovery is less painful," says Marilyn Miller, D.M.D., co-director of the Princeton Dental Resource Center in Princeton, N.J. But she adds that healing may be slightly slower, because the laser also seals off blood vessels, which would bring in clotting factors to help heal cut tissues. Laser Basics Since the mid-1960s, lasers have proven to be powerful surgical tools. The word "laser" is an acronym for "light amplification by stimulated emission of radiation," which means that the intense and narrow beam of light is of one wavelength. Ordinary "white" sunlight, in contrast, is a continuum of light of many wavelengths, corresponding to the colors of the visible spectrum plus the infrared (heat) and ultraviolet wavelengths that sandwich them. Sunlight passing through a prism separates into its component colors; a laser light remains a single color. A medical laser device includes a source of electricity, mirrors to direct the beam, a crystal or gas that is stimulated to emit the light, and tubing to deliver the light energy. The nature of the material through which the light passes determines the specific properties of the laser--and therefore what it can do in the human body. Instrument design is tailored to specific uses. Many dental lasers, for example, include long narrow tubing so that the dentist can use it in the narrow confines of a person's mouth. Types of Dental Lasers FDA has cleared four types of lasers for dental use: carbon dioxide, Nd:YAG, argon, and holmium:YAG. A carbon dioxide (CO2) laser uses CO2 gas. Watery tissue absorbs this type of laser energy, which doesn't penetrate very deeply, but vaporizes surface cells. A CO2 laser leaves a residue of carbon, called char. If a dentist leaves char in place, it serves as a biological dressing, maintaining sterility. Because the beam from a CO2 laser is invisible, a second laser beam, based on the elements helium and neon, adds a red beam, so the dentist can see the laser energy. A CO2 laser is used in gingivectomies, biopsies, and removal of benign and malignant lesions (see accompanying article). A CO2 laser is particularly good for a frenectomy. "The frenum--the tissue under the tongue--is tight in some people, and it can be quickly loosened up with laser treatment," says Michael Yessik, president of Incisive Technologies, a laser manufacturer in San Carlos, Calif. For lesions extending into tissue deeper than the 0.1 millimeter that the CO2 laser penetrates, a neodymium:yttrium- aluminum-garnet (commonly called an Nd:YAG) laser is appropriate. As with the CO2 laser, an accompanying red beam makes the energy visible. A jet of cool water or air limits possible heat damage that can result when a super-heated gas, called a plasma, forms on the tissue surface as it is being treated. An Nd:YAG laser can harm thin tissue, such as the gum in the lower front of the mouth. The CO2 and Nd:YAG lasers are used in some of the same procedures that remove soft tissue. The argon laser is based on gas of the element argon, and emits a bluish-green light. It is cleared for marketing for a different application--curing composite resins. These tooth-colored materials are used in reconstructing chipped teeth, filling cavities in visible areas of the mouth, or sealing teeth to protect them from decay. The dentist paints on the composite, and then focuses a narrow beam of light to harden, or cure, it. The intense light alters the physical properties of the composite, linking its small molecules into longer ones, which adds great strength. Robert Pick, D.D.S., clinical associate professor at Northwestern University Dental School, writes that he thinks the argon laser will soon become the standard method for curing dental composite resins, replacing ultraviolet light. Another device used on soft tissues is the holmium:YAG laser. Oral and maxillofacial surgeons have used it experimentally to surgically remove the damaged disc separating the condyle of the mandible from the base of the skull. The disc can be damaged due to trauma or chronic inflammatory diseases such as osteoarthritis that can cause symptoms commonly known as temporomandibular joint (TMJ) syndrome. (An oral and maxillofacial surgeon is a dentist specializing in correcting abnormalities of the jaws and face with surgical procedures.) TMJ syndrome can cause facial pain, headaches, pain in front of the ear, noise when the jaw opens, ear congestion, dizziness, ringing in the ears, difficulty swallowing, nervousness, insomnia, difficulty chewing, sensitive teeth, numb fingertips, and backache. Choosing the Best Laser The challenge to dentists is finding the best laser type and strength for a particular application. Lasers can vary in chemical basis (CO2, Nd:YAG, argon, holmium:YAG, and others), wavelength of emitted light, power, whether it is applied continuously or in short pulses, and whether the laser is applied directly (a contact laser) or through a tip of some sort (non-contact). The effect of a particular laser must be evaluated for each type of dental tissue--such as enamel, dentin, pulp, bone, and gingiva. Light can have one of four fates when it hits a tissue--it may be absorbed, reflected, scattered within the tissue, or transmitted. This is important, because light energy that is transmitted or scattered may harm surrounding tissue. Reflected laser light dissipates so quickly that it does no damage. Whether or not anesthesia is needed for soft tissue dental laser procedures depends on the duration of the treatment and the amount of tissue removed. CO2 laser procedures may require local anesthesia, but Nd:YAG treatment usually does not. "About 70 to 80 percent of procedures using dental lasers are done without anesthesia. It depends on the power level needed to perform the procedure," says Yessik. Safety Measures Several precautions to dental staff and patient must accompany laser use. Everyone in the room must wear protective glasses--dark green tinted for argon and YAG lasers, and clear for CO lasers. Wet gauze pads are placed in the patient's mouth surrounding the treated area. Reflective surfaces, such as instruments and mirrors, are covered so that stray light beams cannot ricochet around the room. It is very important that all anesthetic gases be removed from the room. They are explosive, and could be ignited by a laser beam. The dentist must also suction off vaporized soft tissue, and the smoke, or laser "plume," emitted during procedures. The plume can carry viruses. This is one reason that some dentists do not like to use a laser to remove herpes lesions in the mouth. Treatment with a CO2 laser provides rapid pain relief and speeds healing. Zapping Away Cavities--Not Yet If you dream of having a cavity treated with a painless, soundless zap of a laser, you will have to wait awhile. Although lasers have great potential for one day replacing the drill, there is still too much danger of their damaging the pulp under the enamel, according to Gerard Kugel, D.M.D., assistant clinical professor of restorative dentistry at Tufts University School of Dental Medicine in Boston. The problem is the amount of heat generated in hard tissue treatment. "It may take a different intensity or type of laser energy to remove debris from soft tissue than to remove the hard calculus or plaque from a tooth's root," says Dennis Mangan, Ph.D., director of the Periodontal Research Program at the National Institute of Dental Research in Bethesda, Md. (A periodontist specializes in diseases of the gums and supporting structures of the teeth.) Also, a laser could not produce the uneven edges carved intentionally with a drill so that dental amalgam or other filling materials can be retained properly. Lasers could not be used to repair existing fillings either, because they would vaporize the amalgam component mercury, which would make it highly toxic. But dental researchers are actively investigating the safety and efficacy of lasers for hard tissue applications on freshly extracted human teeth and in animal and human trials. Researchers at the University of California at San Francisco School of Dentistry carried out one human study using a pulsed Nd:YAG laser at relatively low power. They used the laser on 163 cavities in 97 people at three private dental clinics in 1987 and 1988. At follow-up three years later that included 35 participants, the areas where the laser had removed decay had all remineralized well, with no complications. Still, much more study is needed before the dentist's drill becomes a thing of the past. "The FDA feels there is not enough support for use of lasers on hard tissues, and dental organizations, such as the American Dental Association, do not support non-FDA-approved laser procedures," says Miller. A Look Ahead Despite the slow evolution of lasers in dentistry, researchers say the day will indeed come when a variety of lasers play a more prominent role in maintaining a healthy mouth. "And it won't be just one laser that will do all dental procedures. Researchers envision a laser unit in which you can switch on or off different types of lasers depending upon the procedure," says Miller. "It's an exciting technology, and patients are really intrigued at the idea of a laser. The lay press exaggerated, saying now we can throw away dentists' drills. But research is showing that we will be able to do that--eventually,fl she says. flBut we haven't yet found the right laser." Ricki Lewis is a freelance science writer in Scotia, N.Y., and author of college biology texts. Some Current Dental Laser Procedures Replacing conventional soft tissue dental surgery with lasers often eliminates the need for sutures and anesthesia. Today lasers can: fl Remove excess gum tissue, which can develop as a side effect of taking certain drugs, poor oral hygiene, or orthodontia, in a procedure called gingivectomy. fl Expose dental implants, replacement tooth roots made of steel or titanium surgically embedded in the jawbone, which can become covered with too much soft tissue. A CO2 laser can quickly expose the implant for the dentist to work on. fl Relieve the pain of aphthous ulcers, mouth sores. Both CO2 and Nd:YAG lasers can relieve the pain instantly--used on low power, without an anesthetic. fl Remove excess tissue under the tongue in less than two minutes, in a procedure called frenectomy. fl Biopsy or sample tissue from a lesion to see whether it is cancerous. A laser biopsy does not require suturing and heals well. This is particularly useful on the tongue, where bleeding can be profuse. fl Remove soft tissue in the mouth to even out wrinkles that form when a person smiles. fl Hasten clotting of bleeding caused by other procedures.