Lasers in Dentistry : Part 2

by Food and Drug Administration (FDA)

(Page 2 of 2)

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."

Some Current Dental Laser Procedures

Replacing conventional soft tissue dental surgery with lasers often eliminates the need for sutures and anesthesia. Today lasers can:

• 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.
• 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.
• 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.
• Remove excess tissue under the tongue in less than two minutes, in a procedure called frenectomy.
• 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.
• Remove soft tissue in the mouth to even out wrinkles that form when a person smiles.
• Hasten clotting of bleeding caused by other procedures.

About the Author

www.fda.gov
FDA is A United States government body that oversees medical devices, including contact lenses, intraocular lenses, excimer lasers and eyedrops. In the US, these products must be approved by the FDA before they can be marketed.