Lasers in Dentistry

by Food and Drug Administration (FDA)

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.

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.