LASERS

ID IN it possible to think about laser beams without remembering Sean Connery as James Bond being threatened with one in the film “Goldfinger”? That was fiction, of course. The laser today has been harnessed for prac­ tical use in a wide range of industries, dentistry among them. Its clinical application, many predict, will revolutionize dental care as increasing num­ bers of dentists adopt this emerging technology. Light, commonly found in nature, is composed of various electromag­ netic fields traveling in disoriented fashion and is known as incoherent

THEIR

T E R R Y D. M YER S, D.D.S.

APPLICATION

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CLINICAL.

PRACTICE

light. Laser light is emitted at a specific wavelength of energy and travels in a predictable pattern. This quality, known as coherence, is responsible for most of the laser’s unique characteristics. The laser’s energy is produced within what is called the laser cavity, which consists of three basic components. First is the active medium - the source of the laser’s energy —which can be a solid, liquid or gas. The active medium determines the specific wavelength of energy at which the laser operates. The second component is an incident energy source used to stimu­ late the atoms of the active medium. The third component is the optical res­ onator, which redirects the escaping incoherent photons of the active medium, producing a very bright, directional, monochromatic, coherent form of light—two highly polished, concave mirrors placed at either end of the laser cavity. When the concentrated energy of lasers is absorbed by tis­ sue, a rapid thermal effect results in vaporization and carbonization of that tissue. After several years of clinical use, the surgical benefits of the carbon dioxide (C02) laser are well documented.15Most notably, the C02laser min­ imizes cellular destruction compared with knives and electrosurgery. The laser can also coagulate blood vessels smaller than 0.5 millimeters in diam­ eter to create a fairly dry, bloodfrcc operating site. This has two clinical advantages: the dentist can better observe the surgical site and the risk of bloodborne contamination is dramatically reduced.

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Postoperative wound infection is also minimized because of the laser’s thermal antiseptic effect, as is postoperative pain. The C02lasers operate in the 10.6- micron range, having power outputs up to 20 or 25 watts. Since that wavelength cannot be deliv­ ered through an optic fiber, C02 lasers require some form of articu­ lated arm for a delivery system. The energy is usually directed to the target tissue by hollow wave guides (of either metal or oxides). The operator must not accidentally lase tooth or bone structure. Several months ago, the Food and Drug Administration allowed the introduction of the first laser specifically designed for dentistry by granting permission to market a pulsed neodymium:yttrium-aluminum-garnet (Nd:YAG) laser ( American Dental Laser, manufac­ tured by Sunrise Technologies of Fremont, Calif, for American Dental Laser, Birmingham, Mich.). This instrument emits its pulsed energy at 1.064 microns and its energy is directed through a 320micron silica fiber. Because of its low power output (maximum 3 watts average), the laser is not used for massive tissue removal. The Nd:YAG shares many advantages of the C02 laser, but it is unique in that many clinical proce­ dures can be performed without local anesthesia. The pulsed Nd:YAG laser’s hemo­ static capabilities have been docu­ mented, 6and the instrument is currently used clinically to per­ form gingivoplasties, frenectomies, gingivectomies, and operculectomies. The Nd:YAG laser is also used to remove fibromas, drain abscesses, and perform various types of biopsies. The laser is in the second stage of implant recovery. For crown and bridge soft tissue procedures, the laser can replace the retraction cord, providing a

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T h e laser routinely reduces pocket depth through laser curettage. In this procedure, the optic fiber of the pulsed N d :YA G laser’s contact handpiece is inserted unto the full depth of the periodontal pocket.

high degree of hemostasis that per­ mits improved visualization of pre­ pared margins and improved final impressions. The laser also pro­ vides a fairly dry, bloodless field in crown lengthening procedures. The Nd:YAG laser can remove subgingival mineral deposits when used in conjunction with conven­ tional treatment methods.™ Of greater clinical significance, the laser can routinely reduce pocket depth—a minimum of two up to four millimeters—by a procedure termed laser curettage. Generally a good candidate for this procedure would have periodontal pockets of three to seven millimeters. The 320-micron fiber is inserted to the depth of the pocket and the area is lased in a crisscross manner while the fiber is slowly withdrawn from the pocket. The fiber follows the root contours in a parallel fash­ ion, toward the diseased epithelial lining, causing vaporization. This noninvasive treatment usually causes little or no discomfort to the unanesthetized patient. Home care motivation is high because in-office treatment is painless and produces very little or no post-treatment dis­ comfort. For those patients who suffer from aphthous ulcers, the Nd:YAG

laser has a dramatic effect: soon after passage of the contact fiber over the entire surface of the lesion, patients report that pain is stopped. Using the pulsed Nd:YAG laser for soft tissue cutting procedures requires power outputs between two to three watts with the pulses set between 20 to 30 hertz. Using these settings would deliver, per pulse, 100 to 150 millijoules of energy with each pulse having a length in the microsecond range. Despite the laser’s ability to per­ form many procedures without anesthesia, the instrument is not a magic wand. The laser uses ther­ mal energy to vaporize tissue. If the patient complains of sensitivity dur­ ing any procedure, then anesthesia should be administered. The Nd:YAG dental laser is also used for various hard tissue proce­ dures. For the removal of tooth decay, the laser permits a very con­ servative treatment because the neodymium wavelength (1.06 microns) is not absorbed by enamel. For sealant procedures, the laser can remove the organic and inorganic debris found in pit and fissures without injuring the surrounding healthy enamel. For undermined caries or for caries removal involving preparation for a final restoration, the dentist needs to use the air rotor in conjunction with the laser. Each pulse of the laser vaporizes 40 to 60 microns of decayed tooth sub­ stance. The laser also vaporizes sound dentin and cementum, to aid preparation. Various temperature and pulpal studies have shown the laser’s safety for caries removal, and when used according to the protocol, no adverse reactions have been noted in vivo. In a procedure directly related to caries removal, general practi­ tioners as well as pediatric dentists reported a high rate of success in laser analgesia for young patients.

The effect is temporary, lasting from ten minutes to more than an hour. The technique can also be applied to permanent dentition, but the success rate decreases from anterior to posterior teeth. The den­ tists report only 30 percent to 40 percent success rate for molars with old, large restorations. The technique is simple; it requires two to four minutes of lasing the tooth after which the air rotor can be applied to the tooth for various restorative procedures, including crown preparations, with minimal or no discomfort to the patient. The mechanism involved with laser analgesia is not well understood but may be associated with changing the permeability of the nerve cell membrane or interfering with the sodium pump mechanism. In another hard tissue applica­ tion, the laser can be used to etch enamel in lieu of phosphoric acid.9 Preliminary shearing strengths and clinical observations indicate the laser etch is comparable to phos­ phoric acid etch. The neodymium wavelength is induced to absorb into enamel by the placement of an initiator (a dark organic substance) on the area of enamel in which etching is desired. Clinically, the dentists report a 50 percent savings in time in laser etching, compared with phosphoric acid etching. The need to protect gingival and den­ tinal tissue can be eliminated with While the laser is reducing pocket depth, the energy from the laser kills bacteria as the optic fiber is passed over the root surface.

laser etching. With the power set­ tings used during laser etching, accidental contact with soft tissue causes no vaporization or damage. Lasing of exposed dentin causes closure of tubules; research indi­ cates that lased dentin is actually harder than nonlased dentin. The effects produced by lasing exposed dentin allow successful treatment of patients suffering from dentinal hypersensitivity. The procedure is quick and simple and, usually, totally or dramatically reduces the sensitivity in one treat­ ment, though sometimes a second appointment is required about two weeks after the initial lasing. No clinical change can be noted macroscopically on the lased dentin, but scanning electron micrographs demonstrate that the Nd:YAG den­ tal laser closes dentinal tubules.10 Research also indicates a change in hydraulic conductance (the rate of fluid flow through dentinal tubules) and a morphological change in the odontoblasts occurs with this treatment. Clinically, doc­ tors report that patients have remained asymptomatic for up to two years after a single treatment, although because of the abuse exposed dentin receives, it is unlikely that the patients would remain asymptomatic forever; at some future date, they would require additional laser treatments. Dentists are also lasing restora­ tive and crown and bridge prepara­ tions just before insertion or final cementation and report a dramatic decrease in postinsertion or postcementum sensitivity in these cases. Periodontists and general practitioners alike are lasing newly exposed root surfaces immediately after periodontal surgical tech­ niques and are also reporting a sig­ nificant reduction in dentinal sensitivity. In the long term, peri­ odontal patients may be more apt to follow their home hygiene program

and thus maximize the results of the initial surgery. The number of dentists clinically using the Nd:YAG dental laser grows each month and new clinical applications are shared through the international study clubs which have been meeting quarterly. It is now known that the laser can effecGenerally the periodontal pocket becom es asymptom atic within 4 8 hours of the laser curettage. Patients report minimal o r no discom fort and anesthesia is not normally required. Little or no bleeding occurs.

tively and almost immediately take away the severe sensitivity associ­ ated with aphthous ulcers. A simple technique for bleaching both vital and nonvital teeth has been devel­ oped in North America. Dentists, particularly German practitioners, have found the laser beneficial as an adjunct to standard endodontic therapy. Still another clinical find­ ing involves using the laser in con­ junction with scalpel surgery: by lasing the cut wound surfaces, postsurgical pain is reduced signifi­ cantly to the degree that patients do not require prescribed anal­ gesics. Laser procedures offer highquality, state-of-the-art dentistry because of new treatment modali­ ties and enhancements to tradi­ tional treatments, with reduced need of anesthesia during treat­ ment and a great reduction or lack of post-treatment pain. Laser den­ tistry may also be able to attract much of the nearly 50 percent of the U.S. population who do not reg-

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ularly visit dentists. As laser technology is adopted by more and more clinicians, dentists can evaluate patients to integrate the laser into their treatment plans. Through such commitments, for­ mer techniques can be replaced with innovative approaches. Dr. Myers is Director of the Institute for Laser Dentistry, and in private general practice, 1935N. Pontiac Trail, Walled Lake, Mich. 48088. Address requestsfor reprints to the author. 1. Tiffin JR, Carruth JAS. The carbon dioxide surgical laser. Br Dent J 1980;149:255-8. 2. Frame JW. Removal of oral soft tissue pathology with the C02 laser. J Oral Maxillofac Surg 1985;43:850-5.

3. Pick RM, Pecaro BC, Silberman CJ. The laser gingivectomy: the use of the C02 laser for the removal of phenytoin hyperplasia. J Periodon ol 1985;56:492-6. 4. Chiesa F, Sala L, Costa L, et al. Excision of oral leuko­ plakias by C02 laser on an out-patient basis: A useful proce­ dure for prevention and early detection of oral carcinomas. Timor 1986;72:307-12. 5. Pick RM, Pecaro BC. Use of the C02 laser in soft tissue dental surgery. Laser Surg Med 1987;7:207-13. 6. Myers TD, Myers WD, Stone RM. First soft tissue study utilizing a pulsed Nd:YAG dental laser. Northwest Dent 1989;68:14-17. 7. Myers TD, Myers WD. In vivo caries removal utilizing the YAG laser. Mich Dent Assoc J 1985;67:66-9. 8. Myers TD, Myers WD. The use of a laser for debride­ ment of incipient caries. J Prosthet Dent 1985;53:776-9. 9. Myers TD, Riddle JM. Comparative morphological effects of enamel etching with phosphoric acid and a pulsed Nd:YAG laser. Abstract delivered at the International Society of Laser Dentistry Second World Congress, Paris, May 28-31,1990. 10. White JM, Goodis HE, Rose CM. Effect of Nd:YAG laser treatments on hydraulic conductance of dentin (Abstract 481). J Dent Res 1990;69:169.

HOW SOME USE THE LASER ichard Mungo of the division of pediatric dentistry at Children’s Hospital of Los Angeles has used the C02 laser for several years to treat a variety of clinical cases. Robert Pick of Northwestern University —who has lectured throughout the United States and is considered an expert in dental laser surgical techniques —rou-

Respondents reported that they used the laser in desensitizing teeth 78.6 percent of the time, very similar to the laser curettage results. tinely uses the C02 laser for inci­ sional and excisional biopsies, removal of gingival hyperplasias and lesions including papillomas, fibromas, pyogenic granulomas, nicotinic stomatitis, heman­ giomas, and erythroplakias. In recent study club meetings of dentists using the pulsed Nd:YAG laser in North America (July 1990, San Francisco) and western Europe (September

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1990, Herne, West Germany), clinicians were asked for what percentage of curettage applica­ tions they used the laser. The 31 respondents indicated that they used the laser in performing curettage 79.0 percent of the time, with comments including, “Patient acceptance is excellent,” “Excellent results with little or no postoperative problems," “Using the laser is the only way to do curettage,” and “Very impressive results.” Actual expe­ rience ranged from one to 20 months of clinical use. Practitioners using the pulsed Nd:YAG laser in North America and western Europe were asked for what percentage of their desensitization applications the laser was used. Respondents reported that they used the laser in desensitizing teeth 78.6 per­ cent of the time, very similar to the laser curettage results. Comments included “The laser is the best way to desensitize teeth,” “Excellent results so far,” “I have had good success,” and “Patients are extremely appre­ ciative.”

Lasers in dentistry.

LASERS ID IN it possible to think about laser beams without remembering Sean Connery as James Bond being threatened with one in the film “Goldfinger”...
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