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Esthetics and laser surgery
21 Esthetics and Laser Surgery Robert A. Strauss and Kenneth S. Magid
The use of lasers in dentistry has burgeoned at an astonishing rate over the past few years. Once relegated to use on soft tissue, now even hard tissue esthetic surgery can be done with lasers. Because of their many advantages, lasers are indicated for a wide variety of intraoral and extraoral esthetic procedures. To use them safely and successfully, however, a thorough understanding of their indications, contraindications, and safety parameters is imperative.
HISTORY The word laser is an acronym for light amplification by stimulated emission of radiation. The theory has its roots in several basic principles of physics first described by Einstein in 1917.1 Amazingly it was almost another 50 years before these principles were sufficiently understood and the technology could be converted into practical reality. The first laser to use visible light was developed by a physicist, Dr. Theodore Maiman, in 1960. Maiman used a ruby gemstone as the lasing medium, producing the red beam of intense light typically associated with lasers.2 This was followed in 1961 by another crystal laser using a neodymium-doped crystal of yttrium, aluminum, and garnet (Nd:YAG). In 1964, physicists at Bell Laboratories produced a gaseous laser using carbon dioxide (CO2) as the lasing medium. That same year another gaseous laser that would prove important in dentistry, the argon laser, was invented. Dental scientists investigating the effects of Maiman’s ruby laser on the enamel of teeth found that it caused cracking and fissuring of enamel.3,4 The studies concluded that lasers had no place in dentistry, and few other studies were undertaken. In medicine, however, research and clinical use of lasers proliferated. In 1968, the CO2 laser was used for the first time to perform soft tissue surgery. An increasing variety of laser wavelengths, as well as general and oral surgical indications, evolved. In the mid-1980s, the expanded availability of different wavelengths and the improved understanding of laser physics and tissue interaction created a resurgence of interest in the use of lasers in dentistry for hard tissues such as enamel.5-8 446
Although a few wavelengths, such as that of the Nd:YAG laser, can be artificially manipulated for hard tissue use, their danger potential and lack of specificity for dental tissues make them less than ideal. Other lasers, such as the excited dimer (excimer) laser, which was studied extensively in the late 1980s and early1990s, were shown to cause little damage to teeth. However, they were plagued by problems of cost, size, and efficiency.9 Not until 1997 did the US Food and Drug Administration (FDA) finally approve a well-known laser, the Erbium:YAG (Er:YAG) laser and later the Er, Cr:YSGG laser (henceforth collectively referred to as “erbium” because of their similarities), for hard tissue use.10,11
BASIC CONCEPTS Laser energy is unique in that laser light is coherent. This means that laser light has three distinct properties that distinguish it from regular light. Ideal laser light is monochromatic (composed of a single wavelength of light), collimated (the light waves run parallel to each other instead of diverging), and uniphasic (the peaks and valleys of the waves are synchronous (Fig. 21-1).
Monochromatic Property Because lasers are monochromatic, each has a single frequency and wavelength and therefore a single “color.” Thus, lasers often are defined by their visible color (e.g., red light or green light lasers), their position in the electromagnetic spectrum (e.g., infrared, ultraviolet or radiograph lasers), or the chemicals that create the light (e.g., CO2, argon, or Nd: YAG lasers).
Collimated Property All laser beams are parallel, or collimated, unlike regular light. Because the laser beam does not diverge significantly over distance, the source can be positioned at great length from the target tissue or can be very efficiently focused down to a small spot with a convex focusing lens.
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Danger LASER Monochromatic Danger LASER
Danger LASER Collimated
A
Danger LASER
Danger LASER
B
Uniphasic
F I G U R E 2 1 - 1 A, Regular light showing the different wavelengths present and the random
spread of the beam. Laser demonstrating uniform, coherent light. B, Laser light showing monochromatic wavelength, collimation, and uniformity of phase, which constitute coherent light.
Uniphasic Property The peaks and troughs of a laser light wave are directly in line (synchronous) with one another, making them uniphasic. All the peaks and troughs of the energy beam are stacked on top of each other.
Intensity Property Collimation, monochromaticity, and uniphasicity together produce a very intense and powerful flash or beam of light. The ability to efficiently focus the beam down to a small spot size (an effect of the collimation on a convex lens) produces an extremely powerful, condensed energy source. Laser beams may reflect off, transmit through, scatter (break up) within, or be absorbed by organic target tissue. The first three conditions elicit no effect within the tissue, but when absorbed, a laser beam may produce several different results. The most important is the photothermal effect, or tremendous heat generation that occurs almost instantaneously within the tissue. In soft tissue, this causes the intracellular water to boil or vaporize and literally explodes and disintegrates the cell. In hard tissues, similar effects may be seen in hydroxyapatite. Unlike other heat sources, however, the laser can be applied with incredible precision and with such speed that only microns of tissue can be removed at a time with very controlled and minimal damage to adjacent tissues and structures. Conversely it sometimes is advantageous to have a lateral heat effect in tissue that results in thermal coagulation of adjacent blood vessels and a bloodless field. Lasers can be controlled to provide this as well. The many lasers now available for medical and dental use differ in several aspects. The primary difference is the active medium (i.e., the material that undergoes stimulated emission). The specific material used determines the wavelength of energy produced and therefore the clinical indications. Few materials in nature can undergo this process because the material must be capable of sustaining population inversion, an unnatural condition in which most atoms are in a highly excited state. The ideal system uses fiberoptic delivery of the laser beam to the target tissue. These systems are flexible and precise, they allow for both contact and noncontact surgery, and they are capable of endoscopic delivery. Unfortunately, not all wavelengths (e.g., CO2) can be transmitted through the currently used quartz fiberoptic fibers. These other types of lasers use articulated
arm delivery in which a series of hollow metal tubes connected by mirrored flexible joints or “knuckles” allow the beam to be passed from the laser to the tissues. Although this is functional for superficial tissues, it is less than ideal for deeper tissues or areas of difficult access, such as the oral cavity. Some newer lasers use a hollow wave guide, a variation of the articulated arm. The hollow wave guide is a flexible metal tube internally lined with a mirrored surface or foil, which allows the beam to reflect down the guide to the tissues. Although not as flexible as a fiberoptic fiber and incapable of endoscopic delivery, this system has dramatically improved the dentist’s ability to provide convenient, precise delivery within the oral cavity. Some lasers produce a continuous beam of laser light as long as the machine is energized, whereas others can be pulsed. These very high power, short duration pulses of laser light minimize the time available for lateral tissue heating and damage.12 Other lasers can be electronically enhanced to produce extremely fast, high-powered laser bursts (“superpulsed” or “ultrapulsed”) for situations such as dermatologic skin surgery in which lateral thermal damage produces scarring. Selecting the appropriate laser for a given procedure usually is a simple matter of determining which laser wavelength is best absorbed by the target tissue while producing the least reflection, scatter, and transmission. Laser wavelengths that are absorbed by water (e.g., CO2, erbium) are appropriate for soft tissue surgery. Those well absorbed by hemoglobin are better suited for vascular tissues or lesions (e.g., argon, KTP: YAG, tunable dye, copper vapor lasers). Argon laser wavelengths are well absorbed by composite resin, and the erbium laser wavelength, which is absorbed by both hydroxyapatite and water, allows for hard tissue use. Some lasers with wavelengths that are absorbed by a number of different tissues (i.e., chromophores) may be useful for a variety of tissue effects. In addition, some transmission may actually be desirable in certain situations to allow deeper penetration of tissues (e.g., when deep hemostasis is desired in vascular lesions). To allow for precise tissue effects and clinical uses, some devices can produce more than one wavelength (i.e., CO2 and Er: YAG, KTP: YAG and Nd: YAG, and tunable dye), which allows the operator to select the desired tissue effect by varying the wavelength used. The choice of an appropriate wavelength involves a combination of known tissue effect and the operator’s clinical experience.13
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Currently the most commonly used laser in general dentistry is the diode laser. Used primarily for soft tissue incisional procedures, it has the advantage of being small, relatively inexpensive, and comparatively easy to use. However, its mechanism of action is widely misunderstood. Some lasers function by the direct effect of laser energy on soft tissue, whereas diode lasers used in dentistry do not have sufficient power to cut tissue.13 Therefore the laser tip needs to be activated (initiated) by touching the tip to a light absorbing material such as articulating paper, cork, or other dark substance, which produces a “charring” of the tip. The tip is now capable of absorbing laser light and when activated by the laser will heat up and vaporize the underlying tissue (Fig. 21-2).
Cutting speed 12.5 (mm/s)
6.0
3.0
1.0
0.0 (t 3 s)
General view
Histology
F I G U R E 2 1 - 3 Effects of cutting speed on collateral thermal
Laser Tip Consideration
damage.
Laser tip activation deposits carbon on the tip of the laser fiber, which becomes the target of the diode laser energy.
CLINICAL TIP Initiate the tip and a portion of the side of the laser fiber with light absorbing material.
ADVANTAGES AND DISADVANTAGES
CLINICAL TIP The light-absorbing material used for initiating the laser fiber is not consumed by the laser energy. However, with some lasers it may be wiped or broken off during use. In that situation it must be reinitiated. It is also the cause of more extensive collateral thermal damage as the power of the unconverted laser energy penetrates deeper into the tissues (Fig. 21-3).5 Because the diode laser functions by cutting with a hot tip, the specific wavelength of the diode laser is of less significance than in other lasers. The remaining parameters of power, time, and spot size are, however, still critical. Sufficient power is necessary to maintain the hot tip once it is in contact with the cooler tissue. If the tip cools beyond the temperature required to efficiently incise the tissue the resulting increase in contact time will
Fiber
300 m
Uninitiated non-contact
increase the collateral thermal damage as in other lasers. Spot size (or in the situation of diode laser, fiber size) is significant because the heat of the laser tip is concentrated in a smaller area that increases the heat energy per unit area.
Many laser wavelengths either are absorbed by hemoglobin or constrict vascular wall collagen, allowing for bloodless surgery.14 This allows the dentist to work in a clean, dry environment unobstructed by bleeding. When used correctly, lasers also can remove precise and minimal amounts of tissue with minimal effect on adjacent tissues. They are ideal for detailed, exact tissue manipulation.15 Lasers have an effect on neural tissue that generally results in less pain after surgery compared with other types of treatment.16 In fact, because of their great speed, some pulsed lasers may even be used for soft or hard tissue surgery without the need for anesthesia.17 Minimal postoperative pain and absence of bleeding usually precludes the need for suturing, tissue closure, or coverage with splints or dressings except when cosmetic requirements dictate otherwise. The elimination of lateral tissue damage is especially important in dentistry because of the proximity of such chemically diverse yet clinically vital structures as dental pulp, bone, tooth structure, and oral soft tissue. Lasers also make possible procedures such as perioral cosmetic skin resurfacing, in which even minimal adjacent dermal tissue damage would translate
Fiber
Fiber
300 m
Initiated non-contact
Initiated contact
FIG U R E 2 1 - 2 The experiment shows the inability of the diode laser to cut with either an un-
initiated or initiated tip in non-contact. Only an initiated tip in contact is capable of cutting tissue at power levels found in dental diode lasers.
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into inevitable and devastating scarring. Sealing of the lymphatic system during laser surgery and the minimal tissue trauma result in little or no postoperative edema in most patients.18 Finally because of the minimal tissue damage and the decrease in the number of myofibroblasts in laser-treated wounds compared with wounds made by scalpel or electrosurgical instruments, postoperative scarring and contracture are minimized, allowing dramatic surgery without the fear of significant postoperative cosmetic deformity or functional deficits.19 Disadvantages are few but important. The preeminent concern with lasers in dentistry is safety. Lasers require tremendous diligence to maintain a safe operative environment for both the patient and the dental team (see the section on Laser Safety later in this chapter). Other disadvantages include the generally high cost of purchasing and maintaining the laser, the loss of tactile sensation with noncontact lasers, the learning curve necessary to obtain uniform results, and the specificity of some laser wavelengths, necessitating the occasional need for more than one laser for a particular procedure. Finally although healing after laser surgery generally is excellent, usually much better than with other instruments such as a scalpel or electrosurgical instrument, it also generally is slower because of the vascular sealing.20
CLINICAL INDICATIONS Restorative and intraoral esthetic modification can be divided into soft tissue or combined soft and hard tissue.
CLINICAL TIP To determine which procedures are required, and therefore what types of lasers will be used, measurements and planning must be performed to determine if the changes will violate the biologic width of the teeth involved.
Soft tissue procedures include excision of excess tissue, either normal or pathologic, and recontouring of tissue. There are few soft tissue surgeries in which the laser cannot be used and used advantageously. Teeth or bone intimately involved with the target tissue or lesion must be protected from the laser beam, which increases the difficulty of the procedure, but with reasonable precaution and care, this usually is not a problem. For example, a standard mucoperiosteal flap around the dentition can be created with a laser, but it is more easily and safely accomplished with a scalpel. Once the incision has been made, the rest of the surgery may well be enhanced by the use of lasers. Despite the many different types of lasers available, the techniques for their use do not vary significantly. The three basic techniques are incision, vaporization, and hemostasis.12 The clinician should evaluate the lesion before surgery and determine which of these is most appropriate. Incision is accomplished by placing the laser at its focal length (i.e., the smallest possible spot size) near the tissue or touching the tissue if a contact tip laser is used. This increases the density of the power and condenses the effect into a small area. This laser-target distance varies according to the delivery system and ranges from contact with a contact laser to 0.5 mm for a hollow wave guide to more than 1 cm for an articulated arm laser (Fig. 21-4). Vaporization, also called ablation, allows the removal of large areas of very superficial tissue (e.g., removal of the surface mucosal epithelium) without affecting deeper structures. This is accomplished by defocusing or backing the laser away from the target to increase the spot size. Defocusing effectively lowers the density of the laser energy per unit area and causes the laser to act more superficially over a larger surface area. The target distance may vary dramatically depending on the type of delivery system, the available power, and the desired depth of penetration. Most lasers are intrinsically hemostatic to a degree, depending on the laser’s depth of penetration and whether hemoglobin
Articulated arm
Hollow wave guide
Defocused mode Focused mode
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Focused mode
F I G U R E 2 1 - 4 Focused mode technique (for incision) and defocused mode technique (for
vaporization). Note the different distances from target to laser for the hollow wave guide and the articulated arm.
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or vascular collagen is the chromophore for a particular laser wavelength. The CO2 laser generally seals vessels 500 mm or less in diameter, whereas the more hemoglobin-specific KTP:YAG, Nd:YAG, and argon lasers may provide deeper hemostasis. Even when another modality is used, the laser may be used to control hemorrhage. This is done by passing the laser over the surgical site somewhere between the focusing and defocusing distances to produce a hemostatic effect without causing significant tissue cutting or ablation. The indications for the use of lasers in cosmetic dentistry are presented in Box 21-1. More than one wavelength may be suitable for a specific clinical situation; therefore proper wavelength selection is important. Because of the variety of manufacturers, wavelengths, machines, and clinical variations, there is no “cookbook” for laser surgery. Any clinician using lasers should receive appropriate instruction in that particular wavelength and device and should use known protocols along with individual clinical judgment. The following sections give some examples of laser cosmetic dental procedures and the lasers most commonly used for that purpose, although other lasers may be used.
SOFT TISSUE Gingivoplasty/Gingivectomy Soft tissue procedures can be can be useful in correcting an unesthetic “gummy smile” of delayed passive eruption or medication
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Box 21-1 Soft Tissue Clinical Indications for Esthetic Dental Laser Surgery Frenectomy Gingivoplasty Tissue and papilla resculpting Gingivectomy Access gingivectomy Lesion removal Pigment and tattoo removal
induced hyperplasia (Fig. 21-5). A gingivectomy is also frequently required to expose subgingival root surface carious lesions (Fig. 21-6). This procedure is becoming more common in the aging population using many of the medications that result in decreased salivation. The ability of the laser to remove the soft tissue while leaving a bloodless field permits immediate restoration or impressioning. Gingivectomy or gingivoplasty may be accomplished with a CO2, erbium, diode, or Nd:YAG laser. Each of these has its own advantages and disadvantages. For hyperplastic tissue, the CO2 laser is very effective at altering the location of the gingival margin by incision and then reducing the extensive hyperplastic tissue by ablations. It is, however, necessary to protect the teeth using a thin nonreflecting instrument as a barrier between the tooth and the laser energy, and the noncontact
B FIGURE 21-5 A, Preoperative view. B, Four-week postoperative view showing excellent healing.
A
B FIG U R E 2 1 - 6 A, CO2 laser-assisted access gingivoplasty and recontouring to allow immediate
placement of restorations in a bloodless field. B, Postoperative view of same patient 2 weeks after restoration. (Courtesy Alan Winner, DDS, New York, NY.)
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nature of the CO2 laser21 makes learning its use and control more demanding. Although the erbium laser may be used for gingivoplasty, the pulsed nature of this laser often results in an uneven, ragged cut. Hemostasis and tissue fluid control with the erbium laser can also be problematic even when used without water spray because tissue heating is required for cauterization and the erbium laser’s ablation removes tissue but does not create sufficient collateral heat to cauterize any but the smallest vessels. There has been some improvement in these characteristics with newer Er, Cr:YSGG lasers that use high pulse rate and longer pulse width to smooth the cut and increase the heat transfer to the tissue for hemostasis. Potential damage to tooth structure is possible the erbium laser wavelength if excessive power density is used. The diode laser’s hot tip is used in contact mode, which permits easier control for these procedures than the CO2 or erbium. The dry field left by these devices does not require the removal of soft tissue considerably beyond the desired margin as with erbium lasers and permits immediate restoration. Although lasers are generally said to be “end cutting,” the diode laser hot tip can be used on the side of the tip to the extent the initiation can be maintained. This permits moderate tissue sculpting, which is a benefit in these procedures. Although it is frequently shown that the hydroxyapatite of tooth structure is mostly unaffected by diode laser wavelengths, the hot tip actually used is relatively safe around enamel if contact time is limited but can leave a burned area on root structure or dentin, which is more susceptible to heat damage than enamel.
Frenectomy Almost any dental laser (CO2, diode, erbium, Nd:YAG) can easily and quickly remove either a lingual or facial frenum. The frenum can either be excised in continuous, focused mode (or with a contact tip) or ablated in continuous or pulsed, defocused mode. In any situation, no closure is necessary, and healing generally is excellent. The lack of bleeding and elimination of sutures makes this an ideal technique for children. Some lasers may also permit this procedure to be accomplished without anesthesia, although most generally require an anesthetic unless
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the frenum is small, in which situation a topical anesthetic may suffice (Fig. 21-7).
CLINICAL TIP Although primarily necessary for orthodontic correction, the frenectomy is often performed as part of a restorative diastema closure accomplished with bonding or veneers. In the situation of restorative treatment, the frenectomy should be accomplished in conjunction with a gingivoplasty to alter the gingival papilla shape created by the diastema.
Removal of Benign Lesions The laser (CO2, diode, erbium,) is an ideal tool for removal of cosmetically undesirable benign neoplastic or hamartomatous lesions. If a benign diagnosis has been confirmed, the laser may be used to excise the lesion in focused mode or to ablate it in defocused mode. Fibromas, mucoceles, granulomas, amalgam tattoos, and small lip, gingival, and tongue hemangiomas, and lymphangiomas can be managed in this manner (Fig. 21-8).22
Gingival Troughing The CO2 and diode lasers are useful in bloodless gingival troughing before impressioning. This eliminates the need for retraction cords and vasoconstrictors. The laser tip is placed below the height of the gingival crevice, and the tissue is “ledged” to expose the margin of the preparation. This procedure is technique sensitive and must be done carefully to prevent inadvertent damage to the tooth (Fig. 21-9).
HARD TISSUE Osseous Crown Lengthening Cosmetic and restorative surgery may involve osseous tissue. The erbium laser has been shown to be safe and effective at removing
B F I G U R E 2 1 - 7 A, Immediate postoperative view. B, Two-week postoperative view showing
removal of a maxillary frenum. (Courtesy Alan Winner, DDS, New York, NY.)
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A
B FIG U R E 2 1 - 8 A, Venous lake of mandibular lip. B, Lip after ablation of lesion with argon laser.
(Courtesy John Sexton, DMD, Boston, MA.)
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B F I G U R E 2 1 - 9 A, Intraoperative view of gingiva surrounding crown preparations. B, Gingival
troughing before impression making using a diode laser and fiberoptic delivery.
osseous tissue.23 Because all lasers are “end cutting” and “side safe,” they may be used in a novel approach to osseous crown lengthening. The small fiber diameter and the ability of the erbium laser to affect both soft and hard tissue in the gingival sulcus permit this “flapless” osseous crown lengthening procedure to be used to apically reposition the osseous crest and alter the soft tissue morphology so that proper contours are achieved (Fig. 21-10). Although the healing rate following bone removal with an Er:YAG laser “bone drilling” has been reported to be equivalent or even quicker than that following bone removal with a bur the healing rate observed following “flapless” crown lengthening made possible by using an erbium laser has been seen to be extremely fast relative to standard osseous surgery, usually with no evidence of the surgery after 2 weeks.24 It would be expected that the Er, Cr:YSGG would have similar results (Fig. 21-11).17 Tooth Preparation. The Er:YAG, Er, Cr:YSGG, and excimer lasers can efficiently remove tooth structure without damage to adjacent structures or the dental pulp.i Advantages of laser use include the elimination of anesthesia in some situations26 and the quiet function of the laser compared with the sound of the dental handpiece. Disadvantages include the
lack of long-term clinical studies, the difficulty in performing complex restorative procedures, and the irregular surface produced by the laser, which makes it unsuitable for indirect restorations such as inlay or crown preparations.27 With time and new technological modifications, these disadvantages may become less problematic.27
Cosmetic Skin Resurfacing The Er:YAG laser and the CO2 laser (using a high power, short pulse configuration such as “superpulsing”) can selectively remove the surface epidermis and the papillary dermis of the skin while leaving the underlying reticular dermis and adnexal (epithelial-based) structures. This allows internal wound vertical migration of epithelium as opposed to the adjacent basal cell horizontal migration normally seen. Because the result is rapid healing without scarring, this technique can be used to “resurface” the skin. It can help remove the wrinkles around the lips commonly seen after prosthetic rehabilitation of an overclosed stoma and with chronic smoking, prolonged sun exposure, and aging skin. The procedure is performed by oral and maxillofacial surgeons and can be extended to include the entire perioral region or even the entire face.23,28
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FIGURE 21-10 A cross-section of the dental architecture after
soft-tissue gingivoplasty and access to the crestal bone. (From Magid KS, Strauss RA: Laser use for esthetic soft tissue modification. Dent Clin North Am 51:525-545, 2007).
LASER SAFETY Despite being outstanding surgical tools, lasers are inherently dangerous.29 However, with proper caution and case selection, laser surgery should be as safe as any other modality. Safety parameters vary to some extent based on differing absorption patterns. Each particular wavelength requires a different set of safety glasses to absorb that particular wavelength. One constant, however, is that all persons in the operatory, especially the patient, must wear appropriate eye protection with side shields. Flammable items should be eliminated from the surgical field or thoroughly saturated with water to prevent them
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from igniting. Such items as gauze, cotton rolls, and cotton pellets are especially likely to be a problem if dry and touched by the laser beam. Flammable liquids or gases used for anesthesia or in the operatory should also be considered a danger and avoided. Cleaning agents and alcohol are common flammables. Although oxygen and nitrous oxide are not flammable, they do support combustion and if present in the surgical field could lead to a catastrophic event should something within the field catch fire. The current scientific literature should be consulted before these agents are used in conjunction with lasers. Wet gauze should be placed in the mouth to protect adjacent tissues and teeth. A CO2 laser needs only 1 watt-second (i.e., one watt of power in contact with the tooth for 1 second) to cause enamel damage. A common byproduct of the photothermal laser effect is steam mixed with cellular and tissue debris. This smokelike material, the laser plume, contains intact biologic material, including some particles. It is vital for the surgical team to avoid surface contact or inhalation of the plume to prevent disease transmission. This can be avoided by using high-power smoke evacuators fitted with biologic filters and special laser masks that filter out smaller than usual particulate matter. Because the laser can work at great distances from the target, it is important to take appropriate steps to prevent accidental lasing of unintended targets. This can be prevented by placing the laser in standby mode before removing the handpiece from the mouth using a covered foot pedal and having an assistant engage and disengage the laser for the dentist (in place of the dentist reaching over to put the machine in standby while it is still active). Other safety rules exist, and it is important to consult the current scientific literature before using a laser.
CONCLUSION Laser use in cosmetic dentistry has many advantages. A thorough understanding of related physics, control parameters, indications and contraindications, and safety is essential. As more wavelengths become available, laser use for both hard and soft tissue cosmetic procedures will inevitably increase.
B F I G U R E 2 1 - 1 1 A, Patient with asymmetric gingival architecture between the two maxillary
central incisors. B, The same patient after laser “flapless” surgery and placement of esthetic restorations.
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REFERENCES 1. Einstein A: Zur Quanten Theorie der Stralung, Phys Zeit 18:121, 1917. 2. Maiman TH: Stimulated optical radiation in ruby, Nature 187:493-494, 1960. 3. Stern RH, Sognnaes RF: Laser beam effect on dental hard tissues, J Dent Res 43:873, 1964. 4. Goldman L et al: Effect of laser beam impact on teeth, J Am Dent Assoc 70:601-606, 1965. 5. Myers TD, Myers WD: In vivo caries removal utilizing the Nd:YAG laser, J Mich Dent Assoc 67:66, 1985. 6. Keller V, Hibst R: Experimental studies of the application of the Er:YAG on dental hard substances. I, Lasers Surg Med 9:338, 1989. 7. Keller V, Hibst R: Experimental studies of the application of the Er:YAG on dental hard substances. II, Lasers Surg Med 9:345, 1989. 8. Featherstone JDB, Nelson DGA: Laser effects on dental hard tissues, Adv Dent Res 1(1):22, 1987. 9. Neev J et al: Scanning electron microscopy and thermal characteristics of dentin ablated by a short-pulse XeCl excimer laser, Lasers Surg Med 13:353-362, 1993. 10. Cozean C et al: Dentistry for the 21st century: Erbium:YAG laser for teeth, J Am Dent Assoc 128:1080, 1997. 11. Keller U, Hibst R: Effects of Er:YAG laser in caries treatment: a clinical pilot study, Lasers Surg Med 20(1):32, 1997. 12. Strauss RA: Laser management of discrete lesions. In Catone G, Alling C, editors: Laser applications in oral and maxillofacial surgery, Philadelphia, 1997, Saunders. 13. Bornstein E: Near-infrared dental diode lasers: scientific and photobiologic principles and applications, Dent Today (3):102-108, 2004. 14. Gaspar L, Szabo G: Removal of benign oral tumors and tumor-like lesions by CO2 laser application. J Clin Laser Med Surg 7(5):33-36, 1989. 15. Pogrel MA, McCracken KJ, Daniels TE: Histologic evaluation of width of soft tissue necrosis adjacent to carbon dioxide laser incisions, Oral Surg Med Oral Pathol 70:564568, 1990.
16. Basu MF, Frame JW, Rhys-Evans PH: Wound healing following partial glossectomy using the CO2 laser, diathermy, and scalpel: a histologic study in rats, J Laryngol Otol 102:322, 1988. 17. White JM, Goodis HE, Rose CL: Use of the pulsed Nd:YAG laser for intraoral soft tissue surgery, Lasers Surg Med 11:455, 1991. 18. Aranoff BL: CO2 laser in surgical oncology. In Kaplan J, editor: Laser surgery, Proceedings of the First and Second International Symposiums on Laser Surgery, 1978, Tel Aviv, OTPAZ, pp 191-216. 19. Fisher SE, Frame JW: The effects of the carbon dioxide surgical laser on oral tissues, Br J Oral Maxillofac Surg 22:414, 1984. 20. Rhys Evans PH, Frame JW, Branddrick J: A review of carbon dioxide laser surgery in the oral cavity and pharynx, J Laryngol Otol 100:69, 1986. 21. Wlodawsky RN, Strauss RA: Intraoral laser surgery, Oral Maxillofac Surg Clin North Am 16: 149, 2004. 22. Strauss, RA Coleman M: Lasers in major oral and maxillofacial surgery. In Convissar RA, editor: Principles and practice of laser dentistry. St Louis, 2011, Mosby. 23. Lewandrowski KU, Lorente C, Schomacker TJ, et al: Use of the Er:AYAG laser for improved plating in maxillofacial surgery: comparison of bone healing in laser and drill osteotomies, Lasers Surg Med 19(1):40-45, 1996. 24. McGuire MK, Scheyer ET: Laser-assisted flapless crown lengthening: a case series, Int J Periodont Restor Dent 31(4):357-364, 2011. 25. Dostálová T, Jelínková H, et al. Dentin and pulp response to Erbium:YAG laser ablation: a preliminary evaluation of human teeth, J Clin Laser Med Surg 15(3):117-121, 1997. 26. Zanin F et al: Er:YAG Laser: Clinical experience based upon scientific evidence, SPIE 2(6), 2001. 27. Visuri SR, Walsh JT, Wigdor HA: Erbium laser ablation of dental hard tissue: effect of water cooling, Lasers Surg Med 18:294, 1996.
The use of lasers in dentistry has burgeoned at an astonishing rate over the past few years. Once relegated to use on soft tissue, now even hard tissue esthetic surgery can be done with lasers. Because of their many advantages, lasers are indicated for a wide variety of intraoral and extraoral esthetic procedures. To use them safely and successfully, however, a thorough understanding of their indications, contraindications, and safety parameters is imperative.
HISTORY The word laser is an acronym for light amplification by stimulated emission of radiation. The theory has its roots in several basic principles of physics first described by Einstein in 1917.1 Amazingly it was almost another 50 years before these principles were sufficiently understood and the technology could be converted into practical reality. The first laser to use visible light was developed by a physicist, Dr. Theodore Maiman, in 1960. Maiman used a ruby gemstone as the lasing medium, producing the red beam of intense light typically associated with lasers.2 This was followed in 1961 by another crystal laser using a neodymium-doped crystal of yttrium, aluminum, and garnet (Nd:YAG). In 1964, physicists at Bell Laboratories produced a gaseous laser using carbon dioxide (CO2) as the lasing medium. That same year another gaseous laser that would prove important in dentistry, the argon laser, was invented. Dental scientists investigating the effects of Maiman’s ruby laser on the enamel of teeth found that it caused cracking and fissuring of enamel.3,4 The studies concluded that lasers had no place in dentistry, and few other studies were undertaken. In medicine, however, research and clinical use of lasers proliferated. In 1968, the CO2 laser was used for the first time to perform soft tissue surgery. An increasing variety of laser wavelengths, as well as general and oral surgical indications, evolved. In the mid-1980s, the expanded availability of different wavelengths and the improved understanding of laser physics and tissue interaction created a resurgence of interest in the use of lasers in dentistry for hard tissues such as enamel.5-8 446
Although a few wavelengths, such as that of the Nd:YAG laser, can be artificially manipulated for hard tissue use, their danger potential and lack of specificity for dental tissues make them less than ideal. Other lasers, such as the excited dimer (excimer) laser, which was studied extensively in the late 1980s and early1990s, were shown to cause little damage to teeth. However, they were plagued by problems of cost, size, and efficiency.9 Not until 1997 did the US Food and Drug Administration (FDA) finally approve a well-known laser, the Erbium:YAG (Er:YAG) laser and later the Er, Cr:YSGG laser (henceforth collectively referred to as “erbium” because of their similarities), for hard tissue use.10,11
BASIC CONCEPTS Laser energy is unique in that laser light is coherent. This means that laser light has three distinct properties that distinguish it from regular light. Ideal laser light is monochromatic (composed of a single wavelength of light), collimated (the light waves run parallel to each other instead of diverging), and uniphasic (the peaks and valleys of the waves are synchronous (Fig. 21-1).
Monochromatic Property Because lasers are monochromatic, each has a single frequency and wavelength and therefore a single “color.” Thus, lasers often are defined by their visible color (e.g., red light or green light lasers), their position in the electromagnetic spectrum (e.g., infrared, ultraviolet or radiograph lasers), or the chemicals that create the light (e.g., CO2, argon, or Nd: YAG lasers).
Collimated Property All laser beams are parallel, or collimated, unlike regular light. Because the laser beam does not diverge significantly over distance, the source can be positioned at great length from the target tissue or can be very efficiently focused down to a small spot with a convex focusing lens.
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Danger LASER Monochromatic Danger LASER
Danger LASER Collimated
A
Danger LASER
Danger LASER
B
Uniphasic
F I G U R E 2 1 - 1 A, Regular light showing the different wavelengths present and the random
spread of the beam. Laser demonstrating uniform, coherent light. B, Laser light showing monochromatic wavelength, collimation, and uniformity of phase, which constitute coherent light.
Uniphasic Property The peaks and troughs of a laser light wave are directly in line (synchronous) with one another, making them uniphasic. All the peaks and troughs of the energy beam are stacked on top of each other.
Intensity Property Collimation, monochromaticity, and uniphasicity together produce a very intense and powerful flash or beam of light. The ability to efficiently focus the beam down to a small spot size (an effect of the collimation on a convex lens) produces an extremely powerful, condensed energy source. Laser beams may reflect off, transmit through, scatter (break up) within, or be absorbed by organic target tissue. The first three conditions elicit no effect within the tissue, but when absorbed, a laser beam may produce several different results. The most important is the photothermal effect, or tremendous heat generation that occurs almost instantaneously within the tissue. In soft tissue, this causes the intracellular water to boil or vaporize and literally explodes and disintegrates the cell. In hard tissues, similar effects may be seen in hydroxyapatite. Unlike other heat sources, however, the laser can be applied with incredible precision and with such speed that only microns of tissue can be removed at a time with very controlled and minimal damage to adjacent tissues and structures. Conversely it sometimes is advantageous to have a lateral heat effect in tissue that results in thermal coagulation of adjacent blood vessels and a bloodless field. Lasers can be controlled to provide this as well. The many lasers now available for medical and dental use differ in several aspects. The primary difference is the active medium (i.e., the material that undergoes stimulated emission). The specific material used determines the wavelength of energy produced and therefore the clinical indications. Few materials in nature can undergo this process because the material must be capable of sustaining population inversion, an unnatural condition in which most atoms are in a highly excited state. The ideal system uses fiberoptic delivery of the laser beam to the target tissue. These systems are flexible and precise, they allow for both contact and noncontact surgery, and they are capable of endoscopic delivery. Unfortunately, not all wavelengths (e.g., CO2) can be transmitted through the currently used quartz fiberoptic fibers. These other types of lasers use articulated
arm delivery in which a series of hollow metal tubes connected by mirrored flexible joints or “knuckles” allow the beam to be passed from the laser to the tissues. Although this is functional for superficial tissues, it is less than ideal for deeper tissues or areas of difficult access, such as the oral cavity. Some newer lasers use a hollow wave guide, a variation of the articulated arm. The hollow wave guide is a flexible metal tube internally lined with a mirrored surface or foil, which allows the beam to reflect down the guide to the tissues. Although not as flexible as a fiberoptic fiber and incapable of endoscopic delivery, this system has dramatically improved the dentist’s ability to provide convenient, precise delivery within the oral cavity. Some lasers produce a continuous beam of laser light as long as the machine is energized, whereas others can be pulsed. These very high power, short duration pulses of laser light minimize the time available for lateral tissue heating and damage.12 Other lasers can be electronically enhanced to produce extremely fast, high-powered laser bursts (“superpulsed” or “ultrapulsed”) for situations such as dermatologic skin surgery in which lateral thermal damage produces scarring. Selecting the appropriate laser for a given procedure usually is a simple matter of determining which laser wavelength is best absorbed by the target tissue while producing the least reflection, scatter, and transmission. Laser wavelengths that are absorbed by water (e.g., CO2, erbium) are appropriate for soft tissue surgery. Those well absorbed by hemoglobin are better suited for vascular tissues or lesions (e.g., argon, KTP: YAG, tunable dye, copper vapor lasers). Argon laser wavelengths are well absorbed by composite resin, and the erbium laser wavelength, which is absorbed by both hydroxyapatite and water, allows for hard tissue use. Some lasers with wavelengths that are absorbed by a number of different tissues (i.e., chromophores) may be useful for a variety of tissue effects. In addition, some transmission may actually be desirable in certain situations to allow deeper penetration of tissues (e.g., when deep hemostasis is desired in vascular lesions). To allow for precise tissue effects and clinical uses, some devices can produce more than one wavelength (i.e., CO2 and Er: YAG, KTP: YAG and Nd: YAG, and tunable dye), which allows the operator to select the desired tissue effect by varying the wavelength used. The choice of an appropriate wavelength involves a combination of known tissue effect and the operator’s clinical experience.13
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Currently the most commonly used laser in general dentistry is the diode laser. Used primarily for soft tissue incisional procedures, it has the advantage of being small, relatively inexpensive, and comparatively easy to use. However, its mechanism of action is widely misunderstood. Some lasers function by the direct effect of laser energy on soft tissue, whereas diode lasers used in dentistry do not have sufficient power to cut tissue.13 Therefore the laser tip needs to be activated (initiated) by touching the tip to a light absorbing material such as articulating paper, cork, or other dark substance, which produces a “charring” of the tip. The tip is now capable of absorbing laser light and when activated by the laser will heat up and vaporize the underlying tissue (Fig. 21-2).
Cutting speed 12.5 (mm/s)
6.0
3.0
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0.0 (t 3 s)
General view
Histology
F I G U R E 2 1 - 3 Effects of cutting speed on collateral thermal
Laser Tip Consideration
damage.
Laser tip activation deposits carbon on the tip of the laser fiber, which becomes the target of the diode laser energy.
CLINICAL TIP Initiate the tip and a portion of the side of the laser fiber with light absorbing material.
ADVANTAGES AND DISADVANTAGES
CLINICAL TIP The light-absorbing material used for initiating the laser fiber is not consumed by the laser energy. However, with some lasers it may be wiped or broken off during use. In that situation it must be reinitiated. It is also the cause of more extensive collateral thermal damage as the power of the unconverted laser energy penetrates deeper into the tissues (Fig. 21-3).5 Because the diode laser functions by cutting with a hot tip, the specific wavelength of the diode laser is of less significance than in other lasers. The remaining parameters of power, time, and spot size are, however, still critical. Sufficient power is necessary to maintain the hot tip once it is in contact with the cooler tissue. If the tip cools beyond the temperature required to efficiently incise the tissue the resulting increase in contact time will
Fiber
300 m
Uninitiated non-contact
increase the collateral thermal damage as in other lasers. Spot size (or in the situation of diode laser, fiber size) is significant because the heat of the laser tip is concentrated in a smaller area that increases the heat energy per unit area.
Many laser wavelengths either are absorbed by hemoglobin or constrict vascular wall collagen, allowing for bloodless surgery.14 This allows the dentist to work in a clean, dry environment unobstructed by bleeding. When used correctly, lasers also can remove precise and minimal amounts of tissue with minimal effect on adjacent tissues. They are ideal for detailed, exact tissue manipulation.15 Lasers have an effect on neural tissue that generally results in less pain after surgery compared with other types of treatment.16 In fact, because of their great speed, some pulsed lasers may even be used for soft or hard tissue surgery without the need for anesthesia.17 Minimal postoperative pain and absence of bleeding usually precludes the need for suturing, tissue closure, or coverage with splints or dressings except when cosmetic requirements dictate otherwise. The elimination of lateral tissue damage is especially important in dentistry because of the proximity of such chemically diverse yet clinically vital structures as dental pulp, bone, tooth structure, and oral soft tissue. Lasers also make possible procedures such as perioral cosmetic skin resurfacing, in which even minimal adjacent dermal tissue damage would translate
Fiber
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Initiated contact
FIG U R E 2 1 - 2 The experiment shows the inability of the diode laser to cut with either an un-
initiated or initiated tip in non-contact. Only an initiated tip in contact is capable of cutting tissue at power levels found in dental diode lasers.
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into inevitable and devastating scarring. Sealing of the lymphatic system during laser surgery and the minimal tissue trauma result in little or no postoperative edema in most patients.18 Finally because of the minimal tissue damage and the decrease in the number of myofibroblasts in laser-treated wounds compared with wounds made by scalpel or electrosurgical instruments, postoperative scarring and contracture are minimized, allowing dramatic surgery without the fear of significant postoperative cosmetic deformity or functional deficits.19 Disadvantages are few but important. The preeminent concern with lasers in dentistry is safety. Lasers require tremendous diligence to maintain a safe operative environment for both the patient and the dental team (see the section on Laser Safety later in this chapter). Other disadvantages include the generally high cost of purchasing and maintaining the laser, the loss of tactile sensation with noncontact lasers, the learning curve necessary to obtain uniform results, and the specificity of some laser wavelengths, necessitating the occasional need for more than one laser for a particular procedure. Finally although healing after laser surgery generally is excellent, usually much better than with other instruments such as a scalpel or electrosurgical instrument, it also generally is slower because of the vascular sealing.20
CLINICAL INDICATIONS Restorative and intraoral esthetic modification can be divided into soft tissue or combined soft and hard tissue.
CLINICAL TIP To determine which procedures are required, and therefore what types of lasers will be used, measurements and planning must be performed to determine if the changes will violate the biologic width of the teeth involved.
Soft tissue procedures include excision of excess tissue, either normal or pathologic, and recontouring of tissue. There are few soft tissue surgeries in which the laser cannot be used and used advantageously. Teeth or bone intimately involved with the target tissue or lesion must be protected from the laser beam, which increases the difficulty of the procedure, but with reasonable precaution and care, this usually is not a problem. For example, a standard mucoperiosteal flap around the dentition can be created with a laser, but it is more easily and safely accomplished with a scalpel. Once the incision has been made, the rest of the surgery may well be enhanced by the use of lasers. Despite the many different types of lasers available, the techniques for their use do not vary significantly. The three basic techniques are incision, vaporization, and hemostasis.12 The clinician should evaluate the lesion before surgery and determine which of these is most appropriate. Incision is accomplished by placing the laser at its focal length (i.e., the smallest possible spot size) near the tissue or touching the tissue if a contact tip laser is used. This increases the density of the power and condenses the effect into a small area. This laser-target distance varies according to the delivery system and ranges from contact with a contact laser to 0.5 mm for a hollow wave guide to more than 1 cm for an articulated arm laser (Fig. 21-4). Vaporization, also called ablation, allows the removal of large areas of very superficial tissue (e.g., removal of the surface mucosal epithelium) without affecting deeper structures. This is accomplished by defocusing or backing the laser away from the target to increase the spot size. Defocusing effectively lowers the density of the laser energy per unit area and causes the laser to act more superficially over a larger surface area. The target distance may vary dramatically depending on the type of delivery system, the available power, and the desired depth of penetration. Most lasers are intrinsically hemostatic to a degree, depending on the laser’s depth of penetration and whether hemoglobin
Articulated arm
Hollow wave guide
Defocused mode Focused mode
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F I G U R E 2 1 - 4 Focused mode technique (for incision) and defocused mode technique (for
vaporization). Note the different distances from target to laser for the hollow wave guide and the articulated arm.
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or vascular collagen is the chromophore for a particular laser wavelength. The CO2 laser generally seals vessels 500 mm or less in diameter, whereas the more hemoglobin-specific KTP:YAG, Nd:YAG, and argon lasers may provide deeper hemostasis. Even when another modality is used, the laser may be used to control hemorrhage. This is done by passing the laser over the surgical site somewhere between the focusing and defocusing distances to produce a hemostatic effect without causing significant tissue cutting or ablation. The indications for the use of lasers in cosmetic dentistry are presented in Box 21-1. More than one wavelength may be suitable for a specific clinical situation; therefore proper wavelength selection is important. Because of the variety of manufacturers, wavelengths, machines, and clinical variations, there is no “cookbook” for laser surgery. Any clinician using lasers should receive appropriate instruction in that particular wavelength and device and should use known protocols along with individual clinical judgment. The following sections give some examples of laser cosmetic dental procedures and the lasers most commonly used for that purpose, although other lasers may be used.
SOFT TISSUE Gingivoplasty/Gingivectomy Soft tissue procedures can be can be useful in correcting an unesthetic “gummy smile” of delayed passive eruption or medication
A
Box 21-1 Soft Tissue Clinical Indications for Esthetic Dental Laser Surgery Frenectomy Gingivoplasty Tissue and papilla resculpting Gingivectomy Access gingivectomy Lesion removal Pigment and tattoo removal
induced hyperplasia (Fig. 21-5). A gingivectomy is also frequently required to expose subgingival root surface carious lesions (Fig. 21-6). This procedure is becoming more common in the aging population using many of the medications that result in decreased salivation. The ability of the laser to remove the soft tissue while leaving a bloodless field permits immediate restoration or impressioning. Gingivectomy or gingivoplasty may be accomplished with a CO2, erbium, diode, or Nd:YAG laser. Each of these has its own advantages and disadvantages. For hyperplastic tissue, the CO2 laser is very effective at altering the location of the gingival margin by incision and then reducing the extensive hyperplastic tissue by ablations. It is, however, necessary to protect the teeth using a thin nonreflecting instrument as a barrier between the tooth and the laser energy, and the noncontact
B FIGURE 21-5 A, Preoperative view. B, Four-week postoperative view showing excellent healing.
A
B FIG U R E 2 1 - 6 A, CO2 laser-assisted access gingivoplasty and recontouring to allow immediate
placement of restorations in a bloodless field. B, Postoperative view of same patient 2 weeks after restoration. (Courtesy Alan Winner, DDS, New York, NY.)
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nature of the CO2 laser21 makes learning its use and control more demanding. Although the erbium laser may be used for gingivoplasty, the pulsed nature of this laser often results in an uneven, ragged cut. Hemostasis and tissue fluid control with the erbium laser can also be problematic even when used without water spray because tissue heating is required for cauterization and the erbium laser’s ablation removes tissue but does not create sufficient collateral heat to cauterize any but the smallest vessels. There has been some improvement in these characteristics with newer Er, Cr:YSGG lasers that use high pulse rate and longer pulse width to smooth the cut and increase the heat transfer to the tissue for hemostasis. Potential damage to tooth structure is possible the erbium laser wavelength if excessive power density is used. The diode laser’s hot tip is used in contact mode, which permits easier control for these procedures than the CO2 or erbium. The dry field left by these devices does not require the removal of soft tissue considerably beyond the desired margin as with erbium lasers and permits immediate restoration. Although lasers are generally said to be “end cutting,” the diode laser hot tip can be used on the side of the tip to the extent the initiation can be maintained. This permits moderate tissue sculpting, which is a benefit in these procedures. Although it is frequently shown that the hydroxyapatite of tooth structure is mostly unaffected by diode laser wavelengths, the hot tip actually used is relatively safe around enamel if contact time is limited but can leave a burned area on root structure or dentin, which is more susceptible to heat damage than enamel.
Frenectomy Almost any dental laser (CO2, diode, erbium, Nd:YAG) can easily and quickly remove either a lingual or facial frenum. The frenum can either be excised in continuous, focused mode (or with a contact tip) or ablated in continuous or pulsed, defocused mode. In any situation, no closure is necessary, and healing generally is excellent. The lack of bleeding and elimination of sutures makes this an ideal technique for children. Some lasers may also permit this procedure to be accomplished without anesthesia, although most generally require an anesthetic unless
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the frenum is small, in which situation a topical anesthetic may suffice (Fig. 21-7).
CLINICAL TIP Although primarily necessary for orthodontic correction, the frenectomy is often performed as part of a restorative diastema closure accomplished with bonding or veneers. In the situation of restorative treatment, the frenectomy should be accomplished in conjunction with a gingivoplasty to alter the gingival papilla shape created by the diastema.
Removal of Benign Lesions The laser (CO2, diode, erbium,) is an ideal tool for removal of cosmetically undesirable benign neoplastic or hamartomatous lesions. If a benign diagnosis has been confirmed, the laser may be used to excise the lesion in focused mode or to ablate it in defocused mode. Fibromas, mucoceles, granulomas, amalgam tattoos, and small lip, gingival, and tongue hemangiomas, and lymphangiomas can be managed in this manner (Fig. 21-8).22
Gingival Troughing The CO2 and diode lasers are useful in bloodless gingival troughing before impressioning. This eliminates the need for retraction cords and vasoconstrictors. The laser tip is placed below the height of the gingival crevice, and the tissue is “ledged” to expose the margin of the preparation. This procedure is technique sensitive and must be done carefully to prevent inadvertent damage to the tooth (Fig. 21-9).
HARD TISSUE Osseous Crown Lengthening Cosmetic and restorative surgery may involve osseous tissue. The erbium laser has been shown to be safe and effective at removing
B F I G U R E 2 1 - 7 A, Immediate postoperative view. B, Two-week postoperative view showing
removal of a maxillary frenum. (Courtesy Alan Winner, DDS, New York, NY.)
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A
B FIG U R E 2 1 - 8 A, Venous lake of mandibular lip. B, Lip after ablation of lesion with argon laser.
(Courtesy John Sexton, DMD, Boston, MA.)
A
B F I G U R E 2 1 - 9 A, Intraoperative view of gingiva surrounding crown preparations. B, Gingival
troughing before impression making using a diode laser and fiberoptic delivery.
osseous tissue.23 Because all lasers are “end cutting” and “side safe,” they may be used in a novel approach to osseous crown lengthening. The small fiber diameter and the ability of the erbium laser to affect both soft and hard tissue in the gingival sulcus permit this “flapless” osseous crown lengthening procedure to be used to apically reposition the osseous crest and alter the soft tissue morphology so that proper contours are achieved (Fig. 21-10). Although the healing rate following bone removal with an Er:YAG laser “bone drilling” has been reported to be equivalent or even quicker than that following bone removal with a bur the healing rate observed following “flapless” crown lengthening made possible by using an erbium laser has been seen to be extremely fast relative to standard osseous surgery, usually with no evidence of the surgery after 2 weeks.24 It would be expected that the Er, Cr:YSGG would have similar results (Fig. 21-11).17 Tooth Preparation. The Er:YAG, Er, Cr:YSGG, and excimer lasers can efficiently remove tooth structure without damage to adjacent structures or the dental pulp.i Advantages of laser use include the elimination of anesthesia in some situations26 and the quiet function of the laser compared with the sound of the dental handpiece. Disadvantages include the
lack of long-term clinical studies, the difficulty in performing complex restorative procedures, and the irregular surface produced by the laser, which makes it unsuitable for indirect restorations such as inlay or crown preparations.27 With time and new technological modifications, these disadvantages may become less problematic.27
Cosmetic Skin Resurfacing The Er:YAG laser and the CO2 laser (using a high power, short pulse configuration such as “superpulsing”) can selectively remove the surface epidermis and the papillary dermis of the skin while leaving the underlying reticular dermis and adnexal (epithelial-based) structures. This allows internal wound vertical migration of epithelium as opposed to the adjacent basal cell horizontal migration normally seen. Because the result is rapid healing without scarring, this technique can be used to “resurface” the skin. It can help remove the wrinkles around the lips commonly seen after prosthetic rehabilitation of an overclosed stoma and with chronic smoking, prolonged sun exposure, and aging skin. The procedure is performed by oral and maxillofacial surgeons and can be extended to include the entire perioral region or even the entire face.23,28
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FIGURE 21-10 A cross-section of the dental architecture after
soft-tissue gingivoplasty and access to the crestal bone. (From Magid KS, Strauss RA: Laser use for esthetic soft tissue modification. Dent Clin North Am 51:525-545, 2007).
LASER SAFETY Despite being outstanding surgical tools, lasers are inherently dangerous.29 However, with proper caution and case selection, laser surgery should be as safe as any other modality. Safety parameters vary to some extent based on differing absorption patterns. Each particular wavelength requires a different set of safety glasses to absorb that particular wavelength. One constant, however, is that all persons in the operatory, especially the patient, must wear appropriate eye protection with side shields. Flammable items should be eliminated from the surgical field or thoroughly saturated with water to prevent them
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from igniting. Such items as gauze, cotton rolls, and cotton pellets are especially likely to be a problem if dry and touched by the laser beam. Flammable liquids or gases used for anesthesia or in the operatory should also be considered a danger and avoided. Cleaning agents and alcohol are common flammables. Although oxygen and nitrous oxide are not flammable, they do support combustion and if present in the surgical field could lead to a catastrophic event should something within the field catch fire. The current scientific literature should be consulted before these agents are used in conjunction with lasers. Wet gauze should be placed in the mouth to protect adjacent tissues and teeth. A CO2 laser needs only 1 watt-second (i.e., one watt of power in contact with the tooth for 1 second) to cause enamel damage. A common byproduct of the photothermal laser effect is steam mixed with cellular and tissue debris. This smokelike material, the laser plume, contains intact biologic material, including some particles. It is vital for the surgical team to avoid surface contact or inhalation of the plume to prevent disease transmission. This can be avoided by using high-power smoke evacuators fitted with biologic filters and special laser masks that filter out smaller than usual particulate matter. Because the laser can work at great distances from the target, it is important to take appropriate steps to prevent accidental lasing of unintended targets. This can be prevented by placing the laser in standby mode before removing the handpiece from the mouth using a covered foot pedal and having an assistant engage and disengage the laser for the dentist (in place of the dentist reaching over to put the machine in standby while it is still active). Other safety rules exist, and it is important to consult the current scientific literature before using a laser.
CONCLUSION Laser use in cosmetic dentistry has many advantages. A thorough understanding of related physics, control parameters, indications and contraindications, and safety is essential. As more wavelengths become available, laser use for both hard and soft tissue cosmetic procedures will inevitably increase.
B F I G U R E 2 1 - 1 1 A, Patient with asymmetric gingival architecture between the two maxillary
central incisors. B, The same patient after laser “flapless” surgery and placement of esthetic restorations.
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PART 4 E s t h e t i c s a n d O t h e r Cl i n i c a l Ap p l i c a t i o n s
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