12 Lasers in Pediatric Dentistry

In 1960, Dr. Theodore Maiman, working on the theory of light amplification proposed by Albert Einstein, created the first laser.¹ Eighty years after Einstein’s 1917 paper, the first erbium laser for hard tissue dental use was cleared for marketing by the U.S. Food and Drug Administration (FDA). Since that time, dentistry has undergone dramatic changes in the way both soft tissue and hard tissue disease and abnormalities are treated. In pediatric dentistry, the primary goals are the prevention and the interception of oral diseases and soft tissue abnormalities without making patients reluctant to visit the dentist. If these twin goals of prevention and interception are not attainable, clinicians restore diseased teeth and repair or eliminate soft tissue conditions.

Concerns about the dental visit usually arise from the use of needles to anesthetize the hard and soft tissues. Other noxious stimuli (e.g., sound of high-speed turbine, smell of preparing teeth with high-speed handpiece, vibrations during tooth preparation) contribute to the development of dental phobias. Lasers represent a quantum leap forward in the treatment of all patients, especially the pediatric patient.

Laser Types

Erbium Family of Lasers

The development of the erbium family of lasers (Er:YAG and Er,Cr:YSGG) has made the treatment of children safer and easier. Laser-assisted dental care has changed the way dentists prepare diseased teeth, ablate bone, and treat soft tissue abnormalities and diseases. An entire new standard of care is becoming a reality. The erbium lasers have helped create a positive treatment atmosphere, with most pediatric patients undergoing dental caries treatment without fear.²^,³

The benefits of lasers have become well documented over the past decade. The erbium lasers provide an alternative to conventional drilling and filling, while often allowing a dentist to use the high-speed or slow-speed handpiece to complete procedures (e.g., extensive alloy preparations) without the need for local anesthesia. Erbium lasers have the unique ability to ablate hard tissues (bone, dentin, enamel) as well as perform soft tissue procedures.⁴^–⁷ With similar capabilities, the erbium family of lasers includes the 2940-nm erbium-doped yttrium-aluminum-garnet (Er:YAG) and the 2780-nm erbium, chromium–doped yttrium-scandium-gallium-garnet (Er,Cr:YSGG).

The major differences between different manufacturers’ erbium lasers are the variety of handpieces and tips and, more importantly, the parameters each manufacturer incorporates into the specific device. These parameters include the variability of setting the millijoules (mJ), hertz (Hz), and pulse durations. Other critically important differences include the delivery system (fiber vs. waveguide vs. articulating arm), amount and type of training offered (actual hands-on vs. CD and instruction manual), and the warranty on an expensive piece of equipment (as much as $90,000). Applying knowledge of laser physics allows the dentist to adjust each parameter, reducing the need for local anesthesia and providing good control of bleeding during soft tissue surgical procedures. In addition, proper settings allow the dentist to perform minimally invasive dental care, removing only the diseased tissue and preserving healthy tooth structure.

Soft Tissue Lasers

Complementing the erbium lasers is a second group, the soft tissue lasers. A variety of laser wavelengths are useful for soft tissue procedures. The primary soft tissue lasers currently used include the carbon dioxide (CO₂),⁸^,⁹ neodymium-doped YAG (Nd:YAG),¹⁰ and the diode lasers.¹¹^,¹² These soft tissue lasers have no capability to ablate hard tissue. Although Nd:YAG lasers have FDA clearance for ablating first-degree caries in enamel, the process is extremely slow and tedious and has essentially been replaced by the erbium family of lasers.

Low-Level Lasers

The third group of lasers useful in pediatric care are the photobiostimulating (PBS), or low-level, lasers.¹³^–¹⁵ Wavelengths of CO₂, diode, erbium, and Nd:YAG lasers are classified by the FDA as Class IV lasers because of their ability to ablate tissue. However, the FDA classifies low-level (PBS) devices as Class III lasers with “no significant risk” (NSR) because they produce less than 500 mW of energy. The photobiostimulatory effects of these lasers are usually labeled low-level laser therapy (LLLT).

The low-level (PBS) lasers do not cause temperature elevation within the target tissue, but rather produce their effects from a photobiostimulation (or modulation) effect within the target tissue. These lasers are not capable of ablating tissue. These units are usually semiconductor diode lasers consisting of indium-gallium-aluminum-phosphide (InGaAlP), in the range of 630 to 700 nm, or gallium-aluminum-arsenide (GaAlAs), in the range of 800 to 830 nm. These lasers can penetrate to depths of 2 to 3 cm, depending on the exact wavelength used and the target tissue.

Outside of dentistry, the FDA has cleared low-level laser use in medicine for conditions such as carpal tunnel syndrome and for pain management. Dental applications at this time should be considered off-label use (not cleared by FDA). Although these low-level lasers are safe, caution should be used, and contraindications include pregnancy, presence of malignancies, and use near the eye or, in some cases, over the thyroid gland ¹⁶ (see Chapter 15).

Adjuncts and Benefits

To optimize the benefits of lasers when integrating them into a pediatric dental practice, other technologies should also be considered. Laser-assisted dental procedures are one part of a new approach to practicing conservative, pain-free dentistry involving fluoride, digital radiography, and visual (microscopic) enhancement. Incorporating technologies such as digital radiography allows earlier diagnosis of decay and the use of minimally invasive lasers before lesions become large. When using a hard tissue laser and the improved composite materials now available, the clinician can precisely remove only diseased dental tissue and thus preserve more healthy tooth structure than with conventional techniques.

Some degree of visual enhancement for the dentist is highly recommended when using lasers. Lasers enable the practitioner to perform microdentistry because the laser can remove minute areas of diseased hard tissue not readily visualized. When performing soft tissue procedures, it is beneficial to use magnification to view the surgical area.¹⁷^,¹⁸ Loupes are one excellent option for enhanced visualization; however, the limitation of one magnification setting makes adding a dental operating microscope the optimal investment. The author has used a dental operating microscope since 2001 and finds children accept it without difficulty and remain quite still during dental procedures.

Clinical TIP

Clinical Tip: Pediatric dentists appreciate the many benefits of using rubber dam for tooth isolation. When performing laser-assisted operative dentistry, the use of local anesthetics may not be necessary for decay removal. In order to use a rubber dam without the need for a local anesthetic, the author uses a winged #3 rubber dam clamp with a small amount of topical anesthetic. This technique may allow the dentist to place the rubber dam without causing discomfort to the child. Also, use of a mouth prop during treatment prevents the child from closing on the rubber dam clamp or accidentally biting down and breaking the laser tip. An excellent alternative to the rubber dam is the Isolite system of tooth isolation (Isolite Systems, Santa Barbara, Calif). The Isolite unit incorporates all the benefits of a rubber dam with the addition of a self-contained light source, a mouth prop, and high-speed evacuation. The Isolite unit also prevents water from being pulled away from the tooth during caries removal, unlike the normal high-volume evacuator. This prevents the tooth from dehydrating, which may cause patient discomfort when performing laser dentistry.

Lasers in Pediatric Dental Practice

The erbium family of lasers were initially designed, manufactured, and cleared only for hard tissue procedures involving enamel, dentin, cementum, and bone. Only through subsequent efforts of erbium laser pioneers and manufacturer applications were many soft tissue procedures added to the list of FDA-cleared procedures for erbium lasers.

No single wavelength can be used to complete all dental procedures, but the author believes the erbium family is the best “all-purpose laser” for pediatric dentistry. Erbium lasers primarily target tissue water and hydroxyapatite and eliminate the smell and vibration associated with dental handpieces. Also, the need for local anesthesia is significantly reduced during removal of enamel, dentin, and dental caries. Lasers are bactericidal, thus providing an added defense against infection in soft tissue and recurrent decay in hard tissue.

Lasers have led to a reevaluation of dental cavity preparation and a fundamental change in the practice of restorative dentistry. We now need to reevaluate and often modify G.V. Black’s principle of “extension for prevention” with the concept of minimally invasive microdentistry. The use of erbium lasers for repair of incipient hard tissue disease provides a stress-free means of restoring teeth with minimal invasiveness and usually with no local anesthetic.¹⁹^,²⁰ Other benefits to the patient over conventional methods include reducing the number of office visits required for restorative procedures, decreasing healing time for soft tissue procedures, eliminating the need for suturing, and reducing the need for postoperative pain medication and antibiotics.

The effectiveness of using hard tissue lasers is safe and well documented in the dental literature. The Nd:YAG laser has limited usefulness in the treatment of dental caries but is cleared for removal of superficial pigmented caries.²¹ However, the erbium family is the laser of choice and most practical for deep enamel, dentin, and cementum caries removal. The erbium laser can be used for restoring primary and permanent teeth, again with minimal to no local anesthesia. In most cases, children will not require local anesthetic for Class I, II, III, IV, or V restorative procedures using bonded restorative materials.

Using the concept of minimally invasive restorative procedures, the erbium laser allows the operator to remove only diseased tissue, thus preserving much more of the healthy, unaffected tooth structure. Lasers also prevent the small microfractures that occur in enamel when using conventional dental handpieces. In cases where alloy restorations are preferred, the laser’s low-level analgesic effect may allow the dentist to create a restorative preparation using a conventional handpiece without analgesia. The erbium laser creates its ablation effect by being absorbed by water within the hydroxyapatite of the tooth structure. This heats up the water within the mineral, creating microexplosions of the hydroxyapatite out of the tooth. The erbium laser is absorbed by water, and decayed hard tissue has more water content than healthy hard tissue; therefore, erbium lasers are more specific for decay than conventional instruments. Conventional instruments (handpieces, air abrasion, spoon excavators) remove whatever is in their path. Erbium lasers preferentially remove higher-water-content (decayed) tissue, leaving the lower-water-content (healthy) tissue unaffected ²² (see Chapter 11).

Table 12-1 lists the various uses of lasers in pediatric dentistry.

Table 12-1 Pediatric Dental Procedures and Use of Various Lasers

Hard Tissue Procedures

Analgesia for Sealant Placement and Caries Removal

Both surgical and low-level (PBS) lasers can produce an analgesic effect on teeth. The low-level laser is placed on the occlusal and root areas of the tooth to create this analgesic effect. A similar result may be produced using surgical lasers in the defocused mode for 2 to 3 minutes. Lasers using extremely short pulse durations are very efficient at producing this effect. Placement of sealants, preventive resin restorations, and Class I, Class III, and Class V caries removal may be completed using erbium lasers with minimal to no local anesthesia using this technique. When caries are deep, removing tooth structure with a high-speed or slow-speed dental handpiece with no local anesthetic or patient discomfort may also be performed with this technique. Low-level laser analgesia is technique sensitive (see Chapter 15).

Erbium Laser Caries Removal

Class II preparations are more time-consuming when using lasers; however, use of the correct parameters will allow the procedure to be performed successfully without patient discomfort. In general, preparing the tooth for a stainless steel or other type of crown is possible but not usually practical because this takes so long. Every erbium laser has different pulse durations, Hz/mJ settings, tip diameters (producing different spot sizes) of different materials, and different delivery rates of air and water through the handpiece. Therefore, it is impossible to include suggested settings for each procedure. However, the following generalities apply to all erbium laser operative dentistry procedures, based on how the erbium wavelength is absorbed by the target tissue, the spot size (see Chapter 2), and the erbium laser’s preferential absorption by water:

1. The higher the water content of the tissue, the more easily the erbium lasers will cut the tissue. Therefore, extremely decayed tissue (higher water content) will cut much more easily—and require less power—than slightly decayed tissue.

2. Healthy enamel (lower water content) will be more difficult to cut than any other hard tissue and therefore will require more power than any other tissue.

3. Erbium lasers are absorbed by the water in hydroxyapatite. In fluoridated areas the occlusal surfaces of teeth are usually composed of fluoroapatite, not hydroxyapatite. Because erbium lasers are not well absorbed by fluoroapatite, it may be difficult to begin a preparation for Class I or Class II decay on a permanent lower molar with many pits and fissures of fluoroapatite. For these procedures, treatment should begin with a fissurotomy bur, which can strip off the outer layer of fluoroapatite, leaving the hydroxyapatite exposed. Fissurotomy burs typically can be used on pits and fissures without local anesthetic, because these burs are used only on the surface of the enamel, which has no innervation.

4. Proceeding deeper into the cavity preparation, moving from ablating enamel to ablating dentin, the clinician must adjust the settings from higher energy to lower energy for two reasons:

a. Because enamel is not innervated, but dentin is composed of dentinal tubules, which have nerve tissue, as the enamel is ablated to expose the dentinoenamel junction (DEJ), the settings must be decreased. Most erbium lasers have preset power levels, which are lower for dentin than enamel. As the laser ablates the decayed enamel, and the dentin becomes exposed, the nerve tissue within the exposed dentinal tubules may be affected by the air or water from the laser, which the patient will perceive as pain. By lowering parameters as the clinician nears the DEJ approaches, the patient may have no sensation at all.

b. When moving from a more calcified (healthy) tissue to a less calcified (higher water content) tissue, parameters must be lowered. Dentin has a higher water content than enamel, so the laser will ablate dentin more quickly than enamel, possibly cutting through the dentin too quickly and leading to excessive tooth structure removal.

5. Knowledge of spot size and power density allows selection of the proper sapphire or quartz tip for the procedure (see Chapter 2). As with selecting a #1 or a #6 round bur based on amount of decay, selection of the correct size of laser tip will affect procedural efficiency. Class V preparations are generally wide, yet shallow; therefore a large spot size is wanted for these preparations, with selection of a wide tip recommended. A small occlusal pit may be narrow buccolingually or mesiodistally but extend deep into the tooth. A small spot size would be more effective for this procedure, so a small-diameter laser tip would be appropriate. Other cavity preparations would require different size tips, based on the width and depth of the decay. Because an inverse relationship exists between power density and spot size, a change in tip diameter during the procedure would require a change in laser parameters.

6. When performing Class V preparations that extend subgingivally, it may be impossible to complete the procedure without performing an access gingivectomy. When changing from hard tissue treatment to soft tissue treatment, the water spray should be shut off. Use of the water spray when ablating soft tissue with an erbium laser will not allow for adequate hemostasis of the soft tissue. Once the soft tissue procedure is completed, the water spray should be turned on to complete the procedure. The power parameters must also be adjusted.

Figures 12-1 to 12-5 (pp. 206-207) show erbium laser removal of Class I to V caries. Figure 12-6 (p. 207) shows the result of conventional instrumentation using local anesthesia in a pediatric patient.

FIGURE 12-1 • A, Class I caries. B, Removal with erbium laser.

FIGURE 12-2 • A, Class II caries. Matrix band is placed on adjacent tooth to prevent accidental removal of its structure. B, Class II caries removal with erbium laser.

FIGURE 12-3 • Class III caries removal on permanent central incisors with erbium laser.

FIGURE 12-4 • A, Class V caries removal combined with access gingivectomy. Both procedures were completed with an erbium laser. B, Immediate postoperative view of restoration.

FIGURE 12-5 • A, Class IV erbium laser preparations on maxillary central incisors fractured due to trauma. B, Fractures restored.

FIGURE 12-6 • Lip bite in child resulting from use of local anesthetic. The ability to perform operative dentistry without injection of local anesthetic makes this a relic of twentieth-century dentistry.

Clinical TIP

Clinical Tip: The author suggests placing a metal matrix band on adjacent teeth when using the laser for Class II preparations to prevent accidental etching of the noncarious adjacent tooth (see Figure 12-2, A).

Soft Tissue Procedures

A wide array of soft tissue procedures may be performed with lasers in the pediatric dental office.²³^–²⁹ Erbium lasers may be used to accomplish many soft tissue procedures with little or no bleeding when used at lower energy settings than for hard tissue procedures, and without water spray. In some cases, however, a diode, CO₂, or Nd:YAG laser is better suited for the procedure. Patients with bleeding disorders (e.g., von Willebrand disease, hemophilia) or those receiving anticoagulants (e.g., aspirin, warfarin) will benefit from the superior hemostatic ability of these lasers.

Pediatric soft tissue laser procedures include the following: