A Primer on Dental Lasers for Oral Healthcare Management

Laser technology is centered around light and its respective properties. Light passing through a prism demonstrates a color spectrum. The respective color has a wavelength, and the human eye is sensitive to the colors and visualizes images and objects according to the properties of light. This color spectrum relates to the electromagnetic spectrum, consisting of the range of frequencies of radiation and their respective wavelengths. Lasers used in dentistry extend from the ultraviolet portion of the spectrum through the visible portion and into the infrared regions. A dental laser emits invisible beams in the infrared range. However, dental lasers incorporate a visible light to act as an aiming beam, enabling the clinician to control the infrared beam and direct it to the respective target.

Each wavelength reacts precisely and specifically when contacting oral tissue and certain materials, such as composite, titanium, and ceramic. Wavelengths are absorbed based on their unique absorption characteristics and corresponding depth of penetration. Oral tissues contain chromophores, which are light-absorbing targets. Absorption is the primary determinant in predicting the tissue effect of any laser wavelength and is a function of wavelength, tissue composition, pigmentation, and water content. High absorption results in shallow penetration in tissue, while low absorption allows deeper penetration. (Visit compendiumlive.com/go/cced1860 to view "Table 1. Dental Lasers: Media, Wavelengths, Chromophores."^2,3)

When the wavelength is directed at the target, the following interactions may occur:

Reflection:Laser light is bounced off the surface of the target tissue without penetration or interaction.

Scattering: Individual molecules and atoms deflect the laser beam power into directions other than the intended direction.

Transmission:Laser light travels through the tissue unchanged.

Absorption: Atoms and molecules that make up the tissue convert the laser light into heat, chemical, and acoustic laser energy.

Absorption is the desired, effective interaction and is achieved with the correct wavelength, target chromophore, and settings. All other interactions are ineffective and can create adverse effects and/or safety issues.

Most dental lasers contain the following components: (1) active medium: gas, solid, or liquid that when stimulated emits photons of a specific wavelength; (2) energy source: external energy source that delivers exactly the right amount of energy to excite an atom of the active medium, enabling photon generation; (3) laser cavity: a containment device that enables the production of photons and contains the active medium and optical resonator.

The laser's delivery system movesthe amplified light through a channel and to a mirror to the target tissue. The delivery system may be an articulated arm, hollow wavelength (as in a carbon dioxide [CO₂] laser), or anoptical fiber such as a quartz flexible fiber, and have a quartz or sapphire tip.

Erbium and 9300-nm CO₂ lasers have an affinity for hydroxyapatite and water. Therefore, they can be used in restorative dentistry for caries removal and alterations to tooth structure in preparation for placement of restorative materials such as resins. The action of these types of lasers is insufficient for restorative preparations such as crown/veneer preparation. With the correct settings and appropriate patient selection, these lasers may be utilized for restoration preparations without local anesthesia, especially for deciduous teeth. This is a key advantage for a dental practice with regard to patient management, lessening pain and anxiety. In addition, diode lasers can be used to activate hydrogen peroxide gels for in-office tooth whitening procedures.

The erbium and 9300-nm CO₂ lasers also can have a positive effect on bone recontouring and calculus removal. Possible applications include bone removal over canine impactions, ridge splitting to increase the horizontal width for implant placement, and root preparation within a sulcus for periodontal attachment. A highly appealing characteristic of these lasers is the ability to execute removal of the smear layer. This helps provide a favorable enamel/dentin surface for bonding materials and/or allows for the potential reattachment of various soft-tissue components of the periodontium.

Diode, Nd:YAG, erbium, and 10,600-nm CO₂ lasers are effective for soft-tissue procedures because they are attracted to hemoglobin, pigment, and, to a certain degree, water content of cells. Diode and Nd:YAG lasers are effective with regard to coagulation and hemostasis due to hemoglobin and pigment being their respective chromophores. In general, the use of dental lasers can be effective for a wide range of procedures, including photobiomodulation, treatment of aphthous/herpetic ulcers, root desensitizing, amalgam tattoos, troughing, frenectomies, biopsies, gingival recontouring, implant uncovering, and gingival depigmentation.^4,5

Electrocautery devices utilize thermal energy and may create conduction in tissue up to 1500 microns as compared to dental lasers at 5 microns.⁶ Dental lasers can cut and coagulate gingiva with virtually no or minimal bleeding or collateral damage to healthy tissue. In selected superficial cases, topical anesthesia may be sufficient for a discomfort-free experience. Most dental laser tips have a spot size of <0.6 mm and, thus, enable surgical precision with minimal to no postoperative discomfort and a short healing time.

Management of inflammatory periodontal diseases using lasers may also incorporate other devices for procedures such as: demonstrating a bactericidal effect, removing a diseased sulcular lining, removing calculus, creating root detoxification with smear layer removal, decorticating bone, and promoting repair via selective wound healing. Soft-tissue lasers, such as diode, Nd:YAG, and 10,600-nm CO₂, are limited to decontamination, de-epithelization, degranulation, denaturing proteins, performing gingivectomies, and inhibiting epithelial migration. For diode and Nd:YAG lasers, to carry out all of the necessary steps for an all-encompassing periodontal protocol the clinician must incorporate the use of other devices such as ultrasonics for root preparation and bone decortication in addition to the laser. With erbium and 9300-nm CO₂ lasers, due to their affinity for hydroxyapatite and water, all steps, including smear layer removal, can be performed with the possible addition of an ultrasonic unit to enhance root decontamination.

With endosseous implants becoming increasingly used for replacement of missing teeth, an emphasis has been placed on the long-term management of implants. As the incidence of peri-implantitis rises, many clinicians are limited in their knowledge of how to manage this condition. Current procedures include degranulation of the inflamed tissues and, moreover, decontamination of the implant surface. Certain wavelengths, such as those possessed by diode and Nd:YAG lasers, can create an adverse thermal reaction in a titanium implant and undermine the bone-implant contact with eventual possible loss of the implant. Erbium and 9300-nm CO₂ wavelengths have demonstrated the ability to detoxify implant surfaces without adverse temperature increases and, thus, may assist in managing peri-implantitis.^7-9

Photodynamic therapy utilizes dental lasers absorbed by pigment (eg, diode and Nd:YAG). Dyes and hydrogen peroxide can be used as subgingival irrigants and placed in the sulcus. These laser wavelengths are attracted to the dye, disrupting the intracellular bacterial membranes. The light energy activates the dye, interacts with intracellular oxygen, and destroys the bacteria peroxidation and mitigates the resulting membrane damage.

Biostimulation involves the application of electromagnetic energy in the red and near infrared region to damaged or diseased tissue to enhance repair, induce (connective tissue and bone) regeneration, and render pain relief within those tissues. The noted action is the stimulation of the mitochondria increasing adenosine triphosphate via oxidative phosphorylation and modulation of reactive oxygen. The resulting rise in energy decreases inflammation and enhances wound healing.^10,11

The laser sources used for photobiomodulation are between 600 nm and 1500 nm. This laser action is applicable for postoperative wound healing, temporomandibular joint disorder (TMD) discomfort, paresthesia management, topical anesthesia, treatment of aphthous/herpetic lesions, and acceleration of orthodontic tooth movement.

Lasers provide not only an alternative to current dental procedures but also offer added benefits and solutions for treatment of a variety of oral health conditions. Wavelength selection for a given procedure must align with the respective absorption to the target to ensure effectiveness and avoid adverse events. Laser technology affords the practitioner procedures that reduce pain and anxiety with minimal postoperative issues and non-reliance on prescription analgesics. Dental lasers are safe to use, rendering non-ionizing radiation. However, because most dental lasers are class IV medical devices, clinicians must adhere to safety procedures, including wearing safety glasses and maintaining proper distances as dictated by wavelength guidelines. As with any new technology, clinicians and their team are obligated to receive appropriate training for the indications, device management, safety guidelines, and respective techniques for dental laser usage.

Samuel B. Low, DDS, MS, MEd
Associate Faculty Member, Pankey Institute, Key Biscayne, Florida; Professor Emeritus, University of Florida, College of Dentistry, Gainesville, Florida; Dr. Low has more than 30 years of private practice experience in periodontics, lasers, and implant placement.