Dental lasers have three main benefits:

1. Lasers serve as an adjunct to regular treatments – simplifying some procedures, saving time in others and enhancing outcomes in still others.
2. The laser replaces conventional therapies with equal or improved results.
3. Lasers offer new treatment options that heretofore were not available.

Dental lasers are a family of instruments that are named according to the principal chemical elements contained in the resonating chamber where the laser beam originates. The symbols of the chemical periodic table are used to describe each laser and, in some instances, a treatment of the principal element adds to the description. One example is a YAG laser, so named because of an yttrium, aluminum and garnet coating of the crystal.

The different dental lasers emit energy beams of unique wavelengths within the electromagnetic spectrum. Most lasers available have beam emissions in the invisible infrared portion, also known as thermal non-ionizing. There are two lasers that operate in the visible portion of the spectrum. The first, the helium-neon (HeNe) laser, is primarily used as a red aiming beam in conjunction with other lasers. The second, the argon laser, has a wavelength emission is in the blue-green range.

Laser-Tissue Interaction

The energy in the beams of laser light interact with target substances according to the individual wavelengths. The different wavelengths have varying degrees of relative absorption into the various components of hard and soft tissue. The body pigments of melanin and hemoglobin readily absorb the lasers in the lower end of the spectrum of laser wavelengths. From the middle of the spectrum and above, those wavelengths are readily absorbed in both water and hydroxyapatite. This results in rapidly vaporizing the high water content soft tissue and altering tooth enamel and dentin.

All wavelengths have essentially the same mechanism of tissue interaction. The absorption of energy from the laser beam results in a highly localized conversion to heat, causing disruption of the target tissue. This is called a photothermal reaction. The principal functions served are a wide and significant variety of surgical procedures, curing of dental resins, caries removal and cavity preparation, dentin and enamel modification, and enhanced bleaching of the dentition.

When delivered to the target tissue site, the laser beam can have four different interactions and effects. Generally, all of these interactions occur each time with each wavelength and each tissue type.

1. Reflection is the first interaction; laser energy may reflect off of a surface in a direct or diffuse fashion. This presents a safety concern when laser energy is directed toward unintended targets; appropriate wavelength-specific eye protection is mandatory for patients and all dental personnel.
2. Absorption is the second and the most beneficial tissue interaction. The treatment objective is accomplished with the photothermal effect.
3. Transmission of the laser beam is the third interaction; the energy travels directly through tissue, causing no effect.
4. Scattering is the fourth interaction; the tissue can cause the laser beam to spread out into a larger area. This is useful in photopolymerization of composite resins, but as the beam scatters, its power density eventually decreases to the point where it has no significant biologic effect.

Laser energy, with one exception of wavelength, is delivered through an optical glass fiber. These fibers provide a highly flexible way of conducting the beam onto the target tissue. Fibers are available in small diameters and are sterilizable. The fibers are used in contact with the tissue. The carbon dioxide laser cannot be delivered in a fiber; instead, a hollow waveguide is used, in a non-contact mode.

Laser Wavelengths and Characteristics

Characteristics of commonly used dental laser wavelengths are described below.

Argon
The argon laser (wavelengths of 488nm and 514nm) is well absorbed by pigments in tissues such as melanin and hemoglobin. The first absorption peak of 488nm is the same as the quinoines that catalyze dental resin polymerization. The curing time using an argon laser is markedly reduced and the physical properties of the resin are enhanced. Excellent hemostasis is also achieved with the argon laser. The argon laser uses a great deal of energy in producing the beam and cooling the laser cavity.

Diode
The diode laser (wavelengths of 820 and 830nm) is absorbed readily into pigmented tissues. The laser energy is generated from solid state components permitting smaller sized units with less maintenance.

Nd:YAG (Neodymium: Yttrium Aluminum Garnet)
The Nd:YAG laser (wavelength 1064nm) is the most commonly used wavelength in dentistry. It is available in a continuous wave and free-running pulsed modes. The latter delivers the laser energy in extremely short bursts, allowing the tissue to relax thermally for a long period of time. This can be more comfortable to the patient. The Nd:YAG wavelength is readily absorbed by pigmented tissues, with some absorbance by water.

Ho:YAG (Holmium: Yttrium Aluminum Garnet)
The Ho:YAG laser (wavelength 2120nm) has as its primary action absorption into water. Blanched tissues and cartilaginous or fibrotic sites respond readily. This laser can be delivered in a free-running pulsed mode.

Er:YAG (Erbium: Yttrium Aluminum Garnet)
The Er:YAG laser (wavelength 2940nm) is highly absorbed by both water and hydroxyapatite. Thus, cavity preparation in enamel and dentin and caries removal are possible, as well as hardening the enamel or dentin surface. It is also valuable for use in soft tissue surgery. This wavelength can be delivered through an optic fiber as well as a hollow waveguide. A water coolant must be used with the laser on tooth surfaces.

CO_{2 (Carbon Dioxide)
The CO2 laser (wavelength 10.6µm or 10,600nm) has very active absorption in water and a moderate amount in hydroxyapatite. This wavelength is used for rapid surgical procedures, but cannot be delivered by an optic fiber in contact. Since it is absorbed by tooth structure, cavity preparations and tooth surface hardening for caries resistance are possible.}

 

_{Patient Benefits}

_{Dental lasers offer a number of benefits to the patient. Postoperative comfort is a leading advantage over conventional dissecting types of surgical procedures. Insensitive tissue surfaces, the very seldom occurrence of postoperative swelling and the reduced need for pain medications are all notable. The fiber optic allows increased surgical precision.}

_{The action of the laser results in the elimination of microorganisms at the surgical site; treatment of periodontal disease is thus more successful. The absence of postoperative infections is a further advantage. Sterilization of root canals and success with pulpotomies have been demonstrated.}

_{The dental marketplace offers a variety of lasers from which to select an instrument for the procedures that are most commonly performed in the dental office. In many instances, flexibility of utilization is possible for most different laser types.}