Er:YAG laser applications in dentistry

Keywords:medical, fiber, optics,  Time:10-03-2016

Stimulated emission from Er3+ ions in crystals of yttrium, aluminum and garnet was presented in 1975, preparing the pathway to a new type of laser called Er:YAG.2 Its emitted wavelength of 2940 nm matches exactly the maximal absorption in water, being about 15 times higher than the absorption of a CO2 laser and 20,000 times that of a Nd:YAG laser.3 Also well absorbed in hydroxyapatite, this laser seems to have been made for effective removal of dentin and enamel with only minor side-effects such as thermal damage. The potential of Er:YAG lasers (ERL) for the ablation of hard tissue in dentistry was demonstrated already in 1989.4 Since its first introduction for dental use in 1992, Er:YAG lasers have been increasingly used in dental practice and are becoming more and more a comfortable method for caries removal for patients, as conventional cavity drilling may cause noise and pain. An increasing number of manufacturers have marketed Er:YAG lasers (ERL) since 1997, when this type of laser received FDA approval for caries removal and cavity preparation in the United States.

The first available system on the market, the Key Laser 1, was introduced by KaVoa in 1992 and was further developed in Key Laser 2 and Key Laser 3. Nowadays many manufacturers are marketing Er:YAG lasers with important differences in their technical specifications (Table). The available maximum pulse energies range from 300 mJ (DELightd), over 600 mJ (Key Laser 3), 700 mJ (Smart 2940De), up to 1000 mJ (Fidelis Plus IIc and Opus Duob). The output power, which is the product of pulse energy times repetition rate, goes up to 12 W (Opus Duo) or even 15 W (Fidelis Plus II). For minimally invasive dentistry with an Er:YAG laser as an alternative to conventional mechanical drill a power of 10-12 W seems to be sufficient.5 Consequently, there seems to be no real need for the development of more powerful  Er:YAG  lasers, because  when speeding up treatment by increasing pulse energy and/or repetition rate, more side effects such as leaflets and cracks may appear, especially in enamel. Ablation is already sufficient at a power of around 6 W in dentin and a very fast ablation, especially in deeper dentin layers, is possible with a power of around 10 W. Recently, an increased effectiveness using the so- called very short pulse (VSP) is discussed, pretending that the typical debris cloud formation above the ablated surface negatively influences ablation speed by partially absorbing energy of the following laser pulses.