All four major wavelengths of dental lasers can be used as soft tissue surgical devices. The primary chromophores for diode and Nd:YAG lasers are pigments such as hemoglobin and melanin. Diode lasers when used surgically use the indirect heat generated by the pigment initiated on to the fiber tip. The erbium and CO2 lasers are mostly absorbed by water. All these lasers use photothermal effects to incise tissue whereby photons absorbed are converted to heat energy to do work. Diode and Nd:YAG lasers exhibit much deeper tissue penetration and thermal effects than the erbium lasers and the potential for tissue damage is greater. As such, proper training and an understanding of the biological effects of lasers are imperative for any provider wanting to pursue laser dentistry.
Thermal relaxation varies depending on the laser and parameters employed. Erbium lasers exhibit the greatest thermal relaxation due to their short free running pulses, low hertz, and minimal tissue penetration. Histological examination of erbium incised tissue exhibits almost no tissue damage or inflammatory response. Nd:YAG lasers also run on free running pulsed mode with pulse durations as short as 100 microseconds. However, due to their high absorption by pigment and deeper penetration they exhibit significantly greater heating of tissue and this factor needs to be respected by the practitioner. Diodes and CO2 lasers run in continuous or gated wave mode so they have much less thermal relaxation capabilities. Recent technological advances in so called "superpulsed modes" have helped improve the thermal parameters of these lasers, but it is important to note this is not a true free running pulsed mode.
Er:YAG and Er,Cr:YSGG lasers are also capable of cutting bone and have FDA clearance for osseous use. Multiple studies have shown erbium irradiated bone shows minimal thermal damage, necrosis, or inflammation.12 Clinically this relatively atraumatic cutting of bone results in rapid and comfortable healing observed by laser practitioners. Studies have shown bone cutting with Er:YAG laser to be superior to bur cuts. Er:YAG ablated bone shows no smear layer and no necrotic osteocytes adjacent to the cut.26 Another interesting phenomenon is that Erbium lasers have a local photobiomodulation effect accelerating osteogenesis.27 Erbium lasers have been shown to effectively decontaminate implant surface without damaging titanium and are useful in treating peri-implantitis.22
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