CO2 Lasers have been available in medicine since the early 1970s and have been used in dentistry for more than 25 years. They are a 10,600 nm infrared wavelength, which is highly absorbed by water. Articulated arms or hollow waveguides are used to transmit CO2 laser beams and quartz optical fibers cannot be used. The CO2 gas is in a chamber with nitrogen and helium and the active medium is pumped with an electrical current. CO2 lasers are very efficient and exhibit excellent hemostasis. The traditional 10,600 nm CO2 lasers are currently for soft tissue uses only. They are continuous wave lasers that can be operated in gated wave modes, including what are termed "superpulsed". It is important to note that the superpulsed mode is not a free running pulsed mode. These superpulsed gated modes offer improved surgical control with less charring of tissue.
CO2 lasers are excellent tools for incising tissue for multiple purposes. Incisional and excisional biopsies, frenectomy, gingivectomy, pre prosthetic procedures, and the like are all achieved with excellent hemostasis. Sutures are rarely needed and the controlled thermal effects and sealing of nerve endings often makes for a very comfortable post-operative experience for the patient. This wavelength is also very effective for ablation and vaporization of leukoplakia and dysplasia.
A hard tissue capable CO2 laser became available recently. This laser's CO2 molecule uses an oxygen isotope that crates a beam at 9300 nm. This wavelength has a high absorption affinity for hydroxyapatite that allows for efficient vaporization of tooth structure. Its water absorption is much lower than Erbium lasers so hydroxyapatite absorption and vaporization predominates when cutting enamel, dentin, and bone. Hard tissue ablation with the 9300 nm CO2 laser is a photothermal event, not photoacoustic. As a result much higher temperatures are generated and much higher pulse rates are needed to cut.