Because of the nature of laser light (monochromatic, coherent and collimated) lasers can deliver a very precise burst of energy which is particularly useful in surgical applications.
Depending on the type of laser, the beam of light and energy can cut tissue better than the finest scalpel, it can coagulate blood vessels (like thickening an egg white) so that bleeding during surgery is reduced considerably. Alternatively it can shrink or shrivel tissue, or vaporize it completely.
Medical practitioners take advantage of the fact that different wavelengths of laser energy are absorbed differently in human tissue. This is because certain targets (chromophores) in the skin can absorb specific wavelengths of laser energy without any damage to the surrounding tissue. These include water, melanin (the pigment that gives your skin and hair its color), hemoglobin (the compound that makes blood red), as well as hydroxyapatite (which is found in teeth). In addition the inks in tattoos respond in a similar way to chromophores with different colors of ink absorbing different wavelengths of light energy.
In general shorter wavelengths of laser light energy are absorbed most readily in pigmented tissue such as melanin and hemoglobin whereas higher wavelengths are principally absorbed by water and hydroxyapatite.
By selectively targeting these chromophores the energy of the laser heats them to a point where they are vaporized. In the case of ink, melanin and hemoglobin this causes the pigment to break up into particles which are small enough for the body’s own immune system to remove
Because of this thermal effect on chromophores lasers are increasingly used for hair removal (melanin), tattoo removal (inks) and for the treatment of birthmarks such as Port Wine Stains (hemoglobin).
Longer wavelength lasers are increasingly being used for the removal of fine lines and wrinkles (skin resurfacing). Generally at longer wavelengths laser energy penetrates deeper into the skin. However beyond a certain wavelength the energy of the laser is instead absorbed by water in the skin. When this point is reached the water in the first live cell in the laser’s path will absorb the energy. This makes lasers using mediums such as Erbium ideal for skin resurfacing.
When the laser energy is absorbed by water, the water in the tissue is completely vaporized. This causes the skin treated to shrink and shrivel stimulating the production of new younger-looking firmer skin.
When used on teeth the Erbium laser heats the water in hard tissue causing this to turn to steam. When this happens micro-explosions take place which remove the hard tissue. Because the tissue in decayed teeth (cavities) contains a much higher water content than healthy tissue the laser has a selective effect. This means that when used in dentistry lasers can achieve the precision and effectiveness of conventional drills but without the pain, vibration and unpleasant noise since the laser does not have to come into contact with the tooth.
Whether used in dentistry or dermatology/ aesthetics, to prevent damage to healthy tissue the power of the laser, the diameter of the beam and the duration of the exposure are all controlled by your medical practitioner.