28 samples of human enamel have been studied in order to measure fluoride absorption after treatment with ultraviolet radiations. Samples treated with topical application only presented limited fluoride absorption in enamel surface (up to 0.5 microns deep). The absorption rate was higher, using an U.V. lamp. In samples treated with "excimer" laser, fluoride absorption was much higher in the surface layer and occurred also deeper (3 microns).