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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).

The physical and chemical properties of carbon films, about 0.5 mu thick, deposited at low temperature (40-200 degrees C) by a new physical vapour deposition technique are presented, in comparison with those of pyrolytic carbon normally used in biomedical devices. Several analytical techniques have revealed that the thin carbon films present structural properties similar to those of pyrolytic carbon. For example, similar chemical bondings of C atoms are observed in both samples. Moreover the data suggest the presence in thin C films of both tetrahedral and graphitic bondings, as in the turbostratic structure typical of pyrolytic carbon. These results confirm the similar biocompatibility properties of both types of materials already established by in vivo experiments.