| Popis: |
Three different laser systems were compared according to their applicability in dentistry: a Ho:YAG laser (lambda = 2, 12 microns, pulse duration = 250 microseconds and 4 microseconds, pulse energy up to 300 mJ), an Er:YAG laser (lambda = 2,94 microns, pulse duration = 60-100 microseconds, pulse energy up to 100 mJ) and an in dentistry so far unknown picosecond Nd:YLF laser (lambda = 1,053 microns, pulse duration = 30 ps, pulse energy up to 1 mJ). The morphological changes of the enamel due to laser radiation were studied using light and scanning electron microscopy. Possible enamel fractures were visualized with dye penetration tests. Thermally caused, about 3 mm long enamel fractures were only observed using the Ho:YAG laser. Smaller fractures, up to 300 microns, were generated with the Ho:YAG and the Er:YAG laser. The Nd:YLF laser produced well defined square cavities with a high precision. No enamel fractures could be observed. The dye penetration in the cavity walls was less than 20 microns. |
