Preparation of dental hard tissue with picosecond laser pulses

The aim of this study was to investigate the suitability of picosecond lasers for hard-tissue preparation. Using scanning electron microscopy (SEM) and histological studies, the quality of ablation was examined. There was no thermal or mechanical damage observed. The ablation rates of enamel, dentine and carious enamel and the temperature rise during tissue removal were measured. Using a fast silicon photodiode, the lifetime of the plasma was determined to be 11±3 ns (Nd-YLF, 1.25 mJ pulse−1, pulse duration 30 ps). In order to achieve a better understanding of the ablation process, plasma parameters such as electron density [(5±3)×1017 cm−3] and excitation temperature (4500±2000 ℐg, Nd-YLF, 0.3 mJ pulse−1) were obtained from emission spectra. By examining the line width of singly ionized calcium lines, a difference was found in the ablation of healthy or artificially demineralized enamel, thus allowing the selective removal of caries.