The efficiency of the ablation obtained with a picosecond-pulsed laser system minimizes material collateral damage because of the etching and plasma formation mechanism. It prevents the excessive generation of shock waves and promotes a considerable decrease of mechanical side effects. In this study, a Nd:YAG picosecond-pulsed Q-switched and mode-locked laser (Antares 76-s, Coherent, Palo Alto, CA) was used. Fifteen microcavities were prepared in the enamel, and nine microcavities were prepared in the dentin of three recently extracted human molars. The parameters for irradiating enamel followed a fixed frequency of 100 Hz and an average power level of 1.3 W; for dentin, the frequency was fixed in 15 Hz, and the average power level varied between 800, 700 and 600 mW. Enamel proved more capable to dissipate shock waves than dentin, since cracks originating from microcavities were more frequent in dentin. In conclusion, it seems that in order to keep defined edges, it is important to choose shorter irradiation periods when average power levels are kept high, which results in lower and best-localized total energy delivery.
Laser; Nd:YAG; Enamel; Dentin
