Purpose: The aim of this in vitro study was to measure the influence of heat diffusion and debris screening on the ablation efficiency of Er:YAG laser pulses in enamel, and to maximize cavity preparation speeds by using super short (50 µs) laser pulses.
Materials and Methods: Extracted human teeth were irradiated with Er:YAG laser pulses with fixed pulse energy of 450 mJ and variable pulse durations from 50 (super short pulse) to 1000 µs (very long pulse). The depth and diameter of the craters was measured as a function of pulse duration. The dynamics of ablation debris screening was measured by monitoring the transmission of He-Ne laser light during the formation of the ablation debris cloud.
Results: The analysis of the results show that the ablation efficiency increases by a factor of 5 when pulse durations are decreased from 1000 to 50 µs. The typical debris cloud formation time at 2 mm above the ablated surface was determined to be approximately 50 µs.
Conclusion: The study shows that optimal erbium dental laser pulses are of approximately 50 µs duration. At this duration, both the heat diffusion and debris screening effects are minimized, leading to very efficient laser "drilling". The laser ablation speeds under these conditions are larger than those achieved by classical mechanical burs.
Keywords: lasers, dental cavity preparation, Er:YAG laser irradiation, super short laser pulses, enamel