A comparative study of nanosecond and picosecond laser ablation in enamel:Morphological aspects

Objective: We have investigated and compared the main morphological feature s of human enamel tissue under Nd:YAG nanosecond and picosecond laser ablat ion. Background Data: The use of ultrashort laser pulses on teeth ablation is an alternative to avoid overheating and presents the advantage of minimi zing the volume of damaged material during laser ablation, Comparison of th e morphology obtained in laser ablation using nanosecond and picosecond las er pulses is a way to investigate the advantages of ultrashort laser pulses for ablation, Methods: Trains of pulses with picosecond duration from a Q- switched and mode-locked Nd:YAG laser and pulses with nanosecond duration f rom a Q-switched Nd:YAG laser, both operating at 15 Hz kept at the same ave rage power, were focused in human sound molars for 30 sec. Drilled holes wi th different morphological characteristics were observed using several lase r intensity regimes. Enamel surfaces were examined using a scanning electro n microscope (SEM) and their morphological characteristics compared, Result s: An interesting contrast between the morphology of the enamel when treate d with different level of laser power and pulse duration was observed. Pico second pulses promote a better-defined material removal with a minimum inte rmediate region, whereas nanosecond pulses at the equivalent average power level cause a large intermediate modified region between ablated and normal tissue, as well as a complete superficial modification of the existent ori ginal structure. Conclusion: Our results show an important correlation betw een the surface morphology and the pulse width of the lasers, suggesting ad vantages toward the use of ultrashort laser pulses in dentistry.