ULTRASHORT-PULSE LASERS FOR HARD-TISSUE ABLATION

To date, lasers have not succeeded in replating mechanical tools in ma ny hard tissue applications, Slow material removal rates and unaccepta ble collateral damage has prevented such a successful transition. Ultr ashort pulses (<10 ps) have been shown to generate little thermal or m echanical damage. Recent developments now enable such short-pulse/high -energy laser systems to operate at high pulse repetition rates (PRR's ), Using proper operating parameters, ultrashort pulse lasers (USPL's) could exceed the performance of conventional tissue processing tools and yield significant material volume removal while maintaining their minimal collateral damage advantages, As such, for the first time, USP L's offer real possibility for practical replacement of the air-turbin e dental drill or other mechanical means for cutting hard tissues, In this study, the subpicosecond interaction regime was investigated and compared to nanosecond ablation by using a Titanium:Sapphire Chirped P ulse Amplifier (CPA) system with 1.05-mu m pulses of variable duration , Both 350-fs and l-ns pulse regimes were studied. Ablation rates (AR' s), ablation efficiency, and surface characteristics revealed through electron micrographs were investigated, The study characterized the in teraction with a variety of hard tissue types including nail, midear b one, dentin, and enamel, With 350-fs pulses, tissue type comparison sh owed a remarkably similar pattern of ablation rate and surface charact eristics. Negligible collateral damage and highly efficient per-pulse ablation were observed in this pulse regime. These observations should be contrasted with the I-ns pulse ablation characteristics where stro ng dependence on tissue type was demonstrated and ablation efficiency was approximately an order of magnitude smaller. With efficient intera ction which minimizes collateral damage, and with both cost and size o f ultrashort pulse systems decreasing, the implications of this study are far-reaching for the efficient use of USPL's in several fields of medicine that currently apply traditional surgical methods.