Ablation depths and morphological changes in human enamel and dentin afterEr : YAG laser irradiation with or without water mist

Objective: This investigation was performed quantitatively to determine the ranges of ablation and to evaluate the morphological changes in human enam el and dentin irradiated by Er:YAG laser with or without water mist. Summar y Background Data: Recently, several infrared lasers have been introduced i n the dental clinic to remove carious dental hard tissues in anticipation o f replacing the high-speed dental drill, Among them, the Er:YAG laser has s hown the most promise for hard tissue ablation, Methods: An Er:YAG laser wa s used to ablate human dental hard tissues using a pulse energy that ranged from 100 to 400 mJ at a frequency of 2 Hz for 5 seconds. Ablation rates wi th or without water mist at different pulse energies were measured, and the morphological changes on enamel and dentin were also investigated by stere omicroscopy and scanning electron microscopy (SEM), Results: The relationsh ip between ablation depths and energies was almost linear at both enamel an d dentin samples. The irradiation with water mist reduced the ablation dept hs, but only minimally, when compared to those irradiated without water mis t, Morphological findings by SEM indicated that Er:YAG laser irradiation wi th water mist could produce the cavities without signs of thermal damage to the surrounding enamel and dentin, Conclusions: The results of this study suggest that addition of a fine water mist directed at the ablation sites d oes not greatly decrease the ablation, and does not cause any carbonization and melting in the surrounding dental hard tissues.