ArF excimer laser irradiation of human dentin

Background and Objective: The use of excimer lasers for treatment of dental hard tissues has considerable potential because the combined characteristics of low wavelength and short pulse result in limited heat diffusion and, therefore, tissue ablation without the problems of collateral damage. To date, there are relatively few published studies concerning the effects of excimer laser irradiation on dental hard tissues. Thus the present study was conducted to examine the morphological changes in tooth dentin subsequent to ArF excimer laser irradiation. Study Design/Materials and Methods: The morphologic changes induced in normal, nondiseased human dentin following irradiation by an ArF excimer laser at fluences ranging from 1 to 4 J/cm(2) and the number of laser pulses ranging from 50 to 1,000 were evaluated by scanning electron microscopy. Results: Two modes of ablation, photochemical at low fluences and thermal at high fluences, were observed. A fluence of 1 J/cm(2) when combined with 50 or 100 pulses produced a uniform ablation of the dentin surface without signs of tissue melting. At fluences >1.5 J/cm(2), the thermal mode of ablation was more efficient at removing intertubular dentin than peritubular dentin. Further, when compared to the lower fluences, the higher settings produced a rougher ablation crater surface. Additionally, the higher fluences produced surface melting with each pulse and sealing of exposed dentinal tubules after irradiation with 100-300 laser pulses. Conclusions: The photochemical and thermal mechanisms of tooth dentin ablation were identified based on significant differences in tissue morphology following laser irradiation. The rates of tissue ablation and the observed morphologic changes indicate that the ArF excimer laser could be useful for caries removal and sealing of exposed dentinal tubules. (C) 1997 Wiley-Liss, Inc.