Methods: Human tooth sections were made using a Buhler diamond saw. The specimens were those extracted by orthodontic reasons and pooled in formaldehyde solution before the ethics committee was established. FEL generated at LEBRA, Nihon University, tunable from 2000 nm to 6000 nm, was used in this study. The detailed experimental conditions were as described in Sakae et al. (2005).
Results: With varying the FEL wavelength, difference in the optimum wavelength was confirmed between the enamel and dentin. The formed pit width and deepness were related to the wavelength and fluence. The formed pits and around them showed no traces of burnt.
Conclusions: The results obtained here cannot simply explained by the so-called photothermal and/or water-micro explosion. The pulse-mode difference between FEL and clinical used lasers might be a cause. It is needed a new explanation for FEL-dental hard tissues interaction, which may include the tissue texture and composition. The ultra-micro short pulsed laser may have ability for the further clinical use.