High-Intensity Femtosecond Laser Ablation of Human Enamel and Dentin

Human enamel and dentin were ablated with a 66 fs laser at a wavelength of 800 nm and a repetition rate of 1 kHz. With 3D laser scanning microscope, surface roughness at the bottom and sidewalls of the irradiated enamel and dentin cavity was measured to be well below 100 μm, which satisfies the clinical needs for tooth preparation. Scanning electron microscopy revealed no microcracks or carbonization on the enamel. However, cracks, carbonization and a small amount of crystalline particles were observed on the dentin. During ablation, intrapulpal temperature rose to a maximum of 12.3 °C without cooling and rapidly decreased to 3.0 °C above ambient temperature following air cooling. At a laser fluence of 11 J/cm² and a scanning velocity of 1 mm/s, the ablation rates of enamel and dentin were measured to be 5.7 × 10^–3 mm³/s and 56.0 × 10^–3 mm³/s, respectively. Femtosecond lasers may therefore be useful tools for dental hard tissue ablation.