HARD-TISSUE LASER-ABLATION MECHANISMS

The aim of this work is the experimental and theoretical investigation of the influence of variable laser parameters (wavelength, fluence, p ulse repetition rate) and of the optical and thermophysical properties of bone tissue (absorption coefficient, tissue inhomogeneity) as well as of the sample thickness on ablation thresholds and ablation rate. Ablation and perforation experiments were conducted using a semiconduc tively pre-ionized transverse excitation atmospheric pressure (TEA) ca rbon dioxide (CO2) laser (10.6 mu m) and a sliding discharge TEA [hydr ogen fluoride (HF)] laser (2.9 mu m). The experimental data are discus sed with respect to the following ablation mechanisms: thermal melting and vaporization process, pressure oscillation of gases released by t he thermal decomposition of collagen and/or apatite, stresses due to t he expansion of superheated water.