Laser-induced hard tissue ablation by assisted with a liquid film on target tissue surface

The objective of this study was to investigate the influence of an applied water film on bone hard tissue ablation by pulse CO 2 laser. Fresh bovine shank bone in vitro used in the experiment were put on a PC-controlled motorized linear drive stage and moved repeatedly through focused beam of laser without and with a water film of 0.4 mm and 1 mm on target tissue. The wavelength of pulse CO 2 laser was 10.64 P m, pulse repetition rate was 60 Hz, the energy density was 18-84 J/cm 2 and the beam diameter of about 400 P m. The moving speed of stage was 12 mm/s, scanning times was 5. The surface morphology and microstructure of ablation grooves we re examined by stereomicros cope and scanning electron microscope (SEM) respectively. The geometry of the groove was measured with optical coherence tomography (OCT), and the thermal injury was examined by histology. It shows that water film on the target tissue surface plays an important role during the ablation process. A proper thickness of water film applied to target tissue surface could improve the regular of cut shape, smooth the cut surface, pro duce the same or even larger ablation rate and efficiency, and reduce the thermal injury around the groove by compared with dry ablation condition. Moreover, the addition of water could alter the microstructure of bone sample. Keywords: Laser Ablation, Biological Hard Tissue, Water-mediated ablation, CO