Crater Morphology and Thermal Injury of Bovine Shank Bone Ablated by Pulse CO2 Laser with Different Defocusing Conditions

To evaluate the zone of collateral thermal damage and crater morphology for evidence of defocus irradiation condition´s effect on the ablation of bovine shank bone with pulse CO₂ laser. Bovine shank bone was divided into two groups, each group was put on a PC-controlled motorized linear drive stage which was located on the pre- and post-focus plane with a beam spot size of about 510 mum respectively and moved repeatedly through the focused beam. The wavelength of pulse CO₂ laser was 10.64 mum, pulse repetition rate was 60 Hz. The moving speed of the stage was 20 mm/s, scan times was 6. the zone of thermal damage and crater morphology produced by pulse CO₂ laser ablation were examined by light microscopy following standard histological processing. The results demonstrate that defocus irradiation condition has an important effect on ablation crater profile, crater morphology and the zone of collateral thermal damage. By selecting proper radiant exposure and focusing the beam spot not above but slightly beneath the bone surface, narrower but deeper cut with minimum collateral thermal injury can be obtained.