SCANNING ELECTRON-MICROSCOPY OF OTIC CAPSULE AND CALVARIAL BONE ABLATED BY A HOLMIUM-YAG LASER

Scanning electron microscopy (SEM) was performed on holmium-YAG laser ablated bone in order to study the surface morphology of the ablation crater, An otosurgical bone model of porcine otic capsule and calvaria l cortical bone was used. Otic capsule bone is dense and homogeneous w hereas cortical bone is porous. Both bone tissues were studied under f resh and dehydrated conditions to investigate the role of water in the ablation process. Laser irradiation time was varied from 5 to 60 s. L aser flux was 85 mJ pulse(-1) at 4-Hz pulse repetition rate. Globular spheroids of melted bone material were noted in both wet and dried spe cimens for both tissues. Several of these globules ruptured yielding a n SEM image which suggests a violent ejection process. SEMs of dry cor tical bone demonstrated the presence of fibres which reflect the selec tive removal of inorganic surface bone constituents with preservation of subsurface residual collagen fibres. The ablation crater walls in w et tissues appear rougher and possibly reflect a more violent ablation process due to water vaporization causing expulsion of bone material. In contrast, the crater walls in dry tissue appear smoother.