Effects of CO2 laser beam on cortical bone

Sixteen bone blocks from two freshly amputated legs were used to study the effect of CO2 laser on cortical bone. They were divided into two groups. In Group I, the blocks were treated with CO2 laser using 1 mm spot (focused mode). In Group II, they were treated with CO2 laser using 3 mm spot (defocused mode). Two other variables were investigated: the power and time of exposure. Three histologic zones were observed: a superficial zone with black particle deposits (carbonization), an intermediate zone with fibrillations and enlarged empty lacunae, and a deep zone with normal appearing bone. The bony changes in the first two zones combined were superficial in all specimens and did not exceed 200 microns. Increased energy, a focused beam, and time of exposure were all associated with increased matrix changes. CO2 laser can be applied to cortical bone in vitro with minimal residual thermal damage.