ABLATION OF POLYMETHYLMETHACRYLATE BY HO-YAG, ND-YAG, AND ERB-YAG LASERS

Ho:YAG, Nd:YAG, and Erb:YAG laser ablation of Polymethyl-methacrylate (PMMA) was investigated under in vitro and simulated clinical conditio ns. Ablation rates were measured for all lasers and after ablation, ma croscopic and microscopic appearance of the ablation site was investig ated. The mean ablation rates of the Erb:YAG, Ho:YAG, and Nd:YAG laser increased from 8 mu m per pulse at 100 mJ to 44 mu m per pulse at 300 mJ from 100 mu m per pulse at 200 mJ to 222 mu m per pulse at 800 mJ and from 28 mu m per pulse at 100 mJ to 189 mu m per pulse at 800 mJ, respectively. Macroscopic investigation exhibited melting of bone ceme nt for the Ho:YAG and Nd:YAG lasers and pulse-to-pulse vaporization fo r the Erb:YAG laser. The width of thermal alteration, however, was com parable for all lasers used. Removal of cement from bone specimens und er simulated clinical conditions showed good detachment of cement when the fiber was used parallel; in case of perpendicular use, remainders of cement and carbonization of bone could be observed upon histologic al investigation. (C) 1993 Wiley-Liss, Inc.