| Laser ablation of tissues for surgical purposes has been under investigation for decades. Hard biological tissues, such as bone, possess an inherent molecular complexity that lead to a broad absorption spectrum, and current lasers are inefficient and cause thermal damage that delays healing. Recently, amplified femtosecond laser systems have demonstrated ablation of materials with little thermal damage. The goal of this thesis was to better characterize the damage in bone following femtosecond laser irradiation using both in vitro and in vivo models as well as evaluating the healing outcomes in order to determine if a fs laser system has the potential to be used in a surgical operating room. Using calcified bone samples we determined that the ablation rates of a fs laser system would be at best comparable to current mechanical instruments. We were the first to report on healing of wounds created by femtosecond lasers. Evaluation of the healing of mice calvaria demonstrated that femtosecond laser cutting displays unsurpassed precision when compared to mechanical instruments. Healing was similar among wounding techniques, albeit a trend in lesser bone formation was observed in the laser group. We accelerated the healing using bone morphogenetic protein-7 and showed that the laser cutting does not negatively influence wound closure when compared to mechanical instruments. Tissue damage was assessed in vitro using freshly excised mice calvaria with fluorescence-based tissue staining techniques to monitor the extracellular and intracellular enzymatic activity. We demonstrated that the fs laser produces a damage zone of only 14 +/- 5mum from the cut boundary, the smallest measure reported following laser ablation of viable tissues.;Further, we used transgenic VEGF-luc mice to compare inflammation and neovascularization in wounds created by mechanical instruments or fs laser and the results suggested that more trauma is created with mechanical instruments. Finally, we performed preliminary bone ablation experiments using two novel laser sources irradiating at 1560nm (fs range) and 3mum (ps range) and found evidence of photomechanical effects in bone. Our studies have shown that fs lasers could be used in a clinical setting although major technological advances are required before implementation is recommended. |
