The mechanical tools currently used in orthopedic and dental surgery are imprecise and may cause heat damage. Ultrashort pulse lasers are a promising replacement, but their ablation efficiency must be improved. The goal of this thesis was to achieve high ablation efficiency, precision, and minimal collateral damage using an ultrafast laser on bovine hard tissue. This work used two types of lasers: a Ti:Sapphire laser (210 fs, 800 nm, 1 kHz) and a fiber laser (1 ps, 1035 nm, 100 kHz - 1 MHz).
This thesis begins with a review of the literature on laser-tissue interactions and the effect of certain laser parameters on the ablation process. The next section uses a Ti:Sapphire laser and bovine bone to explore the properties of laser-tissue interactions, including ablation threshold and incubation coefficient. Results showed that as the number of incident pulses goes up, ablation threshold goes down. The threshold range went from 1.08 ± 0.15 J/cm2 at 25 incident pulses to 0.73 ± 0.12 J/cm2 at 1000 pulses. The incubation coefficient, S, was calculated to be 0.90 ± 0.02.
The relationship between ablation depth and fluence, scanning speed, and number of successive passes was characterized as a first step towards preparing large-cavity with high removal efficiency using a Ti:Sapphire and fiber lasers. Depth increased with fluence and number of passes, but it decreased with scanning speed.
The influence of environmental conditions including air, compressed air flow, still water and flowing water on cavity ablation depth, and rate was investigated using a Ti:Sapphire laser with aim to enhance ablation efficiency. Findings showed that the deepest cavities and fastest ablation rates were achieved with compressed air flow. Air flow also resulted in the most precise cuts, the smoothest surfaces, and the absence of microcracks. This thesis also used a fiber laser to explore the effect of fluence and repetition rate on removal rate and ablation quality. Results indicated that ablation rate increases with fluence and pulse rate. When the repetition rate exceeded 600 kHz, the laser caused thermal and mechanical damage, indicated by the presence of amorphous carbon. The effect of environmental conditions and laser parameters such as repetition rate provide valuable insights into the ultrafast laser ablation mechanisms for medicine and biology field. / Thesis / Doctor of Philosophy (PhD)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/23903 |
| Date | January 2019 |
| Creators | Aljekhedab, Fahad |
| Contributors | Fang, Qiyin, Haugen, Harold, Wohl, Greg, Biomedical Engineering |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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