Tissue ablation-rate measurements with a long-pulsed, fibre-deliverable 308 nm excimer laser

This ablation rate study has been carried out with a fibre-deliverable, 308 nm, XeCl laser, producing long pulses of 200 ns as opposed to the usual 10–20 ns. This in-depth study aimed to evaluate the ablation rates for this longer pulse length. The effects on the ablation depth of dentine, enamel, soft tissue and bone were investigated ex vivo. Radiant exposure, number of pulses, pulse repetition rate and spot size were independently varied. For all tissues, ablation depth per pulse was found to increase, initially, linearly with radiant exposure. For both dentine and soft tissue a saturation radiant exposure was determined; thereafter the ablation rate decreased. The depth per pulse increased linearly with repetition rate but decreased logarithmically with both number of pulses and spot size. The ablation depth due to a 200 ns pulse is comparable to that caused by a 10–20 ns pulse but has the advantage of fibre delivery.