For some time now, the diode-pumped Er:YAG laser (Pantec Biosolutions AG) has been available. Due to its high repetition rate of up to 2 kHz, it shows an excellent cutting quality and efficiency in soft tissue. Now, due to the novel special pulse regime, significantly longer effective pulse duration and higher pulse energy of up to 1.5 J is available. The aim of the present study was to evaluate the ablation quality, efficiency and thermal side effects of the new pulse regime. For this purpose, in-vitro experiments were performed on slices of teeth and pig bones with varying laser irradiation parameters. The laser beam was coupled into a sapphire fiber and the fiber end was imaged onto an 800 µm spot on the sample. The sample was shifted with a computer-aided movement unit at different speeds during irradiation. A water spray with 6 ml/min was used for moistening. After irradiation, the resulted ablation quality was recorded under the light microscope and the ablation depth and width were measured. The ablation efficiency in super pulse mode is comparable on enamel and exceeds the values in dentin for standard pulse mode. The maximum ablation efficiency on bone is 0.20 mm3/J and is on average approx. 18,2% above the values achieved in standard operation. The ablation quality and the thermal injury achieved with the novel pulse regime is comparable to the results obtained with the standard operation of the diode-pumped Er:YAG laser. Overall, the tests show that the diode-pumped Er:YAG laser with the novel pulse regime and higher effective pulse energy allows larger spot size and with this more homogeneous ablation.
A novel diode pumped Tm:YAG laser (Pantec Biosolutions AG) with a more flexible temporal pulse regime is available. This study includes first experiments with model stones on the influence of the pulse regime on the fragmentation rate. For this purpose, ablation experiments were performed on rectangular model stones (BEGO, 40 mm x 10 mm x 5 mm). The laser beam was coupled into a 270 μm light guide and the distal fiber end was positioned in <50 μm to the stone surface. This was located in a basin filled with water, which was moved horizontally with the stone at constant velocity by a computer-controlled translation stage. The ablation rate and the ablation efficiency were determined by subsequent measurement of the depth and width of the resulting crater. The experiments were performed with varying parameters of the novel pulse regime and, for comparison, with standard laser settings. The experiments show significant differences in bubble dynamics and shape, depending on the temporal pulse regime. Lowest values for propulsion were measured for the standard pulse regime. The measured and calculated values for ablation depth, -rate and -efficiency are comparable for all investigated pulse regimes. Especially the ablation efficiency is quite high compared to values which were calculated from published data. In conclusion, these preliminary results show a high potential of the diode pumped Tm:YAG laser with novel laser driver for variable and high efficient lithotripsy. The wide range of available peak power should allow fragmentation as well dusting with the same laser system.
Flashlamp pumped Erbium lasers are successfully used clinical for soft and hard tissue ablation. Especially for soft tissue ablation the limited repetition rate is a disadvantage (bleeding; perforation instead of cutting). Now diode pumped solid state (DPSS) Er:YAG laser systems (Pantec Engineering AG) are available, with mean laser power up to 50 W and pulse repetition rate up to 2 kHz. The aim of this study is to investigate the potential of this laser system for increased and defined soft tissue coagulation/manipulation at various irradiation parameters, in particular at repetition rates exceeding 100 Hz. Firstly, an appropriate experimental set-up was realized with laser system, focusing unit, computer-controlled linear stage with sample holder and shutter unit to move the sample (fresh chicken breast) with a defined velocity while irradiation by various laser parameters. While irradiation the tissue effects were recorded by a video camera, adapted on a surgical microscope. After irradiation, the samples were analyzed by light microscopy. In addition, histological sections were prepared and microscopically analyzed. Mainly depending on the fluence, the thermal effect can be limited to coagulation without carbonization. In addition, tissue melting can be observed. The coagulation depth increases with increasing pulse repetition rate and decreasing movement velocity from about 30 µm to above 1 mm. In conclusion, the results of the in vitro studies show that the diode pumped, pulsed Er:YAG laser has the potential to provide one system both, for high efficient hard and soft tissue ablation as well as for soft tissue coagulation and fusion.
Er:YAG lasers (3μm) allow efficient bone ablation caused by the strong absorption in water. Unfortunately, there are only a few and comparable expensive fiber materials for this wavelength available which are suitable for high laser power. The bone ablation efficiency of the Tm:YAG laser is minor (2μm) but inexpensive silica fibers can be used. The aim of this study was to investigate the bone ablation, using novel diode pumped high power Er:YAG (laser power 40W) and Tm:YAG laser system (60W) and adaptive fiber delivery systems. Expected advantage of these lasers is the longer lifetime of the fibers because of the high repetition rate and low pulse energy compared to the flash lamp pumped laser systems. The bare fiber output ends of a sapphire fiber (Er:YAG laser) and of a silica fiber (Tm:YAG laser) were attached under water and a water filled container including the fixed sample (bovine bone slices) was moved by a computer controlled translation stage. In a second set-up we provided a focusing unit and appropriate water spray unit. The generated cut kerfs were analyzed by light microcopy and laser scanning microscopy. The results show that with the diode pumped Er:YAG laser and sapphire fiber a particular high efficient bone ablation (> 0.16mm2/J) is possible both with bare fiber under water and focusing unit with water spray. The higher power of the Tm:YAG laser also results in high ablation rates but causes enlarged thermal damages. In conclusion, this study demonstrates that efficient bone ablation is possible with both diode pumped laser systems. In terms of efficiency the Er:YAG laser is outstanding. The Tm:YAG laser also allows fast bone ablation, provided that the thermal impact is limited by effective cooling and high movement velocity of the laser spot, for example by using an automatic scanner.
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