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ePaper created 2017-11-24, 11:00:53 | version 1.38.0
| research photodamage of pulpa cells Occurance of black spots in DPSC cells Occurance of black spots in CHO cells mW Total of irradiated cells Cells with spots mW Total of irradiated cells Cells with spots 16 18 20 26 10 10 69 72 0 0 1 21 16 18 20 26 Table 1 10 10 69 72 0 0 0 11 Table 2 Results The pulse-stretching unit was adjusted in a way that allowed for each laser wavelength a pulse du- ration of 700 fs ± 50 fs in the focus. Single DPSC cells were scanned 10 x and the effect compared to the non-irradiated surrounding cells was deter- Figs. 3a–f: Verification of the laser-induced formation of ROS. Fig. 3a Fig. 3b Fig. 3c Fig. 3d Fig. 3e Fig. 3f 12 roots 4 2017 mined. In addition, comparative experiments were accomplished using CHO cells. Cells or cell clusters were selected which were widely spaced in order to inhibit any intercellular communication as far as possible. During scanning, the transmission signal was detected and displayed as a picture on the monitor. A total of 325 cells was subjected to mor- phological examinations as well as a life-/dead- test, 50 cells underwent ROS examination. The re- sults were compared to earlier findings with a pulse width of 170 fs. Morphological changes So-called black spots resulted from specific irra- diation power perameters in locations with signifi- cant granulation in the cells. The laser power was gradually increased by 2 mW in order to measure the threshold value for the appearance of the first la- ser-induced morphological changes (Tab. 1). Under these conditions and with optimum focus, the min- imal power for the appearance of black spots was 20 mW for the DPSC cells and 22 mW for the CHO cells (Tab. 2). At a power of 26 mW, 30 % of the DPSC cells and only 15 % of the CHO cells presented these morphological changes. Cells with laser-induced black spots generally revealed morphological changes within the following five hours thus indi- cating a photodamage effect. Life-/Dead-Test First, the DPSC cells were irradiated with different power parameters (4 mW, 12 mW, 16 mW, 20 mW and 32 mW). The irradiated cells were marked, incubated after 5.5 hours with the Life-/Dead-Kit and after 1 hour of incubation tested concerning their fluores- cence behaviour. At an irradiation of 20 mW, 64 of 69 DPSC cells revealed a green cytoplasm fluoresence, while a red fluorescence was observed in 5 DPSC cells (Tab. 3). This corresponds to a damage of 7 %. When the power was raised to 26 mW, already 35 % were sub- jected to a lethal effect. However all of the CHO cells tolerated a power of 20 mW, with 15 % of them dying at 36 mW (Tab. 4 and Fig. 2). The comparison with ex- periments of shorter pulse widths, at which already