Abstract
This experiment was performed to confirm the hypotheses that (a) LLLT had a biostimulative effect on all kinds of cells and that (b) there would be differences in the growth of cells irradiated by different types of pulsed laser. 360 samples were used in this study. The samples were randomly divided into 6 groups according to the pulse type: quasi continuous type (CW), pulse 1 (P1), pulse 7 (P7), pulse 9 (P9), pulse 15 (P15) and sham-irradiated control (Co) groups. Energy fluences of all experimental groups, P1, P7, P9, P15 and CW were 2.12, 2.12, 6.37, 57.32 and 31.85 mJ/cm2, respectively. All samples were each irradiated for 1 minute at 0, 12, 25, 36, 48 and 60 hours. Ten samples of each group were sacrificed at 0 and every 12 hours and then the optical density of all samples was measured with a spectrophotometer. Significant differences were seen amongst the groups depending on the pulse type with which they were irradiated. An increase in the number of cells was markedly stimulated with laser irradiation in P7 and P9 groups, and inhibited in CW, P1, and P15 groups, compared with the controls. It is, therefore, suggested that specific laser pulses could be recommended to have a biostimulative effect on specific tissue or cells, while the biostimulative effect is dose dependent.
