A preliminary comparison between the effects of red and infrared laser irradiation on viability and proliferation of SHED.

The aim of this preliminary study was to compare the effects of different energy densities from red and infrared low-level laser (LLL) on viability and proliferation of stem cells from human exfoliated deciduous teeth (SHED). SHED were irradiated with red laser (R) or infrared laser (IR) set with the following dosimetry: 1.2 J/cm2 (0.05 J), 2.5 J/cm2 (0.1 J), 5.0 J/cm2 (0.2 J), and 7.5 J/cm2 (0.3 J). Positive (C+) and negative (C-) control groups comprised non-irradiated cells. Data were analyzed by two-way ANOVA followed by Tukey's test (P < 0.05). At 24- and 48-h period, group R5.0 showed significantly higher cell viability rates than R1.2 and R2.5. At 48 h, R2.5 also revealed lower proliferation than R5.0. Comparing to the C+ group, R2.5 exhibited lower viability at 72 h, and proliferation at 24 and 48 h. Groups R1.2, IR1.2, and IR5.0 were less viable at 24 h, while R1.2, IR2.5, and IR5.0 revealed lower proliferative capacity at 48 h. Overall, our results showed that LLL can favor viability and proliferation of SHED, especially when cells receive red laser irradiation at 5.0 J/cm2. Therefore, according to this preliminary investigation, 5 J/cm2 applied by red LLL induced high rates of cell viability and proliferation, while the same irradiation dose using infrared laser led to negative effects. LLL irradiation with 1.2 and 2.5 J/cm2 was deleterious to metabolic activity and proliferation of SHED regardless of the type of laser. Further studies are necessary to gain in-depth knowledge about the effects of different wavelengths of LLL on SHED viability and proliferation.