Increased viability of odontoblast-like cells submitted to laser irradiation

Several studies have shown that the increase of cell metabolism depends upon the parameters of low level laser (LLL) used to irradiate the cells. Conversely, the ideal irradiation parameter to stimulate odontoblast-like cells remains unknown. Objectives: For this reason, this study aimed to evaluate the response of odontoblast-like cells (MDPC-23) submitted to distinct LLL irradiation dosages. Methods: The cell line (20,000 cells/cm²) was grown in complete culture medium (DMEM), and incubated at 37ºC, with 5% CO₂. After 24 hours, the DMEM was replaced by a new culture medium with two different concentrations of fetal bovine serum (FBS): 5% FBS (nutritional deficit) or 10% FBS. Three different energy doses (3J/cm², 7 J/cm² and 25 J/cm²) with fixed parameters (808±3 nm, 100 mW) were used to irradiate the cells, giving rise to the following experimental groups: G1: 3J/cm² + 5% FBS; G2: 3J/cm² + 10% FBS; G3: 7J/cm² + 5% FBS; G4: 7J/cm² + 10% FBS ; G5: 25J/cm² + 5% FBS; G6: 25J/cm² + 10% FBS. Besides, non-irradiated cells cultured under 5% or 10% FBS were used as control groups G7 and G8, respectively. The laser therapy was performed in 3 sequential irradiations with a 24-hour interval. A laser device (LASERTable) was specifically designed to provide uniform illumination of the wells. Cell viability (MTT Assay) was performed 3 hours after the last irradiation. Results: Cells cultured under 3J/cm² and 5% FBS showed a statistically significant (Mann-Whitney test, p≤0.05) increase on cell viability, compared to the other groups. Conclusions: According to the experimental conditions, it is possible to conclude that LLL irradiation at 3 J/cm² and under nutritional stress can stimulate odontoblast-like cells by increasing cell viability. The findings concerning this odontoblast-like cell lineage are relevant for further researches on lasers action over odontoblasts.

FAPESP – grant # 2007/50646-3; 06/58793-2; CNPq - grant # 301029/2007-5