Nutritional stress enhances cell viability of odontoblast-like cells subjected to low level laser irradiation

In spite of knowing that cells under stress are biostimulated by low level laser (LLL) irradiation, the ideal condition of stress to different cell lines has not yet been established. Consequently, the aim of the present in vitro study was to evaluate the effects of a defined parameter of LLL irradiation applied on stressed odontoblast-like pulp cells (MDPC-23). The cells were seeded (12500 cells/cm2) in wells of 24-well plates using complete culture medium (DMEM) and incubated for 24 hours. Then, the DMEM was replaced by a new medium with low concentrations (nutritional stress condition) of fetal bovine serum (FBS) giving rise to the following experimental groups: G1: 2% FBS; G2: 5% FBS; and G3: 10% FBS. The cells were irradiated three times with LLL in specific parameters (808±3 nm, 100 mW, 1.5 J/cm2) every 24 hours. No irradiation was carried out in groups G4 (2% FBS-Control), G5 (5% FBS-Control), and G6 (10% FBS-Control). For all groups, the cell metabolism (MTT assay) and morphology (SEM) was evaluated. The experimental groups showed enhanced cell metabolism and normal cell morphology regardless of FBS concentration. A slight increase in the cell metabolism was observed only in group G2. It was concluded that cell nutritional stress caused by reducing the concentration of FBS to 5% is the most suitable method to assess the biostimulation of LLL irradiated MDPC-23 cells.FAPESP (07/50646-3, 08/08424-6, and 08/54785-0)CNPq (476137/2006, 301029/2007-5