Effects of PBM in different energy densities and irradiance on maintaining cell viability and proliferation of pulp fibroblasts from human primary teeth

This study aimed to compare the effects of photobiomodulation (PBM) in different energy densities and irradiances on maintaining cell viability, and proliferation of pulp fibroblasts from human primary teeth (HPF) were cultured in DMEM and used between the fourth and eighth passages. Then, HPF were irradiated with the following different energy densities: 1.25 J/cm² (a), 2.50 J/cm² (b), 3.75 J/cm² (c), 5.00 J/cm² (d), and 6.25 J/cm² (e); but varying either the time of irradiation (groups 1a-1e) or the output power (groups 2a-2e). Positive (groups 1f and 2f) and negative controls (groups 1g and 2g), respectively, comprised non-irradiated cells grown in regular nutritional conditions (10% fetal bovine serum [FBS]) and under nutritional deficit (1% FBS). Cell viability and proliferation were respectively assessed through MTT and crystal violet (CV) assays at 24, 48, and 72 h after irradiation. Statistical analysis was performed by two-way ANOVA, followed by Tukey test (P < 0.05). The negative controls showed significantly lower viability in relation to most of the corresponding subgroups, both for MTT and CV assays. For both assays, the intragroup comparison showed that the periods of 24 h exhibited lower viability than the periods of 48 and 72 h for most of the subgroups, except the negative controls with lower viability. The different irradiation protocols (equal energy densities applied with different irradiances) showed no statistically significant differences on cell viability and proliferation at the evaluated periods. The proposed PBM in different energy densities and irradiance did not affect the viability and proliferation of pulp fibroblasts from human primary teeth.