A Comparative Analysis of Photobiomodulation-Mediated Biological Effects of Single Versus Double Irradiation on Dental Pulp Stem Cells: An In Vitro Study.

Objective: In recent years, fractionated irradiation protocols, rather than a simple plan of exposure, have been proposed as a more effective method in the field of tissue regeneration. Thus, this study aimed at a comparative analysis of single versus double irradiation of an 808-nm diode laser, in terms of dental pulp stem cells' (DPSCs) viability and proliferation in vitro . Methods: Subcultured DPSCs were either irradiated, or not (control group), with energy densities of 3, 7, and 12 J·cm -2 in a single- or double-session manner (24 h apart). On 0, 12, 24, 48, and 72 h postirradiation, cell viability and proliferation were evaluated through Trypan Blue and alamarBlue assays, respectively. Results: During the first 48 h postirradiation, the highest rates of DPSC proliferation were assigned to double irradiation at 3 or single exposure to 7 J⋅cm -2 , with no cytotoxic effects on cell viability. Inversely, single irradiation at 12, or a double session of exposure to 7 or 12 J⋅cm -2 , led to a significant descent in the rates of proliferation and cell viability. Conclusions: Within the limitations of this study, evidence suggests a positive impact on the biological responses of DPSCs following double session of exposure to lower energy densities as well as a single irradiation at a higher energy dosage.