The aim of the current study was to evaluate the proliferative effect of low-level laser therapy on long-term cryopreserved dental pulp stem cells (DPSCS) and stem cells from human exfoliated deciduous teeth (SHEDS). The DPSCS and SHEDS were divided into 2 main groups according to gallium aluminum arsenide (GaAIAs) diode laser irradiation densities as 5 J/cm2 and 7 J/cm2. Each main group was further divided into 4 groups according to laser irradiation periods as 0, 24, 48, 72 h groups. During the incubation periods, cells received laser irradiation in every 24 h according to their groups and were put into incubator after irradiation. Cell groups that were not subjected to laser irradiation were served as control groups. Viabilities of cells were determined via MTT assay at the end of all incubation periods, and data were statistically analyzed. Laser irradiation demonstrated significant effects on proliferation rate of DPSCs and SHEDs in comparison with control. Intragroup comparison data of DPSCS revealed that repetitive laser irradiation for long term (72 h) increased the cellular viability significantly in comparison with all other treatment groups; however, no significant differences were found when energy densities were compared within each time interval, except for 48 h group at which irradiation with 7 J/cm2 provided significantly higher cell viability rates of SHEDS. DPSCs showed significantly higher cellular viability than SHEDs only for the 7 J/cm2 energy density in 72 h. Longer term (72 h) repetitive laser irradiation with energy densities of 5 and 7 J/cm2 (wavelength of 980 nm) may be recommended to induce the proliferative effect on long-term cryopreserved DPSCS and SHEDS.
Keywords: Cryopreservation; LLLT; Proliferation; Stem cell; Viability.