Biological effects of low-level laser irradiation (LLLI) on stem cells from human exfoliated deciduous teeth (SHED)

To investigate the effects of low-level laser irradiation (LLLI) on viability/proliferation, migration, osteo/odontogenic differentiation, and in vitro biomineralization of stem cells from human exfoliated deciduous teeth (SHED).

SHED cultures were established by enzymatic dissociation from pulps of deciduous teeth. SHED were irradiated with a diode laser (InGaAsP; 940 nm; 0.2 W, continuous mode) at energy fluences 4, 8, and 16 J/cm² in the dark, while non-irradiated SHED served as control. Cell viability/proliferation was evaluated by MTT assay and cell mobilization by Transwell™ migration assay. Expression of osteo/odontogenesis-related genes (ALP, BMP-2, BGLAP, DSPP, MSX2, RUNX2) was assessed by real-time PCR, while in vitro biomineralization by Alizarin Red staining. Statistical analysis was performed by two-way ANOVA and Tukey's post hoc tests (*p < 0.05, **p < 0.01).

Statistically significant stimulation of cell viability/proliferation was observed at all energy fluences, reaching the highest effect for the 4 and 16 J/cm². Although the 8 J/cm² fluence showed the lowest stimulatory effect on cell viability/proliferation, it was the most effective in inducing SHED migration, upregulation of odontogenesis-related genes (DSPP, ALP, BMP-2) at specific time-points, and the in vitro biomineralization potential of SHED compared to the other two energy fluences.

LLLI proved beneficial in promoting SHED biological processes critical for pulp repair in deciduous teeth. Overall, the 8 J/cm² energy fluence showed the most beneficiary effects.

These results provide insights on a narrow "therapeutic window" of LLLI application in vital pulp therapies of deciduous teeth, paving the way for the establishment of effective clinical protocols.