Effects of 635 nm Photobiomodulation on Human Gingival Fibroblast Proliferation: A Preliminary In Vitro Study

Objective: The aim of this study was to evaluate the effects of photobiomodulation (PBM) at 635 nm on human gingival fibroblast (HGF) behavior in an in vitro wound-healing model. Background: PBM has gained increasing interest in periodontal therapy due to its potential to modulate inflammation and stimulate regenerative processes. Despite promising applications, the most effective parameters for periodontal tissue remain unclear, particularly regarding wavelength, energy density, and irradiation frequency. Understanding cellular responses under controlled conditions is essential to define PBM’s therapeutic role in periodontal regeneration. Methods: HGFs were cultured in a wound-healing model and subjected to PBM using a 635 nm diode laser. Cell proliferation, migration, wound closure, and morphology were assessed at 24 and 48 h and compared with untreated controls. To distinguish proliferation from migration, wound closure was also evaluated in the presence of mitomycin C, and metabolic activity was measured by MTT [3-(4,5-dimethylthiazol-2-yl)−2,5-diphenyltetrazolium bromide] at 48 h. Results: PBM significantly accelerated defect closure at 24 h, with higher cell density along the wound margin and increased mitotic figures. By 48 h, wound closure percentages converged between groups. In the presence of mitomycin C, PBM did not significantly enhance migration, indicating that the early wound closure is primarily driven by proliferation. PBM-treated cultures also displayed a more uniform wound margin, suggesting moderated migratory activity. MTT assay confirmed increased metabolic activity in PBM-treated cells at 48 h. Conclusions: PBM at 635 nm promotes early enhancement of fibroblast growth and gap colonization in vitro, with effects most evident within the first 24 h. These findings suggest that PBM primarily stimulates cell growth rather than migration in the early phase of wound healing and support its potential as an adjunctive tool in gingival and soft tissue repair, particularly in contexts requiring a balance between cellular proliferation and migration.