635 nm Laser Photobiomodulation Boosts PDL Mesenchymal Cell Proliferation and Osteoblastic Differentiation

Alveolar bone defects following tooth extraction, particularly in severe periodontitis, present significant challenges for dental regeneration. Current standard-of-care often struggles to fully restore the complex periodontal ligament (PDL) and surrounding bone. Photobiomodulation therapy (PBMT) using specific laser wavelengths has emerged as a promising non-invasive approach to stimulate cellular activity, including proliferation and differentiation, which is crucial for tissue repair. This study investigates how different laser wavelengths impact PDL mesenchymal cells, aiming to identify optimal parameters for enhancing their osteogenic potential and addressing the regenerative gap in periodontal therapy.

This in vitro study cultured periodontal ligament (PDL) mesenchymal cells in osteogenic medium. Cells were divided into groups receiving photobiomodulation (PBM) by a 980 nm diode laser, a 635 nm diode laser, or simultaneous irradiation by both lasers. Each laser group had two subgroups: one-time irradiation on day 1, and two irradiations on days 1 and 3. A control group received no intervention. Cell proliferation was assessed using the MTT assay on days 1 and 3. Apoptosis was evaluated by DAPI staining on days 2 and 4. Osteoblastic differentiation was determined on day 14 via Alizarin red staining and real-time PCR for osteogenic genes: osteocalcin (OCN), osteopontin (OPN), and runt-related transcription factor 2 (RUNX2). Data were analyzed by one-way ANOVA.

Cell viability was highest in the 980 nm laser group with one-time irradiation and the 635 nm laser group with two irradiations on day 3. The 635 nm laser group, specifically with two irradiations, exhibited the lowest rate of apoptosis on day 4. This same 635 nm laser group also demonstrated the most favorable outcomes in Alizarin red staining, indicating superior mineralization. Furthermore, it showed the highest expression of all three osteogenic genes: OCN, OPN, and RUNX2 (P < 0.05 for all). These findings collectively suggest a superior osteogenic effect from the 635 nm laser. > PBM by the 635 nm laser, particularly with two irradiations, yielded the most promising results for both proliferation of PDL mesenchymal cells and their differentiation into osteoblasts.