Photobiomodulation therapy and Wnt/β-catenin signaling in periodontal ligament stem cells during orthodontic tooth movement: A hypothesis and literature review

Orthodontic treatment usually takes 18 to 36 months that can lead to time-dependent side effects (like caries and root resorption). Hence, there is growing interest in safely accelerating orthodontic tooth movement (OTM). Photobiomodulation therapy (PBMT) has been proposed as a non-invasive approach to accelerate OTM, but clinical findings are inconsistent. Discrepancies may be due to irradiation protocols (light source, wavelength, energy density, exposure time), the orthodontic stage at which PBMT is applied, and the appliance used. A common component across these settings is the periodontal ligament stem cell (PDLSC). PDLSCs are mechanosensitive progenitor cells that contribute to the stress-strain response underlying OTM, and canonical Wnt/β-catenin signaling is a key, but not the sole, regulator that balances OPG- and RANKL-mediated bone resorption against osteogenic bone formation; inflammatory mediators, non-coding RNAs, epigenetic mechanisms, and patient-related factors also regulate periodontal remodeling. In vitro studies indicate that PBMT affects PDLSC proliferation, osteogenic differentiation, and RANKL/OPG expression; only one preliminary study, in unloaded cells and at transcript level, suggests that it may upregulate Wnt/β-catenin and TGF-β pathway components. On this basis, we propose a hypothetical framework in which PBMT-related mitochondrial and redox signaling might intersect with force-induced Wnt activation, with each link graded by level of evidence. This framework is unconfirmed: no study has combined orthodontic-like loading, characterized PDLSCs, and multi-level assessment of Wnt/β-catenin signaling under PBMT, and faster movement should not be assumed advantageous without periodontal safety data. Mechanistic and in vivo studies, including inhibition experiments, are needed.