Photobiomodulation and the Wnt/β-catenin pathway in apexogenesis: Rationale and evidence gaps.

Apexogenesis is a vital pulp therapy that preserves vascularized pulp in immature teeth and relies on dental pulp stem cells (DPSCs) and stem cells from the apical papilla (SCAPs) for continued root growth and apical closure. Wnt/β-catenin signaling has an established role in odontoblast differentiation, reparative dentinogenesis, and root development, although normal root development requires regulated rather than simply increased Wnt activity. Photobiomodulation therapy (PBMT) is proposed to act through mitochondrial photoreception, and in vitro studies report increased expression of odontogenic/osteogenic markers and angiogenic factors (VEGF, TGF-β2) in DPSCs and SCAPs. Because these markers overlap with Wnt/β-catenin targets, a link between PBMT and this pathway has been hypothesized but not tested in these cells. This review addresses three questions: the role of Wnt/β-catenin signaling in root development and dentin repair; the mechanism that could link PBMT to this pathway; and the in vitro evidence for PBMT effects on DPSCs and SCAPs and its consistency. The evidence is heterogeneous and limited. Increased odontogenic/osteogenic differentiation was the most consistent finding. Reported effects on "proliferation" were inconsistent and were estimated mainly by MTT, a metabolic assay that does not measure cell division; no study used a clonogenic assay, and only one performed direct cell counts. No superior wavelength or fluence was identified. No study has examined PBMT-induced modulation of Wnt/β-catenin signaling in DPSCs or SCAPs, and the markers involved are not pathway-specific. Therapeutic benefit in apexogenesis therefore remains unproven; direct mechanistic studies, light-delivery studies through dentin, and animal models are priorities.