The periodontal ligament-periosteum axis: An underexplored pathway for alveolar bone adaptation.

The periodontal ligament (PDL) and periosteum are mechanosensitive tissues essential for alveolar bone maintenance, remodeling, and regeneration. Their functional interplay, particularly during orthodontic tooth movement, remains underexplored. This review introduces the novel concept of the PDL-periosteum axis as a biologically interactive unit coordinating site-specific alveolar adaptation and periodontal homeostasis. Both tissues share mechanosensitive and osteogenic pathways regulating progenitor recruitment, osteoblastic differentiation, and extracellular matrix remodeling. Through crosstalk with osteocytes, they form a multilevel mechanosensory network integrating internal and external forces across the alveolar complex. Functionally, the PDL transduces forces within the alveolar socket, whereas the periosteum responds to cortical strain by supplying progenitor cells and driving adaptive remodeling. Disruption of either component predisposes to complications, including ankylosis, root resorption, or impaired bone regeneration, whereas preservation of both enables orthodontically induced bone formation even in severe alveolar deficiency. The integrity of the PDL-periosteum axis critically determines clinical outcomes, from favorable healing to maladaptation such as dehiscence, fenestration, or fibrotic adhesions. Recognizing this axis provides a systems biology framework for improved diagnosis, treatment planning, and regenerative strategies, bridging mechanobiology with clinical practice.