- Blood clot → granulation tissue (days 0–7): The fibrin clot stabilizes the space. Neutrophils give way to macrophages, which clear debris and release VEGF, TGF-β, PDGF. Capillaries sprout from the socket walls; fibroblasts migrate in.
- Provisional matrix (week 3-4): Fibroblasts lay type-I collagen and fibronectin, forming a vascular connective tissue. Matrix turnover is driven by MMP-1/8/13 and MMP-2/9, with macrophage phagocytosis of degraded matrix.
- Distance osteogenesis from socket walls (week 4–6): Mesenchymal progenitors at the host bony walls differentiate to osteoblasts (Runx2/Osx↑). Bone forms centripetally—not on a graft—by intramembranous, appositional deposition of osteoid on advancing fronts.
- Primary mineralization of woven bone: Osteoblasts secrete osteoid; TNAP raises the Pi/PPi ratio, and matrix vesicles nucleate apatite. Calcospherites coalesce, giving irregular woven trabeculae with wide osteoid seams and rich vascular marrow between them.
- Secondary mineralization & early remodeling (after ~5–8 weeks): Crystals thicken/mature; some remodeling units begin, converting woven to lamellar bone
- Ridge modeling (parallel process of bone loss): Bundle bone at the crests is resorbed by osteoclasts (loss of periodontal ligament signaling), which contributes to the typical horizontal/vertical ridge contraction while the socket interior fills with new bone.
