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Alveolar bone (Description (It provides osseous attachment to the forming…

- - - - AKA alveolar crest
        
        Runs I I to the line b/w the CEJ of 2 I teeth
        
        1-2mm apical to CEJ radiographically
        
        Variation of crestal height
        
        low crest: crest of alveolar bone more apical to the CEJ
        
        If you have thin gingiva, the low crest will be more likely to have recession –> less bone support
        If you have thick gingiva, and low crestal height –> more likely to have pocket formation
        
        high crest: crest of alveolar bone closer to CEJ
        
        high crest has a higher chance of having biological width violated with caries or crown prep, why? inflammation near the margin of a prep can cause alveolar crest bone loss
        
        the height of the crest is not always 1-2mm
        
        biological width ="supracrestal tissue attachment" term= JE + Supracrestal CT fibers
        Dentogingival complex (DGC) = sulcus + JE + supracrestal fibres
- - - - Etiology not clear
      - Predisposing factors:
        
        Malposition
        
        Labial protrusion of root combined w thin bony plate
        
        Prominent root contour
      - Facial > Lingual; Anteriors > Posteriors, frequently bilateral
      - Occurs in 20% of teeth
- - - - Synthesized by osteoblasts as unmineralized Osteoid
      - mineral nucleation occurs as calcium and phosphate ions are laid down within collagen fibres
        Non collagenous proteins assist in the mineralization of matrix
      - 10% proteoglycans/glycoproteins, carbs/ lipids
        
        Osteopontin: binds to hydroxyapatite
        
        Bone Sialoprotein: Binds osteoblasts to ECM
        
        Osteocalcin: binds to hydroxyapatite
      - 90% Col I
    - - Hydroxyapatite crystals Ca5(PO4)3(OH) )single
  - - - Present in the bone marrow, endosteum and periosteum
      - Differentiation depends on osteoinductive factors: BMPs, IGF, PDGF, FGF
    - - May differentiate into bone lining cells that cover the surface of bone tissue or osteocytes
      - Lack the capacity for migration and proliferation
      - Responsible for formation of bone
      - Progenitors express Ihh and RUNX2 genes
    - - are sensitive to shear stress caused by the flow of fluid within the canaliculi as a result of mechanical stimuli and bone deformation
      - Translate mechanical signals into biochemical mediators for anabolic and catabolic events within bone
      - Have interconnecting dendrites (to other osteocytes and to bvs) in bone canaliculi
      - Participate in blood Ca2+ homeostasis
      - embedded in bone matrix lacunae
    - - Resorb bone by secreting acid and lytic enzymes
      - Originate from the fusions of many monocytes (multinucleated)
      - form Howship's lacunae
      - Differentiation is driven by M-CSF and RANK expression (which responds to RANKL from osteoblasts and stromal cells)