Alveolar Bone Loss

Alveolar Bone Loss

Discuss the patterns and pathogenesis of alveolar bone loss in periodontal disease.
Answer.

Pathogenesis of Alveolar Bone Loss in Periodontal Disease

• Bacterial plaque products induce the differentiation of bone progenitor cells into osteoclasts and stimulate gingival cells to release mediators that have the same effect.
• Plaque products and inflammatory mediators can also act directly on osteoblasts or their progenitors, inhibiting their action and reducing their numbers.
• Bacteria induce tissue destruction indirectly by activating host defense cells, which in turn produce and release mediators that stimulate the effectors of connective tissue breakdown.
• Components of microbial plaque have the capacity to induce the initial infiltration of inflammatory cells, including lymphocytes, macrophages and polymorphonuclear leukocytes (PMNs).
• Microbial components, especially lipopolysaccharide (LPS), have the capacity to activate macrophages to synthesize and secrete a wide array of molecules, including the cytokines, Interleukin-1(IL-l) and tumor necrosis factor-alpha (TNF-α), prostaglandins especially PGE2 and hydrolytic enzymes.
• Bacterial substances activate T lymphocytes and produce IL-1 and lymphotoxin (LT), a molecule having properties similar to TNF-α.

• These cytokines manifest potent proinflammatory and catabolic activities, and play key roles in periodontal tissue breakdown.
• Bacteria mediated; LPSs, lipoteichoic acids, peptidoglycan, capsular and surface-associated material, muramyl dipeptide, lipoprotein.
• Host mediated: Prostaglandins, leukotrienes, heparin, thrombin, bradykinin, cytokines, HA and IL-6, TNF, transforming growth factor-β, platelet-derived growth factor.
• Host factors released by inflammatory cells are capable of inducing bone resorption. These include host-produced prostaglandins and their precursors IL-lα and IL-1β and TNF-α.
• Bone destruction in periodontal disease is caused by local and systemic factors.
  • Local factors fall into the following groups:
    • Those that cause gingival inflammation.
    • Those that cause trauma from occlusion
    • Reduction in the height of alveolar bone is caused by extension of gingival inflammation, whereas trauma from occlusion causes bone loss lateral to the root surface.
  • Systemic Factors
    • When generalized tendency towards the bone resorption exists, bone loss initiated by the local factors magnified by the systemic conditions.
    • Osteoporosis is a physiological condition in postmenopausal women resulting in loss of bone mineral content and structural bone changes.
    • In certain generalized skeletal disturbances like hyperparathyroidism, leukemia and Langerhans cell histiocytosis, periodontal bone loss may occur by mechanisms that are totally unrelated to usual periodontal problem.