Pathogenesis of periodontal disease Flashcards
List the 5 stages of the inflammatory response
- Recognition: body recognizes pathogenic bacterial by-products
- Recruitment of the leukocytes; first neutrophils predominate, then macrophages, plasma cells, and then lymphocytes
- Removal of the agent. However, biofilm cannot be removed by the body’s immune system, thus the need for OH
- Regulation or control of the response- determines the extent of inflammatory response; however, release of substances such as cytokines, interleukins 1, 6 and tumor necrosis alpha results in the destruction of the periodontium
- Resolution- repair cannot occur if the agent is still present
Describe the histo-pathological changes to the periodontium in the stage:
Healthy gingiva
- No plaque
- Shallow gingival sulcus
- JE firmly attached to root, sulcular epithelium and connective tissue (CT)
- Some gingival crevicular fluid (GCF)
Describe the histo-pathological changes to the periodontium in the stage:
Initial lesion
- Bacteria/ plaque is at the gingival margin/ supraginigval
- Bacteria and by-products initiate host response by challenging cells of JE (between 2-4 days)
- In sulcus, polymorphonuclear leukocytes (PMNs) phagocytose bacteria
- PMNs are in the connective tissue
- Connective tissue is destroyed by cytokines (IL-1b, IL-6, TNFα)
- Collagen is lost around blood vessels
Describe the histo-pathological changes to the periodontium in the stage:
Early lesion
- At 4-7 days, plaque biofilm extends more apically
- Bacterial products infiltrate connective tissue, causing increased destruction of connective tissue by PMNs and cytokines
- Recruitment of macrophages causes increased release of cytokines, prostaglandins (PGE2) and matrix metalloproteinase (MMPs)
- Rete pegs develop in junctional epithelium (JE)
- More destruction of collagen at JE
- Fibre groups begin to be destroyed
- Production of new collagen decreases
- Evidence of bleeding at site
Describe the histo-pathological changes to the periodontium in the stage:
Established lesion
- Subgingival plaque biofilm phase
- Plaque biofilm disrupts the attachment of coronal aspect JE
- Bacteria stimulate epithelial cells to secrete cytokines, macrophages, and lymphocytes
- Connective tissue infiltrated by macrophages and lymphocytes
- No pocket formation, loss of attachment, or bone loss
- Host response may or may not overcome the challenge
Describe the histo-pathological changes to the periodontium in the stage:
Advanced lesion
- Plaque biofilm extends apically and laterally on root surface
- Neutrophils, macrophages, epithelial cells produce cytokines
- Macrophages produce high levels of cytokines, MMPs and PGE
- Destruction of connective tissue and periodontal ligament fibers and bone
- Chronic immune response (protecting host against systemic infection)
What is the histological reason for colour changes of gingiva?
Circulatory stagnation
What is the histological reason for smooth and shiny gingiva that pits upon pressure?
Oedema, atrophy of epithelium and degeneration of connective tissue
What is the histological reason for flacidity?
Destruction of gingival fibres and surrounding tissues
What is the reason for bleeding upon probing?
Increased vascularity accompanied with thinning and degeneration of epithelium
What is the reason for firm and pink gingiva?
Fibrosis of inner wall
What is the reason for pain upon probing?
Ulceration of inner wall
What are the immune cells involved in the periodontitis?
Neutrophils
Cytokines
Macrophages
Lymphocytes
Prostaglandins
MMPs
What is the role of neutrophils in periodontitis?
- Phagocytic cells which accumulate within 30-60 minutes
* Phagocytise the intruder and release lysosomal enzymes
What is the role of cytokines in periodontitis?
- Interleukin-1b, interleukin 6 and tumor necrosis factor α (TNF-α)
- Released by macrophages
- Induce adhesion molecules on walls of vascular endothelial cells to which neturophils, monocytes and lymphocytes adhere
- Assist in increasing chemotaxis for leukocytes and increased phagocytosis
What is the role of lymphocytes in periodontitis?
• Responsible for specificity, diversity, memory and self vs non-self discrimination
What is the role of prostaglandins in periodontitis?
- Number of biochemical mediator
* E series of PG are most important in periodontal bone destruction
What is the role of MMPs in periodontitis?
- Matrix MetalloProteinase
- Family of enzymes produced by body that work together to break down connective tissue
- Causes extensive destruction to collagen in periodontal tissues
What is the role of macrophages in periodontitis?
• Phagocytosis and antigen presentation
Discuss the mechanisms of bone loss via bacteria
• Plaque products induce differentiation of bone progenitor cells into osteoclasts and stimulate gingival cells to release mediators that do the same
• Inhibit osteoblasts
Direct effect through contact (E.g. LPS endotoxins producedfrom the periodontal pathogen A. actinomycetemcomitans stimulate bone resorption)
Discuss the mechanisms of bone loss via host cells
- Pro-inflammatory cytokines (signaling molecules) released by host cells stimulate bone resorption
- Macrophages produce cytokines, PGE2 and MMPs
- These mediators stimulate fibroblasts to secrete PGE2 and MMP
- PGE2 stimulates osteoclasts to resorb the crest of the alveolar bone
