OE L22 Cellular Mechanisms of Periodontal Disease

Question 1

Compare gingivitis and periodontitis.

Answer 1

Gingivitis: acute inflammation of gingival tissue, temporary and reverisble

Periodontitis: initiated by bacterial colonisation, persistent and irreversible inflammation which causes both soft and hard tissue damage

Question 2

Describe the 7 steps of periodontitis intiation and progression.

Answer 2

1. Build up of bacterial plaque
2. Inflammation of the gingival margin
3. Inflammation persists causes recession of the gingival margin
4. Loss of periodontal attachment
5. Apical migration of bacteria
6. Resorption of supporting bone
7. Loss of function of periodontal tissues

Question 3

What are the mechanisms of periodontal destruction?

Answer 3

• Bacterial colonisation initiates the disease
• Host repsonse then plays a key role in soft and hard tissue damage

Bacteria alone is not fully responsible for tissue damage.

Question 4

What immune response is responsible for gingival inflammation?

Answer 4

Both innate and adaptive immunity.

Question 5

Describe the role of innate immunity in gingival inflammation.

Answer 5

Innate Immunity:

• Blood vessels in the submucosa and lamina propria provide nutrients and recruit immune cells when necessary
• Neutrophils recruited during bacterial colonisation to phagocytose bacteria and produce chemokines to recruit more immune cells e.g. macrophages
• Dendritic cells migrate antigen to drainage lymph nodes and initate adaptive immune response

Question 6

Describe the role of adaptive immunity in gingival inflammation.

Answer 6

Adaptive Immunity:

• Dendritic cells present antigen to T cells, T cells are activated
• Th2 cells activate B cells to become antibody producing cells
• Plasma B cells produce antibodies and neutralise bacterial toxins, guide macrophages and neutrophils to phagocytose
• Neutrophils produce antimicrobial peptides and other free radicals (ROS and NOS)

Question 7

What is the purpose of inflammtion?

Answer 7

Purpose is to eliminate the offending agent (pathogen).

Question 8

Describe the 4 overall mechanisms of soft tissue damage.

Answer 8

• Cytokines induce inflammation
• Enzymes destroy PDL and gingival fibres
• Angiogenesis
• Collagen deposition

Question 9

How do cytokines damage soft tissue?

Answer 9

• Pro-inflammatory cytokines promote inflammation. E.g. IL-8 recruits neutrophils which produce reactive O/N species which damage soft tissues. E.g. IL-18 induces endothelial cell apoptosis.
• Anti-inflammatory cytokines suppress inflmmation and maintain healthy gingival tissues.

Question 10

How do macrophages and neutrophils damage soft tissue?

Answer 10

Macrophages and neutrophils produce enzymes which destory the PDL and gingival fibres:

• Matrix metalloproteinases
• Elastase
• Collagenase
• Lysozyme

Question 11

How do macrophages damage soft tissue?

Answer 11

Macrophages can produce VEGF (vascular enodthelial growth facators). Causes angiogenesis (formation of new BVs).

• This destorys the PDL structure
• Recruits more inflammatory cells- chronic inflammation.

Question 12

How does collagen deposition damage soft tissue?

Answer 12

Fibroblasts cell activation means collagen is produced to replace damaged collagen.
Collagen made by activated macrophages is not properly structured, fibres are irregular.

Question 13

Bacteria induced inflammation disrupts the balance between osteoblast and osteoclast activity, how does this occur?

Answer 13

Macrophages present due to bacterial products and inflammatory cytokines become osteoclasts due to action of M-CSF and RANKL.
Osteoclast activity > osteoblast activity

Question 14

What is produced to arrest the positive cycle of cytokine production?

Answer 14

Immune system produces anti-inflammtory cytokines.

Question 15

What type of research is being conducted into periodontitis?

Answer 15

• Clinical studies: relationship of periodontitis with other dieases, GCF research
• Animal studies: transgenic and knockout gene models
• Molecular and cell biology studies