The aetiology of periodontal diseases - aspects of host defence

Question 1

Role of saliva in defence of periodontal diseases

Answer 1

Contains IgA
Contains antibacterial substances 
-lactoferrin
-thiocynate
-hydrogen peroxide

Question 2

Role of epithelium

Answer 2

1. Surface epithelium shed together with any attached bacteria
2. Permeability barrier
3. JE may be more permeable than oral epithelium
4. Epithelium can stimulate inflammatory and immune response by releasing cytokines e.g. IL-1

Question 3

The inflammatory response

Answer 3

Crevicular fluid
Tissue damage
> blood flow
Oedema
Neutrophils, macrophages

Question 4

Crevicular fluid

Answer 4

Inflammatory exudate
Contains complement: C1-9
May contain antibodies which act as an ‘opsonin’ & aid phagocytosis
Contains clotting cascade and kininogens

Question 5

Complement C3a, C5a, C9

Answer 5

• C3a & C5a: vascular changes, stimulate histamine release, promote formation of leukotrienes and prostaglandins; attract phagocytes and aid phagocytosis
• C9: membrane attack complex, destroys micro-organisms

Question 6

Clotting cascade

Answer 6

Fibrin forms a barrier to spread of infection

-thrombin and Hageman factor promote the inflammatory response

Question 7

Kininogens

Answer 7

Converted to kinins by proteases

Bradykinin - similar to histamine, promotes inflammatory response

Question 8

What happens to crevicular fluid in the crevice

Answer 8

Becomes modified
Bacteria in plaque can metabolise some components
Complement, immunoglobulin and other components partly consumed and degraded in crevice
Up to 1ml fluid may be lost per day

Question 9

Functions of neutrophils

Answer 9

Production of NETS - neutrophil extracellular traps
Kill microbes by antimicrobial peptides
Neutrophils themselves die in the process

Question 10

Functions of macrophages

Answer 10

Phagocytosis
Antigen presentation - simulate immune response
Growth factors
-stimulation of fibroblasts and endothelial cells to promote healing
Cytokines and chemokines attract inflammatory cells and regulate inflammatory response
-IL-1 & TNF important

Question 11

The inflammatory response: neutrophils

Answer 11

Neutrophils cannot phagocytose - secrete enzymes and NETS
Kill bacteria and solublizes plaque
Washed out by crevicular fluid
Some neutrophils inhibited

Question 12

Evidence that neutrophils are important

Answer 12

Pxs with < neutrophils have > periodontal destruction e.g. cyclic neutropenia
Pxs with defective neutrophil function have > periodontal destruction e.g. Papillon Lefevre syndrome
Impaired neutrophil function may contribute to periodontitis in diabetes and Downs’ syndrome

Question 13

What are macrophages derived from?

Answer 13

Blood monocyte

+IFN-γ T cells

Question 14

The inflammatory response: macrophages

Answer 14

Stimulate immune response
Release cytokines
Phagocytose
Stimulate healing

Question 15

Humoral immunity

Answer 15

B cells

Production of antibody by plasma cells

Question 16

Cell mediated immunity

Answer 16

T cells

Immune regulation and cytotoxic T cell killing of virally infected and neoplastic cells

Question 17

What leads to IgA being secreted in saliva?

Answer 17

Bacteria swallowed and antigens recognised in gut MALT

Question 18

What does IgA secretion lead to?

Answer 18

Antigen penetrates epithelium
Carried to lymph nodes
Initiates immune response
Antibody secreted in plasma
Antibody enters crevice in crevicular fluid
Some antibody produced locally in tissues by plasma cells

Question 19

Role of antibody in defence

Answer 19

Bind to bacteria
-acts as opsonin
-activates neutrophil enzyme secretion
-prevents bacterial attachment
-activates complement
-directly inhibits bacterial metabolism
Bind to soluble factors
-neutralises toxins
-inhibits enzymes

Question 20

Chronic marginal gingivitis

Answer 20

Bleeding on probing

False pocketing

Question 21

What is the cause of the tissue damage and bone loss in periodontal disease?

Answer 21

Bacterial products

Host response

Question 22

Bacterial products

Answer 22

Endotoxins
-may damage epithelium, fibroblasts
Bacterial enzymes e.g. collagenase, hyaluronidase
-break down CT
LPS, capsular material, peptidoglycans, muramyl dipeptide, proteases
-may cause resorption

Question 23

Host products

Answer 23

Release of enzymes from neutrophils
Complement
Production on IL-1, IL-6 by macrophages
-stimulates bone resorption and epithelial proliferation
Inflammatory mediators
-prostaglandins, other cytokines, leukotrienes also stimulate bone resorption

Question 24

Summary of tissue destruction

Answer 24

Some caused by bacteria but effects are limited by host response
Some due to host response - so called bystander cell damage
-IL-1 may be particularly important
Inflammation results in disturbance of normal tissue turnover
Mostly periodontal disease is stable, with tissue damage = repair
Progression when balance altered by host response or bacterial factors