Dental Plaque

Question 1

What is the definition of dental plaque

Answer 1

This is a general term for the complex microbial community embedded in a matrix of salivary and bacterial origin (biofilm) and found on the tooth surface

Question 2

AY BAWS CAN I HABE DE NOTE PLZ

Answer 2

Bacteria gorwingin a biofilm are different to the same cells in a liquid phase/culture

Question 3

What are the general properties of a biofilm

Answer 3

• Protection from desiccation, host defences/predators and antibiotics
• Slow growth rate
• Spatial and environmental heterogeneity - leads to metabolic interactions
• Surface associated physical characteristics

Question 4

What are the micro-organisms in dental plaque more resistant to

Answer 4

They have a reduced sensitivity to chlorhexidine and antibiotics

Question 5

What are the benefits of being an organism in a biofilm

Answer 5

• Enzyme complementation/sharing
• Food chains
• Co-adhesion
• Cell-cell signalling
• Gene transfer
• Environmental modifications

Question 6

What are the disadvantages of being an organism in a biofilm

Answer 6

• Bacteriocin production
• H2O2 production
• Organic acid production/generation of inhibitory pH conditions
• Bacteriophage release
• Competition for essential nutrients
• Predation

Question 7

Where can you find dental plaque around and on a tooth

Answer 7

Fissure plaque - in between cusps
Approximate plaque- between teeth
Gingival crevice plaque - in the crevice between the enamel and gingiva - junctional epithelium?
Denture plaque

Question 8

What is the difference between plaque and calculus

Answer 8

Calculus is calcified plaque

Question 9

What is the first step of the development dental plaque

Answer 9

• the acquired enamel pellicle forms almost immediately, complete 2 hours after cleaning

Question 10

What is the acquired pellicle made up of

Answer 10

Composed of proteins, lipids and glycoproteins from bacteria, saliva and gingival crevicular fluid

Question 11

What can also be found in the acquired pellicle from bacteria and what do these act as

Answer 11

Glycosyl transferases
Glucans, Fructans
Bacterial cell fragments

These bacteria derived components act as receptors for bacterial adhesion

Question 12

What can also be found in the acquired pellicle from the host and what do these act as

Answer 12

Acidic, proline rich proteins - promotes adherence of bacteria

• Amylase
• Lysozymes
• Albumin
• Immunoglobins

Question 13

What is the second stage of the development of the dental plaque

Answer 13

The pioneering species of bacteria will adhere to the acquired pellicle

Question 14

How do bacteria attach to the pellicle/tooth surface

Answer 14

• Passive transport of bacteria to the tooth surface
• Attachment of bacteria to pellicle:
  Vt = Va + Vr
  Va = Van der Waals forces
  Vr = electrostatic repulsion between negatively charged bacterial cell and pellicle surface

Question 15

What is the name of the particles used by bacteria to attach to the tooth surface/pellicle

Answer 15

Adhesins

Question 16

Name some receptors in the pellicle/tooth surface that bacteria adhere to

Answer 16

Salivary agglutinin (streptococci)
Glycoproteins (streptococci)
Glucan (Mutans streps)
Proline rich proteins (Actinomyces Naeslundii)

Question 17

Name some adhesins that bacteria use to bind to the tooth surface/pellicle

Answer 17

Protein antigens (Streptococci)
Lipoteichoic acid (streptococci)
Glucan binding protein (mutans streps)
Fimbrae (Actinomyces Naeslundii)

Question 18

What is the third stage of the development dental plaque

Answer 18

Pioneering species multiply and form a confluent layer

Question 19

What can bacteria start to do in the third stage of the development of dental plaque

Answer 19

Ability to utilise salivary glycoproteins via glycosidases
Ability to cleave IgA via IgA proteases

Also able to use bacterial polysaccharides

Question 20

What is co-aggregation in the third stage of development of dental plaque

Answer 20

Cell-Cell interactions leading to distinctly different bacterial species becoming predetermined partners in forming plaque

Question 21

Give some examples of species that co-aggregate

Answer 21

Strep. sanguinis or S. mitis with Actinomyces spps, Corynebacterium matruchotii or propionibacterium acnes

Question 22

What is co-adherence

Answer 22

Term sometimes used for cell-cell adhesive interaction on a surface rather than in suspension

Question 23

What happens in the 4 stage of dental plaque development

Answer 23

Accumulated bacterial growth leads to:

• decreased oxygen tension
• Eventual growth of anaerobic bacteria
• Increased diversity

Question 24

What is the 5th stage of dental plaque development

Answer 24

Plaque maturity

Question 25

What are the main bacteria found on the in dental plaque during plaque maturity

Answer 25

Streptococci-15% Actinomyces Anaerobic rods and filaments increase

Question 26

What is accumulation of bacteria on the teeth a result of

Answer 26

A balance between adhesion, growth of bacteria and removal of bacteria via physical forces and plaque interactions/competitions

Question 27

Once the dental plaque has developed a microbial homeostasis what are the benefits to the bacteria

Answer 27

- Enhanced catabolism of endogenous nutrients. - Protection from stressful environments - Organisms within the community can persist and grow over a wider habitat range. - Organisms can display synergy in the recycling of nutrients. - Metabolic efficiency of the community is increased.

Question 28

How can a small amount of dental plaque benefit us

Answer 28

Can prevent pathogenic species form entering and becoming established in the mouth

Question 29

How do the bacteria in plaque exclude exogenous organisms

Answer 29

- Competition for adhesion receptor sites - Comepetition for nutrients and co factors - Production of inhibitory substances like acids and H2O2

Question 30

How does the host interact with the dental plaque

Answer 30

Immunity from lysozymes, lactoferrin and peroxidases interact with the plaque and inhibit its growth

Question 31

What does calculus consist of

Answer 31

Mineral deposits, protein and carbohydrates from host and bacteria

Question 32

Where is calculus usually found

Answer 32

Can be supra gingival esp. near salivary ducts or subgingivally in association with dental plaque

Question 33

What does the porosity of calculus cause

Answer 33

Cause retention of bacterial antigens and may be involved with bone resorption

Question 34

How common is calculus

Answer 34

More than 80% of adults have it and increases with age - difficult to remove

Question 35

Name some Gram positive cocci found in dental plaque

Answer 35

Streptococcus Staphylococcus Abiotrphia Peptostreptococcus

Question 36

Name some Gram negative cocci found in dental plaque

Answer 36

Neisseria | Veillonella

Question 37

Name some gram positive rods found in dental plaque

Answer 37

``` Actinomyces Eubacterium Corynebacterium Bifidobacterium Lactobacillus ```

Question 38

Name some gram negative rods found in dental plaque

Answer 38

``` Actinobacillus Campylobacter Capnocytophaga Porphyromonas Wolinella Treponema ```

Question 39

The stagnant sites in denture plaque build up what kind of bacteria

Answer 39

Streptococci and candida sp. - acidogenic | C. albicans