M13- plaque

Question 1

what is plaque?

Answer 1

the general term for the microbial community found on the tooth surface

Question 2

Describe plaque.

Answer 2

– Associated with hard & soft-tissue surfaces
– Contains living & dead bacteria
– Includes extra-cellular bacterial products
– Involves host compounds

Question 3

what is plaque essentially?

Answer 3

biofilm

Question 4

what is a biofilm?

Answer 4

Name given to microbial communities attached to a surface “complex aggregation of bacteria”

Question 5

what are the properties of a typical biofilm?

Answer 5

– spatially organized in a 3 dimensional structure
– bacterial cells enclosed in extra-cellular matrix
– increases habitat range of individual bacteria

Question 6

How much bacteria exists as biofilms?

Answer 6

65% of human infections

Question 7

what is the organic matrix of dental plaque?

Answer 7

glycocalyx or extracellular polymeric substances

Question 8

How much space does the extracellular polymeric substance take up of dental plaque volume?

Answer 8

30%

Question 9

what is the acquired pellicle?

Answer 9

the layer of material acquired by a cleaned tooth

Question 10

what are the features of the acquired pellicle?

Answer 10

– < 1μms thick
– Mucins, salivary glycoproteins, minerals & immunoglobins
– Occurs in seconds (90-120 minutes for maximum thickness)
– Reaches a peak after which composition & form can still change
– Different Pellicles form on different oral surfaces
• (Enamel, Cementum, Oral Mucosa)
– Can be removed by vigorous brushing with an abrasive dentifrice

Question 11

what does bacteria attach to?

Answer 11

Bacteria do not attach/adhere directly to the enamel they attach to the pellicle.

Question 12

what type of reaction is the initial attachment?

Answer 12

reversible and non-specific interaction

Question 13

Describe long range and short range bonding after contact.

Answer 13

• Long range (weak) - 100nm /Van Der Waal’s forces / electrostatic forces
• short range (strong) - <2nm /hydrogen bonding

Question 14

what charge do most salivary glycoproteins have and what is the reason for this?

Answer 14

• negative charged

- sialic acid groups present

Question 15

what forms between enamel and bacterial cell wall?

Answer 15

calcium bridge ( acquired pellicle )

Question 16

how does the calicium bridge form?

Answer 16

• enamel -weak negative charge so positive calico ions stick to the pockets of weak negative charge
• calcium supersaturated

Question 17

Describe the cell wall component of lipoteichoic acid and what it binds to.

Answer 17

– Gram +ve Cell wall
– amphipathic molecules
– one end lipid & hydrophobic (in membrane)
– one end glycerol phosphate & hydrophilic (-ve charge)
– bind blood group substances found in the pellicle

Question 18

what effects adhesion of bacteria to pellicle?

Answer 18

• Ordered accumulation
– (Pioneer to Climax community)
• Frequency & relative affinity of each bacterium for the pellicle
• Attachment/adhesion, growth, and removal
• Changing environment
– aerobic-anaerobic
– pH, nutrients, ions, metabolic products
– New attachment sites, co-aggregation

Question 19

what type of reaction is bacterial adhesion?

Answer 19

specific receptor-mediated interactions

Question 20

what is considered the hallmark of transition to biofilm from pellicle?

Answer 20

bacterial extracellular polymeric substances - production normally associated with irreversible attachment

Question 21

what helps attachment?

Answer 21

• adhesins

- fimbriae

Question 22

what type of response is polysaccharide production?

Answer 22

adaptive response

Question 23

what supports polysaccharide synthesis?

Answer 23

sucrose

Question 24

what enzyme breaks down glucose and produces longer chains of glucose?

Answer 24

glucosyltransferase

Question 25

what can be a major component of extracellular polymeric substances?

Answer 25

extracellular DNA

Question 26

what does DNAse do?

Answer 26

releases bacteria and inhibits biofilm formation

Question 27

what are adhesions?

Answer 27

– specific molecules on
bacterial surface
– recognize specific ligands or receptors on the tooth surface
– Often associated with fimbriae

Question 28

what is lectin?

Answer 28

– Sugar binding proteins
– Recognize carbohydrate groups & bind them
– Often associated with fimbriae

Question 29

What is fimbriae?

Answer 29

– “Hair-like” proteinacous appendages
– adhesion to enamel/pellicle
– adhesion to other bacteria
(which may contain adhesions)

Question 30

Give features of streptococcus crista.

Answer 30

• Fibrils tend to thinner & more flexible than fimbriae
• Characteristic tuft arrangement of fibrils
• Allow coadhesion

Question 31

Give overview of plaque development.

Answer 31

• Gram +ve & Gram -ve cocci within 2 hours
– Gram +ve : Oralis gp (mitis, oralis, sanguinis)
– Gram -ve : Neisseria, Haemophilus
• microcolonies form & spread across the tooth surface
– confluent biofilm develops
• 24 hours Streptococci predominate (95%)
– S. sanguinis most common

Question 32

what are the 3 stages of succession?

Answer 32

Stage 1;
Streptococcus spp. (32-82%) attach to acquired pellicle
Stage 2;
Streps joined/replaced e.g. Actinomyces spp.
Stage 3;
Gram -ve species e.g. Fusobacterium

Question 33

what changes are seen during the first week?

Answer 33

• Increased diversity of Gram +ve bacteria
– Actinomyces naeslundii
– Actinomyces israelii
• Pioneer species reduce Eh (anaerobic)
– anaerobe species survive & multiply
• Actinomyces & anaerobes increase
– Streptococci decrease (as a proportion!)

Question 34

what are the two types of adhesion seen in dental plaque?

Answer 34

homotypic - cell to cell adhesion ( within same cell species )
heterotypic - cell to cell adhesion (different cells)

Question 35

what are the two structures in heterotypic cell-to-cell adhesion?

Answer 35

• corn cob complexes (strep sanguines on corynebacterium)

- test tube brush complexes (gram -ve bacilli on filamentous bacterium)

Question 36

Describe sub gingival plaque.

Answer 36

• Plaque formation – (supra/border)
• Inflammatory response
• Tissue swelling
• Deeper sulcus
– (more anaerobic)
• Inflammatory exudate – (rich in nutrients)
• More loosely structured microbiota develops