Dental Plaque and Biofilms (2)

Question 1

What is an example of an oral reservoir?

Answer 1

tongue

Question 2

What are the 6 stages of plaque formation?

Answer 2

1. Acquired Pellicle Formation
2. Transport of Microorganisms and Reversible Attachment
3. Pioneer Microbial Colonisers and Irreversible Attachment
4. Co-aggregation/Co-adhesion and Microbial Succession
5. Mature Biofilm Formation
6. Detachment From Surfaces

Question 3

What protein are absorbed onto the surface of teeth (enamel)?

Answer 3

salivary glycoproteins

e.g. salivary agglutinin glycoprotein for s. mutants

Question 4

What are the different substances which cover the crown region of the tooth and the root region of the tooth?

Answer 4

crown - saliva

root - gingival crevicular fluid

Question 5

How are microorganisms transported to the tooth surface?

Answer 5

passively through saliva

Question 6

What forces attract bacteria to the dental pellicle?

Answer 6

Van der Waals forces

Question 7

Are van der waals forces weak?

Answer 7

yes

Question 8

Why is the attachment of bacteria to teeth (stage 2) reversible?

Answer 8

As the attraction is weak this stage and is reversible

Question 9

Where are motile organisms usually found?

Answer 9

subgingival

Question 10

What is stage 3 of plaque formation?

Answer 10

Pioneer Microbial Colonisers and Irreversible Attachment

Question 11

How do the physiological interactions of bacteria to teeth become irreversible?

Answer 11

adhesin

Question 12

Does the tooth or bacteria have the receptor for adhesins?

Answer 12

tooth has receptor

bacteria has adhesins

Question 13

What stage and bacteria are show here?

Answer 13

Pioneer Microbial Colonisers and Irreversible Attachment

pioneering bacteria

Question 14

What is the pioneer microbial colonisers?

Answer 14

The initial colonisers constitute a highly selected part of the oral microflora

Question 15

What genus of bacteria are usually the pioneering colonisers?

Answer 15

cocci

usually streptococcus

Question 16

What group of streptococci appear first?

Answer 16

mitis group

Question 17

What are example of the Streptococcus mitis group?

Answer 17

S. sanguinis
S. oralis
S. mitis bioval 1

Question 18

What happens and forms when after the pioneering bacteria adhere to the dental pellicle?

Answer 18

Once attached, these pioneer microorganisms start to divide and form microcolonies

Question 19

What forms the ECM of the biofilm

Answer 19

They become embedded in bacterial extracellular slimes and polysaccharides together with additional layers of adsorbed salivary proteins and glycoproteins

Question 20

What is the stage which bacterial division is fastest?

Answer 20

The fastest rate of multiplication occurs during these early stages of plaque formation

(stage 3)

after the pioneering bacteria colonise

Question 21

What is stage 4 of plaque formation?

Answer 21

Co-aggregation/Co-adhesion and Microbial Succession

Question 22

What happens to the plaque microflora over time?

Answer 22

becomes more diverse

Question 23

What bacteria shift occurs when co-aggregation occurs during stage 4?

Answer 23

Shift away from streptococci to an increased proportion of Actinomyces and other G+ve bacilli

Question 24

What stage of plaque formation is shown here?

Answer 24

stage 4

Co-aggregation/Co-adhesion and Microbial Succession

Question 25

At what stage do secondary colonisers attach to primary colonisers?

Answer 25

stage 4 Co-aggregation/Co-adhesion and Microbial Succession

Question 26

How do secondary colonisers adhere/co-aggregate with primary colonisers?

Answer 26

by intra- and inter-genetic Co-adhesion/Co-aggregation (lectin mediated)

Question 27

What is a type of co-aggregation?

Answer 27

lectin-mediated

Question 28

Why is adhesion and attachment of bacteria essential?

Answer 28

Essential for colonisation and to resist the washing effect of saliva and GCF

Question 29

What can adhesions and attachment occur between? (5)

Answer 29

Bacteria and the tooth surface Bacteria and the matrix Bacteria and the same species Bacteria and different species Bacteria and the pellicle

Question 30

What are mechanisms of adhesion and attachment?

Answer 30

Electrostatic attraction Hydrophobic interaction Surface enzymes and receptors Adhesion structures e.g. fimbriae

Question 31

What is microbial succession?

Answer 31

Due to a series of complex interactions e.g. reduction in redox potential (Eh), changes in pH, nutrient availability, development of food chains etc. the composition of the plaque microflora changes with time can be more favourable or unfavourable to bacteria in the colony

Question 32

What can cause growth rates of bacteria to slow down as the biofilm matures?

Answer 32

microbial succession, possible less nutrients in the middle so these cells reproduce slower makes them more resistant to bacteria

Question 33

Does the biofilm have 3D structure?

Answer 33

yes

Question 34

What are examples of extracellular polymers produced by bacteria?

Answer 34

soluble and insoluble glucans, fructans and heteropolymers add to the plaque matrix

Question 35

What host products contribute to the plaque matrix?

Answer 35

Salivary glycoprotein Dead cells Serum proteins

Question 36

What bacteria products contribute to the plaque matrix?

Answer 36

Polysaccharides

Question 37

What percent of supragingival plaque is the plaque matrix?

Answer 37

50%

Question 38

What percent of subgingival plaque is the plaque matrix?

Answer 38

Almost none found in deep subgingival plaque

Question 39

What is the role of the plaque matrix?

Answer 39

- Source of nutrients for other microorganisms - Chemical scaffold to maintain the shape of the biofilm and structural integrity of the biofilm - Tolerance to environmental factors e.g. desiccation - Biologically active and can retain water, nutrients and enzymes within the biofilm - Can help to restrict or exclude the penetration of other molecules e.g. antimicrobial agents

Question 40

What is stage 5 of plaque formation?

Answer 40

biofilm maturation

Question 41

What is the climax community of a biofilm?

Answer 41

all the bacteria working together common goods division of labour different species may be localised in 1 area as it is the best environment for it to reproduce etc

Question 42

What is stage 6 of plaque formation?

Answer 42

detachment from surface

Question 43

What can cause microorganisms to detach from surface?

Answer 43

Shear forces can remove microorganisms from the tooth surface However some microorganisms can detach themselves from the surface so that they can colonise elsewhere