Dental Plaque and Biofilms (2) Flashcards
What is an example of an oral reservoir?
tongue
What are the 6 stages of plaque formation?
- Acquired Pellicle Formation
- Transport of Microorganisms and Reversible Attachment
- Pioneer Microbial Colonisers and Irreversible Attachment
- Co-aggregation/Co-adhesion and Microbial Succession
- Mature Biofilm Formation
- Detachment From Surfaces
What protein are absorbed onto the surface of teeth (enamel)?
salivary glycoproteins
e.g. salivary agglutinin glycoprotein for s. mutants
What are the different substances which cover the crown region of the tooth and the root region of the tooth?
crown - saliva
root - gingival crevicular fluid
How are microorganisms transported to the tooth surface?
passively through saliva
What forces attract bacteria to the dental pellicle?
Van der Waals forces
Are van der waals forces weak?
yes
Why is the attachment of bacteria to teeth (stage 2) reversible?
As the attraction is weak this stage and is reversible
Where are motile organisms usually found?
subgingival
What is stage 3 of plaque formation?
Pioneer Microbial Colonisers and Irreversible Attachment
How do the physiological interactions of bacteria to teeth become irreversible?
adhesin
Does the tooth or bacteria have the receptor for adhesins?
tooth has receptor
bacteria has adhesins
What stage and bacteria are show here?
Pioneer Microbial Colonisers and Irreversible Attachment
pioneering bacteria
What is the pioneer microbial colonisers?
The initial colonisers constitute a highly selected part of the oral microflora
What genus of bacteria are usually the pioneering colonisers?
cocci
usually streptococcus
What group of streptococci appear first?
mitis group
What are example of the Streptococcus mitis group?
S. sanguinis
S. oralis
S. mitis bioval 1
What happens and forms when after the pioneering bacteria adhere to the dental pellicle?
Once attached, these pioneer microorganisms start to divide and form microcolonies
What forms the ECM of the biofilm
They become embedded in bacterial extracellular slimes and polysaccharides together with additional layers of adsorbed salivary proteins and glycoproteins
What is the stage which bacterial division is fastest?
The fastest rate of multiplication occurs during these early stages of plaque formation
(stage 3)
after the pioneering bacteria colonise
What is stage 4 of plaque formation?
Co-aggregation/Co-adhesion and Microbial Succession
What happens to the plaque microflora over time?
becomes more diverse
What bacteria shift occurs when co-aggregation occurs during stage 4?
Shift away from streptococci to an increased proportion of Actinomyces and other G+ve bacilli
What stage of plaque formation is shown here?
stage 4
Co-aggregation/Co-adhesion and Microbial Succession
At what stage do secondary colonisers attach to primary colonisers?
stage 4
Co-aggregation/Co-adhesion and Microbial Succession
How do secondary colonisers adhere/co-aggregate with primary colonisers?
by intra- and inter-genetic Co-adhesion/Co-aggregation (lectin mediated)
What is a type of co-aggregation?
lectin-mediated
Why is adhesion and attachment of bacteria essential?
Essential for colonisation and to resist the washing effect of saliva and GCF
What can adhesions and attachment occur between? (5)
Bacteria and the tooth surface
Bacteria and the matrix
Bacteria and the same species
Bacteria and different species
Bacteria and the pellicle
What are mechanisms of adhesion and attachment?
Electrostatic attraction
Hydrophobic interaction
Surface enzymes and receptors
Adhesion structures e.g. fimbriae
What is microbial succession?
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
What can cause growth rates of bacteria to slow down as the biofilm matures?
microbial succession, possible less nutrients in the middle so these cells reproduce slower
makes them more resistant to bacteria
Does the biofilm have 3D structure?
yes
What are examples of extracellular polymers produced by bacteria?
soluble and insoluble glucans, fructans and heteropolymers
add to the plaque matrix
What host products contribute to the plaque matrix?
Salivary glycoprotein
Dead cells
Serum proteins
What bacteria products contribute to the plaque matrix?
Polysaccharides
What percent of supragingival plaque is the plaque matrix?
50%
What percent of subgingival plaque is the plaque matrix?
Almost none found in deep subgingival plaque
What is the role of the plaque matrix?
- 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
What is stage 5 of plaque formation?
biofilm maturation
What is the climax community of a biofilm?
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
What is stage 6 of plaque formation?
detachment from surface
What can cause microorganisms to detach from surface?
Shear forces can remove microorganisms from the tooth surface
However some microorganisms can detach themselves from the surface so that they can colonise elsewhere
