L4: Formation, structure and composition of dental plaque

Question 1

What does the host mechanism consists of?

Answer 1

immunity and innate host defences:
eg lysozyme (bacterial lysis), lactoferrin (iron sequestration), 
peroxidases (glycolysis inhibition).

Question 2

what are the 5 stages of the development of dental plaque?

Answer 2

1. acquird enamel pellicle
2. pioneering species
3. confluent layer (pioneering species multiply)
4. accumulated bacterial growth
5. plaque maturity

Question 3

What is the first stage of development of dental plaque?

Answer 3

Acquired enamel pellicle

Question 4

What is the pioneering species of bacteria?

Answer 4

The first layer of bacteria which will adhere to the acquired pellicle

Question 5

What do the host and bacteria derived components act as?

Answer 5

Receptors for bacterial adhesion

Question 6

Properties of pioneering species of bacteria:

Answer 6

Ability to utilize salivary glycoproteins via glycosidases.

Ability to cleave IgA via IgA proteases.

Bacterial micro-colonies

Extracellular bacterial slimes

Bacterial polysaccharides

Salivary proteins

Salivary glycoproteins

Question 7

what are the 4 pioneering species that colonize the tooth surface first (at the acquired enamel pellicle)?

Answer 7

streptococcus sanguinis
streptococcus oralis
srteptococcus mitis
actinomyces ssps.

Question 8

what are the 4 pioneering species that colonize the tooth surface first (at the acquired enamel pellicle)?

Answer 8

streptococcus sanguinis
streptococcus oralis
srteptococcus mitis
actinomyces ssps.

Question 9

how does the host prevent exogenous organisms from entering ad establishing themselves in the mouth?

Answer 9

1. competes for the same adhesion receptor sites
2. competes for nutrients and co-factors
3. prodices inhibitory substances i.e. acids

Question 10

what is co-aggregation?

Answer 10

Process by which cell-to-cell interactions lead to distinctly different bacterial species becoming predetermined ‘partners’ in forming plaque due to similar adhesins

Question 11

where does co-aggregation occur?

Answer 11

within the plaque matrix

Question 12

examples of co-aggregation

Answer 12

Strep. sanguinis or S. mitis with Actinomyces spps

Corynebacterium matruchotii or Propionibacterium acnes.

Fusobacterium nucleatum with streptococci, actinomyces or Prevotella melaninogenicus.

Eubacterium spps with Veillonella spp

Question 13

what happens during microbial homeostasis?

Answer 13

• Enhanced catabolism of endogenous nutrients
• Protection from stressful environments (maintenance of a favourable local environment during periodic unfavourable fluctuations)
• 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 14

what are the general properties of a biofilm? (4)

Answer 14

1) Provide protection from dessication, host-defences/predators, antimicrobials including antibiotics
2) Surface associated physical characteristics (PHENOTYPE) ie different surfaces would have different phenotype
3) Slow growth rate

4) Spatial and environmental heterogeneity
- alot of different types of bacteria with metabolic interactions

Question 15

What happens to the plaque matrix after an increase in number of bacteria and substances in the matrix?

Answer 15

The matrix becomes anaerobic

• decreased oxygen tension (Eh decreased)
• may lead to the eventual growth of anaerobic bacteria

Question 16

what shape forms when fusobacterium nucleatum coaggregates with other bacterial species?

Answer 16

corncob

Question 17

what is the bacterial function of dental plaque

Answer 17

Microbial homeostasis (the maintenance of a stable microflora in a variable environment)

Question 18

What is the host function of dental plaque?

Answer 18

Excludes exogenous organisms (including pathogenic species) from entering and becoming established in the mouth

Question 19

what are the host derived components of the acquired pellicle?

Answer 19

Acidic, proline-rich proteins - promotes adherence of bacteria.

Amylase

Lysozyme

Albumin

Immunoglobulins

Question 20

what is the DVLA theory?

Answer 20

As bacteria get closer to the tooth surface there is a repulsion until van der waals forces develop (due to the extremely close distance between tooth and bacteria)

Question 21

what bonds formed between the bacteria and receptor?

Answer 21

covalent

Question 22

how does bacteria attach to the pellicle?

Answer 22

physio-chemical interaction

Question 23

What are the bacteria derived components of the Acquired Pellicle:

Answer 23

Glycosyl transferases (glucosyl- and fructosyl transferases)

Glucans, Fructans

Bacterial cell fragments

Question 24

what is the equation of physio-chemical interaction?

Answer 24

VT = VA +VR

VT = total interactive energy 
VA = total attractive energy 
VR = total repulsive energy

Question 25

What are opportunistic pathogens?

Answer 25

Cells which cause infections to the host when there is an imbalance in microbial homeostasis (caries, periodontal diseases)

Question 26

What is a unique property of Fusobacterium nucleatum?

Answer 26

It is able to link with many different types of bacteria

Question 27

What is dental plaque?

Answer 27

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 28

What is acquired enamel pellicle?

Answer 28

A layer which is 1µm thick, deposited on clean tooth surface almost immediately (complete in 2 hrs) and is composed of proteins, lipids and glycoproteins from bacteria, saliva and gingival crevicular fluid.