L4: Formation, structure and composition of dental plaque Flashcards
What does the host mechanism consists of?
immunity and innate host defences: eg lysozyme (bacterial lysis), lactoferrin (iron sequestration), peroxidases (glycolysis inhibition).
what are the 5 stages of the development of dental plaque?
- acquird enamel pellicle
- pioneering species
- confluent layer (pioneering species multiply)
- accumulated bacterial growth
- plaque maturity
What is the first stage of development of dental plaque?
Acquired enamel pellicle
What is the pioneering species of bacteria?
The first layer of bacteria which will adhere to the acquired pellicle
What do the host and bacteria derived components act as?
Receptors for bacterial adhesion
Properties of pioneering species of bacteria:
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
what are the 4 pioneering species that colonize the tooth surface first (at the acquired enamel pellicle)?
streptococcus sanguinis
streptococcus oralis
srteptococcus mitis
actinomyces ssps.
what are the 4 pioneering species that colonize the tooth surface first (at the acquired enamel pellicle)?
streptococcus sanguinis
streptococcus oralis
srteptococcus mitis
actinomyces ssps.
how does the host prevent exogenous organisms from entering ad establishing themselves in the mouth?
- competes for the same adhesion receptor sites
- competes for nutrients and co-factors
- prodices inhibitory substances i.e. acids
what is co-aggregation?
Process by which cell-to-cell interactions lead to distinctly different bacterial species becoming predetermined ‘partners’ in forming plaque due to similar adhesins
where does co-aggregation occur?
within the plaque matrix
examples of co-aggregation
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
what happens during microbial homeostasis?
- 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.
what are the general properties of a biofilm? (4)
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
What happens to the plaque matrix after an increase in number of bacteria and substances in the matrix?
The matrix becomes anaerobic
- decreased oxygen tension (Eh decreased)
- may lead to the eventual growth of anaerobic bacteria
what shape forms when fusobacterium nucleatum coaggregates with other bacterial species?
corncob
what is the bacterial function of dental plaque
Microbial homeostasis (the maintenance of a stable microflora in a variable environment)
What is the host function of dental plaque?
Excludes exogenous organisms (including pathogenic species) from entering and becoming established in the mouth
what are the host derived components of the acquired pellicle?
Acidic, proline-rich proteins - promotes adherence of bacteria.
Amylase
Lysozyme
Albumin
Immunoglobulins
what is the DVLA theory?
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)
what bonds formed between the bacteria and receptor?
covalent
how does bacteria attach to the pellicle?
physio-chemical interaction
What are the bacteria derived components of the Acquired Pellicle:
Glycosyl transferases (glucosyl- and fructosyl transferases)
Glucans, Fructans
Bacterial cell fragments
what is the equation of physio-chemical interaction?
VT = VA +VR
VT = total interactive energy VA = total attractive energy VR = total repulsive energy
What are opportunistic pathogens?
Cells which cause infections to the host when there is an imbalance in microbial homeostasis (caries, periodontal diseases)
What is a unique property of Fusobacterium nucleatum?
It is able to link with many different types of bacteria
What is dental plaque?
A general term for the complex microbial community embedded in a matrix of salivary and bacterial origin (biofilm) and found on the tooth surface
What is acquired enamel pellicle?
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.
