L4: Biochemical events in dental plaque Flashcards
What is the main causing factor of dental caries?
Bacteria produces acid & leads to demineralisation = cavities
What is dental plaque?
Aggregation of bacteria and products onto the tooth surface
What is the composition of dental plaque?
1) Water - 80%
2) Solid - 20%
3) Bacterial and Salivary protein - 50%
4) Carbohydrates and lipids - 20%-30%
5) Inorganic components
flip for some funfacts on extra and intracellular polysaccharides (carbs and lipids in dental plaque)
- Synthesized by bacteria
- Bacterial attachment and cohesion
- Reservoir of fermentable substrates
what inorganic components are found in dental plaque?
Ca, P, K, Na, Mg, F
Most Ca is non-ionic, becomes ionized as pH drops Determine rates of enamel dissolution and remineralization
what is plaque fluid?
the extracellular aqueous phase of dental plaque
What is rested plaque fluid?
Composition of plaque one to several hours after eating
What is starved plaque fluid?
Composition of plaque following overnight fasting
What is the main acid involved in caries formation?
Lactic acid
What is the stephan curve?
a model of how plaque bacteria react to fermentable carbohydrates (eg glucose)
What does a steep gradient of recovery to regular pH on a stephan curve mean for a patient?
the protection mechanisms (i.e. saliva) have diminished & px is at a higher risk of developing dental caries
what factors contribute to a drop in pH after glucose challenge?
1) Type and amount of CHO available
2) Bacteria present
3) Salivary composition and flow
4) Other food ingested
5) Thickness and age of dental plaque
Why might RESTING plaque pH be different?
bacteria have sugar stores that are used later = there is a constant low pH and bacteria is constantly producing acid
name 3 cariogenic bacteria
1) Streptococci (S. mutans)
- gram positive, sucrose, fissures,
2) Actinomyces
- gingival plaque, gingivitis
3) Lactobacilli spp,
- produce lactic acid, and lactic acid+acetate, may result in caries, require sucrose
What is the non-specific plaque hypothesis and specific plaque hypothesis?
Nonspecific = plaque is pathogenic and must be removed
Specific = plaque consists of both harmful (cariogenic) and beneficial bacteria
What is the ecological plaque hypothesis?
Change in local environment (e.g. frequent uptake of sugars) = shift in the balance of plaque microflora= Repeated low pH leads to growth of cariogenic bacteria (MS & Lactobacilli) = dental caries
What is acidogenicity?
The ability to produce acid rapidly from fermentable carbohydrate
What is aciduricity?
The ability to survive and continue to produce acid at acidic pH
- most cariogenic bacteria
How is pH maintained in aciduric bacteria?
- Low proton permeability of the cell membrane: cell wall thickening
- Production of bases
- Buffering capacity of the cytoplasm
- Active transport of proton out of cell
Where are the two sites in which bacteria stores polysaccharides?
1) Intracellular
2) Extracellular
What is the intracellular storage form of carbohydrate?
glycogen-amylopectin
How does IPS contribute to acidogenicity?
Caries-prone plaque has prolong production of acid (e.g., after meal) from IPS storage
How does IPS contribute to aciduricity?
IPS –> Energy for ATPase –> Drive protons out of cell –> Adapt to low pH environment
What is the extracellular storage form of carbohydrate?
Sucrose –> Glucans and fructans
Where is the glucans and fructans transported to?
Diffuse into surrounding plaque
What is the function of glucans?
1) Major component of interbacterial matrix
2) Barrier to the outward diffusion of acids from plaque
Describe the storage ability of Glucans and fructans as storage carbohydrates?
Fructans - degrade rapidly within a few hours
Glucans - longer period
What are the three components of the alkalinization phase which causes fluctuations in plaque pH?
1) Acid diffusion
2) Buffering capacity
3) Alkali from bacterial metabolism
