pathogenic mechanism in caries :) Flashcards
what is responsible for demineralisation of enamel
acid production
what is the ability to remineralise dependant on
keeping pH above 5.5
Stephan curve
pH drops below critical point of 5.5
30-40 mins for saliva to vet back to above 5.5
teeth will demineralise if we have something less to eat before saliva has rebuffered
plaqu
3d heterogeneous community encased in a sticky matrix
formation of development of plaque
surface adhesion - reversible - electrostatic charge surface adhesion - irreversible specific molecleualr interactions interbacterial adhesion - bacteria to bacteria binding growth and muliplicaltion
adhesion mechanism
bacteria stick to the acquired pellicle not to th tooth
acquired pellicle
pellicle is a layer of selectively adsorbed salivary proteins (with some serum and bacterial proteins)
describe the heterogenous population build up
groups of colonising bacteria stick to the pellicle
pelican contains proteins, cell frangemtns ect
more species adhere to from the polysaccharide bridges
what is polysaccharide birding
when bacteria stick to each other
what is in the plaque matrix
bacteria colonies have fluid channels within them
- allows oxygen and water to flow through and allows all substances to bind ogether
what is the inter bacterial substances
bacterial products
salivary materal
serum components
what is made of sugars in the diet
extracellular polysaccharide
what are the bacterias two enzymes
glucosyltransferase
fructosyltransferase
GTF FTF
what do bacterial enzymes do
break up the chains of gluten and fructan
insoluble complex that is sticky and contributes to the plaque matrix
effects of EPS on carcinogenicity
creates space between bactera
EPS acts as a diffusion barrier trapping acid near tooth surface
salivary buffering reduced in EPS
EPS contributes to cohesive plaque
how does EPS contribute to cohesive plaque
more difficult to remove physcially
polymer bridging aiding adhesion
how does EPS act as a diffusion barrier
decreased bacterial cell density therefore less no of available biofilm calium binding sites
- calcium cannot be released into biofilm to reduce mineral dissolution
when do bacteria lay down IPS
during high carbohydrate availability
why do bacteria lay down IPS
source of carbohydrtare when starving
what are the most important cariogenic features
acidogenicity
aciduricity
what is acidogenicity
ability to rapidly metabolise sugars
transport and convert to acid
what is aciduricity
ability to metabolise low pH
mechanisms of cariogenesis
acidogenic
proteolytic
what is proteolytic mechaisnms
degradation of enamel matrix by bacterial proteases
sugar transport at normal pH
- Transported through the membrane via PEP transforase system
- Phosphorylates the sucrose an glucose
- Inside cell, phosphorylated glucose is metabolised to pyruvate
- Phosphate recycled to PEP transferase system
- Pyruvate enters ATP cycle
sugar transport at low pH/high sugar
- PEP transferase does not take place
- Permease system, sugars phosphorylated at the same time of movement through the membrane
- Phosphate NOT recycled
- Phosphorylated glucose fermented into lactic acid
acid production in high carbohydrate conditions
Glucose metabolised by enzymes into pyruvate
- Lactate dehydrogenase then converts pyruvate into lactate/lactic acid
S.Mutans has no respiratory chain and produced ATP via glycolysis
- under conditions of glucose excess lactate is the major end product of the metabolism
§
acid production in low carbohydrate conditions
- Glucose enters undergoing reactions with enzymes
- Pyruvate formate lyase converts pyruvate into acetate, formate, ethanote
what is required for acid production
use of enzyms
phosphylation of xylitol
Xylitol is found in the diet
- Transported into the cell via PEP transferase system
- Phosphorylated
- Phosphate group not returned to the transferase system, simply released
- Xylitiol then comes around again through the system but does not enter the glycolytic pathway, no energy is produced
- Uses up all the phosphate from the PEP transferase system, no benefits for the bacterial cell
what does xylitiol do
uses up PEP but cannot enter glycolusis
- competes with other sugar
- no benefits for bacterial cell
how do bacterial maintain their intracellular pH
- Acid pump system (pump protons out of the cell)
- Generation of alkali to neutralise
what do cariogenic bacteria have in relation to pH
- Sugar transport system that operates at low pH
- Very active pump system for removing lactic acid
what do acid tolerance bacteria have
- Low pH optimum ATP-dependant glucose permease
- Low pH optimum H+/ATPase
- Transmembrane pH gradient which transports lactate as lactic acid
to maintain alkaline pH intrcellualrly
neutralisation of acid
buffering action of saliva (bicarbonate and phosphate)
alkali production
both make ammonia
AA decarboylation produces primary amine and CO2
alkali production in neutralisation of acid
- Urea breakdown (produces NH3 + CO2)
- Arginine catabolism (produces ornithine + NH3)
Urea and arginine from saliva
what happens when sugar penetrates into cariogenic biofilm
converted to acid by bacterial metabolism
biofilm fluid becomes understturated with respect to the enamel mineral, demineralisation
effects of fluoride on demineralisation
if fluoride in biofilm fluid and pH is not lower that 4.5:
HA is dissolved the same time that fluoraptite is formed
- decrease in enamel dissolution
effect of fluoride on control of caries
1) interferes with glucose transport
2) reduces cell ability to maintain pH
3) stops the production of IPS
4) interferes with ATP synthases
caries requires enolase
- fluoride prevents PEP transferase system working
Pyruvate not converted to lactate (interferes with ATP synthesis)
Production of caries steps
susceptible tooth surface formation o biofilm and microbial deposits Acid production and pH change shift in dynamic equilibrium of minerals dissolution of minerals initiation of caries
