pathogenic mechanism in caries :) Flashcards by Cassie Lee

what is responsible for demineralisation of enamel

acid production

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what is the ability to remineralise dependant on

keeping pH above 5.5

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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

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plaqu

3d heterogeneous community encased in a sticky matrix

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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

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adhesion mechanism

bacteria stick to the acquired pellicle not to th tooth

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acquired pellicle

pellicle is a layer of selectively adsorbed salivary proteins (with some serum and bacterial proteins)

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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

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what is polysaccharide birding

when bacteria stick to each other

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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

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what is the inter bacterial substances

bacterial products
salivary materal
serum components

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what is made of sugars in the diet

extracellular polysaccharide

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what are the bacterias two enzymes

glucosyltransferase
fructosyltransferase
GTF FTF

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what do bacterial enzymes do

break up the chains of gluten and fructan

insoluble complex that is sticky and contributes to the plaque matrix

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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

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how does EPS contribute to cohesive plaque

more difficult to remove physcially

polymer bridging aiding adhesion

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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 ```