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oral cavity - BDS 1 > pathogenic mechanism in caries :) > Flashcards

pathogenic mechanism in caries :) Flashcards

1
Q

what is responsible for demineralisation of enamel

A

acid production

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2
Q

what is the ability to remineralise dependant on

A

keeping pH above 5.5

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3
Q

Stephan curve

A

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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4
Q

plaqu

A

3d heterogeneous community encased in a sticky matrix

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5
Q

formation of development of plaque

A 
surface adhesion 
- reversible - electrostatic charge
surface adhesion
- irreversible
specific molecleualr interactions
interbacterial adhesion
- bacteria to bacteria binding
growth and muliplicaltion
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6
Q

adhesion mechanism

A

bacteria stick to the acquired pellicle not to th tooth

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7
Q

acquired pellicle

A

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

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8
Q

describe the heterogenous population build up

A

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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9
Q

what is polysaccharide birding

A

when bacteria stick to each other

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10
Q

what is in the plaque matrix

A

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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11
Q

what is the inter bacterial substances

A

bacterial products
salivary materal
serum components

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12
Q

what is made of sugars in the diet

A

extracellular polysaccharide

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13
Q

what are the bacterias two enzymes

A

glucosyltransferase
fructosyltransferase
GTF FTF

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14
Q

what do bacterial enzymes do

A

break up the chains of gluten and fructan

insoluble complex that is sticky and contributes to the plaque matrix

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15
Q

effects of EPS on carcinogenicity

A

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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16
Q

how does EPS contribute to cohesive plaque

A

more difficult to remove physcially

polymer bridging aiding adhesion

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17
Q

how does EPS act as a diffusion barrier

A

decreased bacterial cell density therefore less no of available biofilm calium binding sites
- calcium cannot be released into biofilm to reduce mineral dissolution

18
Q

when do bacteria lay down IPS

A

during high carbohydrate availability

19
Q

why do bacteria lay down IPS

A

source of carbohydrtare when starving

20
Q

what are the most important cariogenic features

A

acidogenicity

aciduricity

21
Q

what is acidogenicity

A

ability to rapidly metabolise sugars

transport and convert to acid

22
Q

what is aciduricity

A

ability to metabolise low pH

23
Q

mechanisms of cariogenesis

A

acidogenic

proteolytic

24
Q

what is proteolytic mechaisnms

A

degradation of enamel matrix by bacterial proteases

25
Q

sugar transport at normal pH

A
  • 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
26
Q

sugar transport at low pH/high sugar

A
  • 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
27
Q

acid production in high carbohydrate conditions

A

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
§

28
Q

acid production in low carbohydrate conditions

A
  • Glucose enters undergoing reactions with enzymes

- Pyruvate formate lyase converts pyruvate into acetate, formate, ethanote

29
Q

what is required for acid production

A

use of enzyms

30
Q

phosphylation of xylitol

A

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
31
Q

what does xylitiol do

A

uses up PEP but cannot enter glycolusis

  • competes with other sugar
  • no benefits for bacterial cell
32
Q

how do bacterial maintain their intracellular pH

A
  • Acid pump system (pump protons out of the cell)

- Generation of alkali to neutralise

33
Q

what do cariogenic bacteria have in relation to pH

A
  • Sugar transport system that operates at low pH

- Very active pump system for removing lactic acid

34
Q

what do acid tolerance bacteria have

A
  • 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
35
Q

neutralisation of acid

A

buffering action of saliva (bicarbonate and phosphate)
alkali production

both make ammonia
AA decarboylation produces primary amine and CO2

36
Q

alkali production in neutralisation of acid

A
  • Urea breakdown (produces NH3 + CO2)
  • Arginine catabolism (produces ornithine + NH3)
    Urea and arginine from saliva
37
Q

what happens when sugar penetrates into cariogenic biofilm

A

converted to acid by bacterial metabolism

biofilm fluid becomes understturated with respect to the enamel mineral, demineralisation

38
Q

effects of fluoride on demineralisation

A

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

39
Q

effect of fluoride on control of caries

A

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)

40
Q

Production of caries steps

A 
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

oral cavity - BDS 1 (66 decks)

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