Microbiology of dental caries 2 Flashcards
Can dental caries/ gingivitis be diagnosed usigmicrobial aetiology?
No
Is the pathogen that causes dental caries/ gingivitis presenting health?
Yes most of the time
Does the pathogen that causes dental caries/ gingivitis satisfy Kochos postulates?
NO
Does the pathogen that causes dental caries/ gingivitis produce specific virulence factors?
No
Can dental caries/ gingivitis be transmitted from person to person
no
How is dental disease describes?
As an example of dysbiosis of a beneficial resident microbiota
Why does dysbiosis occurs in the mouth?
Due to a major ecological pressure for example frequent sugar, reduced saliva and acidic pH
What are he key functions that acidogenic bacteria have in common?
- Produce acid
- Tolerate acid
- Produce EPS / IPS
Name the 3 hypotheses used to explain the transition from health to disease
- Specific plaque hypothesis
- Non-specific plaque hypothesis
- Ecological plaque hypothesis
Which of th 3 plaque hypothesis theories is the most accepted?
The ecological plaque hypothesis
What is disease preventability and controllability determined by?
- Direct inhibition of causative organisms
- Promotion of natural balance
- Interference with factors driving dysbiosis
What is specificity in disease found in?
Microbial function not bacterial name
Give some examples of environmental factors that can drive dysbiosis
- Low pH in biofilm
- Sugar metabolism
- low saliva flow
What does an increase in sugar frequency lead to?
More frequent acid production
Increases low pH challenges
Conc of mutans-streps, lactobacilli, bifidobacteriaetc increases
This leads to caries
Name a common sweetener?
Sucrose
What is sucrose made up of?
Glucose and fructose
What can a cariogenic diet or low salivary flow lead to according to the caries ecological plaque hypothesis?
- Stress due to increase sugar frequency
- This leads to an ENVIRONMENTAL SHIFT as the pH decreases
- This leads to an ECOLOGICAL SHIFT as the concentration of mutans-streps and lactobacilli
bifidobacteria increases - This eventually leads to disease in this case caries
Which properties are associated with mutans streptococci?
- acidogenic
2. Acid tolerating
What drives dysbiosis in dental caries?
SUGAR and PH
What can the breakdown of sugar lead to?
- Organisms can make sticky slime that stops saliva penetrating to the tooth surface
- Organisms break sucrose down into lactic acid which reduces the pH of the mouth
What happens in the mouth if theres an excess of sucrose?
Organisms will make food reserves using intracellular polymers
What is the critical pH?
It is the pH at which enamel starts to demineralise faster than saliva remineralises it
State the critical pH
5.5
When should you not have a sugary snack and why?
Before bed as salivary flow is reduced so biofilm has time to accumulate on the tooth surface
Name some bacteria associated with caries
- S.mutans
2. L casei
Name some bacteria associated with health
- S. gordonii
- S. oralis
- A. Naeslundii
- N. subflava
- V. dispar
What happens to cariogenic bacteria as the pH falls
The lower the pH is allowed to fall in the biofilm the more competitive the cariogenic bacteria become
What does low level of fluoride do in the mouth?
It wont kill bacteria but it slows acid production as ti slows down glycolysis
Give some approaches for controlling dental caries
- PLAQUE CONTROL
- Fluoride
- Sugar substitues
- Antimicrobial and anti plaque agents
- Modify the microbiota
- Vaccination
- Passive immunity
How does fluoride help control dental caries?
It inhibits intra cellular polysaccharides synthesis
It reduces glycolysis and therefor acid production so the pH doesn’t fall bellow the critical level
By eliminating a low ph environment the competitive opportunity for Mutant streptococci is removed
When fluoride goes into enamel what does it do?
It forms fluorapatite
Describe how fluorapatite reacts to acid
It is more tolerantof acid and it promotes remineralisation
What does H+F- do in the mouth?
This whizzes inside the bacteria cell and dissociates into H+ and F-
The F- then inhibits the enzymes
The H+ creates an acidic environment inside the bacteria causing denaturing of enzymes
Which enzyme does fluid inhibit when it reduces glycolysis?
Enolase
Give examples of sugar substitutes
Bulking agents: sorbitol, xylitol
Intense sweeteners: saccharin, aspartame
How do sugar substitutes help control dental caries?
- They can not be converted to acid so they dont create an acidic environment
- They stimulate saliva flow
- They have weak antimicrobial activity
Why is it hard to control dental caries using antimicrobial and anti-plaque agents ?
As theres a mixed community of good and bad bacteria so you need a concentration of anti plaque agent that will only remove harmful bacteria
What have antimicrobial and anti-plaque agents been added to?
Toothpaste and mouthwashes
Name the gold standard anti-plaque agents
chlorhexidine
What is the disadvantage of chlorhexidine
It is very potent so its only used for short incidents
It may stain the teeth
give examples of antimicrobial and anti-plaque substances that can be added yo toothpaste
Triclosan, metal salts, plant extracts, enzymes, innate host defences
Essentially what are antimicrobial and anti-plaque substances doing in bacteria?
They are messing up the bacterias biochemistry but not killing it
How can we modify the microbiota?
By using probiotics
Give examples of probiotics we have tried to use to control dental caries
- Dairy strains like Lactobacillus
2. Strep salivarius
why re probiotics not the most effective way of controlling dental caries?
As the probiotics don’t have time to stay in the mouth as they are swallowed so don’t have enough time to work effectively
Name some bacteria that have been found in people that are seen to be caries free
Streptococcus dentisani
Streptococcus A12
What does Streptococcus dentisani do
Makes an inhibitor of bacteria that inhibits mutant streptococci and create a more alkali environment
Name a more drastic way of modifying a person microbiota
By doing replacement therapy
What do prebiotics do?
They are molecules that stimulate the growth of beneficial bacteria
What is the difference between pre and probiotics?
Pro bionics are living molecules whereas prebiotics are molecules that living things feed f
Give an example of a prebiotic
arginine
How can we achieve passive immunity for dental caries?
We can coat surfaces with antibodies or synthetic antibody fragments
