CSA microbiology of caries Flashcards
how is caries multifactorial?
key oral microorganisms
susceptible host
enviro. factors
what are enviro. factors?
poor diet
poor oral hygiene
low saliva flow rate
what are cofounding factors for caries?
o Fluoride availability
o Diverse natural microbiota
o Non-specific virulence factors
evidence for caries as infectious disease?
- gnotobiotic animal studies
- Human epidemiology studies
What do gnotobiotic studies show?
cant get caries in absence of microorganisms
- showed transmission of caries and
- showed antimicrobial agents work against caries
what is human epidemiology studies?
cross or longitudinal studies
what is cross sec studies?
group of people and sample microorganisms on tooth of people with and w/o caries
What is longitudinal studeies?
- Get a cause relationship
- Microorganisms sampled before & after diagnosis of caries
what are the implicated microorganisms with caries?
Mutans streptococci
Actinomyces
lactobacalli
Bifidobacteria
what mutans streptococci are there?
Strep. Mutans
Strep. sobrinus
Strep. cricetus
Strep. rattus
What actinomyces are there?
A. naeslundii
A. odontolyticus
(A. israelii / A. gerencseriae)
What Lactobacilli are there?
Lactobacillus spp.
What bifidobacteria are there?
Bifidobacterium/ Scardovia spp
what are mutans strepto. ?
• Gram positive cocci that are round organisms
what does mutans streptococcie do?
- colonise hard surfaces such as dentures/teeth (non-shedding surfaces)
• initiate caries if enough of them
what happens if give mutans strep. sucrose?
make extracellular sticky polymers
What is lactobacillus?
Gram positive rod more associated with advanced lesions
Bifidobacterium?
• Gram positive rod that are branched cells
why is it hard to understand aetiology of caries
- Disease occurs at sites with natural diverse microbiota
• Pathogens can found at healthy sites but in small number
• difficult to correlate microorganisms to the status of the enamel
• Lesions can re-mineralise
• Pathogenic traits are relatively non-specific
• Caries is multi factorial
what is microbiological aetiology of caries?
- MS seen in higher proportion at carious sites
* inverse relationship between MS & S. Sanguinis
what does cross sec study of fissure caries show?
3/4 of carious fissure had >10% of MS
what does longitudinal study of fissure caries show?
- higher proportions of MS at caries sites
- MS can be after first signs of demineralisation
- Caries can be apparent in absence of MS
- Role of other species in caries progression
what is role of other bacteria?.
- Acidogenic/Low pH isolated & can survive acidic conditions:
- Lactate-utilising species
- Base generating species
what is childhood caries?
bottle to suck with sugar drink
what is root surface caries>
older and recession and cementum exposed
What does infected dentine culture show?
- Mutans streptococci
- Lactobacilli
- Actinomycesspp. (A. israelii; A. gerencseriae)
- Gram negative anaerobic rods (e.g. Prevotellaspp.)
What do bacteria live off in healthy patient?
- glycoproteins -Microorganisms break them down for energy
• acid production slow & saliva easily buffer it
• Littledemineralization
What do bacteria live off in CARIES patient?
- biofilm exposed to sugars frequently
- Bacteria like MS rapidly metabolise sugars - produce acid
- More demineralization than remineralization
What are characteristics of cariogenic bacteria?
- rapid sugar transport
- rapid acid production
- acidurity
- extracellular/ intracellular polysaccharide
What is the biggest difference between MS and S.sanguinis?
have v different acid tolerance
what is non specific plaque hypothesis?
overall net effect of all these organisms
What is ecological plaque hypothesis?
- enviro. plays a role
o Many species contribute if they have right properties
How is disease prevented?
vaccine
homeostasis
Why can caries occur?
o Is their OH poor?
o Is their saliva flow compromised?
o Do they have lots of sugary snacks?
What does a change in pH lead to?
change in microorg. being selected for
what bacterial properties are selected for, for caries
ACIDOGENIC
ACID TOLERATING
What happens when more time under critical pH is spent?
oral enviro. more time facilitating growth of caries bacteria
Approach to control caries?
- Plaque control
- Fluoride
- Sugar substitutes
- Antimicrobial & anti-plaque therapy
- Replacement therapy
- Vaccination
- Passive immunization
What does plaque control ensure?
biofilm kept thin and less chance of acidic conditions in mouth
What does fluoride produce?
fluoroapatite - remineralization
what does fluoride do?
inhibit bacterial metabolism and inhibit enolase (involved in glycolysis)
What are sugar substitutes?
xylitol/sorbitol - can’t be metabolized by microorg.
what is chlorhexidine active against?
MS
what is replacement therapy?
probiotics in oral cavity, replace orgs. in mouth
are streptococci targetable pathogens for vaccines?
yes
what is passive immunization?
coat surfaces with antibodies or synthetic antibody fragments
