test 2, caries microbiology part 1 Flashcards
bacteria associated with caries were originally thought to be what 2?
streptococcus mutans and lactobacillus
current biofilms models point to what?
multiple pathogens
the ecological plaque hypothesis is the most accepted model to describe the caries process. This model invovles….
- a pH specific disease
- selection process is driven by pH not carb availability
- when acid producing bacteria dominate the biofilm demineralization occurs
how many different bacteria have been identified in the human oral microbiome?
700-800
what is the exteded ecological plaque hypothesis?
commensal bacteria have shown to adapt and live in acidic environments, but they also develop the ability to produce acids themselves contributing to the disease!!!
demineralization always ____ bacteria
preceeds
what are the first colonizers?
gram+ aerobic orgs called non-ms bacteria ( @ this point 95% of bacteria are non MS strep strains)
as the plaque matures, what bacteria join the party?
actinomyces( at htis point only 2 % of the bacteria are MS)
in what zone do the bacteria start to mix and become MS strains?
zone of destruction
As pH starts to drop, who joins the party?
Mutans streptococci
what are themajor bacterial groups in white spot lesions?
actinomyces and non-MS bacteria
what are the major bacterial groups in cavitated dentin lesions?
MS ( ~30%),
what bacteria stick to the pellicle?
the non-MS strains
what do the non-MS strains produce?
extracellular polysacharides (glucans and fructans). These fill in gaps between bacteria and accelerate plaque formation
what do the MS strains stick to?
to the base of plaque the non-MS and actinomyces produce
what do the MS strains use to stick to the plaque?
adhesions- antigen I/II, water insoluable glucatn ( now they can do work!)
After MS join the party what do they produce to start destroying teeth?
acids!
do both non-MS and MS metabolize sugars into acids?
yes
what happens when sugars are in abundance in the mouth?
non-MS & MS store the sugars and intracellular polysacharides for later use( this allows them to work between meals)
non-MS strains produce wha pH after sugar metabolization?
4-5.2
MS strains produce what pH after sugar metabolization?
4
whats the critical value for demineralizaion?
5.5, so both can cause demineralization
do all non-MS strains have the same affect on pH?
no, theyre all over the place ( mosaics)
aciduric bacteria were able to grow on root surface caries at what pH?
4.8
actinomyces are uureolitic which means?
can utilize lactate as a carbon source for growth
a breakthrough on non-Ms strains showed they can change their physiologic charecteristics accoriding the the pH their in. What does this mean?
they actually increased acid production when placed in acidic conditions
Ex: When grown at pH7 and then placed in pH 5.5, their acidogenicity was increased to 3.93-4.12!
even though the non-Ms produce acid, are they more competative than the Ms?
no, competition becomes more apparent at about 4 pH. This is where the non MS lose their ability to grown and produce their glycans. So Ms becomes more aciduric and acidogenic at low pH
as pH starts to drop, which bacteria are prevelant?
MS and lactobacillus
so what do intermittent drops in PH do? ( to threshold of 5.5)
result in increase in “low pH” non-MS and actinomyces spp.
what does prolonged acidic conditions result in? ( below the 5.5 threshold)
causes MS to become prevelant
what happens when pH levels approach 4?
non-Ms become excluded and replaced by MS and lactobacillus
which bacteria can grow in anaerobic conditions?
MS strains , the non MS die out
