Dental caries I Flashcards
how does caries affect the inorganic and organic material of the tooth ?
demineralizes the organic material while destroying the organic
caries is a progressive IRREVERSIBLE damage
what are the essential requirements for development of dental caries ?
-cariogenic bacteria
-dental plaque
-carbohydrate / sugar
-stagnation area
-time
what does acidogenic mean?
able to produce pH low enough to decalcify teeth (<5)
what does aciduric mean?>
able to survive and continue to produce acid at low leverls of pH
adhesive insoluable plaque polysaccharide produced by cariogenic bacteria is known as:
glucan
which microorganisms are mainly responsible for 1.) initiation of dental caries 2.) progression 3.) association with root caries
1.)streptococcus mutans
2.)lactobacilli
3.)actinomyces
intracellular glycogen like , reserve polysaccharide which produce acid when sucrose intake is reduced:
dextran
how do disorders of sucrose metabolism affect caries prevalence?>
decrease
enzyme responsible for converting sucrose to glucan ?
bacterial glucosyl transferase
what are some characteristics that make sucrose especially cariogenic ?
-promotes colonization of teeth by streptococcus mutans
-its disaccharide bond contains enough energy to react with bacterial enzymes to form glucan and dextran
-small molecular size allows it to diffues readily into plaque
-bacterial metabolism to sucrose is rapid
-forms up to third of the average persons diet
what is a pellicle ?
amorphous matrix derived from salivary glycoproteins
plaque contains desqumated epithelial cells
how long does a patient need to not brush their teeth for plaque to start forming ?
12-24 hours
what are the stages of plaque formation ?
1.)deposition of pellicle , a structureless , cell free layer of salivary glycoproteins absorbed on tooth surface
2.) colonization of this cell free layer by bacteria (particularly streptococus mutans )
3.) build up of plaque substance by bacterial polysaccharied (glucans)
4.) proliferation of filamentous and other bacteria as plaque matures
what is responsible for the corn-cob appearance of anaerobic filamentous microorganisms ?
they grow in long interlacing threads , on which , smaller bacilli and cocci become entrapped , giving the corn cob appearance
what types of acid are involved in enamel dissolution ?
1,) lactic acid
2.) acetic acid
3.) propinoic acid
which enzyme is responsible for turning starch into maltose , which can also lead to enamel dissolution :
salivary amylase
how long does it take for pH to fall to a level sufficient to decalcify enamel after sucrose has been introduced to the oral cavity ?>
5-10 minutes
pH remains low for 15-20 minutes
it then rises to its original figure over the next 30-60 minutes
(stephens curve)
why does pH return to it normal figure after a while ?
due to diffusion of acid out of plaque and diffusion of buffered saliva into plaque , which helps to dilute and neutralize the acid
Around a neutral pH, excess mineral ions in the plaque are redeposited on the enamel crystal surface
how does plaque contribute to dental caries?>
-retains acid in high concentration at one area which allows for demineralization of enamel
-liberation of mineral ions from hydroxyapatite crystals and diffusion into plaque
-increase in bulk of plaque slows down the arrival of salivary buffers from saliva , delaying their neutralizing action
