Dental caries I

Question 1

how does caries affect the inorganic and organic material of the tooth ?

Answer 1

demineralizes the organic material while destroying the organic

Question 2

caries is a progressive IRREVERSIBLE damage

Question 3

what are the essential requirements for development of dental caries ?

Answer 3

-cariogenic bacteria
-dental plaque
-carbohydrate / sugar
-stagnation area
-time

Question 4

what does acidogenic mean?

Answer 4

able to produce pH low enough to decalcify teeth (<5)

Question 5

what does aciduric mean?>

Answer 5

able to survive and continue to produce acid at low leverls of pH

Question 6

adhesive insoluable plaque polysaccharide produced by cariogenic bacteria is known as:

Answer 6

glucan

Question 7

which microorganisms are mainly responsible for 1.) initiation of dental caries 2.) progression 3.) association with root caries

Answer 7

1.)streptococcus mutans
2.)lactobacilli
3.)actinomyces

Question 8

intracellular glycogen like , reserve polysaccharide which produce acid when sucrose intake is reduced:

Answer 8

dextran

Question 9

how do disorders of sucrose metabolism affect caries prevalence?>

Answer 9

decrease

Question 10

enzyme responsible for converting sucrose to glucan ?

Answer 10

bacterial glucosyl transferase

Question 11

what are some characteristics that make sucrose especially cariogenic ?

Answer 11

-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

Question 12

what is a pellicle ?

Answer 12

amorphous matrix derived from salivary glycoproteins

Question 13

plaque contains desqumated epithelial cells

Question 14

how long does a patient need to not brush their teeth for plaque to start forming ?

Answer 14

12-24 hours

Question 15

what are the stages of plaque formation ?

Answer 15

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

Question 16

what is responsible for the corn-cob appearance of anaerobic filamentous microorganisms ?

Answer 16

they grow in long interlacing threads , on which , smaller bacilli and cocci become entrapped , giving the corn cob appearance

Question 17

what types of acid are involved in enamel dissolution ?

Answer 17

1,) lactic acid
2.) acetic acid
3.) propinoic acid

Question 18

which enzyme is responsible for turning starch into maltose , which can also lead to enamel dissolution :

Answer 18

salivary amylase

Question 19

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 ?>

Answer 19

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)

Question 20

why does pH return to it normal figure after a while ?

Answer 20

due to diffusion of acid out of plaque and diffusion of buffered saliva into plaque , which helps to dilute and neutralize the acid

Question 21

Around a neutral pH, excess mineral ions in the plaque are redeposited on the enamel crystal surface

Question 22

how does plaque contribute to dental caries?>

Answer 22

-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