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Oral Microbiology > The Microbiology of Dental Caries > Flashcards

The Microbiology of Dental Caries Flashcards

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1
Q

What are the four sites where caries occurs?

A
  1. pits and fissures
  2. smooth surface and proximal caries
  3. root caries
  4. secondary caries
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2
Q

Match the caries site with its description.

  1. pits and fissures
  2. smooth surface and proximal caries
  3. root caries
  4. secondary caries

A. found at restoration margins
B. less common, often diet related, found in patients with moderate to high caries increment
C. found in patients with exposed root surfaces (sequelae of periodontitis)
D. most common, often found in patients with otherwise low caries rates.

A
  1. D
  2. B
  3. C
  4. A
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3
Q

T/F. In optimum oral health, demineralization and remineralization of tooth structure are in dynamic balance.

A

True, as lactic acid produced by bacteria dissolves mineral from enamel, salivary minerals are deposited in enamel. no net change occurs

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4
Q

When is there a net loss of tooth structure?

A

When the body’s remineralization defenses can’t keep pace with bacterial acid
production

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5
Q

Bacteria in ___ on surface of tooth produce ___ ___ from glycolysis of sugars. This drops pH and mineral matrix of tooth dissolves.

A

biofilms; lactic acid;

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6
Q

Tooth surface is stabilized by ___ proteins, so initial demineralization is ___, leaving thin shell of enamel overlying body of the lesion. ___ occurs when subsurface demineralization becomes too severe or extraordinary force applied to surface.

A

pellicle; subsurface; Cavitation;

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7
Q

T/F. Remineralization and “healing” of lesion possible as long as surface is retained.
Once cavitation occurs, biological repair no longer possible.

A

True.

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8
Q

Why is remineralized tooth structure stronger/harder than virgin enamel?

A

because of the incorporation of fluoride into hydroxyappatite
crystal structure

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9
Q

Bacteria can attach and form ___, produce acid (___) and survive acid (___).

A

biofilm; acidogenic; aciduric

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10
Q

Why is it a bad thing that bacteria continue to produce acid at low pH?

A

this will continue to demineralize the tooth

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11
Q

How are bacteria able to survive “famine” between meals?

A
  • use multiple fermentable sugars at low concentrations

* accumulate storage polysaccharides

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12
Q

What bacterial species initiate caries?

A
  • Streptococcus mutans
  • other strep, S. sobrinus, S. salivarius
  • Veillonella metabolizes lactic acid
  • Actinomyces ?
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13
Q

What bacterial species are involved in caries progression?

A
  • S. mutans
  • Lactobacillus casei, rhamnosus, gasseri, fermentum
  • Bifidobacterium & Scardovia?
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14
Q

What are the most common supragingival organisms that are also difficult to distinguish?

A

Strep

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15
Q

Strep mutans is a ___ caries pathogen that is a gram ___, ___, cocci that ferments ___ (its only nutrient source).

A

primary; positive; facultative; carbohydrate

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16
Q

What is the biofilm behavior of S. mutans?

A

attaches to S. sanguinis

makes extracellular polysaccharide matrix

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17
Q

How is S. mutans well adapted for feast or famine?

A 
• active transport during feast time
self-protection by excretion of lactate
• good scavenger during famine
good storage mechanisms
can maintain energy source (and low pH) over long period of time
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18
Q

___ interferes with transport and intracellular processes and is pH dependent- activated at low pH.

A

F-

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19
Q

What is the advantage to host in having S. mutans?

A

protective against β-hemolytic or other pathogenic strep?
lactate
bacteriocins

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20
Q

How does fluoride effect S. mutans?

A

When the pH is low, fluoride is in its non-ionic form and can diffuse into the cell membrane.

Sucrose is actively transported into the cell of S. mutans by glucosyl-transferase and entered into the glycolysis pathway. Glycolysis products are converted to lactic acid via enolase and this causes a decrease in the pH (increasing demineralization).
F- inhibits both glucosyl-transferase and enolase, thereby stopping lactic acid formation.

21
Q

_. ___ is closely related to S. mutans but in lower numbers and has a strong association with caries.

A

S. sobrinus

22
Q

Which bacteria is ubiquitous, the earliest acquired oral bacteria, found bound to salivary amylase and not cariogenic?

A

S. mitis

23
Q

_. ___ is a good colonizer of pelllicle-coated tooth surface in healthy plaque. It is a gram-positive cocci, facultative, and attaches well via adhesins.

A

S. sanguinis

24
Q

S. sanguinis produces ___ and ___ and can survive without ___.

A

carbohydrates; proteins; sugar

25
Q

S. sanguinis produces lactic acid in high pH environment. How is it able to survive?

A

arginine hydrolase pathway raises pH

arginine → urea → NH3

26
Q

What is often the causative agent of infective endocarditis?

A

S. sanguinis

27
Q

Which caries associated bacteria can be found on the tongue, teeth and in saliva (doesn’t grow in saliva)?

A

S. salivarius

excludes S. pyogenes

28
Q

Which bacterial species may contribute to root caries and may be important in early stages of enamel caries that is gram-positive, filamentous, anaerobic or facultative, saccharolytic and acidogenic?

A

Actinomyces

29
Q

Which gram-negative, anaerobic cocci bug does not ferment carbohydrates but instead ferments lactate, which makes propionate that raises pH to protects against acid or help the acidogenic community members survive and contributes to caries?

A

Veillonella

30
Q

Which gram-positive, anaerobic

saccharolytic, acidogenic and extremely acid tolerant rod is important in established or deep lesions?

A

Lactobacilli

31
Q

___ and ___ are gram-positive

anaerobic, saccharolytic and acidogenic and acid tolerant pleomorphic rods that may be important in deep caries.

A

Bifidobacterium; Scardovia

32
Q

S. ___ binds to pellicle via specific adhesins and S. ___ binds to it. S. ___ elaborates extracellular matrix from available ___.

A

sanguinis; mutans; mutans; sucrose

33
Q

How does S. mutans elaborate the ECM?

A

from sucrose it creates a cross-linked, insoluble polysaccharide called glucan and attaches to glucan via glucan-binding proteins.

34
Q

acid tolerant = ___

can survive ___ pH

A

aciduric

low

35
Q

acid producing = ___

can drive pH ___

A

acidogenic

down

36
Q

S. ___ beats S. ___ from fermenting sugars at ___ pH, but S. ___ does much better at ___ pH.

A

sanguinis; mutans; high; low

37
Q

When do healthy and caries bacteria grow and make acid?

A

healthy: high pH
caries: low pH

38
Q

what is the acid tolerance response in S. mutans in response to environmental exposure (change in gene expression)?

A

resistance to acid increase
resistance to UV, O2 increase
enhanced glycolysis
increase acid tolerance and production

39
Q

what is the short term effect of sugar consumption?

A

drop in pH

40
Q

Long term effects of sugar consumption cause selection of S. ___ in plaque, de-selection for ___-generating organisms like S. sanguinis, and removal of protective check on S. ____.

A

mutans; alkali; mutans

41
Q

The overall effect of long-term sugar consumption is that the resting ___ pH is a low as ___ pH unit lower in caries active subjects. There is also a drop after ___ exposure greatly enhanced by changes in bacterial composition.

A

plaque; 1; carbohydrate

42
Q

Explain microbial dysbiosis.

A

selection for acid producing bacteria causes a shift in community for bad bacteria that make low pH

43
Q

explain what happens after a glucose rinse

A
  • the pH falls after rinse but returns 1 hr later to baseline
  • those with low pH stay at a critical pH because their baseline is lower
  • people with severe caries have worse reaction
44
Q

what is the hypothesized “window of infectivity” for the acquisition of S. mutans?

A

26 months based on cultivation but can be acquired much earlier

45
Q

What are the targets for the caries vaccine?

A

glucosyl transferase (GTF) and binding proteins

46
Q

T/F. Caries vaccines to S. mutants include active and passive immunity.

A

true.

47
Q

Replacement therapy aims to replace wild-type strain with genetically engineered strain of S. mutants that does not produce ___.

A

lactate

48
Q

What are STAMPs?

A

specifically targeted antimicrobial peptides (STAMPs)

pheromone or antibody guided antimicrobials kill only target species

Oral Microbiology (11 decks)

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