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AU 15- Oral Micro > Microbiology of Dental Caries > Flashcards

Microbiology of Dental Caries Flashcards

1
Q

Name the four sites where caries occur.

A
  1. Pits and Fissures
  2. Smooth surfaces and Proximal
  3. Root
  4. Restoration margins (secondary)
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2
Q

Which site for caries is most common and is often seen in patients with otherwise low caries rates?

A

Pit and Fissures

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3
Q

Which site for caries is often due to diet-related issues?

A

Smooth surface

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4
Q

Which site for caries is often related to periodontal issues?

A

Root caries

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5
Q

In optimal oral health, _____ and _____ of tooth structure are in dynamic balance.

A

Demineralization

Remineralization

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6
Q

Which bacterial byproduct is responsible for dissolving mineral in enamel?

A

Lactic acid

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7
Q

_______ are deposited in enamel to remineralize areas that were previously demineralized by lactic acid.

A

Salivary Minerals

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8
Q

When does net loss of tooth structure occur?

A

When demin outweighs remin

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9
Q

Bacteria in biofilms (on surface of the tooth) produce lactic acid from ________ of sugars.

A

Glycolysis

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10
Q

How does lactic acid dissolve mineral matrix of the tooth?

A

By dropping the pH

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11
Q

What type of proteins help to stabilize tooth surfaces?

A

Pellicle proteins

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12
Q

Initial demineralization is ________. Why?

A

subsurface

because the surface is stabilized by pellicle proteins

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13
Q

Subsurface demineralization results in ________ overlying the body of the lesion.

A

a thin shell of enamel

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14
Q

After subsurface demineralization, when does “cavitation” occur?

A

when subsurface demineralization becomes too sever or when force is applied to the thin shell of enamel covering the lesion

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15
Q

Remineralization and “healing” of a lesion is possible as long as _____.

A

surface structure is retained; once cavitation occurs, repair is no longer possible

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16
Q

True or False: Remineralized tooth structure is stronger than virgin enamel.

A

True: incorporation of fluoride into HA crystal structure makes it stronger

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17
Q

What does it mean to be acidogenic?

A

produces acid

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18
Q

What does it mean to be aciduric?

A

survives acid

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19
Q

Caries-causing bacteria attach/form biofilm and _______ at low pH.

A

continue to produce acid

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20
Q

How can caries-causing bacteria survive between meals?

A
  1. They’re thrifty (use many types of fermentable sugars at low concentrations)
  2. They store polysaccharides for later use
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21
Q

Bacterial species that cause caries are _______ and ______ upon each other.

A

interactive

dependent

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22
Q

Which bacterial species is related to caries initiation?

A

streptococcus mutans

and other strep: sobrinus, salivarius

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23
Q

Which bacterial species sits next to other bacterial species and metabolizes lactic acid? Why is this important?

A

Veillonella

it allows other species to survive in an otherwise acidic environment

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24
Q

After initial colonization by streptococci, which bacteria will colonize as caries progress?

A

Lactobacillus: L.cassei, L.rhamnosus, L.gasseri, L.fermentum

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25
Q

What species is the most common supragingival organism and therefore very difficult to distinguish?

A

oral streptococci (alpha-hemolytic or viridans)

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26
Q

Streptococci are divided into what two categories?

A

MS (mutans streptococci)

Mitis group

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27
Q

Why is one group of strep referred to as “MS”?

A

Mutans streptococci: selective media doesn’t always distinguish between s. mutans and s.sobrinus

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28
Q

Which three streptococci have protective mechanisms?

A

s. sanguis, s.mitis, s. pneumoniae

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29
Q

Which bacteria is considered to be the primary caries pathogen?

A

S. mutans

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30
Q

S. mutans is gram_____ and it ferments _____ as its only energy source.

A

positive

carbohydrate

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31
Q

True or False: S. mutans is acid tolerant.

A

True

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32
Q

S. mutans attaches to ______ in the biofilm.

A

s. sanguinis (s. sanguis)

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33
Q

What characteristic of s. mutans makes it good at causing caries (what does it produce)?

A

makes extracellular polysaccharide matrix

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34
Q

How is s.mutans adapted for presence or absence of carbohydrate?

A

During Feast: active transport, makes Glucans via glucosyl-transferase

During Fast: Scavenges, stores, and maintains energy source over long period of time (maintains low pH)

35
Q

What does s. mutans excrete that acts as a self-protection mechanism?

A

lactate

36
Q

Fluoride is activated at ____ pH.

A

Low

37
Q

Fluoride interferes with _____ and ______ processes.

A

transport

intracellular

38
Q

Does s.mutans provide any benefits to the host?

A

Possibly protects host against beta-hemolytic or other pathogenic strep by producing lactate and bacteriocins

39
Q

Other than s. mutans, which species is part of the MS group but is found in lower numbers?

A

s. sobrinus

40
Q

How does fluoride respond to decreased pH?

A

more fluoride is transported into the cell

41
Q

When targeting S.mutans, what are the two primary targets?

A
  1. Glucosyl-transferase (primary)

2. Glucan Binding Protein (secondary)

42
Q

What is the earliest acquired oral bacteria?

A

S. mitis

43
Q

S.mitis is bound by _______.

A

salivary amylase

“I try to be MIGHTY(mitis) but I just want to be LAZY (amylase)”

44
Q

True or False: Most strains of S.mitis are not cariogenic.

A

True

45
Q

True or False: S.mitis is ubiquitous (meaning we all have it).

A

True

46
Q

S.sanguinis is gram ____.

A

Positive

47
Q

How does S.sanguinis attach?

A

adhesins

48
Q

Which bacterial species is often the causative agent of Infective Endocarditis (IE)?

A

S.sanguinis

*even though it is found in healthy plaque, it causes issues outside of the mouth.

49
Q

How can S.sanguinis survive without sugar?

A

via the Arginine Hydrolase Pathway

arginine–>urea–>NH3–>increases pH–>protective

50
Q

S.sanguinis is a good ________ of a pellicle-coated tooth structure. Why?

A

initial colonizer

  • adheres well through its adhesins
  • it is facultative
  • survives without sugar
  • produces lactic acid
51
Q

S.sanguinis produces lactic acid well at _____ pH. Why does this matter?

A

High

*it will stop producing acid when the pH gets too low (extremely beneficial)

52
Q

Sucrose is broken down into _____ and ______.

A

glucose

fructose

53
Q

How do glucans attach to bacterial cell walls?

A

Glucan Binding Protein (duh)

54
Q

What are the two niches for S.salivarius?

A

tongue and tooth

55
Q

True or False: S.salivarius grows within saliva and is not associated with caries.

A

FALSE:
it does NOT grow in saliva even though it can be found there.
it HAS been associated with caries

56
Q

Actinomyces is gram ___ and is important in _____stages of enamel caries.

A

Negative

early

57
Q

True or False: Veillonella ferments carbohydrates.

A

False

58
Q

What does Veillonella ferment?

A

ferments lactate (produces propionate… raises pH)

59
Q

How does Veillonella contribute to caries?

A

it digests lactate and allows other bacteria to survive by increasing the pH in the biofilm

60
Q

Veillonella is gram ____.

A

Negative

61
Q

In what kind of lesions are lactobacilli important?

A

established or deep lesions (late stages)

62
Q

Lactobacilli are gram ____.

A

Positive

63
Q

Bifidobacterium and Scardovia are gram ____ pleomorphic rods and may be important in _____ caries.

A

Positive

Deep

64
Q

Which binds first in the development of a biofilm, S.sanguinis or S.mutans?

A

S.sanguinis binds first (to pellicle via adhesins)

65
Q

What is a “glucan”?

A

cross-linked, insoluble polysaccharide

66
Q

How does S.mutans elaborate the extracellular matrix?

A

By using available sucrose (broken into glucose and fructose by glucosyl transferase), it creates GLUCANS:

  • attaches to glucans through Glucan binding proteins
  • provides sites for attachment of other species
67
Q

Where is sucrose broken down into glucose and fructose?

A

In the Glycosyl Transferase Site

68
Q

What does “aciduric” mean?

A

acid tolerant

can survive at low pH

69
Q

What does “acidogenic” mean?

A

acid producing

can drive down pH

70
Q

At HIGH pH, which can ferment sugars better: S.sanguinis or S.mutans?

A

S.sanguinis

71
Q

At LOW pH, which can ferment sugars better: S.sanguinis or S.mutans?

A

S. mutans

72
Q

What is the difference between “healthy” and “caries associated” bacteria with regard to pH and growth?

A 
healthy= grow/make acid at high pH
caries = grow/make acid at low pH
73
Q

How does S.mutans respond to increased environmental acid?

A
  • increases resistance to acid
  • increases resistance to UV and oxygen
  • enhances glycolysis
  • increases acid tolerance
  • increases acid production
74
Q

As pH drops, good bacteria die and bad bacteria increase. This describes “oral ______”

A

dysbiosis

75
Q

The short-term effect of sugar consumption is a drop in pH, whereas the long-term effects are:

A
  • selection for S.mutans
  • de-selection for alkali-generating organisms
  • removal of protective check
  • resting plaque pH decreased
  • greater net-demineralization
  • enhanced drop after carb exposure due to environment changes
76
Q

True or False: Subjects with active caries will begin with a lower resting pH will see a more dramatic drop following a glucose rinse when compared to non-carious subjects.

A

True

77
Q

True or False: Children acquire S.mutans around the age of 26 months, this is called the “window of infectivity”

A

Sort of False:
it is indeed called the “window of infectivity” but this is no longer believed to be true. Kids can acquire bacteria much earlier

78
Q

True or False: Children harbor multiple strains of S.mutans that were acquire from caregivers and many other places.

A

True

79
Q

Can you protect children from S.mutans by reducing the S.mutans in caregivers?

A

Not necessarily, you can’t “catch caries” so most likely any decrease in S.mutans would be due to becoming more aware and conscientious of teeth cleaning

80
Q

What are the two targets (of S.mutans) for caries vaccines?

A
  1. Glucosyl transferase (GTF)

2. binding proteins

81
Q

What would mucosal vaccination provide to the host and why hasn’t this become a practice?

A

Active immunity to S.mutans via secretory antigens injected or inhaled. Adjuvants would be required.
*the risk/benefit ratio is not good enough for companies to produce the product

82
Q

Passive immunity is the administration of ______. Two methods used to cultivate the antibodies include _____ and ______.

A

Antibodies

  1. raised in tobacco plants
  2. in cow’s milk
83
Q

What is replacement therapy? Why is this method for S.mutans vaccination not used in practice?

A

Replacement of wild-type strain with a genetically engineered strain of S.mutans that produced alcohol instead of lactate
*it never made it out of safety trials

84
Q

What are STAMPs?

A

Specifically Targeted Antimicrobial Peptides
-pheromone or antibody-guided antimicrobials that kill only a targeted species most promising option right now for vaccination of S.mutans

AU 15- Oral Micro (11 decks)

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