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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
What species is the most common supragingival organism and therefore very difficult to distinguish?
oral streptococci (alpha-hemolytic or viridans)
26
Streptococci are divided into what two categories?
MS (mutans streptococci) | Mitis group
27
Why is one group of strep referred to as "MS"?
Mutans streptococci: selective media doesn't always distinguish between s. mutans and s.sobrinus
28
Which three streptococci have protective mechanisms?
s. sanguis, s.mitis, s. pneumoniae
29
Which bacteria is considered to be the primary caries pathogen?
S. mutans
30
S. mutans is gram_____ and it ferments _____ as its only energy source.
positive | carbohydrate
31
True or False: S. mutans is acid tolerant.
True
32
S. mutans attaches to ______ in the biofilm.
s. sanguinis (s. sanguis)
33
What characteristic of s. mutans makes it good at causing caries (what does it produce)?
makes extracellular polysaccharide matrix
34
How is s.mutans adapted for presence or absence of carbohydrate?
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
What does s. mutans excrete that acts as a self-protection mechanism?
lactate
36
Fluoride is activated at ____ pH.
Low
37
Fluoride interferes with _____ and ______ processes.
transport | intracellular
38
Does s.mutans provide any benefits to the host?
Possibly protects host against beta-hemolytic or other pathogenic strep by producing lactate and bacteriocins
39
Other than s. mutans, which species is part of the MS group but is found in lower numbers?
s. sobrinus
40
How does fluoride respond to decreased pH?
more fluoride is transported into the cell
41
When targeting S.mutans, what are the two primary targets?
1. Glucosyl-transferase (primary) | 2. Glucan Binding Protein (secondary)
42
What is the earliest acquired oral bacteria?
S. mitis
43
S.mitis is bound by _______.
salivary amylase "I try to be MIGHTY(mitis) but I just want to be LAZY (amylase)"
44
True or False: Most strains of S.mitis are not cariogenic.
True
45
True or False: S.mitis is ubiquitous (meaning we all have it).
True
46
S.sanguinis is gram ____.
Positive
47
How does S.sanguinis attach?
adhesins
48
Which bacterial species is often the causative agent of Infective Endocarditis (IE)?
S.sanguinis | *even though it is found in healthy plaque, it causes issues outside of the mouth.
49
How can S.sanguinis survive without sugar?
via the Arginine Hydrolase Pathway | arginine-->urea-->NH3-->increases pH-->protective
50
S.sanguinis is a good ________ of a pellicle-coated tooth structure. Why?
initial colonizer * adheres well through its adhesins * it is facultative * survives without sugar * produces lactic acid
51
S.sanguinis produces lactic acid well at _____ pH. Why does this matter?
High | *it will stop producing acid when the pH gets too low (extremely beneficial)
52
Sucrose is broken down into _____ and ______.
glucose | fructose
53
How do glucans attach to bacterial cell walls?
Glucan Binding Protein (duh)
54
What are the two niches for S.salivarius?
tongue and tooth
55
True or False: S.salivarius grows within saliva and is not associated with caries.
FALSE: it does NOT grow in saliva even though it can be found there. it HAS been associated with caries
56
Actinomyces is gram ___ and is important in _____stages of enamel caries.
Negative | early
57
True or False: Veillonella ferments carbohydrates.
False
58
What does Veillonella ferment?
ferments lactate (produces propionate... raises pH)
59
How does Veillonella contribute to caries?
it digests lactate and allows other bacteria to survive by increasing the pH in the biofilm
60
Veillonella is gram ____.
Negative
61
In what kind of lesions are lactobacilli important?
established or deep lesions (late stages)
62
Lactobacilli are gram ____.
Positive
63
Bifidobacterium and Scardovia are gram ____ pleomorphic rods and may be important in _____ caries.
Positive | Deep
64
Which binds first in the development of a biofilm, S.sanguinis or S.mutans?
S.sanguinis binds first (to pellicle via adhesins)
65
What is a "glucan"?
cross-linked, insoluble polysaccharide
66
How does S.mutans elaborate the extracellular matrix?
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
Where is sucrose broken down into glucose and fructose?
In the Glycosyl Transferase Site
68
What does "aciduric" mean?
acid tolerant | can survive at low pH
69
What does "acidogenic" mean?
acid producing | can drive down pH
70
At HIGH pH, which can ferment sugars better: S.sanguinis or S.mutans?
S.sanguinis
71
At LOW pH, which can ferment sugars better: S.sanguinis or S.mutans?
S. mutans
72
What is the difference between "healthy" and "caries associated" bacteria with regard to pH and growth?
``` healthy= grow/make acid at high pH caries = grow/make acid at low pH ```
73
How does S.mutans respond to increased environmental acid?
- increases resistance to acid - increases resistance to UV and oxygen - enhances glycolysis - increases acid tolerance - increases acid production
74
As pH drops, good bacteria die and bad bacteria increase. This describes "oral ______"
dysbiosis
75
The short-term effect of sugar consumption is a drop in pH, whereas the long-term effects are:
- 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
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.
True
77
True or False: Children acquire S.mutans around the age of 26 months, this is called the "window of infectivity"
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
True or False: Children harbor multiple strains of S.mutans that were acquire from caregivers and many other places.
True
79
Can you protect children from S.mutans by reducing the S.mutans in caregivers?
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
What are the two targets (of S.mutans) for caries vaccines?
1. Glucosyl transferase (GTF) | 2. binding proteins
81
What would mucosal vaccination provide to the host and why hasn't this become a practice?
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
Passive immunity is the administration of ______. Two methods used to cultivate the antibodies include _____ and ______.
Antibodies 1. raised in tobacco plants 2. in cow's milk
83
What is replacement therapy? Why is this method for S.mutans vaccination not used in practice?
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
What are STAMPs?
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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