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Oral Microbio > Microbiology of Caries > Flashcards

Microbiology of Caries Flashcards

1
Q

What sites are caries found? Which is the most common?

A

Pit and fissures*
Smooth surface and proximal
Root caries
Secondary caries

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2
Q

In optimum oral health, how does demineralization and remineralization dynamically balance each other?

A

Lactic acid is produced by bacteria and dissolved mineral from enamel
Salivary minerals are deposited in enamel
No net change occurs

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3
Q

When does net loss of tooth structure occur?

A

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

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4
Q

Smooth surface caries

A

Often diet-related

found in patients with moderate to high caries increments

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5
Q

Root caries

A

Found in patients with exposed root margins

Sequelae of periodontitis

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6
Q

Secondary caries

A

Found at restoration margins

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7
Q

Where does bacterial lactic acid come from?

A

Produced by bacterial biofilms on the tooth surface from glycolysis of sugars

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8
Q

What does lactic acid produce?

A

A drop in pH and dissolving of tooth mineral matrix

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9
Q

Pellicle proteins

A

Stabalize tooth surface

So the initial demineralization is subsurface, leacing thin shell of enamel overlying body of the lesion

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10
Q

When does cavitation occur?

A

When subsurface demineralization becomes too severe or extraordinary force is applied to the surface

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11
Q

When is remineralization and “healing” of a lesion possible?

A

As long as the surface is retained

Once cavitation occurs, biological repair is no longer possible

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12
Q

Which is stronger: Remineralized enamel or virgin enamel?

A

Remineralized because of the incorporation of fluoride into the HA crystal structure

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13
Q

Remineralized whitespot lesion

A

Surface enamel layer is not broken
Looks chalky white because there’e been enough demineralization to effect light refraction
Can still be repaired

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14
Q

Why might incipient caries feel rough?

A

Microfractures on the surface

Can still be remineralized

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15
Q

What are properties of caries-causing bacteria?

A 
Attach and form biofilm
Produce acid (acidogenic)
Survive acid (aciduric)
Continue to produce acid at low pH
Survive "famine" between meals
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16
Q

What species cause caries initiation?

A

Strep mutans
other streps (S. sobrinus, S. salivarius)
Veillonella (not producers, but enablers)
Actinomyces?

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17
Q

What species are responsible for caries progression

A

S. mutans

Lactobacilli

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18
Q

What are the most common supragingival organisms?

A

Sreps (they’re difficult to distinguish)

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19
Q

S. mutans basic info

A

Primary caries pathogen
Gram-positive cocci, facultative
Ferments carbs (only nutrient source)

20
Q

How do S. mutans behave in biofilm?

A

Attach to S. sanguinis

Makes the ECM

21
Q

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

A

Active transport during feast time to bring in sugar and excretes lactate to protect self
Good scavenger during famine, with good storage mechanisms and can maintain energy source over long time

22
Q

What effect does F- have on S. mutans?

A

It interferes with transport and intracellular processes

pH dependent - activated at low pH

23
Q

S. sobrinus

A

Behaves similar to S. mutans
Strongly associated with caries
Usually found in lower numbers than S. mutans

24
Q

Glucosyl-transferase

A

Surface molecule that grabs sugars for S. mutans
Breaks sucrose into fructose and glucose
Brings fructose in
Uses glucose in the ECM

25
Q

Glucan binding protein

A

Surface protein that allows the S. mutans to bind to ECM

26
Q

Enolase

A

Helps S. mutans secrete lactic acid

27
Q

What steps does F act on in S. mutans?

A

Active transport of glucosyl-transferase

Enolase activity

28
Q

S. mitis

A

Ubiuqitous
Earliest acquired oral bacteria
Bound by salivary amylase
Not cariogenic

29
Q

S. sanguinis

A

Found in healthy plaque
Gram+ cocci, facultatice
Good inititial colonizer of pellicle-coated tooth surface
Attaches via adheins
Ferments carbs and proteins
Can survive w/o sugar
Often the causative agent of Infective Endocarditis

30
Q

S. salivarius

A

Found on tongue and tooth
Associated with caries
Detected in saliva, but doesn’t grow there

31
Q

Actinomyces

A

May contribute to root caries

32
Q

Veillonella

A

Does not ferment carbs

Protects against acid or helps acidogenic community members survive

33
Q

Lactobacilli

A

Important in established or deep lesions

34
Q

Bifidobacterium and Scardovia

A

May be important in deep caries

35
Q

How do bacteria attach and develop biofilm?

A

S. sanguin bind to pellicle via specific adhesins
S. mutans bind to S. sanguin via specific adhesins
S. mutans elaborates ECM from available sucrose making glucan
S. mutans attaches to glucan via glucan binding proteins

36
Q

Aciduric

A

Acid tolerant

Can survive at low pH

37
Q

Acidogenic

A

Acid producing

Can drive down pH

38
Q

What effect on pH do healthy bacteria have?

A

Grow and make acid at pH

Stop at low pH

39
Q

What effect on pH do cariogenic bacteria have?

A

Grow and make acid best at low pH

40
Q

What can a change in gene expression in response to environment do to S. mutans?

A 
Resistance to acid increases
Resistance to UV, O2 increases
Enhanced glycolysis
Increase in acid tolerance
Increase in acid produciton
41
Q

What is the short-term effect of sugar consumption?

A

Drop in pH

42
Q

What are the long term effect of sugar consumption?

A 
Selection of S. mutans in plaque
De-selection for alkali-generating organisms like S. sanguins
Removal of protective check on S. mutans
Drop in pH 
Net demineralization is enhanced
43
Q

How and when are S. mutans acquired?

A

Hypothesized “window of infectivity” is around 26 months, but can be acquired earlier
Children can acquire strains from caregivers or others

44
Q

What can be targets for caries vaccines?

A

Glucosyl transferase

Binding proteins

45
Q

Replacement therapy

A

Replacement of wild-type strain with genetically engineered strain of S. mutans that does not produce lactate

46
Q

Specifically targeted antimicrobial peptides (STAMPs)

A

Pheromone or antibody guided antimicrobials kill only targeted speceis

Oral Microbio (11 decks)

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