The Microbiology of Dental Caries Flashcards
What are the four sites where caries occurs?
- pits and fissures
- smooth surface and proximal caries
- root caries
- secondary caries
Match the caries site with its description.
- pits and fissures
- smooth surface and proximal caries
- root caries
- 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.
- D
- B
- C
- A
T/F. In optimum oral health, demineralization and remineralization of tooth structure are in dynamic balance.
True, as lactic acid produced by bacteria dissolves mineral from enamel, salivary minerals are deposited in enamel. no net change occurs
When is there a net loss of tooth structure?
When the body’s remineralization defenses can’t keep pace with bacterial acid
production
Bacteria in ___ on surface of tooth produce ___ ___ from glycolysis of sugars. This drops pH and mineral matrix of tooth dissolves.
biofilms; lactic acid;
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.
pellicle; subsurface; Cavitation;
T/F. Remineralization and “healing” of lesion possible as long as surface is retained.
Once cavitation occurs, biological repair no longer possible.
True.
Why is remineralized tooth structure stronger/harder than virgin enamel?
because of the incorporation of fluoride into hydroxyappatite
crystal structure
Bacteria can attach and form ___, produce acid (___) and survive acid (___).
biofilm; acidogenic; aciduric
Why is it a bad thing that bacteria continue to produce acid at low pH?
this will continue to demineralize the tooth
How are bacteria able to survive “famine” between meals?
- use multiple fermentable sugars at low concentrations
* accumulate storage polysaccharides
What bacterial species initiate caries?
- Streptococcus mutans
- other strep, S. sobrinus, S. salivarius
- Veillonella metabolizes lactic acid
- Actinomyces ?
What bacterial species are involved in caries progression?
- S. mutans
- Lactobacillus casei, rhamnosus, gasseri, fermentum
- Bifidobacterium & Scardovia?
What are the most common supragingival organisms that are also difficult to distinguish?
Strep
Strep mutans is a ___ caries pathogen that is a gram ___, ___, cocci that ferments ___ (its only nutrient source).
primary; positive; facultative; carbohydrate
What is the biofilm behavior of S. mutans?
attaches to S. sanguinis
makes extracellular polysaccharide matrix
How is S. mutans well adapted for feast or famine?
• 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
___ interferes with transport and intracellular processes and is pH dependent- activated at low pH.
F-
What is the advantage to host in having S. mutans?
protective against β-hemolytic or other pathogenic strep?
lactate
bacteriocins
How does fluoride effect S. mutans?
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.
_. ___ is closely related to S. mutans but in lower numbers and has a strong association with caries.
S. sobrinus
Which bacteria is ubiquitous, the earliest acquired oral bacteria, found bound to salivary amylase and not cariogenic?
S. mitis
_. ___ is a good colonizer of pelllicle-coated tooth surface in healthy plaque. It is a gram-positive cocci, facultative, and attaches well via adhesins.
S. sanguinis
S. sanguinis produces ___ and ___ and can survive without ___.
carbohydrates; proteins; sugar
