Microbiology of Caries Flashcards
What sites are caries found? Which is the most common?
Pit and fissures*
Smooth surface and proximal
Root caries
Secondary caries
In optimum oral health, how does demineralization and remineralization dynamically balance each other?
Lactic acid is produced by bacteria and dissolved mineral from enamel
Salivary minerals are deposited in enamel
No net change occurs
When does net loss of tooth structure occur?
When remineralization defenses can’t keep pace with bacterial acid production
Smooth surface caries
Often diet-related
found in patients with moderate to high caries increments
Root caries
Found in patients with exposed root margins
Sequelae of periodontitis
Secondary caries
Found at restoration margins
Where does bacterial lactic acid come from?
Produced by bacterial biofilms on the tooth surface from glycolysis of sugars
What does lactic acid produce?
A drop in pH and dissolving of tooth mineral matrix
Pellicle proteins
Stabalize tooth surface
So the initial demineralization is subsurface, leacing thin shell of enamel overlying body of the lesion
When does cavitation occur?
When subsurface demineralization becomes too severe or extraordinary force is applied to the surface
When is remineralization and “healing” of a lesion possible?
As long as the surface is retained
Once cavitation occurs, biological repair is no longer possible
Which is stronger: Remineralized enamel or virgin enamel?
Remineralized because of the incorporation of fluoride into the HA crystal structure
Remineralized whitespot lesion
Surface enamel layer is not broken
Looks chalky white because there’e been enough demineralization to effect light refraction
Can still be repaired
Why might incipient caries feel rough?
Microfractures on the surface
Can still be remineralized
What are properties of caries-causing bacteria?
Attach and form biofilm Produce acid (acidogenic) Survive acid (aciduric) Continue to produce acid at low pH Survive "famine" between meals
What species cause caries initiation?
Strep mutans
other streps (S. sobrinus, S. salivarius)
Veillonella (not producers, but enablers)
Actinomyces?
What species are responsible for caries progression
S. mutans
Lactobacilli
What are the most common supragingival organisms?
Sreps (they’re difficult to distinguish)
S. mutans basic info
Primary caries pathogen
Gram-positive cocci, facultative
Ferments carbs (only nutrient source)
How do S. mutans behave in biofilm?
Attach to S. sanguinis
Makes the ECM
How are S. mutans well adapted for feast or famine?
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
What effect does F- have on S. mutans?
It interferes with transport and intracellular processes
pH dependent - activated at low pH
S. sobrinus
Behaves similar to S. mutans
Strongly associated with caries
Usually found in lower numbers than S. mutans
Glucosyl-transferase
Surface molecule that grabs sugars for S. mutans
Breaks sucrose into fructose and glucose
Brings fructose in
Uses glucose in the ECM
