Fluoride and Dental caries Flashcards
When were the benefits of Fluoride discovered?
Paradoxically strong “dark yellow” teeth were noted in 200 ad in Greece
What is the “ideal” concentration of Fluoride in water to maximize caries benefit and minimize fluorosis?
1 ppm
Caries is reduced by 50%
How can fluorosis occur?
Very high physiologic levels of F during the secretory stage can cause pitting and disturbances in scaffolding (not common)
When does Flurosis occur?
To kids when their teeth are forming before they erupt
What occurs during the secretory stage of tooth formation?
Ameloblasts lay down the protein matrix for the crystal rod structure and rods begin to form
Chronic moderately high levels of F during the pre-eruptive stage can cause what?
Disruptions in crystal formation that appear as a chalky whiteness and weakness of enamel
After eruption, the weakened enamel may fracture and stain
Does fluridated water benefit systemically incorporated or by touching the tooth?
Benefits are from F touching the tooth
T/F - there is no benefit of fluoridated water before tooth eruption
True
T/F - in order to continue benefits of fluoridated water, fluoridation must continue throughout life
True
How do topical F products compare to fluoridated water?
They have similar benefits (both touch the tooth)
Topical products are lower risk than systemic products
What is the composition of enamel?
87% mineral (HA)
11% water
2% organic matrix
Newly formed crystals in a young tooth usually contains what?
Impurities
- carbonate
- sodium
- other ions
What is Post-eruptive Enamel Maturation?
After eruption, when bathed in saliva and exposed to F, the HA crystals will tend to perfect itself
- Phosphate replaces carbonate
- Ca replaces Na
- F replaces hydroxyl
What do the mineral replacements in Post-eruptive enamel maturation cause?
They make Ha less soluble and therefore stronger
T/F - older teeth are more succeptible to caries
False - Younger teeth are more susceptible to caries, because post-eruptive enamel maturation strengthens them over time
HA starts to dissolve below what pH?
5.5
How does HA dissolve?
Acid continues to dissolve HA crystals because the surrounding solution remains unsaturated due to the removal of component ions from solution under acidic onditions
How does F prevent dissolving?
When F ions are present, HA dissolves and re-precipitates as flurohydroxyapatite
FHA is less soluble than HA, so enamel is strengthened
Under what conditions does flurohydroxyapatite form?
When pH remains above 4.5 and F ions are avaliable, FHA forms on the surface when HA dissolves
When pH rises above 5.5, F ions do what?
Enhance remineralization of enamel and dentin
Which is more beneficial; F at low levels in solution, or F at high concentrations incorporated into enamel?
F at low levels in solution
Where is enamel the least soluble?
The surface, because it has more F (FHA) and less carbonate
T/F - F diffuses well into the body of a lesion
False - it reacts before it gets there with the outer layers to form FHA
subsurface HA is dissolved while FHA is formed in the surface layers
Why do whitespot lesions have very high F concentrations on their surface?
Because of demin-remin cycles
