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
T/F - Areas covered by plaque have higher F levels
True
T/F - Worn areas (abrasion, erosion) have high levels of F
Falase - low levels of F
What occurs when topical fluoride concentrations are above 100 ppm?
Calcium Fluoride precipitates - and when acid is around, CaF2 is deposited and F is made available in the acidic conditions
CaF2 provides termporary storage of F and is gradually dissolved
CaF2 deposition is increased by what?
Increasing concentration of F
Increasing exposure time
Lowering pH
Protecting (limit rinsing or cover with varnish)
Saliva is supersaturated with what? Why is this important?
Calcium and Phosphate
These help so teeth don’t dissolve
Why doesn’t crystal growth occur on the tooth?
Pellicle proteins
Pellicles also prevent spontaneous precipitation in salivary ducts
What is a negative issue of calcium and phosphate in the saliva?
Can lead to calculus formaiton
Where is F concentration the highest?
Tooth surface - it’s dependent on topical exposure to F, acid exposure, and wear
T/F - Exposure during development is a major determinant of F levels in enamel
False
Extent and severity of fluorosis is increased with what?
Exposure to higher levels during tooth development
T/F - There is a threshold below which no effect of fluorosis will be seen
False - even with low exposure, a certain level of fluorosis can occur
T/F - Mild fluorosis is perceived as attractive by most people
True
What level of F is high risk or cosmetically objectionable fluorosis?
0.1 mg/kg
T/F - Fluoride is highly concentrated in plaque
True
Can bacteria develop resistance to F?
No
What are the methods of Fluoride delivery?
Community-based water fluoridation
Self-applied
Profesionally applied
Self-applied fluoride delivery
High frequency, low concentration (1000 ppm)
Topical products
Systemic suppliments
Profesionally applied fluoride
Low frequency, high concentration
Topical products
What forms of fluoride are most commonly found in toothpaste?
NaF2
Monofluorophosphate (MFP)
Stannous fluoride (SnF2)
How much fluoride can be in Rx toothpastes?
5000 ppm
T/F - There is a positive relationship between toothpaste amount and caries
False
Does frequency matter in F exposure?
Yes - brushing twice a day is better than once a day
T/F - Rinsing does not effect F exposure
False - less rinsing is better
What is more effective, Professional gels and rinses? Or Professional fluoride varnish?
Fluoride varnish
Foam gels and rinses
1.23% acidulated phosphate fluoride
0.9% fluoride as NaF2
30% reduction in caries
Fluoride varnish
2.2% F as NaF
40% reduction in caries
