Mechanisms of Action Fluoride Flashcards
How much ppm of F- is in water? How does that compare to toothpaste?
1 ppm in water
1000-5000 ppm in toothpaste
How much fluoride is in flouride tray applcations?
9000-12300 ppm
What are 2 reasons why fluoride is important in dentistry?
Promote formation of fluorapatite
Fluorapatite is more stable than HA
What are the two theories surrounding the caries preventive effects of fluoride?
Systemic theory
Topical action theory
What is the systemic theory?
F- is incorporated into teeth as FA and protects against dental caries.
It’s known as the bound-only theory
What is the topical action theory?
F- ions that bathe the teeth throughout life prevent caries
also known as free-ion theory
What are the limitations of the systemic theory?
need high amounts of F- in tooth structure to affect solubility
studies that show increased caries risk in populations that move from fluoridated to non-fluoridated regions
potential fluorosis risk
1) Enamel Surface
2) DEJ
3) Dentine-pulp interface
Order the numbers above from highest fluoride concentration to lowest.
3, 1, 2
Deep dentine has more fluoride than surface enamel. True or false?
True
What does this graph show?
Sharks nearly have pure FA in their teeth
Humans do not have pure FA in their teeth
pure FA = 34000
This graph shows the depth of demineralization in enamel. What does this graph demonstrate?
Why is it interesting?
Rinsing with a F- solution almost had the lesion reducing effect as pure HF in sharks.
Interesting because it shows that F- does not need to be chemically bound to teeth to elicit effect (supports free-ion theory)
Second graph to prove the point
What are the conclusions of the shark enamel - human enamel study?
look at slide
What are the products of HA dissociation?
OH- , Ca2+, PO43-
What is this diagram showing?
Write out the chemical formula associated with this diagram
Showing that calcium deficient apatite reprecipitates into HA, and HA reprecipitates into FA at the surface layer, where F concentration is high
The journey is more important than the destination
- James Fernando
Explain what this means and what theory it applies to
topical application theory (2)
Continued supply of F- ions allow products of dissoluted HA to be redeposited into FA, preventing net demineralization. The resulting formation of FA is more stable and less soluble.
Essentially F- intercepts Ca2+ and phosphate ions, before it leaves the tooth.
What is this?
What does it demonstrate?
at 0.1 ppm of F-, what is the white band?
Microradiograph
Demonstrates the dose dependent effect of fluoride
- less mineral loss = higher concentration of flouride
At 2 ppm, no net change in mineral
white band is fluroapatite surface layer
This microradiograph shows a fluoride’s ability to help remineralize teeth. True or False?
False, this is an example of redistribution of calcium phosphate; deposition/mineralization.
Why does dentine require more fluoride than enamel to prevent demineralization?
Smaller crystals
More soluble
Dentine tubules
Why do dentists prescribe higher concentrations of fluoride for patients with Frank Cavitation? Why don’t all patients use prescription (high -) toothpastes if it’s better?
Exposed dentine requires higher than normal F- to prevent demin
reduction of Demin effect of enamel doesn’t change much after 1 ppm
How do the forms of fluoride differ from inside your enamel compared to inside your plaque?
Free F-, CaF2, or FA in enamel
CAF2, bacterial-surface bound F-, or F- within bacteria in plaque
Gingival fluid has less F- compared to saliva. True or false?
False, it has more F-
Why is it important to ingest fluoride?
Fluoride become present in saliva although it returns to basline after 3-6 hours
NAF vs NA2FPO3
Name them and explain which one you would prefer to use
Sodium Fluoride and Sodium Monofluorophosphate
Prefer NaF because NA2FPO3 requires alkaline phosphatase to hydrolyze P-F bond to free fluoride
NaF vs SnF2
Name them and explain which one you would prefer to use
Sodium fluoride and Stannous fluoride
Prefer SnF2 because tin ion also has antibacteiral and demin-inhibiting effects
Name this compound: AgF(NH3)2
What cases would you use it and why?
Silver Diammine Fluoride
It’s strong and potent so it’s good for spot applications to arrest dental caries. However I would only use it on posterior teeth as it can cause tooth to stain black due to the silver ions
What are the 3 most important reactions of F-? Write them out.
What is HF and what can it do?
Neutral ion pair
diffuse through charged membranes and dissociate into F- and H+
access bacteria and cause damage (enzyme disruptor)
Access subsurface lesions
What is CaF and what can it do?
Crystal in enamel or plaque
relatively high solubility product – typically phosphate and protein coat wrap around this crystal making it insoluble. Upon exposure to acid, protonation of proteins and phosphate allow for the release and dissolving of CaF2
Compare FA to HA (4 pts)
FA - less soluble
FA - higher crystallinity
FA- easier to form
FA- forms faster
What are fluorides 3 mechanisms of action?
Inhibit net demineralisation
Promote net remineralisation
Bacterial effects
How does fluoride inhibit net demin?
Intercepts calcium and phosphate and prevens them from diffusing out the tooth.
Fluoroapatite is more resistant to dissolution being more stable
How does fluoride promote net remineralisation?
It has greater thermodynamic driving force for FA formaton
DS is more easily over one and can form FA from saliva ions
FA has low solubility
How is fluoride anti bacterial? What are the limitations?
Inhibit enzymes in oral bacteria
Inhibit carb metabolism
Acidify bacteria –> disrupt cellular function
need high concentrations for this to occur
How does enamel fluorosis occur?
During enamel maturation, proteases degrade amelogenin to allow for crystal maturation
Calcium required for protease function
high conc of fluoride bind to calcium and protease activity decreases
Amelogenin and its by products are not adequetley removed and the result is flouride rich enamel but mineral poor
Try review Questions
Open ended
