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Dental public health > 6 - Fluoride > Flashcards

6 - Fluoride Flashcards

1
Q

what causes the dental caries (permanent teeth) in children to drop?

A

fluoride content in public water supply (0- 3 ppm)

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2
Q

what are the potential benefits of systemic delivery?

A

apatite solubility

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3
Q

what are the potential benefits of topical delivery?

A
  • Inhibits demineralisation
  • Promotes remineralistion
  • Apatite solubility
  • Plaque bacteria
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4
Q

what is fluoride in apatite more resistant to?

A

acid

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5
Q

what are the potential problems of fluoride?

A

Fluorosis and mottling

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6
Q

what is the structure of hydroxyapatite?

A

lactice structure of OH, Ca2+ and PO43- arranged in sheets and stacked in layers

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7
Q

what is the central ion in the structure?

A

OH-

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8
Q

How is the asymmetrical H orientated?

A

in the same direction

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9
Q

what can OH not have?

A

Cannot have H- ions towards each other -becomes unstable and OH is lost

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10
Q

what occurs when OH ion is missing?

A

Voids

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11
Q

what fills the voids and what does this produce?

A

F- ion

- Fluoroapatite

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12
Q

what is this exchange of central ions called?

A

heteroionic exchange

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13
Q

what is the structure when there are no OH ions at all?

A

fluorapatite

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14
Q

what is the critical pH?

A

Below which apatite dissolves

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15
Q

what is the criterial pH for hydroxyapatite?

A

pH 5.5

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16
Q

what is the criterial pH for fluorapatite?

A

pH 4.5

17
Q

what does the difference in critical pH mean?

A

Fluorapatite requires larger pH falls to result in dissolution of mineral

18
Q

what is the main effect form fluoride?

A

topically derived (there is a small systemic benefit but topical is better)

19
Q

what is the result of fluorapatite shark teeth + plaque?

A

less mineral loss than human teeth and plaque

20
Q

what is the result of human teeth + plaque + F- rinse?

A

even less mineral loss than fluorapatite shark teeth and plaque

21
Q

what is the effect plaque on F-?

A

Plaque seems to accumulate fluoride :
– Plaque contains 4-10 ppm F-
– (of which ~ 1-2 ppm is ionic F-)
– saliva contains ~0.02 ppm

22
Q

what effect flies fluoride have on enamel?

A

– adsorbed onto apatite crystal surface
– protects apatite crystals from dissolution
– Inhibits demineralisation

23
Q

what is the outcome if oral or plaque pH is above critical pH?

A

– Fluids are supersaturated

– Dissolution does not occur

24
Q

what is the outcome if oral or plaque pH falls below critical pH?

A

– Fluids are under saturated
– Dissolution occurs
(ions removed from tooth and apatite dissolves)

25
Q

What happens if plaque pH falls below pH 5.5 ?

A

– Plaque becomes undersaturated with respect to
hydroxyapatite
– Dissolution of hydroxyapatite

26
Q

what happens if pH remains above pH 4.5?

A

– still supersaturated with respect to fluorapatite
– in the presence of F-, Fluorapatite will form
– Promotes remineralisation

27
Q

what is the surface zone in enamel caries?

A
  • Relatively intact zone
  • ~30μm thick
  • Highly mineralised – high F- content
28
Q

what is the summary of fluoride?

A

Apatite:
– Stable crystal structure
– Lower critical pH therefore more resistant to dissolution
– Adsorbed fluoride inhibits demineralisation
– Promotes remineralisation

29
Q

what effect does F- have on oral bacteria?

A
  • F- passes through bacterial membranes
  • F- appears to inhibit numerous enzymes involved in glycolysis pathway:
    > e.g. Enolase
    > Result: less lactic acid production
  • Inhibits storage of intracellular poly-saccharides :
    > Prevents acid production between meals
  • Toxic to bacteria:
    > Only in high [F-] – e.g. topical F- therapy
30
Q

what is the overall effect of fluoride have on bacteria?

A

inhibits glycolysis pathway

31
Q

what is mild fluorosis?

A

fine white lines

32
Q

what is moderate fluorosis?

A

Opaque discoloured enamel

33
Q

what is severe fluorosis?

A

loss of enamel

34
Q

what causes fluorosis?

A
  • High F- exposure during tooth development
  • Especially in high F- areas and supplemental ingested F-:
    > F- drops
    >Swallowed toothpaste
35
Q

Describe normal amelogenesis.

A

– Nearly all matrix proteins (amelogenins) are
degraded and removed
– This is a requirement for crystal growth

36
Q

what occurs in fluorosis?

A

– Reduced enamel matrix protein (amelogenin)
degradation
– Increased amelogenin retention
– Incomplete crystal growth

Dental public health (4 decks)

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