fluoride metabolism

Question 1

importance of fluoride

Answer 1

-To form Fluorapatite (FA) (systemic)
-To form CaF2
(topical/in saliva)

Question 2

To form CaF2

topical/in saliva

Answer 2

– Coats the surface of enamel

– Enamel become less soluble, more resistant to acid

Question 3

-To form Fluorapatite (FA) (systemic)

Answer 3

– Nature of fluoride ion: small, highly electronegative,
high charge density
• Allow a better fit & tightly orientated in the lattice compared
to OH
ions
• Offers greater electrostatic interaction between Ca2+ and F
than between Ca2+ and OH–

Question 4

sources of fluoride

Answer 4

drinking water, foods, fresh drinks, dental products, dietary supplement

Question 5

Drinking

water

Answer 5

< 0.3 ppm
0.5-0.9 ppm
Climate:
Warm: low [F]
Cold: high[F]

Question 6

Foods

Answer 6

0.2-0.5 ppm
5-15 ppm (rich)
sources :
Most food
Fish with bones e.g.
Salmon, sardine,
mackerel

Question 7

Fresh drinks

Answer 7

0.1-1.4 ppm
1-7 ppm 
Juice, coffee &
carbonated drinks
Tea

Question 8

Dental

products

Answer 8

500 ppm, low [F]
1100-1500 ppm
>1500 ppm,high [F]
Toothpastes, mouth
rinses, dental gel
*25% of fluoride
swallowed

Question 9

Inorganic salts

Answer 9

sodium fluoride, sodium monofluorophosphate, stannos fluoride, stannous hexafluorozirconate, calcium fluoride, magnesium fluoride, aluminium fluoride

Question 10

Sodium fluoride

Answer 10

solubility : 4%
Used in water fluoridation
Most used in toothpaste &
mouth rinse

Question 11

sodium monofluorophosphate

Answer 11

solubility 25%, Form used in toothpaste &

mouth rinse

Question 12

stannos fluoride

Answer 12

> 10%, Form used in toothpaste &

mouth rinse

Question 13

stannous hexafluorozirconate

Answer 13

> 24%, Highly soluble: rapidly & almost completely absorbed from
gastrointestinal tract

Question 14

Calcium

fluoride

Answer 14

Insoluble
(0.0016%)
less completely absorbed
& at a slow rate

Question 15

Magnesium

fluoride

Answer 15

Insoluble, Absorption occurs by diffusion through gut wall

Question 16

Aluminium

fluoride

Answer 16

Insoluble, Absorption is reduced due
to present of Ca2+
, Mg2+ &
Al3+

Question 17

Fluoride Metabolism

Answer 17

1. Main absorption takes place in stomach
2. Transported/Distributed in plasma
3. Body fluoride is continuously regulated by
   clearance mechanism

Question 18

1. Main absorption takes place in stomach

Answer 18

– Insoluble form: excreted in feces

Question 19

2. Transported/Distributed in plasma

Answer 19

– Soluble form: goes into plasma

Question 20

3. Body fluoride is continuously regulated by

clearance mechanism

Answer 20

– Excretion: Renal clearance

– Retention: Skeletal clearance

Question 21

Fluoride absorption

Answer 21

• Form of fluoride in stomach: > Hydrogen fluoride (HF)
H+ + F- to HF
• Properties of HF: weak acid, pKa = 3.4
• The rate of absorption increases with the acidity of gaster.
• Therefore, absorption of fluoride from sour juice is faster compare to coffee, milk
etc.

Question 22

Mechanism of absorption of Fluoride in stomach:

Answer 22

1. Excess of H+ combine with F
   - and form HF
2. Formation of HF create/ increase a pH
   gradient
3. ## When pH gastric < pH extracellular, Fin the
   form of HF diffuse out across the gastric
   mucosa to the plasma

Question 23

Fluoride in the plasma & its distribution 1

Answer 23

[F]plasma reach a peak
within 15-30 min
after absorption

Question 24

Fluoride in the plasma & its distribution 2

Answer 24

Conc. at the peak is
dependent on:
– amount consumed
– acidity of stomach
– absorption rate
– diet composition

Question 25

Fluoride in the plasma & its distribution 3

Answer 25

Reduction of [F]plasma is due to its clearance mechanism

Question 26

Distribution of fluoride…

Answer 26

in hard tissues, in soft tissues, plasma, body fluid

Question 27

in hard tissues

Answer 27

``` – 99% fluoride in hard tissues: bones & teeth – Concentration varies • Cancellous bones > compact bones • Dentine & bones:  age • Enamel: high plaque covered area low Surfaces with attrition ```

Question 28

• in soft tissues

Answer 28

– Absorption in the form of hydrogen fluoride (HF) | – [F]soft tissues = [F] plasma

Question 29

fluoride in plasma

Answer 29

``` [Fluoride] plasma is influenced by the amount of ingested – Very low conc. in ionised form • When [F] H2O = 1.0 ppm • When [F] plasma = 1.0 micromol/L ```

Question 30

fluoride in body fluid

Answer 30

– [Fluoride]GCF > [Fluoride]plasma, parotid & submandibular saliva – [Fluoride] oral is absorbed by mucosal tissues & dental plaque to released into saliva to into gastrointestinal tract

Question 31

Clearance Mechanism.

Answer 31

skeletal clearance, renal clearance

Question 32

skeletal clearance

Answer 32

Deposition of fluoride to bone (calcified tissues) occurs at fast rate. -50% Fluoride is absorbed Gets deposited within 24 hours 50% of absorbed fluoride is excreted in urine Continues until the equilibrium is reached (Return to normal after 36 hrs after ingestion) Note: Hard tissues are reservoir for fluoride

Question 33

renal clearance

Answer 33

``` Rate of renal clearance – adult 35 ml/min (FAST) – infant < 12 ml/min (SLOW) • Reabsorption of fluoride occurs at the renal tubule: – under the influence of urine pH Very low conc. of F is excreted out via the salivary glands back into the oral cavity ```

Question 34

acid influence for renal clearance , if low phh

Answer 34

> HF > diffusion > F is reabsorbed | • < F  < remain < Fis excreted

Question 35

acid influence for renal clearance , if high ph

Answer 35

< HF < diffusion < Fis reabsorbed | • > F  > remain > Fis excreted

Question 36

• Fluoride is essential

Answer 36

-low conc. of < 1 ppm -Not toxic if taken into the body in sufficient amounts (fatal dose 5.0 mg NaF) -Cations such as Ca2+, Mg2+ & Al3+ can form complexes with fluoride -If not in the complex form, 80-90 % fluoride from the gaster is absorb into the plasma

Question 37

Fluoride Toxicity

Answer 37

Chronic Effects | Acute Effects

Question 38

Acute Effects

Answer 38

``` (Inhibition of the enzyme system & CNS) • Renal dysfunction • Hypocalcemia • Cardiovascular disorder • Death (within 2-3 days) Note: Acute toxicity of fluoride can occur after ingesting one or more doses of fluoride over a short time period which then leads to poisoning ```

Question 39

Chronic Effects

Answer 39

* Dental fluorosis * Skeletal fluorosis * Stomach upset

Question 40

Fluorosis

Answer 40

Dental Fluorosis | Skeletal Fluorosis

Question 41

Skeletal Fluorosis [F] = > 20 ppm

Answer 41

``` Abnormality of the skeletal bone • Radiology data – density of bone is higher Prolonged exposure • Calcification of tendons, ligaments & muscles ```

Question 42

Dental Fluorosis [F] = > 2 ppm

Answer 42

``` Mottled enamel (opaque white spots / irregular white flakes) • Influence of F during the organic & inorganic phases of amelogenesis *Hypoplasia-permanent teeth (Might be due to tetracycline intake during pregnancy) ``` Notes: Happen during tooth development Irreversible effect

Question 43

Dental Fluorosis…How does it occurs?

Answer 43

``` 1. Excess of F ions retain immature matrix proteins (amelogenin & ameloblastin) leading to accumulation of these proteins 2. Results in incomplete crystal growth -Wide gaps develop between enamel rods: cause porosity -Less hydroxyapatite crystals formed: brittle enamel ```

Question 44

Fluorosed enamel

Answer 44

structurally weak & unable to withstand pressure thus prone to breakage Difficult for dental procedures which require drilling & filling