Fluoride

Question 1

Sources of fluoride - environment

Answer 1

Rock and soil
Anionic form (F-) as flurospar and cryolite
Water supplies

Question 2

Ingestion and absorption

Answer 2

Soluble and rapidly absorbed
Passive absorption stomach as HF
Small intestine pH dependant as F-
50% absorbed within 3min
Potential to absorb 80-90% absorbed in absence high Ca2+
Organic sources of F- less readily absorbed
Bioavailability high generally

Question 3

Factors affecting absorption

Answer 3

Increases in highly soluble forms e.g. NaF with water
Decreases with high dietary concentration of Ca2+ or other di/trivalent cations
Decreases when ingested with milk or baby formula
Decreases when ingested with dietary fat
Decreases when on vegetarian diet
Stomach pH

Question 4

What causes body F elimination?

Answer 4

Vegetarian diet
Increased pH of renal tubular fluid
Increased urinary excretion

Divalent/trivalent cations
Formation of F complexes in GIT
Increased faecal excretion

Question 5

What causes systematic F uptake?

Answer 5

Dietary fat
Decreases rate of gastric emptying
Increased stomach F absorption
Diet, toothpaste ingestion and supplements all contribute to total F intake

Question 6

Transport and cellular distribution

Answer 6

Higher pH of extracellular fluid leads to dissociation of HF -> H+ and F-
Bound to proteins as fluorine in blood and tissue
Concentration blood and non-calcified tissues is small
Body fluid and tissue F- concentrations are proportional to long-term dietary intake
50% absorbed F- found in calcified tissues (bone and teeth), 80% in young children
Bone and teeth accounts for 99% total body F-

Question 7

Excretion

Answer 7

50-60% absorbed dietary F- is excreted
Main route of excretion via kidneys as fluoride
Fluoride enters glomerular filtrate
Re-absorbed as HF via passive diffusion
10% excreted in faeces (infants)
24-hour urinary F- used monitor status

Question 8

Factors affecting excretion

Answer 8

Plasma levels F-
High F- reduced glomerular filtration rate
pH urine
Flow of urine

Question 9

Importance of fluoride in caries prevention

Answer 9

Exposure to F is most reasonable explanation for decline in caries
However, excess F causes fluorosis of enamel
Optimising use of F for maximum caries prevention and minimal fluorosis is crucial

Question 10

Action of fluoride

Answer 10

Thought to act by improving tooth structure (systemic effect)
Local intra-oral action is now considered more important
Fluoride aids mineralisation
Fluoride inhibits anaerobic glycolysis and subsequent acid production by oral bacteria

Question 11

The early stages of dental caries can be prevented, reversed or arrested, through the elimination or modification of…

Answer 11

Aetiological factors - dietary or microbial
and or enhancing
Protective factors - fluoride, sealants and salivary stimulation

Question 12

Acute toxicity

Answer 12

Sudden ingestion of large dose
Causes nausea, vomiting, diarrhoea and abdominal pain
Certain lethal dose is 32-64mg/F/kg
Safe tolerated dose is 8-16mg/F/kg

Question 13

Chronic toxicity

Answer 13

Smaller dose over long time
Affects teeth while still forming, up to 6 years
Affects bone continually - skeletal fluorosis
Optimum safe daily dose for dental health benefits is 0.05-0.07mg/kg body weight per day in children under 12

Question 14

Excess fluoride exposure leads to…

Answer 14

Dental and skeletal fluorosis
Chronic kidney disease
Liver damage

Question 15

Fluoride therapy - systemic and topical

Answer 15

Public water fluoridation
School water fluoridation
Fluoridised salt
Fluoridised milk
Fluoride drops or tablets

Question 16

Fluoride therapy - topical

Answer 16

Topical application
Fluoride mouth rinse
Fluoride toothpaste

Question 17

F level in water and prevalence of dental decay follow a … shaped curve relationship

Answer 17

J

Question 18

Water fluoridation at … ppm was the best balance between caries and fluorosis

Answer 18

1

Question 19

Occurrence of dental caries shows a social class trend with … social classes at greatest risk

Answer 19

Lower

Question 20

Fluoride acts … and … to protect teeth from dental caries

Answer 20

Systemically and topically

Question 21

Water fluoridisation at 1 PPM decreases dental caries by…

Answer 21

20-50%

Question 22

Dietary fluoride comes from …

Answer 22

Water, drinks and foods prepared with fluoridated water, seafood and tea

Question 23

What 2 things are used to deliver F?

Answer 23

Milk and salt

Question 24

Milk only works to deliver F where there are…

Answer 24

Existing school milk programmes

Question 25

Sources of fluoride - diet

Answer 25

Natural sources Added: water, milk and salt

Question 26

Sources of fluoride - dental

Answer 26

Toothpaste Mouthwash Fluoride supplements