Community Dentistry Third Year

1. Fluorides
PDS 372

2. • The story of fluoride

5. • Colorado Brown Stain
• Frederick McKay
• H. Trendley Dean, head of the Dental
Hygiene Unit at the National Institute of
Health (NIH)

6. • Desirable F concentration:
– The highest F concentration incapable of
producing a definite degree of mottled enamel
in as much as 10% of the group examined.
• The permissible maximum : 1 ppm F

7. 1945
• During the 15-year project, researchers
monitored the rate of tooth decay among
Grand Rapids' almost 30,000
schoolchildren
• After 11 years, the caries rate among
Grand Rapids children born after fluoride
was added to the water supply dropped
more than 60 percent

8. Environmental Fluoride
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Seawater 1.2-1.4 ppm
Fresh surface water 0.2
Deep well water 29.5 ppm
Over 40 ppm in boreholes in Kenya

9. Sources and F intake
• 0.04 mg F/day from air
• 1~3 mgF for adult from diet and F-water
• Market basket study
– 0.21-0.54 mg F/day (infants 6 months old)
– 0.41-0.61 mg F/day (2 years old)
• For a 12-months child, the upper limit of
intake beyond which fluorosis risk is
greatly increased: 0.43 mg Fday
• F content of food vary. Table 24-1

10. Fluoride physiology
Absorption, retention and excretion
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Absorbed From Upper GIT (95%)
Transported in plasma
Excreted or deposited in the calcified tissue
5 mg F excreted in 8-9 hours
Plasma level of F increase w empty
stomach

11. • Body burden of fluoride: amount can be
safely absorbed, and at which F
absorption become a health concern
– Plasma concentration
• Ionic: fluctuated, see next slide
• Nonionic: the biologic significance is not dtermined
– Urinary excretion
• F balance: net result from the
accumulated effect of F ingestion, degree
of F deposition in bone and teeth,
mobilization rate of F from bone, efficiency
of the kidney in clearing absorbed F.

12. • Plasma concentration
– Normal 0.019 ppm
– Chronic kidney failure 0.05-0.09 ppm
– Nephrotoxic 0.95 ppm
• Dynamic storage
• F has affinity to calcified tissues
• Optimal fluoride intake
– Frank McClure (1943) 1-1.5 mg F
– 0.05-0.07 mg F/Kg per day

13. Fluoride toxicity
• Dose-response relationship
• 5 g F vs. 1-3 mg F daily (toxic vs. beneficial)
• Ingestion of single dose of 5~10 g of NaF by adult
male cause death in 2~4h
• Classic F toxicity study in Denmark 1930s:
– Gastric complications and osteosclerosis.
• Dental Fluorosis:
– Permanent hypomineralization of the enamel, with
surface or subsurface porosity, due to exposure of
excess fluoride during tooth maturation stage

14. Fluoride and caries control
• Work best when there’s constant low level of
F in the oral cavity.
• Work post-eruptively, at tooth plaque interface
• Mechanism of action
– Preeruptive: reduction of enamel solubility in
acids
– Posteruptive: *promote remin-. and inhibit demin-.
Of early lesion. *inhibit Glycolysis of carbs.

15. • Fluoride and plaque:
– Promote remin.
– Partly taken up by plaque in bound form. And
released in response to lower pH and taken
up by demin enamel.
– F in plaque inhibit the glycolysis
– Interfere with plaque adherence to enamel
– Specific bactericidal on cariogenic bacteria
• Fluoride and enamel
– Teil-Culemborg study: fewer enamel lesions
extends to dentinal caries in fluoridated areas
than in non-fluoridated area
– F inhibit further demin and promote remin

16. • Fluoride and saliva
– 0.016 ppm
– 0.006 ppm
– Its role in caries prevention is not well defined
• Effects on different tooth surfaces
– Murray’s study: More reduction on smooth
surface caries.
• Effective use of fluorides
– Systemic fluorides
– Topical fluorides