This document discusses the mode of action of fluoride on dental caries and its effects on human health. It describes how fluoride is incorporated into dental enamel during tooth development, which strengthens enamel and makes it more resistant to acid attacks that cause cavities. It also discusses optimal fluoride intake levels and the risks of dental fluorosis from excessive fluoride ingestion during tooth development.

2.  To provide an overview of the mode of action
of fluoride on caries and its effect on human
health.

3. “ COLORADO BROWN STAIN”
 Dr. Frederick McKay early 1900s started practice is
Colorado springs.
 1908 McKay started investigation of Colorado brown
stain

4.  He wrote colorado brown stain as “ mottled enamel”
 CHURCHILL in 1931 identified F in water of colonardo
spring area in amounts ranging up to 14ppm.

5.  In the mid 1930s Dean replaced the term mottled enamel
to FLUOROSIS
 By the mid of 1930s he concluded that 1ppm F is the
minimal threshold and soon after he defined it as
PERMISSIBLE MAXIMUM.

7. smooth, glossy, pale creamy white color.
slight translucency, white flecks to occasional white
spots.
small, opaque, scattered paper white areas involving 25%
of the tooth surface.
white opaque areas, but don't involve as much as 50% of the
tooth.
enamel surfaces effected, attrition is noticed, brown stain
is frequently a disfiguring feature.
all enamel surfaces effected, hypoplasia. Widespread brown
stains , and corroded appearance.

9. Plants like tea contains fluoride.
Fish has high content of fluoride b/c ocean
contains about 1ppm of fluoride.
In the hydrosphere it is seen that all water
contains fluorides although in varying content.
The highest fluoride value has been recorded in
the Nakaru Rift Valley of Kenya(2800 mg/ltr-
5600mg in soil.

10. F derived from volcanic eruptions or mining
industries is present in the atmosphere and
enters soil by deposition as dust, snow, fog or
rain.
Leaches from the soil into ground water and is
taken up by vegetation.
Plants take up F by absorption from air and soil
and deposition from dust.
Enters food chain, returns to soil as waste.

11.  Frank McClure estimated “average daily diet”
contained 1.0-1.5 mg F or about 0.05 mg F/kg
body weight per day in children up to 12 years
age.
0.06mg F/kg per kg body weight per day was
optimal F intake.

12. Absorption and distribution
Fluoride in blood plasma
Fluoride in soft tissue
Fluoride in hard tissue
Bones
Teeth
Fluoride in placenta and fetus
Fluoride excretion

13. Major route of absorption is GIT.
 Fluoride w/c is absorbed mainly from the
stomach and from small intestinal mucosa.
Carried by blood plasma and distributed to
various tissues like:
 Mineralizing tissues, teeth and bone
 Salivary gland
 Soft tissues

14. Plasma levels are high in people living in
fluoridated area then people in non-fluoridated
area.
In plasma it exist in two general forms:
1. Ionic
2. Non ionic
Normal plasma fluoride concentration (0.7-2.4
microns/ml).

15.  Fluoride from the plasma is distributed to all
the tissues and organs of the body.
The rate of delivery is dependent on the blood
flow to the tissue.
Fluoride is concentrated at high levels in kidney
tubules.

16.  about 99% of all Fluoride in the human body is
found in calcified tissue such as bone and teeth.
Great extent during active bone formation.
Greater extent in cancellous bone.
Fluoride content of bone depend on plasma
Fluoride which in turn reflects the availability
from food, drink and inhalation.

17.  Fluoride in teeth is present in the highest concentration
in cementum.
 Developing enamel tends to absorb Fluoride actively
due to its porous nature.
 Once eruption occurs, it is seen that the surface layer of
enamel has the highest rate of Fluoride .
 Fluoride in dentine is more than that of enamel.
 Post eruptive changes are reflected in the outer layer of
enamel owing to diffusion from saliva, ingested food
stuff, plaque etc.
 Surface enamel content of Fluoride is 500-4000mg/kg
while deep enamel contains 50-100mg/kg.

18. • 10-25% of the daily intake of Fluoride is not
absorbed and is excreted in feaces.
• The elimination of absorbed Fluoride occurs
exclusively via kidneys.
• Fluoride is present in sweat, feaces, tears,
breast milk etc.

19.  symptoms of overdose
-GI, CNS – death in 4hours
Probable toxic dose:
-5mgF/kg
Certain lethal dose:
-16-32mgF/kg

20. Dental fluorosis is a permanent hypo-
mineralization of enamel that is characterized
by greater surface and sub surface porosities
than in normal enamel and that results from
excess fluoride reaching and developing tooth
during developmental stages.

21. Enamel with fluorosis is very prone to
fracture.
It is also prone to caries in severe cases
due to pitting.

22. POSTERUPTIVE:
-promotion of remineralization and inhibition of
demineralization of early carious lesions.
-inhibition of glycolysis.
 PRE-ERUPTIVE:
some reduction in enamel solubility in acid by pre-eruptive
incorporation of fluoride into the hydroxyapatite crystals.

23.  Fluoride introduced into the mouth is partly taken up by
dental plaque
 95% of F is held in bound form
 5-10mg F/kg wet weight in low F area
 10-20mg F/kg wet weight in fluoridated area.

24.  Fluoride inhibition of caries depends on its pre eruptive
incorporation into developing dental enamel solubility in
demineralizing acids.
 Only fewer enamel lesions progress to dentinal caries in
a fluoridated area than in a non fluoridated area.

25. Resting salivary fluoride concentrations are
low, they are three times higher in fluoridated
areas.
After tooth brushing and mouth rinsing salivary
fluoride levels can rise 100 to 1000 fold.

26.  caries reduction is greatest for the free
smooth surfaces and proximal surfaces of
teeth.
Less pronounced for pits and fissure surfaces.

27. Effective use of fluoride
 The most effective community wide use of F is in
frequent low-concentration intraoral exposures such
as in drinking water or tooth paste.
 Less effective form is gel.