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Fluorine is a common element that does not occur in the elemental state in nature
because of its high reactivity. It accounts for about 0.3 g/kg of the Earth’s crust and
exists in the form of fluorides in a number of minerals, of which fluorspar, cryolite
Hydrogen fluoride (HF) is a colourless, pungent liquid or gas with a boiling point
of 19.5 °C. It is highly soluble in water, in which it forms hydrofluoric acid.
Sodium fluoride (NaF) is a colourless to white solid that is moderately soluble in
Fluorosilicic acid (H2SiF6), which is also known as hexafluorosilicic acid, is a
colourless solid that is highly soluble in water. And fluorapatite are the most
common. The oxidation state of the fluoride ion is -1.
Inorganic fluorine compounds are used in industry for a wide range of purposes.
They are used in aluminium production and as a flux in the steel and glass fibre
industries. They can also be released to the environment during the production of
phosphate fertilizers (which contain an average of 3.8% fluorine), bricks, tiles and
ceramics. Fluorosilicic acid, sodium hexafluorosilicate and sodium fluoride are
used in municipal water fluoridation schemes also sodium monoflourophosphate
are used in manufacturing of toothpaste.
In the human body, fluoride is mainly associated with bones and teeth. It plays an
important role in the prevention of dental caries. Although the primary mechanism
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of action of fluoride in preventing dental caries is topical, systemic mechanisms are
Fluoride acts in the following ways to prevent dental caries:
1. It enhances remineralization of the tooth enamel. This is the most
important effect of fluoride in caries prevention.
2. It inhibits demineralization of the tooth enamel. Mineral structure of the
tooth that includes fluoride (fluorapatite) is more resistant to demineralization than
one without fluoride (hydroxyapatite).
3. It makes cariogenic bacteria less able to produce acid from carbohydrates.
Fluoride has been available in the United States since the mid-1940. In 2008,
64.3% of the population served by public water systems received optimally
fluoridated water. Public water fluoridation practice varies by city and state.
Water fluoridation was recognized by the Centers for Disease Control and
Prevention (CDC) as one of the 10 greatest public health achievements of the 20th
century. There is strong evidence that community water fluoridation is effective
in preventing dental caries. The recommended concentration of fluoride in
drinking water was decreased in 2011 from 0.7-1.2 mg/L to 0.7 mg/L.Clinicians
should balance the benefits of fluoride against the risk of fluorosis when deciding
whether to fluoridate water. Water filters may decrease the fluoride content of
community water. Activated charcoal filters and cellulose filters have a negligible
effect; reverse osmosis filters and water distillation remove almost all fluoride
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Occurrence and sources
Many fluoride minerals are known, but of paramount commercial importance is
fluorite. It is composed of calcium fluoride, with small impurities. The soft,
colorful mineral is found worldwide and is common. In seawater, fluoride
concentration averages 1.3 parts per million (ppm). For comparison, chloride
concentration in seawater is about 19,000 ppm. The low concentration of fluoride
reflects the insolubility of the alkaline earth fluorides, e.g., CaF2.
Sources of fluoride
Systemic Sources of Fluoride
Fluoride can be ingested through
Traces of fluorides are present in many waters; higher concentrations are often
associated with underground sources. In seawater, a total fluoride concentration of
1.3 mg/litre has been reported (Slooff et al., 1988). In areas rich in fluoride
containing minerals, well water may contain up to about 10 mg of fluoride per
litre. The highest natural level reported is 2800 mg/litre. Fluorides may also enter a
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river as a result of industrial discharges (Slooff et al., 1988). In groundwater,
fluoride concentrations vary with the type of rock the water flows through but do
not usually exceed 10 mg/litre.
In bottled water, no one source exists to tell consumers the fluoride content in
bottled waters. The US Food and Drug Administration (FDA) does not require that
fluoride content be listed on the labels of bottled waters. It is appropriate to assume
that children whose only source of water is bottled are not receiving adequate
amounts of fluoride from that source.
Virtually all foodstuffs contain at least traces of fluorine. All vegetation contains
some fluoride, which is absorbed from soil and water. The highest levels in field
grown vegetables are found in curly kale (up to 40 mg/kg fresh weight) and endive
(0.3–2.8 mg/kg fresh weight). Other foods containing high levels include fish (0.1–
30 mg/kg) and tea. High concentrations in tea can be caused by high natural
concentrations in tea plants or by the use of additives during growth or
fermentation. Levels in dry tea can be 3–300 mg/kg (average 100 mg/kg), so 2–3
cups of tea contain approximately 0.4–0.8 mg. In areas where water with high
fluoride content is used to prepare tea, the intake via tea can be several times
Infant nutrition. Human breast milk contains almost no fluoride, even when the
nursing mother drinks fluoridated water. Powdered infant formula contains little or
no fluoride, unless mixed with fluoridated water. The amount of fluoride ingested
will depend on the volume of fluoridated water mixed with the formula.
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Supplements should be considered especially for patients at high risk for dental
caries whose community water source is suboptimal. Supplements are available in
liquid, tablet, or lozenge form.
0.25–1 mg per tablet;
The 2010 ADA guideline recommends fluoride supplements be prescribed only to
children at high risk for caries development. The United States Preventive Services
Task Force recommends fluoride supplementation be prescribed at recommended
doses to children older than 6 months whose primary water source is deficient in
Topical Sources of Fluoride
Toothpaste is the most recognizable source of topical fluoride.
The addition of fluoride to toothpaste began in the 1950s.
Brushing with fluoridated toothpaste is associated with a 24%
reduction in decayed, missing, and filled tooth surfaces.
A recent review by the Cochrane Collaboration concluded that
regular use of fluoridated toothpaste is associated with a “clear
reduction in caries increment.”
Mouthrinses containing fluoride are recommended in a “swish and spit” manner.
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Mouthrinses are available over the counter. Frequency of use ranges from daily to
According to the Cochrane Collaboration, regular fluoride mouthrinses use reduces
tooth decay in children, regardless of other fluoride sources, with an average 26%
reduction in decayed, missing, and filled tooth surfaces. Fluoride mouthrinse
programs are sometimes utilized in schools.
Fluoride gels are professionally applied or prescribed for home use under
professional supervision. They are typically recommended for use twice per year.
The gel is placed in two trays (one tray for the upper teeth, and one tray for the
bottom teeth), which are then placed in the patient’s mouth. The patient is then
asked to bite down on the trays for 4 minutes. Due to the high acidity of the gel
(pH 3.5), saliva flow is markedly increased during the course of the treatment, thus
increasing the percentage of the gel that is ingested. The high acidity also enables
the fluoride to cross directly through the gum membrane
When scientists discovered in the 1980s the enormous spikes in blood fluoride
levels that occur after fluoride gel treatment (see below), the dental community
implemented measures to reduce the amount of
fluoride ingested from the gel
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These measures include:
A. ensuring that the patient is sitting upright
B. reducing the amount of gel used for young children;
C. placing a suction device in the mouth during the course of the treatment to
vacuum out the excess saliva; and
D. encouraging the patient to spit (i.e., expectorate) for up to one minute when
the trays are removed from the mouth
Varnishes are a professionally applied, sticky resin of highly concentrated fluoride
(up to 22,600 ppm).
In the United States, fluoride varnish has
been approved by the FDA for use as a
cavity liner and root desensitizer, but not
specifically as an anti-caries agent. For
caries prevention, fluoride varnish is an “off
Varnishes have been used extensively in
Europe, Scandinavia, and Canada as
preventive intervention for dental caries.
Application frequency for fluoride varnish ranges from 2 to 6 times per year.
The use of fluoride varnish leads to a 33% reduction in decayed, missing, and
filled tooth surfaces in the primary teeth and a 46% reduction in the permanent
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Community Water Fluoridation and Deflouridation.
The goal of community water fluoridation is to maximize dental caries prevention
while minimizing the frequency of enamel fluorosis. A 1994 World Health
Organization expert committee suggested a level of fluoride from 0.5 to 1.0 mg/L
(milligrams per litre), depending on climate. Bottled water typically has unknown
fluoride levels, and some domestic water filters remove some or all fluoride.
Defluoridation is needed when the naturally occurring fluoride level exceeds
recommended limits especially for our country which reported to have exceeded
amount. Common methods of Defluoridation are
Synthetic ion exchange
reverse osmosis and
This technique most used in our country for deflouridation. The Nalgonda
technique is a means of fluoride removal that depends on the flocculation,
sedimentation, and filtration of fluoride with the addition of aluminum sulfate and
lime. This technique was developed by the National Environmental Engineering
Research Institute in India in 1975 in response to fluorosis concerns. Aluminum
sulfate (Al2 (SO4)318H2O) is added to the water to acts as a flocculent. Though
aluminum sulfate is commonly used in general water treatment as a flocculent, the
amounts used in defluoridation are much higher (150 mg/mgF or 1000mg/L or 20
times normal). As is typical with flocculation processes, the water must be
thoroughly stirred to ensure dispersal of the flocculating agent. Because the
reaction results in an excess of H+ ions, Lime (Ca (OH)2) is added to the water
during the process to help maintain a neutral pH and hasten the settling of the
sediment. The amount of lime added is typically 5% (by mass) of the aluminum
sulfate added though some sources say significantly more (20-50% of alum by
mass) should be added. The chemical processes, though admittedly are not fully
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A possible home set up for implementing the Nalgonda technique.
Reverse osmosis is a technology that has been used more successfully in the
developed world than the developing world. This process is achieved by applying
high pressure to water against a semi permeable membrane that is capable of
rejecting undesired ions from passing through. A variation of this process is
known as electrodialysis that relies on DC potential to remove specific ions. In
fact, reverse osmosis can be used to remove a variety of undesired quantities from
the water depending on the nature of the membrane used.
Being a purely physical process, it eliminates many of the problems seen with
other defluoridation techniques, like pH balancing and the need for regeneration.
Reverse Osmosis has been shown to successfully treat water with fluoride
concentrations up to 12 mg/L. Unfortunately, reverse osmosis has not been
successfully implemented in the developing world for a number of reasons. The
primary being that it is a very costly defluoridation option. Additionally, reverse
osmosis requires much electrical power to operate. Also, 20-40% of water is lost in
this treatment process, possibly much more. Technological improvements in
materials and larger scale operations may someday make this technology
affordable to more people in need of defluoridation technology
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Synthetic ion exchange.
There are a number of strong base anion exchangers that are able to perform an ion
exchange process to remove fluoride from water, typically exchanging for chloride
ions. Many of these are not specifically designed for use in removing fluoride, but
rather all anions.
Thus because they are not specifically designed for removing fluoride, their
actually fluoride removal capacities are relatively low. Though able to be
regenerated with the use of chloride salts, they are not necessarily the most
economical and available in areas where they are not produced, and thus, at this
point, are not able to really be considered an alternative in the developing world
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KINETICS AND METABOLISM IN LABORATORY ANIMALS AND
After oral uptake, water-soluble fluorides are rapidly and almost completely
absorbed in the gastrointestinal tract. Absorbed fluoride is transported via the
blood; with prolonged intake of fluoride from drinking-water, concentrations in the
blood are the same as those in drinking-water, a relationship that remains valid up
to a concentration in drinking-water of 10 mg/litre.
Distribution of fluoride is a rapid process. It is incorporated into teeth and bones;
there is virtually no storage in in soft tissues. Incorporation into teeth and skeletal
tissues is reversible: after cessation of exposure, mobilization from these tissues
takes place. Fluoride is excreted via urine, faeces and sweat (IPCS, 1984; US EPA,
1985a; Janssen et al., 1988).
Fluoride in inhaled particles is also absorbed, the extent of absorption depending
on the size of the particles and the solubility of fluoride compounds present.
There are numerous fluoride “belts” throughout the world where groundwater
contain unsafe levels of fluoride. These belts span over 14 countries in Africa, 8
countries in Asia, and 6 countries in the Americas that all having water considered
unsafe by the World Health Organization (WHO) this may result in fluorosis .And
fluorosis is caused by an increased intake of fluoride. There are general two
categories which are:
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Dental fluorosis is by far the most common manifestation of over-consumption of
fluoride. It is visible by white, yellow, and brown streaks on the teeth,
characteristic of the hypoplasia and hypocalcification.
This damage is more than cosmetic, as it tends to be associated with painful
"cavity-like" feelings. Additionally, there are social stigmas against those suffering
from fluorosis. It had once been postulated that men were more disposed to
suffering from dental fluorosis than women, however, it is now believed that this
inference was incorrect, and that women are more likely to try to hide the effects of
While all teeth are affected, the incisors (especially the maxillary incisors) and
permanenet molars are often the teeth most affected by fluorosis. It is speculated
that this is because these are the first teeth to develop.
Normally dental fluorosis described as: check photograph bellow
Mild forms of fluorosis appear as chalk-like, lacy markings on the tooth’s enamel.
Moderate form of dental fluorosis, a white opacity can be seen on more than 50%
of the tooth.
Severe fluorosis results in brown, pitted, brittle enameluorosis
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Though it generally takes far more time, and higher concentrations (typically over
10mg/l) to develop, skeletal fluorosis is far more severe than its dental counterpart.
Though not initially obvious to diagnose,
skeletal fluorosis can be detected early on
radiologically. Skeletal fluorosis is
characterized by deformation of bone structure.
Movement of the spine, pelvis, and joints
become increasing arduous as fluoride deposits
collect on ligaments and tendons and within
the bones themselves. Skeletal fluorosis to the
point of crippling is not uncommon.
Skeletal fluorosis is non-curable, thus efforts
should be directed toward prevention and
attempting to alleviate some of the symptoms
There are increasing accounts of the neurological affects that fluoride can have on
the body. It is suspected that these complications are caused by fluorides effects on
the spine and compression on the spinal cord. Studies have shown that high levels
of fluoride can cause headaches, insomnia, and reductions in the IQs of children.
Fluorosis has significant economic impacts in the developing world. In addition to
fluorosis removing people from the workforce, water supply programs have thrown
away significant finances while providing costly boreholes that become useless
upon the discovery of the toxic levels of fluoride that they contain.
Perceptions and Education on Fluoride and Fluorosis
Because fluoride does not cause water to have any abnormal, taste, and odor, it is
difficult to determine if water has significant fluoride concentrations. Because of
this and the cumulative nature of fluoride as a toxin (that is, the results of
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consumption are not immediate), many peoples do not automatically connect water
consumption to fluorosis. The effects of the disease have been attributed to a wide
range of sources by different peoples including genetics, infection, and diet. (One
people group in Kenya believes that fluorosis is caused by eating of potatoes that
are too hot.)
Therefore, there is a great need for education on and awareness of fluorosis in
fluorotic areas and to connect water consumption to the symptoms of fluorosis. In
many of these areas, little priority is given to water defluoridation because water
sources are scarce enough that peoples are not concerned with water quality.
And because fluoride consumption has no immediate health effects and
defluoridation methods are generally more time and money intensive than other
water treatment types, there is generally a lack of motivation on the part of the
people to be concerned with defluoridation. Even when defluoridation methods are
used, the lack of immediate results is a hindrance in encouraging the continued use
1. American Academy of Pediatric Dentistry. Guideline on Infant Oral Health
Care. Council on Clinical Affairs. Reference Manual 2011. 33(6): 124-128.
2. American Academy of Pediatric Dentistry. Policy on Early Childhood Caries
(ECC): Classifications, Consequences, and Preventive Strategies. Pediatr Dent
2011, 33(6): 47-49.
3. American Dental Association Council on Scientific Affairs. Professionally
applied topical fluoride. Evidence-based clinical recommendations. JADA. August
1, 2006. 137(8): 1151-1159.
4. Berg J, Gerweck C, Hujoel PP, et al. Evidence-Based Clinical
Recommendations Regarding Fluoride Intake from Reconstituted Infant Formula
and Enamel Fluorosis. A Report of the American Dental Association Council on
Scientific Affairs. JAMA. January 2011 vol. 142(1): 79-87.
5. Centers for Disease Control and Prevention. Recommendations for using
fluoride to prevent and control dental caries in the United States. MMWR. 2001;