Fluoride & Fluorosis Ashish Sharma
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Geochemistry of Fluorine
The name fluorine originated from the Latin word ‘fluere’ (meaning ‘to flow’). Fluorine is the 13th most ubiquitous pollutant, abundant on earth. In its elemental form, it is a pale yellow, highly toxic and corrosive gas (Glasser, 1979). French scientists Henri Moissan discovered it in 1886. He has been awarded Nobel Prize in chemistry for this discovery in 1906 (Glasser, 1979). It combines with all elements except oxygen and noble gases to form fluorides. Fluorides are ubiquitous in nature and are present in rocks, soil, water, plants, foods and even air.
Several natural and anthropogenic sources contribute to the geochemical cycling of fluorine. The most important industrial processes that release fluorine compounds are—aluminium smelting, coal burning, phosphate fertilizer and cement production, and brick and ceramic firing. Fluorine is the lightest member of the halogen group and is one of the most reactive of all chemical elements. It is not, therefore, found as fluorine in the environment. It is the most electronegative of all the elements (Hem, 1989) which means that it has a strong tendency to acquire a negative charge, and in solution forms fluoride ions.
Geochemists have established that the fluorine content of the earth's crust is 950 parts per million (ppm), while chlorine content is seven times less than that. Despite that, sea water contains 1.3 mg/L fluoride as against 19,500 mg/L chloride. This indicates that the natural environment of the earth has a favorable mechanism to immobilize toxic fluoride for the safe existence of life.
In the humid, temperate tracts of the world, groundwater is distinctly acidic particularly due to acid rains caused by industrial pollution and contains little fluoride even when local rocks and soils contain high fluorine. People living in such tracts are prone to caries, necessitating fluoridation of drinking water supplies.
In the arid/semiarid tracts of the world including India, groundwater is distinctly alkaline to contain high fluoride even when local rocks and soils contain less fluorine. 2People living in such tracts are prone to fluorosis unless provided with low-fluoride drinking water.
If groundwater contains more than 1.0 mg/L of fluoride and is used for a long time for drinking and cooking purpose then it may cause fluorosis in living beings.
Forms of Fluorine
Fluorine can be isolated in two different forms including the molecular, diatomic gas, F2, and the ionic form, F. It is very difficult to isolate fluorine in its atomic form due to its high reactivity and electronegativity.
Fluorine is the most reactive of the halogens. Fluorine is the most electronegative element currently known. This means the elemental form, F, will actively seek another electron to satisfy the octet rule (8 electrons in the outer s and p shells). This extra electron could come from anything. Because of this, fluorine is the strongest known oxidizer. It is only found naturally on earth as 19F, its only stable isotope. Aqueous HF [hydrofluoric acid], is weakly acidic. This acid will dissociate in water, but only to small extent. In its dissociated form, F, it is a fairly strong base. Anhydrous HF (hydrogen fluoride) is a strong acid and its strength can be greatly increased through the addition of a lewis acid such as antimony pentafluoride.
Fluorine is not produced in a monatomic, uncharged form. It is generally always manufactured from the mineral fluorite, which is the major source of fluorine on earth. Though it is not produced as an elemental form, fluorine can be produced in its ionic and diatomic gas forms. This is done by a method developed by Henri Moissan in 1886. The method begins by reacting potassium fluoride and hydrogen fluoride, KF and HF respectively, to form potassium hydrogen bifluoride, KHF2. This compound is produced in an aqueous solution and is further electrolyzed to form gaseous hydrogen, gaseous fluorine, and ionic fluorine in an aqueous solution, H2, F2 and F respectively.
Molecular fluorine will act as an oxidant in most reactions. In electrochemistry, strong oxidizers have a high standard reduction potential. This value refers to the tendency of the compound or element in question to be reduced, or gain electrons. Fluorine has the highest standard reduction potential, +2.87V, making it the strongest oxidizer. Fluorine is known to react violently with hydrogen and alkali metals. It will react with alkali earth metals less violently and may form an insoluble salt. It is also know to form covalent bonds with transition metals, noble gases, and organic compounds. Due to its high reactivity, 3gaseous fluorine must be kept under dry conditions. If it comes in contact with moisture, it will decompose to form HF gas.
Available Forms
Fluorine can be very dangerous in its gaseous form. However, it is still available for purchase from chemical suppliers around the world. It can also be obtained by the purchase of fluorine containing compounds. It would have to be produced by one method or another of chemical conversion and isolation from these compounds.
Fluoride is the negatively charged ionic form of the element fluorine that has a high affinity for calcium. In the human body, it is mainly associated with bones and teeth. Fluoride plays a very important role in the prevention of dental caries. Although the primary mechanism of action of fluoride in preventing dental caries is topical, systemic mechanisms are also important.
Fluoride acts in the following 3 ways to prevent dental caries (listed in order of importance):
  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. A mineral structure of the tooth that includes fluoride (fluorapatite) is more resistant to demineralization than one without fluoride.
    Hydroxyapatite: A complex phosphate of calcium Ca5(PO4)3OH that occurs as a mineral and is the chief structural element of vertebrate bone.
  3. It makes cariogenic bacteria (e.g. streptococcus mutans) less able to produce acid from carbohydrates.
Magnitude of Problem
Fluoride in water is mostly of geological origin. Waters with high levels of fluoride content are mostly found at the foot of high mountains and in areas where the sea has made geological deposits. Known fluoride belts on land include—one that stretches from Syria through Jordan, Egypt, Libya, Algeria, Sudan and Kenya, and another that stretches from Turkey through Iraq, Iran, Afghanistan, India, northern Thailand and China. There are similar belts in the Americas and Japan. In these areas fluorosis has been reported.4
Fluoride in Water
Since some fluoride compounds in the earth's upper crust are soluble in water, fluoride is found in both surface waters and groundwater. In surface freshwater, however, fluoride concentrations are usually low—0.01 ppm to 0.3 ppm.
In groundwater, the natural concentration of fluoride depends on the geological, chemical and physical characteristics of the aquifer, the porosity and acidity of the soil and rocks, the temperature, the action of other chemical elements, and the depth of wells. Because of the large number of variables, the fluoride concentrations in groundwater can range from well under 1 ppm to more than 35 ppm. In Kenya and South Africa, the levels can exceed 25 ppm. In India, concentrations up to 38.5 ppm have been reported.
Scope of the Problem
The prevalence of dental and skeletal fluorosis is not entirely clear. It is believed that fluorosis affects millions of people around the world, but as regards dental fluorosis the very mild or mild forms are the most frequent.
International Status
The following countries have been identified for the problem of fluorosis: Pakistan, Bangladesh, Argentina, United States of America, Morocco, Middle East countries, Japan, South African Countries, New Zealand, and Thailand, etc.
In India
High groundwater fluoride concentrations associated with igneous and metamorphic rocks such as granites and gneisses have been reported from India, Pakistan, West Africa, Thailand, China, Sri Lanka, and Southern Africa.
In Gujarat
The groundwater of 4341 or 52.6% villages of the total 8252 villages in Gujarat is contaminated with more than 1.5 mg/L of fluoride. But WHO's recommendation for permissible fluoride is 1.0 mg/L. The people of all these villages are under the risk of fluorosis. However, all of them may not be afflicted by fluorosis because it largely depends on the metabolism and the degree of immunity of a person (Shah and Indu).
The geological survey of India has brought out considerable data which reveal that fluorite, topaz, apatite, rock phosphate, phosphatic nodules and phosphorites are widespread in India and contain high percentage of fluorides.
Fluoride is a highly reactive poison, which is not essential in drinking water by any scientific measure. In India, fluorosis was first detected in Nellore district of Andhra Pradesh during early nineteen thirties by farmers. They found it among their cattle. Later they found the same symptoms of ache and pains in joints, etc among themselves and among the people of neighborhood villages. The first medical report on Fluorosis was published during 1937 in the Indian Journal of Medical Research.
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Figure 1.1: Average concentration of fluorine in main rock types[Source: Athavale, R.N. and Das, R.K. (1999). Down to Earth, 8(6): 24–25].
Since then a lot of research work had been published primarily from Andhra and later from many other places of India.
The problem has reached alarming proportions affecting at least 17 states of India. Out of those 5 are hyper endemic, where 50–100% districts are affected viz. Andhra Pradesh, Tamil Nadu, Uttar Pradesh, Gujarat, Rajasthan. Major sources of fluoride for human exposures are water, food, air, medicament and cosmetics. It is roughly estimated that 60% of the total intake of fluoride is through drinking water. In India, it has been observed that tea, fluoridated tooth paste and high fluoride water make a major contribution for human ingestion.
Fluorosis is a water-borne non-communicable disease. Fluorosis is a disease caused due to excessive ingestion of fluoride in human or animal body. Fluorosis is a crippling and painful disease caused by intake of fluoride. Fluorides are the compounds of fluorine. Fluorine is the 13th most abundant element available in the earth crust. As the surface 6water passes through the fluoride rich rocks it carries fluoride with it, hence most of the fluoride is found in ground water than surface water.
What is fluorosis and how it can harm you?
  • If the presence of fluoride is more than one milligram in one litre water, it is considered harmful
  • Consumption of excess fluoride causes three types of fluorosis—dental, skeletal and non-skeletal
  • Dental fluorosis can be evident from chalky white teeth and yellow-to-brown pigmentation on teeth
  • Skeletal fluorosis leads to anterior bowing of lower limb bones and stiffness to back and neck muscles
  • A person with non-skeletal fluorosis has neurological and muscular ailments like weakness, nervousness, tingling sensation to fingers and stiffness.
Source: himalnews.wordpress.com
Fluorosis can occur as:
  • Water-borne fluorosis (hydrofluorosis)
  • Food-borne fluorosis
  • Drug and cosmetic induced fluorosis
  • Industrial fluorosis.
Historical Facts about Fluorosis
  • In 1866, fluoride was discovered by French scientist Henri Moissan
  • In early part of 20th century residents of certain areas of USA developed brown stains on teeth
  • In 1925, the term fluorosis was coined and used by Cristian and Guatier
  • In 1930, relationship between mottled enamel and fluoride in water was established
  • In 1930, Feil mentioned fluorosis in human as an occupational disease
  • In 1932, skeletal fluorosis was reported in humans as an occupational disease
  • In 1937, skeletal fluorosis was 1st reported in India
  • Feil first mentioned fluorosis in humans as an occupational disease in 1930. This was substantiated when the occurrence of skeletal fluorosis in cryolite miners in Denmark was reported (Moller and Gudjonsson 1932). In India, fluorosis was first reported in the then Madras Presidency in 1937.
The Disease and How It Affects People
Ingestion of excess fluoride, most commonly in drinking-water, can cause fluorosis which affects the teeth and bones. Moderate amounts lead to dental effects, but long-term ingestion of large amounts can lead to potentially severe skeletal problems. Paradoxically, low levels of fluoride intake help to prevent dental caries. The control of drinking-water quality is therefore critical in preventing fluorosis.7
The Condition and Its Effect on People
Fluorosis is caused by excessive intake of fluoride. The dental effects of fluorosis develop much earlier than the skeletal effects in people exposed to large amounts of fluoride. Clinical dental fluorosis is characterized by staining and pitting of the teeth. In more severe cases all the enamel may be damaged. However, fluoride may not be the only cause of dental enamel defects. Enamel opacities similar to dental fluorosis are associated with other conditions, such as malnutrition with deficiency of vitamins D and A or a low protein-energy diet. Ingestion of fluoride after six years of age will not cause dental fluorosis.
Chronic high-level exposure to fluoride can lead to skeletal fluorosis. In skeletal fluorosis, fluoride accumulates in the bone progressively over many years. The early symptoms of skeletal fluorosis, include stiffness and pain in the joints. In severe cases, the bone structure may change and ligaments may calcify, with resulting impairment of muscles and pain.
Acute high-level exposure to fluoride causes immediate effects of abdominal pain, excessive saliva, nausea and vomiting. Seizures and muscle spasms may also occur.
The Cause
Acute high-level exposure to fluoride is rare and usually due to accidental contamination of drinking-water or due to fires or explosions. Moderate-level chronic exposure (above 1.5 mg/L of water—the WHO guideline value for fluoride in water) is more common. People affected by fluorosis are often exposed to multiple sources of fluoride, such as in food, water, air (due to gaseous industrial waste), and excessive use of toothpaste. However, drinking water is typically the most significant source. A person's diet, general state of health as well as the body's ability to dispose of fluoride all affects how the exposure to fluoride manifests itself. Fluoride ingestion occurs through fluoridated beverages, fluoride-rich foods such as tea, ocean fish, gelatin, skin of chicken, fluoridated salt, food contaminated with fluoride-containing insect or post-harvest fumigants (e.g. sulfuryl fluoride) and pesticides (e.g. cryolite, sodium aluminium fluoride, Na3AlF6, which may be used on grapes) etc., fluoridated toothpastes, fluoride from any other environmental source, including cigarette smoke and industrial pollution, e.g. fluoride in dust and fumes from industries such as those manufacturing steel, aluminum, enamel, pottery, glass, bricks, phosphate fertilizer, and others involved with power, welding, water fluoridation plants, refrigeration, rust removal, oil refining, plastics, pharmaceuticals, tooth-paste, chemicals, and automobiles.
Fluoride is ingested from other sources apart from fluoridated water such as pesticides, post-harvest fumigants, air, food, salt, medications, toothpaste, dental restorations, health supplements, medications containing fluoride and fluoride mouth rinses, black rock salt (fluorite, CaF2) and foods containing black rock salt (Kala Namak) for flavor, e.g. Dhalmoth, other salty snacks, chat masala, etc., red rock salt and foods made using red rock salt and tobacco or supari (Aracanut) when they are chewed by themselves. Regardless of the 8fluoride ingested by all sources, severity of fluorosis increases with an increase in the malnutrition of people.
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Figure 1.2: Geographical distribution of fluorosis in India
9Nevertheless, in the most affected states listed above, half or more of the districts have some villages with ground water supplies having high fluoride concentrations. In these states, 10 to 25 per cent of the rural population has been estimated to be at risk, and perhaps a total of 60–70 million people in India as a whole may be considered to be so (UNICEF, 1999).
Worldwide domestic use of water is about 10% (FAO; 2002b; Crops and Drops); in India, the domestic use is 4.5% (IRMA/UNICEF, 2002) and ‘groundwater accounts for nearly 50% of the urban domestic and 80% of the rural domestic water need in India’ (Dinesh Kumar et al, 2004).
Long back it was believed that fluorosis is a problem of elderly age group but it have been found that children in the age group of 0 to 12 years are most prone to fluorosis as their body tissues are in formative/growth stage during this period. The problem is so severe that if expectant mothers ingest high fluoride water, it can create many problems with developing fetus. It not only affects the body of a person but also renders them socially and culturally crippled.
The Factors, Which Govern the Development of Fluorosis, are the following
  1. High levels of fluoride in drinking water supplies and in the foodstuffs grown in these endemic areas.
  2. Tropical weather and hard manual labor by affecting the intake of water.
  3. Poor nutrition and diets deficient in their content of calcium, magnesium and vitamin C aggravate fluoride toxicity. High intake of calcium reduces the amount of absorbed into the bones.
  4. Magnesium has a peculiar relationship with fluoride and its optimum intake helps in elimination of fluoride from the body. Vitamin C is beneficial in some way in reducing fluoride toxicity. Diets deficient in calories and calcium intake increase the incidence of fluorosis (WHO-2002).
  5. Renal disease aggravates fluorosis by increased deposition of fluoride in the bones. A diseased kidney cannot handle fluoride excretion from the body and hence its increased deposition in the bones.
  6. Presence of abnormal amounts of certain trace elements in the drinking water supplies such as strontium, uranium, etc. Strontium levels in drinking water supplies in some endemic areas are high and strontium is a bone-seeking element like fluoride and both these aggravate the bony changes.
Other conditions may look like fluorosis. Developmental defects and problems with the skull or bones of the face can disrupt the enamel or dentin of the teeth. In addition, high fevers or trauma (such as a fall that injures a tooth) in infants or young children may discolor teeth. Young children can get cavities in their primary teeth, so any tooth discoloration should be checked at the dental office.10
Differential Diagnoses
The differential diagnosis for this condition may include Turner's hypoplasia (although this is usually more localized), some mild forms of amelogenesis imperfecta, and other environmental enamel defects of diffuse and demarcated opacities. All three types of presentations in fluorosis need to be differentiated from simulating illnesses.
Difficulty in Diagnosing
Fluorosis is a crippling disorder due to entry of fluoride in the body. A proper thorough and in-depth pathological, radiological and physiological diagnosis is necessary before declaring a case or ‘stamped’ the case, as ‘fluorosis’ one. It also needs to test the water being used by the patient and to know how long the patient is using the same water. The incubation period of fluorosis is very long. Many symptoms of Fluorosis are somewhat alike with other diseases such as ‘Va’, arthritis, osteoporosis, etc. At the village level, as told by the Medical Officers, it is very difficult to diagnose a patient properly, which requires analysis of X-ray, blood and urine by a good experienced doctor. Hence ‘stamped’ (the coin word used by the Government Medical Officers, Gujarat) cases of Fluorosis are not available. However, it does not mean that there is no incidence of Fluorosis particularly, when it is known that water is contaminated with fluoride and being used for a long time in the location. Hence cases of fluorosis are mixed with MSD and recorded as general MSD [musculo-skeletal disease] in hospitals and NGO's Health Centers as government did not want to recognize the incidences of fluorosis (Shah and Indu).
Dental Fluorosis
Like any other organs in the body; teeth are also affected by various factors leading to diseases. The differential diagnosis of flluorosis should be done for two aspects:
  1. Related to the pitting and chipping in fluorosis
  2. Related to discoloration of teeth.
Common Dental Diseases Relating to the Pitting and Chipping in Fluorosis are:
  1. Dental caries or decay/cavity formation
  2. Periodontal disease or pyorrhea
  3. Dental fluorosis.
Caries appear as black spots or cavity in the tooth when decay reaches dentin. Person complains of sensitiveness and acute pain when decay reaches pulp. Pyorrhea is caused by action of bacteria present in the mouth on food, resulting in the form of brownish hard deposit on the surface of teeth near gum. Periodontal disease is the inflammation of gingival gum and periodontal ligament leads to deposition of inorganic salts known as tartar, it irritates gum resulting in bleeding of gums and bad breath. Tartar cannot be removed by brushing. Periodontal disease is more common amongst persons suffering from diabetes mellitus, nutritional deficiency, especially protein and Vitamin C deficiency.
Fluorosis affects permanent teeth though decay of temporary teeth is also reported.11
Diseases Related to Discoloration of Teeth
There may be two types of staining of teeth:
  1. Internal staining
  2. External staining.
Fluorosis causes internal staining of teeth, whereas other causes like brinjal eating, banana biting, palm leaf biting, coconut leaf chewing cause external staining of teeth and may be mistaken for dental fluorosis.
Expected Duration
The spots and stains left by fluorosis are permanent. They may be darken over time.
Permissible Limit of Fluoride
To a certain extent (as per WHO; 0.6 ppm) fluoride ingestion is useful for bone and teeth development, but excessive ingestion causes fluorosis.
WHO and BIS 10500: 1991standards permit only 1.5 mg/L as a safe limit for human consumption. (http://www.krassindia.org/downloads/ebook1.pdf on fluoride and Fluorosis).
The 1984 WHO guidelines suggested that in areas with a warm climate, the optimal fluoride concentration in drinking water should remain below 1 mg/L (1ppm or part per million), while in cooler climates it could go up to 1.2 mg/L. The differentiation derives from the fact that we perspire more in hot weather and consequently drink more water. The guideline value (permissible upper limit) for fluoride in drinking water was set at 1.5 mg/L, considered a threshold where the benefit of resistance to tooth decay did not yet shade into a significant risk of dental fluorosis.
(The WHO guideline value for fluoride in water is not universal: India, for example, lowered its permissible upper limit from 1.5 ppm to 1.0 ppm in 1998.)
Ingested fluoride is rapidly absorbed through gastrointestinal tract and lungs. Approximately 75–90 per cent of ingested fluoride is absorbed. In an acidic stomach, fluoride is converted into hydrogen fluoride (HF) and up to about 40 per cent of the ingested fluoride is absorbed from the stomach as HF. High stomach pH decreases gastric absorption by decreasing the concentration uptake of HF. Fluoride not absorbed in the stomach is absorbed in the intestine and is unaffected by pH at this site (Whitford, 1997; IPCS, 2002). Relative to the amount of fluoride ingested, high concentrations of cations that form insoluble complexes with fluoride (e.g. calcium, magnesium and aluminium) can markedly decrease gastrointestinal fluoride absorption (Whitford, 1997; IPCS, 2002).
The peaks are reached after 30 minutes in blood. The rapid excretion takes place through renal system over a period of 4 to 6 hours. In children less than 3 years of age only about 50% of total absorbed amount is excreted, but in adults and children over 123 years—about 90% is excreted. Approximately 90% of the fluoride retained in the body is deposited in the skeleton and teeth. The biological half-life of bound fluoride is several years. Fluoride also passes through the placenta and also appears in low concentrations in saliva, sweat, and milk.
Much of the fluoride ingested by human beings is excreted by the kidney, guts and skin and, in the case of women, lost also through menstruation, offspring and lactation.
The toxic effects of fluorine retained by the body are minimal owing to more than 95% of it getting immobilized by substituting for hydroxyl ions in apatite present in dental and skeletal structures (hard tissues) to become fluor-apatite. Although initial entry of fluorine into the hard tissues is beneficial for the health of teeth and bones, entry of more fluorine results in dental and skeletal fluorosis. Once fluorine levels in the hard tissues reach physiologic saturation, which ranges from 0.02 to 0.83%, further ingestion of fluoride leads to flooding of fluoride in the soft tissues leading to skin, urinary, gastric, muscular and neurological problems, besides death due to some inter-current infection.
Fluoride added to water supplies is a byproduct of the manufacture of superphosphate and aluminum. It is also a byproduct of manufacture of steel, lead, copper, and nickel. Fluoride is quite toxic and was once widely used in insecticides and rodenticides. Goodman and Gilman write, “The pharmacological actions of fluoride, with the possible exception of its effect on bone and teeth, can be classified as toxic.
Of great concern is what has been termed the “Genetic Toxicity of Fluoride.” Fluoride causes chromosome aberrations in plants. Chromosome aberrations have also been observed in animal and human cell cultures. One study concludes that “the weight of the evidence leads to the conclusion that F (fluoride) exposure results in chromosome aberrations.
The mechanism of how fluoride does its damage is now fairly well understood. Fluoride can form a strong bond with protein structures within living systems. Fluoride has a very strong affinity for hydrogen. Hydrogen is the major molecule which links DNA together. “Thus some of the serious charges that are being laid at its door—genetic damage, birth defects, cancer and allergy response—may arise from fluoride interference after all.”
Fluoride interferes with the formation of normal collagen, the protein cement which holds body structures together. Total collagen is increased, as much as 50% in one study, but the collagen is imperfect. Structures heavily dependent upon collagen include tooth enamel and dentin, bone, cartilage, and muscle and skin. Teeth could be more heavily mineralized, while being imperfect. This is what we appear to see with water fluoridation.
Fluoride also appears to disturb mineralization and may contribute to mineralization of soft tissues.
  • 96–99% of fluoride retained in body combines with mineralized bones
  • When the ingestion is >5 mg, 50% is retained by skeleton and the rest is excreted through urine
  • Normal plasma fluoride levels are 0.14–0.19 PPM in non-endemic areas
  • Fluoride levels in soft tissues are < 1PPM, in brain 0.4–0.68 PPM, in CSF it is 0.1 PPM
  • Fluoride uptakes is faster in young bones
  • Fluoride content in skeletal bones varies, it is highest in bones of pelvis and vertebrae.
Excretion of Fluorides
1. Feces
Fluoride present in feces results from two sources—the ingested fluoride that is not absorbed and the absorbed fluoride that is excreted into the gastrointestinal tract. About 10–25% of daily intake of fluoride is excreted in the feces.
2. Urinary
The elimination of absorbed fluoride occurs almost exclusively via the kidneys. Urinary fluoride in normal individuals fluctuates widely between 0 and 1.2 PPM with an average of about 0.4 PPM when fluoride content of drinking water is 0.3PPM. Urinary levels of fluoride are higher in individuals exposed to higher intake of fluoride. The renal clearance of fluoride is directly related to urinary pH, and under some conditions, to urinary flow rate. In alkaline urine the fluoride is present in ionic form and hence its renal clearance is rapid. In the acidic urine on the other hand, fluoride is present in nonionic form (HF) and hence it is rapidly reabsorbed in renal tubules. The excretion of fluoride is much less if person concerned is suffering from chronic kidney disease resulting in renal failure, which inevitably leads to high concentrations of fluoride in serum as well as bone.14
3. Sweat
Some fluoride is also lost from the body through sweat and so appreciable amounts may be lost in situations marked by excessive sweating. Sweat fluoride concentrations are similar to plasma.
4. Other Routes
The amount of fluoride in breast milk is low and same is true of saliva.
Table 1.1   Effect of Fluoride concentration on teeth
Fluoride concentration (mg/L)
Limited growth and fertility
< 0.5
Dental caries
Promotes dental health, prevents tooth decay
Dental fluorosis (mottling and pitting of teeth)
Dental fluorosis, skeletal fluorosis (pain in neck bones and back)
> 10.00
Crippling fluorosis
Source: International Drinking Water Standards (1971), WHO, Geneva
Dental fluorosis occurs because of the excessive intake of fluoride, either through fluoride in the water supply, naturally occurring or added to it; or through other sources. The damage in tooth development occurs between the ages of 3 months to 8 years, from the overexposure to fluoride. Teeth are generally composed of hydroxyapatite and carbonated hydroxyapatite; when fluoride is present, some fluorapatite is generated. Excessive fluoride can cause white spots, and in severe cases, brown stains or pitting or mottling of enamel.
Fluorosis cannot occur once the tooth has erupted into the oral cavity. At this point, fluorapatite is beneficial because it is more resistant to dissolution by acids (demineralization). Although, it is usually the permanent teeth which are affected, occasionally the primary teeth may be involved.
Long back it was believed that fluorosis is a problem of elderly age group but it have been found that children in the age group of 0 to 12 years are most prone to fluorosis as their body tissues are in formative/growth stage during this period. The problem is so severe that if expectant mothers ingest high fluoride water, it can create many problems with developing fetus. It not only affects the body of a person but also renders them socially and culturally crippled.
In high concentrations, soluble fluoride salts are toxic and skin or eye contact with high concentrations of many fluoride salts is dangerous. Referring to a common salt of fluoride, sodium fluoride (NaF), the lethal dose for most adult humans is estimated at 5 to 10g (which is equivalent to 32 to 64 mg/kg elemental fluoride/kg body weight). A toxic dose that may lead to adverse health effects is estimated at 3 to 5 mg/kg of elemental fluoride. Ingestion of fluoride can produce gastrointestinal discomfort at doses at least 15 to 20 times lower (0.2–0.3 mg/kg) than lethal doses. Although helpful for dental health in low dosage, chronic exposure to fluoride in large amounts interferes with bone formation. In this way, the greatest examples of fluoride poisoning arise from fluoride-rich ground water.
Quantification of Fluoride Toxicity on Human Health
Smith and Hodge have related the concentrations or doses of fluoride to the biological effects indicated in the tabulation below:
Table 1.2   Effect of fluoride toxicity on human health
Fluoride concentration (mg/L)
Destructive effect on plants
Prevention of dental caries
≥ 2
Affect dental enamel
Affect bones and muscles
Food and water
Changes in thyroid
Food and water
Defective development
Food and water
Changes in kidney
Acute Toxicity
Like most soluble materials, fluoride compounds are readily absorbed by the stomach, intestines and excreted through the urine. Urine tests have been used to ascertain rates of excretion in order to set upper limits in exposure to fluoride compounds and associated detrimental health effects. Ingested fluoride initially acts locally on the intestinal mucosa, where it forms hydrofluoric acid in the stomach. Thereafter it binds calcium and interferes with various enzymes.
Historically, most cases of fluoride toxicity have followed accidental ingestion of sodium fluoride based insecticides or rodenticides. Currently, in advanced countries most cases of fluoride exposure are due to the ingestion of dental fluoride products. Although exposure to these product does not often cause toxicity.
Organofluorine Compounds
Organofluorine compounds only rarely release F under biological conditions and thus are rarely sources of fluoride poisoning. In order for fluoride poisoning to occur, a compound must release fluoride (F) ions. Whereas most organofluorine compounds may not release F because of the strength of the carbon–fluorine bond and its tendency to strengthen as more fluorine atoms are added to a carbon, others do, such as methoxyflurane. The fluorine atom is pervasive in drugs, e.g. prozac, and many other substances such as freon, teflon, and blood serum (PFOS, PFOA, and PFNA).
Poisoning comes from ingesting a large amount of fluoride in a short period of time. Ingesting 3–5 mg/kg may cause symptoms to appear, while the estimated lethal dose is 5–10 g (32–64 mg/kg) in adults and 16 mg/kg in children. Severity of symptoms depends upon the amount of fluoride ingested. These include abdominal pain, diarrhea, dysphagia, hypersalivation, mucosal injury, nausea, vomiting. Electrolyte abnormalities including hyperkalemia, hypocalcemia, hypoglycemia, and hypomagnesemia may occur. Neurological symptoms include headache, muscle weakness, hyperactive reflexes, muscular spasms, paresthesia seizures, tetanic contractions, and tremors. In severe cases, multi-organ failure will occur. Death typically results from cardiac arrest, shock, widening of QRS, and various arrhythmias occur.
Fluoride in Toothpaste
Children may experience gastrointestinal distress upon ingesting sufficient amounts of flavored toothpaste. Gastrointestinal symptoms appear to be the most common problem reported.17
Treatment of Acute Toxicity
  1. Monitor and support vital signs, including cardiac monitoring
  2. Gastric lavage, if emesis has not occurred. Charcoal is probably not of benefit
  3. Monitor serum electrolyte, calcium, and magnesium levels
  4. Treat hypocalcemia, hypomagnesemia and hyperkalemia or hypokalemia
  5. Administer milk, oral calcium salts, or aluminum or magnesium based antacids to bind fluoride
  6. Consider hemodialysis in patients with significant toxicity
  7. Treat arrhythmia, especially in the presence of refractory hyperkalemia
  8. Consult a regional poison center for the latest treatment recommendations.
Chronic Toxicity
In India an estimated 60 million people have been poisoned by well water contaminated by excessive fluoride, which is dissolved from the granite rocks. The effects are particularly evident in the bone deformations of children. Similar or larger problems are anticipated in other countries including China, Uzbekistan, and Ethiopia.
Although fluoride may be present in a medication or an anesthetic agent, it may be less toxic by being in a bound rather than a free form. Unless fluorinated organic chemicals are metabolized in the body to release the fluoride they contain, the covalently bound fluoride may be eliminated from the body without having been released as free fluoride ions. A small increase in the serumd fluoride level occurs with the partially metabolized ciprofloxacin, a fluoroquinolone antibiotic, while a larger increase occurs with fluorinated anesthetics such as halothane, which are metabolized to a greater extent. It is possible that small amounts of fluoride released from fluoride-containing medications may be a cause of illness, particularly if the release is in an area, such as the brain, where even minute concentrations may have a very potent effect.
Symptoms of Chronic Fluoride Poisoning
  1. Chronic fatigue not relieved by extra sleep or rest
  2. Headaches
  3. Dryness of the throat and excessive water consumption
  4. Frequent need to urinate
  5. Urinary tract irritation
  6. Aches and stiffness in muscles/bones (sarthritic like pain), in lower back, in neck area, in jaws, in arms, shoulders and legs
  7. Muscular weakness
  8. Muscles spasms (involuntary twitching)
  9. Tingling sensations in fingers (especially) and feet
  10. Gastrointestinal disturbances:
    The intestinal lining or mucosa of the duodenal region normally has cells with small protrusions on them (microvilli) and a layer of slimy substance (mucus). The 18microvilli and mucus are lost with chronic fluoride toxicity giving rise to symptoms such as nausea, loss of appetite, pain in the stomach, gas formation and a bloated feeling, constipation followed by intermittent diarrhea, and headache. These symptoms of non-ulcer dyspepsia are early warning signs of fluoride toxicity.
    • Abdominal pains
    • Diarrhea
    • Constipation
    • Blood in stools
    • Bloated feeling (gas)
    • Tenderness in stomach area
    • Feeling of nausea (flu like symptoms)
  11. Pinkish red or bluish red spots (like bruises but round or oval) on the skin that fade and clear up in 7–10 days
  12. Loss of mental acuity and ability to concentrate
  13. Depression
  14. Excessive nervousness
  15. Dizziness
  16. Tendency to lose balance
  17. Visual disturbances like Temporary blind spots in field of vision and diminished ability to focus (possible retinal damage)
  18. Brittle nails
  19. Repeated miscarriages or still births
  20. Male infertility: Male infertility with abnormalities in sperm morphology, a deficiency in the number of spermatozoa in the semen (oligospermia), the absence of spermatozoa from the semen (azoospermia), and low testosterone levels are very common in those residing in areas of India where chronic fluoride toxicity is common due to fluoride-contaminated water
  21. Dental fluorosis with discoloration of the enamel of the front teeth, the central or lateral incisors of the upper and lower jaws.
The only generally accepted adverse effect of fluoride at levels used for water fluoridation is dental fluorosis, which can alter the appearance of children's teeth during tooth development; this is mostly mild and usually only an aesthetic concern.
Consumption of fluoride at levels beyond those used in fluoridated water for a long period of time causes skeletal fluorosis. In some areas, particularly the Asian subcontinent, skeletal fluorosis is endemic. It is known to cause irritable-bowel symptoms and joint pain. Early stages are not clinically obvious, and may be misdiagnosed as (seronegative) rheumatoid arthritis or ankylosing spondylitis.
Other adverse effects may be possible at fluoride intake levels above the recommended dosage, and defluoridation is recommended in these cases.19
Excess Fluoride Consumption has been Studied as a Factor in the following
  • A weakening of bones, leading to an increase in hip and wrist fracture.
  • Adverse effects on the kidney. Within the recommended dose, no effects are expected, but chronic ingestion in excess of 12 mg/day are expected to cause adverse effects, and an intake that high is possible when fluoride levels are around 4 mg/L. Those with impaired kidney function are more susceptible to adverse effects.
  • Fluoride's suppressive effect on the thyroid is more severe when iodine is deficient, and fluoride is associated with lower levels of iodine. Thyroid effects in humans were associated with fluoride levels 0.05–0.13 mg/kg/day when iodine intake was adequate and 0.01–0.03 mg/kg/day when iodine intake was inadequate.
Fluoride has beneficial effects on teeth at low concentrations in drinking-water, but excessive exposure to fluoride in drinking-water, or in combination with exposure to fluoride from other sources, can give rise to a number of adverse effects. These range from mild dental fluorosis to crippling skeletal fluorosis as the level and period of exposure increases. Crippling skeletal fluorosis is a significant cause of morbidity in a number of regions of the world.
Toxic Effects on Human Beings
Fluorosis may cause skeletal fluorosis, dental fluorosis, non-skeletal manifestations, or any combination of the above and in final stages it causes premature aging.
Dental Fluorosis
Dental Fluorosis is the most convenient biomarker of exposure to fluoride. Dental fluorosis is a reflection of what's happening in our bones and is the first visible sign of fluoride poisoning.
It is defined as a change in the mineralization of the dental hard tissues (enamel, dentin, and cementum) caused by long-term ingestion (eating and drinking) of fluoride during the period of tooth development prior to eruption into the mouth (first 8 years of life for most permanent teeth excluding third molars). Once the tooth erupts, dental fluorosis refers to a range of visually detectable changes in enamel. The severity of dental fluorosis depends on when and for how long the overexposure to fluoride occurs, the individual response, weight, degree of physical activity, nutritional factors and bone growth, suggesting that similar dose of fluoride may lead to different levels of dental fluorosis.
Other factors that may increase the individual susceptibility to dental fluorosis are:
  • Altitude
  • Malnutrition
  • Renal insufficiency.
Dental fluorosis is a developmental disturbance of dental enamel, caused by successive exposures to high concentrations of fluoride during tooth development, leading to enamel with lower mineral content and increased porosity. The severity of dental fluorosis depends on when and for how long the overexposure to fluoride occurs, the individual response, weight, degree of physical activity, nutritional factors and bone growth. The risk period for esthetic changes in permanent teeth is between 20 and 30 months of age.
The recommended level for daily fluoride intake is 0.05–0.07mgF/kg/day, which is considered of great help in preventing dental caries, acting in remineralization. A daily intake above this safe level leads to an increased risk of dental fluorosis.
Dental fluorosis is a known adverse effect of fluoride overuse. Enamel or dental fluorosis is a condition caused by ‘excessive’ intake of fluoride over an extended period of time.
As described by Cutress and Suckling, the first clinical signs of dental fluorosis are thin white striae across the teeth surfaces. These fine opaque lines seem to follow the perikymata pattern. The cusp tips, incisal edges and marginal ridges may appear completely opaque, a condition that has been defined as “snow-capping.” In moderately affected teeth, the white lines appear more pronounced. The lines may merge and produce areas that will appear cloudy and will be scattered over the tooth surface. With increasing severity, the entire surface exhibits opaque, cloudy areas that may be mixed with areas of brownish discoloration. In the most severe cases, pitting of the enamel surface occurs. The most common symptom of dental fluorosis is a chalk-like discoloration of teeth with white spots or lines on tooth enamel. In more severe cases, the affected areas have a yellow or brown discoloration. In extreme forms, fluorosis may result in a pitted tooth surface.
Fluorosis is a cosmetic problem and not a dental disease. Teeth are strong and healthy, but the spots and stains left by fluorosis are permanent and may darken over time. Dental fluorosis can be cosmetically treated by a dentist by microabrasion or tooth bleaching.
Dental or enamel fluorosis occurs only while the teeth are still developing under the gums, before their eruption. Dental fluorosis occurs during the development of the tooth, 21with permanent teeth being more susceptible than primary teeth. Further, dental fluorosis is less prevalent and less severe in the primary teeth than in the permanent dentition.
The most critical ages of susceptibility are from 0 to 6 years, especially between the ages of 15 and 30 months (15–24 months for boys, 21–30 months for girls). After 7 or 8 years of age, dental fluorosis cannot occur because the permanent teeth are fully developed, although not erupted.
Fluoride causes dental fluorosis by damaging the cells that form the enamel, called ameloblasts. Damage to these cells results in a mineralization disorder of the teeth, whereby the porosity of the sub-surface enamel is increased. Fluorosis occurs when fluoride interacts with mineralizing tissues, causing alterations in the mineralization process. In dental enamel, fluorosis causes subsurface hypomineralizations or porosity, which extend toward the dentinal-enamel junction as severity increases. This subsurface porosity is most likely caused by a delay in the hydrolysis and removal of enamel proteins, particularly amelogenins, as the enamel matures. This delay could be due to the direct effect of fluoride on the ameloblasts or to an interaction of fluoride with the proteins or proteinases in the mineralizing matrix. The specific mechanisms by which fluoride causes the changes leading to enamel fluorosis are not well defined; though the early-maturation stage of enamel formation appears to be particularly sensitive to fluoride exposure. The development of fluorosis is highly dependent on the dose, duration and timing of fluoride exposure. The risk of enamel fluorosis is lowest when exposure takes place only during the secretory stage, but highest when exposure occurs in both secretory and maturation stages. The incidence of dental fluorosis is best correlated with the total cumulative fluoride exposure to the developing dentition. Fluoride supplements can contribute to the total fluoride exposure of children, and if the total fluoride exposure to the developing teeth is excessive, fluorosis will result.
Fluoride consumption can exceed the safe dose when a child drinks a lot of fluoride containing water in combination with other dietary fluoride sources (foods with high fluoride content), or by just swallowing fluoridated toothpaste.
Dental fluorosis is a health condition caused by a child receiving too much fluoride during tooth development. The critical period of exposure is between 1 and 4 years old; children over age 8 are not at risk. Dental fluorosis can develop in children but not in adults. Dental fluorosis in an adult is a result of high fluoride exposure when the adult was a child or adolescent. Teeth with fluorosis also have an increased porosity of the enamel. Even with mild fluorosis, enamel is subject to increased erosion and attrition because the structural integrity of enamel is compromised. As enamel breaks away, small pits are become visible.
In the milder forms, the porosity is mostly limited to the sub-surface enamel, whereas in the more advanced forms, the porosity impacts the surface enamel as well, resulting in extensive pitting, chipping, fracturing and decay of the teeth.
The discoloration induced by fluorosis—particularly in its advanced forms—can cause significant embarrassment and stress to the impacted child, resulting in adverse effects on esteem, emotional health, and career success.
White opacities, faint yellow stain, pitting, chipped off, black discoloration, enamel hypoplasia, delayed eruption, etc. may result due to dental fluorosis. The incidences of mottled teeth were observed even with range of 0.7–1.5 mg F/L in drinking water. The minimal daily fluoride intake in infants that may cause very mild or mild fluorosis in human beings was estimated to be about 0.1 mg per kg body weight. The severity of dental fluorosis depends on the amount of fluoride exposure, the age of the child, individual response, as well as other factors including nutrition. Although water fluoridation can cause fluorosis, most of this is mild and not usually of esthetic concern. Severe cases can be caused by exposure to water that is naturally fluoridated to levels well above the recommended levels, or by exposure to other fluoride sources such as brick tea or pollution from high fluoride coal. Teeth may show dental caries with cavities when drinking water has less than around 1 mg/L. Teeth are generally free of caries and fluorosis when fluoride is around 1 mg/L. Mild dental fluorosis is developed when fluoride is in between 1 and 2.5 mg/L.
Severe dental fluorosis is developed when fluoride is more than 2.5 mg/L.
Epidemiologic Indices
Several indices have been used to describe the clinical appearance of dental fluorosis. The three principal epidemiologic indices used for measuring the clinical manifestations of dental fluorosis which are in use nowadays are—those developed by Dean (1934, 1942), Thylstrup and Fejerskov (1978), and Horowitz et al. (1984) and a recent index (Fluorosis Risk Index) developed by Pendrys (1990).
The continued use of Dean's classification system and derived index (CFI) for more than a half century is testimony to its simplicity and utility. The index has been criticized because the unit of analysis is the person, because criteria are unclear for some categories, or that they lack sensitivity, particularly for severe fluorosis, and because of the way in which data are summarized and reported. The Thylstrup and Fejerskov Index is appealing to clinicians and epidemiologists alike in that it corresponds closely to histological changes that occur in dental fluorosis and to enamel fluoride concentrations, thereby having biological validity. The TSIF described by Horowitz, et al. makes a useful contribution because it provides clearer diagnostic criteria and provides for an analysis based on esthetic concerns. The Fluorosis Risk Index appears to be particularly useful for analytical epidemiologic studies, because it is designed to permit a more accurate identification of associations between age-specific exposures to fluoride and the development of dental 23fluorosis. All three indices in common use today provide useful indices for the study of dental fluorosis. The utility of the Fluorosis Risk Index will be determined as it receives wider use. The selection of one of these indices for use in an epidemiologic study depends in large measure on the purpose of the study. Research needs to continue on the validity of these indices, particularly for mild fluorosis, and on the public's perception of the cosmetic appearance of teeth with different severity levels of fluorosis.
The histological examination shows hypomineralized, porous sub-surface enamel below a well mineralized surface layer. The most affected teeth (in decreasing order) are premolars, 2nd molars, followed by maxillary incisors, canines and 1st molars. Mandibular incisors are affected least.
Following are the Vital Criterias to Determine Dental Fluorosis:
  • Discoloration of the teeth with a pattern
  • Discoloration horizontally aligned/never vertical
  • Discoloration away from the gums
  • Discoloration is bilaterally symmetrical.
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Figure 1.4: Different criterias to determine dental fluorosis
Grades of Fluorosis
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Figures 1.5A to F: (A) Normal; (B) Questionable; (C) Very mild; (D) Mild; (E) Moderate; (F) SevereSource: http://www.cdc.gov/fluoridation/safety/dental_fluorosis.htm
Severe Dental Fluorosis
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Figure 1.6: Severe dental fluorosisSource: http://en.wikipedia.org/wiki/Dental_fluorosis
Dental Fluorosis
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Figure 1.7: Dental fluorosisSource: The public perception of dental fluorosis George Glasser and Jane Jones* http://g-tigerclaw.com/mm/percdf.htm
Grades of Dental Fluorosis
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Figures 1.8A to C: (A) Mild dental fluorosis; (B) Severe dental fluorosis; (C) Moderate dental fluorosisSource: http://www.waterloowatch.com/Index_files/Fluoride%20and%20Dental%20Fluorosis.pdf
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Figure 1.9: Moderate effects of fluoridated water. Arrow point to discolored, cracked or pitted areasSource: http://clouddragon.files.wordpress.com/2009/12/dental-fluorosis.gif
Picture of Dental Fluorosis
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Figures 1.11A to K: (A) Mild fluorosis(Photo by Hardy Limeback, DDS); (B) Mild fluorosis (Photo by Elke Babiuk); (C) Mild fluorosis (Photo by Hardy Limeback, DDS); (D) Mild fluorosis (Photo by David Kennedy, DDS); (E) Mild fluorosis (Photo by Jeffrey Hamilton, DDS); (F) Mild/moderate fluorosis (Photo by Elke Babiuk); (G) Moderate/severe fluorosis (Photo by David Kennedy, DDS); (H) Moderate/severe fluorosis (Photo by David Kennedy, DDS); (I) Severe fluorosis (Photo by Hardy Limeback, DDS); (J) Severe fluorosis (Photo by Hardy Limeback, DDS); (K) Severe fluorosis (Photo by John Colquhoun, DDS) Source:http://www.fluoridealert.org/dentalfluorosis.htm
Dental Fluorosis
Six types of fluorosis (Source: Fluoride Free, Ireland):
Type 1: [Top] The earliest sign of dental fluorosis is thin white lines running across tooth. [Bottom] The tips of teeth are white and opaque.
Type 2: [Top] Unsightly white lines are more defined and are thicker. [Bottom] The tooth shows cloudy areas or thick opaque bands. Greater enamel damage.
Type 3: [Top] Brown stain superimposed on white cloudy areas. Brown stain equals enamel loss. [Bottom] Entire tooth is opaque and cloudy white. There is complete loss of translucency.
Type 4: [Top] The teeth erupt chalky white. Later the tooth displays surface damage i.e. brown discoloration. [Bottom] Further, brown pits arise due to excessive fluoride. This damage is irreversible.
Type 5: [Top] The enamel damage effects more teeth. Unsightly and weakened teeth result. [Bottom] Most of enamel has been lost from tooth surface. The protective layer is gone.
Type 6: [Top] Barely any normal enamel left. All teeth are severely effected. [Bottom] The teeth have many pits and holes. Now these teeth are more likely to decay and crumble.
Diagnosis of Dental Fluorosis from Dental Caries
  • Unlike dental fluorosis, dental caries is a bacterial disorder.
  • Dental caries also reveal discoloration of teeth; but unlike dental fluorosis, the discoloration in dental caries may be brown with no pattern.
  • Unlike dental fluorosis, dental caries shall reveal prominent cavities visible to the naked eye. The acids produced by the bacteria shall chew up the teeth; only the stub of the teeth shall remain towards later stages.29
  • The cavities in dental caries shall begin between two teeth or near the base of the crown, closer to the gums where the tooth brush does not reach and food debris collects enabling the bacteria to breed and produce acids.
A typical set of teeth with dental fluorosis and dental caries are seen below:
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Figures 1.13A and B: (A) Dental fluorosis; (B) Dental caries
Note: Fluoride has very little role to play in rectifying cavities; except it can kill the bacteria so that no acids are formed. The same fluoride does more damage to tissue enzymes and therefore diseases surface. Using fluoride for preventing dental caries is an out dated and unethical concept.
Diagnosis of Dental Fluorosis from Dirty Teeth
  • In dental fluorosis the discoloration will be on the enamel surface
  • In the child shown below, the teeth of the upper jaw, the two central incisors have discoloration horizontally aligned on the enamel surface, away from the gums. It is due to dental fluorosis and is a permanent feature of the teeth
  • In dirty teeth there will be discoloration of all shades but the discoloration will be along the gums (masuda) and not on the enamel surface.
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    Figure 1.14: Diagnosis of dental fluorosis from dirty teeth
  • The dirty teeth can be cleaned and polished by a dentist; but not in fluorosis. Whereas in the teeth of the lower jaw, there is discoloration along the gums and is due to dirty teeth, which can be cleaned by a dentist.
Skeletal Fluorosis
Skeletal fluorosis, a complicated illness caused by the accumulation of too much fluoride in the bones, has a number of stages.
The first two stages are preclinical, that is, the patient feels no symptoms but changes have taken place in the body. In the first preclinical stage, biochemical abnormalities occur in the blood and in bone composition; in the second, histological changes can be observed in the bone in biopsies. Some experts call these changes harmful because they are precursors of more serious conditions. Others say they are harmless.
In the early clinical stage of skeletal fluorosis, symptoms include pains in the bones and joints; sensations of burning, pricking, and tingling in the limbs; muscle weakness; chronic fatigue; and gastrointestinal disorders and reduced appetite. During this phase, changes in the pelvis and spinal column can be detected on X-rays. The bone has both a more prominent and more blurred structure.
In the second clinical stage, pains in the bones become constant and some of the ligaments begin to calcify. Osteoporosis may occur in the long bones, and early symptoms of osteosclerosis (a condition in which the bones become more dense and have abnormal crystalline structure) are present. Bony spurs may also appear on the limb bones, especially around the knee, the elbow and on the surface of tibia and ulna.
In advanced skeletal fluorosis, called crippling skeletal fluorosis, the extremities become weak and moving the joints is difficult. The vertebrae partially fuse together, crippling the patient.
Skeletal fluorosis, especially in its early stages, is a difficult disease to diagnose, and can be readily confused with various forms of arthritis including osteoarthritis and rheumatoid arthritis.
In the advanced stages, fluorosis can resemble a multitude of bone/joint diseases, including: osteosclerosis, renal osteodystrophy, DISH, spondylosis, osteomalacia, osteoporosis, and secondary hyperparathyroidism.
The risk of developing fluorosis, and the course the disease will take, is influenced by the presence of certain predisposing factors, including impaired kidney function; dietary deficiencies; gastric acidity; and repetitive stress.
“Crippling skeletal fluorosis might occur in people who have ingested 10–20 mg of fluoride per day for 10–20 years.
Radiological Presentations
Osteosclerosis, periosteal bone formation, calcification of interosseous membrane, ligaments, capsules, muscular attachments, tendons. Exostoses, osteophytosis, associated metabolic bone disease.
Clinical Presentation of Skeletal Fluorosis
Heel pain, painful and restricted joint movements, deformities in limbs, hunch back.
In Extreme Cases
Paralysis, muscular wasting, premature ageing.
Skeletal Fluorosis Phases
Osteosclerotic phase
Ash concentration (mgF/kg)
Symptoms and signs
Normal bone
500 to 1,000
Preclinical phase
3,500 to 5,500
Asymptomatic; slight radiographically-detectable increases in bone mass
Clinical phase I
6,000 to 7,000
Sporadic pain; stiffness of joints; osteosclerosis of pelvis and vertebral spine
Clinical phase II
7,500 to 9,000
Chronic joint pain; arthritic symptoms; slight calcification of ligaments' increased osteosclerosis and cancellous bones; with/without osteoporosis of long bones
Phase III: Crippling fluorosis
Limitation of joint movement; calcification of ligaments of neck vertebral column; crippling deformities of the spine and major joints; muscle wasting; neurological defects/ compression of spinal cord
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Figures 1.15A and B: (A) Normal forearm X-ray showing smooth outer and inner surfaces of the bone; (B) Forearm X-ray of a patient showing increase in bone density and calcification of the interosseous membrane
32The Figure 1.15 showing increase in bone density and calcification of the interosseous membrane due to overexposure of fluoride.
Source: Journal of the International Society for Fluoride Research: http://www.fluorideresearch.org/forearm/files/forearm.pdf
Non-skeletal Manifestations
Neurological manifestation: Nervousness and depression, tingling sensation in fingers and toes, excessive thirst and tendency to urinate frequently (polydypsia and plyurea): the control by brain appears to be adversely affected.
Muscular manifestations: Muscle weakness and stiffness, pain in the muscle and loss of muscle power.
Gastro - intestinal problems: Acute abdominal pain, diarrhea, constipation, blood in stool.
Edentate (Loss of teeth at an early age).
Fluoride and mental efficiency: Reduces mental work capacity (MWC) and hair zinc content.
Fluoride and thyroid: Fluoride has inhibitory effect on iodine uptake hence causing thyroid enlargement.
Fluoride and diabetes: The study showed that chronic fluoride toxicity in humans could result in significant abnormalities in glucose tolerance, which is reversible upon removal of the excess fluoride.
Fluorosis Diagnostic Tests
(For skeletal and non-skeletal fluorosis).
Fluorosis Diagnostic Tests in Adults
Fluoride to be tested in
  • Drinking water (to collect in plastic bottle only)
  • Blood (serum) [fasting not required]33
  • Urine (spot urine sample)
  • Radiograph of the forearm
  • Hemoglobin.
Fluorosis Diagnostic Tests in Children
  • Fluoride in drinking water of the child; if an infant or new born, the drinking water of the mother
  • Blood (serum) of the child; if an infant or new born, the blood serum of the mother
  • Urine of the child/infant.
Additional Tests
  • Thyroid hormone levels T3 and T4
  • Thyroid stimulating hormone (TSH)
  • Iodine in urine.
In Industrial Workers Fluoride to be tested in:
  • Drinking water
  • Blood (serum)
  • Urine and urinary pH
  • Nail clippings
  • Hemoglobin
  • Retrieval of health complaints
  • Retrieval of information related to food habits.
There is a crying need to overcome the problem of fluorosis.
Three approaches are suggested:
  1. Health education
  2. Treatment of the children
  3. Preventive measures.
Health Education
The main area of interest will be as follows:
Creating Disease Awareness
Creating awareness about the disease should be in form of figures and presentation of the final consequences of the disease to the extent possible.
If required live presentation of the patients, who are suffering from the severe form of the disease, in areas where the gravity of problem has not reached to that extent. It may be 34of use, to demonstrate the most severe extent of the disease and to motivate them to use the preventive or therapeutic measures.
Creating Awareness about the Sources of the Fluoride
The creation of awareness will help in implementing the need based preventive measures in the affected community.
Community Education and Mobilization
It can be done through the booklets and several leaflets and posters (IEC materials) regarding fluorosis and its prevention.
Treatment of the Fluorosis
  • Vitamins C, E and D and salts of calcium or magnesium can be used to treat chronic Fluoride toxicity.
  • Antioxidants such as b-carotene, glutathione, quercetin, allicin, capasaican, ellagic acid, gallic acid, epicatechin, lycopene, glucosinolates, lutein and zeaxanthin. Antioxidants are particularly important in protecting the body from fluoride toxicity. They act as “scavengers” to remove “free radicals” and occur naturally in fresh fruit and vegetables. Vitamin E (a-tocopherol), a potent antioxidant, exerts its protective effect primarily through destruction of cell damaging free oxygen species. Vitamin C (ascorbic acid) is an antioxidant with detoxification properties. Calcium may help overcome the hypocalcemia induced by fluoride and act synergistically with vitamin C.
  • The damage that dental fluorosis causes to the teeth enamel is permanent and not reversible. Dental fluorosis treatment is targeting in hiding the discoloration of the teeth.
The Treatment Options Depend on the Severity of Dental Fluorosis
Tooth Whitening: Only for Mild Fluorosis Cases
The whitening is achieved by the abrasion of the outer layer of the enamel in order to remove surface stains.
In cases of severe dental fluorosis, the tooth enamel usually becomes porous, and tooth whitening methods are not recommended as treatment. Dental fluorosis treatment for severe cases of fluorosis requires covering the affected teeth with restorations, such as :
Composite bonding: After etching the enamel, a composite resin (with a color matching the other teeth) is “glued” on to the exterior of the tooth.35
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Figures 1.16A and B: (A) Fluorosis before treatment; (B) After treatment (porcelain laminate veneers)Source: http://en.wikipedia.org/wiki/Dental_fluorosis
Porcelain veneers: Made out of porcelain, veneers form a ceramic shell over the surface of the tooth, covering the stains and discoloration caused by the dental fluorosis.
  • Tooth bonding and porcelain veneers are relatively expensive dental fluorosis treatments but they can provide excellent cosmetic results.
  • The presence of calcium in gut directly affects the absorption of fluoride ions and will also improve serum calcium levels as observed by Teotia, et al.
  • Vitamin D3 in low doses enhances calcium absorption and retention without causing hypercalcemia and thus directly affects the absorption of fluoride ions.
  • Vitamin C (ascorbic acid) controls collagen formation, maintains the teeth structure and is also essential for bone formation. These structures are adversely affected by higher fluoride intake.
Preventing Dental Fluorosis
  • Parents should take the necessary measures for preventing dental fluorosis on their children teeth
  • Powdered or liquid concentrate infant formula should be mixed with water that is fluoride-free or contains low levels of fluoride
  • Do not use fluoride toothpaste until the child is 2 years old unless advised to do so by a dentist
  • For children age two and older, place only a pea-sized amount of fluoride toothpaste on the toothbrush at each brushing
  • Avoid toothpastes with flavors that may encourage swallowing, An adult should supervise the use of fluoride-containing dental products by children younger than 6 years old, and check that they do not swallow it.
What consumer product industries and health agencies can do to reduce the occurrence of dental fluorosis?
  • Label the fluoride concentration of bottled water. Producers of bottled water should label the fluoride concentration of their products. Such labeling would allow consumers to make informed decisions.36
  • Promote the use of a small amount of fluoride toothpaste for children younger than 6 years. Labels and advertisements for fluoride toothpaste should promote using only a pea-sized amount (0.25g) of toothpaste on a child-sized toothbrush for children younger than 6 years. Parents and caregivers should be encouraged to supervise their children's toothbrushing to reduce the swallowing of excess toothpaste.
  • Collaborate: Professional health care organizations, public health agencies, and suppliers of oral care products should collaborate to educate health care professionals and the public.
Two alternatives have been suggested to reduce the consumption of fluoride:
  • Firstly, a reduction in the amount of toothpaste used should be achieved by educating parents to offer small, and therefore safe, amounts of toothpaste. For children between 4 and 6 years old, parents can be taught to use an amount equivalent to “a pea size”, dispending toothpaste over the toothbrush with the “transverse technique”. For children in a more tender age, parents should simply touch the toothbrush inside the toothpaste cover or tube, instead of squeezing it on the toothbrush. It has to be always reminded that children under 6 years old should be monitored during tooth brushing, encouraged not to swallow toothpaste, and not to use fluoridated mouth rinses.
  • The second alternative is the development of dentifrices with low fluoride concentration, which are already available in many countries.
Providing Defluoridated Water for Drinking Purpose
Desirable characteristics of defluoridation process
  • Cost-effective
  • Easy to handle/operate by rural population—the major sufferer
  • Independent of input fluoride concentration, alkalinity, pH, temperature
  • Not affect taste of water
  • Not add other undesirable substances (e.g. aluminium) to treated water as it can cause toxicity.
Keeping in view the cost involved in defluoridating the water it is desirable that the defluoridation of water should be restricted to drinking water only. Hence, the only economical and practicable choice left is Domestic Defluoridation.
It is now desirable to test the various domestic defluoridation processes, especially in terms of acceptance by people without the need of any supervising agency, and recommend suitable alternatives so that effective long-term implementation can be achieved.
It is estimated that the daily consumption of water for all purposes per capita is about 135 lpcd in urban areas and about 40 lpcd in rural areas, whereas for drinking and food preparing purposes it is only 8 lpcd. Keeping in view the cost involved in defluoridating the water it is desirable that the defluoridation of water should be restricted to drinking water only. Hence the only economical and practicable choice left is Domestic defluoridation.37
The important role of fluoride in the prevention of dental caries is evident and turns the water fluoridation into a public health measure. The fluoride level supplied in water can vary from 0.7 to 1.0 ppm, depending on the seasons of the year. Thus, as the ambient temperature gets warmer, the water intake increases, requiring lower levels of fluoride in drinking water. Fluoridated water is, directly or indirectly, responsible for 40% of dental fluorosis, through water intake or children's formula and food prepared with drinking water. The other 60% are attributed to other sources of fluoride. In a systematic review, where 214 studies were analyzed, McDonagh, et al. observed a decrease in the number of caries-affected teeth and an increase in dental fluorosis, depending on the fluoride intake. They also stated that the prevalence of dental fluorosis indicates that children are ingesting other sources of fluoride besides drinking water. In areas where drinking water is obtained directly from deep wells, dental fluorosis is often endemic and in many cases, the deeper the wells, the higher the fluoride concentration in drinking water. In order to prevent fluorosis, the pediatric dentist has to instruct parents about the fluoride content in the drinking water and when it is not known, look for this information in the local water supply service. If a child drinks well water or bottled water, the pediatric dentist may assist the parents or caregivers in getting an analysis of its fluoride content, and afterwards decide together whether the child needs a fluoride supplement or not. Dentists also should educate parents about diet, such as children's formula, food or sodas that need water to be manufactured and can indirectly participate in the development of dental fluorosis. Therefore, parents should also limit the amount of fluoride in bottled beverages.
It is now desirable to test the various domestic defluoridation processes, especially in terms of acceptance by people without the need of any supervising agency, and recommend suitable alternatives so that effective long-term implementation can be achieved.
Surprisingly none of the domestic defluoridation processes available today have been much successful in the field. Relative merits and demerits of some of these processes are as follows:
Nalgonda Process
It is a cumbersome technique not suitable for use by uneducated rural population—the section that needs it the most. Further, it is difficult to control the alum dose because it is different for each source of water. The process can be used only for water having a fluoride content of less than 10 ppm. If the alum dose is not properly controlled it may result in high residual aluminum content in output drinking water. The IS 10500 sets an absolute maximum limit of 0.2 ppm of aluminum in drinking water. Excess of alum also renders metallic taste to the water.
Activated Alumina Process
It is an expensive process. Reactivation of filter material is cumbersome and it can be done only with the help of trained persons generally not available in most of our villages. This process also results in high residual aluminum in output water ranging from 0.16 ppm to 0.45 ppm.38
Other Processes
Processes like electrodialysis, reverse osmosis, etc. require special equipment, electrical energy and especially trained persons to operate these units. Operation and maintenance of these units is also very expensive and hence these are not suitable as domestic defluoridation processes for use in rural areas.
Recently KRASS have come out with new defluoridation process named KDP (KRASS defluoridation process), which have shown promising results.
The salient features are given below:
In this process the fluoride contaminated water passed through the bed of media by any means such as filter to get the defluoridated water. This process differs from the known processes in its simplicity, cost effectiveness and very low traces of residual aluminum in outlet water. There is no limit on fluoride concentration in input water. Temperature, pH, alkalinity and total dissolved solids of input water do not affect this process. The ambient conditions like atmospheric temperature and humidity do not have any effect on this process. It is a practical approach especially for our rural population.
The importance of the process is a defluoridation process, which is easy, to use by illiterate villagers, requires minimal involvement of technical personnel, is harmless and is cost-effective. In the process, once the filter are laid at a door step, the inflow of the fluoride rich water is without further expenditure in terms of cost except recharging according to the capacity of filter. The exhausted media bed can be easily recharged again without replacing the material at least upto 40 cycles. As a product, the process achieves better removal of suspended matter, betters clarity and maintains taste of water. The treatment cost is about 0.6–0.8 paisa per liter at 10 ppm of influent fluoride.
Changing the Dietary Habits
Deflouridation of drinking water alone shall not bring the fluoride level to a safe limit. It would be necessary to overcome the toxic effects of the remaining fluoride ingested through other source. This can be done by effecting minor changes in the diet and dietary habits of the population compatible with their social system and available resources. The main aim should be to:
  • Restrict use of fluoride rich food
  • Avoiding use of fluoride rich toothpastes
  • Use of food rich in calcium, vitamin C and proteins like Amla, Shalgam ka sag, Hara dhania, Ajwayan, Til, skimmed milk powder, etc.
The clinicians must be aware of the optimum concentration of fluoride needed in water, before prescribing them. Fluorosis can be prevented if pediatricians, as well as dentists, follow the new guidelines for fluoride supplements, and be aware that these supplements are not recommended for children who are exposed to water supplies with an adequate amount of fluoride.39
Fluorosis can be prevented by monitoring the amount of fluoride that children up to 6 years old are exposed, therefore, the dentist must be aware of the main sources of fluoride to prevent fluorosis and instruct parents or caregivers on how daily dose should be managed in order to achieve success in prevention.
The excessive fluoride intake, in consequence to the inadequate use or swallowing of fluoride-containing toothpastes, is also responsible for the development of dental fluorosis. Children up to 5 years old swallow around 30% of the amount of toothpaste used every time they brush their teeth. If fluoridated water is consumed at the same time, a potential risk of dental fluorosis occurs.
Water Harvesting (Alternative Water Source)
Fluoride not only affects the people but it also affects the animals. The water harvesting technologies should be aimed not only to provide fluoride-free water to human beings but also to animals. Rainwater storage can be a major source of fluoride-free drinking water for the animals.
This three pronged attack can prove to be a blessing for the population especially for the younger generation living in fluoride rich areas having no choice except to drink the water contaminated with fluoride and suffer the inevitable consequences including permanent deformities.
From this research study the people of North Gujarat who are already afflicted with fluorosis will be benefitted. This study aims to bring a close insight into the gravity of the fluorosis problem and the causative factors responsible for it. It will also assess the effect of mitigation measures undertaken to alleviate fluorosis like Dharoi water supply and subsequently what is needed further.
“Fluoride is a worldwide menace” as Fred Pearce expressed in his article
Fluorosis doesn't cause any severe mortality and morbidity but it can make the person cripple which is more deplorable rather than being dead. There is decrease in working efficiency of the people because of joint and back pain. These people become burden to society and their families as there is decrease in working capacity, earnings and self confidence. Another social aspect of the problem is that young girls have difficulty in marriages because of discoloration of teeth.
There is paucity of information and scientific study on fluorosis. This study has been undertaken to have a deeper insight in comprehending the fluorosis condition in endemic areas of North Gujarat. This study also aims to throw light on the impact of mitigation measures taken to curb fluorosis in North Gujarat like water supply from Dharoi dam. The 40perception and knowledge of the people regarding water quality and fluorosis has also been taken into account to capture overall impact of fluorosis on society.
There have been no comprehensive health surveys for dental fluorosis from which the overall extent of the problem could be assessed. The dental fluorosis has been captured deeply in this study in endemic areas of North Gujarat based on Deans Fluorosis Indices. The thing which is most peculiar in this study is that DF not always means discolored tooth but also white opacities which can be classified into mild DF and this issue has been taken into consideration in this study.
Overall the effort has been made to capture physical, social, economical and cultural aspects of fluorosis on society. A comparison has also been made with previous studies on fluorosis which were done in same villages of North Gujarat by studying the same families as it was done in the following survey (Shah and Indu).