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Year : 2014  |  Volume : 5  |  Issue : 1  |  Page : 42-45

A Review of fluoride and its diverse effects

1 Department of Oral Pathology, Vinayaka Missions Sankarachariyar Dental College, Salem, India
2 Department of Molecular Medicine, Penang International College, VMU, Salem, India
3 Department of Oral Pathology, SRU, Chennai, Tamil Nadu, India
4 Department of Pedodontics, Vinayaka Missions Sankarachariyar Dental College, Salem, India

Date of Web Publication19-Mar-2014

Correspondence Address:
Maya Ramesh
100, Nagaramalai Road, Kittu Residency, Alagapuram, Salem - 636 016, Tamil Nadu
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0976-433X.129072

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Increased intake of fluoride in water and diet results in dental and skeletal fluorosis. Many states in India are affected by fluorosis. The optimum level of fluoride in drinking water for anti-cariogenic effect was thought to be 1 ppm. Various effects of fluoride on plants, animals and humans are discussed here. Currently, it is identified that fluoride has significant role in gene polymorphisms and lowered intelligent quotient.

Keywords: Dental fluorosis, diverse effects, fluoride, skeletal fluorosis

How to cite this article:
Ramesh M, Aruna RM, Malathi N, Krishnan R. A Review of fluoride and its diverse effects. SRM J Res Dent Sci 2014;5:42-5

How to cite this URL:
Ramesh M, Aruna RM, Malathi N, Krishnan R. A Review of fluoride and its diverse effects. SRM J Res Dent Sci [serial online] 2014 [cited 2023 Jan 28];5:42-5. Available from:

  Introduction Top

Increased fluoride is known to have diverse effects on the body other than dental fluorosis. Hydrofluorosis is a major issue in the country of India and 18 states are affected by it. When the fluoride level is above 1 ppm in drinking water, fluorosis results.

  Flouride - Historical Perspective Top

Kuehns stated in 1888 that "the family members grown up in Durango had black stains on their teeth, "similar to the polished areas in caries nigra", the intensity depending on how long they had been living there." [1]

Eager in 1901 who lived in Naples, Italy, noticed that people living in that area had black teeth "denti neri" or teeth with black marks "denti scritti." The black color was thought to be due to water used for drinking in childhood. [2]

In 1901, McKay noticed discolored teeth in the people of Colarado spring area which he described as "Colarado Brown Stain." McKay had moved to Colorado Springs in 1901. In 1926, McKay wrote to the U.S. Public Health Service about this condition. When the government was discussing about this, the people changed the water supply and drinking water to avoid disfigurement. [3]

  Fluoride - Teeth and Dental Caries Top

Fluoride causes reduction of dental caries in optimal amounts. Dean studied caries reduction in 21 cities and reported that when the water fluoride level was a little above 1 ppm, anticariogenecity was maximum and dental fluorosis was minimized. When the fluoride level was above 1-1.2 p.m., reduction in dental caries was not significant. [4]

A study of Heller et al. adjusted the fluoride level taking the climate and temperature into account and reported that above 0.7 ppm of F, a caries reduction was very less, there are more sources of fluoride other than drinking water in recent times. [5]

The dental indices mainly used in today's studies include: Dean's Index (1934, 1942), Thylstrup and Fejerskov Index (1978) and Horowitz Index (1984). Pendrys developed Fluorosis Risk Index 1990 for use in analytical epidemiological studies. [6]

The research done by many researchers state that caries in erupted teeth of humans is prevented by topical and systemic forms of fluoride. The action of fluoride is by preventing demineralization, increasing remineralization and by preventing the action of bacteria. [7]

Primary tooth fluorosis is relatively uncommon and is a post natal phenomenon and is proven by the studies of Warren. He reported that primary teeth formed in later stages of development like the primary second molar can be affected due to high fluoride level. [8]

  Flouride - Effect in Plants and Animals Top

Fluoride affects the growth of root and shoot of seedlings. Pant et al. studied the growth of shoot and root in many seedlings at 0.02 M NaF and noted that the length of shoots was reduced more even though the root length is also reduced except the root lengths in tomato seedlings. [9]

Fluoride level affects the health of animals. Burgstahler et al. noted that chinchillas showed " lowered quality of furs, early death and still births while caimans and alligators showed swelling and ulceration of eye membranes and later bloated bellies, liver silicosis, spinal deformity, tumors and shortened life spans" when they consumed the municipality water which was fluoridated. The animals became healthy when they were shifted to distilled water. [10]

Another animal study was carried out by Spittle in donkeys and he reported that "dental fluorosis with irregular wearing and excessive abrasions of the teeth, intermittent lameness, hoof deformities, tendon hardening, colic, diarrhea, retention of urine, repeated abortions, and sterility." [11]

  Flouride - and Humans Top

Fluoride affects the digestive system in humans. An 87-year-old female was ill for long with dyspepsia" and Spittle identified that fluoride in the drinking water was the reason for that. She became healthy when she started drinking purified water. [12]

Fluoride levels affect the intelligence level of the humans. The average Intelligent Quotient (IQ) of 7-13 year old children affected by dental fluorosis was studied using Binet IQ test by Guo et al. They were affected by coal burning-related fluoride poisoning. There were more children with lower IQ and even the average IQ was markedly low compared with children in non-fluoridated area. [13]

Fluoride affects the nervous system of humans. Brain tissues were taken from the aborted fetuses of endemic fluorosed areas and Yu et al. studied the levels of neurotransmitters and receptors. He reported that fluoride can accumulate in the brain tissue which can affect the synthesis of certain neurotransmitters and receptors in nerve cells, leading to nerve damages. [14] Sharma et al. in their study have reported that the percentage of adults with headache, sleeplessness and lack of energy was less in the low and medium F villages and it was more in the F endemic villages. [15]

Fluoride disturbs the male reproductive system. Long et al. reported that F exposures cause changes in the structure and function of spermatozoa, disturb spermatogenesis and affect hormones that control male reproduction. [16]

The effects of fluoride in teeth and bone are dependent on living habits and occupation. Choubisa et al. in 2009 studied dental fluorosis in different socio-economic strata and identified that "laborers > farmers > businessmen > servicemen > housewives > students" as the decreasing order of severity of dental fluorosis. [17]

  Flouride and Genes Top

COL2A1 gene and fluorosis. Wentao et al. did an animal study of Collagen gene in Cashmere goats grown up in fluorosed and non-fluorosed areas. He identified a "high expression of COL2A1 in rib cartilage of those animals" stating the involvement of genes. [18]

COL1A1 gene and DPP gene are targets for dental fluorosis. Han et al. compared fluorosed and non-fluorosed group and reported that the "expression level of the COL1A1 gene in the fluorosis group was reduced in the dentin by 39.6% in the incisor teeth and 69.8% in the molar teeth, respectively." The DPP gene in the fluorosed group was reduced by 50% in the incisors and 34.3% in the molars, respectively." [19]

COL1A2 gene and Fluorosis. Huang et al. studied COL1A2 PvuII polymorphism in children and reported that "children with homozygous P allele of COL1A2 PvuII had about five times the risk of dental fluorosis compared with children with homozygous p allele after adjusting for age and gender." [20]

Dawson reported that an "association can be seen between the presence of dental fluorosis and collagen type I, alpha 2, Osteopontin and Tuftelin 1 after adjusting for fluoride intake from 0 to 24 months." [21]

  Fluoride - and The Diet Top

Diet has a very important role in fluorosis. Choubisa et al. studied people having different habits such as tea, tobacco, betel nuts and alcohol and reported that a high incidence of dental and skeletal fluorosis in them. The use of citrus fruits and ghee were associated with very low fluorosis also. [17] Tea especially black tea can cause dental as well as skeletal fluorosis. Li et al. reported that the F accumulates in tea leaves and during tea infusion and nearly about 94.9% of F is released, which is absorbed by tea consumers. Children drinking brick tea have dental and skeletal fluorosis and adults drinking instant tea with 3.3 ppm F have skeletal fluorosis. [22] Tamarind pulp is proven as having protective effect against fluoride. Ekambaram et al. reported that the tamarind pulp had antioxidant property and contains high level of calcium and that may prevent the oxidative damage of liver in fluorosed female rats. [23] Addition of shrimp to the diet can give protection against fluoride. Yin et al. studied mature Adélie penguins who live on F rich krill diet and reported that they don't have skeletal fluorosis even when the fluoride level in bone is very high. Two third of bone F is organic in penguins and they don't get fluorosis. [24]

Sugarcane can be used to purify fluoride contaminated water. Santos-Díaz et al. reported that at 4 mg F/L, sugar cane (Saccharum officinarum) removed 40% of F. However above a concentration of 5 mg F/L this property is not seen. [25]

A plant called Tulsi, or Holy Basil can be used for defluoridation in India. Researchers at Rajasthan University have conducted the experiment in a village of Narketpally Mandal by soaking 75 mg of Holy Basil leaves in 100 ml of water containing over 7 parts/million of fluoride for 8 h and found that the fluoride was reduced to just 1.1 parts/million. [26]

Spray dried natural fruit powder has protective effect against fluoride. Vasant and Narasimhacharya identified the anti-oxidant activity of LA fruit powder and stated that it can be used as a nutritional supplement which offers protection against F-induced hepatic and renal oxidative stress. [27]

  Fluoride - Biomarkers Top

Biomarker is defined as "an indicator of change in biological system that could lead to a clinical disease". According to World Health Organization "a fluoride biomarker is of value primarily for identifying and monitoring deficient or excessive intakes of biologically available fluoride." These biomarkers can be divided into:

Historic markers

Calcified tissues like bone and teeth can be used for studying fluoride levels. It varies with age, sex, genetic background, renal function and remodeling rate. However, it is an invasive procedure and is difficult to get bone for studies. But dentin from extracted third molars can be used for studying fluoride levels.

Contemporary markers

The fluoride concentrations in urine, plasma, saliva fluids reflect the fluoride levels in the recent hours. Urinary fluoride excretions and concentrations are variable due to variations in urinary flow and pH. Plasma and saliva samples taken from fasting subjects have the best value.

Recent markers

The F concentrations in hair and nail reflect the average plasma fluoride concentrations over time. They can be non-invasively obtained and nail collection is more accepted. But both these can be contaminated externally. In any type of index, reference values should be identified. [28]

  Conclusion Top

Research is bringing about the ill-effects of high fluoride levels in drinking water and diet. Clarity is needed in the level of F in the public supply of drinking water. As bottled water containing low levels of F is used for drinking by many, community water fluoridation plants are becoming less important. Hence research should be undertaken on fluorosis with consideration of socio-economic status, diet, drinking water and habits and more light should be thrown on this topic.

  References Top

1.Kuhns C. Dtsch. Mschr. Zahnheilk. 1988;6:446-7.  Back to cited text no. 1
2.Eager JM. "Denti di Chiaie (Chiaie teeth)". Public Health Rep; 1901;16:2576-77. (and abstr. in Dental Cosmos 44 (1902) 300).  Back to cited text no. 2
3.Accessed on 26.02.2014 from  Back to cited text no. 3
4.Dean HT. On the epidemiology of fluorine and dental caries. In: Gies WJ, editor. Fluorine in Dental Public Health. New York: New York Institute of Clinical Oral Pathology; 1945. p. 19-30.  Back to cited text no. 4
5.Heller KE, Eklund SA, Burt BA. Dental caries and dental fluorosis at varying water fluoride concentrations. J Public Health Dent 1997;57:136-43.  Back to cited text no. 5
6.Rozier RG. Epidemiologic indices for measuring the clinical manifestations of dental fluorosis: Overview and critique. Adv Dent Res 1994;8:39-55.   Back to cited text no. 6
7.Featherstone JD. Prevention and reversal of dental caries: Role of low level fluoride. Community Dent Oral Epidemiol 1999;27:31-40.  Back to cited text no. 7
8.Warren JJ, Levy SM, Kanellis MJ. Prevalence of dental fluorosis in the primary dentition. J Public Health Dent 2001;61:87-91.  Back to cited text no. 8
9.Pant S, Pant P, Bhiravamurthy PV. Prasanthinilayam, effects of fluoride on early root and shoot growth of typical crop plants of India, research report. Fluoride 2008;41:57-60.  Back to cited text no. 9
10.Burgstahler AW, Freeman RF, Jacobs PN. Toxic effects of silicoflouridated water in chinchillas, caimans, alligators, and rats held in capticity, research report. Fluoride 2008;41:83-8.  Back to cited text no. 10
11.Spittle B. Flouride toxicity and donkeys, editorial. Fluoride 2010; 43:4.  Back to cited text no. 11
12.Spittle B. Dyspepsia associated with fluoridated water, research report. Fluoride 2008;41:89-92.  Back to cited text no. 12
13.Guo X, Wang R, Cheng C, Wei W, Tang L, Wang Q, et al. A preliminary investigation of the IQ s of 7-13 year old children from an area with coal burning related fluoride poisoning, translated research report. Fluoride 2008;41:125-8. [Translated by Julian Brooke and Published with the concurrence of the Chin J Endemiology 1991;10:98-100.  Back to cited text no. 13
14.Yu Y, Yang W, Zhong D, Wan C, Zhang J, Liu J, et al. Neurotransmitter and receptor changes in brains of fetuses from areas of endemic flourosis, translated research report. Fluoride 2008;41:134-8. [Translated by Julian Brooke and published with the concurrence of the Chin J Endemiology 1996;15:257-9].  Back to cited text no. 14
15.Sharma JD, Sohu D, Jain P. Prevalence of neurological manifestations in a human population exposed to fluoride in drinking water, research report. Fluoride 2009;42:127-32.  Back to cited text no. 15
16.Long H, Jin Y, Lin M, Sun Y, Zhanga L, Clinch C. Chengdu, China, and Waterloo. Flouride toxicity in male reproductive system, Canada research review. Fluoride 2009;42:260-76.  Back to cited text no. 16
17.Choubisa SL, Choubisa L, Choubisa D. Osteo dental flourosis in relation to nutritional status, living habits and occupation in rural tribal areas of Rajasthan, India, research report. Fluoride 2009;42:210-5.  Back to cited text no. 17
18.Wentao L, Yang L, Zhou B, Yan X, Wang J. Effect of industrial fluoride pollution on COL2A1 gene expression in rib cartilage of inner Mongolia Cashmere goats, research report. Fluoride 2006;39:285-92.  Back to cited text no. 18
19.Han T, Wang M, Yan X, Niu R, Wang J. Decreased expression of Type I collagen and dentin phosphoprotein in teeth of flourosed sheep. Fluoride 2010;43:19-24.  Back to cited text no. 19
20.Huang H, Ba Y, Cui L, Cheng X, Zhu J, Zhang Y, et al. COL1A2 gene polymorphisms (Pvu II and Rsa I), serum calciotropic hormone levels, and dental fluorosis. Community Dent Oral Epidemiol 2008;36:517-22.  Back to cited text no. 20
21.Accesed on 26.02.2014 from  Back to cited text no. 21
22.Li C, Wuhan DN. Effect of fluoride on chemical constituents of tea leaves, China, research report. Fluoride 2009;42:237-43.  Back to cited text no. 22
23.Ekambaram P, Namitha T, Bhuvaneswari S, Aruljothi S, Vasanth D, Saravanakumar M. Therapeutic efficacy of Tamarindus indica (L) to protect against fluoride induced oxidative stress in the liver of female rats. Fluoride 2010;43:134-40.  Back to cited text no. 23
24.Yin X, Liang C, Sun L, Wang M, Luo H, Ruan D, et al. Why do penguins not develop skeletal flourosis? Fluoride 2010;43:108-18.  Back to cited text no. 24
25.Santos-Díaz MD, Zamora-Pedraza C. Flouride removal from water by plant species that are tolerant and highly tolerant to hydrogen fluoride, research report. Fluoride 2010;43:150-6.  Back to cited text no. 25
26.Accesed on 26.02.2014 from  Back to cited text no. 26
27.Vasant RA, Narasimhacharya AV. Alleviation of fluoride - induced hepatic and renal oxidative stress in rats by the fruit of Limonia acidissima, research report. Fluoride 2011;44:14-20.  Back to cited text no. 27
28.Biomarkers of fluoride exposure in human body. Indian Journal of Dentistry. 2013;4:207-10.  Back to cited text no. 28

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Fluoride - Teeth...
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Flouride - and H...
Flouride and Genes
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