Effects of calcium supplements on oral bioavailability of fluoride in soil based on In Vivo and In Vitro methods.

Dietary calcium (Ca) intake can alleviate fluoride (F) induced fluorosis to maintain bone health. However, it is unclear whether calcium supplements can reduce the oral bioavailability of F present in contaminated soils. Here we evaluated the effects of Ca supplements on F bioavailability in three soils using an in vitro method (Physiologically Based Extraction Test) and an in vivo mouse model. Seven Ca salts, commonly used in calcium supplements, significantly reduced the F bioaccessibility in the gastric and small intestinal phases. Particularly for Ca phosphate at 150 mg Ca supplementation, F bioaccessibility in the small intestinal phase was reduced from 35.1-38.8% to 0.7-1.9% where soluble F concentrations were less than 1 mg/L. Overall, the eight Ca tablets tested in this study showed greater efficiency at decreasing F solubility. The in vitro bioaccessibility after Ca supplementation was consistent with the relative bioavailability of F. As supported by X-ray photoelectron spectroscopy, a possible mechanism is that freed F can be bound by Ca to form insoluble CaF2 and exchanged with OH groups from Al/Fe hydroxide to strongly adsorb F. These findings provide evidence of Ca supplementation in reducing health risks associated soil F exposure.

A comprehensive review on endemic and experimental fluorosis in sheep: Its diverse effects and prevention.

Fluoride is a natural element widely distributed in the environment and plays an important role in the growth of humans and animals. However, in many species, high concentrations of fluoride induce several problems, such as dental, skeletal, and non-skeletal fluorosis. Sheep living in endemic areas are sensitive to the chronic toxicity of fluoride, and they have been found to suffer not only from teeth and bone problems but also from other organs. Studies indicating the chronic harmful effects of fluoride on teeth, bones, blood biochemical parameters, kidney, liver, heart, reproductive system and growth in sheep have been clearly summarized in this review. Besides, this work also includes updated progress in terms of prevention or reduction of fluoride toxicity in this species.

Exogenous Intake of Fluorides in Caries Prevention: Benefits and Risks.

Caries incidence and prevalence have decreased significantly over the last few decades due to widespread use of fluoride. However, an increase in the prevalence of dental fluorosis has been reported in both fluoridated and non-fluoridated communities. Care must be taken to ensure that a balance between the optimal fluoride preventive effect at the individual and community level and minimal risk of dental fluorosis is maintained. This review describes the main sources of fluoride intake that have been identified: fluoridated drinking water, dietary fluoride supplement, and topical forms comprising toothpastes, rinses, gels and varnishes. The cited data were taken from meta-analytic studies and reports from Cochrane database systematic reviews up to December 2019. Efficiency, but safety, of topically applied fluorides in individual home care is dependent on the degree of compliance of individuals/parents and on the level of competence of providers of preventive counselling. The broad spectrum of these resources allows individualization of fluoride prevention based on risk analysis of caries attack and taking into consideration other preventive measures.

Efficacy of Calcium-Containing Eggshell Powder Supplementation on Urinary Fluoride and Fluorosis Symptoms in Women in the Ethiopian Rift Valley.

Dietary calcium binds Fluoride (F), thus preventing excess F absorption. We aimed to assess the efficacy of supplementing calcium-containing Eggshell Powder (ESP) on F absorption using urine F excretion and on fluorosis symptoms. In total, 82 women (41 Intervention Group, IG; 41 Control Group, CG) were recruited; overall, 39 in each group completed the trial. Morning spot urine was collected before (baseline, BL) and after (endline, EL) the intervention that was 6-months daily supplementation with 2.4 g ESP (providing ~1000 mg of calcium). Dental, skeletal, and non-skeletal fluorosis assessments was carried out at BL and, except for dental, at EL. Relative risk (RR) and linear generalized estimating equation were used to compare outcomes between groups. At BL, urinary F excretion in the IG and CG groups was similar, ~10 mg/L. At EL, urinary F excretion in IG women was six-fold lower (ß = -6.1 (95% CI: -7.1, -5.1)) compared to CG. The risk of developing skeletal and non-skeletal fluorosis were significantly (p < 0.001) reduced in the intervention group. A significant reduction in urinary F excretion and reduction in many fluorosis symptoms were observed among women supplemented with calcium-containing ESP, thus providing evidence for using this dietary calcium source for mitigation of fluorosis. Clinical trials registration: NCT03355222.

Supplementation of Calcium and Fluoride-Free Water Mitigates Skeletal Fluorosis in Fluoride-Intoxicated Rats.

Fluorosis is a public health concern in 25 countries around the globe. The present study is about the mitigation of fluoride (F) toxicity by giving F-free water (FFW) and calcium (Ca). A study was conducted by taking 76 Wistar rats in two phases, phase I (6 months), where rats were randomly divided into four groups: normal-Ca diet (NCD) 0.5%; low-Ca diet (LCD) 0.25%; NCD + 100 ppm F and LCD + 100 ppm F in groups 1, 2, 3 and 4, respectively. F and Ca were given through water and diet respectively. Phase II is the reversal of fluorosis for 3 months, where LCD group 2 was treated with NCD. Groups 3 and 4 were divided into two subgroups each: 3X and 3Y, and 4X and 4Y, respectively. Groups 3X and 4X received FFW with NCD. Group 3Y continued as phase I and 4Y NCD and F. The biochemical expression, gene expression, biomechanical properties and DXA were studied by standard methods. The results revealed that in phase I, bone turnover was significantly increased whereas bone mineral content and biomechanical properties of group 4 were significantly decreased (p ≤ 0.05) as compared with that of all other groups. Trabecular separation and total porosity increased in groups 2 and 4. Expression of osteocalcin, osteonectin and osteopontin genes was significantly downregulated in group 4. Bone turnover in group 4X was normalised. Expressions of osteocalcin, osteonectin and osteopontin were upregulated after providing NCD and FFW. In conclusion, low calcium aggravates skeletal fluorosis which could be mitigated on supplementation of Ca and FFW.

ClC-7/Ostm1 contribute to the ability of tea polyphenols to maintain bone homeostasis in C57BL/6 mice, protecting against fluorosis.

Epidemiological investigations indicate that certain ingredients in tea bricks can antagonize the adverse effects of fluoride. Tea polyphenols (TPs), the most bioactive ingredient in tea bricks, have been demonstrated to be potent bone-supporting agents. ClC­7 is known to be crucial for osteoclast (OC) bone resorption. Thus, in this study, we investigated the potential protective effects of TPs against fluorosis using a mouse model and explored the underlying mechanisms with particular focus on ClC­7. A total of 40, healthy, 3­week­old male C57BL/6 mice were randomly divided into 4 groups (n=10/group) by weight as follows: distilled water (control group), 100 mg/l fluoridated water (F group), water containing 10 g/l TPs (TP group) and water containing 100 mg/l fluoride and 10 g/l TPs (F + TP group). After 15 weeks, and after the mice were sacrificed, the long bones were removed and bone marrow-derived macrophages were cultured ex vivo in order to perform several experiments. OCs were identified and counted by tartrate­resistant acid phosphatase (TRAP) staining. The consumption of fluoride resulted in severe fluorosis and in an impaired OC function [impaired bone resorption, and a low mRNA expression of nuclear factor of activated T-cells 1 (NFATc1), ATPase H+ transporting V0 subunit D2 (ATP6v0d2) and osteopetrosis­associated transmembrane protein 1 (Ostm1)]. In the F + TP group, fluorosis was attenuated and OC function was restored, but not the high bone fluoride content. Compared with the F group, mature OCs in the F + TP group expressed higher mRNA levels of ClC­7 and Ostm1; the transportation and retaining of Cl­ was improved, as shown by the fluorescence intensity experiment. On the whole, our findings indicate that TPs mitigate fluorosis in C57BL/6 mice by regulating OC bone resorption. Fluoride inhibits OC resorption by inhibiting ClC­7 and Ostm1, whereas TPs attenuate this inhibitory effect of fluoride.

Molecular mechanism of brain impairment caused by drinking-acquired fluorosis and selenium intervention.

This study investigated the molecular mechanism of brain impairment induced by drinking fluoridated water and selenium intervention. Results showed that the learning and memory of rats in NaF group significantly decreased. Moreover, the number of apoptotic cells, the expression levels of Cytc mRNA and protein, and the expression levels of Caspase-9 and Caspase-3 mRNA significantly increased; by contrast, Caspase-9 and Caspase-3 protein levels significantly decreased. Compared with the NaF group, the mRNA levels of Cytc and Caspase-9, as well as the protein levels of Cytc in NaF+Se group, significantly decreased. Conversely, the protein levels of Caspase-3 and Caspase-9, as well as the mRNA levels of Caspase-3, significantly increased. Thus, the mitochondrial CytC-Caspase-9-Caspase-3 apoptosis pathway in the hippocampus was one of the mechanisms leading to fluorosis-induced brain damage. Furthermore, the Cytc signaling molecules were possibly the key target molecules in fluorosis-induced apoptosis, and selenium could alleviate fluorosis-induced brain injury.

Maize purple plant pigment protects against fluoride-induced oxidative damage of liver and kidney in rats.

Anthocyanins are polyphenols and well known for their biological antioxidative benefits. Maize purple plant pigment (MPPP) extracted and separated from maize purple plant is rich in anthocyanins. In the present study, MPPP was used to alleviate the adverse effects generated by fluoride on liver and kidney in rats. The results showed that the ultrastructure of the liver and kidney in fluoride treated rats displayed shrinkage of nuclear and cell volume, swollen mitochondria and endoplasmic reticulum and vacuols formation in the liver and kidney cells. MPPP significantly attenuated these fluoride-induced pathological changes. The MDA levels in serum and liver tissue of fluoride alone treated group were significantly higher than those of the control group (p < 0.05). The presence of 5 g/kg MPPP in the diet reduced the elevation of MDA levels in blood and liver, and increased the SOD and GSH-Px activities in kidney and GSH level in liver and kidney compared with the fluoride alone treated group (p < 0.05). In addition, MPPP alleviated the decrease of Bcl-2 protein expression and the increase of Bax protein expression induced by fluoride. This study demonstrated the protective role of MPPP against fluoride-induced oxidative stress in liver and kidney of rats.

Water fluoridation and oral health.

UNLABELLED: Water fluoridation, is the controlled addition of fluoride to the water supply, with the aim of reducing the prevalence of dental caries. Current estimates suggest that approximately 370 million people in 27 countries consume fluoridated water, with an additional 50 million consuming water in which fluoride is naturally occurring. A pre-eruptive effect of fluoride exists in reducing caries levels in pit and fissure surfaces of permanent teeth and fluoride concentrated in plaque and saliva inhibits the demineralisation of sound enamel and enhances the remineralisation of demineralised enamel. A large number of studies conducted worldwide demonstrate the effectiveness of water fluoridation. Objections to water fluoridation have been raised since its inception and centre mainly on safety and autonomy. Systematic reviews of the safety and efficacy of water fluoridation attest to its safety and efficacy; dental fluorosis identified as the only adverse outcome. CONCLUSION: Water fluoridation is an effective safe means of preventing dental caries, reaching all populations, irrespective of the presence of other dental services. Regular monitoring of dental caries and fluorosis is essential particularly with the lifelong challenge which dental caries presents.

Influence of selenium and fluoride on blood antioxidant capacity of rats.

This study is to explore the effect of selenium and fluoride on blood antioxidant capacity of rats, and try to find out the optimal level of selenium in drinking water against fluorosis. Animals were divided into control group, sodium fluoride treated group (NaF, 50 mg/L) and selenium+NaF treated group (sodium selenite 0.375, 0.75, 1.5 mg/L) in water were respectively administered to male rats, which were decapitated after 6 months. Their blood was collected for GSH-Px activity, plasma SOD activity, T-AOC assay, uric acid assay, sialic acid (SA) content and MDA content, and the fluidity of erythrocyte membrane by electron spin resonance (ESR) was analyzed. The results showed that, compared with the control group, the blood antioxidant capacity of the rats exposed to fluoride was down-regulated significantly (P<0.05, P<0.01), MDA content increased significantly (P<0.05), the fluidity of erythrocyte membrane decreased (P<0.05, P<0.01). Meanwhile, the treatments of selenium along with NaF compared with fluorosis group, SOD activity, GSH-Px activity and T-AOC assay increased respectively, MDA content decreased significantly (P<0.05) in NaF+Se (Se 0.75, 1.5 mg/L) treated groups, uric acid level was up-regulated, but had no statistical significant difference (P>0.05). The fluidity of erythrocyte membrane showed significant increase (P<0.05), the content of SA was lower. Fluorosis could induce the decline of blood antioxidant capacity and the fluidity of erythrocyte membrane, as evident in this study, and Se at different levels possess some antagonistic effects on blood induced by fluoride. However, high dose of selenium (1.5 mg/L) is the optimum concentration.

Systemic fluoride.

There is substantial evidence that fluoride, through different applications and formulas, works to control caries development. The first observations of fluoride's effects on dental caries were linked to fluoride naturally present in the drinking water, and then from controlled water fluoridation programs. Other systemic methods to deliver fluoride were later suggested, including dietary fluoride supplements such as salt and milk. These systemic methods are now being questioned due to the fact that many studies have indicated that fluoride's action relies mainly on its post-eruptive effect from topical contact with the tooth structure. It is known that even the methods of delivering fluoride known as 'systemic' act mainly through a topical effect when they are in contact with the teeth. The effectiveness of water fluoridation in many geographic areas is lower than in previous eras due to the widespread use of other fluoride modalities. Nevertheless, this evidence should not be interpreted as an indication that systemic methods are no longer relevant ways to deliver fluoride on an individual basis or for collective health programs. Caution must be taken to avoid excess ingestion of fluoride when prescribing dietary fluoride supplements for children in order to minimize the risk of dental fluorosis, particularly if there are other relevant sources of fluoride intake - such as drinking water, salt or milk and/or dentifrice. Safe and effective doses of fluoride can be achieved when combining topical and systemic methods.

Análise dos fatores de risco ou de proteção para fluorose dentária em crianças de 6 a 8 anos em Fortaleza, Brasil / Analysis of protection or risk factors for dental fluorosis in 6 to 8 year-old children in Fortaleza, Brazil

OBJETIVO: Investigar os fatores de risco ou de proteção para a fluorose dentária na dentição permanente de crianças de 6 a 8 anos em um bairro no Município de Fortaleza, Brasil. MÉTODOS: Este estudo de caso-controle incluiu 67 crianças com fluorose nos incisivos superiores e inferiores permanentes erupcionados, conforme o índice de Dean, e 57 controles. A presença de fluorose foi determinada como variável dependente. Os dados acerca das variáveis independentes foram obtidos através de entrevistas com os pais das crianças. O teste exato de Fisher foi utilizado para verificar a existência de associação entre fluorose e as variáveis independentes. Foi calculada a razão de chances (odds ratio, OR) para verificar a associação e a probabilidade de fluorose no grupo-caso, ambos com significância de 95 por cento. RESULTADOS: Houve associação significativa da fluorose com tipo de moradia (própria, alugada ou ocupada), mas não com fonte de água para consumo ou uso de dentifrícios fluoretados e suplementos de flúor. Na análise univariada, o risco de fluorose foi maior em crianças que iniciaram o consumo de leite em pó reconstituído com água antes dos 2 anos de idade (OR = 4,53; IC95 por cento: 1,07 a 26,74) e nas que não mamaram (OR = 6,66; IC95 por cento: 1,61 a 38,62). Na análise multivariada, somente a amamentação apresentou associação com a fluorose (4,54; IC95 por cento: 1,21 a 16,66). CONCLUSÕES: A amamentação se configurou como fator de proteção contra a fluorose. É preciso estabelecer critérios de classificação mais específicos para permitir a investigação de relações entre fluorose e classe socioeconômica.

OBJECTIVE: To investigate protection or risk factors for dental fluorosis in permanent teeth of 6 to 8 year-old children in a neighborhood of Fortaleza, Brazil. METHODS: This case-control study included 57 controls and 67 children with fluorosis affecting superior and inferior incisors teeth as determined by the Dean classification criteria. Presence of fluorosis was considered as the dependent variable. Data concerning independent variables were obtained through interviews with the parents. Fisher's exact test was used to determine associations between fluorosis and the independent variables. Odds ratios (OR) were calculated to investigate associations and likelihood of fluorosis in the case group, with 95 percent significance level. RESULTS: Fluorosis was significantly associated with type of housing (owned, rented or squatted), but not with the source of drinking water or use of fluoridated toothpaste and fluoride supplements. Univariate analysis showed that the risk of fluorosis was higher in children who began drinking powdered milk mixed with water before 2 years of age (OR = 4.53; IC95 percent: 1.07-26.74) and in those who did not breastfeed (OR = 6.66; IC95 percent: 1.61-38.62). In the multivariate analysis, only breastfeeding was associated with fluorosis (4.54; IC95 percent: 1.21-16.66). CONCLUSIONS: Breastfeeding was a protection factor against fluorosis. More specific categorization criteria must be established to investigate relationships between fluorosis and socioeconomic class.

[Analysis of protection or risk factors for dental fluorosis in 6 to 8 year-old children in Fortaleza, Brazil]. / Análise dos fatores de risco ou de proteção para fluorose dentária em crianças de 6 a 8 anos em Fortaleza, Brasil.

OBJECTIVE: To investigate protection or risk factors for dental fluorosis in permanent teeth of 6 to 8 year-old children in a neighborhood of Fortaleza, Brazil. METHODS: This case-control study included 57 controls and 67 children with fluorosis affecting superior and inferior incisors teeth as determined by the Dean classification criteria. Presence of fluorosis was considered as the dependent variable. Data concerning independent variables were obtained through interviews with the parents. Fisher's exact test was used to determine associations between fluorosis and the independent variables. Odds ratios (OR) were calculated to investigate associations and likelihood of fluorosis in the case group, with 95% significance level. RESULTS: Fluorosis was significantly associated with type of housing (owned, rented or squatted), but not with the source of drinking water or use of fluoridated toothpaste and fluoride supplements. Univariate analysis showed that the risk of fluorosis was higher in children who began drinking powdered milk mixed with water before 2 years of age (OR = 4.53; IC95%: 1.07-26.74) and in those who did not breastfeed (OR = 6.66; IC95%: 1.61-38.62). In the multivariate analysis, only breastfeeding was associated with fluorosis (4.54; IC95%: 1.21-16.66). CONCLUSIONS: Breastfeeding was a protection factor against fluorosis. More specific categorization criteria must be established to investigate relationships between fluorosis and socioeconomic class.

[Fluoride content in potable water and drinks. Connection with dental caries prevention and dental fluorosis].

Content of fluoride by ion selective electrode in potable water (municipal water supply, bottled, from draw-wells and springs), in juices of industrial and compotes of domestic preparation, in drinks of various grades of the tea made by water with unequal contents of fluorine was analyzed. Fluoride entered organism of the population in non-control mode more often in minimum quantities that explained, in certain measures a wide caries incidence. Granting of the information upon concentration of fluorides in potable water, juices and drinks used by population would allow people to adjust this microelement intake in the organism with the purpose of preventing of dental caries and fluorosis.

In vitro evaluation of dentifrice with low fluoride content supplemented with trimetaphosphate.

One way to reduce dental fluorosis is by reducing the fluoride (F) concentration in dentifrice, but low-F dentifrice should be as effective as a standard dentifrice. This study evaluated in vitro whether the supplementation with sodium trimetaphosphate (TMP) of a dentifrice with low F content (500 microg/g) would provide a similar effect to that of a standard dentifrice. Bovine enamel blocks were submitted to a pH cycling regime incorporating daily exposures to a slurry of dentifrice: a low-F dentifrice with or without 0.1-3.0% TMP; an F-free, phosphate-free dentifrice (negative control), or a dentifrice with 1,100 microg/g F (positive control). The addition of TMP to dentifrice with or without F was associated with higher surface hardness and decreased loss of integrated subsurface hardness after pH cycling. The combination of 1% TMP and 500 microg F/g had a greater effect than the positive control dentifrice. It is concluded that the addition of TMP to the 500-microg F/g dentifrice allowed a similar or larger effect as compared with a standard dentifrice in this in vitro model.

Medical geology in tropical countries with special reference to Sri Lanka.

Sri Lanka provides an ideal opportunity for the study of the effect of geology on human health. The vast majority of the people of Sri Lanka still live in rural areas within areas termed geochemical provinces. Very broadly, one could say that a geochemical province has characteristic chemical composition in soil, water stream sediments and rocks, enabling their delineation from others. The chemical composition is presumed to be have an impact on the health of the inhabitants of the particular geochemical province, particularly because of the fact that their food and water are obtained mostly from the terrain itself. This leads to the concept of "diseases of geochemical origin". Among these are dental fluorosis, iodine deficiency disorders (IDDs) and selenium-based diseases. The Dry Zone of Sri Lanka has several areas rich in groundwater fluoride, the ingestion of which leads to dental fluorosis. Iodine deficiency diseases are more common in the Wet Zone, though their aetiologies are more complicated. Interestingly, it has also been observed that significant proportions of the female population of Sri Lanka are selenium-deficient, which could well be related to the geological environment. Chronic renal failure (CRF) has been observed in some areas of the Dry Zone of Sri Lanka, where there is a relationship of CRF with the mineral content of drinking water. This subject matter falls under the auspices of Medical Geology, a scientific discipline still in its infancy, and much more concerted studies are needed to attract the attention of medical research.

[Fluoride content of soft drinks produced in Poland]. / Zawartosc fluoru w napojach bezalkoholowych produkowanych w Polsce.

Fluoride content of 81 commercial brands of soft drinks and bottled waters were determined using potentiometric method with ion selective electrode. In the beverages produced in the same factory fluoride level were similar. The connection between elevation of fluoride levels and ingredients of investigated products such as juice or cola extract was not found. However, in some samples of ice tea drinks containing the tea extract fluoride levels might have been raised up to 1.28 mg/l. Fluoride contents of beverages from 28 producers ranged from 0.01 to 0.30 mg/l and only from 4 producers up to 0.60 mg/l. The highest level of fluoride (1.39 mg/l) has been determined in one sample of mineral water. In conclusion, ice tea beverages and certain mineral water, made and sold in Poland, may constitute an important source of fluoride in diet. Their consumption, particularly in case of children, must be controlled.

Sociodemographic and behavioural correlates of severe dental fluorosis.

OBJECTIVES: The aim of this study was to identify sociodemographic and behavioural factors associated with the prevalence of severe dental fluorosis in moderate- and high-fluoride areas of the Ethiopian Rift Valley. METHODS: Three hundred and six adolescents (12-15 years) and 233 mothers participated in the study. The children were examined for dental fluorosis according to the Thylstrup-Fejerskov Index (TFI). The children and their mothers were subsequently interviewed. Sixty mothers had more than one participating child. In order to perform a paired parent/child analysis, a total of 73 younger siblings had to be excluded. RESULTS: Among the remaining 233 children, the prevalence of severe dental fluorosis (TFI >or= 5) was 24.1% and 75.9% in the moderate- and high-fluoride areas, respectively. According to bivariate as well as multivariate analyses, a number of sociodemographic and behavioural factors were related to severe fluorosis. The odds for having severe fluorosis varied according to the fluoride concentration of the drinking water, age, consumption of tea, length of breastfeeding and method of storing water. The adjusted odds ratios ranged from 2.6 to 26.1. Breastfeeding for > 18 months and the use of clay pots for storing drinking water helped protect against severe dental fluorosis. Bivariate analyses indicated that being male and consuming fish might be associated with higher TFI scores. CONCLUSION: In order to avoid dental fluorosis, low-fluoride drinking water should be provided in the relevant villages. A prolonged period of breastfeeding, the use of clay pots for storing water, and possibly a reduced intake of tea and whole fish in infants might also help to avoid severe fluorosis in children growing up in traditionally fluoride-endemic areas.

Additional beneficial effect of tamarind ingestion over defluoridated water supply to adolescent boys in a fluorotic area.

OBJECTIVE: We evaluated the effect of tamarind (Tamarindus indicus) on ingestion and whether it provides additional beneficial effects on mobilization of fluoride from the bone after children are provided defluoridated water. METHODS: A randomized, diet control study was conducted in 30 subjects from a fluoride endemic area after significantly decreasing urinary fluoride excretion by supplying defluoridated water for 2 wk. Subjects were then assigned to one of two groups, with 15 in each group. One group was supplemented with tamarind (experimental group) for 3 wk and the other (control) group was given only defluoridated water for the same period. RESULTS: The mean changes in urinary components after tamarind ingestion (volume, pH, fluoride calcium, copper, and magnesium) in the control and experimental groups were compared. There was a significant increase (P < 0.01) in fluoride excretion and urinary pH and a significant decrease in urinary calcium (P < 0.01) and copper (P < 0.05) excretion in the experimental group as compared with the control group. There was no change in urinary volume between groups. CONCLUSIONS: Tamarind intake appears to have an additional beneficial effect on the mobilization of deposited fluoride from bone, by enhancing urinary excretion of fluoride.

Prevention and control of brick-tea type fluorosis--a 3-year observation in Dangxiong, Tibet.

To evaluate the effects of preventing and controlling brick-tea type fluorosis, we carried out a 3-year field observation and assayed the total daily fluoride intake, urinary and serum fluoride level, and dental fluorosis prevalence and index in a boarding school in Dangxiong, Tibet, in students aged 8-15. We replaced the traditional brick tea with low-fluoride brick tea (LFBT). Reduction in the traditional brick-tea consumption decreased the total daily fluoride intake among the children, which still remained within the level of chronic intoxication but at a safe level. The study suggests that the LFBT is effective in the prevention and control of endemics of brick tea type fluorosis, although further improvement of the LFBT is required.