Dietary intake of fluoride ashed (total fluoride) v. unashed (inorganic fluoride) analysis of individual foods

Clinical and Forensic Signs Resulting from Exposure to Heavy Metals and Other Chemical Elements of the Periodic Table

Several heavy metals and other chemical elements are natural components of the Earth’s crust and their properties and toxicity have been recognized for thousands of years. Moreover, their use in industries presents a major source of environmental and occupational pollution. Therefore, this ubiquity in daily life may result in several potential exposures coming from natural sources (e.g., through food and water contamination), industrial processes, and commercial products, among others. The toxicity of most chemical elements of the periodic table accrues from their highly reactive nature, resulting in the formation of complexes with intracellular compounds that impair cellular pathways, leading to dysfunction, necrosis, and apoptosis. Nervous, gastrointestinal, hematopoietic, renal, and dermatological systems are the main targets. This manuscript aims to collect the clinical and forensic signs related to poisoning from heavy metals, such as thallium, lead, copper, mercury, iron, cadmium, and bismuth, as well as other chemical elements such as arsenic, selenium, and fluorine. Furthermore, their main sources of occupational and environmental exposure are highlighted in this review. The importance of rapid recognition is related to the fact that, through a high degree of suspicion, the clinician could rapidly initiate treatment even before the toxicological results are available, which can make a huge difference in these patients’ outcomes.

An Analytical Protocol for the Differentiation and the Potentiometric Determination of Fluorine-Containing Fractions in Bovine Milk

Free fluoride ions are effective in combating caries in children, and their supplementation in milk has been widely used worldwide for this purpose. Furthermore, it is known that ionic fluoride added to milk is distributed among its components, but little is known about their quantitative relationships. This is likely due to the absence of an analytical protocol aimed at differentiating and quantifying the most important forms of fluorine present in milk. For the first time, a comprehensive protocol made up of six potentiometric methods devoted to quantifying the most important fractions of fluorine in milk (i.e., the free inorganic fluoride, the inorganic bonded fluorine, the caseins-bonded fluorine, the whey-bonded fluorine, the lipid-bonded fluorine, and the total fluorine) has been developed and tested on real samples. Four of the six methods of the procedure are original, and all have been validated in terms of limit of detection and quantification, precision, and trueness. The data obtained show that 9% of all fluorine was in ionic form, while 66.3% of total fluorine was bound to proteins and lipids, therefore unavailable for human absorption. Beyond applications in dental research, this protocol could be extended also to other foods, or used in environmental monitoring.

Upregulation of miR-200c-3p induced by NaF promotes endothelial apoptosis by activating Fas pathway

Fluoride has been considered as a risk factor of cardiovascular disease due to its endothelial toxicology. However, the mechanism underlying the endothelial toxicity of fluoride has not been clearly illustrated. MiR-200c-3p was strongly linked with endothelial function and its level is increased in serum of fluorosis patients, but it is unclear the role of miR-200c-3p in the fluoride induced endothelial dysfunction. In this study, we confirmed that fluoride exposure induced the apoptosis of endothelial cells both in established rats model and cultured human umbilical vein endothelial cells (HUVECs). And miR-200c-3p was found to be upregulated in NaF treated HUVECs. Fluoride stimulation increased caspase-dependent apoptosis through miR-200c-3p upregulation, with repressing expression of its target gene Fas-associated phosphatase 1 (Fap-1), which functioned as Fas inhibitor. This resulted in activation of Fas-associated extrinsic apoptosis via interaction with increased Fas, Fadd, Cleaved Caspase-8 and Cleaved Caspase-3. The activation of Fas-associated extrinsic apoptosis was abrogated by miR-200c-3p inhibitor. Furthermore, the antiapoptotic effect of downregulated miR-200c-3p was restored by Fap-1 siRNA. These results suggested a determinant role of the miR-200c-3p/Fap-1 axis in fluoride induced endothelial apoptosis.

Toxicity of fluoride: critical evaluation of evidence for human developmental neurotoxicity in epidemiological studies, animal experiments and in vitro analyses

Recently, epidemiological studies have suggested that fluoride is a human developmental neurotoxicant that reduces measures of intelligence in children, placing it into the same category as toxic metals (lead, methylmercury, arsenic) and polychlorinated biphenyls. If true, this assessment would be highly relevant considering the widespread fluoridation of drinking water and the worldwide use of fluoride in oral hygiene products such as toothpaste. To gain a deeper understanding of these assertions, we reviewed the levels of human exposure, as well as results from animal experiments, particularly focusing on developmental toxicity, and the molecular mechanisms by which fluoride can cause adverse effects. Moreover, in vitro studies investigating fluoride in neuronal cells and precursor/stem cells were analyzed, and 23 epidemiological studies published since 2012 were considered. The results show that the margin of exposure (MoE) between no observed adverse effect levels (NOAELs) in animal studies and the current adequate intake (AI) of fluoride (50 µg/kg b.w./day) in humans ranges between 50 and 210, depending on the specific animal experiment used as reference. Even for unusually high fluoride exposure levels, an MoE of at least ten was obtained. Furthermore, concentrations of fluoride in human plasma are much lower than fluoride concentrations, causing effects in cell cultures. In contrast, 21 of 23 recent epidemiological studies report an association between high fluoride exposure and reduced intelligence. The discrepancy between experimental and epidemiological evidence may be reconciled with deficiencies inherent in most of these epidemiological studies on a putative association between fluoride and intelligence, especially with respect to adequate consideration of potential confounding factors, e.g., socioeconomic status, residence, breast feeding, low birth weight, maternal intelligence, and exposure to other neurotoxic chemicals. In conclusion, based on the totality of currently available scientific evidence, the present review does not support the presumption that fluoride should be assessed as a human developmental neurotoxicant at the current exposure levels in Europe.

Fluoride contamination, health problems and remediation methods in Asian groundwater: A comprehensive review

In low concentration, fluoride is considered a necessary compound for human health. Exposure to high concentrations of fluoride is the reason for a serious disease called fluorosis. Fluorosis is categorized as Skeletal and Dental fluorosis. Several Asian countries, such as India, face contamination of water resources with fluoride. In this study, a comprehensive overview on fluoride contamination in Asian water resources has been presented. Since water contamination with fluoride in India is higher than other Asian countries, a separate section was dedicated to review published articles on fluoride contamination in this country. The status of health effects in Asian countries was another topic that was reviewed in this study. The effects of fluoride on human organs/systems such as urinary, renal, endocrine, gastrointestinal, cardiovascular, brain, and reproductive systems were another topic that was reviewed in this study. Different methods to remove fluoride from water such as reverse osmosis, electrocoagulation, nanofiltration, adsorption, ion-exchange and precipitation/coagulation were introduced in this study. Although several studies have been carried out on contamination of water resources with fluoride, the situation of water contamination with fluoride and newly developed technology to remove fluoride from water in Asian countries has not been reviewed. Therefore, this review is focused on these issues: 1) The status of fluoride contamination in Asian countries, 2) health effects of fluoride contamination in drinking water in Asia, and 3) the existing current technologies for defluoridation in Asia.

Evaluation of Fluoride Retention Due to Most Commonly Consumed Estuarine Fishes Among Fish Consuming Population of Andhra Pradesh as a Contributing Factor to Dental Fluorosis: A Cross-Sectional Study

BACKGROUND

Fluoride in drinking water is known for both beneficial and detrimental effects on health. The principal sources of fluoride include water, some species of vegetation, certain edible marine animals, dust and industrial processes. The purpose of this study was to evaluate the fluoride retention of most commonly consumed estuarine fishes among fish consuming population of Andhra Pradesh.

MATERIALS AND METHODS

A cross-sectional study was conducted to evaluate the amount of fluoride retention due to ten most commonly consumed estuarine fishes as a contributing factor to Fluorosis by SPADNS Spectrophotometric method. The presence and severity of dental fluorosis among fish consuming population was recorded using Community Fluorosis Index. Statistical analysis was done using MedCalc v12.2.1.0 software.

RESULTS

For Sea water fishes, the fluoride levels in bone were maximum in Indian Sardine (4.22 ppm). Amongst the river water fishes, the fluoride levels in bone were maximum in Catla (1.51 ppm). Also, the mean total fluoride concentrations of all the river fishes in skin, muscle and bone were less (0.86 ppm) as compared to the sea water fishes (2.59 ppm). It was unveiled that sea fishes accumulate relatively large amounts of Fluoride as compared to the river water fishes. The mean Community Fluorosis Index was found to be 1.06 amongst a sampled fish consuming population. Evaluation by Community Index for Dental fluorosis (CFI) suggested that fluorosis is of medium public health importance.

CONCLUSION

It was analysed that bone tends to accumulate more amount of fluoride followed by muscle and skin which might be due to the increased permeability and chemical trapping of fluoride inside the tissues. The amount of fluoride present in the fishes is directly related to the severity of fluorosis amongst fish consuming population, suggesting fishes as a contributing factor to fluorosis depending upon the dietary consumption.

Quantification of fluoride in food by microwave acid digestion and fluoride ion-selective electrode

To quantify fluoride in food it is necessary to extract the fluoride from the matrix. Dry ashing (alkali fusion) and facilitated diffusion are the methods most commonly used, but their application requires lengthy treatments. The present study proposes the use of a microwave oven and 7 mol/L nitric acid for simple, rapid digestion of foods for fluoride analysis. The analyte is subsequently quantified by fluoride ion-selective electrode. The various steps of the method were optimized and an in-house validation was performed. The limit of quantification (0.130 mg/kg), trueness (92%), recovery (84-101%), and precision (1-8%) were determined. These analytical characteristics are satisfactory and show the suitability of the method for analysis of fluoride in foods of various kinds. The method's ease of application and the use of equipment normally found in food analysis laboratories may help to further increase research on fluoride concentrations in foods consumed by the population.

Total fluoride intake and urinary excretion in 4–year–old Iranian children residing in low-fluoride areas

Knowledge of levels of fluoride ingestion and excretion is important in planning optimum fluoride therapy for young children. In previous literature, it has been assumed that only about one-third of ingested fluoride is excreted in young children. The aims of the present study were (a) to measure total fluoride intake, urinary fluoride excretion and fluoride balance, and (b) to investigate the effect of air temperature on fluoride intake and urinary fluoride excretion, in young children. Children (4 years old) living in a city, a small town and rural areas of Fars province, Iran, where drinking water contained 0·30–0·39 mg F/l, were invited to participate. Selection of subjects was by random sampling of kindergartens or health centres. The children were surveyed twice, once in summer and once in winter. Diet was obtained by 3 d diaries with interview. Samples of most foods and drinks were analysed for fluoride content. Ingestion of fluoride from toothpaste was estimated for each child. Each child's urine was collected over 24 h and analysed for fluoride content. Seventy-eight of the 116 volunteers completed all aspects of the study, which was conducted in 1995–6. For all children, the mean fluoride ingestion from diet was 0·390 (sd 0·122) mg/d or 0·028 (sd 0·008) mg/kg body weight per d. Fluoride ingestion from diet was higher in summer and higher in rural areas. The mean ingestion of fluoride from all sources was 0·426 (sd 0·126) mg/d and the mean fluoride urinary excretion was 0·339 (sd 0·100) mg/d. The difference between ingestion and urinary excretion was +0·087 (sd 0·143) mg, equivalent to 80 % excretion. Faecal excretion was not estimated. The results indicate fluoride retention at 4 years to be much lower than previously assumed.

Relationship between daily fluoride intake from diet and the use of dentifrice and human plasma fluoride concentrations

The literature contains reports of the relationship between the fluoride concentrations in drinking water and human plasma. None of these studies, however, documented individual levels of daily fluoride intake, which can vary considerably among individuals served by the same water supply. Furthermore, while water can be an important source of fluoride, other sources, especially fluoridated dentifrices, also contribute substantially. This 2-day study with five 25-35-year-old subjects in each of three communities (Bauru, 0.6-0.8 ppm F; Domelia, 0.7 ppm F; Floresta, 0.3 ppm F) determined plasma fluoride concentrations and fluoride intake from diet and the use of dentifrice which, together, approximate total daily fluoride intake. The purposes were to determine: (1) the extent to which plasma fluoride concentrations approached levels known to affect the quality and quantity of bone; (2) the relationship between fluoride intake and plasma concentrations. Plasma was collected at 4-h intervals starting at 0800 h and ending at 2000 h each day. Average fluoride intakes from diet and the use of dentifrice in the three communities ranged from 0.16 to 0.82 mg/day and from 0.29 to 3.16 mg/day, respectively. The overall average plasma concentrations in the three communities were 0.44, 0.45 and 0.54 micromol/l (P<0.005). They were directly related to intake from the use of dentifrice (P=0.030) and to total intake (P=0.033), but were not related to dietary intake (P=0.176). In conclusion, despite fluoride intake from various sources, the plasma fluoride concentrations of the study subjects remained at levels far below those associated with effects on bone production.

Fluoride, calcium and magnesium intake in children living in a high-fluoride area in Ethiopia. Intake through food

OBJECTIVE

The aim of this study was to assess the daily dietary fluoride intake in children living in two neighbouring villages in the Wonji Shoa Sugar Estate, a rural part of the Ethiopian Rift Valley.

METHODS

The villages depended on water from different sources: Village A used either river water (Awash River, with 1.8 mg F(-)/L) or ground water (2.1 mg F(-)/L), while village K was served ground water with 14 mg F(-)/L. Fifteen fully weaned children below the age of 5 years were selected in each of the villages. Over a four-day period the total food intake for these children was assessed by using a duplicate portion technique. The food was analysed for fluoride by using a fluoride ion-selective electrode after the dry ashing. Furthermore, the energy of the food was measured, as well as the calcium and magnesium contents (atomic absorption spectrometry after microwave digestion with nitric acid and hydrogen peroxide). The mothers gave a description of the ingredients used for preparing the food. Relevant background information concerning food habits, etc. was collected through a food frequency questionnaire.

RESULTS

This study shows that considerable amounts of fluoride may be retained in food prepared on high-fluoride water. In village A, food contributed 2.3 mg F(-)/day, while a dietary fluoride intake of 4.8 mg/day was found in children in village K. Interestingly, the sevenfold higher fluoride concentration of the water used for food preparation in village K compared to village A, gave only a doubling in fluoride intake through food. Calcium intake was relatively low while magnesium intake was above the recommended level.

CONCLUSION

As the energy intake by both groups was low, some systematic underreporting might be suspected. Thus, the fluoride intake in the group may be even higher than what was actually found in this study.

FLUORIDE ANALYSIS OF FOODS FOR INFANTS AND ESTIMATION OF DAILY FLUORIDE INTAKE

The mean daily fluoride intake in infants was estimated on the basis of their intake of commercial foods for infants in Japan and evaluated in order to establish the effectiveness and safety criteria for water fluoridation, which is practiced as a preventive measure for dental caries suitable in life stages from children to the elderly. Based upon the intakes of foods for infants, the mean daily fluoride intake was estimated to be 0.166 mg in infants aged 3-4 months, 0.202 mg in those aged 5-6 months, and 0.266 mg in those aged 7-8 months. The mean daily fluoride intake per kg of body weight at these ages was in the range of 0.023-0.029 mg/kg, which was about half of the standard daily fluoride intake for infants and children advocated by Ophaug et al., as 0.05-0.07 mg/kg. From our results, the daily fluoride intake of infants from foods in Japan is estimated to be equivalent to or lower than the values of previous reports in non-fluoridated areas. Consequently, our data support the argument that water fluoridation and the appropriate use of fluoride for dental caries prevention in Japan are needed on the basis of scientific criteria in terms of fluoride exposure related to food intake during tooth formation.

Fluoride levels in drinking water in the Central Province of Saudi Arabia

BACKGROUND

This study was designed to assess the fluoride levels in drinking water in the Central Province of Saudi Arabia.

MATERIALS AND METHODS

A total of 817 water samples were collected from 260 locations in Central Saudi Arabia. An atomic absorption spectrophotometer [HACH instrument, model DR 3000] was used in the analyses of water samples for fluoride levels.

RESULTS

The results showed that fluoride levels vary between 0.00 and 6.20 ppm. About 75% and 6% of the population in Riyadh and Qassim regions, respectively, were exposed to very low fluoride levels (0.00-0.03 ppm), while less than 3% of the population in both regions were exposed to fluoride levels ranging from 0.61 to 0.80 ppm. A higher percentage of the population in Qassim than Riyadh region were exposed to high fluoride levels (>0.81 ppm); 28.63% than in Riyadh with 9.24%.

CONCLUSION

The findings of this study can serve as a baseline data for water fluoridation and other dental preventive programs in the area.

The fluoride content of foods and beverages from negligibly and optimally fluoridated communities

In the spring of 1996, foods and beverages most commonly consumed by adolescents were analyzed for fluoride as part of a larger investigation. These foods were selected by interviewing 711 adolescents, 12-14 years of age, who were long-time residents of either an optimally or negligibly fluoridated community. The brand names of the identified foods and beverages most commonly purchased were determined by interviews with the parents. A total of 441 brand-name food and beverage items were purchased from both communities and were individually analyzed for fluoride. These analyses were done in order to estimate the fluoride content of various kinds of foods and beverages and to determine whether or not there was a significant difference between the two communities in the amount of fluoride ingested from these dietary sources. The food and beverage items were classified into dietary groups based on US Department of Agriculture (USDA) guidelines. Overall, the fluoride content of the sampled foods and beverages was low. In addition, there was no significant difference in the fluoride content of the same pre-packaged or ready-to-eat food or beverage items purchased in the two communities. However, a significant difference was found between the two communities in the fluoride content of fountain beverages and in cooked or reconstituted foods prepared using local water from the respective communities. Based on these results, we have estimated the mean daily, dietary fluoride intake for 3-5-year-old children who are more susceptible to developing dental fluorosis.

Occurrence and management of dental fluorosis

The prevalence of dental fluorosis is on the increase in different parts of the world, even in areas with fluoride-deficient public water supplies. This may be due to increased use of fluoride in preventive dentistry. In some countries, exposure to apparently low fluoride concentrations in drinking water has resulted in severe dental fluorosis in some children. This underscores the importance of taking into consideration all sources of fluoride intake in a community before prescribing fluoride supplements or recommending appropriate fluoride concentration for the public water supply. Preventive management of dental fluorosis includes de-fluoridation of drinking water in endemic areas, cautious use of fluoride supplements and supervision of the use of fluoride toothpaste by children aged below 5 years. Aesthetically objectionable discolouration of fluorosed teeth may be managed by bleaching, micro-abrasion, veneering or crowning. The choice between these treatments depends on the severity of the fluorosis and this may be satisfactorily determined by the Thylstrup and Fejerskov index.

Fluoride content of foods made with mechanically separated chicken

The goal of the present study was to determine the extent to which foods made with mechanically separated chicken can contribute to total fluoride intake. Fluoride content of each blended sample was determined with a fluoride combination electrode following perchloric-acid-facilitated diffusion of hydrogen fluoride. Infant foods had the highest fluoride content followed by chicken sticks, luncheon meats, and canned meats. A single serving of chicken sticks alone would provide about half of a child's upper limit of safety for fluoride. Fluoride content of foods made with mechanically separated chicken was significantly correlated with calcium content, which is consistent with the possibility that the mechanical separation process was the source of the extra fluoride. Foods made with mechanically separated turkey were not a major source of fluoride.

The bio-availability of fluoride from black tea

OBJECTIVES

To investigate the oral retention of fluoride from tea and its association with the tooth surface and acquired pellicle.

METHODS

Oral retention of fluoride after rinsing in vivo was assessed from expectorated samples with an ion specific electrode methodology. Interaction of fluoride with the tooth surface and acquired pellicle was examined in situ with enamel blocks mounted on partial removable appliances. In vitro models were used to examine fluoride binding to enamel particles.

RESULTS

Thirty four percent of the fluoride was retained in the oral cavity after rinsing with tea. Differences in retention at the tooth surface in the presence and absence of an acquired pellicle were not statistically significant at incisor or molar sites. Fluoride from tea showed strong binding to enamel particles, which was only partially dissociated by solutions of ionic strength considerably greater than that of saliva. Binding studies demonstrated strong avidity of enamel for tea and salivary pellicle components.

CONCLUSIONS

This study has demonstrated that tea can provide an effective vehicle for fluoride delivery to the oral cavity where it may interact with the oral tissues and their surface integuments. This may lead to local topical effects of the ingested fluoride as well as systemic effects following oral and gastro-intestinal absorption.

Dental fluorosis in 12-15-year-old rural children exposed to fluorides from well drinking water in the Hail region of Saudi Arabia

To investigate the relationship between fluoride levels in well drinking water, severity of dental fluorosis and dental caries in the Hail region of Saudi Arabia, 2355 rural children aged 12-15 years were examined. Over 90% of the children had fluorosed teeth and chi-square tests showed a strong association (P < 0.001) between fluoride level (0.5-2.8 ppm) in well drinking water and severity of dental fluorosis. Although regression analysis showed a statistically significant relationship (P < 0.001) between fluoride concentration and caries experience, the amount of variation explained was very low (R2 = 0.9%). Since fluoride in well water had little influence on caries experience and is causing dental fluorosis, it should be removed by defluoridation or the rural population should be provided with an alternative source of drinking water with lower fluoride concentration.

Fluoride and silicon intake in normal and endemic fluorotic areas

Precise quantitative information on (a) the contribution of diet to the daily intake of fluoride; and (b) the intake of silicon, which the current work suggests can aggravate fluorosis, is not available for fluorotic and non-fluorotic areas of India. Therefore, an attempt has been made in the present study to collect the above information in normal and fluorotic villages. The daily intake of fluoride (mean +/- SD) over water and diet in normal villages was 1.2 +/- 0.67 mg and 1.0 +/- 0.60 mg, while the corresponding values in a normal urban area were 0.5 +/- 0.03 mg and 1.2 +/- 0.73 mg, respectively. With respect to the intake over water the mean values in normal areas (urban vs. rural) were significantly different (P < 0.001), while there was no significant difference in dietary contribution in the normal areas. In fluorotic villages the daily intake of fluoride was 12.1 +/- 4.11 mg over water and 3.4 +/- 2.43 mg over the diet. These values from fluorotic villages were significantly higher (P < 0.001) than those observed in the normal rural areas. The total intake of silicon (mean +/- SD) in rural and urban normal areas was 204 +/- 58.6 mg and 143 +/- 29.4 mg per day, respectively. The corresponding value from fluorotic villages was 277 +/- 65.5 mg, which was significantly higher (P < 0.01) than those observed in both the normal areas. The situation was similar in fluorotic villages with respect to silicon intake over diet and water. However, the intake of this element over water in the normal rural area (74.0 +/- 18.51 mg per day) was significantly higher (P < 0.001) than the value obtained in the normal urban area (7.5 +/- 1.82 mg per day). This study clearly shows that in the fluorosis-affected areas studied, (a) the total intake of both fluoride and silicon is significantly higher than the intake in non-fluorotic areas; and (b) diets contribute significantly to the intake of both these elements. Our observations on silicon intake and its probable relation to fluorosis are the first of their kind in the literature.

Intake and metabolism of fluoride

The purpose of this paper is to discuss the major factors that determine the body burden of inorganic fluoride. Fluoride intake 25 or more years ago was determined mainly by measurement of the concentration of the ion in the drinking water supply. This is not necessarily true today because of ingestion from fluoride-containing dental products, the "halo effect", the consumption of bottled water, and the use of water purification systems in the home. Therefore, the concentration of fluoride in drinking water may not be a reliable indicator of previous intake. Under most conditions, fluoride is rapidly and extensively absorbed from the gastrointestinal tract. The rate of gastric absorption is inversely related to the pH of the gastric contents. Overall absorption is reduced by calcium and certain other cations and by elevated plasma fluoride levels. Fluoride removal from plasma occurs by calcified tissue uptake and urinary excretion. About 99% of the body burden of fluoride is associated with calcified tissues, and most of it is not exchangeable. In general, the clearance of fluoride from plasma by the skeleton is inversely related to the stage of skeletal development. Skeletal uptake, however, can be positive or negative, depending on the level of fluoride intake, hormonal status, and other factors. Dentin fluoride concentrations tend to increase throughout life and appear to be similar to those in bone. Research to determine whether dentin is a reliable biomarker for the body burden of fluoride is recommended. The renal clearance of fluoride is high compared with other halogens. It is directly related to urinary pH. Factors that acidify the urine increase the retention of fluoride and vice versa. The renal clearance of fluoride decreases and tissue levels increase when the glomerular filtration rate is depressed on a chronic basis.

Determination of fluorine in biological materials: a review

This review on determination of fluorine in biological materials briefly covers (a) a discussion of various forms of fluorine in body fluids and tissues [and also in foods]; (b) methods of their determination, including pretreatment of samples, separation and concentration of F and its final measurement; (c) an evaluation of the analytical methods used and interpretation of results; and (d) some recommendations for future research in fluorine analytical methods applicable to biological materials.

Dental tissue effects of fluoride

It is now well-established that a linear relationship exists between fluoride dose and enamel fluorosis in human populations. With increasing severity, the subsurface enamel all along the tooth becomes increasingly porous (hypomineralized), and the lesion extends toward the inner enamel. In dentin, hypomineralization results in an enhancement of the incremental lines. After eruption, the more severe forms are subject to extensive mechanical breakdown of the surface. The continuum of fluoride-induced changes can best be classified by the TF index, which reflects, on an ordinal scale, the histopathological features and increases in enamel fluoride concentrations. Human and animal studies have shown that it is possible to develop dental fluorosis by exposure during enamel maturation alone. It is less apparent whether an effect of fluoride on the stage of enamel matrix secretion, alone, is able to produce changes in enamel similar to those described as dental fluorosis in man. The clinical concept of post-eruptive maturation of erupting sound human enamel, resulting in fluoride uptake, most likely reflects subclinical caries. Incorporation of fluoride into enamel is principally possible only as a result of concomitant enamel dissolution (caries lesion development). At higher fluoride concentrations, calcium-fluoride-like material may form, although the formation, identification, and dissolution of this compound are far from resolved. It is concluded that dental fluorosis is a sensitive way of recording past fluoride exposure because, so far, no other agent or condition in man is known to create changes within the dentition similar to those induced by fluoride. Since the predominant cariostatic effect of fluoride is not due to its uptake by the enamel during tooth development, it is possible to obtain extensive caries reductions without a concomitant risk of dental fluorosis.

Benefits and risks of fluoride supplementation: caries prevention versus dental fluorosis

To assess the risks (dental fluorosis) and the benefits (caries prevention) of fluoride (F) tablets and F toothpaste, we surveyed 2003 schoolchildren aged 5-20 years old (mean = 10.82, SD = 3.40). Children were scored for dental caries by means of the decayed, missing, filled teeth index (DMFT index). Frequent use of F toothpaste (toothbrushing frequency) is poorly linked to caries (Spearman r = 0.05, P = 0.02) and dental fluorosis (r = 0.05, P = 0.03). Children who use F tablets regularly and appropriately exhibit mild fluorosis more often than non- or occasional users (odds ratio = 9.58), and have a mean DMFT index 50% lower than other children. We conclude that using F tablets is an effective means of preventing caries. When used appropriately in non fluoridated areas, using F tablets results in minor damage.

The changing patterns of systemic fluoride intake

Fluorosis prevalence has increased in North America since the 1930's-1940's. It may also have increased since 1970, though the evidence for that is less clear. Continued monitoring will help determine whether increased fluorosis prevalence in children in the United States is a cohort effect from the 1970's. This review considers the evidence for an increase in fluoride ingestion from all sources since the 1970's. If an increase has occurred, the most likely sources are fluoride dietary supplements, inadvertent swallowing of fluoride toothpastes, and increased fluoride in food and beverages. For adults, there is no evidence from dietary surveys to show that fluoride intake has increased over the last generation. Dietary surveys for children aged six months to two years are similarly inconclusive, though the great variation in fluoride content of various infant foods might be obscuring real effects. The data on fluoride intake by children from food and beverages, infant foods included, are not strong enough to conclude that an increase in fluoride ingestion has occurred since the 1970's. However, the suggested upper limit of fluoride intake is substantially being reached in many children by ingestion of fluoride from food and drink (0.2-0.3 mg per day) and from fluoride toothpaste (0.2-0.3 mg per day). Two public health issues that arise from this review are: (a) the need for a downward revision in the schedule for fluoride supplementation, and (b) education on the potential for high fluoride concentration of soft drinks and processed fruit juices.

A quantitative comparison of methods measuring fluoride in solutions or in enamel

Fluoride in solution is most usually measured with the ion-specific electrode, although a few other methods are available. The electrode can be used in a straightforward manner, its lower concentration limit may be extended by special methods such as the standard addition of fluoride, or microdiffusion methods may be used to extract fluoride from the sample and concentrate it in base. Specifications of all methods are tabulated. A choice of method depends on the requirements in terms of specifications but also on the personal experience of the investigator and the required robustness. Microdiffusion of some kind is preferable for concentrations below 5 mumol/L or when electrode-interfering molecules such as proteins are present in rather high concentrations. Fluoride in enamel may be determined by removal of layers by etching, abrasion, or microdrilling, followed by dissolution of the layer removed. Specifications of depth and area resolution are tabulated. Alternatively, probing methods of a physical nature can be used. These methods require sophisticated instruments that are not widely available. Some of them are destructive, others are not. All but one require exposure to vacuum. However, most of them combine a very good sensitivity with a very good resolution in depth and/or measured area. Therefore, their use in research (requiring cooperation with instrument specialists/owners) may well be worth the effort.

Minerals and trace elements in milk

The nutritional roles, requirements, and metabolism and the quantitative relationship between dietary intakes and health for a number of the minerals and trace elements have been more clearly defined in recent years, but there are still considerable deficiencies in our understanding of these issues, e.g., the significance of calcium in the etiology and treatment of osteoporosis and hypertension. Reliable information is now available on the content, and the principal factors affecting it, of most of the minerals and trace elements in human and cow's milks. However, for some of the trace elements, there is still a wide variation in reported values in the literature, which is due, at least in part, to analytical difficulties. The contribution of cow milk and milk products to the diet in Western countries is significant for sodium, potassium, chloride, calcium, phosphorus, zinc, and iodine. Iodine is the only trace element for which there has been any suggestion of excessive amounts in cow milk. However, there is evidence of a decline in milk iodine concentrations in the United States in recent years, although the situation in other countries less clear. Breast milk usually has adequate mineral and trace element contents for feeding full-term infants, with the exceptions of fluoride, for which supplementation of infants is recommended, and of selenium in some countries, such as Finland and New Zealand, where maternal intakes are low. However, breast milk selenium contents have increased in these countries in recent years due to increased maternal selenium intakes. The concentrations of minerals and trace elements in infant formulas for full-term infants are generally higher than in human milk, and all appear to be more than adequate, with the possible exception of selenium, which may need to be increased in some formulas. Considerable changes in the mineral and trace element contents of formulas have been instituted in recent years in the light of improved knowledge of infant requirements. While the chemical forms of the macrominerals and some of the trace elements (iron, zinc, copper, and manganese) in milks are fairly well defined, the forms of many of the trace elements are unknown. Sodium, potassium, chloride, and iodine are believed to be almost totally absorbed from milks and infant formulas.(ABSTRACT TRUNCATED AT 400 WORDS)

Evaluation of analytical methods for fluorine in biological and related materials

During the past two decades, some major pitfalls in fluorine analysis have been recognized and overcome. Therefore, it is important that facts be separated from fallacies in published literature on levels and forms of fluorine (ionic, bound, covalent, etc.) in biological materials, in order that correct perceptions of physiological, biochemical, and toxicological aspects of inorganic as well as organic fluorine compounds can be formed. Trace amounts of inorganic fluoride in biological samples can now be accurately determined with the fluoride electrode either directly or following diffusion, adsorption, or reverse extraction of fluoride (when necessary). The aluminum monofluoride molecular absorption technique provides an excellent rapid method for determination of trace amounts of inorganic fluoride (in the absence of organic fluorine). Fluorine in most organic fluorine compounds is not available for distillation, diffusion, or reverse-extraction. The sample needs to be ashed (open ashing) or combusted (oxygen flask, oxygen bomb, pyrohydrolysis) for covalently bound fluorine to be converted to fluoride ions. This can now be readily accomplished at room temperature by the reductive cleavage of the C-F bond with the sodium biphenyl reagent. Some recommendations for future research have been made.

Relationship of total fluoride intake to beneficial effects and enamel fluorosis

Recent studies indicate that the prevalence of very mild to moderate dental fluorosis, as classified by Dean, has increased relative to that found in earlier investigations. To date, fluoridated water, fluoride supplements, the diet, fluoride dentifrices, and other topical fluoride applications have been identified as sources of systemic fluoride. Recent evidence suggests that there is a strong association between mild to moderate enamel fluorosis and the use of fluoride supplements during early childhood, and that the presently recommended supplementation schedule for U.S. children above the age of 2 years may be too high. Evidence also suggests that there is a strong association between fluoride dentifrice use during early childhood and enamel fluorosis in fluoridated populations. These findings support the need for a careful review of existing supplementation schedules and early oral hygiene practices. There is a pressing need for additional analytical epidemiological studies to confirm existing findings and to determine whether other fluoride sources may be associated with enamel fluorosis. Further, since exposure to combinations of individual risk factors has been shown to carry more than merely an additive increase in the risk of fluorosis, these studies must be multifactorial in design. There is also a need for more fluorosis prevalence and severity data to be gathered, so that the development of enamel fluorosis as a public health problem can be assessed, and so that the success of measures implemented to maximize efficacy while minimizing unwanted side-effects can be monitored.

The nature and mechanisms of dental fluorosis in man

Any use of fluorides, whether systemic or topical, in caries prevention and treatment in children results in ingestion and absorption of fluoride into the blood circulation. The mineralization of teeth under formation may be affected so that dental fluorosis may occur. Dental fluorosis reflects an increasing porosity of the surface and subsurface enamel, causing the enamel to appear opaque. The clinical features represent a continuum of changes ranging from fine white opaque lines running across the tooth on all parts of the enamel to entirely chalky white teeth. In the latter cases, the enamel may be so porous (or hypomineralized) that the outer enamel breaks apart posteruptively and the exposed porous subsurface enamel becomes discolored. These changes can be classified clinically by the TF index to reflect, in an ordinal scale, the histopathological changes associated with dental fluorosis. Compared with Dean's and the TSIF index, we consider the TF index to be more precise. Recent studies on human enamel representing the entire spectrum of dental fluorosis have demonstrated a clear association between increasing TF score and increasing fluoride content of the enamel. So far, no useful data on dose (expressed in mg fluoride/kg b.w.)-response (dental fluorosis) relationships are available. In this paper, we have, therefore, re-evaluated the original data by Dean et al. (1941, 1942), Richards et al. (1967), and Butler et al. (1985) from the USA, by applying the equation of Galagan and Vermillion (1957) which permits the calculation of water intake as a function of temperature.(ABSTRACT TRUNCATED AT 250 WORDS)

Dietary fluoride intake of 15-19-year-old male adults residing in the United States

The average daily dietary fluoride intakes of 15-to-19-year-old males were estimated from the analysis of 24 FDA "market basket" food collections made from 1975 to 1982. The data indicate that 15-to-19-year-old males residing in fluoridated (greater than 0.7 ppm) cities had an average daily dietary fluoride intake of 1.85 mg/day when the diet provided an estimated caloric intake of 11.72 megajoules (2800 calories). In non-fluoridated cities, with less than 0.3 ppm in the drinking water, the average dietary fluoride intake was 0.86 mg/day. The beverages and drinking water contributed an average of 75 +/- 2% of the daily dietary fluoride intake.

Fluoride content of selected human food, pet food and related materials

A survey was made of the fluoride content of selected human foods, some animal feeds, and related materials, with the purpose of a better characterization of products whose fluoride may contribute to the intake of fluoride by man as well as by some kinds of animals. Uptake of fluoride, especially from food with or without a foregoing food chain, was found to be more widely spread than has been documented previously. The major source of fluoride is represented by marine organisms, regardless of the ways by which man or animals are exposed to fluoride. As a consequence of the detailed analytical data given, recommendations would extend towards i) a more wide-spread analytical control of foods and feeds for fluoride, ii) an intensified assessment of fluoride bioavailabilities from foods and feeds, and iii) the consideration of such data in the evaluation of fluoride supplementations for optimized intakes, as recommended.