Evaluation of analytical methods for fluorine in biological and related materials

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.

Hair as biomarker of fluoride exposure in a fluoride endemic area and a low fluoridated area

AIM

The aim of the present study was to determine whether hair could be used as biomarker of fluoride exposure.

MATERIALS AND METHODS

The study was carried out on 30 people living in an endemically fluoridated area and a low fluoridated area. Samples of hair from the occipital were taken and subjected to fluoride analysis by a fluoride ion electrode.

RESULTS

Lower fluoride levels in water supplies correlated with lower levels of fluoride in hair and more over higher fluoride levels in water correlated with higher levels of fluoride in hair. A direct relationship was evident between fluoride levels in water supplies and concentration of fluoride in hair (P < 0.01).

CONCLUSIONS

The results of the present study indicate hair can be used as an indicator of fluoride exposure.

Fluoride levels and osteosarcoma

Context:

Osteosarcoma is a rare malignant bone tumor, commonly occurring in the age group of 10 to 24 years. Recent reports have indicated that there is a link between fluoride exposure and osteosarcoma.

Aims:

The present study was planned to analyze serum levels of fluoride in patients of osteosarcoma and fluoride content of their drinking water.

Settings and Design:

The present study was carried out comparing 10 patients of osteosarcoma and 10 healthy volunteers (who served as controls).

Materials and Methods:

Serum and drinking water fluoride levels were estimated by ion selective electrode.

Statistical analysis used:

The data were computed as mean ± SD and Student’s t test was applied.

Results:

Both, the serum and drinking water fluoride levels, were significant by higher in patients with osteosarcoma as compared to controls (P > 0.05, P > 0.001, respectively).

Conclusions:

These results suggest a link between fluoride exposure and osteosarcoma.

Serum fluoride and sialic acid levels in osteosarcoma

Osteosarcoma is a rare malignant bone tumor most commonly occurring in children and young adults presenting with painful swelling. Various etiological factors for osteosarcoma are ionizing radiation, family history of bone disorders and cancer, chemicals (fluoride, beryllium, and vinyl chloride), and viruses. Status of fluoride levels in serum of osteosarcoma is still not clear. Recent reports have indicated that there is a link between fluoride exposure and osteosarcoma. Glycoproteins and glycosaminoglycans are an integral part of bone and prolonged exposure to fluoride for long duration has been shown to cause degradation of collagen and ground substance in bones. The present study was planned to analyze serum fluoride, sialic acid, calcium, phosphorus, and alkaline phosphatase levels in 25 patients of osteosarcoma and age- and sex-matched subjects with bone-forming tumours other than osteosarcoma and musculo-skeletal pain (controls, 25 each). Fluoride levels were analyzed by ISE and sialic acid was analyzed by Warren's method. Mean serum fluoride concentration was found to be significantly higher in patients with osteosarcoma as compared to the other two groups. The mean value of flouride in patients with other bone-forming tumors was approximately 50% of the group of osteosarcoma; however, it was significantly higher when compared with patients of group I. Serum sialic acid concentration was found to be significantly raised in patients with osteosarcoma as well as in the group with other bone-forming tumors as compared to the group of controls. There was, however, no significant difference in the group of patients of osteosarcoma when compared with group of patients with other bone-forming tumors. These results showing higher level of fluoride with osteosarcoma compared to others suggesting a role of fluoride in the disease.

Development of gold standard ion-selective electrode-based methods for fluoride analysis

BACKGROUND/AIMS

Currently available techniques for fluoride analysis are not standardized. Therefore, this study was designed to develop standardized methods for analyzing fluoride in biological and nonbiological samples used for dental research.

METHODS

A group of nine laboratories analyzed a set of standardized samples for fluoride concentration using their own methods. The group then reviewed existing analytical techniques for fluoride analysis, identified inconsistencies in the use of these techniques and conducted testing to resolve differences. Based on the results of the testing undertaken to define the best approaches for the analysis, the group developed recommendations for direct and microdiffusion methods using the fluoride ion-selective electrode.

RESULTS

Initial results demonstrated that there was no consensus regarding the choice of analytical techniques for different types of samples. Although for several types of samples, the results of the fluoride analyses were similar among some laboratories, greater differences were observed for saliva, food and beverage samples. In spite of these initial differences, precise and true values of fluoride concentration, as well as smaller differences between laboratories, were obtained once the standardized methodologies were used. Intraclass correlation coefficients ranged from 0.90 to 0.93, for the analysis of a certified reference material, using the standardized methodologies.

CONCLUSION

The results of this study demonstrate that the development and use of standardized protocols for F analysis significantly decreased differences among laboratories and resulted in more precise and true values.

Fluorosis risk in grade 2 students residing in a rural area with widely varying natural fluoride

OBJECTIVES

This pilot study was performed to determine the prevalence of dental fluorosis and the association between fluorosis and a number of risk factors in a group of second grade students in a rural, non-fluoridated area of Ontario, Canada.

METHODS

Of 1739 students screened during routine health surveillance, 1367 had erupted maxillary central incisors. Fluorosis was scored on these children using the Tooth Surface Index of Fluorosis (TSIF). A fluoride exposure questionnaire and water sample vial was sent home from school with each child.

RESULTS

Valid responses were obtained for 752 children (55%). The prevalence of fluorosis in respondents was 23.3%, with 4.9% scoring TSIF of 2 or more. In bivariate analysis, several variables were significantly associated with the prevalence and/or severity of fluorosis. These included: water fluoride concentration, breast-feeding duration, professionally applied topical fluoride, fluoride supplement use, bottle-feeding, fluoridated mouthwash use, and early parental toothbrushing with toothpaste. In logistic regression analysis limited to children living at the current residence for 4 years or more, only four variables had significant independent effects. These were water fluoride concentration, breast-feeding duration, fluoride supplement use, and fluoridated mouthwash use.

CONCLUSIONS

These findings indicate that fluorosis is an important concern in non-fluoridated areas. Fluoride supplements should not be recommended unless an independent home water test is performed. Breast-feeding for 6 months or more may protect children from developing dental fluorosis in the permanent incisors.

A simplified micromethod for fluoride analysis

A simplified method for the determination ionic fluoride (F-) concentrations in microvolume samples using a F(-)-selective electrode is described. Portions (20 microl) of a series of F- standard solutions (1000-0.4 parts/10(9) F-) were placed between the surface of the F- electrode and the surface of a reference electrode mounted end to end with the aid of a steel holder. In this position the two surfaces were used as an analysis chamber, retaining the sample by surface tension without the use of sleeves or other devices. The precision of the results and the absolute detection limit of the modified method were determined. The analytical performance of this set-up was tested by comparing the results with those obtained from the conventional method. The regression between the modified-method data and the conventional-technique data showed a strong correlation (R2 = 0.993) between the results obtained using the two techniques. In the range of F- concentrations from 1000 and 0.48 parts/10(9), the precision of the results (coefficient of variation) was of 5-6%, improving to 0.9% at 0.9 parts/10(9) level.

Distribution of fluoride in the oral cavity after application of a bioadhesive fluoride-releasing tablet

Bioadhesive fluoride tablets are fluoride-releasing devices that can be applied to the oral mucosa by the patient and release fluoride for several hours. From earlier research, it is known that a single fluoride source in the mouth can lead to an uneven distribution of fluoride in the oral cavity. In this study, fluoride concentrations were determined at different sites of the oral cavities of 13 healthy human volunteers after the application of a bioadhesive fluoride tablet containing 0.5 mg fluoride. The sites were: (1) labial surfaces of the upper central incisors, (2) lingual surfaces of the lower central incisors, (3) labial surface of the first upper left molar, and (4) labial surface of the lower right first molar. The tablet was fixed either centrally on the palate or in the lower labial sulcus in two consecutive experiments. Saliva was sampled with polyethylene sponges 5, 10, 20, 30, 60, 120, 180, and 240 minutes after tablet insertion. Fluoride was determined electrochemically. It could be shown that the area under the curve (AUC) values were significantly (p < 0.05) higher after tablet insertion in the lower labial sulcus at sampling site 1, a trend (p = 0.06) could be calculated for sampling sites 2 and 3, and no difference was found at sampling site 4. Fluoride could be detected in concentrations above 0.01 mmol.L-1 at all sampling sites after tablet insertion in the lower labial sulcus. This location seems to be a more appropriate tablet location than the palate.

Commentary on and recommendations for the proper uses of fluoride

Fluorosis has been associated with the fluoride concentration of drinking water, use of dietary fluoride supplements, early use of dentifrices, and prolonged use of infant formula. The literature, however, does not show associations between fluorosis and use of fluoride mouthrinses, professionally applied fluorides, bottled waters, carbonated beverages, and juices. It is unwise to issue laundry lists of items that may be implicated as problem-causing when, in fact, they may not be. Although usually classified without fluorosis, children in Dean's "questionable" category would be classified with the condition if the TFI or TSIF were used. Accordingly, Dean, in 1942, really reported only 52.8 percent of children without fluorosis in Kewanee, a community with 0.9 ppm fluoride in drinking water. Because the morbidity and sequelae of dental caries have declined, undue emphasis has been placed recently on the risks of using fluoride rather than on its profound beneficial effects. Although of paramount importance, conclusions cannot be drawn on whether fluoride protects against, contributes to, or has no effect on bone fractures or is valuable in treating osteoporosis. Careful thought is required before making recommendations that may reduce health benefits because of unfounded concerns about perceived risks. There should be greater regulation of extraneous fluoride sources, rather than reliance on educational efforts or recommendations to eliminate use of highly effective preventive regimens.

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.

Determination of fluorine in biological materials: reaction paper

Although the fluorine in human tissues may exist in both inorganic and organic (covalently bound) forms, the inorganic fraction is clearly the most relevant for assessing human exposure to, and utilization of, environmental fluoride. There is now general agreement that the inorganic fraction of total tissue fluorine can be accurately determined by a variety of analytical techniques. One of the basic questions considered at this workshop is whether the analysis of a specific tissue or body fluid can provide an estimate of how much of the fluoride to which an individual is exposed actually enters and accumulates in the body. The analysis of hair and nails has been used as an indicator of exposure and utilization for several trace elements, including fluoride. Due to methodological uncertainties regarding sampling and pre-analysis treatment, however, it is presently not possible clearly to distinguish fluoride which is incorporated into hair and nails during formation (endogenous) from that which becomes associated with the tissues following exposure to the environment (exogenous). Consequently, although the fluoride content of hair and nails is clearly increased by environmental exposure to fluoride, the conclusion that these tissues are suitable indicators of fluoride utilization and accumulation in the body is premature.

Biological markers: their use in quantitative assessments

Biological markers can be conceptualized in terms of categories of markers that form a continuum representing a sequence of events from exposure to disease. These categories include markers of internal dose, biologically effective dose, early response, and disease. Outside of this sequence are susceptibility factors that can act at any point along the way to modify the effects of external exposures on disease outcomes. Examples of the use of these different types of markers in epidemiologic research are provided. There are many factors that one must consider when selecting a biological marker for use in an epidemiologic study. These factors include: the objectives of the study, the availability and specificity of potential markers, the feasibility of measuring the markers in various biological media, the invasiveness of the techniques necessary to measure the markers, the amount of biological specimen needed for analysis, the time to appearance of the markers in the biological media, the persistence of the markers in biological media, the variability of marker levels within and between individuals, the stability of markers in storage, as well as the cost, sensitivity, specificity, and reliability of the assays used to measure the markers. Each of these characteristics is discussed. The usefulness of biological markers in an epidemiologic study depends on the objectives of the study and whether the properties of the markers fulfill the objectives of the study in a feasible and cost-effective manner.

Intra-oral models to assess cariogenicity: evaluation of oral fluoride and pH

The main purpose of this paper is to review the various methods used for evaluation of fluoride retention in saliva, plaque, and enamel following application of topical anti-caries treatments such as F dentifrices and F mouthwashes. Such methods monitor delivery of fluoride to the site of action, the mouth, and so can be regarded as assessing potential for treatment action. It is concluded that intra-oral fluoride measurements are appropriate to support bioequivalence claims for anti-caries treatments, provided that particular chosen methods have been calibrated against clinical data. Studies purporting to show superiority are of interest mechanistically, but links to caries are not sufficiently understood to define superiority claims. A wide variety of methods has been used for determination of the fluoride content of enamel. Of these, well-established methods such as the micro-drill and acid-etch procedures are appropriate for routine comparative testing, whereas sophisticated instrumental techniques such as SIMS are more appropriate for detailed mechanistic studies. Intra-oral pH measurements are also relevant to many topical treatments. Single-site determinations in plaque are preferred, but for comparative studies non-specific determinations may be adequate.

Fluoride, calcium and phosphorus metabolism in the rat: comparison of 'natural ingredient' with semipurified diets

Three groups of weanling female rats were fed different, commercially available, 'natural ingredient' diets containing 12, 28 or 45 parts/10(6) F, mainly as bone meal, for six weeks. Two other groups were fed a low-fluoride (0.76 parts/10(6)) semipurified diet. They received fluoride doses, either in the drinking water or by daily intraperitoneal injection, which were approximately equal to the average dose of the other three groups. Rats on the 'natural ingredient' diets ingested more food and water and excreted more faeces and urine, effects which were attributed to the higher amounts of dietary fibre, Na, K and Cl. Thus, at any given concentration of fluoride in the food or water, the level of fluoride ingestion and the ensuing effects would be influenced by the type of diet used. The values for fractional fluoride absorption (45-49%) and retention (38-47%) were similar among the groups given 'natural ingredient' diets. In the groups given semipurified diet, the corresponding values were about twice as high with the exception that fractional absorption was negative (-41%) in the injected group, which indicated net intestinal secretion of fluoride. Fluoride balances and tissue concentrations were highest in the groups fed the semipurified diet, even though the level of intake was not always higher. The fractional values for calcium and phosphorus absorption (41-51%) and retention (33-43%) were also similar among the groups given 'natural ingredient' diets. The corresponding values were about twice as high in the groups fed the semipurified diet. In terms of supporting maximum bone calcification, phosphorus absorption was marginal in two of the groups on the 'natural ingredient' diets.(ABSTRACT TRUNCATED AT 250 WORDS)