Availability Of Fluoride Research Articles

The distribution of fluoride in carious human enamel.

The proton probe has been used to map F concentration changes in the enamel of 15 teeth showing clinical evidence of caries. Thin sections through the lesions were microradiographed and measurements made of the surface zone (radiodense) and body (radiolucent) areas. Each section was then scanned with a focused beam of 2.5 MeV protons, 2000 spot analyses being performed over areas up to 2 x 3 mm. F was determined by detecting gamma rays from a nuclear reaction and the data used to construct 3-D surface plots. The maximum F concentration in the lesion surface zone was extremely variable, ranging from 1750 to 21,700 ppm, and rarely occurred over the deepest part of the lesion. F levels were elevated in the lesion body but usually to a small extent only. A large increase in F throughout the lesion body was found in 3 lesions only, and was associated with a surface zone that was thin or of low x-ray density. Relatively small F increases in the lesion body were associated with either a thick, x-ray dense surface layer having a greatly increased F level (> 10,000 ppm) or, conversely, with a surface layer having a relatively small F increase. Since F uptake can be regarded as a "marker" of past remineralization events, this study shows that remineralization can and does occur in the body of natural enamel caries lesions, especially when the surface layer is thin or lost. Fluoride availability that encourages the formation of an extremely dense surface layer may result in under-achievement of this natural repair process in the lesion body.

Fluoride accumulation and toxicity in wild small mammals

Populations of two species of small mammal, the field vole ( Microtus agrestis L.) and the bank vole ( Clethrionomys glareolus L.), inhabiting grasslands contaminated by industrial sources of fluoride were examined for fluoride concentrations in skeletal tissue and for morphological changes in the teeth. Concentrations of fluoride in teeth and bones were higher for C. glareolus than for M. agrestis at the chemical works and smelter sites. Severe dental lesions were recorded on the incisor and molar teeth of both species at the chemical works and smelter sites, with less marked damage at the mine tailings dam. This is attributed to inter-site differences in fluoride speciation and the consequent effects on the availability of fluoride in the diet for bioassimilation.

Evaluation of phenylmethanesulfonyl fluoride (PMSF) as a tracer candidate mapping acetylcholinesterase in vivo

The availability of phenylmethanesulfonyl fluoride (PMSF), an irreversible cholinesterase inhibitor, for a tracer mapping acetylcholinesterase (AchE) in vivo in brain and other organs was evaluated using [ 35S]PMSF in mice and rats. [ 35S]PMSF was well taken up into the brain, heart and muscle, and the radioactivities were trapped in these organs. Pretreatment with non-labeled PMSF decreased 33–40% of the trapped radioactivities in the brain and other organs in mice. However, regional distribution of [ 35S]PMSF in rat brain did not correlate well with that of AchE activity, suggesting that the selectivity of PMSF toward AchE may be insufficient for use as an in vivo tracer mapping AchE.

Biological chick procedure to determine fluoride availability in sepiolite

1. A modified fluoride (F) bioassay procedure based on the method of standard additions and using chicks was tested for the determination of F availability in sepiolite. Chicks were distributed between a control group fed on a basal diet and experimental groups fed on this diet supplemented with 100, 200 or 300 mg/kg F as sodium fluoride. A further group was fed on the basal diet plus 2 g/kg sepiolite. 2. Body weight gain and food consumption during a 60 or 90 d study were similar for all treatments. 3. Ileal digestibility of F from the basal diet or from the diet supplemented with 200 mg/kg F as sodium fluoride was higher (0.907) than for chicks fed on the sepiolite diet (0.152). 4. Increases in the F contents of tibia ash were linearly related to dietary F concentration as sodium fluoride. 5. F contents of tibiae from the sepiolite group (at 60 or 90 d of age) were plotted against tibia F concentrations from groups receiving additional sodium fluoride in the diet. A weighted regression was performed. The values obtained for the relative available F from sepiolite were 0.213 and 0.150, respectively, at 60 and 90 d of age.

Prevalence of enamel defects/fluorosis in fluoridated and non-fluoridated areas in Ireland.

Water fluoridation was introduced in Ireland in 1964 and in recent years the availability of fluoride from other sources had increased. As part of a National Survey of Children's Health in Ireland Dean's and the DDE indices were used to determine the prevalence of enamel fluorosis/defects in 8- and 15-yr-old children in fluoridated and non-fluoridated areas. Over 94% of the children examined in all areas were regarded as having normal enamel, as defined by Dean's index, the remainder showing evidence of either questionable, very mild or mild fluorosis. Between 52% and 63% of the children had one or more teeth affected by enamel defects when measured by the DDE index. The prevalence of enamel fluorosis/defects was similar in children living in fluoridated and non-fluoridated areas but the prevalence of diffuse opacities (DDE) was higher in the fluoridated areas.

The level and timing of systemic exposure to fluoride with respect to caries resistance.

Material related to water fluoridation and fluoride availability has been examined for changing patterns of fluoride intake by humans over recent years. The difficulty of separating systemic and topical fluoride action from water and foods from that found in fluoride agents used in preventive treatment programs is discussed. Recommendations are made that water fluoridation is a well-proven program and should be continued, but that fluoride supplementation programs under the control of the individual should be carefully evaluated and, if used, should be restricted to periods after the secretory stage of enamel formation is normally finished for anterior teeth, with supplements commenced during the pre-eruption maturation period and continuing until permanent tooth eruption is complete. Although supplements can also give a topical source to the teeth, depending on the way the supplement is consumed and the duration of time it is available in the mouth, other methods of topical fluoride provision are endorsed, and these should continue through life. It is suggested, in respect of epidemiology studies, that data collected before the availability of fluoride dentifrices in 1971 should be re-examined.

歯石中のフッ素濃度分布

A knowledge of fluoride uptake and distribution in tooth deposits and underlying tooth surfaces could provide useful information about availability and action of fluoride in the oral environment and oral fluids. Fluoride concentration and distribution were therefore measured in supra- and subgingival calculus and at the underlying enamel or cementum surfaces using a mechanical sampling technique and a fluoride electrode (Weatherell et al., 1985).In this study, twenty extracted teeth with supragingival calculus and twenty teeth with subgingival calculus removed from subjects aged 44 to 67 years old were used. Phosphorus distributions were also determined using a x-ray microanalyser.The results were as follows;1) Fluoride concenerations were highest at the surface of dental calculus. There was a lower level plateau for the interior, which rose again as the tooth surface was approached.2) Supragingival calculus tended to show a smoother profile compared with that of subgingival calculus.

Availability of fluoride from glass‐ionomer luting cements in human saliva

Fluoride availability from two glass-ionomer luting agents, Ketac-Cement and Aqua-Cement, was monitored after a 1-h treatment in distilled water at pH 7. The recorded results were then compared to the ones obtained from those same cements, after 1 h, in saliva, in water pretreated with saliva (pH 7 and 4.5), and in albumen and phosphate buffer solutions (pH 7). The Mann-Whitney two-sample rank test was utilized in order to identify the differences. The presence of proteins and phosphate reduced fluoride availability. A reduction in the pH from 7 to 4.5 resulted in an increased rate of fluoride release, in water, from glass-ionomers pretreated with saliva. The present study indicates that fluoride availability from glass-ionomers, in vivo, is pH controlled. The rate controlling factors appear to be phosphate and proteins.

Water Fluoridation and Fluoride Supplementation: Considerations for the Future

The extensive literature on water fluoridation and fluoride supplementation is discussed, looking critically at the benefits of systemic fluoride availability in the prevention of dental caries and at the adverse factors of enamel fluorosis which can occur from the ingestion of too much fluoride during the period of tooth development. Recommendations are made for the future use of fluorides, emphasizing that water fluoridation is a safe and proven health measure which should be continued. Caution in the use of other fluoride supplementation methods is raised, especially when related to compliance and the use of fluoride supplements which are under the control of the individual. Targeting of children who would benefit from fluorides and additional preventive dental health measures is recommended.

Potentiometric determination of fluoride and iodide in natural and processed waters of Bahrain using ion-selective electrodes

To assess the natural availability of fluoride and iodide in Bahrain, natural and processed waters which included ground water, tap waters, Adari Lake water and streams and waters from reverse osmosis (RO), ion-exchange (IE), multistage flash desalination (MSF) and solar desalination (SD) plants, in addition to blended waters, were monitored for 3 months (Oct.–Dec. 1985). The fluoride ion concentration ranges from 0.45 to 1.51 ± 0.26 mg dm −3 in natural waters; 0.003 to 0.33 ± 0.016 mg dm −3 in the processed waters and 0.15 to 0.24 ± 0.095 mg dm −3 in the blended waters. As for the iodide ion, concentration ranges from 0.02 to 1.08 ± 0.07 mg dm −3 in natural waters; 0.01 to 0.02 ± 0.002 mg dm −3 in both processed and blended water.

Distribution of trace element pollutants in a contaminated ecosystem established on metalliferous fluorspar tailings. 3: Fluoride

High total soil fluoride (10 000 μg g −1) in the metalliferous fluorspar tailings was reflected by elevated concentrations in standing live vegetation (300–1000 μg g −1); plant roots ( c. 6000 μg g −1); plant litter ( c. 4000 μg g −1); total body concentrations of invertebrates (400–4000 μg g −1) and the small mammals Microtus agrestis (120–360 μg g −1) and Sorex araneus (140–250 μg g −1). Seasonal changes in the standing live vegetation and the availability of soil fluoride to plants are discussed. Seasonal changes in total body concentrations of the small mammals were related to the age structure of the populations as well as dietary levels. In the small mammals, the concentration ratios were < 0·5 at the tailings dam and > 1·1 at the control site, indicating that both species were able to regulate fluoride accumulation at the higher levels of intake. Soft tissue concentrations were, as expected, very low compared to the hard tissues but, still, were generally significantly higher at the tailings dam compared to the control site. Evidence of dental fluorosis was found in Microtus agrestis, but not Sorex araneus.

The Pre‐and Posteruptive Effects of Fluoride in the Caries Decline

The widespread availability of fluoride from many sources is accepted as a major reason for the caries decline among children in developed countries. There is still controversy, however, about its principal mode of action. This article reviews the evidence on fluoride's preeruptive and posteruptive effects, and suggests reasons for its continuing role in the caries decline. Early fluoridation studies accepted that fluoride acted preruptively through incorporation into developing enamel; but further research could not explain why fluoride levels were not clearly higher in enamel exposed to fluoride, nor why there were no clear correlations between caries experience and enamel fluoride concentration. Instead, considerable evidence suggests that fluoride acts mainly, though not entirely, through posteruptive remineralization of demineralized enamel. Caries experience has declined in nonfluoridated as well as in fluoridated areas, though DMF scores are still consistently lower in fluoridated areas. Posteruptive remineralization effects are seen from fluoridated drinking water as well as with fluoride from other sources. The continuing caries decline, beyond the level suggested by early fluoridation field trials, can be attributed either to more efficient remineralization or to long-term, intraoral ecological change, or to both.

Studies on distribution of fluoride in water sources of hyderabad, AP. (India)

Hyderabad city is situated adjacent to a known severe endemic area of fluorosis. The area comprises a granitic rock terrain, which contains fluoride bearing minerals. Comprehensive studies have therefore been conducted to evaluate the incidence of fluoride in water sources and determine the factors influencing the distribution of fluorides. Results have shown that the important factors influencing the excessive incidence of flouride in water are likely to be (a) availability of soluble fluoride in weathered rocks and soils (b) adequate contact with circulating water (c) evaporation and evapotranspiration (d) low calcium and magnesium content of soils and circulating water and excessive bi-carbonate of water.

Carbon isotopic composition and lattice-bound carbonate of Peru-Chile margin phosphorites

New light-stable carbonate-carbon isotope and lattice-bound CO 2 data from Quaternary Peru-Chile margin phosphatic nodules, crusts and pelletal grains, and from associated dolomicritic concretions, are presented, which provide constraints on the timing and mechanisms of growth of these phases in organic carbon-rich sediments. Comparison of δ 13C values from carbonate fluorapatite (CFA) nodules and pelletal grains (−4.8 to 0.0‰ and −2.9 to +1.0‰ PDB, respectively) with pore-water total dissolved δ 13C values from these sediments suggests early authigenic CFA precipitation from pore waters within a few centimeters of the sediment-water interface in association with suboxic to perhaps anoxic microbial degradation of organic matter. In contrast, the dolomicritic cores of nodules recovered from about 12°S display both strongly negative to positive δ 13C values (−10.8 to +6.1‰) characteristic of formation deeper in the sediments in association with methanogenic and perhaps sulfate reduction microbial processes. The amount of structural carbonate in CFA suggests that carbonate substitution generally increases as δ 13C in CFA decreases, a probable consequence of increasing carbonate and accompanying charge-balancing substitutions in the CFA lattice in response to increasing pore-water carbonate ion concentrations with depth below the sediment-water interface. In one buried upward-growing nodule, decreasing CFA δ 13C and increasing structural CO 2 also correspond to decreasing CFA growth rates. These data suggest that in addition to other constraints such as pore-water phosphorus and fluoride availability, the lower limit of CFA precipitation in suboxic to anoxic sediments may be controlled by lattice poisoning due to excessive dissolved carbonate ion concentrations. In organic-rich Peru-Chile margin sediments this depth threshold appears to be at approximately 5–10 cm below the sediment-water interface where maximum CFA CO 2 contents of about 6 Wt.% occur; in less organic-rich settings, greater depths of precipitation of CFA may be anticipated. Below this relatively shallow depth of CFA precipitation on the Peru shelf, high pore-water alkalinity and associated elevated total dissolved carbon and carbonate ion concentration apparently favor the precipitation of authigenic carbonates.

Fluoride intake from beverage consumption.

Previous studies have shown that fluoride is present in beverages prepared with fluoridated water. The purpose of this study was to determine the availability of fluoride from beverages consumed in adjacent fluoridated and non-fluoridated communities taking into account fluoride supplementation regimens. Children in grade six were invited to participate in recording of beverage intake in two cities in Alberta, Canada: Wetaskiwin, with water supplies fluoridated at 1.08 ppm F, and Camrose, non-fluoridated with water supplies at 0.23 ppm F. Three-day beverage intake records--"Drink Diaries"--were collected from 179 children in Wetaskiwin and 230 children in Camrose. Fluoride values, based on the analyses of Hargreaves, were assigned to the reported consumption of the children with the three highest and three lowest total beverage intakes in each community. A wide range of available fluoride was found. A substantial source of fluoride was shown to be available in the non-fluoridated community from beverages other than water, primarily from carbonated beverages commercially prepared with fluoridated water. Available beverages and actual consumption should be considered in the prescription of fluoride supplementation for children with minimal fluoride in their drinking water.

Availability of fluoride at different sites in the buccal sulcus.

After rinsing with a fluoride solution, the amounts of fluoride taken up by small pieces of dentine placed strategically about the mouth varied considerably from site to site in the oral cavity. The pattern of fluoride availability in this subject's mouth was in line with previous findings about fluoride distribution in his labial sulcus. The present results therefore suggest by analogy that considerable variations in fluoride clearance and concentration must exist throughout the oral cavity. These previous studies of fluoride clearance from the labial sulcus also showed that there are marked differences between individuals. The present findings, emerging from a study of 1 subject, therefore imply a need for more information about the variations in the availability, concentration and clearance of fluoride and, by extrapolation, of other substances throughout the mouths of different individuals.

The role of 'CaF2-like' material in topical fluoridation of enamel in situ.

In this paper the role and importance of 'CaF2-like' material deposited on enamel (Fon) by means of an APF gel and the varnishes Duraphat and Fluor Protector are described and discussed. The amount of Fon, determined by KOH extraction, is a measure of the amount of CaF2-like material on the enamel surface. Fluoride in the enamel (Fin), determined by etching, is the amount of F- bound in the solid enamel. Fon and Fin data are presented after various F- treatments and after wearing enamel slabs in dentures for a period of 1 week. The results of this work show that if we compare the three fluoridating agents, APF gel, Duraphat varnish, and Fluor Protector varnish in situ, only Fluor Protector shows a measurable amount of Fon after 1 week. The amounts of Fon acquired by the enamel surface (one application) rank as APF gel approximately Duraphat much less than Fluor Protector. Most likely, Fon in situ leaches away through the pellicle, with an apparent diffusion coefficient of about 10(-6) cm2.sec-1. The Fin data show that after APF gel or Duraphat treatment a substantial amount of Fin leaches away during 1 week in situ; the Fin values of Fluor Protector do not change. The efficiency of the fluoridating agents is most likely determined by the application period and fluoride availability. For APF gel, Duraphat, and Fluor Protector about 5%, 1%, and 44% of the available fluoride participates in the fluoridation process. CaF2-like globules are known to precipitate after gel or varnish treatment on the enamel surfaces and can be dissolved in KOH solution.(ABSTRACT TRUNCATED AT 250 WORDS)

Fluoride turnover in ad�lie penguins (Pygoscelis adeliae) and other brid species

Fluoride concentrations found in soft tissues of free ranging birds are below 10 mg/kg d.w. In ducks (Anas platyrhynchos) 99.5% of all fluoride is bound in the skeleton. Krill-eating adelie penguins (Pygoscelis adeliae) reached equilibrium concentrations in the order of 10000 mg F/kg d.w. in femur. Fluoride uptake with the diet is buffered by the skeleton where it has a half-life of 3–4 weeks. Fluoride from fresh krill does not reach the organs of adelie penguins to the same extent as NaF. Most fluoride remains bound to the krill cuticle and is not absorbed by the penguin gut during digestion. The availability of krill fluoride was in the range of 21%–30% for muscle and 48%–68% for femur of adelie penguins as compared to NaF (100%). The role of the salt glands in fluoride excretion is neglegible. The uptake of approx. 240 mg F daily with the krill diet is balanced by excretion via the cloaca.

Effect of flavour and detergent on fluoride availability in whole saliva after use of NaF and MFP dentifrices.

This study was designed to assess the effect of flavour and detergent in NaF and MFP dentifrices on the availability of fluoride in whole saliva after toothbrushing. Saliva samples were collected in 13 subjects at different times up to 60 min after brushing with controlled amounts of dentifrices with various compositions. The availability of fluoride in whole saliva was determined in terms of areas under the elimination curves (AUC) after linearization of the data by application of the Weibull function. This distribution provided the best quality of fit of all individual elimination data in contrast to commonly used data transformations. Analyses of variance showed a highly significant effect of individuals on the AUC values. Addition of flavour consistently reduced the AUCs whereas addition of detergent always increased the AUCs. The detergent had a negative effect on the observed intraoral hydrolysis of MFP. It was suggested that F^–– AUC is a fundamental parameter for the cariostatic potential of F dentifrices.

Influence of Zinc and Iron on Dietary Fluoride Utilization in the Rat

Two experiments were conducted with the weanling rat fed a purified diet to determine the influence of dietary zinc (6, 30, 150 ppm) and iron (7, 35, 175 ppm) on fluoride bioavailability. Dietary fluoride in each case was 2 or 10 ppm as sodium fluoride. During a 6-wk trial, neither divalent zinc nor divalent iron affected fluoride bioavailability based on skeletal uptake of fluoride. Our studies were specifically designed to provide concepts about the effects of dietary trace element supplementation practices on dietary fluoride bioavailability especially in terms of fluoride originating from foods prepared in fluoridated water. Our results suggest that either iron or zinc can be added to foods to improve nutritional value without compromising the availability of food fluoride.