Enamel fluoride in nursing rats with mothers drinking water with high fluoride concentrations

The purpose of this study was to determine the F levels in plasma and molar enamel from rat pups whose mothers had received various levels of F during pregnancy and/or lactation. Rats were started on water containing 0 (Group I), 50 (Group II), or 100 (Group III) ppm F at the beginning of pregnancy or on the day of delivery. The mothers and pups were killed 13 days after delivery, and plasma F levels, milk F levels, and pup molar enamel F levels were determined. The mean maternal plasma F concentrations were 0.02 +/- 0.005 ppm in Group I, 0.10 +/- 0.031 ppm in Group II, and 0.21 +/- 0.057 ppm in Group III. The milk F values were about twice as high as the respective plasma concentrations. The plasma F concentration in control pups was 0.003 +/- 0.0002 ppm, and there was a rise to 0.006 +/- 0.0002 ppm in Group III. Enamel F concentrations were 0.62 +/- 0.13 ppm, 4.72 +/- 0.79 ppm, and 8.80 +/- 1.74 ppm, respectively. The plasma and enamel F values obtained from pups were not significantly different between the pre-natal/post-natal, and the post-natal-only groups. It was concluded that: fluoride levels in the plasma and enamel of control rat pups were much lower than those found in adult rats, such values could be increased only slightly when high doses of F were given to the mother, and unlike values reported for other species, rat milk fluoride concentrations were higher than the respective plasma values.     

The in vitro uptake of fluoride by secretory and maturation stage bovine enamel

The objectives of this study were to determine the specific surface area of secretory-stage and of maturation-stage enamel, to compare the fluoride uptake by isolated enamel at these two stages on a surface-area basis, and to examine the effect of the organic matrix on the fluoride uptake by whole enamel. Fetal bovine secretory and maturation stage enamel samples were collected, and a portion of the enamel at each developmental stage was treated with hydrazine for removal of the organic matrix. The specific surface areas of the enamel mineral, as determined by the multi-point BET method, were 59.3 m2/g in the secretory stage and 37.9 m2/g in the maturation stage. Whole and deproteinated enamel samples were equilibrated in buffered solutions containing 10(-5) to 10(-3) mol/L fluoride, and the uptake was measured with a fluoride specific electrode. The results indicate that the in vitro fluoride uptake was controlled solely by the surface area of the apatitic mineral and that the organic matrix did not contribute to the fluoride uptake.     

Enamel fluoride and caries in Icelandic children and a comparison of enamel fluoride in Swedish and Icelandic children

The fluoride content in surface enamel and its relationship to caries experience was studied in a group of Icelandic schoolchildren living in a low-fluoride area. Fluoride content was assessed by means of in vivo enamel biopsies sampled from 248 subjects aged 11 and 12 years. Dental examinations were performed in conjunction with the biopsy sampling and by the same examiner 1 year later. The prevalence and incidence of initial (DSI) and manifest (DFS) caries lesions were recorded separately. A median fluoride concentration of 610 ppm at a median biopsy depth of 4.2 microns was observed. A significant positive correlation was found between DSI and enamel fluoride content in girls and all older children. Additionally, surface enamel fluoride was measured in 72 Swedish children from a low-fluoride area but exposed to regular topical fluoride treatments. The difference in mean fluoride concentrations between the Icelandic and Swedish study populations was highly significant. From the measured fluoride concentrations the enamel fluoride profiles for both study populations were constructed. The differences in fluoride content were most pronounced in the outermost layer, apparently reflecting the higher exposure to and acquisition of topical fluoride in the Swedish children.     

The appearance of tooth enamel in children ingesting water with a high fluoride content for a limited period during early tooth development

Sixteen Japanese children, inadvertently exposed to drinking water containing 7.8 ppm fluoride (F) from birth, were aged 11 to 42 months when a low-F water supply was substituted. The appearance of the enamel of their permanent teeth was assessed 11 years later (children aged 12-15 years) and recorded using Dean's and the FDI indices. All grades of Dean's classification were seen. The enamel lesions were more severe in the older than in the younger children, in the incisal compared with the gingival halves of the teeth, and in the early- compared with the late-forming teeth. Small, localized, chalky-white areas of enamel were found at or close to the incisal margins of the anterior teeth of six children. The characteristics and the distribution of the lesions in this study add to our knowledge of the mechanism by which fluoride produces dental fluorosis.     

Effects of fluoride on matrix proteins and their properties in rat secretory enamel

This publication concerns the selective adsorption of rat enamel proteins onto hydroxyapatite, their solubility in aqueous solutions, and the effect that systemic fluoride has on these properties. The enamel proteins used as adsorbates were extracted in 0.5 mol/L acetic acid from the secretory enamel of the upper and lower incisors of SD rats (females, 200-220 g body weight). Equilibration of the proteins with hydroxyapatite was performed in two solutions: (i) 50 mmol/L acetate buffer at pH 6.0 and 0 degrees C, and (ii) 50 mmol/L Tris buffer containing 4 mol/L guanidine at pH 7.4 and room temperature. Enamel was dissected from animals, which were given either de-ionized water (control group) or water containing 25, 50, 75, or 100 ppm fluoride as NaF for four weeks. From these enamel samples, the proteins were extracted in sequence with 160 mmol/L NaCl and 3 mmol/L phosphate (pH 7.3), 50 mmol/L carbonate buffer (pH 10.8), and finally, with 0.5 mol/L acetic acid for dissolution of the enamel mineral. The F, Ca, and P contents of the various enamel samples were determined.(ABSTRACT TRUNCATED AT 250 WORDS)     

Relationship of strontium in drinking water and surface enamel.

The Sr content of surface enamel of 233 teeth from nine communities was related to drinking water Sr concentrations. These water concentrations ranged from 0.02 microgram/ml to 33.9 microgram/ml. The relationship between enamel concentrations and water concentrations was linear for water concentrations less than 10 microgram/ml Sr, but leveled off at approximately 300 microgram/gm Sr in the enamel for communities with greater than 10 microgram/ml Sr in drinking water. Binding of Sr to components in the oral environment is proposed as an explanation of this effect.     

Problems in exposure assessment of fluoride in drinking water

OBJECTIVES: We developed a source documentation approach that identified fluoride content of drinking water at the state or local level to estimate fluoride concentrations from public water systems. We then compared estimates from this approach with estimates obtained from a single source, the 1992 Centers for Disease Control and Prevention (CDC) Fluoridation Census. METHODS: We used residential histories from a case-control study. For each residence we attempted to determine fluoride concentrations using the 1992 CDC Fluoridation Census. For the source documentation method we utilized multiple sources from state and local contacts to verify and collect additional data. We compared the fluoride estimates obtained by the two methods. RESULTS: When fluoride values were found using both methods, there was good correlation (Kendall's tau = 0.85; 95% confidence interval = 0.79, 0.90) and concordance was 96 percent. We obtained over 99 percent of the fluoride values needed using source documentation as compared to 49 percent of the values needed when we used a single publication. When fluoride values were missing using the 1992 CDC Fluoridation Census, 21 percent had source documentation estimates of at least 0.7 ppm. CONCLUSIONS: Researchers need to consider limitations of using a secondary data source to estimate fluoride in drinking water, particularly in studies where exposure to fluoride is the primary exposure of interest.     

Dental caries and developmental defects of enamel in relation to fluoride levels in drinking water in an arid area of Sri Lanka

The study was conducted to assess caries and developmental defects of enamel in relation to fluoride levels in drinking water and the association between caries experience and the severity of diffuse opacities in children living in Uda Walawe, an area with varying concentrations of fluoride in drinking water in Sri Lanka. A total of 518 14-year-old children who were lifelong residents in this area were examined for dental caries and developmental defects of enamel. But the present analysis is confined to 486 children from whom drinking water samples were collected. The prevalence of enamel defects and diffuse opacities ranged from 27 to 57% while the prevalence of caries ranged from 18 to 29% in the different fluoride exposure groups. The prevalence of enamel defects increased significantly with the increase in the fluoride level in drinking water. Both the caries prevalence and the mean caries experience were significantly higher in children with diffuse opacities than in those without in the group consuming water containing >0.70 mg/l of fluoride. The association between dental caries and the severity of diffuse opacities was also significant only in this group. Children with the mildest form of opacities (DDE scores 3 and 4) had the lowest DMFS (0.25 +/- 0.7), and the highest DMFS (1.1 +/- 1.7) was found in those with the most severe form of opacities (DDE score 6). In conclusion, the relationship that was observed in this study between fluoride levels in drinking water, diffuse opacities and caries suggests that the appropriate level of fluoride in drinking water for arid areas of Sri Lanka is around 0.3 mg/l. Also individuals with severe forms of enamel defects in high-fluoride areas are susceptible to dental caries.     

Prevalence and distribution of enamel defects and dental caries in a region with different concentrations of fluoride in drinking water in Sri Lanka

AIMS: To assess the prevalence and distribution of developmental defects of enamel and caries in 14-year-old children who had been lifetime residents in a region with different concentrations of fluoride in drinking water in Sri Lanka. DESIGN: A cross-sectional survey. SETTING: Uda Walawe--a rural area in southern Sri Lanka where fluoride concentration in ground water is reported to be within the range of 0.05-6.10 mg/l. METHOD: A total of 518 children from six representative schools from this area were examined for developmental defects of enamel and dental caries using the modified DDE index and WHO criteria. The present analysis is limited to 486 children from whom drinking water samples were collected. RESULTS: Based on the fluoride concentration of the drinking water source the children were categorised into four groups: <0.3, 0.31-0.49, 0.5-0.7 and >0.7 mg/l. The prevalence of enamel defects ranged from 29-57% whilst 27-55% of children were affected by diffuse opacities in the four groups. Of the ten teeth examined, between 1.6-3.6 teeth per child were affected by enamel defects. Maxillary first premolars were the most commonly affected by diffuse opacities followed by the maxillary canines. Caries prevalence varied between 18-25% whilst the mean DMFT and DMFS values ranged from 0.29-0.54 and 0.45-0.67 respectively. Occlusal surfaces were the most affected by caries. CONCLUSIONS: The wide differences observed in the prevalence and severity of enamel defects indicate that there are variations in individual response to high fluoride levels in drinking water. It also demonstrates the need to ascertain the factors that could contribute to the prevalence and severity of enamel defects other than high fluoride levels in drinking water.     

A map of natural fluoride in drinking water in Pakistan

AIM: The assessment of fluoride levels in domestic water supplies in Pakistan. METHOD: Water samples were collected from sources supplying the majority of the population: taps in places where piped water supply was available, tube-wells, boreholes and wells in rural areas, and stream water where appropriate. RESULTS: Analysis of 987 water supplies showed that they are predominantly low in fluoride content, 84% containing less than 0.7ppm of fluoride. CONCLUSION: For the majority of the population in Pakistan there is a clear indication for use of alternate sources of fluoride to ensure optimal intake necessary for the control of dental caries.