Ultrastructural study and comparative analysis of fluoride content of enameloid in sea-water and fresh-water sharks

The ultrastructural and chemical similarity of enameloid of Carcharhinus leucas (living in fresh water) and sea-water sharks (Prionace glauca, Dalatias lichas) was confirmed by scanning electron microscopy, high resolution electron microscopy, X-ray diffraction analysis, electron microprobe point analysis and direct potentiometric analysis in a iono-analyser with specific electrode. The mean thickness and width measurements of enameloid crystals performed in high resolution TEM were respectively, 47.1 nm (standard deviation 6.8) and 52.3 nm (standard deviation 7.3). The fluoride content of selachian enameloid was nearly as high as that of fluorapatite. However, the fluoride concentration was higher in non-erupted than in erupted teeth of fresh-water sharks, indicating that fluoride content in enameloid is programmed by the ameloblasts and not due to diffusion from the environment.     

Enameloid formation in two tetraodontiform fish species with high and low fluoride contents in enameloid

Forming teeth of parrotfish and pufferfish were viewed by transmission electron microscopy to correlate cytological features of the enameloid organ with the species' fluoride (F) content in mature enameloid. Secretory-stage inner dental epithelial cells (IDE) of parrotfish (high F) and pufferfish (low F) secreted procollagen granules into the enameloid collagen matrix. The odontoblasts of both species, less numerous than IDE cells, also contained procollagen granules at the enameloid matrix formation stage. After the full thickness of enameloid matrix collagen had been deposited, enameloid crystallites formed parallel to the long axis of the enameloid collagen fibres. Concurrently, the plasma membranes of the outer dental epithelial cells (ODE) became invaginated in both species, but to a much greater extent in parrotfish. Highly undulating parrotfish ODE cells surrounded numerous fenestrated capillaries. In contrast, pufferfish ODE cells remained straight with few adjacent capillaries. Extensive tight junctions formed between ODE and IDE cells of both species, sealing the extracellular space. With increased mineralization, enameloid collagen fibres were no longer discernible. A thin layer of amorphous material, which subsequently mineralized, was secreted on to the enameloid surface by IDE cells in both species. Pufferfish odontoblasts secreted a mineralizing amorphous layer on the pulpal aspect of the enameloid. The results suggest that at the mineralization stage, a triad of cytostructural features, highly invaginated ODE cells, highly vascularized ODE cells, and extensive tight junctions are strongly correlated with high fluoride content of mature enameloid mineral. Species without any one of these features have lower fluoride in the enameloid.     

Silver and fluoride content and short-term stability of 38% silver diamine fluoride

Background

As silver diamine fluoride (SDF) gains popularity for caries arrest, the authors aimed to investigate the content of fluoride and silver in 38% SDF produced for the US market and its short-term stability.

Relation between dental plaque fluoride content and caries

The purpose of this study was to investigate the effect of plaque fluoride content on dental caries in children aged 12 years, from the area with minimal (Valjevo) and optimal and/or higher fluoride concentrations (Vranjska Banja) in drinking water. The caries prevalence was determined by the standardized epidemiological method. The fluoride concentration in dental plaques was measured with the Ion-selective electrode. The fluoride content in the plaque of children from Valjevo (7.8 ppm) was significantly smaller than in children from Vranjska Banja (36.5 ppm). In 12-year old individuals with the lowest fluoride concentrations in the plaque the greatest values of the caries prevalence were found. The increase in plaque fluoride content provoked the decrease in caries prevalence. The lowest values of caries index were found in children with 21 to 30 ppF in dental plaque.     

氟化物对实验家兔牙胚及牙齿氟含量的影响

为进一步探明氟斑牙的发病机理，通过建立氟斑牙动物模型，在组织学及超微结构方面观察高氟对动物牙胚的影响。结果发现氟中毒时造釉器在形态、合成釉基质功能上的改变主要表现在造釉细胞出现空泡性变性，釉基质上出现蜂窝状改变。与此同时，造牙本质细胞以及牙本质也一并受到损伤，造牙本质细胞伯分化必须依靠内釉细胞的诱导，同样釉基质一定要在牙本质形成的基础上才能完成，两者互相依存的密切关系决定了一旦二者出现病理改变时，相互功能必然受到影响，氟中毒时即可在牙齿表面出现氟斑牙的体征     

The fluoride content of Melbourne's treated public water

One hundred and twenty-one water samples from one hundred different city and suburban outlets in the Melbourne metropolitan area were analysed quantitatively for fluoride concentration. Excluding ten samples, corresponding to a period when the relevant fluoridation equipment was functioning only intermittently, 89 per cent were within the range 0.7 to 1.2 ppm fluoride specified by the Victorian Health Commission, three per cent were greater and eight per cent were below this range.     

The fluoride content of human tooth enamel in relation to environmental exposure to fluoride

A bstract — Double-layer superimposed biopsies were used for sampling sound labial enamel of upper permanent central incisor teeth of 189 children (mean age 8.4 years, SD = 0.36), comprising five groups, representing life-long exposure to contrasting concentrations of F in the water (range ≤0.12 ppm to 2.8 ppm) and to supplements of 200 or 350 mg F/kg domestic salt. The mean F concentrations of enamel ranged through the groups from 924 ppm to 2401 ppm in the surface layer (average central depth = 0.49 um) and from 450 ppm to 1428 ppm in the subsurface layer (average central depth = 2.62 um). The differences between the mean F concentrations of the groups were significant in each instance and the values consistently reflected the extent of F exposure. It was concluded that the F content of enamel is a reliable indicator of environmental exposure to F for populations, but not for every individual.     

Iron in the enameloid of perciform fish.

It is known that a high concentration of iron is deposited in the enameloid of some teleostean fish. Previously, Suga et al. (1989) pointed out that the iron concentration in the enameloid is related to the phylogeny of fish rather than to the feeding habits, according to the results of quantitative iron analyses on the teeth of marine teleost fish of the Tetraodontiformes. In the present study, in order for the previous idea to be verified, quantitative iron analysis was made with an electron microprobe on the enameloid of fish belonging to the Perciformes, which is the largest group of teleostean fish in the world and consists of both marine and freshwater species. The enameloid of all the fish examined (57 species) contained high iron concentrations ranging from 0.2% to 10.2% at the surface or middle layer, whereas that of an advanced suborder, Tetraodontoidei, of the Tetraodontiformes was very low in iron, at a level which could not be discriminated from the background value of the emission intensity. The distribution pattern of iron in the enameloid was classified into at least two types, namely, type A, in which a high iron concentration was observed mainly in the surface layer, and type B, in which iron was deposited throughout the entire layer, although there were differences in concentration. There were some differences in the concentration and distribution of iron in the enameloid for the families; for example, those of the Scaridae had a type A distribution, with about 0.2% iron only at the surface layer, whereas those of the Cichlidae, Centrarchidae, and Acanthuridae, which showed a type B distribution, contained iron ranging from 2.9% to 10.5% at the surface or middle layer of enameloid. Such differences seemed to be associated with the difference in timing of the commencement of the iron deposition into the developing enameloid, which is probably related to the phylogeny of fish. There was no evidence to support the idea that the iron concentration in the enameloid is associated with the feeding habits of fish, as proposed by previous investigators.     

Total and soluble fluoride content in commercial dentifrices in Chile

Abstract Objective. Regardless of the total amount of fluoride (F) in a dentifrice, only the soluble fraction presents anti-caries activity and its concentration must be above 1000 ppm. No information regarding the quality of F in Chilean toothpastes is available. The aim of this study, therefore, was to determine the F concentration present in commercially-available toothpastes in Chile. Materials and methods: Eighteen toothpastes of five different brands were tested, each purchased from three different chain drugstores in Chile. For each toothpaste, total, total soluble and ionic F concentrations were assessed and expressed as ppm of F (μg F/g). Results. Among the dentifrices evaluated, 77.8% contained NaF (sodium fluoride), 16.7% MFP (monofluorphosphate) and 5.6% both types of F salts; 77.2% of the dentifrices showed similar total F content to that declared by the manufacturer in the labeling with only five with lower concentration than expected, beyond a 5% disagreement tolerance range. Total soluble F ranged from 958.8-1496.3 ppm (mean ± SD: 1270.5 ± 183.7). Five toothpastes showed lower total soluble F than total F. Only one toothpaste showed soluble salt levels below the recommended dose for this type of dentifrice. Conclusion: Most Chilean dentifrices evaluated contained soluble F within the range of 1000-1500 ppm and, therefore, may have anti-caries activity.     

The fluoride content of some teas available in Australia

A bstract — Analysis of brews of a selection of teas available in Australia using the fluoride ion-selective electrode gave after a five-minute infusion an average fluoride level of (1.34 ± 0.17 ppm) F. Brews of two brands of tea contained >2 ppm F; using fluoridated water a cup of tea made with one of these brands may contain 0.5 mg F. Its potential significance for young children on fluoride supplements should be recognized.