Bones, fluorine

Groff, D. W., Gas Chromatography Methods for Bone Fluorine and Nitro-... 

The F uptake of flint takes a much longer time than that for bone. Fluorine diffusion into the depth of flint material is controlled by defect clusters. The diffusion coefficient determined by implanting a model compound (amorphous silica bombarded with heavy ions and hydrated at 100°C) is 9.10—21 cm2/s at room temperature. The corresponding penetration depth of F under ambient conditions in a 1000-year-old artefact can be estimated via x — (Dt)1/2 = 0.17. im [50], Thus, F accumulates only in the first micrometre of the surface. The surface of ancient flint artefacts can be altered by dissolution. The occurrence of this phenomenon is especially important in basic media. However, in some cases, the thickness of the dissolved layer can be neglected compared to the F penetration depth at low temperatures. Therefore, Walter et al. [35] proposed relative dating of chipped flint by measuring the full width at half maximum (FWHM) of F diffusion profiles in theses cases. 

Fluorine occurs widely in nature as insoluble fluorides. Calcium fluoride occurs as jluospar or fluorite, for example in Derbyshire where it is coloured blue and called bluejohn . Other important minerals are cryolite NajAlFg (p. 141) and Jluorapatite CaFjSCaj (P04)2. Bones and teeth contain fluorides and some natural water contains traces. 

Mineral Feed. Mineral feed supplements for domestic animals and fowl usually contain a pure form of pulverized limestone. In fact, some state laws require the supplement to be at least 35% available calcium. Other sources of calcium are bone meal and dicalcium phosphate. Use as mineral feed has been a steadily growing market for limestone. The material is ground to 90% minus 0.15 mm (100 mesh) or 80% minus 0.9074 mm (200 mesh), is low in silica, and has strict tolerances on arsenic and fluorine (see Feeds and feed additives). 

Fluorine. Fluoride is present in the bones and teeth in very small quantities. Human ingestion is from 0.7—3.4 mg/d from food and water. Evidence for the essentiaUty of fluorine was obtained by maintaining rats on a duoride-free diet, resulting in decreased growth rate, decreased fertihty, and anemia. These impairments were remedied by supplementing the diets with duoride (81). Similar effects have been reported in goats (82). 

Among the D vitamins, multiple fluonne substituents in the side chain of 25-hydroxy-D3 (4) markedly increases bone resorptive activity [21, 22] The enhanced activity may be due to blockade of degradation caused by the presence of fluorine in specific positions. 

Fluorine as the anion F(I) is found in bone and tooth. Enhanced levels are toxic. 

Bones and teeth consist of hydroxyl-apatite (Ca phosphate). Tiny amounts of fluorine improves their resistance dramatically. Fluorine compounds in toothpaste prevent cavities. 

The bones and teeth of humans and other vertebrate animals, for example, consist mainly of a composite material made up of an organic substance, collagen, and a biomineral, calcium carbonate phosphate (see Textboxes 32 and 61). The latter, which makes up about two-thirds of the total dry weight of bone, is composed of calcium phosphate containing between 4-6% calcite (composed of calcium carbonate) as well as small amounts of sodium, magnesium, fluorine, and other trace elements. The formula Ca HPChXPChMCChXOH) approximately represents its composition its crystal structure is akin to that... 

Fluorine Dating. Probably the oldest scientific dating technique is fluorine dating, which, although seldom used today, is discussed here because of its historic interest. Fluorine dating of bone centers on an irreversible process whereby the inorganic component of buried bone is slowly and gradually, transformed into a more stable compound (see Textbox 67) (Camot 1893 Middleton 1845). 

Once fluoride ions react with bone, they are not easily dissolved out or exchanged by other elements. If bone is buried for long periods of time, the relative amount of fluorine in the bone gradually increases as a function of time the "fluoridation" process continues until the maximum amount of fluorine (necessary to convert all the hydroxyapatite to fluorapatite) is reached. The total concentration of fluor in carbonated fluorapatite can reach levels as high as above 3%. There is ample room, therefore, for an increase in the relative amount of fluorine in buried bone. Determining the relative amount of fluorine in buried bone may thus serve as a tool for dating bone. 

Fluoride ions may be relatively abundant in groundwater at one location and practically absent in that at another site hence the rate of fluoridation of the bone (the rate of increase in the relative amount of fluorine in the bone) varies from site to site. For instance, bones buried for a short time at a site in which the groundwater is rich in fluoride may acquire much more fluorine than bones buried for a very long time at a place where there is little fluoride in the groundwater. Therefore, fluorine analysis does not provide a tool for estimating the absolute age of buried bone, but only for dating bones at the same site, comparative to each other. The relative amount of fluoride in buried bone at a particular site thus provides a clue as to the length of time the bone has been buried. 

In the first half of the twentieth century much bone was dated using this method, and dates derived with it greatly contributed, for example, to unfolding the nature of the Piltdown bones (see Chapter 18). Experience has shown that bones buried in sand or gravel are suitable for dating with fluorine, while those buried in volcanic soils rarely yield useful dates dates derived from fluorine analysis results should, therefore, be used with caution (Schurr 1989 Oakley and Hoskins 1950). 

Oakley, K.P. (1963). Fluorine, uranium and nitrogen dating of bones. In The Scientist and Archaeology, ed. Pyddoke, E., Roy Publishers, New York, pp. 111-119. 

Each step of the synthesis usually needs optimisation of reaction conditions (time, temperature, solvents, concentrations). Different techniques of reaction activation can also be used. Microwave heating has been shown to give faster, cleaner and more selective reactions [22,23] than conventional heating. Ultrasound, although promising [24], has not known the same development. Finally, catalysed reactions involving palladium complexes have been developed in car-bone- 11 chemistry [25 ] over the last few years. They have not been widely studied in fluorine-18 chemistry. 

The essential microelements are only required in trace amounts (see also p.2). This group includes iron (Fe), zinc (Zn), manganese (Mn), copper (Cu), cobalt (Co), chromium (Cr), selenium (Se), and molybdenum (Mo). Fluorine (F) is not essential for life, but does promote healthy bones and teeth. It is still a matter of controversy whether vanadium, nickel, tin, boron, and silicon also belong to the essential trace elements. 

Fluoride is the salt, such as sodium fluoride, of the element fluorine. It is readily absorbed by the intestine and is incorporated into bone or tooth enamel. When incorporated into teeth, fluoride strengthens the outer layers of enamel, thus reducing dental caries. It is generally accepted that addition of fluoride to the drinking water (approximately 1 ppm) is beneficial for the reduction in childhood dental caries. 

M. Welch, J.F. Litton, P.P. Caspar, Production of F for bone scanning from the 2°Ne(d,alpha) F reaction via fluorine-18 labeled nitrosyl fluoride. A selective fluorinating agent, J. Nucl. Med. 12 (1971) 405. 

M. Blau, W. Nagler, M.A. Bender, Fluorine-18 A new isotope for bone scanning,... 

Fluorine is an essential element involved in several enzymatic reactions in various organs, it is present as a trace element in bone mineral, dentine and tooth enamel and is considered as one of the most efficient elements for the prophylaxis and treatment of dental caries. In addition to their direct effect on cell biology, fluoride ions can also modify the physico-chemical properties of materials (solubility, structure and microstructure, surface properties), resulting in indirect biological effects. The biological and physico-chemical roles of fluoride ions are the main reasons for their incorporation in biomaterials, with a pre-eminence for the biological role and often both in conjunction. This chapter focuses on fluoridated bioceramics and related materials, including cements. The specific role of fluorinated polymers and molecules will not be reviewed here. 

In contrast to skeletal bone and dentine, which accumulate fluoride throughout life and whose levels are proportional to the absorbed dose of fluoride, fluoride in enamel is not an appropriate biomarker, because most of its fluorine was taken up during tooth formation [2]. The post-eruptive fluoride uptake of enamel is expressed only in the outer layer and depends on the concentration of fluoride in the oral cavity [6]. 

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