Bone and teeth

Adult bone contains about 45% water, but after its removal the composition can be expressed very approximately as 

The various minor components present in bone include Mg +, Na+, CO and various trace metals which are believed to be substituted in the hydroxyapatite lattice (Chapter 5.3). Some carbonate is on the bone surface, thus contributing to its high reactivity. About 0.05% pyrophosphate is usually detectable and proteoglycans, phosphatase enzymes and ATP are also present, as well as -0.1% phospholipids. Most bone samples have Ca/P 1.50, compared to pure hydroxyapatite in which Ca/P = 1.67. The lower ratio has been explained variously as arising from cation substitution, add phosphate or carbonate anion substitution (5.52) and (5.54) or inclusions of octacaldum phosphate (Chapter 5.2). 

Bone serves many purposes which include 

Sites (in bone marrow) for blood cell formation 

Bone structure is very complex, but it incorporates a material with a high tensile and compressive strength of the same order as that of mild steel. Unlike the latter, however, bone is much lighter, more elastic and has the capacity to regenerate itself by new growth. 

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M.p. 190-192 C. The enolic form of 3-oxo-L-gulofuranolactone. It can be prepared by synthesis from glucose, or extracted from plant sources such as rose hips, blackcurrants or citrus fruits. Easily oxidized. It is essential for the formation of collagen and intercellular material, bone and teeth, and for the healing of wounds. It is used in the treatment of scurvy. Man is one of the few mammals unable to manufacture ascorbic acid in his liver. Used as a photographic developing agent in alkaline solution. 

Phosphorus, like nitrogen, is an essential constituent of living matter where it may be partly in combination (as phosphate groups) with organic groups, for example in lecithin and egg yolk, or mainly in inorganic form, as calcium phosphate(V), in bones and teeth. 

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. 

Phosphorus. Eighty-five percent of the phosphoms, the second most abundant element in the human body, is located in bones and teeth (24,35). Whereas there is constant exchange of calcium and phosphoms between bones and blood, there is very Httle turnover in teeth (25). The Ca P ratio in bones is constant at about 2 1. Every tissue and cell contains phosphoms, generally as a salt or ester of mono-, di-, or tribasic phosphoric acid, as phosphoHpids, or as phosphorylated sugars (24). Phosphoms is involved in a large number and wide variety of metaboHc functions. Examples are carbohydrate metaboHsm (36,37), adenosine triphosphate (ATP) from fatty acid metaboHsm (38), and oxidative phosphorylation (36,39). Common food sources rich in phosphoms are Hsted in Table 5 (see also Phosphorus compounds). 

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). 

Calcium Phosphates. The alkaline-earth phosphates are generally much less soluble than those of the alkaH metals. Calcium phosphates include the most abundant natural form of phosphoms, ie, apatites, Ca2Q(P0 3X2, where X = OH, F, Cl, etc. Apatite ores are the predominant basic raw material for the production of phosphoms and its derivatives. Calcium phosphates are the main component of bones and teeth. After sodium phosphates, the calcium salts are the next largest volume technical- and food-grade phosphates. Many commercial appHcations of the calcium phosphates depend on thek low solubiHties. 

Four of the main-group cations are essential in human nutrition (Table A). Of these, the most important is Ca2+. About 90% of the calcium in the body is found in bones and teeth, largely in the form of hydroxyapatite, CatOH)2 - SCa PO. Calcium ions in bones and teeth exchange readily with those in the blood about 0.6 g of Ca2+ enters and leaves your bones every day. In a normal adult this exchange is in balance, but in elderly people, particularly women, there is sometimes a net loss of bone calcium, leading to the disease known as osteoporosis. 

Up to this point, we have focused on aqueous equilibria involving proton transfer. Now we apply the same principles to the equilibrium that exists between a solid salt and its dissolved ions in a saturated solution. We can use the equilibrium constant for the dissolution of a substance to predict the solubility of a salt and to control precipitate formation. These methods are used in the laboratory to separate and analyze mixtures of salts. They also have important practical applications in municipal wastewater treatment, the extraction of minerals from seawater, the formation and loss of bones and teeth, and the global carbon cycle. 

The preservation of biogenic isotopic signals ( C, N) in fossil bones and teeth is critical in order to interpret paleodiets. Some patterns of variation of these biogenic isotopic signals are characteristic of modern mammals, and their recognition in fossil samples provides a clue for the preservation of biogenic paleodietaiy signals. 

In this paper, I attempt to refine the predictable isotopic differences between collagen and carbonate that can be found in modem faunas from temperate and cold areas, using samples from Europe, Siberia and northwestern North America. Some of the results presented here have been published previously (Bocherens et a/. 1991a, 1991b, 1994, 1995a, 1995b, 1 6 Bocherens and Mariotti 1992 Fizet et al. 1995) but additional new data are reviewed as well in order to present a new synthesis. This should provide a framework that can be used to assess the quality of preservation of the isotopic signatures in Pleistocene mammal bones and teeth from these areas. 

The approach proposed to check the preservation of isotopic signals in fossil vertebrate bones and teeth is appropriate not only for Pleistocene cold and temperate areas, but also during geological periods before the... 

The properties described above have important consequences for the way in which these skeletal tissues are subsequently preserved, and hence their usefulness or otherwise as recorders of dietary signals. Several points from the discussion above are relevant here. It is useful to ask what are the most important mechanisms or routes for change in buried bones and teeth One could divide these processes into those with simple addition of new non-apatitic material (various minerals such as pyrites, silicates and simple carbonates) in pores and spaces (Hassan and Ortner 1977), and those related to change within the apatite crystals, usually in the form of recrystallization and crystal growth. The first kind of process has severe implications for alteration of bone and dentine, partly because they are porous materials with high surface area initially and because the approximately 20-30% by volume occupied by collagen is subsequently lost by hydrolysis and/or consumption by bacteria and the void filled by new minerals. Enamel is much denser and contains no pores or Haversian canals and there is very, little organic material to lose and replace with extraneous material. Cracks are the only interstices available for deposition of material. 

Isotopic Integrity of FossU Bones and Teeth in South Africa... 

Advanced Seminar volume reflects the greatly expanded awareness of the importance of diet reconstruction for understanding past human health and behavior. It also reflects the growing number of applications of stable isotope and trace element analyses of bones and teeth. 

Bones and teeth, however, are primary archaeological materials and are common to many archaeological sites. Bones bearing cut marks from stone tools are a clear proxy for human occupation of a site, and in the study of human evolution, hominid remains provide the primary archive material. Hence, many attempts have been made to directly date bones and teeth using the U-series method. Unlike calcite, however, bones and teeth are open systems. Living bone, for example, contains a few parts per billion (ppb) of Uranium, but archaeological bone may contain 1-100 parts per million (ppm) of Uranium, taken up from the burial environment. Implicit in the calculation of a date from °Th/U or Pa/ U is a model for this Uranium uptake, and the reliability of a U-series date is dependent on the validity of this uptake model. 

An alternative to the early uptake assumption, linear uptake, assumes that bones and teeth continue to take up Uranium at a constant rate (Ikeya 1982 Bischoff et al. 1995), giving a U-series date something over twice that calculated using the EU assumption. Although more common for teeth than for bone, both EU and LU dates are often quoted for the same sample, with the implication that the true age of the sample probably lies somewhere in between. 

EU and LU are not the only uptake models that have been proposed. More mathematically sophisticated models have been developed (e.g., Szabo and Rosholt 1969 Hille 1979 Chen and Yuan 1988), in some cases using both the U and U decay chains (see Ivanovich 1982 Millard and Pike 1999 for summaries). While there have been some apparently successful applications of these models, none have been found to be universally applicable, and the search for a reliable method of U-series dating of bones and teeth continues. In the last decade or so, two important new approaches to the modeling of U uptake in bones and in teeth have been developed. These are discussed in detail below. 

There are a few developments on the horizon that will increase our ability to date bones and teeth reliability. Both y- and a-spectrometric methods can measure Pa/ U and °Th/U and concordance between dates calculated using the two can provide a measure of reliability. However, the discordance between the two is not very sensitive to different uptake regimes, and it is difficult to resolve, for example, bones that have undergone EU from those that have undergone LU with the analytical errors commonly encountered in measurements by y- and a-spectrometry. On the other hand, it has been shown recently that TIMS can measure both isotopic ratios with a precision usually better than 1% (Edwards et al. 1997). TIMS measurements of Pa/ U and °Th/U have yet to be routinely applied to dating fossil remains, but in the future, concordance between the two decay series will provide further evidence of the validity of a particular uptake model to a particular sample. 

The measurement of U-series isotopes using laser ablation will potentially reduce the damage inflicted on specimens to almost zero. The increased spatial resolution will allow profiles, as required by the D-A model, to be measured quickly and simply in the smallest of bone samples and across thin layers of enamel (e g.. Fig. 11). Early studies (e.g., Belshaw et al. 2002 Eggins et al. 2002) have demonstrated the potential of the technique to provide U-series profiles for bones and teeth, but consistent and fully quantitative results are still a little way off. 

In 1988, Chen and Yuan published U-series dates on bones and teeth for more than 20 Chinese sites, providing the first extensive Palaeolithic chronology for China. They used a-spectrometric measurements of °Th/U, and and used concordance... 

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