Strontium tooth enamel

Evans, J.A., Chenery, C.A. and Fitzpatrick, A.P. (2006). Bronze Age childhood migration of individuals near Stonhenge, revealed by strontium and oxygen isotope tooth enamel analysis. Archaeometry 48 309-321. 

Because of its mineral composition, the large size of its phosphate crystals and the small amount of pore space, mature tooth enamel is rarely affected by diagenetic contamination (40-42). This has been supported by experimental data that show that enamel reliably retains biogenic strontium isotope signatures (30, 43-48). 

While the strontium isotope signatures in archaeological human tooth enamel and bone from tombs at Conchopata are very similar, the five trophy heads have more heterogeneous strontium isotope signatures, as shown in Table I and Figure 1. Three trophy heads exhibit enamel and bone strontium isotope... 

Strontium isotope signatures in tooth enamel and bone from five adults and one infant buried in two tombs at Conchopata are very similar. This implies that these individuals consumed food from the same geologic zone, or from geologic zones with similar strontium isotope signatures. Since the strontium isotope ratios in these individuals matched the expected Ayacucho Basin strontium isotope signature, it is most likely that these individuals lived in or near Conchopata for the first and last years of life. 

In the mouth, mineralization is controlled partly by proteins such as statherin from the salivary gland, which maintains a supersaturation of calcium and phosphate in the mouth. The basic mineral in tooth enamel is hydroxyapatite, in which it is possible to substitute Sr(II) for Ca(II), and F for OH isomorphously, hence the use of strontium and fluoride salts in toothpastes, said to confer extra strength to the enamel and antibacterial properties. 

The analysis proceeds through the sampling of tooth enamel to obtain the isotopic signal of the place of birth. The local isotopic signal can be determined in several ways in human bone from the individuals whose teeth are analyzed, from the bones of humans or archaeological fauna at the site, or from modem fauna in the vicinity. The local geological isotope signals of strontium have been constant over the last several 1,000 years. These isotope ratios have been reported for the rocks. 

The place of origin of prehistoric people can also be determined. The isotopic proveniencing of human remains, using ratios of strontium isotopes, has been employed in archaeology for approximately 20 years. Strontium isotope analyses have been used successfully in a number of studies. The basic principle involves comparison of isotope ratios in human tooth enamel with local levels in bone or other materials. Because isotopic ratios vary geographically, values in human teeth (marking place of birth) that differ from the local ratio (place of death) indicate migration. This method of analysis is described in more detail in Chap. 8, Provenience and Provenance. 

Mass spectrometers usually measure two or more isotopes at one time and calculate their ratio. Standards are measured at the same time in order to confirm the precision of the instrument and allow corrections to be made if needed. The results of the analysis provide the ratio measurements along with several other kinds of information. Table 4.2 shows some typical results from a mass spectrometer, in this case a Ust of calculated strontium isotope ratios on human tooth enamel measured on TIMS. The first column in the table gives the sequential lab number for each individual sample. The site is the place from where the sample comes. The corrected Sr/ Sr is the isotope ratio for strontium in the sample, corrected on the... 

Table 4.2 Typical data from mass spectrometer measurement of strontium isotope ratios in human tooth enamel...

In order to examine the question of his origin in more detail, Muller and colleagues undertook an isotopic study of the Iceman s tooth enamel, bone, and stomach contents to determine his birthplace, habitat, and range. Their study focused on strontium, lead, and oxygen isotopes to determine his movements. 

Hoppe, K.A., P.L.Koch, and T.T. Furutani. 2003. Assessing the preservation of biogenic strontium in fossil bones and tooth enamel. International Journal of Osteoarchaeology 13 20-28. 

This article details how scientists used strontium isotope dating of tooth enamel to conclude that some Neanderthals traveled widely, which had been debated by other anthropologists. 

Helsby, C.A. (1974). Determination of strontium in human tooth enamel by atomic absorption spectrometry. Anal. Chim. Acta 69, 259-265 Helsby, C.A. (1976). Determination of mercury in finger nails and body hair. Anal. Chim. Acta 82, 427-430... 

Standard addition graph. Tooth enamel consists mainly of the mineral calcium hydroxyapatite, Caio(P04)6(OH)2. Trace elements in teeth of archeological specimens provide anthropologists with clues about diet and diseases of ancient people. Students at Hamline University measured the trace element strontium in enamel from extracted wisdom teeth by atomic absorption spectroscopy. Solutions were prepared with a constant total volume of 10.0 mL containing 0.750 mg dissolved tooth enamel plus variable concentrations of added Sr. 

Copeland, S.R., Sponheimer, M., Le Roux, P.X, Grimes, V, Lee-Thorp, X A., De Ruiter, D.X, Richards, M.P. (2008) Strontium isotope ratios (87Sr/86Sr) of tooth enamel a comparison of solution and laser ablation multicollector inductively coupled plasma mass spectrometry methods. Rapid Communications in Mass Spectrometry, 22(20), 3187-3194. 

Horstwood et al. [Ill] reported results of experiments to determine strontium isotopes in archaeological tooth enamel using LA-MC-ICP-MS and pointed out the need for careful attention to interferences from the calcium phosphate matrix. In another study, Richards et al. [112] detected evidence of Neanderthal mobility via LA-MC-ICP-MS characterization of strontium isotope ratios in tooth enamel. Enamel values from a Neanderthal molar recovered from a coastal limestone environment in Greece were found to be consistent with... 

Montgomery, (. (2010) Passports from the past investigating human dispersals using strontium isotope analysis of tooth enamel. Ann. Human Biol, 37 (3), 325-346. 

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