Using Dentine as well as Enamel in ESR Dating

Both tooth enamel and dentine contain hydroxyapatite, the mineral which provides the strong electron spin resonance (ESR) signal used in enamel dating. The radiation-induced signals in dentine are considerably weaker than those in enamel and also appear less stable. Clearly, enamel is preferred for ESR dating. Some teeth, however, do not possess enough enamel to date. Even if some enamel is present, dating the dentine yields additional age estimates for the tooth. While the dentine ESR signal is weak, its properties (e.g., dose response and response to power saturation) are the same as for enamel. Measurement can be improved by signal averaging. For the samples in this study, no significant signals from organic contamination were found, although the presence of organic material seriously complicated isothermal measurements of the signal lifetime. Evaluating the internal dose rate has been problematic, because U mobility affects dentine to a much greater extent than enamel. Moreover, multiple uptake events are more common in dentine. The best results were obtained with teeth aged between 40 and 400 ka. Dentine will not replace enamel as a dosimeter. Every new material that can be used, however, even in limited cases, widens the range of sites and samples that can be dated by ESR.