Investigation of ancient teeth using Raman spectroscopy and synchrotron radiation Fourier-transform infrared (SR-µFTIR): mapping and novel method of dating

Abstract

Raman spectroscopy and Synchrotron Radiation Fourier-Transform Infrared (SR-µFTIR): Mapping have been increasingly applied as a good tool in archaeological research. The chronology of ancient samples is an essential step in archeology, and carbon dating using atomic force microscopy is the main technique. Nevertheless, the availability of instrumentation, sample preparation, and cost are barriers that limit the wide usage. The study was aimed to develop a method utilizing Raman spectroscopy and Synchrotron Radiation Fourier-Transform Infrared (SR-µFTIR) Mapping to identify ancient teeth and sort them chronologically. Furthermore, Raman spectroscopy was used to evaluate the preservation of collagen and the crystallinity of Apatite in ancient teeth. The age of fourteen ancient teeth descent from different individuals (8 from Roman period-1500BC and 4 from Byzantine period-641AD) was confirmed using carbon dating via atomic force spectrometry. The ancient teeth along with modern teeth were investigated using microRaman spectroscopy (oscillation and mapping). The typical Raman spectrum of the dentin for ancient samples was recorded and then compared to the modern teeth. The ratio of the phosphate 𝑃𝑂4 3− the band at 963 cm-1 to organic CH band at 2950 cm-1 was calculated for all samples. Raman mapping was recorded for cross-section teeth samples. The AMS data showed that the ages of the samples were 3400-3800 and 1240-1350 years for Roman and Byzantine teeth, respectively. The phosphate ν1 𝑃𝑂4 3− vibration band at (963 cm-1 ) in ancient teeth was shifted 3 cm-1 toward higher wavenumber compared to modern dentin samples (960 cm-1 ). The intensity and broadening of the carbonate apatite band at 1050 cm-1 were directly proportional to the aging. The intensity of the organic part triplet peaks at (2882, 2950, 2962) decreased with age. The ratio of phosphate band to organic C-H band was 0.346-0.388 and 0.122-0.136 for Roman and Byzantine teeth, respectively. According to the Raman mapping, the organic material in ancient teeth degraded and diffused, while in modern tooth it concentrated. Raman spectroscopy (intensity at 963 cm1 to 2950 cm-1) can be used as a qualitative tool to chronologically sort the archeological teeth samples before the use of carbon dating. The preliminary dating by Raman spectroscopy can recognize if a tooth or bone sample is archaeological or not. This step may save time and money and shall be assigned as a pre-request for AMS analysis. Raman mapping may help to explore archeological samples for best-preserved organic matter, hence identify the best candidates for further analysis (DNA extraction). In the future, the proposed method can be expanded and applied in specific cases in ancient osteology.