Method of micro-sampling human dentine collagen for stable isotope analysis

Abstract

Rationale: Sampling of dentine for stable carbon (δ¹³ C) and nitrogen (δ¹⁵ N) isotope ratios in the direction of tooth growth allows the study of temporal changes to the diet and physiological stress of an individual during tooth formation. Current methods of sampling permanent teeth using 1 mm increments provide temporal resolution of 6-9 months at best depending on the tooth chosen. Although this gives sufficient sample sizes for reliable analysis by mass spectrometry, sectioning the dentine across the incremental structures results in a rolling average of the isotope ratios. A novel method of incremental dentine collagen sampling has been developed to decrease the collagen increment size to 0.35 mm along the incremental structures, thus reducing averaging and improving the temporal resolution of short-term changes within the δ¹³ C and δ¹⁵ N values.

Methods: This study presents data for a MicroMill-assisted sampling method that allows for sampling at 0.35 mm width × 1 mm depth increments following the incremental growth pattern of dentine. A NewWave MicroMill was used to sample the demineralised dentine section of modern donated human third molars from Sudan and compared to data from the same teeth using the 1 mm incremental sectioning method 2 established by Beaumont et al. RESULTS: The δ¹³ C and δ¹⁵ N isotopic data showed an increased temporal resolution, with each increment providing data for 2-4 months of dentine formation.

Conclusions: The data show the potential of this method for studying dietary reconstruction, nutritional stress, and physiological change with greater temporal resolution potentially to seasonal level and with less attenuation of the δ¹³ C and δ¹⁵ N values than was previously possible from human dentine.