Micro‐punches versus micro‐slices for serial sampling of human dentine: Striking a balance between improved temporal resolution and measuring additional isotope systems

Abstract

Rationale The last decade has seen a dramatic increase in the application of serial sampling of human dentine in archaeology. Rapid development in the field has provided many improvements in the methodology, in terms of both time resolution as well as the ability to integrate more isotope systems in the analysis. This study provides a comparison of two common sampling approaches, allowing researchers to select the most suitable approach for addressing specific research questions. Methods Two common approaches for sequential sampling of human dentine (micro‐punches and micro‐slices) are compared in terms of viability and efficacy. Using archaeological deciduous second molars and permanent first molars, this study demonstrates how the two approaches capture aspects of the weaning process in different ways. In addition, different aspects related to the extraction protocols, such as the thickness of the central slide and the solubilisation step, are also evaluated. Results While both approaches show similar intra‐tooth isotopic patterns, the micro‐punches approach is preferable for research that requires a very fine temporal resolution, while the micro‐slices approach is best for research where δ 34 S values are needed, or when the samples are poorly preserved. In addition, the solubilisation step has a large effect on collagen yield, and, to a lesser extent, on isotopic compositions. Therefore, it is important to ensure that only samples that have undergone the same pre‐treatment protocol are directly compared. Conclusions We present the pros and cons of the two micro‐sampling approaches and offer possible mitigation strategies to address some of the most important issues related to each approach.

Bone of contention: Intra-element variability in remodelling of human femora based on histomorphometric and isotope analyses

“…However, reconstructing life histories has always been a challenge. Incremental sampling of dentine has allowed health and diet to be tracked through early life [ 88 , 89 ], with recent improved approaches to micro-sampling providing greater temporal resolution [ 90 , 91 ]. For later life, resolution is much more challenging, with comparisons of bulk collagen analyses of elements considered to have radically different remodelling rates often employed [often femur versus rib, e.g., 5, 76].…”

Diets, stress, and disease in the Etruscan society: Isotope analysis and infantile skeletal palaeopathology from Pontecagnano (Campania, southern Italy, 730–580 BCE)

“…These limitations stem from the natural growth pattern of teeth, characterized by a dome-shaped anatomical structure, which contributes to the complexity of conical dentine incremental growth, involving intricate factors such as growth rates and direction [220,221]. Alternative anatomically sensitive methods have been recently published with the aim at enhancing temporal resolution [222][223][224][225][226]. These methods, based on micro-punches dentine sampling, along with an age-alignment scheme predicated on average growth rates for different anatomical dentine zones, revealed that horizontal increments capture multiple dentine layers, with time average for each increment being higher compared to, leading to potential errors in estimating weaning ages.…”

Spatial analysis of the ancient proteome of archeological teeth using mass spectrometry imaging

“…36 There have been developments to improve the temporal resolution of microsamples, such as comparing small punches on the outer layer of dentine versus microslices of dentine. 38 Despite the value of this approach, it remains unclear how the potential spatial distribution of protein in teeth would affect sequential stable isotope analysis and if microsamples would contain a consistently representative proteome. Additionally, not all tissues are suitable for microsampling due to the size and composition of the sample, for example primarily due to its small size it is not current practice to perform sequential proteomic analysis of dental calculus.…”

“…However, the standard sampling method of cutting transverse sections from crown to root for sequential sampling does not directly follow the direction of growth and the resulting microsamples will consist of multiple growth increments, which reduce the temporal resolution of the sample 36 . There have been developments to improve the temporal resolution of microsamples, such as comparing small punches on the outer layer of dentine versus microslices of dentine 38 . Despite the value of this approach, it remains unclear how the potential spatial distribution of protein in teeth would affect sequential stable isotope analysis and if microsamples would contain a consistently representative proteome.…”