Virtual histology of archaeological human deciduous prenatal enamel through synchrotron X-ray computed microtomography images

Alessia Nava,Diego Dreossi,Alfredo Coppa,Lucia Mancini,Luca Bondioli,Luciano Fattore,Gina Mcfarlane,Emanuela Cristiani,Patrick Mahoney

doi:10.1107/s160057752101208x

Abstract

Virtual histology is increasingly utilized to reconstruct the cell mechanisms underlying dental morphology for fragile fossils when physical thin sections are not permitted. Yet, the comparability of data derived from virtual and physical thin sections is rarely tested. Here, the results from archaeological human deciduous incisor physical sections are compared with virtual ones obtained by phase-contrast synchrotron radiation computed microtomography (SRµCT) of intact specimens using a multi-scale approach. Moreover, virtual prenatal daily enamel secretion rates are compared with those calculated from physical thin sections of the same tooth class from the same archaeological skeletal series. Results showed overall good visibility of the enamel microstructures in the virtual sections which are comparable to that of physical ones. The highest spatial resolution SRµCT setting (effective pixel size = 0.9 µm) produced daily secretion rates that matched those calculated from physical sections. Rates obtained using the lowest spatial resolution setup (effective pixel size = 2.0 µm) were higher than those obtained from physical sections. The results demonstrate that virtual histology can be applied to the investigated samples to obtain reliable and quantitative measurements of prenatal daily enamel secretion rates.

Highlights

Human teeth hold a wealth of information about an individual’s growth, development, diet, chemistry and non-specific illnesses (Hillson, 2014; Guatelli-Steinberg, 2016)
Histologists routinely draw on the cell mechanisms underlying tooth morphology to reconstruct enamel growth in order to contribute insights into the evolution of hominins, their phylogenies and life history (Dean, 2016)
DSRs calculated from physical thin sections have been used to reconstruct the speed at which enamel cells form a human tooth crown in archaeological and contemporary series (Birch & Dean, 2014; Mahoney, 2012; Nava, Bondioli et al, 2017), and have provided insight into the evolution of hominin dental development and life history through the analysis of fossil dental specimens (Nava et al, 2020; Macchiarelli et al, 2006; Dean et al, 1993, 2001, 2010, 2016; Smith et al, 2018; Austin et al, 2013; Rosas et al, 2017; Lacruz et al, 2008; Dean & Smith, 2009; Joannes-Boyau et al, 2019)

Summary

Introduction

Human teeth hold a wealth of information about an individual’s growth, development, diet, chemistry and non-specific illnesses (Hillson, 2014; Guatelli-Steinberg, 2016). Prenatal enamel usually shows less distinct microstructures with respect to the postnatal one, possibly as a consequence of the protected and buffered intrauterine environment in which the tissue develops (Nava, Bondioli et al, 2017; Noren, 1983; Rythen et al, 2008) For this reason, data on prenatal enamel DSRs are scarce and mostly available from modern reference collections of exfoliated/extracted deciduous teeth (Mahoney, 2012, 2015; Birch & Dean, 2014; Nava, Bondioli et al, 2017; Dean et al, 2020)

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