New quantitative methods for the analysis of linear enamel hypoplasia (LEH) in bioarchaeology

Abstract

Linear enamel hypoplasia (LEH) is the term used to describe dental developmental defects that occur following childhood exposure to systemic physiological stress. The identification and analysis of LEH is standard practice in bioarchaeological studies, as the occurrence of these defects can be utilised to measure the relative level of health of past populations, identify adaptive life strategies, reconstruct childhood patterns of illness, and produce life histories of individuals. Despite being studied in numerous populations over the last 300 years, the standards used to assess these hypoplastic defects still vary considerably in terms of the methods employed, the resolution at which they are examined, and the reporting of results. Technological advances over the last couple of decades has given rise to the development of more refined and objective methods that allow for a quantitative analysis of these stress events. However, quite often, archaeological samples are unsuitable to be examined using these methods due to significant levels of labial/buccal surface wear.

This thesis aims to improve and add to the bioarchaeological toolkit used for the identification and analysis of LEH while demonstrating the benefits of extracting additional quantitative data to investigate multiple aspects of LEH. This thesis addresses the limitations and issues of existing approaches through the development of several new methods, and a new comprehensive approach that relies solely on objective high-resolution methods for the analysis of LEH. Moreover, it makes the case for the standardisation of reporting protocols to ensure the comparability of results between published studies. Additionally, this thesis aims to develop a software program that incorporates the newly developed objective approach, which automates the analytical process of these stress events, while ensuring that these methods are useful, usable, and accessible to any researcher wanting to undertake the analysis of LEH in archaeological samples. Finally, these methods and tools will be used to assess LEH in a large dental sample from a late Iron Age archaeological site in Southeast Asia. This will constitute the first-ever comprehensive microscopic examination of LEH for the region to rely on a complete set of objective methods for the identification, and assessment of ten different parameters, including frequency, prevalence, chronology, duration, and periodicity of defects. In doing so, this thesis will provide new insights into health trends in the region following the intensification of agriculture and period of early state development. Show more