Seasonal variations directly impacted the social and economic activities of past human populations. Cementochronology is one of the methods available to address seasonality questions. It relies on the cyclic deposition rate of dental cementum observed microscopically on petrographic thin‐sections of animal teeth from archaeological contexts. However, no protocol exists to select a Region of Interest (ROI) or to identify the last cementum increment. This chapter proposes consensual biological and optical criteria for the selection of optimal ROIs and their analysis. Interobserver tests were performed to assess the criteria, as well as age and season of death, on thirty thin‐sections of modern documented reindeer teeth. Results demonstrate the accuracy, and replicability of this protocol, and emphasize the influence of training and experience for the proper implementation of cementochronology.

For human dental cementum research, sample preparation protocol is now widely tested, validated, and standardized, thanks to the low variability in teeth morphology. For non-human mammals, posterior teeth are typically preferred. However, the taxa diversity implies a significant variation in morphology or specific characteristics for certain species (equids, suids), leading to multiple unstandardized protocols. This work aims to improve protocols for producing a thin section by optimizing the parameters, minimizing the risk of errors, and offering an easily reproducible quality of thin-sections. The result of 26 experiments and 124 analyses during stages of consolidation (embedding), cutting, gluing, and finishing (grinding) allowed the co-authors' combined experience from multiple laboratories to propose standardized humans and ungulates (large teeth) protocols for the systematic analysis of dental research collections.

Acellular cementum anchors the root to the alveolar socket via the periodontal ligament and grows in layers continuously throughout life, unlike enamel and dentin. Increments are deposited in a biannual light-dark pattern correlated to age and season at death in transmitted light microscopy. This study investigates the still debated structure of individual acellular increments using x-ray fluorescence and x-ray diffraction mapping with synchrotron radiation microbeams on reindeer, red deer, cattle, and human samples. Results show that Ca or Zn x-ray fluorescent intensities and cAp diffracted intensity reveal cementum band structure. Average crystallographic texture (of cAp nanoplatelets’ orientation and collagen fibril orientations) is constant for each specimen. Microtextural variation is also present across individual bands, demonstrating that the overall collagen fibril orientation undergoes subtle changes with season. Patterns of “feast or famine” and concomitant changes in amount and intensity of PDL loading might produce altered collagen (and cAp) orientations between the “good” and the “bad” seasons for ungulates but maybe not for modern human populations.