Optimizing Preparation Protocols and Microscopy for Cementochronology

Abstract

Counting dental acellular cementum (AC) annulations is used to estimate age at death in anthropological contexts by embedding the tooth, sectioning the root, and imaging the thin sections. However, there are several published protocols creating confusion to optimize these steps. We compared three standard illumination techniques (differential interference contrast; transmitted bright field; transmitted polarized) on sections with the same thickness, field of view, on three types of samples: fresh teeth embedded in both MMA and epoxy; archeological samples embedded in epoxy. We compared the quality of AC increment visibility on longitudinal and transversal sections of the same root, to optimize the quality of AC micrographs for age estimation. Results suggest that differential interference contrast microscopy might be ideal, even though brightfield consistently provides a decent image; epoxy resin with quick polymerization time doesn't affect AC structure and allows for higher contrast than traditional MMA; transverse sections are more consistent. These results emphasize the need for cementum-specific procedures not always compatible with traditional dental analyses.