Assessing use and suitability of scanning electron microscopy in the analysis of micro remains in dental calculus

Abstract

Dental calculus is increasingly recognized as a major reservoir of dietary information. Palaeodietary studies using plant and animal micro remains (e.g. phytoliths, pollen, sponge spicules, and starch grains) trapped in calculus have the potential to revise our knowledge of the dietary role of plants in past populations. The conventional methods used to isolate and identify these micro remains rely on removing them from their microenvironment in the calculus, thus the microenvironment that traps and preserves micro remains is not understood. By using scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM–EDX) on modern chimpanzee calculus from the Taï Forest, Côte d'Ivoire, and human calculus from the Chalcolithic site of Camino del Molino, Spain, we present the first reported observations on characteristics of the matrix setting that are conducive to the survival of starch in dental calculus. We also assess the potential for SEM–EDX to detect starch and differentiate it from structurally and molecularly similar substrates. We demonstrate that SEM–EDX may offer a non-destructive technique for studying micro remains in certain contexts. Finally, we compare traditional optical analytical techniques (OM) with less invasive electron microscopy. The results indicate that SEM–EDX and OM are both effective for observing micro remains in calculus, but differ in their analytical resolution to identify different micro remains, and we therefore recommend a sequential use of both techniques.