5 May 2014
A cluster of starches trapped
in dental calculus.
Scanning electron microscopy identifies starch in situ in calculus
Dental calculus is increasingly used as a source of information about past diets. Plant microremains trapped in calculus have the potential to revise our knowledge of diet in past populations. Despite this growing interest in dental calculus, there are still many unresolved questions about the mechanisms by which plant microremains are preserved within the calculus. For instance, the means by which starch grains become embedded and subsequently are preserved in calculus is still unclear due to the difficulties with starch preservation in the oral cavity. There is also the possibility that the starches that have been recovered from calculus are actually the result of modern contamination. Modern starches can occur in the air and working surfaces of some facilities, making environmental contamination a risk.
A new study led by Robert Power and Amanda Henry published online ahead of print in the Journal of Archaeological Science reveals that SEM coupled with energy-dispersive X-ray spectroscopy (EDX) documents for the first time starch in situ in calculus. The results demonstrate that SEM-EDX can be an effective means for identifying starch and other microremains in intact human and chimpanzee dental calculus. This approach provides the ability to detect microremains, including starch grains, by their morphology and elemental composition in their original context in the calculus, thus ruling out contamination. It also allows exploration of the kinds of environments within the calculus that may permit starch preservation.
Importantly SEM-EDX may offer a non-destructive technique for studying microremains in certain contexts. By comparing traditional optical analytical techniques (OM) with less invasive electron microscopy it is clear that SEM-EDX and OM are both effective for observing microremains in calculus, but differ in their analytical resolution to identify different microremains, and therefore are best used combined in a sequential way.
Power RC, Salazar-García DC, Wittig RM, Henry AG (2014). Assessing use and suitability of scanning electron microscopy in the analysis of microremains in dental calculus. Journal of Archaeological Science, doi: 10.1016/j.jas.2014.04.016.