Scientists Discover New Research Use for Ancient Dental Plaque

Posted on May 5, 2012

Centuries ago, dental calculus would build up through the years, layer after layer, like a stalagmite. This calculus would sometimes reaching impressive proportions, like in the photograph above. University of Nevada, Reno researchers G. Richard Scott and Simon R. Poulson have discovered that analysis of tiny fragments of this material can be used effectively in paleodietary research, the study of diets of earlier ancient and populations. It can be done without destroying bone, as other methods do.

Scott obtained samples of dental calculus from 58 skeletons buried in the Cathedral of Santa Maria in northern Spain dating from the 11th to 19th centuries to conduct research on the diet of this ancient population. After his first methodology met with mixed results, he decided to send five samples of dental calculus to Poulson at the University's Stable Isotope Lab, in the off chance they might contain enough carbon and nitrogen to allow them to estimate stable isotope ratios.

Scott says, "It's chemistry and is pretty complex, but basically, since only protein has nitrogen, the more nitrogen that is present, the more animal products were consumed as part of the diet. Carbon provides information on the types of plants consumed."

The material was crushed in the lab and then a mass spectrometer was used to obtain stable carbon and nitrogen isotope ratios.

Scott says, "It was a long shot. No one really thought there would be enough carbon and nitrogen in these tiny, 5- to 10- milligram samples to be measurable, but Dr. Poulson's work revealed there was. The lab results yielded stable carbon and nitrogen isotope ratios very similar to studies that used bone collagen, which is the typical material used for this type of analysis."

Scott says the common practice of using bone to conduct such research is both cumbersome and expensive, requiring several acid baths to extract the collagen for analysis. The process also destroys bone and often isn't permitted by museum curators. Scott says hair, muscle and nails work great for such research, but they are not always easy to find because they decompose too quickly. Dental calculus, however, stays around for a very long time.

Scott said that although additional work is necessary to firmly establish this new method of using dental calculus for paleodietary research, the results of this initial study indicate it holds great potential. He says, "It could save a lot of time and effort, and also allow for analysis when things like hair, muscle and nails are no longer available."

The research study is published here in the May 2012 issue of the Journal of Archaeological Science.