Methods - What are starches and phytoliths and what do they do in our dental calculus?
credits for the slider pictures see imprint
Dental calculus is formed by the fossilization of the bacterial microfilm (plaque) in the mouth, the same one that we go to remove twice a year. While it is formed microscopic particles of the different things that enters our mouth can get trapped in the plaque, and preserve when it fossilizes. PEKULI project focuses first and foremost on identifying two plant micro-remains: starch granules and phytoliths.
Starch granules are the plant energy storage system. Storage starch granules which are often diagnostic to the species level are formed in fruits (seeds) and storage organs (e.g., tubers). In addition to identifying plant taxa, food preparation can cause distinctive damage to starch granules, which can help us reconstruct human behavior (e.g., freezing, grinding, cooking).
Phytoliths are silicified bodies (hydrated opaline silica SiO2·nH2O) resulting from the deposition of opal within the plant intracellular and extracellular structures. Phytoliths are inorganic, resist acidic pH that dissolves other materials and temperatures up to 700ºC without major changes, and therefore are very durable. They supply information on plant taxa and the anatomical origin of the phytolith.
The samples are then dissolved with a weak acid, a process that can take a few days, and are finally mounted on a glass slide to be inspected under the microscope. Because starch granules can be found everywhere, and starch is used in many modern applications, from soaps to tissues and so on, it is very important to work in an extremely clean environment and control for contamination.
Image 1: Sample Preparation © S. Gur-Arieh
Image 2: Sample Analysis © S. Gur-Arieh