Just moments after you brush your teeth, the surfaces of your teeth will be colonized by bacteria. This colonization results in a biofilm, which is a very thin layer on the surface of your teeth, also known as dental plaque. In the presence of saliva, which contains necessary minerals, this plaque begins to calcify. The periodic mineralization results in a layered cement-like substance, which is dental calculus (see figure). In 1683, Dutch scientist Antoni van Leeuwenhoek described in a letter to the Royal Society of London that there, were as he called it, ‘animacules’ living in dental plaque, establishing it as a valuable source to study the microorganisms of the mouth.
“Observing it I judged that, although I could not see anything
moving in it, there were yet living animalcules in it […]
there were so enormous a number of living animalcules[..]”
– Antoni van Leeuwenhoek (1632 – 1723)
Nowadays we know that van Leeuwenhoek’s observations were correct. Studies show many microorganisms in dental plaque. Some of these microorganisms are considered pathogens, disease-causing organisms, that are involved in diseases like periodontal disease and dental caries. The dentist or oral hygienist therefore removes the plaque and its microorganisms, usually before plaques mineralizes and results in dental calculus. However, it was only after World War II that the practice of brushing our teeth became widespread. Dental calculus is therefore almost ubiquitous in archaeological populations, making it an interesting source to study our past.
Biomolecular archaeology lies at the cross-section of archaeology and biology, in particular evolutionary and population biology. Due to the advent of molecular methods, biomolecules, including nucleic acids (DNA/RNA), proteins, lipids and carbohydrates, can now be extracted from ancient material as well. As dental calculus is densely mineralized it preserves biomolecules over a long period of time. Via these biomolecules in dental calculus we are now able to study the microorganisms that inhabit the mouth and nasal passage,s as well as immunological proteins associated with inflammation and infection of many populations. These results give insight into diet, health and disease from Neanderthals to populations that lived in the 19th century. The amount of DNA that can be obtained from dental calculus is astonishing, and we typically find 1,000 times more DNA by weight in dental calculus than in bone. Hence, this is the first time that diet, health and disease can be studied with a molecular approach without requiring exceptionally well preserved samples (e.g., samples obtained from permafrost or mummified remains). Furthermore, we are now able to study the evolution, virulence (the ability to make people sick), and spread of pathogens, which could have important implications for modern medicine.
So please, for all future biomolecular archaeologists, do not brush your teeth!!
Slide Picture on home page provided by Christina Warinner.