|2D deformation mesh|
Alicante, 21st June 2012
A laboratory of the University of Alicante keeps between 50,000 and 60,000 models of human teeth carefully classified as well as of their predecessors in genetic evolution. The purpose of this registry is to provide a database for anthropological studies of the species, their origins and the diversity of past and present populations.
The laboratory is led by Alejandro Romero, lecturer in Biotechnology and the Director of the research group conducting studies based on anthropological collections of replicas of teeth around the world and all eras, from hominids of hundreds of thousands of years to current human groups of special characteristics or at risk of extinction. The laboratory is part of the Department of Biotechnology led by Professor Joaquín de Juan.
"The teeth reveal our evolutionary history", says Alejandro Romero. This scientist, currently working on a project with U.S. universities and the prestigious jounal and documentary producer National Geographic, explains that the teeth have an advantage over the rest of the skeleton for the purpose of conservation: they are covered with enamel, a natural mineral with a hardness similar to quartz, which best preserves them from destruction or during fossilization.
For researchers teeth morphologic features are informative in the studies of human diversity, the result of an evolution that began 6 or 7 million years ago whenthe primate branch was separated, after different types of hominids,which would lead to the Homo genus and this to the homo sapiens.
However, since the ancestors of humans dispersed from Africa leaving the rest of the continents, time and adaptation to the environment, they have introduced anatomical, physiological and genetic modifications in modern human being. And Africa is the continent that still retains the largest human variety. At the other extreme is Europe, where genetic mixing is making the studies difficult long ago.
Molds of teeth of some 200 types of different populations have been accumulated on the shelves of the laboratory of Alejandro Romero, some with names familiar to the public, for example Mongols, Australian Aborigines or Pygmies in different regions but not others, as Negritos of the Philippines or Andamanese. Some still have not been extinguished and preserve purity of traits, Aboriginal hunter-gatherer societies to which "Coca-Cola has not yet reached" as described graphically, and maintaining an isolation that has prevented the exchange of genes with individuals from other populations. Other molds have scored the team members in museums and other institutions around the world with collections of eighteenth and nineteenth centuries of fossils and human types now extinct or that have diluted their uniqueness. Sometimes, the rules on protection of populations living individuals at risk of extinction are so stringent that researchers prefer to get the molds of existing collections to face the administrative complications involving take them from live people.
For a specialist, the shape and size of a tooth is revealing both in genetic, physiologic, anatomic and even cultural terms: there are groups that file their teeth for ornamental reasons or to facilitate the process of fleshing animals. Also, their abrasion and breakage can give important clues about the environment or habits, in fact Alejandro Romero is part of a group of researchers specializing in dental microwaste.
The molds are made using common instrumental techniques and dentistry, which is obtained which is then positivised negative in the laboratory. Resin using two types of polyurethane, cheaper, and epoxy, is considerably more expensive but allows special treatments such as surface metallization for electron microscopic study.
A subsequent step is to describe digital models. For two-dimensional image using a camera, then the image is treated with geometric morphometric methods, a technique that links biology and geometry. In the digital representation of the teeth cusps and grooves of the crown are particularly defining its shape. The situation of the different reference points are transformed into two-dimensional coordinates from a computer program which plots a mesh deformation to allow numerical comparisons between different pieces. Alejandro Romero notes that the future, however, is to generalize the three-dimensional scanning, a practice more laborious and requires more complex instrumentation. Thus, any researcher can have immediate access through the network to models kept by their colleagues from all over the world.
|Modelos en 3D|