To modify the development of their teeth, the team from the Institute of Biotechnology of the University of Helsinki worked with embryonic teeth cultures from mice not coded by the ectodysplasin A (EDA) protein, which regulates the formation of structures and differentiation of organs in the embryo throughout its development. The teeth obtained with these cultures which present this mutation develop into very basic forms, with very uniform crowns. Scientists gradually added different amounts of the EDA protein to the embryonic cells and let them develop.
The researchers observed that the teeth formed with different degrees of complexity in their crown. The more primitive changes observed coincide with those which took place in animals of the Triassic period, some two hundred million years ago. The development of more posterior patterns coincides with the different stages of evolution found in rodents which became extinct already in the Palaeocene Epoch, some 60 million years ago. Researchers have thus achieved experimentally to reproduce the transitions observed in the fossil registry of mammal teeth.