Figure 3. Scheme for the dissociation-re-association experiments. (1) About 60 tooth germs at the cap stage were dissociated by trypsin treatment, so that the dental mesenchyme could be separated from the dental epithelia. (2) The epithelia were further dissociated into single cells. (3) After filtration and centrifugation, the pellet containing mixed epithelial cells from 4 sources (SR, IDE, ODE, PEK) was fragmented and re-associated with dental mesenchyme. (4) These re-associations were cultured for 3 days to achieve the cap stage and illustrate the restoration of epithelial histogenesis.