An in vivo and in vitro study of dissociated tooth germs of rats

Single-cell suspensions of dissociated rat molar tooth germs were grown in vitro in modified Rose chambers and in vivo in diffusion chambers implanted subcutaneously in host rats. Using phase contrast microscopy and time lapse cinemicrophotography, the cells were observed in vitro to form aggregates consisting of groups of mesenchyme-like and epithelium-like cells. In material from the in vivo study, it was also observed that the dissociated cells re-aggregated to form sheets of epithelial and mesenchymal cells and sometimes to form more organized structures resembling epithelial cell rests of Malassez. Storage of the tooth germs at ?196 °C for 3 weeks prior to trypsinization aided dissociation and appeared to have no deleterious effect on the subsequent viability and behaviour of the stored cells.