SURVIVAL OF MOUSE TOOTH GERMS AFTER FREEZING IN LIQUID NITROGEN AS DEMONSTRATED BY DIFFERENTIATION OF ISOLOGOUS TRANSPLANTS

¹ Department of Anatomy, The University of Texas Dental Branch, Houston, Texas

1. First molars of C3H fetal mice were dissected out, pretreated in 30 per cent glycerol, frozen rapidly in liquid nitrogen (-195° C.), rewarmed rapidly at 37° C. in Tyrode's solution, and then transplanted to the anterior eye chambers or axillae of adult mice. Transplants were considered successful when odontoblasts and ameloblasts differentiated and formed dentin and enamel.

2. Tooth germs frozen without pretreatment in glycerol almost always failed to take on transplantation.

3. Pretreatment with glycerol increased the proportion of successful transplants among frozen tooth germs from 0 to 33 per cent in the case of anterior eye chamber transplants and from 4 to 57 per cent in tooth germs transplanted to the axilla.

4. Tooth germs that were exposed to glycerol but not frozen showed less damage than glycerol-treated frozen tooth germs. However, the glycerol solution in itself caused some injury under the conditions of this experiment.

5. The group of tooth germs that were neither treated in glycerol nor frozen showed the highest proportion of successful takes, about 85 per cent in both the anterior eye chamber and axilla.

6. Under the conditions of this experiment, the axilla proved to be more favorable than the anterior eye chamber as a site for transplantation. No difference was noted in the case of control transplants.