Histology, innervation and radiographic appearance of fetal rat tooth germs developing in oculo

Rat molar and incisor tooth germs from gestational days 18-21 were homologously grafted to the anterior eye chamber of adult recipients. The fetal tooth transplants survived and grew considerably in the eye, attached to and vascularized from the anterior surface of the host iris. Grafts were examined histologically and compared with in situ controls after up to 6 months in oculo. Radiographic examinations of the grafts showed a normal rate of mineralization and a distinct enamel/dentin border after intraocular development. The size of the tooth grafts was somewhat smaller than in situ but the grafted teeth attained a form much resembling in situ incisors and molars. Light microscopy revealed a regular dentin and predentin, a distinct dentin/enamel border and a well innervated and vascularized pulp. No degenerative changes in dentin or enamel layers could be found in long-term grafts (6 months). Thus, intraocular tooth grafts in rats develop many histologic and anatomic features typical of normal teeth, emphasizing the importance of intrinsic regulatory mechanisms in tooth development.