Tooth transplantation in the mouse. I. The use of procion dyes and tritiated proline in a study of syngeneic tooth germ transplantation.

Tooth germs of first molars from fourto six-day old mice were transplanted heterotopically into the connective tissue under the dorsal skin of adult syngeneic recipients. The fate of the transplants was studied by histologic staining, vital staining with procion dyes, and autoradiography. Together these methods provided the following picture of the development of the transplant. Extraction of the tooth germ severs its vascular connections and disturbs the nutritional environment of the tooth so that many cells undergo necrosis and degeneration. The resulting inflammatory response clears the transplant of necrotic tissue, leaving a fibrous pulp of low cellularity and an extensively disrupted odontoblastic layer; the enamel organ is reduced to only a few epithelial cells. In the second week following transplantation, however, the surviving cells start to proliferate and the tissues of the transplant begin to reorganize. Reorganization starts at the apical foramen and spreads to the rest of the tooth. The central pulp is penetrated by new blood vessels, its cellular content is reestablished, and its morphology returns to normal. Odontoblasts start producing dentin which at first is highly irregular and contains many cells (osteodentin). Later the dentin formation becomes more and more regular and the dentin assumes its normal tubular structure. New enamel is not formed at any time after transplantation. The cells of the enamel organ undergo squamous metaplasia and form epithelial cysts. Abortive root formation is observed but typical roots never develop. Rudiments of periodontal ligament develop rarely. The transplants are enclosed in a capsule of connective tissue. It is concluded that the heterotopically transplanted tooth germs maintain their capability to recover, develop, and differentiate in syngeneic recipients. Although almost all of the developmental processes continue in the transplant after a period of adjustment, some of them are abortive. The literature on tooth transplantation is enormous. A bibliography compiled in 1962 (Ivhnyi, '62) lists over 300 publications, and since then some 300 more have appeared (Natiella et al., '70). Widely contrasting views on the antigenicity of teeth have been expressed. It has been reported that tooth xenografts survive (Flemming, '55; Cserepfalvi and Price, '68), which implies that the tooth tissues are non-antigenic. Other investigators, however, have concluded that even syngeneic grafts do not survive (Lefkowitz, '61) and that transplantation of teeth is not possible AM. J. ANAT., 131: 371-386. technically. Between these two extremes lie various concepts, for example, hosttissue acceptance of both syngeneic and allogeneic grafts (Haley and Costich, '69), acceptance of syngeneic grafts and rejection of allografts (IvBnyi and Vacek, '64), rejection of some allografts and acceptance of others according to the strength of the histocompatibility barrier (IvAnyi, '68; f Supported by grant DE-02731 from the National Institute for Dental Research, PHS. 2 Portions of this investigation are being submitted as partial fulfillment of the requirements for the Master of Science deeree in oral surgery, Horace H. Rackham School of Graduate Studies, Ann Arbor, Michigan.