In the field of oral surgery we apply replantation or transplantation of a tooth as one of the methods to supplement the defect of the tooth. Using puppies experimental studies were conducted on the healing process of a developing tooth after its replantation, especially on the regeneration of blood vessels in the dental pulp and periodontium that had been once depleted of its nutrient, by morphological and three-dimensional observations after the intravenous injection of chloro-percha, as well as by roentgenological and histopathological observations. The results of the observations may briefly be summarized as follows. 1) Roentgenological findings: Up to the 10th day after replantation there could be observed a spreading of pathological abnormality in the periodontal space, but after 20 days the bone regeneration could be observed, after 30 days the lamina dura appeared, and after 90 days the findings seemed to be practically normal. 2) Regenerated blood vessels in the replanted dental pulp: Up to 20 postoperative days the regenerated blood vessels increased with many fusions and windings, but after the completion of new blood flow the number of blood vessels grew less and the blood flow also became orderly, thereafter the vessels became finer with the regeneration of bony hard tissue within the dental pulp making the pulp space more narrow. 3) There could be detected no bony adhesion or absorption as observable at the replantation of a complete tooth. 4) In the fate of replanted tooth the dental pulp and periodontium play an important role. 5) There could be recognized a certain correlation in the roentgenological findings, changes of vascular pictures, and pathohistological findings.