Periodontal cell migration into the apical pulp during the repair process after pulpectomy in immature teeth: an autoradiographic study.

The migration of dental papilla cells into the periodontium during the process of root development may occur as part of the process involved in the formation of the periodontal tissues. The question posed is whether such cells under pathological conditions could retromigrate from periodontium into dental pulp and together with other apical pulp cells of immature teeth, take part in the production of additional dental tissue, e.g. 1) the tertiary/dentine under deep carious lesion where odontoblasts had been destroyed 2) the dentine bridge on an amputation wound and 3) calcified tissue which closes an apex during the apexification process in immature teeth. The migration of periodontal cells locally marked by H3 thymidine immediately after partial pulpectomy in immature dog's teeth was analysed at observation periods of 2, 24 and 50 h and also without H3 thymidine labelling of periodontal cells 8 weeks after pulpectomy. The marked cells were found in the early observation periods after pulpectomy just in the places where the hard tissues were formed in the later observation period of 8 weeks. They were found in large numbers just around the coagulated necrotic foci. The finding supports the assumption that firm necrotic masses are a very important stimulative factor in the reparation process in pulp and periodontium. The experiment also corroborated the existence of periodontal cell retromigration into apical dental papilla of immature teeth. Future research should assess the possible role of the pathological condition in the determination of undifferentiated odontogenic ectomesenchymal periodontal cells into odontoblasts.