Epithelial cells in PDL are critical in resuming the integral relation between tooth root and supporting bone after trauma—A transplantation experiment

ObjectiveThe aim of this study was to determine the response of the residual epithelial network following traumatic breakdown of the periodontal ligament (PDL).MethodsMandibular incisor sections with PDL (experimental) and sections denuded of PDL (control) from 4- to 6-week-old Wistar–Furth rats were transplanted into the defects created in the frontal bone of the recipient syngeneic rats. At intervals, the defects with implanted teeth roots were collected and processed for histological and biochemical examination. Immunolocalization of epithelial cells was performed to monitor their phenotypic changes during transplantation healing period.Results(1) Histological observation of the experimental sample revealed the sequence of cellular response characterized by an initial degeneration of PDL followed by a proliferation of granulation tissue. There was also a marked odontoblastic reaction with extensive deposition of regular dentine within the pulp chambers. In the control group, initial signs of bony fusion with dentine led to an extensive ankylosis and bone replacement between roots and defects. (2) Immunostaining indicated that, in experimental groups, the pattern of regularly spaced epithelial cells lying in close approximation to the root surface was distinct 10 days post-transplantation but became diminished afterwards. The immunoreaction against epithelial cells was negative in the control.ConclusionResidual PDL is essential to prevent ankylosis after trauma and epithelial cells may facilitate the re-establishment of root–PDL–bone complex by transforming into mesenchymal cells.