Repair of periodontal tissues in vivo and in vitro

Repair of experimental cavities in dental roots and of periodontal wounds was studied in vivo and in vitro. Incisors from monkeys were extracted and experimental cavities were made in the roots. The teeth were either replanted immediately or cultured for 1-12 weeks in tissue culture medium. After 8 weeks the tissue reaction around the replanted teeth was evaluated on demineralized histological sections and undecalcified freeze-sections incubated for histochemical demonstration of certain enzymes. The cultured teeth were evaluated on decalcified histological sections. In the experimental cavities of the replanted teeth reparative cementum was found. It was frequently separated from the denuded dentin while a firm attachment was always established to the intermediate cementum and dental cementum at the periphery of the cavities. The reparative cementum was also firmly attached to some small areas on the exposed dentin surface where resorption had taken place. The activity of alkaline and acid phosphatase was lower in the connective tissue in the experimental cavities than in the surrounding PDM, suggesting an incomplete regeneration of the periodontal membrane in these areas. A loose connective tissue devoid of demonstrable collagen fibers was found in the cavities in vitro. The reparative cementum did not fill the experimental cavities in the replanted teeth. The alveolar bone extended into the experimental cavities and made the width of the PDM normal also in the experimental cavities. Epithelial and endothelial cells were numerous in the connective tissue separating the reparative cementum from the alveolar bone in the experimental cavities. It is possible that they contribute to the integrity of the PDM and prevent resorption of the dental root.