Evidence for a role of odontogenic epithelium in maintaining the periodontal space.

Explants of enamel organ epithelium or squamous epithelium from the oral cavity were placed in experimental cavities in the root surfaces of extracted and subsequently replanted monkey incisors. Control cavities without explants were also prepared. After an observation period of 8 weeks, histological evaluation of the cavities originally containing odontogenic epithelium showed a reparative cementum layer on the dentine surface and islands of epithelium in the periodontal connective tissue in the experimental cavities. Bone was not found in the cavities and the alveolar bone had been resorbed around the epithelial islands to a distance corresponding to the periodontal space adjacent to the cavities. Control cavities and cavities originally containing squamous epithelium also showed repair with reparative cementum, but the alveolar bone had grown into the cavities not, however, into contact with the dentine surface. These findings indicate a physiological rôle for odontogenic epithelium, in particular the epithelial rests of Malassez in the periodontal membrane for maintaining the width of the periodontal space and preventing dento-alveolar ankylosis.