Human junctional epithelium as a pathway for inflammatory exudation.

Photographic montages of transmission electron micrographs of the dentogingival region have made it possible to assess the morphologic alterations that occur in the junctional and the oral sulcular epithelium as a result of mild gingival inflammation. Enlargements of the intracellular spaces in the junctional epithelium varied in size and shape from isolated alveolate enlargements, often containing isolated granulocytes, to channel-like pathways oriented in an apico-coronal direction and frequently filled with rows of granulocytes. In contrast to artifactitious spaces, these enlarged intercellular spaces failed to reveal the presence of ruptured intercellular bridges and contained well preserved undistorted granulocytes with round profiles. Moderately electron dense material within the enlarged intercellular spaces probably represented proteins from the fluid exudate, precipitated by the fixation process. The rate of normal junctional epithelial turnover appeared to be insufficient to compensate for the above morphological alterations brought about by the inflammatory process. Mononuclear cells, mostly lymphocytes, were preferentially located in the connective tissue side of the junctional epithelium. Their low numbers in the gingival sulcus suggest that they are passively carried into the sulcus as a result of normal turnover of the junctional epithelium, whereas granulocytes, which account for the majority of leucocytes in the sulcus, actively migrate through the junctional epithelium.