Structure of approximal human dental plaque as observed by scanning electron microscopy

Abstract

The first bacterial layer to be deposited on the tooth surface was usually dominated by coccal forms, or a mixture of coccal cells and filaments. The superficial layer in thicker regions consisted of a varied flora, including filaments lying parallel to the tooth surface and, sometimes, parallel to each other. Occasionally colony-type groupings of coccoid cells were evident. Filaments in the deeper layers appeared to be arranged parallel to one another and at right angles to the tooth surface. Organisms frequently showed evidence of attachment to one another and of extensions from their outer surfaces. Where clinical evidence of gingivitis immediately prior to extraction had been slight or absent, the apical limit of plaque was sharply demarcated by the gingival margin. Where there had been signs of gingival inflammation, the plaque was usually observed extending on to the enamel in what had been the crevice region. It is suggested that the arrangement of cells enmeshed with one another in intimate networks of great complexity, as observed by this method, is an important factor in the maintenance of the structural integrity of plaque. It is concluded that scanning electron microscopy is an eminently suitable method for the examination of naturally occurring plaque structure.