Middle zone of the root surface integument of human teeth affected by chronic periodontitis.

This study has confirmed the presence on the root surface of teeth affected by chronic periodontitis of a zoned organic integument analogous to that on enamel. Measurements showed a highly significant correlation between the levels of the bounding structures of this zone, that is, the apical plaque border and the coronal border of residual periodontal ligament, for both shallow and deep pockets. The middle zone between these two was on average 1 mm wide.