Collagen Formation at the Tooth‐Cell Interface: Comparative Ultrastructural Study on the Effect of Partial Demineralization of Cementum With Dentin

In order to compare the effect of partial demineralization with root planing and partial demineralization of cementum with that of dentin on healing, the ultrastructural morphology of the interface between the layer of human periodontal ligament‐derived, fibroblast‐like cells (HPF) and the treated root surface was studied in an in vitro culture system. Sixty (60) pairs made from transversally‐cut root slices, 500 μm thick, were obtained from extracted human periodontally diseased teeth. Thirty (30) pairs of the root slices were preliminarily root planed (RP). The remaining half were root planed and then partially demineralized in a solution of citric acid (RP+CA). The opposite surface of paired slices was made uniform by using either cementum or dentin. Consequently, all root slices were classified into four experimental groups: RP‐cementum and RP‐cementum pairs (group 1), RP‐dentin and RP‐dentin pairs (group 2), RP+CA‐cementum and RP+CA‐cementum pairs (group 3), and RP+CA‐dentin and RP+CA‐dentin pairs (group 4). Each pair of root slices was placed on the floor of a 35‐mm culture dish. HPF were seeded at a concentration of 4×105 cells/dish. Co‐cultures of HPF and the root slices were examined using phase contrast and electron microscope after 4, 6, and 10 weeks. Electron‐dense material covered non‐demineralized root surfaces and the lining cells in accumulating cell layers were oriented parallel to the root surface and attached to the material in groups 1 and 2. In groups 3 and 4, the underlying cells in several accumulating cell layers were oriented approximately perpendicular to the lower aspect of the vertical surface of the root slice. The underlying continuous cells were separated from the demineralized root surface by newly synthesized collagen fibrils after 6 to 10 weeks. The features of cell attachment and formation of collagen fibrils on the surface of cementum did not differ from those on the dentinal surface in both RP and RP+CA groups. J Periodontol 1995; 66:267–273.