Cellular colonization of denuded root surfaces in vivo: cell morphology in dentin resorption and cementum repair.

Cellular colonization of denuded root surfaces on replanted teeth was examined with scanning electron microscopy. The dentin surface was rapidly colonized by a few macrophage-like cells which resorbed dentin in limited areas. They had well-developed ruffled borders but no clear zones. The resorptive activity was gradually inhibited by the ingrowth of a monolayer of fibroblast-like cells from the periphery of the denuded area. At the advancing front, the ingrowing fibroblast-like cells were long and slender, with long tail-like projections trailing the nuclear domain. The invading cells behind these were well-spread and tightly packed. They had a granulated surface and showed morphological signs of fibre synthesis. After 6 weeks, the entire cavity was covered by a monolayer of these cells. Removal of the cells with sodium hypochlorite revealed that a cementum-like tissue had been formed under the invading cells, indicating that they were cementoblasts. It was concluded that wound repair on the root surface is dependent upon the differentiation and proliferation of pre-cementoblasts in the periphery of the wound and that cells in the main body of the periodontal membrane are of little significance in the healing process on the root surface.