Ultrastructural study of initial attachment by human fibroblast-like cells on tooth roots in vitro

The purpose of this study was to determine the longitudinal effect of demineralized treatment of root surfaces on initial attachment, growth and differentiation of human periodontal ligament fibroblast-like cells in vitro. Cementum and dentin fragments were prepared from intact extracted human teeth for orthodontic reason. The root fragments of one group were not demineralized. Those of the other groups were demineralized by either citric acid (pH = 1.0, 3 min) or EDTA (pH = 7.4, 30 min). Plastic sheets served as controls. Human periodontal ligament fibroblast-like cells were incubated on root fragments and plastic sheets. After incubation, the root fragments and plastic sheets were examined by electron microscopy. The collagen fibers were exposed to the root surface by demineralized root surface. The exposed collagen fibers showed an effect on the cell attachment and growth, and the cells produced collagen fibers in the extra-cellular space of the root surface. Demineralization of dentin fragments were more strongly affected in cell attachment, growth and differentiation than demineralization of cementum fragments. Citric acid demineralization of dentin fragments had a greater effect on cell attachment, growth and differentiation than EDTA demineralization of dentin fragments. The results suggest that citric acid demineralization of dentin fragments may provide the most effective dental surface for the establishment of connective tissue attachment after periodontal treatment.