Scanning electron microscopic observation on the dentin surface of rat enamel-free areas

Formation of the enamel covering on the dentin of the tooth crown is thought to depend upon the dentin surface structure during the early stages of enamel development. For this reason, observations were made of the dentin surfaces of both the enamel-free area (EFA) and the region beneath the enamel area. After treatment with sodium hypochlorite and formic acid, scanning electron microscope observations were made of the EFA surface and the exposed dentin surface beneath the enamel of unerupted rat mandibular first molars. Cone-like projections consisting of matrix fibers were observed on the dentin surface covered with the enamel. These cone-like projections formed continuous ridges that connected with the network structure. At the concavities of these network structures these projections were distributed sparsely. Instead of the cone-like projections, the matrix fibers formed a coarse network structure along the surface at the EFA.