[The ultrastructure of the circumpulpal dentin of the human tooth]

Ultrastructure of cellular and extracellular constituents of the predentin and adjacent strip of dentin was investigated in both erupted and unerupted but completely shaped third molars of human adults using cautious fixation and demineralization techniques. The odontoblast processes (OP) were slightly bent at their bases to run further straight and parallel to each other across dentin and predentin. The OP cytoplasm contained numerous microfilaments and solitary microtubules. Occasional mitochondria, lysosomes, microvesicles, lipid globules and endoplasmatic reticulum profiles could be found throughout the whole length of the OP under study. Axons and their terminals of apparently efferent type attached to some of the OPs were found in both dentin and predentin. A great bulk of dentin was occupied with the collagen fibers intermingled with the amorphous matrix and occasional dense precipitates next to dentin. Intensive mineralization was found in dentin except the spaces occupied by dentin canaliculi.