Histological and cytological organization confer specificity to the odontoblasts. These postmitotic, neural crest derived, polarized cells are aligned in a single layer at the periphery of the dental pulp and secrete the organic components of predentin-dentin. The developmental history of these cells demands a cascade of epigenetic signalling events comprising the acquisition of odontogenic potential by neural crest cells, their patterning in the developing jaws, the initiation of odontogenesis through interaction with the oral epithelium, commitment, and tooth-specific spatial distribution of competent preodontoblasts able to overtly differentiate. Recent experimental investigations are critically summarized, many open questions are stressed, and current hypotheses concerning the control of terminal odontoblast differentiation are outlined.

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The biological effects of isolated soluble dentin extracellular matrix components on the induction of reparative dentinogenesis in exposed cavities in ferret canine teeth have been shown to be blocked by immobilizing the extracellular matrix components on nitrocellulose or Millipore membranes during implantation. This contrasts with the picture of induction of odontoblast-like cell differentiation and reparative dentin deposition on existing insoluble dentin matrix of the exposure walls when the extracellular matrix components are implanted in lyophilized form. These data indicate the importance of an existing insoluble dentin matrix in providing a substrate to potentiate the growth factor-like activity of soluble isolated dentin extracellular matrix components in the induction of reparative dentinogenesis.

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