Odontoblasts and dentin formation
The cells that build dentin, why they are not replaced when lost, and what forms in their place.
Odontoblasts line the outer edge of the pulp and produce dentin, leaving a long cellular process trailing back through the dentinal tubule they have just built. That geometry is why dentin is not a solid mineral but a tubular tissue — and why it can transmit sensation.
They are post-mitotic. Once differentiated, an odontoblast does not divide, so cells lost to injury are not directly replaced. Under mild stimulus, surviving odontoblasts can deposit reactionary dentin; where they die, progenitors within the pulp may differentiate into odontoblast-like cells and lay down reparative dentin. That second, less organised tissue is a repair response rather than true regeneration, in the sense of Repair versus regeneration.
Directing progenitors down this path deliberately is the aim of much dental research. Calcium silicate and bioactive materials appear to encourage it, and DPSCs can form odontoblast-like cells in culture. See The dentin-pulp complex.
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