The early distribution and possible role of nerves during odontogenesis.

Neural crest cells migrate along specific pathways to reach the mandibular and maxillary arches where they condense under specific areas of the ectoderm which will give rise to the primary and permanent dentition. In the mouse, the trigeminal ganglion becomes evident on E9 and the superior cervical sympathetic ganglion E13. Several studies have suggested that nerves in the vicinity of the developing teeth could influence the surrounding tissues and initiate tooth development, whereas other investigators have suggested that tooth development will proceed without an intact innervation. Innervation of the dental papilla has been reported as early as the cap stage in human teeth using an antibody to PGP 9.5. A large variety of putative neurotransmitters have been localized in the nerves of the dental pulp. Many of the putative neurotransmitters function in vasoregulation while others have unknown functions. A hypothesis is presented describing a possible signal transduction pathway between odontoblasts and nerve terminals.