dentinal papilla

n.
  1. A projection of the mesenchymal tissue of the developing jaw into the cup of the enamel organ; its outer layer becomes odontoblasts that form the dentin of the tooth.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.