odontoblast

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun One of the cells forming the outer surface of dental pulp that produces the dentin of a tooth.

from The Century Dictionary.

• noun A cell by which dentine is developed; a cell which produces dentinal tissue, the special substance which largely composes teeth.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Anat.) One of the more or less columnar cells on the outer surface of the pulp of a tooth; an odontoplast. They are supposed to be connected with the formation of dentine.
• noun (Zoöl.) One of the cells which secrete the chitinous teeth of Mollusca.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A cell on the outer surface of dental pulp that produces tooth dentin