dentin -
The hard, dense calcareous material that makes up the bulk of a tooth.
Wikipedia
Dentin is a calcified tissue of the body, and along with enamel, cementum, and pulp is one of the four major components of teeth. Usually, it is covered by enamel on the crown and cementum on the root and surrounds the entire pulp. By weight, seventy percent of dentin consists of the mineral hydroxylapatite, twenty percent is organic material and ten percent is water.
