Hertwig root sheath
Hertwig root sheath(hert′wig, ′vik)
[Wilhelm August Oscar Hertwig, Ger. physiologist, 1849–1922]
A downgrowth of epithelium from the cervical loop of the enamel organ that induces dentin formation of the forming tooth root and determines its shape. The epithelial diaphragm, a horizontal extension of the Hertwig's root sheath, will determine the number and size of the tooth roots.