Dentine
Also: dentin
The mineralized tissue beneath a tooth's enameloid that forms the bulk of the crown and most of the root. The dark bourrelet band is exposed dentine.
Dentine (also spelled dentin) is the mineralized tissue lying beneath the enameloid cap. It makes up the bulk of a tooth's interior and nearly all of the root, and is generally more porous and less glossy than the enameloid above it.
On a megatooth tooth the bourrelet — the dark chevron band at the base of the crown — is a strip of exposed dentine, which is why it reads darker than the polished blade.