Final answer:
Cementum is the hardened material that covers the root of a tooth. It helps to anchor the tooth in the jaw bone.
Step-by-step explanation:
The hardened material that ensheaths each root of a tooth is called cementum. Cementum is a bone-like layer that covers the dentin in the roots of teeth. It plays a role in anchoring the tooth in the jaw bone, working with the periodontal ligament.