Enamel: The most outer layer. Hardest substance of the body.
Dentin: The layer under the enamel. Because dentin is softer than enamel, cavities enlarge faster.
Pulp: The nerve of a tooth.
Gum: Surface tissue that covers alveolar bone.
Cementum: The outer layer of the root of the tooth.
Periodontal ligament: Tissue that joins the alveolar bone and cementum.
Alveolar bone: Bone under the gums that anchors the roots of tooth.
Blood vessel and nerve: Nerve tissue that connected to the pulp.