The visible portion of the tooth is the crown, which is made of enamel. Just beneath the enamel is dentin, a substance harder than bone. The gum surrounds the base of the tooth.
The root of the tooth, with its blood vessels and nerves, extends down into the jaw bone and provides circulation and sensation to the tooth. The tooth sits in a socket in the bone.
The jaw bone contains all the teeth and provides stability and mobility for the mouth and teeth for chewing. The lower jaw bone is called the mandible and the upper jaw bone is called the maxilla.
by Gevorg A. Poghosian, Ph.D.