Teeth, like bones, are living structures. They rest in a specially designed cavity in the bones of the jaw and at least while they are growing they have a supply of blood and nutrients to them through their base. The crown is the outside of the part of the tooth that is above the jaw bone, it is the part that does all the hard work. It is capped with an extra hard substance called enamel. The rest of the tooth is softer, but still harder than bone. Beneath the enamel, making up the bulk of the tooth is the Dentine and within the centre is the pulp cavity.