is the almost translucent material made of calcified salts which covers the crown of a tooth. It comprises millions of long, six-sided prisms set on end on the dentine (see below), and is thickest over the biting surface of the tooth. With increasing age the teeth may be worn away on the surface, so that the dentine becomes visible. The outer sides of some teeth may be worn away by bad tooth-brushing technique.

is a dense yellowish-white material from which the bulk and the basic shape of a tooth are formed. It is like ivory and is harder than bone but softer than enamel. The crown of the tooth is covered by the hard protective enamel and the root is covered by a bone-like substance called cement. Decay can erode dentine faster than enamel (see TEETH, DISORDERS OF – Caries of the teeth).

or cementum is a thin bone-like material which covers the roots of teeth and helps hold them in the bone. Fibres of the periodontal membrane (see below) are embedded in the cement and the bone. When the gums recede, part of the cement may be exposed and the cells die. Once this has happened, the periodontal membrane can no longer be attached to the tooth and, if sufficient cement is destroyed, the tooth-support will be so weakened that the tooth will become loose.

This is the inner core of the tooth and is composed of a highly vascular, delicate fibrous tissue with many fine nerve-fibres. The pulp is very sensitive to temperature variation and to touch. If the pulp becomes exposed it is likely to become infected with the result that root-canal treatment or extraction of the tooth may be necessary.

A layer of fibrous tissue arranged in groups of fibres which surround and support the root of a tooth in its bone socket. The fibres are interspersed with blood vessels and nerves. Loss of the membrane leads to loss of the tooth. The membrane can release and re-attach the fibres to allow the tooth to move when it erupts, or (to correct dental deformities) is being moved by orthodontic springs.