Read the following text

Structure of Teeth

Teeth are small, calcified, hard, whitish structures found in the mouth. They function in mechanically breaking down items of food by cutting and crushing them in preparation for swallowing and digestion.

The roots of teeth are embedded in the maxilla (upper jaw) or the mandible (lower jaw). Teeth are made of multiple tissues of varying density and hardness.

The tooth has two anatomical parts. The anatomic crown is that part of the tooth which is usually visible in the mouth. The crown is above the cement-enamel junction or "neck" of the tooth. Most of the crown is composed of dentine (dentin in American English) with the pulp chamber inside. The crown is covered with enamel.

The root is the part embedded in the jaw. The root keeps the tooth in its bony socket and is normally not visible. The end of the root is called the apex. At the end of the root there is a small opening called apical foramen. Blood vessels and nerves pass through this opening to enter the tooth.

The root is covered with cementum. As with the crown, dentin composes most of the root and beneath it there is the pulp cavity. This part of the pulp cavity (located in the root) is called the pulp canal or the root canal.

A tooth may have multiple roots or just one root (single-rooted teeth).

Different types of teeth have different root formations. Incisors and canines have a single root. Molars may have one, two or three roots depending on their type and location in the mouth. Additional roots are called supernumerary roots.

Enamel is the hard outer layer of the crown. Enamel is the hardest substance in the body.

Dentine is not as hard as enamel; it forms the bulk of the tooth and can be sensitive if the protection of the enamel is lost.

Pulp is the soft tissue containing the blood and nerve supply to the tooth. The pulp extends from the crown to the tip (apex) of the root.

Cementum is the layer of bone-like tissue covering the root. It is not as hard as enamel.

Structures around the tooth:

Periodontal ligament is made up of thousands of fibres which fasten the cementum to the bony socket. These fibres anchor the tooth to the jaw bone and act as shock absorbers for the tooth which is subjected to heavy forces during chewing.

Gingivae (gums) are made of soft tissue that surrounds the teeth and bone. It protects the bone and the roots of the teeth.

The bone provides a socket which surrounds and supports the roots of the teeth.

Each tooth and periodontal ligament has a nerve supply and the teeth are sensitive to a wide variety of stimuli. The blood supply is necessary to maintain the vitality of the tooth.