Structure of Tooth

Anatomical tooth consists of mainly two parts. The part which is visible in the oral cavity is called crown. And the rest which is embedded in the gum and bone of the jaw is called root. The crown of different tooth may vary in shape and size. The root may be single as it is in the incisors and the canines or they may be multiple as it is in the molars. The part of the root area immediately adjacent to the crown is called the neck of the tooth.

The tooth enamel is a protective tooth structure that covers the exposed part of tooth; crown. It is the hardest of the parts of the tooth and also the hardest of all the tissues of human body. It is a highly mineralized structure. It is thickest over the cusps of molars and incisal edge of incisors. It thins down to a knife edge at the cervical margin. Enamel dissolves in acid media. Inorganic substances forms the main constituent of enamel. The inorganic element is composed of apatite molecules, chiefly hydroxyapatite. Calcium and phosphorus [Ca10(OH)2(PO4)6] form the major constituent of enamel.

Beneath the enamel (and sometimes exposed to the surface if the enamel is missing or worn away) is an intermediate layer of tissues which forms the main mass of tooth is called Dentin. It is also similar to bone but not nearly as hard as enamel. It supports the tooth enamel and absorbs the pressure of mastication. The dentin consists of number of micro-fibers embedded in a dense homogeneous matrix of collagenous protein.

Cementum covers the anatomical root outside the dentin (under the gum line) and it is attached to the bone of the jaw with little elastic fibers(Periodontal Ligaments). Cementum is hard as bone but not as hard as the tooth enamel. The cementum also consists of organic and inorganic matter. Some of the functions of cementum are: 1. It attaches one end of the periodontal ligament and helps to keep the tooth in the socket. 2. It protects root surface from injury and resorption by continuous formation. It repairs any defect in the root. 3. Helps eruption by apposition which compensates for occlusal wear.4. Helps to maintain width of the periodontal ligament.

Inside the dentin there is a cavity called pulp cavity which is filled with pulp. The pulp cavity in the crown area is called the pulp chamber and in the root portion it is known as the pulp canal or the root canal. Dental pulp is found inside the pulp chamber and the root canal. It is a soft connective tissue containing nerves and blood vessels that nourish the tooth. It is the most internal structure of tooth. The nerve fibers and the blood vessels enter into the tooth through an opening called apical foramen. The major functions of pulp are 1. Formative: formation of dentin 2. Sensory: the sensation of tooth is felt through the nerves of the pulp. 3. Nutritive: It supplies nutrition to the dentin through blood vessels and maintain vitality of tooth.4. Defensive: Pulp protect itself and the vitality of the tooth by producing secondary dentin.