By Akshima Sahi, BDS, www.news-medical.net
Teeth contribute to the important functions of food mastication, swallowing, digestion, speech, and aesthetics in humans. Each tooth component serves a specific purpose.
The development of human teeth begins in the womb. Children generally have their primary tooth (deciduous tooth) eruption around 6 months of age. By the age of 12, most primary teeth have been lost and secondary teeth continue to replace those teeth until adulthood.
The human tooth is divided into three different parts:
*Crown – This is the visible portion of the tooth. It covers nearly two-thirds of the total tooth structure. The crown lies above the gums (gingiva).
*Neck- The small and narrow portion lying between the crown and root of the tooth.
*Root – It consists of one-third of the tooth and is deeply seated inside the bone supporting the tooth. This part of the tooth lies below the gums and is usually not visible in healthy teeth.
Human teeth are composed of multiple layers of both hard and soft tissue. Enamel, dentin, and cementum are harder sections, whereas pulp is the softer portion of tooth.
Enamel surrounds the crown and acts as a protective covering. It varies in thickness in different parts of the tooth. It is thickest at the cuspal region of the molars and premolars. The thinnest enamel is at the neck of the tooth.
The enamel color ranges from yellow to grayish white, and generally reflects the degree of mineralization and staining on tooth surfaces.
Composition of Enamel
Enamel is formed by the ameloblast cells and it is the hardest substance of the human body due to high percentage of mineral salts in crystalline state.
Enamel consists of 95% to 98% inorganic and 1% organic substances, with water constituting 1% to 4% of the enamel.
Inorganic substances mainly consist of calcium and phosphate ions. These combine to form a high strength hydroxyapatite crystal that allows the enamel to bear high masticatory forces.
The organic substance in teeth mainly consists of enamelin proteins.
The organic and inorganic components and water are structured systematically in enamel. A well-organized structure results in the formation of long, thin enamel rods. These enamel rods are 4 to 8 µm in diameter and number approximately 5 to 12 million per tooth. They are surrounded by the enamelins, and the space between each rod is known as interrod enamel or cement.
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