The dentine forms the main bulk, or core, of each tooth and extends almost the entire length of the tooth, being covered by enamel on the crown portion and by cementum on the roots. The middle layer of the tooth is composed of dentine, which is less hard than enamel and similar in composition to bone. In mammals an outer layer of enamel, which is wholly inorganic and is the hardest tissue in the body, covers part or all of the crown of the tooth. The structure of teethĪll true teeth have the same general structure and consist of three layers. The shape of the crown and root vary among different teeth and among different species of animals. The “neck” of the root is embraced by the fleshy gum tissue (a specialized area of connective tissue covered with mucous membrane that lines the mouth cavity). The root is attached to the tooth-bearing bone-the alveolar processes-of the jaws by a fibrous ligament called the periodontal ligament or membrane. The root is the unseen portion that supports and fastens the tooth in the jawbone. The crown is the functional part that is visible above the gum. A tooth consists of a crown and one or more roots. The teeth of vertebrates represent the modified descendants of bony dermal (skin) plates that armoured ancestral fishes. Teeth are used for catching and masticating food, for defense, and for other specialized purposes. Tooth, plural teeth, any of the hard, resistant structures occurring on the jaws and in or around the mouth and pharynx areas of vertebrates. SpaceNext50 Britannica presents SpaceNext50, From the race to the Moon to space stewardship, we explore a wide range of subjects that feed our curiosity about space!.Learn about the major environmental problems facing our planet and what can be done about them! Saving Earth Britannica Presents Earth’s To-Do List for the 21st Century.Britannica Beyond We’ve created a new place where questions are at the center of learning.100 Women Britannica celebrates the centennial of the Nineteenth Amendment, highlighting suffragists and history-making politicians.
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