Histology and embryology / José F. Nonidez.

  • Nonidez, José F. (José Fernandez), 1892-1947.
Date:
1941
Catalogue details

Licence: In copyright

Credit: Histology and embryology / José F. Nonidez. Source: Wellcome Collection.

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    THE TEETH V. The Teeth A tooth consists of a crown, projecting above the gum, and a root or roots imbedded in the dental alveolus. The bulk of the tooth is composed of dentine which in the crown is covered by the enamel and in the root by the cementum. The tooth is hollow. Its central cavity (pulp chamber) is occupied by a soft connective tissue (den- tal pulp); the cavity extends throughout the root as the root canal. A. Enamel. It is the hardest substance of the body, and it is mostly inorganic matter. It is made up of very slender rod-like columns (enamel prisms) cemented together; the prisms are grouped into bundles, but the latter are not parallel. It is thickest over the crown and gradually decreases in thickness until the neck of the tooth is reached, where it stops. B. Dentine. It is somewhat harder than bone, but it differs from the latter in that it lacks cells, although it contains canaliculae (dentinal canals). Blood vessels are absent. 1. Dentinal canals. They begin at the dental pulp and pass out- ward radially. They are more or less parallel, but they describe an S-shaped curve and, in addition, they are twisted spirally. The canals give off minute branches which anastomose with similar branches from other canals. They contain prolongations of the odontoblasts (see below). 2. Ground substance. This occupies the spaces between the den- tinal canals and contains systems of very thin collagenous fibrils arranged in bundles; their general direction is parallel to the long axis of the tooth (i.e. perpendicular to the dentinal canals). They correspond to the fine collagenous fibrils of the bone matrix (p. 16). The ground substance is calcified. C. Cementum. Like bone tissue it contains lacunae and osteocytes, which are irregularly distributed and may not occur in considerable areas. Canaliculae radiating from the lacunae are also present. Sharpey fibers (p. 17) enter the cementum, which is non-vascular. D. Peridental (periodontal) membrane. Is a layer of dense fibrous connective tissue which surrounds the root of the tooth and fills the space between it and the alveolus. It serves to attach the tooth to the walls of the alveolus. E. Dental pulp. Fills the pulp cavity. It contains the odontoblasts and an embryonic or poorly differentiated form of connective tissue. [55]