Histology of Tooth T Y B Sc Semester

Histology of Tooth T. Y. B. Sc. Semester III, Paper No. II BY. DR. S. B. PATIL HEAD DEPARTMENT OF ZOOLOGY HUTATMA RAJGURU MAHAVIDYALAYA, RAJGURUNAGAR.

Histology of Tooth Teeth are the efficient masticatory organs which are the derivatives of integument. They arise by the Calcification of mucous membrane of buccal cavity along the margin of jaws. Typically the tooth is distinguished into crown, neck and root. It is rooted in the socket over the jaw bones. 1) Root: It is that part of the tooth which is in the bony socket or alveolus. 2)Neck: It is that part of the tooth which is above the root but inside the gum. 3)Crown: It is the distal part of the tooth which projects out of the jaws in the mouth cavity and is white gilstening in appearance.

The verticle section of the tooth shows following histological parts. a) Pulp cavity b) Dentine c) Cement d) Enamel a)Pulp cavity: At the center of tooth there is a pulp canal called pulp cavity which contains a mass of cells , blood vessels and nerves enter the pulp canal through the apical foramen which is located at the apex of the root.

The dental pulp consists of connective tissue with many spindle shaped and star shaped cells, delicate collagen fibres. The nerve fibres are partly sensory and partly sympathetic. The pulp cavity is lined by two layers of cells in the development stages. 1) Odontoblast layer 2) Ameloblast layer Odontoblast are dentine forming cells where as ameloblast are enamel forming cells. Both these layers lay down layer upon layer of dentine and enamel respectively and thus, the two layers in full grown tooth are separated from each other. Ultimately ameloblasts come to line the external aspect of the enamel and are removed by surface friction after the tooth erupts. The odontoblasts remain as lining for the pulp cavity. The cytoplasmic processes are seen to be extended from the cells into the dentical tubules. Function of Pulp: It is sensation and nurishment

b) Dentine: Dentine is a hard material similar to bone surronding the pulp cavity. It gives strength to the tooth and forms the bulk of the tooth. The dentine layer is formed by the odontoblasts and consists of calcified grond substance ( calcium carbonate) with number of collagen fibres and 70% amorphous salts and the inorganic salts. There are numerous fine canaliculi passing radially from the palp cavity towards the enamel or cement called dental tubules. The tubules get branched near enamel – dentine junction. Some tubules even enter into the enamel as enamel spindles. Each dentinal tubule contains a protoplasmic process of odontoblast. At the junction of dentine with the pulp cavity, there is a layer of predentine which is not mineralized mantle dentine. The main part of dentine between predentine and mantal dentine is called the circum pulpal dentine. Dentine formed before eruption of the tooth is called primary dentine, while that formed after eruption is known as secondary dentine.

c) Cement: It is the bony material surronding the dentine and root of the tooth. It is distinguished into acellular part of cement and cellular part of cement. The cellular part of cement has cementocytes similar to osteocytes situated into the lacunae. Cement is covered by fibrous membrane called periodontal membrane or peristeum of the cement. The membrane is formed of collagen fibres which fix the toothin its socket. It contains numerous nerve ending that provide sensory information. d) Enamel: It is partly dead matter and the hardest material in the body. It covers the dentine as white and glistening crown. It is made up of 96% of inorganic salts. The salts are mainly in the form of crystals. The crystals contain calcium phosphate and calcium carbonate. The crystals are arranged in the form of rod shaped prisms. Prisms are separated by interprismatic material. Dentine tubules may extend into the enamel forming enamel spindles. There are increment lines of Retzius on the surface of enamel. The enamel crown morphologically differ as to suit feeding habit. Incisor tooth has a sharp. Cutting edge. The canines have a pointed crown for tearing The molars have a crown consisting of elevations called Cusps for grinding purpose. Thus, enamelcrowns are modified for efficiant mastication.

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