root formation tooth development
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root formation tooth development

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root formation tooth development root formation tooth development Presentation Transcript

  • Root Formation
  • Objectives At the end of this lecture the student should be able to understand the process of root formation.,. including the role and function of the root sheath . Sub topics • Topic 1. Root sheath development • Topic 2. Formation of root • Topic 3. Fate of epithelial root sheath
  • 1 Root sheath development  The root starts to develop after the crown is completed  Epithelial cells of the inner and outer enamel epithelium proliferate from the cervical loop to form two layers of epithelium called Hertwig’s root sheath  The first formed part of the root sheath bends to form a disc like structure  The rim of this disc like structure is called the epithelial diaphragm  The epithelial diaphragm encloses the primary apical foramen
  • 2 Formation of Root • After the formation of epithelial root sheath and the epithelial diaphragm the root grows in length • The diaphragm maintains a constant size while the root sheath grows in length at the angle of the diaphragm and not at its tip • The cells of the lengthening root sheath induce the adjacent dental papilla cells to differentiate into odontoblasts • The newly formed odontoblasts then form the root dentine • As the root lengthens the crown moves occlusally
  • Single roots and multiple roots • For single-rooted teeth the root sheath grows like a cuff or tube around the newly forming pulp • Development of multi-rooted teeth takes place in a same manner until the furcation area. • When the furcation area is reached the epithelial diaphragm develops tongue like extensions that grow until they contact each other • This the divides the root into two or three
  • Root formation anomalies • If the continuity of the root sheath is broken before the dentine is formed it results in missing or abnormal epithelial cells • When the epithelial cells are missing the Odontoblasts do not differentiate and dentine doesn’t form opposite the defect that occurred in the root sheath • The result will be a small lateral canal. This lateral canal is also called as supplemental canal or accessory canal • Accessory canals connect the main root canal with the periodontal ligament
  • • If the epithelial root sheath does not degenerate at the proper time and remain stuck to the surface of the root dentine, then that area becomes devoid of cementum • Areas of root without cementum can be a cause of sensitivity if the there is gingival recession
  • 3 Fate of epithelial root sheath • After dentine formation in root takes place, the epithelial root sheath breaks down and its remnants migrate away from the dentinal surface • They lie in the periodontal ligament and are called epithelial rests of Malassez • The epithelial rests of Malassez are found the in the periodontal ligament through out the life • Sometimes when there is chronic inflammation the epithelial cell rest of Malassez proliferate into cysts and tumours