tooth development


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tooth development

  1. 1. Structure of the Oral Tissues & Tooth Development I
  2. 2.  Tooth function:  Mastication.  Speech.  Esthetic.  Tooth consists of:  Enamel.  Dentin.  Pulp.  Cementum.
  3. 3. Tooth Attachments:  Cementum.  PDL.  Alveolar bone.  Gingiva.
  4. 4.  The entire primary dentition is initiated between 6 and 8 weeks of embryonic development.  The successional permanent teeth between week 20 in utero and 10 months after birth; and the permanent molars between week 20 in utero (first molar) and 5 years of age (third molar).
  5. 5. Primary Epithelial Band  a continuous band of thickened epithelium forms around the mouth in the presumptive upper and lower jaws. These bands are roughly horseshoe-shaped and correspond in position to the future dental arches  Each band of epithelium will give rise to 2 sub divisions: 1. Dental lamina 2. Vestibular lamina
  6. 6. DENTAL LAMINA  continued and localized proliferative activity leads to the formation of a series of epithelial outgrowths into the mesenchyme at sites corresponding to the positions of the future deciduous teeth
  7. 7. A. Bud Stage B. Cap Stage C. Bell Stage D and E. Dentinogenesis and amelogenesis F. Crown formation G. Root Formation and eruption H. Function
  8. 8. Characterized by:  First incursion into the ecto-mesenchyme of the jaw.  Little change of the shape and function of epithelial cells  Condensation of ecto-mesenchyme.
  9. 9. Bud stage is characterized by rounded, localized growth of epithelium surrounded by proliferating mesenchymal cells, which are packed closely beneath and around the epithelial buds
  10. 10. In the bud stage, the enamel organ consists of peripherally located low columnar cells and centrally located polygonal cells
  11. 11. Characterized by: 1. Tooth bud is separated from the dental lamina by lateral lamina. 2. Tooth germ will be called enamel organ. 3. Enamel niche, enamel knot, enamel cord, and stellate reticulum. 4. Dental papilla  pulp and dentin. 5. Dental follicle or sac  PDL and cementum. 6. Dental organ consists of (enamel organ, dental papilla, and dental follicle). 7. Histodifferentiation.
  12. 12. V.L.
  13. 13. Condensation of the ectomesenchyme immediately subjacent to the tooth bud caused by lack of extracellular matrix secretion by the cells thus preventing separation. Histodifferentiation begins at the end of cap stage.
  14. 14. Epithelial outgrowth called Enamel Organ because it will eventually form the enamel Dental Papilla: Ball of condensed ectomesenchymal cells (it will form dentin and pulp). The peripheral cells adjacent to the inner dental epithelium will enlarge and later differentiate into odontoblasts
  15. 15. Dental follicle or dental sac is the condensed ectomesenchymal tissue surrounding the enamel organ and dental papilla. This gives rise to cementum and the periodontal ligament (support structures for tooth) Enamel Organ Enamel Knot Dental Papilla
  16. 16. Enamel niche: It is an artifact produced during sectioning of the tissue. It occurs because the enamel organ is a sheet of proliferating cells rather than a single strand and contains a concavity filled with ectomesenchyme dental lamina lip furrow vestibular lamina enamel niche
  17. 17. Enamel Knot: Densely packed accumulation of cells projecting from the inner enamel epithelium into dental papilla. Exact role not known, but currently believed to be the organizational center for cusp development.
  18. 18. Continued growth leads to bell stage, where the enamel organ resembles a bell with deepening of the epithelium over the dental papilla Continuation of histodifferentiation (ameloblasts and odontoblasts are defined) and beginning of morphodifferentiation (tooth crown assumes its final shape)  It can be divided into: 1. Early bell stage. 2. Late or advance bell stage.
  19. 19. Stellate reticulum: Star-shaped cells with processes, present between the outer and the inner dental epithelium. They have a cushion-like consistency that may support and protect the delicate enamel organ. Outer Enamel Epithelium Stellate reticulum Stratum intermedium Inner Enamel epithelium Dental papilla
  20. 20. Stratum intermedium: Cell layer between the inner dental epithelium and stellate reticulum which have high alkaline phosphatase activity. They assist inner enamel epithelium (ameloblasts) to form enamel. A - dental papilla B - inner enamel epithelial cells C - outer enamel epithelium D - stellate reticulum E - stratum intermedium F - odontoblasts
  21. 21. Cervical loop: Area where the inner and the outer dental epithelium meet at the rim of the enamel organ. This point is where the cells will continue to divide until the tooth crown attains its full size and which after crown formation will give rise to the epithelium for root formation.
  22. 22. You must remember the following:  Hard tissue formation starts at the late stages of the bell stage  Differentiation of cells into odontoblasts and ameloblasts  Dentin is formed before enamel  Dentin initiates the formation of enamel