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Tooth development for the embryology..


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Tooth development for the embryology..

  1. 1. Tooth Development (Odontogenesis) By: Hasu.Chaudhari
  2. 2. Dentition Primary dentition – develops during prenatal period • 20 teeth – Permanent dentition – develops as the jaw grows and matures • 32 teeth period in between – during the preteen years (mixed dentition period) –
  3. 3. TOOTH DEVELOPMENT Multiple stages:initiation stage – 6th to 7th week bud stage – 8th week cap stage – 9th to 10th weeks bell stage – 11th to 12th weeks apposition stage – varies per tooth maturation stage – varies per tooth • • • • • •
  4. 4. BUD STAGE Tooth formation  Proliferation of ectoderm lining the Alveolar Process & Epithelium become thick on convex side of this process form Dental lamina Dental lamina where tooth formation will occur - on the 1st branchial arch. Dental lamina, even apparent before the alveolar process itself is defined. Alveolar process – Semicircular in outline Similarly, Dental lamina – Curved. • • • •
  5. 5.  Dental lamina shows local thickening which results to form 1 milk tooth.  Deeper part of dental lamina enlarges to form enamel organ.  These thickening called enamel organs.  10 in number – 5 on each side of alveolar process.
  6. 6. Stages in the formation of an enamel organ & developing tooth CAP STAGE  As the enamel organ downwards into the mesenchyme its lower end forms a cup shape appearance.  Then cup occupied by mass of mesenchyme called a dental papilla.  This mesenchyme originate from neural crest cells.  Enamel organ + Dental papilla = Tooth germ.  At this stage developing tooth looks like a cap.
  7. 7. BELL STAGE  The cells of the enamel organ that line the papilla become columnar these are called ameloblasts.  Mesodermal cells of the papilla that are adjacent to the ameloblast cells arrange themselves as a continuous epithelium like layer. Cells of this layer are called Odontoblasts.  The ameloblasts & odontoblasts are separated by a basement membrane.  The remaining cells of the papilla form the pulp of tooth.  The developing tooth looks like a bell.
  8. 8. APPOSITIONAL STAGE  Ameloblasts secrete enamel on the superficial surface of the basement membrane.  The odontoblasts secretes dentine on its deeper surface.  The process of secretion of enamel & dentine is similar to that of formation of bone by osteoblasts.  Ameloblasts & odontoblasts move far away from each other by increasing layers of enamel & dentine.
  9. 9. MATURATION STAGE After the enamel is fully formed, the ameloblast disappear leaving a thin membrane, the dental cuticle, over the enamel. The odontoblasts, continue to separate the dentine from pulp throughout the life of the tooth. Alveolar part of the maxillae & the mandible are formed by ossification. As ossification progresses, roots of the teeth become surrounded by bone.
  10. 10. The root of the tooth is established by continued growth into underlying mesenchyme. Odontoblasts in this region secrete dentine (no ameloblasts cells). As layers of dentine deposited, the pulp space becomes narrower & converted into a canal through which nerves & blood vessels pass into the tooth. Dentine is covered by mesenchymal cells that differentiate into cementoblasts. These cells lay down a layer of dense bone called Cementum. Mesenchymal cells form a periodontal ligament which connects the root with the socket in the jaw bone.
  11. 11. Formation of permanent tooth  The dental lamina gives off a series of buds, one of which lies on the medial side of each developing milk tooth.  These buds form the enamel organs.  They give rise to permanent incisors, canines & premolars. The permanent molars are formed from buds that arise from the dental lamina posterior to the region of last milk tooth.
  12. 12. Dental lamina is established in the 6th week of intrauterine life. The germ of 3rd molar is formed after birth & germ of premolar & 2nd molar are not very developed & rest of all show considerable development at birth. The developing tooth germs undergo calcification (accumulation of calcium salts in a body tissue). All the temporary teeth & permanent lower 1st molar begin to calcify before birth. The permanent teeth begin to calcify at varying ages after birth.
  13. 13. Anomalies of teeth 1. Anodentia :- one or more teeth may be absent or complete absence.
  14. 14. Supernumerary teeth may be present
  15. 15. Gemination :- Two or more teeth may be fused to each other.
  16. 16. Malocclusion :- Alignment of the upper & the lower teeth may be incorrect.
  17. 17. The End :D