(2)

• Development of the teeth:

  • Buccopharyngeal Membrane/Oropharyngeal Membrane: union of ectodermal cells and endodermal cells at the bottom of the stomodeum or primitive oral cavity, ruptures at 4th to 5th week of fetal life, initiating tooth development at the 6th week
• Physiological Process in Tooth Growth:

  1. Induction: dental lamina and tooth bud are sites of tooth formations

  2. Proliferation: results in the increase in size of the tooth germ

  3. Histodifferentiation: formative cells of the tooth germs develop Ameloblasts (enamel) and Odontoblasts (dentin)

  4. Morphodifferentiation: establishes the form and size of the future tooth

  5. Apposition: additive growth as a result of deposition of matrix
• Distinct cell layers in the tooth germ:

  • Enamel organ: outer enamel epithelium, inner enamel epithelium, stellate reticulum
  • Dental Papilla: ectomesenchymal cells forming dentin and pulp
  • Dental Follicle/Dental Sac: ectomesenchymal cells forming cementum, periodontal ligament, and alveolar bone
• Developmental Stages Of the teeth:

  1. Initiation

  2. Bud stage

  3. Cap stage

  4. Bell stage

  5. Apposition

  6. Maturation
• Pathophysiology of Leong’s premolar:

  • Abnormal proliferation and folding of a portion of the inner enamel epithelium and subjacent ectomesenchymal cells of the dental papilla into the stellate reticulum of the enamel organ during the bell stage of tooth formation
• Hertwig’s Epithelial Root Sheath (HERS):

  • Inner and outer enamel epithelium form the cervical loop or epithelial diaphragm, elongating to become the HERS, which dictates the shape, length, and number of roots of a tooth