Quiz 2 (Prelim)

• Root development:

  • Dentin covered by cementum
  • Embedded in the alveolar bone
• Root formation begins after enamel and dentin formation has reached the future cementoenamel junction (CEJ)

  • Crown formation is completed, epithelial cells of the inner and outer enamel epithelium proliferate from the cervical loop of the enamel organ to form a double layer of cells known as Hertwig's epithelial root sheath
  • Hertwig’s epithelial root sheath (HERS) outlines the future root and is responsible for the shape, length, size, and number of roots
• The continuity of Hertwig’s epithelial root sheath must be broken in order for cementum to be deposited during tooth development
• • The cementum occurs as a thinner acellular layer around the root neck, with thicker cellular cementum covering the lower part of the root up to the apex, but there is no sharp border between these forms
• Cementogenesis:

  • After the first root dentin is deposited, the cervical portion of Hertwig's epithelial root sheath breaks down and this new dentin comes in contact with the dental sac, stimulating cells to differentiate into cementoblasts which produce cementum
  • Cementoblasts lay down organic matrix with collagenous fibers where the hydroxyapatite becomes crystallized and the cementum mineralization proceeds
  • The cementum is connected to the dentin layer by collagen fibers and with the bony alveolus by Sharpey’s fibers
• Epithelial rests of Malassez:

  • Remnants of Hertwig’s epithelial root sheath and can be found as a group of epithelial cells in the periodontal ligament
  • Some degenerate and others become calcified (cementicles)