Periodontal Ligament Chapter
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Questions and Answers

During the initial stages of root formation, which cells of the follicle differentiate into cementoblasts?

  • Outermost cells
  • Innermost cells (correct)
  • Centrally located cells
  • Fibroblasts

    • What is the direction of the developing fibers of the periodontal ligament initially?

  • Horizontal direction
  • Coronal direction (correct)
  • Oblique direction
  • Apical direction

    • What is the name of the fibers present in the cementum and alveolar bone?

  • Sharpey’s fibers (correct)
  • Periodontal ligament fibers
  • Principal fibers
  • Dentoalveolar fibers

    • Which group of fibers is located near the cervical region?

    <p>Alveolar crest group</p> Signup and view all the answers

    What is the function of fibroblasts in the periodontal ligament?

    <p>Production of periodontal ligament fibers</p> Signup and view all the answers

    During root formation, which cells of the follicle differentiate into osteoblasts?

    <p>Outermost cells</p> Signup and view all the answers

    How many groups of principal fibers are there in the periodontal ligament?

    <p>5</p> Signup and view all the answers

    What is the primary function of the periodontal ligament?

    <p>To connect the cementum of the root to the alveolar bone proper</p> Signup and view all the answers

    What is the characteristic of the width of the periodontal ligament with age?

    <p>It shows a progressive decrease with age</p> Signup and view all the answers

    What is the type of cells present in the periodontal ligament?

    <p>Mesenchymal cells</p> Signup and view all the answers

    What is the function of fibroblasts in the periodontal ligament?

    <p>To form cementum and alveolar bone</p> Signup and view all the answers

    What is the thinnest portion of the periodontal ligament located?

    <p>Near the middle of the root</p> Signup and view all the answers

    What is the function of the factors secreted by PDL fibroblasts?

    <p>To inhibit ankylosis of the tooth and prevent mineralization</p> Signup and view all the answers

    How many functions of the periodontal ligament are mentioned in the text?

    <p>5</p> Signup and view all the answers

    Which group of fibers has the greatest number of fiber bundles and performs the main support of the tooth against masticatory force?

    <p>Oblique group</p> Signup and view all the answers

    What is the direction of the fiber bundles in the Horizontal group?

    <p>At right angle to the long axis of the tooth</p> Signup and view all the answers

    Which group of fibers extends from the cervical cementum of one tooth to the cervical cementum of another?

    <p>Transseptal fibres</p> Signup and view all the answers

    What is the origin of the fiber bundles in the Apical group?

    <p>Apical region of the root</p> Signup and view all the answers

    Which group of fibers attaches itself to the cervical part of the cementum and radiates from the alveolar crest?

    <p>Alveolar crest group</p> Signup and view all the answers

    What is the direction of the fiber bundles in the Oblique group?

    <p>Oblique to the long axis of the tooth</p> Signup and view all the answers

    Which group of fibers is the most numerous and extends from the cervical cementum to the lamina propria of the gingiva?

    <p>Dentogingival group</p> Signup and view all the answers

    What is the primary function of the periodontal ligament?

    <p>Supportive function, including shock absorption and transmission of occlusal forces</p> Signup and view all the answers

    What is the composition of the ground substance in the periodontal ligament?

    <p>70% water, 20% glycosaminoglycans, and 10% proteoglycans</p> Signup and view all the answers

    What type of fibers make up the majority of the periodontal ligament?

    <p>Type I collagenous fibers</p> Signup and view all the answers

    What is the function of the interstitial spaces in the periodontal ligament?

    <p>To contain blood vessels, lymph channels, and nerves</p> Signup and view all the answers

    What is the role of fibroblasts in the periodontal ligament?

    <p>To produce ground substance and fibers</p> Signup and view all the answers

    What is the result of aging on the periodontal ligament?

    <p>Decreased vascularity and cell thickness</p> Signup and view all the answers

    What type of cells are involved in the resorption of bone and cementum in the periodontal ligament?

    <p>Osteoclasts and cementoclasts</p> Signup and view all the answers

    What is the role of the epithelial root sheath of Hertwig in the periodontal ligament?

    <p>To produce remnants of the epithelial root sheath</p> Signup and view all the answers

    What is the function of the periodontal ligament in relation to the eruption of teeth?

    <p>To facilitate the eruption of teeth</p> Signup and view all the answers

    What is the composition of the proteoglycans in the ground substance of the periodontal ligament?

    <p>Dermatan sulphates and chondroitin sulphates</p> Signup and view all the answers

    Study Notes

    Development of PDL

    • During the initial stages of root formation, follicular cells show increased proliferation.
    • Innermost cells of the follicle differentiate into cementoblasts, while outermost cells differentiate into osteoblasts.
    • Centrally located cells differentiate into fibroblasts, which produce periodontal ligament fibers.
    • These fibers get embedded in the developing cementum and alveolar bone.
    • Initially, all developing fibers of the periodontal ligament run obliquely in a coronal direction from tooth to bone.
    • The part of PDL fibers present in the cementum and alveolar bone are called Sharpey's fibers.

    Structure of Periodontal Ligament

    • The fibre bundles that exit the cementum and alveolar bone and form the periodontal ligament are called principal fibres.
    • Principal fibres are grouped into:
      • Alveolar crest group (near the cervical region)
      • Horizontal fibre group (near the midroot)
      • Oblique fibre group (immediately above apical group)
      • Apical fibre group (near the apical area of the root)
      • Interradicular group (between two roots)
    • Gingival fibre group includes:
      • Dentogingival group (extending from the cervical cementum to the lamina propria of the gingiva)
      • Alveologingival group (extending from the alveolar crest to the lamina propria of the gingiva)
      • Circular or Circumferential fibres (continuous around the neck of the tooth)
      • Transseptal fibres (extending from the cervical cementum of one tooth to the cervical cementum of the other)

    Histology of Periodontal Ligament

    • The periodontal ligament consists of:
      • Cells (synthetic, resorptive, progenitor, defensive, and epithelial cells)
      • Fibers (collagenous, reticulin, and elastic fibers)
      • Ground substance (water, glycosaminoglycans, proteoglycans, and glycoproteins)
      • Intercellular substances (blood vessels, nerves, and lymphatics)

    Functions of PDL

    • Formative
    • Supportive
    • Protective
    • Sensory
    • Nutritive
    • Functions of PDL fibers include:
      • Supportive (shock absorption and transmission of occlusal forces)
      • Sensory
      • Nutritive
      • Homeostatic
      • Eruptive

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    Description

    Learn about the development process, structure, and histology of periodontal ligament. Understand the connective tissue that connects the cementum of the root to the alveolar bone proper. Test your knowledge on the introduction, development, structure, and histology of periodontal ligament.

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