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Periodontal Ligament (PDL) Structure and Function
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Periodontal Ligament (PDL) Structure and Function

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@IrresistibleTroll

Questions and Answers

What is the main function of fibroblasts in the periodontal ligament?

  • Resorption of bone
  • Formation of ground substance and collagen fibers (correct)
  • Synthesis of alkaline phosphatase
  • Formation of cellular cementum

    • What is the characteristic of periodontal ligament that enables it to replace and remodel damaged fibers?

  • Degeneration of old fibers
  • Renewal capability (correct)
  • Inflammation
  • Formation of new fibers

    • What is the primary function of osteoblasts in the periodontal ligament?

  • Formation of cellular cementum
  • Bone formation and growth (correct)
  • Formation of ground substance and collagen fibers
  • Bone resorption

    • What is the characteristic feature of osteoclasts?

    <p>Eosinophilic cytoplasm rich in acid phosphatase</p> Signup and view all the answers

    What is the function of cementoblasts in the periodontal ligament?

    <p>Formation of cellular cementum</p> Signup and view all the answers

    What is the process of bone resorption by osteoclasts?

    <p>Removal of mineral at bone margins followed by disintegration of organic matrix</p> Signup and view all the answers

    What is the characteristic feature of cementoclasts?

    <p>Resemble osteoclasts</p> Signup and view all the answers

    What percentage of cells in the periodontal ligament are fibroblasts?

    <p>65%</p> Signup and view all the answers

    Which of the following is NOT a source of arterial blood supply to the periodontal ligament?

    <p>Branches from the periosteum</p> Signup and view all the answers

    What is the primary composition of the principal fibers of the periodontal ligament?

    <p>Type I collagen fibrils</p> Signup and view all the answers

    What is the function of the small nerve fibers in the periodontal ligament?

    <p>Pain sensation</p> Signup and view all the answers

    Which of the following groups of periodontal ligament fibers is NOT mentioned as a principle fiber group?

    <p>Interdental fibers</p> Signup and view all the answers

    What is the role of Sharpey's fibers in the periodontal ligament?

    <p>They attach the principal fibers to the cementum and alveolar bone.</p> Signup and view all the answers

    What is the primary source of the nerve supply to the periodontal ligament?

    <p>Trigeminal nerve</p> Signup and view all the answers

    Which of the following statements about dental implants is TRUE?

    <p>Dental implants lack periodontal ligament fibers.</p> Signup and view all the answers

    What is the main function of the periodontal ligament?

    <p>To connect the tooth to the alveolar bone.</p> Signup and view all the answers

    What is the main function of fibroblasts in the periodontal ligament?

    <p>Both synthesize and resorb collagen fibers</p> Signup and view all the answers

    Where are progenitor cells primarily found in the periodontal ligament?

    <p>Close to blood vessels</p> Signup and view all the answers

    What do epithelial cell rests of Mallassez primarily indicate?

    <p>Remnants of the Hertwig's epithelial root sheath</p> Signup and view all the answers

    What characterizes the defensive role of macrophage cells in the periodontal ligament?

    <p>Phagocytosing dead cells and secreting growth factors</p> Signup and view all the answers

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

    <p>Mucopolysaccharides and glycoproteins</p> Signup and view all the answers

    What distinguishes cementoclasts from osteoclasts?

    <p>Cementoclasts specifically resorb cementum</p> Signup and view all the answers

    Which of the following statements about mast cells is TRUE?

    <p>They contain heparin and histamine, promoting inflammation.</p> Signup and view all the answers

    What happens to the number of epithelial cell rests of Mallassez with age?

    <p>They reduce in number</p> Signup and view all the answers

    What is the primary function of the periodontal ligament (PDL)?

    <p>To attach teeth to the jawbone</p> Signup and view all the answers

    What is the width range of the periodontal ligament?

    <p>0.15-0.38 mm</p> Signup and view all the answers

    Which type of cells in the PDL is responsible for resorption?

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

    How does the thickness of the PDL change with age?

    <p>Decreases slightly</p> Signup and view all the answers

    What type of connective tissue makes up the periodontal ligament?

    <p>Fibrous specialized connective tissue</p> Signup and view all the answers

    Which of the following is NOT a synthetic cell found in the PDL?

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

    What is the shape of the periodontal ligament?

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

    Which of the following components is NOT found in the periodontal ligament?

    <p>Muscle fibers</p> Signup and view all the answers

    Study Notes

    Periodontal Ligament (PDL)

    • The periodontal ligament is a soft, fibrous specialized connective tissue situated between the cementum and bone in the periodontal space.
    • It extends coronally up to the most apical part of connective tissue of gingiva.
    • The collagen fibers are attached to the cementum and alveolar bone, providing soft tissue continuity between the mineralized connective tissues of periodontium.
    • The PDL has the shape of an hour glass and ranges in width from 0.15-0.38mm, being thinnest in the mid-root area and decreasing slightly in thickness with age.

    Histological Structure of PDL

    • The PDL is formed from:
      • Intercellular substances
      • Synthetic fibers
      • Resorptive cells
      • Progenitor cells
      • Defensive cells
      • Blood vessels
      • Nerves and lymphatics

    Synthetic Cells

    • Fibroblasts:
      • Most common cells in PDL, constituting about 65% of total population
      • Found usually running parallel to the collagen fibers of PDL
      • Responsible for formation of ground substance and collagen fibers of PDL
      • Produce:
        • Collagen fibers
        • Reticulin fibers
        • Oxytalan fibers
      • Have the ability to replace and remodel damaged periodontal fibers (RENEWAL CAPABILITY)
    • Osteoblasts:
      • Responsible for bone formation and growth of bone tissue
      • Situated along the surface of the bone lining the dental socket
      • Synthesize collagen and ground substance of bone matrix
    • Cementoblasts:
      • Responsible for formation of cellular cementum
      • Found covering the periodontal surface of the cementum
      • Have ultrastructural characteristics typically of cells synthesizing protein

    Resorptive Cells

    • Osteoclasts:
      • Resorb bone and tend to be large and multinucleated
      • Have eosinophilic cytoplasm rich in acid phosphatase
      • Usually present in depression in bone known as Howship’s lacunae
      • Resorption occurs in two stages: removal of mineral and then exposed organic matrix disintegrates
    • Cementoclasts:
      • Resemble osteoclasts and are occasionally found in normal functioning PDL
      • Found on the surface of cementum

    Fibroblasts

    • Capable of both synthesis and resorption of collagen fibers of PDL
    • Presence of collagen-resorbing fibroblasts in a normal functioning periodontal ligament indicates resorption of fibers occurring during remodeling of periodontal ligament

    Progenitor Cells

    • Undifferentiated mesenchymal cells
    • Can undergo mitotic division
    • Can differentiate to different types of cells
    • Have small, closed-face nucleus and little amount of cytoplasm
    • Found close to blood vessels

    Epithelial Cell Rests of Mallassez

    • Remnants of Hertwig's epithelial root sheath
    • Found in the PDL close to cementum
    • Most numerous in the apical and cervical areas
    • Can undergo calcification to form cementicles

    Defensive Cells

    • Macrophage cells (Histiocytes):
      • Predominantly present in PDL
      • Embedded adjacent to blood vessels and nerves
      • Role:
        • Phagocytosing dead cells
        • Secreting growth factors that regulate the proliferation of adjacent fibroblasts
    • Mast cells:
      • Small round or oval cells containing numerous cytoplasmic granules
      • Contain heparin and histamine
      • Occasionally seen in healthy PDL
      • May cause proliferation of endothelial and mesenchymal cells

    Ground Substance and Interstitial Tissues

    • Ground substance:
      • Mainly consists of mucopolysaccharides and glycoprotein
      • Fills the space between cells, blood vessels, and nerves
    • Interstitial tissues:
      • Found between the fibers of the periodontal ligament
      • Areas that contain some of the blood vessels, lymphatic, and nerves
      • Surrounded by loose connective tissue

    Blood Supply and Nerve Supply

    • Arterial blood supply:
      • Derived from three sources: gingival vessels, intra-alveolar vessels, and apical vessels
    • Nerve supply:
      • Comes from either the inferior or superior dental nerves
      • Nerve fibers are either of large diameter (responsible for touch and pressure) or small diameter (responsible for pain sensation)

    Principle Fibers of the Periodontal Ligaments

    • The most important element of periodontal ligament
    • Principal fibers are collagenous in nature and arranged in bundles
    • Primarily composed of bundles of type I collagen fibrils
    • Vitamin C helps in formation and repair of collagen
    • Classified into several groups based on their anatomic location:
      • Alveolar crest fibers
      • Horizontal fibers
      • Oblique fibers
      • Apical fibers
      • Interradicular fibers

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    Learn about the periodontal ligament's composition, location, and role in connecting the cementum and alveolar bone in the periodontal space.

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