4th Class Periodontology 2022/2023: Periodontal Ligament

Periodontal Ligament (PDL)

• Definition: Connective tissue structure surrounding the root, connecting it to the bone
• Structure: Hourglass-shaped, narrowest at the mid-root level, approximately 0.25 mm wide

Cellular Composition

• Synthetic cells:
  • Osteoblasts: Cover periodontal surface of alveolar bone, responsible for alveolar bone formation
  • Fibroblasts (most prominent, 65%): Produce collagen fibers, reticulin fibers, oxytalan fibers, and elastin fibers; synthesize connective tissue matrix
  • Cementoblasts: Line cementum, responsible for cementum deposition
• Resorptive cells:
  • Osteoclasts: Multinucleated, resorb bone
  • Fibroblasts: Synthesize collagen, resorb and degrade old collagen fibers
  • Cementoclasts: Resorb cementum in certain circumstances
• Progenitor cells: Differentiate into functional connective tissue cells
• Epithelial rest of Malassez: Found close to cementum, can proliferate and produce cysts and tumors in certain pathologic conditions
• Connective tissue cells:
  • Mast cells: Involved in inflammatory reactions
  • Macrophages: Capable of phagocytosis

Extracellular Components

• Fibers:
  • Collagen
  • Oxytalan
• Ground substances:
  • Proteoglycans
  • Glycoproteins

Periodontal Fibers

• Principal fibers: Collagenous in nature, arranged in bundles, and follow a wavy course
• Terminal portion of principal fibers: Sharpey’s fibers, inserted into cementum and bone
• Five groups of principal fibers:
  • Alveolar crest fibers: Resist lateral movement, retain tooth in socket
  • Horizontal group: Resist axial forces, extend from cementum to alveolar bone
  • Oblique group: Resist axial forces, largest group, extending coronally from cementum to bone
  • Apical group: Prevents tooth tipping, resists luxation, protects blood, lymph, and nerve supply of the tooth
  • Inter-radicular fibers: Resist luxation, tipping, and torquing, extend from cementum of bifurcation areas to furcal bone

This quiz covers the definition, structure, and cellular composition of the periodontal ligament (PDL), a crucial connective tissue in periodontal health. Topics include the shape and width of the PDL space, and the types of cells involved.