4th Class Periodontology 2022/2023: Periodontal Ligament

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

What is the approximate width of the periodontal ligament?

Which type of cells are responsible for resorbing cementum?

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

What is the shape of the periodontal ligament space?

What is the percentage of fibroblasts in the periodontal ligament?

What is the function of epithelial rest of Malassez?

What type of cells can differentiate into functional types of connective tissue cells?

What is the role of mast cells in the body?

What is the main function of alveolar crest fibers?

What is the function of oblique group of principal fibers?

What is the composition of ground substance?

What is the function of inter-radicular fibers?

What is the main component of principal fibers?

What is the function of apical group of principal fibers?

What is the function of macrophages?

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.