Periodontal Structures and Components Quiz

Periodontal Structures and Components

• Gingiva: A protective barrier against mechanical forces and immune defense. It's pink, keratinized, and exhibits a stippled appearance in healthy individuals.

  • Free gingiva: Surrounds the tooth crown.
  • Attached gingiva: Anchored to the bone and cementum.
  • Interdental gingiva (papilla): Fills the space between teeth.

• Periodontal Ligament (PDL): Acts as a shock absorber, providing sensory and proprioceptive function. Maintains homeostasis through fibroblast activity.

  • Fiber Groups: Alveolar crest, horizontal, oblique, apical fibers (resist various tooth movements) and interradicular fibers (multi-rooted teeth).

• Cementum: Anchors PDL fibers to the root surface. Compensates for tooth wear through continuous deposition occurring in layers.

  • Acellular cementum: Majority of attachment in the cervical region.
  • Cellular cementum: Contains cementocytes and found in the apical third and furcation areas.

• Alveolar Bone: Provides structural support to teeth and has continuous remodeling responding to forces.

  • Alveolar Bone Proper (Lamina Dura): Thin compact bone lining the tooth socket.
  • Cortical bone: Outer layer of dense bone defining the bone contour.
  • Cancellous bone: Spongy bone between cortical layers. More abundant in the maxilla.

Gingival Epithelium

• Types:

  • Oral epithelium: Keratinized for protection, four layers: stratum corneum, stratum granulosum, stratum spinosum, and stratum basale.
  • Sulcular epithelium: Non-keratinized, lines the gingival sulcus.
  • Junctional epithelium: Non-keratinized, directly attached to the tooth; more permeable, high turnover.

• Cellular Elements:

  • Keratinocytes: Primary cells producing keratin.
  • Non-keratinocytes:
    • Melanocytes: Produce melanin.
    • Langerhans cells: Antigen-presenting cells.
    • Merkel cells: Involved in mechanoreception.
    • Inflammatory cells: Participate in the immune response.

• Cell Junctions:

  • Desmosomes: Attach epithelial cells.
  • Hemidesmosomes: Anchor cells to the basement membrane.
  • Basement membrane: Composed of lamina lucida and lamina densa; connects epithelium to connective tissue.

Extracellular Matrix (ECM)

• Components:

  • Collagen: Provides tensile strength and integrity.
  • Elastin: Contributions to tissue elasticity.
  • Proteoglycans: Regulate hydration and signaling.
  • Glycosaminoglycans (GAGs): Maintain tissue hydration and flexibility.
  • Fibronectin & Laminin: Facilitate cell adhesion and migration.

• GAGs and Proteoglycans: GAGs (linear polysaccharides) bind to proteins (proteoglycans) influencing hydration and signaling.

  • Major Types of GAGs: Hyaluronic acid, dermatan sulfate, chondroitin sulfate, heparan sulfate, and keratan sulfate.

• Collagen: Essential structural component (approx. 30% of total protein). In periodontium, type I (tensile resistance in gingiva, bone, cementum, PDL), type III (gingival CT integrity), type IV (basement membranes), and type V (connective tissues, cementum) are key.

Bone Remodeling and Collagen

• Bone Remodeling: Bone undergoes continuous remodeling in response to mechanical forces and maintenance homeostasis.

  • Phases: Resting, resorption (osteoclasts degrade matrix), reversal (prep for new matrix), formation (osteoblasts build matrix → mineralization).

• Regulation:

  • RANKL/OPG: RANKL stimulates osteoclasts, OPG blocks RANKL, influencing bone resorption.
  • TGF-β & BMPs: Stimulate bone formation.

• Periodontal Disease's Impact: Inflammation (periodontitis) leads to excessive RANKL activation → prolonged osteoclast activity → bone loss. Pro-inflammatory cytokines accelerate osteoclastogenesis, harming the balance between resorption and formation.