Easy Dentistry Lecture Notes: Oral Mucous Membrane Part 4

Introduction

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• Today's focus: Gingival Sulcus and Dentogenival Junction.
• Recommended to review Parts 1-3 for foundational knowledge.

Gingival Sulcus

• Definition: Narrow space between inner aspect of gingiva and tooth, also known as gingival crevice.
• Extension: From upper border of free gingiva to dento-gingival junction.
• Structure:
  • Surrounded by circular epithelium.
  • The epithelium in the sulcus is termed sulcular epithelium, attached to the tooth by junctional epithelium.
  • All three types of epithelium (gingival, circular, and junctional) share a common basal lamina.
• Microscopic Features:
  • Non-keratinized, thin epithelium without ridges (straight interaction with connective tissue).
• Depth:
  • Average depth: 0.5 to 1.8 mm (typically around 2 mm).
  • Deepens in periodontal infections.

Dentogenival Junction

• Definition: Junction between tooth and gingiva, where junctional epithelium attaches to the tooth surface (about 2 mm).
• Structure:
  • Made of a single layer of basal cells lined with flatulent cells.
  • Presence of intercellular spaces:
    • Disadvantage: Allows bacteria and toxins to enter, increasing infection risk.
    • Advantage: Facilitates migration of immune cells (neutrophils, macrophages, Langerhans cells) from connective tissue.
• Development of Junction:
  • Follows the eruption of teeth.
  • The reduced enamel epithelium protects the enamel before the tooth erupts.
• Stages of Eruption:
  • Active Eruption: Movement of the tooth towards the occlusal plane.
  • Passive Eruption: Separation of the primary attachment epithelium from the tooth after reaching the occlusal plane.

Stages of Dento-Gingival Junction Shift

1. Stage 1: Gingival sulcus on enamel, attachment epithelium at cemento-enamel junction. Seen in primary teeth and early permanent teeth.
2. Stage 2: Sulcus remains on enamel; apical end of attachment is partly on cementum and enamel.
3. Stage 3: Sulcus shifts to the CEJ; attachment entirely on cementum (slow process).
4. Stage 4: Recession of gingiva occurs; attachment is entirely on cementum (common in older age).

Anatomic vs Clinical Crown

• Anatomic Crown: The part of the tooth covered by enamel.
• Clinical Crown: The visible part of the tooth in the oral cavity (usually smaller due to free gingiva).
• Pathological Conditions:
  • Stages 1 and 2: Clinical crown < Anatomic crown (physiological).
  • Stage 3: Clinical crown = Anatomic crown (pathological).
  • Stage 4: Clinical crown > Anatomic crown (pathological).

Conclusion

• Completion of oral mucous membrane chapter.
• Next lecture topic: Cementum.
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