Oral Anatomy: Gingiva and Periodontium

The Gingiva

• The gingiva is part of the oral mucosa, covering the alveolar processes of the jaws and surrounding the teeth, but not adherent to them.
• It extends to the mucogingival junction, with a varying width of 1-9 mm.
• The gingiva is divided anatomically into:
  • Marginal gingiva
  • Attached gingiva
  • Interdental areas

Marginal Gingiva

• The free gingiva is a knife-edge part of the gingiva, located coronal or above the CEJ, surrounding the tooth in a turtleneck or collar-like manner.
• It forms the soft tissue wall of the gingival sulcus.
• The gingival sulcus is a shallow crevice or space around the tooth neck, bounded by the tooth surface and epithelium lining the free margin.
• The depth of the gingival sulcus is an important clinical parameter, ideally being 0 mm, but clinically normal sulcus is 2-3 mm.

Attached Gingiva

• It is firm, resilient, and extends from the free gingival groove to the mucogingival junction.
• The width of the attached gingiva is an important clinical parameter, differing in various areas of the mouth.
• The width is greatest in the incisor area (3.5-4.5 mm) and narrower in the posterior area (1.8-1.9 mm).
• The width increases with age and in supraerupted teeth.

Interdental Gingiva

• It is the part of the gingiva filling in the embrasure beneath the contact point.
• It is either pyramidal or can have a col shape, determined by tooth contact and the width of neighboring teeth.
• It is completely missing in case of diastema.

Microscopic Features

• The gingiva is composed of:
  • Overlying stratified squamous epithelium (SSE)
  • Core of connective tissue (lamina propria)
  • A dividing line between the two, called the basement membrane
• The epithelium is joined to the underlying connective tissue by the basal lamina, which consists of lamina lucida and lamina densa.
• The basal lamina acts as a barrier to particulate matter, with a width of 300-400 A°.

Gingival Epithelium

• It consists of a continuous lining of SSE, with three different areas:
  1. The oral epithelium, extending from the gingival margin to the mucogingival junction.
  2. The sulcular epithelium, facing the tooth.
  3. The junctional epithelium, apical to the sulcular epithelium, where the gingiva is joined to the tooth.
• The principal cell type of the gingival epithelium is the keratinocyte, with other cells including Langerhans cells, Merkel cells, and melanocytes.

Gingival Epithelium Subtypes

• Oral epithelium: 0.2-0.3 mm in thickness, orthokeratinized or parakeratinized, with rete pegs.
• Sulcular epithelium: thin, non-keratinized, lacking granulosum and corneum strata, and normally having no Merkel cells.
• Junctional epithelium: 3-4 layers thick, composed of 2 strata, with a length ranging from 0.25-1.35 mm, and expressing K19.

Connective Tissue

• Mainly formed by collagen fibers (60%), fibroblasts, vessels, nerves, and matrix (35%).
• Consists of two layers:
  1. Papillary layer
  2. Reticular layer
• Has a cellular and extracellular compartment, with fibroblasts, mast cells, plasma cells, lymphocytes, and neutrophils, and a ground substance composed of proteoglycans, glycoprotein, and fibers.

Gingival Fibers

• Arranged in groups, including:
  1. Dentogingival group: originating from the cementum, extending in fan-like conformation toward the crest and outer marginal gingiva.
  2. Circular group: coursing through the connective tissue of marginal and interdental in a ring-like fashion.
  3. Transseptal group: located interproximally, forming horizontal bundles extending between the cementum of approximating teeth.
• Functions include:
  1. Bracing the marginal gingiva firmly against the tooth.
  2. Providing the rigidity necessary to withstand the forces of mastication.
  3. Uniting the free marginal gingiva with the cementum of the root and the adjacent attached gingiva.

Blood and Nerve Supply

• Blood supply is provided through three sources:
  1. Supraperiosteal arterioles
  2. Vessels of the periodontal ligament
  3. Arterioles that emerge from the crest of the interdental septa
• Nerve supply is provided by the fifth cranial nerve.

Clinical Features of Normal Gingiva

• Color: coral pink or salmon red, depending on the degree of vascularity, thickness of keratinization, and presence of pigmented cells.
• Shape: having a knife-edge with the tooth.
• Contour: normally following the contour of the tooth, but usually scalloped.
• Consistency: firm and resilient.
• Surface texture: orange-peel (stippled) appearance.
• Position: the position of the gingiva refers to the level at which the gingival margin is attached to the tooth.