Gingival Anatomy and Physiology Quiz

Periodontology

• Periodontology is the study of the periodontium, a specialized system of hard and soft tissues supporting the teeth and maintaining their position.

Tissues of the Periodontium

• Gingiva
• Cementum
• Periodontal ligament
• Alveolar bone

The Normal Periodontium

• The supporting apparatus of the teeth, attaching the tooth to the bone and providing support needed for tooth function.

Gingiva

• Covers the alveolar bone and tooth root to a level just coronal to the cementoenamel junction (CEJ).
• Protects the underlying tissues of the periodontium (bone and periodontal ligament) from the oral environment.
• Includes alveolar mucosa, mucogingival junction, attached gingiva, marginal gingiva, and interdental gingiva.

Oral Mucosa

• The moist lining of the oral cavity.
• Comprised of masticatory, lining, and specialized mucosa.
• Masticatory mucosa covers the hard palate and gingiva (part of oral mucosa covering alveolar processes and surrounds the necks of the teeth).
• Specialized mucosa covers the dorsum of the tongue.
• Lining mucosa is loosely attached to underlying structures and covered with non-keratinized epithelium (lips, cheeks, floor of the mouth).

Gingival Defense Mechanisms

• Cell turnover and surface shedding (desquamation)
• Anatomical epithelial seal
• Gingival fluid containing defensive components

Gingiva - Macroscopic Anatomy

• Free gingiva
• Interdental gingiva
• Attached gingiva

Free (Marginal) Gingiva

• The terminal edge or border of the gingiva surrounding the teeth neck in a collar-like fashion.
• 1-3 mm wide.
• Demarcated from adjacent attached gingiva by a shallow linear depression called the free gingival groove.

Free Gingival Groove

• A shallow crevice or space around the tooth.
• V-shaped and barely permits the entrance of a periodontal probe.
• Depth in healthy humans is 0-3 mm.

Interdental Gingiva

• Occupies the gingival embrasure (interproximal space beneath the area of tooth contact).
• Shape can be pyramidal or tent-shaped.
• Anterior teeth have a pyramidal shape, molar papillae are flattened in buccolingual direction (tent-shaped).

Col Region

• Valley-like depression that connects facial and lingual papillae, conforming to the shape of the interproximal contact in teeth with contact surfaces.
• In the presence of diastema, the interdental gingiva is flat or rounded.
• Covered by non-keratinized epithelium.

Attached Gingiva

• Continuous with marginal gingiva.
• Firm, resilient, and tightly bound to the underlying periosteum of the alveolar bone.
• Extends to the relatively loose and movable alveolar mucosa; it is demarcated by the mucogingival junction
• Surface is stippled like orange peel.
• Width, generally greatest in incisor region (3.5-4.5 mm in maxilla, 3.3-3.9 mm in mandible) and narrower in posterior segments (1.9 mm in maxilla, 1.8 mm in mandible).

Alveolar Mucosa

• Separated from periosteum by a loose, highly vascular connective tissue.
• Relatively loose and mobile tissue; deep red in contrast to the pale pink attached gingiva.

Clinical Criteria of Normal/Inflamed Gingiva

• Normal:*
• Color: pale pink
• Form: knife-edged
• Contour: festooned appearance
• Consistency: firm, resilient
• Sulcular depth: 0-3 mm
• Probing should not cause bleeding
• Inflamed:*
• Color: reddish
• Form: blunt-edged
• Contour: Loss of festooned appearance
• Consistency: edematous, spongy, and friable

Microscopic Features

• Gingival epithelium: stratified squamous epithelium.
• Oral (outer) epithelium: keratinized and extends from the mucogingival junction to the gingival margin.
• Sulcular epithelium: thin non-keratinized stratified squamous epithelium without rete pegs, coronal limit of junctional epithelium.
• Junctional epithelium: collar-like band of stratified squamous non-keratinizing epithelium located at the CEJ in healthy tissue.
• 10-30 cells thick coronally and 1-2 cells apically.
• Turnover: 1-6 days.
• Larger intercellular spaces.

Gingival Crevicular Fluid (GCF)

• Physiological fluid (transudate in normal conditions) and inflammatory exudate (in inflammation), originating from the gingival plexus of blood vessels in the gingival corium, adjacent to the epithelium lining of the dentogingival space.

Periodontal Ligament

• Connective tissue (complex vascular and highly cellular) surrounding the root, connecting it to the bone.
• Continuous with connective tissue of gingiva; communicates with marrow spaces through vascular channels in the bone.
• Average width: ~0.2 mm.
• Principal Fibers (Type I & III mainly collagen):
• Alveolar crest group: prevent extrusion and resist lateral tooth movements.
• Horizontal group: run from cementum to bone at right angles to tooth.
• Oblique group: run obliquely from cementum to bone; main support against masticatory force.
• Apical group: radiate from apical region of root to surrounding bone.
• Interradicular group: radiate from interradicular septum to furcation of multirooted teeth.
• Accessory Fibers: collagenous, run from bone to cementum in different planes to prevent tooth rotation; found in horizontal region.
• Oxytalan fibers: immature form of elastic fibers that play a part in supporting blood vessels.

Alveolar Bone

• Formed by intramembranous ossification during fetal growth.
• Consists of a calcified matrix with osteocytes enclosed in lacunae.

Cribriform Plate (Lamina Dura)

• Radiographically called lamina dura; dense radiopaque appearance
• Socket wall / alveolar bone proper; compact bone lining the tooth socket.

Supporting Alveolar Bone

• Alveolar Bone Proper: formed of compact bone
• Lamina Dura
• Supporting Alveolar Bone
• Cortical Plate
• Cancellous
• Interproximal Bone (Interdental Septum, Interradicular Bone, and Radicular Bone)

Periosteum and Endosteum

• Periosteum covers all bone surfaces.
  • Inner layer (osteogenic layer): composed of osteoblasts and osteoprogenitor cells.
  • Outer layer (fibrous layer): rich in blood vessels and composed of collagen fibers.
• Endosteum: lines internal bone cavities; single layer of osteoblasts and sometimes connective tissue.

Fenestration and Dehiscence

• Fenestration: window-like defect in bone, where the root surface is denuded of bone and overlaid by periosteum only.
• Dehiscence: denuded areas extend through the marginal bone.