Unit
- Gingiva: The gingiva is the oral mucosa that surrounds the teeth and covers the alveolar bone. It is divided into free gingiva, attached gingiva, and interdental papilla. Healthy gingiva appears pink, firm, and stippled, providing a protective seal around the tooth cervix.
- Periodontal ligament (PDL): The PDL is a dense connective tissue that anchors the tooth to the alveolar bone via Sharpey's fibers. It transmits occlusal forces, supports sensory innervation, and supplies nutrients to the cementum and bone.
- Cementum: This mineralized tissue covers the tooth root and provides attachment for PDL fibers. It is avascular and continues to form throughout life, compensating for occlusal wear. Cementum resists resorption and aids in root surface repair.
- Alveolar bone: The alveolar process forms and supports the tooth sockets. It is composed of bundle bone, compact bone, and spongy bone. This bone remodels in response to occlusal forces and resorbs rapidly when periodontal attachment is lost.
- Junctional epithelium: This specialized epithelium attaches to the tooth surface via hemidesmosomes, forming the biological seal at the gingival sulcus. Its integrity is critical for preventing bacterial invasion into the underlying connective tissue.
- Gingival sulcus: The shallow space between the tooth and free gingiva, normally 1-3 mm deep. Sulcus depth is measured with a periodontal probe. The sulcular epithelium is thin and permeable, making it a common entry point for pathogens.
- Blood supply and innervation: The periodontium receives blood from the superior and inferior alveolar arteries, with rich anastomoses. Sensory innervation comes from the maxillary and mandibular divisions of the trigeminal nerve, enabling pain, pressure, and proprioception.
- Aging changes: With age, the gingiva may become thinner and less vascular, the PDL width decreases, and cementum thickness increases. These changes affect healing capacity and susceptibility to periodontal disease.
- Alveolar mucosa: The alveolar mucosa is the movable, non-keratinized tissue apical to the mucogingival junction. It appears red and loosely attached to the underlying bone. This tissue is more vascular and permeable than attached gingiva, and its mobility allows for movement of the cheeks and lips during function.
- Mucogingival junction: This distinct line separates the keratinized attached gingiva from the non-keratinized alveolar mucosa. It is a clinically important landmark for assessing periodontal health, as the width of attached gingiva and the position of the junction influence susceptibility to recession and inflammation.
- Gingival crevicular fluid (GCF): GCF is a serum-like exudate that originates from the gingival plexus. Its flow rate increases with inflammation, making it a valuable diagnostic marker for periodontal disease. GCF contains inflammatory mediators, enzymes, and immune cells that reflect the host response to bacterial plaque.
- Biologic width: The biologic width consists of the junctional epithelium and connective tissue attachment above the alveolar crest, measuring about 2-3 mm total. This dimension is critical in restorative dentistry; violation of the biologic width can lead to chronic inflammation, bone loss, and periodontal pocket formation.
Terminology
- Periodontium
- The supporting structures of the tooth, including gingiva, PDL, cementum, and alveolar bone.
- Sharpey's fibers
- Collagen bundles that insert into cementum and bone, anchoring PDL fibers.
- Hemidesmosomes
- Specialized protein structures that attach epithelial cells to the tooth surface.
Quick Revision
- The periodontium comprises four tissues: gingiva, PDL, cementum, and alveolar bone.
- Each component has distinct functions in support, protection, and homeostasis.
- The junctional epithelium serves as the critical biological barrier against pathogens.
- Understanding normal anatomy is essential for recognizing pathological changes in gum disease.