THE GINGIVA
The gingiva is that part of the oral mucosa (masticatory mucosa) that covers the alveolar process of the jaws and surrounds the necks of the teeth. Anatomically the gingiva is divided into—marginal, attached and interdental.
Marginal Gingiva or Free Gingiva or Unattached Gingiva
It is defined as the terminal edge or border of the gingiva surrounding the teeth in a collar-like fashion. In some 3cases it is demarcated apically by a shallow linear depression called the “free gingival groove”.
Gingival Sulcus
It is defined as the space or shallow crevice between the tooth and the free gingiva, which extends apical to the junctional epithelium. It is V-shaped and barely permits 4the entrance of a periodontal probe. The so-called probing depth of a clinically normal gingival sulcus in humans is 2 to 3 mm.
Attached Gingiva
It is defined as that part of the gingiva that is firm, resilient and tightly-bound to the underlying periosteum of the alveolar bone.5
Interdental Gingiva
Usually occupies the gingival embrasure. There are three parts of interdental gingiva; facial papilla, lingual papilla and col, which is a valley-like depression that connects the facial and lingual papilla.
Microscopic Features
The gingiva consists of a central core of connective tissue covered by stratified squamous epithelium. Three types of epithelium exists in the gingiva.
- The oral or outer epithelium (keratinized epithelium).
- The sulcular epithelium.
- The junctional epithelium (non-keratinized epithe-lium).
In the keratinized epithelium, the principal cell type is the keratinocyte, which can synthesize keratin.
The non-keratinized epithelium contains clear cells, which include melanocytes, Langerhans' cells, supra-alveolar connective tissue.
The connective tissue supporting the oral epithelium is termed as the lamina propria and for descriptive purpose it can be divided into two layers:
- The superficial papillary layer—associated with the epithelial ridges.
- Deeper reticular layer—that lies between the papillary layer and the underlying structures.
Merkel cells and lymphocytes The lamina propria consists of cells, fibers, blood vessels embedded in amorphous ground substances.
- Cells: Different types of cells present are:
- Fibroblast
- Mast cells
- Macrophages
- Inflammatory cells.
- Fibers: The connective tissue fibers are produced by fibroblasts and can be divided into:
- Collagen fibers
- Reticulin fibers
- Oxytalan fibers
- Elastin fibers.
Collagen type I forms the bulk of the lamina propria and provides the tensile strength to the gingival tissues.
TOOTH-SUPPORTING STRUCTURES
Tooth-supporting structures include, the periodontal ligament, cementum and alveolar bone.
PERIODONTAL LIGAMENT
Definition
The periodontal ligament is a connective tissue structure that surrounds the root and connects it with the bone.
Structure
The periodontal ligament space has the shape of an hourglass and is narrowest at the mid-root level. The width of periodontal ligament is approximately 0.25 mm ± 50 percent.
Cellular Composition
Cells of periodontal ligament are categorized as:
- Synthetic cells
- Resorptive cells
- Progenitor cells
- Other epithelial cells
- Connective tissue cells.
Extracellular Components
- Fibers:
- Collagen
- Oxytalin.
- Ground substance:
- Proteoglycans
- Glycoproteins.
The principal fibers of periodontal ligament are arranged in six groups that develop sequentially in the developing root. They are:
- Trans-septal group
- Alveolar crest, horizontal, oblique, apical and inter-radicular fibers.
Structures Present in the Connective Tissue
- Blood vessels
- Lymphatics
- Nerve innervation
- Cementicles.
Blood vessels: Periodontal ligament is supplied by branches derived from three sources dental, interradicular and interdental arteries.
ALVEOLAR BONE
Definition
It is that portion of the maxilla and mandible that forms and supports the tooth socket (alveoli).
Parts
Alveolar bone consists of the following:
- Inner and outer cortical plate.
- The bone lining the socket.
- An interior portion of cancellous bone.
The bone lining the socket is also compact bone and can be known as any of the following:
- Bundle bone, since bundles of Sharpey's fibers from the periodontal ligament are embedded in it.
- The cribriform plate, because it is perforated by numerous vascular channels.
- Alveolar bone proper, as it provides direct bony support for the teeth.
- Lamina dura, which is radiographically seen as a dense plate.
Composition
It has two basic constituents:
- The cells consist of osteoblasts, osteoclasts, and osteocytes.
- Extracellular matrix consists of 65 percent inorganic and 35 percent organic matter.
CEMENTUM
Definition
Cementum is a calcified avascular mesenchymal tissue that forms the outer covering of the anatomic root.
Cementum is a calcified avascular mesenchymal tissue that forms the outer covering of the anatomic root.
Acellular cementum forms during root formation and is seen at the coronal portion of the root, whereas cellular cementum forms after eruption of the tooth and is seen apically on the root.
Cementum consists of 46 percent inorganic matter and the rest 90 percent organic being type I collagen and the remaining consists of non-collagenous proteins.
