Periodontics 4th Grade/Lecture (2) Dr. Basma F. Alanbari Normal microscopic features of the gingiva

The gingival epithelium is comprised of oral epithelium (OE), (SE) and (JE) figure 1.

• Oral epithelium (OE) /outer epithelium: It covers the crest and outer surface of marginal gingiva and surface of the attached gingiva. • It is a keratinized stratified squamous epithelium. • The keratinization makes it resistant to abrasion from rough and hard food particles. • It is the keratin that results in the mechanical toughness of the most superficial epithelium. Figure-1- gingival epithelium • Keratinization varies in different areas of the oral cavity, i.e. it is maximum in the , gingiva, ventral aspect of , cheeks in the descending order . • Following are the layers of oral epithelium: Stratum basale, Stratum spinosum, Stratum granulosum & Stratum corneum. • The epithelial cells are formed as basal cells and gradually change to the characteristics of each of the cell layers as they migrate toward the surface .this process is known as (keratinization). • Under normal conditions ,there is a complete equilibrium between cell renwell and desuamation (cell turnover).it takes approximately 3-4 weeks for keratinocyte to reach the outer epithelial surface where it becomes desuamated from the strarym corneum.the basal cells are found immediately adjacent to the connetctive tissue (CT) and are separated from it by a basement membrane, epithelial cells are joined by desmosomes.

Cells of the OE Keratinocytes: These make up 90% of the total cell population. Langerhans cells (LCs): are modified monocytes responsible for communication with immune system. Merkel cells Merkel cells are sensory in nature and respond to touch. Melanocytes are the cells which are responsible for the barrier to UV damage and synthesize melanin which is responsible for providing color to gingiva. Non specific cells: involved in the formation of other types of cells.

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I. Sulcular epithelium (SE): It lines the . It is a thin non-keratinized, stratified squamous epithelium without retepegs which extends from the coronal end of the junctional epithelium to the crest of the . The sulcular epithelium is extremely important because it may act as a semipermeable membrane through which injurious bacterial products pass into the gingiva and tissue fluid from the gingiva seeps into the Sulcus.

II. Junctional epithelium (JE): The junctional epithelium consists of a collar-like band of stratified squamous nonkeratinizing epithelium. The length of the junctional epithelium ranges from 0.25 to 1.35 mm. The attachment of the junctional epithelium to the tooth is reinforced by the gingival fibers, which brace the marginal gingiva against the tooth surface. For this reason, the junctional epithelium and the gingival fibers are considered a functional unit, referred to as the dentogingival unit.

Function: first, JE is firmly attached to the tooth surface, providing an epithelial barrier against plaque bacteria. second, it allows access of gingival fluid,inflammatory cells and components of the immune system to the gingival margin. third, JE cells exhibit rapid turnover,which contribute to the rapid repair of the damaged tissue. fourth, JE cells have a endocytic capacity and a protective activity equal to that of macrophage and neutrophils.

There are distinct differences between the junctional, sulcular and oral epithelium : 1) the size of the cells in the JE is relatively larger than in the OE & SE. 2) the intracellular space in the JE is wider than in the OE.the intra cellular space of the JE is the preferred route for tissue fluids & inflammatory cells migrating from the connective tissue to the gingival Sulcus. 3) The number of desmosomes (intercellular junctions) is fewer in the JE .the Presence of large number of desmosomes reflects the solid epithelial cells attachment. 4) The SE & JE are not thick as the OE ,not keratinized and in health status have no retepeges.

Gingival Crevicular Fluid (GCF): The gingival sulcus contains a fluid that seeps into it from the gingival connective tissue through the thin Sulcular epithelium. The gingival fluid is believed to: 1) Cleanse material from the sulcus. 2) Contain plasma proteins that may improve adhesion of the epithelium to the tooth. 3) Possess antimicrobial properties. 4) Exert antibody activity to defend the gingiva. Little fluid is found in the healthy gingival Sulcus, but the fluid flow increase in the presence of & the resulting gingival inflammation, it increase in response to brushing,

2 mastication or other stimulation of the gingiva.the amount of the GCF can be measured By inserting a filter paper in the gingival Sulcus, the paper will absorb the fluid present.the measured amount can be used as an index to the gingival inflammation.

Gingival connective tissue: The connective tissue of the gingiva is known as the lamina propria and consists of two layers: 1) a papillary layer subjacent to the epithelium, which consists of papillary projections between the epithelial rete pegs, and 2) a reticular layer contiguous with the periosteum of the alveolar bone. Connective tissue has a cellular and an extracellular compartment composed of fibers and ground substance. According to their insertion and course in the tissue, the oriented bundles in the gingiva can be divided into the following groups (figure 2): 1. Circular fibers (CF) run their course in the free gingiva and encircle the tooth in a cuff or ring-like fashion. 2. Dentogingival fibers (DGF) are embedded in the of the supra-alveolar portion of the root and project from the cementum in a fan-like configuration out into the free gingival tissue of the facial, lingual and interproximal surfaces. 3. Dentoperiosteal fibers (DPF) are embedded in the same portion of the cementum as the dentogingival fibers, but run their course apically over the vestibular and lingual bone crest and terminate in the tissue of the attached gingiva. In the border area between the free and attached gingiva, the epithelium often lacks support by underlying oriented collagen fiber bundles. In this area the free gingival groove (GG) is often present. 4. Alveologingival group (AG): These fibers arise from the alveolar crest and insert coronally into lamina propria of the gingiva. Attaches attached gingiva to alveolar bone. 5.Transseptal fibers (TF) extend between the supra-alveolar cementum of approximating teeth. The transseptal fibers run straight across the interdental septum and are embedded in the cementum of adjacent teeth. These fibers are responsible for returning teeth to their original state after orthodontic therapy.

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Figure-2- gingival fibers Types of connective tissue fibers according to structure: Collagen: major constitutes, produced by fibroblast sometimes by osteoblast & cementoblast, arranged in bundles. Reticulin: found near the basement membrane & blood vessels. Oxytalan: thin fibrils parallel to the teeth long axis, unknown function. Elastic: only around the blood vessels.

Cells of the gingival connective tissue: (1) fibroblasts: The fibroblast (65% of the total cell population). Responsible for the production of collagen fibers & synthesis of the connective tissue matrix. (2) mast cells: responsible for the production of certain components of the matrix also produces vasoactive substances, which can affect the function of the microvascular system and control the flow of blood through the tissue. (3) macrophages: with phagocytic and synthetic functions. (4) inflammatory cells: these cells have a diverse immunological functions.

Matrix of the gingival connective tissue: The matrix of the connective tissue is produced mainly by the fibroblasts, although some constituents are produced by mast cells, and other components are derived from the blood. The matrix is the medium in which the connective tissue cells are embedded and the transportation of water, electrolytes, nutrients, metabolites, etc., to and from the individual connective tissue cells occurs within the matrix. The main constituents of the connective tissue matrix are protein carbohydrate macromolecules.Biologic Width Concept Biologic width is defined as the dimension of healthy gingival tissue, which is attached to the tooth coronal to the crest of the alveolar tissue. Average length of connective tissue attachment is 1.07 mm and of junctional epithelium is 0.97 mm which makes total biologic width of 2.04 mm (Fig.3).

Significance of biologic width: violation of the biologic width take place when the restorative margin is placed into biologic width area consequently there will be gingival inflammation, pocket formation and loss of crestal bone in order to reestablish the biologic width back. Fig.3 the biologic width

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Blood supply of the gingiva (figure 4): All periodontal tissues have a copious blood supply even in the healthy state. This is due to 1) the high metabolism of this cell- and fiber- rich tissue 2) the peculiar mechanical/functional demands on the , Occlusal forces are resisted not only by the periodontal ligament and the , but also by means of the tissue fluid and its transfer within the periodontal ligament space (hydraulic pressure distribution, dampening effect). The most important afferent vessels for the alveolar process and the periodontium are: • In the maxilla, the anterior and posterior alveolar arteries, the infraorbital artery and the Figure-3- gingival blood supply palatine artery • In the mandible, the mandibular artery, the sublingual artery, the mental artery, and the buccal and facial arteries.

Lymphatic drainage of the gingiva (figure 5): Lymph vessels follow for the most part the blood vascular tree. The lymph from the periodontal tissues drains to the lymph nodes of the head and the neck. • The labial and lingual gingiva of the mandibular incisor region is drained to the submental lymph nodes (sme). • The palatal gingiva of the maxilla is drained to the deep cervical lymph nodes (cp). The buccal gingiva of the maxilla and the buccal and lingual gingiva in the mandibular premolar–molar region are drained to submandibular lymph nodes(sma). • Except for the third molars and mandibular incisors, all teeth with their adjacent periodontal tissues are drained to the submandibular lymph nodes (sma). Figure-5- gingival lymphatics

• The third molars are drained to the jugulodigastric lymph node (jd) and the mandibular incisors to the submental lymph nodes (sme).

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Innervations of the gingival connective tissue (figure 6) : the periodontium contains receptors which record pain, touch, and pressure (nociceptors and mechanoreceptors). the gingival innervations is mediated by the maxillary & mandibular branches of the trigeminal nerve. • The gingiva on the labial aspect of maxillary incisors, canines, premolars is innervated by the superior labial branches from infraorbital nerve. • Buccal gingiva in maxillary molar region is innervated by branches from posterior superior dental nerve. • Palatal gingiva is innervated by greater palatal nerve except incisors area which is innervated by sphenopalatine nerve. • Lingual gingiva in mandible is innervated by sublingual nerve, a branch of lingual nerve. • Gingiva on the labial aspect of mandibular incisiors and canines is innervated by mental nerve. • Buccal aspect of molars is innervated by buccal nerve. • Innervations of mandibular premolars is by both mental and buccal nerve.

Figure-6- gingival innervation

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