Gingiva ppt

gingiva, microscopic features

1. GINGIVA Dr.T.HUDSON JONATHAN

2. contents Introduction Parts of gingiva Microscopic features Gingival epithelium Functions Cells Layer Types Cytokeratins Antimicrobial peptides

3. contents Gingival connective tissue Gingival fibers Cells Macroscopic features Blood supply Lymphatics Nerve supply Conclusion Reference

4. Introduction: The gingiva is the part of oral mucosa that covers the alveolar processes of the jaws and surrounds the neck of the tooth. Parts of gingiva: Marginal gingiva Attached gingiva Interdental gingiva

5. Marginal gingiva The marginal or unattached gingiva is the terminal edge or border of the gingiva that surrounds the teeth in collar like fashion. In about 50%of case it is demarcated from the adjacent attached gingiva by a shallow linear depression called the free gingival groove.(v-shaped notch) The marginal gingiva is usually of 1mm wide and it forms the soft tissue wall of the gingival sulcus.

6. The most apical point of the marginal gingival scallop is called the gingival zenith. Its apicocoronal and mesiodistal dimensions vary between 0.06-0.96 mm

7. Attached gingiva It is the part of the gingiva that is firm,resilient and tightly –bound to the underlying periosteum of the alveolar bone. The facial aspect extends to the relatively loose and movable alveolar mucosa ;it is demarcated by the mucogingival junction. The width of attached gingiva is another important clinical parameter.

8. It is the distance between the mucogingival junction and the projection on the external surface of the bottom of the gingival sulcus or periodontal pocket The width of attached gingiva on the facial aspect differs in different areas incisors - maxilla:3.5-4.5mm mandible:3.3-3.9mm It is narrower in posterior segments max 1 st premolars-1.9mm man 1 st premolars-1.8mm

9. On lingual aspect ,the attached gingiva terminates at the junction of the lingual mucosa,which is continuous with the mucous membrane that lines the floor of the mouth

10. Controversies in Width of Attached Gingiva Lang and Loe:First controlled clinical trail When the tooth surface kept free of clinically detectable plaque Surfaces >2mm of keratinized gingiva= healthy Surfaces <2mm of keratinized gingiva=inflammed Which means 1mm or less than 1mm of attached gingiva remain inflammed.

11. The authors strongly suggest that 2mm width of keratinized gingiva is important for maintaining the health. According to Wennstrom, the lack of minimum amount of attached gingiva does not necessarily result in soft tissue recession. Proper plaque control prevents soft tissue recession even when it is out of adequate width.

12. A Study by Mehta P, Lim LP :A review to outline the significance of width of attached gingiva states that Width of attached gingiva is not significant to maintain periodontal health in the presence of adequate oral hygiene. Gingival tissue around teeth with restorations or undergoing labial orthodontic tooth movement may be more susceptible to recession. Functional need for attached gingiva around implant has not been established but its esthetic value has been widely accepted.

13. Interdental gingiva It occupies the gingival embrassure,which is the interdental space beneath the tooth contact. The interdental papilla can be a pyramidal or COL shape. Pyramidal-the tip of the papilla is located immediately beneath the contact point COL-it is a valley like depression that connects the facial and lingual papilla and that conforms to the shape of the interproximal contact

14. The shape of the gingiva in the interdental space depends on: The presence or absence of a contact point between the adjacent teeth. The distance between the contact point and the osseous crest. Presence or absence of some degree of recession.

15. Gingival sulcus It is the shallow crevice or space around the teeth bounded by the surface of the tooth on one side and the epithelium lining the free margin of the gingiva on the other side. It is v shaped and barely allow the entrance of a periodontal probe. Under absolute normal or ideal conditons the depth of the gingival sulcus is 0mm or close to 0mm

16. The probing depth is not necessarily exactly equal to the histologic depth of the sulcus. The so-called probing depth of a clinically normal gingival sulcus in humans is about 2-3mm

17. Microscopic features Microscopic examination reveals that gingiva is composed of the overlying stratified squamous epithelium and the underlying central core of connective tissue. Epithelium -cellular in nature. Connective tissue -less cellular and composed primarily of collagen fibers and ground subtance.

18. Epithelium Basal lamina Connective tissue Epithelium Connective tissue Oral Cells Sulcular fibers Junctional neurovascular structures

19. Gingival epithelium Historically it is thought to provide only a physical barrier to infection and underlying gingival attachment. But now we believe They participate actively in responding to infection In signaling further host reaction In integrating innate and acquired immune responses.

20. Cells -keratinocytes -non-keratinocytes Non-keratinocytes Merkel cells melanocytes langerhans cells

21. Keratinocytes: Principle cell type of the gingival epithelium as well as of other stratified squamous epithelia in the keratinocyte It is so called keratinocyte as it can synthesize keratin ,which is 90./. Of the cell population. The main function of epithelium is to protect deep structures while allowing for a selective interchange with the oral environment which is achieved through proliferation and differentiation of keratinocytes.

22. The proliferation of keratinocytes takes place by mitosis in the basal layer and less frequently in the suprabasal layers, in which a small proportion of cells remain as a proliferative compartment while a larger number begin to migrate to the surface. Differentiation involves the process of keratinization, which consists of progressions of biochemical and morphologic events that occur in the cell as they migrate from the basal layer

23. The main morphologic changes include the following: (1) The progressive flattening of the cell with an increasing prevalence of tonofilaments; (2) The couple of intercellular junctions with the production of keratohyalin granules (3) The disappearance of the nucleus.

24. Three types of surface keratinization can occur in gingival epithelium. Keratinization: A complete keratinization process leads to the production of an orthokeratinized, superficial horny layer similar to that of skin with no nuclei in stratum corneum and a well defined stratum granulosum. Only some areas of the outer gingival epithelium are orthokeratinized.

25. Parakeratinized: It is considered to be an intermediate stage of keratinization and is the most prevalent surface area of the gingival epithelium. These area can progress to maturity or dedifferentiation under different physiologic or pathological conditions. In parakeratinized epithelia, the stratum corneum retains pyknotic nuclei,and the keratohyalin granules are dispersed rather than giving rise to a stratum granulosum.

26. Non-keratinization: The non-keratinized epithelium (although cytokeratins are the major component as in all epithelia) neither granulosum or corneum strata,whereas superficial cells have viable nuclei. Melanocytes: These are the dendritic cells located in the basal and spinous layers of the gingival epithelium. They synthesize melanin in organelles called premelanosomes or melanosomes . These contain tyrosinase which hydroxylates tyrosine to DOPA.

27. Merkel cells: These are located in the deeper layers of the epithelium. They harbour nerve endings, and they are connected to adjacent cells by desmosomes and have been identified as tactile Perceptors. Langerhans cells: Langerhans cells are dendritic cells located among keratinocytes at all suprabasal levels. They belong to the mononuclear phagocyte system as modified monocytes derived from the bone marrow. Langerhans cells have an important role in the immune reaction as antigen-presenting cells for lymphocytes.

28. They contain g-specific granules (Birbeck granules), and they have marked adenosine triphosphatase activity. Epithelial cell junction: Electron microscopy reveals that keratinocytes are interconnected by structures on the cell periphery called desmosomes . These desmosomes have a typical structure that consists of two dense attachment plaques into which tonofibrils insert and an intermediate electron dense line in the extracellular compartment.

29. Tonofibrils which are morphologic expression of the cytoskeleton of keratin proteins radiate in brush like fashion from the attachment plaques into the cytoplasm of the cells.

30. Less frequently observed forms of epithelial cell connections are tight junctions(zonae occludens) in which the membranes of the adjoining cells are thought to be fused. Specialised structures called hemidesmosomes are also seen on the basal layer. They consist of a single attachment plaque, the adjacent plasma membrane, and an associated extracellular structure.

31. Recent data suggest that the hemidesmosomes may also act as specific sites of signal transduction and thus may participate in the regulation of gene expression, cell proliferation, and cell differentiation. Desmosomes Transmembraneous protein Proteins within the cell

32. Transmembraneous proteins, the desmogleins and desmocollin are members of cadherins family. The desmosomal cadherins are linked to the keratin cytoskeleton via several cytoplasmic attachment plaque proteins including desmoplakin, plakoglobulin, plakophilins, envoplakin and periplakin.

33. LAYERS OF GINGIVAL EPITHELIUM It has the four cell layers Stratum basale Stratum spinosum Stratum granulosum Stratum corneum

34. Stratum basale: The basal layer is made up of a single layer of cuboidal cells that synthesize DNA and undergo mitosis , thus providing new cells. The basal cells and parabasal spinous cells are referred to as the stratum germinativum but only the basal cells can divide. Basal cells are made up of two populations Serrrated basal cells Non serrated

35. Stratum spinosum: Spinous cells which make up this layer are irregularly polyhedral and larger than the basal cells. The spinous or prickle cell layer resemble a cocklebur or sticker that has each spine ending at a desmosome. In light microscopy it appears that the cells are joined by intercellular bridges.Of the four layers it is the most active in protein synthesis.

36. Keratinosomes or Odland bodies: The uppermost cells of the stratum spinosum contain numerous dense granules called keratinosomes or Odland bodies , which are modified lysosomes. They contain a large amount of acid phosphatase , an enzyme involved in the destruction of organelle membranes, which occurs suddenly between the granulosum and corneum strata and during the intercellular cementation of cornified cells.

37. Stratum granulosum: This layer contains flatter and wider cells. These cells are larger than spinous cells. This layer is named for the basophilic keratohyalin granules that it contains. The nuclei show signs of degeneration and pyknosis

38. Stratum corneum: It is made up of keratinized squamae which are larger and flatter than the granular cells. Ultrastructurally the cells of the cornified layer are composed of densely packed filaments developed from the tonofilaments, altered, and coated by the basic protein of the keratohyalin granule, filaggrin. The degree of gingival keratinization diminishes with age and the onset of menopause.

39. Keratinization of the oral mucosa varies in different areas in the following order: Palate gingiva ventral aspect of the cheek tongue

40. Basement membrane: The interface between the connective tissue and the epithelium in light microscopy appears thick and it includes the reticular fibers. It is a zone that is 1-4 և m wide and is relatively cell free. Ultra structurally basement membrane is known as basal lamina .

41. The basal lamina is made up of a clear zone( lamina lucida ) just below the epithelial cells and a dark zone( lamina densa ) beyond the lamina lucida and adjacent to the connective tissue. Anchoring fibrils which contain type VII collagen, forms loops and are inserted into the lamina densa. Lamina densa contains type IV collagen coated with heparin sulfate in chicken wire (net like) configuration.

42. Lamina lucida has been shown to contain laminin and bullous pemhigoid antigen. Laminin and type IV collagen. Basement membranes promote differentiation, peripheral nerve regeneration and growth, and they tend to prevent metastases.

43. Epithelium is of three types Outer or oral epithelium Junctional epithelium Sulcular epithelium

44. Oral (Outer) Epithelium: The oral or outer epithelium covers the crest and outer surface of the marginal gingiva and the surface of the attached gingiva. On average, the oral epithelium is 0.2 to 0.3 mm in thickness. It is keratinized or parakeratinized, Oral epithelial cells have the lowest rate of proliferation in comparison to JE and OSE cells. It has been suggested that this may be due to the physiologic restricting effect of TGF – β on epithelial cell proliferation.

45. Sulcular epithelium: The sulcular epithelium lines the gingival sulcus. It is a thin, nonkeratinized stratified squamous epithelium without rete pegs, and it extends from the coronal limit of the junctional epithelium to the crest of the gingival margin. As with other nonkeratinized epithelia, the sulcular epithelium lacks granulosum and corneum strata and K1, K2, and K10 through K12 cytokeratins, but it contains K4 and K13, the so-called “esophageal-type cytokeratins.”

46. It also expresses K19, and it normally does not contain Merkel cells. The sulcular epithelium is extremely important; it may act as a semipermeable membrane through which injurious bacterial products pass into the gingiva and through which tissue fluid from the gingiva seeps into the sulcus.

47. Junctional epithelium: The junctional epithelium consists of a collar like band of stratified squamous non-keratinizing epithelium. It is 3 to 4 layers thick in early life, but the number of layers increases with age to 10 or even 20 layers. The length of the junctional epithelium ranges from 0.25 to 1.35 mm.

48. Formation of JE: When the enamel formation is completed ameloblasts become reduced in height to form the REE.

49. As the erupting tooth approaches the oral epithelium the REE and oral epithelium start migrate in to the underlying connective tissue. During the later phases of tooth eruption all cells of the REE are replaced by a JE. This is continuous with the oral epithelium and provides the attachment between the tooth and the gingiva. However, the reduced enamel epithelium is not essential for its formation; in fact, the junctional epithelium is completely restored after pocket instrumentation or surgery, and it forms around an implant.

50. CONCEPTS REGARDING JUNCTIONAL EPITHELIUM WAERHAUG’S CONCEPT 1960 He presented the concept of epithelial cuff. This concept was based on the insertion of thin blades between the tooth surface and the gingiva. It was concluded that gingival tissues and tooth are closely adapted but organically not united.

51. SCHROEDER AND LISTGARTEN CONCEPT (1971 ) Primary epithelial attachment refers to the epithelial attachment lamina released by the REE. It lies in direct contact with enamel and epithelial cells attached to it by hemi-desmosomes. When REE cells transform into JE cells the primary epithelial attachment becomes secondary epithelial attachment . It is made of epithelial attachment between basal lamina and hemi-desmosomes.

52. The junctional epithelium is attached to the tooth surface by means of an internal basal lamina. It is attached to the gingival connective tissue by an external basal lamina.

53. DAT cells: The attachment of the junctional epithelium to the tooth is mediated through an ultramicroscopic mechanism defined as the epithelial attachment apparatus. Adhesion to the tooth is mediated by specific group of cells in that the JE that have been termed as DAT(directly attached to tooth) cells.

54. The DAT cells are those cells which directly attach to the tooth through cytoskeletal/integrin complex. The DAT cells thought to proliferate more rapidly than the neighbouring cells The components of the internal basal lamina are synthesized by the DAT cells in the absence of the immediate vicinity of connective tissue. Internal basal lamina proteins include laminin and type VIII collagen.

55. At the coronal part of the junctional epithelium, the DAT cells typically express a high density of transferrin receptors which supports the idea of their active metabolism and high turnover. The findings suggest that the DAT cells have a more important role in tissue dynamics and reparative capacity of the junctional epithelium. (Schroeder H, et al)

56. Junctional epithelium in the antimicrobial defense: Junctional epithelium consists of active populations of cells and antimicrobial functions, which together form the first line of defense against microbial invasion into tissue. First, junctional epithelium is firmly attached to the tooth surface, thereby forming an epithelial barrier against plaque bacteria. Second, it allows access of gingival fluid, inflammatory cells, and components of the immunologic host defense to the gingival margin.

57. Third, junctional epithelial cells exhibit rapid turnover, which contributes to the host–parasite equilibrium and the rapid repair of damaged tissue.

58. The different keratin polypeptides of the junctional epithelium have a particular histochemical pattern. Junctional epithelium expresses K19, which is absent from keratinized epithelia, and the stratification-specific cytokeratins K5 and K14. Dentogingival unit: 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 together as a functional unit referred to as the dentogingival unit

59. Role of GCF: Its constituents participate in the normal maintenance of function of the junctional epithelium throughout its lateral and vertical dimensions, including the most coronal DAT cells.

60. Cytokeratins: Cytokeratins are the basic structural proteins of epithelial cells. They are abundant in oral cavity, salivary gland epithelia and are expressed during odontogenesis. Also, cytokeratins are the leading biomarkers in diagnostic pathology. Cytokeratins are seen not only within the cell but also in contact areas like desmosomes.

61. They serve to provide mechanical linkages and distribute the forces over a wide area. They function as stress bearing structures within the epithelial cell and are important in maintaining cell shape. The molecular weights of cytokeratins however vary widely from 40 to 200 Kda than microtubules and microfilaments.

62. Significance of cytokeratins in diagnostic oral pathology: Cytokeratins are the ‘gold standard markers’ in immunohistochemical diagnosis, classification and subtyping of carcinomas and detection of unclear metastasis. Key characteristic of keratins that makes them useful in pathology is the relative stability of expression even after transformation to pathological states.

63. Expression of cell surface adhesion molecules in gingiva: Integrins are large family of transmembrane glycoproteins which serve to attach cells to a large number of extracellular matrix ligands such as fibronectin, laminin, vitronectin, tenascin and osteopontin. Recent studies have demonstrated that basal cells and suprabasal cells of the JE, OSE and OGE express the integrins α 2 β 1, α 3 β 1 and α 6 β 1 . (Delcastillo et al 1996) Hemidesmosomes contain the α 6 β 1 integrin localized on both the internal and external basal lamina of the JE.

64. Another class of cell surface adhesion molecules that is of significance to the biology of gingival tissues is the immunoglobulin class , of which Intercellular adhesion molecule 1 Endothelial leukocyte adhesion molecule 1 and Vascular cell adhesion molecule 1 ,are known to increase in gingiva during inflammation. There is evidence that ICAM 1 is downregulated in epithelia of chronic periodontal inflammatory lesions

65. Another adhesion factor important for leukocyte transmigration in inflammatory lesions is ELAM 1. it has been localized on blood vessels of gingivitis lesions. This molecule is expressed on endothelial cells that have been activated by cytokines such as TNF- α , IL-1, and bacterial lipopolysaccharides.

66. Antimicrobial peptides expressed in gingiva: The α and β defensins and LL-37 are localized in different sites in the gingiva, suggesting that they may serve different roles in the several ecological niches of the periodontium .(GREER et al 2013) The β defensin peptides Hbd-1 and Hbd-2 are localized in different layers of gingival epithelium in a pattern of expression consistent with function as a microbial barrier.

67. Thus JE is protected by α defensins and LL 37 released from neutrophils, whereas the differentiated stratified epithelia are protected by α and β defensins. Their expression is particularly strong in marginal gingiva. While β defensins poorly expressed in the undifferentiated cells of JE, the α defensins and LL 37 are present in high amounts in neutrophils that migrate through the JE to the gingival sulcus.

68. TURNOVER RATE OF THE ATTACHMENT EPITHELIUM: Epithelial cells in the attached gingiva exhibited a renewal rate of 10.4 days whereas the corresponding rate for the epithelial cuff was 5.8 days. The turnover rate of JE is exceptionally rapid. In non human primates it is about 5 days and approximately twice the rate of oral gingival epithelium. (Skougard et al)

69. Gingival connective tissue Connective tissue Cellular component Extra cellular component -Fibroblast -Mast cells -Fixed macrophages -Adipose cells -Histiocytes -Eosinophils -Inflammatory cells Fibers Ground substance -Collagen -Reticular -Elastic -Proteoglycans -Glycoproteins

70. The connective tissue of the gingiva is known as the lamina propria, and it consists of two layers: (1) a papillary layer subjacent to the epithelium that consists of papillary projections between the epithelial rete pegs. (2) a reticular layer that is contiguous with the periosteum of the alveolar bone.

71. The three types of connective tissue fibers are collagen, reticular, and elastic. Collagen type I forms the bulk of the lamina propria and provides the tensile strength to the gingival tissue. Type IV collagen (argyrophilic reticulum fiber) branches between the collagen type I bundles, and it is continuous with fibers of the basement membrane and the blood vessel walls. The elastic fiber system is composed of oxytalan, elaunin, and elastin fibers distributed among collagen fibers.

72. The ground substance fills the space between fibers and cells; it is amorphous, and it has a high water content. It is composed of proteoglycans (mainly hyaluronic acid and chondroitin sulfate) and glycoproteins (mainly fibronectin). Glycoproteins account for the faint periodic acid–Schiff–positive reaction of the ground substance. Fibronectin binds fibroblasts to the fibers and many other components of the intercellular matrix, thereby helping to mediate cell adhesion and migration. Laminin, which is another glycoprotein found in the basal lamina, serves to attach it to epithelial cells.

73. GINGIVAL FIBERS FUNCTIONS: To brace the marginal gingiva firmly against the tooth To provide the rigidity necessary to withstand the forces of mastication without being deflected away from the tooth surface. To unite the free marginal gingiva with the cementum of the root and adjacent attached gingiva. The gingival fibers are arranged in three groups Gingivo dental group The circular group The transseptal group

74. - The circular group The circular fibers course through the connective tissue of the marginal and interdental gingivae and encircle the tooth in ring like fashion. Gingivo dental group The gingivodental fibers are those on the facial, lingual, and interproximal surfaces. They are embedded in the cementum just beneath the epithelium at the base of the gingival sulcus

75. On the facial and lingual surfaces, they project from the cementum in a fanlike conformation toward the crest and outer surface of the marginal gingiva, where they terminate short of the epithelium. Interproximally, the gingivodental fibers extend toward the crest of the interdental gingiva.

76. The transseptal group The transseptal fibers, which are located interproximally, form horizontal bundles that extend between the cementum of the approximating teeth into which they are embedded. Page et al described a group of semicircular fibers that attach at the proximal surface of the tooth immediately below the CEJ go around the facial or lingual marginal gingiva of the tooth and attach on to the other proximal surface of the same tooth.

77. CELLULAR ELEMENTS: FIBROBLAST: Numerous fibroblasts are found in between the fiber bundles. These are mesenchymal origin and play a important role in development, maintenance and repair of gingival connective tissue. They synthesize collagen and elastic fibers as well as the glycoproteins and glycosaminoglycans of the amorphous intercellular substance. Fibroblast also regulate collagen degradation through phagocytosis and the secretion of collagenases.

78. Tractional forces in the extracellular matrix produced by fibroblasts are believed to be the forces responsible for generating tension in the collagen. This keeps the teeth tightly bound to each other and to the alveolar bone. Mast cells: They are distributed throughout the body, are numerous in the connective tissue of the oral mucosa and the gingiva. Fixed macrophages and histiocytes are present in the gingival connective tissue as components of the mononuclear phagocyte system (reticuloendothelial system) and are derived from blood monocytes. Adipose cells and eosinophils , although scarce, are also present in the lamina propria.

79. In clinically normal gingiva, small foci of plasma cells and lymphocytes are found in the connective tissue near the base of the sulcus. Neutrophils can be seen in relatively high numbers in both the gingival connective tissue and the sulcus. These inflammatory cells are usually present in small amounts in clinically normal gingiva.

80. Repair of gingival connective tissue Because of the high turnover rate, the connective tissue of the gingiva has remarkably good healing and regenerative capacity. Indeed, it may be one of the best healing tissues in the body, and it generally shows little evidence of scarring after surgical procedures. This is likely caused by the rapid reconstruction of the fibrous architecture of the tissues. However, the reparative capacity of gingival connective tissue is not as great as that of the periodontal ligament or the epithelial tissue.

81. CUTICULAR STRUCTURES: The term cuticle describes a thin acellular structure with a homogenous matrix that is sometimes enclosed within clearly demarcated linear borders. CUTICLE Acquired coatings (saliva, calculus,bacteria, and surface stains) Developmental coatings (REE, coronal cementum and dental cuticle)

82. Correlation of Clinical and Microscopic Features Colour The colour of the attached and marginal gingiva is generally described as “coral pink”. It is produced by the vascular supply, the thickness and degree of keratinization of the epithelium, and the presence of pigment-containing cells. Size The size of gingiva corresponds to the sum total of the bulk of cellular and intercellular elements and their vascular supply. Alteration in size is a common feature of gingival disease.

83. Contour The contour or shape of the gingiva varies considerably and depends on the; Shape of the teeth and their alignment in the arch. The location and size of the area of proximal contact . The dimensions of the facial and lingual gingival embrasures. The marginal gingiva envelops the teeth in collar like fashion and follows a scalloped outline on the facial and lingual surfaces.

84. Consistency: The gingiva is firm and resilient and, with the exception of the movable free margin, tightly bound to the underlying bone. Surface Texture: The gingiva presents a textured surface similar to that of an orange peel and is referred to as stippled. Stippling is best viewed by drying the gingiva. The attached gingiva is stippled; the marginal gingiva is not.

85. Microscopically, stippling is produced by alternate rounded protuberances and depressions in the gingival surface. The papillary layer of the connective tissue projects into the elevations, and the elevated and depressed areas are covered by stratified squamous epithelium. Position: The position of the gingiva is the level at which the gingival margin is attached to the tooth. When the tooth erupts into the oral cavity, the margin and sulcus are at the tip of the crown;as the eruption progresses,they are seen closer to the root.

86. BLOOD SUPPLY: Supra periosteal arterioles Vessels of the PDL Arterioles

87. LYMPHATIC DRAINAGE:

88. Nerve supply Within the gingival connective tissues most nerve fibers are myelinated and closely associated with the blood vessels. Gingival innervation is derived from fibers that arise from nerves in the PDL and from the labial,bucccal and palatal nerves. Nerves of connective tissue- A meshwork of terminal argyrophilic fibers,some of which extend into epithelium;meissner-type tactile corpuscles;krause-type end bulbs,which are temperature receptors;and encapsulated spindles.

89. Conclusion Although each type of gingiva exhibits considerable variation in differentiation,histology and thickness according to its functional demands,all types are specifically structured to function appropriately against mechanical and microbial damage. In other words the specific structure of different types of gingiva reflects each one effectiveness as a barrier to the penetration by microbes and noxious agents into the deeper tissue.

90. REFERENCES Carranza’s clinical periodontology – 12 th edition Clinical periodontology – Lindhe 5 th edition Periodontics revisited – Shalu bathla Orban’s oral histology and embryology – 13 th edition Ten cates oral histology Molecular and cell biology of the gingiva – Bartold , perio 2000 vol24, 2000 Oral Cytokeratins in Health and Disease - Roopa S Rao et al J Contemp Dent Pract 2014; Molecular and cell biology of healthy and diseased periodontal tissues – Bartold et al periodontology 2000 volume 40, 2006 Defensins and LL 37 a review of function in the gingival epthelium – Greer et al periodontology 2000 volume 63, 2013

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