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STRUCTURE AND FUNCTIONS OF THE GINGIVA

STRUCTURE AND FUNCTIONS OF THE GINGIVA. CONTENTS. Introduction. Definition Classification. Macroscopic features of the gingiva and its functions Microscopic features - Epithelium. - Connective tissue. Vascular supply of gingiva Clinical features of gingiva in health and disease

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STRUCTURE AND FUNCTIONS OF THE GINGIVA

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  1. STRUCTURE AND FUNCTIONS OF THE GINGIVA

  2. CONTENTS • Introduction. • Definition • Classification. • Macroscopic features of the gingiva and its functions • Microscopic features - Epithelium. - Connective tissue.

  3. Vascular supply of gingiva • Clinical features of gingiva in health and disease • Conclusion • References

  4. INTRODUCTION • Dental unit is an organ made up of the teeth and their supporting tissues. • Periodontium is the functional unit of tissues supporting the tooth. • Tissues of the periodontium include the gingiva, junctional epithelium, periodontal ligament, cementum, alveolar process.

  5. The harmonious relationship b/w the different parts of the periodontium is maintained under normal conditions despite the constant changes that take place in the periodontal tissue throughout life. • The maintenance of these tissues in health depends upon normal cellular activity that permits normal tissue responses to environmental conditions or insult. • These adaptations may be seen on gross anatomic, microscopic, ultramicroscopic and biological levels.

  6. GENERAL FEATURES OF THE GINGIVA Oral cavity lined by mucous membrane The oral mucous membrane is dived into 3 zones based on its function: • Masticatory or mucostable mucosa • Specialized mucosa • Lining or reflecting mucosa

  7. Gingiva is the part of oral mucosa that covers the alveolar processes of the jaws and surrounds the neck of the teeth.

  8. Gingiva is divided anatomically into Free Marginal gingiva Attached gingiva Interdental areas

  9. Marginal or unattached gingiva • Terminal edge or border . • 50% of cases, it is demarcated from adjacent, attached gingiva by a shallow linear depression c/a “ free gingival groove” • Distance of 0.5- 2mm from margin of gingiva (orban 1948)

  10. Facial and lingual aspects • Ainamo and loe 1966 showed presense of gingival groove in 27% in maxilla and 38% in mandible • Development – • orban 1953- develop at the level or of slightly apical to the top of the epithelial attachment orban 1955- histologically appears as epithelial ridges • 1mm wide forms soft tissue wall of ging. sulcus • Separated from tooth surface with periodontal probe

  11. The tissues that make up the marginal gingiva include the oral gingival epithelium coronal to gingival groove, the oral sulcular epithelium, the junctional epithelium • Clinical significance: Region of junction b/w the soft tissue and surface of crown or root, and are the site of initiation of gingivitis and periodontitis

  12. Gingival sulcus • Crevice or space around the tooth. • Bounded by tooth and epithelium. • Clinical determination of depth of gingival sulcus imp Diagnostic parameter. • In clinically healthy gingiva of humans some depth of the ging sulcus can be found depth determined in Histological sections reported 1.8 mm with variations from 0-6 mm. Other studies by gargiulo reported it to be 0.6- 1.5 mm. • Healthy gingiva- clinical depth is 2-3mm

  13. Gingival sulcus/ crevice } FREE GINGIVA ATTACHED GINGIVA

  14. Histological features of the gingival sulcus • Sulcus lined by thin non keratinized stratified squamous epithelium without rete pegs Functions: • Acts as a semi permeable membrane

  15. GINGIVAL FLUID • Enters sulcus from connective tissue through sulcular membrane • Cleanses material from sulcus • Contains plasma proteins that may improve adhesion of epithelium to the tooth • Possess antimicrobial properties • Exerts antibody activity in defense of gingiva

  16. Attached gingiva • Continuous marginal gingiva. • Firm, resilient, tightly bound to underlying periosteum of alveolar bone. • Distance b/w MGJ and projection on the external surface of the bottom of the ging. Sulcus or the periodontal pocket. • Width varies in different areas of the mouth.

  17. Histological feature of attached gingiva • AG is covered by keratinized epithelium surface of which presents minute depressions and elevation giving the surface an orange peel appearance known as stippling • Stippling is a form of adaptive specialization or reinforcement for function. • It is a feature of healthy gingiva. • Reduction or loss of stippling is a common sign of gingival disease. • When the gingiva is restored to health the stippled appearance returns.

  18. Less prominent on lingual than in facial, in some persons it may be absent. • Stippling varies with age. • It is absent in infancy, appears in some children at about 5 years of age, increases until adulthood and frequently begins to disappear in old age. • Microscopically stippling is produced by alternate rounded protuberances and depressions in the gingival surface. • The papillary layer of the CT projects into the elevations, and the elevated and depressed areas are covered by stratified squamous epithelium. • The degree of keratinization and the prominence of stippling appear to be related.

  19. Mucogingival junction • The mucogingival junction remains the same throughout life. • Changes in the width of attached gingiva are caused by modifications in the position of its coronal end. • Increase with age and in supraerupted tooth. • lingual aspect of mandible terminates at the junction with lingual alveolar mucosa, continuous MM lining floor of the mouth • Maxilla, palatal surface blends imperceptibly equally firm resilient palatal mucosa

  20. Functions of attached gingiva • Stress bearing area • Prevention of gingival recession • Unaltered levels of CT attachment

  21. Interdental gingiva • Occupies the gingival embrasure. • Pyramidal or conical shape referred as interdental papilla* • Shape depends on the contact points of two adjacent teeth.

  22. Col is non keratinizing epithelium . • Structure is particularly susceptible to noxious substances or physical trauma. • Represents the site for initiation of pathologic breakdown of the tooth supporting apparatus.

  23. Functions of gingiva

  24. Defendagainst the noxious external environmental influences that are present in the oral cavity. • Maintain the integrity of the body surface by separating the external and internal environment. • Attachthe teeth to their bony housing and to one another. • Resist and resolve the forces generated by mastication speech and deglutition. • Adjust for structural changes associated with wear and aging through continuous remodeling and regeneration.

  25. MICROSCOPIC FEATURES

  26. Gingival epithelium • Every epithelial tissue is characterized by 3 critical features: • Cells closely opposed, attached via specialized cell-cell junction • Epithelial cells secret basal lamina on to which cells organize as a tissue, separates epithelium from connective tissue 3. Epithelial cells characterized by the presence of a cytoskeleton composed of keratin intermediate filaments.

  27. Gingival epithelium • Three areas of gingival epithelium: • Oral or outer epithelium • Oral Sulcular epithelium • Junctional epithelium

  28. General Aspects of all Gingival Epithelium

  29. Layers of Gingival Epithelium • Based on the degree to which keratin producing cells are differentiated • Absence of cell nuclei- orthokeratinized • Remnants of cell nuclei present in the stratum corneum -parakeratinized

  30. Basal layer / Stratum basale or stratum germinativum- nonkeratinized • Prickle cell layer/ Stratum spinosum-Nonkeratinized • Granular cell layer/Stratum granulosum -parakeratinized • Keratinized cell layer/ Stratum Corneum - keratinized • Junctional and Sulcular epithelium have only spinosum and basal layers

  31. Basal cell layer/Stratum basale/stratum germinativum • Heterogenous population of cuboidal or low columnar cells that contact the basal layer • Positive reaction to periodic acid schiff stain – presence of CHO (glycoprotein) • Cells exhibit 2 primary functions: - severe as source of new cells for constant renewal of tissue • Produce and secrete materials that make up – basal lamina

  32. Various cells present in the stratum basale : Keratinocyte Melanocyte Lagerhan cells

  33. Prickle cell layer/ spinous layer/ stratum spinosum • Located immediately peripheral to basal layer • Cells are polygonal by shape ,equipped with short cytoplasmic processes resembling spines, do not divide • Increased cytoplasmic filaments, decreased mitchondria • Function: Cells exhibit features of increased specialization and maturation

  34. Granular layer/ stratum granulosum • Cells are flattened and parallel to tissue surfaces • Nuclei become flattened • Electron dense keratohyalin bodies few cluster of glycogen granuels • Desmosomes are more prevalant • Size of intercellular space is reduced cellular interdigitations less prominent than in deeper layers

  35. Keratinized cell layer/stratum corneum • Keratinazation of cells , conversion into thin parallel and anucleated corneocyte • Entire synthetic and energy producing apparatus is removed from cells by enzymatic breakdown • Gingival corneocyte is filled with keratin matrix of homogenous fined grained structure.

  36. Layers of gingival epithelium

  37. Junction between the cells • Occluding (tight junctions) 2. Anchoring junctions – • Microfilament attachment sites • Cell- cell adhesion belts • Cell – matrix adherent junctions • Intermediate filament attachment sites • Cell – cell (desmosomes) • Cell –matrix (hemidesmosomes) 3. Communicating or gap junctions

  38. Occluding (tight) junctions -interlocking system of occluding ridges b/w cell membrane of adjacent cells Anchoring junctions • cell-cell adherent junctions • Occurs as belts (zonulae) around cell or b/w cell and matrix • Made up of bundles of actin filaments • Desmosomes – restricted to epithelial cells - spot- welds b/w adjacent cells -hemidesmosomes – half of an desmosome -attachment of gingival epithelium tooth Communicating or gap junctions -spot like outline in region of opposing cells

  39. Functions- -support to cells -facilitate intracellular transport - support cell junctions - permits cell motility

  40. Principal cell – keratinocyte • large round or oval nucleus with 1 or more prominent nucleoli • cytoplasm densely packed with organelles • prominent Golgi complex • mitochondria located in perinuclear position in the basal part of cell • Function: • - Destined to transverse the epithelium and keratinize

  41. Main function of gingival epithelium achieved by Proliferation Differentiation of keratinocyte • Proliferation of keratinocytes by mitosis at basal cell layer • Differentiation is process of keratinization as the cell migrates from the basal layer to the surface layer

  42. Differentiation g process keratinization g biochemical and morphological events • Main morphologic change -Progressive flattening of cell increasing prevalence of tonofilaments -Intercellular junction coupled to production of keratohyaline granuels -Disappearance of the nucleus

  43. NONKERATINOCYTE CELLS IN GINGIVAL EPITHELIUM

  44. Non keratinocytes/clear cells • melanocytes • langerhan cells • merkel cells

  45. Melanocytes • Dendritic cells basal and spinous layers of gingival epithelium • synthesize melanin pigment in organelles c/a premelanosomes or melanosomes • TYROSINE g DOPA g MELANIN • Unlike keratinocytes melanocytes attach neither to basal lamina nor to adjacent cells of stratum basale • Function – produce melanin pigment • serves protect against ionizing effects of electromagnetic radiation • Distribute it to keratinocyte

  46. Langerhans cells • Described by langerhans 1868 • Dendritic cells located among keratinocytes at all suprabasal layers • These are modified monocytes derived from bone marrow • Contain elongated granules • Have an important role in the immune reaction as antigen-presenting cells for lymphocytes • Contain g- specific granules (birbeck’s granules) • Found in OE, smaller amounts in SE • Play a pivotal role in the host response to microbiological insult at gingival margin

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