HISTOLOGY OF ORAL MUCOUS MEMBRANE AND GINGIVA
Vinay Pavan Kumar .K
1st year MDS
AECS Maaruti College of Dental Sciences
HISTOLOGY OF ORAL MUCOUS MEMBRANE AND GINGIVA
Definition
Functions Classification
Structure
Organization
Histology of gingiva
Prosthetic consideration
Biological width
The oral cavity is in many respects a very
interesting part of the human body .
Many different kind of tissue from the hardest teeth to the softest, the salivary glands are found therein.
The oral cavity is lined with an uninterrupted mucosa which is continuous with the skin near vermillion border of the lips and with the pharyngeal mucosa in the region of soft palate
INTRODUCTION
Functions of oral mucosa
Protection : Barrier for mechanical trauma and microbiological insults
Sensation : Temperature (heat and cold), touch, pain, Reflexes such as swallowing, gagging and salivation
Absorption : Nitrates are absorbed sublingually
Secretion:
Salivary secretion creates a moist oral cavity helps in speech, swallowing, mastication and in the perception of taste.
Thermal regulation:
Important in dogs not in humans
Excretion:
excretion of certain metabolites
Esthetics :
Lips and gingiva enhance facial esthetics
Classification of oral mucosa
Based upon primary function served
1. Masticatory Mucosa (25%)
2. Lining Mucosa (Covers 60% of total area)
3. Specialised Mucosa (15%)
Based upon keratinisation
1. KeratinisedOrthokeratinized
Parakeratinized
2. Non-keratinised.
Based upon Location
1. Buccal Mucosa.
2. Lingual Mucosa.
3. Palatal Mucosa.
4. Labial Mucosa.
5. Alveolar Mucosa.
Structure of Oral Mucosa
Epithelium
Lamina Propria.
Submucosa
EpitheliumEpithelium of the oral mucosa is stratified squamous
epithelium.
It may be
1.Keratinized 2.Non keratinized Keratinized layer ortho keratinized Para keratinized
Oral epithelium
Consists of two populations of cells:Progenitor populationMaturing population
Progenitor cells function is to divide and provide new cells
Maturing cells continually undergo a process of differentiation or maturation to form a protective layer
Amplifying CellsStem cells
Progenitor Cells
• Slow dividing • Maintain basal cell layer
• Rapidly dividing• Form other cell layers.
Turn over time
Skin : 52 – 75 days
Gut : 4 – 14 days
Gingiva : 41 – 57 days
Cheek : 25 days
Junctional Epithelium : 5 - 6 days
The time taken for a proginetor cell to pass through the entire epithelial thickness and reach the surface
Keratinized oral mucous membrane
Keratinised Epithelium (light microscopy)
Keratinised Epithelium (Electron Microscopy)
Basal layer made of cell that synthesize DNA & undergo mitosis.
Stratum Basale
Basal cells show ribosomes & elements of rough endoplasmic reticulum indicative of protein synthesizing activity.
Structureless zone seen under light microscope is basement membrane.
1 – 4 microns wide.
Under electron microscope, Basal lamina
lamina lucida – light zone lamina densa – dark
zone
Basal cells are attached to basal lamina by hemidesmosomes.
Epithelial cell-cell contact is made through desmosomes - macula adherens. These are anchored intracellularly by tonofibrils.
i) Serrated- heavily packed with tonofilaments which are adaptations for attachment.
ii) Non-serrated – stem cells – slowly dividing cells which serve to protect genetic information of the tissue.
Stratum spinosum or prickle cell layer:
It is a layer of relatively large irregular polyhedral cells.
Show first sign of maturation.
Nuclei stains less intense the intercellular spaces of the prickle layer are large and distended, with more prominent desmosomes
Stratum granulosum
Flatter & wider & nuclei show signs of degeneration & pyknosis.
Active in protein synthesis.
Involucrin - soluble precursor protein of the cornified envelope appears first in the spinosum.
Protein synthesis rate progressively gets diminished as cell approaches stratum corneum.
In the upper part cells of stratum granulosum, shows granules called ODLAND BODIES.
Keratinosome or odland bodies or membrane containing granulesModified lysosomes
0.25µm in length.
Rich in phospholipids.
Structure - layers of parallel lamellae, probably originating from golgi apparatus.
Lamellar granules discharge their contents - permeability barrier.
Stratum corneum
Made up of keratinised squamae, which are larger & flatter than the granular cells.
Nuclei & other organelles disappear.
Cell surfaces in this layer are more regular & more closely adapted to adjacent cell surfaces.
The filaggrin a non fibrous inter-filamentous matrix protien helps in this close adaptation.
Types of keratinized epithelium Parakeratinized Epithelium :The superficial cells are dead but retain the nucleus
Orthokeratinized Epithelium : The nuclei are lost in epithelium
Non – keratinized epithelium
Nonkeratinized epithelial cells in the superfacial layers do not have keratin filaments in the cytoplasm
The surface cells also have nuclei
This epithelium is associated with lining of the oral cavity
Difference Keratinized
Layers - basal, spinosum, granular, cornified layer.
Produce a cornified surface layer.
Prickly appearance.
Nonkeratinized
Layers-basal,intermediate, surface layer.
Do not produce a cornified surface layer.
Intercellular spaces not obvious-no prickly appearance.
No nuclei-orthokeratinised
Pyknotic nuclei-parakeratinised
Filaggrin present.
Numerous tonofilaments,keratohyaline granules present.
Lack filaggrin,but contain involucrin.
Less developed and dispersed tonofilments,lack keratohyaline granules.
Stratum superficiale contains nucleated cells
Lamina Propria Two Layers Papillary layer
Close to epithelial ridges.
Arranged loosely.
Reticular layer
Parallel to epithelium.
Fibers are very thick.
Consists of cells , blood vessels, neural elements & fibers embedded in amorphous ground substance.
Cells found in lamina propriaFibroblast Histiocytes Macrophages Mast cell Polymorph nuclear leucocytes Lymphocytes Plasma cells Endothelial cells
Submucosa
It attaches the mucous membrane to the underlying structures – muscle or bone
loose or a firm attachment and consists of glands, blood vessels, nerves, & adipose tissues.
connective tissue of various thickness
Nonkeratinocytes
Langerhan’s cells:Dendritic cells.
Merkel cell: touch receptors
Melanocytes: melanin systhesis
Inflammatory cells
Organization of the Oral Mucosa
3 types according to function:
Masticatory Mucosa:25% of total mucosa.
Lining Mucosa:60% of total mucosa
Specialized Mucosa:15% of total mucosa.
Lining mucosaCovers the floor of mouth, ventral (underside) tongue, alveolar mucosa, cheeks, lips and soft palate.
Lip
Lip is covered by lining mucosa
Vermilion borderJunction between the skin and mucous membrane
of the lip
Floor of the mouthLoosely attached to the underlying structures
Submucosa – adipose tissue
Ventral surface of the tongueThe mucous membrane is tightly bound to the muscle bundles of the tongue smooth and relatively thin
Cheek Submucosa contains fat cells and small mixed salivary glands
Mucosa of the Tongue - Specialised mucosa
Anatomical division It is divided into two parts by a V-shaped groove known as sulcus terminalis.
Anterior 2/3rd or papillary portion or body of the tongue contains lingual papillae.
Posterior 1/3rd is lymphatic portion or base of the
tongue contains lingual tonsil.
The different papillae found on the dorsal surface of the tongue are:
1. Filliform papillae
2. Fungiform papillae
3. Circumvallate papillae
4. Foliate papillae
1. Filliform papillae
Pointed extensions of the keratinized epithelial cells
Most numerous papillae of the tongue
Not associated with taste buds
Scanning electron micrograph of Filliform papillae(arrow)
2. Fungiform papillae
Fewer than the filliform papillae and are scattered over the dorsal surface of the tongue
Rounded elevations above the surface of the tongue
Have taste buds on their superior surfaces
Not keratinized
3. Circumvallate papillae
Located at the junction of the anterior two thirds (body) and posterior one thirds (base) of the tongue
There are eight to twelve in number
Lined with taste buds and also openings of serous glands
The secretion from the serous glands washes away food for renewal of taste
4. Foliate papillae
Located in the furrows along the posterior sides of the tongue
Lined with taste buds
Not prominent in human beings
Taste Buds They are small ovoid barrel shaped organs
40 micron thick and 80 micron high
Their outer surface is covered by flat cells which surround a small opening called the Taste Pore
Areolar mucosaThe areolar mucosa is a reddish-pink tissue with blue vascular areas.
The epithelium is extremely thin non-keratinized mucosa with a lamina propria
Hard Palate
Covered by masticatory mucosa
lateral regions of the posterior part contains palatine glands
Gingiva
Covers the alveolar process of jaws and surrounds the cervical portion of teeth.
It develops from the union of oral epithelium and reduced enamel epithelium
Gingiva can be classified as
Free gingiva,
Attached gingiva and
Interdental papilla
Part of the oral mucosa that surrounds the necks of the teeth and forms the free margin of the gingival tissue
differentiated apically by the free gingival groove
Free gingiva (marginal gingiva)
Attached gingivaBetween the free gingival groove and the alveolar mucosa
The junction of the attached gingiva and the alveolar mucosa is called mucogingival junction
In healthy mouth attached gingiva shows stippling
Interdental papilla Appear in-between teeth apical to the contact points
Valley like depression in the interdental papilla called Col.
Gingival sulcus
Space or potential space between the tooth surface and the free gingiva.
It is lined with sulcular epithelium
Extends from free gingival margin to the junctional epithelium.
Junctional epitheliumForms the seal of the gingival epithelium and the tooth
Floor of the gingival sulcus and extends apically to the enamel of the tooth
Disturbances of epithelial attachment results in deepening of the sulcus which is a sign of gingival/periodontal disease
Sulcular epithelium
It is nonkeratinized.
No rete pegs in sulcular epithelium.
Sulcular epithelium is continuous With gingival epithelium & the attachment epithelium
Gingiva contains dense fibers of collagen:
Dentogingival : extends from the
cervical cementum into the lamina
propria of the gingiva.
Circular: small group of fibers
that circle the tooth & interlace
with other fibers.
Dentoperiosteal: fibers can be followed from the cementum into periosteum of the alveolar crest & of the buccal & palatal or lingual surface of the alveolar bone.
Alveologingival: fibers arise from the alveolar crest & extends into lamina propria.
Biologic Width
Biologic widthThe dimension of space that the healthy gingival tissues occupy above the alveolar bone is the biologic width.
Connective Tissue attachment + junctional epithelium constitutes Biologic width 1.07mm +0.97mm= 2.04 mm
Any restoration should be atleast 3mm above the alveolar crest to prevent the violation of the biologic width.
Passive Eruption
Effect Of Aging On The Oral Mucosa
Epithelial thinning Decreased keratinization Less prominent rete pegs Decreased cellular proliferation Loss of submucosal elastin and fat Increased fibrotic connective tissue with
degenerative alteration in the collagen.
Prosthetic considerations
Behaviour of oral mucosa under stress
Under compression behaves in a viscoelastic fashion.
Loaded epithelium demonstrates decrease in the depth of epithelial ridges & connective tissue papillae
Care to be taken during impression procedures by applying minimal pressures.
Tissue response
A. Recently made dentures:Inflammation .Soft tissue distortion.Impingement of gingival margin.Accumulation of dental plaque.
B. Dentures in use for > 1 yearHyperkeratosis.Scarring of tissue in border area.Gross tissue distortion.
Soft tissue changes in oral mucosa due to prostheses
soft tissue hyperplasiafibrous hyperplasia.epulis fissurata.papillary hyperplasia.inflammatory process under denture basesdenture stomatitis.Candidiasis.ulcerative lesionsangular chelitis.
Soft tissue hyperplasiaRolls of hyperplastic tissues under denture base
Due to bone resorption, with lesion filling the space under denture base.
Develops slowly, painless.
Surgical removal.New dentures.
Papillary hyperplasia
Granular type of inflammation seen in palatal region.
Numerous papillary projections give a warty appearance.
They show precancerous tendencies.
Discontinue denture wearing. Surgery. New dentures
Epulis Fissuratum
It is a pathologic condition that appears in the mouth as an overgrowth of fibrous connective tissue.
Also known as inflammatory fibrous hyperplasia, denture epulis and denture induced fibrous hyperplasia.
It is mainly caused due to ill fitting dentures
Denture stomatitis
Chronic inflammation Ill fitting denture. Nocturnal denture wearing.Hypersensitivity.Poor oral hygiene.Infections –Candida albicans.
Candidiasis
Debilitated patients.
Systemic disease such as diabetes.
Unhygienic conditions.
- Discard the existing denture.
- Anti fungal therapy
- New dentures.
Angular chelitisSIGNSBilateral lesion that develops at the angle of the lips.
Deep fissure or crack may be seen.Appear ulcerated.Exudatve crust may be present.
Anti fungal therapy.
Denture bearing area
Points to be considered while fabrication of
denture:
Selective placement of forces by denture
base on supporting tissues.
Form and placement of denture borders to
accommodate normal function.
Selective placement of force can be achieved by employing different impression techniques depending on the patients oral condition
Minimal pressure technique/Mucostatic technique .
Selective pressure technique.
Pressure / Muco-compressive technique.
Crest of the residual ridge (maxillary)
Firmly attached to the bone.Keratinized epithelium.Dense collagen fibers .Sub mucosa – fat or glandular cells.
Primary support for denture.
Palatine rugae
Irregularly shaped rolls of soft tissue in the anterior part of hard palate.
Clinical considerations Secondary stress bearing area. Resists forward movement of denture. Tissue rebound phenomenon. Maxillary major connector should end into
depressions between the rugae.
Mucous membrane of hamular notch
Space between the posterior part of the maxillary tuberosity & pterygoid hamulus.
It is thick and made of loose areolar tissue.
Marks the distal end of
denture.
Buccal shelf area
Partially keratinized.
Loosely attached.
Bone – compact bone.
Clinical implication
Impression should cover
the entire available area.
Slope of the residual ridge (mandibular)
Keratinized epithelium .
When the soft tissue is
movable in the crest of the
ridge ,impression should be
recorded in its resting position.
F.P.D & oral mucosa
Sub gingival finish esthetics.
old restoration extending into the intracrevicular space.
Insufficient vertical length or height
Margins should be smooth with proper fit.
Esthetics & oral mucosa
Case of Altered passive eruption(APE)
Implants and Biological width
It has been found that the biological width need not be a vertical dimension but can have a horizontal component.
Platform switching provides this horizontal distance and so preserves the crestal bone.
CONCLUSION
References
Ten Cate A R, Oral histology development,structure and function, 5th edition, India, Mosby, 1999, pp 345-385.
Kumar G S, Orban’s oral histology and embryology, 12th edition,India, Elsevier,2006, pp 210-257
Zarb G.A, Bolender C L, Prosthodontic treatment for edentulous patients, 12th edition, India, Elsevier, 2004, pp 84-86, 211-223,233-241
Avery J K, Oral development and histology, 3rd edition, New York, Thieme, 2002, pp 243-252.
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