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.