The Gingiva

8/21/2019 The Gingiva

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The Gingiva


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The oral mucosa consists of three zones:

the Gingiva and the covering of the hard palate,

termed the masticatory mucosa.

the Dorsum of the tongue, covered by specializedmucosa.

and the Oral mucous membrane lining the

remainder of the oral cavity.


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The gingiva is the part of the oral mucosa that

covers the alveolar processes of the jaws and

surrounds the necks of the teeth.

CLINICAL FEATURES

The gingiva is divided anatomically into:

1. Marginal

2. Attached

3. and Interdental areas.


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1- Marginal Gingiva

The marginal, or unattached, gingiva is the terminal

edge or border of the gingiva surrounding the teeth in

collarlike fashion.

Usually about 1 mm wide, it forms the soft tissue

wall of the gingival sulcus. It may be separated from

the tooth surface with a periodontal probe.


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Gingival grooven


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Gingival Sulcus

The gingival sulcus is the shallow crevice or spacearound the tooth bounded by the surface of the toothon one side and the epithelium lining the free marginof the gingiva on the other.

It is V shaped and barely permits the entrance of aperiodontal probe. The clinical determination of thedepth of the gingival sulcus is an important diagnostic

parameter. The probing depth of a clinically normal gingival

sulcus in humans is 2 to 3 mm.


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2- Attached Gingiva

The attached gingiva is continuous with the marginalgingiva. It is firm, resilient, and tightly bound to theunderlying periosteum of alveolar bone.

The width of the attached gingiva is another

important clinical parameter. It is the distancebetween the mucogingival junction and the projectionon the external surface of the bottom of the gingival

sulcus or the periodontal pocket. It should not beconfused with the width of the keratinized gingivabecause the latter also includes the marginal gingiva


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The width of the attached gingiva on the facial aspectdiffers in different areas of the mouth. It is generallygreatest in the incisor region (3.5 to 4.5 mm in themaxilla and 3.3 to 3.9 mm in the mandible) and lessin the posterior segments, with the least width in the

first premolar area (1.9 mm in the maxilla and 1.8mm in the mandible)

Because the mucogingival junction remains stationarythroughout adult life, changes in the width of the

attached gingiva are caused by modifications in theposition of its coronal end. The width of the attachedgingiva increases with age and in supraerupted teeth


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3- Interdental Gingiva

The interdental gingiva occupies the gingivalembrasure, which is the interproximal space beneaththe area of tooth contact.

The interdental gingiva can be pyramidal or have acol shape.

The shape of the gingiva in a given interdental spacedepends on the contact point between the two

adjoining teeth and the presence or absence of somedegree of recession.


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Diagram comparing anatomic variations of the interdental col in the normal gingiva

(left side) and after gingival recession (right side).

A, B, Mandibular anterior segment, facial and buccolingual views, respectively.

C, D, Mandibular posterior region, facial and buccolingual views, respectively.Tooth contact points are shown in B and D.


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Absence of interdental papillae and col where proximal tooth contact is missing.

If a diastema is present, the gingiva is firmly bound over

the interdental bone and forms a smooth, rounded

surface without interdental papillae


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The lateral borders and tips of the interdentalpapillae are formed by a continuation of the

marginal gingiva from the adjacent teeth. The

intervening portion consists of attachedgingiva


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Gingival Epithelium

General Aspects of Gingival Epithelium Biology

Although it constitutes a continuous lining of stratified

squamous epithelium, three different areas can be defined from

the morphologic and functional points of view:1. the oral or outer epithelium

2. sulcular epithelium

3. and junctional epithelium.


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The principal cell type of the gingival epithelium,

as well as of other stratified squamous epithelia, isthe keratinocyte.

Other cells found in the epithelium are the clear

cells or nonkeratinocytes, which include:1. Langerhans cells.

2. Merkel cells

3. and Melanocytes.


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The main function of the gingival epithelium is to protect thedeep structures while allowing a selective interchange with theoral environment. This is achieved by proliferation and

differentiationof the keratinocyte.

Proliferation of keratinocytes takes place by mitosis in thebasal layer and less frequently in the suprabasal layers, wherea small proportion of cells remain as a proliferativecompartment while a larger number begins to migrate to thesurface.

Differentiation involves the process of keratinization, whichconsists of a sequence of biochemical and morphologic eventsthat occur in the cell as it migrates from the basal layer .


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Diagram showing representative cells from the various layers of stratified

squamous epithelium as seen by electron microscopy.


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The main morphologic change is a

progressive flattening of the cell with anincreasing prevalence of tonofilaments

and intercellular junctions coupled to the

production of keratohyaline granules and

the disappearance of the nucleus.


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Only some areas of the outer gingival epithelium are

orthokeratinized; the other gingival areas are covered

by parakeratinized or nonkeratinized epithelium,

considered to be at intermediate stages ofkeratinization.


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In parakeratinized epithelia, the stratum corneum

retains pyknotic nuclei and the keratohyalin granulesare dispersed, not giving rise to a stratum

granulosum.

The nonkeratinized epithelium (although cytokeratinsare the major component, as in all epithelia) has

neither granulosum nor corneum strata, and

superficial cells have viable nuclei.


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Nonkeratinocyte cells are present in gingival epitheliumas in other malpighian epithelia. Melanocytes are

dendritic cells located in the basal and spinous layers ofthe gingival epithelium. They synthesize melanin inorganelles called premelanosomes or melanosomes

These contain tyrosinase, which hydroxylates tyrosine todihydroxyphenylalanine (dopa), which in turn isprogressively converted to melanin. Melanin granulesare phagocytosed and contained within other cells of theepithelium and connective tissue, called melanophagesor melanophores.


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Variations in gingival epithelium. A, Keratinized. B, Nonkeratinized. C,

Parakeratinized. Horny layer (H), granular layer (G), prickle cell layer (P), basal cell

layer (Ba), flattened surface cells (S), parakeratotic layer (Pk).


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Langerhans cells are dendritic cells located among

keratinocytes at all suprabasal levels. They belong tothe mononuclear phagocyte system(reticuloendothelial system) as modified monocytesderived from the bone marrow.

Langerhans cells have an important role in theimmune reaction as antigen-presenting cells forlymphocytes.


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Merkel cells are located in the deeper layers of the

epithelium, harbor nerve endings, and are connected

to adjacent cells by desmosomes. They have been

identified as tactile perceptors.


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The epithelium is joined to the underlying connectivetissue by a basal lamina, lying beneath the epithelialbasal layer.

The basal lamina consists of lamina lucida and laminadensa.

Hemidesmosomes of the basal epithelial cells abut the

lamina lucida, which is mainly composed of theglycoprotein laminin.

The lamina densa is composed of type IV collagen.


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The complex of basal lamina and fibrils is the

periodic acid-Schiff (paS) positive andargyrophilic line observed at the optical level.

The basal lamina is permeable to fluids but

acts as a barrier to particulate matter.


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The basement membrane (B) is seen between the epithelium (E) and the

underlying connective tissue (C). In the epithelium, glycoprotein material

occurs in cells and cell membrane of the superficial hornified (H) and

underlying granular layers (G). The connective tissue presents a diffuse

amorphous ground substance and collagen fibers. The blood vessel walls

stand out clearly in the papillary projections of the connective tissue (P).


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Development of the Gingival Sulcus

After enamel formation is complete, the enamel iscovered with reduced enamel epithelium, which is

attached to the tooth by a basal lamina andhemidesmosomes.

When the tooth penetrates the oral mucosa, the

reduced enamel epithelium unites with the oralepithelium and transforms into the junctionalepithelium.

As the tooth erupts, this united epithelium condenses

along the crown, and the ameloblasts, which form theinner layer of the reduced enamel epitheliumgradually become squamous epithelial cells.


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Eruption process in cat's tooth. A,

Unerupted tooth. Dentine (D),

remnants of enamel matrix (E),reduced enamel epithelium (REE),

oral epithelium (OE), artifact (a).


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remnants of enamel matrix (E),

reduced enamel epithelium (REE),

oral epithelium (OE), artifact (a).B, Erupting tooth forming

junctional epithelium (JE).


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remnants of enamel matrix (E),

oral epithelium (OE), Erupting

tooth forming junctional epithelium(JE)., Completely erupted tooth.

Sulcus with epithelial debris (S),

cementum (C), and epithelial rests

(ER).


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The junctional epithelium is a continuallyselfrenewing structure with mitotic activity occurringin all cell layers. The regenerating epithelial cellsmove toward the tooth surface and along it in acoronal direction to the gingival sulcus, where they

are shed The sulcus consists of the shallow space that is

coronal to the attachment of the junctional epithelium

and bounded by the tooth on one side and the sulcularepithelium on the other. The coronal extent of thegingival sulcus is the gingival margin.


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Junctional epithelium on an erupting

tooth. The junctional epithelium (JE)

is formed by the joining of the oralepithelium (OE) and the reduced

enamel epithelium (REE). Afibrillar

cementum, sometimes formed on

enamel after degeneration of the

REE, is shown at AC. The arrowsindicate the coronal movement of the

regenerating epithelial cells, which

multiply more rapidly in the JE than

in the OE. E, Enamel; C, root

cementum. A similar cell turnoverpattern exists in the fully erupted

tooth.


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Gingival Fluid (Sulcular Fluid)

The gingival sulcus contains a fluid that seeps into itfrom the gingival connective tissue through the thinsulcular epithelium. The gingival fluid is believed to:

1) cleansematerial from the sulcus.

2) contain plasma proteins that may improve adhesionof the epithelium to the tooth.

3) possess antimicrobialproperties.

and 4) exert antibody activityto defend the gingiva.


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Gingival Connective Tissue The connective tissue of the gingiva is 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.


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Connective tissue has a cellular and an extracellularcompartment composed of fibers and ground substance.

The ground substance fills the space between fibers and cells,is amorphous, and has a high content of water. It is composed

of proteoglycans, mainly hyaluronic acid and chondroitinsulfate, and glycoproteins, mainly fibronectin. Glycoproteins account for the faint paS positive reaction of the ground

substance.

Fibronectin binds fibroblasts to the fibers and many other components of

the intercellular matrix, helping mediate cell adhesion and migration. Laminin is another glycoprotein found in the basal laminae, which serves

to attach it to epithelial cells.


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The three types of connective tissue fibers arecollagen, reticular, and elastic.

1. Collagen type Iforms the bulk of the lamina

propria and provides the tensile strengthto thegingival tissue.

2. Type IV collagen(argyrophilic reticulum fiber)

branches between the collagen type I bundles and iscontinuous with fibers of the basement membraneand blood vessel walls.

3. The elastic fibersystem is composed of oxytalan,elaunin, and elastin fibersdistributed amongcollagen fibers.


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The gingival fibers have the following functions:

1. To brace the marginal gingiva firmly against thetooth

2. To provide the rigidity necessary to withstand theforces ofmasticationwithout being deflected awayfrom the tooth surface

3. To unite the free marginal gingiva with thecementum of the root and the adjacent attachedgingiva


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The gingival fibers are arranged in three groups:gingivodental, circular, and transseptal.

GINGIVODENTAL GROUP. The gingivodentalfibers are those on the facial, lingual, and interproximalsurfaces. They are embedded in the cementum justbeneath the epithelium at the base of the gingivalsulcus.

CIRCULAR GROUP. The circular fibers course

through the connective tissue of the marginal andinterdental gingivae and encircle the tooth in ringlikefashion.


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TRANSSEPTAL GROUP. Located interproximally,the transseptal fibers form horizontal bundles that

extend between the cementum of approximating teeth

into which they are embedded. They lie in the areabetween the epithelium at the base of the gingival

sulcus and the crest of the interdental bone and are

sometimes classified with the principal fibers of theperiodontal ligament.


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Page and co-workers also have described (1) agroup of semicircular fibers, which attach at the

proximal surface of a tooth, immediately below thecementoenamel junction, go around the facial orlingual marginal gingiva of the tooth, and attach onthe other proximal surface of the same tooth; and (2)

a group of transgingival fibers, that attach in theproximal surface of one tooth, traverse the interdentalspace diagonally, go around the facial or lingualsurface of the adjacent tooth, again traversediagonally the interdental space, and attach in the

proximal surface of the next tooth.


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Diagram of the

gingivodental fibers

extending from thecementum (1) to the

crest of the gingiva,

(2) to the outer

surface, and (3)

external to theperiosteum of the

labial plate. Circular

fibers (4) are shown

in cross-section.


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Cellular Elements of gingiva connective tissue

The preponderant cellular element in the gingival

connective tissue is the Fibroblast.

Fibroblasts synthesize collagen and elastic fibersas

well as the glycoproteins and glycosaminoglycans of

the amorphous intercellular substance.

Fibroblasts also regulate collagen degradation.


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Mast cells, which are distributed throughout thebody, are numerous in the connective tissue of theoral mucosa and the gingiva.

Neutrophils can be seen in relatively high numbersin both the gingival connective tissue and the sulcus.These inflammatory cells usually are present in smallamounts in clinically normal gingiva.


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Blood Supply, Lymphatics, and Nerves

Three sources of blood supply to the gingiva are as follows:

1. Supraperiosteal arteriolesalong the facial and lingual surfacesof the alveolar bone.

2. Vessels of the periodontal ligament, which extend into the

gingiva and anastomose with capillaries in the sulcus area.3. Arterioles, which emerge from the crest of the interdental

septaand extend parallel to the crest of the bone to anastomosewith vessels of the periodontal ligament, with capillaries in the

gingival crevicular areas and vessels that run over the alveolarcrest.


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Diagram of arteriole penetrating the interdental alveolarbone to supply the interdental tissues (left) and a

supraperiosteal arteriole overlying the facial alveolar

bone, sending branches to the surrounding tissue (right).


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The lymphatic drainage of the gingiva brings in thelymphatics of the connective tissue papillae. It

progresses into the collecting network external to theperiosteum of the alveolar process and then to theregional lymph nodes(particularly the submaxillary

group). In addition, lymphatics just beneath thejunctional epithelium extend into the periodontalligament and accompany the blood vessels.


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Gingival innervation is derived from fibers arising

from nerves in the periodontal ligament and fromthe labial, buccal, and palatal nerves. The followingnerve structures are present in the connective tissue: a

meshwork of terminal argyrophilic fibers, some ofwhich extend into the epithelium; Meissner-typetactile corpuscles; Krause-type end bulbs, which aretemperature receptors; and encapsulated spindles.


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CORRELATION OF CLINICAL

AND MICROSCOPICFEATURES


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An understanding of the normal clinical features of

the gingiva requires the ability to interpret them in

terms of the microscopic structures they represent.

C l


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Color

The color of the attached and marginal gingivae isgenerally described as coral pinkand is produced by

the vascular supply, the thickness and degree ofkeratinizationof the epithelium, and the presence of

pigment-containing cells.

The attached gingiva is demarcated from the adjacentalveolar mucosa on the buccal aspect by a clearlydefined mucogingival line. The alveolar mucosa is

red, smooth, and shiny rather than pink and stippled.


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Si


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Size

The size of the gingiva corresponds with the sum

total of the bulk of cellular and intercellular elements

and their vascular supply. Alteration in size is acommon feature of gingival disease.

C t


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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 proximalcontact, and the dimensions

of the facial and lingual

gingival embrasures.

Shape


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Shape

The shape of the interdental gingiva is governed bythe contour of the proximal tooth surfaces and the

location and shape of gingival embrasures.

Consistency


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Consistency

The gingiva is firm and resilient and, with theexception of the movable free margin, tightly bound

to the underlying bone.

Surface Texture


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Surface Texture

The gingiva presents a textured surface similar to an orangepeel and is referred to as being stippled . Stippling is best

viewed by drying the gingiva. The attached gingiva isstippled; the marginal gingiva is not.

The pattern and extent of stippling varies among individualsand different areas of the same mouth.

The central portion of the interdental papillae is usuallystippled, but the marginal borders are smooth.

Stippling varies with age. It is absent in infancy, appears insome children at about 5 years of age, increases until

adulthood, and frequently begins to disappear in old age.


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Position

The position of the gingiva refers to the level at

which the gingival margin is attached to the tooth.

When the tooth erupts into the oral cavity, the marginand sulcus are at the tip of the crown; as eruption

progresses, they are seen closer to the root.


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Continuous Tooth Eruption. According to theconcept of continuous eruption, eruption does not

cease when teeth meet their functional antagonists butcontinues throughout life. It consists of an active anda passive phase. Active eruption is the movement of

the teeth in the direction of the occlusal plane,whereas passive eruption is the exposure of theteeth by apical migration of the gingiva.

Passive eruption is divided into four stages :


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Stage 1: The teeth reach the line of occlusion. The junctionalepithelium and base of the gingival sulcus are on the enamel.

Stage 2: The junctional epithelium proliferates so that part is onthe cementum and part is on the enamel. The base of the sulcus

is still on the enamel.


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Stage 3: The entire junctional epithelium is on

the cementum, and the base of the sulcus is atthe cementoenamel junction. As the junctional

epithelium proliferates from the crown onto

the root, it does not remain at the

cementoenamel junction any longer than at

any other area of the tooth.


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Stage 4: The junctional epithelium has

proliferated farther on thecementum. The base of the sulcus ison the cementum, a portion ofwhich is exposed. Proliferation of

the junctional epithelium onto theroot is accompanied bydegeneration of gingival and

periodontal ligament fibers and theirdetachment from the tooth.


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Any Questions?


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The Gingiva