Dental College AzamgarhDepartment of Periodontology

Seminar On : Junctional Epithelium

Guided By: Submitted byDr. Leka Dr.Rahul KesharwaniDr. Kapil Garg PG 1st year Dr. RajeshDr. Anjum VishwasDr. Abhishek SinhaDr. Vivek TripathiDr. Payal Gupta

• Introduction

• Junctional epithelium

– Development of junctional epithelium

– Structure

– Epithelial attachment

– Dynamic aspects of junctional epithelium

– Expression of various molecules and their functions

– Permeability

– Functions

– Regeneration

– role of JE in initiation of pocket formation

• Junctional epithelium around implants

• Biologic width

• Conclusion

Introduction

• Teeth are trans-mucosal organs.

• This is a unique association in the human body where a hard

tissue emerges through the soft tissue.

• Permanently wet, warm, nutrient rich oral cavity

Perfect environment for microorganisms

forms complex ecological system

attaches to glycoprotein layer on solid/ non shedding surfaces

Tissue in vicinity are constantly challenged.

• The tooth-epithelial interface thus call for a specialized

structural and functional adaptation

• Listgarten MA, 1970:Dento-gingival unit refers to the

functional unit comprising of junctional epithelium and the

gingival fibers

• Gingival apparatus maintains free gingival and functional

epithelium in close approximation to tooth.

• The attachment of functional epithelium to tooth is reinforced

with gingival fibers, which support the gingiva against tooth

surface.

• So that, gingival fibers along with junctional epithelium

functional unit

Dentogingival unit

History

• Gottlieb (1921) was the first to describe the junctional

epithelium

• Schroeder and Listgarten (1977) clarified the anatomy and

histology of the dentogingival junction in their monograph:

‘Fine structure of developing epithelial attachment of human

teeth’.

• The oral epithelium around a tooth is divided into three functional compartments– gingival, sulcular, and junctional epithelium

• The gingival epithelium extends from the mucogingivaljunction to the gingival margin where crevicular/sulcular epithelium lines the sulcus

• At the base of the sulcus connection between gingivaand tooth is mediated with JUNCTIONAL EPITHELIUM

Three zones of the gingival epithelium

Crevicular (sulcular) epithelium

Oral epithelium

Junctionalepithelium

Development Of JE

• During transformation process,

reduced ameloblasts undergo structural change

short columnar flattened cells that orient

parallel to enamel surface

Structure of junctional epithelium

• Anatomical aspects

• Junctional epithelium and interstitial cells

• Epithelial attachment

Anatomical aspects

• part of marginal free gingiva Forms a collar

• Interproximal area ---- fuse to form

epithelial lining of interdental col

• The coronal termination of the

junctional epithelium corresponds

usually to the bottom of the

gingival sulcus.

JE and Interstitial cell

• JE is a collar-like band of nonkeratinised stratified squamousepithelium extending from cemento-enamel junction to bottom of gingival sulcus

• Coronally it is 15-30 cells thick and apically narrows to 1-3 cells

• Its length varies from 0.25 – 1.35mm

stratum basale ( towards CT )

• Made up of 2 layers

stratum suprabasale

(facing tooth surface)

• Organelles- lysosomal bodies, golgi fields, polyribosomes,

cisternae of RER(rough endoplasmic reticulum) are abundant.

• All JE cells express unique set of cytokeratins 5, 13, 14, 19

& occasionally 8, 16, 18.

• Cells are connected by Desmosomes.

• Fluid filled intercellular spaces may vary in width.

EPITHELIAL ATTACHMENT APPARATUS

• The term epithelial attachment refers to the attachment

apparatus, i.e. internal basal lamina & hemidesmosomes

that connects the junctional epithelium to the tooth surface.

• It consists of hemidesmosomes at the plasma membrane of the

cells directly attached to the tooth (DAT cells) and a basal

lamina-like extracellular matrix, termed the internal basal

lamina, on the tooth surface

HISTORICAL CONCEPTS OF

ATTACHMENT

Gottlieb’s concept (1921)

• Soft tissue of gingiva is organically united to enamel surface.

• He termed the epithelium contacting the tooth “epithelial

attachment”.

Orban’s concept (1953)

• He stated that the separation of the epithelial attachment cells

from the tooth surface involved preparatory degenerative

changes in the epithelium.

Waerhaug’s concept (1960)

• He presented the concept of epithelial cuff. This concept was

based on insertion of thin blades between the surface of tooth

and the gingiva

• Blades could be easily passed apically to the connective tissue

attachment at CEJ without resistance.

• It was concluded that gingival tissue and tooth are closely

adapted but not organically united.

Schroeder and Listgarten concept

(1971)

• The previous controversy was resolved after evolution of transmission electron microscopy.

• 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.

• Basement membrane – specialized extracellular matrix

• Functions-

a. Compartmentalization

b. Filtration

(selective permeability barrier function)

c. Cell polarization, migration.

d. Cell adhesions

e. Cell differentiation.

Epithelial attachment at molecular level

• The junctional epithelium faces both the gingival connective

tissue (i.e., the lamina propria of the gingiva) and the tooth

surface

JE

• consists of lamina lucida

lamina densa

lamina fibroreticularis

• Typical matrix constituents of basement membrane

1. Collagen types IV & VII

2. Laminin

3. Heparin sulfate proteoglycan

4. Fibronectin

5. Nidogen

6. Proteoglycan

7. perlecan

REPRESENTATION DETAIL OF THE INTERNAL

BASAL LAMINA

It consists of two layers: the

lamina lucida and lamina

densa.

Hemidesmosomes (HD)

originate from the lamina

lucida, and tonofilaments

splay out from each

hemidesmosome.

• The internal basement membrane was initially described as an

80-120nm wide homogeneous layer. It directly faces the enamel,

with an intervening laminated or non-laminated layer of cuticles

(Listgarten, 1966) or afibrillar cementum (Kobayashi et al.,

1976).

• There are numerous fine strands crossing the lamina densa of the

internal basement membrane at the hemidesmosomes. These

strands may have been the anchoring filaments of

hemidesmosomes (Eady, 1994; Garrod, 1993).

• In the cytoplasm of the cells of the junctional epithelium, the

tonofibrils are associated with hemidesmosomes.

• The internal basement membrane of the dentogingival border is

uniquely specialized for mechanical strength, sealing off the

periodontal tissues from the oral environment (Sawada &

Inoue, 1996).

• The internal basement membrane takes the form of both thin

and multilayered thick basement membranes

• Multilayered internal basement membrane may provide

mechanical strength for firm attachment of the tooth to the

gingiva and the sealing off of the periodontal tissues from the

oral environment.

INTERNAL BASEMENT MEMBRANE

Internal basement membrane is

composed of single broad

lamina densa

Internal basement membrane is

composed of multi-layers

of lamina densa

• The finer level structure of the internal basement membrane is,

the “cord” network. The basic texture of the lamina densa is

made up of a 3-dimensional network formed by anatomizing,

irregular, thread-like structures referred to as “cords” (Inoue,

1994; Sawada & Inoue, 2001).

Lamina densa is composed of fine network of irregular

anatomizing cords

MECHANISM OF BINDING OF NORMAL TOOTH TO

GINGIVA THROUGH CORD LIKE STRUCTURES IN

LAMINA DENSA

• The lamina densa of the internal basement membrane is

closely associated with an additional layer referred to as the

supplementary lamina densa found on the enamel side of the

tooth.

• One part of the basement membrane, the supplementary

lamina densa, is mineralized. This mineral deposit is

continuous with that of the enamel of the tooth, and thus this

deposit on the supplementary lamina densa forms an

advancing edge of mineralization.

(Sawada & Inoue, 2003)

• In the mineralized portion of the lamina densa, mineral

crystals were arranged in a network pattern which was

comparable to the pattern of the cord network.

• This may assist more powerful gripping, and further

demonstrates the elaborate mechanism by which firm binding

of the mineral and organic phases is achieved.

DENTO-GINGIVAL BORDER OF TOOTH FROM DEMINERALIZED

AND NON-DEMINERALIZED SAMPLES

DEMINERALIZED SECTION

SHOWING THE EMPTY SPACE

OF SUBLAMINA DENSA

MINERALISED SECTION

SHOWING MINERALISED

SUBLAMINA DENSA LUCIDA

CONTINUOUS WITH ENAMEL

Dynamic aspects of junctional epithelium

• Cells and extracellular dynamics of JE – essential for its

protective & regenerative function.

• Exfoliation must occur at extremely high rate ( Loe & Karring

1969)

• Since DAT cells are connected to basal lamina via

hemidesmosomes, a remodelling of epithelial attachment must

occur.

• Thus epithelial attachment normally is not static but dynamic.

• Intercellular spaces of JE

provides pathway for fluid & transmigratory leukocytes

a variety of molecules + leukocytes ( host defense system)

Expression of various molecules and their

function

• JE cells have surface or cell membrane molecules that play a

role in cell matrix and cell-cell interactions. JE cells express

numerous cell adhesion molecules (CAM’s), such as integrins

and cadherins.

• Knowledge about structure and molecules involved in the

maintenance of cell-cell contact is particularly important in

view of the pathological changes that the epithelium undergoes

during its conversion to a pocket lining.

• Integrins – are cell surface receptors that mediate interactions

between cell and extracellular matrix, and also contribute to

cell to cell adhesion.

• The cadherins are responsible for tight contacts between cells.

• E-cadherin, an epithelium specific cell adhesion molecule,

plays a crucial role in maintaining the structural integrity.

• Intercellular adhesion molecule-1(ICAM-1) and lymphocytic

function antigen- 3(LFA-3) are additional cell adhesion

molecules.

• Cells in contact with the internal basal lamina express the

integrins.

(CAM1)—a transmembrane cell-adhesion molecule that is

expressed on leukocytes, epithelia, and blood vessel endothelia

.

high expression of interleukin-8 (IL-8), a chemotactic

cytokine, is seen in the coronal-most cells of the junctional

epithelium

interleukin-1α (IL-1α),

interleukin-1β (IL-1β),

tumor necrosis factor-α (TNF-α)—are strongly expressed in

the coronal half of the junctional epithelium

N-acetyllactosamine—the type 2 chain H precursor of the

blood group A-specific carbohydrate, which is usually

associated with the lowest level of cell differentiation.

• Antimicrobial molecules--- α and β defensins

cathelicidin family

calprotectin

DYNAMICS (TURNOVER RATE) OF JE

• The turnover rate of JE cells is rapid.

• The DAT cells express a high density of transferring receptors

supporting the idea of active metabolism and high turnover.

• DAT cells have an important role in tissue dynamics and

reparative capacity of the JE.

• The existence of a dividing population of DAT cells in a

suprabasal location in several layers from connective tissue is

a unique feature of JE.

Mechanism of JE cells turnover

(1)The daughter cells are produced by dividing

DAT cells and replace degenerating cells on the

tooth surface.

(2) The daughter cells enter the exfoliation

pathway and gradually migrate coronally

between the basal cells and the DAT cells to

eventually break off into the sulcus, or

(3)Epithelial cells move/migrate in the coronal

direction along the tooth surface and are

replaced by basal cells migrating round the

apical termination of the junctional epithelium.

PERMEABILITY OF JUNCTIONAL

EPITHELIUM

• The bi-directional arrows indicate

that the junctional epithelium is the

most permeable portion of the

gingival epithelia.

• Because of its permeability to

bacterial products and other

assorted antigens, the connective

tissue adjacent to the junctional

epithelium tends to become

infiltrated with chronic

inflammatory cells, primarily

lymphocytes and plasma cells.

FUNCTIONS OF JUNCTIONAL EPITHELIUM

• Has attachment role and protective role.

• Permeability allows GCF and defence cells to pass across to

protect underlying tissues from disease processes (periodontal

disease).

• Helps maintain integrity of tooth/periodontium structure

• GCF contains gamma globulins and poly-morphonuclearleukocytes (PMNs) giving it immunological/phagocyticproperties to combat disease processes.

• Such molecules pass readily across JE to underlying tissues.

• JE may contain neutrophils & other inflammatory cells indicating disease & state of health of periodontium.

• The junctional epithelium plays a crucial role since it

essentially seals off periodontal tissues from the oral

environment.

• Its integrity is thus essential for maintaining a healthy

periodontium.

• Periodontal disease sets in when the structure of the junctional

epithelium starts to fail, an excellent example of how structure

determines function.

JE in antimicrobial defense(1) JE cells exfoliate because of rapid cell division

(2) funneling of junctional epithelial cells towards the sulcus hinder bacterial

colonization.

(3) Active antimicrobial substances are produced in junctional epithelial cells.

(4) Epithelial cells activated by microbial substances secrete chemokines, that

attract and activate professional defense cells, PMN.

• Role of JE in pocket formation

Role of JE in the initiation of pocket formation

• Conversion of the JE to pocket epithelium is regarded as a

hallmark in the development of periodontitis.

• Schroeder – 1996 pointed to a biologically relevant and

clinically important question that still awaits resolution: ‘what

happens to the JE under conditions of sub-gingival microbial

attack i.e. in context with pocket formation and deepening?’

• Schluger et al 1977: Pocket formation is attributed to a loss of

cellular continuity in the coronal most portion of the JE

• Thus the initiation of pocket formation may be attributed to the

detachment of the DAT cells from the tooth surface or to the

development of intraepithelial split.

• Takata and Donath (1988) observed degenerative changes in

the second or third layer of the DAT cells in the coronal most

portion of the JE cells facing the biofilm.

• Schroeder and Listgarten 1977: An increased number of

mononuclear leukocytes (T and B cells, macrophages) together

with PMNs are considered as factors contributing to the

disintegration of the JE.

The degeneration and

detachment of DAT cells

exposes tooth surface and

creates a sub-gingival niche

suitable for the colonization

of anaerobic gram-negative

bacteria and apical growth of

dental plaque.

• Hintermann et al 2002: Gingipains degrade the epithelial cell-

cell junctional complexes and cells exposed to proteinases

derived from P.gingivalis showed reduced adhesion to

extracellular matrix.

• Destruction of cell-cell and cell to ECM perturbs the structural

and functional integrity of the JE.

• Regeneration of JE

• Injury to JE may occur due to intentional or accidental trauma.

• Accidental trauma can occur during probing, flossing or tooth

margin preparations for restorations.

• Intentional trauma occurs during periodontal surgeries where

the JE is completely lost.

• Many studies have been done to investigate the renewal of JE.

These include studies done on renewal of JE on tooth and

implant surface after mechanical detachment by probing.

• Studies have been done on mechanical trauma during flossing

and on regeneration of JE after gingivectomy procedure which

completely removes JE.

• Taylor and Campbell 1972: A new and complete attachment

indistinguishable from that in control was established 5 days

after complete separation of the JE from the tooth surface.

• Frank et al 1972: A study demonstrated that newly

differentiated attachment apparatus with normal

hemidesmosomal attachment is possible following surgery.

This new attachment apparatus was seen on cementum as well

as dentin.

• Listgarten 1972:Hemidesmosomes appeared to form prior to

the basal lamina. The basal lamina is initially formed in close

proximity to the hemidesmosomes at both the tooth and

connective tissue interface. At 4 to 7 weeks, the basal lamina

appeared complete. Studies have shown that regeneration of JE

after procedure usually occurs within 20 days.

• JE AROUND IMPLANTS

• The junctional epithelium around implants always originates

from epithelial cells of the oral mucosa, as opposed to the

junctional epithelium around teeth which originates from the

reduced enamel epithelium.

BIOLOGIC WIDTH

• BIOLOGIC WIDTH is defined

as the dimension of the soft

tissue which is attached to the

portion of the tooth coronal to

the crest of the alveolar bone

• It is important from the

restorative point of view

because its violation leads to

complications like gingival

enlargement alveolar bone loss

and improper fit of the

restoration.

NATURAL TOOTH

• Epithelium tapers

towards the depth

• Large number of

cell organelles

• Fibers are

arranged

perpendicular

IMPLANT

•Epithelium is

thicker

•Few organelles

•Fibers are arranged

parallely

•Numerous kerato-

hyalin granules

• Gargiulo et al (1961) in their study described the dimensions

and relations of dentogingival junction in humans. The average

histological width of connective tissue attachment was

1.07mm. The mean average length of epithelial attachment

was 0.97mm with the range of 0.71mm-1.35mm.

• The average combined histological width of connective tissue

attachment and junctional epithelium was 2.04mm, which is

referred to as the BIOLOGIC WIDTH.

CONCLUSION

• DENTOGINGIVAL UNIT is important because of its

anatomical location.

• It is the site of host-bacterial interaction in initiation of

periodontal disease.

• There is a constant presence of bacteria and their products in

the gingival sulcus which makes this an important structural

component of periodontal defense mechanism.

• The conversion of the junctional epithelium to pocket

epithelium is regarded as hallmark in the development of

periodontitis.

Future scope

• To find out the therapeutic strategies that stop the disease

progression at this important tooth-tissue interface.

References

• CARRANZA 11TH EDITION

• JAN LYNDHE 5TH EDITION

• DD Bosshardt and NP Lang. The Junctional Epithelium: from health to disease. J Dent Res 2005, 84 (1): 9-20

• Moon-Il Cho & Philias R. Garant. Development and general structure of the periodontium. Periodontology 2000, Vol. 24, 2000, 9–27.

• Mark Bartold, Laurence J. Walsh & A. Sampath Narayanan. Molecular and cell biology of the gingiva.P. Periodontology 2000, Vol. 24, 2000, 28–55.

• Thomas M Hassell. Tissues and cells of the periodontium. Periodontology2000, Vol. 3, 1993, 9-38

• Huberte . Schroede & R M Listgarten. The gingival tissues: The architecture of periodontal Protection. Periodontology 2000, Vol. 13, 1997, 91-120.

• Takashi Sawada1 and Sadayuki Inoue. Ultrastructure of DentogingivalBorder of Normal and Replanted Tooth and Dental Implant, chapter 11www.intechopen.com/books/implantdentistry