Junctional epithelium

Definitions
History
Development of junctional epithelium
Structure
Dynamic aspects of junctional epithelium
Expression of various molecules and their functions
Permeability
Functions
Role of JE in gingivitis
Role of JE in initiation of pocket formation
Passive Eruption
Effect of Trauma from Occlusion on JE
Junctional Epithelium Adjacent to Oral Implants
Syndromes Affecting JE
Regeneration of junctional epithelium
Conclusion
References

1. Dr. BEENA VIJAYAN PARVATHY 1st YEAR POST GRADUATE Dept of Periodontics and Implantology JUNCTIONAL EPITHELIUM

2. CONTENTS Definitions History Development of junctional epithelium Structure Dynamic aspects of junctional epithelium Expression of various molecules and their functions Permeability Functions Role of JE in gingivitis Role of JE in initiation of pocket formation Passive Eruption Effect of Trauma from Occlusion on JE Junctional Epithelium Adjacent to Oral Implants Syndromes Affecting JE Regeneration of junctional epithelium Conclusion References

3. INTRODUCTION Junctional epithelium is the non-keratinizing stratified squamous epithelium, that surrounds the tooth like a collar with a cross- section resembling a thin wedge. Epithelium of the gingiva which gets attached to the tooth is junctional or attachment epithelium. Derived from the reduced enamel epithelium (REE) during tooth development. Forms the floor of sulcus and attaches gingiva to tooth surface. The union between this epithelium and tooth is referred to as epithelial attachment. Resembles REE in its structure in that they have a basal layer and few layers of flattened cells

4. DEFINITIONS The junctional epithelium consists of a collar like band of stratified squamous non- keratinizing epithelium. (Joseph P, Carranza’s 10 th Edition) A single or multiple layer of non-keratinizing cells adhering to the tooth surface at the base of the gingival crevice. (Glossary of Periodontal Terms) The innermost cells of the junctional epithelium form and maintain a tight seal against the mineralized tooth surface. (Schroeder and Listgarten , 1977)

5. TERMINOLOGIES Epithelial attachment – Gottlieb 1921 Epithelial cuff - Waerhaug 1952 Attached epithelial cuff - Orban 1956 Attachment epithelium - Grant, Stern 1968 Junctional epithelium - Anderson and Stern1967

6. HISTORY The first to describe the junctional epithelium.

7. Based on his animal experiments(in dogs).

8. DEVELOPMENT OF JE

9. STRUCTURE • Anatomical aspects • Junctional epithelium and interstitial cells • Epithelial attachment

10. Anatomical aspects Part of marginal free gingiva • Forms a collar • Interproximal area, fuse to form epithelial lining of interdental col • Coronal termination – free surface: -Pristine conditions: CEJ to gingival margin (~2 mm height) ( Gargiulo et al,1961) . -Normal gingiva : subclinical inflammation bottom of gingival sulcus ( Brecx et al,1987) • Apically & laterally – bordered by soft connective tissue – smooth surface; mild undulation coronally . • Coronal-most – sulcular epithelium • Apical termination – Epithelium in continuity with network of epithelial cell rests of Malassez . (Spouge,1984)

11. JE is a collar-like band of nonkeratinised stratified squamous epithelium 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. • Made up of 2 layers, stratum basale ( towards CT) and stratum suprabasale (facing tooth surface). • Organelles- lysosomal bodies, golgi fields, polyribosomes , cisternae of RER 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. Junctional epithelium and interstitial cells

12. 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. 1. LAMINA LUCIDA or lamina rara 2. LAMINA DENSA 3. LAMINA FIBRORETICULARIS (sub-basal lamina)

13. Dynamic Aspects Of Junctional Epithelium DAT Cells (Directly Attached to Tooth cells) • The turnover of the junctional epithelium is exceptionally rapid. • At the coronal part of the JE, the DAT cells typically express a high density of transferrin receptors. • Any structural or molecular changes in the internal basal lamina can potentially influence the vital functions of the DAT cells and contribute to the effectiveness or failure of the junctional epithelial defense or vice versa. • Changes in the cell metabolism may affect the Internal Basal Lamina (IBL). – migrate towards the sulcus bottom – Connected via hemidesmosomes to basal lamina → not static but dynamic

14. Expression Of Various Molecules And Their Functions

15. PERMEABILITY 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.

16. FUNCTIONS 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 γ globulins and poly- morphonuclear leukocytes (PMNs) giving it immunological/ phagocytic properties 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 .

17. ROLE OF JE IN GINGIVITIS

18. Role Of JE In Initiation Of Pocket Formation

19. ROLE IN Passive Eruption

20. Effect of Trauma from Occlusion on JE TFO causes widening of the marginal PDL space, a narrowing of the interproximal alveolar bone. In case of TFO, the junctional epithelium will be intact and there will be no degeneration of the epithelial tissues unless there is any plaque accumulation.

21. Junctional Epithelium Adjacent to Oral Implants Junctional epithelium around implants always originates from epithelial cells of oral mucosa. Despite different origins of the 2 epithelia, a functional adaptation occurs when oral epithelia form an epithelial attachment around implants. Evidence of several of the mentioned marker molecules involved in the defense mechanisms against the bacterial also being expressed in the peri -implant epithelium.

22. Syndromes Affecting JE Kindler syndrome: A rare skin blistering disorder along with early onset aggressive periodontitis . Due to loss of kindlin-1 protein which is involved in integrin activation. JE fails to attach to the tooth surface. ( Yildirim et al,2017 ) Haim-Munk syndrome and Papillon-Lefèvre syndrome : Due to allelic mutations in cathepsin C. JE gives rise to episodic inflammation and destruction of gingiva . (Hartal,2000)

23. REGENERATION OF JUNCTIONAL EPITHELIUM A new junctional epithelium after gingivectomy may form within 20 days. ( Listgarten , Schroeder, 1977) A new and complete attachment indistinguishable from that in control was established 5 days after complete separation of the JE from the tooth surface. (Taylor and Campbell, 1972) The reestablishment of the epithelial seal around implant after probing around implant is around 5 days. ( Etter et al., 2002) Detachment of cells persistes for 24 hrs and new attachment of junctional epithelial cell started 3 days after flossing ceased. ( Waerhug , 1981)

24. These studies show that the junctional epithelium is a highly dynamic and adaptive tissue with a fast capacity for self-renewal or de novo formation from basal cells of the oral gingival epithelium.

25. CONCLUSION The junctional epithelium is a unique tissue that fulfills a challenging function at the border between the oral cavity, colonized by bacteria, and the tooth attachment apparatus. It represent key mechanism in host parasite interraction , since it actively participates in the host defense mechanism rather than simply providing an attachment to the tooth surface. These defense mechanisms may be overwhelmed by bacterial virulence factors, and the gingival lesion could progress to periodontitis .

26. REFERENCES • Carranza’s-Clinical Periodontology , 11th Edition • Lindhe -Clinical Periodontology and Implant Dentistry, 5 th Edition. • Periodontology 2000, Volume 3, 1993-Tissues and Cells of the periodontium . • Periodontology 2000, Volume 13, 1997-Molecular and cell biology of the gingiva . • Periodontology 2000, Volume 24, 2000-Structure and function of the tooth-epithelial interface in the health and disease. • D. D. Bosshardt and N. P. Lang Review on the Junctional Epithelium: from Health to Disease. Journal of Dental Research 2005.