Epithelial Remnants Derivatives

Definition

• The epithelial remnants are the rests of an epitheliathat served once as a meaningful tissue in embryoniclife or during the tooth formation.

• While this epithelial cells are supposed to disintegrate due to ectomesenchymal invasion and/or programmed cell death, others persist !!

• These Remnants may develop into Cysts, Tumors, and Hamartomas.

Epithelial Remnants

Odontogenic Remnants Other Remnants in H&N

Odontogenic Remnants

Rests of Malassez

Reduced enamel epithelium

Rests of Serres

Rests of Serres(Remnants of dental lamina)

Reduced enamel epithelium

Rests of Malassez

Why do these remnants proliferate?

It is widely held that the majority of epithelial residues persist throughout life as vital, by large inactive (resting) single cells or cell clusters. Some of the cell rests seem to be triggered to proliferation by hitherto unknown mechanisms (apart from instances of possible inflammatory stimuli), resulting in production later in life of well-recognized pathological entities.

The origin of epithelial odontogenic neoplasms, hamartomas and cysts is inextricably bound up with a discussion of the parent cells of these lesions.

• Radicular Cyst (+ Residual + Lateral)Rests of Malassez

• Paradental Cyst (Craig 1976)

• Calcifying Odontogenic Cyst(Prætorius et al. 1981)

• Dentigerous cyst• Eruption Cyst

Reduced enamel epithelium

• Odontogenic keratocyst• Lateral periodontal Cyst• Gingival Cyst• Glandular odontogenic Cyst

Rests of Serres

cysts originated from odontogenic epithelial remnants

• Ameloblastomas• Squamous Odontogenic

Tumour

Rests of Malassez

• AmeloblastomasReduced enamel

epithelium • Ameloblastomas (Peripheral Ameloblastoma)

• Squamous Odontogenic Tumour • Calcifying Epithelial Odontogenic

Tumor• Adenomatoid Odontogenic Tumour• Keratinising Cystic Odontogenic

Tumour• Odontogenic Gingival Epithelial

Hamartoma

Rests of Serres

Tumours originated from odontogenic epithelial remnants

Epithelial Remnants

Odontogenic Remnants Other Remnants in H&N

• Arises from epithelial remnants of the embryonic thyroglossal duct.

Thyroglossal tract cyst

• Arises from epithelial remnants (of the branchial arches or of salivary origin) within cervical lymph nodes.

Branchial cleft cyst

• Arises from epithelial remnants of the embryonic nasopalatine duct.

Nasopalatine Canal Cyst

Derivatives of other epithelial remnants in H&N

• Arises from epithelial remnants of the lower part of the embryonic nasolacrimal duct.

Nasolabial Cyst

• Arises from epithelial remnants in the midline during closure of 1st & 2nd branchial arches

Dermoid & Epidermoid

cyst

•Arises from salivary epithelium remnants in extracapsular lymphnodes

Warthin’s Tumour

Derivatives of other epithelial remnants in H&N

In recent years, the existence of this group of lesions as separate entities has been questioned and they were excluded from the 1992 WHO Classification of epithelial jaw cysts (Kramer et al., 1992).

Previously, it had been thought that these cysts developed from epithelium entrapped in the process of fusion of embryonic processes.

It is now believed that they represent :- posterior extension of an incisive canal cyst in the case of median palatine cyst; - anterior extension in the case of median alveolar cyst; - and a range of other odontogenic cysts, frequently an odontogenic keratocyst, in

the case of the globulomaxillary cysts.- Moreover, the so-called median alveolar cyst may also, in a number of instances,

be a keratocyst derived from dental lamina in the midline of the maxilla.

“NOTE ON THE SO-CALLED : MEDIAN PALATINE, MEDIAN ALVEOLAR, MEDIAN MANDIBULAR AND GLOBULOMAXILLARY CYSTS”

Ahmad Amro Baradee

Under the supervision of :

Dr.Ayman Sarraj

Thanks for your precious

attention

& I Wish You A Very

Restful Epithelium Rests

References

• Philipsen HP, Reichart PA

(2004) The Development and Fate of Epithelial Residues after Completion of the Human Odontogenesis

• Regezi Clinical Pathologic Correlations 5th edition

• Oral Pathology J. V. Soames & J. C. Southam, Oxford University Press 4th Edition

• Cysts of the Oral and Maxillofacial Regions,4th Edition

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