Faculty of Dentistry

Oral Histology

About Root Formation

Dr. Amira Fares(Head of oral histology department )

By

ShadwaHesham

MahmoudSaleh

Nora Mohamed

DarineAshraf

AmiraAbdallah

Root sheath development The root starts to develop after

the crown is completed through the formation of a cervical loop

(The CL is the most cervical portion of the enamel -dental organ – two layers consisting of IEE and OEE ).

The CL begins to grow down into the dental sac it forms a Hertwigs rootsheath grows down to encompass all but the basal portion of the pulp this sheath shapes the root and induces dentin formation in the root area by the ODCs of the dental papilla .

The first formed part of the root sheath bends to form a disc like structure

The rim of this disc like structure is called the epithelial diaphgram

The epithelial diaphgram encloses the primary apical foramen

This sheath lacks the stellate reticulum and stratum intermedium .

The root of the tooth : is composed by dentin and cementum.

Dentin forms when the outer cells of the dental papilla are induced to differentiation into ODCs .

Similar to what occurs at the crown area .

Single roots and multiple roots

For single-rootedteeth :

the root sheathgrows like a cuff ortube around thenewly forming pulp

For multi-rooted teeth :

Development of multi-rooted teeth takes place in a same manner until the furcation area.

When the furcation area is reached the epithelial diaphragm develops tongue like extensions that grow until they contact each other

This the divides the root into two or three

Tongue like extentionike

Extensions

Epithelial diaphragm

Fate of epithelial root sheath

After dentine formation in root takes place, the epithelial root sheath breaks down and its remnants migrate away from the dentinal surface

They lie in the periodontal ligament and are called epithelial rests of Malassez

The epithelial rests of Malassez are found the in the periodontal ligament through out the life

Sometimes when there is chronic inflammation the epithelial cell rest of Malassez proliferate into cysts and tumours