The root of a tooth develops after the crown is completed. The inner and outer enamel epithelium proliferate to form Hertwig's root sheath, which consists of two epithelial layers that bend to form a disc-like structure called the epithelial diaphragm. As the root sheath lengthens at the angle of the diaphragm, it induces the dental papilla cells beneath it to differentiate into odontoblasts, which then go on to form the root dentin. In multi-rooted teeth, the epithelial diaphragm develops extensions that divide the root into two or three parts. After dentin formation, the epithelial root sheath breaks down and its remnants become epithelial rests of Malassez

1. Development of Tooth:
Root Formation

2. Sub topics
Root sheath development
Formation of root
Fate of epithelial root sheathFate of epithelial root sheath

3. Root sheath development
The root starts to develop after the crown is completed
 Epithelial cells of the inner and outer enamel epithelium proliferate from the
cervical loop to form two layers of epithelium called Hertwigs root sheath
 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 diaphragm
The epithelial diaphragm encloses the primary apical foramen

10. Formation of Root
After the formation of epithelial root sheath and the epithelial diaphragm
the root grows in length
The diaphragm maintains a constant size while the root sheath grows in
length at the angle of the diaphragm and not at its tip
 The cells of the lengthening root sheath induce the adjacent dental
papilla cells to differentiate into odontoblasts
 The newly formed odontoblasts then form the root dentine
 As the root lengthens the crown moves occlusally

11. Single roots and multiple roots
For single-rooted teeth the root sheath grows like a cuff or
tube around the newly forming pulp
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 divides the root into two or three

14. Root formation anomalies
If the continuity of the root sheath is broken before the
dentine is formed it results in missing or abnormal epithelial
cells
 When the epithelial cells are missing the Odontoblasts do
not differentiate, and dentine does not form opposite to the
defect that occurred in the root sheath
The result will be a small lateral canal. This lateral canal is
also called as supplemental canal or accessory canal
Accessory canals connect the main root canal with the
periodontal ligament

16. If the epithelial root sheath does not degenerate at the
proper time and remain stuck to the surface of the root
dentine, then that area becomes devoid of cementum
 Areas of root without cementum can be a cause of
sensitivity if the there is gingival recession

17. 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