The document discusses the stages of tooth development. It focuses on the cap stage, where unequal growth of tooth buds leads to the formation of a shallow invagination. The enamel organ is composed of three cell types - inner enamel epithelium, outer enamel epithelium, and stellate reticulum. The stellate reticulum contains glycosaminoglycans that pull water into the enamel organ, forcing the polyhedral cells to become star-shaped. Several transitory structures are also discussed, including the enamel knot, cord, septum, navel, and niche.

1. TOOTH DEVELOPMENT
MARWA TARIQ
FIRST PROFESSIONAL BDS
KHYBER COLLEGE OF DENTISTRY PESHAWAR

2. 3 stages:
1.Bud Stage
2.Cap Stage
3.Bell Stage
TOOTH DEVELOPMENT

3. CAP STAGE

4. CAP STAGE
• Unequal growth in different parts of tooth buds
• leads to formation of cap stage
• shallow invagination on deep surface of the bud

5. HISTOLOGY OF CAP STAGE
• Enamel organ composed of three
different types of cells:
1) Inner Enamel Epithelium
2) Outer Enamel Epithelium
3) Stellate Reticulum

7. OUTER ENAMEL
EPITHELIUM
• Covers the convex
part of enamel
organ.
• tall columnar cells.
• Seperated from
dental sac by a
distinct basement
membrane.

8. INNER ENAMEL EPITHELIUM
• Covers the concave part
of enamel organ.
• These are cuboidal
cells.
• Seperated from dental
papillae by a distinct
basement membrane

9. STELLATE RETICULUM
• Polygonal shaped
cells located in the
center of enamel
organ of cap and bell
stage

10. Conversion of Polygonal shaped cells
into Star shaped cells
Mechanism
• Stellate reticulum GLYCOSAMINOGLYCANS(GAGS)
into intercellular spaces between epithelial cells.
• GAGs being hydrophilic pulling of water into enamel organ
• forcing apart of cells results in the change of polyhedral cells into star-shaped
cells.
• Star shaped cells is refered to as stellate reticulum.
FUNCTION:
1) Shock absorber
2) Protects enamel forming cells.

11. Conversion of Polygonal shaped
cells into Star shaped cells

12. TRANSITORY STRUCTURES OF
ENAMEL ORGAN
1) ENAMEL KNOT
2) ENAMEL CORD
3) ENAMEL SEPTUM
3) ENAMEL NAVEL
4) ENAMEL NICHE

13. TRANSITORY STRUCTURES OF
ENAMEL ORGAN
ENAMEL KNOT
•Non-dividing ectodermal
cells at deepest part of
enamel organ which projects
into enamel organ.
FUNCTIONS
1. Signalling centre
2. Determines shape of
tooth

14. TRANSITORY STRUCTURES OF
ENAMEL ORGAN
ENAMEL CORD
Condensation of
ectodermal cells in a
linear pattern extending
from enamel knot to
outer enamel epithelium

15. TRANSITORY STRUCTURES OF
ENAMEL ORGAN
ENAMEL SEPTUM
Sometimes enamel
cord becomes thick in
buccolingual direction
forming a septum
dividing the enamel
organ.

16. TRANSITORY STRUCTURES OF
ENAMEL ORGAN
ENAMEL NAVEL
• Small depression seen in
the area where enamel cord
joins the outer enamel
epithelium

17. TRANSITORY STRUCTURES OF
ENAMEL ORGAN
ENAMEL NICHE:
 Enamel organ is attached to
oral epithelium by two dental
laminae;one buccal and one
lingual seprated by area
filled with mesenchymal
tissue referred to as enamel
niche.