DEVELOPMENT OF TOOTH
By:
Assistant Professor Dr. Baydaa Ali Al Rawi
Just for looking
Stages in the life cycle of a
tooth
1. Growth
Physiologic process
a.
Initiation
b.
Prolifiration
c.
Histodifferentiation
d.
Morphodifferentiation
e.
Apposition
2. Calcification
3. Eruption
Tooth Development
A. Bud Stage
B. Cap Stage
C. Bell Stage
D and E. Dentinogenesis
and amelogenesis
F. Crown formation
G. Root Formation and
eruption
H. Function
Three developmental process
before function:
1. Grow
2. Calcify
3. Erupt

Unlike kidney and heart.. Afte growth .. Function

Unlike bone… growth and calcify… function
MORPHOLOGICAL
1. Dental lamina
2. Bud stage
3. Cap stage
4. Early bell stage
5. Advanced bell stage
6. Formation of enamel
and dentin matrix
PHYSIOLOGICAL
Initiation
Proliferation
Histodifferentiation
Morphodifferentiation
Apposition
Just for looking
Initiation of Tooth Development
The initiation of tooth development begins at 6th weeks of
development with formation of a continuous horseshoe-band of
thickened epithelium in the location of upper and lower jaws –
Primary Epithelial Band
Each band of epithelium will give rise to 2 sub divisions:
1. Dental lamina and
2. Vestibular lamina
Initiation stage

6th weeks intra uterine
life: first sign of tooth
development

Dental lamina:
represent the first sign
of tooth development.
DENTAL LAMINA
 continued
and localized proliferative activity leads
to the formation of a series of epithelial outgrowths
into the mesenchyme at sites corresponding to the
positions of the future deciduous teeth
• At about 6th - 7th week the primary epithelial band divides into an
inner (lingual) process called Dental Lamina & an outer ( buccal)
process called Vestibular Lamina
A - dental
lamina
B - vestibular
lamina
• Later during the development of jaws, permanent molars arise
directly from the distal extension of the dental lamina
• The successors of the deciduous teeth develop from a lingual
extension of the free end of the dental lamina opposite to the
enamel organ of each deciduous teeth.
The lingual extension of the dental lamina is named the
successional lamina & develops from the 5th month in utero (
permanent central incisor) to the 10th month of age (second
premolar)
Successional Lamina :
It is a lingual extension of dental lamina.

It is responsible for the development of permanent
incisors , canine and premolars.
Function of dental lamina:
Function
ofentire
dental
lamina
1. initiation
of the
deciduous
dentition that begins at
the 6 weeks of intra-uterin life of embryo.
2. initiation of the successors of the deciduous teeth. It is
preceded by the growth of the free end of the dental lamina
(successional lamina), lingual to the enamel organ of each
deciduous tooth, and occurs from about the fifth month in
embryo for the permanent central incisors to 10 months of
age for the second premolar
3. preceded by the extension of the dental lamina distal to
the enamel organ of the second deciduous molar and the
formation of permanent molar tooth germs.
Fate of Dental Lamina :-

After initiation of tooth development , the dental
lamina degenerates.
Bud stage

At certain point on DL representing the location
of 10 manibular and 10 maxillary deciduous
teeth cells multiply still more rapidly and form a
knob like projections.
Bud stage
Bud stage is characterized by rounded,
localized growth of epithelium surrounded
by proliferating mesenchymal cells.
Bud Stage
In the bud stage, the enamel organ
consists of peripherally located low
columnar cells and centrally located
polygonal cells
Cap stage

The epithelial bud will continue to
proliferate and expand laterally

Different part of the bud will show unequal
growth leading to the formation of a cap
stage dental organ( with invagination)
3. Bell Stage
http://www.usc.edu/hsc/dental/ohisto/
Dental lamina
Outer dental
epithelium
Inner dental
epithelium
Dental papilla
Dental follicle
Cervical loop
• Continued growth leads to bell stage, where the enamel organ resembles a
bell with deepening of the epithelium over the dental papilla
• Continuation of histodifferentiation (ameloblasts and odontoblasts are defined)
and beginning of morphodifferentiation (tooth crown assumes its final shape)
ROOT FORMATION
• The development of roots begin
after enamel & dentin formation
has
reached
the
future
cementoenamel junction
• The enamel organ plays an
important role in root development
by forming HERS (Hertwig’s Epithelial
Root Sheath), which models the
shape of the root
• HERS consists of outer & inner
enamel epithelium only
Question? Homework
What
are The meaning
of successors ?