The document discusses the stages of tooth development from initiation to root formation. It describes the morphological stages as dental lamina, bud, cap, and bell stages. The histophysiological stages are initiation, proliferation, histodifferentiation, morphodifferentiation, and apposition. Key events include formation of the dental lamina and tooth buds, invagination of the enamel organ during the cap and bell stages, differentiation of ameloblasts and odontoblasts, and deposition of enamel and dentin. During the root stage, the cervical loop forms the root sheath to guide root formation.

2. )بِسْمِ اللهِ الرَّحْ منِ الرَّحِيمِ (
سَنُرِيهِمْ آيَاتِنَا فِي الآفَاقِ وَفِي أَنف سِهِمْ حَتَّى يَتَبَيَّنَ لَهُمْ أَنَّهُ الحَقُّ
) أَوَ لَمْ يَكْفِ بِرَب كَ أَنَّهُ عَلَى كُ ل يََْ هََِيد ) فصلت الآية 53
"صدق الله العظيم"

3.  The development of the tooth involves
many complex biological processes.
 The fundamental developmental
processes is similar for all teeth.
Dr Hesham Dameer

4. STAGES OF TOOTH DEVELOPMENT MAY BE
DESCRIBED ACCORDING TO :
1- Changes in the morphology of the developing tooth
(MORPHOLOGICAL STAGES) .
2- Its physiological changes (HISTOPHYSIOLOGICAL
STAGES).
Note: both the morphological and the histophysiological
changes are shearing in the different tooth development
stages.

5. Stages of teeth development
MORPHOLOGICAL STAGES
1. Dental lamina
2. Bud stage
3. Cap stage
4. Bell stage ( early & advanced )
5. Root Stage
By hesham Dameer

6. HISTOPHYSIOLOGICAL STAGES
1- INITIATION.
2- PROLIFERATION.
3- HISTO-DIFFERENTIATION.
4- MORPHO-DIFFERENTIATION.
5- APPOSITION.
Dr Hesham Dameer

7. Initiation of Tooth Development
The initiation of tooth development begins at 37 days 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
Dr Hesham Dameer

8. Early Dental Lamina
Tongue Dental lamina Vestibular lamina

9. Primary epithelial
band
Ectomesenchyme

10. Vestibular lamina:-
It is a wedge of epithelial cells facial to dental lamina.
It proliferates into ectomesenchyme. Then degenerates at
the center to form cleft which becomes the oral vestibules.
Dr Hesham Dameer

11. Dr Hesham Dameer

12. The dental lamina
ECTODERM
MESODERM
(Connective
tissue)
Flat cells
Columnar cells
Basement
membrane

13. Also
No teeth without dental lamina
No fruits without a tree
Dr Hesham Dameer

14. 
Dental lamina appears as a thickening of the oral
epithelium adjacent to condensation of ectomesenchyme
• 20 areas of enlargement or knobs appear, which will form
tooth buds for the 20 primary teeth
•Not all will appear at the same time . The first to develop are
those of the anterior mandible region

15. •At this early stage the tooth buds have already determined
their crown morphology .
 Successional lamina : lamina from which permanent
teeth develop which replace the primary teeth except for
the permanent molars.
Dr Hesham Dameer

16.  Dental lamina formation and development of tooth buds

18. mesenchymal proliferation
Dental lamina

19. • M
Max. bone development
Mand. bone dev.
Tongue
Dental lamina &Tooth bud
Meckel's cartilage

20. B
• F. Developing
mandibular bone
• G. Meckel's cartilage
• A. Dental lamina
• B. Tooth bud
• C. Mesenchymal
cells condensation
A
B
C
F
Dr Hesham Dameer

21. Function of the dental lamina
1. Initiation of deciduous dentition ( 2 MIU ) .
2. Initiation of successors of deciduous dentition . This is preceded
by the growth of the terminal end of the dental lamina lingual to
the deciduous enamel organ . ( 5 MIU. For central incisors, 10 M.
of age for second premolars ) .
3. Initiation of permanent molars .
This is preceded by the extension of dental lamina distal to the
enamel organ of the second deciduous molar to form the
permanent molar tooth buds
( first molar 4MIU. , second molar 1 year , third molar 4-5 years )
 It is thus evident that the activity of the dental lamina extends
over a period of about five years and disintegrates completely or
remains as epithelial rests of Serres.

22. Fate of the dental lamina
1) The broad connection of the dental lamina with the
dental organ seen in the cap stage is broken in the bell
stage by mesenchymal invasion .
2) The mesenchymal invasion at first divides the general
dental lamina into lateral dental lamina and dental
lamina proper. The dental lamina proper, growths at its
terminal end ( successional lamina ) which form the
primordium of the permanent tooth germ . The lateral
dental lamina which connected to the deciduous tooth
germ degenerates .
Sometimes , the remnants of the dental lamina persists as
epithelial rests and known epithelial rests of serres .

23. GENERAL DENTAL
LAMINA
SUCCESSIONAL
LAMINA ( DENTAL
LAMIA PROPER )
LATERAL
DENTAL
LAMINA

24. Epithelial rests of serres
mesenchymal
invasion
Epithelial rests

25. Epithelial rests of Serres

26. Dr Hesham Dameer

27. Tooth bud stage :
• At certain regions along the
dental lamina , 10 rounded or
ovoid localized growth of
epithelium ( Tooth bud ) in each
arch correspond to the
primordia of the enamel organs
of the decidous teeth . These
buds were surrounded by
proliferating mesenchymal cells,
which are packed closely
beneath and around the
epithelial buds
Dr Hesham Dameer

28. The mesoderm exerts
a pressure at the base
of tooth bud . The
pressure of the
mesoderm leads to
invagination of the
undersurface of the
tooth bud , while the
lower margin of the
concavity proliferates
downward to
surround the actively
growing mesoderm .
Pressure of the mesoderm
Dr Hesham Dameer

29. • As a result of this topographic alteration , the round shaped
tooth bud is transformed to a cap shaped structure .
Later on , the cap shape structure can be distinguished into different
cell layers , as follows :
Dr Hesham Dameer

30. Dr Hesham
Dameer

31. Early cap stage:-
The inner cell become low columnar called inner epithelium
or inner dental epithelium.
The outer cells become flat and called outer dental epithelium
or outer enamel epithelium.
The ectomesenchymal tissue becomes condensed in the
concave surface and called dental papilla (much cells, low
fibers).
Some ectomesenchymal fibers surround the cap called dental
follicle (sac) (low cells, much fibers).
Enamel knot may be formed due to localized thickening at
the inner dental epithelium at center.
Strands of epithelial cells also may be formed and called
enamel cord .
Dr Hesham Dameer

32. Inner Enamel Epithelium
Cell Free Zone
Enamel cord
Cap stage
DENTAL
(follicle )
Dr Hesham Dameer

33. Cap stage

34. Late cap stage:-
A fourth layer of epithelial cells is formed between the inner
dental epithelium and stellate reticulum called stratum
intermedium. It is formed of two layers of rounded cells which
have high activity of alkaline phosphatase enzyme that
responsible for enamel formation.
Cervical loop:-
It is the most peripheral areas in both sides of cap (the
proliferation zone) the outer and inner enamel epithelial cells
come together with minimal inclusion of the stratum
intermedium and stellate reticulum.
After crown formation cervical loop cells proliferate to form
bilayer of cells (outer and inner enamel epithelium) called root
sheath of Hertwig's
Dr Hesham Dameer

35. 1- Cap-shaped stage
2- Tooth bell stage
Dr Hesham Dameer

36. A. Early bell stage
B. Advanced bell stage

37. bell stage
A . Early bell stage :
This stage is reached when the invagination of the dental organ is deepened and also
the margin of the dental organ ( cervical loop )grows deeper into the underlying
mesenchyme .
1. Enamel organ tissues begin to differentiate.
2. Enamel organ begins to fold into shape of finished
crown.
3. Dental papilla tissues begin to differentiate.
Associated with these changes , other changes occur in the dental
organ as :
1. Outer enamel epithelium become cells transformed into folded
layer instead of the previous smooth layer . The adjacent
ectomesenchyme invade these folds.
The ectomesenchyme contain a rich capillary buds to provide
nutrition for the highly and metabolically active dental organ .
By hesham Dameer

38. 2. Inner enamel epithelium become tall columnar and measure
4 to 5 micrometer in diameter and about 40 micrometer in
length . These cells exert an inductive effect on the
underlying ectomesenchymal cells found in the dental
papilla resulting in there differentiation into odontoblasts .
3. Stellate reticulum The mucoid fluids in the intercellular
spaces increases , thus the cells of the stellate reticulum
appear star shaped . As amelogenesis starts , the reticulum
will collapse and reduce in size . Thus the capillaries of the
invading ectomesenchyme found in the folds of the outer
enamel epithelium will come in close relation to the inner
enamel epithelium .
Dr Hesham Dameer

39. 3. Stratum intermedium Several squamous cells develop between
the stellate reticulum and the inner enamel epithelium . These
cells have a high degree of metabolic activity and appear to be
essential for enamel formation .
3. Dental papilla Before amelogenesis, the inductive effect exerted
by the organized inner enamel epithelium ( tall columnar cells ),
causes transformation of the peripheral ectomesenchymal cells of
the dental papilla into odontoblasts and become potentially
capable to form dentin .
4. Dental sac The fibrillar components of the dental sac arrange
themselves in a circular pattern . As the root start to develop and
cementum is being is being deposited on dentin surface, the fibers of
the dental sac differentiate into periodontal fibers and become
embedded into the developing cementum and alveolar bone .
Dr Hesham Dameer

40. Functions of the enamel organ
1- Outer enamel epithelium :
Active transport of nutrient materials specially, after hard tissues
formation .
2- Stellate reticulum :
a. Act as a buffer against physical forces that may distort the
configurations of the developing tooth .
b. It permit a limited flow of nutritional elements from the
capillaries of the invading ectomesenchyme found in the folds to
the formative cells .
c. It keep a room for the developing enamel .
Dr Hesham Dameer

41. 3. Stratum intermedium:
The function of this layer is not understood :
a. It is believed to control fluid diffusion into and out of the
ameloblasts .
b. It provides the enamel organ with alkaline phosphate
enzyme needed for mineralization .
c. These cells plus the inner dental epithelium are considered
as a single unite responsible for enamel formation .
4. Inner enamel epithelium :
a. It exerts an inductive effect on the undifferentiated cells
of the dental papilla to differentiate into odontoblasts.
b. Transport of the nutritive materials from the dental papilla
to the enamel organ before dental hard tissues formation.

42. c. It arranged in a pattern to determine the morphology
of the crown .
d. It lays down enamel matrix and helps in its mineralization .
e. It shares in the root formation.
g. It secretes primary enamel cuticle and share in the
formation of the reduced enamel epithelium which help in
protection of the newly formed enamel against resorption
and preventing precipitation of cementum .
5- Dental papilla :
Gives rise to dentin and dental pulp .
6- Dental sac :
Give rise to cementum, periodontal ligament and alveolar
bone.

43. Early bell stage

44. • A= cervical loop
• B= stellate
reticulum
• C= enamel cord
• D= inner enamel
epithelium
• E= stratum
intermedium
• F= dental lamina
• G= outer enamel
epithelium
• H= dental papilla

45. • A= dental papilla (a
very condensed
group of cells)
• B= ameloblast cell
layer of the inner
enamel epithelium
cells are columnar
• C= outer enamel
epithelium cells
• D= stellate
reticulum
• E= stratum
intermedium
• F= outer cells of
dental papilla or
differentiating
odontoblasts

46. Future crown patterning occurs in the bell stage, by folding of the
inner dental epithelium.

47. Bell Stage
Diagram of early bell stage

48. B. Advanced bell stage
Formation of hard
tissue structure
• A= odontoblasts
• B= dental papilla
• C= dentin
• D= organizing
ameloblast layer of
inner dental epithelium
• E= outer enamel
epithelium
• F= stellate reticulum
• G = stratum intermedium
Dr Hesham Dameer

49. Histological structure of the tooth germ during advanced
bell stage
STRATUM
INTER.
STELLATE
RETICULUM
INNER
DENT.
EPITH.
PREDENTIN
ODONTOBLASTS

50. Ameloblast & odontoblast
• Ameloblast and
Odontoblast layers
move apart, leaving
enamel and dentine
between them
Dr Hesham Dameer

51. Advanced bell stage

52. Advanced bell stage
• 1 - ameloblasts
2 - enamel
3 - dentine
(predentine)
4 - odontoblasts
5 - dental pulp
Dr Hesham Dameer

54. Dentin
Predentin
Odontoblasts
Enamel
Ameloblas

55. Advanced bell stage
Histological structure of the tooth germ
OUTER DENTAL
EPITHELIUM
CAPILLARY LOOP
ENAMEL
DENTIN
PREDENTIN

57. Diagram of advanced bell stage

58. Dr Hesham Dameer

59. Root Stage
 After complete formation of the crown , both the inner
and outer enamel epithelium at the cervical end of the
crown is known cervical loop . The vertical cervical loop
grows in horizontal direction to form the epithelial
diaphragm .
The epithelial cells, at the cervical area or cervical to the
epithelial diaphragm proliferate leading to the formation
of the first portion of the root sheath . Both the root sheath
and the epithelial diaphragm only consists of outer and
inner enamel epithelium .
 The inner enamel epithelium cells of the root sheath will
induce the adjacent ectomesenchymal cells to
differentiate into odontoblasts .

60.  The odontoblasts deposit dentin on the inner side of the root
sheath . As a result of dentin deposition , the root sheath will
degenerate , thus exposing newly for dentin surface into the
adjacent ectomesenchyme .
 The surrounding ectomesenchymal cells begin to differentiate
to cementoblasts .
 Cementoblasts start cementum formation , to which the fibers
of the dental sac will be embedded .
 Occasionally , an incomplete degeneration of root sheath may
occur, resulting in the presence of some epithelial cells in the
form of nests which known epithelial rests of Malassez .
 In case of multiroot formation, tongue like processes arise from
the margin of epithelial diaphragm, thus dividing the primitive
apical foramen into more one, corresponding to the number of
the growing processes . At first these processes grow in horizontal
direction, but later their free ends grow vertically .

61.  The inner enamel epithelial cells of the processes induce the
the adjacent mesenchymal cells to differentiate into
odontoblasts that in turn deposit dentin . The margins of the
process will grow downwards with downgrowth of the root
sheath, resulting in the formation of multiroot .
Dr Hesham Dameer

62. FORMATION OF SUPPORTING TISSUES
• Supporting tissues develops during root formation from
dental follicle.
• As the root sheath fragments ectomesenchymal cells of the
dental follicle penetrate between the epithelial fenestrations
and become opposed to the newly formed dentine of root.
• These cells differentiate into cementoblasts.
• Cementoblasts elaborate an organic matrix that become
mineralize.
• Collagen fiber bundles of periodontal ligament become
anchored .
• Cells of PDL and fiber bundles differentiate from dental
follicle.
• Cells forming the bone in which PDL fibers anchored also
differentiate from dental follicle.
Dr Hesham Dameer

63. A= Epithelial root sheath
B= Ectomesenchymal cells
C=Dental follicle
D= Odontoblast
Dr Hesham Dameer

64. • A= cervix of
tooth
• B= epithelial
diaphragm (part
of root sheath) –
these cells don’t
become tall
(columnar)
because they are
not going to be
secreting
anything like in
the crown.
• C= odontoblast
layer
• D= dentin
• E= pulp
• F = alveolar bone
Dr Hesham Dameer

65. • Developmental process: eruptive
stage of tooth development
• Region or location: Root shealth
• A= crown
• B = root
• C= DEJ (artifact space)
• D= ameloblasts
• E= dentin
• F = odontoblast layer
• G = Hertwig’s epithelial root sheath
• Specific components or positional
parts of HERS:
• 1= epithelial diaphragm (curve
between root sheath and diaphram)
• 2= root sheath
• 3= cervix of tooth
Dr Hesham Dameer

66. Cell rest (of Malassez)
Differentiation of dental follicle cells
Dr Hesham Dameer

67. Root Formation (Cervical loop forms the epithelialroot sheath
of Hertwig)
Cervical loop
Dental papilla

68. Cervical loop
Hertwig’s epithelial root sheath

70. Tongue-like extentions
Dr Hesham Dameer

71.  Tongue like processes arise from the margin of epithelial diaphragm, thus
dividing the primitive root trunk into more one, corresponding to the
number of the growing processes .

72. Root Formation
Dr Hesham Dameer

73. Root Formation
Dr Hesham Dameer

74. • Developmental
process: Late crown
or early eruptive
stage of tooth
development. This
tooth is erupted,
however apical
foramen are still
open.
• Region or location:
Multirooted tooth
• A= what’s left of root
sheath
• B= apical foramen
• C= dentin
• D= interradicular
septum (furcation
area)
• E= pulp
• Interradicular
septum is in the
middle (D)