developmental stages and anomalies related to teeth

1. DEVELOPMENT OF TOOTH
PRESENTED BY :
DR.ANUKRATI DONERIA

2. ContentS
1. Introduction
2. Dental Lamina
3. Vestibular Lamina
4. Tooth development
5. Developmental stages
• Bud stage
• Cap stage
• Bell stage
• Advanced bell stage
6. Hertwig’s epithelial root sheath and root formation
7. References

3. Introduction

4. • The primitive oral cavity, or stomodeum, is
lined by stratified squamous epithelium
called the oral ectoderm.
• The oral ectoderm contacts the endoderm of
the foregut and form the buccopharyngeal
membrane.
• Membrane ruptures at about 27th day of
gestation and the primitive oral cavity
establishes a connection with the foregut

5. 1.
2.
3.

6. • Most of the connective tissue
cells underlying the oral
ectoderm are of neural crest
or ectomesenchyme in origin
• These cells instruct the
overlying ectoderm to start
the tooth development, which
begins in the anterior portion
of the future maxilla &
mandible and proceeds
posteriorly

7. Dental
lamina

8. • 2- 3 weeks after the rupture of buccopharyngeal
membrane, certain areas of basal cells of oral
ectoderm proliferate rapidly, leading to the formation
of primary epithelial band.
• At about 7th week the primary epithelial band
divides into an inner (lingual) process called Dental
Lamina & an outer ( buccal) process called
Vestibular Lamina.

10. • The dental lamina serves as the primordium for the ectodermal
portion of the deciduous teeth .
• Later during the development of jaws, permanent molars arise
directly from the distal extension of the dental lamina

11. • The successors of the deciduous teeth develop
from a lingual extension of the free end of the
dental lamina.
• 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)

12. FATE OF DENTAL LAMINA
• Total activity of dental lamina exceeds over a period
of at least 5 years.
• As the teeth continue to develop, they loose their
connection with the dental lamina.
• They later break up by mesenchymal invasion.

13. • Fragmentation of the dental lamina progresses toward the
developing enamel organ.
• Any particular portion of the dental lamina functions for a much
brief period, since only a relatively short time is there between
initiation of tooth development and degeneration of dental lamina
begins.
• However the dental lamina may still be active in the third molar
region after it has disappeared elsewhere.

15. Vestibular lamina
• Labial and buccal to the dental
lamina in each dental arch,
another epithelial thickening
develops independently.
• It is Vestibular Lamina also
termed as lip furrow band.
• Subsequently it hollows and
form the oral vestibule between
the alveolar portion of the jaws
and the lips and cheeks.

16. TOOTH DEVELOPMENT
• At certain points along the dental lamina, each representing the location
of one of the 10 mandibular & 10 maxillary teeth, ectodermal cells
multiply rapidly & form little knobs that grow into the underlying
mesenchyme.
• Each of these little down growths from the dental lamina represents the
beginning of the enamel organ of the tooth bud of a deciduous tooth.
• First to appear are those of anterior mandibular region.
• As the cell proliferation occurs each enamel organ takes a shape that
resembles a cap.

17. • Development of tooth results from –
interaction between epithelium derived from
first arch and ectomesenchymal cells derived
from neural crest cells.
• First arch epithelium retains ability to form
tooth like structures up to 12 days only then
after they are lost and potential is transferred
to neural crest cells.

18. Developmental stages
MORPHOLOGICAL
• FORMATION OF DENTAL
LAMINA
• BUD STAGE
• CAP STAGE
• BELL STAGE
• ADVANCED BELL STAGE
PHYSIOLOGICAL
• INITIATION
• PROLIFERATION
• HISTODIFFRENTIATION
• MORPHODIFFRENTIATION
• APPOSITION

19. BUD STAGE
• The epithelium of the dental lamina is
separated from the underlying
ectomesenchyme by a basement
membrane.
• Simultaneous with the differentiation of
each dental lamina, round or ovoid
swellings arise from the basement
membrane at 10 different points,
corresponding to the future positions of
the deciduous teeth.

20. BUD STAGE
• These are the primordia of the
enamel organs, the tooth buds.
• Thus the development of tooth
germs is initiated, and the cells
continue to proliferate faster than
adjacent cells.
• This is the initial stage of tooth
formation where enamel organ
resembles a small bud .

21. BUD STAGE
• During the bud stage, the enamel organ
consists of peripherally located low
columnar cells & centrally located polygonal
cells .
• The area of ectomesenchymal condensation
immediately subjacent to the enamel organ
is the dental papilla.
• The condensed ectomesenchyme that
surrounds the tooth bud and the dental
papilla is the dental sac

22. BUD STAGE

23. CAP STAGE
• unequal growth in different parts of the tooth bud
leads to the cap stage which is characterized by a
shallow invagination on the deep surface of the bud.
OUTER AND INNER ENAMEL EPITHELIUM
• The peripheral cells-cuboidal, cover the convexity of
the ‘cap,’ and are called the outer enamel epithelium.
• The cells in the concavity of the ‘cap’ are tall,
columnar cells and represent the inner enamel
epithelium

24. CAP STAGE
• The outer enamel epithelium is separated from the dental sac, &
the inner enamel epithelium from the dental papilla, by a delicate
basement membrane.
• Attached to basement membrane by – Hemidesmosomes.
STELLATE RETICULUM
• Polygonal cells located in the center of the enamel organ,
between the outer and inner enamel epithelia, begin to separate
due to water being drawn into the enamel organ.

25. CAP STAGE

26. CAP STAGE
• As a result the polygonal cells become star shaped but maintain
contact with each other by their cytoplasmic process .
• As the star shaped cells form a cellular network, they are called
the stellate reticulum.
ENAMEL KNOT
• The cells in the center of the enamel organ are densely packed
and form the enamel knot.
• This knot projects toward the underlying dental papilla

27. CAP STAGE
• At the same time a vertical extension of the
enamel knot, called the enamel cord occurs .
• When the enamel cord extends to meet the
outer enamel epithelium it is termed as
enamel septum .
• These structures disappears before the
enamel formation begins.

28. DENTAL PAPILLA
• In inner part of the cap, the
ectomesenchymal cells increase
in number.
• The cells appears more dense
than the surrounding
mesenchyme and represents the
beginning of the dental papilla.
• Leads to formation of future
dentin and acts as primordium
for dental pulp.

29. Dental Sac/Dental follicle
• Dental sac/follicle forms the surrounding of enamel organ and
dental papilla.
• It consists of ectomesenchymal cells and fibers.
• Thus the tooth germ consists of ectodermal component- the
enamel organ and the ectomesenchymal components- the
dental papilla & the dental follicle

31. • The depression occupied by
the dental papilla deepens until
the enamel organ assumes a
shape resembling a bell.
• The dental lamina becomes
longer, thinner & finally loses
its connection with the
epithelium of the primitive oral
cavity

32. BELL STAGE
• As the invagination of epithelium occurs and
margins continues to grow, the enamel organ
assumes a bell shape.
• In bell stage crown shape is determined.
• The folding of enamel organ to cause different
crown shapes is shown to be due to different
rates of mitosis & difference in cell
differentiation time.

33. BELL STAGE
• The inner enamel epithelial cells which lie in the future cusp tip
or incisor region stop dividing earlier and begin to differentiate
first.
• Four different types of epithelial cells can be distinguished on
light microscopic examination of the bell stage of the enamel
organ.
• The cells form the inner enamel epithelium, the stratum
intermedium, the stellate reticulum, and the outer enamel
epithelium.
• The junction between inner and outer enamel epithelium is
called cervical loop and it is an area of intense mitotic activity.

34. INNER ENAMEL EPITHELIUM
• The inner enamel epithelium consists of a
single layer of cells that differentiate prior to
amelogenesis into tall columnar cells called
ameloblasts.
• These elongated cells are attached to one
another by junctional complexes laterally & to
cells in the stratum intermedium by
desmosomes.

35. STRATUM INTERMEDIUM
• A few layers of squamous cells form the stratum
intermedium , between the inner enamel epithelium & the
stellate reticulum.
• These cells are closely attached by desmosomes & gap
junctions.
• This layer seems to be essential to enamel formation

36. STELLATE RETICULUM
• The stellate reticulum expands further due to
continued accumulation of intra-cellular fluid.
• These star shaped cells, having a large processes, that
anastomose with those of adjacent cells.
• As the enamel formation starts., the Stellate reticulum
collapses to a narrow zone thereby reducing the
distance between the outer & inner enamel epithelium

37. OUTER ENAMEL EPITHELIUM
• The cells of the outer enamel epithelium flatten to form low
cuboidal cells.
• The outer enamel epithelium is thrown into folds which are
rich in capillary network, this provides a source of nutrition for
the enamel organ.
• Before the inner enamel epithelium begins to produce enamel.
Peripheral cells of the dental papilla differentiate into
odontoblasts.
• These cuboidal cells later assumes a columnar form & produce
dentin .

38. BELL STAGE

40. DENTAL PAPILLA
• Before the inner enamel epithelium begins to produce
enamel, the peripheral mesenchymal cells differentiate
into odontoblasts.
• First, they assume a cuboidal form; later they assume a
columnar form and acquire the specific potential to
produce dentin.
• The dental papilla ultimately gives rise to dental pulp,
once the dentin formation begins at the cuspal tip of the
bell stage tooth germ.

41. DENTAL SAC
• The dental sac exhibits a circular arrangement of fibers
& resembles a capsule around the enamel organ.
• The fibers of the dental sac form the periodontal
ligament fibers that span between the root & the bone.
• The junction between the inner enamel epithelium &
odontoblasts outlines the future Dentino-enamel
junction.

42. Advanced bell stage / morphodiffrentiation
• Characterized by the commencement of mineralization & root
formation .
• The boundary between the inner enamel epithelium & odontoblasts
outline the future dentinoenamel junction
• Formation of dentin occurs first as a layer along the future
dentinoenamel junction in the region of future cusps & proceeds
pulpally & apically
• After the first layer of dentin is formed, the ameloblasts lay down
enamel over the dentin in the future incisal & cuspal areas

43. Advanced bell stage / morphodiffrentiation

44. Advanced bell stage / morphodiffrentiation

45. HISTOPHYSIOLOGY
• A number of physiologic processes participates
in the physiologic development of teeth.
• Except for their initiation, which is a momentary event,
these processes overlap considerably, and many are
continuous throughout the various morphologic
stages of odontogenesis.

46. HISTOPHYSIOLOGY
1. INITIATION:
• Specific cells within the dental lamina have the potential to form
the enamel organ of certain teeth by responding to those factors
that initiate or induce tooth development.
• Different teeth are initiated at definite times.
• Initiation induction requires ectomesenchymal–epithelial
interaction.

47. HISTOPHYSIOLOGY
2. PROLIFERATION
• There is increased proliferative activity at point of
initiation and it results in bud, cap, bell stages of enamel
organ.
3. HISTODIFFRENTIATION
• The formative cells of tooth germ that developed during
proliferative stage undergoes morphological and
functional changes.
• These cells undergoes differentiation and gives up their
potential to multiply.

48. HISTOPHYSIOLOGY
4. MORPHODIFFRENTIATION
• Means differential growth
• The morphologic pattern and relative size of the future tooth, is
established by morphodifferentiation.
• The advanced bell stage marks not only active
histodifferentiation but also an important stage of
morphodifferentiation in the crown

49. Formation of enamel/dentin matrix (apposition)
• Apposition is the deposition of the matrix of the hard
enamel structures
• Appositional growth of the enamel & dentin is a layer
like deposition of an extracellular matrix. This type of
growth is therefore additive .
• Appositional growth is characterized by regular &
rhythmic deposition of the extracellular matrix,
which is of itself incapable of further growth

51. ROOT
FORMATION

52. • The development of roots begin after enamel & dentin
formation has reached the future cement-enamel junction .
• The enamel organ plays an important role in root development
by forming HERS, which models the shape of the root .
• HERS consists of outer & inner enamel epithelium only
• As the first layer of the dentin has been laid down, the
epithelial root sheath loses its structural continuity and is
close relation to the surface of the root.
• Its remnants persists as an epithelial network of strands or
clumps near the external surface of the root .

53. • These epithelial remnants are found in the periodontal ligament of
erupted teeth and are called as rests of mallasez.
• Prior to the beginning of root formation, the root sheath forms the
epithelial diaphragm.
• The outer & the inner enamel epithelium bend at the future
cementoenamel junction into a horizontal plane, narrowing the
wide cervical opening to form epithelial diaphragm.
• The proliferation of the cells of the epithelial diaphragm is
accompanied by the proliferation of the cells of the connective
tissues of the pulp, adjacent to the diaphragm.
• The free end of diaphragm does not grow into the connective
tissue but the epithelium proliferates coronal to the epithelial
diaphragm

55. • Connective tissue of the dental sac surrounding the root sheath
proliferates & invades the continuous double epithelial layer
dividing it into network of epithelial strands .
• In the last stages of the root development, the proliferation of
the epithelium in the diaphragm lags behind that of the pulpal
connective tissue .
• The wide apical foramen is reduced first to the width of the
diaphragmatic opening itself & later is further narrowed by
opposition of dentin & cementum to the apex of the root

56. • Differential growth of the epithelial diaphragm in the multi-rooted
teeth causes the division of root trunk into 2 or 3 roots.
• During the general growth of the enamel organ the expansion of its
cervical opening occurs in such a way that long tongue like extensions
of the horizontal diaphragm develop.
• Two such extensions are found in the germs of lower molars and
three in the germs of upper molars.
• During the general growth of enamel organ, expansion of its cervical
opening occurs in such a way that long tongue like extensions of the
horizontal diaphragm develop.
• Before division of the root trunk occurs, free ends of the horizontal
epithelial flaps grow towards each other & fuse.

57. CLINICAL
CONSIDERATIONS

58. • Anodontia, also called anodontia vera,
is a rare genetic disorder
characterized by the congenital
absence of all primary or permanent
teeth.
• It is of following types :
1. Complete anodontia/ total anodontia
2. Partial anodontia/ sub-Total
anodontia
• Forms of partial anodontia:
1. True anodontia
2. Psuedo anodontia
3. False anodontia
anodontia

59. 1. Complete anodontia
• Congenital absence of teeth, absence of both deciduous and
permanent teeth in mouth.
• Seen associated with- hereditary ectodermal dysplasia, in many
cases cuspids are present in this disease but mostly characterized
by complete anodontia.
• Also seen among infants who have received high doses of radiation
to the jaws.
anodontia

60. 2. Partial anodontia:
• Commonly seen
• Congenital Absence of one or few teeth.
• Most commonly associated with 3rd molars.
Forms :
a. True anodontia –
• When there is failure of development of tooth in jaw bone.
anodontia

61. b. Pseudo anodontia:
• When teeth are present in jaw bone but not visible in oral
cavity eg; impacted teeth.
c. Flase anodontia:
• Teeth missing due to previous extractions.
anodontia

62. Dentinogenesis imperfecta
● Dentinogenesis is the formation of dentin, which starts before
Amelogenesis.
● Dentin is formed by odontoblast cells. Dentinogenesis takes
place in two phases:
1. formation of organic collagen matrix
2. deposition of hydroxyapetite crystals
● Is an inherited disorder of dentin formation
● Autosomal dominant condition
● Affects deciduous and permanent teeth

63. Dentinogenesis imperfecta

64. Dentinogenesis imperfect classification
● SHIELDS CLASSIFICATION
1. TYPE - I - Occurs in patients affected with
osteogenesis imperfect
2. TYPE - II - Is not associated with osteogenesis
imperfect
3. TYPE- III - “Brandywine type” rare condition, seen
in racial isolate of Maryland, exhibits multiple pulp
exposures and Periapical lesions in deciduous
dentition

65. Dentinogenesis imperfect classification
● REVISED CLASSIFICATION
1. DENTINOGENESIS IMPERFECTA1 –
 Without osteogenesis imperfecta
 Corresponds to type II of shields classification
2. DENTINOGENESIS IMPERFECTA2
 Corresponds to type III of shields classification .
● WITKOP CLASSIFICATION
1. DENTINOGENESIS IMPERFECTA
2. HEREDITARY OPALASCENT DENTIN
3. BRANDYWINE ISOLATE

66. ● ETIOLOGY :
1. mutation in the dentin sialo phospho protein (dspp) gene
2. encoding dentin phosphoprotein and dentin sialoprotein.
● CLINICAL FEATURES :
● opalescent teeth & affects only the teeth.
● No increased frequency of bone fracture is seen
● Affects males and females equally
● Teeth are blue gray or amber brown and opalescent
● Few days after eruption teeth may achieve a normal color, following which
they become translucent

67. CLINICAL FEATURES :
● Severe attrition of teeth
● Obliterated pulp chamber
● Teeth are not sensitive
● Dentin is soft and easily penetrable but not caries prone because of
structural change in dentin
● In some case there may be hypomineralised area on the enamel

68. RADIOGRAPHIC FEATURES
● Bulb shaped or bell shaped crowns of teeth
with constricted cervical areas
● Roots - thin and spiked
● Obliteration of coronal and radicular pulp
chamber depending on age
● Cementum, alveolar bone and PDL appears
normal
● Type 2 -> large pulp chambers with thin
shell of dentin and enamel “shell teeth”

69. AMELOGENESIS IMPERFECTA
• Also known as hereditary enamel dysplasia or hereditary
brown enamel.
• It is heterogenous group of hereditary disorders of enamel
formation affecting both deciduous and permanent teeth.
• Involves only ectodermal part of tooth i.e. enamel
• 3 types :
a. Hypoplastic
b. Hypocalcified
c. Hypomature

70. AMELOGENESIS IMPERFECTA
1. Hypoplastic
Matrix formation is affected.
Enamel thickness is less than normal enamel or
there may be complete absence of enamel.
2. Hypocalcification type:
Disturbance in process of early mineralization of
enamel.
Soft enamel that can be easy removed by
instrumentation.

71. AMELOGENESIS IMPERFECTA
3. Hypomaturation type:
Due to interruption in process of enamel
maturation.
Normal thickness of enamel but doesn’t
have normal hardness and it is
translucent.

72. AMELOGENESIS IMPERFECTA
Clinical features :
• Color of teeth – chalky white or yellow or dark brown
• Open contact points
• Severely abaraded occlusal or incisal surfaces
• Enamel may have cheesy consistency
• Snow capped teeth – presence of white opaque flecks
at incisal areas of teeth.
Treatment
Composite veneering can be done.

74. ● Dilaceration refers to an angulation or a sharp bend or curve
anywhere along the root portion of a tooth.
● Condition probably occurs subsequent to trauma or any other
defect of development which alters the angulation of the tooth
germ during root formation.
● Can easily be detected by radiographs.
● Care should be taken during extraction since these teeth are
more prone to fracture
DILACERATION

75. DILACERATION

76. ● Concrescence is a condition of
teeth where the cementum
overlying the roots of at least
two teeth join together.
● The cause can sometimes be
attributed to trauma or crowding
of teeth.
● Radiographic diagnosis is
mandatory before attempting
tooth extraction
CONCRESCENCE

77. ● The phenomenon of tooth fusion
arises through union of two normally
separated tooth germs, and
depending upon the stage of
development of the teeth at the time
of union, it may be either complete
or incomplete.
● However, fusion can also be the
union of a normal tooth bud to a
supernumerary tooth germ. In these
cases, the number of teeth is fewer
if the anomalous tooth is counted as
one tooth.
fusion

78. ● Gemination arises when two
teeth develop from one tooth
bud and, as a result, the
patient has an extra tooth
GEMINATION

79. • Supernumerary teeth can be classified by shape and by
position.
• The shapes include:
1. Supplemental(where the tooth has a normal shape for
the teeth in that series);
2. Tuberculate (also called "barrel shaped");
3. Conical (also called "peg shaped");
4. Compound odontome (multiple small tooth-like
forms);
Supernumerary teeth

81. ● Hyperdontia is the
condition of having so
many supernumerary
teeth, or teeth which
appear in addition to the
regular number of teeth
Supernumerary teeth

82. MESODENS
PARAMOLAR/DISTO-
MOLAR
• When classified by position, a
supernumerary tooth may be referred to
as a mesiodens, a paramolar, or a
distomolar.

83. REFRENCES
• Orban’s, Textbook of oral histology &
embryology
• Ten cates, Textbook of oral
histology
• Shaefer’s. Textbook of oral pathology

84. THANK YOU