The document discusses the development of teeth from the dental lamina stage through the various bell stages. It describes how the enamel organ, dental papilla, and dental sac form and their roles in tooth development. The stages of tooth development including bud, cap, and bell stages are summarized. Clinical conditions related to abnormalities in tooth development like dentinogenesis imperfecta, Hutchinson's incisor, and fusion are also mentioned.

1. DEVELOPMENT OF TOOTH
CHAITANYA.P
I MDS
Dept of Public Health Dentistry

2. Previous questions
• Anodontia. (jun 14)
• Write in detail about development of tooth.
(may,08).
• Describe the theories of eruption of teeth.
2

3. 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. Review of literature
8. Conclusion
9. References
3

4. INTRODUCTION
4

5. • 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 to form the
buccopharyngeal membrane
Ref : Orban’s Oral histology & Embryology,G S Kumar, pg.no. 24-46, 13th edition, 2013
5

6. DENTAL LAMINA
6

7. 6th week of intrauterine
Tooth formation
the formation of primary epithelial band
7th weekprimary epithelial band
dental lamina vestibular lamina
lingual extension distal extension
All deciduous teeth
Permanent teeth permanent molars oral vestibule
Ref : Orban’s Oral histology & Embryology,G S Kumar, pg.no. 24-46, 13th edition, 2013
7

8. FATE OF DENTAL LAMINA
• It is evident that total activity of dental lamina exceeds over a period of atleast 5 yrs
• As the teeth continue to develop, they loose their connection with the dental lamina
•They later break up by mesenchymal invasion, which is at first incomplete and does not
perforate the total thickness of the lamina .
• However the dental lamina may still be active in the third molar region after it has
disappeared elsewhere, except for occasional epithelial remnants
•Remnants of dental lamina persist as epithelial pearls or
cell rest of serres.
Ref : Orban’s Oral histology & Embryology, G S Kumar, pg.no. 24-46, 13th edition, 2013
8

9. 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 hollows and form the oral vestibule between the alveolar portion of
the jaws and the lips and cheeks.
Ref : Orban’s Oral histology & Embryology,G S Kumar, pg.no. 24-46, 13th edition, 2013
9

10. CLINICAL CONSIDERATIONS
10

11. ANODONTIA
• 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-
1. True anodontia
2. Psuedo anodontia
3. False anodontia
COMPLETE
PARTIAL
Ref : Neville, Oral and maxilla facial pathology, pg.no.77-98, 3rd edition,2009. 11

12. SUPERNUMERARY TEETH
Supernumerary teeth can be classified by
shape and by position. The shapes include:
• Supplemental(where the tooth has a
normal shape for the teeth in that series);
• Tuberculate (also called "barrel shaped");
• Conical (also called "peg shaped");
• Compound odontome (multiple small
tooth-like forms);
• Complex odontome (a disorganized mass of
dental tissue)
Hyperdontia is the condition of
having supernumerary teeth, or teeth which
appear in addition to the regular number of
teeth
When classified by position, a supernumerary
tooth may be referred to as a mesiodens, a
paramolar, or a distomolar.
Ref : Neville, Oral and maxilla facial pathology, pg.no.77-98, 3rd edition,2009.
12

13. 13

14. • At certain points along the dental lamina each representing the location of
one of the 10 mandibular & 10 maxillary teeth, ectodermal cells multiply
rapidly & 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
Ref : Orban’s Oral histology & Embryology,G S Kumar, pg.no. 24-46, 13th edition, 2013
14

15. DENTAL PAPILLA
On the inside of the cap, the ectomesenchymal cells increase in number. The
tissue appears more dense than the surrounding mesenchyme and represents
the beginning of the dental papilla
B = Dental Papilla
Ref : Orban’s Oral histology & Embryology,G S Kumar, pg.no. 24-46, 13th edition, 2013
15

16. DENTAL SAC/ DENTAL FOLLICLE
Surrounding the combined enamel organ or dental papilla, the third part of the tooth
bud forms. It is known as dental sac/follicle and it consists of ectomesenchymal cells and
fibers that surrounds the dental papilla and the enamel organ.
C= Dental sac
Ref : Orban’s Oral histology & Embryology,G S Kumar, pg.no. 24-46, 13th edition, 2013
16

17. • Thus the tooth germ consists of ectodermal
component- the enamel organ, the
ectomesenchymal components- the dental papilla
& the dental follicle
• The enamel is formed from the enamel organ,
the dentin and the pulp from the dental papilla
and the supporting tissues namely the cementum,
periodontal ligament & the alveolar bone from the
dental follicle
• During & after these developments the shape of
the enamel organ continues to change
• 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
Ref : Orban’s Oral histology & Embryology,G S Kumar, pg.no. 24-46, 13th edition, 2013
17

18. DEVELOPMENTAL STAGES
18

19. 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
Ref : Orban’s Oral histology & Embryology,G S Kumar, pg.no. 24-46, 13th edition, 2013
19

20. BUD STAGE / PROLIFERATION
• This is the initial stage of tooth formation
where enamel organ resembles a small bud
• During the bud stage, the enamel organ
consists of peripherally located low columnar
cells & centrally located polygonal cells
• The surrounding mesenchymal cells
proliferate, which results in their
condensation in two areas
• The area of condensation immediately
below the enamel organ is the dental papilla
• The ectomesenchymal condensation that
surrounds the tooth bud & the dental papilla
is the tooth sac
Ref : Orban’s Oral histology & Embryology,G S Kumar, pg.no. 24-46, 13th edition, 2013
20

21. • The dental papilla as well as the dental sac are not well defined during the bud stage,
they become more defined during the subsequent cap & bell stages
• The cells of the dental papilla form the dentin and pulp while the dental sac forms
cementum & periodontal ligament
21

22. CAP STAGE / PROLIFERATION
• As the tooth bud continues to proliferate, it does not expand uniformly into a
large sphere
• Instead 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
22

23. OUTER & INNER ENAMEL EPITHELIUM
• The peripheral cells of the cap stage are
cuboidal , cover the convexity of the cap &
are called the outer enamel epithelium
• The cells in the concavity of the cap
become tall columnar cells & represent the
inner enamel epithelium
Ref : Orban’s Oral histology & Embryology,G S Kumar, pg.no. 24-46, 13th edition, 2013
23

24. •The outer enamel epithelium is separated from the
dental sac, & the inner enamel epithelium from the
dental papilla, by a delicate basement membrane
24

25. STELLATE RETICULUM
• Polygonal cells located between the outer and the inner enamel epithelium, begin to
separate due to water being drawn into the enamel organ from the surrounding dental
papilla
• 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
25

26. • 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
Ref : Orban’s Oral histology & Embryology,G S Kumar, pg.no. 24-46, 13th edition, 2013
26

27. • At the same time a vertical extension of the enamel knot,
called the enamel cord occurs
27

28. • The function of enamel knot & cord
may act as a reservoir of the dividing
cells for the growing enamel organ
• The enamel knot act as a signaling
centers as many important growth
factors are expressed by the cells of
the enamel knot & thus play an
important role in determining the
shape of the tooth
• The ectomesenchymal
condensation i.e the dental papilla &
the dental sac are pronounced
during this stage of dental
development
Ref : Orban’s Oral histology & Embryology, G S Kumar, pg.no. 24-46, 13th edition, 2013
Ref :Avery JK: Embryology of the tooth. J Dent Res 30:490,1951
Ref : Avery JK: Primary induction of tooth formation. JDent Res 33:702,1954
28

29. BELL STAGE / HISTODIFFERENTIATION
• Due to continued uneven growth of the
enamel organ it acquires a bell shape
• In bell stage crown shape is determined
• It was thought that the shape of the crown
is due to pressure exerted by the growing
dental papilla cells on the inner enamel
epithelium
• This pressure however was shown to be
opposed equally by the pressure exerted by
fluid present in the stellate reticulum
• 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
Ref : Orban’s Oral histology & Embryology,G S Kumar, pg.no. 24-46, 13th edition, 2013
29

30. ADVANCED BELL STAGE / MORPHODIFFERENTIATION
 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
Ref : Orban’s Oral histology & Embryology,G S Kumar, pg.no. 24-46, 13th edition, 2013
30

31.  The enamel formation then proceeds
coronally & cervically in all the regions
from the dentinoenamel junction toward
the surface
 The cervical portion of enamel organ
gives rise to Hertwig Epithelial Root
Sheath (HERS)
 This HERS outlines the future root &
thus responsible for the size, shape,
length & number of roots
Ref : Orban’s Oral histology & Embryology,G S Kumar, pg.no. 24-46, 13th edition, 2013
31

32. 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
• The cells of the inner enamel epithelium exert a strong influence on the underlying
mesenchymal cells of the dental papilla, which later differentiate into odontoblasts
32

33. 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
33

34. STELLATE RETICULUM
• The stellate reticulum expands further due to continued accumulation of intra-cellular
fluid
• These star shaped cells, having a large processes 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
34

35. 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
35

36. 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
Ref : Orban’s Oral histology & Embryology,G S Kumar, pg.no. 24-46, 13th edition, 2013
36

37. FORMATION OF ENAMEL & DENTIN MATIX
( 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 characterised by regular & rhythmic
deposition of the extracellular matrix, which is of itself incapable of
further growth
Ref : Orban’s Oral histology & Embryology,G S Kumar, pg.no. 24-46, 13th edition, 201337

38. 38

39. CLINICAL CONSIDERATIONS
39

40. DENTINOGENESIS IMPERFECTA
• Dentinogenesis imperfecta (hereditary
Opalescent Dentin) is a genetic
disorder of tooth development.
• This condition causes teeth to be
discolored (most often a blue-gray or
yellow-brown color) and translucent. Teeth
are also weaker than normal, making them
prone to rapid wear, breakage, and loss.
• These problems can affect both primary
(baby) teeth and permanent teeth.
• This condition is inherited in
an autosomal dominant pattern, which
means one copy of the altered gene in
each cell is sufficient to cause the disorder.
Ref : Neville, Oral and maxilla facial pathology, pg.no.77-98, 3rd edition,2009. 40

41. HUTCHINSON’S INCISOR
MULBERRY MOLARS
Ref : Neville, Oral and maxilla facial pathology, pg.no.77-98, 3rd edition,2009. 41

42. FUSION
• 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.
Ref : Neville, Oral and maxilla facial pathology, pg.no.77-98, 3rd edition,2009. 42

43. GEMINATION
Gemination arises when two
teeth develop from one tooth
bud and, as a result, the
patient has an extra tooth
Ref : Neville, Oral and maxilla facial pathology, pg.no.77-98, 3rd edition,2009. 43

44. ENAMEL HYPOPLASIA
Enamel hypoplasia is the
defect of the teeth in which
the tooth enamel is hard but
thin and deficient in amount
This is caused by defective
enamel matrix formation
with a deficiency in the
cementing substance
Ref : Neville, Oral and maxilla facial pathology, pg.no.77-98, 3rd edition,2009. 44

45. AMELOGENESIS IMPERFECTA
• Amelogenesis imperfecta presents with
abnormal formation of the enamel or
external layer of teeth. Enamel is composed
mostly of mineral, that is formed and
regulated by the proteins in it. Amelogenesis
imperfecta is due to the malfunction of the
proteins in the enamel:
ameloblastin, enamelin, tuftelin, amelogenin
• People afflicted with amelogenesis
imperfecta have teeth with abnormal color:
yellow, brown or grey. The teeth have a
higher risk for dental cavities and are
hypersensitive to temperature changes. This
disorder can afflict many number of teeth.
Ref : Neville, Oral and maxilla facial pathology, pg.no.77-98, 3rd edition,2009. 45

46. Dens- In- Dente ( DENS INVAGINATUS)
• Represents a defect of tooth in which a
focal area on the tooth surface is folded or
invaginated pulpally to a variable extent.
• Defect in generally localized to a single
tooth & interestingly maxillary lateral
incisors are more commonly affected.
• Bilateral involvement is often seen &
sometimes defect can involve multiple teeth
involving the supernumeraries.
• In case of pulp involvement with or
without apical pathology, endodontic
treatment should be attempted. However in
more severe form extraction should be
done.
Ref : Neville, Oral and maxilla facial pathology, pg.no.77-98, 3rd edition,2009. 46

47. DENS EVAGINATUS
• Dens evaginatus is a condition found
in teeth where the outer surface appears
to form an extra bump or cusp.
• Premolars are more likely to be
affected than any other tooth. This may
be seen more frequently in Asians
• The pulp of the tooth may extend into
the dens evaginatus.
• There is a risk of the dens evaginatus
chipping off in normal function
• Hence this condition requires
monitoring as the tooth can lose its blood
and nerve supply as a result and may
need root canal treatment.
Ref : Neville, Oral and maxilla facial pathology, pg.no.77-98, 3rd edition,2009. 47

48. TALON CUSP
• A talon cusp, also known as an
"eagle's talon", is an extra cusp on an
anterior tooth.
• Of all cases, 55% occur on the
permanent maxillary lateral incisor,
and 33% occur on the
permanent maxillary central incisor.
They are found rarely in primary teeth
• Whenever the lingual pits are
present restorative treatments should
be done to prevent caries
• When talon cusp interferes with
normal occlusion preventive care
should be taken by performing
endodontic treatment
Ref : Neville, Oral and maxilla facial pathology, pg.no.77-98, 3rd edition,2009. 48

49. ROOT FORMATION
49

50. • 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,
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
Ref : Orban’s Oral histology & Embryology, G S Kumar, pg.no. 24-46, 13th edition, 2013
Ref :Avery JK: Embryology of the tooth. J Dent Res 30:490,1951
Ref : Avery JK: Primary induction of tooth formation. JDent Res 33:702,1954
50

51. •Its remnants persists as an
epithelial network of strands or
clumps near the external surface of
the root
• These epithelial remnants are
found in the periodontal ligament
of erupted teeth and are called as
rests of mallasez
Ref : Orban’s Oral histology & Embryology,G S Kumar, pg.no. 24-46, 13th edition, 2013
51

52. • 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
• 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
52

53. • Connective tissue of the dental sac
surrounding the root sheath proliferates
& invades the continuous double
epithelial layer dividing it into network of
epithelial strands
• The rapid sequence of proliferation &
destruction of Hertwig’s root sheath
explains the fact that it cannot be seen as
a continuous layer on the surface of
developing root
• 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 53

54. • Differential growth of the epithelial
diaphragm in the multirooted teeth causes
the division of root trunk into 2 or 3 roots
• 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
• The single cervical opening is divided into
2 or 3 openings
Ref : Orban’s Oral histology & Embryology,G S Kumar, pg.no. 24-46, 13th edition, 2013
54

55. • On the pulpal surface of
the dividing epithelial
bridges, dentin formation
starts
• On the periphery of each
opening, root development
follows in the same way as
described for single rooted
teeth 55

56. CLINICAL CONSIDERATIONS
56

57. DILACERATION
• 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
Ref : Neville, Oral and maxilla facial pathology, pg.no.77-98, 3rd edition,2009. 57

58. CONCRESCENCE
Concrescence is a condition
of teeth where
the cementum overlying the roots
of at least two teeth join together.
The cause can sometimes be
attribute to trauma or crowding of
teeth.
Radiographic diagnosis is
mandatory before attempting tooth
extraction
Ref : Neville, Oral and maxilla facial pathology, pg.no.77-98, 3rd edition,2009. 58

59. Tooth Eruption
59

60. 1 Phases of tooth eruption
Eruption is the movement of the developing teeth through the bone
and the overlying mucosa of the jaws to appear in the oral cavity
and reach the occlusal plane
Movements of teeth leading to eruption take place in three
phases
1. Preeruptive phase
2. Eruptive phase
3. Functional phase
Ref : Orban’s Oral histology & Embryology, G S Kumar, pg.no. 24-46, 13th edition, 2013
Ref :Avery JK: Embryology of the tooth. J Dent Res 30:490,1951
Ref : Avery JK: Primary induction of tooth formation. JDent Res 33:702,1954 60

61. 61

62. 1. Preeruptive phase
 The movements in preeruptive phase are the movements of the
developing tooth before the root begins to form.
 It consists of movements of the developing tooth within the
alveolar process.
 The tooth germs move outward and upward/downward with
the increasing length, width and height of the jaws.
62

63.  Preeruptive movements involve bodily movement and eccentric
movement of the developing tooth germ.
 Bodily movement is the shift of the entire tooth germ.
 Eccentric movement is the relative growth in one part of the
tooth, leading to a change in the centre of the tooth germ.
Ref : Orban’s Oral histology & Embryology, G S Kumar, pg.no. 24-46, 13th edition, 2013
Ref :Avery JK: Embryology of the tooth. J Dent Res 30:490,1951
Ref : Avery JK: Primary induction of tooth formation. JDent Res 33:702,1954
63

64. 64

65. 2. Eruptive phase (Prefunctional phase)
 Eruptive phase begins when the root starts to form and ends
when the tooth reaches occlusal plane.
 After initiation of root formation PDL also starts to develop.
 PDL is remodelled continuously to accommodate the eruptive
tooth movement.
 The end of secretory phase of amelogenesis also coincides with
the start of the eruptive phase.
65

66.  During the eruptive phase the tooth germ undergoes
intraosseous movements and supraosseous movements.
 The rate of supraosseous movements is a lot faster than the
intraosseous movements.
 The tissue in front of an erupting primary tooth is different from
that of a permanent tooth.
 A strand of fibrous tissue containing the remnants of the dental
lamina, know as gobernacular cord forms a pathway in advance
of developing permanent tooth.
66

67.  During the eruptive stage the crown breaks the double layer
epithelium overlying it and enters the oral cavity.
 The eruption causes the tissue around it form the junctional
epithelium and the gingiva.
 This phase is also called as prefunctional phase.
Ref : Orban’s Oral histology & Embryology, G S Kumar, pg.no. 24-46, 13th edition, 2013
Ref :Avery JK: Embryology of the tooth. J Dent Res 30:490,1951
Ref : Avery JK: Primary induction of tooth formation. JDent Res 33:702,1954
67

68. 3. Functional phase (Post eruptive phase)
 The functional phase begins when the tooth reaches the
occlusal plane and continues as long as the tooth remains in the
oral cavity.
 Movements in the early stages of this phase accommodates the
growth of root and the jaws.
 This phase is also called the post eruptive phase.
Ref : Orban’s Oral histology & Embryology, G S Kumar, pg.no. 24-46, 13th edition, 2013
Ref :Avery JK: Embryology of the tooth. J Dent Res 30:490,1951
Ref : Avery JK: Primary induction of tooth formation. JDent Res 33:702,1954
68

69. 2 Mechanism of tooth eruption
There are many theories that explain the mechanism of tooth
eruption
Vascularity
Vascularity plays an important role in tooth eruption
Sufficient blood supply to the tooth germ has proven to cause
eruptive tooth movement
 Localized hyperamia has shown to causes increased vascularity
of the periodontal tissue and also increased eruption of adjacent
tooth
69

70. Pressure
Decreased pressure overlying a tooth and increased
pressure around the tooth are major factors in tooth eruption.
When the root formation begins an eruption pathway
develops overlying the tooth.
Remodelling of tissue around the developing tooth brings
about an increase in pressure tooth which causes the tooth
movement.
70

71. Root formation
Root formation causes an overall increase in the length of
the tooth.
It produces enough force that leads to the resorption of
bone.
However, this force in itself does not cause tooth movement.
Rootless teeth also erupt.
71

72. Bone remodelling
The selective resorption and formation of bone surrounding
the tooth cause its movement.
This theory also explains the tooth movement during
preeuptive phase.
Dental Follicle
There is signalling between the reduced enamel epithelium
and the dental follicle.
This signalling regulates the timing of eruption of teeth –
known as ‘biologic clock’.
72

73. Periodontal ligament
The remodelling of PDL has also been considered as a
factor for tooth eruption.
The fibroblasts possess traction power that causes tooth
movement.
The PDL helps lift the tooth to its occlusal plane during
the supraosseous phase of eruption.
Ref : Orban’s Oral histology & Embryology, G S Kumar, pg.no. 24-46, 13th edition, 2013
Ref :Avery JK: Embryology of the tooth. J Dent Res 30:490,1951
Ref : Avery JK: Primary induction of tooth formation. JDent Res 33:702,1954
73

74. Review of literature
Ref. K. Heikinheimo Stage-specific Expression of Decapentaplegic-Vg-related Genes 2, 4, and 6 (Bone
Morphogenetic Proteins 2, 4,and 6) During HumanTooth Morphogenesis, J Dent Res 73(3): 590-597,74
K. Heikinheimo (1994) conducted a study on Stage-specific Expression of
Decapentaplegic-Vg-related Genes 2, 4, and 6 (Bone Morphogenetic Proteins 2, 4,and
6) During Human Tooth Morphogenesis.
Expression of DVR/bone morphogenetic
protein (BMP) 2, 4, and 6 was studied in human
fetal teeth. Sequential morphogenetic stage-
specific studies of DVR/BMP 2 and 4
mRNAexpression by in situ hybridization
revealed transcripts for
DVR/BMP4duringcompactionof the dental
mesenchyme.
Results suggest that DVR/BMP 4 is
involved in the early tooth morphogenesis.
DVR/BMP 6 may, in particular, be
implicated inepithelial-
mesenchymalinteractionscontrolling
cytodifferentiation. DVR/BMP2 and
6mayalso be involved in odontoblast
secretory function.

75. 75
K. Heikinheimo and T. Salo (1995) conducted a study onExpression of Basement
Membrane Type IV Collagen and Type IV Collagenases (MMP-2 and MMP-9) in
Human Fetal Teeth .
During cap and bell stages, in situ
hybridization located transcripts for ccl type
IV collagen chain in the fibroblasts
surrounding the enamel organ. No oxl type IV
collagen chain mRNA was detected in tooth
germ epithelium or dental papilla.
Transcripts for MMP-2 were located mostly
in the cells of the dental papilla and follicle.
Transient expression of MMP-2 mRNA was
observed in the inner enamel epithelium of
late cap/early bell-stage teeth. During early
apposition, a high level of MMP-2 was
confined to secretory odontoblasts
Results suggest that dental BM, acl type
IV collagen chain may be of mesenchymal
cell origin. Further, MMP-2 but not MMP-
9 may participate in remodeling and
degradation of BM during human tooth
morphogenesis.
Ref:K. Heikinheimo and T. Salo, Expression of Basement Membrane Type IV Collagen and Type IV
Collagenases (MMP-2 and MMP-9) in Human Fetal Teeth, J Dent Res 74(5): 1226-1234, May, 1995

76. 76
L. Ye et al (2006) conducted a study on Amelogenins in Human Developing and Mature
Dental Pulp.
Developing human tooth buds were
immunostained for amelogenin, and mRNA
was detected by in situ hybridization. The
effects of recombinant amelogenins on pulp
and papilla cell proliferation were measured by
Brd U immunoassay, and differentiation was
monitored by alkaline phosphatase expression.
Results suggest that odontoblasts actively
synthesize and secrete amelogenin protein
during human tooth development, and that
low-molecular-weight amelogenins can
enhance pulp cell proliferation.
Ref : L.Ye et al, Amelogenins in Human Developing and Mature Dental Pulp, J Dent Res

77. CONCLUSION
Since development of tooth forms the base of
dentistry, a thorough understanding and a sound
knowledge is required by a dentist regarding the
development stages of tooth & the anomalies related
to it, so as to identify & treat them in a proper fashion.
77

78. REFERENCES
1. Orban’s Oral histology & Embryology, G S Kumar, pg.no. 24-46, 13th edition,
2013.
2. Neville, Oral and maxilla facial pathology, pg.no.77-98, 3rd edition,2009
3. Avery JK: Embryology of the tooth. J Dent Res 30:490,1951
4. Avery JK: Primary induction of tooth formation. JDent Res 33:702,1954
5. L. Ye et al, Amelogenins in Human Developing and Mature Dental Pulp, J
Dent Res 85(9):814-818, 2006
6. K. Heikinheimo and T. Salo, Expression of Basement Membrane Type IV
Collagen and Type IV Collagenases (MMP-2 and MMP-9) in Human Fetal
Teeth, J Dent Res 74(5): 1226-1234, May, 1995
7. K. Heikinheimo Stage-specific Expression of Decapentaplegic-Vg-related
Genes 2, 4, and 6 (Bone Morphogenetic Proteins 2, 4,and 6) During Human
Tooth Morphogenesis, J Dent Res 73(3): 590-597, March, 1994