Concise Summary of tooth development, root formation, eruption and defects at each stage

1. TOOTH
DEVELOPMENT
, ERUPTION &
APPLIED
ASPECTS
Saurabh Roy
09.03.2016

2. CONTENTS :
■ Introduction
■ Initiation
– Dental lamina, Its fate
– Vestibular Lamina
– Defects
■ Proliferation
– Bud stage
– Cap stage
– Defects
■ Histodifferentiation – Early bell
■ Morphodifferentiation – Advanced bell
– Defects
2

3. CONTENTS :
■ Apposition :
– Defects
■ Root formation :
– Defects
■ Eruption
– Phases
– Mechanism
– Defects
■ Conclusion
■ References
3

4. INTRODUCTION :
4

5. INTRODUCTION :
■ As an oral diagnostician it is worth learning aboutTooth developmental
stages and eruption for the following reasons :
– Check for developmental milestones
– Co relate dental with skeletal maturity
– To anticipate developing malocclusion and prevent it before it happens
– To check for dental anomalies in syndromic and non - syndromic
patients
– In case of premature deciduous tooth loss or delayed eruption of
permanent teeth (patient guardian re assurance)
– Age estimation in neonates and children may be deduced by
pinpointing the stage of tooth development (forensic odontology)
5

6. Initiation in IUL :
■ Tooth formation occurs in the 6th week of intrauterine life with the
formation of primary epithelial band
■ 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
6

7. Initiation in IUL :
■ At about 7th week the primary epithelial band divides into a lingual process
called dental lamina & a buccal process called vestibular lamina
■ All deciduous teeth arises from dental lamina, later the permanent
successors arise from its lingual extension & permanent molars from its
distal extension
■ Post 37 days of development, a horseshoe shaped band of thickened
epithelium is formed at the presumptive upper & lower jaws
7

8. Timeline of tooth development :
8

9. Stages ofTooth Development :
Formation of Dental lamina Initiation
Bud & Cap Stage
Early bell stage
Proliferation
Formation of enamel & dentin
matrix
Advanced bell stage Morphodifferentiation
Histodifferentiation
Apposition
MORPHOLOGICAL PHYSIOLOGICAL
9

10. INITIATION :
10

11. INITIATION :
• The dental lamina serves as the primordium for the ectodermal
portion of the deciduous teeth
• 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)
• Total activity of the dental lamina exceed atleast 5 years
Dental Lamina :
11

12. Fate of Dental Lamina :
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
Fragmentation of the
dental lamina
progresses toward the
developing enamel
organ
Any particular portion
of the dental lamina
functions for a much
briefer period since
only a relatively short
time elapses after
initiation of tooth
development before
the dental lamina
begins to degenerate
However the dental
lamina may still be
active in the third
molar region after it
has disappeared
elsewhere, except for
occasional epithelial
remnants
12

13. 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
13

14. DEFECTS IN
INITIATION:
14

15. Defects :
■ Anodontia vera
■ Rare genetic disorder characterized by the congential
absence of all primary or permanent teeth
Initiation
COMPLETE
PARTIAL
FORMS
True
False
Pseudo
MUTATION OF PAX9 MSX1 AND AXIN2
Anodontia :
15
Mokhtari et al; Christ-Siemens-Touraine Syndrome: A Case Report and
Review of the Literature; Case Reports in Dentistry ; Hindawi Publishing
Corporation; Article ID 586418

16. Defects :
■ Anodontia :
Initiation
Multiple developmentally missing permanent teeth and several retained deciduous teeth in a
female adult.
The panoramic radiograph shows no unerupted teeth in either jaw. 16

17. Defects :
■ Associated syndromes :
– Ectodermal dysplasia
– Cleft lip & palate
– Ellis van creveld
– Ehlers danlos
– Goldenhar
– Hurler
– Gorlin goltz
– Lipoid proteinosis
– Progeria
– Sturge weber’
– Turners
Initiation
Anodontia :
17

18. Supernumerary tooth :
■ Results from continued proliferation of primary dental lamina to form 3rd
tooth germ
Initiation
Upper distomolars
Mesiodens
Premolars
Lower distomolars
Canines
18
Garvey et al; SupernumeraryTeeth -An Overview of Classification,
Diagnosis and Management; J Can Dent Assoc 1999; 65:612-6

19. Supernumerary tooth :
■ Associated syndromes :
– Apert
– Cleido cranial dysplasia
– Crouzon
– Down
– Ehlers danlos
– Gardner
– Sturge weber
– Curtius
– Fabry anderson
Initiation
19

20. Supernumerary tooth :
■ Post permanent dentition :
– The rare appearance of supernumerary teeth after loss of permanent
teeth
– Most teeth that appear after extraction of permanent teeth are due to
eruption of previously impacted teeth
Initiation
20

21. Ectopic initiation :
■ Dermoid cyst :
– An example of a teratoma
– Teratoma is a true neoplasm arising from
totipotent cells made up cell types
representative of more than 1 germ layer;
usually all 3
– Containing ectodermal cells have been
known to appear in
■ Ovary
■ Spinal cord tumours
■ Periorbital areas
– The common factor is the presence of a
solitary or multiple hamartomous tumour
Initiation
Yashwant Ingale et al; EctopicTeeth in OvarianTeratoma: A Rare Appearance; Hindawi Publishing
Corporation;Case Reports in Dentistry;Volume 2013, Article ID 970464, 3 pages 21

22. PROLIFERATION :
22

23. 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 dental sac
Bud stage : Early bud
Late bud
23

24. Bud stage :
• 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
Proliferation
24

25. 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
Proliferation
25

26. Cap stage :
■ Outer & inner enamel epithelium :
– Peripheral cells of the cap stage
are cuboidal, cover the
convexity of the “cap” called
Outer Enamel Epithelium
– The cells in the concavity of the
“cap” become tall, columnar
cells represent Inner Enamel
Epithelium
– The OEE is separated from the
dental sac and IEE from the
dental follicle by a delicate
basement membrane
– Hemidesmosomes anchor the
cells to the basal lamina
Proliferation
26

27. Cap stage :
■ Stellate reticulum :
– Initially Polygonal cells
– Between the OEE and IEE
– Endosmosis of water into enamel organ results in cells being star
shaped with inter connected processes
– As the enamel formation starts., the Stellate reticulum collapses to a
narrow zone thereby reducing the distance between the outer & inner
enamel epithelium
Proliferation
27

28. Cap stage :
■ Dental sac(follicle) :
– Concomitant with the development of the enamel organ and the dental
papilla, there is marginal condensation in the ectomesenchyme
surrounding both
– Gradually, a denser and more fibrous layer develops, which is the
primitive dental sac
Proliferation
28

29. Cap stage :
■ Dental papilla :
– Partial enclosure of ectomesenchyme by the invaginated portion of IEE
results in its proliferation and condensation into dental papilla
– Formative organ of the dentin & pulp primordium
– It shows active budding of capillaries and mitotic figures, & its
peripheral cells adjacent to the inner enamel epithelium enlarge and
later differentiate into odontoblasts
Proliferation
29

30. DEFECTS :
30

31. Microdontia :
1. True generalized microdontia :
■ All teeth smaller than normal
2. Relative microdontia : (misnomer?)
■ Normal or slightly smaller than normal teeth
■ Normal sized teeth may appear small when present in
widely spaced jaw larger than normal (macrognathia)
3. Focal or localized microdontia :
■ Common condition
■ Most affected – maxillary lateral incisor & 3rd molar
■ Most common form – Peg shaped lateral
Proliferation
31

32. Macrodontia :
– Appiled only when teeth are physically larger than usual and should
NOT include normal-sized teeth crowded within a small jaw (relative
macrodontia)
– Additionally, this term should NOT be used to describe teeth altered by
fusion or gemination
Proliferation
32

33. HISTODIFFERENTIATION
:
33

34. HISTODIFFERENTIATION :
■ Deepening of epithelial invagination and
growth of its margins, leads to assumption of
bell shape
■ The folding of enamel organ to cause different
crown shapes is shown to be due to differential
rates of mitosis & differences in cell
differentiation time
■ Determination of crown shapes is under the
control of genes and their signalling molecules
and growth factors
Early bell stage :
34

35. Early bell stage :
■ Inner enamel epithelium :
– Single layer of cells differentiate into tall columnar cells – Ameloblasts
■ Stratum intermedium :
– Few layers of squamous cells between the inner enamel epithelium and
stellate reticulum
■ Stellate reticulum ;
– This stage leads to further expansion, with an increase in the amount of
intercellular fluid
– Before enamel formation begins, the stellate reticulum collapses,
reducing distance between ameloblasts and nutrient capillaries near
outer enamel epithelium
Histodifferentiation
35

36. Early bell stage :
■ Outer enamel epithelium : flattening to a low cuboidal form
■ Dental lamina :
– Extends lingually and gives rise to successional lamina
– Gives rise to enamel organs of permanent successors of deciduous
teeth
■ Dental papilla :
– Enclosed in the invaginated portion of the enamel organ
– The basement membrane that separates the enamel organ and dental
papilla just prior to dentin formation is called membrana preformativa
■ Dental sac :
– Shows a circular arrangement of its fibres & resembles a capsular
structure
Histodifferentiation
36

37. MORPHODIFFERENTIATION
:
37

38. 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
Advanced bell stage :
38

39. Advanced bell stage :
■ 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
Morphodifferentiation
39

40. DEFECTS :
40

41. Gemination :
– Single enlarged tooth or joined(double) tooth in
which tooth count is normal when anomalous
tooth is counted as 1
– Partial or complete cleavage of single tooth
germ
– Large single rooted tooth with one pulp cavity
exhibits “twinning” in crown area
– The etiology of geminated teeth remains
unknown
– Possible cause-nutritional deficiency, endocrinal
disturbance, infectious/inflammatory processes,
hereditary or congenital diseases, and local
traumas and by ionizing radiation is also
considered
Morphodifferentiation
41

42. Fusion :
– Defined as a single enlarged tooth or joined(double)
tooth in which the tooth count reveals a missing tooth
when the anomalous tooth is counted as 1
– Either complete or incomplete union of two normally
separated tooth germs
– The dentin always confluent in cases of true fusion
Morphodifferentiation
If this contact occurs
Before calcification
begins
The 2 teeth may be
completely united to
form a single large
tooth
Later, when a portion
of tooth crown has
completed formation
The may be union of
the roots only
42

43. APPOSITION :
43

44. APPOSITION :
■ Appositional growth of enamel and dentin is a layer like deposition of an
extracellular matrix
■ Hence, this type of growth is additive
■ It signifies fulfilment of the plans outlined at the stages of histodifferentiation
and morphodifferentiation
■ Appositional growth is characterized by regular and rhythmic deposition of the
extracellular matrix, which is by itself incapable of further growth
■ Periods of activity and rest alternate at definite intervals during tooth formation
44

45. DEFECTS :
45

46. Dens invaginatus (Dens-in-dente) :
■ Represents a defect of tooth in which a focal area on
the tooth surface is folded or invaginated pulpally to
a variable extent.
■ Malformation of teeth probably resulting from an
infolding of the dental papilla before calcification.
■ Maxillary lateral incisors, central incisors, premolars,
canines and molars are affected in the order of
fashion
Apposition :
M. Hülsmann, “Dens invaginatus: aetiology, classification, prevalence, diagnosis, and treatment
considerations,” International Endodontic Journal, vol. 30, no. 2, 79–90, 1997. 46

47. Dens invaginatus (Dens-in-dente) :
■ Dens invaginatus (Dens-in-dente) :
Apposition
:
Coronal dens
invaginatus
Type I - Invagination
confined to the crown
Type II – extends past
the CEJ but does not
involve the periapical
tissues
Type III – extends past
the CEJ & may result
in formation of a 2nd
apical foramen
Oehler’s classification
47

48. Dens evaginatus :
■ central tubercle, tuberculated cusp, accessory
tubercle, occlusal pearl, evaginated
odontome,Leong premolar, tuberculated premolar
■ Cusp like elevation of enamel located in the central
groove or lingual ridge of the buccal cusp of
premolar or molar teeth
■ Accessory cusps are frequently associated with
occlusal interferences and pulpal pathoses
Apposition :
result of outward folding of
inner enamel epithelial cells and transient focal
hyperplasia of the peripheral cells of mesenchymal
dental papilla
48

49. Enamel pearl :
■ The formation of ectopic enamel requires the presence of differentiated
ameloblasts apical to the CEJ. In humans, Hertwig's epithelial root sheath
(HERS) or its residues, the epithelial rests of Malassez have been implicated as
the likely sources of ectopic ameloblasts
Apposition :
Shivani sharma et al Enamel pearl on an unusual location associated with localized periodontal disease: A
clinical report, J Indian Soc Periodontol. 2013 Nov-Dec; 17(6): 796–800
Radiopaque nodule on the mesial surface of the root
of the maxillary third molar.
Another less distinct enamel pearl is present on the
distal root of the second molar
Mass of ectopic enamel located in
the furcation area of a molar tooth
Enamel pearls are found
most frequently on the roots
of maxillary molars
(mandibular molars are the
second most frequent site)
49

50. Talon’s cusp :
■ Well delineated additional cusp located on the surface of an anterior tooth
and extends at least half the distance from the CEJ to the incisal edge
Apposition :
Normal
cingulum
Enlarged
cingulum
Small accessory
cusp
Full fledged
Talon’s cusp
As a result of outward folding of
inner enamel epithelial cells and transient focal
hyperplasia of the cells of mesenchymal
dental papilla
Permanent lateral incisors(55%), central (33%),
mandibular incisors (6%), maxillary canines (4%)
50

51. Talon’s cusp :
■ Hattab et al classified talons cusps as :
– Type 1, major talon: A morphologically well delineated additional cusp that
prominently projects from the facial or palatal/lingual surface of an anterior
tooth and extends at least half the distance from the CEJ to the incisal edge.
– Type 2, minor talon: A morphologically well-defined additional cusp that
projects from the facial or palatal/lingual surface of an anterior tooth and
extends more than onefourth, but less than half the distance from the CEJ to
the incisal edge.
– Type 3, trace talon: Enlarged or prominent cingula and their variations, which
occupy less than one-fourth the distance from the CEJ to the incisal edge
Apposition :
Hattab FN, Yassin OM, Al-Nimri KS. Talon cusp in the permanent dentition associated with other
dental anomalies: Review of literature and reports of seven cases. J Dent Child 1996;63:368-76 51

52. Taurodontism :
■ Enlargement of the body and pulp chamber of a multirooted tooth, with apical
displacement of the pulpal floor and bifurcation of the roots
■ Failure of Hertwig's epithelial sheath diaphragm to invaginate at the proper
horizontal level
■ Shape of the taurodont resembles that of the molar teeth of cud-chewing
animals (tauro = bull; dont = tooth)
Apposition :
52

53. Taurodontism :
:
Apposition :
Illustration exhibiting the classification of taurodontism according
to the degree of apical displacement of the pulpal floor
53

54. Enamel hypoplasia :
■ occurs in the form of pits, grooves, or larger areas of missing enamel
Apposition :
Factors producing injury to ameloblasts during
tooth formation:
Nutritional deficiency (vit. A,C,D)
Diseases like measles, chicken pox, scarlet fever
Congenital syphilis
Hypocalcaemia
Birth injury
Local infection or trauma
Ingestion of chemicals
Tissue irradiation
Bilaterally symmetrical pattern of
horizontal enamel hypoplasia of the
anterior dentition. Maxillary central
incisors have been restored previously
54

55. Amelogenesis imperfecta :
■ Encompasses a complicated group of conditions that demonstrate
developmental alterations in the structure of enamel in the absence of a
systemic disorder
Apposition :
The DLX3 gene is in a group of genes that code for a number of proteins that are critical for craniofacial ,
Tooth, hair, brain, and neural development
Elaboration of organic matrix
• Hypoplastic
Mineralization of the matrix
• Hypocalcified
Maturation of the enamel
• Hypomaturation
Related gene Protein Variants
AMLEX AMELOGENI
N
smooth hypoplastic and hypomaturation
ENAM ENAMELIN Hypoplastic (minor pitting to diffuse
generalized thin enamel)
MMP-20 ENAMELYSI
N
pigmented hypomaturation
KLK4 KALLIKREI
N
Hypomaturation
DLX3 hypoplastic-hypomaturation
55

56. Amelogenesis imperfecta : Apposition :
Hypoplastic amelogenesis imperfecta, generalized pitted pattern
56

57. Dentinogenesis imperfecta :
■ Hereditary opalescent dentin, capdepont’s teeth
■ Hereditary developmental disturbance of the dentin the absence of any
systemic disorder
■ Dentitions have a blue to brown discoloration, often with a distinctive
transluscence
■ Teeth are constitutionally weaker, prone to rapid wear, breakage, caries and
ultimately loss
Apposition :
A B
57

58. Dentinogenesis imperfecta : Apposition :
Aswathy Raj,Deepa.M.S,Ahmed Hasan Farooqi GENETICSANDTOOTH ANOMALIES - AN UPDATE
Oral & Maxillofacial Pathology JournalVol. 4 No. 1 Jan - June 2013 58

59. Dentinogenesis imperfecta : Apposition :
■ Classified into 3 basic types :
ShieldsType I (associated with Osteogenesis Imperfecta)-
Features- periapical radiolucencies, bulbous crowns, obliteration of pulp chambers, root fractures and
amber translucent tooth color
ShieldsType II (Hereditary Opalescent Dentin)
Features are same as ShieldsType I apart from Osteogenesis Imperfecta
ShieldsType III (Brandywine Type)
Teeth have a shell-like appearance with bell-shaped crowns.
Occurs exclusively in a isolated group in Maryland called Brandywine population
59

60. Dentinogenesis imperfecta : Apposition :
SHELLTEETH
■ :
NORMALTEETH
60

61. Regional odontodysplasia : Apposition :
Posterior mandibular dentition exhibiting enlarged
pulps and extremely thin enamel and dentin
■ Localized, nonhereditary developmental abnormality of teeth with
extensive adverse effects on the formation of enamel, dentin, and pulp
61

62. Dentin dysplasia : Apposition :
2 types :
Type I (radicular
dentin dysplasia)
Type II (coronal
dentin dysplasia)
62

63. Dentin dysplasia : Apposition :
■ Dentin dysplasia type I (radicular dentin dysplasia) :
– has been referred to as rootless teeth, because the loss of
organization of the root dentin often leads to a shortened root
length
FEATURES- Because of the shortened roots, the
initial clinical signs are extreme tooth mobility
and premature exfoliation, spontaneously or
secondary to minor trauma. Less frequently,
delayed eruption is the presenting symptom
Posterior dentition exhibiting shortened roots,
absence of pulp canals, and small, crescent-shaped
pulp chambers. 63

64. Dentin dysplasia : Apposition :
■ Dentin dysplasia type I (radicular dentin dysplasia) :
Subclassifcation of Dentin DysplasiaType I
DDIa: No pulp chambers, no root formation,
DDIb: A single small horizontally oriented and crescent-shaped pulp, roots only a few millimeters in length,
DDIc: Two horizontally oriented and crescent-shaped pulpal remnants surrounding a central island of dentin, significant but shortened
root length,
DDId: Visible pulp chambers and canals, near normal root length, enlarged pulp stones that are located in the coronal portion of the
canal and create a localized bulging of the canal and root, constriction of the pulp canal apical to the stone.
64

65. Dentin dysplasia : Apposition :
■ Dentin dysplasia type II (coronal dentin dysplasia) :
– The root length is normal in both dentitions.
– Radiographically, the dental changes include bulbous crowns, cervical
constriction, thin roots, and early obliteration of the pulp.
– The pulp chamber exhibit significant enlargement and apical extension which is
described as thistle tube–shaped or flame-shaped
Permanent dentition that does not exhibit translucence,
as noted in the deciduous teeth.
The patient also exhibits mild fluorosis of the enamel 65

66. ROOT FORMATION :
66

67. 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, 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 roots
67

68. ROOT FORMATION :
■ The rim of this root
sheath, the epithelial
diaphragm, encloses
the primary apical
foramen
■ These cells eventually
form dentin of the
tooth leading to
formation of a single
root
68

69. ROOT FORMATION :
■ Remnants of HERS 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
69

70. DEFECTS :
70

71. Concrescence : Root formation :
■ Two fully formed teeth, adhered along the root surface by cementum.
■ 2nd molar is frequently involved.
■ Clinically radiographic diagnosis is mandatory before attempting tooth extraction.
■ Deciduous dentition can result in crowding, abnormal spacing, and delayed or ectopic
eruption of the underlying permanent teeth
The space restriction during
development, local trauma,
excessive occlusal force or local
infection after development may be
the suspected causative factors
Concrescence. Union by cementum
of adjacent
Molars and it’s Radiograph
Jyoti S. Khedgikar, Shirish B. Khedgikar Concrescence of a Maxillary First and Second Molar: A Case
Report, Journal of Medical and Dental Science ResearchVolume 2 Issue 1 (2015) 71

72. Dilaceration : Root formation :
• Dilaceration refers to an abnormal angulation or a sharp bend or curve anywhere
along the root portion of a tooth
• Occurs due to trauma that displaces the calcified portion of the tooth germ which
alters the angulation of the tooth during root formation
72

73. Supernumerary roots :
■ The term supernumerary roots refers to the development of an increased
number of roots on a tooth compared with that classically described in
dental anatomy
■ These supernumerary roots may be due to the disturbances of the
Hertwig's epithelial root sheath forming the root
Apposition :
A, Gross photograph showing a
mandibular molar with a supernumerary
root.
B, Periapical radiograph of the extracted
tooth
73

74. ERUPTION :
74

75. ERUPTION :
■ The axial or occlusal movement of the tooth from its developmental
position within the jaw to its functional position in the occlusal plane
■ Maurya , massler & schour (1941) defined it as
Process whereby forming tooth migrates from its intra osseous
location within the jaw to its functional position within the oral cavity
75

76. Phases of tooth movements :
Pre – eruptive
• Made by deciduous
and permanent
tooth germs intra-
osseously before
eruption
• This phase occurs in
concordance with
jaw growth for
compensation
Eruptive
• Tooth moves from
its position within
the bone to its
functional position in
occlusion
• However, since jaw
growth is still
occurring,
movement in planes
other than axial
movement
supersedes eruptive
phase
Post – eruptive
• Maintains the
position of the
erupted tooth while
the jaw continues to
grow
• Also compensates
for occlusal and
proximal wear
76

77. Mechanism of tooth movements :
■ Still debatable but is likely to be a combination of several factors
Root growth
Bone
remodelling
Vascular
pressure
PDL traction
E
R
U
P
TI
O
N
77

78. Mechanism of tooth movements :
■ Bone remodelling :
– The end result of bone remodelling is a considerable bone deposition at
the bottom of the socket
– Selective formation & resorption of bone brings about eruption
– Dental follicle provides the source for new bone forming cells and is the
conduit for osteoclasts through its vascular supply, establishing its
absolute requirement
– Fallacies :
■ Alveolar bone remodelling which occurs around the root, concluding by bone
deposition is the outcome and NOT the cause of axial tooth movement
78

79. Mechanism of tooth movements :
■ Root formation :
– Proliferating root impinges on a fixed base, thus
converting an apically directed force of the tooth into
occlusal movement
– Fallacies :
■ Rootless teeth do erupt (most obvious in cases of dentin
dysplasia type I & following irradiation)
■ Teeth do NOT erupt after completion of root formation
■ Some teeth erupt a distance > total length of the root
Therefore, root formation is accommodated during tooth
eruption & is a consequence, NOT a cause of eruption process
Marks and Schroeder;Tooth eruption: theories and facts. Anat Rec 1996; June;
245(2):374-93 79

80. Mechanism of tooth movements :
■ Vascular pressure theory :
– Present in pulpal tissues as well as PDL
– The pressure exerted by the blood vessels at the apex of the tooth help
in tooth eruption
– Fallacies :
■ Question marks remain if the pressure exerted is enough to help in eruption
■ Teeth erupt even when vascular supply is cut
Marks and Schroeder;Tooth eruption: theories and facts. Anat Rec 1996; June;
245(2):374-93
80

81. Mechanism of tooth movements :
■ Ligament traction theory :
Marks and Schroeder;Tooth eruption: theories and facts. Anat Rec 1996; June;
245(2):374-93
Contractile
elements –
collagen in
fibroblasts
Constriction
Force initiation
by Fibroblasts
Transmitted to
extracellular
compartments
by fibronexus
and collagen
bundles by root
formation
ERUPTION
Fallacies :
• Examples of
PDL being
present but
tooth not
erupting and
vice versa have
been reported
81

82. DEFECTS :
82

83. Natal teeth : Eruption :
■ These are extra teeth that are present at birth.
■ Maybe considered an example of pre deciduous dentition
■ The most common natal teeth are lower incisors.
■ Clinical aspects :
– Clinically, in the majority of cases, both natal and neonatal teeth are
characterized by small immature conical dental structures, of a brown-
yellowish color, with an undeveloped root
– These anomalous aspects permit great mobility, facilitating
spontaneous loss or exfoliation, with gingival edema and inflammation,
and some bleeding areas
■ Treatment:
– These teeth are defective and their removal is generally recommended,
particularly if mobility poses a threat of aspiration.
– These teeth also make feeding difficult
Fátima Andrélo GONÇALVES et al; NatalTeeth: Review of the Literature and
Report of an Unusual Case; Braz Dent J (1998) 9(1): 53-56 83

84. Neo Natal teeth : Eruption :
■ Neonatal teeth are teeth that emerge through the gingiva during the first
month of life (the neonatal period)
Guidelines prior to extraction :
• Mandatory protection of airways by placing a gauze on the back of the
mouth
• Checking medical history for infantile jaundice
• Hypoprothrombinemia contra indicates extraction
Syndromes associated with presence of natal and pre natal teeth :
• Chondroectodermal dysplasia
• Pierre- Robin syndrome
• Ellis van creveld syndrome
• Sotos syndrome
• Rigafede disease
84

85. Eruption cyst / hematoma : Eruption :
■ The cyst develops as a result of separation of the dental follicle from around the crown of an
erupting tooth that is within the soft tissues overlying the alveolar bone
■ The epithelial lining of eruption cyst is similar to that of the dentigerous cyst (non-
keratinized stratified squamous epithelium), so the eruption cyst is considered a superficial
dentigerous cyst
■ Appears as a soft, often translucent swelling in the gingival mucosa overlying crown of an
erupting deciduous or permanent tooth
■ Most commonly associated with deciduous mandibular centrals, 1st permanent molars and the
deciduous maxillary incisors
This soft gingival swelling contains considerable
blood and can also be designated as an eruption
hematoma
85

86. Impaction : Eruption :
■ Teeth that cease to erupt before emergence are impacted
■ Causes:
– Crowding
– Insufficient maxillofacial development
– Overlying cysts and tumours
– Trauma
– Reconstructive surgery
– Systemic disorders and syndromes
86

87. Ankylosis : Eruption :
■ The cessation of eruption after emergence is termed ankylosis and occurs from
anatomic fusion of tooth cementum or dentin with the alveolar bone
■ Causes :
– Trauma
– Local failure from bone growth
– Abnormal pressure form the tongue
■ PDL acts as a barrier that prevents osteoblasts from applying bone directly
into the cementum
■ Ankylosis arises from a variety of factors that result in a deficiency of this
natural barrier
87

88. Eruption sequestrum : Eruption :
■ A small spicule of non vital bone may be seen radiographically or clinically
overlying the crown of partially erupted permanent posterior tooth.
■ The process is termed an eruption sequestrum
■ It’s occurs when the osseous fragment becomes separated from the
contiguous bone during eruption of the associated tooth
A radiopaque fragment of sequestrating bone
can be seen overlying an impacted third molar.
88

89. Timeline of tooth development:
92

90. Summary of tooth development:
93

91. Conclusion :
■ As an oral diagnostician it is imperative we know about the normal
developmental stages and morphology so as to differentiate it from
abnormal
■ Syndromic association may also be deduced by learning about tooth
abnormalities
■ Learning about the timeline of tooth development will help us in avoiding
unnecessary panic to the patient guardian in cases where we suspect
early exfoliation and/or delayed eruption
94

92. References :
■ Oral and Maxillofacial Pathology; Neville, Allen, Bouquot,; 2nd edition,
pages 52 – 100
■ Orban’s Oral Histology and Embryology ; GS Kumar; 12th edition; pages
22 - 43
■ Tencate’s Oral Histology; Antonio Nanci; SE Asia Edition; 79 – 107
■ Mokhtari et al; Christ-Siemens-Touraine Syndrome: A Case Report and
Review of the Literature; Case Reports in Dentistry ; Hindawi Publishing
Corporation;Article ID 586418
■ M. Hülsmann, “Dens invaginatus: aetiology, classification, prevalence,
diagnosis, and treatment considerations,” International Endodontic
Journal, vol. 30, no. 2, 79–90, 1997.
95

93. References :
■ Shivani sharma et al Enamel pearl on an unusual location associated
with localized periodontal disease: A clinical report, J Indian Soc
Periodontol. 2013 Nov-Dec; 17(6): 796–800
■ Hattab FN,Yassin OM, Al-Nimri KS.Talon cusp in the permanent
dentition associated with other dental anomalies: Review of literature
and reports of seven cases. J Dent Child 1996;63:368-76
■ Aswathy Raj,Deepa.M.S, Ahmed Hasan Farooqi GENETICS ANDTOOTH
ANOMALIES - AN UPDATE; Oral & Maxillofacial Pathology JournalVol.
4 No. 1 Jan - June 2013
■ Jyoti S. Khedgikar, Shirish B. Khedgikar Concrescence of a Maxillary
First and Second Molar: A Case Report, Journal of Medical and Dental
Science ResearchVolume 2 Issue 1 (2015)
96

94. References :
■ Marks and Schroeder;Tooth eruption: theories and facts. Anat Rec
1996; June; 245(2):374-93
■ Fátima Andrélo GONÇALVES et al; NatalTeeth: Review of the Literature
and Report of an Unusual Case; Braz Dent J (1998) 9(1): 53-56
■ Yashwant Ingale et al; EctopicTeeth in OvarianTeratoma: A Rare
Appearance; Hindawi Publishing Corporation;Case Reports in
Dentistry;Volume 2013, Article ID 970464, 3 pages
97

95. THANKYOU AND
GOOD DAY
98