teeth Eruption time and shedding

2. CONTENTS
• INTRODUCTION
eruption of teeth
• STAGES IN TOOTH ERUPTION
• THEORIES OF ERUPTION
• PUTATIVE MOLECULES IN TOOTH
ERUPTION SIGNALING CASCADE
• CURRENT CONCEPTS IN TOOTH
ERUPTION
• TEETH ERUPTION CHART

3. EXFOLIATION of teeth
• PATTERN OF EXFOLIATION
• FACTORS THAT AFFECT SHEDDING
• MECHANISM OF RESORPTION AND
SHEDDING
• APPLIED ANATOMY
• CONCLUSION
• REFERENCES

4. ERUPTION
The word eruption properly means “cutting of
the tooth through the gum”
It derives from the latin erumpere, meaning “to
break out’’
Tooth eruption is defined as the process of
movement of a tooth from its developmental
position within the jaws to its functional
position in the oral cavity.

5. ACTIVE TOOTH ERUPTION
• The term active tooth eruption implies the
emergence of crown into the oral cavity.
• This eruptive process is usually divided into 3
stages
1. Preeruptive stage
2.Eruptive stage
3.Post eruptive stage

6. Intra-oral phase
TOOTH ERUPTION
Pre-oral phase

7. PREERUPTIVE STAGE
• This movement is made by both deciduous
and permanent tooth germs within tissues of
the jaw before they begin to erupt.
• It is also known as ‘Follicular phase of
eruption’
• Cahill DR, Marks SC Jr. Tooth eruption: Evidence for the central role of the dental follicle. J
Oral Path 1980; 9

8. PREERUPTIVE STAGE
• The preeruptive stage begins as the crown
starts to develop.
• The eruptive movement associated is of two
varities:
1.Spatial
2.Excentric

9. PREERUPTIVE STAGE
• Total bodily movement of the tooth germ
• Growth in which one part of the tooth germ
remains fixed while the rest continues to grow,
leading to a change in the center of the tooth
germ.

10. ERUPTIVE STAGE
 During the phase of eruptive tooth movement
the tooth moves from its position within the
bone of the jaw to its functional position in
occlusion.
 The eruptive or prefunctional stage begins with
the development of root.
 The principal direction of movement is occlusal
or axial.

11. ERUPTIVE STAGE
• Eruptive tooth movements are involved in
primary eruption, supraeruption, impaction,
alveolar compensation following wear, as well
as failure of eruption.
• During this phase of eruption,the movement
of tooth takes place at the rate of 4mm in
14weeks.

12. RELATIVE POSITION OF PRIMARY
AND PERMANENT INCISOR TEETH
Preeruptive
period
Prefunctional
eruptive
period.

13. RELATIVE POSITION OF PRIMARY
AND PERMANENT MOLAR TEETH.
Preeruptive
period
Prefunctional
eruptive
period.

14. • This stage continues until the erupting teeth
meet the opposing teeth.
• The tooth movement tends to be occlusal and
facial,more facial in case of anteriors.

15. Once the teeth meet in
occlusion, their further
eruption separates the jaws
TOOTH ERUPTION
Once the teeth meet in
occlusion, they influence
each other mechanically

16. POSTERUPTIVE STAGE
• The stage begins when the teeth come into
occlusion and continues until they are lost or
death occurs.
• The type of movement is axial and mesial
migration.

17. POSTERUPTIVE STAGE
• Also acts as a compensatory mechanism.
• It is most active between the ages of 14 and
18 years of age.

18. EXPERIMENTAL STUDY RESULT
• Compagnon and Woda studied the unopposed
upper first molar in both healthy mouths and
those with some periodontal pathology
present.
• The study found that after 10 years of
remaining unopposed, this periodontal
migration reversed and root exposure
occurred.
Compagnon D, Woda A. Supra-eruption of the unopposed maxillary molar. J Prosthet
Dent 1991: 66(29).

19. DRIFTING e.g., mesially, laterally
AXIAL - in long axis of the tooth
Basil
ROTATORY
TILTING
By root growth &
bone remodelling
By bone remodelling &
PDL reorganization
TOOTH MOVEMENTS OCCURING IN
ERUPTION

20. POST ERUPTIVE STAGE

21. Gingival recession onto &
down the cementum with loss
of alveolar-crest bone
PASSIVE ERUPTION
Raising the banana, then peeling the banana

22. ERUPTION RHYTHM CIRCARDIAN
RHYTHM
• The mean daily eruption velocity was seen to
be 71µm / day.
• It is also believed that the effect of eruption
significantly increases in supine position
overnight.
• Berkovitz BK. How teeth erupt. Dent Update 1990: 206–210.

23. • The tertiary maturation of the erupting
tooth needs much more time than it is
supposed in literature.
• Possibly the completion is in accord with
the decline of the caries activity at the end
of the second decade of lifetime

24. • With the aid of polarizing microscopy, electron
microprobe, microhardness testing (Vickers)
and scanning electron microscopy different
stages of posteruptive maturation from
human and other mammalian teeth were
analysed.
Zentrums für Zahn-, Mund- und Kieferheilkunde der Martin-Luther-Universität
Halle-Wittenberg. Maturation of enamel and tooth eruption ; Dtsch Stomatol.
1991;41(9)

25. • There are few physical as well as chemical studies
of post-eruptive changes in enamel, although it is
widely believed that the surface layer of tooth
enamel reacts shortly after eruption, mainly by
the exchange of ions, and that the caries-
susceptibility decreases with the increase of post-
eruptive age.
• Matsumoto Daisuke ;A Study of Post-eruptive Maturation in Immature Permanent Teeth. Analysis
by Enamel Biopsy in Lower Central Incisors; Journal of the Japanese Association for Dental Science;
2002(21)

26. HISTOLOGY OF TOOTH ERUPTION
• While the root continues to lengthen,the
tooth begins to move toward the surface of
the oral cavity.
• During the intraosseous phase,the rate of
osteoclastic activity averages 1 to 10 μm
per day,it increases to about 75μm per day
once the tooth escapes from its bony cell.

27. DIAGRAM OF RUFFLED BORDER OF
AN OSTEOCLAST

28. STAGES OF TOOTH ERUPTION.

29. HISTOLOGY OF TOOTH ERUPTION
(permanent tooth)
• The fibrous cord,the gubernacular cord leads
the way and with the help of macrophages
and osteoclasts,breaks down the bone
between the tooth and the surface oral
epithelium.

30. Gubernacular cord of
fibrous tissue
Gubernacular cord
runs through a canal
left in the bony crypt,
where the dental
lamina extended
down to establish the
germ for the 2nd
tooth
Permanent
tooth
Go
Gubba!!

31. HISTOLOGY OF TOOTH ERUPTION
• As the successional tooth erupts ,its
gubernaculum canal is widened rapidly by
local osteoclastic activity , delineating the
eruptive pathway for the tooth.

32. HISTOLOGY OF TOOTH ERUPTION
• In a dried skull holes
can be identified which
are the once containing
the gubernacular
canals.

33. HUMAN JAWS AT 8 TO 9 YEARS OF AGE,
DURING THE MIXED DENTITION PERIOD
• The relationship
between primary and
permanent teeth during
the mixed dentition
period.

34. THEORIES OF ERUPTION
• Ten Cate recognized that the process of tooth
eruption is not precisely understood, and that
text described the four possible mechanisms
for eruption, that have been investigated.

35. These are
• Root formation, during which space for the
growing root is accommodated by occlusal
movement of the tooth crown.
• Hydrostatic pressure within the periapical
tissues pushing the tooth occlusally.

36. • Bony remodelling
• Pulling of the tooth in an occlusal direction by
the cells and fibres of the periodontal
ligament.

37. Deposition of alveolar bone?
MECHANISMS OF ERUPTION
Formation of the root
Construction & Reorganization of PDL
Remodelling of bone overall
FURTHER INFLUENCES from: tooth/teeth in occlusion; muscle actions

38. CAUSES OF ERUPTION
(THEORIES…… )
1. Root growth
2.alveolar bone formation and changes
3.periodontal ligament traction
4.vascular pressure in dental tissues
5.The role of tooth itself

39. ROOT GROWTH
• It has been said that the
increase in root
length,or root
elongation,forces the
tooth into oral cavity.
• But many experiments
disproved this concept,
but probably has a
relationship to the
process.
Marks SC Jr, Cahill DR. Experimental study in the dog of the non-active role of the tooth in the eruptive process. Archs Oral Biol
1984; 29

40. ALVEOLAR BONE FORMATION AND
CHANGES
• The alveolar process forms in areas where
teeth are developing and is deficient in
areas where teeth fail to develop.
• Alveolar bone changes involve both
formation and resorption,and these
metabolic events are dependent on the
presence of the various parts of the dental
sac or dental follicle.

41. • The cycle of bone development is rythmic
both in crest and crypt of the alveolar
bone, i.e instances of osteoblastic followed
by osteoclastic activity.
• In multirooted teeth the interradicular
bone seems to have a fairly significant role
in the eruption process.

42. EXPERIMENTAL STUDY RESULT
• The Marks and Cahill study eloquently
demonstrated that the dental follicle needs to
be present for tooth eruption of final tooth
position.
Cahill DR, Marks SC Jr. Tooth eruption: Evidence for the central role of the dental
follicle. J Oral Path 1980; 9(189).

43. • Bony remodelling occurs around the erupting follicle
regardless of the presence of a tooth crown or tooth,
suggesting that the remodelling process may be
under the control of the dental follicle.
• These experiments however, provide no evidence
that the follicle is involved in determination.
Berkovitz BK. How teeth erupt. Dent Update 1990: 206–210.

44. PERIODONTAL LIGAMENT TRACTION
• Periodontal ligament has a role to
play,probably more so toward the end of
the eruption than at the beginning.
• It was believed that the contractile fibers
play a role in eruption,but it is not proved.

45. • Ten Cate looked for evidence to support the
theory of the periodontal ligament having a
major role in determining tooth eruption.
• Strong evidence exists to show that the
periodontal ligament, which is derived from
the dental follicle, provides the force required
for eruption.

46. • Although informative, this study consisted of
histological observations, and did not provide
sufficient data on the origins of the tissues
studied.
• Ten Cate AR, Deporter DA, Freeman E. The role of fibroblasts in the remodeling of
periodontal ligament during physiological tooth movement. Am J Orthod 1976; 69: 155–168.

47. VASCULAR PRESSURE IN DENTAL
TISSUE
• THE VASCULAR PRESSURES are present in
pulpal tissues as well as in the periodontal
ligament.
• These pulsating pressure not only enhance
cellular activity but seem to have a direct
eruptive role.

48. EXPERIMENTAL STUDY RESULT
• The hydrostatic theory was investigated by
Van Hassel and McMinn again using dogs, who
found that the tissue pressure apical to the
erupting tooth was greater than occlusally,
theoretically generating an eruptive force.
Van Hassell H J, McMinn RG. Pressure differential favouring tooth eruption in the dog.
Archs oral Biol 1972; 17

49. • However, no association was demonstrated
between the magnitude of the force and the
rate of eruption.
• Van Hassell H J, McMinn RG. Pressure differential favouring tooth eruption in the dog. Archs
oral Biol 1972; 17

50. ROLE OF TOOTH ITSELF
• A study by Marks and Cahill using dogs,
showed the tooth itself played no part in the
eruptive process
• So it becomes an unanswered fact that tooth
it self plays a role in its
eruption………………..???

51. Then what causes
tooth eruption??

52.  Tooth eruption is
definitely a
multifactorial process
involving all or few
factors of the above.
 More research is now
being focused on the
biochemistry and cell
and molecular biology
aspects of the subject.
That’s good!!

53. • Ten Cate's theories have been further studied
by Berkovitz, who also agreed that no one
hypothesis can fully explain the mechanism of
tooth eruption. He proposed a multifactorial
concept of tooth eruption.

54. PUTATIVE MOLECULES IN TOOTH
ERUPTION SIGNALING CASCADE
 Bone morphogenic
protein-2
 Osteoprotegerin
 Nuclear factor κβ
 Runt related
transcription factor-2
 Interleukin 1α
 BMP-2
 OPG
 NF κβ
 RUNX-2
 IL-1 α
Wise GE,Frazier-Bowers S,D’SouzaRN: Crit Rev Oral Biol Med 2002;
13:323

55. CURRENT CONCEPTS IN TOOTH
ERUPTION
• The dental follicle is a loose connective tissue
layer that surrounds the erupting tooth.
• The follicle is necessary for tooth eruption.
• Specific cellular changes occur in and around the
follicle when a tooth erupts.

56. CURRENT CONCEPTS. . .
• An eruption pathway is formed when the bone and
roots of deciduous teeth are resorbed—events
initiated by the dental follicle during eruption.
• Because tooth eruption depends on the dental
follicle and activities around it, studies of the follicle
may shed some light on eruption mechanism.

57. CURRENT CONCEPTS. . .
• selective fragmentation of dental follicle
protein DF-95 correlates with the presence
of elevatedlevels of follicular collagenase
and stromelysin, and with the onset of
movement.
• Developmental Bilogy programme.1999: 126(13) 2911-2920,Company of
Biologists

58. CURRENT CONCEPTS. . .
 A dramatic decrease in these
metalloproteinasesfollowed initiation of
movement.
 A biochemical and cell biologicalmodel for
regulation of tooth eruption is proposed
based upon these new and existing data.

59. CURRENT CONCEPTS. . .
• CONTROL OF ERUPTION:
Hormonal control mechanisms
Physical control mechanisms

60. 5 YEAR OLD MOUTH…

61. TEETH ERUPTION CHART…

62. 1 32 54 760YEARS
YOUNG CHILD’S ERUPTION SEQUENCE
Time of emergence
Root formingCrown forming
KEY
10 2nd Molar
20 Incisor
20 Cuspid
20 2nd PreMolar
Deciduous
Permanent

63. 10 Incisor
10 Cuspid
1 32 54 760YEARS
YOUNG CHILD’S ERUPTION SEQUENCE
10 2nd Molar
20 Incisor
20 Cuspid
20 2nd PreMolar

64. PRIMARY TEETH ERUPTION CHART

65. IMPORTANCE OF PRIMARY TEETH
 Help a child to chew
and speak
• Hold space for the adult
teeth & guide teeth
during eruption
• Aid in jaw and face
formation
• Influence the child’s
overall health

66. PERMANENT TEETH ERUPTION
CHART

67. SHEDDING OF TEETH

68. EXFOLIATION
• The physiologic process resulting in the elimination
of the deciduous dentition is called shedding or
exfoliation.
• The main factors which play role in shedding of
teeth are the odontoclast and pressure from the
successional tooth.
• External pressures generated by cheeks and tongue
also play a minor role in shedding

69. PATTERN OF EXFOLIATION
• Shedding or exfoliation occurs as a result of
progressive resorption of roots of the teeth and their
supporting tissue,the periodontal ligament.
• In general,the pressure generated by the growing
and erupting permanent tooth dictates the pattern
of deciduous tooth resorption.

70. PATTERN OF EXFOLIATION
• At first the pressure is directed against the vestibular
direction, resorption of the roots of the deciduous
incissors and canines begins on their lingual surfaces.
• Later, the developing tooth germs occupy a position
directly apical to the deciduous tooth.

71. PATTERN OF EXFOLIATION
• In case of mandibular molars,the permanent tooth
erupts lingual to the still functioning deciduous
tooth.
• Resorption of the roots of deciduous molars often
begins on their inner surfaces and bicuspids are
found between them.

72. PATTERN OF EXFOLIATION
• The areas of early
resorption are repaired
by the deposition of a
cementum-like tissue.

73. Osteoclasts
resorbing bone
PDL fibers
incorporated in bone
as Sharpey’s fibers
FUNCTIONAL ERUPTION
& TOOTH MOVEMENT
Osteoblasts
laying down
bundle bone
Cellular cementum added to apex
Compensates for occlusal wear?
Occlusal wear
Bony
interdental
septum
Basil

74. FACTORS THAT PLAY ROLE IN
SHEDDING
1.Odontoclast
2.Pressure

75. ODONTOCLAST
• When root resorption is almost
complete,these odontoclasts degenerate,and
mononuclear cells emerge from pulpal vessels
and migrate to the predentin surface.
• Less is known about the resorption of soft
tissues as it sheds.

76. ODONTOCLAST
• Just before exfoliation,resorption ceases as
the odontoclasts migrate away from the
dentin surface.
• The tooth sheds with some pulpal tissues
intact.

77. 10/Deciduous tooth
PDL attachment is
surprising persistent
Close to EXFOLIATION of
Deciduous 10 Tooth
Bone trabeculae
added by layers at
base of alveolus
Odontoclasts have
resorbed most of
deciduous root
Pulp is left
alive
Bone remodellling
has brought 20 tooth
under 10
20 tooth would be
LARGER than shown
20 tooth

78. PRESSURE
• The pressure exerted by the erupting permanent
teeth seem to play an important role in resorption of
deciduous teeth.
• The local pressure is responsible for initiation of
resorption.
• In addition to this local pressure, heavy masticatory
and muscular forces play a role in resorption.

79. MECHANISM OF RESORPTION AND
SHEDDING
• The mechanism involved in bringing about tooth
resorption and exfoliation are not yet fully
proven, however it is clear that the odontoclast
attaches to the hard tissue surface peripherally,
thereby creating a sealed space lined by the
ruffled border .

80. STARTING EXFOLIATION of DECIDUOUS MOLAR I
ALVEOLAR
BONE
DENTINE
ENAMEL
Permanent Tooth under deciduous
molar, & between its roots
Inter-radicular septum of bone
also houses 2nd tooth germ & is
its crypt
Root resorption
by osteoclasts
PDL
PULP

81. EXFOLIATION of DECIDUOUS MOLAR II
ALVEOLAR
BONE
DENTINE
ENAMEL
Focal erosion along this line
leaves a ROOT FRAGMENT
which may be retained
Resorbed dentine partly
repaired by new cementum
Crypt bone
eroded here
PDL
PDL is disrupted in regions of
root resorption & repair

82. EXFOLIATION of DECIDUOUS MOLAR III
Erosion of bone and the deciduous root is not steady &
continuous, but may cease briefly, when some repair of
eroded cementum & dentine can occur (by cementum).
Bone remodelling also goes on, and the alveolus and
crypt are changing all the time - repeated all along the jaw
DENTINE
ENAMEL

83. MECHANISM OF RESORPTION AND
SHEDDING
• The membrane of the ruffled border acts as a
proton pump, adding hydrogen ions to the
extracellular environment and acidifying it so that
the mineral dissolution occurs.

84. APPLIED ANATOMY
PREMATURE ERUPTION :
• Premature eruption of teeth occurs
infrequently, for example in case of Riga fede
diesease we see early eruption (natal teeth).
• They erupt in the first 30days of life and the
teeth most often involved are deciduous
mandibular incissors.

85. • The etiology is unknown, but experimental studies
report this to be an endocrinal cause.
• Premature eruption of permanent teeth is usually a
sequela of the premature loss of deciduous teeth,
and here again an endocrinal disturbance is
considered.

86. DELAYED TOOTH ERUPTION
1. Bonnet-Dechaume-Blanc syndrome
2.Cleidocranial dysplasia
3.Coffin syndrome
4.Cornelia de Lange syndrome
5.Cytotoxic therapeutic agents
6.Down syndrome
7.Gaucher’s syndrome

87. 8.Frontometaphyseal dysplasia
9.congenital hypothyroidism
10.Rutherfurd syndrome
11.Osteopetrosis
12.Radiotherapy
13.Muccopolysachridosis Type 6

88. THE EFFECT OF PREMATURE LOSS
OF THE FIRST PERMANENT MOLAR
• Diminished local function
• Drifting of teeth
• Mid line deviation
• Continued eruption of opposing teeth

89. ERUPTION SEQUESTRUM
• It is a tiny irregular
spicule of bone
overlying the crown of
an erupting permanent
molar.
• In most cases,this
fragment probably
undergoes total
resorption prior to
eruption.

90. ERUPTION HEMATOMA
• A bluish purple,
elevated area of tissue,
commonly called an
eruption hematoma.
• The blood-filled cyst is
most frequently seen in
the primary second
molar or the first
permanent molar
regions

91. DIMINISHED LOCAL FUNCTION
• Diminished local function result in a reduction
in chewing efficiency as great as 50%.
• Shifting of the load of mastication to the
unaffected side.
• An unhygienic condition of the unused side

92. INFRA OCCLUSION
• This is the preferred term for submerged or
ankylosed teeth.
• It describes teeth that have failed to achieve
or maintain their occlusal relationship to
adjacent and opposing teeth.

93. INFRA OCCLUSION
• 1-9% MALE = FEMALE
• Primary > Permanent
• Mandibular first
primary molar most
frequently affected

94. INFRA OCCLUSION
• There is a higher incidence of infra occlusion
associated with missing permanent successors, but
the lower deciduous molars are at the same occlusal
level as the other deciduous teeth at this stage and
therefore not yet infra occluded.

95. INFRA OCCLUSION
• The lower second premolar is the most commonly
congenitally absent tooth after the third molars.
• There is no root resorption of the lower second
primary molars apparent

96. INFRA OCCLUSION
• Female patient age 14
• No relevant medical history
• Congenitally absent lower second premolars
Lower second primary molars not
infraoccluded
• No root resorption apparent

97. ANKYLOSIS
• Thought to be due to an imbalance in the normal
pattern of resorption and repair in primary teeth.
• Trauma and infection have been suggested as
precursors.

98. ANKYLOSIS
• Most likely cause here is congenitally absent lower
permanent second premolars.
• If the teeth are ankylosed they will be more difficult
to remove, and may require minor oral surgery

99. EMBEDDED TEETH
• These are teeth that fail to erupt in the oral
cavity due to various local factors

100. ECTOPIC ERUPTION
• Term used to describe a tooth or teeth that
erupt in an abnormal position.
• The prevalence of ectopic eruption was
significantly higher in the mandible.
doi: 10.2319/072506-306.1 The Angle Orthodontist: Vol. 77, No. 5, pp. 773–778.
Prevalence of Ectopic Eruption, Impaction, Retention and Agenesis of the Permanent Second
Molar ,Lars Bondemark;Jola Tsiopa

101. ECTOPIC ERUPTION
• It is believed that ectopic eruption is due to an
abnormal change in position of the dental
follicle, delayed loss of primary tooth, loss of
space in the alveolar arch.
• But, not yet the true reason for this condition
is concluded.

102. EPSTEIN PEARLS,BOHN NODULES ,
DENTAL LAMINA CYSTS
• Epstein pearls are formed along the
midpalatine raphe. (remnants of
epithelial tissue trapped along the
raphe)
• Bohn nodules are formed along the
buccal and lingual aspects of the
dental ridges and on the palate away
from the raphe. (remnants of mucous
gland tissue).
• Dental lamina cysts are found on the
crest of the maxillary and mandibular
dental ridges (remnants of the dental
lamina).

103. TEETHING
• Teething is a term limited by common usage
to eruption of primary teeth.
• Clinical features:
1.Local signs
2.Systemic signs

104. RESEARCH RESULTS OF EXFOLIATED
TOOTH
I . EXFOLIATED TOOTH IN STEM CELL RESEARCH
It is studied that exfoliated human deciduous tooth
contains multipotent stem cells [stem cells from human
exfoliated deciduous teeth (SHED)]i.e highly
proliferative, clonogenic cells capable of differentiating
into a variety of cell types including neural cells,
adipocytes, and odontoblasts
After in vivo transplantation, SHED were found to be able
to induce bone formation, generate dentin, and survive
in mouse brain along with expression of neural markers.

105. • SHED are not only derived from a very
accessible tissue resource but are also capable
of providing enough cells for potential clinical
application.
• *Craniofacial and Skeletal Diseases Branch, National Institute of Dental and Craniofacial
Research, National Institutes of Health, Bethesda, MD 20892; †Mesenchymal Stem Cell
Group, Division of Haematology, Institute of Medical and Veterinary Science, Australia

106. • Because bones and permanent teeth accumulate
lead, exfoliated deciduous teeth have been utilized
as retrospective markers of cumulative exposure in
epidemiological surveys.
• Relationships between serial blood lead levels and exfoliated tooth dentin lead levels:
Models of tooth lead kinetics ;JCTI;1993;53(5)

107. REFERENCES
• Brand and isselhard, anatomy of orofacial structures Text book of dental
anatomy,2004,7th edition.
• Orban,Oral histology and embryology,2001,12th edition.
• Ten cate’s, Text book of oral histology, 2008,7th edition.
• Marks SC Jr, Cahill DR. Experimental study in the dog of the non-active role of the
tooth in the eruptive process. Archs Oral Biol 1984; 29(311).
• Cahill DR, Marks SC Jr. Tooth eruption: Evidence for the central role of the dental
follicle. J Oral Path 1980; 9(189).
• Moxham BJ. The effects of some vaso-active drugs on the eruption of the rabbit
mandibular incisor. Archs Oral Biol 1979;24(681).
• Berkovitz BK. How teeth erupt. Dent Update 1990: 206–210.
• Van Hassell H J, McMinn RG. Pressure differential favouring tooth eruption in the
dog. Archs oral Biol 1972; 17(183).
• Ten Cate AR, Deporter DA, Freeman E. The role of fibroblasts in the remodeling of
periodontal ligament during physiological tooth movement. Am J Orthod
1976;69(155).

108. • Compagnon D, Woda A. Supra-eruption of the unopposed maxillary molar.
J Prosthet Dent 1991: 66(29).
• Relationships between serial blood lead levels and exfoliated tooth dentin
lead levels: Models of tooth lead kinetics ;JCTL;1993;53(5)
• Wise GE,Frazier-Bowers S,D’SouzaRN: Crit Rev Oral Biol Med 13:323,2002)
• Developmental Biology programme, Vol 126, Issue 13 2911-2920,
Copyright © 1999 by Company of Biologists
 The Angle Orthodontist: Vol. 77, No. 5, pp. 773–778. Prevalence of Ectopic
Eruption, Impaction, Retention and Agenesis of the Permanent Second
Molar ,Lars Bondemark;Jola Tsiopa