THEORIES OF ERUPTION ERUPTION SEQUENCE PHYSIOLOGY OF TOOTH ERUPTION CELLULAR BASIS MOLECULAR BASIS PRODUCTION OF OSTEOCLAST ANOMOLIES OF TOOTH ERUPTION

1. THEORIES AND MECHANISM OF
ERUPTION OF PRIMARY AND
PERMANENT DENTITION
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2. CONTENTS
• INTRODUCTION
• THEORIES OF ERUPTION
• ERUPTION SEQUENCE
• PHYSIOLOGY OF TOOTH ERUPTION
• CELLULAR BASIS
• MOLECULAR BASIS
• PRODUCTION OF OSTEOCLAST
• ANOMOLIES OF TOOTH ERUPTION
• CONCLUSION
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3. INTRODUCTION
The timely initiation and eruption of teeth into the oral
cavity is very important for healthy dentition . It is the
process by which tooth moves within the jaw bone,
comes into the oral cavity and comes up to the occlusal
contact and maintains its clinical position.
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4. Human tooth eruption is a unique developmental
process.
Eruption
Latin word
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5. Human beings are Diphyodont
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MONOPHYODONT

6. THEORIES OF TOOTH ERUPTION
• Bone remodeling
• Root formation theory
• Vascular hydrostatic pressure
• Periodontal ligament traction
• Dental follicle
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7. The growth pattern of maxilla and mandible moves teeth by
selective deposition and resorption of bone.
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BONE REMODELLING THEORY
Results in eruption

8. According to root
growth theory
Cushion hammock
ligament
• The cushion hammock ligament straddles the base of the socket
from one bony wall to the other like a sling.
• Function : provides a strong base for the growing root to grow
against.
• But the cushion hammock ligament is a
pulp-delinating membrane that runs across the apex of
the tooth and has no bony insertion.
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ROOT FORMATION

9. But if occlusal movement is prevented, resorption of bone
occurs at the base of the socket.
This illustrates that if root formation is to result in
eruptive force, the apical growth of root needs to be
translated to occlusal movement and requires a
fixed base.
There is no fixed base because pressure on bony
base result in resorption.
Root formation may be a necessary pre-requisite
for eruption
Manson JD et al, 1967
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10. VASCULAR PRESSURE
Rich vascular supply between the teeth
and bony structures
Increased pressure by vessels
Vascular supply generate an erupting
force
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Facilitate eruption

11. PERIODONTAL LIGAMENT TRACTION
• Formation and renewal of PDL fibres has been considered a
factor in tooth eruption because of the traction power that
fibroblasts have.
• This force is transmitted from the extracellular compartment to
collagen fibres, which is aligned in an appropriate inclination to
bring about tooth movement.
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12. • Impacted teeth with well developed PDL fibres
does not erupt.
• Rootless teeth also erupt.
Gowgiel, 1961
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13. ROLE OF DENTAL FOLLICLE
Cahill and Marks (1980)
• Demonstrated a study to show the importance of dental follicle
in eruption.
• Removal of dental follicle from premolar prior to eruption
prevented unerupted tooth from erupting
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In 1984
• Keeping the dental follicle intact, they removed the tooth bud
and inserted artificial replica of tooth
Resulted in eruption of artificial tooth
Cahill and Marks (1984)

14. 2.CONTRACTILE
FORCE
GENERATED BY
DENTAL
FOLLICLE
3. BONE
FORMATION
&
RESORPTION
1.VASCULAR
PRESSURE AT
THE APEX OF
TOOTH
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15. ERUPTION SEQUENCE
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16. PHYSIOLOGY
OF TOOTH
MOVEMENT
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17. PRE-ERUPTIVE TOOTH MOVEMENT
ERUPTIVE TOOTH MOVEMENT
POSTERUPTIVE TOOTH MOVEMENT
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18. PRE-ERUPTIVE MOVEMENT
Made by deciduous and permanent tooth germ within the tissues of
the jaw before they begin to erupt.
Tooth germs
grow rapidly
Crowded
Relieved by
lengthening of
jaw
Deciduous
second molar
tooth germ
move backward
Anterior tooth
germ move
forward
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19. Permanent anterior tooth germ
develop lingual to the primary
anterior teeth and later primary
teeth erupt, the permanent crowns
lie at apical 3rd of primary tooth.
Premolar tooth germs lie
between the divergent roots
of deciduous molars
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20. The permanent molars which have no deciduous
predecessors also exhibit movement
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21. Histological features
• Remodelling of bony wall of crypt by
selective deposition and resorption of
bone by osteoblast and osteoclast.
• Normal skeletal morphogenesis is
involved in determining tooth position.
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22. ERUPTIVE MOVEMENT
Root starts to form and ends when the tooth reaches the occlusal plane
PDL fibres start to develop
Remodeling of PDL fibres to accommodate the eruptive tooth movement
Intraosseous and Supraosseous movement
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23. The tissue in front of the erupting primary tooth is different from that of the
permanent tooth.
A strand of fibrous tissue, known as Gubernacular cord forms a pathway in
advance of developing permanent teeth.
During eruptive phase the crown breaks the double layer epithelium,
overlying it and enters the oral cavity.
This causes the tissue around it to form junctional epithelium and gingiva
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24. Gubernacular canal and cord
play a role in the guiding the
course of tooth eruption
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25. 25

26. As the tooth erupts , space is created underneath the tooth to
accommodate the root
Fibroblast around the tooth apex form collagen and
attach to the newly formed cementum
Bony trabecular fill the space underneath in the pattern of ladder which
gets denser as the tooth erupts
Once tooth reaches the functional occlusion the PDL
fibres attach to the cementum and adjacent bone.
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27. STAGES OF TOOTH ERUPTION
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28. POST ERUPTIVE TOOTH MOVEMENTS
Movements made by tooth once it has reached its functional
position in occlusal plane.
Accommodation for growth
Compensation for occlusal wear
Accommodation for interproximal wear
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29. • Mostly occurs between 14-18 years by
formation of new bone at the base of
socket to keep pace with increasing
height of jaws.
Accommodation
for growth
• Compensation primarily occurs by
continuous deposition of cementum
around the apex of the tooth. This
deposition occurs only after the tooth
moves.
Compensation
for occlusal wear
• Compensated by mesial or approximal
drift
Accommodation
for interproximal
wear
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30. CELLULAR BASIS OF ERUPTION
Prior to onset of eruption
Influx of mononuclear cells into coronal portion of dental follicle
Increase in the number of osteoclast in the coronal third of
alveolar crypts
Resorb bone in the eruptive pathway
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31. • Morphologically, dental follicle is interposed between the
alveolar bone and the tooth.
• An ideal location to regulate cellular events of eruption.
• As the dental follicle delivers resorptive cells to the alveolar
bone, it is also in a position to receive signals from the tooth.
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Wise et al, 1998

32. MOLECULAR BASIS OF ERUPTION
Tooth eruption appears to be a programmed event in which a given
tooth erupts at its appointed time.
• The molecules that initiate eruption
• their localization
• their regulation of the cellular events of eruption
All must fit within the context that each tooth erupts independently.
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33. • The eruption molecules and their genes are localized primarly
in the dental follicles or stellate reticulum.
• Dental follicles produce majority of the potential eruption
molecules.
• The remaining molecules reside in the stellate reticulum and
adjacent dental follicle.
 Interlukein -1 reside in the dental follicle
D-95 reside in the stellate reticulum
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34. Molecules required for eruption began with isolation of:
• EGF(Cohen1962)
• TGFα(Tam 1985)
• Colony stimulating factor 1
TGFα and EGF share the same receptor for their action and
have the same result on eruption.
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35. In mice devoid of TGFα gene the teeth still erupted on time
suggesting that EGF alone can initiate incisor
eruption.(Mann et al;1999)
Unerupted teeth is seen in osteoporitic mice lacking CSF-1
CSF-1 TRAP- positive
monuclear cells osteoclast
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36. Comparing EGF and CSF-1 it was found that EGF accelerated
incisor eruption but not the molar eruption and CSF-1 caused the
opposite.
(Cielinski et al,1995)
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• c-fos
• NFkB1 & NFkB2
• ODF
• Interluekin-1a
Other molecules that help
in eruption
Kong et al,1999

37. Tooth eruption fails in the absence of parathyroid hormone
related protein(PTHrP)
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Failure of osteoclastic bone resorption on the coronal tooth
surface to form an eruption pathway
Nakchibandhi et al,2000

38. PRODUCTION OF OSTEOCLAST IN TOOTH
ERUPTION
• Signaling cascade initiate the influx of mononuclear cells into
dental follicle.
CSF-1 AND MCP-1
Prime candidates for recruiting
osteoclastic precursor cells
Act as chemokines
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39. 40

40. Current concept of osteoclast formation shows two major
molecules:
• RANKL
• OPG
RANKL IS EXPRESSED IN THE DENTAL FOLLICLE BUT ITS
EXPRESSION IS REDUCED BY CSF-1 OR PTHrP SYNTHESIZED IN
THE DENTAL FOLLICLE OR STELLATE RETICULUM
Wise et al, 1999
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41. 42

42. OPG is expressed in the dental follicle but the expression is
reduced by CSF-1 or PTHrP synthesized in the dental follicle.
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Presence of osteoblast is required for activation of osteoclast via
the RANKL/OPG pathway.

43. ANOMALIES OF TOOTH ERUPTION
• MISSING TEETH
• DISTRUBANCE OF ERUPTION
• ECTOPIC ERUPTION
• LOCAL ERUPTION DEVIATION
• DENTAL PAPPILAE DESTROYED AS A RESULT OF
INFECTION
PREMATURE
ERUPTION
DELAYED
ERUPTION
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44. MISSING TEETH
Hypodontia
Oligodontia
Anodontia
missing teeth as a result of their failure of
development
multiple (usually more than six) teeth are missing
total lack of teeth of one on both dentitions
In the primary dentition, missing teeth occur more commonly in the maxilla
and typically the maxillary lateral incisor is the tooth involved.
Missing permanent teeth are seen in 30–50% of patients who have missing
primary teeth
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45. ETIOLOGY
• Low birth weight
• Increased maternal age
• Rubella
• Thalidomide embryopathies
Multiple missing teeth, as well as teeth with small crowns, may be
seen in:
• Ectodermal dysplasia
• Ellis–van creveld syndrome
• Down syndrome (trisomy 21)
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46. PREMATURE AND DELAYED ERUPTION
HERIDITARY FACTORS
POOR NUTRITION
HYPOTHYROIDISM
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HYPERTHYROIDISM

47. • inadequate breastfeeding
• low supplementation from infant formula.
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48. • Maxillary canines
• Etiology –
– genetic factors
– Small jaws
– Early tooth extraction
– Retained primary tooth
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ECTOPIC ERUPTION
Peck et al, 1994

49. • Pathologies of jaw
• Supernumerary teeth
• Hyper IgE syndrome
• Primary or secondary retention of permanent molars
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LOCAL ERUPTON DEVIATION

50. Cementum fused to alveolar bone - ANKYLOSIS
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ANKYLOSED TOOTH- WHY IT DOES NOT ERUPT ???
Ankylosed teeth different from
impacted teeth
Eruption potential is
destroyed
Bone grows by surface deposition
Biderman et al,AJO 1962

51. CONCLUSION
Human tooth eruption is a unique developmental
process in the organism. The scientific literature in the
field is extremely sparse and studies are still being
conducted.
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52. REFERENCES
• Peck, Sheldon, Leena Peck, and Matti Kataja. "The palatally displaced
canine as a dental anomaly of genetic origin." The Angle orthodontist 64.4
(1994): 250-256.
• Kjær, Inger. "Mechanism of human tooth eruption: review article including
a new theory for future studies on the eruption process." Scientifica 2014
(2014).
• Biederman, William. "Etiology and treatment of tooth ankylosis." American
Journal of Orthodontics 48.9 (1962): 670-684.
• Marks, Sandy C., and Hubert E. Schroeder. "Tooth eruption: theories and
facts." The Anatomical Record 245.2 (1996): 374-393.
• Orban, Balint Joseph, and Harry Sicher, eds. Oral histology and
embryology. Mosby, 1962.
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53. • Wise, G. E., B. G. Que, and H. Huang. "Synthesis and secretion of
MCP-1 by dental follicle cells-implications for tooth eruption." Journal of
dental research 78.11 (1999): 1677-1681.
• Kong, Young-Yun, et al. "OPGL is a key regulator of osteoclastogenesis,
lymphocyte development and lymph-node
organogenesis." Nature 397.6717 (1999): 315-323.
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