This document discusses tooth eruption, including: 1. Tooth eruption involves the axial movement of teeth from their developmental position in the jaw bone to their functional position in occlusion. 2. There are three phases of eruption - pre-eruptive, eruptive, and post-eruptive phases. The eruptive phase involves both intraosseous and extraosseous stages as the tooth moves from within the bone to reaching the occlusal plane. 3. Several theories have been proposed to explain the mechanism of tooth eruption, including root formation theory, bone remodeling theory, periodontal ligament traction theory, and dental follicle theory. However, it is now believed

1. Tooth Eruption
Dr. Mona Denewar

3. Objectives:
At the end of this chapter the student should be
able to understand the following:
• Phases of tooth eruption.
• Theories of tooth eruption.

4. Contents
• Definition
• Pattern of tooth movements
• Phases of eruption
• Theories of eruption
• Clinical considerations

5. Definition:
It is the axial or occlusal
movement of teeth from its
developmental position within
the jaw bone to its functional
position in occlusion.
To break
out

6. Pattern of
Tooth
Movement
Axial
movement
Bodily
Movement
(drifting)
Tilting
(tipping)
Rotatory
movement
Occlusal
movement in
the direction
of the long
axis of the
tooth
Movement as one unite to
one direction
mesial,distal
buccal or lingual
Movement
around a
transverse
axis
Movement
around a
longitudinal
axis
Eccentric
growth
One end (crown) of the
developing tooth move
toward eruption
whereas, other end
(growing root) remain
stable. Shift of
the center

7. Phases of eruption:
Pre eruptive phase
Eruptive phase
Post eruptive phase

8. Phases of Eruption
Pre-eruptive
phase
Eruptive
phase
Post-eruptive
phase

10. Pre eruptive phase:
This phase begins in the early bell stage and ends at the
beginning of root formation.
Made by the deciduous and permanent tooth germs within tissues
of the jaw before they begin to erupt.

11. First
Then
Pattern of movement of deciduous teeth:
• teeth germs are small
• have good space in the jaw bones
• grow rapidly
• become crowded.

12. This crowding is relieved by
Anterior forward
E
E
backward
All
teeth
Outward
(vestibular)
Upward
(Downword)
Jaw growth:
• In length
• In width
• In height

13. Types of movements:
• Bone resorption on the crypt
wall toward which the tooth
moves.
• Bone depositon on the crypt
wall behind it.
• Bone resorption only occurs on
the crypt wall facing the
growing tooth germ.
• Shift of the center.
Bodily movement (Drifting) Eccentric growth

14. Pattern of movement of permanent teeth:
A: Permanent incisors and
canine, first develop lingual to the
deciduous tooth germs in the
same crypt.
B: As the deciduous germs
erupt, they move to be apical in
position and occupy their own
bony crypts.

15.  Permanent premolars develop lingual to their
predecessors at the level of their occlusal surfaces and in
the same bony crypt
 Then shift to be situated in their own crypts beneath the
divergent roots of the deciduous molars.

16. Radiograph of the mixed dentition of a 7-year-old child

17. Deciduous 1st molar and
permanent 1st premolar
of the mandible from birth to
14 years

18. • Permanent molars have no
predecessors; develop from
backward extension of dental
lamina.
• Maxillary molars develop in the
maxillary tuberosity with their
occlusal surfaces facing distally.
• Mandibular molars develop in
the base of the mandibular
ramus with their occlusal
surfaces facing mesially.

19. Permanent Molars
Maxillary molars
in the tuberosity
facing distally
Swing around with
growth of the maxilla
Mandibular molars
in the base of the ramus
facing mesially
tilt to be upwright
with growth of the mandible

20. Histologic changes:
1. Growth of tooth germs.
2. Formation of bony crypt (bone remodeling).
3. Movement of the developing tooth within the
growing jaw.

22. • It begins by root formation and ends when the tooth
reaches the occlusal plan.
• Made by a tooth to move from its position within the
bone of the jaw to its functional position in
occlusion.
Eruptive phase:
• This stage is subdivided into:
1- Intraosseous stage.
2-Extraosseous stage.

23. Active eruption: Passive eruption:

24. The above description in eruptive phase is applied to all teeth
however the succestional teeth possess an additional anatomic
features which are:
1- The Gubernacular canal.
2-The Gubernacular cord.
.

25. At first both deciduous and
permanent buds occupy the
same crypt
But when the deciduous tooth
erupt …. The permanent will
be completely enclosed by
bone except for a small canal .

26. The fibrocellular follicle
surrounding the successional
tooth retains its connection
with the lamina propria of the
oral mucosa by means of
stands of fibrous tissue
containing remnants of the
dental lamina called
Gubernacular cord.

27. This canal it is widened by
osteoclast to guide
permanent teeth to erupt.

28.  For the anterior teeth the
canal open in the lingual bony
surface of the jaw.
 For premolars, the canals open
within the sockets of
corresponding deciduous
molars.

29. They have an influence
in determining
Eruptive path

30. Gubernacular cord: The connective tissue overlying a
successional tooth that connects with the lamina propria of
the oral mucosa by means of a strand of fibrous connective
tissue that contains remnants of dental lamina
Gubernacular canal: Holes noted in a dry skull noted lingual
to primary teeth in jaws that represent openings of
gubernacular cord
As the successional teeth erupt, gubernacular canal widens
enabling tooth to erupt.

31. Eruptive path:

32. Once the tooth has broken through the
oral mucosa, further emergency of the
tooth results from active eruption
movements and passive separation of the
oral epithelium from the crown surface.
So,
Until, it reaches the occlusal plane and meets
its antagonist.

33. • The principal direction of
movement is occlusal or axial
(for deciduous and permanent
teeth).
• However, movement in other
planes also occur such as
bodily, tilting, and rotating
movement.
Types of movements:

34. 1. Root formation.
2. Formation of the PDL.
3. Epithelial plug formation.
4. Formation of the dento-gingival junction.
Histologic changes:

35. Root Formation:
Apical proliferation of epith. root
sheath of Hertwig
Bone resorption of the crypt floor
Onset of eruptive movement
During root formation
Bone deposition on the crypt walls
Cementum formation at root
surface.
Organization of periodontal
ligament fibers.

36. Development of principal fibers
of the PDL and Dentogingival
junction:

37.  Tooth is covered by; REE, CT, bony
crypt and oral epith.
 Pressure exerted by the developing
tooth induces bone resorption.
 REE produces desmolytic enzymes to
degrade CT.
 REE+ oral epith.= epithelial plug.
 Central cells of this plug degenerate
forming an epithelial lined canal
through which the tooth will erupt
without hemorrhage.
 REE shares in the formation of dento-
gingival junction.
Epithelial plug formation.

38. Post eruptive phase
• It begins after the tooth has reached its
functional position in the occlusal plane,
continues through the whole life of the tooth.
• Its movements divided into three categories:
Accommodation for
growth
Compensation for
occlusal wear
Accommodation for
interproximal wear

39. Accommodation for
growth
• Deposition of bone at the
alveolar crest and at the base of
the socket
Compensation for
occlusal wear
•Axial movement of the tooth
•Cementum deposition around the
apex.
Compensation for
interproximal wear
•By Mesial drift

40. Several factors control mesial drift:
(a) Contraction of the transseptal fibers.
(b) Adaptability of bone tissue.
(c) Anterior compartment of occlusal force.
(d) Pressure from soft tissues.
Remember,

41. Histologic changes:
• More cementum and alveolar bone apposition.
• Alveolar bone remodeling due to an occluso-mesial drift.
• Organization of PDL fibers.
Types of movements:
• Axial movement
• Mesial movement

43. Mechanisms of
tooth
movements
(Theories)

44. Root formation
theory
Proliferating root
impinges on a fixed base
Apically directed force
Occlusal movement

45. Root Formation:
But
• Some teeth move a distance greater than
the length of their roots.
• Rootless teeth erupt.
• When the tissues forming the root are
surgically removed the tooth erupt.
• Force exerted on bone lead to resorption.

46. Bone Remodeling
theory
Selective bone resorption and deposition
causes tooth eruption.
In human, the base of the 1st & 3rd molars
showing a continuous bony resorption in the
fundus floor. While, 2nd molar, 1st and 2nd
premolars showed bony deposition in the
fundus floor.

47. Osteoclasts resorb jaw bone to
make way for erupting tooth

48. But ,
• The selective bone remodeling which
occur around the root are the result
not the causeof tooth movement.

49. Periodontal ligament
traction theory
Tooth movement is brought about by:
Fibroblast contractile properties
Connection with collagen fibers
extra-cellular “fibronexus”
Oblique alignment of PDL collagen
fibers

50. Vascular pressure
theory
Local increase in blood pressure at
apical area lead to occlusal
movement of the tooth.
Increased bl. press. rates increase
eruption rate & increased number
of bl. cap at the apical region in
comparison with alveolar crest
region.

51. Dental follicle
theory
The REE initiates the production of:
• Osteoclasts from the dental follicle to facilitate
bone resorption.
• Protease that assist in the breakdown of the

52. Pattern cellular activity involving the REE and the DF
associated with tooth eruption, which facilitates CT
degradation and bone resorption as the tooth erupts.
Molecular determination of tooth eruption

54. The bone resorption initiated to open an eruption pathway by REE which release
Epidermal growth factor (EGF), Transforming growth factor beta (TGF β) and interleukin-1α.(IL1
α).
These signaling molecules induce the release of colony stimulating factor 1 (CSF1) from the
follicular cells which in turn promotes the differentiation and fusion of monocytes into
osteoclasts.
The role of the REE also includes the production of the enzymes proteases that break
down the connective tissue of the lamina propria providing a path of least resistance for tooth
eruption and allowing fusion of the REE and the oral epithelium to form a double epithelial
layer over the tip of the crown which subsequently rupture to permit tooth eruption.

56. • Recent studies have shown the
dental follicle to be of prime
importance in tooth eruption.
• Removal of the dental follicle
prevents the eruption.

57. • Although no one theory is yet supported by sufficient experimental
evidence, it is probably multifactorial in that more than one agent or
factor share in the eruptive movement.
• The dental follicle, the enamel organ (REE), the surrounding PDL and the
alveolar bone share in the eruption process.
• The tooth movement results from a balance between tissue destruction
(coronal bone, C.T. and surface epithelium) and tissue formation (root,
PDL and bone).
• The study of molecular biology showed that many growth factors and
other cellular molecules are responsible for the eruption process.

58. ClinicalConsiderations
Early
eruption
Delayed
eruption

59. Systemic cause: Due to hormonal
disturbances
Local causes:
1-Premature loss of deciduous teeth…space
loss
2-missed successor
3-Ankylosed deciduas teeth.
4-Gingival fibromatosis
Delayed eruption

61. Thank
you