Stages, Mechanism of Eruption

1. Menatalla M. Elhindawy

2. Eruption

3. Eruption
 Definition
 Phases of Eruption
 Pre- Eruptive
 Eruptive
 Post- Eruptive
 Mechanism of Eruption

4. Eruption
Definition

5. Eruption
Definition
 It is the axial or occlusal movement
of teeth
 From its developmental position
within the jaw bone to its functional
position in occlusion.

6. Eruption
 Definition
 Phases of Eruption
 Pre- Eruptive
 Eruptive
 Post- Eruptive
 Mechanism of Eruption

7. Phases
Pre-
Eruptive
Eruptive
Post-
Eruptive
Eruption
Phases of Eruption

8. I. Pre- Eruptive phase
Eruption
Phases of Eruption
Early bell stage Beginning of root formation
Tooth bony crypt

9. I. Pre- Eruptive phase “ pattern”
A. Deciduous teeth
Eruption
Phases of Eruption
Teeth germs are small & have good space
in the jaw bones
Grow rapidly & become
crowded.

10. I. Pre- Eruptive phase “ pattern”
A. Deciduous teeth
Eruption
Phases of Eruption
Bone
 In length
 In width
 In height
Teeth
 Anterior……. Forward “mesial”
 Posterior ….. Backward “ distal”
 Both….. Vestibular “ outward” &
occlusal “ upward or backward”

11. Eruption
Phases of Eruption
I. Pre- Eruptive phase “ pattern”
B. Permanent teeth
Anterior teeth

12. Eruption
Phases of Eruption
I. Pre- Eruptive phase “ pattern”
B. Permanent teeth
Premolars teeth

13. Eruption
Phases of Eruption
I. Pre- Eruptive phase “ pattern”
B. Permanent teeth
Molar teeth

14. Eruption
Phases of Eruption
I. Pre- Eruptive phase “ histology”
a) Growth of tooth germs.
b) Bone remodeling.

15. Eruption
 Definition
 Phases of Eruption
 Pre- Eruptive
 Eruptive
 Post- Eruptive
 Mechanism of Eruption

16. Eruption
Phases of Eruption
II. Eruptive phase
Pre- Functional phase
Root formation Occlusal plan
Developing position
Bony crypt
Functional position
Oral cavity

17. Eruption
Phases of Eruption
II. Eruptive phase “Pre- Functional phase”
A. Root formation
 Dentine & Cementum formation.
 Bone resorption of the crypt floor
 Bone deposition on the crypt walls
 Organization of PL fibers.

18. Eruption
Phases of Eruption
II. Eruptive phase “Pre- Functional phase”
B. PL fibers
 Fibroblasts
• Produce and ingest collagen
• Adhere to each other
• Adhere to the extracellular matrix “ fibronexus”
 Intermediate plexus
• Permits remodeling of the PL fibers at the middle area without
the need of fibers to re-embed themselves in cementum and
bone.
• Only present in rodents and not in humans.

19. Eruption
Phases of Eruption
II. Eruptive phase “Pre- Functional phase”
C. Alveolar ridge.
Deposition of bone trabeculae parallel to the fundus of the
socket to aid in tooth eruption

20. Eruption
Phases of Eruption
II. Eruptive phase “Pre- Functional phase”
D. Epithelial plug

21. Eruption
Phases of Eruption
II. Eruptive phase “Pre- Functional phase”
E. Gubernacular cord & Gubernacular canal
 Gubernacular cord is a strand of fibrous tissue “CT” containing
remnants of the dental lamina.
 Gubernacular canal widened by osteoclast to guide permeant teeth
to erupt.

22. Eruption
 Definition
 Phases of Eruption
 Pre- Eruptive
 Eruptive
 Post- Eruptive
 Mechanism of Eruption

23. Eruption
Phases of Eruption
III. Post- Eruptive phase
It begins after the tooth has reached its in the
occlusal plane, continues through the whole life of
the tooth
Purpose
 Accommodate growth
 Compensate occlusal or proximal wear.

24. Eruption
 Definition
 Phases of Eruption
 Pre- Eruptive
 Eruptive
 Post- Eruptive
 Mechanism of Eruption

25. Eruption
Mechanism of Eruption
Theories or mechanisms of tooth eruption
I. Bone remodeling
II. Dental follicle
III. Root formation
IV. Vascular pressure
V. PL traction

26. I. Bone remodeling
Selective bone resorption and deposition causes tooth eruption
Eruption
Mechanism of Eruption
But
1st & 3rd molars showing a continuous bone resorption in the fundus
floor.
2nd molar, 2nd premolars showed bony deposition in the fundus floor

27. II. Dental follicle
 provides the source for new bone-forming cells and the
conduit for osteoclasts derived from monocytes through
its vascular supply.
 lack of factors that stimulates differentiation of
osteoclasts, eruption is prevented because no mechanism
for bone removal exists.
 Local administration of this factor permits the
differentiation of osteoclasts, and eruption occurs.
Eruption
Mechanism of Eruption

28. II. Dental follicle
 Removal of developing premolar without disturbing the DF, or if
eruption is prevented by wiring the tooth germ down to the lower
border of the mandible, an eruptive pathway still forms within the
bone as osteoclasts widen the gubernacular canal.
 If the DF is removed, however, no eruptive pathway forms.
Furthermore, if a metal or silicone replica replaces the tooth germ,
and so long as the DF is retained, the replica will erupt, with the
formation of an eruptive pathway.
Eruption
Mechanism of Eruption

29. III. Root formation
 Force exerted on bone lead to resorption
Cushion hammock ligament
o Straddling the base of the socket from one bony wall to the
other like a sling.
o Its function was to provide a fixed base.
But
o The structure described as the cushion hammock ligament is
the pulp lineating membrane that runs across the apex of the
tooth and has no bony insertion.
o It cannot act as a fixed base.
Eruption
Mechanism of Eruption

30. III. Root formation
Some teeth move a distance greater than the length of their roots as
upper canine.
Eruption of Rootless teeth.
When the ERSH is surgically removed the tooth erupt.
Eruption
Mechanism of Eruption

31. IV. Vascular pressure “Hydrostatic pressure”
 Based on the fact that dental papilla is highly vascular
 Fenestrated capillaries, increases with the eruption rate; more numbers
of fenestrated capillaries are seen near the base of the crypt than at the
alveolar crest
 Ground substance can swell by up to 50% with the addition of water
which add more pressure
 Vasoconstrictor decreases in eruption rate
This theory is not recommended now as in the absence of blood vessels (in
periapical region) also, tooth eruption occurs
Eruption
Mechanism of Eruption

32. V. PL traction
• Fibroblasts have contractile forces.
• Fibroblasts transmit forces to the collagen bundles
through fibro-nexuses.
• These collagen bundles apart from undergoing
remodeling are also inclined at the correct angle to
bring about eruptive movement.
Eruption
Mechanism of Eruption

33. Any questions??

34. Thank you..