Tooth eruption is a complex process involving the movement of teeth from their development position in the jawbone to their functional position in the mouth. The key structures involved are the root follicle, periodontal membrane, and crown follicle. Multiple theories have been proposed to explain the mechanism of eruption, including root formation theory, vascular pressure theory, and dental follicle theory. Clinically, natal and neonatal teeth as well as eruption cysts can occur during the eruption process.

1. TOOTH ERUPTION
PRESENTED BY,
DR. MANJULA MARANDI

2. CONTENTS
 INTRODUCTION
 ERUPTION
 STAGES OF TOOTH ERUPTION
 MOVEMENT OF TOOTH ERUPTION
 HISTOLOGY OF TOOTH MOVEMENT
 THEORIES OF TOOTH ERUPTION
 SEQUENCE AND CHRONOLOGY OF TOOTH
ERUPTION
 CLINICAL CONSIDERATION
 CONCLUSION

3. • Tooth eruption is an essential process for the
survival of many species.
• The term ‘eruption’ (derived from the Latin
word erumpere =break out) refers to the axial
or occlusal movement of the tooth from its
developmental position in the alveolar bone to
the occlusal plane in the oral cavity.
• In common usage, it signifies the cutting of the
tooth through gum.

4. Correlation between Eruption, Dental
Maturity, Skeletal Maturity, and Age
• Eruption times are coordinated with the osseous maturity
which means third molar impaction in the mandible is a
consequence of late third molar maturation and early
skeletal maturation.
• A strong correlation present between eruption time and
dental maturity.
• The teeth normally erupt when they have reached 2/3 root
length.
• Under pathological conditions, like Hyper IgE syndrome,
the teeth even though they have reached full root length do
not erupt at all.

5. Correlation between Eruption of
Different Teeth
• A significant bilateral congruence between the
eruption of the individual teeth.
• As an example the eruption times of the four
permanent first molars are very closely
correlated, while the eruption times of the first
molars are not correlated with those of non-
molars.

6. Length of Eruption Process
• The period from moving of the tooth bud with the
early root formation, until the appearance of the
teeth in the mouth is called the eruption time.
• There is great difference between the eruption
times of different teeth and the time it takes for
tooth to erupt is therefore different.
• eruption times are gender specific. Girls’ teeth
erupt sooner than boys’

7. Variations in Eruption Intensity
• a continuous eruption takes place after the teeth
have reached occlusion.
• the two developmental processes, eruption and
growth of the alveolar process, are mutually
correlated.
• It has thus also been demonstrated that the growth
of the alveolar process is weak in the prepubertal
period when height growth is also weak, while
growth of the alveolar process increases
significantly during puberty.

8. STAGES OF TOOTH ERUPTION
• The tooth eruption is a complex and tightly
regulated process which is divided into five
stages:
• pre-eruptive stage,
• intraosseous stage,
• mucosal penetration,
• pre-occlusal and
• post-occlusal stage.

9. Tooth eruption

10. MOVEMENTS OF TOOTH
ERUPTION
• Pre-eruptive tooth movement
• Eruptive tooth movement
• Post-eruptive tooth movement

11. PRE-ERUPTIVE TOOTH
MOVEMENT
• Development of tooth and jaws occur simultaneously.
• As the jaw grows the developing teeth are carried along
in their direction of growth.
• Thus the deciduous molar tooth germ moves or is
carried in a backward direction, the anterior tooth germ
in a forward direction.
• The change in the position of the tooth germ is the
result of number of factors:
1. Body movement of the tooth germ
2. Growth of tooth germ
3. Relative change in position of associated & permanent
tooth

12. ERUPTIVE TOOTH MOVEMENT
• During the phase of eruptive tooth movement the tooth
moves from its position within the bone of the jaws to
its functional position in occlusion & the principal
direction of movement is occlusal or axial.
• However, jaw growth is still occurring while most
teeth are erupting so that movement in planes other
than axial movement is superimposed on eruptive
movement.
• They are the movement made by the tooth after it has
reached its functional position in the occlusal plane.

13. POST-ERUPTIVE TOOTH
MOVEMENT
They are the movements made by the tooth after
it has reached its functional position in the
occlusal plane.
Post eruptive tooth movements are those which:
•Maintain the position of the erupted tooth while
the jaw continues to grow
•Compensate for occlusal and proximal wear

14. Tooth movement

15. The Mechanism behind Tooth
Eruption
• The mechanism of eruption depends on the
correlation between space in the eruption course,
created by the crown follicle, eruption pressure
triggered by innervation in the apical root
membrane, and the ability of the periodontal
ligament to adapt to eruptive movements.
• could involve a combination of fibroblast activity
and vascular and/or tissue hydrostatic pressures.
• multifactorial, more that one agent makes
important contributions to the overall eruptive
force

16. The Causes of Tooth Eruption
• eruption force and root extension
• root growth and pulpal pressure.
• cell proliferation, increased vascularity, and increased bone
formation around the teeth.
• endocrine influence, vascular changes, and enzymatic
degradation.
• elongation of the root and modification of the alveolar
bone and periodontal ligament are thought to be the most
important factors.
• Root growth, existence of a temporary ligament, vascular
pressure, contractile collagen, and hormonal signals
genetic targets all have been used to explain eruption.
• The dental follicle surrounding the tooth crown has also
been described as a factor decisive for the eruption process

17. HISTOLOGY OF TOOTH
MOVEMENT
PRE ERUPTIVE PHASE
This phase involve drifting or growth of tooth
germs, demands remodeling of Bony wall of
crypts.
This is achieved by the selective deposition &
removal of bone by osteoblastic and osteoclastic
activity.
Normal skeletal morphogenesis might be
involved in determining the tooth position

18. ERUPTIVE PHASE
During the eruptive phase of physiologic tooth
movement, significant developmental events occurs
that are associated with eruptive tooth movement.
They include:
Root formation
Periodontal ligament
The dentinogingival function

19. Root formation
• It is initiated by the Hertwig’s epithelial root sheath
• initiates the differentiation of odontoblast from dental papilla.
• Odontoblasts form root dentin,
• causing the overall increase in length of the tooth
• bone lining the crypt wall -formed.
•Fibroblast of the PDL consist of contractile protein, which
has the ability to ingest & degrade the extracellular collagen.

21. POST ERUPTIVE PHASE
• In post eruptive phase, the teeth has to
maintain its functional position as the jaws
grow and also to compensate for occlusal and
proximal wearing of teeth.
• The movement of the teeth is in mesio-
occlusal direction. Therefore this movement is
also called physiological mesial drift.

22. THEORIES OF TOOTH
ERUPTION
• Numerous theories of tooth eruption have
been proposed.
They are:
• Bone remodelling theory
• Vascular pressure theory
• Cushioned hammock theory
• Root formation theory
• Periodontal ligament theory
• Dental follicle theory

23. BONE REMODELING THEORY
• The bone growth theory states selective
bony formation and bone resorption which
occurs is the cause for the tooth
eruption.
• Major proof is when a tooth is removed
without disturbing its follicle tooth germ,
an eruptive pathway still forms within
bone as osteoclasts widen the
gubernacular canal.
• If dental follicle is removed, no eruption
pathway forms because it is the follicle
that provides the source for new bone

24. BONE REMODELING THEORY

25. VASCULAR PRESSURE
THEORY
• The vascular pressure theory states that the
increase vascular pressure present in the
developing root produces the force for eruption.
• supported by several studies that confirm tooth
eruption after a local injection of vasodilators.
Whereas injection of vasoconstrictors caused
decrease in the rate of eruption.
• However, this is debatable because root and local
vasculature excision, does not prevent tooth
eruption.

26. Fig- increased vascular supply result into eruption of tooth

27. CUSHIONED HAMMOCK
THEORY
• It was proposed by Harry Sicher. This theory
assumed that ligament (cushioned hammock
ligament) below a tooth is responsible for
eruption .
• However the ligament described by Sicher was an
artifact in slide preparation.

28. Diagram of the rat incisor showing cushion hammock ligament

29. ROOT FORMATION THEORY
• The root formation theory assumes that the
proliferating root encounters a fixed structure; and the
apically directed force is converted into a reactive
occlusal force that causes coronal movement of the
erupting tooth .
• However, there are facts refuted this hypothesis such
as; rootless teeth can erupt, some teeth erupt greater
distance than the total root length; and the teeth erupt
after completion of root formation or when the tissue
forming the root is removed.
• Also, the onset of root formation does not coincide
with the eruptive movement.

30. Photomicrograph showing root formation

31. PERIODONTAL LIGAMENT
TRACTION THEORY
• This theory states that fibroblasts of dental
follicle by their contraction can generate a
force which can pull the teeth into occlusion.
• The fibroblast have their processes attach to
the collagen fibres by the sticky protein called
fibro-nectin and as their processes are in
contact with each other it produces summative
force for tooth eruption.

33. DENTAL FOLLICLE THEORY
• The follicular theory postulates that the dental
follicle is capable of inducing, bone resorption above
the developing crown and bone apposition below it.
• This enables the formation of an eruptive path to
occur through which the tooth will be passively
conducted
• It is suggested that the coronal aspect of the dental
follicle regulates osteoclastogenesis (bone
resorption) and the basal aspect of the dental follicle
regulates osteogenesis (bone formation)

34. Photomicrograph of a developing dog tooth indicating the
position of the dental follicle (F) around the developing tooth,
developing mandibular alveolar bone (M) and overlying oral
epithelium (E)

35. The New Theory of Eruption
Hypothesis: A tooth that will erupt depends on
• (1)space in the eruption path- The crown follicle destroys
overlying bone tissue and thus creates the necessary space
in the eruption path.
• (2)lift or pressure from below- The root membrane
functions as a glandular membrane. The innervation in the
membrane causes, as in the glandular end-cells, an
overpressure that supplants to the root surface, periodontal
membrane, and pulp tissue. This pressure causes the tooth
to elevate in the eruption direction.
• (3)adaptability in the periodontal membrane- The
adaptability or reorganization in the periodontal membrane
is the third factor that is essential for eruption

36. Early Jaw Formation
• The cells with the different origins migrate to the
different regions, also known as fields, to the jaw
• The fields are characterized by having a separate
innervation and regionally specific ectomesoderm.
• The molecular-biological fields are different not
just in the cranium and jaws but also in the dental
arches.
• The fields have different molecular origins and
different innervations.

37. The embryological development of the jaws and teeth from the neural crest, shown
schematically in colours on a panoramic radiograph. The different fields in the
mandible are marked in blue. The white lines show three different courses of
peripheral nerves to the teeth and bone in the mandible. In the maxilla, the bilateral
frontonasal fields are marked in yellow, the bilateral maxillary fields in red, and the
bimaxillary palatinal fields in orange. The black lines show three different courses of
peripheral nerves to the teeth and bone in the maxilla.

38. • Schematic drawing of the palate. White semicircles
mark the location of the maxillary teeth according to
the coloured maxillary fields: yellow fields indicate
frontonasal fields, red fields indicate maxillary fields,
and orange fields indicate palatinal fields.

39. Early Tooth Formation
• an ectodermal epithelial bud surrounded by
regionally specific ectomesenchyme forming
the early tooth primodium
• Which develops through the cap and bell stages.
• During these stages the innervation spreads and
surrounds both the apical and the coronal parts
of the primordium.
• the reaction for nerve tissue is seen most
strongly apically.

41. Late Tooth Formation
• The crown follicle is comprised of an inner layer of
ectoderm and an external layer of cell-dense
ectomesenchyme.
• The periodontal membrane close to the root is called
the peri-root sheet and is comprised of an inner nerve
layer covered by a closely knit fibre layer of
ectomesenchyme and outermost an ectodermal cell
layer (Malassez cell layer).
• The apical root sheet or root membrane, suggested to
be called the root follicle, is comprised of a strong layer
of innervation and of a membrane-like layer of
ectomesenchyme.

42. Schematic drawing and radiograph showing the morphology of a
mandibular first molar shortly before eruption. Note the
ectodermal cell layer of the follicle surrounding the crown and
the strong innervation in the root sheet.

43. Schematic drawing of the cell layer in the root-close part of the periodontal membrane. D
is root dentin and the cement layer C is marked on the surface. A layer of peripheral
nerves (yellow dots) is seen the closest to the cement layer. Above is a dense fibre layer
of ectomesenchymal origin (green lines) and outermost towards the more loose
periodontal membrane the epithelial rests of Malassez are located (reddish-brown). This
structured layer is called the peri-root sheet. Inserted in the figure are previously
published histological sections showing the three cell layers

44. • Hypothesis. A tooth that will erupt depends on
• (1)space in the eruption path,
• (2)lift or pressure from below,
• (3)adaptability in the periodontal membrane
• The summary of the Theory: the aetiology behind the eruption
process is that an innervation-provoked pressure in the apical part
of the tooth results in an eruption that requires continuous
adaptation from the periodontal membrane and the active
movement of the crown follicle, destroying overlying bone tissue.
• Conclusively, the membrane covering the apical part of the tooth
root, the periodontal membrane, and the crown follicle are the three
structures, which are involved in the eruption process.
• These three structures are interrelated, a pressure apically changes
the periodontal membrane and at the same time triggers the crown
follicle to resorption of the surrounding tissue.

45. Tooth Eruption Sequence

46. CLINICAL COSIDERATION
• Natal and Neonatal Teeth
• Deciduous teeth that have erupted
into oral cavity are occasionally
seen in infants at birth. These
are called natal teeth
• Neonatal teeth have been defined
as those teeth erupting in first
30 days of life.

47. Teething
• Teeth break through general
the oral mucosa, there is
often some pain, slight fever,
and general malaise, all signs
of an inflammatory process.
In infants these symptoms are
called “teething”.

48. Eruption Cyst
An eruption cyst, or eruption
hematoma, is a bluish swelling
that occurs on the soft tissue
over an erupting tooth. It is
usually found in children.
The fluid in the cyst is sometimes
clear creating a pale-coloured cyst
although often they are blue.
An eruption cyst (eruption
hematoma) is a developmental
soft-tissue cyst of odontogenic origin that forms over
an erupting tooth.

49. EPSTEIN PEARLS
These are formed along the mid
palatine raphe, they are considered
remnants of epithelial tissue trapped
along the raphe as the fetus grew.
Bohn Nodules
These are formed along the buccal
and lingual aspects of the dental ridges
and on the palate away from the raphe.
The nodules considered as remnant of
mucous gland tissue and histologically
different from epstein pearls.

50. CONCLUSION
• To sum up, tooth eruption must be considered as a stage
of tooth development.
• Root follicle, periodontal membrane, and crown follicle
are involved in the eruption process.
• The orientation of PDL fibroblasts determines the tooth
directional movement.
• Root formation produces compressive coronal and
tensile apical hydrostatic stress resulting in tooth
eruption.
• Each of the eruption theories has a say to some portion
of the eruption process.

51. QUESTIONS?
• Define eruption?
• What are the different theories of tooth
eruption?
• What are the clinical considerations of tooth
eruption?
• Which is the most accepted theory of tooth
eruption and why?