Tooth eruption is when a developing tooth moves from its initial nonfunctional position within the alveolar bone to its final functional location within the oral cavity

CONTENTS
 INTRODUCTION
 ERUPTION
 PATTERN OF TOOTH MOVEMENT
Preeruptive tooth movement
Eruptive tooth movement
Posteruptive tooth movement
 HISTOLOGY OF TOOTH MOVEMENT
Preeruptive phase
Eruptive phase
Posteruptive phase

 MECHANISM OF TOOTH MOVEMENT
Bone remodeling
Root formation
Vascular pressure
Periodontal ligament traction
 Cellular and molecular events in eruption
 Chronology and sequence of tooth eruption
 CLINICAL CONSIDERATIONS
 CONCLUSION
 REFERENCES

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.

ERUPTION
• The word “eruption” refers to cutting of teeth
through gums (from the Latin erumpere,
meaning “to break out”).
• Its developmental position within the jaw to its
functional position in the occlusal plane.
• Teeth undergo complex movements related to
maintaining their position in the growing jaws
and compensating for masticatory wear.
[1]

 Physiological tooth movements consists of the
following:
Pre eruptive tooth movement
Eruptive tooth movement
Post eruptive tooth movement

Phases of tooth eruption
 Preeruptive phase: made by the deciduous and permanent
tooth germs within tissues of the jaw before they begin to
erupt.
 Eruptive phase: Starts with initiation of root formation
and made by teeth to move from its position within bone of
the jaw to its functional position in occlusion. Has an
intraosseous and extraosseous compartments.
 Posteruptive phase: Takes place after the teeth are
functioning to maintain the position of the erupted tooth in
occlusion while the jaws are continuing to grow and
compensate for occlusal and proximal tooth wear.
[2]

PREERUPTIVE TOOTH MOVEMENT
 When deciduous tooth germs first differentiate
they are very small and have good space in
between them.
 This space is soon used because of rapid growth
of the tooth germs, and crowding results,
especially in incisors and canine region.
 This crowding is then relieved by growth of the
jaws in length, which permits the drifting of tooth
germs.
[1]

 Bony remodeling of crypts wall occurs to facilitate
movements of growing tooth germs.
 Permanent teeth with deciduous predecessor also
move before they reach the position form which they
erupt.

 The change in the position of the tooth
germ is the result of number of factors:-
Body movement of tooth
germ
Growth of tooth germ
Relative change in position of
associated deciduous and
permanent tooth germ

 The permanent molars, which develop in the
tuberosity of the maxilla, at first have their occlusal
surfaces facing distally and swing around only when
the maxilla has grown sufficiently to provide
necessary space.
Pre eruptive tooth movement should be
considered as movement positioning the tooth
& its crypt within the growing jaws
preparatory to tooth eruption.

Tooth eruption is when a developing tooth moves from its initial nonfunctional position within the alveolar bone to its final functional location within the oral cavity

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
[1]

Permanent anterior
tooth germs develop
lingual to the primary
anterior teeth and
later as primary teeth
erupt, the permanent
crowns lie at the
apical 3rd
of primary
roots.
Premolars tooth
germs are finally
positioned between
the divergent roots of
deciduous molars.
[2]

POST ERUPTIVE TOOTH
MOVEMENT
 Post eruptive tooth movement are those
that :-
Maintains the position of the erupted
tooth while the jaw continues to grow.
Compensate for occlusal & proximal
wear.
[1]

 The former movement, like eruptive movement
occurs principally in an axial direction to keep pace
with the increase in height of the jaws. It involves
both tooth & its socket & ceases when jaw growth is
completed.
 The movement compensating for occlusal &
proximal wear continue throughout life & consist of
axial & mesial migration, respectively.

HISTOLOGY OF TOOTH
MOVEMENT
 PERERUPTIVE PHASE: Preeruptive
tooth movement, involves drifting or growth of
tooth germs, demands remodeling of the bony
wall of the crypts. This is achieved by the
selective deposition and removal of bone by
osteoblastic and osteoclastic activity.
[1]

 ERUPTIVE PHASE: During the eruptive
phase of physiologic tooth movement,
significant developmental events occurs that are
associated with eruptive tooth movement. They
include:
The formation of root.
The periodontal ligament.
The dentogingival junction.

 “ROOT FORMATION”
It is initiated by growth of HERTWIG’s
epithelial root sheath, which initiates the
differentiation of odontoblasts from the dental
papilla.
The odontoblasts then form root dentine,
bringing about an overall increase in length of
the tooth that is largely accommodated by
eruptive tooth movement, which begins at
approximately the same time as root formation
is initiated.

 After the onset of root formation cementum,
periodontal ligament, and the bone lining crypt
wall are formed.
 Fibroblasts of the periodontal ligament possess as
part of their cytoskeleton intermediate filaments
that consist of contractile proteins.
The ligament fibroblast has the ability of ingest
and degrade extracellular collagen while forming
new collagen fibrils.

 Bone removal is necessary for permanent teeth to
erupt. In case of those teeth with deciduous
predecessors there is an additional anatomic
feature, the GUBERNACULAR CANAL and its
contents, the gubernacular cord, which may have
influence on eruptive tooth movement.
When the successional tooth germ
first develop within the same crypt as its
deciduous predecessor, bone surrounds both
tooth germs but does not completely close over
them.

• As the deciduous tooth
erupts, the permanent
tooth germ become
situated apically and is
entirely enclosed by the
bone except for a small
canal that is filled with
connective tissue and
often contains epithelial
remnants of the dental
lamina. This connective
tissue mass is termed the
“gubernacular cord”

 Gubernacular
canal: Holes noted
in a dry skull noted
lingual to primary
teeth in jaws that
represent openings
of gubernacular cord
.

 After removal of any overlying bone there is
loss of the intervening soft tissue between the
reduced enamel epithelium covering the crown
of the tooth and the overlying oral epithelium.

 Once the tooth has broken through the oral
mucosa, it continuous to erupt at the same rate
until its reaches the occlusal plane and meet its
antagonist. Rapid eruptive movement then
ceases.

The rate of tooth eruption depends on the
type of movement
• 1 to 10
µm/day
INTRAOOSEOU
S PHASE
• 75 μm/day
EXTRAOSSEOUS
PHASE
[3]

POST ERUPTIVE TOOTH
MOVEMENT
 In posteruptive phase the tooth makes
movements primarily to accommodate the
growth of jaws.
The principal movement is in an axial direction.
It occurs most actively between the ages of 14
and 18 and is associated with condylar growth,
which separates the jaw and teeth.
[1]

 Movements are also made to compensate for
occlusal and proximal wear of the tooth.
 Wear also takes place at the contact points
between teeth, and to maintain tooth contact
mesial or proximal drift takes place.
Histologically, this drift is seen as a selective
deposition and resorption of bone on the socket
wall by osteoblasts and osteoclasts respectively.

Essentials of Oral Histology and Embryology. James Avery, 2nd
edition
STAGES OF TOOTH ERUPTION [2]

MECHANISM OF TOOTH
MOVEMENT
 The mechanism that brings about tooth
movement is still debatable and is likely to be
combination of number of factors.
 Various factors were proposed, but only four
merits are considered. They are:-
[1]

BONE REMODELING
ROOT FORMATION
VASCULAR PRESSURE
PERIODONTAL
LIGAMENT TRACTION

BONE REMODELING
• The growth pattern of the maxilla and the
mandible moves teeth by selective deposition and
resorption of bone.
• 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.
This establish the absolute requirement for
dental follicle to achieve bony remodeling and
tooth eruption, for it is the follicle that provide the
source for new bone-forming cells and conduit for
osteoclasts derived from monocytes through its
vascular supply.

ROOT FORMATION
 Root formation follows crown formation and
involves cellular proliferation and formation of
new tissue that must be accommodated by either
movement of crown of the tooth or resorption of
bone at the base of its socket.
 If root formation results in an eruptive force, the
apical growth needs to be translated into
occlusal movement and requires a fixed base.

The bone at the base of the socket cannot act as a
fixed base because pressure on the bone results
into resorption.
“THE ROOT GROWTH THEORY” of tooth
eruption postulate the existence of a ligament, the
cushion-hammock ligament, straddling the base of
the of the socket from one bony wall to the other
like a sling.
Its function is to provide a fixed base for the
growing root.

VASCULAR PRESSURE
 It is known that teeth move in synchrony with
the arterial pulse, so local volume changes can
produce limited tooth movement.
 Experimentally, increase of hydrostatic pressure
induced by hypotensive drugs, increases the rate
of eruption while stimulation of sympathetic
nerves, which cause vasoconstriction and
decrease of the rate of eruption.

 It has been observed that the number of
fenestrated capillaries, increase with the eruption
and their distribution varies; more numbers of
fenestrated capillaries are seen near the base of
the crypt than at alveolar crest.

 Injection of 2% lignocaine with adrenaline
1:100,000 above the root of erupting
premolars(prefunctional phase), causes a burst in
the increase of eruption of teeth receiving the
injection with or without vasoconstrictor.
However, the teeth receiving
vasoconstrictor showed decrease in eruption rate,
suggesting that vascular changes affect
perfunctional eruption.

PERIODONTAL LIGAMNENT
TRACTION
 Available evidences strongly indicate that the
force for eruptive tooth movement lies in PDL.
 The PDL and dental follicle from where it forms
are implicated in the process of tooth eruption
linked to contractility of fibroblasts.
 PDL fibroblasts are able to provide a force
sufficient to move the tooth and certainly the
proper structural elements exist to translate such
force into eruptive tooth movement.

CELLULAR AND MOLECULAR
EVENTS IN ERUPTION [3]

CELLULAR EVENTS
Bone formation at the basal end
Bone resorption at coronal half of the dental
follicle
Osteoclast/osteoblast
The recruitment of the mononuclear cells at
dental follicle
Prior to onset of eruption
Differtiation
Activation

 Thus dental follicle serves not only as target
tissue for mononuclear cells but also regulate
cellular events of eruption.

MOLECULAR EVENTS
 Eruption is a localized genetically programmed
event. The dental follicle contains genes that encode
expression of various transcription factors and
involve series of signaling interaction between the
dental follicle cells and cells of bony crypts.
 Eruption molecules
The molecules that initiate eruption, their
localization and the regulation of the cellular
events of eruption all must fit within the context that
each tooth erupts independently.

Determination of the molecules that may be required
for eruption began with the isolation of –
 EGF (epidermal growth factor )
 TGF α (transforming growth factor )
 Colony stimulating factor 1

 TGF α , EGF ↑ in incisor eruption
 Colony stimulating ↑ in molar eruption
factor 1
According to Nakchbandi IA et al (June 2000)
Experiments in vivo have established that tooth eruption fails
in the absence of parathyroid hormone (PTH)-related protein
(PTHrP) action in the microenvironment of the tooth because
of the failure of osteoclastic bone resorption on the coronal
tooth surface to form an eruption pathway.

Localization of eruption molecules:
 Studies have demonstrated that the eruption genes
and their products are localized primarily in either
the dental follicle or stellate reticulum.
 The tissue required for eruption , the dental
follicle produces the majority of the potential
eruption molecules.
 The remainder of the molecules reside in the
stellate reticulum adjacent to the dental follicle.
E.g IL – 1 – resides in dental follicle
DF -95 resides in stellate reticulum

Sequence and chronology of tooth eruption [2]

Chronology and sequence Human Permanent Dentition
[2]

CLINICAL CONSIDRATIONS
[4] [5]

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

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”

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.

Submerged primary teeth
Submerged teeth are deciduous teeth, most
commonly mandibular second molars , that have
undergone a variable degree of root resorption and
then have ankylosed to the bone.
This process prevents their exfoliation and
subsequent replacement by permanent teeth.
After the permanent teeth is erupted, the ankylosed
appears to be submerged below the level of
occlusion.

Impaction
• Teeth that cease to erupt before emergence are
impacted.
• Causes of impaction are subdivided into:-
- impaction of unerupted tooth due to
obstructions by physical barriers.
- impaction due to lack of eruptive force.

Conclusion
 For the clinicians to treat dental problems
knowledge of proper eruption time is very
important .
 A variety of developmental defects that are
evident after eruption of the primary and
permanent teeth can be related to local and
systemic factors.

References
1.Orban‘s Textbook of Oral histology and
embryology 12th
edition; pg no. 372 - 386.
2.Avery James Textbook of oral development and
histology 3rd
edition pg no.92-105.
3.Nancin Antonio Ten Cate's Oral Histology
Development, Structure, and Function 2012
8th
edition pg no. 268-289.
4.Shafer;Hine;Levy Shafer’s text book of oral
pathology 6th
edition : pg no. 58-62.
5.Ghom Anil Textbook of Oral Medicine 2nd
edition
pg no. 74-76.

Tooth eruption is when a developing tooth moves from its initial nonfunctional position within the alveolar bone to its final functional location within the oral cavity

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Tooth eruption is when a developing tooth moves from its initial nonfunctional position within the alveolar bone to its final functional location within the oral cavity