DEPARTMENT OF PUBLIC
MDS 1ST YEAR
PATTERN OF TOOTH MOVEMENT
Preeruptive tooth movement
Eruptive tooth movement
Posteruptive tooth movement
HISTOLOGY OF TOOTH MOVEMENT
MECHANISM OF TOOTH MOVEMENT
Periodontal ligament traction
Cellular and molecular events in eruption
Chronology and sequence of tooth eruption
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.
• 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.
Physiological tooth movements consists of the
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
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.
When deciduous tooth germs first differentiate
they are very small and have good space in
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
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
The change in the position of the tooth
germ is the result of number of factors:-
Body movement of tooth
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
Pre eruptive tooth movement should be
considered as movement positioning the tooth
& its crypt within the growing jaws
preparatory to tooth eruption.
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
The term pre functional eruptive
movement is used to describe the
movement of tooth after its appearance in
the oral cavity till it attains the functional
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
germs are finally
the divergent roots of
POST ERUPTIVE TOOTH
Post eruptive tooth movement are those
Maintains the position of the erupted
tooth while the jaw continues to grow.
Compensate for occlusal & proximal
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
The movement compensating for occlusal &
proximal wear continue throughout life & consist of
axial & mesial migration, respectively.
HISTOLOGY OF TOOTH
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.
Normal skeletal morphogenesis might be
involved in determining tooth position.
ERUPTIVE PHASE: During the eruptive
phase of physiologic tooth movement,
significant developmental events occurs that are
associated with eruptive tooth movement. They
The formation of root.
The periodontal ligament.
The dentogingival junction.
It is initiated by growth of HERTWIG’s
epithelial root sheath, which initiates the
differentiation of odontoblasts from the dental
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
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
canal: Holes noted
in a dry skull noted
lingual to primary
teeth in jaws that
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.
“Why tooth eruption occurs without
The changes occurring in the connective tissues
affect the epithelia it sustains and both the
reduced enamel epithelium and the overlying oral
epithelium begins to proliferate and migrate into
disorganized connective tissue so that eventually
a solid plug of epithelium forms in advance of the
erupting tooth. The central cells of epithelium
mass degenerate and form an epithelium-lined
canal through which tooth erupts without any
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
The rate of tooth eruption depends on the
type of movement
• 1 to 10
• 75 μm/day
POST ERUPTIVE TOOTH
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.
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 
MECHANISM OF TOOTH
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:-
• 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
If dental follicle is removed , no eruption pathway
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
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
“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
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.
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 
Bone formation at the basal end
Bone resorption at coronal half of the dental
The recruitment of the mononuclear cells at
Prior to onset of eruption
Thus dental follicle serves not only as target
tissue for mononuclear cells but also regulate
cellular events of eruption.
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.
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
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
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
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
Chronology and sequence Human Permanent Dentition
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
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
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
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
• Teeth that cease to erupt before emergence are
• Causes of impaction are subdivided into:-
- impaction of unerupted tooth due to
obstructions by physical barriers.
- impaction due to lack of eruptive force.
For the clinicians to treat dental problems
knowledge of proper eruption time is very
A variety of developmental defects that are
evident after eruption of the primary and
permanent teeth can be related to local and
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.