1. Submitted by:
Calibo, Jansen
DMD2AA

2. TOOTH
ERUPTION
DEFINITION………..2
A close look at tooth
eruption……….…….3
Eruptive or PreFunctional Phase…..5
Five Major Events
take place during PreEruptive Phase……..5
Mammalian Teeth
Three Categories
on the Basis of
Eruptive
Characteristics
Continuously Growing
Teeth……….……….8
MECHANISM OF
TOOTH
ERUPTION
Post-Eruptive or
Functional Phase…..6
Continuously
Extruding Tooth…….9
PRE-ERUPTIVE
PHASE……………...3
Continuously Erupting
Tooth………………..9
2 Types of Tooth
Movement in
Preeruptive Phase...5

3. Eruption – Mechanism of Tooth Eruption
Page 2
Eruption is the movement of the developing teeth through the bone and the
overlying mucosa of the jaws to appear in the oral cavity and reach the occlusal plane.
(Figure 1 & 2)
Tooth eruption is a process in tooth development in which the teeth enter the
mouth and become visible. It is currently believed that the periodontal ligaments play
an important role in tooth eruption. The first human teeth to appear, the deciduous
(primary) teeth (also known as baby or milk teeth), erupt into the mouth from around 6
months until 2 years of age, in a process known as "teething". These teeth are the only
ones in the mouth until a person is about 6 years old. At that time, the first permanent
tooth erupts and begins a time in which there is a combination of primary and
permanent teeth. This stage, known as the mixed stage, lasts until the last primary tooth
is lost. Then, the remaining permanent teeth erupt into the mouth.
Figure 1
Figure 2

4. Eruption – Mechanism of Tooth Eruption
Page 3
A Close Look at Tooth Eruption:
Baby teeth are lost naturally due to the pressure of the permanent teeth erupting
from below. This process is called root resorption. Note the continued development of
the permanent crown and root as it erupts. (Figure 3)
Figure 3
Mechanism of Tooth Eruption
1. Pre-eruptive Phase
Preparatory to the eruptive phases.
It consists of the movements to the developing and growing tooth germs within
the alveolar process before root formation. (Figure 4)
During this phase, the growing teeth move in various directions to maintain their
position in the expanding jaws. This is accomplished by both bodily movement
eccentric growth. Bodily movement is a shift of the entire tooth germ, which
causes bone resorption in the direction of tooth movement and bone apposition
from behind. These movement occur as the jaws grow. (Figure 5)

5. Eruption – Mechanism of Tooth Eruption
Figure 4 – Pre-eruptive Phase of Tooth
Eruption
Figure 5 – Bodily Movement of Crown during Pre-eruptive
Phase
Page 4
Early in the pre-eruptive phase,
the successional permanent teeth
develop lingual to, and near the incisal
or occlusal level of, their primary
predecessors. (Figure 6A & 7A)
At the end of this phase, the
developing anterior permanent teeth
are positioned lingually and near the
apical third of the primary anterior
teeth. (Figure 6B)
The premolars are located
under the roots of the primary molars.
(Figure 7B)
The upper molars develop in
the tuberosities of the maxilla, with
their
occlusal
surfaces
slanting
distally. The lower molars develop in
the base of the mandibular rami, and
their occlusal surfaces slant messially.
(Figure 8)
Figure 6 – Relative position of primary and
permanent teeth in (A)pre-eruptive and
(B)eruptive phases.
Figure 8 – Human jaws during mixed dentition.
Permanent maxillary molar in tuberosity.
Figure 7 – Relative position of primary molar and
permanent premolar teeth in (A)pre-eruptive and
(B)eruptive phases.

6. Eruption – Mechanism of Tooth Eruption
Page 5
Two types of tooth movement in pre-eruptive phase:
1. Total bodily movement
2. Movement where one part remains fixed while the rest
continues to grow leading to change in the center of the
tooth germ
2. Eruptive or Pre-functional Phase
Begins with the initiation of root formation and ends when the teeth reach
occlusal contact.
Five major events take place during this phase:
1. The secretory phase of amelogenesis is completed just before the onset of
root formation and perfunctional eruption. There is realtion between the
cessation of mineralization and activation of the epithelial cells beyaond
the enamel-forming area.
2. The intraosseous stage occurs when the root formation begins as a result
of the proliferation of both the epithelial root sheath and the mesenchymal
tissue of the dental papilla and dental follicle. (Figure 9)
3. The supraosseous stage begins when the erupting tooth moves occlusally
through the boneof the crypt and the connective tissue of the oral mucosa,
so that the reduced enamel epithelium covering the crown comes into
contact with the oral epithelium (Figure 10). As this occurs, the reduced
enamel epithelium of the crown proliferates and forms a firm attachment
with the oral epithelium. A fused, double epithelial layer over the
erupting crown is then formed. (Figure 11)
4. The tip of the crown enters the oral cavity by breaking through the center
of the double -layered epithelial cells. This breakthrough is accomplished
by the cusp tip causing degeneration of the membrane and is the
beginning stage of clinical eruption (Figure 12). The crown erupts further,
and the lateral borders of the oral mucosa become the dentogingival
junction (Figure 12A). The reduced enamel epithelium, now surrounding
the crown like a cuff, becomes known as the junctional or attchment
epithelium. When the tip of the crown appears in the oral cavity, about
one-half to two-thirds of the roots are formed. (Figure 12B)

7. Eruption – Mechanism of Tooth Eruption
Page 6
5. The erupting tooth continues to move occlusally at a maximum rate, and
there is gradual exposure of more of the clinical crown. (Figure 13)
Figure 9 – Pre-Functional Eruptive Phase in
formation of root
Figure 10 – Crown tip approaching oral epithelium
Figure 12 – Clinical appearance of the crown.
Figure 11 – Contact and fusion of reduced
enamel epithelium and oral mucosa.
3. Post-Eruptive or Functional Phase
Begins when the teeth reach occlusion, and continues for as long as each tooth
remains in the oral cavity.

8. Eruption – Mechanism of Tooth Eruption
Page 7
Alveolar processes increase
in height and the roots continue to
grow.
Teeth continue to move
occlusally, which accomodates jaw
growth and allows for root
elongation. The most marked
changes occur as occlusion is
established.
Alveolar
bone
density
increases, and the principle fibers of
the periodontal ligaments establish
Figure 13 – Primary tooth at the end of the eruptive phase.
themselves into separate groups
Permanent successor in preeruptive phase.
oriented
about the gingiva, the
alveolar crest, and the alveolar surface around the root.
The diameter of the fiber bundles increase from delicate, fine groups of fibers to
heavy, scurely stabilized bundles.
When root canal narrows, as a result of root tip maturation, apical fibers develop
to help cushion the forces of occlusal impact. (Figure 14)
Later in life, attrition may wear down the
occlusal surfaces of the teeth. (Figure 15)
Figure 14 – Increased density of periodontal ligament fibers
during eruption
Figure 15 – Formation of the junctional epithelium.
A, B Preeruptive, C Prefunctional eruptive phase,
D-F Functional occlusion.

9. Eruption – Three Categories on the Basis of Eruptive
Characteristics
Page 8
The teeth erupt slightly to compensate for loss of
tooth structure and to prevent occlusal overclosure.
If the occlusal wear is excessive, cementum deposited
on the apical third of the root; it is deposited in the
furcation region of molars to compensate for
hypereruption of these teeth. (Figure 16)
Three Categories on the Basis of Eruptive
Characteristics
1. Continuously Growing Teeth
no gross separation between the anatomical crown &
Figure 16 – Posteruptive
changes: attrition and
anatomical root.
compensative formation of
continuous growth of the tooth at the apex &
cementum.
continuous eruption occur throughout the life of the
animal.
clinical crown is constantly replaced by root covered with enamel in the
progressive stages of development.
with the loss of tooth substance due to occlusal attrition, more tooth substance is
extruded from the socket to maintain the clinical crown
this form of tooth is characteristic of animals with rapid occlusal wear &
eruption. (ex. Rodent incisor teeth – Figure 17 & 18)
Figure 17 - Rabbit
Figure 18 - Rat

10. Eruption – Three Categories on the Basis of Eruptive
Characteristics
Page 9
2. Continuously Extruding Tooth
has a defined crown & anatomical root.
as the tooth is worn, more of the anatomical crown extrudes & epithelial
attachment migrates apically. (Figure 19)
since no new tooth structure is being formed, it results to gradual loosening &
final exfoliation of the tooth.
this tooth form is characteristic of the lower incisors of sheep & cattle. (Figure 20
& 21)
Figure 19
Figure 20 – Teeth of a sheep.
Figure 21 – Teeth of a cattle.
3. Continuously Erupting Tooth
eruption does not occur by enlargement of the clinical crown but rather by
addition to the alveolar process.
this is characteristic of human teeth. (Figure 22)
Figure 22 – Human teeth.