The document discusses the eruption and shedding of deciduous teeth. It covers: 1) The process of eruption where a tooth moves from its developmental position in the jaw to its functional position in the mouth. 2) Pre-eruptive, eruptive, and post-eruptive phases of tooth movement. 3) Patterns and mechanisms of shedding deciduous teeth, including root resorption and the role of developing permanent teeth.

1. Eruption
&
Shedding
Of
DECIDUOS
TEETHAssignment by
Sarang Suresh Hotchandani
BADC Batch 01
Roll # 21

2. Eruption of Deciduous Teeth
Eruption
Eruption is essentially the process whereby a tooth moves from its developmental
position in the jaw into its functional position in the mouth. There is no evidence to
suggest that eruption entirely ceases once a tooth meets its antagonist in the mouth, and
outward axial movements occurring during the functional phase may also be eruptive
movements. (viz. overeruption following removal of the antagonist tooth in the opposite
jaw).
While the main direction of the eruptive force is axial (i.e. related to the long axis of
the tooth), movement also occurs in other planes, accounting for tilting and drifting.
Eruption rates of teeth are greatest at the time of crown emergence. Rates also differ
according to tooth type. Permanent maxillary central incisors are reported to erupt at
about 1mm/month; the rates for mandibular second premolars have been determined to be
as great as 4.5mm in 14 weeks. For permanent third molars, where space is available,
eruption rates of 1mm in 3 months have been recorded. In crowded dentitions, however,
the rates are less than 1mm in 6 months.
As a tooth approaches the oral cavity, the overlying bone is resorbed and there are
marked changes in the overlying soft tissues. The enamel surface is covered by the
reduced enamel epithelium, which is a vestige of the enamel organ.
Pre-eruptive tooth movement: Pre-eruptive phase, which starts with the initiation
of tooth developmentn.
2) Eruptive: Tooth eruption, which begins once the roots begin to form.
3) Post-eruptive tooth movement: After the teeth have emerged into the oral cavity,
there is a protracted phase concerned with the development and maintenance of occlusion
(the functional phase).
Eruption of TEETH
(I)Patten of tooth movement
1. Pre-eruptive tooth movement
When deciduous tooth germs first differentiate, there is a good deal of space
between them. Because of their rapid growth, this available space is utilized and the
developing teeth become crowded together, especially in the incisor and canine
region.
This crowding is relieved by growth in the length of the infant jaws,
which provides room for the second deciduous molars to drift backward and anterior
teeth to drift forward.

3. At the same time the tooth germs also move outward as the jaws increase
in width, and upward( downward in the upper jaw) as the jaws increase in height.
2. Eruptive tooth movement
During the phase of eruptive tooth movement the tooth moves from its
position within the bone of the jaw to its functional position in occlusion and the
principal direction of movement is occlual or axial .
It is important to recognize that jaw growth is normally occurring while most
teeth are erupting, so that movement in planes other than axial is superimposed on
eruptive movement.
3. Post-eruptive tooth movement
(1) maintain the position of theee erupted tooth while the jaw continues to grow
(2) compensate for occlusal and proximal wear.
The former movement, like eruptive movement, occurs principally in an axial
direction so as to keep pace with the increase in height of the jaws. It involves both the
tooth its socket and ceases when jaw growth is completed. The movements compensating
for occlusal and proximal wear continue throughout life and consist of axial
and mesial migration, respectively.
Histology of Tooth Movement
Pre eruptive phase:
1. Total bodily movement of the germ
2. There is its excentric growth:
excentric growth: one part of the developing tooth germ remains stationary while the
remainder continues to grow, leading to a shift in its center.
Eruptive phase:
During the eruptive phase of physiologic tooth movement, significant developmental
changes occur:
1. Formation of root
2. Formation of periodontal ligament,
3. Formation of dentogingival junction
4. Another specialized feature associated with the erupting permanent tooth is the
presence of a gubernacular canal.or cord.
Post-eruptive phase:
(III) Mechanism of tooth movement
1. Root growth
2. Vascular pressure Root growth
3. Bone growth
4. Ligament traction

4. Shedding of deciduous teeth
(I) Patten of Shedding
For a deciduous incisor or canine, root resorption initially occurs on the lingual
surface adjacent to the developing permanent tooth. With subsequent movement and
relocation of the teeth in the growing jaws, the developing permanent tooth comes to lie
directly beneath the deciduous tooth and further resorption occurs from the apex.
For a deciduous molar, root resorption often commences on the inner surfaces
where the permanent premolars initially develop.
The premolars later come to lie beneath the roots of the deciduous molar and
further resorption occurs from the root apices. The shift in position of the deciduous tooth
relative to the permanent successor may account for the intermittent nature of
root resorption.
(II) Mechanism of resorption and histology of shedding
The initiation of root resorption may be an inherent developmental process or it may
be related to pressure from the permanent successor against the overlying bone or tooth.
Mechanism of TOOTH Eruption
Tooth eruption is traditionally considered to be a developmental process whereby the
tooth moves in an axial direction from its position within the alveolar crypt of the jaw
into a functional position within the oral cavity. However, eruption can be regarded as a
lifelong process since a tooth will often move axially in response to changing functional
situations (e.g. overeruption resulting from the removal of an antagonist, and
compensatory eruption related to attrition).
The rate of eruption represents a balance between forces tending to move the tooth into
the mouth (eruptive force) and forces tending to prevent this movement (resistive force).
Resistance may be produced by overlying soft tissues and alveolar bone, the viscosity
of the surrounding periodontal ligament and occlusal forces. Thus, changes in the rate of
tooth movement may be brought about by changes in either the eruptive forces and/or the
resistive forces.
At present, little is known about the nature, source and magnitude of either the eruptive
or resistive forces. Furthermore, it is not known whether the forces are of the same nature
and value at various stages of the eruptive cycle. By and large, this situation results from
difficulties encountered in producing experimental systems which isolate for study single
possible agents associated with the eruptive process.
All tissues within the vicinity of the tooth thought capable of generating a force have,
at one time or another, been implicated in the eruptive process.
The tooth is pushed out as a result of forces generated beneath and around it, either
by alveolar bone growth, root growth, blood-pressure/tissue fluid pressure, or cell
proliferation. Alternatively, the tooth may be pulled out as a result of tension within the
connective tissue of the periodontal ligament. Although no one theory is yet supported by
sufficient experimental evidence.