Tooth Eruption and Exfoliation Flashcards
The primary and permanent dentitions develop
— as the jaws increase in size
from infancy to adolescence.
simultaneously
Jaws of the infant accommodate development of —
deciduous teeth
20
At 4-5 yrs of age, the jaws accommodate
20 erupted
teeth and 28 developing teeth
The mixed dentition stage, —yrs of age, involves
the concomitant exfoliation of deciduous teeth and
eruption of permanent teeth
8-12
Tooth eruption is defined as the
movement of a
tooth from its site of development within the
alveolar process to its functional position in
the oral cavity
Tooth eruption is divided into
three developmental stages:
Pre-eruptive phase
Pre-functional eruptive phase
Functional phase (post-eruptive phase)
Pre-eruptive tooth movement results from: (3)
Growth of jaws
Growth of tooth buds
Remodeling of the walls of the bony crypt
(e.g., mesial migration results when there is resorption
of the mesial wall with concomitant apposition of bone
on the distal wall)
Over time, the jaws increase in: (4)
Length of jaw (anterior-posterior)
Width of jaw (coronal plane)
Alveolar ridge height
Buccal-lingual width of the alveolus
Pre-eruptive Phase
Initially the deciduous teeth develop within the jaw and
have considerable room. However, the individual tooth
germs grow rapidly and due to jaw length, they become
crowded in the anterior region. As the jaws increase in
length, the crowding is alleviated by migration of teeth
distally which allows a more even distribution.
With increased jaw size, the developing teeth move (2)
outward (facially) and towards the oral cavity (upward or downward).
Because of jaw length, the permanent developing molars have
angled inclinations prior to and during eruption and achieve
vertical alignment only when
jaw length is sufficient to allow
it.
Root Growth
Elongation of the roots in relation to stability of the
fundus of the socket
Vascular Pressure
Increased hydrostatic pressures in the apical dental sac
or periodontal ligament
Selective Bone Deposition and Resorption
Coronal bone resorption concomitant with bone apposition
in the fundus area
Pulpal Pressure
Tissue pressure differential in the pulp compared to
the PDL
Periodontal and Gingival Fiber Ligaments
Cells (myofibroblasts) exert traction on the tooth through
the collagen network and cell-to-cell contacts
Of the numerous causes of tooth eruption, the
most frequently cited are (3)
root growth, alveolar
bone remodeling, and periodontal ligament
formation.
Other factors that influence tooth eruption include: (2)
Parathyroid hormone (influences mineralization and
resorption of roots)
MMPs produced by fibroblasts, osteoclasts, macrophages
Gubernacular canal (a.k.a. gubernacular cord or eruptive pathway):
A strand of connective tissue that contains
remnants of dental lamina epithelium
(derived from the successional lamina)
The rate of eruption is not constant but best
described as a “burst of eruption” that
averages about
3 mm every 3 months
Occlusal Surface Wear: (2)
Oblique fiber groups of the PDL continually pull the tooth
into occlusion as enamel is abraded.
Apical cementum deposition also serves as a
compensatory eruptive mechanism to continual occlusal
abrasion.
Proximal Wear (Mesial Drift):
Mesial inclination of teeth in full contact will yield an
anterior force vector and when coupled with the pull of the
transseptal fibers, results in mesial drift.
Cell mediated tooth resorption involves the
“—”
odontoclast
Derived from monocytes that exit capillaries to
become connective tissue macrophages which, in
turn,
fuse together to form a (syncytum) large
multinucleated giant cell that functions like an
osteoclast.
Odontoclasts degrade both the
collagenous and
non-collagenous matrix of cementum and dentin
(lysosomal enzymes) and the hydroxyapatite
mineral phase (acids).
Fibroclast
Specialized fibroblast-like cells are thought to
destroy the collagen fibers of the PDL associated
with the resorbing tooth root.
The finding of apoptotic cell death in the resorbing
PDL suggests that shedding of teeth is a
programmed event.
The finding of apoptotic cell death in the resorbing
PDL suggests that shedding of teeth is a
programmed event.
• Support for this theory is found in studies of tooth
eruption in monozygotic twins, which indicates that
tooth
eruption and shedding is determined by genetic factors
(approximately 80% genetic).