Tooth Eruption and Exfoliation

Question 1

The primary and permanent dentitions develop
— as the jaws increase in size
from infancy to adolescence.

Answer 1

simultaneously

Question 2

Jaws of the infant accommodate development of —

deciduous teeth

Answer 2

20

Question 3

At 4-5 yrs of age, the jaws accommodate

Answer 3

20 erupted

teeth and 28 developing teeth

Question 4

The mixed dentition stage, —yrs of age, involves
the concomitant exfoliation of deciduous teeth and
eruption of permanent teeth

Answer 4

8-12

Question 5

Tooth eruption is defined as the

Answer 5

movement of a
tooth from its site of development within the
alveolar process to its functional position in
the oral cavity

Question 6

Tooth eruption is divided into

three developmental stages:

Answer 6

 Pre-eruptive phase
 Pre-functional eruptive phase
 Functional phase (post-eruptive phase)

Question 7

Pre-eruptive tooth movement results from: (3)

Answer 7

 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)

Question 8

Over time, the jaws increase in: (4)

Answer 8

 Length of jaw (anterior-posterior)
 Width of jaw (coronal plane)
 Alveolar ridge height
 Buccal-lingual width of the alveolus

Question 9

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

Answer 9

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.

Question 10

With increased jaw size, the developing teeth move (2)

Answer 10

outward (facially) and towards the oral cavity (upward or downward).

Question 11

Because of jaw length, the permanent developing molars have
angled inclinations prior to and during eruption and achieve
vertical alignment only when

Answer 11

jaw length is sufficient to allow

it.

Question 12

Root Growth

Answer 12

 Elongation of the roots in relation to stability of the

fundus of the socket

Question 13

Vascular Pressure

Answer 13

 Increased hydrostatic pressures in the apical dental sac

or periodontal ligament

Question 14

Selective Bone Deposition and Resorption

Answer 14

 Coronal bone resorption concomitant with bone apposition

in the fundus area

Question 15

Pulpal Pressure

Answer 15

 Tissue pressure differential in the pulp compared to

the PDL

Question 16

Periodontal and Gingival Fiber Ligaments

Answer 16

 Cells (myofibroblasts) exert traction on the tooth through

the collagen network and cell-to-cell contacts

Question 17

Of the numerous causes of tooth eruption, the

most frequently cited are (3)

Answer 17

root growth, alveolar
bone remodeling, and periodontal ligament
formation.

Question 18

Other factors that influence tooth eruption include: (2)

Answer 18

 Parathyroid hormone (influences mineralization and
resorption of roots)
 MMPs produced by fibroblasts, osteoclasts, macrophages

Question 19

Gubernacular canal (a.k.a. gubernacular
cord or eruptive pathway):

Answer 19

 A strand of connective tissue that contains
remnants of dental lamina epithelium
(derived from the successional lamina)

Question 20

The rate of eruption is not constant but best
described as a “burst of eruption” that
averages about

Answer 20

3 mm every 3 months

Question 21

Occlusal Surface Wear: (2)

Answer 21

 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.

Question 22

Proximal Wear (Mesial Drift):

Answer 22

 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.

Question 23

Cell mediated tooth resorption involves the

“—”

Answer 23

odontoclast

Question 24

Derived from monocytes that exit capillaries to
become connective tissue macrophages which, in
turn,

Answer 24

fuse together to form a (syncytum) large
multinucleated giant cell that functions like an
osteoclast.

Question 25

Odontoclasts degrade both the

Answer 25

collagenous and
non-collagenous matrix of cementum and dentin
(lysosomal enzymes) and the hydroxyapatite
mineral phase (acids).

Question 26

Fibroclast

Answer 26

 Specialized fibroblast-like cells are thought to
destroy the collagen fibers of the PDL associated
with the resorbing tooth root.

Question 27

The finding of apoptotic cell death in the resorbing

PDL suggests that shedding of teeth is a

Answer 27

programmed event.

Question 28

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

Answer 28

tooth
eruption and shedding is determined by genetic factors
(approximately 80% genetic).