eruption and exfoliation of teeth

Question 1

primary and permanent dentition develop together?

Answer 1

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

Question 2

infant jaws accommodate?
4-5 years accommodate?
mixed dentition?

Answer 2

 Jaws of the infant accommodate development of 20
deciduous teeth
 At 4-5 yrs of age, the jaws accommodate 20 erupted teeth and 28 developing teeth
 The mixed dentition stage, 8-12 yrs of age, involves the concomitant exfoliation of deciduous teeth and eruption of permanent teeth

Question 3

eruption defined/ stages

Answer 3

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)

Question 4

Pre-eruptive Phase tooth movement results from?

Answer 4

Pre-eruptive tooth movement results from:
 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 5

Pre-eruptive Phase: Over time, the jaws increase in:

Answer 5

Over time, the jaws increase in: 
  Length of jaw (anterior-posterior) 
  Width of jaw (coronal plane) 
  Alveolar ridge height 
  Buccal-lingual width of the alveolus

Question 6

Pre-eruptive Phase tooth space initally/as we progress and results of increased jaw size (migration patterns)
molar angulation?

Answer 6

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 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.

Question 7

Theories of Tooth Eruption

Answer 7

 Root Growth

 Vascular Pressure

 Selective Bone Deposition and Resorption

 Pulpal Pressure theory

 Periodontal and Gingival Fiber Ligaments theory

Question 8

Root Growth theory

Answer 8

Elongation of the roots in relation to stability of the fundus of the socket

Question 9

Vascular Pressure theory

Answer 9

Increased hydrostatic pressures in the apical dental sac or periodontal ligament

Question 10

Selective Bone Deposition and Resorption theory

Answer 10

Coronal bone resorption concomitant with bone apposition in the fundus area

Question 11

Pulpal Pressure theory

Answer 11

Tissue pressure differential in the pulp compared to the PDL

Question 12

Periodontal and Gingival Fiber Ligaments theory

Answer 12

myofibroblasts exert traction on the tooth through the collagen network and cell-to-cell contacts

Question 13

which theories of eruption are most used?

Answer 13

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

Question 14

other factors of tooth eruption include

Answer 14

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

Question 15

eruptive phase: gubernacular canal, rate of eruption?

Answer 15

canal that tooth eruption will follow

 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

Question 16

functional phase types of wear/compensations

Answer 16

 Occlusal Surface Wear:
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.

Question 17

cell mediated tooth resorbtion of exfoliation

origin of cells

Answer 17

involves odontoclast derived from monocytes exiting the capillaries to become conn tissue macrophages which fuse to form a syncitium/giant cell to work as an osteoclast

 Odontoclasts degrade both the collagenous and non-collagenous matrix of cementum and dentin (lysosomal enzymes) and the hydroxyapatite mineral phase (acids)
will degrade minerilzed tissues for eruption to occur

Question 18

fibroclasts of exfoliation

shedding of teeth programmed evidence?

Answer 18

 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 resorting 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).

Question 19

malocclusions of eruption

Answer 19

can occur for many reasons:
teeth do not form directly under precursor
teeth with excessive tilts M/D=impaction
basically due to not following guberneculum

Question 20

impacted eruptions

Answer 20

can occur when there isnt enough room for eruption
erupting teeth may cause resorbtion of existing teeth due to follicular cysts containing odontoclasts (some 3rd molar cases)