CHAPTER 14
Oral Cavity
267
Tooth Development (Odontogenesis)
5. Apposition stage
(dentinogenesis)
6. Apposition stage
(amelogenesis)
7. Root formation
and eruption
8. Function
2. Bud stage
(weeks 8–9)
1. Initiation stage
(weeks 6–7)
3. Cap stage
(weeks 10–11)
4. Bell stage
(weeks 12–14)
Dental
lamina
Dental
Dental
lamina
lamina
Dental
lamina
Dental
Dental
Dental
papilla
Dental
Dental
papilla
papilla
Dental
Dental
papilla
papilla
Dental
papilla
Dental
Dental
papilla
papilla
Dental
papilla
Dental
Dental
pulp
pulp
Dental
papilla
Dental
pulp
Dentin
Dentin
Dentin
Enamel
Enamel
Enamel
E
n
a
m
e
l
o
rg
a
n
Enamel
organ
Enamel
Enamel
organ
organ
Enamel
organ
Primary
epithelial band
Figure 14-8.
Overview of tooth development (odontogenesis)
. H&E,
3
5 to
3
128
Tooth development
is also called
odontogenesis
. The tooth derives from two types of tissues:
ectoderm
(oral epithelium) and
mesenchymal
tissues that originate from the neural crest. The oral epithelium forms a U-shaped structure called the
dental lamina
,
which develops into an
enamel organ
. The mesenchymal tissue develops into a
dental papilla
and also forms a dental sac (follicle),
which surrounds the dental papilla and enamel organ. The enamel organ, dental papilla, and dental sac (follicle) collectively are
described as a
tooth germ
. Tooth development is a continuous process and can be described in several stages (like snapshots) based on
the shape of the tooth germs:
initiation
,
bud
,
cap
,
bell
, and
apposition stages
. The illustrations represent the process of tooth develop-
ment. (1)
Initiation stage
: Proliferating oral epithelial cells become thickened and form a primary epithelial band. (2)
Bud stage
: The
dental lamina (derived from the primary epithelial band) forms a U-shaped structure (tooth bud). (3)
Cap stage
: The enamel organ
develops into a cap shaped structure. At the same time mesenchymal tissue becomes condensed and forms the dental papilla. (4)
Bell
stage
: The enamel organ continues to grow into a bell shape that has F ve distinct cell layers (±ig. 14-10A,B). (5)
Apposition stage
(
dentinogenesis
): Odontoblasts begin to form dentin on the crown region. (6)
Apposition stage
(
amelogenesis
): After a layer of dentin
is formed at the crown of the tooth, the formation of enamel begins (produced by ameloblasts). (7)
Root formation and eruption
:
When the shape of the crown and the dentin and enamel of the crown have completed, the tooth begins to develop its root structure
(cementum, PDL). During this process, the tooth gradually erupts into the oral cavity. (8)
Function
: Development of the tooth root
and its associated structures continues until the tooth is functional.
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