ODONTOGENESIS Flashcards
4 STAGES REQUIRED FOR TOOTH FORMATION
Initiation Stage
Morphodifferentiation Stage
Histodifferentiation Stage
Apposition Stage
Bud stage
Formation of tooth germs
along the dental lamina
Initiation Stage
Differential
growth causes change in shape
Morphodifferentiation Stage
Bell stage
Specialization of cells
Histodifferentiation stage
Mineralization of tissues
Apposition Stage
Tooth Formation is dependent on:
*Genetic Factors
*Environmental Factors
Tooth Formation is dependent on:
hundreds to several
thousand genes likely involved
Genetic Factors
Tooth Formation is dependent on:
nutrition,
physical phenomenon, infection
Environmental Factors
Oral epithelium thickens and
invaginates in to the mesenchyme to form a primary epithelial band
Future dental arches
6TH week
Primary epithelial band divides into two
processes: dental lamina and vestibular lamina
7th week
- lingual; 1st to appear
- contributes to the tooth
development
Dental lamina
- facial/buccal
- cells rapidly enlarge to form a clef o vestibule between the cheeks and the tooth-bearing areas
Vestibular lamina
series of swellings develop on the deep
surface of the dental lamina
tooth development proceeds in three stages: the bud, cap, and bell stages
enamel organ appears as simple
spherical to avoid epithelial
condensation
poorly morphodifferentiated and
histodifferentiated
8th week
8th week
dental lamina is a knob-like projection toward the mesoderm
beginning of dental organ formation
BUD STAGE
10th week
morphogenesis has progressed
the deeper surface of the dental organ
invaginating to form a cap-shaped structure
enamel organ appearing poorly
histodifferentiated
at this early stage, tooth development is
already possible to identify the
formative element of tooth and its
supporting tissues: dental organ/ enamel organ dental papilla dental follicle/ dental sac
CAP STAGE
CAP STAGE
10TH WEEK
3 COMPONENTS OF THE TOOTH BUD AT CAP STAGE:
Dental organ
Dental papilla
Dental follicle
COMPONENT OF THE TOOTH BUD AT CAP STAGE:
forms the enamel
Dental organ
COMPONENT OF THE TOOTH BUD AT CAP STAGE:
forms the dentin and
pulp
Dental papilla
COMPONENT OF THE TOOTH BUD AT CAP STAGE:
forms the supporting structures of teeth
Dental follicle
3 COMPONENTS OF THE TOOTH AT EARLY CAP STAGE:
Dental organ
Dental papilla
Dental follicle
COMPONENT OF THE TOOTH AT EARLY CAP STAGE:
eventually forms enamel
Dental organ
COMPONENT OF THE TOOTH AT EARLY CAP STAGE:
Odontoblasts (periphery) =
dentin Fibroblasts (center) = pulp
Dental papilla
COMPONENT OF THE TOOTH AT EARLY CAP STAGE:
Cementoblasts (inner) = cementum Fibroblasts (middle) =
periodontal ligament Osteoblasts (outer) = alveolar
bone
Dental follicle
Late during cap stage, dental organ histodifferentiated into morphogically and
functionally different components:
Stellate reticulum
External or outer enamel epithelium
Internal or inner enamel epithelium
Stratum intermedium
- cells at the center of
the dental organ
Stellate reticulum
tall cuboidal cells at the periphery of
the dental organ
External or outer enamel epithelium
columnar cells immediately adjacent to the dental papilla
Internal or inner enamel epithelium
epithelial cells
between the internal dental epithelium
and the newly formed stellate reticulum
Stratum intermedium
14th week
Further morphodifferentiation and
histodifferentiation
Dental organ increases in size changes
in shape
Invagination (IEE) becomes deeper
BELL STAGE
14th week
Area where the inner and the outer enamel epithelium come together
Established the CEJ
CERVICAL LOOP
During the early stages of tooth
development three transitory structures may be seen:
A. Enamel knot (Ahern’s knot)
B. Enamel navel
C. Enamel cord
TRANSITORY STRUCTURES
Localized mass cells in
the center of IEE
Enamel knot (Ahern’s knot)
Slight indentation to the outer enamel
epithelium caused by the inward pull of the
enamel cord
Enamel navel
Strand of cells seen at
the early bell stage extending from the stratum intermedium towards the outer enamel epithelium
Together with the
enamel knot, form the
site of the future cusp tip or incisal edge
Enamel cord
Associated with the formation of the
dental hard tissues, commencing at
about the 18th week
Dentin formation always precedes enamel formation
LATE BELL STAGE (appositional stage)
Also known as cup stage
Proliferation stage
primitive oral cavity ○ Lined by stratified
squamous epithelium - oral
ectoderm
Stomodeum
Stomodeum lined by stratified squamous epithelium called ___.
oral ectoderm
○ oral ectoderm endoderm
contacts with the foregut
Buccopharyngeal membrane
- the
buccopharyngeal membrane
ruptures
27th day of gestation
○ connective tissue cells
underlying the oral ectoderm
○ Essential for the face and the
teeth
Neural crest or ectomesenchyme
first deciduous teeth to erupt
Mandibular Central Incisors
○ Appears at the 37th day of
development
○ A band of odontogenic
epithelium that forms around
the mouth
○ Horseshoe shaped
Primary Epithelial band
○ Localized thickenings
within the primary
epithelial bonds ○ Key feature of
initiation of tooth
development
Placodes
PEB gives rise to:
Dental lamina Vestibular lamina
It first forms from PEB
Dental lamina
forms after Dental
lamina
Vestibular lamina
○ Embryo is 6 weeks wold
certain areas of basal cell of
the oral ectoderm proliferate
rapidly
○ Leads to dental lamina
invading the underlying
ectomesenchyme
○ Serves as primordium of the
ectodermal portion
Dental Lamina
- first
recognizable stage in
embryonic
development
Primordium
6 or 6 ½ weeks of
tooth development
First sign of tooth
development
When is development of first permanent molar initiated?
at the fourth month of
utero
When does deciduous teeth develop
from lingual extension of
the free end of the dental
lamina
5th month in utero to the
10th month of age
Fate of the dental lamina
Extends over 5 years
It hollows and forms the oral
vestibule
Vestibular Lamina/Lip furrow
band
What develops first in the tooth development
Mandibular teeth
The tooth are named after ___________
the shape of epithelium
Earliest evidence of tooth
Tooth Germ
Development stages
- Growth stage
- Calcification stage
- Eruption stage
Under growth stage:
a. Initiation stage
b. Proliferation stage
c. Histodifferentiation stage
d.Morphodifferentiation stage
e. Apposition stage
The epithelium of the dental lamina
is separated from the underlying
ectomesenchyme
Initiation Stage (bud stage)
Ovoid swellings arise from 10
different points -> future position ○ Primordia of enamel organ
Initiation Stage (bud stage)
○Consist of :
■ Low columnar cells
■ Centrally located
polygonal cell
Enamel organ
○ Cells around the tooth bud
undergo mitosis
■ Results to migration
of migration of neural
crest cells to
ectomesenchymal
cells that surrounds
the tooth bud
Enamel organ
○ Area of ectomesenchymal
condensation, subjacent to
the enamel organ
Dental Papilla
Cells of dental papilla forms:
Dentin and pulp
condensed
mesenchyme that surrounds the
tooth bud
Dental sac
Dental sac forms
■ Cementum
■ Periodontal ligament
Parts of tooth bud:
■ dental/ enamel
organ
■ Dental papilla
■ Dental sac
Part of tooth bud:
produce
enamel
dental/ enamel
organ
Part of tooth bud:
produce pulp and
dentin
Dental papilla
Part of tooth bud:
produce
cementum and
periodontal ligament
Dental sac
a soft
connective tissue between the inner
wall of the alveolar socket and the
roots of the teeth.
Periodontal ligament
Embryonic cells of dental/enamel organ-ameloblasts-enamel
ectoderm
Embryonic cells of dental papilla-connective tissue- odontoblast - dentin and pulp
ectomesenchyme
Embryonic cells of dental sac or follicle-connective tissue-cementum and periodontal ligament
ectomesenchyme
A slight indentation to the
outside epithelium
Enamel navel
○ Reservoir of dividing cells ○ Cells in the center of the
enamel organ
Enamel knot
○ Vertical extension of the
enamel knot ○ seems to divide the dental
organ into two
Enamel cord(temporary structure)
○ Concavity filled with
connective tissue
Enamel niche
○ Formative organ of the dentin
and pulp
Dental papilla
○ Surrounds the dental organ
○ Made up of mesenchymal sac
○ Important in the formation of
cementum and periodontal
ligament
Dental Sac
○ Basement membrane that
separates the enamel organ
and the dental papilla ○ Future DEJ (dentino enamel
junction)
Membrana preformativa
○ Consist of cells that
differentiate prior to
amelogenesis
Inner enamel epithelium
○ Cells in the center of the
organ
○ Star shaped cells
Stellate reticulum
○ Flattened low cuboidal cells
○ Provides a rich nutritional
supply for intense metabolic
activity
Outer epithelium
Advance bell stage:
○ Rises from the cervical
portion of the enamel organ
○ Enamel organ forms the
HERS which is essential for
root formation
Hertwig’s epithelial root sheath
(HERS)
Advance bell stage:
Where inner and outer
epithelia comes together
Cervical loop
Advance bell stage:
○ Periodontal ligament of an
erupted teeth where
remnants are found ■ Remnants - lost
structure of HERS
Rest of malassez
Fusion of crown
Fusion
Globule of enamel is present
Dens Evaginatus
○ Hypoplasia
○ Notches are present
Hutchinson’s teeth
○ Small island of enamel
usually present in the CEJ
Enamel pearls
○ Angulation of tooth
Dilaceration