Tooth Development (complete) Flashcards
What is the stomatodeum
the primitive oral cavity
What borders the stomatodeum
the neural plate
the cardiac plate
What separates the stomatodeum from the foregut
the buccopharyngeal membrane
What happens to the buccopharyngeal membrane
it disintegrates in the 4th week
what lines the stomatodeum
ectoderm
what initiates the development of the face
the formation of the stomatodeum
what is the oral epithelium
a primitive two or three cell thick layer of epithelium that covers embryonic connective tissue
from what does the dental lamina develop
a portion of the oral epithelium
What is dental lamina
the horse shoe shaped band of epithelial tissue that will develop into the teeth and periodontium (along with ectomesenchyme)
When does odontogenesis begin
the 6th week
What are the two tissues that develop into teeth
- dental lamina
2. ectomesenchyme
When do primary teeth begin to form
4 months in utero
when do permanent teeth begin to form
at birth
What initiates and governs tooth development
ectomesenchymal interactions
What leads to the differentiation of ectomesenchyme
secretion of growth factor by the dental lamina
What is the ectomesenchyme formed from
mesoderm with neural crest cells sprinkled in
What separates the dental lamina from the ectomesenchyme
a well defined basal lamina
What signifies the start of odontogenesis
the appearance of the dental lamina
What are the stages of dental lamina development
- oral epithelium (no invagination)
- primary epithelial band (slight invagination)
- Dental lamina (invagination)
What is adontia
congenital absence of all teeth
what causes adontia
ectodermal dysplasia
(defect in the ectoderm derived tissues)
no tooth buds are formed
What is hypodontia
1-5 teeth missing
what is oligodontia
6 or more teeth missing
What is hyperdontia
extra teeth (supernumerary teeth)
in what dentition do we see hyperdontia
permanent dentition
What is the most common supernumerary tooth
mesioden
What causes hyperdontia
an extra tooth germ forms
tooth formation is initiated by factors residing in the ____
1st arch oral epithelium
What are the stages of tooth development
Bud
Cap
Bell
What is the stage that follows the invagination of the dental lamina
the Bud stages begins as the invagination of dental lamina becomes deep into the ectomesenchyme
What connects the bud to the dental lamina
the lateral lamina
what happens with the shape and function of the epithelial cells in the bud stage
there is little change in shape or function of epithelial cells in the bud stage
how many placodes or outgrowths dive down into the ectomesencyhme
20
what do the 20 placodes that invaginate into the ectomesenchyme form
the 20 primary teeth
does the development of teeth correspond to the erpution of teeth
yes
what are the first teeth to develop, and what follows
the anterior mandibular teeth are first, then the anterior maxilla, and lastly going anterior to posterior in both jaws
what are other names for tooth buds
dental buds, tooth primordia, or tooth germs
what are the abnormalities associated with the bud stage
- microdontia
2. macrodontia
What is microdontia
abnormally small tooth
which teeth are most affected by microdontia
maxillary lateral incisors and third molars
what is macrodontia
abnormally large teeth
what causes macrodontia of single teeth
hemifacial hypertrophy
What signals that the tooth germ has reached the cap stage
- the appearance of a cap
2. the creation of a three layered enamel organ
what are the three layers of the enamel organ
OEE (outer enamel epithelium)
IEE (inner enamel epithelium)
SR (stellate reticulum)
The cap begins to form around a condensed pile of ectomesenchyme, what is that pile called.
Dental papilla (underneath the cap)
What are the three parts of the tooth germ
- the enamel organ
- the dental papilla
- the dental follicle
what is the origin of the enamel organ
ectoderm
What does the dental papilla become
the dentin and pulp of the tooth
what does the dental follicle become
the periodontium
what are the 5 parts of the enamel organ
OEE (outer enamel epithelium) SE (stellate reticulum) SI (stellate/stratum intermediate) IEE (inner enamel epithelium) cervical loop
What is the OEE
the convex layer (top or outside layer)
What is the SR
cells between the IEE and OEE
What is the SI
it is the lowest layer of SR between the SR and the IEE
What does the SR do
it produces proteoglycans to maintain morphology of the enamel organ
What does the SI do
it elaborates emnamel
it initiates the formation of dentin from the dental papilla cells
What is the IEE
the concave layer (the part that is encasing the dental papilla)
What is the cervical loop
it represents the preemptive cervix of the tooth (CEJ)
this is where the IEE and OEE meet
What cells of the dental papilla do what
the inner cells will form the dental pulp
the peripheral cells will form the dentin
where are the peripheral dental papilla cells located
against the basement membrane, opposite to the IEE
How do those peripheral dental papilla cells end up making dentin
they differentiate into odontoblasts, then secrete dentin
how does the structure of the dental follicle differ from the structure of the dental papilla
it is less cellular and more fibrous
The dental papilla is the ectomesenchyme underneath the cap of enamel organ, where is the dental follicle
it surrounds both the enamel organ and the dental papilla
What do the inner cells of the dental follicle become
they become cementocytes that will lay down cementum
What do the outer cells of the dental follicle become
they become the PDL and contribute to alveolar bone formation
How do the succedaneous teeth form
for the incisors, canines, and premolars, a succedaneous tooth germ breaks off of the deciduous tooth germ and will become the succedaneous teeth
on which side of the deciduous tooth germ does the succedaneous tooth germ break off
the lingual side of the deciduous tooth germ
how does the development of succadaneous teeth differ from the development of deciduous teeth
they develop in the same way that the deciduous teeth do
how do the permanent molars develop
posterior extensions of the dental lamina on the flattened bony ramus of the mandible give rise to 3 tooth germs each
are the permanent molars succedaneous
no, they are accessional teeth
When do the permanent molars develop
the 5th month of gestation
What is the vestibular lamina
another thickening and invagination intto the ectomesenchyme
what does the vestibular lamina develop into
The epithelial lining of the
oral vestibule, alveolar mucosa, parts of the gingival mucosa, inner lip mucosa, mucosal space between the teeth and the cheeks or lips
it can also form salivary glands
What are developmental abnormalities that arise during the cap stage of tooth development
- Dens in dente (dens invaginalis)
- Fusion
- Gemination
What causes dens in dente
when the enamel organ expands too much and invaginates into the dental papilla
What is fusion of teeth
when two teeth germs fuse it leads to two teeth that look like they are one (fewer # of teeth)
What is gemination
one tooth germ trying to divide into another causes one tooth to look like two fused together (correct # of teeth)
what supports the inferior most portion of the cervical loop
the basal lamina
from a radiographic point of view what distinguises the bell stage from the cap stage
the lenthening of the cervical loop
what are the two differentiations taking place during the bell stage
Morphodifferentiation
histodifferentiation
what is morphodifferentiation mean in the bell stage
that the enamel organ takes the shape of an incisor, canine. or molar
what is histodifferentiation in the bell stage
ameloblasts are odontoblasts aquire their phenotype
What does the stellate reticulum do in the bell stage
- syntesize and secrete GAGs
- Draws in water
- desmosomal contacts are forced apart and become star shaped
- the cells transport nutrients and calcium from blood vessels to the ameloblasts
what are the flat cells between the IEE and the SR
the stratum intermediate (SI)
what kind of junctions are in the stratum intermediate
gap junctions
what do the SI cells do
they have high alkaline phosphatase activity and they transport phosphate from blood vessles near the SI into the enamel organ
What two layers work synergistically for the formation of enamel
the IEE and the SI
What is the IEE
the group of short columnar cells facing the dental papilla
What does the basal lamina become
it becomes the DEJ (dentinoenamel junction)
is glycogen in high or low concentrations in the IEE
High
What do the IEE cells become
they become ameloblasts
Where is the OEE
the outer edge of the enamel organ
What happens to the OEE is the bell stage
the cells elongate and the invaginated areas become occupied by blood vessels
What is the name of the place where the OEE and the IEE meet?
cervical loop
What is the thing called when the OEE and the IEE join
HERS (Hetwigs epithelial root sheat)
what does HERS do
initaites root formation
are cells at the cervical loop dividing quickly or slowely
quickly
what marks the place where the crown and root meet
the cervical loop
What are two important and specific events that take place during the bell stage
- Dental lamina/lateral lamina disintegrates
2. morphodifferentation establishes crown pattern and the number of cusps
What reestablishes the tooths connection with the oral epithelium
junctional epithelium
What must form before a tooth can function
the juncctional epitheliun
which portion of the dental lamina doesn’t disintegrate
the posteriormost extent
why does the posteriormost extent of the dental lamina not disintegrate
becuase itll elongate and be the precursor to the 12 permanent molars
What initiates the crown pattern and number of cusps of a tooth (morphogenesis)
folding of the IEE
what DOESN’T cause the specific folding of teeth to obtain correct crown shapes
growth pressures of the dental papilla
what DOES cause the specific folding of teeth to obtain correct crown shapes
differential rates of mitotic division within the IEE
Where do the odontoblasts and ameloblasts begin to lay down dentin and enamel
at the crest of the folded IEE (highest point of the papilla)
What does the fragmentation of the dental lamina leave behind
discrete clusters of epithelial cells
what is the name for the discrete clusters of epithelial cells that the fragmented dental lamina leaves behid
- epithelial pearls
2. Rests of Serres
what happens to the epithelial pearls
they either become macrophages or they persist
if they persist they can become eruption cysts, or odontomes
what kind of problems can come from epithelial pearls
they can form both eruption cysts
what may also come of epithelial pearls
they may give rise to super numarary teeth
what is an eruption cyst
a cyst formed by epithelial pearls
what is a complication that eruption cysts can cause
they may keep a tooth from erupting
How does the buckling of the IEE happen
the IEE is constrained between the cervicl loop and the cusp tip. so if that distance is fixed when there is rapid cell divisions, the IEE becomes buckled
what does the buckling of the IEE create
the cuspal outline
Where does IEE cell differentiation first occur
the site of future cusp development (growth center)
what are the certain number of places where IEE cell differentiation first occurs
where the future cusps will be
where are enamel and composite first deposited, and how does it progress from there
at the basal membrane at the tips of the papilla where the cusp tips will eventually be (growth centers)
which parts of the tooth are mesodermal in origin
dentin, pulp, cementum, PDL
which parts of the tooth are ectodermal in origin
the enamel
which parts of the tooth are derived from neural crest cells
all but the enamel
how much of the root has been formed by the time the tooth erupts
1/3 of the root has formed
