Tooth Development Flashcards
The _______ is the only portion of the tooth we can see.
Enamel
Describe the mature tooth structure.
Enamel
Dentin
Pulp Cavity- Innervation and Vascularization
The tooth rests in a _______ and held in place by the ________ called the ______.
boney socket , connective tissue
Periodontal pocket
What innervates and vascularizes a tooth?
Pulp chamber in dentin
What are the 5 stages of tooth development?
Initiation
1. Bud
2. Cap
3. Bell
4. Apposition
5. Maturation
Which stage of tooth development is enamel and dentin laid?
Bell stage is the earliest point of the first enamel and dentin while a majority is laid during the Apposition Stage
Early tooth development results from interactions between_________.
What is this process called?
Ectoderm of the stomodeum
Ectomesenchyme
INDUCTION
What is ectomesenchyme?
Derived from neural crest cells that migrate into the the developing head
What is stomodeum?
The embryonic mouth
What is induction?
Inductions of process were one tissue directed development of another adjacent tissue. It is mediated by cell contact or factors released by the inducing tissue.
The induction signals usually regulate gene transcription, thereby leading the target cell toward differentiating into a specific cell type.
Induction can be serial and reciprocal.
For example tissue A can influence B and then C.
Or tissue A can influence tissue B and tissue B can induce tissue A
What mediates induction?
It is mediated by cell contact or factors released by the inducing tissue.
What is the major embryologic feature that gives rise to teeth?
When does it appear in the embryo?
At 37 days, the primary epithelial band is present on the maxilla and the mandible of the embryo mouth. (NOT ON EXAM)
It gives rise to the dental lamina and the vestibular lamina as a result of mitosis and a change of orientation of mitotic cells.
What is dental lamina?
Formed by primary epithelial band to give rise to teeth
What is vestibular lamina?
Formed by primary epithelial band to give rise to skin between cheeks and teeth (gums)
What indicates the tooth formation?
In the initiation stage, the formation of a placode in the primary epithelial band due to an increase of mitosis is what indicates the site of tooth formation
What are Meckel’s Cartilage?
Meckel’s Cartilage are small circular rings on either side of the mandibular arch in an embryo. It gives rise to parts of the inner ear and portion of the mandible.
It is also part of the ectomesenchyme.
What directs tooth development?
The ectomesoderm
What two things are REQUIRED for proper teeth development?
Neural Crest AND mandibular epithelium
Neural and limb epithelium will result in
NO Teeth
Yes to bone, cartilage ,neural crest
Neural Crest alone will result in
NO teeth or bone
Yes to cartilage and neural crest
Mandibular epithelium alone will result in
NO teeth,bone, cartilage or neural crest
The mandibular epithelium induces the neural crest to make teeth. True or False
True
Does neural crest have to come from the cranial region to allow tooth development as long as there is mandibular epithelium?
NO! Any neural crest can be used AS LONG AS mandibular epithelium is present
Initiation Stage
In certain regions of the primary epithelial band and increase in mitosis and change of orientation of mitotic cells, create a placode code, which is a thickening of tissue in a localized area.
This is what indicates sites of tooth formation.
First the dental lamina forms by invaginating into the arch. There will be an accumulation of EMS cells by the invagination
The EMS cells will eventually give rise to the dental sac and papilla
EMS cells come from the __________.
Mandibular epithelium comes from the ________.
Neural Crest
Ectoderm
What are two key players in tooth development that regulate pattern of gene expression?
How does it regulate gene expression?
Fibroblast Growth Factors (FGF)
Bone Morphogenetic Proteins (BMP)
Induction of signals by tissues to release ligand that bind to a receptor to initiate a signal transduction cascade. This triggers transcription factor activity in the nucleus.
FGF-8 is derived from the ___________ and regulates gene expression in _________ by triggering transcription factors ______.
Ectoderm, Ectomesenchyme
LHX-6 and LHX-7
Why is FGF-8 important?
FGF-8 is produced by the ectoderm to induce the ectomesenchyme cells to begin tooth development.
ONLY FIRST ARCH ECTODERM can be used. Second arch ectoderm is not relevant to jaw development. It has LOW FGF-8 expression and placodes do not form.
What is first arch ectoderm?
What is second arch ectoderm?
First arch ectoderm consists of the maxillary and mandibular process and is responsible for giving rise to structures, such as oral epithelium, enamel lips and teeth.
Second arch ectoderm has nothing to do with tooth development. It is responsible for giving rise to part of the external ear lining of the faring and facial muscles.
Primary dentition consists of how many teeth?
20
How is the positioning of teeth determined?
Expression of the Pax9 transcription factor in ECM cells is required to differentiate into DENTAL ectomesenchymal cells after induction of FGF8.
Which transcription factor is responsible for tooth position?
Pax9
Differentiates ectomesenchyme to DENTAL version
Which transcription factor is responsible for inducing tooth formation in ECM cells?
LHX-6 and LHX-7 TF induced by FGF8
_____ turns ON Pax9 transcription factor while ______ turns it off.
FGF8
BMP4
What ligand and transcription factor are required to induce tooth formation.
FGF8 and Pax 9