OE L2 Early Tooth Development (Mes-Epi Interactions) Flashcards
In the early stages of tooth development, we know that the primary epithelial band forms, we know that it thickens and invaginates to form the vestibular and dental lamina, what drives this event?
- Changes in mitotic spindle orientation
- Cleavage plane of dividing epithelial cells changes
These changes mean growth occurs in certain directions.
What feature exists of the dental lamina that is involved in permanent dentition?
The successional lamina can be seen coming off from the dental lamina.
The successional lamina does not exist for the 1st, 2nd or 3rd permanent molars.
Why do we call the mesenchymal tissue involved in tooth development ectomesenchyme?
Because there is a contribution of neural crest cells from the neural tissues at the hind brain.
These cells migrate to the branchial arches and then contribute to the mesenchymal tissue- therefore creating ectomesenchymal tissue.
Describe how initial tooth induction occurs. How do epithelial cells know where to form the primary epithelial band and where to form tooth buds along this band?
- The epithlium of the mandibular and maxillary processes play an instructional role in initiating tooth development and positioning of tooth buds.
- Neural crest cells migrate to the mesenchyme to form ectomesenchyme, and require the correct signals from the oral epithelium to become odontogenic.
At the very early stages of tooth development what is the driving force/which structure is in control?
The oral epithelium of the 1st branchial arch.
Instructs the neural crest cells to become odontogenic.
From bud stage until late bell stage, what is the driving force/which structure is in control?
The underlying ectomesenchyme exerts the instructive influence on the epithelium and determines its fate.
These signals determine the shape of the tooth.
How does mesenchyme control tooth shape?
The mesenchyme drives the folding of the inner enamel epithelium, therefore defining the tooth shape.
At late bell stage, what is the driving force/which structure is now in control?
The enamel organ.
Induces the outer layers of the dental papilla cells to differentiate into odontoblasts.
Does the enamel organ need to be in direct contact with the dental papilla for tooth formation?
No, cell-cell contact isn’t needed, but the signals need to be able to reach the papilla.
Chemical messengers are released and pass through a filter (basement membrane).
The basement membrane allows signals such as growth factors, transcription factors and cytokines to move between the ectomesenchyme and epithelium.
Describe the action of growth factors.
Growth factors are small bioactive proteins which bind to cell receptors.
This binding causes a series of signalling cascades leading to the activation of transcription factors.
Describe the action of transcription factors.
Once trancription factors have been activated by growth factors, they bind to the promoter sequence for a specific gene and promote the translation of that gene.
Give examples of transcription factors.
- Msx1
- Msx2
- Pitx2
- Pax9
- Edar
Give examples of growth factors and signalling proteins.
- BMP
- Shh
- FGF
- WNT
Which structure marks the number of cusps of a tooth?
The enamel knot.
Enamel knot communicates with mesenchyme and cells of IEE, regulates cell division and organisation of mitotic spindles so cells migrate in downward direction to form cervical loop.
Describe the role of FGF.
Fibroblast growth factor stimulates cells either side of enamel knot to proliferate and migrate- formation of cervical loops through mitosis (orientation/spindle involvement)
