OCB02-1009 Early tooth development Flashcards
What stages are involved in morphogenesis?
bud
cap
bell
Where do the upper incisors develop from?
the frontonasal process
Where do all the upper teeth except for the incisors develop from?
the maxillary process
Where do all of the lower teeth develop from?
the mandibular arch
Where did the epithelium derive from?
The ectoderm
Where did mesenchyme derive from?
cranial neural crest cells
What does the epithelium give rise to?
enamel
What does the mesenchyme give rise to?
dentin, dental pulp, cementum, periodontal ligament, alveolar bone socket
How do cranial neural cells form ectomesenchyme?
They delaminate at the border of the neural and non-neural ectoderm
CnCCs undergo an epithelial to mesenchyme transition
This gives rise to cells known as the ectomesencyme
How is ecotmesenchyme different from mesenchyme?
Because ectomesenchyme arises from neural crest cells
What happens to the mesenchyme that is formed by CNCCs?
The mesenchyme migrate towards the first brachial arch to fill the ventral part of the face and gives rise to swellings
Where does the first brachial arch receive CNCCs from?
rhombomeres 1 and 2 from the hindbrain and some from the midbrain
What is treacher collins syndrome?
Mutation if the TCOF1 gene, which is essential for NCC survival
If there is not enough CNCC, not enough teeth will be made
Where is oral epithelium present?
It covers the present oral cavity, the first brachial arch, the maxillary process and the frontonasal process
What gene is expressed in the epithelium the covers the first brachial arch, maxillary process and mandibular process?
Pitx2 gene
What gene gives rise to multicusped teeth?
Barx1
What occurs in the initiation stage?
A continuous band of thickened epithelium known as the primary epithelial band forms on the upper and lower jaw
It invaginates into the underlying mesenchyme
The primary epithelial band corresponds to a thickening of the oral epithelium.
The thickening process is due to a change in orientation of the cells, they go from parallel to perpendicular
What are the two subdivisions of the primary epithelial band?
The dental lamina, which connects the developing tooth bud to the oral epithelium
Vestibular lamina, of which cells die to give rise to the space between the teeth and lips or inner cheek
When does the formation of dental lamina occur?
6-7th week
What is tooth agenesis?
Mesenchyme does not condense properly at bud stage
What occurs during the bud stage?
A series of swelling on the surface of the dental lamina make way for deciduous teeth
Each one of the swellings is known as a dental placode that makes way for a tooth
As the swellings are created, a signal is sent to the mesenchyme to induce Pax9 gene expression, which labels the sites involved in tooth development
What will happen if Pax9 is not expressed correctly?
The tooth will remain at the bud stage
What is the dental mesenchyme?
The mesenchyme which condenses around the enamel
What is the enamel organ?
The epithelial bud which only gives rise to the enamel
What make up the tooth germ?
The dental mesenchyme and epithelial bud
What happens during the cap stage?
A small group of ectomesenchymal cells stop producing extracellular substances, which results in an aggregation of these cells called dental papillae
Blood vessels grow in the dental follicles and enter the dental papilla at the cap stage
At this point, the tooth bud grows around the ectomesenchymal aggregation and becomes the enamel organ
What is the dental follicle?
The condensation of ectomesenchymal cells that surrounds the enamel organ and limits the growth of the dental papilla
What are the two populations of condensed mesenchyme?
Dental follicle and dental papilla
What does the dental papilla give rise to?
Dentin and dental pulp
What does the dental follicle give rise to?
cementum, periodontal ligament and alveolar bone socket
What are the different cell types in the enamel organ?
Outer enamel epithelium: cuboidal cells
Inner enamel epithelium: columnar cells
Stellate reticulum: cells in the centre of the cap
Stratum intermedium: lines the inside of the inner enamel epithelium
