Tooth development Flashcards
Which tissues do facial neural crest cells not contribute to?
Tooth enamel
What is the oral cavity formed by?
The oral cavity is formed by the ectoderm of the stomatodeum (lips & gums) and by endoderm of pharynx (tongue and FOM), with the inner surface of gingivae as the dividing line. It is bounded by the fused maxillary & mandibular processes
What does each arch contain?
mesenchyme that is derived in part from neural crest and in part from mesoderm and the arches are covered with ectoderm
Name the stages of tooth development
- Initiation (dental lamina)
- Morphogenesis (bud, cap)
- Cell differentiation (bell)
- Matrix secretion (eruption)
What is initiation?
deciding where teeth will be formed and beginning the process
What happens at the 6th week of odontogenesis?
At the 6th week, the neural crest cells accumulate immediately below oral epithelium
These tooth germs are associated with a plexus of blood capillaries
The oral epithelium proliferates down into the neural crest cell layer and forms the primary epithelial band
What happens at the 7th week?
During the 7th week, the vestibular & dental laminae form
The vestibular lamina will become the oral vestibule and the dental lamina will form the teeth
Epithelial swellings appear – these are the enamel organs
From within the dental lamina, individual teeth are initiated, and this process can be seen, at least in mammals, by a gradual restriction of Shh and Pitx2 (pituitary homeobox 2) expression to the specific domains, referred to as placodes, that give rise to teeth. Moreover, ectopic recombinant Shh protein placed on dental epithelium in mouse embryos results in the formation of additional early tooth buds
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What is morphogenesis?
bud, cap & bell forms of developing tooth germ
What happens by the 10th week?
By the 10th week, there are 5 developing tooth germs in each quadrant.
These will form the deciduous teeth
What happens by the 16th week?
By the 16th week, the 1st permanent molar tooth germ is visible with the 2nd & 3rd permanent molar tooth germs appear long after birth
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What shape is the enamel organ in the bud stage?
simple spherical to ovoid epithelial ball
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- Enamel organ
- Mesenchymal condensation
What happens suring early cap stage and when does this occur?
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During the early cap stage, by the 11th week, the deeper surface forms a cap-like structure
- Stellate reticulum
- External enamel epithelium
- Internal enamel epithelium
- Dental Papilla
What does the external epithelium and stellate reticulum do in the Bell stages?
In the Bell stages, the external enamel epithelium maintains the shape of enamel organ and has a role in root formation
the stellate reticulum is involved in protection of tooth shape & nutrition of the enamel epithelium, the internal enamel epithelium is responsible for the induction of odontoblasts from the dental papilla
What happens in the bell stages?
n the dental papilla, small blood vessels start to invade preparatory to hard tissue genesis. The dental follicle forms between tooth germ and developing bony crypt. Cells rapidly multiply in internal enamel epithelium – except at enamel knot which is responsible for crown patterning
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What happens during differentiation?
cells become specialised and form enamel, dentine, etc. During the late bell stage, the dental hard tissue is formed by ameloblasts and odontoblasts
The enamel organs of the permanent teeth become visible. These will eventually form through the same processes as the deciduous teeth.
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