Tooth development

Question 1

Which tissues do facial neural crest cells not contribute to?

Answer 1

Tooth enamel

Question 2

What is the oral cavity formed by?

Answer 2

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

Question 3

What does each arch contain?

Answer 3

mesenchyme that is derived in part from neural crest and in part from mesoderm and the arches are covered with ectoderm

Question 4

Name the stages of tooth development

Answer 4

1. Initiation (dental lamina)
2. Morphogenesis (bud, cap)
3. Cell differentiation (bell)
4. Matrix secretion (eruption)

Question 5

What is initiation?

Answer 5

deciding where teeth will be formed and beginning the process

Question 6

What happens at the 6th week of odontogenesis?

Answer 6

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

Question 7

What happens at the 7th week?

Answer 7

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

Question 8

Label this image:

Answer 8

Question 9

What is morphogenesis?

Answer 9

bud, cap & bell forms of developing tooth germ

Question 10

What happens by the 10th week?

Answer 10

By the 10th week, there are 5 developing tooth germs in each quadrant.

These will form the deciduous teeth

Question 11

What happens by the 16th week?

Answer 11

By the 16th week, the 1st permanent molar tooth germ is visible with the 2nd & 3rd permanent molar tooth germs appear long after birth

Question 12

Label this image

Answer 12

Question 13

What shape is the enamel organ in the bud stage?

Answer 13

simple spherical to ovoid epithelial ball

Question 14

Label this image

Answer 14

1. Enamel organ
2. Mesenchymal condensation

Question 15

What happens suring early cap stage and when does this occur?

Label the following image

Answer 15

During the early cap stage, by the 11th week, the deeper surface forms a cap-like structure

1. Stellate reticulum
2. External enamel epithelium
3. Internal enamel epithelium
4. Dental Papilla

Question 16

What does the external epithelium and stellate reticulum do in the Bell stages?

Answer 16

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

Question 17

What happens in the bell stages?

Answer 17

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

Question 18

Label this image

Answer 18

Question 19

What happens during differentiation?

Answer 19

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.

Question 20

Label this image

Answer 20