Early Odontogenesis

Question 1

What are the first histological signs of tooth development?

Answer 1

Neural crest cells migrate into the jaws and start inducing thickening of oral epithelium

Question 2

Explain the over, general process of early odontogenesis.

Answer 2

1. Thickening of oral epithelium & invagination into mesenchyme –> Primary epithelial band [6 weeks]
2. Primary epithelial band divides into vestibular lamina (buccal) and dental lamina (lingual) [7 weeks]
3. Dental lamina elongates and swellings develop on deep surface –> tooth bud [8 weeks]
4. Bud Stage: emergence of enamel organs
5. Cap Stage: Morphogenesis of enamel organ and emergence of, dental papilla, and successional lamina (dental lamina)
6. Early Bell stage: histodifferentiation - ameloblasts and odontoblasts
   external enamel epithelium, stellate reticulum, stratum intermedium and internal enamel epithelium formation

Late Bell stage: Distengration of dental lamina, hard tissue formation, reduction in stellate reticulum, cervial loop formation.

Question 3

Mutation A causes a deleterious, but non-fatal mutation in the formation of vestibular lamina during odontogenesis.

When examining the patients teeth; what irregularities would you see?

Answer 3

None because dental lamina contributes to tooth-bearing regions only.

Vestibular lamina forms the vestibule of the mouth.

Question 4

What stage is this tooth in?

Answer 4

Late bell stage

Question 5

What stage is this tooth in?

Answer 5

Bud stage

Question 6

What stage is this tooth in?

Answer 6

Cap stage

Question 7

What are the 3 transitory structures of odontogenesis?

Answer 7

Enamel knot, Enamel Niche, Enamel Cord

Question 8

Where is the enamel knot seen? What is it?

Answer 8

bud stage; localized clusters of non-proliferating cells from the centre of the enamel organ

Apotosis at end of cap stage

Question 9

What’s the significance of the enamel knot?

Answer 9

Secondary knots in posterior teeth (premolars and molars) = sites of future cusps

Signaling centre

Question 10

What are enamel niches? What is it’s signficance?

Answer 10

Area where tooth germ has double attachment to dental lamina ; concavity with connective tissue

Question 11

What are enamel cords? What’s it’s signficance?

Answer 11

seen at early bell stage; overlies incisal margin or apex of the first cusp

function as a mechanical tie for tranforming cap stage to bell stage

Question 12

What structures are aetiological factors in cyst formation?

Answer 12

Epithelial rests of Serres (disintegrated dental lamina remnants)

Question 13

Function of stellate reticulum? Which stage do you see it in?

Answer 13

Early bell stage

Mechanical protection of underlying dental tissues

Question 14

What is the difference of functionality of external and internal enamel epithelium during the early bell stage?

Answer 14

Inner enamel epithelium are short columnar cells that differentiate into ameloblasts

External enamel epithelium are cuboidal cells that maintains shape and exchange substances

Question 15

What is the function of the stratum intermedium? (early bell stage)

Answer 15

Synthesize proteins and transport mateirals into the inner enamel epithelium

Question 16

How does odontogenesis initiate?

Answer 16

1) Odontogenic potential exists intially in the first pharyngel arch (mandibular arch)

2) Odontogenic potential is transferred to ectomesenchyme

3) Dental papilla maintains odontogenic potential

Question 17

We’re in year 2080 and Zhu Corporation has unlimited funds. Explain how you would make a chicken grow teeth successfully. You don’t need to specifically explain the methodology but explain what needs to change and why.

Answer 17

Replace chick neural crest cells with mouse neural crest cells. This is to induce the latent odontogenic potential of chick epithelial/mesenchyme tissues.

Repair or insert genes that are related to production of enamel matrix; as chick genomes are missing these genes

Question 18

Which stage does the enamel organ detach from the oral epithelium?

Answer 18

Late bell stage

Question 19

Explain the process of reciprocal induction starting from pre-ameloblast from the internal enamel epithelium?

Answer 19

IEE –> pre-ameloblast

Pre-ameloblast needs to stimulate neuromesenchymal stem cells, which stimulat odontoblasts, causing formation of predentine.

Pre-dentine stimulates pre-ameloblast again

Double stimulation causes ameloblast formation and subsequent pre-enamel

Question 20

A patient with missing teeth comes into a clinic. The patient has no history of losing teeth due to external forces. What can you diagnose this patient with given that you know there is some family lineage history with embryological defects.

Answer 20

Ectodermal Dysplasia