Tooth Development 1

Question 1

What’s the very first thing developed in the oral cavity at wk 6?

Answer 1

• primary epithelial band thickens (2 arch shaped bands)

Question 2

What occurs at wk 7 (after epithelial bands are formed)?

Answer 2

• formation of dental lamina via thickening of primary epithelial band into the underlying ectomesenchymal cells

Question 3

What’s the induction effect on cells?

Answer 3

• the effect one cell has on another
• signalling molecules bind to receptors -> cascade

Question 4

What occurs at wk 8 (Bud stage)?
- what does tooth germ look like?
- any histo/morphodifferentiation occurred?

Answer 4

• ‘bulge’
• no morpho/histo
• proliferation of epithelial cells into underlying ecotmesenchyme
• ecotmesenchyme condensing around tooth bud

Question 5

What occurs at wk 10-12, cap stage?
- What shape?
- any morpho/histodifferentiation?

Answer 5

• ‘cap’ shape
• no morpho
• early histo (IEE, OEE, Stellate reticulum)
• condensation of ectomesenchymal cells = dental papilla + follicle)

Question 6

What occurs in wk 14, early bell stage?
- what’s the shape?
- any morpho/histodifferentiation?

Answer 6

• morpho-> shape of crown visible
• histo -> IEE cells become columnar
  -> peripheral cells of papilla -> odontoblasts
• dental follicle encloses papilla that isn’t already enclosed by enamel organ

Question 7

What occurs at wk 18, late bell stage (after dental follicle formation)?
-what processes occur?
-any morpho/histodifferentiation?

Answer 7

-morpho of crown complete
-histo = pre-ameloblast differentiation from IEE
= odontoblasts -> columnar cells on periphery of dental papilla
-Dentinogenesis
-Amelogenesis

Question 8

When does amelogenesis occur in relation to Dentinogenesis?

Answer 8

Simultaneously (but dentine matrix is secreted slightly before)

Question 9

What happens to enamel after amelogenesis?

Answer 9

• Layers of enamel organ are compressed
• REE
• REE fuses with epithelium of oral cavity
• break down of oral dental lamina

Question 10

Describe the steps in root development following crown formation.

Answer 10

1. IEE + OEE loop & form double layered epithelial root sheath at cervical loop (HERS)
2. Double layered root sheath (HERS) encloses dental papilla and outlines root shape
3. Maintains the same length at all times
   
   • grows apically
   • stimulates root formation
   • fragments
   • repeats

Question 11

What does the dental follicle form?

Answer 11

Cementum
PDL
Alveolar bone

Question 12

What occurs after REE forms?

Answer 12

Fuses with oral epithelium
Break down of dental lamina
Rests of Serres