OB D2- Tooth development 1

Question 1

what is histogenesis?

Answer 1

differentiation of undifferentiated cells to make new tissues

Question 2

what are mineralised dental tissues?

Answer 2

enamel, dentine and cementum

Question 3

what are unmineralised dental tissues?

Answer 3

dental pulp and periodontium

Question 4

what does the dental lamina contribute to?

Answer 4

the development of teeth

Question 5

what does the vestibular lamina contribute to?

Answer 5

the vestibule of the mouth, delineating the lips and

cheek from the teeth formation of sulcus

Question 6

what is the initation stage?

Answer 6

first stage of tooth development

Question 7

what is the bud stage?

Answer 7

second stage simple, spherical to ovoid, epithelial condensation poorly morphodifferentiated and histodifferentiated

Question 8

what is the cap stage ?

Answer 8

third stage of tooth development, in which the tooth

germ grows into cap shape

Question 9

what is the bell stage?

Answer 9

Fourth stage, in which differentiation occurs to furthest extent and starts to resemble a bell

Question 10

what is the crown stage?

Answer 10

Some text books count as a stage-some call it late bell stage-this is with fully developed tooth

Question 11

what is the external enamel epithelium?

Answer 11

outer layer of cuboidal cells that limits the enamel organ.

Question 12

what is the stellate reticulum?

Answer 12

of epithelial origin but behave like mesenchymal cells-synthesis of Collagen I, II and III

Question 13

what is stratum intermedium?

Answer 13

two or three layers of cells sitting above IEE. Express Alkaline Phosphatase like SR but not IEE

Question 14

what is the inner enamel epithelium?

Answer 14

Columnar shaped cells rich in RNA. Connected by desmosomes to each other

Question 15

what is the ectomesenchyme?

Answer 15

interesting group of cells whose origin is very controversial. Some think neural crest others mesodermal somites

Question 16

what occurs at 6 weeks?

Answer 16

condensation of ectomesenchyme

Question 17

Describe the formation of the sulcus.

Answer 17

-Primary epithelial band gives rise to:
◦ Dental Lamina
◦ Vestibular lamina
Vestibular lamina grows then and then breaks down to forms vestibule between teeth and lips/cheeks

Question 18

what are the 3 overlapping phases of tooth development?

Answer 18

• initiation
• morphogenesis
• histogenesis

Question 19

what is tooth development an interaction between?

Answer 19

epithelium and mesenchyme (ectomesenchyme)

Question 20

what does epithelium give rise to?

Answer 20

• enamel

- hyaline layer of the root

Question 21

what does mesenchyme give rise to?

Answer 21

• dentine
• pulp
• cementum
• periodontium (PDL and bone)

Question 22

when does initation of tooth development start?

Answer 22

6 weeks i.u

Question 23

what happens in initiation?

Answer 23

Localised epithelial thickening in incisor and molar regions

Question 24

which tissue initiates tooth development?

Answer 24

◦ Epithelium, ectomesenchyme or nerve?
◦ Evidence from tissue recombination experiments…..
◦ Epithelium initially has the odontogenic potential, then the ectomesenchyme

Question 25

In what circumstances will a tooth grow?

Answer 25

Dental epithelium + non-dental ecto-mesenchyme

Question 26

In what circumstance will a tooth not grow?

Answer 26

• dental epithelium + non-dental mesenchyme

- non-dental epithelium + dental ectoderm-mesenchyme

Question 27

what are the stages of the tooth germ?

Answer 27

• bud stage
• cap stage
• bell stage
• crown stage

Question 28

what happens to the dental lamina during stages of the tooth germ?

Answer 28

• continues to lengthen

- changes shape

Question 29

what happens to the ectomesenchymal during stages of the tooth germ?

Answer 29

condensation

Question 30

what is classification of the stages based on?

Answer 30

appearance

Question 31

what are the components of tooth germ?

Answer 31

• enamel organ
• dental papilla
• dental follicle

Question 32

what happens in the bud stage (8th week)?

Answer 32

• Spherical/ovoid epithelial condensation
• Cell proliferation
• No histodifferentiation or morphogenesis

Question 33

what happens in the cap stage (11th week)?

Answer 33

• Cap shaped enamel organ - Poorly histodifferentiated
• Little morphogenesis

Question 34

what happens in the early bell stage (14th week)?

Answer 34

Morpho- and histo-differentiation
Enamel Organ:
◦ Inner enamel epithelium 
◦ Stratum Intermedium
◦ Stellate reticulum
◦ Outer enamel epithelium
Ectomesenchyme: 
◦ Dental Papilla
◦ forms odontoblasts (dentine) and pulp 
◦ Dental Follicle
◦ forms cementum, PDL and bone

Question 35

what is inner enamel epithelium (enamel organ component)?

Answer 35

◦ Basal lamina conforms to future ADJ ◦ Columnar cells at cusp tips
◦ Role: forms ameloblasts -> enamel

Question 36

what is stratum intermedium (enamel organ component)?

Answer 36

◦ Flattened cells

◦ Role: Synthesis and transport to and from IEE

Question 37

what is stellate reticulum (enamel organ component)?

Answer 37

◦ Star shaped
◦ Fluid filled extracellular space
◦ Osmotic gradient due to extracellular GAGs.
◦ Role: maintenance of shape and protection

Question 38

what is outer enamel epithelium (enamel organ component)?

Answer 38

◦ Cuboidal cells

◦ Role: maintenance of shape and exchange

Question 39

what happens at bell stage (week 17)?

Answer 39

-Breakdown of dental lamina -> formation of cell rests, cell nest (cystic potential )

Question 40

What is the Extracellular matrix and what happens in development?

Answer 40

• Important in morphogenesis and differentiation.
• Adhesion, migration, proliferation, polarisation and differentiation.
• Expression of type I, III, IV collagens, laminin, various proteoglycans- basement membrane of developing tooth
• Changes in fibronectin, tenascin, type I and type III collagen and syndecan.
• Changes in integrin expression especially alpha v beta 5.
• Need intact basement membrane for differentiation of mesenchyme to odontoblast.