6-Development of the tooth

Question 1

Three main developmental layers

Answer 1

Ectoderm
Mesoderm
Endoderm

Question 2

Mesoderm develops into

Answer 2

• Connective tissue
• Muscle
• Mesothelium

Question 3

Ectoderm develops into

Answer 3

Epithelium

-CNS, PNS cells, Neural crest cells, surface ectoderm

Question 4

What dental tissues develop from neural crest cells?

Answer 4

neural crest cells==>Ectomesenchyme==>

• Dentin
• Cementum
• PDL
• Alveolar bone

Question 5

What dental tissues develop from ectoderm?

Answer 5

Epithelium/enamel

Question 6

Endoderm(epithelium) develops into

Answer 6

Gut tube and it derivatives

Question 7

Primary epithelial band

Answer 7

• day 37 of development
• proliferated epithelium at the site of future dental arches
• Split into dental and vestibular lamina

Question 8

vestibular lamina

Answer 8

Cells enlarge then degenerate to become the vestibule.

Question 9

Dental Lamina

Answer 9

• initial fold starting tooth development made of ectoderm(epithelium)
• develops 10 centers of proliferation

Question 10

Ectomesenchyme location in initial tooth developement

Answer 10

Right under the fold of the dental lamina

Question 11

3 main stages of tooth development and time of development

Answer 11

Bud stage(8-9 weeks)
Cap stage (10-11 weeks)
Bell stage(12-14 weeks)

Question 12

Enamel organ

Answer 12

• Epithelium ingrowth

- Enamel

Question 13

Dental papilla

Answer 13

Condensed ectomesenchyme

-Dentin

Question 14

Dental follicle/sac

Answer 14

Condensed ectomesenchyme surrounding enamel organ and the dental papilla
-cementum, PDL, and alveolar bone

Question 15

Dental organ or tooth germ

Answer 15

Enamel organ, dental papilla, and dental folicle

Question 16

Bud stage

Answer 16

• Tooth bud grow into the ectomesenchyme.
• Form the deciduous teeth
• cells only proliferate no change in function

Question 17

Cap stage

Answer 17

• The deep surface of the bud invaginates and becomes cap shaped.
• Peripheral cells become cuboidal and columnar
• matrix of enamel organ is increasing in amount of glycoaminoglycans
• Become hydrated and cells grow but maintain contact

Question 18

Bell stage regions

Answer 18

1) Outer enamel epithelium
2) Stellate reticulum
3) Stratum intermedium
4) inner dental epithelium

Question 19

Outer enamel epithelium

Answer 19

thick basement membrane separates it from ectomesnchyme

Question 20

Stellate reticulum

Answer 20

mechanical role(protects dental tissue and produces signaling molecules)

Question 21

Stratum intermedium

Answer 21

Flatened cells overlying inner dental epithelium.

-produces and transports proteins ti the inner dental epithelium

Question 22

Inner dental epithelium

Answer 22

-Columnar shaped cells elongate prior to producing enamel then change polarity to secrete adjacent to the basement membrane

Question 23

Cervical loop

Answer 23

• Inner and outer enamel epithelium meet here

- Gives rise to the epithelium that will signal root development

Question 24

early bell stage development

Answer 24

Dental and lateral lamina begin to degenerate

• Developing tooth loses connection to oral cavity
• the tooth cron assumes it final shape

Question 25

Vasularization of tooth developemtn

Answer 25

• Enamel organ/stellate reticulum avascular

- Dental sac/follicle well vascularized

Question 26

Ameloblast origin

Answer 26

Inner dental epithelium develop into ameloblasts

Question 27

Odontoblasts origin

Answer 27

Outer dental papillae develop into odontoblasts

Question 28

What is starts to work first(ameloblasts or odontoblasts)

Answer 28

Odontoblasts

-amelo- and odontoblasts signal each other to develop normally

Question 29

Inner enamel epithelium(late cap stage)

Answer 29

Mitotic activity will cease when dentin starts being produced
-Some ectomesenchyme cells can become odontoblasts due to pre-ameloblast

Question 30

Dentin formation

Answer 30

Pre ameloblast signal cells of the dental papilla into odontoblasts

• Odontoblasts secrete predentin that cacifies into dentin in ~ 1 day
• As calcification occurs the odontoblasts move towards the papilla

Question 31

Odontoblasts

Answer 31

-Have long processes that span the dentin forming dentinal tubules/canaliculi

Question 32

Dentin sensitivity theories

Answer 32

1) Nerve runs with the odontoblast processes
2) odontoblast act as a receptor
3) fluid movement stimulates receptors in the pulp

Question 33

mineralization of enamel

Answer 33

• produced when ameloblasts touched by dentin

- Mineralizes almost immediately

Question 34

Where do ameloblasts get nourishment?

Answer 34

Blood vessels in dental papilla and surrounding the enamel organ
Stellate reticulum collapses and brings peripheral blood vessels closer to active site of ameloblasts

Question 35

Where does development start and continue?

Answer 35

Ameloblast and odontoblast produce their respective secretions ameloblast moivng outward odontoblasts move inward creating DEJ

Question 36

What happens to ameloblasts after they finish enamel production?

Answer 36

they form the reduced dental epithelium with stratum intermedium, stellate reticulum and outer enamel epithelium

Question 37

Dental follicle

Answer 37

develop supporting tissue of the tooth like cementoblast (create cementum), PDL

Question 38

PDL(Periodontal ligament)

Answer 38

• derived from dental follicle
• located between alveolar bone and cementum
• CT w/ type I collagen

Question 39

Tooth eruption

Answer 39

Bone overlying the tooth is resorbed, CT over the tooth breaks down in advance.
Reduced enamel epithelium and oral epithelium fuse
-central epithelial cells degenerate
-Dentinogingival junction formed