Dental Development

Question 1

What are the 3 primary ebryonic layers

Answer 1

Ectoderm​

Mesoderm​

Endoderm

Question 2

What is enamel derived from

Answer 2

Ectoderm

Question 3

What is derived from ectomesenchyme

Answer 3

All parts of the teeth aside from enamel

Question 4

What do teeth develop from

Answer 4

Tooth germs

Question 5

What forms between the ectoderm and the neural tube

Answer 5

Ectomesenchyme

Question 6

What does failed migration of the ectomesenchymal cells cause

Answer 6

Malformation of facail structures and jaw

Question 7

What are the names of the stages in tooth development

Answer 7

Dental lamina
Bud
Cap
Bell
Erupting tooth
Erupted tooth

Question 8

When does the primary epithelial band develop

Answer 8

Approx 6 weeks IUL

Question 9

How does the primary epithelial band appear histologically

Answer 9

Appears as thickening in epithelium of embryonic mouth (stomodaeum)

Question 10

What are brachial archs

Answer 10

Migration of the neural crest tissue to form face and jaw

Question 11

When is the dental lamina formed

Answer 11

approx 7 weeks IUL

Question 12

What are the steps of organ formation

Answer 12

Initiation
Marphogenesis
Cytodifferentiation
Matrix secretion

Question 13

What 2 parts does the PEB split into

Answer 13

Vestibular lamina (forms buccal sulcus)
Dental lamina (forms enamel organs)

Question 14

What process separates the primary epithelial band

Answer 14

Apoptosis

Question 15

What is the first stage of morphogenisis

Answer 15

‘bud’ stage

Question 16

When does the bud stage occur

Answer 16

8-10 weeks IUL

Question 17

What cells make up the cap and the dental papilla

Answer 17

Bud/Cap composed of ectoderm cells
Dental papilla is made of ectomesenchymal cells

Question 18

What happens in the cap stage

Answer 18

The enamel organ forms a cap over the dental papilla forming internal enamel epithelium and internal enamel epithelium (beside dental papilla)

Question 19

What is the cervical loop

Answer 19

Where the internal and external enamel epithelium meet

Question 20

What other features are formed similarly to teeth

Answer 20

Hair follicles
Mammary glands
Nails

Hence why disorders usually affect multiple of these aspects

Question 21

What are the main points of the bell stage

Answer 21

Tooth takes shape
Cells differentiate into ameloblasts and odontoblasts

Question 22

What are the 4 cell layers present at the bell stage

Answer 22

Stratum intermedium
Stellate reticulum
Internal enamel epithelium
Externaml enamel epithelium

Question 23

Where does process of differentiation occur first within the crown

Answer 23

At apex of tooth and works its way down to cervical loop, enamel is formed first at apex/tips of teeth

Question 24

When do permanent tooth germs form

Answer 24

approx 12th week

Question 25

When does enamel formation begin

Answer 25

Once dentine formation is established within the Late Bell stage

Question 26

What cells are differentiated first

Answer 26

The Dental papilla cells adjacent to the IEE differentiate into odontoblasts first Once the dentine matrix formation has begun IEE cells differentiate into ameloblasts, which form enamel

Question 27

What cells differentiate into ameloblasts

Answer 27

IEE cells

Question 28

What are the two stages of enamel formation

Answer 28

1. Protein matrix deposited​ Matrix is partially mineralised (30%)​ 2. Once this framework is established, the organic part is removed,and mineralisation is completed (‘maturation’)

Question 29

What are the stages of ameloblast differentiation

Answer 29

Morphogenic​ Histodifferentiation​ Secretory (initial)​ Secretory (tomes process)​ Maturative (ruffle-ended)​ Maturative(smooth)​ Protective

Question 30

What happens to ameloblasts during differentialtion step 1

Answer 30

They elongate, becoming columnar​ The nucleus migrates to the basal end of the cell

Question 31

What happens to ameloblasts during secretory phase

Answer 31

Ameloblasts become secretory cells​ They synthesise and secrete the enamel matrix proteins (amelogenins)​ The matrix is partially mineralised (30% mineral as seeded crystallites)

Question 32

What occurs during maturation phase

Answer 32

Most of the matrix proteins are removed​ Mineral content of enamel is increased​ Mature enamel is 95% mineral

Question 33

What is the reduced enamel epithelium

Answer 33

Regressed ameloblasts protective layer involved in eruption and eventually forms epithelial attachment

Question 34

What type of disorder is amelogenesis imperfecta

Answer 34

Autosomal recessive

Question 35

What are the impacts of amelogenesis imperfecta

Answer 35

Enamel fails to develop properly leading to small yellow or brown teeth which are prone to damage and fracture

Question 36

What is dentinogenesis imperfecta

Answer 36

Disorder in which dentine is not fully mineralised Enamel is easily fractured due to inadequate support from malformed dentine

Question 37

What defines root shape

Answer 37

Cervical loop

Question 38

What does the cervical loop be called once root formation begins

Answer 38

Hertwig's epithelial root sheath

Question 39

When does the HERS break up

Answer 39

Once the initial layer of root dentine is formed

Question 40

What is remaining HERS called

Answer 40

Debris of malassez (may develop into cysts)

Question 41

Why are the cysts caused by remaining HERS called odontogenic cysts

Answer 41

As the cells which form the cysts are associated with the formation of odontoblasts

Question 42

What does the dental follicle form

Answer 42

Cementum, PDL and part of alveolar bone

Question 43

What does the enamel organ form

Answer 43

Enamel

Question 44

What does the dental papilla form

Answer 44

Dentine, pulp

Question 45

What is an example of an aquired enamel defect

Answer 45

Infection - measels Affect development of enamel

Question 46

What is gemination

Answer 46

When a tooth has broken into two and is fused together

Question 47

What does the stellate retoculum store

Answer 47

Glycaogen/energy