Tooth Development

Question 1

what are the 3 primary embryonic layers?

Answer 1

ectoderm, mesoderm and endoderm

Question 2

what is tooth enamel derived from?

Answer 2

ectoderm

Question 3

what are all tooth structures apart from the enamel derived from?

Answer 3

ectomesenchyme

Question 4

what is the ectomesenchyme?

Answer 4

part of the neural crest that develops beside the primitive nervous system (ectoderm)

Question 5

what do teeth develop from?

Answer 5

tooth germs

Question 6

what is another name for the neural crest?

Answer 6

ectomesenchyme

Question 7

what is developed in the intiation stage?

Answer 7

dental lamina

Question 8

what are the 5 different stages of tooth development?

Answer 8

initiation, morphogenesis, cytodifferentiation, matrix secretion, root formation

Question 9

name in order of first to last the parts of tooth that are developed

Answer 9

dental lamina - bud - cap - bell - erupting tooth - bone

Question 10

when does the primary epithelial band develop?

Answer 10

approximately 6 weeks

Question 11

what does the primary epithelial band appear as?

Answer 11

thickening in epithelium of embryonic mouth (stomodaeum)

Question 12

when does the dental lamina develop?

Answer 12

approximately 7 weeks

Question 13

what does the primary epithelial band divide into?

Answer 13

vestibular lamina and dental lamina

Question 14

what does the vestibular lamina form?

Answer 14

buccal sulcus

Question 15

what does the dental lamina form?

Answer 15

enamel organ

Question 16

what develops at the morphogenesis stage?

Answer 16

bud and cap

Question 17

when does the enamel bud develop?

Answer 17

8-10 weeks

Question 18

what happens during the bud stage?

Answer 18

dental lamina thickens into an enamel bud and the dental papilla appears

Question 19

when does the enamel cap develop?

Answer 19

11 weeks

Question 20

what happens during the cap stage?

Answer 20

enamel organ forms a cap over the papilla and the external enamel epithelium and internal enamel epithelium meet at the cervical loop

Question 21

what develops during cytodifferentation?

Answer 21

bell

Question 22

when does the bell develop?

Answer 22

14 weeks

Question 23

what happens during the bell stage?

Answer 23

there are more cell layers differentiated and tooth shape is being define?

Question 24

what are the 4 layers of enamel organ at the bell stage?

Answer 24

internal enamel epithelium, stratum intermedium, external enamel epithelium and stellate reticulum

Question 25

what happens at 12 weeks?

Answer 25

an extension appears on the lingual side of the dental lamina - this is the dental lamina of the permanent tooth

Question 26

what develops during matrix secretion?

Answer 26

the eruption of the tooth

Question 27

when does the late bell stage take place?

Answer 27

18 weeks

Question 28

what does the late bell stage look like?

Answer 28

crown shape is well defined, apposition of enamel and dentine begins

Question 29

what develops into odontoblasts?

Answer 29

dental papilla cells adjacent to the IEE

Question 30

what do odontoblasts do?

Answer 30

lay down dentine matrix

Question 31

what forms enamel?

Answer 31

ameloblasts

Question 32

what happens during dentinogenesis?

Answer 32

odontoblast differentiation from IEE, deposition of dentine matrix, mineralisation of dentine

Question 33

what is unmineralised dentine called?

Answer 33

predentine

Question 34

how is enamel formed?

Answer 34

first the protein matrix is deposited (partially mineralised) and then the organic part is removed and mineralisation is completed (maturation)

Question 35

what happens during ameloblast differentiation?

Answer 35

dentine induces IEE cells to differentiate into ameloblasts which elongate becoming columnar and the nucleus migrates to the basal end of the cell

Question 36

what happens during the secretory phase of amelogenesis

Answer 36

ameloblasts become secretory cells which synthesise and secrete the enamel matrix proteins. the matrix is then partially mineralised

Question 37

what happens during the maturation phase of amelogenesis?

Answer 37

most of the matrix proteins are removed, mineral content of enamel is increased, mature enamel is 95% mineral

Question 38

what happens during the protection phase of amelogenesis?

Answer 38

ameloblasts regress to form a protective layer - the reduced enamel epithelium. Eruption takes place and formation of epithelial attachment

Question 39

what is root shape define by?

Answer 39

the apical growth of the cervical loop

Question 40

when in root formation what is the cervical loop now called

Answer 40

Hertwig's epithelial root sheath

Question 41

what is hertwig's epithelial root sheath?

Answer 41

2-cell-layered structure

Question 42

what does HERS induce?

Answer 42

formation of root dentine

Question 43

what happens once the initial layer of root dentine is formed?

Answer 43

HERS breaks up

Question 44

what do the remnants of HERS appear as once they are broken up?

Answer 44

debris of malassez which may develop into a cyst

Question 45

what differentiates into cementoblasts?

Answer 45

mesenchymal cells from the follicle

Question 46

what do cementoblasts form?

Answer 46

cementum

Question 47

what are Sharpey's fibres?

Answer 47

fibres from the developing PDL

Question 48

name the type of tissue, origin and products of the enamel organ?

Answer 48

epithelium, ectoderm, enamel

Question 49

name the type of tissue, origin and products of the dental papilla?

Answer 49

ectomesenchyme, neural crest, dentine and pulp

Question 50

name the type of tissue, origin and products of the dental follicle?

Answer 50

ectomesenchyme, neural crest, cementum and PDL and part of the alveolar bone

Question 51

what is hypodontia?

Answer 51

less teeth than you're supposed to have

Question 52

what is supernumerary?

Answer 52

an extra tooth