Dental development

Question 1

what are the 3 primary embryonic layers that all body tissues develop from?

Answer 1

ectoderm
mesoderm
endoderm

Question 2

what of the 3 embryonic layers does tooth enamel derive from?

Answer 2

ectoderm

Question 3

what do teeth develop from?

Answer 3

tooth germs

Question 4

what is ectomesenchyme?

Answer 4

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

Question 5

what do all parts of teeth and supporting structures except enamel derive from?

Answer 5

ectomesenchyme

Question 6

what is the neural crest/ectomesenchyme?

Answer 6

a 4th cell type that forms between the ectoderm and neural tube

Question 7

what is mandibulofacial dysostosis?

Answer 7

failure of ectomesenchymal cells to migrate
increased pupillary distance
ears malformed and lower position

Question 8

what is involved in tooth initiation?

Answer 8

primary epithelial band

dental lamina

Question 9

how does tooth initiation begin in a 5-6 w/o embryo?

Answer 9

2 mandibular process come together
stomadaeum-embryonic mouth
2 maxillary process seam with fronto-nasal process

Question 10

what is a primary epithelial band?

Answer 10

change in epithelium
approx 6 weeks
thickening in epithelium of embryonic mouth

Question 11

how does epithelium -> band -> dental lamina

Answer 11

period of cell proliferation

Question 12

describe the dental lamina?

Answer 12

approx 7 wks
PEB grown into jaw and divided by apoptosis
vestibular lamina breaks down to form buccal sulcus
dental lamina goes on to develop enamel organ

Question 13

what are the components of morphogenesis?

Answer 13

bud
cap
of enamel organ

Question 14

describe the bud stage

Answer 14

8-10 wks
lamina thickens into a bud stage enamel organ
ectomesenchymal condensation appears - later aggregated to form dental papilla

Question 15

describe the cap stage

Answer 15

11 wks
enamel organ forms cap over papilla
cap contains:
external enamel epithelium
internal enamel epithelium
-meet at cervical loop

Question 16

what is hypohidrotic ectodermal dysplasia?

Answer 16

absence of some teeth

Question 17

what is severe hypohidrotic ectodermal dysplasia?

Answer 17

absence of hair and teeth

Question 18

how can a genetic disorder be reversed?

Answer 18

gene therapy

Question 19

what is included in cytodifferentiation?

Answer 19

cells function differentiates
-ameloblast/odontoblast
bell stage
crown pattern formation
permanent tooth germ

Question 20

describe the bell stage

Answer 20

14 wks
bell stage enamel organ
tooth has shape and form
more cell layers differentiated
tooth shape is being defined

Question 21

what are the 4 cell layers in bell stage?

Answer 21

internal enamel epithelium
external enamel epithelium
stratum intermedium
-shape of tooth
stellate reticulum
-organised to hold energy material - sugars necessary to work & develop enamel matrix

Question 22

describe the crown pattern formation

Answer 22

differentiation doesn’t occur all over enamel wall
apical differentiation begins and trickles down cervically
matrix follows differentiation

Question 23

describe the permanent tooth germ

Answer 23

12 wks
extension appears on lingual side of dental lamina
dental lamina for permanent successor
at 16 wks 1st permanent molar germ develops as a backwards extension of dental lamina

Question 24

what is included in matrix secretion?

Answer 24

late bell stage
dentinogenesis
enamel formation
ameloblast differentiation
amelogenesis

Question 25

describe the late bell stage

Answer 25

18 wks crown shape well defined apposition of enamel and dentine begins

Question 26

how is enamel and dentine formed?

Answer 26

dental papilla cells adjacent to IEE differentiate into odontoblasts odontoblasts lay down dentine matrix, which is later mineralised once dentine formation has begun, IEE cells differentiate into ameloblasts which form enamel

Question 27

describe dentinogenesis

Answer 27

odontoblast differentiation from IEE deposition of dentine matrix (mainly collagen) this unmineralised dentine=predentine mineralisation of dentine (HA)

Question 28

describe enamel formation

Answer 28

protein matrix deposited (30%) mineralised | once framework established, organic part removed and mineralisation is complete (96%)

Question 29

what are the stages of ameloblast differentiation?

Answer 29

``` differentiation secretion maturation regression -later becomes junctional epithelium ```

Question 30

what are the stages of ameloblast differentiation?

Answer 30

1. mophogenic 2. histodifferentiation 3. secretory-initial 4. secretory- tomes process 5. maturative- ruffle ended 6. maturative- smooth 7. protective

Question 31

describe ameloblast differentiation

Answer 31

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

Question 32

describe the secretory phase of amelogenesis

Answer 32

ameloblasts become secretory cells synthesise and secrete enamel matrix proteins (amelogenins) matrix partially mineralised (30%)

Question 33

describe the maturation phase of amelogenesis?

Answer 33

most of matrix proteins removed mineral content of enamel increased mature enamel 95% mineral

Question 34

describe the protection phase of amelogenesis

Answer 34

ameloblasts regress to form a protective layer- reduced enamel epithelium involved in eruption formation of epithelial attachment

Question 35

what is amelogenesis imperfecta?

Answer 35

autosomal recessive hypoplastic hypomaturation amelogenesis imperfecta matrix metallopeptidase 20 gene long arm or chromosome 11 provides instructions for making enamelysin enamelysis cleaves other proteins into smaller pieces enamel dull not shiny/smooth low mineralisation

Question 36

how does root formation shape the crown?

Answer 36

enamel organ maps out shape of crown EEE & IEE meet at cervical loop migration of the cervical loop maps crown shape

Question 37

what is hertwig's epithelial root sheath?

Answer 37

2 cell layered structure used to be cervical loop defines root shape by apical growth

Question 38

describe the process of root formation

Answer 38

HERS induces formation of root dentine once initial layer dentine formed, HERS breaks up -no enamel in root debris of malassez remain which may develop into a cyst mesenchymal cells from the follicle contract the dentine, and differentiate into cementoblasts -form cementum fibres from developing PDL embedded in cementum (sharpey's)

Question 39

what does the dental follicle surround? (tooth germ)

Answer 39

enamel organ | dental papilla

Question 40

what can developmental abnormalities affect?

Answer 40

``` number shape size structure eruption ```

Question 41

when can developmental abnormalities occur?

Answer 41

prenatal postnatal inherited acquired

Question 42

what is gemination?

Answer 42

one tooth splits into 2

Question 43

what is fusion?

Answer 43

2 teeth fuse during development

Question 44

what is concrescence?

Answer 44

teeth together by cementum

Question 45

what type of tissue is enamel organ?

Answer 45

epithelium

Question 46

what type of tissue is dental papilla and follicle?

Answer 46

ectomesencyme

Question 47

what is the product of enamel organ?

Answer 47

enamel

Question 48

what are the products of dental papilla?

Answer 48

dentine, pulp

Question 49

what are the products of dental follicle?

Answer 49

cementum, PDL, alveolar bone