Dental Development

Question 1

all body tissue develop from 3 primary embryonic layers

Answer 1

ectoderm, mesoderm, endoderm

Question 2

tooth enamel is derived from

Answer 2

ectoderm

Question 3

tooth structure other than enamel derived from

Answer 3

ectomesenchyme

Question 4

teeth develop from

Answer 4

tooth germs

Question 5

ectomesenchyme

Answer 5

part of neural crest that develops beside primitive nervous system

Question 6

neural crest

Answer 6

forms between ectoderm and neural tube, collection of stem cells
also called ectomesenchyme
migrates into developing face and jaw

Question 7

mandibulofacial dysostosis

Answer 7

failure of ectomesenchyme cells to migrate
distance between interpupillary is greater, ear position is low amd malformation, smaller mandible, crowding of mouth

Question 8

tooth initiation stages

Answer 8

1. initiation
2. morphogenesis
3. cytodifferentiation
4. matrix secretion
5. dentine and enamel formation
6. root formation

Question 9

initiation stage

Answer 9

process forming face, mandibular process joins together to form mandible
frontal nasial process and maxillary process sync together to from maxilla
primary epithelial band is formed

Question 10

primary epithelial band

Answer 10

develops 6weeks i.u.l
appears as thickening in epithelium of embryonic mouth
oral epithelium is thickening forming epithelial badnand then forms dental lamina

Question 11

dentinal lamina

Answer 11

approx 7 weeks i.u.l
PEB grown into jaw and divided into 2 parts
- vestibular lamina = breaks down to buccal sulcus
- dental lamina = enamel organ develops from

horse shoe structure, thickness of regions called tooth germs

Question 12

morphogenesis

Answer 12

after dental lamina - beginning of shape and structure
2 stages - bud and cap

Question 13

bud stage

Answer 13

enamel organ
8-10i.u.l
dental lamina thickens into bud stage enamel organ
ectomesenchymal appears around bud = dental papilla

Question 14

bud to cap stage

Answer 14

rearrangemet of shape, becomes like a cap, enamel organ associated with ectomesenchyme cells

Question 15

cap stage

Answer 15

11weeks i.u.l
enamel forms cap over papilla
- internal enamel epithelium
- external enamel epithelium
IEE AND EEE meet and cervical loop

Question 16

placodes

Answer 16

different way bud stage forms

Question 17

ectodermal dysplasia

Answer 17

affects embryonic structures gives rise to har follicles, teeth, nails
syndrome
all derived from same, not teeth but others as well

Question 18

hypohidrotic ectodermal dysplasia

Answer 18

absence/hypodontia of a number of teeth
severe - absence of teeth and hair, both affected due to dental placodes in same process
gene therapy

Question 19

cytodifferentiation

Answer 19

shape of the tooth is formed, cells start to function differenly, differentiating into ameloblasts and odontoblasts

Question 20

cytodifferentiation bell stage

Answer 20

14weeks i.u.l
tooth has shape/form, matrix produced to generate tooth structures,shape being defined
4 layers of enamel
- stratum intermedium
- stellate reticulum
- IEE
- EEE

Question 21

stellate reticulum

Answer 21

formed un bell stage
filled with glycogen providing ameloblasts for energy and produce matrix
odontoblasts forming dentine take energy fom dental papilla

Question 22

direction of differentiation

Answer 22

DOWNWARDS
starts apically, continues down towards cervical loop

Question 23

permanent tooth germ

Answer 23

as deciduous being formed, permanent start to be organised
12weeks, extension of lingual side of dental lamina, forms permanent teeth
16weeks, 1st perm molar tooth germ develops

Question 24

matrix secretion

Answer 24

after differentiation, organisation of enamel and dentine occurs

Question 25

late bell stage matrix secretion

Answer 25

18weeks i.u.l production of enamel and dentine crown shape well defined, apposition enamel/dentine

Question 26

dentine and enamel formation

Answer 26

dental papilla adjacent to IEE differentiate into odontoblasts odontoblasts lay down dentine, later mineralised once detine formatio begun, IEE differentiates into ameloblasts which form enamel

Question 27

dentinogenesis

Answer 27

odontoblasts from IEE, deposition of dentine matrix unmineralised - predentine, mineralised by hydroxyapatite stem cells dufferentiate into odontoblasts and tertiary dentine

Question 28

enamel formation

Answer 28

highly mineralised 96% 2 stages - protein matrix deposited, partially mineralised 30% - once framework established, organic part removed and mineralisation complete [MATURATION] ameloblasts change form and function several during amelogenesis

Question 29

amelogenesis phases

Answer 29

1. morphogenic 2. histodifferentiation 3. secretory initial 4. secretory tomes process 5. maturation ruffl ended 6. maturative smooth 7. protective

Question 30

amelogenesis differentiation

Answer 30

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

Question 31

secretory amelogenesis

Answer 31

ameloblasts become secretory cells, synthesis and secrete enamel matrix proteins, partially mineralised

Question 32

maturation amelogenesis

Answer 32

most matrix proteins removed, mineral content of enamel is increased to 95%

Question 33

protection amelogenesis

Answer 33

ameloblasts regress to from protective layer, reduced enamel epithelium, involved in eruption, formation of epithelial attachment

Question 34

amelogenesis imperfecta

Answer 34

autosomal recessive hypoplastic hypomaturation dull namel, lower mineralisation, easy caries, frail, breaks easy

Question 35

dentinogenesis imperfecta

Answer 35

dentine not developed or mineralised to the level it should be, no base for enamel so clean break, tooth wear, very damaging cant see pulp, no pulp chamber, dentine low mineralisation so cannot differentiate from pulpal tissue

Question 36

root formation

Answer 36

crown formation complete before root formation begins shape, arrangement and cervical loop must be present first

Question 37

how is the root formed

Answer 37

enamel organ maps shape of crown, EEE IEE meet at cervical loop, moving downwards root shape defined by apical growth of cervical loop, now called Hertwig's epithelial root sheath [HERS] 2 cell layer structure

Question 38

HERS

Answer 38

root dentine formation induced by odontoblasts once initial layer of root dentine formed, HERS breaks up remaining stays as debris of Malassez, could form cyst mesenchymal cells from follicle contact dentine, differentiate into cementoblasts whcih form cementum fibres from PDL in cementum = sharpeys fibres

Question 39

enamel organ info

Answer 39

tissue - epithelium origin - ectoderm products - enamel

Question 40

dental papilla info

Answer 40

tissue - ectomesenchyme origin - neural crest products - dentine, pulp

Question 41

dental follicle info

Answer 41

tissue - ectomesenchyme origin - neural crest products - cementum, PDL, alveolar bone