Tooth Development

Question 1

what are the 3 embryonic layers

Answer 1

ectoderm
mesoderm
endoderm
(ectomesencyme / neural crest)

Question 2

what embryonic layer are tooth structures formed from

Answer 2

enamel = ectoderm

pulp , dentine , cementum etc = ectomesenchyme

Question 3

mandibulofacial dystosis

Answer 3

failure of neural crest cells to migrate
sees deformities of ears, eyes , cheekbones and chin
also known as treacher collins syndrome

Question 4

at what age does the primary epithelial band develop and divide

Answer 4

around 6 weeks

divides to form the vestibular lamina (buccal surfaces) and the dental lamina (enamel organ)

Question 5

describe the morphogenesis stage of tooth development (8-11wks)

Answer 5

dental lamina thickens into bud stage enamel organ - ectomesenchymal condensation appears around it this is the dental papilla
enamel organ develops into cap stage over papilla , enamel organ at this stage has 2 layers IEE and EEE

Question 6

describe cytodifferentiation of tooth development (approx 14 wks)

Answer 6

bell stage enamel organ
has 4 layers - IEE, EEE , stratum intermedium and stellate reticulum
SR = innermost and contains energy for ameloblast function e.g sugar and glycogen

Question 7

does differentiation occur across the enamel organ simultaneously

Answer 7

no , starts at apical regions first then trickles down to cervical

Question 8

describe matrix secretion (approx 18wks)

Answer 8

dental papilla cells differentiate into ondontoblasts which lay down unmineralised dentine (pre dentine)
dentine formation induces IEE cells to diferentiate into ameloblasts

Question 9

do all dental papilla cells differentiate into odontoblasts

Answer 9

no some differentiate into stem cells so that if dentine = damaged or ondontoblasts die they can form tertiary dentine

Question 10

describe amelogenesis

Answer 10

1 - dentine induces IEE cells to differentiate into ameloblasts
2 - ameloblasts synthesise and secrete enamel matrix proteins (secretory phase)
3 - matrix proteins removed and mineral content increases (maturation)
4 - ameloblasts regress to form a protective ayer that is involved in tooth eruption

Question 11

does amelogenesis occur simultaneously across the enamel organ

Answer 11

no - apical regions first

Question 12

debris of mallasez

Answer 12

remnants of HERS , potential to develop into a cyst (ondontogeic cyst)

Question 13

hertwigs epithelial root sheath

Answer 13

defines root shape

has 2 layers - IEE and EEE

Question 14

what cells differentiate into cementoblasts

Answer 14

mesenchymal cells from the dental follicle when they come into contact with dentine

Question 15

placodes

Answer 15

embryonic structures that give rise to various structures including hair follicles and teeth
hypohidrotic ectodermal dysplasia affects placed structures

Question 16

amelogenesis imperfecta

Answer 16

teeth = yellow/brown , small and very prone to damage
caused by a gene mutation that gives instructions for making enamelysin
hard to differentiate between enamel and dentine on radiographs due to low mineral content

Question 17

dentinogenesis imperfecta

Answer 17

dentine not developed or under mineralised
difficult to distinguish dentine and pulp on radiographs
teeth = blue/grey or yellow/brown and translucent

Question 18

gemination

Answer 18

tooth germ broken into 2

looks like 2 teeth in one

Question 19

fusion

Answer 19

teeth fuse together during development

Question 20

concrescence

Answer 20

2 teeth joined together at cementum

Question 21

tomes process

Answer 21

defines position of crystallites in enamel rod , one per rod

Question 22

mantle dentine

Answer 22

thin dentine layer closest to enamel that is formed first, has no tubules

Question 23

calcospherites

Answer 23

centres of dentine mineralisation

Question 24

meckels cartilage

Answer 24

cartilage from which the mandible is formed

Question 25

what do the palatal shelves form

Answer 25

secondary palate - part of the hard palate