Tooth Development

Question 1

What are the 3 primary embryonic layers?

Answer 1

• Ectoderm
• Mesoderm
• Endoderm

Question 2

Which one of the 3 primary embryonic layers is tooth enamel derived from?

Answer 2

ectoderm

Question 3

Which one of the 4 primary embryonic layers are all the parts of the teeth and supporting structure apart from tooth enamel derived from?

Answer 3

Ectomesenchyme

Question 4

What is the Ectomesenchyme?

Answer 4

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

Question 5

What do teeth develop from?

Answer 5

germs

Question 6

What is the first stage of tooth development?

Answer 6

initiation

Question 7

What is a depression between the brain and the pericardium in an embryo which is the precursor to the mouth called?

Answer 7

stomodaeum

Question 8

Approximately when does the primary epithelial band develop?

Answer 8

6 weeks

Question 9

What does the primary epithelial band appear as?

Answer 9

thickening of epithelium at the embryonic mouth (stomodaeum)

Question 10

What is the embryonic mouth called?

Answer 10

stomodaeum

Question 11

What 2 parts does the primary epithelial band divide into?

Answer 11

• Vestibular lamina, which will form the buccal sulcus
• Dental lamina, from which the enamel organ develops

Question 12

Approximately when does the dental lamina develop?

Answer 12

7 weeks

Question 13

What shape is the dental lamina?

Answer 13

horse-shoe

Question 14

What is the second stage in tooth development?

Answer 14

morphogenesis (bud stage)

Question 15

What does morphogenesis mean?

Answer 15

generation of shape

Question 16

When does the enamel organ - ‘bud’ stage 2 occur?

Answer 16

8-10 weeks

Question 17

What happens at the ‘bud’ stage of dental development?

Answer 17

• Dental lamina invaginate and thickens into a ‘bud’ stage enamel organ
• An Ectomesenchymeal cell collection appears and this is the dental papilla

Question 18

When does the enamel organ - ‘cap’ stage 3 occur?

Answer 18

11 weeks

Question 19

What 2 epitheliums are present in the enamel ‘cap stage’?

Answer 19

• External enamel epithelium
• Internal enamel epithelium
• EEE and IEE meet at the cervical loop

Question 20

What is the acculmation of ectomesencymal cells around the enamel organ called?

Answer 20

dental follicule

Question 21

What is the fourth stage of tooth development?

Answer 21

bell stage

Question 22

When does the enamel organ - ‘bell’ (cytodifferentiation) stage occur?

Answer 22

14 weeks

Question 23

At what stage is the tooth shape starting to be defined?

Answer 23

bell stage

Question 24

What are the 4 cell layers present in the ‘bell’ stage?

Answer 24

• Stratum intermedium
• Internal enamel epithelium
• External enamel epithelium
• Stellate reticulum

Question 25

What is the function of stellate reticulum in the bell stage?

Answer 25

keeping storage of nutrients for tissues comprises of glycoaminosglycans (attract water) which allows space for developing crown

Question 26

At what time does an extension appear on the lingual side of the dental lamina - this is the dental lamina for the adult tooth?

Answer 26

12 weeks

Question 27

At what time does the 1st permanent molar germ develop as a backwards extension of the dental lamina?

Answer 27

16 weeks

Question 28

What is the fifth stage of tooth development?

Answer 28

matrix secretion (late bell)

Question 29

At what time does matrix secretion (late bell stage) occur?

Answer 29

18 weeks

Question 30

In what stage does the positioning of enamel and dentine begin?

Answer 30

late bell stage within matrix secretion

Question 31

At what stage do cells become specialised?

Answer 31

late bell stage within matrix secretion

Question 32

What do dental papilla cells (adjacent to the internal enamel epithelium) differentiate into?

Answer 32

odontoblasts

Question 33

What do odontoblasts do?

Answer 33

lay down dentine matrix which is later mineralised (predefine)

Question 34

What do ameloblasts do?

Answer 34

form enamel

Question 35

What is the process of dentinogenesis?

Answer 35

Odontoblast differentiation from dental papilla cells near IEE Deposition of dentine matrix (mainly collagen) This unmineralised dentine is predentine Mineralisation of dentine (hydroxyapatite)

Question 36

What do IEE cells differentiate into?

Answer 36

ameloblasts

Question 37

What are the 2 phases of formation of enamel?

Answer 37

1- Protein matrix deposition (30% mineralised matrix 2- Framework established, organic part removed, mineralisation is complete

Question 38

What happens during the differentiation stage of amelogenesis?

Answer 38

IEE cells elongate becomes columnar and the nucleus moves to the basal end to become ameloblasts

Question 39

What happens during the secretory stage of amelogenesis?

Answer 39

ameloblasts secrete and synthesise matrix proteins form the crystallites and rods (no mineralisation/hydroxyapatite)

Question 40

What happens during the maturation phase?

Answer 40

proteins are removed, mineral content is increased

Question 41

What happens during protection stage in ameloblasts?

Answer 41

ameloblasts regress (become smaller) to form a protective layer around enamel involved in eruption and epithelial attachment

Question 42

What is the 5th stage in tooth development?

Answer 42

root formation

Question 43

What must be completed before the root begins to form?

Answer 43

crown

Question 44

Where do the EEE and IEE meet?

Answer 44

cervical loop

Question 45

What does migration of the cervical loop map out?

Answer 45

crown shape

Question 46

What is the root shape defined by in root formation?

Answer 46

The length, curvature, thickness, and number of roots are all dependent on the inner root sheath cells.

Question 47

What is the apical growth (proliferation of cervical root cells) of cervical root known as?

Answer 47

hertwig's epithelial root sheath

Question 48

What does the Hertwig's epithelial root sheath induce?

Answer 48

formation of root dentine

Question 49

What is 'debris of Malassez'?

Answer 49

epithelial cells on the PDL that are remains of HERS -may develop into cyst

Question 50

What are cementoblasts?

Answer 50

differentiated ectomesenchymal cells from the follicle

Question 51

What is the type of tissue, origin and product of the enamel organ?

Answer 51

epithelium, ectoderm, enamel

Question 52

What is the type of tissue, origin and product of the dental papilla?

Answer 52

ectomesenchyme, neural crest, dentine, pulp

Question 53

What is the type of tissue, origin and product of the dental follicle?

Answer 53

ectomesenchyme, neural crest, cementum, PDL, alv bone

Question 54

What are the possible characteristics of dental development disorders?

Answer 54

shape, size, structure, number, presence, eruption

Question 55

What is hypodontia

Answer 55

absence of some teeth

Question 56

What is supernumerary 'mesio-dens'?

Answer 56

presence of extra tooth between two teeth

Question 57

What is germination?

Answer 57

two teeth in one space

Question 58

What is fusion?

Answer 58

similar to germination but more defined

Question 59

What is dentinogenesis imperfecta?

Answer 59

incorrect formation of dentine

Question 60

What type of shape are stratum intermedium and stellate reticulum cells?

Answer 60

stratum intermedium - spindle shaped stellate reticulum - star shaped

Question 61

What do dental follicle cells differentiate into?

Answer 61

oestoblasts (alv bone) fibroblasts (PDL) cemenotoblasts (cementum)

Question 62

What are the dental follicle cells?

Answer 62

cells surrounding the sides of the enamel organ (dental lamina is at the bottom)

Question 63

What is the role of the epithelial cell rests of malassez?

Answer 63

remnants of hertwigs epithelial root sheath, that allow dental follicle cells to come into contact with the root dentine and to differentiate into cementoblasts