WEEK 5

Question 1

What is odontogenesis?

Answer 1

tooth development

Question 2

When does odontogenesis begin?

Answer 2

6-7th week of prenatal development

Question 3

3 stages of prenatal development + times

Answer 3

1. pre-implantation period (first week)
2. embryonic period ( 2nd - 8th week )
3. foetal period ( 9th week - birth)

Question 4

pre implantation period

Answer 4

• fertilisation occurs creating zygote
• day 3 - 4 = morula
• day 5 = blastocyst
• day 5 - 6 = Implantation occurs

Question 5

embryonic period

Answer 5

• cells proliferate, differentiate and intergrate
• end of 8th week = embryo becomes foetus
• form germ layers –> ectoderm/ mesoderm/ endoderm

Question 6

ectoderm germ layer gives rise to

Answer 6

enamel

Question 7

mesoderm germ layer gives rise to

Answer 7

dentin, pulp, cementum, periodontal ligament

Question 8

endoderm germ layer gives rise to

Answer 8

GI tract epithelium and associated glands

Question 9

foetal stage

Answer 9

• growth + maturation
• distinguishable ears, arms, hands, legs, feet, foot and fingerprints

Question 10

first brachial (mandibular) arch

Answer 10

cranial nerve - trigeminal
cartilage - meckels cartilage
muscles - muscles of mastication/ mylohyoid and anterior belly of digastric/ tensor tympani, tensor veli palatini
skeletal structures - malleus/incus
ligaments - sphenomandibular ligament

Question 11

second brachial (hyoid) arch

Answer 11

cranial nerve - facial
cartilage - Reichert cartilagee
muscles - muscles of facial expression/ stapedius/ stylohyoid/ posterior belly of digastric
skeletal structures - stapes/ styloid process/ upper part of body and lesser cornu of hyoid bone
ligaments - stylohyoid ligament

Question 12

third brachial arch

Answer 12

cranial nerve - glossopharyngeal
muscles - stylopharyngeusus
skeletal structures - lower part of body and greater cornu of hyoid bone/ superior cornu of thyroid cartilage

Question 13

fourth and sixth branchial arches

Answer 13

cranial nerve - superior laryngeal and recurrent laryngeal branch of vagus
muscles - cricothyroid/ levator veli palatini/ constrictors of pharynx/ intrinsic muscles of the larynx/ striated muscles of the oesophagus
skeletal structures - thyroid, cricoid, arytenoid, corniculate, cuneiform cartilage/ body of hyoid bone
ligaments -

Question 14

fifth branchial arch

Answer 14

degenerates and becomes unrecognisable

Question 15

formation of the face is established by

Answer 15

1. frontonasal prominence overlying the forebrain
2. 2 maxillary prominences
3. 2 mandibular promences

Question 16

formation of the face occours during

Answer 16

4th and 10th week

Question 17

formation of the face
end of 4th week

Answer 17

5 facial swellings/ prominences form

Question 18

formation of the face
week 5

Answer 18

pair of ectodermal lining thickenings called nasal/ olfactory placodes form and enlarge

Question 19

formation of the face
week 6

Answer 19

nasal pit froms which divides nasal prominance into medial and lateral processes

Question 20

formation of the face
week 7

Answer 20

medial nasal processes fuse at midline forming intermaxillary process
gives rise to philtrum and primary palate

Question 21

formation of the palate occurs during

Answer 21

week 5 - 10

Question 22

formation of the palate is derived from

Answer 22

unpaired median palatine process
pair of lateral palatine process

Question 23

formation of secondary palate

Answer 23

• occurs between 7th-8th week
• lateral palatine process fuse to form secondary palate
• separated by palatine raphe

Question 24

formation of the tounge

Answer 24

3 mesenchymal swellings form anterior 2/3 of tongue
1. 2 lateral lingual swellings
2. 1 medial lingual swelling

posterior part of tongue arises from hypobranchial eminence

Question 25

formation of the mandible steps

Answer 25

1. mandibular process fuse in midline to form arch 2. mandible bone forms mesenchymal tissue --> cartilage starts to disappear 3. bone forms a trough (mandibular canal) which contains inferior alveolar nerve 4. bone above trough forms compartments/ alveoli for teeth

Question 26

formation of maxilla

Answer 26

no cartilage exists intramembranous ossification --> converts mesenchymal tissue to bone

Question 27

What are the two types of odontogenesis cells

Answer 27

oral ectodermal and ectomesenchymal

Question 28

What do oral ectodermal cells form?

Answer 28

enamel organ

Question 29

What do ectomesenchymal cells form?

Answer 29

dental papilla

Question 30

tooth germ

Answer 30

enamel organ / dental papilae/ dental sac

Question 31

What is the stomatodeum?

Answer 31

primitive oral cavity

Question 32

What happens to the stomatodeum at the 6th week of development?

Answer 32

it is lined by ectoderm which gives rise to the oral epithelial

Question 33

What is deep to the oral epithelium in stomatodeums?

Answer 33

ectomesenchyme

Question 34

What do neural crest cells give rise to?

Answer 34

nervous system

Question 35

Where is embryonic connective tissue derived from?

Answer 35

mesoderm

Question 36

In dental context, the proper migration of neural crest cells is essential for developing what?

Answer 36

the craniofacial skeleton and teeth

Question 37

How is the dental lamina formed in utero?

Answer 37

during the 7th week, the oral epithelium grows deeper penetrating the ectomesenchyme

Question 38

What are the three stages of tooth development?

Answer 38

bud, cap, bell

Question 39

When does the bud stage occur?

Answer 39

8th week

Question 40

What surrounds the bud stage

Answer 40

ectomesenchymal condensation

Question 41

When does the cap stage occur?

Answer 41

9th to 10th week

Question 42

What happens during the cap stage?

Answer 42

Proliferation, differentiation, and morphogenesis.

Question 43

What are the different levels of differentiation during the cap stage?

Answer 43

inner and outer enamel epithelium, enamel knot, dental papilla, and dental sac

Question 44

What is inner enamel epithelium

Answer 44

lined by columnar cells

Question 45

What is outer enamel epithelium

Answer 45

single layer of cuboidal cells

Question 46

What is enamel knot and cord

Answer 46

rounded cells that connect inner enamel and outer enamel. may give rise to stratum intermedium

Question 47

For the component enamel organ, what is the histological feature?

Answer 47

formation of tooth bud in cap shape with deep central depression

Question 48

For the component enamel organ, what is the future dental tissue it forms

Answer 48

enamel

Question 49

What is the histological feature of the dental papilla?

Answer 49

ectomesenchyme within concavity of enamel organ

Question 50

What does the dental papilla form?

Answer 50

dentin and pulp

Question 51

What is the histological feature of the dental sac

Answer 51

mass of ectomesenchyme surrounding enamel organ

Question 52

what does the dental sac form?

Answer 52

cementum, periodontal ligament, alveolar bone

Question 53

what new cells are found within the enamel organ during the early bell stage

Answer 53

outer enamel epithelium stellate reticulum stratum intermediate inner enamel epithelium

Question 54

What is the histological feature of outer enamel epithelium?

Answer 54

outer cuboidal cells of enamel organ

Question 55

What is the role of the outer enamel epithelium in tooth formation?

Answer 55

protective barrier for enamel

Question 56

What is the histological feature of the stellate reticulum?

Answer 56

network of star shaped cells

Question 57

what is the function of the stellate reticulum in tooth formation?

Answer 57

supports production of enamel matrix

Question 58

What is the histological feature of the stratum intermedium?

Answer 58

Inner compressed layer of flat to cuboidal cells

Question 59

What is the function of the stratum intermediate in tooth development?

Answer 59

supports production of enamel matrix

Question 60

what is the histological feature of inner enamel epithelium?

Answer 60

innermost tall columnar cells of enamel organ

Question 61

What is the role of inner enamel epithelium in tooth development?

Answer 61

differentiates into ameloblasts that form enamel matrix

Question 62

What are the histological features of outer cells of dental papilla?

Answer 62

basement membrane is between outer layer and inner layer epithelium

Question 63

What is the difference between the early and late bell stages

Answer 63

deposition of the first layer of dentin

Question 64

What happens to the outermost cells of the dental papilla during the late stage?

Answer 64

they differentiate into odontoblasts which produce the dentin of the teeth

Question 65

When does dentine production start?

Answer 65

the third month in utero when the odontoblasts begin to secrete the non-mineralized matrix called predentine

Question 66

What are the remains of dental lamina called?

Answer 66

epithelial rests of serves

Question 67

The preamoblasts are formed during dentinogensis and differentiate into

Answer 67

ameloblasts and begins amelogenesis

Question 68

When does root formation occur?

Answer 68

after the crown has formed

Question 69

what is the structure responsible for the formation of the root

Answer 69

cervical loop

Question 70

What makes up the cervical loop

Answer 70

a bilayer rim consisting of inner and outer enamel epithelium

Question 71

a bilayer rim consisting of inner and outer enamel epithelium

Answer 71

Hertwig Epithelial root sheeth

Question 72

What determines if a root is going to be straight or curved?

Answer 72

Hertwig Epithelial root sheeth

Question 73

How does root dentin form?

Answer 73

outer cells of the papilla undergo differentiation to become odontoblasts

Question 74

What is cementogenesis?

Answer 74

occurs when HERS disentegrates and the cementum grows

Question 75

What forms an enamel pearl?

Answer 75

late degeneration of ERSH leads to the formation of enamel on the root

Question 76

What causes dilaceration?

Answer 76

trauma to the tooth germ during root development

Question 77

root completion occours _____ after eruption

Answer 77

2-3 yrs