Tooth Histology and Development

Question 1

Epithelium (ectoderm) gives rise to

Answer 1

Enamel

Question 2

Mesenchyme (ectomesenchyme) gives rise to

Answer 2

Dentine, pulp, cementum and periodontium

Question 3

When are first signs of tooth development

Answer 3

6 weeks

Question 4

Stages of tooth germ

Answer 4

Bud → cap → bell → late bell → crown

Question 5

Dentinogenesis stages

Answer 5

Cytodifferentiation → matrix formation → mineralization

Question 6

What is cytodifferentiation

Answer 6

Dental papilla cells form odontoblasts

Question 7

What do odontoblasts produce

Answer 7

Collage-rich predentine

Question 8

What do odontoblasts do

Answer 8

Retreat inwards

Question 9

What do odontoblasts have

Answer 9

Long cell processes that form the dental tube

Question 10

What does predentine do

Answer 10

Mineralises to form dentine

Question 11

What is amelogenesis

Answer 11

Inner enamel epithelium forms ameloblasts

Question 12

What do ameloblasts secrete

Answer 12

Enamel protein matrix

Question 13

Virtually immediate mineralization

Answer 13

~ 15 % mineral, 65% water, 20% proteins

Question 14

Gradual mineralization

Answer 14

Further mineralization to ~95 %

Question 15

Root formation

Answer 15

Dentine plus cementum

Question 16

What are dentine and cementum derived from

Answer 16

Ectomesenchyme

Question 17

What is required to signal root formation

Answer 17

Hertwig’s epithelial root sheath (hers)

Question 18

Composition of enamel

Answer 18

96% mineral, 1-2% matrix, 2% water

Question 19

Composition of dentine

Answer 19

70% mineral, 20% matrix, 10% water

Question 20

Composition of cementum

Answer 20

65% mineral, 23% matrix, 12% water

Question 21

Composition of bone

Answer 21

60% mineral, 25% matrix, 15% water

Question 22

What does enamel cover

Answer 22

Anatomical crown of teeth

Question 23

Thickness of enamel

Answer 23

2 mm

Question 24

Hardness of enamel

Answer 24

KHN 360 - 390

Question 25

Hardness of dentine

Answer 25

KHN 75

Question 26

Components of dentine

Answer 26

~7% mineral and ~20% (collagen)

Question 27

What does cementum do

Answer 27

Covers the root of the teeth

Question 28

How to study enamel histologically

Answer 28

Vitally, extracted, decalcified and as a ground section

Question 29

Enamel structure

Answer 29

Tightly packed hydroxyapatite crystals

Question 30

Basic unit of enamel

Answer 30

Enamel prism

Question 31

Shape of enamel prisms

Answer 31

Complex key-hole shape

Question 32

Prism core

Answer 32

Tightly packed hydroxyapatite crystals

Question 33

Prism sheath

Answer 33

Different crystal orientations less tightly packed to allow space for organic components

Question 34

Gnarled enamel

Answer 34

At the cusps, the prisms appear twisted around each other → strength

Question 35

Striae of retzius

Answer 35

Incremental growth lines

Question 36

Perikymata

Answer 36

Shallow furrow where the striae reach the surface

Question 37

Structure of dentine

Answer 37

Highly tubular

Question 38

What may dentinal tubules contain

Answer 38

Cell processes, nerves and fluid (flows out)

Question 39

Extent of odontoblast process in dentine

Answer 39

Likely extends approximately a third of the way through denting

Question 40

Where does the innervation lie in dentine

Answer 40

The inner aspect

Question 41

Where are most neves in dentine found

Answer 41

Pre-dentine / inner denting in pulp horns

Question 42

Primary denting

Answer 42

Formed during tooth development (up to root completion)

Question 43

Secondary dentine

Answer 43

Forms after root completion and slowly throughout life of the tooth

Question 44

Tertiary dentine

Answer 44

Response to pulpal insult

Question 45

Reactionary tertiary dentine

Answer 45

Slow-forming, uses existing odontoblasts

Question 46

Reparative tertiary dentine

Answer 46

Existing odontoblasts destroyed, recruitment of newly differentiated odontoblasts, rapid formation and poor structure

Question 47

Function of tertiary denting

Answer 47

Remove pulp from stimulus

Question 48

How do fillings stay in

Answer 48

Mechanical undercut, bonded to enamel (utilise structure enamel and acid etch), bonded to dentine (acid demineralisation, infiltrate collagen with resin, penetrate tubules with resin)

Question 49

Types of cementum

Answer 49

Acellular and cellular

Question 50

What is cementum resistant to

Answer 50

Resorption

Question 51

Gross structure of dental pulp

Answer 51

Pulp horns, coronal pulp chamber, radicular pulp, apical foramen, lateral canal and apical delta

Question 52

Layers of dentine (outer to inner)

Answer 52

Odontoblast→ cell-free zone of Weil → cell-rich zone → pulp core

Question 53

Pulpal innovation

Answer 53

70 - 80 % non-myelinated, plexus of Raschkow, marginal plexus