Enamel And Dentine

Question 1

List 4 mineralised tissues

Answer 1

Alveolar bone
Cementum
Dentine
Enamel

Question 2

List 4 non mineralised tissues

Answer 2

Oral mucosae
Dental pulp
Gingivae
Periodontal ligament

Question 3

What forms the bulk of the tooth tissue

Answer 3

Dentine

Question 4

What covers the crown of the dentine

Answer 4

Enamel

Question 5

What covers the root of the dentine

Answer 5

Cementum

Question 6

What is the appearance of dentine

Answer 6

Fine parallel tubules within a collagenous matrix for permeability
Rigid elastic tissue pale yellow

Question 7

What is the unmineralised dentine pulp junction known as

Answer 7

Predentine

Question 8

What creates dentine

Answer 8

Odontoblasts which then stimulate ameloblasts

Question 9

Is dentine a vital tissue

Answer 9

Yes

Question 10

What is the function of dentine

Answer 10

To act as a shock absorber dissipating large loads and force throughout the tooth structure highly elastic

Question 11

How hard is dentine compared to other structures of the tooth

Answer 11

Harder than bone and cementum but softer than enamel

Question 12

What is dentine composed of

Answer 12

70% inorganic mineral salts (hydroxyapatite crystals embedded in a collagen matrix)
20% organic substance (proteins)
10% water

Question 13

List 6 non collagenous proteins in dentine

Answer 13

Dentine sialo phosphoproteins (DSPP)
Proteoglycans
Gla proteins
Acidic proteins
Growth factors
Lipids

Question 14

What is the define between tubules called

Answer 14

Intertubular dentine

Question 15

What shape does dentine follow

Answer 15

A curved sigmoid route known as primary curvatures (aka schreger lines)

Question 16

What is the major feature of dentine

Answer 16

It’s dentinal tubules

Question 17

What are lines of Owen

Answer 17

The small changes in direction in dentine known as secondary curvatures

Question 18

When does secondary dentine appear

Answer 18

After completion of tooth formation increased crowding of odontoblasts

Question 19

Where are dentinal tubules mostly formed

Answer 19

By the pulpal floor

Question 20

Where do dentinal tubules mainly branch

Answer 20

At the periphery of the enamel dentine junction

Question 21

What is translucent dentine

Answer 21

Forms with ageing due to tubule occlusion by deposits of peritubular dentine

Question 22

Where is translucent dentine more pronounced

Answer 22

At the root apex

Question 23

What are the 2 tertiary dentine synonyms

Answer 23

Reactionary dentine
Reparative dentine

Question 24

What is tertiary dentine

Answer 24

Pulp induced to form calcified material in addition to 1st and 2nd dentine by a variety of external stimuli

Question 25

What are the 5 external stimuli for tertiary dentine

Answer 25

Caries Attrition Cavity preparation Microleakage around restorations Trauma

Question 26

What is reactionary dentine

Answer 26

Define formed in response to injury/insult made from existing odontoblasts

Question 27

What is reparative dentine

Answer 27

Dentine formed in response to stimulus made from progenitor cells/newly formed odontoblasts

Question 28

Where is peritubular dentine found

Answer 28

In wall of tubules highly calcified

Question 29

Where is intertubular dentine found

Answer 29

Between tubules highly calcified

Question 30

where is mantle dentine found

Answer 30

Outermost layer 1st dentine formed

Question 31

Where is circumpulpal dentine found

Answer 31

Around the pulp uniform in structure except at the edges is the bulk of the dentine

Question 32

What is primary dentine

Answer 32

Formed prior to apical completion formed more rapidly and more mineralised

Question 33

What is secondary dentine

Answer 33

Formed after completion of root formation formed more slowly and is less mineralised than primary

Question 34

Where is enamel thickest

Answer 34

At the cusps/incisal regions

Question 35

What is special about the primary dentition of enamel

Answer 35

It is more opaque crystalline form therefore appears whiter

Question 36

List 4 enamel functions

Answer 36

Mastication Aesthetic Protection Dissipation of forces

Question 37

How hard is enamel in knoop

Answer 37

296

Question 38

How hard is dentine in knoop

Answer 38

64

Question 39

What is enamels composition

Answer 39

96-97% mineral salts (hydroxyapatites, fluorides, carbohydrates) 3-4% organic substance (fibrillar matrix)

Question 40

How is enamel structured

Answer 40

It is organised into rods (prisms) and interrods (interprismatic substance)

Question 41

Where do ameloblasts come from

Answer 41

The inner enamel epithelium

Question 42

What does amelogenesis do

Answer 42

Secrete matrix proteins that are responsible for creating and maintaining an extra cellular environment favourable to mineral deposition

Question 43

What are the 3 main stages of amelogenesis

Answer 43

Presecretory stage Secretory stage Maturation stage

Question 44

What does the first step of amelogenesis produce

Answer 44

A partially mineralised enamel 30%

Question 45

what does the second step of amelogenesis involve

Answer 45

An influx of additional mineral content with the removal of material and water resulting in the 96% mineralisation

Question 46

What are the 2 parts to maturation stage of enamel

Answer 46

Transitional phase Maturation proper

Question 47

What is maturation proper

Answer 47

The ABs become involved in the removal of water and organic material

Question 48

What is the transitional phase

Answer 48

After the enamel has formed ABs undergo significant morphological changes preparing for maturation Reduction of AB height and a decrease in their volume and organelle content

Question 49

What are the ABs in enamel

Answer 49

Referred to as post secretory cells although they still secrete other essential proteins

Question 50

What is the maturative stage

Answer 50

Water and organic material is selectively removed from enamel with addition of inorganic material

Question 51

What do ruffle ended ameloblasts do

Answer 51

Release of inorganic material Proximal junctions are leaky and distal junctions are tight

Question 52

What do smooth ended ameloblasts do

Answer 52

Remove proteins and water Distal junctions are leaky while proximal junctions are tight

Question 53

What is amelogenin

Answer 53

Accumulates during the secretory stage

Question 54

What is enamalin

Answer 54

Crystal nucleation and growth

Question 55

What is ameloblastin

Answer 55

Undergoes rapid degradation Promotes mineral formation and crystal elongation Highest concentration at enamel growth sites Secreted together with amelogenins

Question 56

What is the life of sulfated glycoproteins

Answer 56

Short half life in the enamel

Question 57

Where is the tuftelin and what does it do

Answer 57

Localises at the DEJ and participates in its establishment

Question 58

What pattern does enamel have

Answer 58

Striae of retzius

Question 59

How does the pattern of enamel form

Answer 59

Because of a weekly rhythm of enamel production resulting in structural alterations of the rods

Question 60

What type of striation does enamel have

Answer 60

Cross striations forming intervals across the rods

Question 61

What is bands of hunter and schreger

Answer 61

Optical phenomenon produced by the changing orientations of adjacent groups of rods

Question 62

What is gnarled enamel

Answer 62

Enamel tufts and lamellae Perikymata aka imbrication lines

Question 63

What contains the greatest concentration of enamel than the rest of the enamel

Answer 63

Gnarled enamel Is projected from the DEJ for a short distance into the enamel

Question 64

How is enamel formed

Answer 64

Secreted by ameloblasts via amelogenesis