OCB02-1016 Dentine

Question 1

What is responsible for the yellow colour of the tooth?

Answer 1

Dentine

Question 2

What is dentin perforated by?

Answer 2

Tubules

Question 3

What are tubules?

Answer 3

They go from the pulp to EDJ and carry fluid from the pulp

Question 4

What % of dentine is inorganic?

Answer 4

70%

Question 5

What % of dentine is organic ?

Answer 5

20%

Question 6

What % of the organic dentine is type I collagen?

Answer 6

90%

Question 7

What % of the organic dentine is non collagenous proteins?

Answer 7

8%

Question 8

What % of the organic dentine are lipids?

Answer 8

2%

Question 9

What % of dentine is water?

Answer 9

10%

Question 10

How does the hydrophobic composite filing pose a problem?

Answer 10

fluid flow creates a wet environment around the oral cavity

The outward fluid flow limits the penetration of bonding agents

Question 11

What are the two types of dentine?

Answer 11

coronal and radicular dentine

Question 12

What are the two types of coronal dentine?

Answer 12

Mantle dentine and circumpulpal dentine

Question 13

What is mantle dentine?

Answer 13

The outermost layer of dentine that lies just below the enamel

Question 14

What is circumpulpal dentine?

Answer 14

Circumpulpal dentine lies below the mantle dentine and extends round the crown and down into the root

Question 15

What is the difference between mantle and circumpulpal dentine?

Answer 15

Mantle dentine is slightly less mineralised and more porous than circumpulpal dentine

Question 16

What are the two types of radicular dentine?

Answer 16

Hyaline layer of Hopewell Smith

Granular layer of Tomes

Question 17

What is the hyaline layer of Hopewell Smith?

Answer 17

Next to the cementum and has no dentinal tubules

May serve to bond the cementum to the dentine and is the last dentine layer to mineralise

Question 18

What is the granular layer of Tomes?

Answer 18

Beneath the hyaline layer
Its less mineralised than the circumpulpal layer
Collagen fibres run parallel to the root surface

Question 19

What pattern does the primary curvature of the tubules follow from the EDJ?

Answer 19

A sigmoidal S-shaped pattern due to overcrowding of odontoblasts

Question 20

When is the secondary curvature of the dentinal tubules formed?

Answer 20

The tubules change direction every few micrometer

Question 21

What layer of dentine are the branching and loops of the dentinal tubules responsible for?

Answer 21

Granular layer of Tomes in root dentine

Question 22

What is the odontoblast process responsible for?

Answer 22

Secretion of hydroxyapatite crystals and mineralisation of the matrix

Question 23

Where is peritubular space not present with dentinal tubules?

Answer 23

Predentine level or innermost mineralised dentine

Question 24

What is another word for peritubular dentin?

Answer 24

Intratubular dentine

Question 25

What is the peritubular space filled with?

Answer 25

Dentinal fluid which exerts a positive outwards pressure

Question 26

What does peritubular dentin do?

Answer 26

It creates the wall of the dentinal tubules

Question 27

How does the growth of pertiubular dentine affect the diameter of the dentinal tubules?

Answer 27

As the peritubular dentine grows, it reduces the size of the dental tubules

Question 28

How does the amount of peritubular dentine change with age?

Answer 28

It increases and eventually occludes the tube

Question 29

What is the difference between peritubular and interlobular dentine?

Answer 29

Peritubular dentine is hyper calcified compared to interlobular

Question 30

Where about are the diameter and density of the tubules the greatest?

Answer 30

Near the pulp

Question 31

What is the purpose of etching?

Answer 31

To remove the smear layer of microcrystalline and organic particle debris on root canal walls to prevent bacteria entering the dentinal tubules

Question 32

What are von-ebner lines?

Answer 32

Visible as light-dark band patterns that run perpendicular to dentinal tubules

Question 33

Where are von-ebner lines present?

Answer 33

Circumpulpal dentine

Question 34

What conditions can Andersen lines be seen?

Answer 34

Under polarised light

Question 35

What slows the development of Andersen lines?

Answer 35

Birth or death

Question 36

Where is the neonatal line seen?

Answer 36

All primary teeth and permanent molars

Question 37

How does the neonatal line differ from other Retzius lines?

Answer 37

It is darker and larger

Question 38

What does the initial matrix become?

Answer 38

Mantle dentin

Question 39

What are the collagen fibres in the mantle dentin that are perpendicular to IEE called?

Answer 39

Von Korff Fibres

Question 40

What is unmineralised dentine called?

Answer 40

Predentine

Question 41

What staining appearance does predentine have?

Answer 41

Pale

Question 42

What is the area between predentine and mineralised dentine called?

Answer 42

Metadentine

Question 43

What are circular areas of mineralisation called?

Answer 43

Calcospherites

Question 44

What is interglobuar dentine?

Answer 44

Areas that haven't been fully calcified and only primary mineralisation has occurred in the predentine Formed by the failure of calcospherites to fuse

Question 45

Where is interlobular dentine located?

Answer 45

Below the mantle dentin the the granular layer

Question 46

When is secondary dentin formed?

Answer 46

Formed after root formation is complete, after the tooth has erupted

Question 47

What is the structure of secondary dentin?

Answer 47

Simiar to primary dentin- contain tubules Tubular patterns are less regular Odontoblasts become more crowded

Question 48

How does growth of secondary dentin differ to that of primary?

Answer 48

Secondary dentin grows much slower in increments

Question 49

What clinical impact does secondary dentin have?

Answer 49

It reduced the size of the pulp chamber and root canal diameter with age which can make endodontics more difficult

Question 50

When does tertiary dentine form?

Answer 50

In response to external stimulations such as cavities

Question 51

What are the two mechanisms by which tertiary dentine is formed?

Answer 51

Reactionary formation | Reparative formation

Question 52

What is reactionary formation of tertiary dentine?

Answer 52

Dentin is formed from pre-existing odontoblast

Question 53

What is reparative formation of tertiary dentine?

Answer 53

New odontoblasts are formed from pulpal progenitor cells due to death of previous odontoblasts

Question 54

How is translucent dentin formed?

Answer 54

Due to dentinal tubules being filled in response to external stimuli such as attrition or slow advancing caries

Question 55

In what way is the mineral composition of translucent dentine and peritubular dentine different?

Answer 55

Translucent is composed of crystalline and may contain salivary components due to caries

Question 56

What are dead tracts?

Answer 56

Empty tubules that are sealed at the pulpal end by tertiary dentin

Question 57

How are empty tubules formed?

Answer 57

Due to the death of odontoblasts or odontoblasts that have stopped their function

Question 58

Where are dead tracts more common

Answer 58

Secondary dentin