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I.O.E Dental anatomy and Histology > Dentine > Flashcards

Dentine Flashcards

1
Q

What type of material is dentine and what is it made up of?

A

It is a composite material consisting of apatite crystal on an organic scaffold predominantly composed of collagen

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2
Q

What is the bulk of the teeth made up of?

A

Dentine

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3
Q

Describe dentine

A

It is a bone like material which has a protein matrix

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4
Q

Is the dentine usually visible?

A

No it is only visible is severe occlusal attrition has occurred causing the enamel to wear away

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5
Q

What colour is dentine?

A

A yellow colour

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6
Q

What happens to the pulp as you get older?

A

It shrinks with age as more dentine is laid down on its inner surface

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7
Q

What is the inorganic mineral component of dentine?

A

The inorganic mineral component is in the form of hydroxyapatite crystals

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8
Q

What do some hydroxyapatite crystals contain?

A

Impurities in tiny amount such as carbonate

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9
Q

What is the difference between hydroxyapatite found in enamel and dentine?

A

The hydroxyapatite found in dentine is a similar shape but much smaller than those in enamel

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10
Q

What are the dimensions of dentine hydroxyapatite in comparison to enamel hydroxyapatite?

A

Dentine: 35nm x 10nm Enamel: 68nm x 28nm

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11
Q

How are the hydroxyapatite crystals in dentine arranged?

A

Arranged along and between collagen fibres

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12
Q

What makes up the organic dentine extracellular matrix ?

A

Collagen Proteoglycans Glycoproteins Phosphoproteins Lipids Serum derived proteins Growth factors

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13
Q

What makes up 90% of the organic matrix in dentine?

A

Collagen fibrils

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14
Q

What type of collagen makes up the dentine organic extracellular matrix?

A

The principle collagen fibril is type 1 collagen Traces of type III and V are also present

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15
Q

What is the difference between pre dentine collagen and mature dentine collagen?

A

Collagen fibrils in mineralised dentine are of larger diameter and are more closely packed than in pre dentine

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16
Q

What is the difference between collagen in the periodontal ligament and mature dentine collagen?

A

The fibrils in dentine are not assembled into bundles as they are in the periodontal ligament

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17
Q

How are the collagen fibrils arranged in dentine?

A

Most of the collagen fibrils in dentine run parallel to the Enamel dentine junction

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18
Q

What makes up 8% of the organic matrix in dentine?

A

Non collagenous proteins

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19
Q

Give examples of non collagenous proteins?

A

Dentine phosphoproteins, Proteoglycans Glycoproteins Growth factors

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20
Q

Give examples of proteoglycans found in dentine

A

Chondroitin 4-sulphate- containing proteoglycans

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21
Q

Give examples of glycoproteins found in dentine

A

Osteonectin Dentine sialoproteins Bone sialoproteins Osteopontin

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22
Q

Give examples of phosphoproteins

A

Dentine phosphoproteins Dentine matrix protein 1

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23
Q

Give examples of growth factors

A

TGF betas Bone morphogenic proteins (BMPS) Insulin like growth factors (IGFs)

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24
Q

Which proteins are important during mineralisation?

A

Dentine phosphophoryn (phosphoprotein) and dentine matrix protein 1 (DMP-1)

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25
Q

Which proteins have an important role in collagen fibril assembly and cell-mediated effects ?

A

Proteoglycans

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26
Q

What are some cell mediated effects?

A

Cell adhesion, migration, proliferation and differentiation.

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27
Q

When are growth factors released?

A

They can be released during the progress of dental caries and induce the production of reactionary or reparative dentine

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28
Q

What makes up 2% of the organic content of the dentine’s extracellular matrix?

A

Lipids

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29
Q

Where are lipids detected ?

A

They are detected at the mineralising front and they are thought to play a role in mineralisation

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30
Q

What forms can lipids take?

A

They can take the form of phospholipids and cholesterol

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31
Q

What does dentine consists of?

A

Consists of a large numbers of small parallel dentinal tubules in a mineralised collagen matrix

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32
Q

Inorganic hydroxyapatite crystals makes up how much of the dentine (by weight)?

A

65-70% inorganic hydroxyapatite crystals

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33
Q

Organic matrix makes up how much of the dentine (by weight)?

A

20% organic matrix

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34
Q

Water makes up how much of the dentine (by weight)?

A

10% water

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35
Q

Describe the physical properties of dentine

A

Dentine is rigid but elastic tissue Dentine is elastic, not brittle Dentine has a higher fracture toughness in comparison to enamel

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36
Q

Describe the physical properties of enamel

A

Enamel is hard and inflexible

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37
Q

What gives dentine its compressive and flexural strength?

A

Its organic matrix and tubular architecture provide it with greater compressive and flexural strength than enamel

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38
Q

What makes dentine more resistant to propagation of cracks than enamel?

A

Its intimate association of small apatite crystal with strong protein fibres

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39
Q

How hard is dentine in comparison to enamel (in Knoop numbers)?

A

Dentine: 64 Enamel: 296 Enamel is harder

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40
Q

How stiff is dentine in comparison to enamel (in Young’s modules)?

A

Dentine: 12 GN/m^2 Enamel: 131 GN/m^2 Enamel is more stiff (GN/m^2 = giganewtons (N x10^9)

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41
Q

How does the compressive strength of dentine compare to enamel?

A

Dentine: 262 MN/m^2 Enamel: 76 MN/m^2 Dentine has a higher compressive strength (MN/m^2 = meganewtons N x10^6)

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42
Q

How does the tensile strength of dentine compare to enamel?

A

Dentine: 33 MN/m^2 Enamel: 46 MN/m^2 (MN/m^2 = meganewtons N x10^6)

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43
Q

Where are the dentinal tubules found?

A

They run from the pulpal surface to the enamel-dentine and cementum-dentine junctions

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44
Q

What are the tubules between the dentine called?

A

Intertubular dentine

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45
Q

What forms the walls of recently formed tubules?

A

Intertubular dentine

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46
Q

Where and when are peritubular dentine deposited?

A

As the dentine matures, peritubular dentine is deposited on the walls of the dentinal tubules narrowing their lumens.

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47
Q

What are primary curvatures?

A

They are tubules that follow a curves, sigmoid course The convexity of these curvatures nearest the pulp is towards the root

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48
Q

What are secondary curvatures?

A

Smaller changes in direction of the tubules Where curvatures that are adjacent to each other coincide (Contour line of Owen may be seen)

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49
Q

Where is the contour line of Owen usually seen?

A

It is evident at the junction of the primary and secondary dentine

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50
Q

What happens to the terminal part of the tubules in the roots?

A

They branch and then the branches loop

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51
Q

What arises due to the looping of branches in the thermal part of the root?

A

This looping may be responsible for the appearance of the granular layer of Tomes

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52
Q

What is the range of the diameter to the dentinal tubules?

A

1 micrometer or less at the EDJ to 2.5 micrometres at the pulp

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53
Q

Where are dentinal tubules more spread out?

A

Dentinal tubules are more widely separated at their peripheries, near the EDJ,

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54
Q

Where are dentinal tubules less spread out?

A

Dentinal tubules are more tightly packed near the pulp

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55
Q

Why are dentinal tubules more spread out at the peripheries?

A

Because the odontoblasts migrate inwards and occupy a smaller surface as dentinogenesis progresses away from the EDJ

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56
Q

How many dentinal tubules are there in the outer and inner dentine?

A

20,000/mm2 in the outer dentine 50,000mm/2 in the inner dentine

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57
Q

What can happen if the dentine surface is exposed by caries, tooth surface loss, trauma, cavity preparation etc

A

The potential for bacteria of dental caries and the toxins they produce to pass through tubules to the pulp increases

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58
Q

Which processes do dentinal tubules contain?

A

They contain the process of the odontoblasts that are responsible for their formation In some parts of the tissue they also contain afferent nerve terminals

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59
Q

Where are the processes from antigen presenting cells found?

A

They are found in the peripheral pulp and can extend into the dentinal tubules

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60
Q

What are the perio-odontoblastic space and post-odontoblastic space thought to be filled with?

A

They are thought to be filled with extracellular dentinal fluid

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61
Q

Where do the processes from antigen presenting cells reside from?

A

Peri-odontoblastic space, and possibly post-odontoblastic space

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62
Q

In the early stages what does the odontoblast process occupy?

A

Occupies the full width of the dentinal tubule in the predestine and innermost mineralised circumpulpal dentine

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63
Q

What happen to the number of odontoblast processes as we move to the outer dentine?

A

The number of tubules seen to be occupied by odontoblasts processes decreases

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64
Q

When do odontoblast processes occupy the full width of the dentinal tubules?

A

n the predentine and innermost mineralised circumpulpal dentine, when dentine is in the early stages of development.

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65
Q

When does dentine formation occur?

A

Immediately before enamel formation

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66
Q

What do the odontoblasts do during dentine formation?

A

Odontoblasts lay down extracellular collagen matrix as they begin to move away from the future enamel dentine junction

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67
Q

Tubules that form an ‘S’ shaped pathway are called what?

A

Primary curvatures

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68
Q

Where does dentine formation begin?

A

Dentine formation begins at areas adjacent to the cusp tip or incisal edge and gradually progresses to the apex of the root

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69
Q

What is a key difference between enamel and dentine formation?

A

Dentine formation continues after tooth eruption and throughout the life of the pulp

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70
Q

What is the mineralisation of the collagen matrix facilitated by?

A

Facilitated by the modification of the collagen matrix by various non collagenous proteins

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71
Q

When does mineralisation of the collagen matrix happen?

A

Gradually follows the secretion of the extracellular collagen matix

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72
Q

Where is the most recently formed layer of dentine found?

A

The most recently formed layer of dentine is always on the pulpal surface.

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73
Q

What is the pre dentine?

A

The organic fibrillar matrix of the dentin before its calcification. It is the dentin matrix produced by the odontoblasts that makes up the inner layer of the dentin and when matured becomes dentin.

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74
Q

Of what origin is dentine?

A

It is of ectomesenchymal origin

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75
Q

Where does dentine develop from?

A

Develops from the peripheral cells of the dental papilla of the tooth germ

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76
Q

What is the principle role of the odontoblasts process in pre dentine?

A

It is vital for the secretion of matrix components

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77
Q

What is the principle role of the odontoblasts process in mineralising dentine?

A

Its roes into participate in the modification of the matrix and its mineralisation

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78
Q

At what pace is the new organic material deposited?

A

The deposition of new organic matrix proceeds at a pace similar to that of mineralisation, such that there is always a layer of un-mineralised matrix (the predentine) on the plural surface of the tissue

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79
Q

What is collagen secreted by?

A

Collagen is primarily secreted by the cell body of the odontoblasts

80
Q

What does the odontoblast process secrete?

A
  1. Secretes the other non-collagenous proteins such that a complex of collagen and non-collagenous proteins is formed at the junction of the predentine and calcified dentine (the mineralisation front) 2. Non-collagenous protein dentine phosphoprotein is released from the odontoblast process consistent with its important role in mineralisation and allowing it to bypass some of the predentine.
81
Q

What are odontoblasts a key component of?

A

Initiating and controlling mineralisation

82
Q

What happens to the calcium transported by the odontoblasts?

A

Calcium transported by the odontoblasts becomes a crystalline mineral in the dentine by deposition onto a template formed by type I collagen fibrils.

83
Q

What are dentine phosphoproteins thought to be involved in?

A

Dentine phosphoproteins are thought to be involved in hydroxyapatite nucleation and control of crystal growth.

84
Q

What is the key difference between dentine mineralisation and normal bone mineralisation?

A

Dentine mineralises in mostly the same way as bone with mineral crystals being added along a mineralisation front. However, unlike bone, it also mineralises by the combining of isolated islands of mineral called calcospherites.

85
Q

What are calcospherites?

A

Isolated islands of mineral

86
Q

What 2 other processes have been implicated in addition to the DPP mediated nucleation on collagen fibrils in the initiation of mineralisation?

A
  1. Very early in mantle dentine formation matrix vesicles in which mineral crystals develop may have a role in initiating mineralisation 2. Calcospherite formation and fusion may account for the irregular appearance of the mineralising front seen at some sites.
87
Q

What is the difference between Peritubular and interlobular dentine ?

A

Peritubular dentine lacks a collagenous fibrous matrix Peritubular dentine is also about 5-12% more mineralised than intertubular dentine

88
Q

What is Peritubular dentine made up of?

A

It consists of small crystals in an amorphous (non fibrillar) matrix consisting of glycoproteins, proteoglycans, lipids, osteonectin, osteocalcin and bone sialoprotein

89
Q

What is the main mineral component os peritubular dentine?

A

The mineral component of peritubular dentine is mainly carbonated apatite but its crystalline form is distinct from that of intertubular dentine

90
Q

Where is peritubular dentine found?

A

Mainly found in un-erupted teeth Predominantly distributed in apical dentine

91
Q

What type of tissue is petirubular dentine: a response change tissue or an age change tissue?

A

An age change tissue

92
Q

When are peritubular dentine formed?

A

Peritubular dentine is formed at about the same time as intertubular dentine

93
Q

Describe some things that have happened once primary dentine formation is complete

A

All peripheral tubules have a lining of peritubular dentine that extends from the enamel–dentine junction to within 50–100 μm of the predentine.

94
Q

How much of the outer dentine does the peritubular dentine occupy?

A

In outer dentine, peritubular dentine occupies two-thirds of the cross-sectional area of the tissue near to the predentine it occupies only approximately 3%

95
Q

Why and how does translucent dentine arise?

A

With physiological ageing (Especially in the tooth dentine) the dentinal tubules become completely occluded with peritubular dentine formation The contents of the tubule acquire the same refractive index as the intertubular dentine

96
Q

What happens to the amount of translucent dentine as you get older?

A

The amount of ttranslucent dentine increases linearly with age and is not affected by function or external irritation

97
Q

If the contents of the tubule acquire the same refractive index as the intertubular dentine what will happen if the dentine is put into water

A

As water has a similar refractive index to dentine regions blocked by peritubular dentine will appear translucent (‘translucent dentine’), while regions with patent tubules will fill with water and appear opaque

98
Q

As you get older what happens tot he dentine tubules?

A

Dentine tubules become infilled at the root apex adjacent to the cementum and extend cervically and towards the root canal with age.

99
Q

What part of dentistry can translucent dentistry be helpful in and how?

A

Useful in forensic dentistry to determine the age of teeth.

100
Q

What other dentine type has similar features o translucent dentine?

A

Scierotic dentine

101
Q

What are 2 examples of responsive tissue found in dentine?

A

Scierotic dentine Dead tracts

102
Q

What causes the formation of sclerotic dentine?

A

The filling of dentinal tubules due to an external stimuli such as under slowly advancing caries or beneath areas of severe attrition

103
Q

What is a similarity between both sclerotic and translucent dentine?

A

Both appear transparent

104
Q

What mineral are thought to make up sclerotic dentine?

A

The mineral is crystalline and possibly an apatite, although plate-like crystals of octocalcium phosphate have also been reported.

105
Q

What are dead tracts in dentine?

A

If the primary odontoblasts are killed by an eternal stimulus, or they retract before particular dentine occludes the tubules then empty tubules will be left and these empty tubules are described as dead tracts Dead tracts can be sealed at their pulpal end by tertiary dentine

106
Q

Why are dead tracts called dead tracts?

A

Because under the microscope, transmitted light will be totally internally reflected and empty tubules will appear as dark ‘dead tracts’.

107
Q

Why is the pulp important to the dentine

A

It maintains the dentine structure Takes part in the innervation of the tooth Provides a defensive mechanism which is activated in response to caries, tooth wear and trauma via formation of tertiary dentine

108
Q

Describe the pulp and its where its main blood vessels enter from

A

It is a richly vascularised and innervated tissue with the main arterioles, venules and nerves entering via the apical foramen and occupying the central core of the pulp

109
Q

What is the major cell type that occupies pulpal tissue

A

Bulk of pulpal tissue is occupied by loose connective tissue, the major cell type being the fibroblasts

110
Q

What is the plexus of small nerves beneath the cell rich zone called?

A

The Raschkow’s plexus

111
Q

What exits the Raschkows plexus?

A

Small, unmyleinated nerves exit this plexus and travel up to and terminate around the odontoblasts

112
Q

What are the 4 main lines in the dentine

A
  1. Von Ebner lines 2. Adresen lines 3. Contour lines of Owen 4. Schreger lines
113
Q

How do incremental lines arise?

A

Incremental lines arise from the incremental deposition of dentine matrix and its subsequent mineralisation

114
Q

What are the 2 types of incremental lines dentine has?

A

Dentine has regular. incremental: Short period or long period marking

115
Q

What are the long period incremental lines called?

A

Adresen lines

116
Q

How do Adresen lines form?

A

Long period lines are associated with changes in collagen fibrils orientation about every week 20 micrometres apart

117
Q

What are found between each long period line?

A

6-10 pairs of short period lines giving this 6-10 day periodicity similar to the long- period striae of Retzius in enamel

118
Q

What are short period incremental lines called?

A

Von Ebner lines

119
Q

What do von ebner lines appear as?

A

Alternating dark and light bands Each pair reflects the diurnal rhythm of dentine formation

120
Q

How far apart adjacent dark bands of von ebner in the cusp dentine?

A

In cuspal dentine deposition is most rapid The distance between adjacent dark bands is approximately 4 μm

121
Q

How far apart adjacent dark bands of von ebner in the root dentine?

A

In the root dentine deposition is slower and the distance is 2 μm.

122
Q

Where do the Contour lines of Owen and Schreger lines originate from?

A

These lines originate from coincidence of curvatures in the dentinal tubules (optical effects)

123
Q

Which lines are associated with the primary curvatures of the dentinal tubules?

A

The Schreger lines

124
Q

Where are schreger bands broader?

A

Where the peaks of the sigmoid primary curvatures coincide they form broad bands

125
Q

Which lines are associated with the secondary curvatures of the dentinal tubules?

A

The contour lines of Owen

126
Q

What happens when the secondary curvatures coincide?

A

They give rise to an optical effect, resulting in the appearance of contour lines of Owen

127
Q

What is the neonatal line?

A

A line seen between dentine formed before and dentine formed after birth

128
Q

What are the 8 regional variations in dentine

A

Mantle dentine Interglobular dentine Granular layer in dentine Hyaline layer in dentine Circumpulpal dentine Predentine Secondary dentine Tertiary dentine

129
Q

Where is the mantle dentine found?

A

Periphery of dentine in the crown

130
Q

Where is the interglobular dentine found?

A

Typically outer part of crown

131
Q

Where is the granular layer in dentine found?

A

In the outer part of root dentine beneath hyaline layer

132
Q

Where is the hyaline layer in dental found?

A

Outermost part of the root dentine

133
Q

Where is the circumpulpal dentine found?

A

Bulk of dentine in crown and root dentine

134
Q

Where is the predentine found?

A

Unmineralised innermost dentine in crown and root

135
Q

Where is the secondary dentine found?

A

Innermost layer of dentine between circumpulpal dentine and predentine

136
Q

Where is the tertiary dentine found?

A

Inner layer of dentine formed mainly in crown response to serious insult

137
Q

What are the 9 regions of varying dentine structure?

A

Enamel Mantle dentine Circumpulpal dentine Hyaline layer Granular layer Cementum Predentine Secondary dentine Tertiary dentine

138
Q

Describe the mantle dentine

A

It is in the crown this first formed and most peripheral layer beneath the enamel

139
Q

How do the mantle dentine and the circumpulpal dentine differ?

A

The special properties of mantle dentine help prevent small cracks developing in the enamel near the EDJ from spreading into the dentine Mantle dentine is slightly less mineralised (approx 5%) Mantle dentine displays branching of dentinal tubules Mantle dentine has fibrils orientated perpendicular to the EDJ.

140
Q

What does circumpulpal dentine form?

A

Forms the bulk of the dentine between the mantle layer and the zone of mineralisation It is uniform in structure except at its edges where peripherally, interglobular dentine marks incomplete initial mineralisation and, centrally, the mineralising front represents ongoing mineralisation

141
Q

Describe the interglobular dentine

A

It is the outer part of the circumpulpal dentine beneath the mantle layer It is often incompletely mineralised and has a characteristic appearance when seen in ground sections

142
Q

What is interglobular dentine

A

If a significant number of calcospherites do not fuse completely with the advancing mineralisation front then an area of interglobular dentine results

143
Q

Where is pre dentine formed?

A

Predentine is the innermost un-mineralised layer, where new dentine is being deposited throughout life

144
Q

What does predentine represent

A

Represents the initially laid down dentine matrix before its mineralisation

145
Q

What colour does pre dentine have when stained with haematoxylin and eosin?

A

It has a distinct pale staining appearance due to a difference in the composition of its matrix from that of the matrix of the mineralised circumpulpal dentine

146
Q

What outline might the mineralising front have?

A

May show a globular or linear outline reflecting the mineralisation process

147
Q

Where is secondary dentine seen?

A

In older teeth at the inner, pulpal part of the circumpulpal dentine

148
Q

Describe what happens to the odontoblast in the secondary dentine as you age

A

Increased crowding of odontoblasts as secondary dentine formation continues throughout life and the slower rate of deposition makes the tubular pattern of a little less regular than that of primary dentine.

149
Q

Dentine is laid down as an ________- related change

A

Age related change

150
Q

What rate is the secondary dentine laid down at?

A

Secondary dentine is laid down as an age-related change in the rate of dentine formation once a genetically predetermined thickness of primary circumpulpal dentine has been deposited and root development is complete

151
Q

What does tertiary dentine describe?

A

It is a term used for all hard tissues deposited on the pulpal surface in response to an external stimuli

152
Q

What are examples of some external stimuli that can lead to the deposition of hard tissue on the pulpal surface (tertiary dentine)

A

Caries Attrition Cavity preparation Microleakage at restoration margins Trauma

153
Q

Where is tertiary dentine found?

A

It is found pulpal to the circumpulpal dentine (and in older teeth the secondary dentine) It is restricted to the region beneath the irritation

154
Q

What does the deposition of tertiary dentine provide?

A

The deposition of tertiary dentine provides a barrier to the progress of caries and toxins

155
Q

What can stimuli of different types and severity being applied to teeth at different stages of development or ageing lead to?

A

Can result in a response tissue that may vary considerably in appearance and composition: It may resemble secondary dentine in having a regular tubular structure It may have few irregularly arranged tubules OR be atubular and resemble bone.

156
Q

Give examples of some signalling molecules

A

TGF beta Bone morphogenic proteins (BMPs)

157
Q

What does the term reactionary dentine refer to?

A

Refers to the dentine forming in response to an insult in which the existing odontoblasts (some may have died or been damaged) recover and continue to form dentine But the dentine may ave an irregular appearance with fewer tubules

158
Q

What are signalling molecules release by and why?

A

May be released by acids produced during progress of dental caries

159
Q

What do signalling molecules in dentine do?

A

They are produced by acids in dental caries and can diffuse through the dentine to stimulate activity in the original odontoblasts Or they can induce the differentiation of new odontoblasts from stem cells

160
Q

What does the term reparative dentine refer to?

A

Relates to the dentine forming after a stimulus in which the original odontoblasts in the associated region have been destroyed and new calcified tissue has been formed by newly differentiated ‘odontoblast-like’ cells

161
Q

Compare reparative dentine and circumpulpal dentine

A

Reparative dentine is much more irregular than circumpulpal dentine

162
Q

Where do the odontoblast like cells differentiate from in reparative dentine?

A

differentiate from a stem cell population in the absence of any epithelial contribution

163
Q

Where are the appropriate bioactive molecules necessary for differentiation of odontoblast like cells found?

A

They may be locally synthesised and released during the inflammatory process accompanying the stimulus

164
Q

What are the 2 theories explaining why there is a granular layer at the peripheral region in root dentine

A
  1. The currently accepted view is that the dentinal tubules in this area branch more profusely and loop back on themselves creating air spaces in ground sections that result in internal reflection of transmitted light 2. An alternative explanation for the granular appearance is that it is due to the incomplete fusion of calcospherites (much smaller than those found in the crown)
165
Q

What is the granular later at the peripheral region in root dentine called?

A

The granular layer of Tomes

166
Q

What is reparative dentine produced by?

A

The dentin is produced by differentiation of sub-odontoblastic stem cells that replace the primary odontoblasts killed from the effects of caries. The tubules are less regular and not continuous with those of the overlying dentine.

167
Q

What is the EDJ?

A

The enamel dentine junction It is the three-dimensional scalloped architecture, particularly evident beneath cusps and incisal edges

168
Q

What is the role of the enamel dentine junction?§

A

It is crucial to limiting propagation of cracks through the tooth and providing resistance to shearing forces

169
Q

What are the 5 types of dentine?

A
  1. Mantle and circumpulpal 2. Primary, secondary and regular dentine 3. Peritubular and intertubular dentine 4. Irregular secondary dentine (tertiary or reparative) 5. Dead tracts
170
Q

Describe what mantle and circumpulpal dentine looks like and where it is found

A

It is found directly beneath the enamel It looks different to dentine

171
Q

When is primary dentine formed?

A

Dentine formed during tooth development It is the most rapidly formed dentine

172
Q

When are secondary and regular dentine formed?

A

Formed more slowly over the life of the tooth and gradually fills the pulp

173
Q

What is ‘true’ denticles’?

A

Dentine formed by odontoblast like cells and that have tubules

174
Q

What is ‘false’ denticles?

A

Dentine formed by odontoblast like cells BUT DO NOT have tubules

175
Q

What can the presence of denticles do?

A

May complicate endodontic procedures

176
Q

What are the 6 layers of the dentine pulp interface?

A
  1. Mineralised dentine 2. Pre-dentine 3. Odontoblasts 4. Cell free zone 5. Cell rich zone 6. Body of the pulp
177
Q

What is interglobular dentine?

A

When 2 calcopherites are close enough to each other they can fuse together This results in an area of trapped air that os cut off from its mineral supple so it doesn’t mineralise at all This area is described as being hypomineralised and becomes fossils with the mineralised dentine producing interglobular dentine

178
Q

What are the 3 proposed mechanisms of dentine sensitivity?

A
  1. Direct innervation 2. Odontoblasts act as a sensory ending 3. Hydrodynamics (fluid flow)
179
Q

What is usually the response to any stimulus on dentine and why?

A

Pain as dentine is very sensitive

180
Q

What is the hydrodynamic theory of dentine sensitivity?

A

An effective stimulus triggers a flow of fluid within the tubules This movement is sufficient to depolarise nerve endings either within the inner parts of tubules or between odontoblasts at the pulp–predentine junction and from there to the subodontoblastic neural plexus. The induced response is the same whether the flow is in or out.

181
Q

What does the direct innervation theory of dentine sensitivity say?

A

That the pain in the dentine is due to pain ‘receptors’ being directly linked to nerves in the tubules

182
Q

What does the odontoblasts acting as sensory endings theory of dentine sensitivity say?

A

That the odontoblasts act as a receptor of pain and that these are the target for the stimulus But theres is no evidence for synapses between odontoblasts and adjacent nerve fibres

183
Q

What is the most sensitive part of the dentine?

A

The outermost part underneath the enamel or cementum

184
Q

How can sensitivity be reduced?

A

By occluding the tubules

185
Q

Which of the 3 Proposed mechanisms of dentine sensitivity seems to be the most likely and why?

A

The hydrodynamic theory seems most likely as it is irrespective go the precise position or number of nerve endings

186
Q

What are the weaknesses of the dontoblasts acting as sensory endings theory of dentine sensitivity ?

A

Theres is no evidence for synapses between odontoblasts and adjacent nerve fibres

187
Q

What are the weaknesses of the innervation theory of dentine sensitivity?

A

Deciduous teeth are just as sensitive as adult teeth even though deciduous teeth possess much fewer intratubular axons

188
Q

What can increase the potential of bacteria from dental caries and the toxins they produce passing through tubules to the pulp?

A

if the the dentine surface is exposed by: Caries Tooth surface loss Trauma Cavity preparation Microleakage at restoration margins.

189
Q

Where is extracellular dentinal fluid found?

A

In the peri-odontoblastic space, and possibly post-odontoblastic space

190
Q

What is always found on the pulpal surface?

A

The most recently formed layer of dentine

191
Q

What is the dentin matrix produced by the odontoblasts that makes up the inner layer of the dentin called?

A

Predentine which later matures to give dentine

192
Q

What is the raschkow’s plexus?

A

It is the plexus of small nerves beneath the cell rich zone

193
Q

Which 2 lines form as due to coincidence of curvatures in the dentinal tubules (optical effects).

A

Contour lines of owen and Schreger lines

194
Q

The Schreger lines are associated with what?

A

The primary curvatures of the dentinal tubules

195
Q

What happens when the primary curvatures coincide?

A

Where the peaks of the sigmoid primary curvatures coincide they form broad bands

I.O.E Dental anatomy and Histology (7 decks)

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