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Oral Biology > Components of the Teeth - Dentine and Pulp > Flashcards

Components of the Teeth - Dentine and Pulp Flashcards

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1
Q

give a brief outline on dentine and its features

A

dentine forms the bulk of the tooth, and is harder than both bone and cementum. it is softer than enamel.
it has great compressive and tensile strength. it is permeable, contains cell processes (making it a living tissue) and is yellowish in colour

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2
Q

describe the importance of the compressive and tensile strength of dentine

A

it is important for the cushioning of enamel

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3
Q

explain how dentine is permeable

A

it contains tubules. if the dentine is exposed, any material that can be exposed to the dentine will pass through it and go to the pulp. the permeability of the dentine depends on the depth

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4
Q

give a breakdown of the different components of dentine

A
  • hydroxyapatite makes up about 70% of the weight, and 50% of the volume
  • water makes up about 10% weight, 20% volume
  • organic matrix makes up about 20% weight and 30% volume
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5
Q

what are the different contents of the dentinal tubules

A

odontoblast processes, unmyelinated nerve terminals, dendritic cells, and dentinal fluid

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6
Q

give a brief description of pulp and its contents

A
  • pulp is the connective tissue “core” of the tooth.
  • it contains cells, extracellular components, nerves, blood vessels and lymphatics
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7
Q

what cells are found in the pulp of the tooth

A

odontoblasts, fibroblasts, defence cells

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8
Q

what are the extracellular components of the dental pulp

A

fibres like collagen and oxytalan
the matrix, which includes proteoglycans, chondroitin, dermatan

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9
Q

what nerves are found in the pulp of the tooth

A

the peripheral nerve which is innervated by one of the trigeminal nerves

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10
Q

what are the different functions of dental pulp

A

nutrition
dentine growth
dentine repair
defence (immune cells and the lymphatic drainage system)
neural functions (sensory and control of dentinogenesis)

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11
Q

what is the difference between weight composition and volume composition associated with

A

the density of the different components

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12
Q

what is the mineral content of dentine like compared to enamel

A

there is less mineral content within dentine

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13
Q

what is the content of water and organic content like in dentine compared to enamel

A

there is more water and organic content in dentine compared to enamel

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14
Q

what can loss of water content in a tooth lead to

A

fragility in the dry tooth, as it is the dehydrated dentine that leads to this fragility, rather than the enamel.

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15
Q

what can the pulp be thought of as in relation to the tooth

A

it is like the core, the vascular bed of the tooth

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16
Q

how can the strength of a tooth after a root canal be compared to the strength before

A

it is weaker post root canal due to the loss of hydration after the removal of the pulp. this makes the restorative process more complex

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17
Q

in what direction does dentine grow

A

the dentinal tubules grow inward over time

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18
Q

what can be understood by the term lumen

A

the lumen is the space within “tubes” of the body, like tubules in dentine, veins, arteries etc. it is essentially just space where things can move

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19
Q

how does the shape of dentine change over time

A

the tubules slowly grow inward

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20
Q

what are the different shapes of dentine tubules found within normal dentine

A

narrow and wide are both found within the dentin. wide tubules are close to the pulp, and narrow tubules are near to the ameli dentino junction

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21
Q

what are the different ways that slides can be prepared for viewing dental tubules

A

there are ground sections, and demineralised sections. in the demineralised sections, a special treatment like an acid or chelating agent is used to remove the mineral content, and this can use the 30% of organic content within the dentin to stain pinkish. for ground staining, it is sanded down from either side, and any cells will no longer be there, but it is possible to see where the cells were due to the presence of black dots

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22
Q

what are the s shapes of the tubules that can be viewed when looking at the cross section of dentine

A

these are the tubules which run from the amelo dentino junction to the pulp. there are primary and secondary curvatures of the dentine - the primary is the s shape that they adopt. secondary curvature are smaller curves that can be viewed on the primary curvature which show the changed direction of odontoblasts

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23
Q

why is it important to note that the dentinal tubules adopt an s shape when going from the amelo dentino junction to the pulp

A

because any damage will not be linear, since the damage will travel along the s shape.

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24
Q

can you see dentine and pulp as separate things

A

not really unless you are looking to a restorative procedure

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25
Q

describe the inside of the pulp

A

it is a connective tissue, with fibroblasts being the intrinsic cell found within.

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26
Q

describe the production of dentine

A

odontoblasts function to produce dentine. the production of dentine is special because it means the space is reduced over time since it grows inward. the odontoblasts produce the matrix that mineralises into dentine, known as predentine.

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27
Q

what is the difference between dentine and predentine

A

dentine is just mineralised predentine

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28
Q

what can be understood by globular dentine

A

this is dentine before it has been completely mineralised

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29
Q

how are tubules formed

A

each odontoblast is responsible for a tubule, and each one will send an arm into the dentine which creates a tubule and produces a matrix. as more is produced, the arm moves further away

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30
Q

where can sensory unmyelinated nerve terminals be located in tubules

A

in some sections of the tissue

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31
Q

what can be found within the dentine

A

sensory unmyelinated nerve terminals
dendritic cells from the immune system
dentinal fluid
dentinal tubules which provide the nutrients

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32
Q

what cells can be found within the pulp

A

odontoblasts, fibroblasts and defence cells

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33
Q

what are the extracellular components of dental pulp

A

fibres like collagen and oxytalan
the matrix with proteoglycans, chondroitin, dermatan

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34
Q

what are proteoglycans

A

proteins with glycosaminoglycans attached to them, found mainly in connective tissue to provide structural support and hydration

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35
Q

what are glycoproteins

A

these are proteins with carbohydrates (sugars), where the stem is a protein chain and there are polysaccharide structures attached to it

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36
Q

what are glycoprotein structure and function

A

protein with short, simple oligosaccharide molecules attached to them.
found in cell membranes to provide receptoin, adhesion and transport.

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37
Q

what else can be located within the pulp that aid with the function of the pulp

A

lymphatics, which are a drainage system, and blood vessels

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38
Q

what are the functions of dental pulp

A

they provide nutrition, growth and repair of dentine. they also provide defence

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39
Q

how does the pulp repair the dentine

A

when dentine becomes exposed, there is a reaction from the odontoblasts to close the tubules. this is the repair action. this can also produce more dentin, but a strange form of dentine that lacks any tubules which is known as tertiary dentine

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40
Q

how does the pulp defend the tooth

A

through immune cells and lymphatics (support of the defence system)

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41
Q

how are nerve cells involved in pulp function

A

these have a sensory function but also help control of more dentine generation

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42
Q

what is dentinogenesis

A

the generation of dentin

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43
Q

describe the role of blood vessels within pulp

A

they are present but they do not perforate the dentine. this means there is a space between where the dentine is and where the odontoblasts are. this is important as it represents when you have gone from pulp to dentine.

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44
Q

how does tissue react to damage

A

there is redness, swelling, pain and heat ie an inflammatory response

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45
Q

what happens when there is damage to the pulp which leads to swelling

A

the swelling is in an enclosed space, where pressure will build up as there is an increasing volume that cant be controlled. the increased pressure of the tissue means that blood vessels cant work properly and are unable to exchange components like nutrients. this leads to stagnation of the system, which leads to cell starvation of the pulp

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46
Q

what can dentine be though of as

A

the mineralised connective tissue that forms the bulk of the tooth

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47
Q

how does the size of hydroxyapatite crystals in enamel compare to the size in dentine

A

they are smaller in dentine than in enamel

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48
Q

what can be found within the dentinal tubule

A

the odontoblast processes, dentinal fluid, a nerve fibre and a process from a dendritic cell

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49
Q

how is tertiary dentine formed

A

the recruitment of stem cells lying in the dental pulp in response to trauma

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50
Q

how does the combination of enamel and dentine aid the mouth

A

it provides a rigid, hard structure suitable for chewing and tearing that resists both abrasion and fracture

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51
Q

does dentine stop growing once the tooth has erupted

A

no, it develops throughout life at the expense of the pulp, as it grows inward

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52
Q

is dentine considered to be sensitive

A

yes

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53
Q

what is predentine compared to dentine

A

the unmineralised layer of dentine matrix at the pulpal surface

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54
Q

where does the cell body of odontoblasts lie

A

at the periphery of the dental pulp

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55
Q

what are the reasons for dentine and pulp being approached as a dentine-pulp complex

A
  • they both originate from the dental papilla
  • the structures pass from the dental pulp to the dentinal tubules like cell bodies of odontoblasts, nerve fibres and dendritic processes of the antigen presenting cells
  • tissue fluid that passes along the dentinal tubules is derived from the vasculature of the dental pulp
  • the responsiveness of dentine to the external stimuli resulting in the formation of tertiary dentine is mediated by the recruitment of stem cells within the dental pulp
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56
Q

why is dentine more resistant to the propagation of cracks than enamel

A

because of the intimate associated of the small apatite crystals with strong protein fibres. cracking will only occur in dentine when it has been weakened by caries or cavity preparation

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57
Q

which stresses are more likely to result in the fracture of dentine

A

those that are parallel to the direction of the tubules

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58
Q

what are the chemical properties of dentine

A
  • consists of apatite crystals on an organic scaffold predominantly composed of collagen
  • inorganic mineral component is in the form of calcium hydroxyapatite crystals
  • crystallites are calcium poor and carbon rich in comparison to the pure hydroxyapatite, and are much smaller than those in enamel
  • the crystallites also contain fluoride
  • hydroxyapatite crystallites in mineralised dentine are found on and between collagen fibrils
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59
Q

where are the hydroxyapatite crystallites in the mineralised dentine foud

A

on and between the collagen fibrils

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60
Q

what do most of the collagen fibrils run in the direction of

A

they run in the direction parallel to the pulpal surface

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61
Q

what is found embedded in the organic matrix of dentine

A

crystallites

62
Q

where are the fibrils of dentine found

A

embedded in an amorphous ground substance.

63
Q

how are collagen fibrils in dentine assembled compared to many non mineralised connective tissues like tendons and periodontal ligament

A

they are not assembled into bundles in dentine

64
Q

what are the non collagenous proteins that can be found in the organic matrix of dentine

A
  • phosphoproteins
  • proteoglycans
  • gla-proteins
  • other acid proteins and growth factors
65
Q

what are many of the non collagenous proteins in the organic matrix involved in

A

mineralisation

66
Q

what does dentine phosphoprotein refer to

A

highly phosphorylated protein species. they have a high phosphate content and a high calcium ion binding properties which implicates it in the process of mineralisation

67
Q

what is dentine sialophosphoprotein responsible for

A

synthesising both dentine phosphoprotein and dentine sialoprotein.

68
Q

give a brief outline on the phospholipids found in dentine

A

they are detected in both predentine and mineralised dentine. they are more heavily concentrated near the mineralising front. phospholipids are needlike crystal ghosts and may be involved in the formation and growth of crystals

69
Q

what course do dentine tubules follow

A

they follow a curved, sigmoid course known as the primary curvature. the convexity of primary curvatures nearest the pulp chamber faces rootward

70
Q

what is the dentine found between tubules called

A

intertubular dentine

71
Q

what are secondary curvatures

A

these are small changes of direction found on the primary curvature

72
Q

where do tubules branch most profusely and why

A

they do so nearest to the enamel dentine junction due to the numerous processes the early odontoblast has. some end blindly and some join with other branches

73
Q

what causes obliteration of dentinal tubules

A

the formation of peritubular dentine

74
Q

what does peritubular dentin lack

A

collagenous fibrous matrix

75
Q

why will peritubular dentine be lost as dentine is routinely demineralised

A

it lacks the stabilising feature of collagen

76
Q

what happens if dentine is fractured, and what does this suggest

A

fluid exudes from the tubules and forms droplets on the surface of the dentine.
this suggests that there is a positive force, presumably pulpal tissue pressure, that is exerted outward

77
Q

what do the properties and composition of mineralised dentine vary with

A

distance from the predentine to the amelo dentino junction. mineral content of dentine decreases and thickness of the mineral crystals will increase toward the amelo dentino junction

78
Q

what are the different regions of dentine

A
  • mantle dentine
  • interglobular dentine
  • granular layer
  • hyaline layer
  • circumpulpal layer
  • predentine
  • secondary dentine
  • tertiary dentine
79
Q

where is mantle dentine found

A

the periphery of the dentiine in the crown

80
Q

what is interglobular dentine found

A

in the outer part of the crown

81
Q

where is granular dentine found

A

in the outer part of the root dentine beneath the hyaline layer

82
Q

where is hyaline dentine found

A

the outermost part of the root dentine

83
Q

where is circumpulpal dentine found

A

this is the bulk of the dentine in the crown and the root

84
Q

where is predentine found

A

unmineralised innermost dentine in the crown and the root

85
Q

where is secondary dentine found

A

innermost layer of dentine between the circumpulpal and predentine

86
Q

where is tertiary dentine found

A

the inner layer of the dentine formed mainly in the crown in response to serious insult

87
Q

give an outline on the regional dentine

A

underneath the dentoenamel junction there is mantle dentine. underneath this is the primary dentine (dentine made before birth). below this is secondary dentine, which is softer and grows continuously.

88
Q

give an outline of dentinogenesis

A
  • formation of dentine is inward, and begins with the formation of the mantle dentine
  • odontoblasts form predentine, a soft organic matrix made of proteins
  • fibroblasts assist by creating thick collagen fibres called korfs fibres, which create a framework for dentinogenesis
  • odontogenic processes secrete calcium hydroxyapatite which forms crystals to mineralise predentine to make it strong and flexible
  • the end result of this is mantle dentine
  • after this, the odontoblasts get bigger and form primary dentine. the fibroblasts move to the pulp for rest. they form the primary from the outside in
89
Q

which layer of dentine is the thickest

A

primary dentine

90
Q

how do odonotblasts change once they have formed mantle dentine

A

they get bigger and make primary dentine.

91
Q

when does secondary dentine form

A

after root formation, growing at a slow rate throughout life, maintaining tooth strength

92
Q

what borders the pulp

A

predentine

93
Q

where is tertiary dentine found

A

at sites of dental caries and attrition

94
Q

how is blood supplied to the pulp

A

external carotid artery - branches to become maxillary artery. this provides both rows of teeth with blood.
- deoxygenated blood leaves the pulp and ends up in the maxillary vein which travels back toward the heart
- the apical foramen is the narrow passage at the centre of the apex of the root where blood vessels and nerves can enter

95
Q

what are the two parts to pulp called

A

central and peripheral pulp

96
Q

where is pulp found

A

the pulp chamber

97
Q

what are the four functions of pulp

A

formation
nutrition
protection
defence

98
Q

how does the pulp represent the tooth outline

A

it forms the layer of dentine evenly in every direction which means it reflects the external form of the enamel

99
Q

what are odontoblast processes

A

cellular extensions of odontoblasts used to form dentine and dentinal fluid

100
Q

where is peripheral pulp found

A

adjacent to the calcified dentine, and the compartment closes to the central pulp is cell rich with lots of fibroblasts and undifferentiated mesenchymal cells

101
Q

how do undifferentiated mesenchymal cells support the population of odontoblasts

A

by proliferation and differentiation

102
Q

what is peripheral pulp

A

the interface of the dentine pulp complex. it is a layer of columnar odontoblast cells.

103
Q

how do dentine tubules go from the pulp to the enamel dentine junction

A

extend through the pulp, through the dentine, to the junction

104
Q

what is central pulp outlined by

A

the edge of the cell rich layer of peripheral pulp

105
Q

what is the function of central pulp

A

main support system for peripheral pulp. contains large blood vessels, nerves and fibroblasts

106
Q

what is the primary function of columnar odontoblast cells

A

the development of dentine

107
Q

how does dentine form over the lifetime of a person

A

incrementally

108
Q

dentine is a living tissue. what does this suggest about it

A

that it is formed throughout life, sensitive and can react to trauma

109
Q

how does dentine react to trauma

A

formation of tertiary dentine

110
Q

can dentine be thought of as elastic

A

yes, as well as being rigid

111
Q

what does it mean to say that dentine is heterogenous

A

it has different zones and different physical features.

112
Q

what are the features of mantle dentine

A

it is less mineralised and the dentinal tubules branch profusely

113
Q

what are the features of granular dentine

A

it is dark as the dentinal tubules may loop back on themselves. it is hypomineralised

114
Q

what are the features of interglobular dentine

A

the globules deposited in the mineral in dentine fuse to form uniformly calcified tissue. the uncalcified tissue is interglobular dentine

115
Q

how much of the composition of dentine is hydroxyapatite

A

70%

116
Q

how much of the composition of dentine is water

A

10%

117
Q

how much of the composition of dentine is organic

A

20%

118
Q

what makes up the organic matter found in dentine

A

90% is collagen type 1 and 10% is non collagenous proteins like phosphoproteins

119
Q

why do dentinal tubules reduce in diameter as they go develop

A

the lumen is narrowed by the formation of peritubular dentine

120
Q

how are odontoblasts related to dentine

A

these are the cells responsible for forming dentine. their long processes extend into the dentinal tubules. their cell body lines the border between dentine and pulp

121
Q

what forms the single layer of cells attached to the predentine surface

A

odontoblasts

122
Q

describe the epithelial structure of an odontoblast when it is fully differentiated

A

polarised columnar with a long cell process

123
Q

how does the odontoblast process extend into the dentine and pre dentine

A

through the dentinal tubules

124
Q

how do the odontoblast cells form the layer attached to the predentine surface

A

through cell junctions

125
Q

what are the different cell junctions between the odontoblasts on the cell layer attached to the predentine surface

A
  • macula adheren’s junction
  • tight junctions
  • gap junctions
126
Q

describe macula adherens junctions

A

these are desmosomes. they anchor fibrils to form a mechanical union

127
Q

describe tight junctions

A

these create near fusion of the opposing cell membranes. it limits permeability of the cell layer

128
Q

describe the gap junctions

A

these junctions allow the movement of small molecules between the adjacent cells

129
Q

why are there cell junctions between the odontoblasts on the cell layer attached to the predentine

A

to provide integrity to the cell layer

130
Q

where are capillaries located in the dentine pulp complex

A

they are found within and below the odontoblast layer.

131
Q

what is the subodontoblastic capillary plexus

A

the capillaries found below the odontoblast layer on the predentine

132
Q

why are there capillaries near the odontoblast layer

A

to supply oxygen and nutrients during dentinogenesis

133
Q

do the capillaries enter the dentinal tubules

A

no

134
Q

what are the blood vessels present in the dentine and pulp

A

there are arteriols and venules that enter via the apical foramina. they run longitudinally through the root canals.

135
Q

what is the blood flow into pulp under the control of

A

nervous control. the smooth muscle of the arteriols is innervated by the terminals of the sympathetic nerves

136
Q

how much of the weight of the pulp is water

A

75%

137
Q

how much of the weight of pulp is organic material

A

25%

138
Q

what is found at the periphery of pulp

A

a layer of odontoblasts, as well as elements capable of detecting external stimuli.

139
Q

what are the elements at the pulp periphery that are able to detect external stimuli

A

nerve terminals of the trigmeninal affarents and specialised dendritic antigen presenting cells

140
Q

what are the nerves of the pulp

A

there is sympathetic innervation within the pulp. nerve bundles run centrally in the pulp of the root in close association with one another, although some leave the central root and go to the periphery

141
Q

what is the plexus of raschkow

A

a pronounced plexus of nerves beneath the odontoblasts

142
Q

where are specialised dendritic antigen presenting cells located in the pulp

A

they are most densely found in the periphery, around nerves and blood vessels

143
Q

what are the connective tissue cells found within the dental pulp

A

fibroblasts and fibronectin

144
Q

what is fibronectin

A

a glycoprotein found in several forms that achors cells. may be important in determining shape.

145
Q

why are fibroblasts important

A

they produce the extracellular fibres and ground substance for the dental pulp. they also participate in the degradation

146
Q

what are the main fibres of the dental pulp

A

collagen

147
Q

what is the composition of collagen types in the pulp

A

60% are type 1 and 40% are type 3

148
Q

where is the arrangement of collagen within the pulp most organised

A

the periphery

149
Q

what is compressive strength

A

compressive strength is the ability to resist force, absorb it, and then come back to normal position

150
Q

what is tensile strength

A

tensile strength is associated with sheer movements, and the amount of strength required to break through

151
Q
A

Oral Biology (27 decks)

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