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Dentistry Module 4 > Tooth Development > Flashcards

Tooth Development Flashcards

1
Q

What is the basic repeating structure of hydroxyapatite?

A

OH- ion surrounded by 3 Ca2+ ions, surrounded by 3 PO43- ions, enclosed by 6 Ca2+ ions

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2
Q

What is the result of F- substituting OH- in hydroxyapatite?

A
  • stabilises the lattice
  • makes it more acid resistant
  • F- and prevention
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3
Q

What is the critical pH of hydroxyapatite and fluorapatite?

A

Hydroxyapatite: 5.5
Fluorapatite: 4.5

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4
Q

what are the three theories of mineralisation?

A
  1. Alkaline phosphotase hypothesis
  2. Nucleation ( homogeneous and heterogeneous)
  3. Matrix vesicles
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5
Q

What is the alkaline phosphatase hypothesis of mineralisation?

A

Alkaline phosphatase, an enzyme present in developing teeth and bones, drives the formation of apatite.

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6
Q

What is the homogeneous nucleation theory of mineralisation?

A

The formation of a 1st solid from a solution of ions in which no solid previously existed

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7
Q

Can homogeneous nucleation occur for hydroxyapatite?

A

No, hydroxyapatite crystals do not form spontaneously in a supersaturated solution

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8
Q

what is heterogenous nucleation?

A

A foreign solid will assist nucleation of a crystal

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9
Q

What may act as an epitactic agent in heterogeneous nucleation, promoting formation of crystals?

A

Organic matrix

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10
Q

what are possible nucleators of heterogenous nucleation?

A

Collagen
Proteoglycans
Lipids
Phosphoproteins

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11
Q

Where do crystals form in collagen structures?

A

In the gaps

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12
Q

what are the accepted theories of mineralisation?

A
  • heterogeneous nucleation
  • matrix vesicles
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13
Q

What is the first central tissue to form?

A

Dentine

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14
Q

What are matrix vesicles?

A

Membrane packages produced by cells, that contain high concentrations of Ca2+ and PO43- ions

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15
Q

What is the main benefit of matrix vesicles in mineralisation?

A

They provide an ideal micro environment for crystal formation and growth (mineralisation)

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16
Q

What is the function of matrix vesicles?

A

They help to initiate mineralisation in a tissue

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17
Q

What is the sequence of hard tissue mineralisation for a tooth?

A
  1. Dentine
  2. Enamel
  3. Cementum
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18
Q

Matrix vesicles are involved in the formation of what hard tissue?

A

Mantle dentine

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19
Q

What type of cells is dentine derived from?

A

Ectomesenchymal cells

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20
Q

What are the 4 stages of a tooth germ?

A
  1. Bud stage
  2. Cap stage
  3. Bell stage
  4. Crown stage
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21
Q

In what stage of tooth germ do hard tissues start to appear?

A

End of bell stage, start of crown stage

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22
Q

what cells form dentine?

A

Odontoblasts

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23
Q

Where are odontoblasts derived from?

A

From the cells of the dental papilla

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24
Q

At what part of the developing tooth does dentine formation begin?

A

At the cusp tip

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25
Q

What are the three stages of dentine formation?

A
  • cytodifferentiation
  • matrix formation
  • mineralisation
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26
Q

what happens during the cytodifferentiation stage of dentine formation?

A

Cells change from papilla cells to odontoblasts. This requires instruction from epithelial cells.

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27
Q

what happens during the matrix formation stage of dentine formation?

A

Odontoblasts produce matrix and promote mineralisation

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28
Q

What type of cells are found in the enamel organ, and what does it form?

A

Cell type: epithelial cells
Forms: enamel

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29
Q

What type of cells are found in the dental papilla, and what does it form?

A

Cell type: ectomesenchymal cells
Forms: odontoblasts

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30
Q

What type of cells are found in the dental follicle, and what does it form?

A

Cell type: ectomesenchymal cells
Forms: supporting tissues ( PDL, bone, socket and cementum)

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31
Q

what are the five components of the enamel organ?

A
  1. Outer enamel epithelium
  2. Stellate reticulum
  3. Stratum intermedium
  4. Inner enamel epithelium
  5. Cervical loop
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32
Q

Give the 6 steps involved in the formation of dentine from the dental papilla

A
  1. Dental papilla cells divide
  2. Cells enlarge and cross acellular space
  3. Increased synthetic/ secretory organelles
  4. The organic matrix is secreted = predentine
  5. Odontoblasts retreat secreting predentine
  6. Predentine mineralises forming dentine
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33
Q

What process signals the start of enamel formation?

A

Disintegration of the basal lamina

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34
Q

What are the two initial types of dentine?

A
  1. Mantle dentine
  2. Circumpulpal dentine
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35
Q

What is the first formed dentine?

A

Mantle dentine

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36
Q

What is the mantle dentine characterised by?

A
  • large collagen fibrils at 90 degrees to the ADJ
  • matrix vesicles are involved in it’s formation
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37
Q

What will the inner enamel epithelium cells mature into?

A

Ameloblasts

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38
Q

what happens to epithelial cells as they mature?

A

They elongate

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39
Q

What direction do ameloblast’s move during enamel formation?

A

Upwards and outwards

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40
Q

What process has allowed for enamel prisms to crucially exist?

A

Tomes process

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41
Q

What governs the shape of enamel prisms?

A
  • tomes process
  • direction of retreat of ameloblasts
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42
Q

What is the final cue for onset of amelogenesis?

A
  1. Dentine formation
  2. Breakdown of basal lamina
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43
Q

What is the enamel organic matrix made up of?

A

Amorphous gel containing enamel proteins and enzymes

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44
Q

What are the three enamel proteins within the amorphous gel organic matrix?

A
  • amelogenins (90%)
  • enamelins (2%)
  • tuftelin (confined to ADJ)
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45
Q

what are amelogenins rich in?

A

Proline and glutamine

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46
Q

What two features characterise amelogenins?

A
  • hydrophobic
  • thixotropic (changes in properties depending on conditions)
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47
Q

What are the three main roles of enamel proteins?

A
  • aid nucleation of hydroxyapatite
  • orientate and stabilise crystal growth
  • broken down and lost during maturation
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48
Q

What does enamel require to mature?

A

Mineral ions to move IN and enamel matrix to move OUT

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49
Q

What proteins are contained in the enamel matrix that flows out?

A

Amelogenins

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50
Q

What proteins are contained in the enamel matrix that remains once mineral ions start to flow into enamel?

A

Enamelin

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51
Q

when is the tomes process lost?

A

When most of the enamel thickness is laid down

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52
Q

Why is the last formed enamel aprismatic?

A

Because there is no Tomes process present, it is lost once most of enamel thickness is laid down.

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53
Q

What is the protein layer, formed when maturation of enamel is complete and is the final ameloblast secretion, called?

A

Enamel cuticle or reduced enamel epithelium

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54
Q

When does the ‘reduced enamel epithelium’ form?

A

When enamel formation is complete

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55
Q

What are the three functions of reduced enamel epithelium?

A
  1. Protection of enamel surface from resorption or prevention of cementum formation
  2. Provide an epithelial lined pathway for eruption
  3. Forms initial junctional epithelium
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56
Q

Define:

The differentiation of cells into specialised tissues and organs during growth

A

Histogenesis

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57
Q

Define:

First stage of tooth development

A

Initiation stage

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58
Q

what is the vestibular lamina?

A

Contributes to the vestibule of the mouth, delineating the lips and cheeks from the teeth. Involved in formation of sulcus.

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59
Q

Define:

The second stage of tooth germ development

A

Bud stage

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60
Q

Define:

The third stage of tooth germ development

A

Cap stage

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61
Q

Define:

The fourth stage of tooth germ development

A

Bell stage

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62
Q

Define:

The last stage of tooth germ development

A

Crown stage or late bell stage

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63
Q

Define:

Outer layer of cuboidal cells that limits the enamel organ

A

External enamel epithelium

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64
Q

Define:

Two or three layers of cells sitting above the inner enamel epithelium

A

Stratum intermedium

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65
Q

Define:

A group of star-shaped cells located in the centre of the enamel organ

A

Stellate reticulum

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66
Q

Define:

Columnar shaped cells rich in RNA, connected by desmosomes to each other. Part of the enamel organ.

A

Inner enamel epithelium

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67
Q

Define:

A form of mesenchyme, in the embryo, consisting of neural crest cells and forms he tissues of the neck and cranium.

A

Ectomesenchyme

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68
Q

What growth factor does ectomesenchyme have receptors for which allows its condensation to occur?

A

FGF8

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69
Q

What does the primary epithelial band give rise to?

A
  • dental lamina
  • vestibular lamina
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70
Q

What process does the vestibular lamina undergo to form the vestibule between teeth and lips/cheeks?

A

Apoptosis

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71
Q

What week in tooth development does differentiation between dental and vestibular lamina occur?

A

Week 7

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72
Q

What week in tooth development does apoptosis of the vestibular lamina begin?

A

Week 9

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73
Q

What week in tooth development is apoptosis of vestibular lamina complete, leaving a sulcus ?

A

Week 12

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74
Q

what are the three overlapping phases of tooth development?

A
  1. Initiation
  2. Morphogenesis
  3. Histogenesis
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75
Q

What does epithelium (ectoderm) give rise to?

A
  • enamel
  • hyaline layer of root
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76
Q

what does mesenchyme (ectomesenchyme) give rise to?

A
  • dentine
  • pulp
  • cementum
  • periodontium
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77
Q

which tissue is thought to have odontogenic potential so initiates tooth development?

A

Epithelium

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78
Q

what are the three components of a tooth germ?

A
  • enamel organ
  • dental papilla
  • dental follicle
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79
Q

What stage of tooth development is described here?:

  • spherical/ovoid epithelial condensation
  • cell proliferation
  • no histodifferentiation or morphogenesis
A

Bud stage

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80
Q

What stage of tooth development is described here?:

  • enamel organ formation
  • histodifferentiation and morphogenesis
A

Bell stage

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81
Q

What stage of tooth development is described here?:

  • cap shaped enamel organ
  • little morphogenesis
  • poorly histodifferentiatied
82
Q

what is the role of inner enamel epithelium?

A

Forms ameloblasts which from enamel

83
Q

what is the role of the stratum intermedium?

A

Synthesis and transport to and from the inner enamel epithelium

84
Q

what is the role of the Stellate reticulum?

A

Maintenance of shape and protection

85
Q

what is the role of outer enamel epithelium?

A

Maintenance of shape and exchange

86
Q

What are the three transitory (temporary) structures of a developing tooth germ?

A
  1. Enamel knot
  2. Enamel niche
  3. Enamel septum
87
Q

which transitory structure aids change in shape from cap to bell stage?

A

Enamel septum

88
Q

Give examples of important genes involved in the initiation stage of tooth development

A
  • Bmp2
  • EGF
  • MSX1
  • msx2
    -Shh
89
Q

why does the basement membrane have to be intact in a developing tooth?

A

So that differentiation of mesenchyme to odontoblast can occur

90
Q

What week of tooth development is initiation stage?

91
Q

What week of tooth development is bud stage?

92
Q

What week of tooth development is cap stage?

93
Q

What week of tooth development is bell stage?

A

Week 11/12

94
Q

In bell and crown stages, when dental papilla cells signal to IEE cells, what happens to the IEE cells?

A

They elongate and polarise

95
Q

What happens to the cervical loop during bell and crown stages?

A

Cells divide

96
Q

During bell and crown stage, which cells invade acellular zone ( what will become the dental pulp in the long term)?

A

Mature Dental papilla cells

97
Q

what do dental papilla cells mature into?

A

Odontoblasts

98
Q

What do inner enamel epithelial cells develop into?

A

Ameloblasts

99
Q

Where OEE cells and IEE cells meet, what is this called?

A

Cervical loop

100
Q

What, in the long-term, is the cervical loop responsible for?

A

Root development

101
Q

How does the odontoblast process form?

A

Pre-odontoblasts start to differentiate upon signalling from the ameloblasts, synthetic organelles are made and the nucleus retreats basally.

102
Q

what happens to the basement membrane as odontoblast process forms?

A

It breaks down and is replaced by predentine

103
Q

What are the stages of life for an ameloblast?

A
  1. Pre-secretory
  2. Secretory
  3. Transition
  4. Maturation
  5. Postmaturation
104
Q

What stage of an ameloblast’s life is described:

Undergoes cytodifferentiation, morphodifferentiation, resorption of basal lamina and epithelial-mesenchymal interactions

A

Pre-secretory

105
Q

What stage of an ameloblast’s life is described:

Ameloblasts shorten and 50% die

A

Transition

106
Q

What stage of an ameloblast’s life is described:

Final degradation and withdrawal of matrix

A

Maturation

107
Q

What stage of an ameloblast’s life is described:

Initial layer of aprismatic enamel formed, tomes process develops, matrix secretion to final thickness and development of prismatic structure

108
Q

What stage of an ameloblast’s life is described:

Enamel organ degenerates, eruption and exposure of enamel to oral cavity

A

Postmaturation

109
Q

what is pre-dentine?

A

The organic matrix that makes up dentine before it is calcified

110
Q

During what stage of an ameloblasts life cycle is BMP4 expressed?

111
Q

At what stage of tooth development does tooth shape determination occur?

A

Late cap stage and early bell stage

112
Q

What determines tooth shape?

A

Differential rates of cell division/maturation

113
Q

What feature of the developing tooth signals for tooth shape?

A

Dental papilla

114
Q

What feature of the enamel organ determines the tooth shape and type?

A

Inner enamel epithelial cell maturation

115
Q

What is the key transcription factor, found in the dental epithelium, that MUST be switched on in order for any tooth development to occur?

116
Q

Expression of what transcription factor drives incisive development?

117
Q

Expression of what transcription factor drives molar development?

A

Barx-1 and Dlx1/2

118
Q

What would happen to development of teeth if Dlx1/2 expression was switched off?

A

There will be no maxillary molars present

119
Q

What would happen to teeth development if Barx-1 is over expressed?

A

The whole jaw would be covered in molars

120
Q

What enzyme does the reduced enamel epithelium secrete to facilitate the breakdown of connective tissue to form am eruption pathway?

121
Q

Which features of the developing tooth germ play a key role in bone resorption as the tooth erupts?

A

Reduced enamel epithelium and dental follicle

122
Q

what two layers form the reduced enamel epithelium?

A

A layer of ameloblasts and the adjacent layer of cuboidal cells (outer enamel epithelium) from the dental lamina

123
Q

what epithelium does the reduced enamel epithelium form?

A

Junctional epithelium

124
Q

What common dental developments disturbances can occur in the initiation stage?

A
  • hypodontia
  • oligodontia
  • anodontia
  • supernumerary tooth or teeth
125
Q

What common dental developments disturbances can occur in the bud stage?

A

Microdontia and macrodontia

126
Q

What common dental developments disturbances can occur in the cap stage?

A
  • dens in dente
  • fusion
  • gemination
127
Q

What is dens in dente?

A

A rare developmental tooth anomaly characterised by invagination of the enamel organ into the dental papilla

128
Q

What three components interact to from the root of a tooth?

A
  • dental follicle
  • Hertwig’s epithelial root sheath (HERS)
  • dental papilla
129
Q

Where do HERS cells originate from?

A

The apical region of the enamel organ (cervical loop)

130
Q

what two cell layers does the enamel organ consist of?

A

The inner and outer enamel epithelium

131
Q

What direction does HERS proliferate?

132
Q

What direction does HERS disintegrate?

A

Cervically

133
Q

what two processes do HERS cells influence?

A
  • root dentinogenesis
  • cementogenesis
134
Q

What cells of tooth support does the dental follicle give rise to?

A
  • Cementoblasts
  • fibroblasts
  • osteoblasts
135
Q

What do Cementoblasts form?

136
Q

what do fibroblasts form?

A

PDL collagen fibres

137
Q

What do osteoblasts form?

A

Alveolar bone

138
Q

What are the three layers of the dental follicle?

A
  1. Inner investing layer ( becomes cementoblasts)
  2. loose connective tissue layer ( mainly fibroblasts)
  3. Outer layer (lines alveolar bone)
139
Q

how do hyaline layers of Hopewell Smith form?

A

Enamel matrix proteins bind to dentine and predentine

140
Q

What is the hyaline layer of Hopewell Smith?

A

The most peripheral layer of initially unmineralised dentin that forms immediately below the cementodentinal junction.

141
Q

HERS produces what growth factors?

A

BMP4
EGF
TGF beta family
Transcription factor Shh

142
Q

What process does HERS induce?

A

Odontoblast formation

143
Q

what shape are fully differentiated odontoblasts in the coronal site (crown) of the tooth?

144
Q

what shape are fully differentiated odontoblasts in the root of the tooth?

145
Q

What enamel matrix proteins do HERS cells secrete on pre-dentine surface?

A

Amelogenins

146
Q

What does HERS stand for?

A

Hertwig’s epithelial root sheath

147
Q

How are cementoblasts formed?

A

By the induction of follicle cells that migrate to root surface of tooth and differentiate into cementoblasts

148
Q

What happens when the cementum matrix mineralises?

A

Entraps PDL fibres (mainly type 1 collagen)

149
Q

After disintegration of HERS, remnants are left over. What do they form?

A

Cell rests of Malassez in PDL

150
Q

What are cell rests of Malassez in PDL?

A

Represent a group of cells in the PDL that have cystic potential

151
Q

What two structures is the hyaline layer found between?

A

Dentine and cementum

152
Q

What are the two main roles of the hyaline layer?

A
  1. Induces cementoblast formation
  2. Cements cementum to the tooth
153
Q

What are the two types of cementogenesis?

A
  1. Acellular (primary)
  2. Cellular (secondary)
154
Q

Where does the alveolar bone originate from?

A

The outer layer of condensed mesenchyme

155
Q

Through what process to HERS cells form bone cells?

A

Osteogenic differentiation

156
Q

what is the gubernacular canal?

A

An anatomical structure, which carries the gubernacular cord within it, that starts in the dental follicle and goes through to the alveolar bone crest behind the deciduous tooth

157
Q

What is the main cell type found in the PDL?

A

Spindle-shaped fibroblasts

158
Q

What two structures is the PDL found between?

A

Cementum and alveolar bone

159
Q

In crown formation:

What does the epithelium form?

A

Enamel organ

160
Q

In crown formation:

What cells does the enamel organ produce?

A

Ameloblasts

161
Q

In crown formation:

What do ameloblasts form?

162
Q

In crown formation:

What does the ectomesenchyme form?

A
  • dental papilla
  • dental follicle
163
Q

In crown formation:

What cells does the dental papilla produce?

A

Odontoblasts

164
Q

In crown formation:

What do the odontoblasts form?

165
Q

In root formation:

What does the epithelium form?

A

Hertwig’s epithelial root sheath (HERS)

166
Q

In root formation:

What does HERS form?

A

Hyaline layer of Hopewell Smith

167
Q

In root formation:

What does the ectomesenchyme form?

A

-dental papilla
-dental follicle

168
Q

In root formation:

What cells does the dental follicle produce?

A
  • cementoblasts
  • fibroblasts
  • osteoblasts
169
Q

Where does the permanent successor tend to sit in comparison to the primary predecessor tooth?

A

Lingually (lower) /palatally (upper)

170
Q

What does ‘active’ eruption mean?

A

Bodily movement of the tooth

171
Q

what does ‘passive’ eruption mean?

A

Uncovering of the tooth by apical gingival migration

172
Q

What is the term used to describe the primary tooth eruptive movement?

A

Bloodless eruption

173
Q

How could early loss of primary teeth delay the eruption of permanent teeth?

A

The cortical bone will heal fully, which is thick and more difficult for permanent teeth to erupt through

174
Q

What are the 3 “PUSH’ eruption theories ?

A
  • root formation
  • bone formation
  • fluid pressure
175
Q

What are the 3 ‘PULL” theories of eruption, involving the PDL?

A
  • collagen contraction
  • fibroblast contraction
  • fibroblast migration
176
Q

What two theories of eruption are most likely to be correct?

A

Pull: by PDL fibroblasts
Push: hydrostatic pressure

177
Q

In what direction do fibroblasts in the PDL move on eruption?

A

Cervically

178
Q

What is bloodless eruption?

A

When a primary tooth passes through an epithelial-lined channel/pathway to erupt

179
Q

What cells resorb primary teeth?

A

Odontoclasts

180
Q

What can cementum be classed into?

A

Acellular and cellular cementum

181
Q

what type of cementum is thin and covers the cervical root?

A

Acellular cementum

182
Q

What type of cementum is thick and covers the apical root?

A

Cellular cementum

183
Q

What percentages of cementum make up mineral, matrix and water?

A

Mineral: 65%
Matrix: 23%
Water: 12%

184
Q

What role does HERS play in root formation?

A

Guides root formation and determines size, shape and number of tooth roots

185
Q

When HERS cells secrete enamel matrix proteins onto dentine, what forms when they mineralise?

A

Hyaline layer of Hopewell Smith

186
Q

What is the role of the hyaline layer?

A
  1. Induces cementoblast formation
  2. Cements cementum to the tooth
187
Q

what is the traditional view of how cementum forms?

A

Cementum formed by cementoblasts derived from the dental follicle

188
Q

What has new evidence found in regard to cementum formation?

A

At least some cementoblasts may be derived from HERS cells, undergoing EMT.

189
Q

What happens upon cementum matrix mineralising?

A

PDL collagen fibres become trapped

190
Q

What do remnants of HERS form, which have cystic potential?

A

Cells rests of Mallassez in PDL

191
Q

Proteins in enamel can induce cementogensis. True or false?

192
Q

What enamel matrix derivative us used clinically to induce cementogenesis?

193
Q

What four layers make up the enamel organ?

A
  1. Inner enamel epithelium
  2. Outer enamel epithelium
  3. Stellate reticulum
  4. Stratum intermedium
194
Q

What happens to the shape of maturing inner enamel epithelial cells?

A

They become more columnar and the nuclei polarise to basal end

195
Q

What is the earliest week in utero that initiation stage of tooth development can occur?

196
Q

What is the week in utero that bud stage of tooth development can occur?

197
Q

What is the earliest week in utero that cap stage of tooth development can occur?

198
Q

What week in utero can bell stage of tooth development occur?

199
Q

What is the earliest week in utero that late bell/crown/appositional stage of tooth development can occur?

200
Q

What genes cause selective tooth agenesis in humans?

A

PAX9 and MSX1

Dentistry Module 4 (20 decks)

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