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BDS2 - oral biology > tooth development > Flashcards

tooth development Flashcards

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1
Q

what are the 3 embryonic layers all body tissue develop from

A
  • ectoderm
  • mesoderm
  • endoderm
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2
Q

what is tooth enamel derived from

A
  • ectoderm
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3
Q

what are the supporting elements of the teeth derived from

A
  • ectomesenchyme
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4
Q

what is the ectomesenchyme part of

A
  • the neural crest that develops beside the primitive nervous system (ectoderm)
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5
Q

what do teeth develop from

A
  • tooth germs
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6
Q

what is the neural crest

A
  • a fourth cell type that forms between the ectoderm and the neural tube
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7
Q

what is the neural crest tissue also called

A
  • ectomesenchyme
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8
Q

how does the neural crest form

A
  • the neural plate folds into a groove
  • then becomes the neural tube
  • the top of this is the neural crest
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9
Q

what does the neural crest form

A
  • ectomesenchymal cells
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10
Q

what does neural crest tissue migrate to form

A
  • the developing face and jaws

- finger like projections form the face

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11
Q

what can failure of the neural crest projections to migrate lead to

A
  • pathological situations that affect the formation of the tooth
  • mandiblofacial dysostosis
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12
Q

what is mandibulofacial dysostosis

A
  • mandible looks smaller
  • eye sockets are further apart than normal
  • ears position is not in the same place as normal = lower
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13
Q

what cause mandibulofacial dysostosis

A
  • failure of cells creates a specific phenotype seen in the reduction of size of mandible and absence of teeth
  • in both permanent and deciduous teeth
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14
Q

what are the stages in tooth development

A
  • initiation
  • morphogenesis
  • cytodifferentiation
  • matrix secretion
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15
Q

what occurs during initiation

A
  • brachiosaurus arches project themselves to form the face

- mandible is formed by 2 process that join together

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16
Q

does the mandible or maxillary processes fuse first

A
  • mandible
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17
Q

at what time of development does intitiation take place

A
  • 5-6 weeks development
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18
Q

at what time does the primary epithelial band form

A
  • 6 weeks IUL
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19
Q

what does the primary epithelial band look like

A
  • a thickening in epithelium of the embryonic mouth (stomadeum)
  • thickening of the surface of the mandible
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20
Q

at what time does the dental lamina form

A
  • approx 7 weeks IUL

- the primary epithelial band has grown into the jaw and divided into 2 parts

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21
Q

what is the dental lamina

A
  • vestibular lamina which will break down to form the buccal sulcus and the dental lamina, from which the enamel organ develops
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22
Q

what is needed for the vestibular lamina to form the vestibule

A
  • a space is needed which is formed by apoptosis
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23
Q

what shape is dental lamina

A
  • horse shoe shaped structure
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24
Q

what is the second stage of tooth development

A
  • morphogenesis
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25
Q

what is the first stage of tooth development

A
  • initiation
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26
Q

what occurs in the second stage of tooth development

A

shape formation of organs

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27
Q

at how many weeks is the bud stage within morphogenesis

A

approx 8 weeks IUL

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28
Q

what happens in the bud stage

A
  • dental lamina thickens into a bud stage enamel organ
  • ectomesenchymal condensation appears and this is the dental papilla = cells around the bud condensate
  • first event of the shape seen by the dental papilla
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29
Q

what is the shape of the tooth determined by

A

enamel organ

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30
Q

at how many weeks is the cap stage within morphogenesis

A

approx 11 weeks

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31
Q

what happens during the cap stage

A
  • the enamel organ forms a ‘cap’ over the papilla

- ‘cap stage’ enamel organ

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32
Q

how many types of epithelium does the cap stage have

A
  • external enamel epithelium (EEE)

- internal enamel epithelium (IEE)

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33
Q

where do IEE and EEE meet

A
  • meet at the cervical loop
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34
Q

what is the cervical loop

A
  • where the formation of the root starts
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35
Q

what is the general term for the enamel organ

A
  • placode
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36
Q

what are placodes also seen for

A
  • nails, hair and mammary glands

- it is the same process for all organs: hair, nails, mammary glands and teeth

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37
Q

what is hypohidrotic ectodermal dysplasia

A
  • absence of teeth
  • shape of teeth are different
  • some teeth can be impacted and not erupt
  • changes can also impact other areas of the body as well = absence and reduction in number and size of hair, nails and mammary glands
  • is a genetic disease = means it can help with those who are pregnant as can give baby gene therapy treatment early on
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38
Q

what can prevent hypohidrotic ectodermal dysplasia

A
  • gene therapy

- must be done at an early stage of development

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39
Q

what is the third stage of tooth development

A
  • cytodifferentiation
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40
Q

what happens during cytodifferentiation

A
  • formation of tooth into a ‘bell’
  • enamel organ ‘bell stage’
  • more cell layers differentiate
  • tooth shape is being defined = have whole shape of tooth
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41
Q

at how many weeks is the bell stage

A
  • approx 14 weeks
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42
Q

how many cell layers does the bell stage enamel organ have

A
  • 4
  • stratum intermedium
  • internal enamel epithelium
  • external enamel epithelium
  • stellate reticulum
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43
Q

what is the function of stratum intermedium and stellate reticulum

A
  • protect and maintain

- define the shape of the tooth

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44
Q

where does the process of crown formation take place

A
  • process doesnt occur throughout the whole structure
  • starts at cusp area = differentiated cells form dentine then enamel
  • differentiation occurs from cusp downward to cervical area
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45
Q

why is tetracycline not allowed for children or pregnant women

A
  • causes tooth staining during development and will show as a line on the tooth
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46
Q

at how many weeks is the permanent tooth germ present

A
  • approx 12th week, an extension appears on the lingual side of the dental lamina
  • this is the dental lamina for the permanent successor
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47
Q

at what week does the 1st permanent molar develop as backwards extension of dental lamina

A
  • around 16th week
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48
Q

what is the 4th stage of tooth development

A
  • matrix secretion
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49
Q

what happens in the matrix secretion stage

A
  • enamel organ late bell stage
  • crown shape is well defined
  • apposition of enamel and dentine begins
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50
Q

at how many weeks is the enamel organ late bell stage

A
  • approx 18 weeks IUL
51
Q

what forms first between enamel and dentine

A
  • always have initial formation of dentine before enamel

- enamel organ defines the process and dental papilla follows

52
Q

what is the process of formation of enamel and dentine

A
  • dental papilla cells adjacent to the IEE differentiate into odontoblasts
  • odontoblasts lay down dentine matrix, which is later mineralised
  • once dentine formation has begun, IEE cells differentiate into ameloblasts, which form enamel
  • for dental papilla to differentiate, it requires the presence of the enamel organ
53
Q

what is dentinogeneis

A
  • formation fo dentine
54
Q

what happens in dentinogenesis

A
  • odontoblast differentiation form IEE
  • deposition of dentine matrix (mainly collagen)
  • this un mineralised dentine is called pre-dentine
  • mineralisation of dentine
55
Q

what happens in stage 3 of dentinogenesis

A
  • cell division of ectomesenchymal cells and keeps one ectomesenchymal cell waiting to become the stem cell
56
Q

what is secondary dentine

A
  • a slowed down version of primary dentine
57
Q

what is tertiary dentine

A
  • dentine formed in response to trauma
58
Q

what 2 ways can tertiary dentine be formed

A
  • 1 = by odontoblast recognising the threat and then begin to make it
  • 2 = or the threat is too bad that the odontoblasts die so the ectomesenchymal cells that were dormant are recruited to form tertiary dentine
59
Q

what does tertiary dentine formation depend on

A
  • presence or absence of those primary odontoblasts
60
Q

what is the matrix

A
  • major nutritional source coming from the vascularised side
61
Q

how is enamel made

A
  • enamel is very highly mineralised
  • made in two stages
  • ameloblasts change form and function several times during amelogensis
62
Q

what are the 2 stages of enamel formation

A
  • 1 - protein matrix is deposited = matrix partially mineralised (30%)
  • 2 - once this framework is established, the organic part is removed, and mineralisation is complete (‘maturation’)
63
Q

what are the 4 main stages of ameloblast differentiation

A
  • differentiation
  • secretion
  • maturation
  • regression
64
Q

what occurs during the first stage of ameloblast differentiation

A
  • differentiation

- change in position on basement membrane and the cell becomes polarised to produce the organic matrix

65
Q

what occurs during the second stage of ameloblast differentiation

A
  • secretion

- effective arrangement to create energy/protein

66
Q

what happens in the third stage of ameloblast differentiation

A
  • maturation

- protein is removed

67
Q

what happens in the fourth stage of ameloblast differentiation

A
  • regression
  • ameloblasts stop having active functional process but instead a protective function
  • these cells that are formed in the regression stage form the junctional epithelium
68
Q

what are other stages of ameloblast formation

A
  • morphogenic
  • histodifferentiation
  • secretory (initial)
  • secretory (tomes process)
  • maturative (ruffle-ended)
  • maturative (smooth)
  • protective
69
Q

where do the stages of ameloblast formation take place

A
  • all stages happen at the same time but in different regions
  • late stages occur at the cusp, early stages occur at the cervical region
70
Q

what occurs during ameloblast differentiation

A
  • dentine induces IEE cells to differentiate into ameloblasts
  • they elongate, becoming columnar
  • the nucleus migrates to the basal and of the cell
71
Q

what occurs during the secretory phase of amelognenesis

A
  • ameloblast become secretory cells
  • they synthesise and secrete the enamel matrix proteins (amelogenins)
  • the matrix is partially mineralised (30% mineral as seeded crystallites)
72
Q

what allows crystallisation of ameloblasts

A
  • when the ameloblasts become secretory cells and secrete and synthesis the enamel matrix this allows crystallisation
73
Q

what occurs during maturation phase of amelogenesis

A
  • most of the matrix proteins are removed to allow mineral content to increase to 95%
  • mineral content of enamel is increased
  • erupted teeth have increased carbonated hydroxyapatite and that is reduced as you age and so you get more hydroxyapatite
74
Q

does mature enamel have pure hydroxyapatite

A
  • no
  • although mineral content is matured it doesn’t mean you have pure hydroxyapatite
  • still have a mixture of carbonated apatite
75
Q

what occurs during protection phase of amelogenesis

A
  • ameloblasts regress to form a protective layer = the reduced enamel epithelium
  • involved in eruption
  • formation of epithelial attachment
76
Q

why do we prescribe fissure sealants at school age

A
  • as newly erupted teeth are more susceptible to caries

- around 6 years old look to give sealant as they are effective at that age when teeth have just erupted

77
Q

what are the 3 times when there is a peak of caries

A
  • starting primary school
  • secondary school
  • college/uni
78
Q

what is amelogenesis imperfecta

A
  • genesis of enamel if not perfect
  • autosomal recessvie hypoplastic hypomaturation amelogenesis imperfecta
  • can get different types
  • matrix metallopeptidase 20 gene or MMP20 = located on long arm of chromosome 11 at position 22.3
79
Q

what does gene MMP20 do

A
  • provides instruction lion for proteins for making enamelysin
  • creates proteins that make crystallites
  • absorbed protein content so that the mineral content increases
80
Q

what does enamelysin do

A
  • cleaves other proteins such as amelogenin and ameloblastin into smaller pieces = means it is easier to remove
81
Q

why are teeth more yellow than normal in amelogenesis imperfecta

A
  • protein
  • staining
  • translucency may be decreased = it is based on mineral content and if that is reduced then so is the translucency so can see the colour of dentine shining through the enamel
82
Q

what do teeth look like in amelogenesis imperfecta

A
  • look rough, dull

- premolars look weird, they don’t have that round shape

83
Q

what do you do when the 1st molar erupts in those with amelogenesis imperfecta

A
  • place a stamp crown on it

- used as it is too difficult to do large restorations in that tooth

84
Q

what is a stamp crown

A
  • hollow pieces of stainless steel stamped into the shape of the tooth
85
Q

why are stamp crowns sued

A
  • restoring teeth on patients with amelogenesis imperfecta is very difficult as composite doesn’t adhere the same
  • it is good as it covers the whole tooth
86
Q

why is vertical bone loss called vertical bone loss

A
  • doesn’t follow the reach of the bone
87
Q

what is bad about the stamp crown

A
  • can cause vertical bone loss
  • crown is larger than needed so invade biological space
  • they are not made to be perfect = why they work well with paediatric dentistry as the teeth will be lost anyway
88
Q

why can’t you see the interface between the dentine and enamel in amelogenesis imperfecta

A
  • enamel is so mineralised that it has the same density as dentine so shows the same
89
Q

how do you know if the absence of gene MMP20 is complete

A
  • if the tooth still looks slightly shiny then the gene is not completely gone as still have some level of mineralisation
90
Q

what is the only treatment that will work on patients with amelogenesis imperfecta

A
  • crown

- everything else will probably fail

91
Q

what are amelogenesis imperfecta patients more at risk of

A
  • caries

- but means they know how to prevent it as much as they can

92
Q

what is dentinogenesis imperfecta

A
  • enamel is properly formed but the dentine hasn’t

- there is lots of tooth wear =

93
Q

how does dentinogenesis imperfecta cause tooth wear

A
  • enamel relies on the resilience of dentine and without then enamel can’t flex as well and so tooth wear is quick
94
Q

how does dentinogenesis imperfecta show on a x-ray

A
  • can see the different between enamel and dentine as enamel is mineralised
  • can’t really see root canal as the density of the dentine is lower and quite similar to absence of dentine all together
  • don’t see the difference between dentine and pulp
95
Q

what is the 4th stage in tooth development

A
  • root formation
96
Q

when does root formation begin

A
  • when crown formation is complete
97
Q

what maps out the shape of the crown

A
  • the enamel organ

- migration of the cervical loop maps the crown shape

98
Q

where do the IEE and EEE meet

A
  • at the cervical loop
99
Q

what is apical growth of the cervical loop now called

A
  • Hertwig’s Epithelial root sheath (HERS)

- defines root shape

100
Q

what is Hertwig’s epithelial root sheath

A
  • 2-cell-layered structure, in contrast to the 4 cell layered enamel organ
101
Q

what does HERS induce formation of

A
  • root dentine
102
Q

when does HERS break up

A
  • once the initial layer of root dentine is formed it breaks up as no enamel is formed in the root
103
Q

what do remains of HERS be

A
  • debris of Malassez
104
Q

what can debris of Malassez become

A
  • can develop into a cyst

- called odontogenic cysts

105
Q

what differentiates into cementoblasts

A
  • mesenchymal cells from the follicle contact the dentine and differentiate into cementoblasts
106
Q

what do cementoblasts do

A
  • form the cementum
107
Q

what are Sharpay’s fibres

A
  • fibres from developing PDL than are embedded in the cementum
  • embedded and then they form the true fibre cementum
108
Q

what are true cysts

A
  • have a direct connection with epithelium
109
Q

what type of tissue s enamel organ and what is its origin and products

A
  • type of tissue = epithelium
  • origin = ectoderm
  • products = enamel
110
Q

what type of tissue is dental papilla and what is its origin and products

A
  • type = ectomesenchyme
  • origin = neural crest
  • products = dentine, pulp
111
Q

what type of tissue is dental follicle and what is its origin and products

A
  • type = ectomesenchyme
  • origin = neural crest
  • products = cementum, PDL, alveolar bone (partly)
112
Q

when can you get tooth developmental abnormalities

A
  • prenatal
  • postnatal
  • inherited
  • acquired = enamel defects
113
Q

what are the effects of tooth developmental abnormalities

A
  • number
  • shape
  • size
  • structure
  • eruption
114
Q

what is gemination

A
  • means twins
  • from one tooth, 2 are born
  • can be difficult to distinguish between fusion
115
Q

what is fusion

A
  • two teeth have fused together

- difficult to tell between gemination and fusion

116
Q

what is concrescence

A
  • connection between cementum
117
Q

what is the vestibule lamina

A
  • projection of epithelium cells entering the mesenchymal structure
  • apoptosis drives shape and formation
118
Q

how many processes form the palate

A
  • 3
119
Q

why is cleft palate more common than cleft lip

A
  • palate has longer to grow and there is a tongue that is to grow as well
120
Q

when is the first surgery for cleft palate done

A
  • as soon as the baby is born
  • because they are still growing, and baby needs to breast feed and can’t do that without a plate
  • first surgery gives baby a soft structure at this stage
121
Q

what is cartilage responsible for forming

A
  • 2 bones in the ear

- has nothing to do with the formation of the mandible

122
Q

what is the function of the dental papilla

A
  • to produce the dentine and pulp
123
Q

what is a cysts

A
  • it is a balloon of epithelium cells filled with a liquid inside allowing them to expand
  • ability to expand is the issue with cysts
124
Q

what do cysts have their name of

A
  • have their name after genesis of tooth

BDS2 - oral biology (5 decks)

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