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Growth and Development > Tooth Development > Flashcards

Tooth Development Flashcards

1
Q

what is the pattern of tooth eruption of the primary dentition with timeline

A
  • mandibular central incisors: 5-8 mo.
    -maxillary central incisors: 6-10 months
    -mandibular lateral incisors: 7-10 mo.
  • maxillary lateral incisors: 8-12 months
  • mandibular canine: 16-20 months
  • maxillary canine: 16-20 months
  • mandibular first molars: 11-18 months
  • maxillary first molars: 11-18 months
  • mandibular second molars: 20-30 months
  • maxillary second molars: 20-30 months
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2
Q

when does calcification of the permanent dentition begin

A
  • central incisors: 3-4 months
  • maxillary lateral incisors: 10-12 months
  • mandibular lateral incisors: 3-4 months
  • canines: 4-5 months
  • first premolars: 18-24 months
  • second premolars: 24-30 months
  • first molars: birth
  • second molars: 30-26 months
  • maxillary third molars: 7-9 years
  • mandibular third molars: 8-10 years
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3
Q

when is the crown completely calcified in permanent dentition

A
  • central incisors: 4-5 years
  • lateral incisors: 4-5 years
  • canines: 6-7 years
  • first premolars: 5-6 years
  • second premolars: 6-7 years
  • first molars: 30-36 months
  • second molars: 7-8 years
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4
Q

when is the first sign of tooth development in utero

A

6-7 weeks

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5
Q

when do deciduous teeth begin to calcify in untero

A

13-20 weeks

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6
Q

how long in utero for all deciduous teeth have begun to calcify

A

18-20 weeks

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7
Q

when do deciduous teeth erupt

A

6-30 months

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8
Q

what part of the tooth is the first to calcify

A

the crown

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9
Q

what gene is responsible for tooth development in the dental mesenchyme stage

A

msx1

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10
Q

what are the stages of tooth development in order

A
  • crown formation
  • root formation
  • supporting structures
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11
Q

what are the steps in crown formation

A

-initiation
- bud stage
-cap stage
- bell stage
- enamel and dentin formation

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12
Q

describe the primary epithelial band

A

-horseshoe shaped
- correspond to future dental arches

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13
Q

what does the primary epithelial band give rise to

A

dental lamina and vestibular lamina

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14
Q

what is expressed in the epithelium where the tooth bud would form

A

SHH

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15
Q

what is expressed in the mesenchyme where the tooth bud would form

A

Pax9

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16
Q

describe the initiation of tooth development

A
  • placode formation- epithelial thickening
  • epithelial outgrowth into the mesenchyme
  • initial odontogenic potential lies in the epithelium subsequently shifts to mesenchyme - the neural crest mesenchyme induces the oral ectoderm to become the dental lamina
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17
Q

what happens in the bud stage

A

-epithelial cells show no major changes
- Shh, Lef-1 and Eda-Edar involved in placode formation
- mesenchyme beneath starts to condense by the factors secreted by the epithelium
- cross talk between the epithelium and the mesenchyme
-odontogenic potential in the epithelium

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18
Q

what happens in the cap stage

A
  • epithelium proliferates, mesenchyme continue to condense. looks like cap sitting on a ball of mesenchyme
  • tooth germ: enamel organ and dental papilla
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19
Q

what is the bud to cap stage regulated by

A

signaling molecules and transcription factors

20
Q

what does the enamel organ become

A

enamel of the tooth

21
Q

what does the dental papilla form

A

dentin (outer) and pulp ( inner)

22
Q

what does the dental follicle or dental sac differentiate into

A

supporting structures such as cementum/ periodontium/ alveolar bone proper

23
Q

what is the enamel knot

A

a key signaling center consisting of cluster of non dividing cells that determine cusp formation

24
Q

describe cap stage histodifferentiation

A

-cells in the enamel organ synthesize glycosaminoglycans in the ECM. hydrophilic and pull water in to the enamel organ
- increase in fluid volume forces the cells apart leading to formation of star shpaed stellate reticulum cells

25
Q

what do the enamel organ epithelial cells form

A
  • inner enamel epithelium
    -outer enamel epithelium
26
Q

whats happening in the bell stage

A
  • under surface of the epithelium deepens and resembles a bell
  • stratum intermedium formation
  • crown attains full size and shape
27
Q

where does permanent dentition form in relation to the deciduous dentition

A

lingual to deciduous

28
Q

in the bell stage what does the OEE and IEE look like

A

-OEE: low cuboidal shaped outer enamel epithelium
- IEE: short columnar shaped inner enamel epithelium

29
Q

what will the IEE differentiate into

A

ameloblasts

30
Q

what is the junction of IEE and OEE called

A

the cervical loop
- future site of the CEJ

31
Q

what happens during the late bell stage

A
  • dental lamina breaks and separates the tooth from oral epithelium
  • IEE completes folding forming the future crown pattern
  • folding is due to differential rates of mitotic division in IEE
  • under the influence of IEE mesenchymal cells differentiate into odontoblasts that makes dentin
  • IEE differentiates in to ameloblasts and make enamel
32
Q

what determines future cusp formation

A

site at which IEE differentiates

33
Q

what are the stages in the life cycle of ameloblasts

A
  • morphogenetic stage
  • histodifferentiation stage
  • initial secretory stage
  • secretory stage (tome’s processes present)
  • ruffle ended ameloblast of the maturation stagae
  • smooth ended ameloblast of the maturation stge
  • protective stage
34
Q

what happens in secreotry stage ameloblasts

A
  • intense synthetic and secretory activity
  • forms enamel rod and inter rod
  • secrete granules on the newly formed mantle dentin
35
Q

what are the secretory products of the secretory stage ameloblasts

A
  • proteins: amelogenin, ameloblastin, enamelin
  • proteases: enamelysin (MMP20), and kallikrein
36
Q

under the influence of epithelial cells, mesenchymal cells differentiate into:_____

A

odontoblasts that make dentin

37
Q

what is mantle dentin

A
  • first layer of dentin formed by the enwly differentiated odonotblasts, hypomineralized and only in the crown of the tooth 30-50 um thick)
38
Q

what is primary dentin

A

formed during tooth development - 4 um/day

39
Q

what is secondary dentin

A

dentin formed after tooth eruption (0.4 um/day)

40
Q

what is tertiary dentin

A

dentin produced in response to injury to protect the pulp

41
Q

describe root formation

A
  • IEE and OEE form the cervical loop proliferate downward to form double layered structure called Hertwig’s epithelial root sheath
  • odontoblasts differentiation and dentin formation
  • completion of root formation
42
Q

when is Hertwigs epithelial root sheath removed

A

mostly removed before cementum is laid down

43
Q

what do cementoblasts differentiate from

A

HERS or dental follicle cells

44
Q

what are remnants of HERS called

A

epithelial rests of Malassez

45
Q

what are the 2 types of cementum

A

acellular and cellular

Growth and Development (15 decks)

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