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BDS3 Orthodontics > Facial Growth > Flashcards

Facial Growth Flashcards

1
Q

What are the two stages in in utero life?

A
  • embryonic
    • 1-8 weeks
  • foetal
    • 8 weeks-term
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2
Q

What are the 3 tissues found in an embryo?

A
  • endoderm
  • ectoderm
  • mesoderm
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3
Q

What forms the neural tube?

A
  • somites
    • blocks of mesoderm
  • fused by 4 weeks
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4
Q

What type of cells from the neural tube are important for facial development?

A
  • neural crest cells
    • migrate froward after neural tube fusion
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5
Q

What embryonic tissue do dental tissues develop from?

A
  • ectomesenchyme
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6
Q

How do the pharyngeal arches contribute to facial growth?

A
  • face formed by movement of pharyngeal arches
    • arch one
      - trigeminal nerve
      - muscles of mastication
    • arch two
      - facial nerve
      - muscles of facial expression
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7
Q

What are the two different methods of bone formation?

A
  • intramembranous
  • endochondral
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8
Q

What is intramembranous bone formation?

A
  • bone deposited directly into primitive mesenchymal tissue
    • needle-like spicules form and progressively radiate
    • from primary ossification centres to periphery
    • fusion of adjacent bony centres
  • skull vault
  • maxilla
  • majority of mandible
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9
Q

What is endochondral bone formation?

A
  • bones preceded by a hyaline cartilage model
    • several centres of ossification
    • bone length increased by epiphyseal plates
  • base of skull
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10
Q

Where do growth centres remain after birth in the base of the skull?

A
  • between sphenoid and occipital bones
  • in nasal septum
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11
Q

What is Meckel’s cartilage?

A
  • temporary cartilaginous structure
    • scaffold for mandible formation
  • present from weeks 4-8 of embryonic development
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12
Q

How are the mandibular processes formed?

A
  • develops as several units
    • condylar unit
      - forms articulation
      - largest secondary cartilage formation
    • angular unit
      - response to medial pterygoid and masseter development
    • coronoid unit
      - response to temporalis development
    • alveolar unit
      - only formed if teeth are developing
    • body
      - response to formation of inferior alveolar nerve
  • 3 main sites of secondary cartilage formation
    • condylar
    • coronoid
      - disappears before birth
    • symphyseal
      - disappears just after birth
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13
Q

When does ossification of the face and skull commence?

A

7-8 weeks

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14
Q

What is a primary abnormality?

A

defect in the structure of an organ or part of an organ that can be traced back to an anomaly during development

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15
Q

What is a secondary abnormality?

A

interruption of normal development of an organ that can be traced back to other influences

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16
Q

What facial syndromes involve maxillary hypoplasia?

A
  • apert’s syndrome
  • crouzon’s syndroms
  • oro-facial digital syndrome
  • binder’s syndrome
  • achondroplasia
  • down’s sundrome
  • foetal alcohol syndrome
  • cleft lip and palate (associated with many others)
17
Q

What facial syndromes involve mandibular problems?

A
  • treacher-collins syndrome
  • Pierre-robin
  • sticklers syndrome
  • turners syndrome
  • hemifacial microsomia
18
Q

When do facial syndromes arise?

A

1-8 weeks

19
Q

What is foetal alcohol syndrome?

A
  • due to high maternal alcohol intake
    • around day 17
  • microcephaly
  • distinct facial features
    • short palpebral fissures
    • short noses
    • long upper lip with deficient philtre
    • small midface
    • small mandible
  • spectrum of intellectual impairment
20
Q

What is hemifacial microsomia?

A
  • multifactorial
    • neural crest cell migration
      - 19-28 days
  • progressive facial asymmetry
    • unilateral mandibular hypoplasia
    • zygomatic arch hypoplasia
    • high arched palate
    • malformed pinna
  • normal intellect
  • deafness
  • cardiac and renal problems
21
Q

What is Treacher Collins?

A
  • mandibulofacial dystopia
    • deformity of 1st and 2nd branchial arches
    • autosomal dominant
    • neural crest cells not present on either side
  • anti-mongoloid slant palpebral fissures
  • colomboma of lower lid
  • hypoplastic or missing zygomatic arches
  • hypoplastic mandible with pronounced antigonial notch
  • deformed pinna, deafness
22
Q

What is cleft lip and palate?

A
  • sporadic failure of closure of lip or palate
  • genetic and environmental factors
    • family pattern
    • smoking
    • alcohol
  • dental features
    • impacted teeth
    • crowding
    • hypodontia
    • supernumeraries
    • hypoplastic teeth
    • caries
  • lip surgically closed at 6-9 weeks
  • palate closed at 9 months
23
Q

What is achondroplasia?

A
  • problem with endrochondral ossification
    • defect in long bones resulting in short limbs
    • defects in base of skull
      - recursive middle third of face
      - frontal bossing
      - depressed nasal bridge
24
Q

What is Crouzon’s

A
  • craniofacial dystosis
    • premature closure of cranial sutures
      - coronial and lambdoid especially
  • proptosis
  • orbital dystopia
  • mild hypertelorism
  • recursion and vertical shortening of mid face
  • prominent nose
  • class III malocclusion
  • narrow spaced teeth
  • treated by distraction osteogenesis
    • bones broken and pulled apart 1mm daily
25
Q

What is Apert’s?

A
  • acrosyndactyly
    • premature closure of almost all cranial sutures
      - increased cranial pressure
  • expothalamos
  • hypertelorism
  • maxillary hypoplasia
  • class III occlusion
  • anterior open bite
  • narrow spaced teeth
  • parrot’s beak nose
  • syndactyly of fingers and toes
    • no skin between digits
  • narrow, high arched palate
  • sometimes cleft palate
  • conductive deafness
26
Q

What are the key features of a neonatal face?

A
  • small face compared to cranium
  • large eyes
  • low set ears
  • upright, bulbous forehead
  • broad, round face
  • vertically shallow nasal region
27
Q

What are the sites of facial growth?

A
  • sutures
  • synchondroses
  • surface deposition
28
Q

What are sutures?

A
  • fibrous joints between intramembranous bone
    • allow growth
    • fuse once growth is complete
29
Q

What are synchondroses?

A
  • located in midline
    • between ethmoid, occipital and sphenoid
  • cartilage based growth centres
    • cartilage at periphery is transformed into bone
30
Q

What is surface deposition?

A
  • new bone deposited beneath periosteum
    • resorption takes place at same time to maintain shape
    • remodelling
  • change of bone position
    • drift
31
Q

When do the sphenoid-occipital synchondrosis close and fuse?

A
  • close around 15
  • fuse around 20
32
Q

How does the growth of the maxilla occur?

A
  • maxilla displaced downwards and forwards
  • sutural growth
    • zygomatic and frontal bones
    • mid-palatine suture
  • surface deposition and remodelling
    • deposition on lower border of the hard palate
    • deposition on alveolar process
    • resorption on floor of nasal cavity
    • resorption on floor of orbits
33
Q

How does growth in the mandible occur?

A
  • downwards and forwards
  • condylar cartilage
  • surface growth

BDS3 Orthodontics (5 decks)

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