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3 Orthodontics > Facial Growth 1 > Flashcards

Facial Growth 1 Flashcards

1
Q

Why is facial growth important?

A

The size, shape and position of the underlying jaws determines the position of the teeth and therefore the malocclusion

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2
Q

What are the phases of life in utero?

A

Embryonic - 1-8 weeks
Foetal - 8 weeks to term

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3
Q

Describe neural crest cells

A

During folding of neural plate, cells develop from the ectoderm called neural crest cells
These migrate and differentiate into different cell types

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4
Q

What happens if the neural tube fails to fuse or form?

A

If fails to fuse - spina bifida
If fails to form - anencephaly

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5
Q

When does formation of the face occur?

A

First eight weeks after fertilisation

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6
Q

What causes cleft formation?

A

Failure of fusion between facial processes

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7
Q

When do the third and fourth pharyngeal arches develop?

A

Third and fourth - 5th week

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8
Q

Describe intramembranous bone formation

A

Bone is deposited into primitive mesenchymal tissue
Intramembranous bones include the vault of the skull, the maxilla and most of the mandible
Needle-like bone spicules form which radiate from the primary ossification centres to the periphery

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9
Q

Describe endochondral bone formation

A

Bones are preceded by hyaline cartilage
Forms the base of the skull
Several centres of ossification which eventually fuse

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10
Q

How does the base of the skull develop?

A

Series of cartilages forms the base of the skull
These undergo endochondral ossification starting at 10-12 weeks
At birth cartilaginous growth centres remain

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11
Q

How is the vault of the skull formed?

A

Intramembranous ossification starts in the third month in several centres
Fusion is incomplete at birth leaving fontanelles to allow flexibility in the skull
Growth occurs at fibrous sutures in response to intracranial pressure
Growth of the skull continues until the seventh year

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12
Q

What are the embryonic facial cartilages?

A

The maxilla and mandible develop adjacent to pre-existing cartilaginous skeletons - the nasal capsule and Meckel’s cartilage

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13
Q

What are the different mandibular processes and what stimulates their developments?

A

Condylar unit - forms articulation
Coronoid unit - lateral pterygoid and masseter
Angular unit - temporalis
Alveolar unit - if teeth are developing
Body - IAN

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14
Q

What are the main sites of secondary cartilage formation in the mandible?

A

Condylar cartilage
Coronoid cartilage
Symphyseal

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15
Q

When does ossification of the face and skull commence?

A

7-8 weeks

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16
Q

What is primary abnormality?

A

Defect in the structure of an organ or part of an organ that can be traced back to an anomaly in it’s development
Eg - spina bifida, cleft lip

17
Q

What is a secondary abnormality?

A

Interruption of the normal development of an organ that can be traced back to other influences
Eg - infection (rubella), trauma - amniotic bands

18
Q

What is a deformation?

A

Anomalies that occur due to outer mechanical effects on existing structures

19
Q

What is agenesia?

A

Absence of an organ due to failed development during the embryonic period

20
Q

What is a sequence?

A

Single factor results in numerous secondary effects
Eg - Pierre-Robin

21
Q

What is a syndrome?

A

A group of anomalies that can be traced to a common origin
Eg - Trisomy 21 in Down’s syndome

22
Q

Give examples of maxillary facial syndromes

A

Down’s syndrome
Cleft lip/palate
Achondroplasia

23
Q

Give examples of facial syndromes affecting the mandible

A

Treacher Collin’s syndrome
Pierre-Robin
Stickler’s syndrome

24
Q

Give some features of foetal alcohol syndrome

A

Small head
Short nose
Small mandible
Mild mental retardation

25
Q

What is hemifacial microsomia and how many births does it affect?

A

3D progressive facial asymmetry due to neural crest migration
Affects 1 in 3,500 births
Normal intellect but can cause deafness, cardiac and renal problems

26
Q

What is Treacher Collin’s syndrome and how many births does it affect?

A

Deformity of the first and second branchial arches
Affects 1 in 10,000 births

27
Q

What malformations can be seen in Treacher Collin’s syndrome?

A

Hypoplastic or missing zygomatic arches
Hypoplastic mandible
Ptosis of upper eyelid

28
Q

What is the prevalence of cleft lip and/or palate?

A

1 in 700 births
CP = CL in Scotland
Males over females - 3:1

29
Q

What are aetiological elements of cleft lip/palate?

A

Genetic - monozygotic twins, syndromes, familial pattern
Environment - smoking, alcohol, social deprivation, low on multivitamins

30
Q

What are the dental features of cleft lip/palate?

A

Impacted teeth
Crowding
Hypodontia
Supernumeraries
Hypoplastic teeth
Caries

31
Q

What is achondroplasia and how many births are affected?

A

Problem with endochondral ossification
Affects 1 in 14,000 births

32
Q

What can be seen in achondroplasia?

A

Affects the base of skull and long bones resulting in dwarfism
Causes retrusive middle third of face, frontal bossing and depressed nasal bridge

33
Q

What is Crouzon’s and how many births does it affect?

A

(Craneofacial dysostosis)
Premature closure of cranial sutures - especially coronal and lambdoid
Affects 1 in 25,000 births

34
Q

What can be seen in Crouzon’s

A

Shallow orbits
Prominent nose
Class III malocclusion
Narrow spaced teeth

35
Q

How is Crouzon’s treated?

A

Surgical intervention - distraction osteogenesis

36
Q

What is Apert’s and who does it affect?

A

(Acrosyndactyly)
Premature closure of almost all cranial sutures
Affects 1 in 160,000 births

37
Q

What can be seen in Apert’s?

A

Exopthalamos
Maxillary hypoplasia
Class III occlusion
AOB
Narrow spaced teeth
Parrot’s beak nose

3 Orthodontics (12 decks)

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