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BDS3 CLINICAL Ortho > Facial Growth I > Flashcards

Facial Growth I 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

Why is the study of facial growth important to orthodontists

A

It provides insight into the growth of the face
Allows us to understand development of facial anomalies
To measure changes in growth and tx using cephalometry

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3
Q

Why is insight into the growth of the face important

A

predict changes
utilize growth to correct malocclusion
time our ortho and surgery

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4
Q

What are the 2 phases in utero

A

embryonic

foetal

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5
Q

When does the embryonic stage occur

A

1-8 weeks

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6
Q

When does the foetal stage occur

A

8 weeks to term

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7
Q

What forms within the first two months

A

all of the limbs, organs including the face have formed within the first 2 months and embryo has a characteristic human form

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8
Q

What can the external environment influence cause

A

cranio facial abnormalities very early on in pregnancy

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9
Q

What occurs at stage 1

A

its around 0.1-0.15mm in size and its an egg

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10
Q

What occurs in stage 2

A

0.1-0.2mm
the egg keeps dividing into more and more cells
up to about 8-16 cells and they float down the fallopian tubes
called the morula

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11
Q

What occurs in stage 3

A 
same size
made of up to 62 cells in total
cells divide to make a cyst/blastocyst 
there is an inner cell mass 
before pre-implantation the egg hatches and loses its zone halucida and starts to get first of germ layers
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12
Q

What has happened by stage 6

A

there is a germ disc made up of ectoderm and inside is the endoderm and you also have the primitive node and streak

the ectoderm has a third layer called mesoderm and they form everything

about 4 weeks in you get somites which are blocks of material at the back and get grooves forming first which form neural tube

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13
Q

What is neural crest cell migration important for

A

development of the face

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14
Q

What does the neural folds fuse to form

A

neural tube, towards the end of week 3

failure to fuse will lead to spina bifida

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15
Q

What does the neural tube develop into

A

brain and spinal cord

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16
Q

What does failure of neural tube development had to

A

anecephaly

in which cerebral hemispheres and cranial vault are absent

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17
Q

During the folding of the neural plate, what cells develop

A

neural crest cells develop from the ectoderm along the edge of the groove

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18
Q

What is the importance of neural crest cells

A

they undergo extensive migration within the developing embryo and ultimately differentiate into many cell types e.g spinal and autonomic ganglia etc

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19
Q

What are neural crest cells derived from

A

ectomesencyhme

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20
Q

What do the the ectomesenchyme contribute to

A

branchial arch cartilage
bone
connective tissue proper
dentalm tissues

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21
Q

By stage 12 what has formed

A

beginning of pharyngeal arches

maxillary process of first arch and mandibular process too

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22
Q

By stage 13 what has formed

A

fourth pharyngeal arch

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23
Q

What happens by stage 15

A

has folded over

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24
Q

When does formation of the face occur

A

first 8 weeks after fertilization

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25
Q

What are defects of the face linked to

A

defects of the face, particularly in the midline, may be closely related to defects of the anterior parts of the brain

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26
Q

What does most of the face form from

A

migrating neural crest cells
either in the fronto-nasal process or the branchial arches
interference with this migration can lead to severe facial abnormalities

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27
Q

What does failure of fusion between the various facial processes/palatine processes result in

A

cleft formation

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28
Q

Why can cleft lip and alveolus occur independently of cleft palate

A

upper lip and anterior part of palate have different embryological origins from the posterior palate and they fuse at different times

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29
Q

At week 4 what forms

A

migrating neural crest cells form the frontonasal processes and laterally the branchial arches

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30
Q

At week 5-7 what is seen in the facial processes

A

extension and fusion of the facial processes

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31
Q

What can the skull be divided into

A

neuro and viscerocranium

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32
Q

What is the neurocranium

A

forms a protective case around the brain

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33
Q

What is the viscerocranium

A

forms the skeleton of the face

34
Q

What can the neurocranium be divided into

A

flat bones of the vault which develop intramembranously

endochondreal elements of the base of the skull

35
Q

What happens in intrammebranous bone formation

A

bone is deposited directly 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 progressively radiate from the primary ossification centre to the periphery
progressive bone formation results in fusion of adjacent bony centres

36
Q

What happens in endochondral bone formation

A

bones are preceded by a hyaline cartilage ‘model’
forms the base of the skull
several centers of ossification which eventually fuse

37
Q

How does the base of the skull grow and form

A

a series of cartilages form the base of the skull

these undergo endochondral ossification from multiple centers starting with the base-occiput at 10-12 weeks

at birth, cartilaginous growth centers remain between the sphenoid and occipital bones and in the nasal septum

38
Q

When does the intramembranous ossification of the vault of the skull commence

A

in third month in several centers

39
Q

Describe how the intramembranous ossification of the vault of the skull forms fontanelles

A

the fusion is incomplete at birth leaving widening known as fontanelles to allow flexibility in the skull during birth

40
Q

When does the anterior and posterior fontanelle close

A

A - 2 years

P - 1 year

41
Q

How does growth occur at the fibrous sutures of the vault

A

in response to intracranial pressure

42
Q

When does growth of the skull continue until

A

seventh year

some of the sutures remain open until adulthood

43
Q

What are the embryonic facial cartilages and what is their relevance

A

maxilla and mandible form intramembranously but develop adjacent to pre-existing cartilaginous skeletons - nasal capsule and Meckel’s cartilage (6 wks)

44
Q

How does the mandible develop

A

as several units all responding to different growth stimuli

45
Q

What are the different mandibular units

A

condylar unit
angular unit
coronoid unit
alveolar unit

46
Q

What does the condylar unit form

A

the articulation

contains the larges secondary cartilage formation

47
Q

What does the angular unit form in response to

A

LP and masseter muscles

48
Q

What does the coronoid unit respond to

A

temporalis muscle development (muscular processes)

49
Q

What does the alveolar unit formation depend on

A

development of teeth

50
Q

What does the body of the mandible form in response to

A

IDN

51
Q

What are the 3 main sites of secondary cartilage formation in the mandible

A

condylar cartilage
coronoid cartilage
symphyseal end of each half of the bony mandible

52
Q

When do the cartilages appear in the mandible

A

12-14 weeks IU

53
Q

When do the mandibular cartilages disappear

A

condylar - before birth

symphesal - just after birth

54
Q

When does growth at condylar cartilage stop

A

20 YO

55
Q

What are the two halves of the mandible fused by

A

midline symphysis

fuses few months after

56
Q

When does ossification of the face and skull commence

A

7-8 weeks

57
Q

What is a primary abnormality

A

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

e.g spina bifida, cleft lip, CHD

58
Q

What are secondary abnormalities

A

interruption of the normal development of an organ that can be traced back to other influences e.g teratogenic agents, trauma, amniotic bands

59
Q

What are teratogenic agents

A

infection e.g rubella
chemical e.g thalidomide
chemical e.g lithium

60
Q

What is a deformation

A

anomalies that occur due to outer mechanical effects on existing structures

61
Q

What is agenesia

A

absence of an organ due to failed development during embryonic period

62
Q

What is sequence

A

single factor results in numerous secondary effects e.g pierre robin

63
Q

What is a syndrome

A

group of anomalies that can be traced back to a common origin

64
Q

What are facial syndromes where maxillary hypoplasia is seen

A 
Apert's syndrome
croutons syndrome
oral-facial digital syndrome
binder's syndrome
achondroplasia
down's syndrome
cleidocranial dystosis
foetal alcohol syndrome
cleft lip/palate
65
Q

What are conditions where there is mandibular problems

A 
treacher colin's syndrome
pierre robin
stickler's syndrome
van der wood syndrome
turners syndrome
hemifacial microsomia
66
Q

What are environmental facial syndromes arising from early problems with facial developments (1-8 wks)

A

foetal alcohol syndrome

67
Q

What are multifactorial facial syndromes arising from early problems with facial developments (1-8 wks)

A

hemifacial microsomia
treacher colins syndrome (mandibulofacial dysostosis)
clefts of lip and palate

68
Q

What do those with foetal alcohol syndrome habve

A

microcephaly

mild mental retardation

69
Q

What are the typical facies having of those with foetal alcohol syndrome

A 
short palpebral fissures
short nose
long upper lip with deficient  philtrum
small midface
small mandible
70
Q

What is femifacial microsomes

A

unilateral mandibular hypoplasia, zygomatic arch hypoplasia, high arched palate, malformed pinna

but clonal spectrum (ear tags only, to complete lack of condyle, coronoid and ramus)

normal intellect, deafness cardiac and renal problems

71
Q

What is the theoretical cause of hemifacial microsomia

A

neural crest cell migration

72
Q

What is the cause of treacher collins

A

deformity of 1st and 2nd branchial arches

day 19-28

73
Q

What are features of treacher collins

A 
anti-mongoloid slant palperable fissure
coloboma of lower lid outer1/3
hypoplastic or missing zygomatic arches
hypoplastic mandible with antimonial notch
deformed pinna, conductive deafness
74
Q

What is the genetic etiology of cleft lip /palate

A

monozygotic twins
syndromes
familial patterns

75
Q

What is the environment etiology of cleft lip and palate

A 
social deprivation
smoking
alcohol
anti epileptics
multivitamins reduce
76
Q

What are dental features of cleft lip

A 
impacted teeth
crowding
hypodontia
super numeraries
hypoplasitc teeth
caries
77
Q

Why does cleft palate not have dental features

A

it does not cross over the alveolus, cleft lip does

78
Q

What is achondroplasia

A

problem with endochondrial ossification

defects in long bones, short limbs (dwarfism)

defects in base of the skull, restrusive middle third of face, frontal bossing, depressed nasal bridge

79
Q

What is cruouzon’s

A

premature closure of cranial sutures (esp coronal and lamdoid)

80
Q

What is the features of Crouzon’s

A 
proptosis (shallow orbits)
orbital dystopia
mild hypertelorism
recursion and vertical shortening of the midface
prominent nose 
class III malocclusion
narrow spaced teeth
81
Q

What’s Apert’s

A

premature closure of almost all cranial sutures

82
Q

What are features of Apert’s

A 
exopthalmos
hypertolarism
maxillary hypoplasia 
class III occlusion, AOB, narrow spaced teeth
parrot's beak nose
syndactyly of finger and toes

BDS3 CLINICAL Ortho (11 decks)

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