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BDS3 Orthodontics > Facial Growth II > Flashcards

Facial Growth II Flashcards

1
Q

majority of the face derived from

A

neural crest cells

ectomesenchyme

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2
Q

what regions of the embryo make up the skeleton which the face will develop from

A

frontonasal process and the maxillary and mandibular processes of the first brachial arch

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3
Q

maxilla and mandible form

A

intramembranously

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4
Q

2 pre-existing carilaginous skeletons of face

A
  • nasal capsule for the maxilla
  • Meckel’s cartilage for the mandible

little remanence by birth

secondary cartilages begin to form in utero (3)

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5
Q

neo natal face Vs adult

A

not miniature version

infant face is:

  • small compared to a large cranium
    • face 1/2 heigh of skull, in adults 3/4
      • change in length due to height of maxilla
  • eyes are large
  • ears are low set
  • forehead upright and bulbous
  • face appears broad
  • nasal region is vertically shallow - nasal floor close to the infraorbital rim
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6
Q

3 sites of facial growth

A

sutures

synchondroses

surface deposition

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7
Q

sutures

A

Specialised fibrous joints situated between intramembranous bone

  • Each suture is a band of connective tissue which has osteogenic cells in the centre and the most peripheral of these cells provide new bone growth
    • bone deposition at periphery
      *
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8
Q

growth at sutures

A

Growth at the sutures occurs in response to growing structures separating the bone

  • e.g. growth of the calvarium in response to development of the brain. Where the bones are pushed apart new bone forms in the suture. In the suture growth occurs in areas of tension.

When facial growth is complete the sutures fuse and become inactive

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9
Q

synchondroses found

A

found in midline (midsagittal plane)

  • exist between the ethmoid, sphenoid and occipital bones
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10
Q

synchondroses growth

A

A cartilage – based growth centre with growth occurring in both directions. The bones on either side of the synchondrosis are moved apart as growth takes place.

  • Cartilaginous growth plate with growth at either end of the plates

New cartilage is formed in the centre of a synchondrosis as cartilage at the periphery is transformed into bone

  • bones pushed apart, cartilage is laid down in centre of synchondroses, ossified at its edges
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11
Q

surface deposition growth

A

New bone is deposited beneath the periosteum over the surfaces of the bother the cranial and facial bones

  • In order for bones to maintain their shape as they grow, resorption is also taking place
    • This process of deposition and resorption is known as remodelling

The change in position of a bone due to remodelling is known as ‘drift’ (cortical drift)

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12
Q

cranial vault comprised of (4)

A

frontal

temporal

occipital

parietal

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13
Q

2 ways of growth in cranial vault

A
  • Bone growth at the sutures
  • External and internal surfaces are remodelled through surface deposition and resorption to displace the bones radially
    • Resorption internal calvarium
    • Deposition external
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14
Q

why does the forehead continue to grow after neural growth ceases

A

to accomondate exapanding air sinuses (pneumatisation)

generally more pronounced in males

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15
Q

when does neural growth cease

A

7 years

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16
Q

fontanelles exist

A

where more than 2 bones meet

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17
Q

how mant fotanelles are present at birth

A
  • 6 fontanelles are present at birth and these close by age 18 months.
    • Allow skull bones to move slightly in relation to each during childbirth
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18
Q

when do sutures fuse

A

when facial growth is complete

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19
Q

how does the cranial base grown

A

synchondroses growth

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20
Q

cranial base composed of (5)

A

frontal

ethmoid

sphenoid

temporal

occipital

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21
Q

what synchondroses has the most effect on post natal fatal growth

A

spheno occipital synchondroses

as open for longest time

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22
Q

how does growth occur at synchondroses (2 ways)

A

endochondral ossification

surface remodelling

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23
Q

timeline for cranial base growth

A

Half the growth in this area is completed by age 3 years

  • spheno-ethmoidal synchondrosis fuses at around 7 years
  • spheno-occipital synchondrosis closes at around 13 -15 years in females and 15-17 years in males
    • The spheno-occipital synchondroses fuses at around 20 years
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24
Q

what is the relevance of growth of the cranial base

A

Growth between the ages of 4 to 20 years causes an overall increase in length of the cranial base.

  • However, the anterior cranial base is relatively stable after the age of 4 years and so has been used for superimposition in cephalometric analysis.
    • This allows the orthodontist to assess skeletal changes due to growth and /or treatment.
    • Superimpose sequential lat cephs to see change
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25
Q

how does the cranial base influence how the maxilla and mandible relate

A

The cranial base plays an important role in determining how the maxilla and mandible relate to each other. The shape or angle of the cranial base affects the jaw relationship:

  • A small angle is more likely to be associated with a class III skeletal relationship
  • A large angle more likely to be associated with a class II skeletal pattern
    • Mandible more posteriorly
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26
Q

anterior cranial base is from

A

sella turcica and junction between nasal bone and frontal bone

mid point is sella to nasion (on lat cephs)

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27
Q

small cranial base angle

A

more likely to assoicated with class III skeletal repationsip

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28
Q

large cranial base angle

A

more likely to be associated with class II skeletal pattern

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29
Q

maxilla/nasomaxillary complex

includes

A

orbits

nasal cavity

upper jaw

zygomatic process

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30
Q

bone displacement

A

When a mass of bone is moved relative to its neighbours this is termed displacement. Displacement is brought about by forces exerted by the soft tissues and by intrinsic growth of the bone itself.

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31
Q

maxilla/nasomaxillary complex is displaced

A

downwards and forwards relative to the anterior cranial base

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32
Q

growth rate of maxilla/nasomaxillary complex

A

tends to follow neural growth of the brain early on and and so slows down towards Age 7 years.

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33
Q

why is the maxilla displaced forward

A

creates space posteriorly for development of the maxillary tuberosities and space for eruption of molar teeth

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34
Q

2 bone growth types in maxilla/nasomaxillary complex

A
  • Sutural growth takes place at the zygomatic and frontal bones and mid palatine suture
  • Surface deposition and resorption
    • e.g. deposition on the lower border of the hard palate and the alveolar process and resorption on the floor of the nasal cavity and the floor of the orbits.
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35
Q

why is sutural growth between zygomatic and frontal bones and mid palatine suture relevant to ortho

A

widen upper jaw make use of patent midpalatine suture

36
Q

example of surface deposition and resorption in maxillar/nasomaxillary complex growth

A

deposition on the lower border of the hard palate and the alveolar process and resorption on the floor of the nasal cavity and the floor of the orbits.

37
Q

growth direction of mandible

A

downwards and forwards

38
Q

where does growth occur in mandible

A

condylar cartilage

(maybe adaptive growth rather than intrinsic)

no active sutures post birth

39
Q

mode of growth in mandible

A

surface remodelling

(resorption and deposition of bone)

40
Q

differences in growth of maxilla and mandible

length

A

mandible

increases in length by 26mm in males and 20mm in females between 4-20

maxilla

increases in length by 8mm in males and 5.5mm in females between 4-20

41
Q

differences in growth of maxilla and mandible

rate

A

mandible

acceslerates significantly during pubertal growth spurt

slows to around adult levels around 17 in females and 19 in males

maxilla

after age 7, proceeds slowly

slows to around adult levels around 12

42
Q

differences in growth of maxilla and mandible

rates of growth in width Vs length

A

For both the maxilla and the mandible growth in width slows first, then growth in length and finally growth in height.

(permanent canines tend to be cease in width of jaws)

43
Q

treatment which utilises growth of mandible will work best if carried out

A

during pubertal growth spurt

12-13 girls

14-15 boys

44
Q

treatment which utilises growth of maxilla will work best

A

before the circumaxillary sutures and palate have fused

i.e. early teenage years (pre-pubertal growth spurt)

45
Q

can we predict facial growth

A

Not really with any degree of precision

Most clinicians will consider patient height in relation to chronological age and presence of secondary sex characteristics to help determine whether or not a patient has entered the pubertal growth spurt

  • Shoe size – feet tend to stop growing before height – ask if they are to get indication of whether growth potential there
  • Usually same rough height as parent
46
Q

4 theories of craniofacial growth

A

remodelling theory

sutural theory

cartilaginous theory

functional matrix theory

tend to be though as combination

47
Q

remodelling theory of craniofacial growth

A

Everything just grows by a process of deposition and resorption. The sutures and cartilages do not exert an intrinsic force

48
Q

sutural theory of craniofacial growth

A
  • Growth occurs at the sutures and cartilages but the growth at the sutures is the prime factor
49
Q

cartilaginous theory of craniofacial growth

A
  • The cartilages i.e.nasal septal cartilage and the synchondrosis generate the force to develop the bones in a specific direction
50
Q

functional matrix theory of craniofacial growth

A

later 1960s

  • Growth occurs in response to individual units which are developing to provide a function.
  • Each unit (functional matrix) is composed of tissues/organs and spaces.
  • Thus, it’s the force exerted by the growing soft tissues that determines the direction and extent of growth
51
Q

control of craniofacial gowth

A
  • combination of genetic and environmental influences are involved
  • Growth in one part of the skull influences another.

primary cartilages of the cranial base and nasal septum have intrinsic growth potential and exert a genetic influence over growth.

  • The condylar cartilage (secondary cartilage) of the mandible seems to act differently.
    • Controversy exists as to whether it is a primary growth force or purely adaptive.
      • possible that the mandible responds to changes in maxillary position with adaptive growth to maintain the position of the condyle within the glenoid fossa and maintain occlusal relationships
52
Q

3 impacts of facial growth on orthodontic tx

A
  • Growth can affect the severity of a malocclusion - either improving it or making it worse
  • Growth can be utilised by the orthodontist to facilitate treatment outcome
    • use of functional appliances
    • use of rapid maxillary expansion pre 16
    • use of protraction headgear pre 16
  • Continued “unfavourable” growth patterns following orthodontic treatment can lead to relapse of the orthodontic treatment result
53
Q

rapid maxillary expansion device

A
  • Fixed*
  • Many designs – turn screw twice daily, many weeks*
  • Pre 16 years*
  • used to facilitate ortho tx outcome*
54
Q

functional appliances used to faciliate ortho tx outcome by growth

A
  • Twin block*
  • Functional appliance treat class II div 1*
  • Reposition mandible anteriorly, encourages growth of the mandible*
55
Q

adult facial growth

(3 characteristics)

A

Very variable

Continues slowly throughout life

  • Growth in length of face continues into early 20’s in males, late teens in females
  • Tendency to increased overall length and prominence of nose and chin (and forehead in men)
    • Height of face is the last to stop
  • Lips become thinner and more retrusive (soft tissue changes)
56
Q

growth rotation

A

due to an imbalance in the growth of the anterior and posterior face heights

  • forward or backwards rotations

Originally described by Bjork using implant studies in the 1950’s and 60’s

57
Q

forward growth rotation

A

leads to short face

Green arrow – reduction from orange (child to fully grown)

  • Posterior and anterior face height has little difference when young
  • However, large difference when grown – more posterior face height growth

Mandible tends to rotate anticlockwise

58
Q

backwards growth rotation

A

leads to long face

Mandible tends to rotate clockwise- more anterior than posterior face height growth

59
Q

adverse growth effects on malocclusion

A

extremes of growth rotations make malocclusions worse

  • Continued growth when there is significant growth rotation can make a malocclusion worse
60
Q

growth rotation here

A

Forward growth rotation can lead to the development

  • deep bite – increase in vertical overlap of teeth
  • Decreased lower face height
  • Reduced Frankfort mandibular plane angle
61
Q

growth rotation here

A

Backwards growth rotation can lead to development

  • anterior open bite
  • increased lower face height – long face
62
Q

in general facial growth is

A
  • downward and forward, but there is considerable individual variation with growth rotations
63
Q

growth rate throughout life

A

slows after 16-17 years in girls and 18-20 in boys but continues throughout adulthood in very small amounts with the face getting ‘flatter’ and longer

64
Q

3 types/sites of bone growth influence the shape of the face

A
  • Sutures – fibrous joints
  • Synchondroses – cartilage based growth centre (cranial base?)
  • Surface deposition and resorption = remodelling
65
Q

growth of cranial base role

A

Plays an important role in determining how the maxilla and mandible relate to each other, the shape or angle of the cranial base affects jaw relationship

  • Smaller angle – more likely class III
  • Larger angle – more likely class II

The spheno-occipital synchondrosis continues growing into teenage years

The anterior cranial base is relatively stable after the age of 4 years and so has been used for superimposition in cephalometric analysis

66
Q

growth of maxilla/nasomaxillary complex summary

A

The maxilla is displaced downwards and forwards relative to the anterior cranial base

  • Sutural growth takes place at the zygomatic and frontal bones and mid palatine suture
  • Surface deposition and resorption
    • E.g. deposition on the lower border of the hard palate and the alveolar process and resorption on the floor of the nasal cavity and floor of the orbits
67
Q

mandible growth by

A
  • Growth occurs by surface remodelling (resorption and deposition of bone)
  • Resorption mainly anteriorly and lingually and deposition posteriorly and laterally
    • Increase in length dentition and height of face

at condylar cartilage

68
Q

when is mandible tx best

A

pubertal growth spurt

growing fastes

69
Q

when is maxilla tx best

A

before pubertal growth spurt

midpalatine suture and circummaxillary suture not fused yet

70
Q

more posterior face height growth from infant to adult causes

A

forward growth rotation

deep bite

71
Q

more anterior to posterior face height growth causes

A

backwards growth rotation

AOB

72
Q

negative impact on facial growth on ortho

A

can cause relapse

can make malocclusions worse

73
Q

radiographic technique for lat ceph

A
  • Fixed distances
  • ALARA
  • Aluminium soft tissue filter
  • Thyroid collar
  • Triangular collimation
  • NHP
  • Rare earth screen
    • LANEX screen
  • Fastest film possible (60- 70kV)
74
Q

lat ceph analysis

A

Hand traced on paper

Digitised using a computer

  • Relationship between jaws and cranial base
  • Relationship between the jaws
  • Position of teeth relative to the jaws
  • Soft tissue profile
  • Identify
    • Points, landmarks with precise definitions
    • Lines
  • Measure
    • Lengths, Heights, Angles
75
Q

12 reference points on lat ceph

A
  • Sella
  • Nasion
  • A Point
  • B Point
  • Anterior Nasal Spine
  • Posterior Nasal Spine
  • Pogonion
  • Menton
  • Gonion
  • Porion
  • Orbitale
  • Basion
76
Q

6 reference lines on lat ceph

A
  • Sella-nasion
  • Frankfort plane
  • Maxillary plane
  • Occlusal line
  • Mandibular plane
  • A-Po line
77
Q

3 aspects of eastman analysis of lat cephs

A

Antero-posterior position of the maxilla and mandible relative to the base of skull

  • SNA, SNB

Position of mandible relative to the maxilla

  • ANB (anteroposterior)
  • MMPA or FMPA (vertical)

Angulation of teeth to maxilla or mandible

  • UIMxP
  • LIMnP
78
Q

Anterio-Posterior discrepanancy (ANB) values

A

Class II (sev)

>8o

Class II (mod)

6-8 o

Class II (mild)

4-6 o

Class I

2-4 o

Class III (mild)

0-2 o

Class III (mod)

-3-0 o

Class III (sev)

o

79
Q

vertical discrepanacy (MMPA) values

A

Increased

>37o

Increased

32-37 o

Increased

27-32 o

Average

27 o

Decreased

22-27 o

Decreased

17-22 o

Decreased

<17 o

80
Q

dentoalveolar measurements

A
  • Ui/MxP 109 +/- 6 o
  • Li/MnP 93 +/- 6 o
  • Ui/Li 135 +/- 10 o
  • Li-Apo 0-2mm
81
Q

3 commonly used soft tissue planes

A
  • facial plane
  • holdaway line
  • rickett’s e plane
82
Q

7 uses of cephalograms

A
  • Gross inspection (anatomy/pathology)
  • Assess dentoskeletal relationships
  • Assess soft tissues relationship to underlying hard tissues
  • Prognosis and treatment planning
  • Monitoring facial growth
  • Predict future growth?
  • Assess changes due to treatment and growth
83
Q

possible indications for taking a ceph (4 classes)

A
  • To aid diagnosis
    • Sk class II or III (marked AP discrepancy)
    • Vertical discrepancy
    • Class III malocclusion
  • Pretreatment record
    • Upper and lower fixed appliances
  • Monitoring progress
    • Upper and lower fixed appliances
    • Functional appliances
  • Research project
84
Q

tx here

A

class III low angle

single jaw

mandibular setback

85
Q

tx here

A

class II high angle

bimaxillary osteotomy. maxillary impaction and mandibular advancement

86
Q

3 limitation categories for lat cephs

A
  • Radiographic projection errors
    • magnification
    • distortion
  • Errors within the measuring system
    • non-linear fields
  • Errors in landmark identification
    • quality of image
    • landmark definition and location
    • operator and registration procedure

BDS3 Orthodontics (13 decks)

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