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BDS3 Orthodontics > Facial Growth II > Flashcards

Facial Growth II Flashcards

1
Q

What are the two forms of ossification?

A
  • Intramembranous or endochondral
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2
Q

What are the two pre-exisitng cartilaginous skeletons for the face?

A
  • Nasal capsule
  • Meckel’s cartilage
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3
Q

What are the two pre-existing cartilaginous skeletons for face?

A
  • Nasal capsule
  • Meckel’s cartilage
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4
Q

How is the infant face different compared to the adult face?

A
  • Face is small compared to adult cranium
  • Eyes are large
  • Ears low set
  • Forehead upright and bulbous
  • Face appears broad
  • Nasal region vertically shallow
  • Nasal floor close to inferior orbital rim
  • In adult midface expands and nasal floor descends
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5
Q

What are the sites of facial growth?

A
  • Sutures
  • Synchondroses
  • Surface deposition
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6
Q

What are sutures?

A
  • Specialised fibrous joints situated between intramembranous bone
  • Band of connective tissue which has osteogenic cells in centre (most peripheral provide new bone growth)
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7
Q

How does growth at sutures occur?

A
  • Occurs in response to growing sutures separating the bone
  • E.g. growth of calvarium in response to development of brain
  • Where the bones are pushed apart new bones forms in suture
  • Occurs in areas of tension
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8
Q

What happens to the sutures when facial growth is complete?

A
  • Sutures fuse and become inactive
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9
Q

What are synchondroses?

A
  • A cartilage based growth centre with growth occurring in both direction
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10
Q

Where are synchondroses found?

A
  • Found in midline
  • Exist between ethmoid, sphenoid and occipital bones
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11
Q

How is new cartilage formed at synchondroses?

A
  • Bones either side of synchondrosis moved apart as growth takes places
  • New cartilage formed in centre of synchondrosis
  • Periphery transformed into bone
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12
Q

What is surface deposition?

A
  • New bone deposited beneath periosteum over surfaces of both the cranial and facial bones
  • Resorption also takes place as bones need to maintain their shape
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13
Q

What is the process of deposition and resorption known as?

A
  • Remodelling
  • Change in position of bone due to remodelling known as drift (cortical drift)
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14
Q

What is the cranial vault comprised of?

A
  • Frontal
  • Temporal
  • Occipital
  • Parietal
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15
Q

When does the cranial vault stop expanding?

A
  • Expands in response to growing brain until 7years
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16
Q

When is the rate of growth the greatest in the cranial vault?

A
  • Greatest first 3 years of life
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17
Q

What are the ways the cranial vault grows?

A
  • Bone growth at sutures
  • External and internal surfaces are remodelled through surface deposition and resorption to displace bones radially
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18
Q

Why does the forehead continue to enlarge even after neural growth has stopped?

A
  • Continues to enlarger in response to expanding air sinuses (pneumatisation)
  • More pronounced in males
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19
Q

How many fontanelles are present at birth and when do they close?

A
  • 6 Fontanelles present at birth
  • Close by 18months
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20
Q

What happens to the sutures when facial growth is complete?

A
  • Sutures fuse
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21
Q

What bones is the cranial base made of?

A
  • Frontal
  • Ethmoid
  • Sphenoid
  • Temporal
  • Occipital
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22
Q

What two ways does growth occur in the cranial base?

A
  • Endochondral ossification
  • Surface remodelling
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23
Q

When do the synchondrosis of the cranial base fuse?

A
  • Spheno-ethmoidal synchondrosis fuses at 7years
  • Spehno-occipital closes at 13-15 in females and 15-17 in males
  • Spheno-occipital fuses at 20years
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24
Q

When does the growth of cranial base occur?

A
  • Between 4 and 20years
  • Causes overall increase in length of cranial base
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25
Q

How is the anterior cranial base used for orthodontists?

A
  • Anterior cranial base relatively stable at 7 years
  • Use for superimposition in cephalometric analysis
  • Allows orthodontist to assess skeletal changes due to growth and/or treatment
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26
Q

How does the cranial base determine the relationship of maxilla and mandible?

A
  • Shape or angle of cranial base affects jaw relationship
  • Maxilla articulate with anterior cranial base
  • Mandible with posterior cranial base and suspended beneath middle cranial fossa
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27
Q

What does a small angle in cranial base determine?

A
  • Class III skeletal relationship
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28
Q

What does a large angle in cranial base determine?

A
  • Class II skeletal pattern
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29
Q

What is included within the maxilla/ nasomaxillary complex?

A
  • Orbits
  • Nasal cavity
  • Upper jaw
  • Zygomatic processes
30
Q

How is the maxilla displaced in relation to anterior cranial base?

A
  • Downwards and forwards
31
Q

What is meant by the term displaced in this context?

A
  • When mass of bone moved relative to neighbours
  • Brought about by forces exerted by soft tissues and intrinsic growth of bone
32
Q

Where does sutural growth occur in maxilla/ nasomaxillary complex?

A
  • At zygomatic and frontal bones
  • Mid palatine suture
33
Q

What surface remodelling occurs at maxilla/ nasomaxillary complex?

A
  • Deposition on lower border of hard palate and alveolar process
  • Resorption on floor of nasal cavity and floor or orbits
34
Q

How does the mandible grow?

A
  • Downwards and forward
35
Q

Where does growth of the mandible occur?

A
  • At condylar cartilage
  • Adaptive growth not intrinsic
36
Q

Where does surface remodelling occur in mandible?

A
  • Resorption mainly anteriorly and lingually
  • Deposition posteriorly and laterally
37
Q

What are the results of surface remodelling in the mandible?

A
  • Increase in height of ramus
  • Increase in length of dental arch to accommodate permanent teeth
38
Q

Why is forward displacement of maxillary complex important?

A
  • Creates space posteriorly for development of maxillary tuberosities
  • Space for eruption of molar teeth
39
Q

How much does the mandible increase in length for females and males?

A
  • 26mm in males
  • 20mm in females
  • Between 4-20years
40
Q

When is growth the most of the mandible?

A
  • During pubertal growth spurt
41
Q

When does growth of the mandible slow for females and males?

A
  • 17 in females
  • 19 in males
42
Q

How much does the maxilla increase in length by for females and males?

A
  • 8mm in males
  • 5.5mm in females
  • Between ages 4-20years
43
Q

When does growth of the maxilla slow down significantly?

A
  • 7 years
  • Slows to adult levels at 12years
44
Q

When will orthodontic treatment work best?

A
  • Treatment that utilises growth of mandible Best during the pubertal growth spurt
  • Treatment that utilises growth of maxilla work bet in early teenage years (before circumaxillary sutures and palates have fused)
45
Q

What is the remodelling theory of craniofacial growth?

A
  • Everything grows by process of deposition and reposition
  • Sutures and cartilages don’t exert intrinsic force
  • Historical theory
46
Q

What is the sutural theory?

A
  • Growth occurs at sutures and cartilages (genetically controlled)
  • Growth at sutures is main factor for development of cranial vault and maxilla
  • Historical theory
47
Q

What is the cartilaginous theory?

A
  • Cartilages like nasal septal cartilage and synchondrosis generate force
  • Develops the bones in specific direction under genetic control
48
Q

What is the functional matrix theory?

A
  • Growth occurs in response to individual units that are developing to provide a function
  • Each unit (functional matrix) composed of tissues, organs and spaces
  • Force exerted by growing soft tissues determines direction and extent of growth
49
Q

What are the most recent views on the control of growth?

A
  • Combo of genetic and environmental factors
  • Growth in one part of skull influences other
  • Primary cartilages have intrinsic growth potential and exert genetic influence over growth
  • Condylar (secondary) cartilage of mandible different
  • Mandible responds to maxillary position changes to adapt growth?
50
Q

How can growth be utilised by orthodontist to facilitate treatment outcome?

A
  • Functional appliances
  • Rapid maxillary expansion (RME)
  • Protraction headgear
  • Overbite reduction
51
Q

When was a growth rotation originally described and who by?

A
  • Bjork using implant studies in 1950’s and 60’s
52
Q

Why does a growth rotation form?

A
  • Imbalance in growth of anterior and posterior face heights
53
Q

What does a forward rotation lead to?

A
  • Short face
  • Development of deep bite
54
Q

What does a backwards rotation lead to?

A
  • Long face
  • Development of anterior open bite
55
Q

What is adverse growth?

A
  • Continued growth when there is significant growth rotation
  • Can make malocclusion worse
56
Q

What are the characteristics of adult facial growth?

A
  • Very variable
  • Continues slowly throughout life
  • Length continues until 20 in males and late teens in females
  • Increased overall length and prominence of nose and chin (forehead in males)
  • Lips thinner and more retrusive
57
Q

How can we measure facial growth changes?

A
  • Casts of the face
  • Cephalometry
  • 3D laser scanning
  • 3D photogrammetry
58
Q

What are the indications for taking a lateral cephalogram?

A
  • To aid diagnosis (vertical discrepancy or skeletal class)
  • Treatment planning
  • Progress monitoring
  • Research projects
59
Q

What is cephalometry?

A
  • Analysis and interpretation of lateral cephalographs
  • Need to be reproducible (patient positioned in cephalostat at set distance from cone and film)
60
Q

How should the head be set up for a cephalograph?

A
  • Frankfort plane horizontal
  • Teeth in RCP
  • Head kept steady by contacting soft tissues at nasion and bilaterally with ear rods in EAM
61
Q

How can we analyse a lateral ceph?

A
  • Identify any points/ landmarks / lines
  • Measure lengths/ heights/ angles
62
Q

Upon analysis what can a lateral ceph show us?

A
  • Relationship between jaws and cranial base
  • Relationship between the upper and lower jaw
  • Position of teeth relative to the jaws
  • Soft tissue profile
63
Q

What are some reference landmarks?

A

Sella
- Nasion
- A Point
- B Point
- Anterior Nasal Spine
- Posterior Nasal Spine
- Pogonion
- Menton
- Gonion
- Porion
- Orbitale

64
Q

What are some reference lines?

A
  • Sella-nasion
  • Frankfort plane
  • Maxillary plane
  • Occlusal line
  • Mandibular plane
65
Q

What are the angles measured in the Eastman Analysis?

A
  • Antero-posterior pos of maxilla and mandible relative to base of skull (SNA, SNB)
  • Position of mandible relative to maxilla (ANB = anteroposterior, MMPA or FMPA= vertical)
  • Angulation of teeth to maxilla and mandible (UIMxP, LIMnp)
  • Vertical facial proportions (LAFH/TAFH ratio)
66
Q

What are the values of class I in ANB?

A

2-4°

67
Q

What are the values for class II in ANB?

A

4->8°

68
Q

What are the values for class III in ANB?

A

<3 - 2°

69
Q

What is the value for average vertical discrepancy?

A

27°

70
Q

What are some errors in cephalometry?

A
  • Radiographic projection errors like magnification or distortion
  • Errors within measuring system like non-linear fields
  • Errors in landmark identification like quality of image, landmark definition and location
71
Q

What are some stable structures that sequential lateral cephalograms can be superimposed?

A
  • Anterior wall of sella
  • Middle cranial fossa
  • Anterior surface of zygomatic process
  • Anterior border of chin
  • Inner cortical plate mandibular symphysis
  • Outline of mandibular canal

BDS3 Orthodontics (10 decks)

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