Facial Growth II Flashcards
majority of the face derived from
neural crest cells
ectomesenchyme
what regions of the embryo make up the skeleton which the face will develop from
frontonasal process and the maxillary and mandibular processes of the first brachial arch
maxilla and mandible form
intramembranously
2 pre-existing carilaginous skeletons of face
- nasal capsule for the maxilla
- Meckel’s cartilage for the mandible
little remanence by birth
secondary cartilages begin to form in utero (3)
neo natal face Vs adult
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
- face 1/2 heigh of skull, in adults 3/4
- 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
3 sites of facial growth
sutures
synchondroses
surface deposition
sutures
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
*
-
bone deposition at periphery
growth at sutures
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
synchondroses found
found in midline (midsagittal plane)
- exist between the ethmoid, sphenoid and occipital bones
synchondroses growth
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
surface deposition growth
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)
cranial vault comprised of (4)
frontal
temporal
occipital
parietal
2 ways of growth in cranial vault
- 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
why does the forehead continue to grow after neural growth ceases
to accomondate exapanding air sinuses (pneumatisation)
generally more pronounced in males
when does neural growth cease
7 years
fontanelles exist
where more than 2 bones meet
how mant fotanelles are present at birth
- 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
when do sutures fuse
when facial growth is complete
how does the cranial base grown
synchondroses growth
cranial base composed of (5)
frontal
ethmoid
sphenoid
temporal
occipital
what synchondroses has the most effect on post natal fatal growth
spheno occipital synchondroses
as open for longest time
how does growth occur at synchondroses (2 ways)
endochondral ossification
surface remodelling
timeline for cranial base growth
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
what is the relevance of growth of the cranial base
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
how does the cranial base influence how the maxilla and mandible relate
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
anterior cranial base is from
sella turcica and junction between nasal bone and frontal bone
mid point is sella to nasion (on lat cephs)
small cranial base angle
more likely to assoicated with class III skeletal repationsip
large cranial base angle
more likely to be associated with class II skeletal pattern
maxilla/nasomaxillary complex
includes
orbits
nasal cavity
upper jaw
zygomatic process
bone displacement
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.
maxilla/nasomaxillary complex is displaced
downwards and forwards relative to the anterior cranial base
growth rate of maxilla/nasomaxillary complex
tends to follow neural growth of the brain early on and and so slows down towards Age 7 years.
why is the maxilla displaced forward
creates space posteriorly for development of the maxillary tuberosities and space for eruption of molar teeth
2 bone growth types in maxilla/nasomaxillary complex
- 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.
why is sutural growth between zygomatic and frontal bones and mid palatine suture relevant to ortho
widen upper jaw make use of patent midpalatine suture
example of surface deposition and resorption in maxillar/nasomaxillary complex growth
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.
growth direction of mandible
downwards and forwards
where does growth occur in mandible
condylar cartilage
(maybe adaptive growth rather than intrinsic)
no active sutures post birth
mode of growth in mandible
surface remodelling
(resorption and deposition of bone)
differences in growth of maxilla and mandible
length
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
differences in growth of maxilla and mandible
rate
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
differences in growth of maxilla and mandible
rates of growth in width Vs length
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)
treatment which utilises growth of mandible will work best if carried out
during pubertal growth spurt
12-13 girls
14-15 boys
treatment which utilises growth of maxilla will work best
before the circumaxillary sutures and palate have fused
i.e. early teenage years (pre-pubertal growth spurt)
can we predict facial growth
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
4 theories of craniofacial growth
remodelling theory
sutural theory
cartilaginous theory
functional matrix theory
tend to be though as combination
remodelling theory of craniofacial growth
Everything just grows by a process of deposition and resorption. The sutures and cartilages do not exert an intrinsic force
sutural theory of craniofacial growth
- Growth occurs at the sutures and cartilages but the growth at the sutures is the prime factor
cartilaginous theory of craniofacial growth
- The cartilages i.e.nasal septal cartilage and the synchondrosis generate the force to develop the bones in a specific direction
functional matrix theory of craniofacial growth
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
control of craniofacial gowth
- 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
- Controversy exists as to whether it is a primary growth force or purely adaptive.
3 impacts of facial growth on orthodontic tx
- 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
rapid maxillary expansion device
- Fixed*
- Many designs – turn screw twice daily, many weeks*
- Pre 16 years*
- used to facilitate ortho tx outcome*
functional appliances used to faciliate ortho tx outcome by growth
- Twin block*
- Functional appliance treat class II div 1*
- Reposition mandible anteriorly, encourages growth of the mandible*
adult facial growth
(3 characteristics)
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)
growth rotation
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
forward growth rotation
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
backwards growth rotation
leads to long face
Mandible tends to rotate clockwise- more anterior than posterior face height growth
adverse growth effects on malocclusion
extremes of growth rotations make malocclusions worse
- Continued growth when there is significant growth rotation can make a malocclusion worse
growth rotation here
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
growth rotation here
Backwards growth rotation can lead to development
- anterior open bite
- increased lower face height – long face
in general facial growth is
- downward and forward, but there is considerable individual variation with growth rotations
growth rate throughout life
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
3 types/sites of bone growth influence the shape of the face
- Sutures – fibrous joints
- Synchondroses – cartilage based growth centre (cranial base?)
- Surface deposition and resorption = remodelling
growth of cranial base role
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
growth of maxilla/nasomaxillary complex summary
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
mandible growth by
- 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
when is mandible tx best
pubertal growth spurt
growing fastes
when is maxilla tx best
before pubertal growth spurt
midpalatine suture and circummaxillary suture not fused yet
more posterior face height growth from infant to adult causes
forward growth rotation
deep bite
more anterior to posterior face height growth causes
backwards growth rotation
AOB
negative impact on facial growth on ortho
can cause relapse
can make malocclusions worse
radiographic technique for lat ceph
- Fixed distances
- ALARA
- Aluminium soft tissue filter
- Thyroid collar
- Triangular collimation
- NHP
- Rare earth screen
- LANEX screen
- Fastest film possible (60- 70kV)
lat ceph analysis
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
12 reference points on lat ceph
- Sella
- Nasion
- A Point
- B Point
- Anterior Nasal Spine
- Posterior Nasal Spine
- Pogonion
- Menton
- Gonion
- Porion
- Orbitale
- Basion
6 reference lines on lat ceph
- Sella-nasion
- Frankfort plane
- Maxillary plane
- Occlusal line
- Mandibular plane
- A-Po line
3 aspects of eastman analysis of lat cephs
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
Anterio-Posterior discrepanancy (ANB) values
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
vertical discrepanacy (MMPA) values
Increased
>37o
Increased
32-37 o
Increased
27-32 o
Average
27 o
Decreased
22-27 o
Decreased
17-22 o
Decreased
<17 o
dentoalveolar measurements
- Ui/MxP 109 +/- 6 o
- Li/MnP 93 +/- 6 o
- Ui/Li 135 +/- 10 o
- Li-Apo 0-2mm
3 commonly used soft tissue planes
- facial plane
- holdaway line
- rickett’s e plane
7 uses of cephalograms
- 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
possible indications for taking a ceph (4 classes)
- 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
tx here
class III low angle
single jaw
mandibular setback
tx here
class II high angle
bimaxillary osteotomy. maxillary impaction and mandibular advancement
3 limitation categories for lat cephs
- 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
