Facial growth II Flashcards
What is the majority of the face derived from
neural crest cells
What brachial arch do the frontonasal process come from
1st
What is the pre existing cartilaginous skeleton for the maxilla
nasal capsule
What is the pre existing cartilaginous skeleton for the mandible
Meckel’s cartilage
What are features of the neo natal face
infant face is small compared to the cranium
eyes are large and ears are low set
forehead is upright and bulbous and face appears broad
nasal region is vertically shallow with nasal floor close to inferior orbital rim
in the adult the mid face expands the nasal floor descends
What are the sites of facial growth occur
sutures
synchondroses
surface deposition
What are sutures
specialized fibrous joints situated between intra membranous bone
each suture is a band of CT which has osteogenic cells in the centre and the most peripheral of these cells provide new bone growth
What does growth at the sutures occur in response to
growing structures separating the bone e.g growth of calvarium in response to development of brain
where the bones are pushed apart new bone forms in the suture
in the suture growth occurs in area of tension
Where are synchondroses
found at midline
Where do the synchondroses exist
between the ethmoid, sphenoid and occipital bone
How does growth occur at the synchondroses
it is 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
new cartilage is formed in the centre of a synchondrosis as cartilage at the periphery’s transformed into bone
What is surface deposition
new bone is deposited beneath the periosteum over the surfaces of both cranial and facial bones
in order for the bones to maintain their shape as they grow, resorption is also taking place
What is the process of reposition and deposition known as
remodeling
What is the change in position of bone due to remodeling
known as drift (cortical drift)
What does the cranial vault expand in response to
growing brain until age of 7
When is the rate of growth of the cranial vault greatest
first 3 years of life
What are the 2 ways growth of cranial vault occurs
bone growth at sutures
external and internal surfaces are remodeled through surface deposition and resorption to displace the bones radially
After neural growth ceases what happens
the forehead continues to enlarge in response to accommodate expanding air sinuses
generally more pronounced in males
Where do fontanelles exist
where more than 2 bones meet
6 fontanelles are present at birth and these close by the age of 18 months
when facial growth is complete, all of the sutures fuse
What are the two ways the cranial base grows
endochondral ossification
surface remodeling
When is half the growth of the cranial base finished
by age 3
When does the sphene-ethmoidal synchondrosis fuse
7 years old
When does the sphenoid-occipital synchondrosis close
at around 13-15 years in females and 15-17 years in males
When does the sphenoid-occipital synchondroses fuses
at around 20 years
What does growth of cranial base between 4-20 year result in
overall increase in length of the cranial base
When does the anterior cranial base become stable
around 4 YO
has been used for superimposition in cephalometric analysis
this allows the orthodontist to assess skeletal changes due to growth and / or treatment
Why is the cranial base so important for ortho
it plays a role a role in determining how the maxilla and mandible relate to each other
the shape or angle of the cranial base effects the jaw relationship
What does a small angle of the cranial base result in
more likely to be associated w class III
What does a large angle of the cranial base result in
more likely to be associated w class II
What does the maxilla/nasomaxillary complex include
orbits
nasal cavity
upper jaw
zygomatic processes
What is displacement
when a mass of bone is moved relative to its neighbor
is brought about by focus exerted by the soft tissues and by intrinsic growth of bone itself
How is the mandible displaced
downwards and forwards relative to anterior cranial base
What is rate of growth of maxilla
follows neural growth of brain
slows down at age 7
What does forward displacement of maxillary complex create
space posteriorly for development of maxillary tuber-sixties and space for eruption of molar teeth
Where does sutural growth take place
at zygomatic and frontal bones and mid palatine suture
What is surface deposition and resorption in the maxilla
deposition on the lower border of the hard palate and alveolar processes and resorption on floor of nasal cavity and the floor of the orbits
How do both the mandible and maxilla slow
width slows first
then length
then height
What are differences in growth in length of mandible and maxilla
increase in length by 26mm in males and 20mm in females between ages 4-20 in MANDIBLE
increase in length by 8mm in males and 5.5mm in females between ages 4-20 in MAXILLA
What is the difference in rate of growth in mandible and maxilla
growth accelerates significantly during pubertal growth spurt in mandible
at age 7 years, growth of maxilla proceeds very slowly
What is the difference in growth slowing in mandible and maxilla
in mandible growth slows to adult level around age of 17 in F and 19 in M
in maxilla growth slots to adult levels at around 12
What are the theories of craniofacial growth
remodeling theory
sutural theory
cartilaginous theory
functional matrix theory
What is the remodeling theory
Everything just grows by a process of deposition and resorption
The sutures and cartilages do not exert an intrinsic force
What is the sutural theory
growth occurs at the sutures and cartilages but the growth at the sutures is the prime factor
What is the cartilaginous theory
the cartilages i.e nasal septal cartilages and synchondrosis generate the force to developmthe bones in a specific direction
What is the functional matrix theory
growth occurs in response to individual units which are developed to provide a function
each unit (functional matrix) is composed of tissue organs and spaces thus its the force exerted by the growing soft tissues that determines the direction and extent of growth
What are the recent views on the control of growth
combo of genetic and environmental influences involved
growth in one part of skull influences anotehr
What are the primary cartilage control on growth
primary cartilages of cranial base and nasal septum have intrinsic growth potential and exert a genetic influence over growth
What are the condylar cartilage control on growth
it seems to act differently
controversy exists as to whether its a primary growth force or purely adaptive
What is the impact of growth on malocclusion
can improve or worsen malocclusion
How can growth be utilized by orthodontic for tx outcome
use of functional appliance
use of rapid maxillary expansion
use of protraction head gear
If there is a continued unfoavourable growth pattern what is the impact on ortho tx
relapse can occur
What is adult facial growth like
continues through life
growth in length of face continues into early 20s in males, late teens in females
tendency to increased overall length and prominence of nose and chin (and forehead in men)
lips become thinner and more recursive (soft tissue changes)
What is a growth rotation
due to imbalance in growth of anterior and posterior face heights
What does forward growth rotation lead to
short face
can lead to development of deep bite
What does backward growth rotation lead to
long face
can lead to anterior open bite
What is adverse growth
continued growth when there is a significant growth rotation that can make malocclusion worse
