Facial Growth II Flashcards
what are the two ways in which the bones of the face and skull form
intramembranous or endochondral ossification
what are examples of the pre-exising cartilaginous skeletons for the face
nasal capsule
meckel’s cartilage
by which growth pattern does the maxilla and mandible develop by
intramembranous
by which type of ossification does the cranial base form by
endochondral ossification
by which type of ossification does the cranial vault develop by
intramembranous ossifiaction
what are the differences in the neo-natal face
small compared to the cranium
large eyes
ears low set
what are the three sites for facial growth
sutures
synchondroses
surface deposition
what type of joints are sutures
specialised fibrous joints
what does each suture contain
band of connective tissue with osteogenic cells in the centre
cells in what area of the sutures matrix causes bone growth
on the periphery
in what does growth at sutures occur in response to
growing structures separating the bones (ie the brain)
what occurs with sutures when facial growth is complete
sutures fuse and become inactive
where are synchondroses found
midline
in what direction does growth occur in synchondroses
both direction
what happens to the bone on either side of a synchondrosis when growth occurs
they are moved apart
what occurs in the synchondrosis when the bones either side are pushed apart
new cartilage is formed in the centre of the synchondrosis and the cartilage at the periphery is turned into bone
what occurs during the process of surface deposition
new bone is deposited beneath the periosteum over the surface of both cranial and facial bones
what occurs during surface deposition that allows bones to maintain their shape
resorption
what is another term for change in position of bone due to remodelling
cortical drift
at what age does the cranial vault stop expanding
age 7
when is rate of growth of the cranial vault at its highest
first 3 years of life
what two ways does bone growth occur in the cranial vault
bone growth at sutures
external and internal surfaces are remodelled through surface deposition
why does the forehead continue to enlarge after neural growth ceases
to accommodate expanding air sinuses (pneumatisation)
in what two ways does growth occur in the cranial base
endochondral ossification
surface remodelling
what age does the soheno-ethmoidal synchondrosis fuse at
around 7 years old
what age does the spheno-occipital synchondrosis close at
13-15 in females
15-17 in males
what age does the spheno-occipital synchondrosis fuse at
around 20 years old
what does a small angle of the cranial base infer
associated with a class III skeletal relationship
what does a large angle of the cranial base infer
associated with class II skeletal pattern
what does forward displacement of the maxilla complex provide
space posteriorly for the development of the maxillary tubersosities and eruption of the molars
where does sutural growth occur in the maxilla
zygomatic and frontal bones and mid palatine suture
where does surface deposition occur in the maxilla
deposition on the lower border of the hard palate and the alveolar process
resorption of the floor of the nasal cavities and the floor of the orbits
what are three sites of growth
sutures
synchondroses
surface deposition
what are sutures
connective tissues that lay down bone when structures push it apart
what are synchondroses
cartilage based growth centre with growth occuring in both directions as they are moved apart
what is surface deposition
new bone deposited under the periosteum
what is cortical drift
change in position of a bone due to remodelling
what are the two way growth occurs in the cranial vault
bone growth at sutures
external and internal surfaces are remodelled through surface deposition
when does the spehnoid-occipital synchondroses fuse
20 years
when does the speheno-ethmoidal synchondroses fuse
7 years
what does the maxilla articulate with
anterior cranial base
what is the mandible closely associated with
posterior cranial base
how does the maxilla grow
displaced downwards and forwards
where does sutural growth occur in the maxilla
zygomatic and frontal bones
mid palatine suture
how does the mandible grow
downwards and forwards
where does sutural growth occur in the mandible
condylar cartilage by surface remodelling
what are three differences in growth between maxilla and mandible
mandible increases in length more
growth accelerates in the mandible during pubertal growth spurt but maxilla stops around 7 years old
growth slows earlier in maxilla
in what order do the different ways in growth stop in the mandible and maxilla
width first
then length
then height
when is growth in width of both jaws finished
before pubertal growth spurt
what are the theories of craniofacial growth
remodelling theory
sutural theory
cartilaginous theory
functional matrix theory
what is the accepted theory of control of growth
combination of genetic and envirnemtal influences
growth in one part of the skull influences another
what two structures are considered to have intrinsic growth potential and exert a genetic influence on growth
primary cartilages of cranial base and the nasal septum
what is considered to maintain the occlusal relationship when jaws are growing
maxilla grows first and then the mandible grows to reflect this so it can sit in the glenoid fossa
what can functional appliances be used for during growth
to correct a class II malocclusion
what is rapid maxillary expansion appliances (RME)
used to widen the palate
patient is asked to turn the midline screw every 2 weeks
once this is achieved it needs to remain in this position
when is protraction headgear used
to treat class III malocclusion early on
less than aged 10 years works best
how are overbites treated
encourage continual growth of the alveolar bone of the maxilla
what are growth rotations
occurs due to an imbalance in the anterior and posterior face height
what is the growth of the anterior face height controlled by
teeth erupting
growth of alveolus and anterior muscles of face and neck
what is growth of the posterior face height influenced by
condylar growth
spheno-occipital synchondrosis
what is a forward rotation of the mandible (anticlockwise rotation)
greater growth in posterior part of the face compared to anterior
what is backwards rotation of the mandible (clockwise rotation)
less growth in posterior part of the face than the anterior
what do forward growth rotations result in
short face and deep bite
what do backwards growth rotations result in
long face and anterior opern bite
how can you measure facial growth changes
casts of the face
cephalometry
3D laser scanning
3d photogrammetry
what are indications for taking a lateral cephalogram
aid diagnosis
treatment planning
progressive monitoring
how do you take a lateral cephalogram
position patient in cephalostat - head held still with ear rods and forehead rest
what is essential in a lateral cephalogram
Frankfort plane horizontal to the floor and the teeth in retruded contact position
mid sagittal plane parallel to the film
what information does a lateral cephalogram provide
relationship between upper and lower jaw
relationship between jaws and cranial base
soft tissue profile
position of teeth relative to jaws
what is the S point referring to on a lateral ceph
midpoint of the sella turcica
what is the N point referring to on a lateral ceph
nasion - meeting point of frontal bone and nasal bone
what is the A point on a lateral ceph
maximum concavity on the anterior maxilla
what is the B point on a lateral ceph
maximum concavity on the anterior mandible
what is ANS and PNS on a lateral ceph
anterior nasal spine and posterior nasal spine
what is the P point on a lateral ceph
pogonion - most anterior part on bony symphysis of the chin
what is the Or point on a lateral ceph
orbitale - inferior border of orbit
what is the Or point on a lateral ceph
orbitale - inferior border of orbit
what is the Me point on a lateral ceph
menton - most inferior point on bony symphysis of chin
what is the Po point on a lateral ceph
where the EAM is
what landmarks make up the sella-nasion plane
sella turcica and nasion (anterior cranial base)
what landmarks makes up the Frankfort plane
porion and orbitale
what landmarks on a lateral ceph make up the maxillary plane
ANS to PNS
what angles would you use to measure the AP position of the maxilla and mandible relative to base of skull
SNA and SNB
what angles would you use to measure the position of the mandible relative to the maxilla
ANB (AP)
MMPA or FMPA (vertical)
what is the relative face height
the ratio of the LAFH to the total face height
what are some errors in cephalometry
magnification/ distortion
non-linear fields
