Facial Growth 2 Flashcards
what are the primary cartilages of the face
nasal capsule and meckels cartilage
by which way do the maxilla and mandible develop
intramembranously
what is the base of the skull formed by
endochondral ossification
what is the vault of the skull formed by
intramembranous ossification
what are the sites of facial growth
sutures
synchondroses
surface deposition
what are sutures
specialised fibrous joints situated between intramembranous bone
why does growth at sutures occur
in response to growing structures separating the bone (growth of calvarium in development of brain)
where are synchondroses found
in midline
where do synchondroses exist
between ethmoid, sphenoid and occipital bones
what is a synchondroses
a cartilage based growth centre with growth occurring in both directions
what happens at synchondroses when growth occurs
bones on either side are moved apart
new cartilage formed in centre of synchondrosis as cartilage at periphery is transformed into bone
what is surface deposition
new bone deposited beneath periosteum over the surfaces of both cranial and facial bones
what is the process of deposition and resorption known as
remodelling
what is the change in position of a bone due to remodelling known as
drift
why does the cranial vault expand
in response to growing brain
what age does the cranial vault expand until
7
how does the cranial vault grow
bone growth at sutures
external and internal surface remodelling
how does the cranial base grow
endochondral ossification
surface remodelling
when is the cranial base finished growing
20 years
what does the shape or angle of the cranial base affect
jaw relationship
what is a small cranial base angle associated with
class 3
what is a large cranial base angle associated with
class 2
what does displacement mean
when a mass of bone is moved relative to its neighbours
what is displacement brought about by
forces exerted by the soft tissues and intrinsic bone growth
what does forward displacement of the mandible allow
space posteriorly for maxillary tuberosities and eruption of molars
where in the maxilla/nasomaxillary complex does sutural growth take place
zygomatic and frontal bones and mid palatine suture
where does mandibular growth occur from
condylar cartilage
how does mandibular growth occur
surface remodelling
in what direction does the mandible grow
down and forward
where is resorption in the mandible
anteriorly, lingually
where is deposition in the mandible
posteriorly and laterally
what does growth of the mandible allow
increase in heigh of ramus and increase in length of dental arch to accommodate permanent teeth
when does growth slow in the mandible
17 years in females
19 years in males
when does growth slow in the maxilla
12 years
when does growth accelerate in the mandible
during puberty
what order does growth slow first in maxilla and mandible
width
length
height
when will treatment best work if aimed at the mandible
during pubertal growth spurt
when will treatment best work if aimed at the maxilla
before circumaxillary sutures and palate have fused (teenage years)
what is the impact of growth on orthodontic treatment
can affect severity of malocclusion
can be utilised to facilitate treatment
continued unfavourable growth after treatment can mean relapse
what is a growth rotation due to
imbalance in the growth of anterior and posterior face height
what do forward rotations lead to
short face
deep bite
what do backwards rotations lead to
long face
anterior open bite
what bone is referred to for growth rotations
mandible
how do you measure facial growth changes
casts of face
cephalometry
3D laser scanning
3D photogrammetry
what are the indications for taking a lateral ceph
aid diagnosis
treatment planning
progress monitoring
what is lateral cephalometry
standardised lateral radiographs of face and base of skull
what should the patient be positioned like for a lateral ceph
frankfurt plane parallel to floor
teeth in RCP
how is the head kept steady in a lateral ceph
contacting soft tissues at nasion and ear rods in external acoustic meatus
how do we analyse lateral cephs
identify landmarks and lines
measure length/height/angles
what do we look at on a lateral ceph
relationship between jaws and cranial base
relationship between jaws
position of teeth relative to jaws
soft tissue profile
what reference landmarks are used in a lateral ceph
sella
nasion
a point
b point
anterior and posterior nasal spine
pogonion
mention
gonion
porion
orbitale
what reference lines are used in a lateral ceph
sella-nasion
frankfurt plane
maxillary plane
occlusal line
mandibular plane
what does the eastman analysis measure
antero posterior position of maxilla and mandible relative to base of skull
position of mandible relative to maxilla
angulation of teeth to maxilla and mandible
vertical facial proportions
what are the errors with cephalometry
radiographic projection errors
errors with measuring system
errors in landmark identification
