facial growth 2 Flashcards
How are bones of the face formed
intramembranous or endochondral
ossification
What are the pre-existing cartilaginous skeletons for the face
nasal capule and meckels cartlidge
What of the mandilbe dissapears shortly after birth
condylar cartilage
wha are the differences between an adult and an neonatal face
The infant the face is small compared to
the cranium the eyes are large and the ears
are low set.
The forehead is upright and bulbous and
the face appears broad.
The nasal region is vertically shallow, with
the nasal floor close to the inferior orbital
rim. In the adult the midface expands and
the nasal floor has descends
What are the sites of facial growth
Sutures
Synchondroses
Surface deposition
Talk about 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
Growth at the sutures occurs in response to growing
structures separating the bone
When facial growth is complete they fuse together
Talk about Synchondroses
These are found in the midline
They exist between the ethmoid, sphenoid and
occipital bones
A cartilage – based growth centre with growth
occurring in both directions
New cartilage is formed in the centre of a synchondrosis as cartilage at the periphery is transformed into bone
Talk about surface deposition
New bone is deposited beneath the periosteum over the surfaces of the both the cranial and facial
bones
The change in position of a bone due to remodelling is known as “drift”. (cortical
drift)
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
When does the cranial vault stop growing and what are the two ways in which it grows
7 years
Bone growth at the sutures
External and internal surfaces are remodelled through surface
deposition and resorption to displace the bones radially
What bones consist of the cranial base
Frontal, ethmoid, sphenoid , temporal and occipital bones
What bones consist of the cranial base
Frontal, ethmoid, sphenoid , temporal and occipital bones
How does growth in the cranial base occur
Endochondral ossification
Surface remodelling
Why is growth of cranial base relevant
Growth occurs between the ages of 4 to 20 years and causes an overall increase in
length of the cranial base. However, the anterior cranial base is relatively stable after the age of 7 years and so has been used for superimposition in cephalometric analysis
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
The maxilla articulates with the anterior cranial base and the mandible is closely associated with the posterior cranial base being suspended beneath the middle cranial fossa
What angles relate to what skeletal 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
How does the mandible grow
Grows downwards and forwards
Growth occurs at the condylar cartilage
Growth occurs by surface remodelling (resorption
and deposition of bone)
Resorption mainly anteriorly and lingually and
deposition posteriorly and laterally
Results in increase in height of the ramus and
increase in length of the dental arch to
accommodate the permanent teeth
What are the differences in growth of the mandible
Mandible:
Increases in length by 26mm in males 2 0mm in females between ages 4-20 years
Growth accelerates significantly during the pubertal growth spurt
Growth slows to adult level around age17 years in females and 19 years in
males
What are the differences in growth of the maxilla
Increases in length by 8mm in males 5.5mm ( females) between ages 4-20 years
After age 7 years growth of the maxilla proceeds very slowly
Growth slows to adult levels at around age 12 years
What are the timings in facial growth
Both the maxilla and the mandible growth in width slows first, then growth in length and finally growth in height
Both width is finished before puberty growth spurt
Growth in length continues throughout puberty. It slows in girls about 14- 15 years and in boys about 18 years
Growth in height does not decline to the adult rate in girls till age 17-18 years and in boys into their early 20’s
What did Behrents show in his study
growth continues during adult life. He reported an increase in all dimension but particularly the vertical.
Forsberg (1991) has shown an average 1.6mm increase in anterior face height in adults
When would treatment utilising growth of the mandible be best
During puberty growth spurt
When would treatment utilising growth of maxilla be best
Before the circumaxillary sutures and palate
have fused (early teenage years)
What controls growth
A combination of genetic and environmental influences
As wel as growth in one part of skull influnces another
The synchondrosis of the cranial base and nasal septum have intrinsic
growth potential and exert a genetic influence over growth
What is the impact of growth on ortho treatment
affect the severity of a malocclusion
can be utilised by the orthodontist to facilitate treatment outcome
Can lead to ‘relapse’
What is a growth rotation
An imbalance in the growth of the anterior and posterior face heights
Continued growth rotation can lead to malocclusion geting worst
What type of growth rotations are there and what does it lead to
Forward rotations lead to a “short face ”
Backwards rotations lead to a “long face”
What happens in adult facial growth
Its very variable
Continues slowly through out life
in very small amounts with the face getting flatter and longer
In general how does theface grow
Downwards and forwards
How do you measure facial growth changes
Casts of the face
Cephalometry
3D laser scanning
3D photogrammetry
What are the indications of a lateral cephalometric
To aid diagnosis
-e.g. Skeletal class II or III
-Vertical discrepancy
Treatment planning
-Help clarify the tooth movements to be achieved
-Orthognathic planning
Progress monitoring
-Fixed appliance treatment
-Functional appliance treatment
-Monitoring facial growth
-Predict future growth
What is lateral cephalometry
Standardised lateral radiographs of the face and base of skull
Cephalometry is the analysis and interpretation of these radiographs
The Frankfort plane should be horizontal ( parallel to the floor) and the teeth should be in RCP
What can you analyse on a lateral ceph.
Relationship between jaws and cranial base
Relationship between the upper and lower jaw
Position of teeth relative to the jaws
Soft tissue profile
What falls under the eastman cephalometric standards
SNA
SNB
ANB
Ulnc to MxPl
LInc to MnPl
inter-incisal angle
MMPA
Facial proportion
what does the SNA angle show
This angle represents the relative anterioposterior position of the maxilla to the cranial base
What does the SNB angle show
This angle represents the relative anterioposterior position of the mandible to the cranial base
What does the ANB angle show
This angle represents the relative anterioposterior position of the maxilla to the mandible and can be used to determine skeletal class
What does MMPA mean and show
Maxillary-mandibular plane angle (MMPA)
The angle formed between the Maxillary Plane and Mandibular Plane
What does UInc to MxPI mean and show
Maxillary Incisal Inclination(UInc to MxPl)
The angle between the maxillary plane and the axis of the maxillary incisors (UInc)
What does LInc to MnPI mean and show
Mandibular Incisal Inclination (LInc to MnPl)
The angle between the mandibular plane and the axis of the mandibular incisors (LInc)
What is the inter incisal angle
The angle between the long axis of the maxillary incisors and the long axis of the mandibular incisors
