Facial Growth II Flashcards
What are the sites of facial growth?
- sutures
- synchondroses
- surface deposition
What are sutures?
Specialised fibrous joints situated between intramembranous bone
- band of connective tissue
what cells are found within the connective tissue in sutures?
osteogenic cells
What are synchondroses?
A cartilage found in the midline between the ethmoid, sphenoid and occipital bones
- new cartilage is formed in the centre of a synchondrosis as cartilage, the periphery is transformed into bone
What type of ossification does the base of the skull form by?
Endochondral ossification
What do the bones of the vault form by?
Intramembranous ossification
What is the change in position of a bone due to remodelling known as?
“drift”
cortical drift
For how many years does the cranial vault expand for?
Expands in response to the growing brain until age 7
When is rate of growth greatest in the cranial vault?
first 3 years of life
How does growth in the cranial vault occur?
- bone growth at the sutures
- external and internal surfaces are remodelled through surface deposition and resorption to displace the bone radially
After neural growth ceases, why does the forehead continue to enlarge?
In response to accommodate expanding air sinuses
How many fontanelles are present at birth?
6
When does the sphenoid-ethmoidal synchondrosis fuse? (roughly)
around 7 years
When does the sphenoid-occipital synchondrosis close? (roughly)
13-15 years in females
15-17 years in males
When does the sphenoid-occipital synchondrosis fuse? (roughly
20 years old
What does the shape or angle of the cranial base affect?
The jaw relationship
Why is there forward displacement of the maxillary complex?
To create space posteriorly for development of the maxillary tuberosities and space for eruption of molar teeth
In what direction does the mandible grow?
Downwards and forwards
Where does growth occur in the mandible?
At the condylar cartilage & occurs by surface remodelling (resorption and deposition of bone)
Resorption during growth of the mandible mainly occurrs where?
Anteriorly and lingually
Deposition during growth of the mandible mainly occurrs where?
posteriorly and laterally
By how much does the mandible increase in length between ages 4-20?
Males = 26mm (approx)
Females = 20mm (approx)
By how much does the maxilla increase in length between ages 4-20?
Males = 8 mm
Females = 5.5mm
When does growth of the mandible increase significantly?
During pubertal growth spurt
When does growth slow of the mandible?
Females = 17 years old
Males = 19 years old
When does growth of the maxilla slow?
Around 12 years old
What type of growth (of the maxilla and mandible) slows first?
Width slows first —> then length —> then height
When is treatment the utilises the growth of the mandible best carried out?
During pubertal growth spirt
When is treatment the utilises the growth of the maxilla best carried out?
before the circumaxillary sutures and palate have fused (early teenage years)
Can we predict facial growth?
Not really
What controls growth?
Combination of genetic and environmental influences
What impact does facial growth have on orthodontic treatment?
Can affect the severity of a malocclusion (improving or making worse)
Why do growth rotations occur?
Due to an imbalance in the growth of the anterior and posterior face heights
What does forward rotation lead to?
Short face
What does backwards rotation lead to?
long face
How does adult facial growth present?
- continues slowly though life
- tendency to see increased overall length & prominence of nose & chin
- lips become thinner & more retrusive
What are examples of measurements that can note facial growth changes?
- casts of face
- cephalometry
- 3D laser scanning
- 3D photogrammetry
What are the indications for taking a lateral cephalogram?
- to aid diagnosis (skeletal class or vertical discrepancy etc)
- treatment planning
- progress monitoring
What are lateral cephalograms? why are they good?
Standardised lateral radiographs of the face & base of skull
- reproducible
What analysis is involved when looking at lateral cephs?
- relationship between jaws & cranial base
- relationship between upper & lower jaw
- position of teeth relative to the jaws
- soft tissue profile
What are some reference landmarks on a lateral cephalogram?
- sella
- nasion
- anterior nasal spine
- posterior nasal spout
- pogonion
- menton
- gonion
- porion
What reference lines are relevant in lateral cephalograms?
- Sella-nasion
- Frankfort plane
- Maxillary plane
- Occlusal line
- Mandibular plane
What measures the anterior-posterior position of the maxilla and mandible relative to the base of the skull?
Eastman analysis
What does the eastman analysis measure?
- antero-posterior position of the maxilla and mandible relative to the base of skull
- position of mandible relative to maxilla
- angulation of teeth to maxilla and mandible
- vertical facial proportions
What errors can be present in cephalometry?
- radiographic projection errors
- error is within the measuring system
- errors in landmark identification
What can the SNA and SNB angle tell us?
measures the antero-posterior positon of the maxilla and mandible relative to the base of skull
What can the ANB or the MMPA / FMPA tell us?
Position of mandible relative to maxilla
