Facial Growth 2 Flashcards
How would you describe the size of the face on a baby compared to the head?
The face is small compared to the overall size of the head in newborns
Describe the differences between and adult and neonatal skull.
- infant face is small compared to the cranium, eyes are large and the ears are low set (face takes up 1/2 of face whereas in adult 3/4)
- 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 (height of maxilla less)
- in the adult, the midface expands and nasal floor desends
What are the 3 different types of sites of growth/types of growth in the face?
- sutures
- synchondroses
- surface deposion
What is a suture?
It is a specialised fibrous joint situated between intramembranous bone.
Describe the structure of a suture.
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 sutures occurs due to what? Describe how it works.
Growth occurs in response to growing structures separating the bone (e.g. calvarium in response to development of brain)
Where the bones are pushed apar, new bone forms in the suture
Suture growth happens in areas of TENSION
Where are synchondroses found?
In the midline
They exist between the ethmoid, sphenoid and occipital bones
Describe how growth happens at synchondroses.
Has a cartilage based growth centre with growth occuring in both directions
The bones on either side of the sychondrosis are moved apart as growth takes place
New cartilage is formed in the centre of a synchondrosis as cartilage at the periphery is transformed into bone
Describe the bone growth in the face via surface deposition.
New bone is deposited beneath the periosteum over the surfaces of both the cranial and facial bones
How is the shape of bones maintained during growth?
Resorption also takes place
(the process of growth and deposition is also known as remodelling)
What is the change in positio of a bone due to remodelling known as?
Drift
e.g. cortical drift
What bones is the cranial vault composed of?
Frontal bone
Temporal
Occipital
Parietal bones
What does the cranial vault grow in response to and till what age?
Expands in response to the growing brain until age 7
When is the rate of growth of the cranial vault the greatest?
In the first 3 years of life
What are the 2 ways that the bone grows in the cranial vault?
- bone growth at sutures
- external and internal surfaces are remodelled through surface deposition and resorption to displace the bones radially (resorption on internal surface of calvarian
After neural (brain) growth ceases the forehead continues to enlarge in response to what?
In response to the expanding air sinuses (pneumatisation)
Note: generally more pronounced in males
Where do fontanelles exist? How many are present at birth and when do they close by?
Where more than 2 bones meet together.
6 present at birth and close by 18months
What are the 2 ways that bone grows in the cranial base
After neural growth ceases, what happens to the cranial vault in terms in growth?
The forehead continues to enlarge in response to accommodate expanding air sinuses (pneumatisation)
Note: is generally more pronounced in males
Where do fontanelles exist?
Where more than 2 bones meet
How many fontanelles are present at birth and at what age do they close?
18
-close by 18 months
Growth in the cranial base occurs in what 2 ways?
Endochondral ossification
Surface remodelling
Half of the growth of the cranial vault is completed by what age?
3 years
What is the spheno-ethmoidal synchondrosis and when does it fuse?
- cartilaginous joint between the sphenoid and the ethmoid bones
- fuses at 7 years
What bones form the cranial base?
- frontal
- etmoid
- sphenoid
- temporal
- occipital
When does the spheno-occipital synchondrosis close and when does it fuse?
13-15 in females
15-17 in males
Fuses at around 20
The anterior cranial bases growth is realtively stable after what age and why is this imortant?
After 4 years
Has been used for superimposition in cephalometric analysis. This allows the orthodontist to asses skeletal changes due to growth and/or treatment
How does the cranial base relate to the mandible and maxilla?
The cranial base detemines how the maxilla and mandible relate to each other
The shape or angle of the cranial base affects the jaw relationship
How does the shape/angle of the cranial base affect jaw relationships?
- a small angle is more likely to be associated with a class III skeletal relationsip
- a large angle is more likely to be associated with a class II skeletal pattern
The maxilla/nasomaxillary complex includes what? (bones/structures)
- orbits
- nasal cavity
- upper jaw (maxilla)
- zygomatic processes
When do all of the sutures close?
When facial growth is complete
In what direction does the maxilla/nasomaxillary complex grow?
It is displaced downwards and forwards relative to the anterior cranial base
Displaced is when a mass of bone is moved relative to its neighbours. ITs brought about by forces exerted by soft tissues and by intrinsic growth of the bone itself
The growth of the maxilla/nasomaxillary complex tends to follow what?
Follows neural growth early on and so slows down towards age 7
Forwards displacement of the maxillary complex creates space for what?
It creates space posteriorally for the development of the maxillary tuberosities and space for eruption of molar teeth
Describe how the maxillary complex grows
- Sutural growth takes place at the zygomatic ad frontal bones and mid palatine suture
- Suface deposition and resorption e.g. deposition on lower border of hard palate and the alveolar process and resorption on the floor of the nasal cavity and floor or the orbits
Describe how the mandible grows.
- grows downwards and forwards
- Growth occurs at the condylar cartilage (secondary cartilage)
- Growth occurs by surface remodelling (resorption and deposition of bone)
- resorption is mainly anteriorally and lingually
- deposition is mainly posteriorally and laterally
- this results in the increase of the height of the ramus and increase in the length of the dental arch to accomodate the permanent teeth
What are the differences between the growth of the maxilla and the mandible?
- Mandible increases more in length
- mandible = growth accelerated significantly during pubertal growth spurt whereas maxilla = after 7 growth is very slow
- Mandible growth slows to adult level between 17 and 19 whereas maxilla is around 12
Orthodontic treatment which utilitses the growth of the mandible is best carries out when?
During the pubertal growth spurt (note this is earlier in girls than in boys)
Treatment which utilises the growth of the maxilla is best carried out when?
Before the circumaxilary sutures and palates have fused (early teenage years)
What are growth rotations?
A growth rotation is due to an imbalance in the growth of the anterior and posterior face height and can lead to a ‘short’ or ‘long’ face
Forward/backwards growth rotations lead to what?
Forward roation = ‘short face’
Backwards rotation = ‘long face’
Forwards growth rotation can lead to what?
Development of a deep bite
(reduces Frankford Mandibular Plane)
A backwards growth rotation can lead to what?
The development of an anterior open bite
