growth of head and jaws after birth

Question 1

What are the patterns of head and face growth?

Answer 1

28 bones in head-
~8 cranial
~14 facial
~6 auditory
~maybe 1 hyoid

Ratio change between different proportions of head through growth (not proportional)

Head:body length-
Birth 1:4
Adult 1:8

Question 2

What are the types of growth?

Answer 2

Intramembranous bones via periosteal remodelling

Endochondreal bones via cartilaginous replacement

Question 3

What does the skull look like at birth?

Answer 3

Sutures present
Six fontanelles- posterior, anterior, 2 sphenoid lead, 2 mastoids
~for flexibility (birth canal)

Question 4

What are the areas of growth to adulthood?

Answer 4

Cranial vault

Cranial base

Nasomaxillary complex

Mandible

Question 5

What does the brain weigh?

Answer 5

1 year- 50%
3 years- 75%
7 years- 90%
11 years- 100%

Question 6

How does the cranial vault grow?

Answer 6

Sutural growth-
~fontanelles close at 18 months
~expansion due to brain growth
~some sutures fuse approx 7 years
~all mostly fuse mid-late teens

Question 7

What growth happens in later childhood/adolescence?

Answer 7

Development of lower 2/3 face
Downwards/forwards growth of maxilla/mandible
Elongation of nose

Question 8

What is the cranial base?

Answer 8

Frontal, ethmoid, sphenoid, temporal, occipital

Postnatal growth via-
~endochondral
~surface remodelling

Question 9

What are the cranial base synchondroses?

Answer 9

Isolated regions of cartilage contributes to growth-
Once growth ceased- ossifies

Spheno-ethmoidal- (fuses at 7)- anterior cranial base, neural growth pattern, stable by 8-10 years

Sphenoid-occipital (fuses mid-late teens)- posterior cranial base, somatic growth pattern

Inter-sphenoid (fuses between 2-3 years)

Question 10

How does the maxilla grow?

Answer 10

Downwards and forwards
New bone is added to both sides of sutures
Grows in width due to mid palatal suture (fuses around puberty)
Floor of nose is resorbed
Bone added to FOM
Appears to move down more than forward
Remodelling occurs in opposite direction to bone translation

Question 11

How does the mandible grow?

Answer 11

Grows in height and length
Growth in length by cartilage replacement in condyle
Condylar cartilage resembles epiphyseal plate cartilage of long bones
Condyle becomes ossified
Proliferation cell zone- differentiated into chondroblasts
Appositional not proliferative
Not organised into parallel columns
Resorption from anterior surface
Deposition on posterior surface
Remodelling of glenoid fossa
Growth in length ceases late teens
Growth in height continues v slowly throughout life

Question 12

What is the twin block?

Answer 12

Usually affects dental alveolar

But can bring jaw forward (small amount of bone laid down to correct occlusion

Question 13

What is the rotational growth in the mandible?

Answer 13

Affects anterior/posterior face heights

Majority anterior rotation-
Mandibular plane angle decreases by 2-4 degrees
Increasing overbite
More skeletal III
Leads to late lower incisors crowding/genetic?

Minority posterior rotation-
Mandibular plane angle increases
Anterior open bite
More skeletal II
Leads to late lower incisor crowding/genetic?
Wait til older for stable treatment

Question 14

What is the rotational growth in the maxilla?

Answer 14

Small but variable rotation
Mean 3 degrees anterior
Can be backwards
Genetic?

Question 15

What is growth site?

Answer 15

Location at which growth occurs

Question 16

What is growth center?

Answer 16

Growth site that is independent growth- genetically controlled

Question 17

What is the remodelling theory?

Answer 17

Emphasis on remodelling- all bones in cranio-facial complex grow from this

Question 18

What is the sutural theory?

Answer 18

Primary growth of cranial-facial complex genetically regulated- sutures and cartilage

Question 19

What is the cartilaginous theory?

Answer 19

Role of cartilage as driving force of growth

Eg. nasal-septal cartilage (maxilla)

Question 20

What is the functional matrix theory?

Answer 20

Growth not genetically determined

To do w function of complex

Question 21

What is the part-counterpart principle?

Answer 21

Skull composed of numerous structural components that are relied on

Question 22

What is the servo-system theory?

Answer 22

Genetically regulated growth of primary cartilages within the cranial face and nasal septum
Mandible responds to change in occlusion by muscle adaption and condylar growth

Question 23

What different types of growth are there?

Answer 23

Lymphoid- rapid overgrowth till around 11 years then decreases
Neural- grows rapidly til around 5 years then plateaus
General- grows, then plateaus slightly at 5, then grows again at around 12 where it plateaus again
Genital- plateaued growth initially til around 12 where it grows rapidly

All plateau at 20 years

Question 24

How do you measure jaws?

Answer 24

Predictions after measuring height which is used as proxy for facial growth

Reduces radiographs

Question 25

What measures are not really undertaken for measuring head and face growth?

Answer 25

Hand and wrist radiographs

Cervical spine maturation

Question 26

What is non average postnatal growth?

Answer 26

Congenital- genetics

Primary growth disorders- eg. Condylar hyperactivity

Acquired- eg. Juvenile idiopathic arthritis

Trauma- eg. Fracture condyle

Question 27

What is early fusion?

Answer 27

Craniosynostosis
Crouzon syndrome- fusing on both sides of coronal suture, short skull, flat cheekbones/nose
Apert syndrome- abnormal head shape and small upper jaw
Pfeiffer syndrome- skull, hand, feet, bulging eyes, underdeveloped maxilla so beak shaped nose
Genetic

Question 28

What is achondroplasia?

Answer 28

Short stature
Large head
Prominent forehead
Small mid face
Flattened nasal bridge
Genetic

Question 29

What is cleft lip and palate?

Answer 29

1:700
Unilateral/bilateral

Operated-
~lip minimal effect
~hard palate surgery- maxillary retrusion

Non-operated-
~normal maxilla growth
~mandible smaller