growth of head and jaws after birth Flashcards
What are the patterns of head and face growth?
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
What are the types of growth?
Intramembranous bones via periosteal remodelling
Endochondreal bones via cartilaginous replacement
What does the skull look like at birth?
Sutures present
Six fontanelles- posterior, anterior, 2 sphenoid lead, 2 mastoids
~for flexibility (birth canal)
What are the areas of growth to adulthood?
Cranial vault
Cranial base
Nasomaxillary complex
Mandible
What does the brain weigh?
1 year- 50%
3 years- 75%
7 years- 90%
11 years- 100%
How does the cranial vault grow?
Sutural growth- ~fontanelles close at 18 months ~expansion due to brain growth ~some sutures fuse approx 7 years ~all mostly fuse mid-late teens
What growth happens in later childhood/adolescence?
Development of lower 2/3 face
Downwards/forwards growth of maxilla/mandible
Elongation of nose
What is the cranial base?
Frontal, ethmoid, sphenoid, temporal, occipital
Postnatal growth via-
~endochondral
~surface remodelling
What are the cranial base synchondroses?
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)
How does the maxilla grow?
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
How does the mandible grow?
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
What is the twin block?
Usually affects dental alveolar
But can bring jaw forward (small amount of bone laid down to correct occlusion
What is the rotational growth in the mandible?
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
What is the rotational growth in the maxilla?
Small but variable rotation
Mean 3 degrees anterior
Can be backwards
Genetic?
What is growth site?
Location at which growth occurs
What is growth center?
Growth site that is independent growth- genetically controlled
What is the remodelling theory?
Emphasis on remodelling- all bones in cranio-facial complex grow from this
What is the sutural theory?
Primary growth of cranial-facial complex genetically regulated- sutures and cartilage
What is the cartilaginous theory?
Role of cartilage as driving force of growth
Eg. nasal-septal cartilage (maxilla)
What is the functional matrix theory?
Growth not genetically determined
To do w function of complex
What is the part-counterpart principle?
Skull composed of numerous structural components that are relied on
What is the servo-system theory?
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
What different types of growth are there?
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
How do you measure jaws?
Predictions after measuring height which is used as proxy for facial growth
Reduces radiographs
What measures are not really undertaken for measuring head and face growth?
Hand and wrist radiographs
Cervical spine maturation
What is non average postnatal growth?
Congenital- genetics
Primary growth disorders- eg. Condylar hyperactivity
Acquired- eg. Juvenile idiopathic arthritis
Trauma- eg. Fracture condyle
What is early fusion?
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
What is achondroplasia?
Short stature Large head Prominent forehead Small mid face Flattened nasal bridge Genetic
What is cleft lip and palate?
1:700
Unilateral/bilateral
Operated-
~lip minimal effect
~hard palate surgery- maxillary retrusion
Non-operated-
~normal maxilla growth
~mandible smaller
