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(8) Growth of Facial Skeletal (Slide 56) (Theories of Growth Control…
(8) Growth of Facial Skeletal (Slide 56)
Post-natal Growth
Location
Midface
Precursor:
Splanchnocranium
Growth Factors
:
Majorly
: Anterior/Inferior growth of
Nasal septum
Expansion of
brain
Growth of
Cranial Base
&
Vault
Nasal cavity & naso/oropharynx growth
Membrane-derived (secondary) cartilage at mandibular condyles
Mostly Intramembraneous
(prenatally)
All bones
Suture
growth
Circum-maxillary suture (Connect to Neurocranium)
Intermaxillary suture
In response to midfacial displacement
Ceases when sutures fuse
Premaxillary/Maxillary: 3-5 y/o
Midpalatal & Transpalatal: 15-18 y/o & 20-25 y/o
Surface Remodlling
Nasomaxillary complex
Posterior & Superior aspect
Endochondral
Inferior turbinates
(?) Cartilage of spheno-ethmoidal synchondrosis ossifies
Mandible
Precusor:
Splanchnocranium
Growth Factors
Majorly
: Membrane-derived (secondary) cartilage at
Mandibular Condyles
(Endochondral)
Strength of muscles
Intramembraneous
Periosteal activity (remodelling)
Endochondral
Condylar (Secondary cartilage - From Periosteum NOT chondrocytes)
Meckel's Cartilage
(Disappears by 24wks)
Becomes (Sphenomandibular ligament)
Malleus & Incus
Symphysis (Secondary Cartilage)
Condylar cartilage (Most important growth centre)
Properties
: Intramembranous bone
Functionally
: Hyaline growth cartilage
NOT ARTICULAR DISC
Converted to bone via endochondral ossification
Mental Symphysis
2 halves at birth
Histomorphology
Cranial Vault
Precursor:
Desmocranium
Growth Factors
:
Majorly
dependent on
presence of brain
Mostly Intramembranous
Suture
Growth
Sagittal: Stops age 25
Coronal: Stops age 27-28
Cranial Base
Precursor:
Chondrocranium
Growth Factors
:
Majorly
:
Synchondroses
(Endochondral)
Minorly
dependent on
presence of brain
Mainly Endochondral
Synchondroses
growth
ISS
(Inter-sphenoid Synchondrosis)
No Post-natal
Fuses around birth
SES
(Spheno-ethmoidal Synchondrosis)
Fuses at age 7
Growth at anterior cranial base ceases
SOS
(Spheno-occipital Synchondrosis)
Fuses after puberty
Growth at anterior posterior base ceases
Intramembraneous
Greater wing of Sphenoid
Facial ethmoid
Squamous portion of occipital bone
Theories of Growth Control
Growth Sites
(1)
Extrinsic
factor
(2)
No tissue separating capabilities
Eg. Periosteal bone growth from muscle growth, Sutural bone growth
Growth Centres
(1)
Intrinsically
regulated
(2)
Tissue separating capabilities
(
More regulated
)
Eg. Cranial base, Synchondroses
(2) Cartilage
(3) Soft Tissue Matrix
(1) Bone
Anatomy
Neurocranium/Desmocranium
Intramembranous ossification
1 ethmoid bone
1 frontal bone
1 occipital bone
2 parietal bones
1 sphenoid bone
2 temporal bones
Midface/Splanchnocranium
1 Maxilla
2 Zygomatic bones
2 Nasal bones
2 Lacrimal bones
2 Palatine bones
Vomer
Tubrinates
Lowerface/Splanchnocranium
Mechanism
Intramembraneous Growth
Less genetically programmed
Regulated by
extrinsic
factors
Growth sites
Suture Growth
1) Brain expands
2) Dura mater secretes GF
3) Inner periosteum (Osteogenic)
Secondary
Compensatory
Adaptive
Ossification Centre
Primary Centre
1) Mesenchymal Stem Cells --> Osteoprogenitor
2) Produce Spicule --> Trabecula
Centre is between
trabecula
&
periosteum
Endochondral Growth
More genetically programmed
Regulated by
intrinsic
factors
Growth factors
Cell signalling
Growth centres
Synchondrosal Growth
Synchondroses:
temporary
cartilage joints
Between bones from
endochondral origin
Origin
: Primary hyaline cartilage
Bipolar growth
Obliterated at maturity
Ossification Centres
Primary Centres
First
In
shaft
of bone
Secondary Centres
Second
At
ends
of long bone
Epiphyseal Growth Plate
Between primary & secondary centres
Cartiage plate
Epiphyseal Growth Plate
Origin
: Primary hyaline cartilage
Unipolar growth
Obliterated at maturity
Cartilage
Primary
: From chondrocytes
Secondary
: From periosteum
Movement
Translation
Remodelling
Resorption
Apposition
Consequence: Depending on location, translation and remodeling may 1) oppose each other 2) produce additive effect
Landmarks
Age 7 (Midface):
Brain & Eyes Complete
Nasal Septum decreases growth activity
Cartilage of Spheno-ethmodial synchondrosis ossifies
Surface remodelling
Midface
Maxilla
Resorption
Anterior surface
Overall
Downward & Forward
maxilla
Anterior surface growth lessen
Translation
Downward
Forward
Roof of Mouth
Translation
Downward
Forward
Resorption
Nasal side
Apposition
Oral side
Overall
Downward & Forward
palate
Overall Trends
Anterior-Posterior
Overall:
Palate & Maxilla
down
&
forward
Remodelling
Anterior Maxilla: Resorption
Posterior Margin: Apposition
(For teeth)
Vertical
Overall:
Increase in height by
(1) Displacement
(2) Drift
(3) Dentition / Alveolar Bone
Nasomaxillary complex: Displaced inferiorly
Remodelling
Orbital floor: Apposition (Superior drift)
Palatal surface: Apposition
Nasal cavity floor: Resorb (Inferior drift)
Transverse
Associated with brain expansion
Mandibular
Overall Trends
Downward & Forward (relative to cranium)
Anterior Surface of Ramus
: Resorption (Molar space)
Ramus
: Superior Apposition
