Once a bone is formed, whether intramembranous or endochondral, all growth takes place on bony surfaces through continuous appositional growth, synchronized with bone resorption
How does postnatal bone grow?
1. Periosteal
2. Endosteal
What are the two types of bony surfaces where postnatal bone growth occurs?
Subsequent to both apposition and remodeling
When does positional movement of bone growth occur in the craniofacial skeleton?
1. Cortical Drift
2. Displacement
3. Relocation
4. "V" Principle
What are the 4 types of positional movement of bone?
Cross Sectional because he studied decalcified sections of human face
Was Don Enlow's study to determine if surfaces were resorbing (-) or growing (+) in craniofacial bone growth longitudinal or cross sectional?
1. Condyles of mandible
2. Synchondroses of cranial base
3. Alveolar bone
4. Anatomic surface of any bone (periosteal membrane)
5. Sutures in calvaria and midfacial bones
Where are 5 places that postnatal bone can form?
Cortical drift
What is the process in which the entire cortical plate of bone moves in the direction of growth by the changing of relative positions of individual segments of bone?
Deposition of bone on one surface and resorption on the contra-lateral surface
What causes cortical drift?
Displacement
What is the result of two or more bones and contiguous soft tissues growing in relation to each other?
No, the bone is just moving in space due to growth in association with contiguous tissue or attached bones
In displacement, is the specific tissue under discussion "growing"?
1. Cortical Drift
2. Displacement
Which type(s) of positional bone movement are involved in the morphogenesis of the mandible?
Cortical Drift
Which type of positional bone movement is analogous to a brick wall being built on one side and chipped away on the other on a wagon?
Displacement
Which type of positional bone movement is analogous to the movement of the wagon from one place to another?
Relocation - relocation of the specific bone segment relative to the individual changes around it
Which type of positional bone movement is the result of bone resorption and deposition around a particular bone segment, which isn't changing position?
Relocation
Which type(s) of positional bone movement occurs in the inner structures of the mandible?
Relocation
Which type of positional bone movement is analogous to a black checker that does not change position, but appears to due to changes that have occurred around it?
Inner side of the "V
In the "V" principle, where does bone deposition occur?
Outer side of "V
In the "V" principle, where does bone resorption occur?
- The V-shaped structure moves TOWARDS the wide end, increasing the overall size of the structure
- Growth movement and enlargement toward the wide end of the "V
How is the growth of the "V" principle described?
1. Facial characteristics
2. Cephalic indices
3. Dental Arch form
4. Neuromuscular functioning
Variations in growth direction have been investigated along with which 4 features in the classification of facial types?
1. Mesocephalic
2. Brachycephalic
3. Dolichocephalic
What are the 3 classifications of facial type?
Cephalic index
What term is expressed as the width of the head as a percentage of its length?
Increases
As the head becomes proportionally rounder, does the cephalic index increase or decrease?
Brachycephalic
What type of face class would a cephalic index >80 be?
Dolicocephalic
What type of face class would be a cephalic index <75 be?
Mesocephalic
What type of face class would a cephalic index between 75-80 be?
Skull width x 100
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Skull length
What is the equation for the cephalic index?
Face height x 100
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Bizygomatic width
What is the equation for the facial index?
Mesocephalic/Mesoprosopic
Which face class is characterized by ovoid facies with a normal maxilla-mandibular relationship and harmonious musculature?
Average arch form with favorable prognosis
What type of arch form is typically associated with mesocephalic faces and what is the prognosis for ortho Tx?
Brachycephalic/Euryproscopic
Which face class is associated with a wider and shorter face, a square jaw with a low mandibular plane angle, a mandibular vector of growth more horizontal than vertical (counter clockwise), and normal musculature?
Wide or broad dental arch form. with favorable treatment prognosis
What type of arch form is typically associated with brachycephalic faces and what is the prognosis for ortho Tx?
Deep anterior overbites sometimes present (Class II, division 2 malocclusion)
What types of malocclusion are associated with brachycephalic faces?
Dolicocephalic/Leptoprosopic
Which face class is associated with a long and narrow face, long jaw with high mandibular plane angle, mandibular vector of growth more vertical than horizontal (clockwise), and strained musculature?
- Narrow dental arch form with high palatal vault
Significant difficulties with treatment
What type of arch form is typically associated with dolichocephalic faces and what is the prognosis for ortho Tx?
Anterior open bite common (Class III, Class II, and division 1 malocclusions)
What types of malocclusions are associated with dolichocephalic faces?
Anterior Cranial Base
What does the sella-nasion line represent?
About 7 years old
When does the sella-nasion line stop growing and changing?
Tangent to inferior border of the mandible
What does the mandibular plane angle represent?
Desmocranium
What is the bony portion of the neurocranium formed by intra-membranous ossification?
8th week in utero, they appear as membrane bones
When do bones of the cranium appear and in what form?
Underlying natural epithelium
What is ossification of the mesenchyme covering the developing brain dependent upon?
Sutures
As the calvarial bones mature, the fontanelles develop into what?
A fibrous joint which articulates bones of the skull and face
What is a suture?
Synarthroses
What is another term for a suture?
1. Sites of active bone growth
2. Provide bony union, but permit slight movement in response to mechanical stress
What are 2 functions of a suture?
1. Plane suture
2. Denticulated suture
3. Beveled suture
What are 3 types of sutures?
Age 6-7 (90% by age 6)
At what age is the skull done growing?
Brain growth
What does the growth of the closely neurocranium approximate?
1. Bone is deposited on both periosteal surfaces and resorption of bone occurs on both endosteal surfaces
2. Displacement of bone occurs through brain growth which opens the sutures
3. Bone is deposited at both sutural surfaces to maintain integrity of cl
What are the 3 steps in calvarial bone growth?
2 years old
At what age does the metopic (interfrontal) suture begin to close?
Synostosis
What is the name of the osseous union fusion that sutures undergo?
Fibroblast Growth Factor
Which transcription factor is important in sutural closure?
Fibroblast Growth Factor Receptor (FGFRs)
What is the transmembrane receptor for transcription factors in sutural closures?
Synostosis
What is the fusion of two bones that normally occurs in puberty as the fusion of the epiphysis with the diaphysis in long bones?
Dysostosis
What is the term for abnormal bone fusion?
Craniosynostosis
What is the term for the abnormal fusion of 2 or more cranial bones at the sutures?
Ankylosis
What is the term for synostosis within joints at the PDL?
Syndactyly
What is the term for the abnormal fusion of neighboring digits?
Crouzon Syndrome
What is the autosomal dominant craniosynostoses syndrome associated with a mutation in the FGFR-2 gene?
- Widespread craniosynostosis
- Midface hypoplasia from premature sutural fusion of the membrane bones in the middle 1/3 of the face and a variety of skull bones
What are the symptoms of Crouzon Syndrome?
Tirgonocephaly
What is the term for premature fusion of the metopic/interfrontal suture?
Tirgonocephaly
Which anomaly represents 14% of all forms of craniosynostosis admitted to the children's hospital in Paris?
Desmocranium
A sagittal suture craniosynostoses with premature ossification and fusion is result from a problem in the growth of which structure?
Chondrocranium
What is the bony portion of the neurocranium and mid-face formed by endochondral ossification?
Synchondrosis
What is the term for a cartilaginous joint which connects 2 bones?
No, because they connect the same bone
Are epiphyseal growth plates of long bones considered synchondroses?
Birth
When does the inter-sphenoid cranial base synchondroses ossify?
Active site of growth until age 6
When does the sphenoid-ethmoidal cranial base synchondroses ossify?
Begins fusion at endocranial surfaces around 12 in girls and 15 in boys
When does the sphenoid-occipital cranial base synchondroses ossify?
No, synchondroses grow appositionally in two directions!
Do synchondroses grow in the same way as growth plates in long bones?
1. Foramen Magnum - surface apposition
2. Spheno-occipital synchondroses
3. Spheno-ethmoidal synchondroses
4. Fronto-ethmoidal suture
5. Frontal bone - surface apposition
6. Occipitomastoid suture
What are the 6 growth sites in the human cranial base?
1. Sphenoid-occipital synchondroses
2. Occipitomastoid suture
After age 6 and the sphenoid-ethmoid synchondroses ossifies, where are the growth areas int he cranial base?
6 years old
At what age is most growth in the anterior base completed?
Sella-Nasion Line
What is used as a stable reference and superimposition line for studying growth on cephalometric tracings?
Increase ~ 4 mm through the growth of the sphenoid-occipital synchondroses
Between the ages of 12-20, how much does the posterior cranial base length change?
Achondroplasia
What is the term for premature ossification of cartilaginous growth plates?
Dwarfism
What is the most common form of achondroplasia?
Autosomal dominant with 100% penetrance
What type of genetic inheritance does dwarfism follow?
1. Short limbs
2. Relative macrocephaly
3. Maxillary hypoplasia
What are some characteristics of dwarfism?
Endochondral osteogenesis - cartilage cell proliferation is deficient
Dwarfism is a result of a generalized defect in what?
Chondrocranium - underdevelopment of the middle third of the face
Which component of the cranium experiences deficient growth?
No, because cartilage of the mandibular condyle is produced from periosteal chondrogenesis
Is mandible growth affected in dwarfism? and why/why not?
Class III - maxillary retrognathia produces compensatory proclination of the upper incisor teeth
Normal mandibular growth in an individual with dwarfism leads to what kind of malocclusion?
Human Growth Factor Receptor (HGFR)
Which receptor is responsible for dwarfism?
Due to the precocious development of the eyes
At birth, why is the mid face relatively wide?
Most in height, secondly in depth, and least in width
After age 3, how does the midface grow?
Until age 6
How long does anterior displacement of the mid face continue?
Interstitial cartilaginous growth of the anterior cranial base
What type of growth is occurring in the midface to allow growth to continue after birth?
1. Deposition at mid facial sutures
2. Complex patterns of deposition and resorption of bony surfaces
After age 6, vertical growth dominates from what two things?
Ring of sutures that complete the midface and all contribute to growth
What is the circumaxillary suture system?
1. Nasal
2. Perpendicular plate of ethmoid
3. Vomer
4. Palatal bone
Which 4 bones of the midface are important areas for downward and forward displacement of the midface?
Crista gali
Which portion of the ethmoid bone is an important part of the anterior cranial base?
1. Midface
2. Sphenoid bone of the middle cranial base
What does the palatine bone connect?
Intra-membranous
How are the maxillary and palatine bones formed?
No!
Does interstitial growth continue after age 7?
1. Lack of midface growth
2. Maxillary hypoplasia
3. Class III malocclusion
What does surgical removal of the nasal septum cause?
Smooth surfaces --> Bone apposition
What happens when tensile force is applied to the inter-nasal suture in a growing rabbit?
Scalloped bone surfaces --> Bone resorption
What happens when compressive force is applied to the inter-nasal suture in a growing rabbit?
1. Sutures are active sites of bone growth
2. As growth of other structures forces suture joints apart, they rapidly deposit bone on their surfaces
3. As force from other tissues compress suture joints, less bone is deposited
What are 3 things the rabbit experiment taught us?
Headgear
Which orthodontic appliance is used to retain or decrease mid-facial growth due to Class II malocclusion?
Occipital Pull Headgear
What type of headgear is used for intrusive force to the midface and maxillary teeth?
Cervical Pull Headgear
What type of headgear is used to correct a class II deep bite malocclusion?
Facemask and palatal expander (loosens midface sutures)
Which orthodontic appliance is used to increase mid facial growth due to Class III malocclusion?
Early headgear treatment (2 years in length)
Which orthodontic appliance is used to prevent impaction of maxillary canines?
1. Temporozygomatic suture
2. Sphenomaxillary suture
3. Sphenozygomatic suture
4. Frontozygomatic suture
5. Frontomaxillary suture
6. Lamina cribosa
Where are the 6 anatomic regions where stress distributions are investigated?