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Dentistry Teeth & OCB > Mechanisms of Post-Natal Growth > Flashcards

Mechanisms of Post-Natal Growth Flashcards

1
Q

How many regions is the craniofacial complex divided into?

A

3 regions

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2
Q

How many gaps (frontanelles) are there between the cranial facial bones?

A

6 gaps

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3
Q

Does more growth happen on width or height of the face initially?

A

Width

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4
Q

Post-natal growth of the head:
Are the bones thick or thin?
Is the midline of the face united or not?
What does the nasal septum align with?
What does it mean that the face is small? (absence of what?)
What is the angle at the base of the mandible?

A

Thin

Not united

The orbits

Virtual absence of paranasal air sinuses and small facial bones

Obtuse

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5
Q

What is the ratio of the upper to lower part of the head in an infant compared to an adult?

A

Infant - 8:1

Adult - 3:1

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6
Q

What develops quicker, bones or anything associated with senses and brain?
Does the face follow the somatic growth curve?

A

Senses

Yes except the skeleton around the eye, middle and inner ear which follow neural growth pattern (neural growth has a higher size attained).

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7
Q

By ten years old, what percentage of neural and facial development has occurred?

A 
Neural = 25%
Facial = 95%
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8
Q

Explaining the rate of growth, why is the cranial vault relative to the face?

A

Skull = fast growth, growth linked to expanding brain, almost complete by age 10.
Face = same rate as general body, linked to development of teeth and muscles. Complete with eruption of 3rd molars.
Cranial base = links base and face, growth rate intermediate, neural rate early, somatic rate later childhood.

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9
Q

What are the two types of bone in the head?
What is more common in the body?
What bone is more responsive to pressure? What bone is for structural support?

A

Endochondral and membrane

Endochondral

Membrane bone
Endochondral bone

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10
Q

Where are face skeletal structures derived from? Where is the cranial vault and base derived from?

A

Neural Crest

Mesoderm

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11
Q

What is the role of Mekels cartilage?

A

Acts as support during growth and disappears after growth has occurred.

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12
Q

Explain the neural crest and mesodermal contribution to the head?

A

Neural crest cells arise from the edge of the neural tube. The epithelial cells become mesenchymal cells.

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13
Q

Where does mesoderm sit in relation to the neural crest?

A

Underneath it.

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14
Q

What are the types of growth occurring in primary cartilage (growth plates and remodelling)?

A

Synchondrosis between bast-occipital and bat-sphenoid and nasal septum.

Growth plates = interstitial growth

Remodelling = appositional growth

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15
Q

Where are membrane bones found in the face?

What are the key things found here?

A

They are found between the facial and cranial vault.

Suture - important in early childhood
Surface deposition or remodelling - most important method of growth in late childhood and adolescence.
Secondary cartilage - condylar cartilage (until adolescence)

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16
Q

How does the cranial vault grow?

A

As the brain expands, the cranial brain synchondroses length by adding IM cartilage at the edges of the bone front. Osteoblasts present here make matrix.

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17
Q

Explain how brain development controls skull development

The cranial vault can expand when there is too much water in the brain. What is this called?

A

Works by displacement. The brain expanding pushes the cranial vault apart.
This leads to sutural growth and then remodelling. Bones allow and flattern due to removal of bone cells in the middle to keep the bones light.

This is called hydrocephaly.

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18
Q

How does the cranial base grow?
When does the cranial base stop growing?
How does it impact on development of the upper face?

A

Growth plate - intrinsic growth by chondrocytes. Remodelling of ossified bone.

Girls - 14, boys - 16

It is needed for forward (anterior) growth.

19
Q

What is the cranial base formed from?

What is the only bone in the cranial base?

A

Formed from embryological cartilage fusing together.

Endochondral bone.

20
Q

What synchondrosis has to close for no more growth of the skull to occur?

A

Spheno-occopitial (growth is bidirectional here)

21
Q

What does remodelling do to the face?

A

Moves the cranial base and face anteriorly and inferiorly.

Brain develops and cranial base is lowered due to removal of osteoblasts.

22
Q

What can defects of the cranial base lead to?

A

CB is linked to upper jaw so has secondary effects on upper jaw leading to no space for 3rd molars.

23
Q

Lower jaw:

  1. What pharyngeal arch gives rise to the lower jaw?
  2. How does the lower jaw grow?
  3. When does the midline of the lower jaw stop growing?
  4. How does the lower jaw lengthen and widen posteriorly?
  5. How do developmental defects affect upper jaw development?
A
  1. The 1st pharyngeal arch.
  2. Remodelling, secondary cartilage growth.
  3. Year 1
  4. Remodelling
  5. Defects in Meckel’s cartilage will result in cleft palate.
24
Q

What are key changes that happen in the mandible when becoming an adult?

A
  1. Increase in length
  2. Increase in height (alveolar bone)
  3. Increase in width
  4. Change in angle
  5. Relative size of coronoid and Condylar processes
  6. Position of mental foramen
25
Q

What cartilage is involved in development of the lower jaw?

A 
Mekels cartilage (endochondral cartilage).
It is needed for downward growth of the lower jaw. This means the palatal shelves cannot move up.
26
Q

Give some details on the secondary cartilage and mandible development
(3 types)

A

Secondary cartilage forms within the periosteum.

3 types are condylar cartilage, coronoid cartilage and symphysial cartilage.

27
Q

What are some properties of Condylar cartilage?

A

Very organised structure within the matrix.

The cells continue in their development and then differentiate to form the layers.

28
Q

What does symphysial cartilage unite?

A

The mandible

29
Q

What is the point of remodelling the mandible?

A

Can see where the bone is taken away and added. This lengthens and strengthens the mandible bone.

30
Q

What are the mechanisms for making room for the lower teeth?

A
  • Remodelling at anterior border of ramus
  • Growth of secondary cartilage
  • Size difference between deciduous molars and their successors (the premolars)
  • By forward movement of teeth through alveolar bone
31
Q

Upper jaw growth:

  1. What is the main bone in the upper grow that contributes to growth?
  2. What are the 2 types of bones in the upper jaw?
A
  1. Maxila bone
    (grows by sutural growth)
  2. Endochondral (the nasal septum) and the rest are membrane bones
32
Q

How does the upper jaw grow?

A

Bone deposition occurs in the back of the mouth here.
Displacement at sutures.
Dentition and alveolar bone remodelling (formation of maxillary sinuses, addition of bone)

33
Q

What are the 4 main sutures in the face?

A
  1. Frontomaxillary suture
  2. Frontozygomatic suture
  3. Nasomaxillary suture
  4. Zygomaticomaxillary suture
34
Q

Tongue:
Increase in width happens up to when?
Increase in length happens up to when?

A

2 years

7 years

35
Q

What does displacement cause at sutures?

A

Growth

upper face is expanding due to growing brain - responding to muscle forces

36
Q

What cartilage also contributes to growth?
How long does it contribute to growth until?
What does this cartilage link?

A

Septic cartilage

7 years before it ossifies

Link between the cranial base and the upper jaw

37
Q

What happens to the shape of the palatal shelves during arch development?

A

Flat to start and then become more arched.

38
Q

Remodelling of the maxilla and development of the maxillary sinus:
What does remodelling do to the palatal shelves and the nose?

A

It lowers the palatal shelves and increases the respiratory space in the nose.
The remodelling removes some cells.

39
Q

Where is addition of bone to make space for molars?

A

At the tuberosity to allow space for molar teeth.

40
Q

Give details on the width of the upper face

A

At birth: face is divided by a complete sagittal suture system. This is important for growth in width, then the bones start to unite limiting this potential.
By end of year 1: cartilage between great wings and body of sphenoid ossifies.

Metopic suture united: a single frontal bone

End of year 3: ossification of the cribriform plate of the ethmoid.

41
Q

Give the information on the upper jaw growth summary 1

A 
Suture: until 10 years 
Endochondral Growth (nasal septum/ethmoid): until year 7, contributes to height and length
Remodelling: until adulthood - contribute to height and length and width
42
Q

Summary 2: Making room for upper teeth

A

Maxilla key bone - remodelling and suture growth.
Permanent molars develop in alveolar bulbs at back of maxilla.
These teeth then move forward as deposition on outer surface and resorption on inner surface increase size of maxilla bone.
Linked to cranial base growth.

43
Q

What are the percentages for these face at birth values compared to values:
Width
Height
Depth

A

60%
45%
35%

44
Q

Why is growth in the width of the face less than growth along the other dimensions (and give the years)?

A
  • Union of the two separate mandible bones (year 1)
  • Union of sphenoid and lesser winds of sphenoid (year 1)
  • Union of two frontal bones (year 1)
  • Ossification of Cribiform Plate (year 3)

Dentistry Teeth & OCB (18 decks)

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