CFD9- Skull growth

Question 1

what is the need to understanding facial growth?

Answer 1

• aetiology of malocclusion
• recognise abnormal growth patterns
• Best plan of treatment: functional appliances vs orthognathic surgery
• Understand factors that influence treatment stability

Question 2

Name the primary cartilages.

Answer 2

• meckel’s cartilage : contribute to mandible development
• Reichert’s cartilage the 2nd arches cartilage
• nasal capsule

Question 3

what is the role of primary cartilages?

Answer 3

Primary skeletal support of developing structures

Question 4

what is the structure of primary cartilage?

Answer 4

• hyaline cartilage

- interstitial growth

Question 5

what is the fate of primary cartilages

Answer 5

• ossify e.g. part of nasal capsule (some remain)

- disappear e.g most of meckel’s cartilage

Question 6

what are the 2 craniums of the skull?

Answer 6

• neurocranium

- viserocranium

Question 7

what is the bones that hold the brain (brain case)?

Answer 7

neurocranium

Question 8

what is the bones that form the facial skeleton?

Answer 8

viserocranium

Question 9

what are the 2 divisions of the neurocranium?

Answer 9

• Dermatocranium : cranial vault (intramembranous formed bones)
• Chondrocranium : cranial base (cartilage forms bone)

Question 10

when do the primary cartilages appear?

Answer 10

7 weeks IU

Question 11

name some primary cartilages.

Answer 11

• trabeculum
• parachordal cartilages
• occipital somites

Question 12

what happens to the primary cartilages?

Answer 12

cartilages fuse together and from a network of primary cartilages

Question 13

what are the bones of the cranial base?

Answer 13

• sphenoid bone
• occipital bone
• Temporal bone-petrous part
• ethmoid bone
• frontal bone

Question 14

what type of ossification forms the cranial base?

Answer 14

• ossification centres

- endochondral ossification (cartilage converts to bone)

Question 15

what are the dermal/membranous bones of the cranial vault?

Answer 15

• frontal
• parietal
• squamous part of temporal and occipital bones

Question 16

what ossification forms the cranial vault?

Answer 16

intramembranous

Question 17

what are the bones from anterior to the coronal suture derived from?

Answer 17

ectomesenchyme (neural crest)

Question 18

what are the bones posterior to the coronal suture derived from?

Answer 18

mesenchyme (mesoderm) derived

Question 19

what does ectomesenchyme/ mesenchyme differentiate into?

Answer 19

osteoblasts

Question 20

when does bone formation of cranial vault start?

Answer 20

8 weeks in utero

Question 21

where do bones meet?

Answer 21

sutures

Question 22

what occurs at sutures?

Answer 22

growth

Question 23

what are synchondroses?

Answer 23

cartilage joints at the base of the skull

Question 24

what is the difference in neural and somatic growth?

Answer 24

• Neural growth happens quickly so dermatocranium almost fully formed by the age of 12
• Somatic growth is slower- reaches full size at around age 20

Question 25

what is sutural growth due to?

Answer 25

expansion of underlying structures (i.e brain) - osteoblasts on surface lay down bone - brain expands and the suture is stretched and causes tension between the 2 areas - osteoblasts need to work harder to lay down more bone

Question 26

what are fontanelles?

Answer 26

- Soft spots- in a new born skull the sutures are wide open - fibrous tissue over the brain - gradually close up

Question 27

what are fontanelles for?

Answer 27

skull is flexible so when the baby is born , the head is squished and bones are compressed and overlap

Question 28

How long do the fontanelles take to close?

Answer 28

- anterior (closes 6-18 months) - posterior (closes 1-3 months) - anterolateral (closes 6 months) - posterolateral (closes 6-18 months)

Question 29

what is a sychondrosis?

Answer 29

- Immovable cartilage joint - active growth sites - interstitial growth - pushes bones apart

Question 30

Name the 2 synchondrosis's.

Answer 30

- spheno-ethmoidal | - spheno-occipital

Question 31

when does sphenoid-ethmoidal fuse?

Answer 31

around birth

Question 32

what is the main site of elongation of the cranial base?

Answer 32

spheno-occipital

Question 33

when does the spheno-occipital fuse?

Answer 33

age 12 (female) and 14 (male)

Question 34

what is achondroplasia ?

Answer 34

- impaired cartilaginous growth | - FEATURES: facial shape is concave (don't have any growth at spheno-occipital synchondrosis)

Question 35

what is involved in remodelling of bone?

Answer 35

- surface deposition -ostepblasts | - surface resorption -osteoclasts

Question 36

what is surface deposition?

Answer 36

adding of bone (on the outside)

Question 37

what is surface resorption?

Answer 37

bone taken away (on the inside)

Question 38

when does the maxillary air sinus form?

Answer 38

10 weeks

Question 39

what is primary pneumatisation?

Answer 39

forms pouches in walls of nasal cavity

Question 40

what is secondary pneumatisation?

Answer 40

expansion by resorption of lateral and inferior walls ( not medial)

Question 41

what is the clinical relevance of maxillary air sinus?

Answer 41

- tooth can grow into sinus | - oral antral fistula connection

Question 42

what happens to the sinus during a removal of a tooth?

Answer 42

- sinus enlarges - alveolar height reduces - thin bone

Question 43

Describe secondary cartilages.

Answer 43

- fibrocartilage - not part of the primary skeleton - appositional growth

Question 44

what are the stages of appositional growth in secondary cartilages (endochondral ossification) ?

Answer 44

– Surface deposition of new cartilage – Calcification of sub‐surface cartilage – Resorption of calcified cartilage – Replacement of calcified cartilage with bone

Question 45

Name 3 secondary cartilages.

Answer 45

- symphyseal - coronoid - condylar

Question 46

when does symphyseal cartilage appear and disappear?

Answer 46

- appear : 16 weeks i.u.l | - disappear : 1st year after birth

Question 47

when does coronoid cartilage appear and disappear?

Answer 47

- appear : 14-16 weeks i.u.l | - disappear : before birth

Question 48

when does condylar cartilage appear and disappear?

Answer 48

- appear : 10-12 weeks i.u.l | - disappear : 20 years of age

Question 49

what is the evolution of the mandible?

Answer 49

- birth (small ramus) - Deciduous dentition - Permanent eruption - maturity - partially dentate - edentulous

Question 50

what factors control growth patterns?

Answer 50

1) hormonal -growth spurts 2) intrinsic - within the bone or cartilage (genetic) 3) Extrinisc : - Neural -brain growth - special sense - eyeball - muscle activity - air sinuses - nasal septum growth - soft tissues - cheeks -thumb sucking 4) teeth : - presence - removal - implants - orthdontics (expand plate)