Facial Growth 1

Question 1

Why is facial growth important to consider?

Answer 1

Because the size, shape and position of the underlying jaws determines the position of the teeth and therefore the malocclusion

Question 2

Why is the study of facial growth important to orthodontists?

Answer 2

• Insight into growth of the face
  
  • We are treating children
• Predict changes
• Utilize growth to correct malocclusion
• Time our orthodontics and surgery
  
  • Can help reduce malocclusion
• Understand development of facial anomalies
• To measure changes in growth and treatment using cephalometry

Question 3

What are the 2 phases of life in utero?

Answer 3

• Embryonic – 1-8 weeks
  
  • All the major parts happen within the first 8 weeks
• Foetal – 8 weeks to term
  
  • Are mainly just growing now

Question 4

When have all the limbs and organs including the face developed?

Answer 4

Within the first 2 months

Question 5

What % of babies miscarriage due to developmental problems?

Answer 5

10%

Question 6

In what period do the most developmental problems occur?

Answer 6

In the first 8 weeks - are a very sensitive time

Question 7

Give a breif overview of what happens to the embryo in the first 4 weeks.

Answer 7

• Fertilised egg with male and female pronucleus
• 8-16 cells moving down the fallopian tube called the morula
• 4th-5th day
  
  • 16-32 cells (blastocyst)
  • Inner cells mass (gives rise to you)
  • Outer cell mass
  • First germ layers form
• Implanataion and placenta starts to develop
• Germ disc made of ectoderm and endoderm
• have the neural groove that will form the nerual tube

Question 9

When do the neural grooves fuse to form the neural tube?

Answer 9

At the end of week 3

Question 10

What happens if the neural tubes fail to fuse together?

Answer 10

Leads to spina bifida

Question 11

What does the neural tube develop into

Answer 11

the brain and spinal cord

Question 12

Failure of the neural tube to develop into the brain and spinal cord is called what?

Answer 12

anencephaly (the cerebral hemispheres and the cranial vault are absent). i.e. if you don’t have a neural tube then you won’t have a brain.

Question 13

Neural crest cell migration is very important for what?

Answer 13

Development of the face

Question 14

What are neural crest cells? (where do they develop from)

Answer 14

During the folding of the neural plate cells develop from ectoderm along the edge

These are the neural crest cells

Question 15

What do they neural crest cells differentiate into?

Answer 15

They migrate extensively and differentiage into:

• spinal and autonomic ganglia
• shwann cells
• meninges of brain
• pulp, dentine, cementum and PDL

The cells are vitally important for tooth development

Question 16

Formation of the face happens when?

Answer 16

Within the first 8 weeks after fertilisation

Question 17

What kind of factors may lead to significant malformations in the early development of the face? (first 8 weeks)

Answer 17

Environmental factors

Question 18

Defects of the face, particularly in the midline, may be closely related to defects where?

Answer 18

Defects of the anterior parts of the brain

Question 19

Most of the face develops from what kind of cells?

Answer 19

Migrating neural crest cells (either in the frontal-nasal process or the brachial arches)

Question 20

Interference with the migration of neural crest cells can lead to what?

Answer 20

Seveer facial deformaties

Question 21

Failure of fusion between what can lead to cleft formation?

Answer 21

Cleft lip - failure of fusion between the maxillary processes and lateral and medial nasal processes

Cleft palate - failure of fusion between the palatine processes (of the maxillary process)

Question 22

What is the difference between cleft lip (cleft of the primary palate) and cleft palate?

Answer 22

Cleft lip occurs anteriorally to the incisive foramen. It can involve the nose too as well as the lip and anterior portion of the palate

Cleft palate is cleft of the palate posterior to the incisive foramen

Question 23

Why can cleft of the lip (and anterior palate) occur independently of cleft palate?

Answer 23

Becaiuse the upper lip and anterior portion of the palate have different embryological origins from the posterior palate and they fuse at different times.

Question 24

Approx how many babies are born with cleft lip/palate?

Answer 24

1 in 700

Question 25

When in utero will cleft lip happen?

Answer 25

day 28-38

Question 26

When in utero does cleft palate occur?

Answer 26

day 42-55

Question 27

What is the aetiology of cleft lip and palate?

Answer 27

• genetic component
• multifactoral aetiology (social deprivation, alcohol, smoing, anti-epileptics)

Question 28

What are the dental features of cleft lip and palate?

Answer 28

• impacted teeth
• crowding
• hypodontia
• supernumeracies
• hypoplastic teeth
• caries

Question 29

What professionals are involved in a cleft team?

Answer 29

• specialist cleft nurse
• speech therapist
• orthodontist
• paedatric dentist
• cleft surgeon
• ENT
• geneticist
• psychologist

Question 30

The skull can be divided into what 2 sections?

Answer 30

Neurocranium (protective case around the brain)

Viscerocranium (facial skeleton)

Question 31

The neurocranium can be divided into what?

Answer 31

Flat bones of the vault which develop intramembranously

Endochondrial elements of the base of the skull

Question 32

Describe how intramembranous bone formation occurs.

Answer 32

• Bone is deposited directly into primitive mesenchymal tissue
• Needle-like bone spicules form, which progressively radiate from the primary ossification centres to the periphery
• Progressive bone formation results in the fusion of adjacent bony centres
• Intramembranous bones include the vault of the skull, the maxilla and most of the mandible

Question 33

Describe how endochondiral bone formation occurs.

Answer 33

• Bones are preceded by a hyaline cartilage ‘model’
• There are several centres of ossification which eventually fuse
• Forms the base of the skull