Facial Growth 1

Question 1

Why is facial growth important?

Answer 1

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 orthodontics?

Answer 2

• insight into the growth of the face
• understand development of facial anomalies
• to measure changes in growth and treatment using cephalometry

Question 3

what are the two in utero phases?

Answer 3

1. Embryonic = 1-8 weeks
2. Foetal = 8 weeks to term

Question 4

What is neural crest cell migration very important in?

Answer 4

the development of the face

Question 5

what is the neural tube?

Answer 5

The fusion of the neural folds that develops into the brain & spinal cord

Question 6

what is the failure to fuse of the neural folds known as?

Answer 6

spina bifida

Question 7

what is anencephaly?

Answer 7

failure to develop of the brain & spinal cord

Question 8

what cells develop from the ectoderm during the folding of the neural plate?

Answer 8

neural crest cells

Question 9

where does the ectomesenchyme derive from?

Answer 9

the neural crest

Question 10

what is derived from the ectomesenchyme?

Answer 10

• bone & connective tissue
• pulp
• dentine
• cementum
• PDL

Question 11

what is the function of neural crest cells?

Answer 11

They undergo extensive migration within the developing embryo & differentiates into many cell types
- shwann cells
- autonomic ganglia
- adrenal medulla
- meninges of brain

Question 12

when does formation of the face occur?

Answer 12

during the first eight weeks after fertilisation

Question 13

what can lead to malformations to the development of the face?

Answer 13

environmental factors

Question 14

what are defects of the midline of the face closely related to ?

Answer 14

defects of the anterior parts of the brain

Question 15

What is most of the face formed from?

Answer 15

migrating neural crest cells

Question 16

What occurs if there is failure of fusion between the palatine processes during development?

Answer 16

Cleft formation

Question 17

when are the branchial arches formed?

Answer 17

week 4
- migrating neural crest cells form the lateral branchial arches

Question 18

what can be seen during facial development at weeks 5-7?

Answer 18

the extension and fusion of facial processes

Question 19

what can the skull be divided into?

Answer 19

• neurocranium (protective case around brain)
• viscerocranium (forms skeleton of face)

Question 20

how is the base of the skull formed?

Answer 20

From a series of cartilages
- they undergo endochondral ossification

Question 21

why is fusion of the skull incomplete at birth?

Answer 21

Leaves fontanelles to allow flexibility in the skull during birth

Question 22

what are the three main sites of secondary cartilage formation in the mandible?

Answer 22

• condylar cartilage
• coronoid cartilage
• symphyseal

Question 23

How does the mandible form?

Answer 23

Intramembranous ossification ** (Exam question)

Question 24

The mandible and maxilla form via which method of bone formation?

Answer 24

Intramembranously but are preceded by a cartilaginous facial skeleton
- despite developing adjacent to cartilaginous skeletons

Question 25

What cartilaginous skeletons do the mandible & maxilla form adjacent to?

Answer 25

- Meckel’s cartilage - nasal capsule

Question 26

When does the symphysis fuse?

Answer 26

A few months after birth

Question 27

When does ossification of the face & skull commence?

Answer 27

7-8 weeks (approx.)

Question 28

What is the vault of the skull formed by?

Answer 28

Intramembranous ossification

Question 29

What is the base of the skull formed by?

Answer 29

endochondral ossification

Question 30

what is a primary abnormality?

Answer 30

defect in the structure of an organ or part of an organ that can be traced back to an anomaly in its development

Question 31

what are examples of primary abnormalities?

Answer 31

- spina bifida - cleft lip - CHD

Question 32

what is a secondary abnormality?

Answer 32

interruption of the normal development of an organ that can be traced back to other influences

Question 33

What can cause a secondary abnormality?

Answer 33

- teratogenic agents - trauma

Question 34

What is the definition of a deformation?

Answer 34

anomalies that occur due to outer mechanical effects on existing structures

Question 35

What is the definition of agensia?

Answer 35

absence of an organ due to failed development during embryonic period

Question 36

What is the definition of sequence?

Answer 36

single factor results in numerous secondary effects - Pierre Robin = small mandible. causes other problems ** google

Question 37

what are examples of facial syndromes causing hypoplasia of the maxilla?

Answer 37

- Apert’s Syndrome - Crouzon’s Syndrome - Oral-Facial Digital Syndrome - Cleft lip/palate

Question 38

what are examples of facial syndromes causing mandibular problems?

Answer 38

- Treacher Collin’s Syndrome - Pierre-Robin - Stickler’s Syndrome - Van der Woude SYndrome

Question 39

what environmental facial syndrome is caused by early development problems?

Answer 39

Foetal Alcohol Syndrome

Question 40

What is caused by Foetal Alcohol syndrome?

Answer 40

A high maternal intake of alcohol

Question 41

what is the presentation of foetal alcohol syndrome?

Answer 41

- microcephaly (small head) - short palpebral fissues - short nose - deficient philtrum - small midface - small mandible - mild mental retardation

Question 42

what is hemi facial microsomia?

Answer 42

3D progressive facial asymmetry caused by impaired neural crest cell migration

Question 43

how does hemifacial microsomia present?

Answer 43

- unilateral mandibular hypoplasia - zygomatic arch hypoplasia - high arched palate - malformed pinna

Question 44

what is Treacher Collins caused by?

Answer 44

Deformity of 1st & 2nd branchial arches (day 19-28)

Question 45

How does Treacher Collins syndrome present?

Answer 45

- colomboma of lower lid outer 1/3rd - hypoplastic or missing zygomatic arches - hypoplastic mandible with antigonial notch

Question 46

who is cleft lip more common in?

Answer 46

males > females (3:1)

Question 47

who is cleft palate more common in?

Answer 47

females > males (3:2)

Question 48

what are the genetic aetiological causes of cleft lip/palate?

Answer 48

- monozygotic twins - syndromes - familial pattern - sex ratio

Question 49

what are the dental features of cleft lip/palate?

Answer 49

- impacted teeth - crowding - hypodontia - supernumeraries - caries

Question 50

what is Achondroplasia?

Answer 50

Problem with endochondrial ossification - defects in long bones causing short limbs

Question 51

what is Crouzon’s syndrome ?

Answer 51

Premature closure of cranial sutures

Question 52

How does Crouzon’s syndrome present?

Answer 52

- proptosis - retusion and vertical shortening of midface - prominent nose - class III occlusion - narrow spaced teeth

Question 53

What is Apert’s syndrome?

Answer 53

Premature closure of almost all cranial sutures (acrosyndactyly)

Question 54

how does Apert’s syndrome present?

Answer 54

- exopthalmos - maxillary hypoplasia - class III occlusion - narrow spaced teeth - parrots beak nose - syndactyly of fingers & toes