Facial Growth

Question 1

Why is the study of facial growth important to orthodontics?

Answer 1

Predict changes
Utilise growth to correct malocclusion
Time our orthodontics and surgery
Understand development of facial anomalies
To measure changes in growth and treatment using cephalometry

Question 2

What happens when the neural folds fail to fuse to form the neural tube?
What week does this occur in embryology?

Answer 2

Leads to spina bifida
Occurs at the end of week 3 in vitro

Question 3

What does the neural tube develop into?
What occurs when there is a development failure?

Answer 3

Into the brain and spinal cord
Failure to develop will lead to anencephaly (in which the cerebral hemispheres and the cranial vault are absent)

Question 4

What is the difference between a cleft lip and a cleft palate?

Answer 4

If the cleft is before the incisive foramen it is a cleft lip
If the cleft is behind the incisive foramen it is a cleft palate

Question 5

What is the neurocranium?

Answer 5

Forms a protective case around the brain

Question 6

What is a viscerocranium?

Answer 6

Forms the skeleton of the face

Question 7

What is intramembranous bone formation?

Answer 7

Bone is deposited directly into mesenchymal tissue
Needle like bone spicules form, which progressively radiate from the primary ossification centres to the periphery

Question 8

What is endochondral bone formation?

Answer 8

Bones are preceded by a hyaline cartilage
Forms the base of the skull
Several centres of ossification which eventually fuse

Question 9

Why does growth occur at fibrous sutures at ossification centres?

Answer 9

Due to intracranial pressure

Question 10

What are the 3 main sites of secondary cartilage formation in the mandible?

Answer 10

Condylar cartilage, coronoid cartilage and the symphyseal cartilage at the end of each half of the bony mandible
Appear 12-14 weeks in utero

Question 11

When does ossification of the face and skull commence?

Answer 11

7-8 weeks

Question 12

How is the vault of the skull formed?

Answer 12

Intramembranously

Question 13

How is the base of the skull formed?

Answer 13

Endochondral ossification

Question 14

How are the maxilla and mandible developed? What precedes this?

Answer 14

They both develop intramembranously
They are preceded by a cartilaginous facial skeleton
Meckel’s cartilage precedes the mandible and the nasal capsule is the primary skeleton of the face

Question 15

What is a primary abnormality?

Answer 15

Defect in the structure of an organ or part of an organ that can be traced back to an anomaly in its development (spina bifida, cleft lip)

Question 16

What is a secondary abnormality?

Answer 16

Interruption of the normal development of an organ that can be traced back to other influences
–Tetratogenic agents: infection (rubella virus), chemical (thamidomide)
–Trauma: amniotic bands

Question 17

What is the definition of deformation?

Answer 17

Anomalies that occur due to outer mechanical effects on existing structures

Question 18

What is agenesia?

Answer 18

Absence of an organ due to failed development during embryonic period

Question 19

What is a syndrome?

Answer 19

Group of anomalies that can be traced to a common origin

Question 20

On what day does foetal alcohol syndrome occur?

Answer 20

Day 17

Question 21

What day does hemifacial microsomia occur? What is this due to?

Answer 21

Day 19-28
Neural cell crest migration

Question 22

What does hemifacial microsomia appear as?

Answer 22

Unilateral mandibular hypoplasia, zygomatic arch hypoplasia, high arches palate, malformed pinna
As one side grows the other doesn’t usually
Deafness on one side

Question 23

What day does treacher collins (mandibulofacial dystosis) occur?
What is this due to?

Answer 23

Day 19-28
Deformity of the 1st and 2nd branchial arches

Question 24

What are some clinical signs of Treacher Collins?

Answer 24

Hypoplastic or missing zygomatic arches
Hypoplastic mandible with antigonial notch
Deformed pinna

Question 25

What are some dental features of a cleft lip and/or palate?

Answer 25

Impacted teeth Crowding Hypodontia Supernumeraries Hypoplastic teeth Caries

Question 26

What is the aetiology of clefts? Genetic and environment?

Answer 26

Genetic -monozygotic twins -syndromes -familial pattern -epidemiology Environment -social deprivation -smoking -alcohol -anti-epileptics

Question 27

Who is involved in a cleft team?

Answer 27

Specialist cleft nurse Speech therapist Orthodontist Paediatric dentist Cleft surgeon ENT Geneticist Psychologist

Question 28

What is achondroplasia?

Answer 28

Problem with endochondrial ossification Defects in base of skull, depressed nasal bridge, retrusive middle third of the face Dwarfism in 70%

Question 29

What is Crouzon's syndrome (craniofacial dysostosis)?

Answer 29

Premature closure of cranial sutures Proptosis (shallow orbits) and orbital dystopia, mild hypertelorism Prominent nose Class III malocclusion

Question 30

What is apert's syndrome?

Answer 30

Premature closure of almost all cranial sutures

Question 31

What are the clinical features of Apert's syndrome?

Answer 31

Exopthalmos (bulging or protruding of the eyeballs) Hypertelorism (abnormally large distance between the eyes) Maxillary hypoplasia Class III occlusion, AOB, narrow spaced teeth Parrot's beak nose Syndactyl of fingers and toes

Question 32

What are sutures?

Answer 32

Specialised fibrous joints situated between intramembranous bone Each suture is a band of connective tissue which has osteogenic cells in the centre and the most peripheral of these cells provide new bone growth

Question 33

What are synchondroses?

Answer 33

A cartilage-based growth centre with growth occurring in both directions The bones on either side of the synchondrosis are moved apart as growth takes place New cartilage is formed in the centre as cartilage at the periphery is transformed to bone Found in the midline

Question 34

What is surface deposition?

Answer 34

New bone is deposited beneath the periosteum over the surfaces of both the cranial and facial bone In order for bones to maintain their shape as they grow resorption is also taking place This process of deposition and resorption is known as remodelling

Question 35

What is a growth rotation? What do forwards & backwards rotations lead to?

Answer 35

Is due to an imbalance in the growth of the anterior and posterior face heights Forward rotations lead to a short face Backwards rotations lead to a long face

Question 36

What kind of bites do forwards & backwards rotations lead to?

Answer 36

Forwards growth rotation can lead to the development of a deep bite Backwards growth rotation can lead to the development of an anterior open bite

Question 37

What are the indications for taking a lateral cephalogram?

Answer 37

To aid diagnosis Treatment planning Progress monitoring

Question 38

What position should the teeth be in when taking a lateral cephalogram?

Answer 38

RCP

Question 39

What is the Eastman Analysis?

Answer 39

Measures the antero-posterior position of the maxilla and mandible relative to the base of the skull