Malocclusion

Question 1

Causes of malocclusion

Answer 1

1. Skeletal factors
2. Dento-alveolar factors
3. Soft tissues
4. local factors

Question 2

What is skeletal pattern

Answer 2

The relationship of the maxilla to the mandible

Question 3

What 3 dimensions do we talk about when referring to skeletal pattern?

Answer 3

1. Antero-posterior
2. Transverse
3. Vertical

Question 4

What does skeletal class refer too?

Answer 4

The antero-posterior relationship of the dental bases which support the teeth and alveolar processes

Question 5

Skeletal class I

Answer 5

The maxillary dental base lies 2-3mm anterior to the mandibular dental base when the teeth are in occlusion

Question 6

Skeletal class II

Answer 6

The maxillary dental base is more anterior to the mandibular dental base than in a class I

Question 7

Aetiology of skeletal class II

Answer 7

1. Retrognathic mandible
2. Prognathic maxialla
3. Both

Question 8

Skeletal Class III

Answer 8

The mandibular dental base lies more anterior to the maxillary dental base than in the class I case

Question 9

Aetiology of skeletal class III

Answer 9

1. Prognatic mandible (25%)
2. Retrognathic maxilla (25%)
3. Both (50%)

Question 10

What is dento-alveolar compensation

Answer 10

When the A/P jaw relationship is SK2/3 but the soft tissues are favourable, the lips and tongue guide the erupting teeth into better positions than the skeletal class would suggest

Question 11

How can you judge skeletal class?

Answer 11

Cephalometric analysis - SNA - SNB. 
SK I is 3.4. Bigger degree is class 2, smaller class 3

Question 12

The mandibular-maxillary plane angle should equal

Answer 12

27 +- 5

Question 13

What happens to the mandibular-maxillary plane angle when the lower face height increases

Answer 13

It increases

Question 14

What features can be seen with a greater lower face height

Answer 14

1. reduced overbite or anterior open bite

2. wide separation of the lips

Question 15

Features of a reduced lower face height

Answer 15

1. Prominent chin - increased labio-mental fold
2. Increased overbite
3. Lips completely cover the teeth

Question 16

Reduced FMA

Answer 16

Lines meet further at the back of the head

Question 17

Associated intra-oral features with facial assymetry

Answer 17

1. centre-line discrepancies

2. Posterior crossbites in the buccal segments

Question 18

What influence do soft tissues have?

Answer 18

Tooth CROWN position is determined by soft tissue balance

Question 19

What is the definition of lip competance?

Answer 19

Lips meet together at rest without any muscular activity

Question 20

Incompetent lips

Answer 20

Mild < half the crown height
Markedly > half the crown height

only marked incompetence matters

Question 21

What is the normal lip line

Answer 21

Relates to the lower lip. Normally overlaps 3-6mm of the upper incisor crown at rest

Question 22

What is the relevance of high lip line

Answer 22

1. Tends to cause retroclination of the upper incisors

2. Favours stability of overjet reduction

Question 23

What is the relevance of a low lip line?

Answer 23

1. Tends to permit the proclination of the upper incisors

2. Increases the chance of instability of overject reduction

Question 24

Upper lip length

Answer 24

Influences the amount of the upper incisor that is visible. Normally should be about 2-3 mm.

Question 25

What is meant by an adaptive tongue trust

Answer 25

Adaptation to incompetent lips. It creates an anterior oral seal during swallowing. Often associated with an incomplete overbite

Question 26

What can crowding be caused by?

Answer 26

1. Small arches 2. Big teeth 3. a combination 4. Supernumeraries 5. early loss of deciduous dentition

Question 27

How much spacing should be present in the deciduous dentition in order to prevent crowding in the lower arch?

Answer 27

< 3 mm spacing at 5 years - 50% chance of crowding | >6mm spacing at 5 years - 0% chance of crowding

Question 28

How does early loss of Ds and Es present in the permanent dentition

Answer 28

Crowding in the premolar region due to mesial drifting of the 6s

Question 29

Premolar crowding is always due to...

Answer 29

early loss of deciduous molars

Question 30

How can you treat crowding?

Answer 30

1. Creating space for alignment by extracting teeth | 2. Creating space by expansion laterally and antero-posteriorly

Question 31

What can spacing be caused by?

Answer 31

1. too small teeth 2. Too large an arch 3. Hypodontia

Question 32

How can spacing be treated?

Answer 32

1. Closing spaces | 2. Redistributing space +/- filling prosthetically

Question 33

Class I incisor relationship

Answer 33

The lower incisal edge occludes with the cingulum plateau of the upper central incisor

Question 34

What is the incidence of class I incisal occlusion?

Answer 34

60%

Question 35

What is the ANB angle of a class I occlusion?

Answer 35

3.4 degrees

Question 36

Causes of anterior open bite

Answer 36

1. Skeletal cause due to increased lower face height 2. Habit - due to digit sucking 3. soft tissue cause - due to tongue habit

Question 37

What is the normal transverse arch relationship?

Answer 37

Upper arch is wider than the lower arch

Question 38

What are the causes of a posterior cross bite?

Answer 38

1. A relatively narrow maxilla 2. A digit sucking habit 3. Local problem - often related to local crowding

Question 39

Unilateral crossbites may be associated with...

Answer 39

a mandibular displacement

Question 40

class 2 div 2 incisor relationship

Answer 40

the lower incisor edges lie posterior to the cingulum plateau of the upper central incisors. The upper central incisors are normal inclination or retroclined

Question 41

Incidence of class 2 div 1

Answer 41

22%