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Ortho > Malocclusion > Flashcards

Malocclusion Flashcards

1
Q

Causes of malocclusion

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

What is skeletal pattern

A

The relationship of the maxilla to the mandible

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3
Q

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

A
  1. Antero-posterior
  2. Transverse
  3. Vertical
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4
Q

What does skeletal class refer too?

A

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

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5
Q

Skeletal class I

A

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

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6
Q

Skeletal class II

A

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

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7
Q

Aetiology of skeletal class II

A
  1. Retrognathic mandible
  2. Prognathic maxialla
  3. Both
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8
Q

Skeletal Class III

A

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

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9
Q

Aetiology of skeletal class III

A
  1. Prognatic mandible (25%)
  2. Retrognathic maxilla (25%)
  3. Both (50%)
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10
Q

What is dento-alveolar compensation

A

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

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11
Q

How can you judge skeletal class?

A 
Cephalometric analysis - SNA - SNB. 
SK I is 3.4. Bigger degree is class 2, smaller class 3
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12
Q

The mandibular-maxillary plane angle should equal

A

27 +- 5

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13
Q

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

A

It increases

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14
Q

What features can be seen with a greater lower face height

A
  1. reduced overbite or anterior open bite

2. wide separation of the lips

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15
Q

Features of a reduced lower face height

A
  1. Prominent chin - increased labio-mental fold
  2. Increased overbite
  3. Lips completely cover the teeth
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16
Q

Reduced FMA

A

Lines meet further at the back of the head

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17
Q

Associated intra-oral features with facial assymetry

A
  1. centre-line discrepancies

2. Posterior crossbites in the buccal segments

18
Q

What influence do soft tissues have?

A

Tooth CROWN position is determined by soft tissue balance

19
Q

What is the definition of lip competance?

A

Lips meet together at rest without any muscular activity

20
Q

Incompetent lips

A

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

only marked incompetence matters

21
Q

What is the normal lip line

A

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

22
Q

What is the relevance of high lip line

A
  1. Tends to cause retroclination of the upper incisors

2. Favours stability of overjet reduction

23
Q

What is the relevance of a low lip line?

A
  1. Tends to permit the proclination of the upper incisors

2. Increases the chance of instability of overject reduction

24
Q

Upper lip length

A

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

25
Q

What is meant by an adaptive tongue trust

A

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

26
Q

What can crowding be caused by?

A
  1. Small arches
  2. Big teeth
  3. a combination
  4. Supernumeraries
  5. early loss of deciduous dentition
27
Q

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

A

< 3 mm spacing at 5 years - 50% chance of crowding

>6mm spacing at 5 years - 0% chance of crowding

28
Q

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

A

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

29
Q

Premolar crowding is always due to…

A

early loss of deciduous molars

30
Q

How can you treat crowding?

A
  1. Creating space for alignment by extracting teeth

2. Creating space by expansion laterally and antero-posteriorly

31
Q

What can spacing be caused by?

A
  1. too small teeth
  2. Too large an arch
  3. Hypodontia
32
Q

How can spacing be treated?

A
  1. Closing spaces

2. Redistributing space +/- filling prosthetically

33
Q

Class I incisor relationship

A

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

34
Q

What is the incidence of class I incisal occlusion?

A

60%

35
Q

What is the ANB angle of a class I occlusion?

A

3.4 degrees

36
Q

Causes of anterior open bite

A
  1. Skeletal cause due to increased lower face height
  2. Habit - due to digit sucking
  3. soft tissue cause - due to tongue habit
37
Q

What is the normal transverse arch relationship?

A

Upper arch is wider than the lower arch

38
Q

What are the causes of a posterior cross bite?

A
  1. A relatively narrow maxilla
  2. A digit sucking habit
  3. Local problem - often related to local crowding
39
Q

Unilateral crossbites may be associated with…

A

a mandibular displacement

40
Q

class 2 div 2 incisor relationship

A

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

41
Q

Incidence of class 2 div 1

A

22%

Ortho (4 decks)

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