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BDS4 Orthodontics > 1 - Class 2 div 1 malocclusion > Flashcards

1 - Class 2 div 1 malocclusion Flashcards

1
Q

What is the BSI definition of a class 2 div 1 malocclusion?

A

The lower incisor edges lie posterior to the cingulum plateau of the upper incisors, there is an increased overjet, and the upper central incisors are proclined or of average inclination

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2
Q

What percentage of the population have a class 2 div 1 malocclusion?

A

15-20%

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3
Q

What are the reasons for treating a class 2 div 1 malocclusion?

A
  • aesthetic concerns
  • trauma risk due to incompetent lips
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4
Q

Describe the skeletal patterns associated with class 2 div 1 malocclusion.

A

A/P
- typically class 2 skeletal base
- commonly have retrognathic mandible
- can be seen on class 1 base, if uppers +++ proclined

Vertical
- found with a range of vertical patterns

Transverse
- not associated with transverse problems
- can have narrow maxilla due to thumb sucking

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5
Q

What is the normal SNA value?

A

81 +/- 3

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6
Q

What is the normal SNB value?

A

78 +/- 3

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7
Q

What is the normal ANB value?

A

3 +/- 2

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8
Q

What is the normal MxP/MnP value?

A

27 +/- 4

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9
Q

What is the normal Ui/MxP value?

A

109 +/- 6

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10
Q

What is the normal Li/MnP value?

A

93 +/- 6

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11
Q

What is the SNA value?

A

Sella turcica to soft tissue point A

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12
Q

What is the SNB value?

A

Sella turcica to soft tissue point B

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13
Q

What is the ANB value?

A

Angle between soft tissue point A and B

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14
Q

What is the MxP/MnP value?

A

Angle between the maxillary and mandibular planes

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15
Q

What is the Ui/MxP value?

A

Angulation of upper incisors to maxillary plane

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16
Q

What is the Li/MnP value?

A

Angulation of lower incisors to mandibular plane

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17
Q

What is the normal LAFH/TAFH value?

A

55%

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18
Q

How do soft tissues influence class 2 div 1 malocclusion?

A
  • lips become incompetent due to proclination of upper incisors
  • lip trap can further procline the upper incisors
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19
Q

How is an anterior oral seal achieved with a class 2 div 1 malocclusion?

A
  • lip to lip seal by circum-oral musculature and mandible postured forward
  • lower lip drawn up behind upper incisors / tongue placed forward between incisors
  • combination of above
20
Q

Describe the dental features of a class 2 div 1 malocclusion.

A
  • increased overjet
  • overbite varies
  • habitually parted lips leads to drying of gingiva, that can exacerbate any pre-existing gingivitis (can become hyperplastic)
21
Q

What is NNSH?

A

Non-nutritive sucking habits

22
Q

What are common NNSH?

A
  • thumb
  • fingers
  • blanket
  • lip
23
Q

What are the occlusal features of a sucking habit?

A
  • proclination of upper anteriors
  • retroclination of lower anteriors
  • localised AOB or incomplete OB
  • narrow upper arch (can be seen with unilateral posterior crossbite)
24
Q

Why is a narrow upper arch common in a thumb sucking habit?

A

Buccinator muscles are unopposed due to the tongue being held down by the thumb, the neutral zone is lost

25
How do you manage a patient with a NNSH?
- stop the habit (reinforcement, removable/fixed appliance breaker) - allow spontaneous improvement (6-12 months) - treat any residual malocclusion
26
What are the management option for class 2 div 1 malocclusion?
- accept - attempt growth modification - tipping of teeth - camouflage - orthognathic surgery
27
Describe accepting a class 2 div 1 malocclusion.
- mildly increased overjet suitable - warn of trauma risk and advise re mouthguard - explain that this may complicate treatment in future
28
How does head gear modify growth?
- restrain growth of maxilla horizontally and vertically - works by distilising teeth rather than maxillary change (?)
29
Define a functional appliance.
Functional appliances utilise, eliminate, or guide the forces of muscle function, tooth eruption and growth to correct a malocclusion.
30
How does a twin-block function?
- mandible is postured down and forwards - the MOM pull the mandible back, trying to achieve normal posture - these forces pull maxillary teeth backwards - limited mandibular growth is observed
31
Name other types of functional appliance that can be used in class 2 div 1 malocclusions.
- activator/bionator (tooth-borne) - Frankel (soft tissue borne) - Herbst (fixed)
32
What dento-alveolar changes can be observed after using a twin-block appliance?
- distal movement of upper dentition - mesial movement of lower dentition - retroclination of upper incisors - proclination of lower incisors
33
When can a functional appliance be worn?
- during growth - early use around 10 years old - later use in late mixed dentition
34
When is the period of maximal growth in girls?
11-13 years
35
When is the period of maximal growth in boys?
13-15 years
36
What are the potential disadvantages of early use of a functional appliance?
- early skeletal changes may not be maintained long term - 2 phase treatment
37
What are the potential benefits of early use of a functional appliance?
- improve appearance earlier (combat teasing, psychological benefit) - reduce risk of trauma - better compliance with wear
38
When can a URA be used in the treatment of increased overjets?
- v mild class 2 or class 1 - overjet is due to spaced and proclined upper incisors - overbite is favourable
39
Why is URA treatment not commonly used in the management of class 2 div 1 malocclusions?
Creates a class 2 div 2 malocclusion which is not favourable
40
Describe the design of a URA used for retroclining upper anteriors.
A: Robert's retractor 0.5mm in tubing R: Adam's clasp 16, 26 in 0.7mm HSSW A: mesial stops on 13, 23 B: FABP
41
How is camouflage achieved when treating a class 2 div 1 malocclusion?
- remove teeth (not always the case, sometimes all teeth are moved distally) - control tip of teeth with fixed appliances
42
When is orthognathic surgery indicated in class 2 div 1 malocclusions?
- when growth is complete - when skeletal discrepancy is severe in AP or vertical - fixed appliances are required before, during and after surgery
43
What is maxillary impaction?
Orthognathic surgery where the maxilla is raised to reduce the amount of tooth shown
44
# **QUIZ** What is the approximate prevalence of class II, division 1 malocclusion in the U.K. population?
15-20%
45
# **QUIZ** What other occlusal feature can accompany an increased overjet in patients with a digit sucking habit?
- posterior crossbite - narrow maxillary dental arch - retroclined lower anteriors - anterior open bite
46
# **QUIZ** When analysing a lateral cephalograph of a patient with a class II jaw relationship, you would expect the ANB angle to measure:
Greater than 5 degrees
47
# **QUIZ** The main therapeutic effect of functional appliance treatment, in a growing child with a class II, division 1 malocclusion is:
Reduction of the overjet and correction of the molar relationship through dentoalveolar change.

BDS4 Orthodontics (14 decks)

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