1 - Class 2 div 1 malocclusion Flashcards by Cesca Lang

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

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

15-20%

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

aesthetic concerns
trauma risk due to incompetent lips

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

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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What is the normal SNA value?

81 +/- 3

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What is the normal SNB value?

78 +/- 3

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What is the normal ANB value?

3 +/- 2

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What is the normal MxP/MnP value?

27 +/- 4

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What is the normal Ui/MxP value?

109 +/- 6

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What is the normal Li/MnP value?

93 +/- 6

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What is the SNA value?

Sella turcica to soft tissue point A

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What is the SNB value?

Sella turcica to soft tissue point B

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What is the ANB value?

Angle between soft tissue point A and B

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What is the MxP/MnP value?

Angle between the maxillary and mandibular planes

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What is the Ui/MxP value?

Angulation of upper incisors to maxillary plane

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What is the Li/MnP value?

Angulation of lower incisors to mandibular plane

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What is the normal LAFH/TAFH value?

55%

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How do soft tissues influence class 2 div 1 malocclusion?

lips become incompetent due to proclination of upper incisors
lip trap can further procline the upper incisors

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

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

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

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

What is NNSH?

Non-nutritive sucking habits

What are common NNSH?

thumb
fingers
blanket
lip

What are the occlusal features of a sucking habit?

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

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

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

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

What are the management option for class 2 div 1 malocclusion?

- accept - attempt growth modification - tipping of teeth - camouflage - orthognathic surgery

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

How does head gear modify growth?

- restrain growth of maxilla horizontally and vertically - works by distilising teeth rather than maxillary change (?)

Define a functional appliance.

Functional appliances utilise, eliminate, or guide the forces of muscle function, tooth eruption and growth to correct a malocclusion.

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

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)

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

When can a functional appliance be worn?

- during growth - early use around 10 years old - later use in late mixed dentition

When is the period of maximal growth in girls?

11-13 years

When is the period of maximal growth in boys?

13-15 years

What are the potential disadvantages of early use of a functional appliance?

- early skeletal changes may not be maintained long term - 2 phase treatment

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

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

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

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

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

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

What is maxillary impaction?

Orthognathic surgery where the maxilla is raised to reduce the amount of tooth shown

# **QUIZ** What is the approximate prevalence of class II, division 1 malocclusion in the U.K. population?

15-20%

# **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

# **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

# **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.