2. Class II Division 1 Malocclusion

Question 1

What is the BSI definition of a Class II Div 1 malocclusion ?

Answer 1

Lower incisor edges lie posterior to the cingulum plateau of upper incisors.
Increased OJ.
Upper central incisors are proclaimed or of average inclination.

Question 2

What % of malocclusions are Class II Div 1 ?

Answer 2

15-20%

Question 3

What % of malocclusions are Class I ?

Answer 3

67-72%

Question 4

What % of malocclusions are Class II Div 2 ?

Answer 4

10%

Question 5

What % of malocclusions are Class III ?

Answer 5

3%

Question 6

What are the reasons to treat a patient with Class II Div 1 ?

Answer 6

Aesthetics.
Trauma risk.

Question 7

OJ greater than what are twice as likely to suffer trauma ?

Answer 7

> 9mm OJ (IOTN 5a).

Question 8

What skeletal pattern is a Class II Div 1 associated with ?

Answer 8

Class II AP pattern.

Question 9

What is the most common AP cause of a Class II Div 1 ?

Answer 9

Retrognathic mandible.
Maxillary protrusion is less likely.

Question 10

Normal SNA value ?

Answer 10

81 +/- 3

Question 11

Normal SNB value ?

Answer 11

78 +/- 3

Question 12

Normal ANB value ?

Answer 12

3 +/- 2

Question 13

Normal MxP/MnP value ?

Answer 13

27 +/- 4

Question 14

Normal LAFH/TAFH value ?

Answer 14

55%

Question 15

What are the four occlusal features of a sucking habit ?

Answer 15

Proclination of upper anteriors.
Retroclination of lower anteriors.
Localised AOB or incomplete OB.
Narrow upper arch (may see unilateral posterior cross bite).

Question 16

What are the 5 management options for a Class II Div 1 ?

Answer 16

Accept.
Attempt growth modification.
Simple tipping of teeth.
Camouflage.
Orthognathic surgery.

Question 17

Why is head gear used ?

Answer 17

Restrain growth of maxilla horizontal and/or vertically.

Question 18

What are the two options for growth modification ?

Answer 18

Headgear.
Functional appliance.

Question 19

Explain how a functional appliance works generally.

Answer 19

Utilize, eliminate, or guide the forces of muscles function, tooth eruption and growth to correct a malocclusion.

Question 20

What is the name of the most common functional appliance used for a Class II Div 1 ?

Answer 20

Twin block.

Question 21

Explain how a functional appliance caused growth modification in Class II Div 1 malocclusions specifically.

Answer 21

Aim to produce restraint of maxillary growth and encourage mandibular growth.
Mandible postured down and forwards.

Question 22

What are two factors which will affect how well functional appliances help reducing malocclusions ?

Answer 22

Patient engagement.
Favourable growth age.

Question 23

Describe the dento-alveolar changes seen using a functional appliance to correct a Class II Div 1 malocclusion.

Answer 23

Distal movement upper dentition.
Medial movement lower dentition.
Retroclination of uppers.
Proclination of lowers.

Question 24

Describe the skeletal changes seen using a functional appliance to correct a Class II Div 1 malocclusion.

Answer 24

Small degree of maxillary restraint and mandibular growth - usually small 1-2mm.
But significant variation in response between patients.

Question 25

At what age can functional appliances be used in 2 phase tx ?

Answer 25

10 years old - early use.

Question 26

At what age can functional appliances be used in 1 phase tx ?

Answer 26

Early permanent or late mixed dentition - later use.

Question 27

What are the potential disadvantages with early functional appliance treatment ?

Answer 27

Not maintained in long term.
Tx time increased.
Research shows little difference between early and later stage tx.

Question 28

What are the 2 stages of 2 phase tx (using functional appliance) ?

Answer 28

Early functional appliance + retention.
Fixed appliances in early permanent dentition.

Question 29

What are the potential benefits of early functional appliance tx ?

Answer 29

Improve appearance earlier.
Reduce risk of trauma.
Better compliance.

Question 30

When are functional appliance beneficial to use in tipping of teeth ?

Answer 30

Very mild Class II or Class I.
OJ due to proclaimed and spaced incisors.
Overbite favourable.

Question 31

What active component should be used in retroclining of anterior teeth on a URA ?

Answer 31

Roberts retractor 0.5mm in tubing.
+ Flat anterior bite plane.

Question 32

Describe camouflage technique for Class II Div1.

Answer 32

XLA of upper 5s and retract upper centrals back with fixed appliances for OJ reduction.

Question 33

When is orthognathic surgery carried out ?

Answer 33

When growth is complete.
Skeletal discrepancy is severe in AP or vertical direction.