Classification of malocclusion

Question 1

What are Andrew’s six keys?

Answer 1

• Molar relationship correct (distal of distobuccal cusp U6 coincides with mesial of mesiobuccal cusp L6)
• Tip - correct crown angulation
• Torque - correct crown inclination
• No rotations
• No spacing (tight contacts)
• Curve of spee = flat occlusal plane

Question 2

Define malocclusion

Answer 2

Appreciable deviation from the ideal occlusion, considered functionally or aesthetically unsatisfactory

Question 3

Define normal occlusion

Answer 3

Minor deviations from the ideal occlusion that do not result in any functional or aesthetic issues

Question 4

Methods to assess occlusion?

Answer 4

Extraoral assessment
Intraoral assessment
Radiographic assessment

Question 5

What do you assess in the extra-oral assessment?

Answer 5

Horizontal plane for symmetry
Vertical plane - FMPA, facial thirds and % lower facial height
AP plane - lips and skeletal profile
NLA

Question 6

How to assess symmetry?

Answer 6

Find chin point in relation to the midline

Question 7

How to assess FMPA

Answer 7

Find Frankfort plane and mandibular plane - assess angle between the two

Question 8

What does FMPA tell us?

Answer 8

Increased = increased lower facial height (mandible backwards)

Decreased = dec lower facial height (forward rotation)

Question 9

What are the facial thirds made up of?

Answer 9

• Upper = trichlon to glabella
• Middle - glabella to subnasale
• Lower = subnasale to menton

Question 10

What to assess in the intra-oral assessment?

Answer 10

Incisor relationship
Canine relationship
Molar relationship

• Inclinations, rotations, crowding, spacing

Question 11

What does BSI stand for

Answer 11

British Standard Institute

Question 12

Class 1 incisor relationship (BSI)

Answer 12

Incisal edge of lower central incisors occludes on or below the middle palatal 1/3 of the cingulum plateau of the upper central incisor

Question 13

Class 2 div 1 incisor relationship (BSI)

Answer 13

Lower incisal edge occlude or pre-occlude posterior to the middle palatal 1/3 or cingulum plateau of upper central incisors AND there is an increased overjet with proclined upper incisors

Question 14

Class 2 div 2 incisor relationship (BSI)

Answer 14

Lower incisor edge occlude or pre-occlude posterior to the middle palatal 1/3 or cingulum plateau of upper central incisors AND upper central incisors are retroclined or normal inclination

Question 15

Class 3 incisor relationship (BSI)

Answer 15

Lower incisal edges occlude or pre-occlude anterior to the middle palatal third or cingulum plateau of upper central incisors

Question 16

Class 1 molar relationship (Angle’s)

Answer 16

Mesiobuccal cusp of upper 6 occludes with anterior buccal groove of lower 6

Question 17

Class 2 molar relationship (angles)

Answer 17

Mesiobuccal cusp of upper 6 occludes MESIAL to the buccal groove of the lower 6

Question 18

Class 3 molar relationship (angles)

Answer 18

Mesiobuccal cusp of upper 6 occludes DISTAL to the buccal groove of lower 6

Question 19

How to assess severity of molar malocclusion with units?

Answer 19

One unit = one cusp E.g. full unit class 2 = The mesiobuccal cusp is a full cusp mesial to the groove

Question 20

How to ensure an accurate extra-oral assessment is carried out?

Answer 20

Head is in the natural head positioning - get patient to look directly ahead of them

Question 21

Describe lip tone in relation to Ricketts E-plane

Answer 21

Lower lip anterior to the point = protrusive
Lower lip 0-2mm behind the line = normal
Lower lip >2mm posterior = retrusive

Question 22

When should caution be taken using ricketts e plane?

Answer 22

Large noses as it displaces the plane anteriorly

Question 23

What is the nasolabial angle?

Answer 23

Tangent of the upper lip and columella of the nose

Question 24

What can cause an obtuse NLA?

Answer 24

• Poor upper lip position

- normal upper lip position with upward sloping of columella

Question 25

What can cause an acute NLA?

Answer 25

Protrusive upper lip

Common in afro-carribeans