Classification of malocclusion Flashcards
What are Andrew’s six keys?
- 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
Define malocclusion
Appreciable deviation from the ideal occlusion, considered functionally or aesthetically unsatisfactory
Define normal occlusion
Minor deviations from the ideal occlusion that do not result in any functional or aesthetic issues
Methods to assess occlusion?
Extraoral assessment
Intraoral assessment
Radiographic assessment
What do you assess in the extra-oral assessment?
Horizontal plane for symmetry
Vertical plane - FMPA, facial thirds and % lower facial height
AP plane - lips and skeletal profile
NLA
How to assess symmetry?
Find chin point in relation to the midline
How to assess FMPA
Find Frankfort plane and mandibular plane - assess angle between the two
What does FMPA tell us?
Increased = increased lower facial height (mandible backwards)
Decreased = dec lower facial height (forward rotation)
What are the facial thirds made up of?
- Upper = trichlon to glabella
- Middle - glabella to subnasale
- Lower = subnasale to menton
What to assess in the intra-oral assessment?
Incisor relationship
Canine relationship
Molar relationship
- Inclinations, rotations, crowding, spacing
What does BSI stand for
British Standard Institute
Class 1 incisor relationship (BSI)
Incisal edge of lower central incisors occludes on or below the middle palatal 1/3 of the cingulum plateau of the upper central incisor
Class 2 div 1 incisor relationship (BSI)
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
Class 2 div 2 incisor relationship (BSI)
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
Class 3 incisor relationship (BSI)
Lower incisal edges occlude or pre-occlude anterior to the middle palatal third or cingulum plateau of upper central incisors
Class 1 molar relationship (Angle’s)
Mesiobuccal cusp of upper 6 occludes with anterior buccal groove of lower 6
Class 2 molar relationship (angles)
Mesiobuccal cusp of upper 6 occludes MESIAL to the buccal groove of the lower 6
Class 3 molar relationship (angles)
Mesiobuccal cusp of upper 6 occludes DISTAL to the buccal groove of lower 6
How to assess severity of molar malocclusion with units?
One unit = one cusp E.g. full unit class 2 = The mesiobuccal cusp is a full cusp mesial to the groove
How to ensure an accurate extra-oral assessment is carried out?
Head is in the natural head positioning - get patient to look directly ahead of them
Describe lip tone in relation to Ricketts E-plane
Lower lip anterior to the point = protrusive
Lower lip 0-2mm behind the line = normal
Lower lip >2mm posterior = retrusive
When should caution be taken using ricketts e plane?
Large noses as it displaces the plane anteriorly
What is the nasolabial angle?
Tangent of the upper lip and columella of the nose
What can cause an obtuse NLA?
- Poor upper lip position
- normal upper lip position with upward sloping of columella
What can cause an acute NLA?
Protrusive upper lip
Common in afro-carribeans
