class 2 div 2 malocclusion

Question 1

definition

Answer 1

lower incisors occlude posterior to the cingulum plateau of the upper incisor
upper incisors retroclined
OJ reduced but can also be increased

Question 2

incidence

Answer 2

literature dependent 5-18%

Question 3

broad etiological features

Answer 3

skeletal
soft tissue
dental
pathology e.g. condylar problems

Question 4

AP skeletal pattern

Answer 4

usually associated with a mild/mod class 2 base
can also be class 1 or 3

Question 5

vertical skeletal pattern

Answer 5

typically reduced FMPA
often associated with a forward rotational pattern of growth of the mandible
prominent chin “progenia”

Question 6

soft tissue features

Answer 6

high resting lower lip line - secondary to reduced LFH, retroclines U incisors
marked labio-mental fold
high masseteric forces
 - ortho space closure problems
 - ext cases can be difficult

Question 7

dental features

Answer 7

upper laterals
retroclined U and L incisors
reduced arch length - exacerbates crowding
increased OB - traumatic or non-traumatic
increased inter-incisal angle
L incisors may occlude with the U incisors or palatal mucosa
U incisors may “strip” lower labial gingivae
OJ usually reduced
class 2 buccal segments

Question 8

dental features - upper laterals

Answer 8

shorter clinical crown and poor cingulum
escape the effect of the L lip or trap L lip
often crowded
mesio-labially rotated
may be normal or proclined depending on their position relative to the lip line

Question 9

normal inter-incisal angle

Answer 9

135 degrees

Question 10

association with developmental dental anomalies

Answer 10

50% have a form of congenital dental anomaly, 33% with impacted canine
55% 1 or more developmental anomaly
- 20% impacted canine
- 15% lateral incisor microdontia

Question 11

why tx?

Answer 11

aesthetics - dental or profile

dental health concerns - traumatic OB - IOTN DHC 4f

Question 12

what do the tx options depend on?

Answer 12

severity of the malocclusion
age and motivation of patient
dental health
pts concerns

Question 13

tx options

Answer 13

accept
growth modification
camouflage
orthognathic tx

Question 14

indications to accept

Answer 14

acceptable aesthetics
pt not concerned
pt not suitable for ortho tx
OB not a significant problem - not traumatic

Question 15

indications for growth modification

Answer 15

growing pt - adolescent growth spurt
mild to mod class 2 skeletal base

Question 16

when is the adolescent growth spurt?

Answer 16

boys 14 +/- 2 years

girls 12 +/- 2 years

Question 17

using fct appliances

Answer 17

convert into class 2 div 1 - procline U incisors
detail occlusion with fixed appliances

Question 18

what fct appliance is used?

Answer 18

modified twin block

Question 19

components of a modified twin block

Answer 19

spring at front - expansion labial segment aligner (ELSA), activated chair side, procline upper incisors
screw - anterior screw section (rely on pt compliance)
upper sectional fixed appliance - but aesthetic result quickly so pts lose motivation and aren’t bothered about fixing the rest of the malocclusion

Question 20

camouflage

Answer 20

accept the underlying skeletal base relationship and aim to tx to class 1 incisor relationship

Question 21

why is a careful extraction decision needed in camouflage?

Answer 21

space closure difficult in low angle cases

Question 22

indication for camouflage

Answer 22

mild to mod class 2 skeletal pattern

Question 23

what needs to be achieved with fixed appliances for a stable correction?

Answer 23

OB reduction

correction (reduction) of interincisal angle

Question 24

what will relapse if not corrected?

Answer 24

OB

Question 25

how is the inter-incisal angle corrected with fixed appliances?

Answer 25

palatal root torque U incisors
- needs adequate cancellous bone palatal to U incisors
- risk of RR
proclination of L incisors

Question 26

indications for orthognathic surgery

Answer 26

severe malocclusion - AP/vertical
profile and/or fct concerns
non-growing pts

Question 27

stages of orthognathic tx

Answer 27

pre-surgical ortho 12-18m
 - decompensated retroclination of U incisors
 - make them class 2 div 1
surgery
post-surgical ortho
 - align and detail bite

2.5-3yrs

Question 28

stability and retention

Answer 28

difficult to treat
future facial growth can affect stability
rotated laterals and deep overbite can relapse
long-term bonded retention usually required

Question 29

when to refer?

Answer 29

deep overbite best corrected when pt still growing
- growth mod with fct appliance if AP discrepancy
- URA w FABP
orthognathic if significant skeletal component after growth completed

Question 30

what link is it important to remember with this malocclusion?

Answer 30

link to other dental anomalies

- palpate for canines