Class II div II Flashcards
What is the incidence of class 2 div 2 malocclusions?
10-18%
Common extra oral features of class 2 div 2 patients?
- Short, broad face due to decreased LFH
- Convex shape face
- Prominent chin (labiomental fold)
- High upper lip line
Common intra oral features in class 2 div 2
MOLAR - Usually class 2 molar (medial drift of 6)
OB - Deep overbite - can be incomplete or traumatic
- Increased interincisal angle
OJ - Upper incisors normal or retroclined
- Lower incisors normal or retroclined
- Upper laterals may be tipped labially
Describe the AP skeletal pattern in class 2 div 2 patients? (aetiology)
- usually MILD class II
- Can be moderate-severe class II (rare)
- Class I or III
Why is class 2 div 2 associated with mild class 2 AP skeletal base and not moderate-severe?
- Moderate-severe class 2 patterns is more likely to result in class 2 div 1 because the upper incisors will lie out of control of the the lip
Describe the vertical skeletal relationship in class 2 div 2? what type of growth?
- LFH usually reduced
associated with forwards and upwards mandibular growth
What type of growth is unfavourable in class 2 div 2 patients?
Forwards and upwards growth as this deepens the bite as growth proceeds (unless an occlusal stop is created)
Describe the transverse skeletal relationship in class 2 div 2
- Lingual XB of upper 4s due to wide maxilla and narrow lower interincisal angle
Describe how the deep overbite develops in class 2 div 2 patients
- Lack of occlusal stop for the lower incisors results in continued development of the LLS (increases OB)
- Unfavourable growth which deepens the bite
Dental aetiological factors associated with class 2 div 2 and why
Crowding can be exacerbated by retroclination (smaller spaced occupied = crowding)
Lack of occlusal stop (reduced or absent cingulum plateau of upper incisors)
How may the upper laterals be rotated in class 2/2?
Rotated mesiolabially out of the arch
Describe the arch forms in class 2 div 2
Upper arch - broad and square
LA - narrow or V shaped
Describe the soft tissue factors in class 2 div 2
- Lower lip line is usually higher relative to the upper incisors - covers more than 1/3rd of the upper incisors (causes retroclination)
- Or bimaxillary retroclination due to strap lips
Why may lateral incisors remain in the normal position whilst central incisors retrocline in class 2/2?
Lateral incisors have a shorter crown therefore they may be unaffected by the action of the lip
List the treatment options for class 2 div 2 patients
- Nothing
- Functional appliance
- Fixed appliances
- Surgery
When would class 2 div 2 be accepted / no treatment?
- Aesthetics acceptable
- OB only slightly increased
- Limited crowing
- No traumatic overbite
List the ways you can reduce the inter-incisal angles?
- Fixed appliance - torque incisor roots and procline ULS and LLS
- Functional appliance after proclination of ULS
- Surgery
List the mechanisms to reduce the overbite?
- Intrusion of incisors
- Eruption of molars
- Extrusion of molars
- Proclination of lower incisors
- Surgery
- Restorative therapy
Explain the effects of incisor intrusion in reduction of overbite in class 2 div 2
- Effects are achieved via relative intrusion
- Molars extrude and vertical growth around the incisors
How can anchorage be increased when intruding incisors in class 2/2? why would you need to do this?
- Use of 2nd or 3rd molars
- Aids intrusion of incisors and limits extrusion of the molars
How do you achieve eruption of molars for tx of class 2/2 treatment
- URA with anterior bite plane to free occlusion of buccal segment to allow molar eruption
How does proclination of the lower incisors reduce overbite in class 2/2
Advancement of LLS to reduce overbite as incisors tip labially
Why is proclination of lower incisors for tx of class 2/2 less desirable than other options
Results in a high risk of relapse post op
When should extractions be indicated in class 2/2 tx?
- Moderate-severe crowding
- When space cannot be made by other mechanisms
Why should class 2/2 be treated on a non-extraction basis ideally?
Lower arch extractions may retrocline LLS further (deepens OB)
- It is also difficult to achieve space closure if there is a low MMA
What is the ideal appliance for tx of class 2/2
Fixed because torque is required to bring about correction of the IIA and to proline LLS
What is the limitation of torque movement in class 2/2 tx
- Depends on presence of sufficient cortical bone lingually and palatally
- Places a strain on anchorage
- More likely to cause root resorption
Indications for functional appliances in class 2/2
- Patients in pubertal growth spurt
- Mild-moderate skeletal class 2
- Well aligned lower arch
Phases in functional appliance tx for class 2/2
- Pre-functional - URA to procline ULS (reduce IIA)
- 1st phase = functional
- 2nd phase = fixed
When is ortho camouflage indicated in tx of class 2/2?
- Mild ANB angle
- Mild vertical skeletal discrepancies (OB not grossly increased)
Indications for surgery for class 2/2
- Moderate-severe skeletal class II pattern
- ANB >8
- Non-growing pt and permanent dentition
- Unfavourable growth pattern
- Traumatic bite
Stability of class 2/2 post op depends on…?
- Modification of soft tissue environment
- Growth pattern (favourable)
- Ideal IIA to produce an occlusal stop
- Overbite has been reduced with a positive edge centroid position
What is a positive edge centroid position (class 2/2?)
Lower incisor edge lies 0-2 mm anterior to the midpoint of the root axis of upper incisors
How does strap lip contribute to class 2/2 malocclusion?
Causes bimaxillary retroclination resulting in class 2/2 malocclusion on any underlying skeletal base
Why is extraction of 5s better in class 2/2?
Prevents lingual movement of lower incisors during space closure
What direction do you torque upper and lower incisors for IIA correction in class 2 div 2
Lingual for lower
Palatal for upper
How to achieve eruption of molars for lass 2 div 2 tx
URA with anterior bite plane
Functional appliance with incisor capping
How to achieve extrusion of molars in class 2 div 2 treatment
Cervical pull headgear to upper molars
Intermaxillary elastics with FA
How does surgery correct OB in class 2 div 2
Advances mandible
Achieves lower labial segment set down
Explain restorative management in OB reduction for class 2 div 2
Increase posterior OVD
Use of dahl appliance to intrude lower incisors or erupt lower molars, with palatal restorations on the upper incisors
