Occlusion and Malocclusion - Class II/2 Malocclusions
9 important questions on Occlusion and Malocclusion - Class II/2 Malocclusions
Class II Div 2 Incisor Relationship? (ref)
British Standards Institute, 1983
Aetiology of Class II Div 2 malocclusions? (refs)
- High concordance in twin studies suggesting: (Markovic, 1992)
- Autosomic dominant with incomplete penetrance or
- Polygenic model
- Axial inclinations of incisors is such that the lower incisor edge cannot be maintained on the upper incisor crown - deep OB, reduced OJ
- Strap-like lower lip may retrocline maxillary and mandibular incisors (bimaxillary retroclination) - deep OB, reduced OJ
- High resting lip pressure against maxillary central incisors (Lapatki et al, 2002)
- Lower lip may procline upper lateral incisors
Skeletal features of Class II Div 2 malocclusion? (ref)
- Usually mild class II skeletal base, can be class I or class III
- Increased cranial base angle - mandibular retrognathia (Hopkins et al, 1968)
- Longer cranial base - prognathic maxilla
- Maxilla short, broad and forward relative to mandible - tendency for scissorbite
- Reduced lower face height
- Reduced gonial angle
- Reduced MMP angle
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Soft tissue features of Class II Div 2 malocclusion? (refs)
- High resting lower lip line (due to reduced lower face height)
- Typically strap-like lower lip
- Marked labio-mental fold
- High masseteric muscle forces (Ingervall and Thilander, 1974 and Sciote et al, 2012)
Dental features of Class II Div 2 malocclusion? (ref)
- Retroclined upper and lower incisors
- Upper lateral incisors often proclined, mesially tipped and mesiolabially rotated (lower lip fails to control shorter crown)
- Increased interincisal angle
- OB is usually deep
- OJ is usually reduced
- Extruded upper incisors
- Buccal segments usually Class I or Class II
- Scissorbite common in premolar region due to transverse discrepancy
- Crown-root angle may be decreased
- Incisors may be thin with a poorly defined cingulum (Robertson & Hilton, 1965)
Reasons for treatment of Class II Div 2 malocclusions?
- Improve facial aesthetics
- Remove traumatic bite - trauma to palate, stripping of upper palatal gingiva, recession of lower labial mucosa
- Improve tooth alignment, particularly of the upper lateral incisors
General treatment aims for class II div 2 malocclusions? (6) - refs
- Relieve crowding
- Align and level the arches
- Reduce overbite
- Correct edge-centroid relationship - the upper root centroid should be at least 2mm behind the lower incisor edge (Houston, 1989)
- Reduce interincisal angle - often requires intrusion and palatal root torque of the the upper incisors (Mills, 1973)
- Correct the buccal segment relationships
Stability and Retention of Class II Div 2 Malocclusions? (3) - refs
- Can consider proclining the LLS as it has been trapped (Mills, 1968)
- Proclination of the LLS after intrusion of the ULS has been suggested as stable treatment as lower incisors would take up positions previously occupied by uppers (Selwyn-Barnett, 1996), however this stability has been questioned (Canut & Arias, 1999)
- Consider fixed retention and pericision of rotated upper laterals (Edwards, 1970)
Class II Div 2 References? (7)
- Selwyn-Barnett, 1996 - LLS
- Mills, 1968 and 1973 - LLS and OB
- Houston, 1989 - root centroid
- Dyer et al 2001 - modified functional
- Millett et al 2018 (Cochrane)
- Canut & Arias, 1999 - stability
- Lapatki et al, 2002 - lip line/lip aetiology
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