Occlusion and Malocclusion - Class II/1 Malocclusions
12 important questions on Occlusion and Malocclusion - Class II/1 Malocclusions
Incidence of Class II Div 1 malocclusion? (ref)
CIID1 = 20% (Todd & Lader, 1988)
CII Intermediate = 10% - upper incisors are 'upright', OJ 4-6mm - not commonly used (Williams & Stephens, 1992)
Aetiology of Class II Div 1 malocclusions? (3)
- Skeletal base relationship - usually class II
- Habits, e.g. Thumb-sucking
- Soft tissues, e.g. Lower lip trapping behind upper incisors, short upper lip
Skeletal features of Class II Div 1 malocclusions? (5)
- 76% have skeletal II base, if skeletal I, incisor relationship is usually due to habit
- Increased cranial base angle - mandibular retrognathia (Hopkins et al, 1968)
- Longer cranial base - prognathic maxilla
- May have small mandible and large maxilla
- Average or reduced lower facial height
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Soft tissue features of Class II Div 1 malocclusions? (2)
- Lip pattern important in maintaining a stable result, short upper lip - overjet reduction will be less stable
- Lower lip may have caused malocclusion, e.g. Trapping behind upper incisors or lip-tongue seal
Dental features of Class II Div 1 malocclusions? (4)
- Class II incisor relationship with proclined or average upper incisors
- Overjet is increased
- Overbite is usually deep and often incomplete (adaptive anterior oral seal - tongue to lower lip)
- Buccal segments usually CI or CII, may have crossbites (buccal/lingual)
Considerations of mandibular position in Class II Div 1 malocclusions? (3)
- Ensure that the patient is not habitually posturing
- Treat to centric relation
- Consider the profile
Facial growth in Class II Div 1 malocclusions? (ref)
- Variable facial growth
- Can expect favourable growth but if the patient rotates posteriorly it will not help the buccal segment correction - 20% of patients (Bjork & Skieller, 1972)
Reasons for treatment (4) - refs
- Risk of trauma
- 45% increased risk of trauma with OJ>9mm in 12 year olds (Todd & Dodd, 1983)
- Early treatment has small reduction in risk but not clear if this is cost effective (Batista et al, 2018)
- Improvement in aesthetics
- Some improvement in self concept with early overjet reduction (O'Brien et al, 2003)
- Reducing bullying
- 12.8% of patients referred for treatment are bullied (Seehra et al, 2011)
- Relief of gingival trauma
Aims for orthodontic treatment of Class II Div 1 malocclusions? (5)
- Dental camouflage
- Some mandibular growth
- Some restraint of maxillary growth
- Forwards mandibular rotation
- Combination of above
Favourable features for orthodontics only treatment of Class II Div 1 malocclusions? (5) - ref
- Small ANB difference
- No dental compensation
- Growing patient
- Cessation of habit (if present)
- Greater component of overjet being proclination of upper labial segment (Burden et al, 1999)
Specific orthodontic treatment options for class II div 1 malocclusions?
- URA
- Simple tipping achieves desired movements if:
- Maxillary incisors are proclined
- Canines are mesially angulated
- Lower incisors already lie anterior to the upper root centroid
- Functional appliances
- In growing patients
- Upper and lower fixed appliances
- If bodily tooth movement is required
- If skeletal problem allows camouflage
- Orthognathic surgery
- When too severe for orthodontics alone, ANB>9 degrees
- In non-growing patients
Timing of treatment of class II div 1 malocclusions? (3)
- Primary dentition
- NOT stable as pattern of growth re-establishes later
- Mixed dentition
- Growth modification to be started 1-3 years before peak adolescent growth spurt BUT transition to permanent dentition can be difficult to manage
- Permanent dentition
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