1
Q
What is the incidence of Class III malocclusion in the UK?
A
- 3-7%
2
Q
Where is there a higher incidence compared to UK ?
A
- Higher incidence in Asia
- With geographical variation
3
Q
What is the aetiology of Class III malocclusion?
A
- Strong genetic link (think Habsburg family)
- Environmental factors of Cleft lip and palate and Acromegaly
4
Q
What skeletal aetiology could lead to Class III malocclusion?
A
- Retrognathic maxilla
- Hypoplastic mandible (most common)
- Combo of both
5
Q
What is the relationship of A-P discrepancy to complex txt need?
A
- Greater the A-P discrepency the more complex the malocclusion to treat
6
Q
What skeletal base do Class III malocclusion usually present with?
A
- Usually present with Class III skeletal base
- Can present with Class I and rarely class II
7
Q
What vertical proportions are associated with Class III malocclusion?
A
- May be associated with average , increased or reduced vertical proportions
8
Q
What FMPA angle and what bite (average, increased or reduced) makes Class III malocclusion harder to treat?
A
- Increased FMPA angle
- Anterior open bite
9
Q
What transverse relationship features are commonly seen on Class III malocclusions?
A
- A-P and transverse relationship is linked
- Retrusive maxilla sits on the wider part of mandible , giving bilateral crossbites
10
Q
What molar relationship is common with Class III malocclusion?
A
- Class III molar relationship but not always
11
Q
What overjet is common with Class III malocclusion?
A
- Tendency to reverse overjet
12
Q
What overbite is common with Class III malocclusion?
A
- Reduced overbite
- Or anterior over bite may be present
13
Q
What crossbites are common with class III malocclusion?
A
- Anterior
- Buccal
14
Q
In terms of alignment in maxilla and mandible what is common for Class III malocclusion?
A
- Maxilla often crowded
- Mandible often aligned or spaced
15
Q
What dentoalevolar compensation is common in Class III malocclusion?
A
- Proclined upper incisors
- Retroclined lower incisors
16
Q
Do Class III malocclusions have tendency for displacements?
A
- Yes have tendency for mandibular displacement on closing
17
Q
Are the soft tissues involved in aetiology of Class III malocclusion? What do they do?
A
- Not usually involved in aetiology
- But they do encourage dentoalevolar compensation
- Tongue proclines upper incisors
- Lower lip retroclines lower incisors
18
Q
What are the reasons why someone may want to treat Class III malocclusion?
A
Aesthetics
- Dental
- Profile concerns (need orthognathic surgery)
Dental health reasons
- Mandibular displacement upon closing to gain ICP may cause attrition, gingival recession
Function
- Speech
- Mastication
19
Q
What factors make Class III malocclusion more difficult to treat?
A
- Greater number of teeth in anterior crossbite
- Skeletal element in aetiology
- Greater the A-P discrepancy
- Presence of anterior open bite
20
Q
Why does Facial growth make Class III malocclusions more difficult to treat?
A
- Facial growth tends to be unfavourable
- Mandibular growth continues for longer than maxilla growth meaning a potential for Class III to get worse
**Do not do anything irreversible until growth has stopped as this could affect any future txt if surgery is required
21
Q
How does pubertal growth spurt relate to jaw growth?
A
- Onset of pubertal growth spurt coincides with spurt in jaw growth
22
Q
Growth status of the jaw is hard to predict. What methods can clinicians use to assess this?
A
- Height and weight charts
- Assess cervical vertebral maturation (CVM) on a lateral ceph (assess bodies of C2, C3 and C4) but this is hard to reproduce and has poor reliability
- Hand wrist radiographs historically but unreliable
- Look at parents height
- Ask if feet are still growing
23
Q
What txt options are available for Class III malocclusions?
A
- Accept / Monitor
- Intercept early with URA
- Growth modification
- Camouflage
- Combined orthognathic/ orthodontic txt
24
Q
If the txt option Accept and Monitor is going to be chosen what are the indications for this option?
A
- No concerns from pt
- No dental health indications for example No displacements and No attrition
- Mild Class III cases
25
When is interceptive txt indicated for Class III malocclusions?
- Class III incisors have developed due to early contact permanent incisors i.e. from mandibular displacement
- Correction of anterior crossbite in mixed dentition which has advantage that further forward mandibular growth can be counter-balanced by some dento-alveolar compensation
- Only suitable for correcting lateral crossbite if permanent canines high above lateral roots
26
Why can interceptive txt only be used to correct lateral incisor crossbite if permanent canines are high above lateral roots?
- Delay if canines have dropped into buccal position
- Risk of resorption to lateral incisor
27
What are the factors for a good prognostic indicator for interceptive txt of Class III malocclusion?
- Deep overbite
- Can achieve edge to edge before start of txt
28
What are the aims of growth modification txt option and what age should we consider this option?
- Growing pt of 10-14yrs
- Aimed at reducing and / or redirecting mandibular growth and encourage maxillary growth
29
What functional appliances can be used for growth modification?
- Chin cup (historical)
- Reverse Twin Block
- Frankel III
30
Other than functional appliances what is another growth modification technique utilised in Class III malocclusion?
- Protraction headgear +- Rapid maxillary expansion
31
Historically what was the chin cup used for?
- Lingual tipping of lower incisors
- Rotate mandible down and back
32
How is the Frankel III functional appliance used for Class III malocclusion?
- Pellotes (Shields) labial to upper incisors to hold lip away
- Palatal arch to procline upper incisors
- Lower labial bow to retrocline lower incisors
- Difficult to talk and eat therefore can't be worn 24hrs a day
33
What force is applied each side when utilising protraction headgear?
- 400g each side
34
What are the indications for protraction headgear?
- Co-operative pt as need to wear at least 14hrs a day
- Best results in early mixed dentition (8-10yrs)
35
What sutures are disrupted when using protraction headgear with +- Rapid maxillary expansion?
- Disrupts circum-maxillary sutures
36
What are these implants pictured? What dentition are they used in?
- Bollard implants
- Used in late mixed and permanent dentition
37
Where are the Bollard implants placed?
- Infrazygomatic crest and lower canine region
38
What elastics are used in Bollard Implants and how do they work?
- Class III elastics placed intermaxillary
- Promote maxillary growth
- Restrict mandibular growth
39
Why is a Bollard implant a surgical procedure?
- Mucoperiosteal flaps need to be raised for insertion and removal
40
What is the premise of orthodontic camouflage for Class III malocclusion?
- Accept underlying skeletal base relationship
- Aim for class i incisor relationship
41
What are the aims of Orthodontic camouflage for Class III malocclusion?
- Procline upper incisors
- Retrocline lower incisors
- Correct overjet
42
What are the features that allow for favourable outcome of camouflage txt option for Class III malocclusion?
- Growth has stopped
- Mild to mod Class III Skeletal base with ANB not less than 0
- Average or increased overbite
- Able to reach edge to edge incisors relationship
- Little or no dentoalveolar compensation
43
When opting for orthodontic camouflage extractions are required. What is the extraction pattern usually followed? Why might this not always be possible?
- XLA further back in upper arch
- XLA further forward lower arch
- Uppers 5's and lower 4's
- Dental health of other teeth may dictate xla pattern i.e. MIH or poor prognosis
44
These picture show a pre treatment case. If opting for orthodontic camouflage what is the txt option.
Pt has Class III mild maloccluion
Clinically can produce edge to edge
All 1st perm molars poor prognosis
- XLA first perm molars
- SR LL8 and LR8
- Upper and lower fixed appliances to treat to Class I
- Life long retention (either removable or perm bonded)
45
What is orthognathic surgery?
- Surgical manipulation of mandible and / or maxilla to produce optimal dentofacial aesthetics and function
46
What are the indications of orthodontic / orthognathic txt?
- Pt usually has aesthetic or functional concerns
- Growth is completed
- Moderate / Severe skeletal discrepency (either A-P, Transverse, Vertical)
47
Orthognathic surgical txt requires careful planning and requires a multidisciplinary team approach. Who is involved in the MDT?
- Orthodontist
- Maxillofacial surgeon
- Technician
- Psychologist
48
What feature is common of a hypoplastic maxilla regarding the nasiolabial region?
- Flat nasiolabial region
49
What software can be used for orthognathic txt planning?
- Prediction planning software
50
What are the 3 main stages in orthognathic txt for Class III malocclusions?
- Presurgical orthodontics (approx 18months)
- Orthognathic surgery to reposition the jaws (Mandible / mandible +- maxilla)
- Post surgical orthodontics (approx 6 months)
51
What are the aims of presurgical orthodontics during orthognathic txt?
- Level, align , co-ordinate and decomponsate
- Means remove crowding, rotations, align to curve of spee
- Decompensate means moving the upper incisors to 109degree and lower incisors 90degree (normal angulation)
52
When proclining lower incisors what is a risk the pt needs to be informed of pre accepting txt?
- Gingival recession
53
What do you need to warn pt during their pre-surgical orthodontics?
- Bite will get worse before gets better
54
What is the GDP role for pts with Class III malocclusion?
- Identify Class III malocclusion
- Refer to dental hospital service or specialist practitioner
- URA txt to correct single tooth in anterior cross-bite
55
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