11 - Class III malocclusion Flashcards
Class III is hardest to treat as unpredictable about how it could worsen as they enter later teenage years -esp those with a large mandible
Incisor classification of class III
Meaning edge to edge incisor relationship is also class III
Molar classification of Class III
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Class III malocclusion with have a convex profile.
Often associated with mandibular protrusion and maxillary retrognathia.
- Incisor relationship of Class III malocclusion
List 3 types of incisor relationships:
What often exists in class III malocclusion:
Severity of the incisor relationship varies greatly:
1. Edge to edge
2. Edge to edge with forward displacement into a reverse overjet – The ability to get an edge to edge bite, leads to a good prognosis of any class III case.
3, Frank reverse overjet – Size of the reverse overjet is a good indicator of severity
Incisor Compensation often exists:
- Proclined upper incisors
- Retroclined lower incisors
- This is the body trying to create a bite
- All provide a good guide to severity – The more compensation, the more severe the
case.
Describe incisor relationship
Edge to edge incisor relationship
(Mild class III malocclusion, upper second premolar missing, LLsecond premolar missing, Es are retained, LR quadrant - Lower second premolar tooth germ is distally angulated)
Describe incisor relationship
- can obtain an edge to edge incisor relationship in retruded path of closure, then they displace forwards into maximum intercuspaton which produces a reverse overjet
- important to identify these pts as their intercuspal position suggests a more severe malocclusion than they actually have
- ability to obtain an edge to edge incisor relationship is a good prognostic feature in any class 3 case
Describe this incisor relationship
Frank reverse overjet- patient occludes directly into this with no displacement
Size of reverse overjet indicates severity - which affects treatment
Incisor compensation
During development lower incisors retrocline and upper incisors procline in an attempt to achieve class I incisor relationship
More incisor compensation -> more severe malocclusion
- Posterior crossbites - Class III malocclusion
- Vertical relationship in class III malocclusion
Anterior Open bite – Increased vertical proportions are harder to manage orthodontically. Its hard to make the teeth overlap with fixed appliances. Often need surgery combined with orthodontic treatment.
- Dental arch crowding
Overall features of class III malocclusion
All the FC labelled 1-4
Describe
Cleft palate
Severe crowding
Bilateral crossbite
Narrow maxillary arch
Lower arch- well aligned
Skeletal features of class III malocclusion 1 Anterior-Posterior relationship
Larger reverse overjet often the larger the class III skeletal pattern
Must look out for displacements when assessing skeletal pattern
Skeletal growth is often unfavourable so anterior posterior relationship can often worsen, esp those with high angle - worsening of open bite as pt grows
Which class 3 is mild and which is severe?
Mild - has edge to edge incisor relationship
Severe - has a large reverse overjet
List 3 places skeletal discrepancies can arise in class III malocclusion - anterior posterior relationship
It’s important to know where the skeletal discrepancies arise when planning treatment
In normal the maxilla is slightly ahead of the mandible.
Class III - NTK if its due to:
- Mandible hyperplasia -> Mandible is too big
- Alteration of the cranial base angle -> Moves mandible forward relative to maxilla - Cranial base angle is too acute
- Maxillary hypoplasia -> Maxilla is too small or too far back
Skeletal features of class III malocclusion 2 Vertical relationship
Upwards and forwards are easier to manage
Soft tissue features of class III malocclusion
NO MAJOR INFLUENCE - soft issue feature have no major influence on class III malocclusion
Treatment planning for class III malocclusion
- Simple anterior crossbite
- Interceptive growth modification
- Orthodontic camouflage
- Orthodontics and surgery
Simple anterior crossbite correction
- Mixed dentition
- Correction of incisor relationship
- Elimination of forward displacement
- Incisors should not be too proclined and there should be a positive overbite
Simple anterior crossbite correction
- removable appliance
- fixed
Often present with 1/few upper incisors in crossbite
Often a displacement which can affect position of lower incisors
Use simple removeable or fixed appliance to move upper incisors into correct position
Usually self retaining as incisor assumes a positive overbite
Interceptive growth modification
Frank reverse overjet associated with maxillary hypoplasia
Maxillary protraction combined with maxillary expansion can be effective in correcting a reverse overbite
What is this?
Maxillary expansion - for Interceptive treatment for maxillary retrusion ->In conjunction with headgear
- splits maxillary suture
- loosens maxillary sutures and increases advancement of maxilla
Most effective if those under 10
Attached to this:
Advantages of interceptive treatment?
Orthodontic camouflage
• This means moving the teeth with braces to correct the incisor relationship
• It also involves co-ordinating the arches in three-dimensions and alleviating any crowding
• (can only be done mild to moderate cases - not those associated with significant skeletal discrepancy)
• Normally done in the early permanent dentition
Mild cases:
• non-extraction
More severe cases (requiring more space):
• loss lower premolars OR
• loss four premolar units
• obtain class 1 incisor relationship
• align teeth, correct crossbites
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Crowding in upper arch
Edge to edge incisor relationship so need space in lower arch to retrocline lower incisors and space in upper arch to align crowded canines and lateral incisors
Extracted lower first premolars - to provide space to retrocline lower incisors
Extracted upper second premolars - to align teeth
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Large reverse overjet
Retroclined upper incisors
Upper fixed appliance to procline upper incisors and create a class I relationship
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Severe crowding in maxillary arch
Bilateral posterior crossbite
Expansion of upper arch with quad helix
Alignment of dentition combined with loss of 4 first premolars - crowding more severe in upper arch
Incisor edge to edge relationship
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Mild case
Edge to edge incisor relationship
Amenable to non extraction treatment
Missing second premolars - extract upper Es, lower left E and because of poor position of premolar tooth - extract lower right E and premolar and use space with fixed appliances to correct malocclusion
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Severe crowding in upper arch
Well aligned lower arch
Slightly increased vertical proportions
Extract four first premolars
Used quad helix - as bilateral posterior crossbite
Fixed appliances and elastic to move canine
Bond lateral incisor once canine has been moved backwards
As minimal crowding in lower arch lots of space to retrocline lower incisors and get class I incisor relationship
Basic sequence of treatment for Class III malocclusion - mild to moderate
- Flexible arch wirres
- Expand upper arch
- Align teeth
- Remove quad helix once Rigid steel arch wire
- Residual space - use class III elastics attached to the U6s and between the lower 2 and 3 to produce class III traction
- Retrocline lower incisors and correct incisor relationship
Severe class III malocclusion
Why are more severe cases are difficult to plan?
What 3 things do we need to know?
More severe cases are difficult to plan because growth is unpredictable (mandibular growth)
Need to know:
1. How much incisor compensation is there?
2. How class III is the molar relationship?
3. How old is the patient?
More incisor compensation, more class III and younger they are the worse the prognosis for orthodontic treatment - in these cases wait until most of maxillary and mandibular growth before final assessment
What can you see?
Potential teeth to be extracted ?
A lot of incisor compensation + increased vertical proportion
As it is an adult and not child - we can treat with orthodontics
Palatally impacted UR canine - gross caries in LL5, RCT UL6 and LR6 - so extraction of UR3, UL6, LL5, LR6
Fixed appliances
Severe class III malocclusion
Do we do Interceptive alignment?
Sometimes we do interceptive alignment:
- In severe cases where the patient has a lot of crowding in upper arch as pt may want the upper teeth aligned, but the incisor relationship is not fixed
- Avoid extraction in the lower arch
- We do not want to compromise later set-up for surgery by retroclining the lower incisors
Severe class III malocclusion
Do we camouflage?
Sometimes we do camouflage in severe cases, when the patient is adamant that they do not want to have surgery.
Orthodontics and surgery
For severe cases
Severe cases:
- Correct malocclusion
- Move maxilla forward
- Moving mandible back
- Combination of both
- Increased vertical proportions – in addition to moving the maxilla forwards, you have to impact it at the back
- Autorotation of the mandible to give normal and increased overbite
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maxillary retronathia and mandibular prognathia
Ortho treatment aims to undo any natural compensation
What class is this now? - incisor , canine and molar
Bimaxillary surgery - maxilla forward and mandible backwards
Full unit Class 2 molar relationship - as she lost 2 premolar units in upper arch
Canine and incisor relationship are class I
Summary
1- class III relationship - relationship between lower and upper teeth?
2- easy or hard to Manage?
3- what do you need to correct as early as possible?
4- mild to moderate cases - what can you use:
5- when do you avoid extractions
6- more severe cases require?
