11 - Class III malocclusion

Question 1

Question 2

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

Question 3

Incisor classification of class III

Answer 3

Meaning edge to edge incisor relationship is also class III

Question 4

Molar classification of Class III

Answer 4

Question 5

Click answer

Answer 5

Class III malocclusion with have a convex profile.
Often associated with mandibular protrusion and maxillary retrognathia.

Question 6

1. Incisor relationship of Class III malocclusion

List 3 types of incisor relationships:
What often exists in class III malocclusion:

Answer 6

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.

Question 7

Describe incisor relationship

Answer 7

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)

Question 8

Describe incisor relationship

Answer 8

• 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

Question 9

Describe this incisor relationship

Answer 9

Frank reverse overjet- patient occludes directly into this with no displacement

Size of reverse overjet indicates severity - which affects treatment

Question 10

Incisor compensation

Answer 10

During development lower incisors retrocline and upper incisors procline in an attempt to achieve class I incisor relationship

More incisor compensation -> more severe malocclusion

Question 11

2. Posterior crossbites - Class III malocclusion

Answer 11

Question 12

3. Vertical relationship in class III malocclusion

Answer 12

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.

Question 13

4. Dental arch crowding

Answer 13

Question 14

Overall features of class III malocclusion

Answer 14

All the FC labelled 1-4

Question 15

Describe

Answer 15

Cleft palate
Severe crowding
Bilateral crossbite
Narrow maxillary arch

Lower arch- well aligned

Question 16

Skeletal features of class III malocclusion 1 Anterior-Posterior relationship

Answer 16

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

Question 17

Which class 3 is mild and which is severe?

Answer 17

Mild - has edge to edge incisor relationship

Severe - has a large reverse overjet

Question 18

List 3 places skeletal discrepancies can arise in class III malocclusion - anterior posterior relationship

Answer 18

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

Question 19

Skeletal features of class III malocclusion 2 Vertical relationship

Answer 19

Upwards and forwards are easier to manage

Question 20

Soft tissue features of class III malocclusion

Answer 20

NO MAJOR INFLUENCE - soft issue feature have no major influence on class III malocclusion

Question 21

Treatment planning for class III malocclusion

Answer 21

• Simple anterior crossbite
• Interceptive growth modification
• Orthodontic camouflage
• Orthodontics and surgery

Question 22

Simple anterior crossbite correction

Answer 22

• Mixed dentition
• Correction of incisor relationship
• Elimination of forward displacement
• Incisors should not be too proclined and there should be a positive overbite

Question 23

Simple anterior crossbite correction

Answer 23

• 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

Question 24

Interceptive growth modification

Answer 24

Frank reverse overjet associated with maxillary hypoplasia

Maxillary protraction combined with maxillary expansion can be effective in correcting a reverse overbite

Question 25

What is this?

Answer 25

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:

Question 26

Advantages of interceptive treatment?

Answer 26

Question 27

Question 28

Orthodontic camouflage

Answer 28

• 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

Question 29

Click answer

Answer 29

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

Question 30

Click answer

Answer 30

Large reverse overjet Retroclined upper incisors Upper fixed appliance to procline upper incisors and create a class I relationship

Question 31

Click answer

Answer 31

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

Question 32

Click answer

Answer 32

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

Question 33

Click answer

Answer 33

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

Question 34

Basic sequence of treatment for Class III malocclusion - mild to moderate

Answer 34

1. Flexible arch wirres 2. Expand upper arch 3. Align teeth 4. Remove quad helix once Rigid steel arch wire 5. Residual space - use class III elastics attached to the U6s and between the lower 2 and 3 to produce class III traction 6. Retrocline lower incisors and correct incisor relationship

Question 35

Severe class III malocclusion Why are more severe cases are difficult to plan? What 3 things do we need to know?

Answer 35

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

Question 36

What can you see? Potential teeth to be extracted ?

Answer 36

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

Question 37

Severe class III malocclusion Do we do Interceptive alignment?

Answer 37

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

Question 38

Question 39

Severe class III malocclusion Do we camouflage?

Answer 39

Sometimes we do camouflage in severe cases, when the patient is adamant that they do not want to have surgery.

Question 40

Orthodontics and surgery

Answer 40

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

Question 41

Click answer

Answer 41

maxillary retronathia and mandibular prognathia Ortho treatment aims to undo any natural compensation

Question 42

What class is this now? - incisor , canine and molar

Answer 42

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

Question 43

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?

Answer 43