Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

BDS4 CDS Ortho > Class III > Flashcards

Class III Flashcards

1
Q

all malocclusions are classed by

A

incisor relationship

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

definition of class III malocclusion

A

lower incisor edge occludes anterior to the cingulum plateau of the upper central incisor

3 presentations of class III,Not necessary for reverse OJ or ant Xbite

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

incidence of class III

A

Geographical variation

UK 3-5%
* Higher incidence in west of Scotland
* Higher incidence in Asia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

aetiology of class III

A

**Strong genetic link **
* Patter of transmission controversial (unknown)
* Run in families

Environmental factors
* Cleft lip and palate - Restricted growth of maxilla due to cleft surgery
* Acromegaly - Inc production of growth hormone from pit gland will inc size mandible

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

3 aspects to consider when assessing malocclusion

features

A

skeletal
dental
soft tissues

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

skeletal - consider in

A

3 planes
* antero-posterior
* vertical
* transverse

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

antero-posterior skeletal relationship for class III

A

*All have class III incisor relationship
Left is class I skeletal
Middle is moderate class III
Right is class III skeletal with OB *

Aetiology could be due to
* Small maxilla
* Large mandible
* Combination of both (most)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

vertical class III skeletal relationship

A

may be associated with average, increased or reduced vertical proportions
* Frankfort Mandibular Planes Angle
* Facial Height proportions
* Lateral Cephalometry

↑FMPA and anterior open bite more complex to treat –* likely need orthognathic*

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

transverse relationship of class III

A

A-P and transverse relationship linked

Retrusive maxilla sits on wider part of mandible
* Bilateral Crossbites - Narrow maxilla against wide mandible

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

dental features of class III

8

A

Vary

  • Class III incisor relationship
  • Class III molar relationship (not always)
  • Tendency to reverse overjet
  • Reduced overbite, anterior open bite may be present
  • Crossbites sometimes: Anterior or Buccal

Alignment
* Maxilla often crowded common;
* Mandible often aligned or spaced

Dentoalveolar compensation
* Proclined upper inicors
* Retroclined lower incisors
* teeth erupt towards despite underlying skeletal discrepancy

Tendency for displacements on closing
* Mandible displacement to achieve posterior teeth contact

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

alignment in class III

A
  • Maxilla often crowded common;
  • Mandible often aligned or spaced
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

dentoalveolar compensation in class III

A

Proclined upper inicors
Retroclined lower incisors

teeth erupt towards despite underlying skeletal discrepancy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

tendency for displacement on closing for class III

A

Mandible displacement to achieve posterior teeth contact

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

in general tx difficulty for class III malocclusion

estimate

A

.> number of teeth in anterior crossbite (more than 1-2)
Skeletal element in aetiology
.> the A-P discrepancy (vertical issues e.g. AOB)
Presence of anterior open bite

= more complex case

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

soft tissues in class III

A

Not usually involved in aetiology

Do encourage dentoalveolar compensation
* Tongue proclines the upper incisors
* Lower lip retroclines lower incisors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

why tx class III malocclusions

3

A

aesthetics

dental health reasons

function

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

tx class III malocclusion for aeshtetics

A

dental
profile concerns

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

tx class III malocclusion for dental health reasons

A

attrition - wear on labial of UI and lingual face of LI
gingival recession - occlude healvily on LI, press root through buccal plate
mandibular displacement

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

tx class III malocclusion for function

A

speech - warn improve malocclusion, won’t necessarily alter speech
mastication

20
Q

facial growth for class III malocclusions

A

Tends to be unfavourable

Mandibular growth continues for longer

Potential for Class III to get worse

Do not do anything irreversible until growth has stopped
* Could affect future treatment if surgery required

20
Q

facial growth for class III malocclusions

A

Tends to be unfavourable

Mandibular growth continues for longer

Potential for Class III to get worse

Do not do anything irreversible until growth has stopped
* Could affect future treatment if surgery required

21
Q

how to predict growth status

A

Difficult to predict

Height and weight charts
* ? Cervical vertebral maturation (CVM) on lateral ceph
* Evaluates the shape changes in the bodies of cervical vertebrae C2, C3 and C4 – already taking lat ceph to assess skeletal pattern
* difficult to reproduce, poor reliability and valid

DONT USE - Hand wrist radiographs - low reliability and risks of repeated radiography so not justified

Individual variation - If in doubt watch and wait

onset of pubertal growht spurs coincides with spurt in growth

22
Q

class III management guide

5 options

A

accept and monitor
intercept early with URA
growth modification
camouflage
combined orthognathic/orthodontic tx

23
Q

when to accept and monitor class III

A

no concerns

no dental heatlh indicatins - displacements/attrtion

mild cases

24
interceptive tx for class III malocclusion | when
Suitable if Class III incisors have developed due to early contact on permanent incisors (i.e. mandibular displacement) Correction of anterior crossbite in mixed dentition has the advantage that further forward mandibular growth may be counter-balanced by some dento-alveolar compensation. * Can achieve edge to edge, but displacing into anterior crossbite * If pt continues to grow, mandible grows, dentoalveolar compensation teeth adapt to new position Only suitable for correcting a lateral incisor crossbite if permanent canines are high above lateral roots * Delay if canines have dropped down into buccal position as risk of resorption to lateral incisor
25
URA for interceptive ortho tx
URA procline incisors over the bite * Z spring * Screw section * Need to disclose occlusion – molar capping over buccal segments Good OB will maintain stability
26
growth modification for class III | when and options (4)
growing pt * Aimed at reducing and / or redirecting mandibular growth and encourage maxillary growth Functional appliances * Chin cup * Reverse Twin Block * Frankel III * Protraction headgear ± Rapid Maxillary Expansion
27
chin cup
doesn’t have large skeletal effect Mainly historic form of treatment Lingual tipping of lower incisors Rotates mandible down and back
28
frankel III
Outdated now – sometimes used * One piece appliance – hard to wear all the time * Acrylic heavy - buccal flange, labial culottes - trauma and break easily * Largely dentoalveolar effect Pellotes (Shields) labial to upper incisors to hold lip away Palatal arch to procline the upper incisors Lower labial bow to retrocline the lower incisors
29
reverse twin block
Slope the opposite way to twin block Hard to get pt to bite into wax correctly * Need mandible in most retruded position Best in pt who can have edge to edge at start of tx Mainly dentoalveolar
30
protraction headgear
Co-operative patient 14 hour/day protraction facemask wear 400g/side – large force Best results when used in early mixed dentition ( 8-10 years) * Young pt – co-operation needed ± Rapid maxillary Expansion * Pt needs to turn screw 2x daily – split mid palatal suture * Attach to head gear – theory is disrupts circum-maxillary sutures as well
31
bollard implants
Used in late mixed and permanent dentition Infrazygomatic crest and lower canine region * Mucoperiosteal flaps need to be raised for insertion and removal * GA maybe needed Can be used in conjunction with facemask
32
what is orthodontic camoflauge for class III
accept underlying skeletal base relationship, aim for class 1 incisors
33
3 aims of camoflauge ortho tx
procline upper incisors retrocline lower incisors correct OJ | aim for class 1 incisors
34
favourable features for camoflage tx | 5
Growth stopped Mild to moderate Class III Skeletal base ANB not <0o Average or inc OB Able to reach edge to edge incisor relationship (Ask pt) Little or no dentoalveolar compensation * Don’t want pt to start tx with UI proclined and LI retroclined
35
extractions pattern for camoflage tx of class III
Extract further back in the upper arch Extract further forward in the lower arch Classic pattern - Upper 5’s , lower 4’s * However not always possible * Dental health may dictate extraction pattern
36
example tx plan for class III camoflage
1. XLA all first permanent molars 2. Surgically remove LL8 and LR8 3. Upper and lower fixed appliances to treat to Class I 4. Life long retention
37
what is good to have pre tx for retention of movement post camo tx (class III)
good overbite proportion
38
if pt still growing
do not embark on full correction - can get worse, pt undo results due to growth * Cannot predict growth changes * Consider upper arch alignment only - Keep pt happy until able to deal with underlying jaw relationship Do not XLA in lower arch as this could affect future treatment options * Risk reopen extraction sites in lower arch -> need pros tx
39
orthognathic surgery | def
surgical manipulation of the mandibule and/or maxilla to produce optimal dentofacial aesthetics and function
40
when would orthognathic/ortho tx approach be taken for class III | 3
pt has aesthetic or functional concerns growth completed moderate/severe skeletal discrepanacy * A-P * transverse * vertical
41
orthognathic surgical tx planning
Careful planning Multidisciplinary team approach * Orthodontist * Maxillofacial surgeon * Orthognathic Technician * Psychologist Prediction planning software * Make image up of what pt is expected to look like post surgery
42
3 stages in orthognathic/orthodontic tx for class III
Presurgical orthodontics (approx. 18 months) * Level, align, co-ordinate and decompensate * Rid of curve of spee - want teeth to interdigitate when move jaws, as will make lateral OB * Un-rorate teeth * Coordinate width of arches- avoid lateral discrepancies Uppers 109˚ Lowers 90˚ Orthognathic surgery to reposition the jaws * Mandible * Mandible ± Maxilla Post surgical Orthodontics (approx. 6 months) * settle bite in, with full time intermaxillary elastics usually | sometimes sugery first - want interdigitation after surgeryA
43
GDP role in class III management
identify class III malocclusion - refer to hosp or specialist URA tx? - anterior cross bite correction
44
summary of class III malocclusion management
Challenging malocclusion to treat Complicated by unpredictable growth Careful assessment of aetiology important * Purely dental? Or skeletal involvement? * Is it treatable with orthodontics only?

BDS4 CDS Ortho (9 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions