Stability

Question 1

What are the changes in the untreated dentition?

Answer 1

*Crowding increases
*Lower arch shortens and narrows with age
*Lower incisors become more irregular
*Overbite increases

Question 2

What is the post treatment change?

Answer 2

1. Physiological recovery
2. Unfavourable growth
3. True relapse

Question 3

Physiological recovery

Answer 3

return to original malocclusion (i.e. spaces or rotations)

Question 4

Unfavourable growth

Answer 4

irrespective of
orthodontic treatment

Question 5

True relapse

Answer 5

changes occurring due
to the placement of teeth in unstable positions

Question 6

Key issues with stability?

Answer 6

How do we ensure maximum stability?

*Recognising where stability will be a problem

Question 7

How do we ensure maximum stability?

Answer 7

Finish case correctly (achieve occlusal and soft tissue balance)

*Use appropriate retention protocol

Question 8

Correct finishing- how?

Answer 8

*Expansion/contraction of arches
*Overjets/overbites
*Crossbites
*Interdigitation

Question 9

Expansion/contraction of arches- why does it work?

Answer 9

*Teeth exist in a zone of balance

Question 10

How does it work?

Answer 10

Avoid expansion/contraction
*Use patient’s original archform as a guide
*Maintain inter-canine and inter-molar widths

Question 11

Positive/increased overjet (3)

Answer 11

*Lower lip control is crucial

*Reduce overjet to 2-4 mm

*Over-treatment to 0 mm recommended

Question 12

What to note about the lower lip

Answer 12

Lower lip often trapped behind upper incisors in Class II/1

Ideally lower lip should cover 1/3 of u

Question 13

Negative or reverse overjet

Aim of treatment and important considerations?

Answer 13

Must achieve positive incisal overbite at the end of treatment

*Remember to allow for the reduction in overbite due to proclination of the upper incisors during treatment

Question 14

What could be used to create a positive overbite?

Answer 14

Surgery

Question 15

Increased overbite- aims of treatment?

Answer 15

*Correct inter-incisal angle

*Correct lower incisal edge/cingulum plateau relationship

*Over-treatment to 0 mm is recommended

Question 16

Interincisal angle?

Answer 16

125-135 degrees

Question 17

Transverse (crossbite) stability (2)

Answer 17

Overtreatment
Good buccal overlap

Question 18

Proportional change in transverse (crossbite) from pre to post treatment

Answer 18

AB shoud reduce significantly CD should remain the same

Question 19

What’s important about buccal interdigitation?

Answer 19

*Ensure good buccal interdigitation

*Poor interdigitation can lead to post-treatment change

Question 20

Poor interdigitation?…

Answer 20

Increases
Overbite
Overjet
Crowding

Question 21

Where would stability be a problem?

Answer 21

*Lower incisor crowding
*Median diastema
*Generalised spacing

Question 22

Lower incisor crowding- recognise that…

Answer 22

lower incisor alignment is rarely maintained

Question 23

With lower incisor crowding tell patient…

Answer 23

*Advise patients of the probability of post treatment change (70%)
*Some minor proclination of the lower incisors is possible (1-2mm)
*Permanent retention is the only way to guarantee stability

Question 24

University of Washington study showed that in 600 patients 5 years out of retention
In premolar extraction cases

Answer 24

Majority (half) the patients had moderate crowding and 30 percent had satisfactory and 20 percent severe crowding

Question 25

In non extraction cases

Answer 25

Almost everyone (90 percent) had severe crowding

Question 26

University of Illinois 96 patients 20 post years treatment
In extraction cases

Answer 26

Post treatment overjet and mandibular crowing reduced with mandibular crowding reducing the most

Long term overjet relapsed the least and mandibular crowding relapsed the most

Question 27

In non extraction cases

Answer 27

Overjet and overbite reduced to the same amount post treatment and mandibular crowding reduced to none

Long term overbite nad overeat relapsed a similar amount and mandibular crowding relapsed a bit more

Question 28

OHI and lower incisor crowding

Answer 28

Should be able to fit tepe brushes though lower incisors which should have no crowding post treatment

Question 29

Overall in stability and ortho treatment…

Patients should be made aware (-)

Answer 29

Of the potential for relapse and the need for retention at the outset of treatment

Of the high potential for post treatment change if expansion is used

Question 30

And …

Answer 30

*Arch width and arch length constriction is a normal physiological process.