Fixed Appliances in Orthodontics 2

Question 1

What was the experiment that lead to having 6 keys to normal occlusion

Answer 1

120 sets models: local dentist, orthodontist, university department sent in study models of patients that didn’t have any ortho treatment previously:
Straight teeth
Pleasing appearance
Bite seemed correct
Did not need ortho treatment
1150 models of ortho treated patients with good results
compared results

Question 2

What are the 6 keys?

Answer 2

Correct molar relationship
Correct crown angulation
Correct crown inclination
No rotations 
No spaces
Flat occlusal plane

Question 3

What is a class I molar relationship?

Answer 3

Mosio-buccal cusp of upper 1st molar occlues in buccal groove of lower 1st molar

Question 4

What is meant by correct crown angulation?

Answer 4

Root of the tooth should always be distal to the crown
5 degrees in 1st molars
11 degrees of upper right canine
5 degrees of distal tip on upper right central incisor

Question 5

What is meant by correct crown inclination?

Answer 5

torque

the root should be more palatal making the tooth more proclined

Question 6

What is key 5?

Answer 6

No spaces - tight contacts

no crowding

Question 7

What does the straight wire have built in?

Answer 7

tip values - get teeth in the right angles
torque values
in-out values - different bracket thickness

Question 8

What are the main stages of treatment?

Answer 8

Levelling and aligning
Space closure: overjet reduction, centreline correction
Additional stages: Overbite correction, crossbite correction, finishing and detailing

Question 9

What is the levelling and aligning stage?

Answer 9

Levelling to get them all in the same planes
Bucco-lingually, mesio-distally, correct rotations
Always use NiTi to do this (round wire)

Question 10

What is the problem with tip of canine in brackets?

Answer 10

Crown moves forwards (mesially)
Incisors extrude (upwards)
Overbtie deepens

Question 11

What can be dont to stop the canine from tipping mesially?

Answer 11

Ligature wire under the arch wire
prevents the canine crown moving mesially
posterior teeth can move forwards

Question 12

What wire is used for space closure (and overjet reduction and centreline correction)

Answer 12

Arch wire 0.019x0.025 SS

Question 13

What are the methods of space closure?

Answer 13

NiTi spings/coild

Elastics: Powerchain, Modules (traction ligatures, elastics), temporary anchorache devices

Question 14

What are the types of retainer?

Answer 14

Removable: acrylic (hawley), Vaccum formed (essix)
Fixed: bonded

Question 15

When would you use a hawley retainer?

Answer 15

When have missing teeth, can have prosthetic ones on retainer
made from acrylic baseplate and metal labial bow

Question 16

What are essix retainers?

Answer 16

Vacuum-formed, better at holdning the teeth- clear plastic
cover all the teeth
thinner than gun shield
only drink water with them in

Question 17

What is the advantage of Essix over Hawley?

Answer 17

Superior aesthetics
Less interference with speech
more economical 
quicker to make 
less likely to break
ease of fabrication 
superior retention of lower incisors

Question 18

What happens if have Essix retainer and poor OH?

Answer 18

These are retained by plastic engaging the undercut gingival to the contact point
if OH is poor, then hyperplastic gingivae, this can obliterate the areas of undercut

Question 19

What are bonded retainers?

Answer 19

wire bonded to teeth with composite - OH more difficult, caries, need routine checks

Question 20

When to use bonded retainers?

Answer 20

when there’s a high risk of relapse and final result is unstable
Closure of spaced dentition (median diastemer)
Following correction of severely rotated teeth
Where there has been substantial movement of the lower labial segment
Where an overjet has been reduced, but lips still incompetent
Combined perio and ortho cases where reduced perio support makes relapse more likely

Question 21

What are the problems with bonded retainers?

Answer 21

Technique sensitive process
Can cause periodontitis and caries if OH not maintained
Need to be reviewed regularly for bond failure

Question 22

What is the retainer regime?

Answer 22

12 hours/day for the 1st day
Alternate nights for the 2nd year
Gradual withdrawal, minimum 1 night a week

Question 23

What does the retain regime depend on?

Answer 23

The stability of the result

Question 24

Which cases will have a high relapse potential?

Answer 24

Periodontally involved teeth
Midline diastema
Severe rotations
Teeth out of zone of stability with soft tissues - proclined lower incisors

Question 25

What is a Pericision (circumferential supracrestal fibrotomy)

Answer 25

Adjunct to an retention procedure after correction of rotations - performed to counter the relapse tendency of the stretched gingival fibres
Surgical sectioning of gingical fibres
Performed a few weeks before removal of ortho applicance or at the same time it is removed
Retainer must be inserted immediately