Fixed appliances in ortho - clinical management

Question 1

What are the 6 keys to normal occlusion?

Answer 1

• Molar relationship class I (Mesio-buccal cusp of upper molars sits in buccal groove of lower molar)
• Crown angulation - upper roots tip distally
• Crown inclination (torque)
• No rotations (rotated molars can use more space, incisors less space)
• Tight contacts - no spacing or crowding
• Flat curve of spee (level occlusal plane)

Question 2

What does the straight wire appliance have?

Answer 2

Built in tip values = 11 degrees (upper canine), upper incisor = 5 degrees
Built in torque values
Built in in-out valves (different bracket thickness)
For each individual tooth

Question 3

What are the main stages of treatment with fixed appliances?

Answer 3

Levelling and alignment
Space closure:
- Overjet reduction
- Centreline correction 
Additional stages:
- Overbite correction
- Crossbite correction
- Finishing and detailing

Question 4

In which directions does levelling and alignment occur?

Answer 4

To correct rotations:
Vertically = levelling
Bucco-lingually = alignment
Mesio-distally = alignment - need initial canine retraction for bucco-lingual alignment

Question 5

What can the initial archwire be made up of?

Answer 5

Titanium alloys - round wires:
- NiTi
- Beta titanium
- Superelastic
Stainless steel

Question 6

What is a problem of tip in canine brackets?

Answer 6

Crown moves forward, incisors extrude, bite deepens

Question 7

What are canine lacebacks? Function?

Answer 7

Ligature wire under archwire
Prevent canine crown moving mesially
Posterior teeth can move forwards

Question 8

What archwire is used for space closure?

Answer 8

Archwire 0.019” X 0.025” stainless steel

Question 9

List the space closure methods: sliding mechanics

Answer 9

NiTi springs

Elastics - powerchain, modules - traction ligatures

Question 10

When is bond up done?

Answer 10

After extractions of U4s and L5s - levelling and aligning with round NiTi wire

Question 11

Types of retainers?

Answer 11

Removable
- Acrylic (hawley)
- Vacuum formed (essix)
Fixed
- Bonded

Question 12

Retention regime?

Answer 12

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

Question 13

When is an unstable result/high relapse potential likely?

Answer 13

Periodontally involved teeth
Midline diastema
Severe rotations
Teeth out of zone of stability with soft tissues