Orthodontic Appliances

Question 1

What are the components of a conventional removable appliance?

Answer 1

BARA
Baseplate
Active components
Retentive components
Anchorage

Question 2

Which 3 things affect the force produced by the component?

Answer 2

• length of wire
• radius of wire
• elastic modulus of wire

Question 3

How does the following affect force?
- length of wire
- diameter of wire

Answer 3

• increased length of wire, lighter force exerted
• double diameter of wire, x16 increase in force
• double length of wire, x8 reduction in force
  The larger the diameter of wire, the less deflection is required
  long = less force, thick = more force

Question 4

What is anchorage and how can it be increased?

Answer 4

The resistance to unwanted tooth movements
- clasping more teeth
- moving only one or two teeth at a time
- using lighter forces

Question 5

What are removable appliances mostly used for?
What are their benefits?
Any limitations?

Answer 5

Most commonly used for anterior cross bites in interceptive orthodontics
Benefits:
- good anchorage, cheap, can use in mixed dentition
Limitations:
- require excellent patient compliance, limited ortho movements ~ 1mm per month

Question 6

What are functional appliances?

Answer 6

• ortho appliances which alter the muscle forces against the teeth and craniofacial skeleton
• these are dynamic which depend on altered neuromuscular action to effect bony growth and occlusal development, used in mixed dentition to treat paediatric malocclusion usually
• use natural growth potential of the patient to affect change
• do not grow mandibles
• 70% of change will be dento-alveolar

Question 7

Name some indications of functional appliances:

Answer 7

• class II (common)
• class III (rare)
• mild or moderate skeletal discrepancy
• works best on a growing patient in pre-adolescent growth phase

Question 8

Name some contraindications of functional appliances:

Answer 8

• condylar disease
• unfavourable facial growth e.g. increased vertical
• severe class II skeletal
• poor motivation
• non-growing patients
• poor dental health

Question 9

What is the removable functional appliance used in the UK and how does it work?

Answer 9

Twinblock appliance:
- energy stored in muscles and ligaments - forces applied to soft tissue, bone and teeth

Question 10

What are the advantages and disadvantages of a twin block?

Answer 10

• good for dental health (removable)
• may avoid extractions if good response to treatment
• may accelerate growth
• may reduce incidence of trauma
• may reduce complexity of treatment
• effective in a class II correction in growing patients
  Disadvantages:
• bulky - pt might not comply
• can affect speech
• can cause soft tissue trauma
• lack of detailed tooth movements
• short window of time where treatment is effective

Question 11

What materials are orthodontic wires made from?

Answer 11

• nickel titanium
• stainless steel

Question 12

What are some indications for fixed appliances?

Answer 12

• excellent OH
• motivated
• dentition free of pathology/disease
• IOTN?

Question 13

Advantages and risks of fixed appliances?

Answer 13

Advantages:
- full range of tooth movements possible
- provides optimal tooth control
Risks:
- demineralisation/caries
- gingivitis
- periodontal destruction
- soft tissue trauma
- pulpal necrosis
- root resorption
- gingival recession
- can cause damage if used incorrectly
- practitioner can increase risk of root resorption/pulpal death