Ortho Lab Techniques

Question 1

Stainless steel composition

Answer 1

72% Iron
18% Chromium
8% Nickel
1.7% Titanium
0.3% Carbon

Question 2

Main component of stainless steel

Answer 2

Iron

Question 3

What is the most widely used material for metal parts of ortho appliances?

Answer 3

Stainless steel

Question 4

Two types of stainless steel, and which is used in ortho?

Answer 4

Hard and soft
Hard is used

Question 5

How is hard stainless steel made?

Answer 5

Work hardening done in a cold state

Question 6

4 reasons fractures of stainless steel wire can occur

Answer 6

Overworked
Mechanical abrasion crush or marked
Fatigue
Wed decay

Question 7

What does it mean that stainless steel is AUSTENITIC?

Answer 7

Austenitic is the crystalline space lattice structure of the alloy. The alloy can not be heat hardened and remains in a soft condition unless it has been cold worked

Question 8

What type of stainless steel is used in orthodontics?

Answer 8

18/8 austenitic stainless steel alloy

Question 9

Why is chromium added to stainless steel?

Answer 9

Lowers the temperature at which martensite formed by quenching
Corrosion resistance due to chromium oxide film on surface

Question 10

What is martensite?

Answer 10

The primary component of hard steel, formed by quenching from high temperatures. It consists of intergrown plate-like crystals with a distorted cubic structure arising from the presence of carbon atoms in the iron structure

Question 11

Why is nickel added to stainless steel?

Answer 11

Helps achieve austenitic structure at room temperature by lowering the critical temp at which the austenitic structure breaks down on cooling
Improves strength and corrosion resistance

Question 12

Why is titanium added to stainless steel?

Answer 12

To prevent precipitation of chromium carbides at the grain boundaries when the alloy is heated during welding or soldering
Carbon combines with titanium in preference to the chromium

Question 13

What is the difference between austenite and martensite?

Answer 13

Is austenite the average unit cell is a perfect cube, the transformation to martensite sees it distorted by interstitial carbon atoms that do not have time to diffuse out during quenching.
These defects make the material harder as the layers of particles can no longer slide past one another in an organised fashion

Question 14

What does ARAB stand for?

Answer 14

Active component
Retention
Anchorage
Baseplate

Question 15

What must be included on a URA appliance design sheet?

Answer 15

Drawing
Description of what the appliance design is aiming to achieve
Active component
Retention
Anchorage
Baseplate

Question 16

What is anchorage?

Answer 16

Resistance to unwanted tooth movement

Question 17

What is the active component?

Answer 17

The name of the components that will be moving teeth with the application of force

Question 18

What is retention?

Answer 18

Resistance to displacement forces

Question 19

What is the job of the baseplate?

Answer 19

Connects all components together as a unit, provides anchorage and assists with retention

Question 20

Advantages of URA orthodontics

Answer 20

Tipping action
Excellent anchorage
Generally cheaper than fixed
Shorter chairside time required
OH easier to maintain
Non-destructive to tooth surface
Less specialised training required for management
Can be easily adapted for overbite reduction
Can achieve block movements

Question 21

Why are study casts useful?

Answer 21

Can look at dentition without patient present
Design purposes
Monitor progress
Try in appliances
Can build appliance without patient present

Question 22

Disadvantages of URA orthodontics

Answer 22

Less precise control of tooth movement
Can be easily removed by patient
Only 1-2 teeth can be moved at a time
Specialist technical staff required to construct
Rotations very difficult to correct

Question 23

What diameter of wire should be used for Adams clasps?

Answer 23

0.7mm
(0.6mm can be used for deciduous teeth or newly erupted premolars)

Question 24

Describe placement of Adams clasps

Answer 24

Adams clasps are placed for retention. They used the mesial and distal undercuts of the buccal aspect of the teeth

Question 25

Advantages of the Adams clasp

Answer 25

Small, neat, unobtrusive Can be used on almost any tooth A tooth that has not yet fully erupted can be clasped Highly versatile and can be modified in a number of ways Highly retentive Its bridge provides a site to which the patient can apply pressure with the fingertips to remove appliance Auxiliary springs can be soldered to the bridge of the clasp Hooks can be soldered to the clasp or bent in during its construction to accept inter-maxillary traction Tubes can be soldered to the bridge of the clasp to accommodate a facebow for extra-oral traction

Question 26

Adams clasp checklist

Answer 26

Arrowheads must engage mesial and distal undercuts, except when tooth is rotated The bridge of the clasp stands clear of the tooth at approx 45 degrees to the crown Arrowheads are parallel Arrowheads are at 45 degrees to tooth surface Arrowheads must not touch adjacent teeth Bridge should not protrude above the occlusal surface The wire fits closely over the contact areas There should be a clearance of 0.5-1mm between the wire and tissue in the palate There must be tags present at the ends of the wire to supply addition mechanical retention within the baseplate The gingival margin of any models should only be trimmed if the tooth present has not fully erupted

Question 27

Basic principle of orthodontics

Answer 27

If prolonged force is applied to a tooth, tooth movement will occur

Question 28

What effect does orthodontics have on bone?

Answer 28

Force exerted creates pressure which causes the bone around the tooth to remodel - a process where bone is selectively removed in some areas and added in others

Question 29

Name 3 retentive components of URAs

Answer 29

Adams clasp Southend clasp Labial bow ALL USE 0.7mm HSSW

Question 30

Name potential active components for URAs

Answer 30

Finger springs + guard Z-Spring Flapper spring T-Spring Buccal canine retractors Roberts retractors ALL USE 0.5mm HSSW

Question 31

Name two buccally placed active components

Answer 31

Buccal canine retractors Roberts retractors

Question 32

How to deliver a URA

Answer 32

Right appliance - right patient Check the appliance matches the design Inspect the appliance and run your finger over all surfaces looking for sharp areas Check the wirework for damage or work hardening Insert into patients mouth - check for blanching or soft tissue trauma Check posterior retention Check anterior retention Activate the appliance Demonstrate insertion and removal Book 4-6 week review

Question 33

What is the desired movement/time for ortho?

Answer 33

1mm/month