Ortho lab

Question 1

What are the components of stainless steel?

Answer 1

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

Question 2

What is the function of chromium in SS?

Answer 2

Adds corrosion resistance

Question 3

What do we mean by “hard” stainless steel and why do we use it for orthodontic appliances?

Answer 3

Hard means the SS has been cold worked - cold working increases strength.

It gives the material its spring properties and allows it to be bent into desirable positions.

Question 4

Define overjet and what the ideal is.

Answer 4

Overjet - misalignment in the horizontal relationship between U+L incisors i.e. how much they stick out.
Ideal is 1-2mm

Question 5

What are the active components?

Answer 5

The components that move teeth through application of forces.

Question 6

What size of wire are active components made out of?

Answer 6

0.5mm

Question 7

What are retentive components?

Answer 7

Ones that are resistant to displacement force

Question 8

What are the 5 displacement forces of an orthodontic appliance?

Answer 8

Talking
Gravity
Biting
Tongue
Active components

Question 9

What is anchorage?

Answer 9

Resistance to unwanted tooth movement
*Newton’s 3rd law

Question 10

What is the baseplate of an ortho appliance?

Answer 10

Connector - holds components together

Question 11

What is the main source of anchorage in an ortho appliance?

Answer 11

The baseplate

Question 12

Why should an orthodontic appliance only move 1 or 2 teeth?

Answer 12

To assist with anchorage. You may get too much unwanted tooth movement if you try to move too many teeth
EVERY ACTION HAS AN EQUAL AND OPPOSITE REACTION.

Question 13

What would happen if you applied too much force to a tooth/ tried to move it too quickly?

Answer 13

Run the risk of tooth necrosis as the blood and nerve supply could be cut off if moved too quickly.

Question 14

What is the main tooth movement you can achieve with a removable ortho appliance?

Answer 14

Tipping/ tilting

Question 15

What tooth movement is nearly impossible to achieve with removable ortho appliances?

Answer 15

Rotation

Question 16

What are some advantages of removable orthodontics?

Answer 16

Cheaper than fixed
Non-destructive to tooth surface
Shorter chairside time required
OH easier to maintain
Excellent anchorage
Less specialised training required to manage

Question 17

What are some disadvantages of removable orthodontics?

Answer 17

Non-compliance - patient can take out
Less precise control of tooth movement
Only 1-2 teeth can be moved at a time
Technical staff required to construct appliances
Difficult to correct rotations.

Question 18

What type of PMMA is used for removable ortho and why?

Answer 18

Self-cure

Very quick to make - only 15 minutes

Question 19

What is the mnemonic for the technical instructions for making a removable appliance?

Answer 19

ARAB

Active components
Retentive components
Anchorage
Baseplate

Question 20

What are the 10 steps of fitting a removable appliance?

Answer 20

Check the patient and appliance match
Check the appliance matches the design specifications
Inspect appliance and look for sharp areas
Check the integrity of the wirework
Try in the patient’s mouth and check for blanching
Check the posterior retention - Adam’s clasp - check/ adjust flyovers then arrowheads
Check the anterior retention
Activate the appliance - 1mm per month
Demonstrate insertion and removal of the appliance - get the pt. to show them doing this correctly
Book a review appt. in 4-6 weeks to re-activate appliance as will be passive by this time.

Question 21

How does the baseplate provide anchorage?

Answer 21

The baseplate distributes the force

Question 22

What does ID tubing do?

Answer 22

Encases thin (0.5mm) wire - gives strength and rigidity in the buccal aspect of buccal canine retractors.

Question 23

What are some problems with a high flyover on an Adam’s clasp?

Answer 23

Changes occlusion
Metal fatigue can occur due to repeated stresses
Wire distortion
Damage to soft tissues

Question 24

What is a Flat Anterior Bite Plan used for and how does it work?

Answer 24

Used to correct overbites.
Corrects by the lower molars continuing to erupt while the upper molars do not.

Question 25

Why is it unlikely that lower anteriors will not over-erupt with Posterior Bite Plane (PBP)?

Answer 25

Lower anteriors are not in occlusion anyway and they tend to have a maximum eruption level that they do not tend to pass.

Question 26

What gauge of wire should be used for primary dentition?

Answer 26

0.6mm

Question 27

What is the definition of an overbite?

Answer 27

The VERTICAL misalignment between upper and lower teeth.
i.e. over-closing

Question 28

What is the definition of a posterior crossbite?

Answer 28

Lateral (buccal or lingual) misalignment of the posterior teeth.
The maxillary teeth would be more lingual the mandibular teeth on one or both sides - which is abnormal.

Question 29

What is the definition of an anterior crossbite?

Answer 29

A malocclusion where the anterior teeth are misplaced labially/ palatially with reference to the opposing teeth.

Question 30

What is the function of titanium in SS wires?

Answer 30

Prevents precipitation of chromium-carbides at grain boundaries when heated

Question 31

What are some reasons for stainless steel fracture?

Answer 31

Mechanical abrasion
Over-worked
Weld decay
Fatigue

Question 32

What is the Bauschinger effect?

Answer 32

If a coil is activated in the same direction then the elastic recovery is greater than if deflected in the opposite direction

Question 33

What are the 10 things you should instruct a patient on aftercare for a URA?

Answer 33

Avoid sticky foods
Take out during sports
Wear all the time - compliance is necessary for success of treatment
Saliva may be increased
Speech may be impaired - practice speaking
Emergency contact details incase of breakage
Will feel bulky
Will feel uncomfortable - shouldn’t last long but this is how you know its working
Keep in for eating but remove afterwards to clean