Appliance Design (Labs)

Question 1

What are the main components of stainless steel and their %s?

Answer 1

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

Question 2

What are the properties of stainless steel that makes it good for use in ortho?

Answer 2

• non-corrosive
• can bend without fracturing
• cheap
• flexible
• non-toxic
• strong
• biocompatible
• ductile

Question 3

What are the advantages of study casts?

Answer 3

-Good for record keeping -Good to see the improvements/progress -Good motivation for patients (can cut teeth off and put wax in place - don’t make too realistic) -Can look when patient isnt there -design appliances on it -more information for a more informed decision -teaching purposes -retrospective studies

Question 4

What are the 3 main aims of ortho treatment?

Answer 4

-good aesthetic outcome -functional -stable occlusion

Question 5

What type of action/movement can removable ortho appliances do? (how do they move teeth?)

Answer 5

they can tip/tilt teeth

Question 6

Where is the fulcrum in terms of the tooth when using a removable appliance?

Answer 6

at the midpoint of the tooth (between the crown and root) -[we dont bend teeth]

Question 7

What are the advantages of removable appliances?

Answer 7

• Tipping of teeth (able to move teeth)
• fundamental change. In restorative and dentures we are stabilising teeth
• Give excellent anchorage
• Generally cheaper than fixed orthodontics. Fixed involves attaching brackets on every tooth. URA’s are better tolerated than lowers as tongue
• Shorter chairside time required
• Oral hygiene is easier to maintain (can take them out and clean)
• Non-destructive to tooth surface and no tooth prep required (Composite is used to bond to the teeth - need to etch which is destructive - fixed)
• Less specialised training required to manage
• Can be easily adapted for overbite reduction
• Can achieve block movements (segment and entire section of teeth and move it in one - bit of a problem but will be discussed later)

Question 8

What are the disadvantages of removable appliances?

Answer 8

-Less precise control movement of teeth (aka limited to just tipping/tilting) -Can be easily removed by patient (can forget to put back in or not compliant) -Generally only 1-2 teeth can be moved at one time (fixed can move multiple) -Specialist technical staff required to construct the appliances -Rotations very difficult to correct (aka tooth rotated mesially or distally)

Question 9

What is the acronym used for appliance design?

Answer 9

ARAB: -Active component -Retentive -Anchorage -Baseplate

Question 10

What is the active component of a removable appliance?

Answer 10

Any component that will move the teeth through the application of force

Question 11

When writing the active component on a design sheet, what do you need to state?

Answer 11

The teeth The component The wire thickness

Question 12

What kind of stainless steel wire is used in ortho?

Answer 12

Hard stainless steel wire (soft is never used)

Question 13

What is the thickness of stainless steel wire used for active components?

Answer 13

0.5mm

Question 14

What is the thickness of stainless steel wire used for retentive components?

Answer 14

0.7mm

Question 15

What is the definition of anchorage?

Answer 15

the resistance to unwanted tooth movement (Making sure the teeth we want to move do move and the ones we don’t want to move stay in the same place)

Question 16

Anchorage is resisting displacement forces. What are 5 examples of the displacement forces that will be experienced in the mouth?

Answer 16

-forces from the tongue (click it on and off) -mastication -speaking -gravity -the active component - is applying forces to the teeth which will bounce out and can cause the appliance to pop out

Question 17

Newton’s 3rd law makes anchorage hard. What is Newton’s 3rd law?

Answer 17

for every action, there is an opposite and equal action

Question 18

What are the 3 functions of the baseplate?

Answer 18

-hold all the components together -assists with retention (adhesion and cohesion) -Gives a lot of anchorage

Question 19

What material is the baseplate made from?

Answer 19

Self-cure PMMA

Question 20

What thickness of HSSW would be used for an Adam’s clasp on a deciduous tooth?

Answer 20

0.6mm HSSW

Question 21

What baseplate modification is used to help correct overbites? How does it work?

Answer 21

Flat anterior bite plane

• props open mouth and creates posterior open bite
• Lower teeth continue to erupt and new bone is formed around them
• When FABP is removed the overbite will be reduced

Note: cant be done in older patients as teeth would just over-erupt

Question 22

What is the size of the FABP and why do we make it this size?

Answer 22

OJ + 3mm

If didnt add extra 3mm then patient would change bite and bite behind the plane - result in the lower anterior teeth proclining and increasing the overjet

Question 23

How do you resolve an anterior crossbite?

Answer 23

Z-spring and a posterior bite plane to give anterior open bite to allow movement of the tooth in crossbite

Question 24

How many posterior teeth need to be incorporated to a posterior bite plane and why?

Answer 24

All of them otherwise they will continue to erupt

Question 25

Why will using a posterior bite plane not cause the patients anterior teeth to continue to erupt?

Answer 25

The anteriors dont occlude naturally

Note: sometimes in restorative dentistry a posterior bite plane is used to get the anteriors to erupt - this is for PARTIALLY erupted anterior teeth

Question 26

Why do we continue to reduce an overbite when moving onto the next appliance? (e.g. retracted canines and now retracting the 22-12)

Answer 26

• The canines will retract quicker than the lower teeth erupt and when new bone is formed it is less dense than normal bone.
• The flat anterior bite plane allows this new bone to become dense. Otherwise, the teeth could intrude again.
• As the incisors are tipped back, they will drop ‘lower’ which therefore would increase the overbite

Question 27

Describe the steps in fitting an URA.

Answer 27

Before fitting the appliance should always check that the patient’s medical history has not changed and that the appliance has been disinfected and is ready to fit.

1. Ensure the patients details match the details supplied for the appliance (Right Appliance-Right patient).
2. Check the appliance matches the design specifications.
3. Inspect the appliance and run your finger over all surfaces looking for sharp or potentially traumatic areas.
4. Check the integrity of the wirework (Damage or work-hardening).
   
   1. Work hardening would happen if the wire was bent one way then realised it was wrong and bent the other way. Any force on this area would cause it to break
   2. Can identify these areas as they will be dark (not shiny like normal)
   3. Chromium is what makes the metal shiny and prevents corrosion. If there is damage or work hardening then the chromium will have been removed and the area is prone to corrosion and fracture (will be sharp in the patients mouth if it fractures).
5. Insert the appliance into the patient’s mouth, immediately looking for areas of blanching or soft tissue trauma.
   
   1. If the appliance causes ulceration etc then the patient will not wear it
6. Check the posterior retention (Adam’s clasp. Firstly, check the flyovers aren’t interfering with occlusion, then that the arrowheads are correctly engaging the appropriate undercuts.)
7. Apply the same principles to the anterior retention.
8. Activate the appliance (1mm movement approximately per month).
   
   1. We receive the appliances in a passive state.
9. Demonstrate to the patient the correct procedure for insertion and removal of the appliance (Ensure that the patient demonstrates this correctly).
10. Book a review appointment 4-6 weeks

Question 28

What information and instructions would you give to a patient after fitting an URA?

Answer 28

1. Appliance will feel big & bulky (this is perfectly normal and they will get used to it quickly).
2. My cause initial excessive salivation (this will pass in 24 hours).
3. May impinge speech for a short period of time (practise reading a book aloud at home and this will subside).
4. May cause initial discomfort or ache (this is perfectly normal, and indicates that the appliance is working).
5. To be worn 24/7 including meal times & sleep.
6. Remove after every meal and clean with a soft brush.
7. Remove and store in a protective container when participating in contact or active sports.
8. Avoid hard or sticky foods that may damage the appliance and be cautious with hot food or drinks.
9. Missing appointments and non-compliance will significantly lengthen the treatment time.
10. Provide emergency contact details in case any problems arise.