CSAR 14.3 - Material choices for fixed prosthodontics

Question 1

What advantages and disadvantages of the indirect restorations - pressed/cast (lost wax technique)?

Answer 1

+ very accurate

• risk of porosities
• need technician

Question 2

What advantages and disadvantages of the indirect restorations - hand layered?

Answer 2

+ best aesthetics

- weaker as usually feldspathic ceramic

Question 3

What are the advantages and disadvantages of monolithic restorations?

Answer 3

\+ Stronger
\+ More conservative prep 
\+ Cheaper
- Limited aesthetics
- Can only character with stains

Question 4

What are the advantages and disadvantages of bi-layered restorations?

Answer 4

+ Opportunity for better aesthetics
+ Can combine the best qualities of 2 materials – one coating for strength and other for aesthetics
- Potential weak point at material interface
- Risk of chipping/ fracture
- Need for greater preparation

Question 5

Why would a metal collar on a crown be used?

Answer 5

Means less tooth tissue needs to be removed

Question 6

What is the difference between high translucency zirconia and zirconia?

Answer 6

Zirconia – need layering

High Translucency Zirconia – better aesthetics, don’t need layered (but can also layer), weaker

Question 7

What are the advantages and disadvantages of milling for indirect restorations?

Answer 7

+ use high strength materials
+ no porosities
- accuracy limited with size of cutting bur
- expensive equipment

Question 8

What is the advantage of using monolithic zirconia compared to layered?

Answer 8

Monolithic has biological advantage saving tooth tissue as doesn’t need to be layered

Question 9

What material is Emax?

Answer 9

Lithium disilicate

Question 10

Why would monolithic lithium disilicate be preferred for posterior teeth?

Answer 10

Fracture strength is greater, therefore feldspathic would weaken it

Question 11

Why would monolithic lithium disilicate layered with feldspathic porcelain be preferred for anterior teeth?

Answer 11

Adds character/aesthetics

Question 12

What are the pros and cons of using indirect composite as a material for a crown?

Answer 12

+ Easier to adjust and repair
+ Cheaper
+ Can mill in thinner section that ceramic without fracture
+ Good when supported by enamel

• Flexible, therefore greater strain on bonding causing failure
• If into dentine, same prep as ceramic (stronger)
• Weaker than Emax

Question 13

Give an example of a precious metal used for a crown?

Answer 13

Type 4 Gold

Palladium rich casting alloy

Question 14

Give an example of a non-precious metal used for a crown?

Answer 14

Cobalt chromium

Nickel chromium

Question 15

Give an example of a glass ceramic used for a crown?

Answer 15

Feldspathic porcelain

Lithium disilicate

Question 16

Give an example of a polycrystalline ceramic used for a crown?

Answer 16

Zirconia

Question 17

Give an example of a resin based material used for a crown?

Answer 17

Indirect composite

Question 18

When would a translucent material be a good or bad option for a crown?

Answer 18

Good - greater aesthetics is core is a favourable colour

Bad - if tooth is black

Question 19

Name an opaque (passive) lute.

Answer 19

Zinc phosphate
Zinc polycarboxylate
GIC

Question 20

Name an aesthetic (active) lute.

Answer 20

Light cure resin
Dual cure resin
Self adhesive resin cement - needs resistance form as bond strength is low

Question 21

What is the strength of a material as its translucency increases?

Answer 21

Increased translucency = decreased strength

Question 22

Order these crown materials from low to high strength?

Zirconia, Lithium disilicate, Metal, Feldspathic porcelain, High translucency zirconia, Composite resin

Answer 22

Low to high: 
Feldspathic porcelain 
Composite resin 
Lithium disilicate 
High translucency zirconia
Zirconia 
Metal

Question 23

What are the advantages of an adhesive restoration?

Answer 23

• More conservative
• Less reliant on resistance and retention form
• Advantageous when limited clinical crown height

Question 24

What are the disadvantages of an adhesive restoration?

Answer 24

• Harder to temporise
• Need to be able to isolate
• Bond is unpredictable/vulnerable in dentine margins
• Cementation much more technique sensitive